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Sample records for insulin receptor loss

  1. Loss of Insulin Receptor in Osteoprogenitor Cells Impairs Structural Strength of Bone

    PubMed Central

    Thrailkill, Kathryn; Bunn, R. Clay; Lumpkin, Charles; Cockrell, Gael; Kahn, C. Ronald; Fowlkes, John; Nyman, Jeffry S.

    2014-01-01

    Type 1 diabetes mellitus (T1D) is associated with decreased bone mineral density, a deficit in bone structure, and subsequently an increased risk of fragility fracture. These clinical observations, paralleled by animal models of T1D, suggest that the insulinopenia of T1D has a deleterious effect on bone. To further examine the action of insulin signaling on bone development, we generated mice with an osteoprogenitor-selective (osterix-Cre) ablation of the insulin receptor (IR), designated OIRKO. OIRKO mice exhibited an 80% decrease in IR in osteoblasts. Prenatal elimination of IR did not affect fetal survival or gross morphology. However, loss of IR in mouse osteoblasts resulted in a postnatal growth-constricted phenotype. By 10–12 weeks of age, femurs of OIRKO mice were more slender, with a thinner diaphyseal cortex and, consequently, a decrease in whole bone strength when subjected to bending. In male mice alone, decreased metaphyseal trabecular bone, with thinner and more rodlike trabeculae, was also observed. OIRKO mice did not, however, exhibit abnormal glucose tolerance. The skeletal phenotype of the OIRKO mouse appeared more severe than that of previously reported bone-specific IR knockdown models, and confirms that insulin receptor expression in osteoblasts is critically important for proper bone development and maintenance of structural integrity. PMID:24963495

  2. Loss of the insulin receptor in murine megakaryocytes/platelets causes thrombocytosis and alterations in IGF signalling

    PubMed Central

    Moore, Samantha F.; Williams, Christopher M.; Brown, Edward; Blair, Thomas A.; Harper, Matthew T.; Coward, Richard J.; Poole, Alastair W.; Hers, Ingeborg

    2015-01-01

    Aims Patients with conditions that are associated with insulin resistance such as obesity, type 2 diabetes mellitus, and polycystic ovary syndrome have an increased risk of thrombosis and a concurrent hyperactive platelet phenotype. Our aim was to determine whether insulin resistance of megakaryocytes/platelets promotes platelet hyperactivation. Methods and results We generated a conditional mouse model where the insulin receptor (IR) was specifically knocked out in megakaryocytes/platelets and performed ex vivo platelet activation studies in wild-type (WT) and IR-deficient platelets by measuring aggregation, integrin αIIbβ3 activation, and dense and α-granule secretion. Deletion of IR resulted in an increase in platelet count and volume, and blocked the action of insulin on platelet signalling and function. Platelet aggregation, granule secretion, and integrin αIIbβ3 activation in response to the glycoprotein VI (GPVI) agonist collagen-related peptide (CRP) were significantly reduced in platelets lacking IR. This was accompanied by a reduction in the phosphorylation of effectors downstream of GPVI. Interestingly, loss of IR also resulted in a reduction in insulin-like growth factor-1 (IGF-1)- and insulin-like growth factor-2 (IGF-2)-mediated phosphorylation of IRS-1, Akt, and GSK3β and priming of CRP-mediated platelet activation. Pharmacological inhibition of IR and the IGF-1 receptor in WT platelets recapitulated the platelet phenotype of IR-deficient platelets. Conclusions Deletion of IR (i) increases platelet count and volume, (ii) does not cause platelet hyperactivity, and (iii) reduces GPVI-mediated platelet function and platelet priming by IGF-1 and IGF-2. PMID:25902782

  3. Insulin Receptor Substrate 2 (IRS2)-Deficient Mice Show Sensorineural Hearing Loss That Is Delayed by Concomitant Protein Tyrosine Phosphatase 1B (PTP1B) Loss of Function

    PubMed Central

    Murillo-Cuesta, Silvia; Camarero, Guadalupe; González-Rodríguez, Águeda; de la Rosa, Lourdes Rodríguez; Burks, Deborah J; Avendaño, Carlos; Valverde, Ángela M; Varela-Nieto, Isabel

    2012-01-01

    The insulin receptor substrate (IRS) proteins are key mediators of insulin and insulinlike growth factor 1 (IGF-1) signaling. Protein tyrosine phosphatase (PTP)-1B dephosphorylates and inactivates both insulin and IGF-1 receptors. IRS2-deficient mice present altered hepatic insulin signaling and β-cell failure and develop type 2–like diabetes. In addition, IRS2 deficiency leads to developmental defects in the nervous system. IGF1 gene mutations cause syndromic sensorineural hearing loss in humans and mice. However, the involvement of IRS2 and PTP1B, two IGF-1 downstream signaling mediators, in hearing onset and loss has not been studied. Our objective was to study the hearing function and cochlear morphology of Irs2-null mice and the impact of PTP1B deficiency. We have studied the auditory brainstem responses and the cochlear morphology of systemic Irs2−/−Ptpn1+/+, Irs2+/+Ptpn1−/−and Irs2−/−Ptpn1−/− mice at different postnatal ages. The results indicated that Irs2−/−Ptpn1+/+ mice present a profound congenital sensorineural deafness before the onset of diabetes and altered cochlear morphology with hypoinnervation of the cochlear ganglion and aberrant stria vascularis, compared with wild-type mice. Simultaneous PTP1B deficiency in Irs2−/−Ptpn1−/− mice delays the onset of deafness. We show for the first time that IRS2 is essential for hearing and that PTP1B inhibition may be useful for treating deafness associated with hyperglycemia and type 2 diabetes. PMID:22160220

  4. Insulin resistance and muscle insulin receptor substrate‐1 serine hyperphosphorylation

    PubMed Central

    Stuart, Charles A.; Howell, Mary E. A.; Cartwright, Brian M.; McCurry, Melanie P.; Lee, Michelle L.; Ramsey, Michael W.; Stone, Michael H.

    2014-01-01

    Abstract Insulin resistance in metabolic syndrome subjects is profound in spite of muscle insulin receptor and insulin‐responsive glucose transporter (GLUT4) expression being nearly normal. Insulin receptor tyrosine kinase phosphorylation of insulin receptor substrate‐1 (IRS‐1) at Tyr896 is a necessary step in insulin stimulation of translocation of GLUT4 to the cell surface. Serine phosphorylation of IRS‐1 by some kinases diminishes insulin action in mice. We evaluated the phosphorylation status of muscle IRS‐1 in 33 subjects with the metabolic syndrome and seventeen lean controls. Each underwent euglycemic insulin clamps and a thigh muscle biopsy before and after 8 weeks of either strength or endurance training. Muscle IRS‐1 phosphorylation at six sites was quantified by immunoblots. Metabolic syndrome muscle IRS‐1 had excess phosphorylation at Ser337 and Ser636 but not at Ser307, Ser789, or Ser1101. Ser337 is a target for phosphorylation by glycogen synthase kinase 3 (GSK3) and Ser636 is phosphorylated by c‐Jun N‐terminal kinase 1 (JNK1). Exercise training without weight loss did not change the IRS‐1 serine phosphorylation. These data suggest that baseline hyperphosphorylation of at least two key serines within muscle IRS‐1 diminishes the transmission of the insulin signal and thereby decreases the insulin‐stimulated translocation of GLUT4. Excess fasting phosphorylation of muscle IRS‐1 at Ser636 may be a major cause of the insulin resistance seen in obesity and might prevent improvement in insulin responsiveness when exercise training is not accompanied by weight loss. PMID:25472611

  5. Insulin receptor in Drosophila melanogaster

    SciTech Connect

    Petruzzelli, L.; Herrera, R.; Rosen, O.

    1986-05-01

    A specific, high affinity insulin receptor is present in both adult Drosophila and in Drosophila embryos. Wheat germ lectin-enriched extracts of detergent-solubilized membranes from embryos and adults bind insulin with a K/sub d/ of 15 nM. Binding is specific for insulin; micromolar concentrations of proinsulin, IGFI, and IGFII are required to displace bound /sup 125/I-insulin. Insulin-dependent protein tyrosine kinase activity appears during embryogenesis. It is evident between 6 and 12 hours of development, peaks between 12 and 18 hours and falls in the adult. During 0-6 hours of embryogenesis, and in the adult, a specific protein band (Mr = 135,000) is crosslinked to /sup 125/I-insulin. During 6-12 and 12-18 hours of embryogenesis stages in which insulin-dependent protein tyrosine kinase is high, an additional band (Mr = 100,000) becomes crosslinked to /sup 125/I-insulin. Isolation and DNA sequence analysis of genomic clones encoding the Drosophila insulin receptor will be presented as will the characterization of insulin receptor mRNA's during development.

  6. Phenobarbital and Insulin Reciprocate Activation of the Nuclear Receptor Constitutive Androstane Receptor through the Insulin Receptor

    PubMed Central

    Yasujima, Tomoya; Saito, Kosuke; Moore, Rick

    2016-01-01

    Phenobarbital (PB) antagonized insulin to inactivate the insulin receptor and attenuated the insulin receptor downstream protein kinase B (AKT)–forkhead box protein O1 and extracellular signal-regulated kinase 1/2 signals in mouse primary hepatocytes and HepG2 cells. Hepatic AKT began dephosphorylation in an early stage of PB treatment, and blood glucose levels transiently increased in both wild-type and constitutive androstane receptor (CAR) knockout (KO) mice. On the other hand, blood glucose levels increased in wild-type mice, but not KO mice, in later stages of PB treatment. As a result, PB, acting as an insulin receptor antagonist, elicited CAR-independent increases and CAR-dependent decreases of blood glucose levels at these different stages of treatment, respectively. Reciprocally, insulin activation of the insulin receptor repressed CAR activation and induction of its target CYP2B6 gene in HepG2 cells. Thus, PB and insulin cross-talk through the insulin receptor to regulate glucose and drug metabolism reciprocally. PMID:26994072

  7. Phenobarbital and Insulin Reciprocate Activation of the Nuclear Receptor Constitutive Androstane Receptor through the Insulin Receptor.

    PubMed

    Yasujima, Tomoya; Saito, Kosuke; Moore, Rick; Negishi, Masahiko

    2016-05-01

    Phenobarbital (PB) antagonized insulin to inactivate the insulin receptor and attenuated the insulin receptor downstream protein kinase B (AKT)-forkhead box protein O1 and extracellular signal-regulated kinase 1/2 signals in mouse primary hepatocytes and HepG2 cells. Hepatic AKT began dephosphorylation in an early stage of PB treatment, and blood glucose levels transiently increased in both wild-type and constitutive androstane receptor (CAR) knockout (KO) mice. On the other hand, blood glucose levels increased in wild-type mice, but not KO mice, in later stages of PB treatment. As a result, PB, acting as an insulin receptor antagonist, elicited CAR-independent increases and CAR-dependent decreases of blood glucose levels at these different stages of treatment, respectively. Reciprocally, insulin activation of the insulin receptor repressed CAR activation and induction of its target CYP2B6 gene in HepG2 cells. Thus, PB and insulin cross-talk through the insulin receptor to regulate glucose and drug metabolism reciprocally.

  8. Insulin receptors in the mammary gland

    SciTech Connect

    Smith, D.H.

    1986-01-01

    Insulin binding studies were conducted using mammary membrane preparations to further the authors understanding of insulin's role in regulating mammary metabolism, particularly ruminant mammary metabolism. Specific objectives were to: (1) characterize insulin binding to bovine mammary microsomes and determine if the specificity and kinetics of binding indicate the presence of insulin receptors in bovine mammary gland; (2) examine and compare insulin binding by liver and mammary microsomes of the pig and dairy cow; (3) examine insulin binding to bovine milk fat globule membranes (MFGM) and evaluate this model's usefulness in assessing insulin receptor regulation in the mammary gland of the cow; (4) examine the effect of dietary fat in insulin binding by rat mammary and liver microsomes. The specificity and kinetics of /sup 125/I-insulin binding of bovine mammary microsomes indicated the presence of insulin receptors in bovine mammary gland. Bovine liver and mammary microsomes specifically bound less /sup 125/I-insulin than did the corresponding porcine microsomes, and mammary microsomes, regardless of species, specifically bound less /sup 125/I-insulin than did liver microsomes. These differences in binding suggest differences in insulin responsiveness between pigs and cattle, as well as between the liver and mammary glands.

  9. Acquired resistance to tamoxifen is associated with loss of the type I insulin-like growth factor receptor: implications for breast cancer treatment.

    PubMed

    Fagan, Dedra H; Uselman, Ryan R; Sachdev, Deepali; Yee, Douglas

    2012-07-01

    The role of the insulin-like growth factor (IGF) system in breast cancer is well defined, and inhibitors of this pathway are currently in clinical trials. The majority of anti-IGF1R clinical trials are in estrogen receptor-positive patients who have progressed on prior endocrine therapy; early reports show no benefit for addition of IGF1R inhibitors to endocrine therapy in this setting. In this study, we examined the effectiveness of IGF1R inhibitors in vitro by generating tamoxifen-resistant (TamR) cells. We found that TamR cells had diminished levels of IGF1R with unchanged levels of insulin receptor (IR), and failed to respond to IGF-I-induced Akt activation, proliferation, and anchorage-independent growth while retaining responsiveness to both insulin and IGF-II. The IGF1R antibody dalotuzumab inhibited IGF-I-mediated Akt phosphorylation, proliferation, and anchorage-independent growth in parental cells, but had no effect on TamR cells. An IGF1R tyrosine kinase inhibitor, AEW541, with equal potency for the IGF1R and IR, inhibited IGF-I-, IGF-II-, and insulin-stimulated Akt phosphorylation, proliferation, and anchorage-independent growth in parental cells. Interestingly, AEW541 also inhibited insulin- and IGF-II-stimulated effects in TamR cells. Tamoxifen-treated xenografts also had reduced levels of IGF1R, and dalotuzumab did not enhance the effect of tamoxifen. We conclude that cells selected for tamoxifen resistance in vitro have downregulated IGF1R making antibodies directed against this receptor ineffective. Inhibition of IR may be necessary to manage tamoxifen-resistant breast cancer.

  10. Binding characteristics of swine erythrocyte insulin receptors

    SciTech Connect

    Dieberg, G.; Bryan, G.S.; Sartin, J.L.; Williams, J.C.; Prince, T.J.; Kemppainen, R.J.

    1985-09-01

    Crossbred gilts had 8.8 +/- 1.1% maximum binding of ( SVI)insulin to insulin receptors on erythrocytes. The number of insulin-binding sites per cell was 137 +/- 19, with a binding affinity ranging from 7.4 X 10(7)M-1 to 11.2 X 10(7)M-1 and mean of 8.8 X 10(7)M-1. Pregnant sows had a significant increase in maximum binding due to an increase in number of receptor sites per cell. Lactating sows fed a high-fiber diet and a low-fiber diet did not develop a significant difference in maximum binding of insulin. Sows fed the low-fiber diet had a significantly higher number of binding sites and a significantly lower binding affinity than did sows fed a high-fiber diet. Receptor-binding affinity was lower in the low-fiber diet group than in cycling gilts, whereas data from sows fed the high-fiber diet did not differ from data for cycling gilts. Data from this study indicated that insulin receptors of swine erythrocytes have binding characteristics similar to those in other species. Pregnancy and diet will alter insulin receptor binding in swine.

  11. Insulin and rabbit anti-insulin receptor antibodies stimulate additively the intrinsic receptor kinase activity.

    PubMed Central

    Ponzio, G; Dolais-Kitabgi, J; Louvard, D; Gautier, N; Rossi, B

    1987-01-01

    This paper describes the properties of rabbit polyclonal antibodies directed against purified human insulin receptor which strongly stimulate the intrinsic tyrosine kinase activity. The stimulatory effect of the antibodies on the kinase activity was obtained on the insulin receptor autophosphorylation as well as on the kinase activity towards a synthetic substrate. This stimulation is additive to that induced by insulin. Moreover, rabbit antibodies do not impair insulin binding. These data strongly suggest that antibodies and insulin act through separate pathways. This conclusion is reinforced by the differences observed on the phosphopeptide maps of the receptor's beta subunit whose phosphorylation was performed either in the presence of insulin or rabbit antibodies. Interestingly, these polyclonal antibodies can also induce an activation of the receptor autophosphorylation by interacting only with extracellular determinants. The anti-insulin receptor antibodies mimic insulin in their stimulatory effect on amino acid (AIB) uptake, but they have a different effect to that found on the kinase activity; the simultaneous addition of the antiserum and insulin failed to stimulate this amino acid transport over the level induced by a saturating concentration of hormone. Images Fig. 1. Fig. 3. Fig. 4. Fig. 6. Fig. 7. PMID:3034584

  12. Effects of Autoantibodies to the Insulin Receptor on Isolated Adipocytes

    PubMed Central

    Kahn, C. Ronald; Baird, Kathleen; Flier, Jeffrey S.; Jarrett, David B.

    1977-01-01

    IgG. In addition, the bioactivity was blocked by antihuman IgG but not by anti-insulin antibodies. Enzymatic digestion of adipocytes with trypsin resulted in a complete loss of insulin-stimulated bioactivity of serum B-3, but had only minor effects on the glucose oxidation produced by serum B-1 or B-2. These data suggest that the antibodies present in these three sera bind to different determinants on the insulin receptor. Thus, these antibodies may be useful probes of receptor structure and function. PMID:908753

  13. SORLA facilitates insulin receptor signaling in adipocytes and exacerbates obesity

    PubMed Central

    Schmidt, Vanessa; Schulz, Nadja; Yan, Xin; Schürmann, Annette; Kempa, Stefan; Kern, Matthias; Blüher, Matthias; Poy, Matthew N.

    2016-01-01

    In humans, genetic variation of sortilin-related receptor, L(DLR class) A repeats containing (SORL1), which encodes the intracellular sorting receptor SORLA, is a major genetic risk factor for familial and sporadic forms of Alzheimer’s disease. Recent GWAS analysis has also associated SORL1 with obesity in humans and in mouse models, suggesting that this receptor may play a role in regulating metabolism. Here, using mouse models with genetic loss or tissue-specific overexpression of SORLA as well as data from obese human subjects, we observed a gene-dosage effect that links SORLA expression to obesity and glucose tolerance. Overexpression of human SORLA in murine adipose tissue blocked hydrolysis of triacylglycerides and caused excessive adiposity. In contrast, Sorl1 gene inactivation in mice accelerated breakdown of triacylglycerides in adipocytes and protected animals from diet-induced obesity. We then identified the underlying molecular mechanism whereby SORLA promotes insulin-induced suppression of lipolysis in adipocytes. Specifically, we determined that SORLA acts as a sorting factor for the insulin receptor (IR) that redirects internalized receptor molecules from endosomes to the plasma membrane, thereby enhancing IR surface expression and strengthening insulin signal reception in target cells. Our findings provide a molecular mechanism for the association of SORL1 with human obesity and confirm a genetic link between neurodegeneration and metabolism that converges on the receptor SORLA. PMID:27322061

  14. MARCH1 regulates insulin sensitivity by controlling cell surface insulin receptor levels.

    PubMed

    Nagarajan, Arvindhan; Petersen, Max C; Nasiri, Ali R; Butrico, Gina; Fung, Annie; Ruan, Hai-Bin; Kursawe, Romy; Caprio, Sonia; Thibodeau, Jacques; Bourgeois-Daigneault, Marie-Claude; Sun, Lisha; Gao, Guangping; Bhanot, Sanjay; Jurczak, Michael J; Green, Michael R; Shulman, Gerald I; Wajapeyee, Narendra

    2016-01-01

    Insulin resistance is a key driver of type 2 diabetes (T2D) and is characterized by defective insulin receptor (INSR) signalling. Although surface INSR downregulation is a well-established contributor to insulin resistance, the underlying molecular mechanisms remain obscure. Here we show that the E3 ubiquitin ligase MARCH1 impairs cellular insulin action by degrading cell surface INSR. Using a large-scale RNA interference screen, we identify MARCH1 as a negative regulator of INSR signalling. March1 loss-of-function enhances, and March1 overexpression impairs, hepatic insulin sensitivity in mice. MARCH1 ubiquitinates INSR to decrease cell surface INSR levels, but unlike other INSR ubiquitin ligases, MARCH1 acts in the basal state rather than after insulin stimulation. Thus, MARCH1 may help set the basal gain of insulin signalling. MARCH1 expression is increased in white adipose tissue of obese humans, suggesting that MARCH1 contributes to the pathophysiology of T2D and could be a new therapeutic target. PMID:27577745

  15. MARCH1 regulates insulin sensitivity by controlling cell surface insulin receptor levels

    PubMed Central

    Nagarajan, Arvindhan; Petersen, Max C.; Nasiri, Ali R.; Butrico, Gina; Fung, Annie; Ruan, Hai-Bin; Kursawe, Romy; Caprio, Sonia; Thibodeau, Jacques; Bourgeois-Daigneault, Marie-Claude; Sun, Lisha; Gao, Guangping; Bhanot, Sanjay; Jurczak, Michael J.; Green, Michael R.; Shulman, Gerald I.; Wajapeyee, Narendra

    2016-01-01

    Insulin resistance is a key driver of type 2 diabetes (T2D) and is characterized by defective insulin receptor (INSR) signalling. Although surface INSR downregulation is a well-established contributor to insulin resistance, the underlying molecular mechanisms remain obscure. Here we show that the E3 ubiquitin ligase MARCH1 impairs cellular insulin action by degrading cell surface INSR. Using a large-scale RNA interference screen, we identify MARCH1 as a negative regulator of INSR signalling. March1 loss-of-function enhances, and March1 overexpression impairs, hepatic insulin sensitivity in mice. MARCH1 ubiquitinates INSR to decrease cell surface INSR levels, but unlike other INSR ubiquitin ligases, MARCH1 acts in the basal state rather than after insulin stimulation. Thus, MARCH1 may help set the basal gain of insulin signalling. MARCH1 expression is increased in white adipose tissue of obese humans, suggesting that MARCH1 contributes to the pathophysiology of T2D and could be a new therapeutic target. PMID:27577745

  16. Insulin receptor activation in solitary fibrous tumours.

    PubMed

    Li, Y; Chang, Q; Rubin, B P; Fletcher, C D M; Morgan, T W; Mentzer, S J; Sugarbaker, D J; Fletcher, J A; Xiao, S

    2007-04-01

    Solitary fibrous tumours (SFTs) are known to overexpress insulin-like growth factor 2 (IGF-2). The down-stream oncogenic pathways of IGF-2, however, are not clear. Here we report uniform activation of the insulin receptor (IR) pathway in SFTs, which are mesenchymal tumours frequently associated with hypoglycaemia. Whereas the IR and its downstream signalling pathways were constitutively activated in SFTs, insulin-like growth factor 1 receptor (IGF-1R) was not expressed in these tumours. We also find that SFT cells secrete IGF-2 and proliferate in serum-free medium, consistent with an IGF-2/IR autocrine loop. The aetiological relevance of IGF-2 is supported by expression of IR-A, the IR isoform with high affinity for IGF-2, in all SFTs. Our studies suggest that IR activation plays an oncogenic role in SFTs.

  17. Insulin and insulin like growth factor II endocytosis and signaling via insulin receptor B

    PubMed Central

    2013-01-01

    Background Insulin and insulin-like growth factors (IGFs) act on tetrameric tyrosine kinase receptors controlling essential functions including growth, metabolism, reproduction and longevity. The insulin receptor (IR) binds insulin and IGFs with different affinities triggering different cell responses. Results We showed that IGF-II induces cell proliferation and gene transcription when IR-B is over-expressed. We combined biotinylated ligands with streptavidin conjugated quantum dots and visible fluorescent proteins to visualize the binding of IGF-II and insulin to IR-B and their ensuing internalization. By confocal microscopy and flow cytometry in living cells, we studied the internalization kinetic through the IR-B of both IGF-II, known to elicit proliferative responses, and insulin, a regulator of metabolism. Conclusions IGF-II promotes a faster internalization of IR-B than insulin. We propose that IGF-II differentially activates mitogenic responses through endosomes, while insulin-activated IR-B remains at the plasma membrane. This fact could facilitate the interaction with key effector molecules involved in metabolism regulation. PMID:23497114

  18. Agonism and Antagonism at the Insulin Receptor

    PubMed Central

    Knudsen, Louise; Hansen, Bo Falck; Jensen, Pia; Pedersen, Thomas Åskov; Vestergaard, Kirsten; Schäffer, Lauge; Blagoev, Blagoy; Oleksiewicz, Martin B.; Kiselyov, Vladislav V.; De Meyts, Pierre

    2012-01-01

    Insulin can trigger metabolic as well as mitogenic effects, the latter being pharmaceutically undesirable. An understanding of the structure/function relationships between insulin receptor (IR) binding and mitogenic/metabolic signalling would greatly facilitate the preclinical development of new insulin analogues. The occurrence of ligand agonism and antagonism is well described for G protein-coupled receptors (GPCRs) and other receptors but in general, with the exception of antibodies, not for receptor tyrosine kinases (RTKs). In the case of the IR, no natural ligand or insulin analogue has been shown to exhibit antagonistic properties, with the exception of a crosslinked insulin dimer (B29-B’29). However, synthetic monomeric or dimeric peptides targeting sites 1 or 2 of the IR were shown to be either agonists or antagonists. We found here that the S961 peptide, previously described to be an IR antagonist, exhibited partial agonistic effects in the 1–10 nM range, showing altogether a bell-shaped dose-response curve. Intriguingly, the agonistic effects of S961 were seen only on mitogenic endpoints (3H-thymidine incorporation), and not on metabolic endpoints (14C-glucose incorporation in adipocytes and muscle cells). The agonistic effects of S961 were observed in 3 independent cell lines, with complete concordance between mitogenicity (3H-thymidine incorporation) and phosphorylation of the IR and Akt. Together with the B29-B’29 crosslinked dimer, S961 is a rare example of a mixed agonist/antagonist for the human IR. A plausible mechanistic explanation based on the bivalent crosslinking model of IR activation is proposed. PMID:23300584

  19. [Severe type A insulin resistance syndrome due to a mutation in the insulin receptor gene].

    PubMed

    Ros, P; Colino-Alcol, E; Grasso, V; Barbetti, F; Argente, J

    2015-01-01

    Insulin resistance syndromes without lipodystrophy are an infrequent and heterogeneous group of disorders with variable clinical phenotypes, associated with hyperglycemia and hyperinsulinemia. The three conditions related to mutations in the insulin receptor gene are leprechaunism or Donohue syndrome, Rabson-Mendenhall syndrome, and Type A syndrome. A case is presented on a patient diagnosed with type A insulin resistance, defined by the triad of extreme insulin resistance, acanthosis nigricans, and hyperandrogenism, carrying a heterozygous mutation in exon 19 of the insulin receptor gene coding for its tyrosine kinase domain that is crucial for the catalytic activity of the receptor. The molecular basis of the syndrome is reviewed, focusing on the structure-function relationships of the insulin receptor, knowing that the criteria for survival are linked to residual insulin receptor function. It is also pointed out that, although type A insulin resistance appears to represent a somewhat less severe condition, these patients have a high morbidity and their treatment is still unsatisfactory.

  20. Quercetin suppresses insulin receptor signaling through inhibition of the insulin ligand–receptor binding and therefore impairs cancer cell proliferation

    SciTech Connect

    Wang, Feng; Yang, Yong

    2014-10-03

    Graphical abstract: - Highlights: • Quercetin inhibits insulin ligand–receptor interactions. • Quercetin reduces downstream insulin receptor signaling. • Quercetin blocks insulin induced glucose uptake. • Quercetin suppresses insulin stimulated cancer cell proliferation and tumor growth. - Abstract: Although the flavonoid quercetin is known to inhibit activation of insulin receptor signaling, the inhibitory mechanism is largely unknown. In this study, we demonstrate that quercetin suppresses insulin induced dimerization of the insulin receptor (IR) through interfering with ligand–receptor interactions, which reduces the phosphorylation of IR and Akt. This inhibitory effect further inhibits insulin stimulated glucose uptake due to decreased cell membrane translocation of glucose transporter 4 (GLUT4), resulting in impaired cancer cell proliferation. The effect of quercetin in inhibiting tumor growth was also evident in an in vivo model, indicating a potential future application for quercetin in the treatment of cancers.

  1. Nature and regulation of the insulin receptor: structure and function

    SciTech Connect

    Czech, M.P.

    1985-01-01

    Native, cell-surface insulin receptor consists of two glycoprotein subunit types with apparent masses of about 125,000 daltons (alpha subunit) and 90,000 daltons (beta subunit). The alpha and beta insulin-receptor subunits seem to have distinct functions such that alpha appears to bind hormone whereas beta appears to possess intrinsic tyrosine kinase activity. In detergent extracts, insulin activates receptor autophosphorylation of tyrosine residues on its beta subunit, whereas in the presence of reductant, the alpha subunit is also phosphorylated. In intact cells, insulin activates serine/threonine phosphorylation of insulin receptor beta subunit as well as tyrosine phosphorylation. The biological role of the receptor-associated tyrosine kinase is not known. The insulin receptor kinase is regulated by beta-adrenergic agonists and other agents that elevate cAMP in adipocytes, presumably via the cAMP-dependent protein kinase. Such agents decrease receptor affinity for insulin and partially uncouple receptor tyrosine kinase activity from activation by insulin. These effects appear to contribute to the biological antagonism between insulin and beta-agonists. These data suggest the hypothesis that a complex network of tyrosine and serine/threonine phosphorylations on the insulin receptor modulate its binding and kinase activities in an antagonistic manner.

  2. Down-regulation of insulin receptors is related to insulin internalization

    SciTech Connect

    Geiger, D.; Carpentier, J.L.; Gorden, P.; Orci, L. )

    1989-11-01

    In the present study, we have tested the influence of inhibition of endocytosis by hypertonic medium on the regulation of cell surface insulin receptors. We show that active internalization of {sup 125}I-insulin is markedly inhibited by hypertonic media and that, in parallel, cell surface invaginations are significantly diminished. These two events are accompanied by a marked inhibition of cell surface insulin receptor down-regulation. These data provide further strong evidence that receptor-mediated endocytosis is the major mechanism by which insulin receptors are regulated at the surface of target cells.

  3. Presence of insulin receptors in cultured glial C6 cells. Regulation by butyrate.

    PubMed Central

    Montiel, F; Ortiz-Caro, J; Villa, A; Pascual, A; Aranda, A

    1989-01-01

    The presence of insulin receptor and its regulation by butyrate and other short-chain fatty acids was studied in C6 cells, a rat glioma cell line. Intact C6 cells bind 125I-insulin in a rapid, reversible and specific manner. Scatchard analysis of the binding data gives typical curvilinear plots with apparent affinities of approx. 6 nM and 70 nM for the low-affinity (approx. 90% of total) and high-affinity (approx. 10% of total) sites respectively. Incubation with butyrate results in a time- and dose-dependent decrease of insulin binding to C6 cells. A maximal effect was found with 2 mM-butyrate that decreased the receptor by 40-70% after 48 h. Butyrate decreased numbers of receptors of both classes, but did not significantly alter receptor affinity. Other short-chain fatty acids, as well as keto acids, had a similar effect, but with a lower potency. Cycloheximide caused an accumulation of insulin receptors at the cell surface, since insulin binding increased and receptor affinity did not change after incubation with the inhibitor. Simultaneous addition of butyrate and cycloheximide abolished the loss of receptors produced by the fatty acid. In cells preincubated with butyrate, cycloheximide also produced a large increase in receptor numbers, showing that in the absence of new receptor synthesis a large pool of receptors re-appears at the surface of butyrate-treated cells. PMID:2930502

  4. Insulin and blood pressure during weight loss in obese adolescents.

    PubMed

    Rocchini, A P; Katch, V; Schork, A; Kelch, R P

    1987-09-01

    The role of insulin in the regulation of blood pressure was evaluated in 50 obese adolescents before and after a 20-week weight loss program. When compared with 10 nonobese adolescents, the obese subjects had significantly higher systolic, diastolic, and mean arterial pressures (p = 0.005), an elevated 24-hour urinary sodium excretion (p = 0.002), an elevated fasting insulin concentration (p = 0.001), and an abnormal insulin response to an oral glucose tolerance test (sum of the insulins at 0, 1, and 2 hours post-oral glucose load; p = 0.001). We also observed a significant correlation between systolic and diastolic blood pressure (age and sex normalized) and body weight (r = 0.57, p less than 0.01 and r = 0.7, p less than 0.01), fasting insulin (r = 0.49, p less than 0.01 and r = 0.54, p less than 0.01), and sum of insulins (r = 0.42, p less than 0.01 and r = 0.46, p less than 0.01). To study the effect of weight loss on the relationship between blood pressure and insulin, the obese subjects were randomly assigned to three groups: 15 to a diet and behavior change group, 18 to a diet, behavior change, and exercise group, and 17 to an obese control group. Compared with the obese control group, the two weight loss groups each experienced a significant decrease in insulin (p less than 0.01), sum of the insulins (p less than 0.01), and blood pressure (p less than 0.01). The decrease in blood pressure during the weight loss program significantly correlated with the change in both insulin and body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

  5. Development of real-time reverse transcription polymerase chain reaction assays to quantify insulin-like growth factor receptor and insulin receptor expression in equine tissue.

    PubMed

    Hughes, Stephen B; Quan, Melvyn; Guthrie, Alan; Schulman, Martin

    2013-01-01

    The insulin-like growth factor system (insulin-like growth factor 1, insulin-like growth factor 2, insulin-like growth factor 1 receptor, insulin-like growth factor 2 receptor and six insulin-like growth factor-binding proteins) and insulin are essential to muscle metabolism and most aspects of male and female reproduction. Insulin-like growth factor and insulin play important roles in the regulation of cell growth, differentiation and the maintenance of cell differentiation in mammals. In order to better understand the local factors that regulate equine physiology, such as muscle metabolism and reproduction (e.g., germ cell development and fertilisation), real-time reverse transcription polymerase chain reaction assays for quantification of equine insulin-like growth factor 1 receptor and insulin receptor messenger ribonucleic acid were developed. The assays were sensitive: 192 copies/μL and 891 copies/μL for insulin-like growth factor 1 receptor, messenger ribonucleic acid and insulin receptor respectively (95% limit of detection), and efficient: 1.01 for the insulin-like growth factor 1 receptor assay and 0.95 for the insulin receptor assay. The assays had a broad linear range of detection (seven logs for insulin-like growth factor 1 receptor and six logs for insulin receptor). This allowed for analysis of very small amounts of messenger ribonucleic acid. Low concentrations of both insulin-like growth factor 1 receptor and insulin receptor messenger ribonucleic acid were detected in endometrium, lung and spleen samples, whilst high concentrations were detected in heart, muscle and kidney samples, this was most likely due to the high level of glucose metabolism and glucose utilisation by these tissues. The assays developed for insulin-like growth factor 1 receptor and insulin receptor messenger ribonucleic acid expression have been shown to work on equine tissue and will contribute to the understanding of insulin and insulin-like growth factor 1 receptor

  6. Insulin receptors internalize by a rapid, saturable pathway requiring receptor autophosphorylation and an intact juxtamembrane region

    PubMed Central

    1991-01-01

    The effect of receptor occupancy on insulin receptor endocytosis was examined in CHO cells expressing normal human insulin receptors (CHO/IR), autophosphorylation- and internalization-deficient receptors (CHO/IRA1018), and receptors which undergo autophosphorylation but lack a sequence required for internalization (CHO/IR delta 960). The rate of [125I]insulin internalization in CHO/IR cells at 37 degrees C was rapid at physiological concentrations, but decreased markedly in the presence of increasing unlabeled insulin (ED50 = 1-3 nM insulin, or 75,000 occupied receptors/cell). In contrast, [125I]insulin internalization by CHO/IRA1018 and CHO/IR delta 960 cells was slow and was not inhibited by unlabeled insulin. At saturating insulin concentrations, the rate of internalization by wild-type and mutant receptors was similar. Moreover, depletion of intracellular potassium, which has been shown to disrupt coated pit formation, inhibited the rapid internalization of [125I]insulin at physiological insulin concentrations by CHO/IR cells, but had little or no effect on [125I]insulin uptake by CHO/IR delta 960 and CHO/IRA1018 cells or wild-type cells at high insulin concentrations. These data suggest that the insulin-stimulated entry of the insulin receptor into a rapid, coated pit-mediated internalization pathway is saturable and requires receptor autophosphorylation and an intact juxtamembrane region. Furthermore, CHO cells also contain a constitutive nonsaturable pathway which does not require receptor autophosphorylation or an intact juxtamembrane region; this second pathway is unaffected by depletion of intracellular potassium, and therefore may be independent of coated pits. Our data suggest that the ligand-stimulated internalization of the insulin receptor may require specific saturable interactions between the receptor and components of the endocytic system. PMID:1757462

  7. Identification of nuclear hormone receptor pathways causing insulin resistance by transcriptional and epigenomic analysis.

    PubMed

    Kang, Sona; Tsai, Linus T; Zhou, Yiming; Evertts, Adam; Xu, Su; Griffin, Michael J; Issner, Robbyn; Whitton, Holly J; Garcia, Benjamin A; Epstein, Charles B; Mikkelsen, Tarjei S; Rosen, Evan D

    2015-01-01

    Insulin resistance is a cardinal feature of Type 2 diabetes (T2D) and a frequent complication of multiple clinical conditions, including obesity, ageing and steroid use, among others. How such a panoply of insults can result in a common phenotype is incompletely understood. Furthermore, very little is known about the transcriptional and epigenetic basis of this disorder, despite evidence that such pathways are likely to play a fundamental role. Here, we compare cell autonomous models of insulin resistance induced by the cytokine tumour necrosis factor-α or by the steroid dexamethasone to construct detailed transcriptional and epigenomic maps associated with cellular insulin resistance. These data predict that the glucocorticoid receptor and vitamin D receptor are common mediators of insulin resistance, which we validate using gain- and loss-of-function studies. These studies define a common transcriptional and epigenomic signature in cellular insulin resistance enabling the identification of pathogenic mechanisms. PMID:25503565

  8. Serum Leptin and Insulin Hormone Level in Recurrent Pregnancy Loss

    PubMed Central

    Baban, Rayah S.; Ali, Noor M.; Al-Moayed, Hala A.

    2010-01-01

    Objective To measure serum leptin and insulin levels in women with recurrent pregnancy loss using modified methods of High Performance Liquid Chromatography (HPLC), and to examine their influence on recurrent loss at different pregnancy trimesters. Methods A case control study was conducted from, 1 September 2008 to 30 December 2009 in the Obstetric and Gynecological Department-Al-Khadimiya Teaching Hospital. HPLC technique with new modified method was used to estimate serum leptin and insulin hormones in samples of women with recurrent pregnancy loss (patients group, n=64) and healthy pregnant women at the end of the third gestational trimester as a control group (n=51). Results Both serum leptin and insulin levels were high in women with pregnancy loss in their three trimesters. A significant correlation was found between age (r=0.535, p<0.018) and serum total leptin in women with RPL during the first trimester. Also, a highly significant correlation was found between serum total leptin and insulin in women with RPL during the first, second and third trimesters (r=0.894, r=0.931, and r =0.995) respectively. The number of women who lost their pregnancy during the first trimester was higher than those losing during other trimesters. Conclusion It can be concluded that recurrent pregnancy loss in women at different trimester is associated with endocrine abnormalities where serum leptin and insulin levels increase in a different way compared with normal healthy pregnant women. PMID:22043338

  9. Role of insulin receptor and insulin signaling on αPS2CβPS integrins' lateral diffusion.

    PubMed

    Mainali, Dipak; Syed, Aleem; Arora, Neha; Smith, Emily A

    2014-12-01

    Integrins are ubiquitous transmembrane receptors with adhesion and signaling properties. The influence of insulin receptor and insulin signaling on αPS2CβPS integrins' lateral diffusion was studied using single particle tracking in S2 cells before and after reducing the insulin receptor expression or insulin stimulation. Insulin signaling was monitored by Western blotting for phospho-Akt expression. The expression of the insulin receptor was reduced using RNA interference (RNAi). After insulin receptor RNAi, four significant changes were measured in integrin diffusion properties: (1) there was a 24% increase in the mobile integrin population, (2) 14% of the increase was represented by integrins with Brownian diffusion, (3) for integrins that reside in confined zones of diffusion, there was a 45% increase in the diameter of the confined zone, and (4) there was a 29% increase in the duration integrins spend in confined zones of diffusion. In contrast to reduced expression of the insulin receptor, which alters integrin diffusion properties, insulin stimulation alone or insulin stimulation under conditions of reduced insulin receptor expression have minimal effects on altering the measured integrin diffusion properties. The differences in integrin diffusion measured after insulin receptor RNAi in the presence or absence of insulin stimulation may be the result of other insulin signaling pathways that are activated at reduced insulin receptor conditions. No change in the average integrin diffusion coefficient was measured for any conditions included in this study.

  10. Insulin resistance in uremia: Insulin receptor kinase activity in liver and muscle from chronic uremic rats

    SciTech Connect

    Cecchin, F.; Ittoop, O.; Sinha, M.K.; Caro, J.F. )

    1988-04-01

    The authors have studied the structure and function of the partially purified insulin receptors from liver and skeletal muscle in a rat model of severe chronic uremia. {sup 125}I-insulin binding was higher in the liver from uremic rats when compared with ad libitum- and pair-fed controls. Furthermore, the ability of insulin to stimulate the autophosphorylation of the {beta}-subunit and insulin receptor kinase activity using Glu{sup 80}, Tyr{sup 20} as exogenous phosphoacceptor was increased in the liver of the uremic animals. The structural characteristics of the receptors, as determined by electrophoretic mobilities of affinity labeled {alpha}-subunit and the phosphorylated {beta}-subunit, were normal in uremia. {sup 125}I-insulin binding and insulin receptor kinase activity were similar in the skeletal muscle from uremic and pair- and ad libitum-fed animals. Thus the data are supportive of the hypothesis that in liver and muscle of chronic uremic rats, insulin resistance is due to a defect(s) distal to the insulin receptor kinase.

  11. Biological effects of insulin and its analogs on cancer cells with different insulin family receptor expression.

    PubMed

    Sciacca, Laura; Cassarino, Maria Francesca; Genua, Marco; Vigneri, Paolo; Giovanna Pennisi, Maria; Malandrino, Pasqualino; Squatrito, Sebastiano; Pezzino, Vincenzo; Vigneri, Riccardo

    2014-11-01

    Hyperinsulinemia is a likely cause of the increased cancer incidence and mortality in diabetic patients, but its role is difficult to define in vivo. Previous in vitro studies testing the mitogenic potential of insulin and its analogs provided incomplete and sometimes contradictory results. To better evaluate cancer cell responsiveness to insulin, to its analogs and to IGF-I, we measured under identical experimental conditions cell proliferation, invasiveness, and foci formation in six cancer cell lines with different insulin receptor family expression levels. The cancer cells studied have a different expression of insulin receptor (IR), its isoforms (IR-A and IR-B), and of the IGF-I receptor. The data indicate that insulin stimulates proliferation in all cancer cell lines, invasiveness in some, and foci formation in none. Cancer cell responses to insulin (and IGF-I) are not related to receptor expression levels; moreover, hormone-stimulated proliferation and invasiveness are not correlated. IGF-I is a more potent stimulator than insulin in most but not all cancer cell lines. Insulin analogs including M1 and M2 Glargine metabolites stimulate cancer cells similar to insulin. However, exceptions occur for specific analogs in particular cancer cells. In conclusion, in vitro insulin is an effective growth factor for all cancer cells but the biological response to insulin cannot be predicted on the basis of receptor expression levels. In the clinical setting, these observations should be taken in account when deciding treatment for diabetic patients who are at risk of undiscovered cancer or survivors of oncological diseases.

  12. Development of a Quantitative PCR Assay for Detection of Human Insulin-Like Growth Factor Receptor and Insulin Receptor Isoforms.

    PubMed

    Flannery, Clare A; Rowzee, Anne M; Choe, Gina H; Saleh, Farrah L; Radford, Caitlin C; Taylor, Hugh S; Wood, Teresa L

    2016-04-01

    The biological activity of insulin and the insulin-like growth factor (IGF) ligands, IGF-I and IGF-II, is based in part on the relative abundance and distribution of their target receptors: the insulin receptor (IR) splice variants A (IR-A) and B (IR-B) and IGF 1 receptor (IGF-1R). However, the relative quantity of all three receptors in human tissues has never been measured together on the same scale. Due to the high homology between insulin receptor (IR)-A and IR-B proteins and lack of antibodies that discern the two IR splice variants, their mRNA sequence is the most reliable means of distinguishing between the receptors. Hence, highly specific primers for IR-A, IR-B, and IGF-1R mRNA were designed to accurately detect all three receptors by quantitative RT-PCR and enable direct quantification of relative receptor expression levels. A standard concentration curve of cDNA from each receptor was performed. Assay specificity was tested using competition assays and postamplification analysis by gel electrophoresis and cloning. Forward and reverse primer concentrations were optimized to ensure equal efficiencies across primer pairs. This assay enables a specific molecular signature of IGF/insulin signaling receptors to be assayed in different tissues, cell types, or cancers. PMID:26862994

  13. Insulin receptor alternative splicing is regulated by insulin signaling and modulates beta cell survival

    PubMed Central

    Malakar, Pushkar; Chartarifsky, Lital; Hija, Ayat; Leibowitz, Gil; Glaser, Benjamin; Dor, Yuval; Karni, Rotem

    2016-01-01

    Type 2 Diabetes (T2DM) affects more than 300 million people worldwide. One of the hallmarks of T2DM is peripheral insulin resistance, in part due to unproductive insulin signaling through the insulin receptor. The insulin receptor (INSR) exists as two isoforms, INSR-A and INSR-B, which results from skipping or inclusion of exon 11 respectively. What determines the relative abundance of the different insulin receptor splice variants is unknown. Moreover, it is not yet clear what the physiological roles of each of the isoforms are in normal and diseased beta cells. In this study, we show that insulin induces INSR exon 11 inclusion in pancreatic beta cells in both human and mouse. This occurs through activation of the Ras-MAPK/ERK signaling pathway and up-regulation of the splicing factor SRSF1. Induction of exon 11 skipping by a splice-site competitive antisense oligonucleotide inhibited the MAPK-ERK signaling pathway downstream of the insulin receptor, sensitizing the pancreatic β-cell line MIN6 to stress-induced apoptosis and lipotoxicity. These results assign to insulin a regulatory role in INSR alternative splicing through the Ras-MAPK/ERK signaling pathway. We suggest that in beta cells, INSR-B has a protective role, while INSR-A expression sensitizes beta cells to programmed cell death. PMID:27526875

  14. Purified hybrid insulin/insulin-like growth factor-I receptors bind insulin-like growth factor-I, but not insulin, with high affinity.

    PubMed Central

    Soos, M A; Field, C E; Siddle, K

    1993-01-01

    Hybrid insulin/insulin-like growth factor-I (IGF-I) receptors have previously been described in human placenta, but it has not been possible to study their properties in the presence of classical insulin receptors and type I IGF receptors. To facilitate the purification of hybrids, we produced an anti-peptide monoclonal antibody IGFR 1-2, directed against the C-terminal peptide of the type I IGF receptor beta-subunit. The antibody bound native human and rat type I IGF receptors, and reacted specifically with the beta-subunit on immunoblots. Solubilized placental microsomal membranes were depleted of classical type I IGF receptors by incubation with an immobilized monoclonal antibody IGFR 24-55, which reacts well with type I receptors but very poorly with hybrid receptors. Residual hybrid receptors were then isolated by incubation with immobilized antibody IGFR 1-2, and recovered by elution with excess of synthetic peptide antigen. Binding properties of hybrids were compared with those of immuno-affinity-purified insulin receptors and type I IGF receptors, by using the radioligands 125I-IGF-I and 125I-insulin. Hybrids bound approx. 20 times as much 125I-IGF-I as 125I-insulin at tracer concentrations (approx. 0.1 nM). The binding of 125I-insulin, but not 125I-IGF-I, to hybrids increased after treatment with dithiothreitol to reduce disulphide bonds between the alpha-subunits. Hybrids behaved very similarly to type I receptors with respect to the inhibition of 125I-IGF-I binding by unlabelled IGF-I and insulin. By contrast, the affinity of hybrids for insulin was approx. 10-fold lower than that of classical insulin receptors, as assessed by inhibition of 125I-insulin binding by unlabelled hormone. It is concluded that the properties of insulin receptors, but not IGF receptors, are markedly affected by assembly as hybrid compared with classical structures, and that hybrids are more likely to be responsive to IGF-I than insulin under physiological conditions. Images

  15. Insulin Action is Blocked by a Monoclonal Antibody That Inhibits the Insulin Receptor Kinase

    NASA Astrophysics Data System (ADS)

    Morgan, David O.; Ho, Lisa; Korn, Laurence J.; Roth, Richard A.

    1986-01-01

    Thirty-six monoclonal antibodies to the human insulin receptor were produced. Thirty-four bound the intracellular domain of the receptor β subunit, the domain containing the tyrosine-specific kinase activity. Of these 34 antibodies, 33 recognized the rat receptor and 1 was shown to precipitate the receptors from mice, chickens, and frogs with high affinity. Another of the antibodies inhibited the kinase activities of the human and frog receptors with equal potencies. This antibody inhibited the kinase activities of these receptors by more than 90%, whereas others had no effect on either kinase activity. Microinjection of the inhibiting antibody into Xenopus oocytes blocked the ability of insulin to stimulate oocyte maturation. In contrast, this inhibiting antibody did not block the ability of progesterone to stimulate the same response. Furthermore, control immunoglobulin and a noninhibiting antibody to the receptor β subunit did not block this response to insulin. These results strongly support a role for the tyrosine-specific kinase activity of the insulin receptor in mediating this biological effect of insulin.

  16. Role of insulin receptors in the changing metabolism of adipose tissue during pregnancy and lactation in the rat.

    PubMed Central

    Flint, D J; Sinnett-Smith, P A; Clegg, R A; Vernon, R G

    1979-01-01

    Changes in the volume, the rates of fatty acid synthesis and synthesis of the glycerol moiety of acylglycerols, the activity of lipoprotein lipase, and the number and affinity of insulin receptors of adipocytes, and concentrations of serum insulin, prolactin and progesterone were determined in virgin rats and in rats at various stages of pregnancy and lactation. Changes in the metabolic activities of adipose tissue appeared to be synchronized and primarily comprised a marked decrease in anabolic activity around parturition. In contrast, the number of insulin receptors (Kd 1.5 nM) per adipocyte doubled during pregnancy before returning to normal values around parturition. It is postulated that the increase in the number of insulin receptors is an adaptation to counteract the effects of insulin-antagonistic hormones during pregnancy and that the decrease in the number of receptors is primarily responsible for the loss of anabolic activity around parturition. PMID:508293

  17. Differential Role of Insulin/IGF-1 Receptor Signaling in Muscle Growth and Glucose Homeostasis.

    PubMed

    O'Neill, Brian T; Lauritzen, Hans P M M; Hirshman, Michael F; Smyth, Graham; Goodyear, Laurie J; Kahn, C Ronald

    2015-05-26

    Insulin and insulin-like growth factor 1 (IGF-1) are major regulators of muscle protein and glucose homeostasis. To determine how these pathways interact, we generated mice with muscle-specific knockout of IGF-1 receptor (IGF1R) and insulin receptor (IR). These MIGIRKO mice showed >60% decrease in muscle mass. Despite a complete lack of insulin/IGF-1 signaling in muscle, MIGIRKO mice displayed normal glucose and insulin tolerance. Indeed, MIGIRKO mice showed fasting hypoglycemia and increased basal glucose uptake. This was secondary to decreased TBC1D1 resulting in increased Glut4 and Glut1 membrane localization. Interestingly, overexpression of a dominant-negative IGF1R in muscle induced glucose intolerance in MIGIRKO animals. Thus, loss of insulin/IGF-1 signaling impairs muscle growth, but not whole-body glucose tolerance due to increased membrane localization of glucose transporters. Nonetheless, presence of a dominant-negative receptor, even in the absence of functional IR/IGF1R, induces glucose intolerance, indicating that interactions between these receptors and other proteins in muscle can impair glucose homeostasis. PMID:25981038

  18. Rat Erythrocyte Insulin Receptors: Radioreceptor Assay and Characterization

    PubMed Central

    Ogunwole, John O.; Nerurkar, Shriniwas G.; Hollis, Vincent W.

    1985-01-01

    Highly specific insulin receptors have been identified on the rat erythrocyte. A radioreceptor assay for the evaluation of these receptors has been developed, and the characteristics of these receptors have been investigated. Insulin receptor binding on the rat erythrocytes was found to be dependent on pH, temperature, time, and ionic strength. When incubated for 3½ hours at 15° C, 5.0 × 109 erythrocytes/mL from each of 10 rats were found to bind specifically 7.54 percent (±0.15 SEM) of 40 pg of 125I-insulin. Specific binding was found to be a function of cell concentration. The pH optima for insulin binding were found to be 7.4 and 7.0 in the absence of cations. The presence of cations not only shifted pH optimum to 7.4 from 7.0, but also increased specific insulin binding. These observations suggest the stabilization of negatively charged groups on ligand and receptor, as well as providing a suitable ionic environment for the hormone-receptor interaction. Based on the resistance of rat erythrocytes to the pH of the external buffer, a simple method for determining the internal pH of rat red- blood cells is described. Scatchard analyses of insulin-binding data yielded curvilinear plots, and the number of receptor sites per cell was found to be 762 (±12.1 SD), as opposed to the large variation (410 ± 260 SD) in normal humans. The rat erythrocytes may serve as a useful, precise, sensitive, and efficient model system for future erythrocytic-receptor studies that would be difficult to obtain from human subjects. PMID:3981646

  19. Rat erythrocyte insulin receptors: radioreceptor assay and characterization.

    PubMed

    Ogunwole, J O; Nerurkar, S G; Hollis, V W

    1985-02-01

    Highly specific insulin receptors have been identified on the rat erythrocyte. A radioreceptor assay for the evaluation of these receptors has been developed, and the characteristics of these receptors have been investigated. Insulin receptor binding on the rat erythrocytes was found to be dependent on pH, temperature, time, and ionic strength. When incubated for 3½ hours at 15° C, 5.0 × 10(9) erythrocytes/mL from each of 10 rats were found to bind specifically 7.54 percent (±0.15 SEM) of 40 pg of (125)I-insulin. Specific binding was found to be a function of cell concentration. The pH optima for insulin binding were found to be 7.4 and 7.0 in the absence of cations. The presence of cations not only shifted pH optimum to 7.4 from 7.0, but also increased specific insulin binding.These observations suggest the stabilization of negatively charged groups on ligand and receptor, as well as providing a suitable ionic environment for the hormone-receptor interaction. Based on the resistance of rat erythrocytes to the pH of the external buffer, a simple method for determining the internal pH of rat red- blood cells is described. Scatchard analyses of insulin-binding data yielded curvilinear plots, and the number of receptor sites per cell was found to be 762 (±12.1 SD), as opposed to the large variation (410 ± 260 SD) in normal humans. The rat erythrocytes may serve as a useful, precise, sensitive, and efficient model system for future erythrocytic-receptor studies that would be difficult to obtain from human subjects.

  20. Differential hepatic distribution of insulin receptor substrates causes selective insulin resistance in diabetes and obesity

    PubMed Central

    Kubota, Naoto; Kubota, Tetsuya; Kajiwara, Eiji; Iwamura, Tomokatsu; Kumagai, Hiroki; Watanabe, Taku; Inoue, Mariko; Takamoto, Iseki; Sasako, Takayoshi; Kumagai, Katsuyoshi; Kohjima, Motoyuki; Nakamuta, Makoto; Moroi, Masao; Sugi, Kaoru; Noda, Tetsuo; Terauchi, Yasuo; Ueki, Kohjiro; Kadowaki, Takashi

    2016-01-01

    Hepatic insulin signalling involves insulin receptor substrates (Irs) 1/2, and is normally associated with the inhibition of gluconeogenesis and activation of lipogenesis. In diabetes and obesity, insulin no longer suppresses hepatic gluconeogenesis, while continuing to activate lipogenesis, a state referred to as ‘selective insulin resistance'. Here, we show that ‘selective insulin resistance' is caused by the differential expression of Irs1 and Irs2 in different zones of the liver. We demonstrate that hepatic Irs2-knockout mice develop ‘selective insulin resistance', whereas mice lacking in Irs1, or both Irs1 and Irs2, develop ‘total insulin resistance'. In obese diabetic mice, Irs1/2-mediated insulin signalling is impaired in the periportal zone, which is the primary site of gluconeogenesis, but enhanced in the perivenous zone, which is the primary site of lipogenesis. While hyperinsulinaemia reduces Irs2 expression in both the periportal and perivenous zones, Irs1 expression, which is predominantly in the perivenous zone, remains mostly unaffected. These data suggest that ‘selective insulin resistance' is induced by the differential distribution, and alterations of hepatic Irs1 and Irs2 expression. PMID:27708333

  1. Identification of Host Insulin Binding Sites on Schistosoma japonicum Insulin Receptors

    PubMed Central

    Stephenson, Rachel J.; Toth, Istvan; Liang, Jiening; Mangat, Amanjot; McManus, Donald P.; You, Hong

    2016-01-01

    Schistosoma japonicum insulin receptors (SjIRs) have been identified as encouraging vaccine candidates. Interrupting or blocking the binding between host insulin and the schistosome insulin receptors (IRs) may result in reduced glucose uptake leading to starvation and stunting of worms with a reduction in egg output. To further understand how schistosomes are able to exploit host insulin for development and growth, and whether these parasites and their mammalian hosts compete for the same insulin source, we identified insulin binding sites on the SjIRs. Based on sequence analysis and the predicted antigenic structure of the primary sequences of the SjIRs, we designed nine and eleven peptide analogues from SjIR-1 and SjIR-2, respectively. Using the Octet RED system, we identified analogues derived from SjIR-1 (10) and SjIR-2 (20, 21 and 22) with insulin-binding sequences specific for S. japonicum. Nevertheless, the human insulin receptor (HIR) may compete with the SjIRs in binding human insulin in other positions which are important for HIR binding to insulin. However, no binding occurred between insulin and parasite analogues derived from SjIR-1 (2, 7 and 8) and SjIR-2 (14, 16 and 18) at the same locations as HIR sequences which have been shown to have strong insulin binding affinities. Importantly, we found two analogues (1 and 3), derived from SjIR-1, and two analogues (13 and 15) derived from SjIR-2, were responsible for the major insulin binding affinity in S. japonicum. These peptide analogues were shown to have more than 10 times (in KD value) stronger binding capacity for human insulin compared with peptides derived from the HIR in the same sequence positions. Paradoxically, analogues 1, 3, 13 and 15 do not appear to contain major antigenic determinants which resulted in poor antibody responses to native S. japonicum protein. This argues against their future development as peptide-vaccine candidates. PMID:27441998

  2. Insulin decreases atherosclerosis by inducing endothelin receptor B expression

    PubMed Central

    Park, Kyoungmin; Mima, Akira; Li, Qian; Rask-Madsen, Christian; He, Pingnian; Mizutani, Koji; Katagiri, Sayaka; Maeda, Yasutaka; Wu, I-Hsien; Khamaisi, Mogher; Preil, Simone Rordam; Sørensen, Ditte; Huang, Paul L.; King, George L.

    2016-01-01

    Endothelial cell (EC) insulin resistance and dysfunction, caused by diabetes, accelerates atherosclerosis. It is unknown whether specifically enhancing EC-targeted insulin action can decrease atherosclerosis in diabetes. Accordingly, overexpressing insulin receptor substrate-1 (IRS1) in the endothelia of Apoe–/– mice (Irs1/Apoe–/–) increased insulin signaling and function in the aorta. Atherosclerosis was significantly reduced in Irs1/ApoE–/– mice on diet-induced hyperinsulinemia and hyperglycemia. The mechanism of insulin’s enhanced antiatherogenic actions in EC was related to remarkable induction of NO action, which increases endothelin receptor B (EDNRB) expression and intracellular [Ca2+]. Using the mice with knockin mutation of eNOS, which had Ser1176 mutated to alanine (AKI), deleting the only known mechanism for insulin to activate eNOS/NO pathway, we observed that IRS1 overexpression in the endothelia of Aki/ApoE–/– mice significantly decreased atherosclerosis. Interestingly, endothelial EDNRB expression was selectively reduced in intima of arteries from diabetic patients and rodents. However, endothelial EDNRB expression was upregulated by insulin via P13K/Akt pathway. Finally EDNRB deletion in EC of Ldlr–/– and Irs1/Ldlr–/– mice decreased NO production and accelerated atherosclerosis, compared with Ldlr–/– mice. Accelerated atherosclerosis in diabetes may be reduced by improving insulin signaling selectively via IRS1/Akt in the EC by inducing EDNRB expression and NO production. PMID:27200419

  3. Insulin decreases atherosclerosis by inducing endothelin receptor B expression

    PubMed Central

    Park, Kyoungmin; Mima, Akira; Li, Qian; Rask-Madsen, Christian; He, Pingnian; Mizutani, Koji; Katagiri, Sayaka; Maeda, Yasutaka; Wu, I-Hsien; Khamaisi, Mogher; Preil, Simone Rordam; Maddaloni, Ernesto; Sørensen, Ditte; Rasmussen, Lars Melholt; Huang, Paul L.; King, George L.

    2016-01-01

    Endothelial cell (EC) insulin resistance and dysfunction, caused by diabetes, accelerates atherosclerosis. It is unknown whether specifically enhancing EC-targeted insulin action can decrease atherosclerosis in diabetes. Accordingly, overexpressing insulin receptor substrate-1 (IRS1) in the endothelia of Apoe−/− mice (Irs1/Apoe−/−) increased insulin signaling and function in the aorta. Atherosclerosis was significantly reduced in Irs1/ApoE−/− mice on diet-induced hyperinsulinemia and hyperglycemia. The mechanism of insulin’s enhanced antiatherogenic actions in EC was related to remarkable induction of NO action, which increases endothelin receptor B (EDNRB) expression and intracellular [Ca2+]. Using the mice with knockin mutation of eNOS, which had Ser1176 mutated to alanine (AKI), deleting the only known mechanism for insulin to activate eNOS/NO pathway, we observed that IRS1 overexpression in the endothelia of Aki/ApoE−/− mice significantly decreased atherosclerosis. Interestingly, endothelial EDNRB expression was selectively reduced in intima of arteries from diabetic patients and rodents. However, endothelial EDNRB expression was upregulated by insulin via P13K/Akt pathway. Finally EDNRB deletion in EC of Ldlr−/− and Irs1/Ldlr−/− mice decreased NO production and accelerated atherosclerosis, compared with Ldlr−/− mice. Accelerated atherosclerosis in diabetes may be reduced by improving insulin signaling selectively via IRS1/Akt in the EC by inducing EDNRB expression and NO production. PMID:27200419

  4. Phosphorylation of insulin receptor substrate 1 by glycogen synthase kinase 3 impairs insulin action

    PubMed Central

    Eldar-Finkelman, Hagit; Krebs, Edwin G.

    1997-01-01

    The phosphorylation of insulin receptor substrate 1 (IRS-1) on tyrosine residues by the insulin receptor (IR) tyrosine kinase is involved in most of the biological responses of insulin. IRS-1 mediates insulin signaling by recruiting SH2 proteins through its multiple tyrosine phosphorylation sites. The phosphorylation of IRS-1 on serine/threonine residues also occurs in cells; however, the particular protein kinase(s) promoting this type of phosphorylation are unknown. Here we report that glycogen synthase kinase 3 (GSK-3) is capable of phosphorylating IRS-1 and that this modification converts IRS-1 into an inhibitor of IR tyrosine kinase activity in vitro. Expression of wild-type GSK-3 or an “unregulated” mutant of the kinase (S9A) in CHO cells overexpressing IRS-1 and IR, resulted in increased serine phosphorylation levels of IRS-1, suggesting that IRS-1 is a cellular target of GSK-3. Furthermore, insulin-induced tyrosine phosphorylation of IRS-1 and IR was markedly suppressed in cells expressing wild-type or the S9A mutant, indicating that expression of GSK-3 impairs IR tyrosine kinase activity. Taken together, our studies suggest a new role for GSK-3 in attenuating insulin signaling via its phosphorylation of IRS-1 and may provide new insight into mechanisms important in insulin resistance. PMID:9275179

  5. Signal transduction through the IL-4 and insulin receptor families.

    PubMed

    Wang, L M; Keegan, A; Frankel, M; Paul, W E; Pierce, J H

    1995-07-01

    Activation of tyrosine kinase-containing receptors and intracellular tyrosine kinases by ligand stimulation is known to be crucial for mediating initial and subsequent events involved in mitogenic signal transduction. Receptors for insulin and insulin-like growth factor 1 (IGF-1) contain cytoplasmic tyrosine kinase domains that undergo autophosphorylation upon ligand stimulation. Activation of these receptors also leads to pronounced and rapid tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) in cells of connective tissue origin. A related substrate, designated 4PS, is similarly phosphorylated by insulin and IGF-1 stimulation in many hematopoietic cell types. IRS-1 and 4PS possess a number of tyrosine phosphorylation sites that are within motifs that bind specific SH2-containing molecules known to be involved in mitogenic signaling such as PI-3 kinase, SHPTP-2 (Syp) and Grb-2. Thus, they appear to act as docking substrates for a variety of signaling molecules. The majority of hematopoietic cytokines bind to receptors that do not possess intrinsic kinase activity, and these receptors have been collectively termed as members of the hematopoietin receptor superfamily. Despite their lack of tyrosine kinase domains, stimulation of these receptors has been demonstrated to activate intracellular kinases leading to tyrosine phosphorylation of multiple substrates. Recent evidence has demonstrated that activation of different members of the Janus family of tyrosine kinases is involved in mediating tyrosine phosphorylation events by specific cytokines. Stimulation of the interleukin 4 (IL-4) receptor, a member of the hematopoietin receptor superfamily, is thought to result in activation of Jak1, Jak3, and/or Fes tyrosine kinases.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Insulin Receptor Substrate 2 Is a Negative Regulator of Memory Formation

    ERIC Educational Resources Information Center

    Irvine, Elaine E.; Drinkwater, Laura; Radwanska, Kasia; Al-Qassab, Hind; Smith, Mark A.; O'Brien, Melissa; Kielar, Catherine; Choudhury, Agharul I.; Krauss, Stefan; Cooper, Jonathan D.; Withers, Dominic J.; Giese, Karl Peter

    2011-01-01

    Insulin has been shown to impact on learning and memory in both humans and animals, but the downstream signaling mechanisms involved are poorly characterized. Insulin receptor substrate-2 (Irs2) is an adaptor protein that couples activation of insulin- and insulin-like growth factor-1 receptors to downstream signaling pathways. Here, we have…

  7. Insulin receptor substrates 1 and 2 but not Shc can activate the insulin receptor independent of insulin and induce proliferation in CHO-IR cells

    SciTech Connect

    Niessen, Markus . E-mail: markus.niessen@usz.ch; Jaschinski, Frank; Item, Flurin; McNamara, Morgan P.; Spinas, Giatgen A.; Trueb, Thomas

    2007-02-15

    Ligand-activated insulin receptor (IR) attracts and phosphorylates various substrates such as insulin receptor substrates 1-4 (IRS) and Shc. To investigate how binding affinity for substrate affects signalling we generated chimeric receptors with the {beta}-chain of the insulin receptor containing NPXY motives with different affinities for receptor substrates. We found that the extent of receptor tyrosine phosphorylation positively correlates with binding affinity towards IRS1/2 but not towards Shc. Moreover, overexpression of IRS1 or IRS2 but not of Shc increased IR tyrosine phosphorylation in a dose-dependent manner, also independent of insulin. Molecular truncations of IRS1 revealed that neither the isolated PH and PTB domains nor the C-terminus with the tyrosine phosphorylation sites alone are sufficient for substrate-dependent receptor activation. Overexpression of IRS1 and IRS2 impaired insulin-induced internalization of the IR in a dose-dependent manner suggesting that IRS proteins prevent endosome-associated receptor dephosphorylation/inactivation. IRS1 and IRS2 could therefore target the activated IR to different cellular compartments. Overexpression of IRS1 and IRS2 inhibited insulin-stimulated activation of the MAP kinases Erk1/2 while it increased/induced activation of Akt/PKB. Finally, overexpression of IRS1 and IRS2 but not of Shc induced DNA synthesis in starved CHO-IR cells independent of exogenous growth factors. Our results demonstrate that variations in cellular IRS1 and IRS2 concentration affect insulin signalling both upstream and downstream and that IRS proteins could play instructive rather than just permissive roles in signal transmission.

  8. Mechanical stretch augments insulin-induced vascular smooth muscle cell proliferation by insulin-like growth factor-1 receptor

    SciTech Connect

    Liu, Gang; Hitomi, Hirofumi; Hosomi, Naohisa; Lei, Bai; Nakano, Daisuke; Deguchi, Kazushi; Mori, Hirohito; Masaki, Tsutomu; Ma, Hong; Griendling, Kathy K.; Nishiyama, Akira

    2011-10-15

    Insulin resistance and hypertension have been implicated in the pathogenesis of cardiovascular disease; however, little is known about the roles of insulin and mechanical force in vascular smooth muscle cell (VSMC) remodeling. We investigated the contribution of mechanical stretch to insulin-induced VSMC proliferation. Thymidine incorporation was stimulated by insulin in stretched VSMCs, but not in un-stretched VSMCs. Insulin increased 2-deoxy-glucose incorporation in both stretched and un-stretched VSMCs. Mechanical stretch augmented insulin-induced extracellular signal-regulated kinase (ERK) and Akt phosphorylation. Inhibitors of epidermal growth factor (EGF) receptor tyrosine kinase and Src attenuated insulin-induced ERK and Akt phosphorylation, as well as thymidine incorporation, whereas 2-deoxy-glucose incorporation was not affected by these inhibitors. Moreover, stretch augmented insulin-like growth factor (IGF)-1 receptor expression, although it did not alter the expression of insulin receptor and insulin receptor substrate-1. Insulin-induced ERK and Akt activation, and thymidine incorporation were inhibited by siRNA for the IGF-1 receptor. Mechanical stretch augments insulin-induced VSMC proliferation via upregulation of IGF-1 receptor, and downstream Src/EGF receptor-mediated ERK and Akt activation. Similar to in vitro experiment, IGF-1 receptor expression was also augmented in hypertensive rats. These results provide a basis for clarifying the molecular mechanisms of vascular remodeling in hypertensive patients with hyperinsulinemia. -- Highlights: {yields} Mechanical stretch augments insulin-induced VSMC proliferation via IGF-1 receptor. {yields} Src/EGFR-mediated ERK and Akt phosphorylation are augmented in stretched VSMCs. {yields} Similar to in vitro experiment, IGF-1 receptor is increased in hypertensive rats. {yields} Results provide possible mechanisms of vascular remodeling in hypertension with DM.

  9. The Interactions of Proinsulin with Insulin Receptors on the Plasma Membrane of the Liver

    PubMed Central

    Freychet, Pierre

    1974-01-01

    The interactions of proinsulin with the insulin-specific receptors were investigated in purified rat liver plasma membranes. These studies were designed to characterize the binding of proinsulin to the insulin receptors, to search for proinsulin-specific receptor sites, and to examine the possibility of proinsulin conversion at the insulin receptor site. Proinsulin was only 3-5% as potent as insulin in binding to insulin receptors. Proinsulin reacted with all of the insulin-specific receptors, and direct binding studies of [125I]porcine proinsulin and [125I]rat proinsulin did not reveal proinsulin-specific receptor sites other than the insulin receptors in rat liver membranes. Quantitative data derived from steady-state and transient-state comparative binding studies of both [125I]proinsulin and [125I]insulin indicated that a 20-fold lower association rate constant essentially accounts for the reduced affinity of proinsulin for the insulin receptors. The possibility of proinsulin conversion at the insulin receptor sites was investigated. Material recovered from the membranes upon dissociation of the proinsulin-receptor complex was intact proinsulin and did not exhibit any conversion by a variety of analytical methods. These results indicate that the lower affinity of proinsulin for the insulin receptor in the liver is an intrinsic property of the proinsulin molecule. The lower uptake of proinsulin by the insulin receptor represents, in addition to a slower degradation of the prohormone, a further mechanism by which proinsulin exerts prolonged, albeit reduced, action in vivo. PMID:4421396

  10. Drosophila Adiponectin Receptor in Insulin Producing Cells Regulates Glucose and Lipid Metabolism by Controlling Insulin Secretion

    PubMed Central

    Kwak, Su-Jin; Hong, Seung-Hyun; Bajracharya, Rijan; Yang, Se-Yeol; Lee, Kyu-Sun; Yu, Kweon

    2013-01-01

    Adipokines secreted from adipose tissue are key regulators of metabolism in animals. Adiponectin, one of the adipokines, modulates pancreatic beta cell function to maintain energy homeostasis. Recently, significant conservation between Drosophila melanogaster and mammalian metabolism has been discovered. Drosophila insulin like peptides (Dilps) regulate energy metabolism similarly to mammalian insulin. However, in Drosophila, the regulatory mechanism of insulin producing cells (IPCs) by adipokine signaling is largely unknown. Here, we describe the discovery of the Drosophila adiponectin receptor and its function in IPCs. Drosophila adiponectin receptor (dAdipoR) has high homology with the human adiponectin receptor 1. The dAdipoR antibody staining revealed that dAdipoR was expressed in IPCs of larval and adult brains. IPC- specific dAdipoR inhibition (Dilp2>dAdipoR-Ri) showed the increased sugar level in the hemolymph and the elevated triglyceride level in whole body. Dilps mRNA levels in the Dilp2>dAdipoR-Ri flies were similar with those of controls. However, in the Dilp2>dAdipoR-Ri flies, Dilp2 protein was accumulated in IPCs, the level of circulating Dilp2 was decreased, and insulin signaling was reduced in the fat body. In ex vivo fly brain culture with the human adiponectin, Dilp2 was secreted from IPCs. These results indicate that adiponectin receptor in insulin producing cells regulates insulin secretion and controls glucose and lipid metabolism in Drosophila melanogaster. This study demonstrates a new adipokine signaling in Drosophila and provides insights for the mammalian adiponectin receptor function in pancreatic beta cells, which could be useful for therapeutic application. PMID:23874700

  11. Insulin receptor membrane retention by a traceable chimeric mutant

    PubMed Central

    2013-01-01

    Background The insulin receptor (IR) regulates glucose homeostasis, cell growth and differentiation. It has been hypothesized that the specific signaling characteristics of IR are in part determined by ligand-receptor complexes localization. Downstream signaling could be triggered from the plasma membrane or from endosomes. Regulation of activated receptor's internalization has been proposed as the mechanism responsible for the differential isoform and ligand-specific signaling. Results We generated a traceable IR chimera that allows the labeling of the receptor at the cell surface. This mutant binds insulin but fails to get activated and internalized. However, the mutant heterodimerizes with wild type IR inhibiting its auto-phosphorylation and blocking its internalization. IR membrane retention attenuates AP-1 transcriptional activation favoring Akt activation. Conclusions These results suggest that the mutant acts as a selective dominant negative blocking IR internalization-mediated signaling. PMID:23805988

  12. Combination therapy with GLP-1 receptor agonists and basal insulin: a systematic review of the literature

    PubMed Central

    Balena, R; Hensley, I E; Miller, S; Barnett, A H

    2013-01-01

    Treatment algorithms for type 2 diabetes call for intensification of therapy over time as the disease progresses and glycaemic control worsens. If diet, exercise and oral antihyperglycaemic medications (OAMs) fail to maintain glycaemic control then basal insulin is added and ultimately prandial insulin may be required. However, such an intensification strategy carries risk of increased hypoglycaemia and weight gain, both of which are associated with worse long-term outcomes. An alternative strategy is to intensify therapy by the addition of a short-acting glucagon-like peptide-1 receptor agonist (GLP-1 RA) rather than prandial insulin. Short-acting GLP-1 RAs such as exenatide twice daily are particularly effective at reducing postprandial glucose while basal insulin has a greater effect on fasting glucose, providing a physiological rationale for this complementary approach. This review analyzes the latest randomized controlled clinical trials of insulin/GLP-1 RA combination therapy and examines results from ‘real-world’ use of the combinations as reported through observational and clinical practice studies. The most common finding across all types of studies was that combination therapy improved glycaemic control without weight gain or an increased risk of hypoglycaemia. Many studies reported weight loss and a reduction in insulin use when a GLP-1 RA was added to existing insulin therapy. Overall, the relative degree of benefit to glycaemic control and weight was influenced by the insulin titration employed in conjunction with the GLP-1 RA. The greatest glycaemic benefits were observed in studies with structured titration of insulin to glycaemic targets while the greatest weight benefits were observed in studies with a protocol-specified focus on insulin sparing. The adverse event profile of GLP-1 RAs in the reviewed trials was similar to that reported with GLP-1 RAs as monotherapy or in combination with OAMs with gastrointestinal events being the most commonly

  13. Insulin Resistance Induced by Hyperinsulinemia Coincides with a Persistent Alteration at the Insulin Receptor Tyrosine Kinase Domain

    PubMed Central

    Catalano, Karyn J.; Maddux, Betty A.; Szary, Jaroslaw; Youngren, Jack F.; Goldfine, Ira D.; Schaufele, Fred

    2014-01-01

    Insulin resistance, the diminished response of target tissues to insulin, is associated with the metabolic syndrome and a predisposition towards diabetes in a growing proportion of the worldwide population. Under insulin resistant states, the cellular response of the insulin signaling pathway is diminished and the body typically responds by increasing serum insulin concentrations to maintain insulin signaling. Some evidence indicates that the increased insulin concentration may itself further dampen insulin response. If so, insulin resistance would worsen as the level of circulating insulin increases during compensation, which could contribute to the transition of insulin resistance to more severe disease. Here, we investigated the consequences of excess insulin exposure to insulin receptor (IR) activity. Cells chronically exposed to insulin show a diminished the level of IR tyrosine and serine autophosphorylation below that observed after short-term insulin exposure. The diminished IR response did not originate with IR internalization since IR amounts at the cell membrane were similar after short- and long-term insulin incubation. Förster resonance energy transfer between fluorophores attached to the IR tyrosine kinase (TK) domain showed that a change in the TK domain occurred upon prolonged, but not short-term, insulin exposure. Even though the altered ‘insulin refractory’ IR TK FRET and IR autophosphorylation levels returned to baseline (non-stimulated) levels after wash-out of the original insulin stimulus, subsequent short-term exposure to insulin caused immediate re-establishment of the insulin-refractory levels. This suggests that some cell-based ‘memory’ of chronic hyperinsulinemic exposure acts directly at the IR. An improved understanding of that memory may help define interventions to reset the IR to full insulin responsiveness and impede the progression of insulin resistance to more severe disease states. PMID:25259572

  14. Protective hinge in insulin opens to enable its receptor engagement.

    PubMed

    Menting, John G; Yang, Yanwu; Chan, Shu Jin; Phillips, Nelson B; Smith, Brian J; Whittaker, Jonathan; Wickramasinghe, Nalinda P; Whittaker, Linda J; Pandyarajan, Vijay; Wan, Zhu-li; Yadav, Satya P; Carroll, Julie M; Strokes, Natalie; Roberts, Charles T; Ismail-Beigi, Faramarz; Milewski, Wieslawa; Steiner, Donald F; Chauhan, Virander S; Ward, Colin W; Weiss, Michael A; Lawrence, Michael C

    2014-08-19

    Insulin provides a classical model of a globular protein, yet how the hormone changes conformation to engage its receptor has long been enigmatic. Interest has focused on the C-terminal B-chain segment, critical for protective self-assembly in β cells and receptor binding at target tissues. Insight may be obtained from truncated "microreceptors" that reconstitute the primary hormone-binding site (α-subunit domains L1 and αCT). We demonstrate that, on microreceptor binding, this segment undergoes concerted hinge-like rotation at its B20-B23 β-turn, coupling reorientation of Phe(B24) to a 60° rotation of the B25-B28 β-strand away from the hormone core to lie antiparallel to the receptor's L1-β2 sheet. Opening of this hinge enables conserved nonpolar side chains (Ile(A2), Val(A3), Val(B12), Phe(B24), and Phe(B25)) to engage the receptor. Restraining the hinge by nonstandard mutagenesis preserves native folding but blocks receptor binding, whereas its engineered opening maintains activity at the price of protein instability and nonnative aggregation. Our findings rationalize properties of clinical mutations in the insulin family and provide a previously unidentified foundation for designing therapeutic analogs. We envisage that a switch between free and receptor-bound conformations of insulin evolved as a solution to conflicting structural determinants of biosynthesis and function. PMID:25092300

  15. Direct Demonstration of Separate Receptors for Growth and Metabolic Activities of Insulin and Multiplication-stimulating Activity (an Insulinlike Growth Factor) Using Antibodies to the Insulin Receptor

    PubMed Central

    King, George L.; Kahn, C. Ronald; Rechler, Matthew M.; Nissley, S. Peter

    1980-01-01

    Insulin and such insulinlike growth factors as multiplication stimulating activity (MSA) are related polypeptides that have common biological activities. Both insulin and MSA produce acute metabolic responses (stimulation of glucose oxidation in isolated fat cells) as well as growth effects (stimulation of [3H]thymidine incorporation into DNA in cultured fibroblasts). In addition, most cells have separate receptors for insulin and insulinlike growth factors, and both peptides have weaker affinity for each other's specific receptors than for their own. To determine, therefore, whether these effects are mediated by receptors for insulin, insulinlike growth factors, or both, we have selectively blocked insulin receptors with a specific antagonist, namely Fab fragments derived from naturally occurring antibodies to the insulin receptor. In rat adipocytes, 10 μg/ml of antireceptor Fab inhibited insulin binding by 90%, whereas it inhibited MSA binding <5%. The anti-insulin receptor Fab is without intrinsic biological activity, but acts as a competitive inhibitor of insulin receptors. Blockade of insulin receptors with Fab fragments produced a 30-fold rightward shift in the dose response for stimulation of glucose oxidation by both insulin and MSA. The dose-response curves for stimulation of oxidation by vitamin K5 and spermine, agents that stimulate glucose oxidation through noninsulin receptor pathways, were not affected by the blockade of insulin receptors with Fab antibody fragments. These data suggest that this acute metabolic effect of both insulin and MSA is mediated via the insulin receptor. In cultured human fibroblasts, 10 μg/ml of Fab inhibited insulin binding by 90% and MSA binding by 15%. In fibroblasts, however, blockade of the insulin receptor did not alter the dose response for stimulation of thymidine incorporation into DNA by either insulin or MSA. Furthermore, intact antireceptor antibody immunoglobulin (Ig)G, which produces multiple other insulinlike

  16. Interaction of insulin with the rat diaphragm. Subcellular distribution of insulin and its receptor

    SciTech Connect

    Brush, J.S.; Guzman-Diaz, A.; Celis, J.

    1987-05-01

    In studying the uptake and processing of A-14( SVI)monoiodoinsulin by isolated rat hemidiaphragms it was found that major amounts of the hormone are associated with the debris fraction. A method was developed for separating debris components by discontinuous sucrose density gradient centrifugation. Major amounts of radioactivity were associated with its myofibril component with much lower amounts in its sarcolemmal elements. Using a modified method of Marshall, et. al. insulin receptor was measurable in these fractions with greatest amounts in myofibril and microsomal fractions. Receptor was also detectable in the latter after gel electrophoresis and immunoblotting with receptor antiserum. Sarcolemmal marker enzyme (K -stimulated, ouabain-suppressible p-nitrophenylphosphate phosphatase) activity was insignificant in sarcolemmal and myofibril fractions, but was significant in the microsomal fraction. Sarcolemmal activity becomes significant after hemidiaphragm incubation with 1 M insulin for 90 sec. but does not change in the microsomal fraction. It is concluded that 1) a component bound to the myofibrils in muscle is important in insulin processing, and 2) the largest part of sarcolemmal insulin receptors are incorporated in the microsomal fraction of homogenized tissue.

  17. Direct method for detection and characterization of cell surface receptors for insulin by means of 125I-labeled autoantibodies against the insulin receptor.

    PubMed Central

    Jarrett, D B; Roth, J; Kahn, C R; Flier, J S

    1976-01-01

    Autoantibodies directed against the cell surface receptors for insulin are found in some patients with extreme insulin resistance. These antibodies specifically inhibit the binding of insulin to its receptor. A purified IgG fraction from one patient's plasma was labeled with 125I. The 125I-labeled antireceptor antibody, which initially represented about 0.3% of the total 125I-IgG, was enriched by selective adsorption and subsequent elution from cells rich in insulin receptors. The 125I-antireceptor antibody bound to cells and the binding was inhibited by whole plasma and purified IgG from this patient, as well as whole plasma from another patient with autoantibodies to the insulin receptor. Insulins that differed 300-fold in biological potency and affinity inhibited binding of 125I-antireceptor antibody in direct proportion to their ability to bind to the insulin receptor. The binding of 125I-antireceptor antibody was closely correlated with the binding of 125I-insulin over a wide range of receptor concentrations on different cell types. Experimentally induced reduction of the insulin receptor concentration was associated with parallel decreases in the binding of 125I-antireceptor antibody and 125I-insulin. The preparation of 125I-antireceptor antibody with a high specific activity by cytoadsorption and elution has provided a sensitive method for the detection of receptors and autoantibodies to cell surface components. PMID:1069300

  18. Insulin-like Growth Factor 1-mediated Hyperthermia Involves Anterior Hypothalamic Insulin Receptors*

    PubMed Central

    Sanchez-Alavez, Manuel; Osborn, Olivia; Tabarean, Iustin V.; Holmberg, Kristina H.; Eberwine, James; Kahn, C. Ronald; Bartfai, Tamas

    2011-01-01

    The objective is to investigate the role of insulin-like growth factor 1 (IGF-1) in the regulation of core body temperature. Sequencing cDNA libraries from individual warm-sensitive neurons from the preoptic area (POA) of the hypothalamus, a region involved in the central control of thermoregulation, identified neurons that express both IGF-1 receptor (IGF-1R) and insulin receptor transcripts. The effects of administration of IGF-1 into the POA was measured by radiotelemetry monitoring of core temperature, brown adipose tissue (BAT) temperature, metabolic assessment, and imaging of BAT by positron emission tomography of 2-[18F]fluoro-2-deoxyglucose uptake combined with computed tomography. IGF-1 injection into the POA caused dose-dependent hyperthermia that could be blocked by pretreatment with the IGF-1R tyrosine kinase inhibitor, PQ401. The IGF-1-evoked hyperthermia involved activation of brown adipose tissue and was accompanied by a switch from glycolysis to fatty acid oxidation as a source of energy as shown by lowered respiratory exchange ratio. Transgenic mice that lack neuronal insulin receptor expression in the brain (NIRKO mice) were unable to mount the full hyperthermic response to IGF-1, suggesting that the IGF-1 mediated hyperthermia is partly dependent on expression of functional neuronal insulin receptors. These data indicate a novel thermoregulatory role for both IGF-1R and neuronal insulin receptors in IGF-1 activation of BAT and hyperthermia. These central effects of IGF-1 signaling may play a role in regulation of metabolic rate, aging, and the risk of developing type 2 diabetes. PMID:21330367

  19. MHC Class I Limits Hippocampal Synapse Density by Inhibiting Neuronal Insulin Receptor Signaling

    PubMed Central

    Dixon-Salazar, Tracy J.; Fourgeaud, Lawrence; Tyler, Carolyn M.; Poole, Julianna R.; Park, Joseph J.

    2014-01-01

    Proteins of the major histocompatibility complex class I (MHCI) negatively regulate synapse density in the developing vertebrate brain (Glynn et al., 2011; Elmer et al., 2013; Lee et al., 2014), but the underlying mechanisms remain largely unknown. Here we identify a novel MHCI signaling pathway that involves the inhibition of a known synapse-promoting factor, the insulin receptor. Dominant-negative insulin receptor constructs decrease synapse density in the developing Xenopus visual system (Chiu et al., 2008), and insulin receptor activation increases dendritic spine density in mouse hippocampal neurons in vitro (Lee et al., 2011). We find that genetically reducing cell surface MHCI levels increases synapse density selectively in regions of the hippocampus where insulin receptors are expressed, and occludes the neuronal insulin response by de-repressing insulin receptor signaling. Pharmacologically inhibiting insulin receptor signaling in MHCI-deficient animals rescues synapse density, identifying insulin receptor signaling as a critical mediator of the tonic inhibitory effects of endogenous MHCI on synapse number. Insulin receptors co-immunoprecipitate MHCI from hippocampal lysates, and MHCI unmasks a cytoplasmic epitope of the insulin receptor that mediates downstream signaling. These results identify an important role for an MHCI–insulin receptor signaling pathway in circuit patterning in the developing brain, and suggest that changes in MHCI expression could unexpectedly regulate neuronal insulin sensitivity in the aging and diseased brain. PMID:25164678

  20. Inhibition of insulin receptor binding by phorbol esters.

    PubMed

    Thomopoulos, P; Testa, U; Gourdin, M F; Hervy, C; Titeux, M; Vainchenker, W

    1982-12-15

    Phorbol esters inhibit the binding of insulin to its receptors on U-937 monocyte-like and HL-60 promyelocytic leukemia human cell lines. Within 20-30 min, exposure of these cells to 12-O-tetradecanoylphorbol 13-acetate (TPA) at 37 degrees C results in a 50% reduction of the specific binding of 125I-insulin. Half-maximal inhibition occurs at 1 nM TPA. Other tumor-promoting phorbol esters also inhibit 125I-insulin binding in a dose-dependent manner which parallels their known promoting activity in vivo. TPA does not alter the degradation of the hormone nor does it induce any shedding of its receptors in the medium. The effect of phorbol esters is dependent on temperature and cell type. It is less prominent at 22 degrees C than at 37 degrees C. It is reversible within 2 h at 37 degrees C. TPA reduces the binding of insulin predominantly by increasing its dissociation rate. This effect results in an accelerated turnover of the hormone on its receptors. PMID:6891320

  1. Cannabinoids Inhibit Insulin Receptor Signaling in Pancreatic β-Cells

    PubMed Central

    Kim, Wook; Doyle, Máire E.; Liu, Zhuo; Lao, Qizong; Shin, Yu-Kyong; Carlson, Olga D.; Kim, Hee Seung; Thomas, Sam; Napora, Joshua K.; Lee, Eun Kyung; Moaddel, Ruin; Wang, Yan; Maudsley, Stuart; Martin, Bronwen; Kulkarni, Rohit N.; Egan, Josephine M.

    2011-01-01

    OBJECTIVE Optimal glucose homeostasis requires exquisitely precise adaptation of the number of insulin-secreting β-cells in the islets of Langerhans. Insulin itself positively regulates β-cell proliferation in an autocrine manner through the insulin receptor (IR) signaling pathway. It is now coming to light that cannabinoid 1 receptor (CB1R) agonism/antagonism influences insulin action in insulin-sensitive tissues. However, the cells on which the CB1Rs are expressed and their function in islets have not been firmly established. We undertook the current study to investigate if intraislet endogenous cannabinoids (ECs) regulate β-cell proliferation and if they influence insulin action. RESEARCH DESIGN AND METHODS We measured EC production in isolated human and mouse islets and β-cell line in response to glucose and KCl. We evaluated human and mouse islets, several β-cell lines, and CB1R-null (CB1R−/−) mice for the presence of a fully functioning EC system. We investigated if ECs influence β-cell physiology through regulating insulin action and demonstrated the therapeutic potential of manipulation of the EC system in diabetic (db/db) mice. RESULTS ECs are generated within β-cells, which also express CB1Rs that are fully functioning when activated by ligands. Genetic and pharmacologic blockade of CB1R results in enhanced IR signaling through the insulin receptor substrate 2-AKT pathway in β-cells and leads to increased β-cell proliferation and mass. CB1R antagonism in db/db mice results in reduced blood glucose and increased β-cell proliferation and mass, coupled with enhanced IR signaling in β-cells. Furthermore, CB1R activation impedes insulin-stimulated IR autophosphorylation on β-cells in a Gαi-dependent manner. CONCLUSIONS These findings provide direct evidence for a functional interaction between CB1R and IR signaling involved in the regulation of β-cell proliferation and will serve as a basis for developing new therapeutic interventions to

  2. Insulin and insulin-like growth factor 1 receptors are required for normal expression of imprinted genes.

    PubMed

    Boucher, Jeremie; Charalambous, Marika; Zarse, Kim; Mori, Marcelo A; Kleinridders, Andre; Ristow, Michael; Ferguson-Smith, Anne C; Kahn, C Ronald

    2014-10-01

    In addition to signaling through the classical tyrosine kinase pathway, recent studies indicate that insulin receptors (IRs) and insulin-like growth factor 1 (IGF1) receptors (IGF1Rs) can emit signals in the unoccupied state through some yet-to-be-defined noncanonical pathways. Here we show that cells lacking both IRs and IGF1Rs exhibit a major decrease in expression of multiple imprinted genes and microRNAs, which is partially mimicked by inactivation of IR alone in mouse embryonic fibroblasts or in vivo in brown fat in mice. This down-regulation is accompanied by changes in DNA methylation of differentially methylated regions related to these loci. Different from a loss of imprinting pattern, loss of IR and IGF1R causes down-regulated expression of both maternally and paternally expressed imprinted genes and microRNAs, including neighboring reciprocally imprinted genes. Thus, the unoccupied IR and IGF1R generate previously unidentified signals that control expression of imprinted genes and miRNAs through transcriptional mechanisms that are distinct from classical imprinting control. PMID:25246545

  3. Homologous down-regulation of the insulin receptor is associated with increased receptor biosynthesis in cultured human lymphocytes (IM-9 line)

    SciTech Connect

    Rouiller, D.G.; Gorden, P.

    1987-01-01

    Cultured IM-9 lymphocytes were preincubated with 1 ..mu..M insulin, a condition resulting in a 56% reduction in cell surface insulin receptors. Cellular proteins were then metabolically labeled, and the radioactivity incorporated into the insulin proreceptor and receptor mature subunits was measured over a 4-hr chase period. As early as 30 min of chase, incorporation into the proreceptor was 28 +/- 6% higher in down-regulated cells than in control cells. By 1 hr of chase, the difference reached 41 +/- 14% for the proreceptor and 84 +/- 28% for the ..cap alpha.. subunit, values returned to normal by 2 hr. At 4 hr of chase, labeling of the ..cap alpha.. subunit of down-regulated cells was diminished 36 +/- 9% below control. The increased biosynthetic rate of the proreceptor was more prominent when the chase medium contained 25 ..mu..M monensin, an inhibitor of processing of the proreceptor into mature subunits. Similar effects occurred whether (/sup 3/H)mannose or (/sup 3/H)lysine was used as biosynthetic marker. The effect was specific for the insulin receptor. These data demonstrate that insulin receptor homologous down-regulation is associated with increased proreceptor biosynthesis and processing into mature subunits. This might represent a cellular mechanism compensating for insulin-induced receptor loss.

  4. Monoclonal antibodies to insulin and to the insulin receptor (anti-ID) modify the morphologies of insulin crystals

    NASA Astrophysics Data System (ADS)

    Markman, Ofer; Elias, Dana; Addadi, Lia; Cohen, Irun R.; Berkovitch-Yellin, Ziva

    1992-08-01

    Crystallization of bovine and porcine insulin in the presence of monoclonal antibodies (mAbs) yielded crystals of morphologies which differed from that of insulin crystals grown without the antibodies in solution. The anti-insulin monoclonal antibody ID 7 induced the formation of square plates. The anti-receptor antibodies 312 and A-40 induced deposition of crystals with totally different habit, polar prisms. Four other control mAbs did not have any morphological effect. Systematic work on the growth of crystals of organic and inorganic molecules has shown that morphological modifications, induced when crystals are grown in the presence of selected additives, originate from stereoselective interactions of the additives with the growing crystal faces. The induced morphological modifications can serve as a sensitive tool for the study of these interactions.

  5. Targeting Insulin Receptor with a Novel Internalizing Aptamer

    PubMed Central

    Iaboni, Margherita; Fontanella, Raffaela; Rienzo, Anna; Capuozzo, Maria; Nuzzo, Silvia; Santamaria, Gianluca; Catuogno, Silvia; Condorelli, Gerolama; de Franciscis, Vittorio; Esposito, Carla Lucia

    2016-01-01

    Nucleic acid-based aptamers are emerging as therapeutic antagonists of disease-associated proteins such as receptor tyrosine kinases. They are selected by an in vitro combinatorial chemistry approach, named Systematic Evolution of Ligands by Exponential enrichment (SELEX), and thanks to their small size and unique chemical characteristics, they possess several advantages over antibodies as diagnostics and therapeutics. In addition, aptamers that rapidly internalize into target cells hold as well great potential for their in vivo use as delivery tools of secondary therapeutic agents. Here, we describe a nuclease resistant RNA aptamer, named GL56, which specifically recognizes the insulin receptor (IR). Isolated by a cell-based SELEX method that allows enrichment for internalizing aptamers, GL56 rapidly internalizes into target cells and is able to discriminate IR from the highly homologous insulin-like growth factor receptor 1. Notably, when applied to IR expressing cancer cells, the aptamer inhibits IR dependent signaling. Given the growing interest in the insulin receptor as target for cancer treatment, GL56 reveals a novel molecule with great translational potential as inhibitor and delivery tool for IR-dependent cancers. PMID:27648925

  6. Targeting Insulin Receptor with a Novel Internalizing Aptamer.

    PubMed

    Iaboni, Margherita; Fontanella, Raffaela; Rienzo, Anna; Capuozzo, Maria; Nuzzo, Silvia; Santamaria, Gianluca; Catuogno, Silvia; Condorelli, Gerolama; de Franciscis, Vittorio; Esposito, Carla Lucia

    2016-09-20

    Nucleic acid-based aptamers are emerging as therapeutic antagonists of disease-associated proteins such as receptor tyrosine kinases. They are selected by an in vitro combinatorial chemistry approach, named Systematic Evolution of Ligands by Exponential enrichment (SELEX), and thanks to their small size and unique chemical characteristics, they possess several advantages over antibodies as diagnostics and therapeutics. In addition, aptamers that rapidly internalize into target cells hold as well great potential for their in vivo use as delivery tools of secondary therapeutic agents. Here, we describe a nuclease resistant RNA aptamer, named GL56, which specifically recognizes the insulin receptor (IR). Isolated by a cell-based SELEX method that allows enrichment for internalizing aptamers, GL56 rapidly internalizes into target cells and is able to discriminate IR from the highly homologous insulin-like growth factor receptor 1. Notably, when applied to IR expressing cancer cells, the aptamer inhibits IR dependent signaling. Given the growing interest in the insulin receptor as target for cancer treatment, GL56 reveals a novel molecule with great translational potential as inhibitor and delivery tool for IR-dependent cancers.

  7. Targeting Insulin Receptor with a Novel Internalizing Aptamer.

    PubMed

    Iaboni, Margherita; Fontanella, Raffaela; Rienzo, Anna; Capuozzo, Maria; Nuzzo, Silvia; Santamaria, Gianluca; Catuogno, Silvia; Condorelli, Gerolama; de Franciscis, Vittorio; Esposito, Carla Lucia

    2016-01-01

    Nucleic acid-based aptamers are emerging as therapeutic antagonists of disease-associated proteins such as receptor tyrosine kinases. They are selected by an in vitro combinatorial chemistry approach, named Systematic Evolution of Ligands by Exponential enrichment (SELEX), and thanks to their small size and unique chemical characteristics, they possess several advantages over antibodies as diagnostics and therapeutics. In addition, aptamers that rapidly internalize into target cells hold as well great potential for their in vivo use as delivery tools of secondary therapeutic agents. Here, we describe a nuclease resistant RNA aptamer, named GL56, which specifically recognizes the insulin receptor (IR). Isolated by a cell-based SELEX method that allows enrichment for internalizing aptamers, GL56 rapidly internalizes into target cells and is able to discriminate IR from the highly homologous insulin-like growth factor receptor 1. Notably, when applied to IR expressing cancer cells, the aptamer inhibits IR dependent signaling. Given the growing interest in the insulin receptor as target for cancer treatment, GL56 reveals a novel molecule with great translational potential as inhibitor and delivery tool for IR-dependent cancers. PMID:27648925

  8. Weight-loss changes PPAR expression, reduces atherosclerosis and improves cardiovascular function in obese insulin-resistant mice

    SciTech Connect

    Verreth, Wim; Verhamme, Peter; Pelat, Michael; Ganame, Javier; Bielicki, John K.; Mertens, Ann; Quarck, Rozenn; Benhabiles, Nora; Marguerie, Gerard; Mackness, Bharti; Mackness, Mike; Ninio, Ewa; Herregods, Marie-Christine; Balligand, Jean-Luc; Holvoet, Paul

    2003-09-01

    Weight-loss in obese insulin-resistant, but not in insulin-sensitive, persons reduces CHD risk. It is not known to what extent changes in the adipose gene expression profile are important for reducing CHD risk. We studied the effect of diet restriction-induced weight-loss on gene expression in adipose tissue, atherosclerosis and cardiovascular function in mice with combined leptin and LDL-receptor deficiency. Obesity, hypertriglyceridemia and insulin-resistance are associated with hypertension, impaired left ventricle function and accelerated atherosclerosis in those mice. Diet restriction during 12 weeks caused a 45% weight-loss and changes in the gene expression in adipose tissue of PPARa and PPAR? and of key genes regulating glucose transport and insulin sensitivity, lipid metabolism, oxidative stress and inflammation, most of which are under the transcriptional control of PPARs. These changes were associated with increased insulin-sensitivity, decreased hypertriglyceridemia, reduced mean 24-hour blood pressure and heart rate, restored circadian variations of blood pressure and heart rate, increased ejection fraction, and reduced atherosclerosis. Thus, induction of PPARa and PPAR? in adipose tissue is a key mechanism for reducing atherosclerosis and improving cardiovascular function resulting from weight-loss. Our observations point to the critical role of PPARs in the pathogenesis of cardiovascular features of the metabolic syndrome.

  9. Insulin receptor gene expression in normal and diseased bovine liver.

    PubMed

    Liu, G W; Zhang, Z G; Wang, J G; Wang, Z; Xu, C; Zhu, X L

    2010-11-01

    The aim of the present study was to compare insulin receptor (IR) gene expression in normal bovine liver (n=7) with samples of liver from cows in the perinatal period with ketosis (n=7) and cows with fatty liver (n=7). Gene expression was determined by internally controlled reverse transcriptase polymerase chain reaction (RT-PCR). The expression of IR mRNA in the liver of ketotic dairy cows was higher than in cows with fatty liver, but in both disease groups the expression was substantially lower than that in normal liver. Reduced expression of IR mRNA in fatty liver indicates that responses to insulin are markedly decreased, which might be due to insulin resistance. The relatively lower IR mRNA expression in the liver tissue of dairy cows with ketosis might enhance gluconeogenesis and lipid mobilization to relieve energy negative balance.

  10. Adipocyte insulin receptor activity maintains adipose tissue mass and lifespan.

    PubMed

    Friesen, Max; Hudak, Carolyn S; Warren, Curtis R; Xia, Fang; Cowan, Chad A

    2016-08-01

    Type 2 diabetes follows a well-defined progressive pathogenesis, beginning with insulin resistance in metabolic tissues such as the adipose. Intracellular signaling downstream of insulin receptor activation regulates critical metabolic functions of adipose tissue, including glucose uptake, lipogenesis, lipolysis and adipokine secretion. Previous studies have used the aP2 promoter to drive Cre recombinase expression in adipose tissue. Insulin receptor (IR) knockout mice created using this aP2-Cre strategy (FIRKO mice) were protected from obesity and glucose intolerance. Later studies demonstrated the promiscuity of the aP2 promoter, casting doubts upon the tissue specificity of aP2-Cre models. It is our goal to use the increased precision of the Adipoq promoter to investigate adipocyte-specific IR function. Towards this end we generated an adipocyte-specific IR knockout (AIRKO) mouse using an Adipoq-driven Cre recombinase. Here we report AIRKO mice are less insulin sensitive throughout life, and less glucose tolerant than wild-type (WT) littermates at the age of 16 weeks. In contrast to WT littermates, the insulin sensitivity of AIRKO mice is unaffected by age or dietary regimen. At any age, AIRKO mice are comparably insulin resistant to old or obese WT mice and have a significantly reduced lifespan. Similar results were obtained when these phenotypes were re-examined in FIRKO mice. We also found that the AIRKO mouse is protected from high-fat diet-induced weight gain, corresponding with a 90% reduction in tissue weight of major adipose depots compared to WT littermates. Adipose tissue mass reduction is accompanied by hepatomegaly and increased hepatic steatosis. These data indicate that adipocyte IR function is crucial to systemic energy metabolism and has profound effects on adiposity, hepatic homeostasis and lifespan. PMID:27246738

  11. Deletion of Asn{sup 281} in the {alpha}-subunit of the human insulin receptor causes constitutive activation of the receptor and insulin desensitization

    SciTech Connect

    Desbois-Mouthon, C.; Sert-Langeron, C.; Magre, J.; Blivet, M.J.

    1996-02-01

    We studied the structure and function of the insulin receptor (IR) in two sisters with leprechaunism. The patients had inherited alterations in the IR gene and were compound heterozygotes. Their paternal IR allele carried a major deletion, including exons 10-13, which shifted the reading frame and introduced a premature chain termination codon in the IR sequence. This allele was expressed at a very low level in cultured fibroblasts (<10% of total IR messenger ribonucleic acid content) and encoded a truncated protein lacking transmembrane and tyrosine kinase domains. The maternal IR allele was deleted of 3 bp in exon 3, causing the loss of Asn{sup 281} in the {alpha}-subunit. This allele generated levels of IR messenger ribonucleic acid and cell surface receptors similar to those seen in control fibroblasts. However, IRs from patients` cells had impaired insulin binding and exhibited in vivo and in vitro constitutive activation of autophosphorylation and tyrosine kinase activity. As a result of this IR-preactivated state, the cells were desensitized to insulin stimulation of glycogen and DNA syntheses. These findings strongly suggest that Asn{sup 281} of the IR {alpha}-subunit plays a critical role in the inhibitory constraint exerted by the extracellular {alpha}-subunit over the intracellular kinase activity. 59 refs., 6 figs.

  12. Insulin Receptor Isoform Variations in Prostate Cancer Cells

    PubMed Central

    Perks, Claire M.; Zielinska, H. A.; Wang, Jing; Jarrett, Caroline; Frankow, A.; Ladomery, Michael R.; Bahl, Amit; Rhodes, Anthony; Oxley, Jon; Holly, Jeff M. P.

    2016-01-01

    Men who develop prostate cancer (PCa) increasingly have one of the co-morbidities associated with a Western lifestyle that are characterized by hyperinsulinemia, hyperglycemia and increased expression of insulin-like growth factors-I (IGF-I) and IGF-II. Each have been associated with poor prognosis and more aggressive cancers that exhibit increased metabolism and increased glucose uptake. The insulin receptor (IR) has two splice isoforms IR-A and IR-B: IR-A has a higher affinity for IGF-II comparable to that for insulin, whereas the IR-B isoform predominantly just binds to insulin. In this study, we assessed alterations in the IR-A and IR-B isoform ratio and associated changes in cell proliferation and migration of PCa cell lines following exposure to altered concentrations of glucose and treatment with IGF-II and insulin. We observed that where IR-B predominated insulin had a greater effect on migration than IGF-II and IGF-II was more effective when IR-A was the main isoform. With regard to proliferation IGF-II was more effective than insulin regardless of which isoform was dominant. We assessed the abundance of the IR isoforms both in vivo and in vitro and observed that the majority of the tissue samples and cell lines expressed more IR-A than IR-B. Alterations in the isoforms in response to changes in their hormonal milieu could have a profound impact on how malignant cells behave and play a role in promoting carcinogenesis. A greater understanding of the mechanisms underlying changes in alternative splicing of the IR may provide additional targets for future cancer therapies. PMID:27733843

  13. Molecular Recognition of Insulin by a Synthetic Receptor

    SciTech Connect

    Chinai, Jordan M.; Taylor, Alexander B.; Ryno, Lisa M.; Hargreaves, Nicholas D.; Morris, Christopher A.; Hart, P. John; Urbach, Adam R.

    2011-08-29

    The discovery of molecules that bind tightly and selectively to desired proteins continues to drive innovation at the interface of chemistry and biology. This paper describes the binding of human insulin by the synthetic receptor cucurbit[7]uril (Q7) in vitro. Isothermal titration calorimetry and fluorescence spectroscopy experiments show that Q7 binds to insulin with an equilibrium association constant of 1.5 x 10{sup 6} M{sup -1} and with 50-100-fold selectivity versus proteins that are much larger but lack an N-terminal aromatic residue, and with >1000-fold selectivity versus an insulin variant lacking the N-terminal phenylalanine (Phe) residue. The crystal structure of the Q7{center_dot}insulin complex shows that binding occurs at the N-terminal Phe residue and that the N-terminus unfolds to enable binding. These findings suggest that site-selective recognition is based on the properties inherent to a protein terminus, including the unique chemical epitope presented by the terminal residue and the greater freedom of the terminus to unfold, like the end of a ball of string, to accommodate binding. Insulin recognition was predicted accurately from studies on short peptides and exemplifies an approach to protein recognition by targeting the terminus.

  14. Distinct roles for insulin and insulin-like growth factor-1 receptors in pancreatic beta-cell glucose sensing revealed by RNA silencing.

    PubMed Central

    Da Silva Xavier, Gabriela; Qian, Qingwen; Cullen, Peter J; Rutter, Guy A

    2004-01-01

    The importance of the insulin receptor (IR) and the insulin-like growth factor-1 receptor (IGF-1R) for glucose-regulated insulin secretion and gene expression in pancreatic islet beta-cells is at present unresolved. Here, we have used small interfering RNAs (siRNAs) to silence the expression of each receptor selectively in clonal MIN6 beta-cells. Reduction of IR levels by >90% completely inhibited glucose (30 mM compared with 3 mM)-induced insulin secretion, but had no effect on depolarization-stimulated secretion. IR depletion also blocked the accumulation of preproinsulin (PPI), pancreatic duodenum homoeobox-1 (PDX-1) and glucokinase (GK) mRNAs at elevated glucose concentrations, as assessed by quantitative real-time PCR analysis (TaqMan). Similarly, depletion of IGF-1R inhibited glucose-induced insulin secretion but, in contrast with the effects of IR silencing, had little impact on the regulation of gene expression by glucose. Moreover, loss of IGF-1R, but not IR, markedly inhibited glucose-stimulated increases in cytosolic and mitochondrial ATP, suggesting a role for IGF-1R in the maintenance of oxidative metabolism and in the generation of mitochondrial coupling factors. RNA silencing thus represents a useful tool for the efficient and selective inactivation of receptor tyrosine kinases in isolated beta-cells. By inhibiting glucose-stimulated insulin secretion through the inactivation of IGF-1R, this approach also demonstrates the existence of insulin-independent mechanisms whereby elevated glucose concentrations regulate PPI, PDX-1 and GK gene expression in beta-cells. PMID:14563207

  15. Deletion of exon 3 of the insulin receptor gene in a kindred with a familial form of insulin resistance

    SciTech Connect

    Wertheimer, E.; Barbetti, F.; Accili, D.; Taylor, S.I.; Litvin, Y.; Ebstein, R.P.; Bennet, E.R.

    1994-05-01

    Molecular scanning techniques, such as denaturing gradient gel electrophoresis (DGGE), greatly facilitate screening candidate genes for mutations. The authors have used DGGE to screen for mutations in the insulin receptor gene in a family in which four of five daughters were affected by type A insulin resistance in association with acanthosis nigricans and hyperandrogenism. DGGE did not detect mutations in any of the 22 exons of the insulin receptor gene. Nevertheless, Southern blot analysis suggested that there was a deletion of exon 3 in the other paternal allele of the insulin receptor gene. Analysis of the father`s cDNA confirmed that exon 3 was deleted from mRNA molecules derived from one of his two alleles of the insulin receptor gene. Furthermore, the father was found to be hemizygous for a polymorphic sequence (GAC{sup Asp} at codon 234) in exon 3 that was not inherited by any of the five daughters. Instead, all five daughters inherited the paternal allele with the deletion mutation. They did not detect mutations in the mother`s insulin receptor gene. Furthermore, the clinical syndrome did not segregate with either of the mother`s two alleles of the insulin receptor gene. Although the youngest daughter inherited the mutant allele from her father, she was not clinically affected. The explanation for the incomplete penetrance is not known. These results emphasize the importance of specifically searching for deletion mutations when screening candidate genes for mutations. Furthermore, the existence of apparently asymptomatic carriers of mutations in the insulin receptor gene, such as the father in the present study, suggests that the prevalence of mutations in the insulin receptor gene may be higher than would be predicted on the basis of the observed prevalence of patients with extreme insulin resistance. 34 refs., 6 figs., 1 tab.

  16. Differential Roles of Insulin and IGF-1 Receptors in Adipose Tissue Development and Function.

    PubMed

    Boucher, Jeremie; Softic, Samir; El Ouaamari, Abdelfattah; Krumpoch, Megan T; Kleinridders, Andre; Kulkarni, Rohit N; O'Neill, Brian T; Kahn, C Ronald

    2016-08-01

    To determine the roles of insulin and insulin-like growth factor 1 (IGF-1) action in adipose tissue, we created mice lacking the insulin receptor (IR), IGF-1 receptor (IGF1R), or both using Cre-recombinase driven by the adiponectin promoter. Mice lacking IGF1R only (F-IGFRKO) had a ∼25% reduction in white adipose tissue (WAT) and brown adipose tissue (BAT), whereas mice lacking both IR and IGF1R (F-IR/IGFRKO) showed an almost complete absence of WAT and BAT. Interestingly, mice lacking only the IR (F-IRKO) had a 95% reduction in WAT, but a paradoxical 50% increase in BAT with accumulation of large unilocular lipid droplets. Both F-IRKO and F-IR/IGFRKO mice were unable to maintain body temperature in the cold and developed severe diabetes, ectopic lipid accumulation in liver and muscle, and pancreatic islet hyperplasia. Leptin treatment normalized blood glucose levels in both groups. Glucose levels also improved spontaneously by 1 year of age, despite sustained lipodystrophy and insulin resistance. Thus, loss of IR is sufficient to disrupt white fat formation, but not brown fat formation and/or maintenance, although it is required for normal BAT function and temperature homeostasis. IGF1R has only a modest contribution to both WAT and BAT formation and function.

  17. Differential Roles of Insulin and IGF-1 Receptors in Adipose Tissue Development and Function.

    PubMed

    Boucher, Jeremie; Softic, Samir; El Ouaamari, Abdelfattah; Krumpoch, Megan T; Kleinridders, Andre; Kulkarni, Rohit N; O'Neill, Brian T; Kahn, C Ronald

    2016-08-01

    To determine the roles of insulin and insulin-like growth factor 1 (IGF-1) action in adipose tissue, we created mice lacking the insulin receptor (IR), IGF-1 receptor (IGF1R), or both using Cre-recombinase driven by the adiponectin promoter. Mice lacking IGF1R only (F-IGFRKO) had a ∼25% reduction in white adipose tissue (WAT) and brown adipose tissue (BAT), whereas mice lacking both IR and IGF1R (F-IR/IGFRKO) showed an almost complete absence of WAT and BAT. Interestingly, mice lacking only the IR (F-IRKO) had a 95% reduction in WAT, but a paradoxical 50% increase in BAT with accumulation of large unilocular lipid droplets. Both F-IRKO and F-IR/IGFRKO mice were unable to maintain body temperature in the cold and developed severe diabetes, ectopic lipid accumulation in liver and muscle, and pancreatic islet hyperplasia. Leptin treatment normalized blood glucose levels in both groups. Glucose levels also improved spontaneously by 1 year of age, despite sustained lipodystrophy and insulin resistance. Thus, loss of IR is sufficient to disrupt white fat formation, but not brown fat formation and/or maintenance, although it is required for normal BAT function and temperature homeostasis. IGF1R has only a modest contribution to both WAT and BAT formation and function. PMID:27207537

  18. High-affinity insulin binding to an atypical insulin-like growth factor-I receptor in human breast cancer cells.

    PubMed Central

    Milazzo, G; Yip, C C; Maddux, B A; Vigneri, R; Goldfine, I D

    1992-01-01

    We studied the nature of insulin receptor binding in MCF-7 breast cancer cells. In both intact cells and solubilized receptor preparations, high-affinity insulin binding was seen. However, unlabeled insulin-like growth factor-I (IGF-I) was five-fold more potent in inhibiting 125I-insulin binding than insulin itself. With monoclonal antibodies to the insulin receptor, 30% of 125I-insulin binding was inhibited. In contrast when alpha-IR3, a monoclonal antibody that recognizes typical IGF-I receptor, was employed over 60% of 125I-insulin binding was inhibited. The B29-MAB-125I-insulin photoprobe was then cross-linked to MCF-7 membranes. Cross-linking was inhibited by both unlabeled insulin and IGF-I. Further, the B29-MAB-125I-insulin photoprobe cross-linked to MCF-7 membranes was strongly immunoprecipitated by alpha-IR3. Employing sequential affinity chromatography with insulin-Affi-gel followed by insulin receptor monoclonal antibody agarose, atypical insulin binding activity was separated from insulin receptor binding activity. This atypical receptor had intrinsic tyrosine kinase activity. Both insulin and IGF-I stimulated the phosphorylation of the receptor's beta subunit. In MCF-7 cells both IGF-I and insulin stimulated [3H]thymidine incorporation; alpha-IR3 blocked all of the IGF-I effect but only 50-60% of the insulin effect. This study demonstrates in MCF-7 cells that, in addition to typical insulin and IGF-I receptors, there is another receptor that binds both insulin and IGF-I with high affinity. Images PMID:1311720

  19. Mechanisms of insulin resistance in human obesity: evidence for receptor and postreceptor defects.

    PubMed Central

    Kolterman, O G; Insel, J; Saekow, M; Olefsky, J M

    1980-01-01

    To assess the mechanisms of the insulin resistance in human obesity, we have determined, using a modification of the euglycemic glucose clamp technique, the shape of the in vivo insulin-glucose disposal dose-response curves in 7 control and 13 obese human subjects. Each subject had at least three euglycemic studies performed at insulin infusion rates of 15, 40, 120, 240, or 1,200 mU/M2/min. The glucose disposal rate was decreased in all obese subjects compared with controls (101 +/- 16 vs. 186 +/- 16 mg/M2/min) during the 40 mU/M2/min insulin infusion. The mean dose-response curve for the obese subjects was displaced to the right, i.e., the half-maximally effective insulin concentration was 270 +/- 27 microU/ml for the obese compared with 130 +/- 10 microU/ml for controls. In nine of the obese subjects, the dose-response curves were shifted to the right, and maximal glucose disposal rates (at a maximally effective insulin concentration) were markedly decreased, indicating both a receptor and a postreceptor defect. On the other hand, four obese patients had right-shifted dose-response curves but reached normal maximal glucose disposal rates, consistent with decreased insulin receptors as the only abnormality. When the individual data were analyzed, it was found that the lease hyperinsulinemic, least insulin-resistant patients displayed only the receptor defect, whereas those with the greatest hyperinsulinemia exhibited the largest post-receptor defect, suggesting a continuous spectrum of defects as one advances from mild to severe insulin resistance. When insulin's ability to suppress hepatic glucose output was assessed, hyperinsulinemia produced total suppresssion in all subjects. The dose-response curve for the obese subjects was shifted to the right, indicating a defect in insulin receptors. Insulin binding to isolated adipocytes obtained from the obese subjects was decreased, and a highly significant inverse linear relationship was demonstrated between insulin

  20. S961, an insulin receptor antagonist causes hyperinsulinemia, insulin-resistance and depletion of energy stores in rats

    SciTech Connect

    Vikram, Ajit; Jena, Gopabandhu

    2010-07-23

    Research highlights: {yields}Insulin receptor antagonist S961 causes hyperglycemia, hyperinsulinemia and insulin resistance in rats. {yields}Peroxysome-proliferator-activated-receptor-gamma agonist pioglitazone improves S961 induced hyperglycemia and glucose intolerance. {yields}Long term treatment with insulin receptor antagonist S961 results in the decreased adiposity and hepatic glycogen content. {yields}Improvement in the hyperglycemia and glucose intolerance by pioglitazone clearly demonstrates that S961 treated rats can be successfully used to screen the novel therapeutic interventions having potential to improve glucose disposal through receptor independent mechanisms. -- Abstract: Impairment in the insulin receptor signaling and insulin mediated effects are the key features of type 2 diabetes. Here we report that S961, a peptide insulin receptor antagonist induces hyperglycemia, hyperinsulinemia ({approx}18-fold), glucose intolerance and impairment in the insulin mediated glucose disposal in the Sprague-Dawley rats. Further, long-term S961 treatment (15 day, 10 nM/kg/day) depletes energy storage as evident from decrease in the adiposity and hepatic glycogen content. However, peroxysome-proliferator-activated-receptor-gamma (PPAR{gamma}) agonist pioglitazone significantly (P < 0.001) restored S961 induced hyperglycemia (196.73 {+-} 16.32 vs. 126.37 {+-} 27.07 mg/dl) and glucose intolerance ({approx}78%). Improvement in the hyperglycemia and glucose intolerance by pioglitazone clearly demonstrates that S961 treated rats can be successfully used to screen the novel therapeutic interventions having potential to improve glucose disposal through receptor independent mechanisms. Further, results of the present study reconfirms and provide direct evidence to the crucial role of insulin receptor signaling in the glucose homeostasis and fuel metabolism.

  1. Insulin and insulin-like growth factor-I (IGF-I) receptor phosphorylation in µ-calpain knockout mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous cellular processes are controlled by insulin and IGF-I signaling pathways. Due to previous work in our laboratories, we hypothesized that insulin (IR) and type 1 IGF-I (IGF-IR) receptor signaling is decreased due to increased protein tyrosine phosphatase 1B (PTP1B) activity. C57BL/6J mice...

  2. Evidence of selection at insulin receptor substrate-1 gene loci.

    PubMed

    Yoshiuchi, Issei

    2013-10-01

    Type 2 diabetes mellitus (T2DM) is a complex disease characterized by insulin resistance and defect of insulin secretion. The worldwide prevalence of T2DM is steadily increasing. T2DM is also significantly associated with obesity, coronary artery disease (CAD), and metabolic syndrome. There is a clear difference in the prevalence of T2DM among populations, and T2DM is highly heritable. Human adaptations to environmental changes in food supply, lifestyle, and geography may have pressured the selection of genes associated with the metabolism of glucose, lipids, carbohydrates, and energy. The insulin receptor substrate-1 (IRS1) gene is considered a major T2DM gene, and common genetic variations near the IRS1 gene were found to be associated with T2DM, insulin resistance, adiposity, and CAD. Here, we aimed to find evidence of selection at the IRS1 gene loci using the HapMap population data. We investigated a 3-step test procedure-Wright's F statistics (Fst), the long-range haplotype (LRH) test, and the integrated haplotype score (iHS) test-to detect selection at the IRS1 gene loci using the HapMap population data. We observed that 1 CAD-associated SNP (rs2943634) and 1 adiposity- and insulin resistance-associated SNP (rs2943650) exhibited high Fst values. We also found selection at the IRS1 gene loci by the LRH test and the iHS test. These findings suggest evidence of selection at the IRS1 gene loci and that further studies should examine the adaptive evolution of T2DM genes. PMID:22797928

  3. Small-molecule ghrelin receptor antagonists improve glucose tolerance, suppress appetite, and promote weight loss.

    PubMed

    Esler, William P; Rudolph, Joachim; Claus, Thomas H; Tang, Weifeng; Barucci, Nicole; Brown, Su-Ellen; Bullock, William; Daly, Michelle; Decarr, Lynn; Li, Yaxin; Milardo, Lucinda; Molstad, David; Zhu, Jian; Gardell, Stephen J; Livingston, James N; Sweet, Laurel J

    2007-11-01

    Ghrelin, through action on its receptor, GH secretagogue receptor type 1a (GHS-R1a), exerts a variety of metabolic functions including stimulation of appetite and weight gain and suppression of insulin secretion. In the present study, we examined the effects of novel small-molecule GHS-R1a antagonists on insulin secretion, glucose tolerance, and weight loss. Ghrelin dose-dependently suppressed insulin secretion from dispersed rat islets. This effect was fully blocked by a GHS-R1a antagonist. Consistent with this observation, a single oral dose of a GHS-R1a antagonist improved glucose homeostasis in an ip glucose tolerance test in rat. Improvement in glucose tolerance was attributed to increased insulin secretion. Daily oral administration of a GHS-R1a antagonist to diet-induced obese mice led to reduced food intake and weight loss (up to 15%) due to selective loss of fat mass. Pair-feeding experiments indicated that weight loss was largely a consequence of reduced food intake. The impact of a GHS-R1a antagonist on gastric emptying was also examined. Although the GHS-R1a antagonist modestly delayed gastric emptying at the highest dose tested (10 mg/kg), delayed gastric emptying does not appear to be a requirement for weight loss because lower doses produced weight loss without an effect on gastric emptying. Consistent with the hypothesis that ghrelin regulates feeding centrally, the anorexigenic effects of potent GHS-R1a antagonists in mice appeared to correspond with their brain exposure. These observations demonstrate that GHS-R1a antagonists have the potential to improve the diabetic condition by promoting glucose-dependent insulin secretion and promoting weight loss.

  4. Insulin Receptor Signaling in Long-Term Memory Consolidation Following Spatial Learning

    ERIC Educational Resources Information Center

    Dou, Jing-Tao; Chen, Min; Dufour, Franck; Alkon, Daniel L.; Zhao, Wei-Qin

    2005-01-01

    Evidence has shown that the insulin and insulin receptor (IR) play a role in cognitive function. However, the detailed mechanisms underlying insulin's action on learning and memory are not yet understood. Here we investigated changes in long-term memory-associated expression of the IR and downstream molecules in the rat hippocampus. After…

  5. Hyperinsulinemia is Associated with Increased Soluble Insulin Receptors Release from Hepatocytes

    PubMed Central

    Hiriart, Marcia; Sanchez-Soto, Carmen; Diaz-Garcia, Carlos Manlio; Castanares, Diana T.; Avitia, Morena; Velasco, Myrian; Mas-Oliva, Jaime; Macias-Silva, Marina; González-Villalpando, Clicerio; Delgado-Coello, Blanca; Sosa-Garrocho, Marcela; Vidaltamayo, Román; Fuentes-Silva, Deyanira

    2014-01-01

    It has been generally assumed that insulin circulates freely in blood. However it can also interact with plasma proteins. Insulin receptors are located in the membrane of target cells and consist of an alpha and beta subunits with a tyrosine kinase cytoplasmic domain. The ectodomain, called soluble insulin receptor (SIR) has been found elevated in patients with diabetes mellitus. We explored if insulin binds to SIRs in circulation under physiological conditions and hypothesize that this SIR may be released by hepatocytes in response to high insulin concentrations. The presence of SIR in rat and human plasmas and the culture medium of hepatocytes was explored using Western blot analysis. A purification protocol was performed to isolated SIR using affinity, gel filtration, and ion exchange chromatographies. A modified reverse hemolytic plaque assay was used to measure SIR release from cultured hepatocytes. Incubation with 1 nmol l−1 insulin induces the release of the insulin receptor ectodomains from normal rat hepatocytes. This effect can be partially prevented by blocking protease activity. Furthermore, plasma levels of SIR were higher in a model of metabolic syndrome, where rats are hyperinsulinemic. We also found increased SIR levels in hyperinsulinemic humans. SIR may be an important regulator of the amount of free insulin in circulation. In hyperinsulinemia, the amount of this soluble receptor increases and this could lead to higher amounts of insulin bound to this receptor, rather than free insulin, which is the biologically active form of the hormone. This observation could enlighten the mechanisms of insulin resistance. PMID:24995000

  6. Dissociation of insulin receptor phosphorylation and stimulation of glucose transport in BC3H-1 myocytes

    SciTech Connect

    Mojsilovic, L.P.; Standaert, M.L.; Rosic, N.K.; Pollet, R.J.

    1986-05-01

    The authors have investigated insulin receptor phosphorylation in differentiated cultured BC3H-1 myocytes. As for other insulin-responsive cell systems in partially purified wheat germ agglutinin receptor preparations, insulin stimulates the phosphorylation of its own receptor (95K ..beta..-subunits) in a dose dependent manner (0-400 nM), as identified by immunoprecipitation with antiinsulin receptor antibodies and SDS-PAGE. In the same preparations they show that 12-0-tetradecanyl phorbol acetate (TPA), which in many respect ..beta..-subunits in the same dose dependent manner (0-5 ..mu..M). In addition, antiinsulin receptor antibodies (B-10) also induced phosphorylation of mimics insulin action, also induced phosphorylation of the insulin receptor and HPLC tryptic maps of the /sup 32/P-labeled ..beta..-subunit were identical to those for insulin-induced receptor phosphorylation. However, while insulin and TPA are potent stimulators of glucose transport in these muscle cells, the antireceptor antibodies alone failed to provoke glucose transport at any concentration. The specificity and activity of these antibodies were confirmed in their system by their ability to inhibit insulin binding and insulin-stimulated glucose transport in a concentration-dependent manner. Their results indicate that phosphorylation of insulin receptor is not a crucial event in mediating insulin action, at least with respect to glucose transport. While the effects of the B-10 antibody in the BC3H-1 myocyte differ from those in the adipocyte, their results provide independent confirmation of their essential conclusion that phosphorylation of the insulin receptor may not be necessary nor sufficient for its acute action in promoting glucose transport.

  7. Evidence for an insulin receptor substrate 1 independent insulin signaling pathway that mediates insulin-responsive glucose transporter (GLUT4) translocation.

    PubMed Central

    Morris, A J; Martin, S S; Haruta, T; Nelson, J G; Vollenweider, P; Gustafson, T A; Mueckler, M; Rose, D W; Olefsky, J M

    1996-01-01

    Interaction of the activated insulin receptor (IR) with its substrate, insulin receptor substrate 1 (IRS-1), via the phosphotyrosine binding domain of IRS-1 and the NPXY motif centered at phosphotyrosine 960 of the IR, is important for IRS-1 phosphorylation. We investigated the role of this interaction in the insulin signaling pathway that stimulates glucose transport. Utilizing microinjection of competitive inhibitory reagents in 3T3-L1 adipocytes, we have found that disruption of the IR/IRS-1 interaction has no effect upon translocation of the insulin-responsive glucose transporter (GLUT4). The activity of these reagents was demonstrated by their ability to block insulin stimulation of two distinct insulin bioeffects, membrane ruffling and mitogenesis, in 3T3-L1 adipocytes and insulin-responsive rat 1 fibroblasts. These data suggest that phosphorylated IRS-1 is not an essential component of the metabolic insulin signaling pathway that leads to GLUT4 translocation, yet it appears to be required for other insulin bioeffects. Images Fig. 1 Fig. 2 Fig. 3 PMID:8710883

  8. Mice Lacking the p43 Mitochondrial T3 Receptor Become Glucose Intolerant and Insulin Resistant during Aging

    PubMed Central

    Bertrand, Christelle; Blanchet, Emilie; Pessemesse, Laurence; Annicotte, Jean Sébastien; Feillet-Coudray, Christine; Chabi, Béatrice; Levin, Jonathan; Fajas, Lluis; Cabello, Gérard; Wrutniak-Cabello, Chantal; Casas, François

    2013-01-01

    Thyroid hormones (TH) play an important regulatory role in energy expenditure regulation and are key regulators of mitochondrial activity. We have previously identified a mitochondrial triiodothyronine (T3) receptor (p43) which acts as a mitochondrial transcription factor of the organelle genome, which leads in vitro and in vivo, to a stimulation of mitochondrial biogenesis. Recently, we generated mice carrying a specific p43 invalidation. At 2 months of age, we reported that p43 depletion in mice induced a major defect in insulin secretion both in vivo and in isolated pancreatic islets, and a loss of glucose-stimulated insulin secretion. The present study was designed to determine whether p43 invalidation influences life expectancy and modulates blood glucose and insulin levels as well as glucose tolerance or insulin sensitivity during aging. We report that from 4 months old onwards, mice lacking p43 are leaner than wild-type mice. p43−/− mice also have a moderate reduction of life expectancy compared to wild type. We found no difference in blood glucose levels, excepted at 24 months old where p43−/− mice showed a strong hyperglycemia in fasting conditions compared to controls animals. However, the loss of glucose-stimulated insulin secretion was maintained whatever the age of mice lacking p43. If up to 12 months old, glucose tolerance remained unchanged, beyond this age p43−/− mice became increasingly glucose intolerant. In addition, if up to 12 months old p43 deficient animals were more sensitive to insulin, after this age we observed a loss of this capacity, culminating in 24 months old mice with a decreased sensitivity to the hormone. In conclusion, we demonstrated that during aging the depletion of the mitochondrial T3 receptor p43 in mice progressively induced an increased glycemia in the fasted state, glucose intolerance and an insulin-resistance several features of type-2 diabetes. PMID:24098680

  9. High Fasting Insulin Levels and Insulin Resistance May Be Linked to Idiopathic Recurrent Pregnancy Loss: A Case-Control Study

    PubMed Central

    Ispasoiu, Corina-Alina; Chicea, Radu; Stamatian, Florin Vasile; Ispasoiu, Florin

    2013-01-01

    Objective. Patients with more than two spontaneous pregnancy losses are diagnosed with recurrent pregnancy loss. The aim of this study was to evaluate the IR (insulin resistance) in patients with idiopathic recurrent pregnancy loss. Material and Method. A single center, case control study was performed on one hundred eighteen women divided into case group (with at least two pregnancy losses, earlier than 20 weeks of gestation, and negative for the recurrent pregnancy loss testing) and control group (with at least one live birth, no pregnancy loss). FG (fasting glucose) and FI (fasting insulin) were determined for all patients. IR was evaluated by HOMA-IR index. Results. There were not significant differences between the mean age and BMI in cases and controls (P > 0.05). Fasting glucose was significantly higher in the control group (85.6 versus 79.8 P < 0.01), but fasting insulin (15.24 versus 12.83, P < 0.001) and HOMA-IR (2.98 versus 2.69, P < 0.05) were significantly higher in the case group. Conclusion. In women with idiopathic recurrent pregnancy loss FI and IR are higher than those in women without spontaneous abortion. PMID:24371440

  10. Excessive insulin receptor serine phosphorylation in cultured fibroblasts and in skeletal muscle. A potential mechanism for insulin resistance in the polycystic ovary syndrome.

    PubMed Central

    Dunaif, A; Xia, J; Book, C B; Schenker, E; Tang, Z

    1995-01-01

    We investigated the cellular mechanisms of the unique disorder of insulin action found in the polycystic ovary syndrome (PCOS). Approximately 50% of PCOS women (PCOS-Ser) had a significant increase in insulin-independent beta-subunit [32P]phosphate incorporation (3.7-fold, P < 0.05 vs other groups) in skin fibroblast insulin receptors that was present in serine residues while insulin-induced tyrosine phosphorylation was decreased (both P < 0.05 vs other groups). PCOS skeletal muscle insulin receptors had the same abnormal phosphorylation pattern. The remaining PCOS women (PCOS-n1) had basal and insulin-stimulated receptor autophosphorylation similar to control. Phosphorylation of the artificial substrate poly GLU4:TYR1 by the PCOS-Ser insulin receptors was significantly decreased (P < 0.05) compared to control and PCOS-n1 receptors. The factor responsible for excessive serine phosphorylation appeared to be extrinsic to the receptor since no insulin receptor gene mutations were identified, immunoprecipitation before autophosphorylation corrected the phosphorylation defect and control insulin receptors mixed with lectin eluates from affected PCOS fibroblasts displayed increased serine phosphorylation. Our findings suggest that increased insulin receptor serine phosphorylation decreases its protein tyrosine kinase activity and is one mechanism for the post-binding defect in insulin action characteristic of PCOS. Images PMID:7635975

  11. Changes in erythrocyte insulin receptors in normal dogs and keeshond dogs with inheritable, early onset, insulin dependent diabetes mellitus

    SciTech Connect

    Klaassen, J.K.

    1986-01-01

    Validation of a procedure to evaluate insulin receptors on erythrocytes (RBC-IR) in dogs is described. The specific binding of (/sup 125/I)iodoinsulin to RBC-IR of normal dogs is significantly greater than binding in keeshonds with an inheritable form of early onset diabetes mellitus. This decreased binding was due to a significant decrease in RBC-IR affinity in the diabetic keeshonds. To determine the effect on RBC-IR, normal dogs were treated with either dexamethasone (0.1 mg/kg) or prednisone (0.3 mg/kg) for 10 days: concentrations of plasma cortisol, glucose, and insulin, plus binding characteristics of RBC-IR were determined. In the dexamethasone treated group, plasma glucose concentrations were elevated significantly by day 6 and continued through day 10. Insulin concentrations were elevated significantly by day 3 and remained elevated through day 10. In the prednisone treated group, glucose concentrations were elevated significantly by day 3, while insulin concentrations were elevated significantly by day 8. Maximum binding of RBC-IR was unaffected by prednisone and neither affinities nor receptor numbers were significantly different from day 1. No changes in plasma cortisol concentration were seen. Diabetic keeshonds on daily insulin treatment were removed from exogenous insulin therapy for 48 hours. Significant increases in glucose concentrations were observed, but no significant changes in cortisol, insulin, average receptor binding affinity, or RBC-IR number per cell occurred.

  12. Insulin-Like Activity of Concanavalin A and Wheat Germ Agglutinin—Direct Interactions with Insulin Receptors

    PubMed Central

    Cuatrecasas, Pedro; Tell, Guy P. E.

    1973-01-01

    Concanavalin A and wheat germ agglutinin are as effective as insulin in enhancing the rate of glucose transport and in inhibiting epinephrine-stimulated lipolysis in isolated adipocytes. These lectins, also like insulin, inhibit basal as well as epinephrine-stimulated adenylate cyclase activity of membranes obtained from homogenates of fat cells. Low concentrations of wheat germ agglutinin enhance the specific binding of insulin to receptors of fat cells and liver membranes. Higher concentrations of this plant lectin, as well as of concanavalin A, competitively displace the binding of insulin to receptors in these tissues. These effects are equally apparent in insulin-binding proteins solubilized from membranes, indicating that the plant lectins interact directly with insulin receptors. All of the effects observed with the plant lectins are reversed by simple sugars that bind specifically to these plant proteins. Agarose derivatives of the plant lectins effectively adsorb solubilized insulin-binding proteins, and these can be eluted with buffers containing specific simple sugars. The possible implications of these findings to certain biological properties (mitogenicity) of these lectins and to the mechanism of action of other growth-promoting substances are considered. PMID:4510292

  13. Insulin treatment normalizes retinal neuroinflammation but not markers of synapse loss in diabetic rats

    PubMed Central

    Masser, Dustin R.; VanGuilder Starkey, Heather D.; Bixler, Georgina V.; Dunton, Wendy; Bronson, Sarah K.; Freeman, Willard M.

    2014-01-01

    Diabetic retinopathy is one of the leading causes of blindness in developed countries, and a majority of patients with type I and type II diabetes will develop some degree of vision loss despite blood glucose control regimens. The effects of different insulin therapy regimens on early metabolic, inflammatory and neuronal retinal disease processes such as retinal neuroinflammation and synapse loss have not been extensively investigated. This study compared 3 months non-diabetic and streptozotocin (STZ)-induced diabetic Sprague Dawley rats. Diabetic rats received either no insulin treatment, systemic insulin treatment beginning after 1 week uncontrolled diabetes (early intervention, 11 weeks on insulin), or after 1.5 months uncontrolled diabetes (late intervention, 6 weeks on insulin). Changes in both whole animal metabolic and retinal inflammatory markers were prevented by early initiation of insulin treatment. These metabolic and inflammatory changes were also normalized by the later insulin intervention. Insulin treatment begun 1 week after diabetes induction ameliorated loss of retinal synapse markers. Synapse markers and presumably synapse numbers were equivalent in uncontrolled diabetes and when insulin treatment began at 1.5 months of diabetes. These findings are in agreement with previous demonstrations that retinal synapses are lost within 1 month of uncontrolled diabetes and suggest that synapses are not regained with glycemic control and restoration of insulin signaling. However, increased expression of metabolic and inflammatory markers associated with diabetes was reversed in both groups of insulin treatment. This study also emphasizes the need for insulin treatment groups in diabetic retinopathy studies to provide a more faithful modeling of the human condition. PMID:24931083

  14. Insulin-like factor regulates neural induction through an IGF1 receptor-independent mechanism

    PubMed Central

    Haramoto, Yoshikazu; Takahashi, Shuji; Oshima, Tomomi; Onuma, Yasuko; Ito, Yuzuru; Asashima, Makoto

    2015-01-01

    Insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF1R) signalling is required for normal embryonic growth and development. Previous reports indicated that the IGF/IGF1R/MAPK pathway contributes to neural induction and the IGF/IGF1R/PI3K/Akt pathway to eye development. Here, we report the isolation of insulin3 encoding a novel insulin-like ligand involved in neural induction. Insulin3 has a similar structure to pro-insulin and mature IGF ligands, but cannot activate the IGF1 receptor. However, similar to IGFs, Insulin3 induced the gene expression of an anterior neural marker, otx2, and enlarged anterior head structures by inhibiting Wnt signalling. Insulin3 are predominantly localised to the endoplasmic reticulum when otx2 is induced by insulin3. Insulin3 reduced extracellular Wnts and cell surface localised Lrp6. These results suggest that Insulin3 is a novel cell-autonomous inhibitor of Wnt signalling. This study provides the first evidence that an insulin-like factor regulates neural induction through an IGF1R-independent mechanism. PMID:26112133

  15. Phorbol esters stimulate the phosphorylation of receptors for insulin and somatomedin C.

    PubMed Central

    Jacobs, S; Sahyoun, N E; Saltiel, A R; Cuatrecasas, P

    1983-01-01

    The effect of phorbol esters on the extent of phosphorylation of receptors for insulin and somatomedin C (insulin-like growth factor I) was studied in intact IM-9 cells that were labeled by incubation with H332PO4. The tumor-promoting phorbol esters phorbol tetradecanoate acetate (TPA) and phorbol dibutyrate, but not the inactive 4 alpha-phorbol, enhanced phosphorylation of the beta subunit of both receptors approximately 4-fold; 70 nM TPA maximally stimulated phosphorylation of both receptors, whereas concentrations less than or equal to 0.7 nM had no observable effect. Insulin also enhanced the phosphorylation of the beta subunit of the insulin receptor, and its effects appeared to be additive to those of TPA. Peptide maps indicated that at least some of the residues phosphorylated by these two agents are distinct. These results suggest a possible role of protein kinase C in regulating insulin and somatomedin C receptors. Images PMID:6312447

  16. A domain of the insulin receptor required for endocytosis in rat fibroblasts.

    PubMed

    Thies, R S; Webster, N J; McClain, D A

    1990-06-15

    To study the mechanism and role of ligand-dependent endocytosis, we have engineered a mutant insulin receptor that retains its insulin binding and insulin-stimulated tyrosine kinase activities but does not exhibit ligand-induced internalization. The mutant has a deletion of the 16th exon which encodes 22 amino acids (residues 944-965) on the cytoplasmic side of the transmembrane region of the receptor beta-subunit. When the cDNA is transfected in Rat 1 cells, the mutant receptor (HIR delta ex16) is processed to a glycosylated alpha 2 beta 2 heterotetramer and expressed at the cell surface. HIR delta ex16 receptors bind insulin with lower affinity than normal receptors (ED50 for insulin competition = 1.1 nM compared with 0.2 nM for normal receptors), but binding is normal in detergent solution. The mutant HIR delta ex16 receptor undergoes insulin-dependent autophosphorylation and activation as a tyrosine kinase toward exogenous substrates in vitro. In vivo, the receptor is also enzymatically active, as assessed 1) by the ability of antiphosphotyrosine antibodies to precipitate equivalent proportions (58-60%) of occupied wild type or mutant receptors and 2) by immunoblotting extracts of insulin-stimulated cells using antiphosphotyrosine antibodies. In the latter experiment, cells expressing HIR delta ex16 receptors exhibit tyrosine phosphorylation of insulin receptor beta-subunits as well as of pp 185, a putative substrate of the receptor. Despite the ability to bind insulin and activate as a tyrosine kinase, HIR delta ex16 receptors do not internalize in Rat 1 cells. Whereas normal surface receptors covalently labeled with the photoaffinity reagent 125I-NAPA-DP insulin are 36% intracellular after 1 h at 37 degrees C, only background levels of internalization are seen when HIR delta ex16 receptors are labeled. The HIR delta ex16 receptors mediate no internalization or degradation of 125I-insulin compared with control untransfected Rat 1 cells, and they do not down

  17. Insulin-independent role of adiponectin receptor signaling in Drosophila germline stem cell maintenance.

    PubMed

    Laws, Kaitlin M; Sampson, Leesa L; Drummond-Barbosa, Daniela

    2015-03-15

    Adipocytes have key endocrine roles, mediated in large part by secreted protein hormones termed adipokines. The adipokine adiponectin is well known for its role in sensitizing peripheral tissues to insulin, and several lines of evidence suggest that adiponectin might also modulate stem cells/precursors. It remains unclear, however, how adiponectin signaling controls stem cells and whether this role is secondary to its insulin-sensitizing effects or distinct. Drosophila adipocytes also function as an endocrine organ and, although no obvious adiponectin homolog has been identified, Drosophila AdipoR encodes a well-conserved homolog of mammalian adiponectin receptors. Here, we generate a null AdipoR allele and use clonal analysis to demonstrate an intrinsic requirement for AdipoR in germline stem cell (GSC) maintenance in the Drosophila ovary. AdipoR null GSCs are not fully responsive to bone morphogenetic protein ligands from the niche and have a slight reduction in E-cadherin levels at the GSC-niche junction. Conversely, germline-specific overexpression of AdipoR inhibits natural GSC loss, suggesting that reduction in adiponectin signaling might contribute to the normal decline in GSC numbers observed over time in wild-type females. Surprisingly, AdipoR is not required for insulin sensitization of the germline, leading us to speculate that insulin sensitization is a more recently acquired function than stem cell regulation in the evolutionary history of adiponectin signaling. Our findings establish Drosophila female GSCs as a new system for future studies addressing the molecular mechanisms whereby adiponectin receptor signaling modulates stem cell fate.

  18. 4PS/insulin receptor substrate (IRS)-2 is the alternative substrate of the insulin receptor in IRS-1-deficient mice.

    PubMed

    Patti, M E; Sun, X J; Bruening, J C; Araki, E; Lipes, M A; White, M F; Kahn, C R

    1995-10-20

    Insulin receptor substrate-1 (IRS-1) is the major cytoplasmic substrate of the insulin and insulin-like growth factor (IGF)-1 receptors. Transgenic mice lacking IRS-1 are resistant to insulin and IGF-1, but exhibit significant residual insulin action which corresponds to the presence of an alternative high molecular weight substrate in liver and muscle. Recently, Sun et al. (Sun, X.-J., Wang, L.-M., Zhang, Y., Yenush, L. P., Myers, M. G., Jr., Glasheen, E., Lane, W.S., Pierce, J. H., and White, M. F. (1995) Nature 377, 173-177) purified and cloned 4PS, the major substrate of the IL-4 receptor-associated tyrosine kinase in myeloid cells, which has significant structural similarity to IRS-1. To determine if 4PS is the alternative substrate of the insulin receptor in IRS-1-deficient mice, we performed immunoprecipitation, immunoblotting, and phosphatidylinositol (PI) 3-kinase assays using specific antibodies to 4PS. Following insulin stimulation, 4PS is rapidly phosphorylated in liver and muscle, binds to the p85 subunit of PI 3-kinase, and activates the enzyme. Insulin stimulation also results in the association of 4PS with Grb 2 in both liver and muscle. In IRS-1-deficient mice, both the phosphorylation of 4PS and associated PI 3-kinase activity are enhanced, without an increase in protein expression. Immunodepletion of 4PS from liver and muscle homogenates removes most of the phosphotyrosine-associated PI 3-kinase activity in IRS-1-deficient mice. Thus, 4PS is the primary alternative substrate, i.e. IRS-2, which plays a major role in physiologic insulin signal transduction via both PI 3-kinase activation and Grb 2/Sos association. In IRS-1-deficient mice, 4PS/IRS-2 provides signal transduction to these two major pathways of insulin signaling.

  19. Adiponectin and adiponectin receptors in insulin resistance, diabetes, and the metabolic syndrome

    PubMed Central

    Kadowaki, Takashi; Yamauchi, Toshimasa; Kubota, Naoto; Hara, Kazuo; Ueki, Kohjiro; Tobe, Kazuyuki

    2006-01-01

    Adiponectin is an adipokine that is specifically and abundantly expressed in adipose tissue and directly sensitizes the body to insulin. Hypoadiponectinemia, caused by interactions of genetic factors such as SNPs in the Adiponectin gene and environmental factors causing obesity, appears to play an important causal role in insulin resistance, type 2 diabetes, and the metabolic syndrome, which are linked to obesity. The adiponectin receptors, AdipoR1 and AdipoR2, which mediate the antidiabetic metabolic actions of adiponectin, have been cloned and are downregulated in obesity-linked insulin resistance. Upregulation of adiponectin is a partial cause of the insulin-sensitizing and antidiabetic actions of thiazolidinediones. Therefore, adiponectin and adiponectin receptors represent potential versatile therapeutic targets to combat obesity-linked diseases characterized by insulin resistance. This Review describes the pathophysiology of adiponectin and adiponectin receptors in insulin resistance, diabetes, and the metabolic syndrome. PMID:16823476

  20. Role of the occult insulin receptors in the regulation of atrophy and hypertrophy of skeletal muscles

    SciTech Connect

    McLeod, M.J.

    1980-10-01

    Insulin levels in the plasma are variable, as are insulin receptor numbers on the surface of skeletal muscles. Increased blood supply to the muscle during exercise delivers more insulin to the muscles even though insulin levels are suppressed by epinephrine. Increasing muscle temperatures result in an increased insulin effect, if enough receptors are available for binding. In exhaustive exercise, insulin levels are minimal but the movement of glucose across the cell membrane increases. Since insulin-receptor affinity decreases at high temperature, the only way this increased movement of glucose can be accomplished is by increased insulin binding. Thus more receptors must be available to capture the insulin. Epinephrine levels drop drastically after exercise. Insulin levels increase and the cell can import glucose, amino acids, and nucleotides. As the cell temperature decreases after exercise, insulin binding increases but the total effect decreases because the many surface receptors disappear again over a period of time. If the muscle is immobilized, the number of surface receptors decreases. There is less insulin effect and as a result the muscle atrophies. Acetylcholine (ACh) causes the proper arrangement of the myofibrils in the foetus, and has some effect on the rate of atrophy in an immobilized muscle. It also appears to maintain the cell membrane organization. Disuse atrophy is caused by a decrease in cell size, while exercise hypertrophy is caused by an increase in cell size. Growth hormone (STH) is therefore ruled out as the exercise hypertrophy controlling factor, since STH causes cell division and not hypertrophy. Testosterone can also be ruled out as the controlling factor in the development of hypertrophy and atrophy of muscles. Estrogen can likewise be ruled out. (ERB)

  1. Optimizing transmembrane domain helicity accelerates insulin receptor internalization and lateral mobility.

    PubMed Central

    Goncalves, E; Yamada, K; Thatte, H S; Backer, J M; Golan, D E; Kahn, C R; Shoelson, S E

    1993-01-01

    Transmembrane (TM) domains of integral membrane proteins are generally thought to be helical. However, a Gly-Pro sequence within the TM domain of the insulin receptor is predicted to act as a helix breaker. CD analyses of model TM peptides in a lipid-like environment show that substitution of Gly and Pro by Ala enhances helicity. On this basis, Gly933 and Pro934 within the TM domain of the intact human insulin receptor were mutated to Ala (G-->A, P-->A, GP-->AA) to assess effects of altered helicity on receptor functions. Mutated and wild-type receptors, expressed stably in cultured CHO cells at equivalent levels, were properly assembled, biosynthetically processed, and exhibited similar affinities for insulin. Receptor autophosphorylation and substrate kinase activity in intact cells and soluble receptor preparations were indistinguishable. In contrast, insulin-stimulated receptor internalization was accelerated 2-fold for the GP-->AA mutant, compared to a wild-type control or the G-->A and P-->A mutants. Insulin degradation, which occurs during receptor endocytosis and recycling, was similarly elevated in cells transfected with GP-->AA mutant receptors. Fluorescence photobleaching recovery measurements showed that the lateral mobility of GP-->AA mutant receptors was also increased 2- to 3-fold. These results suggest that lateral mobility directly influences rates of insulin-mediated receptor endocytosis and that rates of endocytosis and lateral mobility are retarded by a kinked TM domain in the wild-type receptor. Invariance of Gly-Pro within insulin receptor TM domain sequences suggests a physiologic advantage for submaximal rates of receptor internalization. Images Fig. 2 Fig. 3 PMID:8390680

  2. Insect insulin receptors: insights from sequence and caste expression analyses of two cloned hymenopteran insulin receptor cDNAs from the fire ant.

    PubMed

    Lu, H-L; Pietrantonio, Patricia V

    2011-10-01

    The insulin and insulin-like growth factor (IGF) signalling (IIS) pathway in the honey bee (Apis mellifera) is linked to reproductive division of labour and foraging behaviour. Two insulin receptor genes are present in the released genomes of other social hymenopterans. Limited information is available on the IIS pathway role in ants. The predicted insulin receptor sequences from the recently released draft genome of the fire ant Solenopsis invicta (Hymenoptera: Formicidae) are incomplete and biologically significant data are also lacking. To elucidate the role of the IIS pathway in the fire ant, two putative insulin receptors (SiInR-1 and SiInR-2) were cloned; the first InR cDNAs cloned from social insects. Analyses of putative post-translational modification sites in SiInRs revealed the potential for differential regulation. We investigated the transcriptional expression of both receptors at different developmental stages, castes and queen tissues. In last instar larvae and pharate pupae of workers and reproductive, transcriptional abundance of both receptors was negatively correlated with body size and nutritional status. The expression level of both receptors in different queen tissues appears to correlate with requirements for queen reproductive physiology and behaviours. This study contributes new information to the understanding of social insects because in fire ants juvenile hormone acts as a gonadotropin and workers are fully sterile, contrary to honey bees.

  3. In situ autoradiography and ligand-dependent tyrosine kinase activity reveal insulin receptors and insulin-like growth factor I receptors in prepancreatic chicken embryos.

    PubMed Central

    Girbau, M; Bassas, L; Alemany, J; de Pablo, F

    1989-01-01

    We previously reported specific cross-linking of 125I-labeled insulin and 125I-labeled insulin-like growth factor I (IGF-I) to the alpha subunit of their respective receptors in chicken embryos of 20 somites and older. To achieve adequate sensitivity and localize spatially the receptors in younger embryos, we adapted an autoradiographic technique using whole-mounted chicken blastoderms. Insulin receptors and IGF-I receptors were expressed and could be localized as early as gastrulation, before the first somite is formed. Relative density was analyzed by a computer-assisted image system, revealing overall slightly higher binding of IGF-I than of insulin. Structures rich in both types of receptors were predominantly of ectodermal origin: Hensen's node in gastrulating embryos and neural folds, neural tube and optic vesicles during neurulation. The signal transduction capability of the receptors in early organogenesis was assessed by their ability to phosphorylate the exogenous substrate poly(Glu80Tyr20). Ligand-dependent tyrosine phosphorylation was demonstrable with both insulin and IGF-I in glycoprotein-enriched preparations from embryos at days 2 through 6 of embryogenesis. There was a developmentally regulated change in ligand-dependent tyrosine kinase activity, with a sharp increase from day 2 to day 4, in contrast with a small increase in the ligand binding. Binding of 125I-labeled IGF-I was, with the solubilized receptors, severalfold higher than binding of 125I-labeled insulin. However, the insulin-dependent phosphorylation was as high as the IGF-I-dependent phosphorylation at each developmental stage. Images PMID:2548191

  4. Selectivity of phospholipase C phosphorylation by the epidermal growth factor receptor, the insulin receptor, and their cytoplasmic domains.

    PubMed Central

    Nishibe, S; Wahl, M I; Wedegaertner, P B; Kim, J W; Rhee, S G; Carpenter, G; Kim, J J

    1990-01-01

    Phosphatidylinositol-specific phospholipase C isozyme gamma (PLC-gamma, Mr 145,000) is an excellent substrate for the epidermal growth factor (EGF) receptor both in vivo and in vitro. PLC-beta-1, another PLC isozyme, is a poor substrate for the EGF receptor. We examined the relative phosphorylation of PLC-gamma and PLC-beta-1 by the 170-kDa native EGF receptor molecule, the 66-kDa cytoplasmic kinase domain of the EGF receptor (Arg647-Ala1186), the alpha 2 beta 2 native insulin receptor, and the 48-kDa cytoplasmic kinase domain of the insulin receptor beta subunit (Gly947-Ser1343). Similar to the intact EGF receptor, the cytoplasmic kinase domain of the EGF receptor preferentially phosphorylated PLC-gamma. High-performance liquid chromatographic comparison of tryptic phosphopeptides from PLC-gamma phosphorylated by both forms of the EGF receptor kinase indicated similar patterns of multiple tyrosine phosphorylations. These results imply that substrate selectivity, at least in terms of PLC isozymes, is independent of the extracellular ligand-binding and membrane anchor domains of the EGF receptor. In comparison, neither the intact insulin receptor nor the beta-chain kinase domain was able to phosphorylate PLC-gamma to a significant extent. Also, insulin failed to stimulate the phosphorylation of PLC-gamma in NIH 3T3/HIR cells, which overexpress the human insulin receptor. Thus PLC-gamma is not a phosphorylation substrate for the insulin receptor in vitro or in the intact cell. Images PMID:2153302

  5. Demonstration of the insulin receptor in vivo in rabbits and its possible role as a reservoir for the plasma hormone.

    PubMed Central

    Zeleznik, A J; Roth, J

    1978-01-01

    Based on studies of the interaction of insulin with its receptors in vitro, we calculated that a receptor compartment should be measurable directly in vivo. For this purpose, rabbits were injected intravenously with a labeled insulin that has low affinity for receptors in combination with a radioiodinated insulin that has high affinity for receptors. Plasma concentrations of labeled insulins were measured at selected intervals after injection. Apparent volumes of distribution were calculated by extrapolation of plasma distribution were calculated by extrapolation of plasma disappearance curves; high affinity insulins consistently distributed into spaces that were two-three times greater than those of the low affinity insulins. Injections of unlabeled pork insulin before tracer insulins decreased the distribution space of the high affinity insulin in a dose-dependent manner while having little or no effect on the distribution space of the low affinity labeled insulin. When unlabeled insulin was injected after the tracer insulins, there was an immediate rise in the plasma concentration of the high affinity insulin with only a slight change in the plasma concentration of the low affinity insulin. These results demonstrate that high affinity insulins distribute into a body compartment which has many properties of the insulin receptor previously studied in vitro. This receptor compartment: (a) recognizes insulins based on their biological potencies; (b) is saturated by elevated concentrations of insulin; and (c) insulin bound to receptors is in equilibrium with free hormone in plasma. Further, the bound to free ratios for hormone, calculated from these data, suggest that in vivo greater than 50% of the extrapancreatic insulin is bound to receptors during normal physiological states. PMID:659598

  6. Effect of insulin on weight loss and tumour growth in a cachexia model.

    PubMed Central

    Beck, S. A.; Tisdale, M. J.

    1989-01-01

    A comparison has been made between the effects of daily insulin injection and a ketogenic diet on weight loss and tumour weight in an experimental model of cancer cachexia (MAC16). Weight loss associated with the MAC16 tumour was significantly reduced both by a ketogenic diet (80% MCT) and by daily insulin injections without an increase in either food or water consumption. Animals fed the 80% MCT diet had a significantly reduced tumour weight compared with controls fed a normal laboratory diet, while in animals administered 20 U insulin kg-1 day-1 the tumour weight was 50% greater than in saline infused controls. The stimulation of tumour growth by insulin was counteracted by the inclusion of 3-hydroxybutyrate in the drinking water without any alteration in the extent of weight loss. Depletion of both carcass fat and muscle dry weight in animals bearing the MAC16 tumour was reversed in animals administered either insulin or an 80% MCT diet. Animals bearing the MAC16 tumour had a reduced nitrogen balance compared with non-tumour-bearing controls, mainly due to excess urea excretion, and this was reversed towards control values in animals fed an 80% MCT diet, but not in animals administered insulin. These results suggest that a ketogenic diet is more effective than insulin administration in reversing the cachectic process and has the advantage of a concomitant reduction in tumour weight. PMID:2736199

  7. Molecular Basis of Signaling Specificity of Insulin and IGF Receptors: Neglected Corners and Recent Advances

    PubMed Central

    Siddle, Kenneth

    2011-01-01

    Insulin and insulin-like growth factor (IGF) receptors utilize common phosphoinositide 3-kinase/Akt and Ras/extracellular signal-regulated kinase signaling pathways to mediate a broad spectrum of “metabolic” and “mitogenic” responses. Specificity of insulin and IGF action in vivo must in part reflect expression of receptors and responsive pathways in different tissues but it is widely assumed that it is also determined by the ligand binding and signaling mechanisms of the receptors. This review focuses on receptor-proximal events in insulin/IGF signaling and examines their contribution to specificity of downstream responses. Insulin and IGF receptors may differ subtly in the efficiency with which they recruit their major substrates (IRS-1 and IRS-2 and Shc) and this could influence effectiveness of signaling to “metabolic” and “mitogenic” responses. Other substrates (Grb2-associated binder, downstream of kinases, SH2Bs, Crk), scaffolds (RACK1, β-arrestins, cytohesins), and pathways (non-receptor tyrosine kinases, phosphoinositide kinases, reactive oxygen species) have been less widely studied. Some of these components appear to be specifically involved in “metabolic” or “mitogenic” signaling but it has not been shown that this reflects receptor-preferential interaction. Very few receptor-specific interactions have been characterized, and their roles in signaling are unclear. Signaling specificity might also be imparted by differences in intracellular trafficking or feedback regulation of receptors, but few studies have directly addressed this possibility. Although published data are not wholly conclusive, no evidence has yet emerged for signaling mechanisms that are specifically engaged by insulin receptors but not IGF receptors or vice versa, and there is only limited evidence for differential activation of signaling mechanisms that are common to both receptors. Cellular context, rather than intrinsic receptor activity, therefore appears

  8. Differential phosphorylation of the progesterone receptor by insulin, epidermal growth factor, and platelet-derived growth factor receptor tyrosine protein kinases.

    PubMed

    Woo, D D; Fay, S P; Griest, R; Coty, W; Goldfine, I; Fox, C F

    1986-01-01

    Purified preparations of insulin, epidermal growth factor (EGF), and platelet-derived growth factor (PDGF) receptors were compared for their abilities to phosphorylate purified hen oviduct progesterone receptors. The specific activities of all three peptide hormone-induced receptor kinases were first defined using a synthetic tridecapeptide tyrosine protein kinase substrate. Next, equivalent ligand-activated activities of the three receptor kinases were tested for their abilities to phosphorylate hen oviduct progesterone receptor. Both the insulin and EGF receptors phosphorylated progesterone receptor at high affinity, exclusively at tyrosine residues and with maximal stoichiometries that were near unity. In contrast, the PDGF receptor did not recognize progesterone receptor as a substrate. Insulin decreased the Km of the insulin receptor for progesterone receptor subunits as substrates, but had no significant effect on Vmax values. On the other hand, EGF increased the Vmax of the EGF receptor for progesterone receptor subunits as substrates. Phosphorylation of progesterone receptor by the insulin and EGF receptor kinases differed in two additional ways. 1) EGF-activated receptor phosphorylated the 80- and 105-kDa progesterone receptor subunits to an equal extent, whereas insulin-activated receptor preferentially phosphorylated the 80-kDa subunit. 2) Phosphopeptide fingerprinting analyses revealed that while insulin and EGF receptors phosphorylated one identical major site on both progesterone receptor subunits, they differed in their specificities for other sites. PMID:3001059

  9. Partial rescue of insulin receptor-deficient mice by transgenic complementation with an activated insulin receptor in the liver.

    PubMed

    Baudry, Anne; Jackerott, Malene; Lamothe, Betty; Kozyrev, Sergey V; Leroux, Loïc; Durel, Béatrice; Saint-Just, Susan; Joshi, Rajiv L

    2002-10-16

    Insulin receptor (IR)-deficient mice develop severe diabetes mellitus, diabetic ketoacidosis (DKA) and liver steatosis and die within 1 week after birth. We examined in this work whether the metabolic phenotype of IR(-/-) mutants could be improved by transgenic complementation with IR selectively in the liver. We first generated transgenic mice expressing a human DNA complementary to RNA encoding a truncated constitutively activated form of IR (IRdelta) under the control of liver-specific phenylalanine hydroxylase (PAH) gene promoter. These mice presented more pronounced fasting hypoglycemia and showed slightly improved glucose tolerance as compared to controls. The transgenic mice were crossed with IR(+/-) mutants to generate IR(-/-) mice carrying the PAH-IRDelta transgene. Although such mutants developed glycosuria, DKA was delayed by more than 1 week and survival was prolonged to 8-20 days in approximately 10% of mice. In these partially rescued pups, serum glucose and triglyceride levels were lowered, hepatic glycogen stores were reconstituted and liver steatosis was absent as compared with pups which developed strong DKA and died earlier. Thus, lack of insulin action in the liver is responsible in large part for the metabolic disorders seen in IR(+/-) mice. This study should stimulate interest in therapeutic strategies aimed at improving hepatic function in diabetes.

  10. GLP-1 Receptor Agonists: Nonglycemic Clinical Effects in Weight Loss and Beyond

    PubMed Central

    Ryan, Donna; Acosta, Andres

    2015-01-01

    Obective Glucagon-like peptide-1 (GLP-1) receptor agonists are indicated for treatment of type 2 diabetes since they mimic the actions of native GLP-1 on pancreatic islet cells, stimulating insulin release, while inhibiting glucagon release, in a glucose-dependent manner. The observation of weight loss has led to exploration of their potential as antiobesity agents, with liraglutide 3.0 mg day−1 approved for weight management in the US on December 23, 2014, and in the EU on March 23, 2015. This review examines the potential nonglycemic effects of GLP-1 receptor agonists. Methods A literature search was conducted to identify preclinical and clinical evidence on nonglycemic effects of GLP-1 receptor agonists. Results GLP-1 receptors are distributed widely in a number of tissues in humans, and their effects are not limited to the well-recognized effects on glycemia. Nonglycemic effects include weight loss, which is perhaps the most widely recognized nonglycemic effect. In addition, effects on the cardiovascular, neurologic, and renal systems and on taste perception may occur independently of weight loss. Conclusions GLP-1 receptor agonists may provide other nonglycemic clinical effects besides weight loss. Understanding these effects is important for prescribers in using GLP-1 receptor agonists for diabetic patients, but also if approved for chronic weight management. PMID:25959380

  11. Inter-domain tagging implicates caveolin-1 in insulin receptor trafficking and Erk signaling bias in pancreatic beta-cells

    PubMed Central

    Boothe, Tobias; Lim, Gareth E.; Cen, Haoning; Skovsø, Søs; Piske, Micah; Li, Shu Nan; Nabi, Ivan R.; Gilon, Patrick; Johnson, James D.

    2016-01-01

    Objective The role and mechanisms of insulin receptor internalization remain incompletely understood. Previous trafficking studies of insulin receptors involved fluorescent protein tagging at their termini, manipulations that may be expected to result in dysfunctional receptors. Our objective was to determine the trafficking route and molecular mechanisms of functional tagged insulin receptors and endogenous insulin receptors in pancreatic beta-cells. Methods We generated functional insulin receptors tagged with pH-resistant fluorescent proteins between domains. Confocal, TIRF and STED imaging revealed a trafficking pattern of inter-domain tagged insulin receptors and endogenous insulin receptors detected with antibodies. Results Surprisingly, interdomain-tagged and endogenous insulin receptors in beta-cells bypassed classical Rab5a- or Rab7-mediated endocytic routes. Instead, we found that removal of insulin receptors from the plasma membrane involved tyrosine-phosphorylated caveolin-1, prior to trafficking within flotillin-1-positive structures to lysosomes. Multiple methods of inhibiting caveolin-1 significantly reduced Erk activation in vitro or in vivo, while leaving Akt signaling mostly intact. Conclusions We conclude that phosphorylated caveolin-1 plays a role in insulin receptor internalization towards lysosomes through flotillin-1-positive structures and that caveolin-1 helps bias physiological beta-cell insulin signaling towards Erk activation. PMID:27110488

  12. [PPAR receptors and insulin sensitivity: new agonists in development].

    PubMed

    Pégorier, J-P

    2005-04-01

    Thiazolidinediones (or glitazones) are synthetic PPARgamma (Peroxisome Proliferator-Activated Receptors gamma) ligands with well recognized effects on glucose and lipid metabolism. The clinical use of these PPARgamma agonists in type 2 diabetic patients leads to an improved glycemic control and an inhanced insulin sensitivity, and at least in animal models, to a protective effect on pancreatic beta-cell function. However, they can produce adverse effects, generally mild or moderate, but some of them (mainly peripheral edema and weight gain) may conduct to treatment cessation. Several pharmacological classes are currently in pre-clinical or clinical development, with the objective to retain the beneficial metabolic properties of PPARgamma agonists, either alone or in association with the PPARalpha agonists (fibrates) benefit on lipid profile, but devoid of the side-effects on weight gain and fluid retention. These new pharmacological classes: partial PPARgamma agonists, PPARgamma antagonists, dual PPARalpha/PPARgamma agonists, pan PPARalpha/beta(delta)/gamma agonists, RXR receptor agonists (rexinoids), are presented in this review. Main results from in vitro cell experiments and animal model studies are discussed, as well as the few published short-term studies in type 2 diabetic patients. PMID:15959400

  13. Arsenite and insulin exhibit opposing effects on epidermal growth factor receptor and keratinocyte proliferative potential

    SciTech Connect

    Patterson, Timothy J.; Rice, Robert H. . E-mail: rhrice@ucdavis.edu

    2007-05-15

    Previous work has suggested that arsenic exposure contributes to skin carcinogenesis by preserving the proliferative potential of human epidermal keratinocytes, thereby slowing the exit of putative target stem cells into the differentiation pathway. To find a molecular basis for this action, present work has explored the influence of arsenite on keratinocyte responses to epidermal growth factor (EGF). The ability of cultured keratinocytes to found colonies upon passaging several days after confluence was preserved by arsenite and EGF in an additive fashion, but neither was effective when the receptor tyrosine kinase activity was inhibited. Arsenite prevented the loss of EGF receptor protein and phosphorylation of tyrosine 1173, preserving its capability to signal. The level of nuclear {beta}-catenin was higher in cells treated with arsenite and EGF in parallel to elevated colony forming ability, and expression of a dominant negative {beta}-catenin suppressed the increase in both colony forming ability and yield of putative stem cells induced by arsenite and EGF. As judged by expression of three genes regulated by {beta}-catenin, this transcription factor had substantially higher activity in the arsenite/EGF-treated cells. Trivalent antimony exhibited the same effects as arsenite. A novel finding is that insulin in the medium induced the loss of EGF receptor protein, which was largely prevented by arsenite exposure.

  14. Early metabolic markers that anticipate loss of insulin independence in type 1 diabetic islet allograft recipients.

    PubMed

    Hirsch, D; Odorico, J; Danobeitia, J S; Alejandro, R; Rickels, M R; Hanson, M; Radke, N; Baidal, D; Hullett, D; Naji, A; Ricordi, C; Kaufman, D; Fernandez, L

    2012-05-01

    The objective of this study was to identify predictors of insulin independence and to establish the best clinical tools to follow patients after pancreatic islet transplantation (PIT). Sequential metabolic responses to intravenous (I.V.) glucose (I.V. glucose tolerance test [IVGTT]), arginine and glucose-potentiated arginine (glucose-potentiated arginine-induced insulin secretion [GPAIS]) were obtained from 30 patients. We determined the correlation between transplanted islet mass and islet engraftment and tested the ability of each assay to predict return to exogenous insulin therapy. We found transplanted islet mass within an average of 16 709 islet equivalents per kg body weight (IEQ/kg BW; range between 6602 and 29 614 IEQ/kg BW) to be a poor predictor of insulin independence at 1 year, having a poor correlation between transplanted islet mass and islet engraftment. Acute insulin response to IVGTT (AIR(GLU) ) and GPAIS (AIR(max) ) were the most accurate methods to determine suboptimal islet mass engraftment. AIR(GLU) performed 3 months after transplant also proved to be a robust early metabolic marker to predict return to insulin therapy and its value was positively correlated with duration of insulin independence. In conclusion, AIR(GLU) is an early metabolic assay capable of anticipating loss of insulin independence at 1 year in T1D patients undergoing PIT and constitutes a valuable, simple and reliable method to follow patients after transplant.

  15. Differential Effects of Camel Milk on Insulin Receptor Signaling – Toward Understanding the Insulin-Like Properties of Camel Milk

    PubMed Central

    Abdulrahman, Abdulrasheed O.; Ismael, Mohammad A.; Al-Hosaini, Khaled; Rame, Christelle; Al-Senaidy, Abdulrahman M.; Dupont, Joëlle; Ayoub, Mohammed Akli

    2016-01-01

    Previous studies on the Arabian camel (Camelus dromedarius) showed beneficial effects of its milk reported in diverse models of human diseases, including a substantial hypoglycemic activity. However, the cellular and molecular mechanisms involved in such effects remain completely unknown. In this study, we hypothesized that camel milk may act at the level of human insulin receptor (hIR) and its related intracellular signaling pathways. Therefore, we examined the effect of camel milk on the activation of hIR transiently expressed in human embryonic kidney 293 (HEK293) cells using bioluminescence resonance energy transfer (BRET) technology. BRET was used to assess, in live cells and real-time, the physical interaction between hIR and insulin receptor signaling proteins (IRS1) and the growth factor receptor-bound protein 2 (Grb2). Our data showed that camel milk did not promote any increase in the BRET signal between hIR and IRS1 or Grb2 in the absence of insulin stimulation. However, it significantly potentiated the maximal insulin-promoted BRET signal between hIR and Grb2 but not IRS1. Interestingly, camel milk appears to differentially impact the downstream signaling since it significantly activated ERK1/2 and potentiated the insulin-induced ERK1/2 but not Akt activation. These observations are to some extent consistent with the BRET data since ERK1/2 and Akt activation are known to reflect the engagement of Grb2 and IRS1 pathways, respectively. The preliminary fractionation of camel milk suggests the peptide/protein nature of the active component in camel milk. Together, our study demonstrates for the first time an allosteric effect of camel milk on insulin receptor conformation and activation with differential effects on its intracellular signaling. These findings should help to shed more light on the hypoglycemic activity of camel milk with potential therapeutic applications. PMID:26858689

  16. Differential Effects of Camel Milk on Insulin Receptor Signaling - Toward Understanding the Insulin-Like Properties of Camel Milk.

    PubMed

    Abdulrahman, Abdulrasheed O; Ismael, Mohammad A; Al-Hosaini, Khaled; Rame, Christelle; Al-Senaidy, Abdulrahman M; Dupont, Joëlle; Ayoub, Mohammed Akli

    2016-01-01

    Previous studies on the Arabian camel (Camelus dromedarius) showed beneficial effects of its milk reported in diverse models of human diseases, including a substantial hypoglycemic activity. However, the cellular and molecular mechanisms involved in such effects remain completely unknown. In this study, we hypothesized that camel milk may act at the level of human insulin receptor (hIR) and its related intracellular signaling pathways. Therefore, we examined the effect of camel milk on the activation of hIR transiently expressed in human embryonic kidney 293 (HEK293) cells using bioluminescence resonance energy transfer (BRET) technology. BRET was used to assess, in live cells and real-time, the physical interaction between hIR and insulin receptor signaling proteins (IRS1) and the growth factor receptor-bound protein 2 (Grb2). Our data showed that camel milk did not promote any increase in the BRET signal between hIR and IRS1 or Grb2 in the absence of insulin stimulation. However, it significantly potentiated the maximal insulin-promoted BRET signal between hIR and Grb2 but not IRS1. Interestingly, camel milk appears to differentially impact the downstream signaling since it significantly activated ERK1/2 and potentiated the insulin-induced ERK1/2 but not Akt activation. These observations are to some extent consistent with the BRET data since ERK1/2 and Akt activation are known to reflect the engagement of Grb2 and IRS1 pathways, respectively. The preliminary fractionation of camel milk suggests the peptide/protein nature of the active component in camel milk. Together, our study demonstrates for the first time an allosteric effect of camel milk on insulin receptor conformation and activation with differential effects on its intracellular signaling. These findings should help to shed more light on the hypoglycemic activity of camel milk with potential therapeutic applications. PMID:26858689

  17. Coated vesicles participate in the receptor-mediated endocytosis of insulin

    PubMed Central

    1983-01-01

    We have purified coated vesicles from rat liver by differential ultracentrifugation. Electron micrographs of these preparations reveal only the polyhedral structures typical of coated vesicles. SDS PAGE of the coated vesicle preparation followed by Coomassie Blue staining of proteins reveals a protein composition also typical of coated vesicles. We determined that these rat liver coated vesicles possess a latent insulin binding capability. That is, little if any specific binding of 125I-insulin to coated vesicles is observed in the absence of detergent. However, coated vesicles treated with the detergent octyl glucoside exhibit a substantial specific 125I-insulin binding capacity. We visualized the insulin binding structure of coated vesicles by cross- linking 125I-insulin to detergent-solubilized coated vesicles using the bifunctional reagent disuccinimidyl suberate followed by electrophoresis and autoradiography. The receptor structure thus identified is identical to that of the high-affinity insulin receptor present in a variety of tissues. We isolated liver coated vesicles from rats which had received injections of 125I-insulin in the hepatic portal vein. We found that insulin administered in this fashion was rapidly and specifically taken up by liver coated vesicles. Taken together, these data are compatible with a functional role for coated vesicles in the receptor-mediated endocytosis of insulin. PMID:6131074

  18. Hepatocyte Toll-like receptor 4 regulates obesity-induced inflammation and insulin resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chronic low-grade inflammation is a hallmark of obesity and thought to contribute to the development of obesity-related insulin resistance. Toll-like receptor 4 (Tlr4) is a key mediator of pro-inflammatory responses. Mice lacking Tlr4s are protected from diet-induced insulin resistance and inflammat...

  19. Localization of insulin receptor mRNA in rat brain by in situ hybridization

    SciTech Connect

    Marks, J.L.; Porte, D. Jr.; Stahl, W.L.; Baskin, D.G. )

    1990-12-01

    Insulin receptor mRNA was demonstrated in rat brain slices by in situ hybridization with three {sup 35}S-oligonucleotide probes and contact film autoradiography. Specificity was confirmed by showing that (a) excess unlabeled probe abolished the signal, (b) an oligonucleotide probe for rat neuropeptide Y mRNA showed a different distribution of hybridization signal, and (c) the distribution of insulin receptor binding was consistent with the distribution of insulin receptor mRNA. Insulin receptor mRNA was most abundant in the granule cell layers of the olfactory bulb, cerebellum and dentate gyrus, in the pyramidal cell body layers of the pyriform cortex and hippocampus, in the choroid plexus and in the arcuate nucleus of the hypothalamus.

  20. Characterization of a second ligand binding site of the insulin receptor

    SciTech Connect

    Hao Caili; Whittaker, Linda; Whittaker, Jonathan . E-mail: jonathan.whittaker@case.edu

    2006-08-18

    Insulin binding to its receptor is characterized by high affinity, curvilinear Scatchard plots, and negative cooperativity. These properties may be the consequence of binding of insulin to two receptor binding sites. The N-terminal L1 domain and the C-terminus of the {alpha} subunit contain one binding site. To locate a second site, we examined the binding properties of chimeric receptors in which the L1 and L2 domains and the first Fibronectin Type III repeat of the insulin-like growth factor-I receptor were replaced by corresponding regions of the insulin receptor. Substitutions of the L2 domain and the first Fibronectin Type III repeat together with the L1 domain produced 80- and 300-fold increases in affinity for insulin. Fusion of these domains to human immunoglobulin Fc fragment produced a protein which bound insulin with a K {sub d} of 2.9 nM. These data strongly suggest that these domains contain an insulin binding site.

  1. Cellular effects of phosphotyrosine-binding domain inhibitors on insulin receptor signaling and trafficking.

    PubMed Central

    Giorgetti-Peraldi, S; Ottinger, E; Wolf, G; Ye, B; Burke, T R; Shoelson, S E

    1997-01-01

    Shc and insulin receptor substrate 1 (IRS-1) are cytoplasmic substrates of tyrosine kinase receptors that engage, localize, and activate downstream SH2 enzymes. Each contains a phosphotyrosine-binding (PTB) domain that is structurally unrelated to SH2 domains. We have designed high-affinity, cellular inhibitors of the Shc PTB domain by incorporating nonnatural, phosphatase-resistant amino acids into short peptides. None of the inhibitors bind the IRS-1 PTB domain, consistent with distinct specificities for domains. The best inhibitor of the Shc domain was introduced by electroporation into Rat1 fibroblasts that express human insulin receptors. Insulin-stimulated phosphorylation of Shc was inhibited, with no effect on IRS-1, and downstream effects on mitogen-activated protein kinase and DNA synthesis were both inhibited. The PTB domain inhibitor had less influence on epidermal growth factor-induced effects and essentially no impact on serum- or phorbol ester-induced effects. The inhibitor did not affect insulin internalization and its degradation. We conclude that the PTB domain of Shc is critical for its phosphorylation by the insulin receptor, that Shc is an important mediator of insulin's mitogenic effects, and that Shc is not central to insulin receptor cycling in these cells. PTB domains can be inhibited selectively in cells and represent potential targets for drug discovery. PMID:9032245

  2. Decreased Insulin Receptors but Normal Glucose Metabolism in Duchenne Muscular Dystrophy

    NASA Astrophysics Data System (ADS)

    de Pirro, Roberto; Lauro, Renato; Testa, Ivano; Ferretti, Ginofabrizio; de Martinis, Carlo; Dellantonio, Renzo

    1982-04-01

    Compared to matched controls, 17 patients with Duchenne muscular dystrophy showed decreased insulin binding to monocytes due to decreased receptor concentration. These patients showed no signs of altered glucose metabolism and retrospective analysis of the clinical records of a further 56 such patients revealed no modification in carbohydrate metabolism. These data suggest that reduced insulin receptor number does not produce overt modifications of glucose metabolism in Duchenne muscular dystrophy.

  3. Structural insights into ligand-induced activation of the insulin receptor

    SciTech Connect

    Ward, C.; Lawrence, M.; Streltsov, V.; Garrett, T.; McKern, N.; Lou, M.-Z.; Lovrecz, G.; Adams, T.

    2008-04-29

    The current model for insulin binding to the insulin receptor proposes that there are two binding sites, referred to as sites 1 and 2, on each monomer in the receptor homodimer and two binding surfaces on insulin, one involving residues predominantly from the dimerization face of insulin (the classical binding surface) and the other residues from the hexamerization face. High-affinity binding involves one insulin molecule using its two surfaces to make bridging contacts with site 1 from one receptor monomer and site 2 from the other. Whilst the receptor dimer has two identical site 1-site 2 pairs, insulin molecules cannot bridge both pairs simultaneously. Our structures of the insulin receptor (IR) ectodomain dimer and the L1-CR-L2 fragments of IR and insulin-like growth factor receptor (IGF-1R) explain many of the features of ligand-receptor binding and allow the two binding sites on the receptor to be described. The IR dimer has an unexpected folded-over conformation which places the C-terminal surface of the first fibronectin-III domain in close juxtaposition to the known L1 domain ligand-binding surface suggesting that the C-terminal surface of FnIII-1 is the second binding site involved in high-affinity binding. This is very different from previous models based on three-dimensional reconstruction from scanning transmission electron micrographs. Our single-molecule images indicate that IGF-1R has a morphology similar to that of IR. In addition, the structures of the first three domains (L1-CR-L2) of the IR and IGF-1R show that there are major differences in the two regions governing ligand specificity. The implications of these findings for ligand-induced receptor activation will be discussed. This review summarizes the key findings regarding the discovery and characterization of the insulin receptor, the identification and arrangement of its structural domains in the sequence and the key features associated with ligand binding. The remainder of the review

  4. Effects of sleep restriction on glucose control and insulin secretion during diet-induced weight loss

    PubMed Central

    Nedeltcheva, A. V.; Imperial, J. G.; Penev, P. D.

    2012-01-01

    Insufficient sleep is associated with changes in glucose tolerance, insulin secretion, and insulin action. Despite widespread use of weight-loss diets for metabolic risk reduction, the effects of insufficient sleep on glucose regulation in overweight dieters are not known. To examine the consequences of recurrent sleep restriction on 24-hour blood glucose control during diet-induced weight loss, 10 overweight and obese adults (3F/7M; mean [SD] age 41 [5] y; BMI 27.4 [2.0] kg/m2) completed two 14-day treatments with hypocaloric diet and 8.5 or 5.5-h nighttime sleep opportunity in random order 7 [3] months apart. Oral and intravenous glucose tolerance test (IVGTT) data, fasting lipids and free-fatty acids (FFA), and 24-hour blood glucose, insulin, C-peptide, and counter-regulatory hormone measurements were collected after each treatment. Participants had comparable weight loss (1.0 [0.3] BMI units) during each treatment. Bedtime restriction reduced sleep by 131 [30] min/day. Recurrent sleep curtailment decreased 24-hour serum insulin concentrations (i.e. enhanced 24-hour insulin economy) without changes in oral glucose tolerance and 24-hour glucose control. This was accompanied by a decline in fasting blood glucose, increased fasting FFA which suppressed normally following glucose ingestion, and lower total and LDL cholesterol concentrations. Sleep-loss-related changes in counter-regulatory hormone secretion during the IVGTT limited the utility of the test in this study. In conclusion, sleep restriction enhanced 24-hour insulin economy without compromising glucose homeostasis in overweight individuals placed on a balanced hypocaloric diet. The changes in fasting blood glucose, insulin, lipid and FFA concentrations in sleep-restricted dieters resembled the pattern of human metabolic adaptation to reduced carbohydrate availability. PMID:22513492

  5. Adipose tissue monomethyl branched chain fatty acids and insulin sensitivity: effects of obesity and weight loss

    PubMed Central

    Su, Xiong; Magkos, Faidon; Zhou, Dequan; Eagon, J. Christopher; Fabbrini, Elisa; Okunade, Adewole L.; Klein, Samuel

    2014-01-01

    Objective An increase in circulating branched-chain amino acids (BCAA) is associated with insulin resistance. Adipose tissue is a potentially important site for BCAA metabolism. We evaluated whether monomethyl branched chain fatty acids (mmBCFA) in adipose tissue, which are likely derived from BCAA catabolism, are associated with insulin sensitivity. Design and Methods Insulin-stimulated glucose disposal was determined by using the hyperinsulinemic-euglycemic clamp procedure with stable isotope glucose tracer infusion, in 9 lean and 9 obese subjects, and in a separate group of 9 obese subjects before and 1 year after Roux-en-Y gastric bypass (RYGB) surgery (38% weight loss). Adipose tissue mmBCFA content was measured in tissue biopsies taken in the basal state. Results Total adipose tissue mmBCFA content was ~30% lower in obese than lean subjects (P = 0.02), and increased by ~65% after weight loss in the RYGB group (P = 0.01). Adipose tissue mmBCFA content correlated positively with skeletal muscle insulin sensitivity (R2 = 35%, P = 0.01, n = 18). Conclusions These results demonstrate a novel association between adipose tissue mmBCFA content and obesity-related insulin resistance. Additional studies are needed to determine whether the association between adipose tissue mmBCFA and muscle insulin sensitivity is causal or a simple association. PMID:25328153

  6. Targeting Anti-Insulin B Cell Receptors Improves Receptor Editing in Type 1 Diabetes-Prone Mice.

    PubMed

    Bonami, Rachel H; Thomas, James W

    2015-11-15

    Autoreactive B lymphocytes that commonly arise in the developing repertoire can be salvaged by receptor editing, a central tolerance mechanism that alters BCR specificity through continued L chain rearrangement. It is unknown whether autoantigens with weak cross-linking potential, such as insulin, elicit receptor editing, or whether this process is dysregulated in related autoimmunity. To resolve these issues, we developed an editing-competent model in which anti-insulin Vκ125 was targeted to the Igκ locus and paired with anti-insulin VH125Tg. Physiologic, circulating insulin increased RAG-2 expression and was associated with BCR replacement that eliminated autoantigen recognition in a proportion of developing anti-insulin B lymphocytes. The proportion of anti-insulin B cells that underwent receptor editing was reduced in the type 1 diabetes-prone NOD strain relative to a nonautoimmune strain. Resistance to editing was associated with increased surface IgM expression on immature (but not transitional or mature) anti-insulin B cells in the NOD strain. The actions of mAb123 on central tolerance were also investigated, because selective targeting of insulin-occupied BCR by mAb123 eliminates anti-insulin B lymphocytes and prevents type 1 diabetes. Autoantigen targeting by mAb123 increased RAG-2 expression and dramatically enhanced BCR replacement in newly developed B lymphocytes. Administering F(ab')2123 induced IgM downregulation and reduced the frequency of anti-insulin B lymphocytes within the polyclonal repertoire of VH125Tg/NOD mice, suggesting enhanced central tolerance by direct BCR interaction. These findings indicate that weak or faulty checkpoints for central tolerance can be overcome by autoantigen-specific immunomodulatory therapy.

  7. All-Atom Structural Models of the Transmembrane Domains of Insulin and Type 1 Insulin-Like Growth Factor Receptors

    PubMed Central

    Mohammadiarani, Hossein; Vashisth, Harish

    2016-01-01

    The receptor tyrosine kinase superfamily comprises many cell-surface receptors including the insulin receptor (IR) and type 1 insulin-like growth factor receptor (IGF1R) that are constitutively homodimeric transmembrane glycoproteins. Therefore, these receptors require ligand-triggered domain rearrangements rather than receptor dimerization for activation. Specifically, binding of peptide ligands to receptor ectodomains transduces signals across the transmembrane domains for trans-autophosphorylation in cytoplasmic kinase domains. The molecular details of these processes are poorly understood in part due to the absence of structures of full-length receptors. Using MD simulations and enhanced conformational sampling algorithms, we present all-atom structural models of peptides containing 51 residues from the transmembrane and juxtamembrane regions of IR and IGF1R. In our models, the transmembrane regions of both receptors adopt helical conformations with kinks at Pro961 (IR) and Pro941 (IGF1R), but the C-terminal residues corresponding to the juxtamembrane region of each receptor adopt unfolded and flexible conformations in IR as opposed to a helix in IGF1R. We also observe that the N-terminal residues in IR form a kinked-helix sitting at the membrane–solvent interface, while homologous residues in IGF1R are unfolded and flexible. These conformational differences result in a larger tilt-angle of the membrane-embedded helix in IGF1R in comparison to IR to compensate for interactions with water molecules at the membrane–solvent interfaces. Our metastable/stable states for the transmembrane domain of IR, observed in a lipid bilayer, are consistent with a known NMR structure of this domain determined in detergent micelles, and similar states in IGF1R are consistent with a previously reported model of the dimerized transmembrane domains of IGF1R. Our all-atom structural models suggest potentially unique structural organization of kinase domains in each receptor. PMID

  8. Insulin binding and receptor tyrosine kinase activity in skeletal muscle of carnivorous and omnivorous fish.

    PubMed

    Párrizas, M; Planas, J; Plisetskaya, E M; Gutiérrez, J

    1994-06-01

    We characterized the insulin receptors in skeletal muscle from several fish species with different nutritional preferences: brown trout (Salmo trutta fario), gilthead sea bream (Sparus aurata), tilapia (Tilapia mossambica), and carp (Cyprinus carpio), semipurified by affinity chromatography (wheat germ agglutinin-agarose). Total specific binding and number of receptors per unit weight of piscine white skeletal muscle were lower than those values found in mammalian skeletal muscle. The same parameters in carp muscle receptor preparations were severalfold higher than in trout muscle (binding capacity 440 +/- 47 fmol/mg glycoprotein in carp and 82 +/- 23 fmol/mg glycoprotein in trout). Piscine insulin receptors phosphorylated exogenous substrate poly(Glu,Tyr) but less so than mammalian receptors. Tyrosine kinase activity of receptors, calculated as percent of 32P incorporated into substrate in the presence of insulin compared with basal incorporation, was also highest in carp (210 +/- 4%) and lowest in trout (150 +/- 2%). In both trout and carp deprived of food for 15 days, specific binding of insulin decreased. Nevertheless, differences between the two species were retained. Our results demonstrate that particular properties of insulin receptors in fish skeletal muscle may be related to nutritional preferences. This finding coincides with the phenomenon of differential glucose tolerance in fish: carnivorous fish, such as trout, are less tolerant, whereas omnivorous fish, such as carp, readily utilize a carbohydrate-rich diet. PMID:8024051

  9. Structural differences between liver- and muscle-derived insulin receptors in rats

    SciTech Connect

    Burant, C.F.; Treutelaar, M.K.; Block, N.E.; Buse, M.G.

    1986-11-05

    The structure of insulin receptors, solubilized from rat skeletal muscle and liver, was studied. The ..cap alpha.. subunit was identified by specific cross-linking to A14 /sup 125/I-insulin with disuccinimidyl suberate. Muscle- and liver-derived ..cap alpha.. subunits migrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with a M/sub r/ of 131,000 and 135,000, respectively. There was no significant difference in insulin binding affinity. Treatment of cross-linked, immunoprecipitated receptors with either neuraminidase or endoglycosidase H decreased the M/sub r/ of muscle- and liver-derived ..cap alpha.. subunits but did not affect the difference in M/sub r/. Autophosphorylated ..beta.. subunits migrated with a M/sub r/ of 98,000 for muscle and 101,000 for liver. After partial V8 digestion of autophosphorylated, immunoprecipitated receptors the major phosphopeptide fragment migrated on SDS-PAGE at M/sub r/ 57,000 from muscle and 60,000 from liver. Glycosidase digestion of autophosphorylated receptors suggested that M/sub r/ heterogeneity was due in part to differences in the sialic acid content of ..beta.. subunits. Muscle and liver are the major target organs of insulin; the apparent heterogeneity of insulin receptor structure may be relevant to tissue-specific differences in insulin action.

  10. Blockade of the Renin-Angiotensin system improves insulin receptor signaling and insulin-stimulated skeletal muscle glucose transport in burn injury.

    PubMed

    Kasper, Sherry O; Phillips, Erin E; Castle, Scott M; Daley, Brian J; Enderson, Blaine L; Karlstad, Michael D

    2011-01-01

    Burn injury is associated with a decline in glucose utilization and insulin sensitivity due to alterations in postreceptor insulin signaling pathways. We have reported that blockade of the renin-angiotensin system with losartan, an angiotensin II type 1 (AT1) receptor blocker, improves whole body insulin sensitivity and glucose metabolism after burn injury. This study examines whether losartan improves insulin signaling pathways and insulin-stimulated glucose transport in skeletal muscle in burn-injured rats. Rats were injured by a 30% full-skin-thickness scalding burn and treated with losartan or placebo for 3 days after burn. Insulin signaling pathways were investigated in rectus abdominus muscle taken before and 90 s after intraportal insulin injection (10 U·kg). Insulin-stimulated insulin receptor substrate 1-associated phosphatidylinositol 3-kinase and plasma membrane-associated GLUT4 transporter were substantially increased with losartan treatment in burn-injured animals (59% above sham). Serine phosphorylated AKT/PKB was decreased with burn injury, and this decrease was attenuated with losartan treatment. In a separate group of rats, the effect of insulin on 2-deoxyglucose transport was significantly impaired in burned as compared with sham soleus muscles, in vitro; however, treatment of burned rats with losartan completely abolished the reduction of insulin-stimulated 2-deoxyglucose transport. These findings demonstrate a cross talk between the AT1 and insulin receptor that negatively modulates insulin receptor signaling and suggest a potential role of renin-angiotensin system blockade as a therapeutic strategy for enhancing insulin sensitivity in skeletal muscle and improving whole-body glucose homeostasis in burn injury.

  11. Acute stimulation of brain mu opioid receptors inhibits glucose-stimulated insulin secretion via sympathetic innervation.

    PubMed

    Tudurí, Eva; Beiroa, Daniel; Stegbauer, Johannes; Fernø, Johan; López, Miguel; Diéguez, Carlos; Nogueiras, Rubén

    2016-11-01

    Pancreatic insulin-secreting β-cells express opioid receptors, whose activation by opioid peptides modulates hormone secretion. Opioid receptors are also expressed in multiple brain regions including the hypothalamus, where they play a role in feeding behavior and energy homeostasis, but their potential role in central regulation of glucose metabolism is unknown. Here, we investigate whether central opioid receptors participate in the regulation of insulin secretion and glucose homeostasis in vivo. C57BL/6J mice were acutely treated by intracerebroventricular (i.c.v.) injection with specific agonists for the three main opioid receptors, kappa (KOR), delta (DOR) and mu (MOR) opioid receptors: activation of KOR and DOR did not alter glucose tolerance, whereas activation of brain MOR with the specific agonist DAMGO blunted glucose-stimulated insulin secretion (GSIS), reduced insulin sensitivity, increased the expression of gluconeogenic genes in the liver and, consequently, impaired glucose tolerance. Pharmacological blockade of α2A-adrenergic receptors prevented DAMGO-induced glucose intolerance and gluconeogenesis. Accordingly, DAMGO failed to inhibit GSIS and to impair glucose tolerance in α2A-adrenoceptor knockout mice, indicating that the effects of central MOR activation on β-cells are mediated via sympathetic innervation. Our results show for the first time a new role of the central opioid system, specifically the MOR, in the regulation of insulin secretion and glucose metabolism. PMID:27511839

  12. A Comparative Structural Bioinformatics Analysis of the Insulin Receptor Family Ectodomain Based on Phylogenetic Information

    PubMed Central

    Rentería, Miguel E.; Gandhi, Neha S.; Vinuesa, Pablo; Helmerhorst, Erik; Mancera, Ricardo L.

    2008-01-01

    The insulin receptor (IR), the insulin-like growth factor 1 receptor (IGF1R) and the insulin receptor-related receptor (IRR) are covalently-linked homodimers made up of several structural domains. The molecular mechanism of ligand binding to the ectodomain of these receptors and the resulting activation of their tyrosine kinase domain is still not well understood. We have carried out an amino acid residue conservation analysis in order to reconstruct the phylogeny of the IR Family. We have confirmed the location of ligand binding site 1 of the IGF1R and IR. Importantly, we have also predicted the likely location of the insulin binding site 2 on the surface of the fibronectin type III domains of the IR. An evolutionary conserved surface on the second leucine-rich domain that may interact with the ligand could not be detected. We suggest a possible mechanical trigger of the activation of the IR that involves a slight ‘twist’ rotation of the last two fibronectin type III domains in order to face the likely location of insulin. Finally, a strong selective pressure was found amongst the IRR orthologous sequences, suggesting that this orphan receptor has a yet unknown physiological role which may be conserved from amphibians to mammals. PMID:18989367

  13. Metabolic, anabolic, and mitogenic insulin responses: A tissue-specific perspective for insulin receptor activators

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Insulin acts as the major regulator of the fasting-to-fed metabolic transition by altering substrate metabolism, promoting energy storage, and helping activate protein synthesis. In addition to its glucoregulatory and other metabolic properties, insulin can also act as a growth factor. The metabolic...

  14. Long lasting cadmium intake is associated with reduction of insulin receptors in rat adipocytes.

    PubMed

    Ficková, M; Eybl, V; Kotyzová, D; Micková, V; Möstbök, S; Brtko, J

    2003-12-01

    The effects of chronic cadmium exposure on adipose tissue have not been extensively reported. In adult Wistar male rats we investigated in vivo effect of 6 weeks lasting cadmium intake in drinking tap water (CdCl2 9,7 mg/l). Insulin receptors in isolated adipocytes from epididymal fat and glucose transporter protein GLUT4 content in fat tissue plasma membranes were determined. Control and Cd treated rats had similar water intake with subsequent heavy augmentation of Cd content in liver of experimental animals. In comparison with controls, Cd intake did not influence body mass increment and fat cell size, but significantly increased serum glycemia and moderately elevated insulinemia. Cadmium intake significantly reduced (approximately 50%) both, total insulin receptors number and density of the receptors in fat cells. No differences in the content of GLUT4 in crude plasma membranes of adipose tissue were observed. Diminished insulin receptors in adipocytes could account for diabetogenic effect of long lasting cadmium intake.

  15. Reduced insulin-receptor mediated modulation of striatal dopamine release by basal insulin as a possible contributing factor to hyperdopaminergia in schizophrenia.

    PubMed

    Caravaggio, Fernando; Hahn, Margaret; Nakajima, Shinichiro; Gerretsen, Philip; Remington, Gary; Graff-Guerrero, Ariel

    2015-10-01

    Schizophrenia is a severe and chronic neuropsychiatric disorder which affects 1% of the world population. Using the brain imaging technique positron emission tomography (PET) it has been demonstrated that persons with schizophrenia have greater dopamine transmission in the striatum compared to healthy controls. However, little progress has been made as to elucidating other biological mechanisms which may account for this hyperdopaminergic state in this disease. Studies in animals have demonstrated that insulin receptors are expressed on midbrain dopamine neurons, and that insulin from the periphery acts on these receptors to modify dopamine transmission in the striatum. This is pertinent given that several lines of evidence suggest that insulin receptor functioning may be abnormal in the brains of persons with schizophrenia. Post-mortem studies have shown that persons with schizophrenia have less than half the number of cortical insulin receptors compared to healthy persons. Moreover, these post-mortem findings are unlikely due to the effects of antipsychotic treatment; studies in cell lines and animals suggest antipsychotics enhance insulin receptor functioning. Further, hyperinsulinemia - even prior to antipsychotic use - seems to be related to less psychotic symptoms in patients with schizophrenia. Collectively, these data suggest that midbrain insulin receptor functioning may be abnormal in persons with schizophrenia, resulting in reduced insulin-mediated regulation of dopamine transmission in the striatum. Such a deficit may account for the hyperdopaminergic state observed in these patients and would help guide the development of novel treatment strategies. We hypothesize that, (i) insulin receptor expression and/or function is reduced in midbrain dopamine neurons in persons with schizophrenia, (ii) basal insulin should reduce dopaminergic transmission in the striatum via these receptors, and (iii) this modulation of dopaminergic transmission by basal insulin

  16. Effects of metformin on insulin receptor tyrosine kinase activity in rat adipocytes.

    PubMed

    Jacobs, D B; Hayes, G R; Truglia, J A; Lockwood, D H

    1986-11-01

    The cellular mechanism(s) by which the biguanide, metformin, exerts its antihyperglycaemic effect was investigated. Rat adipocytes were either treated acutely (2 h) or maintained in a biochemically defined medium (20 h) in the presence or absence of metformin (1 X 10(-4) mol/l). Exposure to the drug resulted in a significant enhancement (p less than 0.01) of hexose transport in both the absence (basal) and presence of insulin. Stimulation of transport was not explained by the increase in the basal state alone, since the incremental response to maximally effective concentrations of insulin was significantly enhanced p less than 0.025. Insulin-receptor tyrosine kinase activity was examined under the same experimental conditions. Activity of the kinase was unaltered as evaluated by phosphorylation of an artificial substrate and by phosphorylation of the receptor in situ. Furthermore, in this investigation neither insulin receptor number nor affinity was changed in adipose tissue treated with metformin. These studies indicate that metformin potentiates the effect of insulin on glucose transport at a site(s) beyond insulin receptor binding and phosphorylation.

  17. PTPRD silencing by DNA hypermethylation decreases insulin receptor signaling and leads to type 2 diabetes.

    PubMed

    Chen, Yng-Tay; Lin, Wei-D; Liao, Wen-Lin; Lin, Ying-Ju; Chang, Jan-Gowth; Tsai, Fuu-Jen

    2015-05-30

    Genome-wide association study (GWAS) data showed that the protein tyrosine phosphatase receptor type delta (PTPRD) is associated with increased susceptibility to type 2 diabetes (T2D) in Han Chinese. A replication study indicated that PTPRD is involved in the insulin signaling pathway; however, the underlying mechanism remains unclear. We evaluated PTPRD expression in patients with T2D and controls. PTPRD expression levels were lower in patients and were correlated with the duration of the disease. Overexpression of the human insulin receptor PPARγ2 in HepG2 cells induced overexpression of PTPRD and the insulin receptor. PTPRD knockdown, using a shRNA, resulted in down-regulation of the insulin receptor. These results indicate that PTPRD activates PPARγ2 in the insulin signaling pathway. Similar results for PTPRD expression were found using a T2D mouse model. Silencing of PTPRD was caused by DNA methylation in T2D mice and patients, and correlated with DNMT1 expression. Furthermore, we showed that a DNMT1 SNP (rs78789647) was correlated with susceptibility to T2D. This study shows for the first time that DNMT1 caused PTPRD DNA hypermethylation and induced insulin signaling silencing in T2D patients. Our findings contribute to a better understanding of the crucial roles of these regulatory elements in human T2D. PMID:26079428

  18. PTPRD silencing by DNA hypermethylation decreases insulin receptor signaling and leads to type 2 diabetes

    PubMed Central

    Chen, Yng-Tay; Lin, Wei-De; Liao, Wen-Lin; Lin, Ying-Ju; Chang, Jan-Gowth; Tsai, Fuu-Jen

    2015-01-01

    Genome-wide association study (GWAS) data showed that the protein tyrosine phosphatase receptor type delta (PTPRD) is associated with increased susceptibility to type 2 diabetes (T2D) in Han Chinese. A replication study indicated that PTPRD is involved in the insulin signaling pathway; however, the underlying mechanism remains unclear. We evaluated PTPRD expression in patients with T2D and controls. PTPRD expression levels were lower in patients and were correlated with the duration of the disease. Overexpression of the human insulin receptor PPARγ2 in HepG2 cells induced overexpression of PTPRD and the insulin receptor. PTPRD knockdown, using a shRNA, resulted in down-regulation of the insulin receptor. These results indicate that PTPRD activates PPARγ2 in the insulin signaling pathway. Similar results for PTPRD expression were found using a T2D mouse model. Silencing of PTPRD was caused by DNA methylation in T2D mice and patients, and correlated with DNMT1 expression. Furthermore, we showed that a DNMT1 SNP (rs78789647) was correlated with susceptibility to T2D. This study shows for the first time that DNMT1 caused PTPRD DNA hypermethylation and induced insulin signaling silencing in T2D patients. Our findings contribute to a better understanding of the crucial roles of these regulatory elements in human T2D. PMID:26079428

  19. PTPRD silencing by DNA hypermethylation decreases insulin receptor signaling and leads to type 2 diabetes.

    PubMed

    Chen, Yng-Tay; Lin, Wei-D; Liao, Wen-Lin; Lin, Ying-Ju; Chang, Jan-Gowth; Tsai, Fuu-Jen

    2015-05-30

    Genome-wide association study (GWAS) data showed that the protein tyrosine phosphatase receptor type delta (PTPRD) is associated with increased susceptibility to type 2 diabetes (T2D) in Han Chinese. A replication study indicated that PTPRD is involved in the insulin signaling pathway; however, the underlying mechanism remains unclear. We evaluated PTPRD expression in patients with T2D and controls. PTPRD expression levels were lower in patients and were correlated with the duration of the disease. Overexpression of the human insulin receptor PPARγ2 in HepG2 cells induced overexpression of PTPRD and the insulin receptor. PTPRD knockdown, using a shRNA, resulted in down-regulation of the insulin receptor. These results indicate that PTPRD activates PPARγ2 in the insulin signaling pathway. Similar results for PTPRD expression were found using a T2D mouse model. Silencing of PTPRD was caused by DNA methylation in T2D mice and patients, and correlated with DNMT1 expression. Furthermore, we showed that a DNMT1 SNP (rs78789647) was correlated with susceptibility to T2D. This study shows for the first time that DNMT1 caused PTPRD DNA hypermethylation and induced insulin signaling silencing in T2D patients. Our findings contribute to a better understanding of the crucial roles of these regulatory elements in human T2D.

  20. Structural and Biochemical Characterization of the KRLB Region in Insulin Receptor Substrate-2

    SciTech Connect

    Wu,J.; Tseng, Y.; Xu, C.; Neubert, T.; White, M.; Hubbard, S.

    2008-01-01

    Insulin receptor substrates 1 and 2 (IRS1 and -2) are crucial adaptor proteins in mediating the metabolic and mitogenic effects of insulin and insulin-like growth factor 1. These proteins consist of a pleckstrin homology domain, a phosphotyrosine binding domain and a C-terminal region containing numerous sites of tyrosine, serine and threonine phosphorylation. Previous yeast two-hybrid studies identified a region unique to IRS2, termed the kinase regulatory-loop binding (KRLB) region, which interacts with the tyrosine kinase domain of the insulin receptor. Here we present the crystal structure of the insulin receptor kinase in complex with a 15-residue peptide from the KRLB region. In the structure, this segment of IRS2 is bound in the kinase active site with Tyr628 positioned for phosphorylation. Although Tyr628 was phosphorylated by the insulin receptor, its catalytic turnover was poor, resulting in kinase inhibition. Our studies indicate that the KRLB region functions to limit tyrosine phosphorylation of IRS2.

  1. Human insulin analogues modified at the B26 site reveal a hormone conformation that is undetected in the receptor complex

    SciTech Connect

    Žáková, Lenka; Kletvíková, Emília; Lepšík, Martin; Collinsová, Michaela; Watson, Christopher J.; Turkenburg, Johan P.; Jiráček, Jiří; Brzozowski, Andrzej M.

    2014-10-01

    [AsnB26]- and [GlyB26]-insulin mutants attain a B26-turn like fold without assistance of chemical modifications. Their structures match the insulin receptor interface and expand the spectrum of insulin conformations. The structural characterization of the insulin–insulin receptor (IR) interaction still lacks the conformation of the crucial B21–B30 insulin region, which must be different from that in its storage forms to ensure effective receptor binding. Here, it is shown that insulin analogues modified by natural amino acids at the TyrB26 site can represent an active form of this hormone. In particular, [AsnB26]-insulin and [GlyB26]-insulin attain a B26-turn-like conformation that differs from that in all known structures of the native hormone. It also matches the receptor interface, avoiding substantial steric clashes. This indicates that insulin may attain a B26-turn-like conformation upon IR binding. Moreover, there is an unexpected, but significant, binding specificity of the AsnB26 mutant for predominantly the metabolic B isoform of the receptor. As it is correlated with the B26 bend of the B-chain of the hormone, the structures of AsnB26 analogues may provide the first structural insight into the structural origins of differential insulin signalling through insulin receptor A and B isoforms.

  2. G Protein–Coupled Receptor Kinase 2 Plays a Relevant Role in Insulin Resistance and Obesity

    PubMed Central

    Garcia-Guerra, Lucia; Nieto-Vazquez, Iria; Vila-Bedmar, Rocio; Jurado-Pueyo, María; Zalba, Guillermo; Díez, Javier; Murga, Cristina; Fernández-Veledo, Sonia; Mayor, Federico; Lorenzo, Margarita

    2010-01-01

    OBJECTIVE Insulin resistance is associated with the pathogenesis of metabolic disorders as type 2 diabetes and obesity. Given the emerging role of signal transduction in these syndromes, we set out to explore the possible role that G protein–coupled receptor kinase 2 (GRK2), first identified as a G protein–coupled receptor regulator, could have as a modulator of insulin responses. RESEARCH DESIGN AND METHODS We analyzed the influence of GRK2 levels in insulin signaling in myoblasts and adipocytes with experimentally increased or silenced levels of GRK2, as well as in GRK2 hemizygous animals expressing 50% lower levels of this kinase in three different models of insulin resistance: tumor necrosis factor-α (TNF-α) infusion, aging, and high-fat diet (HFD). Glucose transport, whole-body glucose and insulin tolerance, the activation status of insulin pathway components, and the circulating levels of important mediators were measured. The development of obesity and adipocyte size with age and HFD was analyzed. RESULTS Altering GRK2 levels markedly modifies insulin-mediated signaling in cultured adipocytes and myocytes. GRK2 levels are increased by ∼2-fold in muscle and adipose tissue in the animal models tested, as well as in lymphocytes from metabolic syndrome patients. In contrast, hemizygous GRK2 mice show enhanced insulin sensitivity and do not develop insulin resistance by TNF-α, aging, or HFD. Furthermore, reduced GRK2 levels induce a lean phenotype and decrease age-related adiposity. CONCLUSIONS Overall, our data identify GRK2 as an important negative regulator of insulin effects, key to the etiopathogenesis of insulin resistance and obesity, which uncovers this protein as a potential therapeutic target in the treatment of these disorders. PMID:20627936

  3. Insulin-Independent GABAA Receptor-Mediated Response in the Barrel Cortex of Mice with Impaired Met Activity

    PubMed Central

    Lo, Fu-Sun; Erzurumlu, Reha S.

    2016-01-01

    Autism spectrum disorder (ASD) is a neurodevelopmental disorder caused by genetic variants, susceptibility alleles, and environmental perturbations. The autism associated gene MET tyrosine kinase has been implicated in many behavioral domains and endophenotypes of autism, including abnormal neural signaling in human sensory cortex. We investigated somatosensory thalamocortical synaptic communication in mice deficient in Met activity in cortical excitatory neurons to gain insights into aberrant somatosensation characteristic of ASD. The ratio of excitation to inhibition is dramatically increased due to decreased postsynaptic GABAA receptor-mediated inhibition in the trigeminal thalamocortical pathway of mice lacking active Met in the cerebral cortex. Furthermore, in contrast to wild-type mice, insulin failed to increase GABAA receptor-mediated response in the barrel cortex of mice with compromised Met signaling. Thus, lacking insulin effects may be a risk factor in ASD pathogenesis. SIGNIFICANCE STATEMENT A proposed common cause of neurodevelopmental disorders is an imbalance in excitatory neural transmission, provided by the glutamatergic neurons, and the inhibitory signals from the GABAergic interneurons. Many genes associated with autism spectrum disorders impair synaptic transmission in the expected cell type. Previously, inactivation of the autism-associated Met tyrosine kinase receptor in GABAergic interneurons led to decreased inhibition. In thus report, decreased Met signaling in glutamatergic neurons had no effect on excitation, but decimated inhibition. Further experiments indicate that loss of Met activity downregulates GABAA receptors on glutamatergic neurons in an insulin independent manner. These data provide a new mechanism for the loss of inhibition and subsequent abnormal excitation/inhibition balance and potential molecular candidates for treatment or prevention. PMID:27030755

  4. Insulin receptor substrate 4 couples the leptin receptor to multiple signaling pathways.

    PubMed

    Wauman, Joris; De Smet, Anne-Sophie; Catteeuw, Dominiek; Belsham, Denise; Tavernier, Jan

    2008-04-01

    Leptin is an adipokine that regulates food intake and energy expenditure by activating its hypothalamic leptin receptor (LR). Members of the insulin receptor substrate (IRS) family serve as adaptor proteins in the signaling pathways of several cytokines and hormones and a role for IRS2 in central leptin physiology is well established. Using mammalian protein-protein interaction trap (MAPPIT), a cytokine receptor-based two-hybrid method, in the N38 hypothalamic cell line, we here demonstrate that also IRS4 interacts with the LR. This recruitment is leptin dependent and requires phosphorylation of the Y1077 motif of the LR. Domain mapping of IRS4 revealed the critical role of the pleckstrin homology domain for full interaction. In line with its function as an adaptor protein, IRS4 interacted with the regulatory p85 subunit of the phosphatidylinositol 3-kinase, phospholipase Cgamma, and the suppressor of cytokine signaling (SOCS) family members SOCS2, SOCS6, and SOCS7 and thus can modulate LR signaling. PMID:18165436

  5. Contrasting effects of insulin and cellular differentiation on expression of the novel insulin receptor substrate APS in skeletal muscle.

    PubMed

    Rea, Rustam; Gray, Samuel; Donnelly, Richard

    2005-11-01

    The novel insulin receptor substrate protein APS is highly expressed in insulin-sensitive tissues and plays an important role in insulin-mediated glucose uptake and GLUT4 translocation via the Cbl/CAP pathway. Tyrosine phosphorylation of APS leads to recruitment of c-Cbl and Crk, while overexpression of APS mutant inhibits GLUT4 translocation in response to insulin, but the regulation of APS expression in skeletal muscle has not been previously reported. L6 myoblasts were differentiated in 2% FBS and serum starved for 24h prior to stimulation for 24h with either insulin 1 microM (n=6), rosiglitazone 10 microM (n=6), resistin 500 nM (n=6) or the MAP kinase inhibitor PD098059 50 microM (n=6) for 30 min, followed by insulin 1 microM for 24h. Semi-quantitative real-time RT-PCR was used to determine the expression of APS mRNA relative to the control gene TF2D. APS expression was markedly upregulated by myoblast differentiation (0.55+/-0.08 versus 1.14+/-0.08, p=0.001), and this effect was augmented by addition of rosiglitazone 10 microM for 24h to the differentiated myotubes (1.50+/-0.09, p=0.025). Insulin caused a 3.1-fold decrease in APS mRNA expression (0.37+/-0.01 versus 1.14+/-0.08, p=0.001), an effect that was attenuated by the MAP kinase inhibitor PD098059 (0.80+/-0.03, p=0.001). Exposure to resistin produced a modest decrease (1.4-fold) in myotube expression of APS (0.8+/-0.09, p=0.025). In conclusion, this is the first study to show that exposure to insulin markedly reduces the expression of APS in skeletal muscle via a MAP kinase dependent pathway, whereas myocyte differentiation and rosiglitazone increase APS expression. Changes in APS expression may be important in the aetiology and therapeutic reversal of insulin resistance in skeletal muscle.

  6. Insulin receptor substrate-1 involvement in epidermal growth factor receptor and insulin-like growth factor receptor signalling: implication for Gefitinib ('Iressa') response and resistance.

    PubMed

    Knowlden, Janice M; Jones, Helen E; Barrow, Denise; Gee, Julia M W; Nicholson, Robert I; Hutcheson, Iain R

    2008-09-01

    Classically the insulin receptor substrate-1 (IRS-1) is an essential component of insulin-like growth factor type 1 receptor (IGF-IR) signalling, providing an interface between the receptor and key downstream signalling cascades. Here, however, we show that in tamoxifen-resistant MCF-7 (Tam-R) breast cancer cells, that are highly dependent on epidermal growth factor receptor (EGFR) for growth, IRS-1 can interact with EGFR and be preferentially phosphorylated on tyrosine (Y) 896, a Grb2 binding site. Indeed, phosphorylation of this site is greatly enhanced by exposure of these cells, and other EGFR-positive cell lines, to EGF. Importantly, while IGF-II promotes phosphorylation of IRS-1 on Y612, a PI3-K recruitment site, it has limited effect on Y896 phosphorylation in Tam-R cells. Furthermore, EGF and IGF-II co-treatment, reduces the ability of IGF-II to phosphorylate Y612, whilst maintaining Y896 phosphorylation, suggesting that the EGFR is the dominant recruiter of IRS-1 in this cell line. Significantly, challenge of Tam-R cells with the EGFR-selective tyrosine kinase inhibitor gefitinib, for 7 days, reduces IRS-1/EGFR association and IRS-1 Y896 phosphorylation, while promoting IRS-1/IGF-IR association and IRS-1 Y612 phosphorylation. Furthermore, gefitinib significantly enhances IGF-II-mediated phosphorylation of IRS-1 Y612 and AKT in Tam-R cells. Importantly, induction of this pathway by gefitinib can be abrogated by inhibition/downregulation of the IGF-IR. Our data would therefore suggest a novel association exists between the EGFR and IRS-1 in several EGFR-positive cancer cell lines. This association acts to promote phosphorylation of IRS-1 at Y896 and drive MAPK signalling whilst preventing recruitment of IRS-1 by the IGF-IR and inhibiting signalling via this receptor. Treatment with gefitinib alters the dynamics of this system, promoting IGF-IR signalling, the dominant gefitinib-resistant growth regulatory pathway in Tam-R cells, thus, potentially limiting

  7. Exploring the Evolutionary Relationship of Insulin Receptor Substrate Family Using Computational Biology

    PubMed Central

    Chakraborty, Chiranjib; Agoramoorthy, Govindasamy; Hsu, Minna J.

    2011-01-01

    Insulin receptor substrate (IRS) harbors proteins such as IRS1, IRS2, IRS3, IRS4, IRS5 and IRS6. These key proteins act as vital downstream regulators in the insulin signaling pathway. However, little is known about the evolutionary relationship among the IRS family members. This study explores the potential to depict the evolutionary relationship among the IRS family using bioinformatics, algorithm analysis and mathematical models. PMID:21364910

  8. Insulin

    MedlinePlus

    ... pump is connected to your body by a flexible tube that has a tip that sticks under your skin. A cartridge of insulin is put in the pump. The insulin flows through the tube into your body. The pump controls how much insulin goes into your body. The ...

  9. Label-Free Proteomic Identification of Endogenous, Insulin-Stimulated Interaction Partners of Insulin Receptor Substrate-1

    NASA Astrophysics Data System (ADS)

    Geetha, Thangiah; Langlais, Paul; Luo, Moulun; Mapes, Rebekka; Lefort, Natalie; Chen, Shu-Chuan; Mandarino, Lawrence J.; Yi, Zhengping

    2011-03-01

    Protein-protein interactions are key to most cellular processes. Tandem mass spectrometry (MS/MS)-based proteomics combined with co-immunoprecipitation (CO-IP) has emerged as a powerful approach for studying protein complexes. However, a majority of systematic proteomics studies on protein-protein interactions involve the use of protein overexpression and/or epitope-tagged bait proteins, which might affect binding stoichiometry and lead to higher false positives. Here, we report an application of a straightforward, label-free CO-IP-MS/MS method, without the use of protein overexpression or protein tags, to the investigation of changes in the abundance of endogenous proteins associated with a bait protein, which is in this case insulin receptor substrate-1 (IRS-1), under basal and insulin stimulated conditions. IRS-1 plays a central role in the insulin signaling cascade. Defects in the protein-protein interactions involving IRS-1 may lead to the development of insulin resistance and type 2 diabetes. HPLC-ESI-MS/MS analyses identified eleven novel endogenous insulin-stimulated IRS-1 interaction partners in L6 myotubes reproducibly, including proteins play an important role in protein dephosphorylation [protein phosphatase 1 regulatory subunit 12A, (PPP1R12A)], muscle contraction and actin cytoskeleton rearrangement, endoplasmic reticulum stress, and protein folding, as well as protein synthesis. This novel application of label-free CO-IP-MS/MS quantification to assess endogenous interaction partners of a specific protein will prove useful for understanding how various cell stimuli regulate insulin signal transduction.

  10. Context-dependent regulation of feeding behaviour by the insulin receptor, DAF-2, in Caenorhabditis elegans.

    PubMed

    Dillon, James; Holden-Dye, Lindy; O'Connor, Vincent; Hopper, Neil A

    2016-06-01

    Insulin signalling plays a significant role in both developmental programmes and pathways modulating the neuronal signalling that controls adult behaviour. Here, we have investigated insulin signalling in food-associated behaviour in adult C. elegans by scoring locomotion and feeding on and off bacteria, the worm's food. This analysis used mutants (daf-2, daf-18) of the insulin signalling pathway, and we provide evidence for an acute role for insulin signalling in the adult nervous system distinct from its impact on developmental programmes. Insulin receptor daf-2 mutants move slower than wild type both on and off food and showed impaired locomotory responses to food deprivation. This latter behaviour is manifest as a failure to instigate dispersal following prolonged food deprivation and suggests a role for insulin signalling in this adaptive response. Insulin receptor daf-2 mutants are also deficient in pharyngeal pumping on food and off food. Pharmacological analysis showed the pharynx of daf-2 is selectively compromised in its response to 5-HT compared to the excitatory neuropeptide FLP-17. By comparing the adaptive pharyngeal behaviour in intact worms and isolated pharyngeal preparations, we determined that an insulin-dependent signal extrinsic to the pharyngeal system is involved in feeding adaptation. Hence, we suggest that reactive insulin signalling modulates both locomotory foraging and pharyngeal pumping as the animal adapts to the absence of food. We discuss this in the context of insulin signalling directing a shift in the sensitivity of neurotransmitter systems to regulate the worm's response to changes in food availability in the environment. PMID:27209024

  11. Phosphorylation of insulin receptor substrate-1 serine 307 correlates with JNK activity in atrophic skeletal muscle

    NASA Technical Reports Server (NTRS)

    Hilder, Thomas L.; Tou, Janet C L.; Grindeland, Richard E.; Wade, Charles E.; Graves, Lee M.

    2003-01-01

    c-Jun NH(2)-terminal kinase (JNK) has been shown to negatively regulate insulin signaling through serine phosphorylation of residue 307 within the insulin receptor substrate-1 (IRS-1) in adipose and liver tissue. Using a rat hindlimb suspension model for muscle disuse atrophy, we found that JNK activity was significantly elevated in atrophic soleus muscle and that IRS-1 was phosphorylated on Ser(307) prior to the degradation of the IRS-1 protein. Moreover, we observed a corresponding reduction in Akt activity, providing biochemical evidence for the development of insulin resistance in atrophic skeletal muscle.

  12. Plasminogen activator inhibitor-1 deficiency ameliorates insulin resistance and hyperlipidemia but not bone loss in obese female mice.

    PubMed

    Tamura, Yukinori; Kawao, Naoyuki; Yano, Masato; Okada, Kiyotaka; Matsuo, Osamu; Kaji, Hiroshi

    2014-05-01

    We previously demonstrated that plasminogen activator inhibitor-1 (PAI-1), an inhibitor of fibrinolysis, is involved in type 1 diabetic bone loss in female mice. PAI-1 is well known as an adipogenic factor induced by obesity. We therefore examined the effects of PAI-1 deficiency on bone and glucose and lipid metabolism in high-fat and high-sucrose diet (HF/HSD)-induced obese female mice. Female wild-type (WT) and PAI-1-deficient mice were fed with HF/HSD or normal diet for 20 weeks from 10 weeks of age. HF/HSD increased the levels of plasma PAI-1 in WT mice. PAI-1 deficiency suppressed the levels of blood glucose, plasma insulin, and total cholesterol elevated by obesity. Moreover, PAI-1 deficiency improved glucose intolerance and insulin resistance induced by obesity. Bone mineral density (BMD) at trabecular bone as well as the levels of osterix, alkaline phosphatase, and receptor activator of nuclear factor κB ligand mRNA in tibia were decreased by HF/HSD in WT mice, and those changes by HF/HSD were not affected by PAI-1 deficiency. HF/HSD increased the levels of plasma TNF-α in both WT and PAI-1-deficient mice, and the levels of plasma TNF-α were negatively correlated with trabecular BMD in tibia of female mice. In conclusion, we revealed that PAI-1 deficiency does not affect the trabecular bone loss induced by obesity despite the amelioration of insulin resistance and hyperlipidemia in female mice. Our data suggest that the changes of BMD and bone metabolism by obesity might be independent of PAI-1 as well as glucose and lipid metabolism.

  13. Nuclear SREBP-1a causes loss of pancreatic {beta}-cells and impaired insulin secretion

    SciTech Connect

    Iwasaki, Yuko; Iwasaki, Hitoshi; Yatoh, Shigeru; Ishikawa, Mayumi; Kato, Toyonori; Matsuzaka, Takashi; Nakagawa, Yoshimi; Yahagi, Naoya; Kobayashi, Kazuto; Takahashi, Akimitsu; Suzuki, Hiroaki; Yamada, Nobuhiro; Shimano, Hitoshi

    2009-01-16

    Transgenic mice expressing nuclear sterol regulatory element-binding protein-1a under the control of the insulin promoter were generated to determine the role of SREBP-1a in pancreatic {beta}-cells. Only low expressors could be established, which exhibited mild hyperglycemia, impaired glucose tolerance, and reduced plasma insulin levels compared to C57BL/6 controls. The islets isolated from the transgenic mice were fewer and smaller, and had decreased insulin content and unaltered glucagon staining. Both glucose- and potassium-stimulated insulin secretions were decreased. The transgenic islets consistently expressed genes for fatty acids and cholesterol synthesis, resulting in accumulation of triglycerides but not cholesterol. PDX-1, {beta}{epsilon}{tau}{alpha}2, MafA, and IRS-2 were suppressed, partially explaining the loss and dysfunction of {beta}-cell mass. The transgenic mice on a high fat/high sucrose diet still exhibited impaired insulin secretion and continuous {beta}-cell growth defect. Therefore, nuclear SREBP-1a, even at a low level, strongly disrupts {beta}-cell mass and function.

  14. The insulin and IGF1 receptor kinase domains are functional dimers in the activated state

    NASA Astrophysics Data System (ADS)

    Cabail, M. Zulema; Li, Shiqing; Lemmon, Eric; Bowen, Mark E.; Hubbard, Stevan R.; Miller, W. Todd

    2015-03-01

    The insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF1R) are highly related receptor tyrosine kinases with a disulfide-linked homodimeric architecture. Ligand binding to the receptor ectodomain triggers tyrosine autophosphorylation of the cytoplasmic domains, which stimulates catalytic activity and creates recruitment sites for downstream signalling proteins. Whether the two phosphorylated tyrosine kinase domains within the receptor dimer function independently or cooperatively to phosphorylate protein substrates is not known. Here we provide crystallographic, biophysical and biochemical evidence demonstrating that the phosphorylated kinase domains of IR and IGF1R form a specific dimeric arrangement involving an exchange of the juxtamembrane region proximal to the kinase domain. In this dimer, the active position of α-helix C in the kinase N lobe is stabilized, which promotes downstream substrate phosphorylation. These studies afford a novel strategy for the design of small-molecule IR agonists as potential therapeutic agents for type 2 diabetes.

  15. Theoretical and Computational Studies of Peptides and Receptors of the Insulin Family

    PubMed Central

    Vashisth, Harish

    2015-01-01

    Synergistic interactions among peptides and receptors of the insulin family are required for glucose homeostasis, normal cellular growth and development, proliferation, differentiation and other metabolic processes. The peptides of the insulin family are disulfide-linked single or dual-chain proteins, while receptors are ligand-activated transmembrane glycoproteins of the receptor tyrosine kinase (RTK) superfamily. Binding of ligands to the extracellular domains of receptors is known to initiate signaling via activation of intracellular kinase domains. While the structure of insulin has been known since 1969, recent decades have seen remarkable progress on the structural biology of apo and liganded receptor fragments. Here, we review how this useful structural information (on ligands and receptors) has enabled large-scale atomically-resolved simulations to elucidate the conformational dynamics of these biomolecules. Particularly, applications of molecular dynamics (MD) and Monte Carlo (MC) simulation methods are discussed in various contexts, including studies of isolated ligands, apo-receptors, ligand/receptor complexes and intracellular kinase domains. The review concludes with a brief overview and future outlook for modeling and computational studies in this family of proteins. PMID:25680077

  16. Nicotinic acetylcholine receptors in glucose homeostasis: the acute hyperglycemic and chronic insulin-sensitive effects of nicotine suggest dual opposing roles of the receptors in male mice.

    PubMed

    Vu, Christine U; Siddiqui, Jawed A; Wadensweiler, Paul; Gayen, Jiaur R; Avolio, Ennio; Bandyopadhyay, Gautam K; Biswas, Nilima; Chi, Nai-Wen; O'Connor, Daniel T; Mahata, Sushil K

    2014-10-01

    Cigarette smoking causes insulin resistance. However, nicotine induces anti-inflammation and improves glucose tolerance in insulin-resistant animal models. Here, we determined the effects of nicotine on glucose metabolism in insulin-sensitive C57BL/J6 mice. Acute nicotine administration (30 min) caused fasting hyperglycemia and lowered insulin sensitivity acutely, which depended on the activation of nicotinic-acetylcholine receptors (nAChRs) and correlated with increased catecholamine secretion, nitric oxide (NO) production, and glycogenolysis. Chlorisondamine, an inhibitor of nAChRs, reduced acute nicotine-induced hyperglycemia. qRT-PCR analysis revealed that the liver and muscle express predominantly β4 > α10 > α3 > α7 and β4 > α10 > β1 > α1 mRNA for nAChR subunits respectively, whereas the adrenal gland expresses β4 > α3 > α7 > α10 mRNA. Chronic nicotine treatment significantly suppressed expression of α3-nAChR (predominant peripheral α-subunit) in liver. Whereas acute nicotine treatment raised plasma norepinephrine (NE) and epinephrine (Epi) levels, chronic nicotine exposure raised only Epi. Acute nicotine treatment raised both basal and glucose-stimulated insulin secretion (GSIS). After chronic nicotine treatment, basal insulin level was elevated, but GSIS after acute saline or nicotine treatment was blunted. Chronic nicotine exposure caused an increased buildup of NO in plasma and liver, leading to decreased glycogen storage, along with a concomitant suppression of Pepck and G6Pase mRNA, thus preventing hyperglycemia. The insulin-sensitizing effect of chronic nicotine was independent of weight loss. Chronic nicotine treatment enhanced PI-3-kinase activities and increased Akt and glycogen synthase kinase (GSK)-3β phosphorylation in an nAChR-dependent manner coupled with decreased cAMP response element-binding protein (CREB) phosphorylation. The latter effects caused suppression of Pepck and G6Pase gene expression. Thus, nicotine causes both

  17. Association of the insulin-receptor variant Met-985 with hyperglycemia and non-insulin-dependent diabetes mellitus in the Netherlands: A population-based study

    SciTech Connect

    `t Hart, L.M.; Maassen, J.A.; Does, F.E.E. van der

    1996-11-01

    One of the characteristics of non-insulin-dependent diabetes mellitus (NIDDM) is the presence of insulin. Most NIDDM patients have a normal sequence of the insulin receptor, indicating that, if insulin-receptor mutations contribute to the development of NIDDM, they will be present only in a minor fraction of the NIDDM population. The goal of the present study was to examine whether insulin-receptor mutations contribute to the development of NIDDM. We examined 161 individuals with NIDDM and 538 healthy controls from the population-based Rotterdam study for the presence of mutations in the insulin-receptor gene by SSCP. A heterozygous mutation changing valine-985 into methionine was detected in 5.6% of diabetic subjects and in 1.3% of individuals with normal oral glucose tolerance test. Adjusted for age, gender, and body-mass index, this revealed a relative risk for diabetes of 4.49 (95% confidence interval 1.59-12.25) for Met-985 carriers. When the total study group was analyzed, the prevalence of the mutation increased with increasing serum glucose levels (test for trend P < .005). We conclude that the Met-985 insulin-receptor variant associates with hyperglycemia and represents a risk factor for NIDDM. 30 refs., 3 figs., 1 tab.

  18. Small molecule activators of the insulin receptor: potential new therapeutic agents for the treatment of diabetes mellitus.

    PubMed

    Laborde, Edgardo; Manchem, Vara Prasad

    2002-12-01

    Diabetes mellitus refers to a spectrum of syndromes characterized by abnormally high levels of glucose in blood. These syndromes are associated with an absolute (Type 1 diabetes) or relative (Type 2 diabetes) deficiency of insulin, coupled with varying degrees of peripheral resistance to the actions of insulin. Clinical studies have shown that controlling hyperglycemia significantly reduces the appearance and progression of the vascular complications associated with diabetes. Insulin's regulation of glucose homeostasis is mediated by a cascade of signaling events that take place upon insulin binding to its cell surface receptor. Autophosphorylation of the receptor and activation of its intrinsic tyrosine kinase are critical processes for transmitting these intracellular signals. Type 1 diabetes patients depend on exogenous insulin to achieve these effects, whereas Type 2 diabetes patients can accomplish a similar response through oral medications that increase the production of endogenous insulin or enhance its actions on the target tissues. Current biochemical and clinical evidence suggests that defects within the insulin receptor itself may be a cause of insulin resistance leading to Type 2 diabetes. This review focuses on the insulin receptor as a target for therapeutic intervention, and describes the recent discovery of small molecules that act on the receptor and either enhance or directly emulate the actions of insulin both in vitro and in vivo.

  19. Targeting colorectal cancer via its microenvironment by inhibiting IGF-1 Receptor-insulin receptor substrate and STAT3 signaling

    PubMed Central

    Sanchez-Lopez, Elsa; Flashner-Abramson, Efrat; Shalapour, Shabnam; Zhong, Zhenyu; Taniguchi, Koji; Levitzki, Alexander; Karin, Michael

    2015-01-01

    The tumor microenvironment (TME) exerts critical pro-tumorigenic effects through cytokines and growth factors that support cancer cell proliferation, survival, motility and invasion. Insulin-like growth factor-1 (IGF-1) and Signal transducer and activator of transcription 3 (STAT3) stimulate colorectal cancer (CRC) development and progression via cell autonomous and microenvironmental effects. Using a unique inhibitor, NT157, which targets both IGF-1 receptor (IGF-1R) and STAT3, we show that these pathways regulate many TME functions associated with sporadic colonic tumorigenesis in CPC-APC mice, in which cancer development is driven by loss of the Apc tumor suppressor gene. NT157 causes a substantial reduction in tumor burden by affecting cancer cells, cancer-associated fibroblasts (CAF) and myeloid cells. Decreased cancer cell proliferation and increased apoptosis were accompanied by inhibition of CAF activation and decreased inflammation. Furthermore, NT157 inhibited expression of pro-tumorigenic cytokines, chemokines and growth factors, including IL-6, IL-11 and IL-23 as well as CCL2, CCL5, CXCL7, CXCL5, ICAM1 and TGFβ; decreased cancer cell migratory activity and reduced their proliferation in the liver. NT157 represents a new class of anti-cancer drugs that affect both the malignant cell and its supportive microenvironment. PMID:26364612

  20. A receptor state space model of the insulin signalling system in glucose transport.

    PubMed

    Gray, Catheryn W; Coster, Adelle C F

    2015-12-01

    Insulin is a potent peptide hormone that regulates glucose levels in the blood. Insulin-sensitive cells respond to insulin stimulation with the translocation of glucose transporter 4 (GLUT4) to the plasma membrane (PM), enabling the clearance of glucose from the blood. Defects in this process can give rise to insulin resistance and ultimately diabetes. One widely cited model of insulin signalling leading to glucose transport is that of Sedaghat et al. (2002) Am. J. Physiol. Endocrinol. Metab. 283, E1084-E1101. Consisting of 20 deterministic ordinary differential equations (ODEs), it is the most comprehensive model of insulin signalling to date. However, the model possesses some major limitations, including the non-conservation of key components. In the current work, we detail mathematical and sensitivity analyses of the Sedaghat model. Based on the results of these analyses, we propose a reduced state space model of the insulin receptor subsystem. This reduced model maintains the input-output relation of the original model but is computationally more efficient, analytically tractable and resolves some of the limitations of the Sedaghat model.

  1. Increase of Calcium Sensing Receptor Expression Is Related to Compensatory Insulin Secretion during Aging in Mice

    PubMed Central

    Oh, Yoon Sin; Seo, Eun-Hui; Lee, Young-Sun; Cho, Sung Chun; Jung, Hye Seung; Park, Sang Chul; Jun, Hee-Sook

    2016-01-01

    Type 2 diabetes is caused by both insulin resistance and relative insulin deficiency. To investigate age-related changes in glucose metabolism and development of type 2 diabetes, we compared glucose homeostasis in different groups of C57BL/6J mice ranging in age from 4 months to 20 months (4, 8, 12, 16 and 20 months). Interestingly, we observed that non-fasting glucose levels were not significantly changed, but glucose tolerance gradually increased by 20 months of age, whereas insulin sensitivity declined with age. We found that the size of islets and glucose-stimulated insulin secretion increased with aging. However, mRNA expression of pancreatic and duodenal homeobox 1 and granuphilin was decreased in islets of older mice compared with that of 4-month-old mice. Serum calcium (Ca2+) levels were significantly decreased at 12, 20 and 28 months of age compared with 4 months and calcium sensing receptor (CaSR) mRNA expression in the islets significantly increased with age. An extracellular calcium depletion agent upregulated CaSR mRNA expression and consequently enhanced insulin secretion in INS-1 cells and mouse islets. In conclusion, we suggest that decreased Ca2+ levels and increased CaSR expression might be involved in increased insulin secretion to compensate for insulin resistance in aged mice. PMID:27441644

  2. Aptamer-based single-molecule imaging of insulin receptors in living cells

    NASA Astrophysics Data System (ADS)

    Chang, Minhyeok; Kwon, Mijin; Kim, Sooran; Yunn, Na-Oh; Kim, Daehyung; Ryu, Sung Ho; Lee, Jong-Bong

    2014-05-01

    We present a single-molecule imaging platform that quantitatively explores the spatiotemporal dynamics of individual insulin receptors in living cells. Modified DNA aptamers that specifically recognize insulin receptors (IRs) with a high affinity were selected through the SELEX process. Using quantum dot-labeled aptamers, we successfully imaged and analyzed the diffusive motions of individual IRs in the plasma membranes of a variety of cell lines (HIR, HEK293, HepG2). We further explored the cholesterol-dependent movement of IRs to address whether cholesterol depletion interferes with IRs and found that cholesterol depletion of the plasma membrane by methyl-β-cyclodextrin reduces the mobility of IRs. The aptamer-based single-molecule imaging of IRs will provide better understanding of insulin signal transduction through the dynamics study of IRs in the plasma membrane.

  3. Genetic analysis of type-1 insulin-like growth factor receptor signaling through insulin receptor substrate-1 and -2 in pancreatic beta cells.

    PubMed

    Xuan, Shouhong; Szabolcs, Matthias; Cinti, Francesca; Perincheri, Suhdir; Accili, Domenico; Efstratiadis, Argiris

    2010-12-24

    Signaling by receptor tyrosine kinases regulates pancreatic β cell function. Inactivation of insulin receptor (InsR), IGF1 receptor (Igf1r), or Irs1 in β cells impairs insulin secretion. Conversely, Irs2 ablation impairs β cell replication. In this study, we examined aspects of the Igf1r regulatory signaling cascade in β cells. To examine genetically the involvement of Irs1 and Irs2 in Igf1r signaling, we generated double mutant mice lacking Igf1r specifically in pancreatic β cells in an Irs1- or Irs2-null background. We show that Igf1r/Irs1 double mutants do not differ phenotypically from Irs1 single mutants and exhibit hyperinsulinemia, while maintaining normal β cell mass and glucose tolerance. In contrast, lack of Igf1r function in β cells aggravates the consequences of Irs2 ablation in double mutants and results in lethal diabetes by 6 weeks of age. This additivity of phenotypic manifestations indicates that Irs2 serves a pathway that is largely independent of Igf1r signaling. Consistent with the view that the latter is the InsR pathway, we show that combined β cell-specific knock-out of both Insr and Igf1r results in a phenocopy of double mutants lacking Igf1r and Irs2. We conclude that Igf1r signals primarily through Irs1 and affects insulin secretion, whereas β cell proliferation is mainly regulated by InsR using Irs2 as a downstream signaling effector. The insulin and IGF pathways appear to control β cell functions independently and selectively.

  4. Insilico docking study of compounds elucidated from helicteres isora fruits with ampkinase- insulin receptor.

    PubMed

    Vennila, Subramanium; Bupesh, Giridharan; Saravanamurali, Krishnan; SenthilKumar, Viajayan; SenthilRaja, Ramalingam; Saran, Natarajan; Magesh, Sachidanandam

    2014-01-01

    Insulin receptor (IR) proteins were essential intracellular signaling peptides in the insulin action cascade. Insulin receptor substrate proteins (IRS-1and IRS-2) serve and regulate the insulin level in the normal insulin action. The broad role of IRS-1 and IRS-2 in cell growth and survival reveals a common regulatory pathway linking development, somatic growth, fertility, neuronal proliferation, and aging to the core mechanisms used by vertebrates for nutrient sensing. Such type of proteins were cyclic adenosine monophosphate-activated protein kinase, this proteins play a key role in the insulin response and regulation. Type -2 Diabetes mellitus occurs during prolonged periods of peripheral insulin resistance due to inactivation of IRS proteins. The compounds isolated from the medicinal plants were safer than synthetic drugs and possess high bio activity. In the present study, four compounds were elucidated from fruits of Helicteres isora. The elucidated compounds were evaluated for the antidiabetic activity using in silico docking study. The receptor was analyzed for the active site and pocket finder tools. The aminoacids such as Phenylalanine, Lysine, Glutamic acid and Asparigine were predicted as active site binding residues. Docking studies were done through Autodock 4 software. All the compounds from fruits of Helicteres isora showed good docking profiles with AMP Kinase, except compound-3 (1,2,3,4-tetrahydro-1,5,6,8-tetramethyl-7-(2-methylprop-1-enylnaphthalene-4-ylpivalate). Finally the result from the study demonstrates that the HS-1, HS-2 and HS-4 posses potent anti diabetic activity against type-2 diabetes mellitus through drug action on AMP kinase cascade system. PMID:24966532

  5. Insilico docking study of compounds elucidated from helicteres isora fruits with ampkinase- insulin receptor

    PubMed Central

    Vennila, Subramanium; Bupesh, Giridharan; Saravanamurali, Krishnan; SenthilKumar, Viajayan; SenthilRaja, Ramalingam; Saran, Natarajan; Magesh, Sachidanandam

    2014-01-01

    Insulin receptor (IR) proteins were essential intracellular signaling peptides in the insulin action cascade. Insulin receptor substrate proteins (IRS-1and IRS-2) serve and regulate the insulin level in the normal insulin action. The broad role of IRS-1 and IRS-2 in cell growth and survival reveals a common regulatory pathway linking development, somatic growth, fertility, neuronal proliferation, and aging to the core mechanisms used by vertebrates for nutrient sensing. Such type of proteins were cyclic adenosine monophosphate-activated protein kinase, this proteins play a key role in the insulin response and regulation. Type -2 Diabetes mellitus occurs during prolonged periods of peripheral insulin resistance due to inactivation of IRS proteins. The compounds isolated from the medicinal plants were safer than synthetic drugs and possess high bio activity. In the present study, four compounds were elucidated from fruits of Helicteres isora. The elucidated compounds were evaluated for the antidiabetic activity using in silico docking study. The receptor was analyzed for the active site and pocket finder tools. The aminoacids such as Phenylalanine, Lysine, Glutamic acid and Asparigine were predicted as active site binding residues. Docking studies were done through Autodock 4 software. All the compounds from fruits of Helicteres isora showed good docking profiles with AMP Kinase, except compound-3 (1,2,3,4-tetrahydro-1,5,6,8-tetramethyl-7-(2-methylprop-1-enylnaphthalene-4-ylpivalate). Finally the result from the study demonstrates that the HS-1, HS-2 and HS-4 posses potent anti diabetic activity against type-2 diabetes mellitus through drug action on AMP kinase cascade system. PMID:24966532

  6. An exon variant in insulin receptor gene is associated with susceptibility to colorectal cancer in women.

    PubMed

    Mahmoudi, Touraj; Majidzadeh-A, Keivan; Karimi, Khatoon; Karimi, Negar; Farahani, Hamid; Dabiri, Reza; Nobakht, Hossein; Dolatmoradi, Hesamodin; Arkani, Maral; Zali, Mohammad Reza

    2015-05-01

    Given the role of insulin resistance in colorectal cancer (CRC), we explored whether genetic variants in insulin (INS), insulin receptor (INSR), insulin receptor substrate 1 (IRS1), insulin receptor substrate 2 (IRS2), insulin-like growth factor 1 (IGF1), and insulin-like growth factor binding protein 3 (IGFBP3) genes were associated with CRC risk. A total of 600 subjects, including 261 cases with CRC and 339 controls, were enrolled in this case-control study. Six polymorphisms in INS (rs689), INSR (rs1799817), IRS1 (rs1801278), IRS2 (rs1805097), IGF1 (rs5742612), and IGFBP3 (rs2854744) genes were genotyped using PCR-RFLP method. No significant difference was observed for INS, INSR, IRS1, IRS2, IGF1, and IGFBP3 genes between the cases and controls. However, the INSR rs1799817 "TT + CT" genotype and "CT" genotype compared with "CC" genotype occurred more frequently in the women with CRC than women controls (P = 0.007; OR = 1.93, 95 %CI = 1.20-3.11 and P = 0.002, OR = 2.15, 95 %CI = 1.31-3.53, respectively), and the difference remained significant after adjustment for confounding factors including age, BMI, smoking status, NSAID use, and family history of CRC (P = 0.018; OR = 1.86, 95 %CI = 1.11-3.10 and P = 0.004, OR = 2.18, 95 %CI = 1.28-3.71, respectively). In conclusion, to our knowledge, this study indicated for the first time that the INSR rs1799817 TT + CT genotype and CT genotype compared with the CC genotype had 1.86-fold and 2.18-fold increased risks for CRC among women, respectively. Furthermore, this finding is in line with previous studies which found significant associations between other variants of the INSR gene and CRC risk. Nevertheless, further studies are required to confirm our findings.

  7. The farnesoid X receptor modulates adiposity and peripheral insulin sensitivity in mice.

    PubMed

    Cariou, Bertrand; van Harmelen, Kirsten; Duran-Sandoval, Daniel; van Dijk, Theo H; Grefhorst, Aldo; Abdelkarim, Mouaadh; Caron, Sandrine; Torpier, Gérard; Fruchart, Jean-Charles; Gonzalez, Frank J; Kuipers, Folkert; Staels, Bart

    2006-04-21

    The farnesoid X receptor (FXR) is a bile acid (BA)-activated nuclear receptor that plays a major role in the regulation of BA and lipid metabolism. Recently, several studies have suggested a potential role of FXR in the control of hepatic carbohydrate metabolism, but its contribution to the maintenance of peripheral glucose homeostasis remains to be established. FXR-deficient mice display decreased adipose tissue mass, lower serum leptin concentrations, and elevated plasma free fatty acid levels. Glucose and insulin tolerance tests revealed that FXR deficiency is associated with impaired glucose tolerance and insulin resistance. Moreover, whole-body glucose disposal during a hyperinsulinemic euglycemic clamp is decreased in FXR-deficient mice. In parallel, FXR deficiency alters distal insulin signaling, as reflected by decreased insulin-dependent Akt phosphorylation in both white adipose tissue and skeletal muscle. Whereas FXR is not expressed in skeletal muscle, it was detected at a low level in white adipose tissue in vivo and induced during adipocyte differentiation in vitro. Moreover, mouse embryonic fibroblasts derived from FXR-deficient mice displayed impaired adipocyte differentiation, identifying a direct role for FXR in adipocyte function. Treatment of differentiated 3T3-L1 adipocytes with the FXR-specific synthetic agonist GW4064 enhanced insulin signaling and insulin-stimulated glucose uptake. Finally, treatment with GW4064 improved insulin resistance in genetically obese ob/ob mice in vivo. Although the underlying molecular mechanisms remain to be unraveled, these results clearly identify a novel role of FXR in the regulation of peripheral insulin sensitivity and adipocyte function. This unexpected function of FXR opens new perspectives for the treatment of type 2 diabetes.

  8. Immunohistochemical localization of glucose transporters and insulin receptors in human fetal membranes at term.

    PubMed

    Wolf, H J; Desoye, G

    1993-11-01

    The localization has been investigated of the isoforms GLUT1, GLUT3 and GLUT4 of glucose transporter proteins as well as of insulin receptors. Fetal membranes (n = 10) were examined by immunohistochemical methods at the light and electron microscopic levels using mono- and polyclonal antibodies. In all amnion epithelial cells, GLUT1 and GLUT3 antibodies were bound to the apical membrane. Very rarely the GLUT1 antibody also immunostained the basolateral membrane and reacted weakly with the endomembrane system and membranes of the lateral cell protrusions. Fibroblasts reacted with the antibodies against GLUT1, GLUT4 and insulin receptor, whereas they were labelled only in one case with GLUT3 antibody. Cytotrophoblast cells were only stained with antibodies against GLUT1 and GLUT3. Antibodies against GLUT4 only reacted with fibroblasts in the membranes. On amnion epithelial cells, weak immunoreactivity with insulin receptor antibodies was detected only at the electron microscopic level. The data indicate: (1) GLUT1 is located on all cells of the amnion, whereas GLUT3 is present in detectable amounts only on amnion epithelial cells and cytotrophoblast; (2) GLUT1 and GLUT3 on amnion epithelial cells are predominantly located on the apical surface; (3) GLUT4 and insulin receptors are not regularly expressed. We suggest that amnion epithelial cells cover their basal glucose requirements from the amniotic fluid and not from the maternal circulation.

  9. Insulin receptor substrate-3, interacting with Bcl-3, enhances p50 NF-{kappa}B activity

    SciTech Connect

    Kabuta, Tomohiro; Hakuno, Fumihiko; Cho, Yoshitake; Yamanaka, Daisuke; Chida, Kazuhiro; Asano, Tomoichiro; Wada, Keiji; Takahashi, Shin-Ichiro

    2010-04-09

    The insulin receptor substrate (IRS) proteins are major substrates of both insulin receptor and insulin-like growth factor (IGF)-I receptor tyrosine kinases. Previously, we reported that IRS-3 is localized to both cytosol and nucleus, and possesses transcriptional activity. In the present study, we identified Bcl-3 as a novel binding protein to IRS-3. Bcl-3 is a nuclear protein, which forms a complex with the homodimer of p50 NF-{kappa}B, leading to enhancement of transcription through p50 NF-{kappa}B. We found that Bcl-3 interacts with the pleckstrin homology domain and the phosphotyrosine binding domain of IRS-3, and that IRS-3 interacts with the ankyrin repeat domain of Bcl-3. In addition, IRS-3 augmented the binding activity of p50 to the NF-{kappa}B DNA binding site, as well as the tumor necrosis factor (TNF)-{alpha}-induced transcriptional activity of NF-{kappa}B. Lastly, IRS-3 enhanced NF-{kappa}B-dependent anti-apoptotic gene induction and consequently inhibited TNF-{alpha}-induced cell death. This series of results proposes a novel function for IRS-3 as a transcriptional regulator in TNF-{alpha} signaling, distinct from its function as a substrate of insulin/IGF receptor kinases.

  10. Receptor-mediated endocytosis of insulin in lower vertebrates: internalization and intracellular processing of 125I-insulin in isolated hepatocytes of lamprey and frog.

    PubMed

    Lappova, Y L; Leibush, B N

    1995-10-01

    The binding of 125I-insulin to cellular insulin receptors and the internalization of insulin-receptor complexes have been studied in isolated hepatocytes of frog and lamprey. Two classes of binding sites (Kd 10(-9) and 10(-8) M) were found in cells of both species. The molecular weight of the insulin receptor alpha-subunit was 130 kDa in both species. Internalization of bound 125I-insulin in both species was found in the temperature range 0 to 20 degrees. Cells "loaded" with 125I-insulin were used to estimate the fate of the internalized ligand. Release of internalized ligand from frog cells increased at temperatures ranging from 0 to 20 degrees. At 0 degrees the degraded 125I-insulin was 5%, at 5 degrees 7%, and at 20 degrees 17% of total radioactivity accumulated in the medium. In lamprey hepatocytes there was neither radioactivity accumulation in the incubation medium nor release from cells at all temperatures studied. The intracellular degradation of internalized 125I-insulin in frog hepatocytes was much lower than that in lamprey cells. In frog hepatocytes the specific binding of 125I-insulin was increased twofold in the presence of the lysosomal inhibitor chloroquine. In contrast no increase was found in lamprey hepatocytes. In conclusion, the processing pathways of internalized insulin in the cells of ectothermal and endothermal vertebrates are generally similar but in ectothermal animals all events take place at lower temperatures and at lower rates. The peculiarities of insulin processing in lamprey hepatocytes most likely result from the transformation of hepatocytes during the nonfeeding prespawning period. PMID:8575649

  11. Circadian Misalignment Augments Markers of Insulin Resistance and Inflammation, Independently of Sleep Loss

    PubMed Central

    Leproult, Rachel; Holmbäck, Ulf; Van Cauter, Eve

    2014-01-01

    Shift workers, who are exposed to irregular sleep schedules resulting in sleep deprivation and misalignment of circadian rhythms, have an increased risk of diabetes relative to day workers. In healthy adults, sleep restriction without circadian misalignment promotes insulin resistance. To determine whether the misalignment of circadian rhythms that typically occurs in shift work involves intrinsic adverse metabolic effects independently of sleep loss, a parallel group design was used to study 26 healthy adults. Both interventions involved 3 inpatient days with 10-h bedtimes, followed by 8 inpatient days of sleep restriction to 5 h with fixed nocturnal bedtimes (circadian alignment) or with bedtimes delayed by 8.5 h on 4 of the 8 days (circadian misalignment). Daily total sleep time (SD) during the intervention was nearly identical in the aligned and misaligned conditions (4 h 48 min [5 min] vs. 4 h 45 min [6 min]). In both groups, insulin sensitivity (SI) significantly decreased after sleep restriction, without a compensatory increase in insulin secretion, and inflammation increased. In male participants exposed to circadian misalignment, the reduction in SI and the increase in inflammation both doubled compared with those who maintained regular nocturnal bedtimes. Circadian misalignment that occurs in shift work may increase diabetes risk and inflammation, independently of sleep loss. PMID:24458353

  12. Disruption of insulin receptor function inhibits proliferation in endocrine resistant breast cancer cells

    PubMed Central

    Chan, Jie Ying; LaPara, Kelly; Yee, Douglas

    2015-01-01

    The insulin-like growth factor (IGF) system is a well-studied growth regulatory pathway implicated in breast cancer biology. Clinical trials testing monoclonal antibodies directed against the type I IGF receptor (IGF1R) in combination with estrogen receptor-α (ER) targeting have been completed, but failed to show benefits in patients with endocrine resistant tumors compared to ER targeting alone. We have previously shown that the closely related insulin receptor (InsR) is expressed in tamoxifen resistant breast cancer cells. Here we examined if inhibition of InsR affected tamoxifen-resistant (TamR) breast cancer cells. InsR function was inhibited by three different mechanisms: InsR shRNA, a small InsR blocking peptide, S961 and an InsR monoclonal antibody (mAb). Suppression of InsR function by these methods in TamR cells successfully blocked insulin-mediated signaling, monolayer proliferation, cell cycle progression and anchorage-independent growth. This strategy was not effective in parental cells likely due to the presence of IGFR/InsR hybrid receptors. Down-regulation of IGF1R in conjunction with InsR inhibition was more effective in blocking IGF- and insulin-mediated signaling and growth in parental cells compared to single receptor targeting alone. Our findings show TamR cells were stimulated by InsR and were not sensitive to IGF1R inhibition, whereas in tamoxifen-sensitive parental cancer cells, the presence of both receptors, especially hybrid receptors, allowed cross-reactivity of ligand-mediated activation and growth. To suppress the IGF system, targeting of both IGF1R and InsR is optimal in endocrine sensitive and resistant breast cancer. PMID:26876199

  13. Glutamate receptors in the hypothalamic paraventricular nucleus contribute to insulin-induced sympathoexcitation

    PubMed Central

    Gordon, Kathryn W.

    2014-01-01

    The sympathoexcitatory response to insulin is mediated by neurons in the arcuate nucleus (ARC) and hypothalamic paraventricular nucleus (PVH). Previous studies have reported that stimulation of ARC neurons increases sympathetic nerve activity (SNA) and arterial blood pressure (ABP) through glutamate receptor activation in the PVH. Therefore, the purpose of the present study was to determine whether glutamatergic neurotransmission in the PVH contributes to insulin-induced sympathoexcitation. Male Sprague-Dawley rats (275–400 g) were infused with isotonic saline or insulin (3.75 mU·kg−1·min−1) plus 50% dextrose to maintain euglycemia. Intravenous infusion of insulin significantly increased lumbar SNA without a significant change in mean ABP, renal SNA, heart rate, or blood glucose. Bilateral PVH injection of the excitatory amino acid antagonist kynurenic acid (KYN) lowered lumbar SNA and ABP of animals infused with insulin. Similarly, a cocktail of the NMDA antagonist dl-2-amino-5-phosphonopentanoic acid (AP5) and non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) reduced lumbar SNA and mean ABP during infusion of insulin. In a final experiment, bilateral PVH injection of AP5 only, but not CNQX, lowered lumbar SNA and mean ABP of animals infused with insulin. The peak changes in lumbar SNA and mean ABP of insulin-treated animals were not different between KYN, AP5 plus CNQX, or AP5 alone. These drug treatments did not alter any variable in animals infused with saline. Altogether, these findings suggest that glutamatergic NMDA neurotransmission in the PVH contributes to insulin-induced sympathoexcitation. PMID:25475355

  14. Heterodimerization of Glycosylated Insulin-Like Growth Factor-1 Receptors and Insulin Receptors in Cancer Cells Sensitive to Anti-IGF1R Antibody

    PubMed Central

    Kim, Jun Gyu; Kang, Min Jueng; Yoon, Young-Kwang; Kim, Hwang-Phill; Park, Jinah; Song, Sang-Hyun; Han, Sae-Won; Park, Jong-Wan; Kang, Gyeong Hoon; Kang, Keon Wook; Oh, Do Youn; Im, Seock-Ah; Bang, Yung-Jue; Yi, Eugene C.; Kim, Tae-You

    2012-01-01

    Background Identification of predictive biomarkers is essential for the successful development of targeted therapy. Insulin-like growth factor 1 receptor (IGF1R) has been examined as a potential therapeutic target for various cancers. However, recent clinical trials showed that anti-IGF1R antibody and chemotherapy are not effective for treating lung cancer. Methodology/Principal Findings In order to define biomarkers for predicting successful IGF1R targeted therapy, we evaluated the anti-proliferation effect of figitumumab (CP-751,871), a humanized anti-IGF1R antibody, against nine gastric and eight hepatocellular cancer cell lines. Out of 17 cancer cell lines, figitumumab effectively inhibited the growth of three cell lines (SNU719, HepG2, and SNU368), decreased p-AKT and p-STAT3 levels, and induced G 1 arrest in a dose-dependent manner. Interestingly, these cells showed co-overexpression and altered mobility of the IGF1R and insulin receptor (IR). Immunoprecipitaion (IP) assays and ELISA confirmed the presence of IGF1R/IR heterodimeric receptors in figitumumab-sensitive cells. Treatment with figitumumab led to the dissociation of IGF1-dependent heterodimeric receptors and inhibited tumor growth with decreased levels of heterodimeric receptors in a mouse xenograft model. We next found that both IGF1R and IR were N-linked glyosylated in figitumumab-sensitive cells. In particular, mass spectrometry showed that IGF1R had N-linked glycans at N913 in three figitumumab-sensitive cell lines. We observed that an absence of N-linked glycosylation at N913 led to a lack of membranous localization of IGF1R and figitumumab insensitivity. Conclusion and Significance The data suggest that the level of N-linked glycosylated IGF1R/IR heterodimeric receptor is highly associated with sensitivity to anti-IGF1R antibody in cancer cells. PMID:22438913

  15. Central Administration of Galanin Receptor 1 Agonist Boosted Insulin Sensitivity in Adipose Cells of Diabetic Rats

    PubMed Central

    Zhang, Zhenwen; Fang, Penghua; He, Biao; Guo, Lili; Runesson, Johan; Langel, Ülo; Shi, Mingyi; Zhu, Yan; Bo, Ping

    2016-01-01

    Our previous studies testified the beneficial effect of central galanin on insulin sensitivity of type 2 diabetic rats. The aim of the study was further to investigate whether central M617, a galanin receptor 1 agonist, can benefit insulin sensitivity. The effects of intracerebroventricular administration of M617 on insulin sensitivity and insulin signaling were evaluated in adipose tissues of type 2 diabetic rats. The results showed that central injection of M617 significantly increased plasma adiponectin contents, glucose infusion rates in hyperinsulinemic-euglycemic clamp tests, GLUT4 mRNA expression levels, GLUT4 contents in plasma membranes, and total cell membranes of the adipose cells but reduced the plasma C-reactive protein concentration in nondiabetic and diabetic rats. The ratios of GLUT4 contents were higher in plasma membranes to total cell membranes in both nondiabetic and diabetic M617 groups than each control. In addition, the central administration of M617 enhanced the ratios of pAkt/Akt and pAS160/AS160, but not phosphorylative cAMP response element-binding protein (pCREB)/CREB in the adipose cells of nondiabetic and diabetic rats. These results suggest that excitation of central galanin receptor 1 facilitates insulin sensitivity via activation of the Akt/AS160 signaling pathway in the fat cells of type 2 diabetic rats. PMID:27127795

  16. Regulator of insulin receptor affinity in rat skeletal muscle sarcolemmal vesicles

    SciTech Connect

    Whitson, R.H.; Barnard, K.J.; Kaplan, S.A.; Itakura, K.

    1986-05-01

    Wheat germ agglutinin (WGA) affinity purification of detergent solubilized insulin receptors (IR) from rat skeletal muscle sarcolemmal vesicles resulted in an apparent increase in total insulin binding activity of greater than 5-fold, suggesting that an inhibitory component had been removed. This was verified when the flow-through fraction from the WGA column was dialyzed and added back to the partially purified receptor. The addition of a 100-fold dilution of the inhibitor preparation caused a 50% reduction in binding to trace amounts of /sup 125/I-insulin. Scatchard analysis revealed that the effect of the inhibitor was to decrease the affinity of the muscle IR. The inhibitor appeared to be tissue specific, inasmuch as the I/sub 50/'s for WGA-purified IR from rat fat and liver were 10 times the I/sub 50/ for muscle IR. The I/sub 50/ for insulin binding to intact IM-9 cells was 30 times the value for muscle IR. The inhibitor eluted in the void volume of Sephadex G-50 columns. Its activity was not destroyed by heating at 90/sup 0/C for 10 minutes, or by prolonged incubation with trypsin or dithiothreitol. The inhibitor described here may have a role in modulating insulin sensitivity in skeletal muscle.

  17. Insulin-like growth factor receptor type I as a target for cancer therapy.

    PubMed

    Corvaia, Nathalie; Beck, Alain; Caussanel, Véronique; Goetsch, Liliane

    2013-01-01

    After more than 20 years of extensive work, insulin-like growth factor receptor 1 (IGF-IR) is still an attractive target for drug development. Due to its close homology to insulin receptor, IGF-IR is of interest for antibody design while antibody great specificity allows to discriminate between the two receptors. Major efforts from a large number of pharmaceutical companies are invested to evaluate the efficacy of such molecules in human without so far an obvious success. Discovery of biomarkers associated with efficacy and patient selection is one of the main challenges that we will have to deal with in order to target the appropriate patient population that will most benefit anti-IGF-IR monoclonal antibody (Mab) and combined treatments. This review will provide an overview of the current knowledge on IGF-IR axis for development of novel therapeutics in Oncology.

  18. Differential insertion of insulin receptor complexes into Triton X-114 bilayer membranes. Evidence for a differential accessibility of the membrane-exposed receptor domain.

    PubMed

    Flörke, R R; Klein, H W; Reinauer, H

    1993-01-15

    In the present study, the Triton X-114 phase-separation system has been used to characterize molecular properties of the membrane-exposed domain of an integral-membrane hormone receptor. This approach provides novel details of the structure/function relationship of insulin receptors. Upon raising the temperature of a micellar Triton X-114 solution above the cloud-point, a detergent enriched phase pellets and coprecipitates 95% of the purified insulin-free (alpha beta)2 receptors. In contrast, 83% of the hormone bound (alpha beta)2 receptor complexes prefer the detergent-depleted phase, exhibiting prominent properties of non-membraneous proteins. Kinetic studies show that, following insulin binding, the amphiphilicity of the receptor complexes is immediately altered. Only monodisperse (alpha beta)2 complexes were detected when receptor/insulin complexes of the detergent-depleted phase were analyzed by detergent-free sucrose density centrifugation in the presence of 10 nM insulin. These results can be explained in the light of the lipid-bilayer-like organization of the precipitating Triton X-114; hormone-induced intramolecular alterations of (alpha beta)2 receptors appear to fundamentally restrict access to the membrane-exposed receptor domain. Basically, different molecular properties are found for alpha beta receptors. Only 67% of the insulin-free receptors coprecipitate with the Triton-X-114-enriched phase; following insulin binding the coprecipitation is only decreased to 42%. In contrast to (alpha beta)2 receptors, formation of noncovalently aggregated receptor complexes, which are detected by sucrose density centrifugation, could account for the exclusion of alpha beta receptor species from Triton X-114 membranes.

  19. Insulin receptor binding motif tagged with IgG4 Fc (Yiminsu) works as an insulin sensitizer to activate Akt signaling in hepatocytes.

    PubMed

    Wang, J; Zou, T; Yang, H X; Gong, Y Z; Xie, X J; Liu, H Y; Liao, D F

    2015-01-01

    Insulin resistance is a key feature of obesity and type 2 diabetes mellitus (T2DM). Interaction of insulin with the insulin receptor (IR) leads to both its auto-phosphorylation and phosphorylation of tyrosine residues on the IR substrate (IRS) proteins, initiating the activation of intracellular signaling cascades. The metabolic effects of IRS are known to be mediated through pathways involving phosphatidyl-inositol 3-kinase (PI-3K), which result in the activation of Akt signaling. The C-terminal region of the IR ectodomain is required to facilitate the conformational changes that are required for high-affinity binding to insulin. Furthermore, the CH2 and CH3 domains in the Fc fragments of immunoglobulins are responsible for their binding to the Fc receptor, which triggers transcytosis. In this study, we created a fusion peptide of the C-terminal end of the human IR ectodomain with the IgG4 Fc fragment, including an intervening polyG fragment to ensure enough space for insulin binding. We named this new peptide "Yiminsu", meaning an insulin sensitizer. The results of our analyses show that Yiminsu significantly facilitates insulin signaling via the activation of Akt in hepatocytes in a dose- and time-dependent manner. Further studies are required to determine whether Yiminsu can act as an insulin sensitizer. PMID:26345813

  20. Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation.

    PubMed

    Yunn, Na-Oh; Koh, Ara; Han, Seungmin; Lim, Jong Hun; Park, Sehoon; Lee, Jiyoun; Kim, Eui; Jang, Sung Key; Berggren, Per-Olof; Ryu, Sung Ho

    2015-09-18

    Due to their high affinity and specificity, aptamers have been widely used as effective inhibitors in clinical applications. However, the ability to activate protein function through aptamer-protein interaction has not been well-elucidated. To investigate their potential as target-specific agonists, we used SELEX to generate aptamers to the insulin receptor (IR) and identified an agonistic aptamer named IR-A48 that specifically binds to IR, but not to IGF-1 receptor. Despite its capacity to stimulate IR autophosphorylation, similar to insulin, we found that IR-A48 not only binds to an allosteric site distinct from the insulin binding site, but also preferentially induces Y1150 phosphorylation in the IR kinase domain. Moreover, Y1150-biased phosphorylation induced by IR-A48 selectively activates specific signaling pathways downstream of IR. In contrast to insulin-mediated activation of IR, IR-A48 binding has little effect on the MAPK pathway and proliferation of cancer cells. Instead, AKT S473 phosphorylation is highly stimulated by IR-A48, resulting in increased glucose uptake both in vitro and in vivo. Here, we present IR-A48 as a biased agonist able to selectively induce the metabolic activity of IR through allosteric binding. Furthermore, our study also suggests that aptamers can be a promising tool for developing artificial biased agonists to targeted receptors. PMID:26245346

  1. Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation

    PubMed Central

    Yunn, Na-Oh; Koh, Ara; Han, Seungmin; Lim, Jong Hun; Park, Sehoon; Lee, Jiyoun; Kim, Eui; Jang, Sung Key; Berggren, Per-Olof; Ryu, Sung Ho

    2015-01-01

    Due to their high affinity and specificity, aptamers have been widely used as effective inhibitors in clinical applications. However, the ability to activate protein function through aptamer-protein interaction has not been well-elucidated. To investigate their potential as target-specific agonists, we used SELEX to generate aptamers to the insulin receptor (IR) and identified an agonistic aptamer named IR-A48 that specifically binds to IR, but not to IGF-1 receptor. Despite its capacity to stimulate IR autophosphorylation, similar to insulin, we found that IR-A48 not only binds to an allosteric site distinct from the insulin binding site, but also preferentially induces Y1150 phosphorylation in the IR kinase domain. Moreover, Y1150-biased phosphorylation induced by IR-A48 selectively activates specific signaling pathways downstream of IR. In contrast to insulin-mediated activation of IR, IR-A48 binding has little effect on the MAPK pathway and proliferation of cancer cells. Instead, AKT S473 phosphorylation is highly stimulated by IR-A48, resulting in increased glucose uptake both in vitro and in vivo. Here, we present IR-A48 as a biased agonist able to selectively induce the metabolic activity of IR through allosteric binding. Furthermore, our study also suggests that aptamers can be a promising tool for developing artificial biased agonists to targeted receptors. PMID:26245346

  2. Identification and evolution of two insulin receptor genes involved in Tribolium castaneum development and reproduction.

    PubMed

    Sang, Ming; Li, Chengjun; Wu, Wei; Li, Bin

    2016-07-10

    The insulin and insulin-like signaling (IIS) pathway exists in a wide range of organisms from mammals to invertebrates and regulates several vital physiological functions. A phylogenetic analysis have indicated that insulin receptors have been duplicated at least twice among vertebrates, whereas only one duplication occurred in insects before the differentiation of Coleoptera, Hymenoptera, and Hemiptera. Thus, we cloned two putative insulin receptor genes, T.cas-ir1 and T.cas-ir2, from T. castaneum and determined that T.cas-ir1 is most strongly expressed during the late adult and early pupal stages, whereas T.cas-ir2 is most strongly expressed during the late larval stage. We found that larval RNAi against T.cas-ir1 and T.cas-ir2 causes 100% and 42.0% insect death, respectively, and that parental RNAi against T.cas-ir1 and T.cas-ir2 leads to 100% and 33.3% reductions in beetle fecundity, respectively. The hatching rate of ds-ir2 insects was 66.2%. Moreover, RNAi against these two genes increased the expression of the pkc, foxo, jnk, cdc42, ikk, and mekk genes but decreased erk gene expression. Despite these similarities, these two genes act via distinct regulatory pathways. These results indicate that these two receptors have functionally diverged with respect to the development and reproduction of T. castaneum, even though they retain some common regulatory signaling pathways.

  3. Inhibition of insulin/IGF-1 receptor signaling protects from mitochondria-mediated kidney failure.

    PubMed

    Ising, Christina; Koehler, Sybille; Brähler, Sebastian; Merkwirth, Carsten; Höhne, Martin; Baris, Olivier R; Hagmann, Henning; Kann, Martin; Fabretti, Francesca; Dafinger, Claudia; Bloch, Wilhelm; Schermer, Bernhard; Linkermann, Andreas; Brüning, Jens C; Kurschat, Christine E; Müller, Roman-Ulrich; Wiesner, Rudolf J; Langer, Thomas; Benzing, Thomas; Brinkkoetter, Paul Thomas

    2015-02-02

    Mitochondrial dysfunction and alterations in energy metabolism have been implicated in a variety of human diseases. Mitochondrial fusion is essential for maintenance of mitochondrial function and requires the prohibitin ring complex subunit prohibitin-2 (PHB2) at the mitochondrial inner membrane. Here, we provide a link between PHB2 deficiency and hyperactive insulin/IGF-1 signaling. Deletion of PHB2 in podocytes of mice, terminally differentiated cells at the kidney filtration barrier, caused progressive proteinuria, kidney failure, and death of the animals and resulted in hyperphosphorylation of S6 ribosomal protein (S6RP), a known mediator of the mTOR signaling pathway. Inhibition of the insulin/IGF-1 signaling system through genetic deletion of the insulin receptor alone or in combination with the IGF-1 receptor or treatment with rapamycin prevented hyperphosphorylation of S6RP without affecting the mitochondrial structural defect, alleviated renal disease, and delayed the onset of kidney failure in PHB2-deficient animals. Evidently, perturbation of insulin/IGF-1 receptor signaling contributes to tissue damage in mitochondrial disease, which may allow therapeutic intervention against a wide spectrum of diseases.

  4. Linkage disequilibrium among RFLPs at the insulin-receptor locus despite intervening alu repeat sequences

    SciTech Connect

    Elbein, S.C. )

    1992-11-01

    Multiple mutations of the insulin receptor (INSR) gene have been identified in individuals with extreme insulin resistance. These mutations have included recombination events between Alu repeat units in the tyrosine kinase-encoding [beta]-chain region of the gene. To evaluate the influence of Alu and dinucleotide repetitive sequences on recombination events within the insulin receptor gene, the author examined the degree of linkage disequilibrium between RFLP pairs spanning the gene. The author established 228 independent haplotypes for seven RFLPs (two each for PstI, RsaI, and SstI and one for MspI and 172 independent haplotypes which included an additional RFLP with BglII) from 19 pedigrees. These RFLPs span >130 kb of this gene, and it was previously demonstrated that multiple Alu sequences separate RFLP pairs. Observed haplotype frequencies deviated significantly from those predicted. Pairwise analysis of RFLP showed high levels of linkage disequilibrium among RFLP in the [beta]-chain region of the insulin receptor, but not between [alpha]-chain RFLPs and those of the [beta]-chain. Disequilibrium was present among [beta]-chain RFLPs, despite separation by one or more Alu repeat sequences. The very strong linkage disequilibrium which was present in sizable regions of the INSR gene despite the presence of both Alu and microsatellite repeats suggested that these regions do not have a major impact on recombinations at this locus. 25 refs., 1 fig., 5 tabs.

  5. [Clinical effects of the alterations that emerge in the signaling mechanisms of the insulin receptor].

    PubMed

    Hernández-Valencia, Marcelino

    2006-01-01

    Phosphorilation of subunit beta from insulin receptor induced mainly by insulin, it begins a series of intracellular complex signaling in cascade. Through this way establish multiple effects, which permits to the cell initiate its biological activity. This activity include the glucose metabolism, the regulation of ions and amino acids transport, lipids metabolism, glycogen synthesis, genetic transcription, mRNA expression, synthesis and degradation of proteins, as well as synthesis of DNA. Therefore, a modification in anyone of the proteins involved in the insulin signaling, can take place a dysfunction in the glucose metabolism. The impaired glucose can be due because there are many proteins, ions and enzymes that participate in the downstream pathways of the insulin signaling, it has become difficult to find a single phatophysiologic level as cause of diabetes. In spite of the advances in the study of this disease, it has been reached the conclusion that the glucose control is not enough to impede the complications that characterize to type 2 diabetes, since the organic worsening does not stop, which indicates that insulin signaling dysfunction is directly involved in all cellular process, and a better understanding in the communication ways of this hormone will take to new forms of treatment to impaired insulin response.

  6. Involvement of PRMT1 in hnRNPQ activation and internalization of insulin receptor

    SciTech Connect

    Iwasaki, Hiroaki

    2008-07-25

    Insulin signaling in skeletal L6 myotubes is known to be affected by arginine methylation catalyzed by protein N-arginine methyltransferase 1 (PRMT1), however, the mechanism by which this occurs has not yet been defined. This study aimed to determine the exact substrate involved in the methylation and regulating insulin signaling in cells. Insulin enhanced arginine methylation of a 66-kDa protein (p66) concomitant with translocation of PRMT1 to the membrane fraction. Peptide mass fingerprinting identified p66 as a heterogeneous nuclear ribonucleoprotein, hnRNPQ that was bound to and methylated by PRMT1. Pharmacological inhibition of methylation (MTA) and small interfering RNA against PRMT1 (PRMT1-siRNA) attenuated insulin-stimulated tyrosine phosphorylation of hnRNPQ and insulin receptor (IR), and the interaction between hnRNPQ and IR. MTA, PRMT1-siRNA, and hnRNPQ-siRNA inhibited internalization of IR in the same manner. These data suggest that the PRMT1-mediated methylation of hnRNPQ is implicated in IR trafficking and insulin signaling in skeletal L6 myotubes.

  7. Additional disulfide bonds in insulin: Prediction, recombinant expression, receptor binding affinity, and stability

    PubMed Central

    Vinther, Tine N; Pettersson, Ingrid; Huus, Kasper; Schlein, Morten; Steensgaard, Dorte B; Sørensen, Anders; Jensen, Knud J; Kjeldsen, Thomas; Hubalek, František

    2015-01-01

    The structure of insulin, a glucose homeostasis-controlling hormone, is highly conserved in all vertebrates and stabilized by three disulfide bonds. Recently, we designed a novel insulin analogue containing a fourth disulfide bond located between positions A10-B4. The N-terminus of insulin's B-chain is flexible and can adapt multiple conformations. We examined how well disulfide bond predictions algorithms could identify disulfide bonds in this region of insulin. In order to identify stable insulin analogues with additional disulfide bonds, which could be expressed, the Cβ cut-off distance had to be increased in many instances and single X-ray structures as well as structures from MD simulations had to be used. The analogues that were identified by the algorithm without extensive adjustments of the prediction parameters were more thermally stable as assessed by DSC and CD and expressed in higher yields in comparison to analogues with additional disulfide bonds that were more difficult to predict. In contrast, addition of the fourth disulfide bond rendered all analogues resistant to fibrillation under stress conditions and all stable analogues bound to the insulin receptor with picomolar affinities. Thus activity and fibrillation propensity did not correlate with the results from the prediction algorithm. PMID:25627966

  8. Specific factors are required for kinase-dependent endocytosis of insulin receptors.

    PubMed Central

    Welsh, J B; Worthylake, R; Wiley, H S; Gill, G N

    1994-01-01

    Mouse B82 cells that support high affinity saturable endocytosis of epidermal growth factor receptors (EGFR) exhibited only low rates of nonsaturable internalization of insulin receptors (InsR). To investigate the defect in endocytosis of InsR in B82 cells, we examined the role of sequence motifs and tyrosine kinase, the two receptor components shown to be required for efficient saturable endocytosis of InsR in Rat 1 cells. Placement of residues encoded by exon 16 of the InsR onto an EGFR truncated to residue 958 restored EGF-induced internalization of this mutant receptor indicating that the sequence codes in exon 16 are recognized by B82 cells. To determine whether the kinase function could be provided in trans, a B82 cell expressing both receptors was established. EGF-activated EGFR kinase was not able to restore insulin-dependent rapid endocytosis to InsR. However, fusion of untransfected Rat1 cells with InsR-expressing B82 cells enabled rapid endocytosis of InsR, indicating that the internalization defect can be complemented. These results indicate that, although internalization codes can function in the context of other receptors, activation of tyrosine kinase receptors requires an additional specific component. Images PMID:7919536

  9. Preclinical and first-in-human phase I studies of KW-2450, an oral tyrosine kinase inhibitor with insulin-like growth factor receptor-1/insulin receptor selectivity.

    PubMed

    Schwartz, Gary K; Dickson, Mark A; LoRusso, Patricia M; Sausville, Edward A; Maekawa, Yoshimi; Watanabe, Yasuo; Kashima, Naomi; Nakashima, Daisuke; Akinaga, Shiro

    2016-04-01

    Numerous solid tumors overexpress or have excessively activated insulin-like growth factor receptor-1 (IGF-1R). We summarize preclinical studies and the first-in-human study of KW-2450, an oral tyrosine kinase inhibitor with IGF-1R and insulin receptor (IR) inhibitory activity. Preclinical activity of KW-2450 was evaluated in various in vitro and in vivo models. It was then evaluated in a phase I clinical trial in 13 patients with advanced solid tumors (NCT00921336). In vitro, KW-2450 inhibited human IGF-1R and IR kinases (IC50 7.39 and 5.64 nmol/L, respectively) and the growth of various human malignant cell lines. KW-2450 40 mg/kg showed modest growth inhibitory activity and inhibited IGF-1-induced signal transduction in the murine HT-29/GFP colon carcinoma xenograft model. The maximum tolerated dose of KW-2450 was 37.5 mg once daily continuously; dose-limiting toxicity occurred in two of six patients at 50 mg/day (both grade 3 hyperglycemia) and in one of seven patients at 37.5 mg/day (grade 3 rash). Four of 10 evaluable patients showed stable disease. Single-agent KW-2450 was associated with modest antitumor activity in heavily pretreated patients with solid tumors and is being further investigated in combination therapy with lapatinib/letrozole in patients with human epidermal growth factor receptor 2-postive metastatic breast cancer. PMID:26850678

  10. A single night of partial sleep loss impairs fasting insulin sensitivity but does not affect cephalic phase insulin release in young men.

    PubMed

    Cedernaes, Jonathan; Lampola, Lauri; Axelsson, Emil K; Liethof, Lisanne; Hassanzadeh, Sara; Yeganeh, Adine; Broman, Jan-Erik; Schiöth, Helgi B; Benedict, Christian

    2016-02-01

    The present study sought to investigate whether a single night of partial sleep deprivation (PSD) would alter fasting insulin sensitivity and cephalic phase insulin release (CPIR) in humans. A rise in circulating insulin in response to food-related sensory stimulation may prepare tissues to break down ingested glucose, e.g. by stimulating rate-limiting glycolytic enzymes. In addition, given insulin's anorexigenic properties once it reaches the brain, the CPIR may serve as an early peripheral satiety signal. Against this background, in the present study 16 men participated in two separate sessions: one night of PSD (4.25 h sleep) versus one night of full sleep (8.5 h sleep). In the morning following each sleep condition, subjects' oral cavities were rinsed with a 1-molar sucrose solution for 45 s, preceded and followed by blood sampling for repeated determination of plasma glucose and serum insulin concentrations (-3, +3, +5, +7, +10 and +20 min). Our main result was that PSD, compared with full sleep, was associated with significantly higher peripheral insulin resistance, as indicated by a higher fasting homeostasis model assessment of insulin resistance index (+16%, P = 0.025). In contrast, no CPIR was observed in any of the two sleep conditions. Our findings indicate that a single night of PSD is already sufficient to impair fasting insulin sensitivity in healthy men. In contrast, brief oral cavity rinsing with sucrose solution did not change serum insulin concentrations, suggesting that a blunted CPIR is an unlikely mechanism through which acute sleep loss causes metabolic perturbations during morning hours in humans. PMID:26361380

  11. Loss of Olfactory Receptor Function in Hominin Evolution

    PubMed Central

    Hughes, Graham M.; Teeling, Emma C.; Higgins, Desmond G.

    2014-01-01

    The mammalian sense of smell is governed by the largest gene family, which encodes the olfactory receptors (ORs). The gain and loss of OR genes is typically correlated with adaptations to various ecological niches. Modern humans have 853 OR genes but 55% of these have lost their function. Here we show evidence of additional OR loss of function in the Neanderthal and Denisovan hominin genomes using comparative genomic methodologies. Ten Neanderthal and 8 Denisovan ORs show evidence of loss of function that differ from the reference modern human OR genome. Some of these losses are also present in a subset of modern humans, while some are unique to each lineage. Morphological changes in the cranium of Neanderthals suggest different sensory arrangements to that of modern humans. We identify differences in functional olfactory receptor genes among modern humans, Neanderthals and Denisovans, suggesting varied loss of function across all three taxa and we highlight the utility of using genomic information to elucidate the sensory niches of extinct species. PMID:24392153

  12. Loss of olfactory receptor function in hominin evolution.

    PubMed

    Hughes, Graham M; Teeling, Emma C; Higgins, Desmond G

    2014-01-01

    The mammalian sense of smell is governed by the largest gene family, which encodes the olfactory receptors (ORs). The gain and loss of OR genes is typically correlated with adaptations to various ecological niches. Modern humans have 853 OR genes but 55% of these have lost their function. Here we show evidence of additional OR loss of function in the Neanderthal and Denisovan hominin genomes using comparative genomic methodologies. Ten Neanderthal and 8 Denisovan ORs show evidence of loss of function that differ from the reference modern human OR genome. Some of these losses are also present in a subset of modern humans, while some are unique to each lineage. Morphological changes in the cranium of Neanderthals suggest different sensory arrangements to that of modern humans. We identify differences in functional olfactory receptor genes among modern humans, Neanderthals and Denisovans, suggesting varied loss of function across all three taxa and we highlight the utility of using genomic information to elucidate the sensory niches of extinct species.

  13. High-level expression of human insulin receptor cDNA in mouse NIH 3T3 cells

    SciTech Connect

    Whittaker, J.; Okamoto, A.K.; Thys, R.; Bell, G.I.; Steiner, D.F.; Hofmann, C.A.

    1987-08-01

    In order to develop a simple, efficient system for the high-level expression of human insulin receptors in eukaryotic cells, a full-length human kidney insulin receptor cDNA was inserted into a bovine papilloma virus vector under the control of the mouse metallothionein promoter. After transfection of mouse NIH 3T3 cells with this construct, seven cell lines expressing insulin receptors were isolated; two cell lines had more than 10/sup 6/ receptors per cell. The cell line with the highest /sup 125/I-insulin binding (NIH 3T3 HIR3.5) had 6 x 10/sup 6/ receptors with a K/sub d/ of 10/sup -9/ M. This level was not dependent on exposure to metals but could be increased further to 2 x 10/sup 7/ receptors per cell by addition of sodium butyrate to the culture medium. The ..cap alpha.. and ..beta.. subunits had apparent molecular weights of 147,000 and 105,000, respectively (compared to 135,000 and 95,000 in IM-9 human lymphocytes), values identical to those of the ..cap alpha.. and ..beta.. subunits of the insulin receptors of nontransformed NIH 3T3 cells. This size difference was due to altered carbohydrate composition, as N-glycanase digestion reduced the apparent receptor subunit size of the transfected cells and IM-9 lymphocytes to identical values. The alteration in N-linked oligosaccharide composition could not be ascribed to differences in the kinetics of posttranslational processing of the insulin receptors, which was comparable to that of other cells studied. The basal rate of glycogen synthesis in the cells overexpressing insulin receptors was increased 4- to 5-fold compared with controls. Low levels of added insulin (0.1 nM) caused a 50% increase in the rate of glycogen synthesis

  14. Inherent insulin sensitivity is a major determinant of multimeric adiponectin responsiveness to short-term weight loss in extreme obesity

    PubMed Central

    Mai, Stefania; Walker, Gillian E.; Brunani, Amelia; Guzzaloni, Gabriele; Grossi, Glenda; Oldani, Alberto; Aimaretti, Gianluca; Scacchi, Massimo; Marzullo, Paolo

    2014-01-01

    High molecular weight (HMW-A) adiponectin levels mirror alterations in glucose homeostasis better than medium (MMW-A) and low molecular weight (LMW-A) components. In 25 patients with wide-range extreme obesity (BMI 40-77 kg/m2), we aimed to explore if improvements of multimeric adiponectin following 4-wk weight loss reflect baseline OGTT-derived insulin sensitivity (ISIOGTT) and disposition index (DIOGTT). Compared to 40 lean controls, adiponectin oligomers were lower in extreme obesity (p < 0.001) and, within this group, HMW-A levels were higher in insulin-sensitive (p < 0.05) than -resistant patients. In obese patients, short-term weight loss did not change total adiponectin levels and insulin resistance, while the distribution pattern of adiponectin oligomers changed due to significant increment of HMW-A (p < 0.01) and reduction of MMW-A (p < 0.05). By multivariate analysis, final HMW-A levels were significantly related to baseline ISIOGTT and final body weight (adjusted R2 = 0.41). Our data suggest that HMW adiponectin may reflect baseline insulin sensitivity appropriately in the context of extreme obesity. Especially, we documented that HMW-A is promptly responsive to short-term weight loss prior to changes in insulin resistance, by a magnitude that is proportioned to whole body insulin sensitivity. This may suggest an insulin sensitivity-dependent control operated by HMW-A on metabolic dynamics of patients with extreme obesity. PMID:25056918

  15. Low-Density Lipoprotein Receptor-Related Protein-1 Protects Against Hepatic Insulin Resistance and Hepatic Steatosis.

    PubMed

    Ding, Yinyuan; Xian, Xunde; Holland, William L; Tsai, Shirling; Herz, Joachim

    2016-05-01

    Low-density lipoprotein receptor-related protein-1 (LRP1) is a multifunctional uptake receptor for chylomicron remnants in the liver. In vascular smooth muscle cells LRP1 controls reverse cholesterol transport through platelet-derived growth factor receptor β (PDGFR-β) trafficking and tyrosine kinase activity. Here we show that LRP1 regulates hepatic energy homeostasis by integrating insulin signaling with lipid uptake and secretion. Somatic inactivation of LRP1 in the liver (hLRP1KO) predisposes to diet-induced insulin resistance with dyslipidemia and non-alcoholic hepatic steatosis. On a high-fat diet, hLRP1KO mice develop a severe Metabolic Syndrome secondary to hepatic insulin resistance, reduced expression of insulin receptors on the hepatocyte surface and decreased glucose transporter 2 (GLUT2) translocation. While LRP1 is also required for efficient cell surface insulin receptor expression in the absence of exogenous lipids, this latent state of insulin resistance is unmasked by exposure to fatty acids. This further impairs insulin receptor trafficking and results in increased hepatic lipogenesis, impaired fatty acid oxidation and reduced very low density lipoprotein (VLDL) triglyceride secretion. PMID:27322467

  16. Monoclonal antibody to the type I insulin-like growth factor (IGF-I) receptor blocks IGF-I receptor-mediated DNA synthesis: clarification of the mitogenic mechanisms of IGF-I and insulin in human skin fibroblasts

    SciTech Connect

    Flier, J.S.; Usher, P.; Moses, A.C.

    1986-02-01

    Insulin and insulin-like growth factor type I (IGF-I) stimulate an overlapping spectrum of biological responses in human skin fibroblasts. Although insulin and IGF-I are known to stimulate the incorporation of (/sup 3/H)thymidine into DNA in these cells, the identify of the receptor(s) that mediates this effect has not been fully clarified. The mouse anti-human IGF-I receptor antibody ..cap alpha..IR-3 binds with specificity to IGF-I but not to insulin receptors in human placental membranes; it also specifically inhibits the binding of /sup 125/I-labeled IGF-I but not /sup 125/I-labeled insulin to suspensions of human skin fibroblasts in a dose-dependent manner. ..cap alpha..IR-3 competitively inhibits IGF-I-mediated stimulation of (/sup 3/H)thymidine incorporation into DNA. This inhibition is dependent on the concentration of ..cap alpha..IR-3 and in the presence of a fixed antibody concentration can be partially overcome by high concentrations of IGF-I. In contrast, at concentrations of < 1 ..mu..g/ml, the effect of insulin to stimulate (/sup 3/H)thymidine incorporation is not inhibited by ..cap alpha..IR-3. However, the incremental effects of higher concentrations (> 1 ..mu..g/ml) of insulin on (/sup 3/H)thymidine incorporation are inhibited by ..cap alpha..IR-3. ..cap alpha..IR-3 is a highly specific antagonist of IGF-I receptor-mediated mitogenesis in human skin fibroblasts. By using this antibody, it is shown directly that insulin can act through the IGF-I receptor to stimulate DNA synthesis but can also activate this effect through the insulin receptor itself.

  17. The human insulin receptor substrate-1 gene (IRS1) is localized on 2q36

    SciTech Connect

    Nishiyama, Masaki; Matsufuji, Senya; Hayashi, Shin-ichi; Furusaka, Akihiro; Tanaka, Teruji ); Inazawa, J.; Nakamura, Yusuke ); Ariyama, Takeshi ); Wands, J.R. )

    1994-03-01

    The chromosomal localization of some of the genes participating in the insulin signaling pathway is known. The insulin and insulin receptor genes have been mapped to chromosomes 11 and 19, respectively. To identify the chromosomal localization of the human IRS1 gene, the fluorescence in situ hybridization technique was employed with Genomic Clone B-10. A total of 50 metaphase cells exhibiting either single or double spots of hybridization signals were examined. Among them, 32 showed the specific signals on 2q36. Therefore, the authors assigned the human IRS1 gene to 2q36. The genes for homeobox sequence (HOX4), fibronectin 1, alkaline phosphatase (intestinal), transition protein 1, villin 1, collagen (type IV), Waardenburg syndrome (type 1), alanine-glyoxylate aminotransferase, and glucagon have been localized in the vicinity of the IRS1 gene.

  18. A Tale of Two Receptors: Insulin and Insulin-Like Growth Factor Signaling in Cancer

    PubMed Central

    Yee, Douglas

    2014-01-01

    Summary Inhibition of the type I IGF receptor (IGF1R) has been the focus of numerous clinical trials. Two reports in this issue describe the results of phase I trials of an IGF1R tyrosine kinase inhibitor OSI-906. This commentary will describe the complex endocrine changes induced by these types of agents. PMID:25303978

  19. Differential interaction of Apolipoprotein-E isoforms with insulin receptors modulates brain insulin signaling in mutant human amyloid precursor protein transgenic mice.

    PubMed

    Chan, Elizabeth S; Chen, Christopher; Cole, Gregory M; Wong, Boon-Seng

    2015-09-08

    It is unclear how human apolipoprotein E4 (ApoE4) increases the risk for Alzheimer's disease (AD). Although Aβ levels can lead to insulin signaling impairment, these experiments were done in the absence of human ApoE. To examine ApoE role, we crossed the human ApoE-targeted replacement mice with mutant human amyloid precursor protein (APP) mice. In 26 week old mice with lower Aβ levels, the expression and phosphorylation of insulin signaling proteins remained comparable among APP, ApoE3xAPP and ApoE4xAPP mouse brains. When the mice aged to 78 weeks, these proteins were markedly reduced in APP and ApoE4xAPP mouse brains. While Aβ can bind to insulin receptor, how ApoE isoforms modulate this interaction remains unknown. Here, we showed that ApoE3 had greater association with insulin receptor as compared to ApoE4, regardless of Aβ42 concentration. In contrast, ApoE4 bound more Aβ42 with increasing peptide levels. Using primary hippocampal neurons, we showed that ApoE3 and ApoE4 neurons are equally sensitive to physiological levels of insulin. However, in the presence of Aβ42, insulin failed to elicit a downstream response only in ApoE4 hippocampal neurons. Taken together, our data show that ApoE genotypes can modulate this Aβ-mediated insulin signaling impairment.

  20. Protein kinase C directly phosphorylates the insulin receptor in vitro and reduces its protein-tyrosine kinase activity.

    PubMed Central

    Bollag, G E; Roth, R A; Beaudoin, J; Mochly-Rosen, D; Koshland, D E

    1986-01-01

    The beta subunit of purified insulin receptor is phosphorylated on a serine residue by purified preparations of protein kinase C (ATP: protein phosphotransferase, EC 2.7.1.37). This phosphorylation is inhibited by antibodies to protein kinase C and stimulated by phospholipids, diacylglycerol, and Ca2+. The phosphorylation of the receptor by protein kinase C does not affect its insulin-binding activity but does inhibit by 65% the receptor's intrinsic tyrosine-specific protein kinase activity (ATP: protein-tyrosine O-phosphotransferase, EC 2.7.1.112). These results indicate that activators of protein kinase C, such as phorbol esters, desensitize cells to insulin by direct protein kinase C action on the insulin receptor. Images PMID:3526339

  1. Mutation in the Drosophila insulin-like receptor substrate, chico, affects the neuroendocrine stress-reaction development.

    PubMed

    Karpova, E K; Rauschenbach, I Yu; Burdina, E V; Gruntenko, N E

    2016-07-01

    It is shown for the first time that the insulin receptor substrate gene chico controls the functioning of the systems of metabolism of dopamine and juvenile hormone in Drosophila melanogaster females under normal conditions and in thermal stress. PMID:27599505

  2. Insulin and IGF receptor signalling in neural-stem-cell homeostasis.

    PubMed

    Ziegler, Amber N; Levison, Steven W; Wood, Teresa L

    2015-03-01

    Neural stem cells (NSCs) are found in two regions in the adult brain: the subgranular zone (SGZ) in the hippocampal dentate gyrus and the subventricular zone (SVZ) adjacent to the lateral ventricles. Similarly to other somatic stem cells, adult NSCs are found within specialized niches that are organized to facilitate NSC self-renewal. Alterations in stem-cell homeostasis can contribute to the consequences of neurodegenerative diseases, healthy ageing and tissue repair after damage. Insulin and the insulin-like growth factors (IGFs) function in stem-cell homeostasis across species. Studies in the mammalian central nervous system support essential roles for IGF and/or insulin signalling in NSC self-renewal, neurogenesis, cognition and sensory function through distinct ligand-receptor interactions. IGF-II is of particular interest as a result of its production by the choroid plexus and presence in cerebrospinal fluid (CSF). CSF regulates and supports the development, division and migration of cells in the adult brain and is required for NSC maintenance. In this Review, we discuss emerging data on the functions of IGF-II and IGF and/or insulin receptor signalling in the context of NSC regulation in the SVZ and SGZ. We also propose a model for IGF-II in which the choroid plexus is a major component of the NSC niche.

  3. Blockade of cannabinoid 1 receptor improves GLP-1R mediated insulin secretion in mice.

    PubMed

    González-Mariscal, Isabel; Krzysik-Walker, Susan M; Kim, Wook; Rouse, Michael; Egan, Josephine M

    2016-03-01

    The cannabinoid 1 receptor (CB1) is an important regulator of energy metabolism. Reports of in vivo and in vitro studies give conflicting results regarding its role in insulin secretion, possibly due to circulatory factors, such as incretins. We hypothesized that this receptor may be a regulator of the entero-insular axis. We found that despite lower food consumption and lower body weight postprandial GLP-1 plasma concentrations were increased in CB1(-/-) mice compared to CB1(+/+) mice administered a standard diet or high fat/sugar diet. Upon exogenous GLP-1 treatment, CB1(-/-) mice had increased glucose-stimulated insulin secretion. In mouse insulinoma cells, cannabinoids reduced GLP-1R-mediated intracellular cAMP accumulation and subsequent insulin secretion. Importantly, such effects were also evident in human islets, and were prevented by pharmacologic blockade of CB1. Collectively, these findings suggest a novel mechanism in which endocannabinoids are negative modulators of incretin-mediated insulin secretion. PMID:26724516

  4. [Differences of males and females regarding the binding capacity of insulin to erythrocyte receptors].

    PubMed

    Juste, M G; Pié, J; Pié, A

    1989-01-01

    The analysis of insulin receptors in erythrocytes demands a relatively small blood sample, which justifies the interest in its use as an index of the cellular capacity for binding hormone. In order to establish criteria for normalcy, the capacity of erythrocytes for binding in vitro insulin labelled with 125I before increasing concentrations of cold insulin (from 0.5 to 10(3) ng/ml), was studied in a group of 41 healthy men and another of 35 women with normal menstrual cycles. In the female group the study was carried out in three different days of the same cycle (days 3, 12 and 21). The binding capacity in the male was higher than in the female (p less than 0.05) in the follicular phase (days 3 and 12) as well as in the luteal phase (day 21) and, among women, it was higher in the follicular phase than in the luteal one (p less than 0.05). The results indicate that progesterone, as well as prolactin and glucagon, may play an important role in the binding capacity of insulin to its receptor. To make the values comparable, it is suggested that blood extraction in women be carried out during the first five days of the cycle.

  5. Insulin

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The manipulation of organic materials--cells, tissues, and even living organisms--offers many exciting possibilities for the future from organic computers to improved aquaculture. Commercial researchers are using the microgravity environment to produce large near perfect protein crystals Research on insulin has yielded crystals that far surpass the quality of insulin crystals grown on the ground. Using these crystals industry partners are working to develop new and improved treatments for diabetes. Other researchers are exploring the possibility of producing antibiotics using plant cell cultures which could lead to both orbital production and the improvement of ground-based antibiotic production.

  6. Glucocorticoid regulation of insulin receptor and substrate IRS-1 tyrosine phosphorylation in rat skeletal muscle in vivo.

    PubMed Central

    Giorgino, F; Almahfouz, A; Goodyear, L J; Smith, R J

    1993-01-01

    To test the hypothesis that glucocorticoid-induced insulin resistance might originate from abnormalities in insulin receptor signaling, we investigated the effects of glucocorticoids on in vivo tyrosine phosphorylation of the insulin receptor and the insulin receptor substrate IRS-1 in rat skeletal muscle. Male Sprague-Dawley rats were treated with cortisone (100 mg/kg for 5 d) and compared to pair-fed controls. Cortisone treatment of rats resulted in both hyperglycemia and hyperinsulinemia. Anesthetized animals were injected with 10 U/kg insulin via cardiac puncture and, after 2 min, hindlimb muscles were removed, snap-frozen, and homogenized in SDS. Protein tyrosine phosphorylation was studied by immunoblotting with phosphotyrosine antibody. Insulin receptors and substrate IRS-1 were identified and quantified with specific antibodies. Cortisone treatment increased the amount of insulin receptor protein by 36%, but decreased the total level of receptor tyrosine phosphorylation (69 +/- 4% of control, P < 0.05). The decreased level of receptor phosphorylation was explained by a reduced number of receptors containing phosphorylated tyrosine residues (64.6 +/- 5% of control, P < 0.05). Glucocorticoid excess decreased skeletal muscle IRS-1 content by 50%, but did not significantly alter the total level of IRS-1 tyrosine phosphorylation. The apparent M(r) of IRS-1 was reduced by approximately 10 kD. Treatment with protein phosphatase-2A reduced IRS-1 M(r) in control but not in glucocorticoid-treated muscle indicating that the lower M(r) likely results from lower phosphoserine and/or phosphothreonine content. To investigate the role of hyperinsulinemia in the glucocorticoid response, rats were made insulin-deficient with streptozotocin (100 mg/kg, i.p.). Subsequent treatment with cortisone for 5 d had no effects on insulin levels, tyrosine phosphorylation of insulin receptors or IRS-1, or the M(r) of IRS-1. In conclusion, glucocorticoid-treated skeletal muscle is

  7. Novel Zn2+ Modulated GPR39 Receptor Agonists Do Not Drive Acute Insulin Secretion in Rodents

    PubMed Central

    Yasuda, Shin-ichiro; Tsuchida, Takuma; Oguma, Takahiro; Marley, Anna; Wennberg-Huldt, Charlotte; Hovdal, Daniel; Fukuda, Hajime; Yoneyama, Yukimi; Sasaki, Kazuyo; Johansson, Anders; Lundqvist, Sara; Brengdahl, Johan; Isaacs, Richard J.; Brown, Daniel; Geschwindner, Stefan; Benthem, Lambertus; Priest, Claire; Turnbull, Andrew

    2015-01-01

    Type 2 diabetes (T2D) occurs when there is insufficient insulin release to control blood glucose, due to insulin resistance and impaired β-cell function. The GPR39 receptor is expressed in metabolic tissues including pancreatic β-cells and has been proposed as a T2D target. Specifically, GPR39 agonists might improve β-cell function leading to more adequate and sustained insulin release and glucose control. The present study aimed to test the hypothesis that GPR39 agonism would improve glucose stimulated insulin secretion in vivo. A high throughput screen, followed by a medicinal chemistry program, identified three novel potent Zn2+ modulated GPR39 agonists. These agonists were evaluated in acute rodent glucose tolerance tests. The results showed a lack of glucose lowering and insulinotropic effects not only in lean mice, but also in diet-induced obese (DIO) mice and Zucker fatty rats. It is concluded that Zn2+ modulated GPR39 agonists do not acutely stimulate insulin release in rodents. PMID:26720709

  8. Structure and receptor-binding activity of insulin from a holostean fish, the bowfin (Amia calva).

    PubMed Central

    Conlon, J M; Youson, J H; Whittaker, J

    1991-01-01

    The holostean fishes are the extant representatives of the primitive ray-finned fishes from which the present-day teleosts may have evolved. The primary structure of insulin from a holostean fish, the bowfin (Amia calva), was established as: A-chain: Gly-Ile-Val-Glu-Gln-Cys-Cys-Leu-Lys-Pro-Cys-Thr-Ile-Tyr-Glu-Met-Glu- Lys-Tyr-Cys-Asn B-chain: Ala-Ala-Ser-Gln-His-Leu-Cys-Gly-Ser-His-Leu-Val-Glu-Ala-Leu-Phe-Leu- Val-Cys-Gly-Glu-Ser-Gly-Phe-Phe-Tyr-Asn-Pro-Asn-Lys-Ser This amino acid sequence contains several substitutions (methionine at A16, phenylalanine at B16 and serine at B22) at sites that have been strongly conserved in other vertebrate species and that may be expected to influence biological activity. Consistent with this prediction, bowfin insulin was approx. 14-fold less potent than pig insulin in inhibiting the binding of [125I-Tyr-A14](human insulin) to transfected mouse NIH 3T3 cells expressing the human insulin receptor. PMID:2039477

  9. DPP4-inhibitor improves neuronal insulin receptor function, brain mitochondrial function and cognitive function in rats with insulin resistance induced by high-fat diet consumption.

    PubMed

    Pipatpiboon, Noppamas; Pintana, Hiranya; Pratchayasakul, Wasana; Chattipakorn, Nipon; Chattipakorn, Siriporn C

    2013-03-01

    High-fat diet (HFD) consumption has been demonstrated to cause peripheral and neuronal insulin resistance, and brain mitochondrial dysfunction in rats. Although the dipeptidyl peptidase-4 inhibitor, vildagliptin, is known to improve peripheral insulin sensitivity, its effects on neuronal insulin resistance and brain mitochondrial dysfunction caused by a HFD are unknown. We tested the hypothesis that vildagliptin prevents neuronal insulin resistance, brain mitochondrial dysfunction, learning and memory deficit caused by HFD. Male rats were divided into two groups to receive either a HFD or normal diet (ND) for 12 weeks, after which rats in each group were fed with either vildagliptin (3 mg/kg/day) or vehicle for 21 days. The cognitive function was tested by the Morris Water Maze prior to brain removal for studying neuronal insulin receptor (IR) and brain mitochondrial function. In HFD rats, neuronal insulin resistance and brain mitochondrial dysfunction were demonstrated, with impaired learning and memory. Vildagliptin prevented neuronal insulin resistance by restoring insulin-induced long-term depression and neuronal IR phosphorylation, IRS-1 phosphorylation and Akt/PKB-ser phosphorylation. It also improved brain mitochondrial dysfunction and cognitive function. Vildagliptin effectively restored neuronal IR function, increased glucagon-like-peptide 1 levels and prevented brain mitochondrial dysfunction, thus attenuating the impaired cognitive function caused by HFD.

  10. The type 2 vascular endothelial growth factor receptor recruits insulin receptor substrate-1 in its signalling pathway.

    PubMed Central

    Senthil, Duraisamy; Ghosh Choudhury, Goutam; Bhandari, Basant K; Kasinath, Balakuntalam S

    2002-01-01

    Vascular endothelial growth factor (VEGF) isoforms exert their biological effects through receptors that possess intrinsic tyrosine kinase activity. Whether VEGF binding to its receptors recruits insulin receptor substrate (IRS) family of docking proteins to the receptor is not known. Following incubation of mouse kidney proximal tubular epithelial cells with VEGF, we observed an increase in tyrosine phosphorylation of several proteins, including one of approximately 200 kDa, suggesting possible regulation of phosphorylation of IRS proteins. VEGF augmented tyrosine phosphorylation of IRS-1 in kidney epithelial cells and rat heart endothelial cells in a time-dependent manner. In the epithelial cells, association of IRS-1 with type 2 VEGF receptor was promoted by VEGF. VEGF also increased association of IRS-1 with the p85 regulatory subunit of phosphoinositide 3-kinase (PI 3-kinase), and PI 3-kinase activity in IRS-1 immunoprecipitates was increased in VEGF-treated cells. Incubation of epithelial cells with antisense IRS-1 oligonucleotide, but not sense oligonucleotide, reduced expression of the protein and VEGF-induced PI 3-kinase activity in IRS-1 immunoprecipitates. Additionally, VEGF-induced protein synthesis was also impaired by antisense but not sense IRS-1 oligonucleotide. These data provide the first evidence that binding of VEGF to its type 2 receptor promotes association of IRS-1 with the receptor complex. This association may account for some of the increase in VEGF-induced PI 3-kinase activity, and the increase in de novo protein synthesis seen in renal epithelial cells. PMID:12153400

  11. Adipose tissue natriuretic peptide receptor expression is related to insulin sensitivity in obesity and diabetes

    PubMed Central

    Kovacova, Zuzana; Tharp, William G.; Liu, Dianxin; Wei, Wan; Xie, Hui

    2016-01-01

    Objective Cardiac natriuretic peptides (NPs) bind to two receptors (NPRA‐mediator of signaling; NPRC‐clearance receptor) whose ratio, NPRR (NPRA/NPRC), determines the NP bioactivity. This study investigated the relationship of NP receptor gene expression in adipose tissue and muscle with obesity and glucose intolerance. Prospectively, the study also assessed whether changes in NP receptor expression and thermogenic gene markers accompanied improvements of insulin sensitivity. Methods A cross‐sectional study of subjects with a wide range of BMI and glucose tolerance (n = 50) was conducted, as well as a randomized 12‐week trial of subjects with type 2 diabetes mellitus (T2DM) treated with pioglitazone (n = 9) or placebo (n = 10). Results NPRR mRNA was significantly lower in adipose tissue of subjects with obesity when compared with lean subjects (P ≤ 0.001). NPRR decreased with progression from normal glucose tolerance to T2DM (P < 0.01) independently of obesity. Treatment of subjects with T2DM with pioglitazone increased NPRR in adipose tissue (P ≤ 0.01) in conjunction with improvements in insulin sensitivity and increases of the thermogenic markers PPARγ coactivator‐1α and uncoupling protein 1 (P ≤ 0.01). Conclusions Decreased adipose tissue NPRR was associated with obesity, glucose intolerance, and insulin resistance. This relationship was not observed for skeletal muscle NPRR. Pharmacological improvement of insulin sensitivity in subjects with T2DM was tied to improvement in NPRR and increased expression of genes involved in thermogenic processes. PMID:26887289

  12. Involvement of mTOR in Type 2 CRF Receptor Inhibition of Insulin Signaling in Muscle Cells.

    PubMed

    Chao, Hongxia; Li, Haochen; Grande, Rebecca; Lira, Vitor; Yan, Zhen; Harris, Thurl E; Li, Chien

    2015-06-01

    Type 2 corticotropin-releasing factor receptor (CRFR2) is expressed in skeletal muscle and stimulation of the receptor has been shown to inhibit the effect of insulin on glucose uptake in muscle cells. Currently, little is known about the mechanisms underlying this process. In this study, we first showed that both in vivo and in vitro CRFR2 expression in muscle was closely correlated with insulin sensitivity, with elevated receptor levels observed in insulin resistant muscle cells. Stimulation of CRFR2 by urocortin 2 (Ucn 2), a CRFR2-selective ligand, in C2C12 myotubes greatly attenuated insulin-induced glucose uptake. The inhibitory effect of CRFR2 signaling required cAMP production and is involved the mammalian target of rapamycine pathway, as rapamycin reversed the inhibitory effect of CRFR2 stimulation on insulin-induced glucose uptake. Moreover, stimulation of CRFR2 failed to inhibit glucose uptake in muscle cells induced by platelet-derived growth factor, which, similar to insulin, signals through Akt-mediated pathway but is independently of insulin receptor substrate (IRS) proteins to promote glucose uptake. This result argues that CRFR2 signaling modulates insulin's action likely at the levels of IRS. Consistent with this notion, Ucn 2 reduced insulin-induced tyrosine phosphorylation of IRS-1, and treatment with rapamycin reversed the inhibitory effect of Ucn 2 on IRS-1 and Akt phosphorylation. In conclusion, the inhibitory effect of CRFR2 signaling on insulin action is mediated by cAMP in a mammalian target of rapamycine-dependent manner, and IRS-1 is a key nodal point where CRFR2 signaling modulates insulin-stimulated glucose uptake in muscle cells.

  13. Development of receptors for insulin and insulin-like growth factor-I in head and brain of chick embryos: Autoradiographic localization

    SciTech Connect

    Bassas, L.; Girbau, M.; Lesniak, M.A.; Roth, J.; de Pablo, F. )

    1989-11-01

    In whole brain of chick embryos insulin receptors are highest at the end of embryonic development, while insulin-like growth factor-I (IGF-I) receptors dominate in the early stages. These studies provided evidence for developmental regulation of both types of receptors, but they did not provide information on possible differences between brain regions at each developmental stage or within one region at different embryonic ages. We have now localized the specific binding of (125I)insulin and (125I)IGF-I in sections of head and brain using autoradiography and computer-assisted densitometric analysis. Embryos have been studied from the latter part of organogenesis (days 6 and 12) through late development (day 18, i.e. 3 days before hatching), and the binding patterns have been compared with those in the adult brain. At all ages the binding of both ligands was to discrete anatomical regions. Interestingly, while in late embryos and adult brain the patterns of (125I)insulin and (125I) IGF-I binding were quite distinct, in young embryos both ligands showed very similar localization of binding. In young embryos the retina and lateral wall of the growing encephalic vesicles had the highest binding of both (125I)insulin and (125I)IGF-I. In older embryos, as in the adult brain, insulin binding was high in the paleostriatum augmentatum and molecular layer of the cerebellum, while IGF-I binding was prominent in the hippocampus and neostriatum. The mapping of receptors in a vertebrate embryo model from early prenatal development until adulthood predicts great overlap in any possible function of insulin and IGF-I in brain development, while it anticipates differential localized actions of the peptides in the mature brain.

  14. Loss of Oncostatin M Signaling in Adipocytes Induces Insulin Resistance and Adipose Tissue Inflammation in Vivo.

    PubMed

    Elks, Carrie M; Zhao, Peng; Grant, Ryan W; Hang, Hardy; Bailey, Jennifer L; Burk, David H; McNulty, Margaret A; Mynatt, Randall L; Stephens, Jacqueline M

    2016-08-12

    Oncostatin M (OSM) is a multifunctional gp130 cytokine. Although OSM is produced in adipose tissue, it is not produced by adipocytes. OSM expression is significantly induced in adipose tissue from obese mice and humans. The OSM-specific receptor, OSM receptor β (OSMR), is expressed in adipocytes, but its function remains largely unknown. To better understand the effects of OSM in adipose tissue, we knocked down Osmr expression in adipocytes in vitro using siRNA. In vivo, we generated a mouse line lacking Osmr in adiponectin-expressing cells (OSMR(FKO) mice). The effects of OSM on gene expression were also assessed in vitro and in vivo OSM exerts proinflammatory effects on cultured adipocytes that are partially rescued by Osmr knockdown. Osm expression is significantly increased in adipose tissue T cells of high fat-fed mice. In addition, adipocyte Osmr expression is increased following high fat feeding. OSMR(FKO) mice exhibit increased insulin resistance and adipose tissue inflammation and have increased lean mass, femoral length, and bone volume. Also, OSMR(FKO) mice exhibit increased expression of Osm, the T cell markers Cd4 and Cd8, and the macrophage markers F4/80 and Cd11c Interestingly, the same proinflammatory genes induced by OSM in adipocytes are induced in the adipose tissue of the OSMR(FKO) mouse, suggesting that increased expression of proinflammatory genes in adipose tissue arises both from adipocytes and other cell types. These findings suggest that adipocyte OSMR signaling is involved in the regulation of adipose tissue homeostasis and that, in obesity, OSMR ablation may exacerbate insulin resistance by promoting adipose tissue inflammation.

  15. Loss of Oncostatin M Signaling in Adipocytes Induces Insulin Resistance and Adipose Tissue Inflammation in Vivo.

    PubMed

    Elks, Carrie M; Zhao, Peng; Grant, Ryan W; Hang, Hardy; Bailey, Jennifer L; Burk, David H; McNulty, Margaret A; Mynatt, Randall L; Stephens, Jacqueline M

    2016-08-12

    Oncostatin M (OSM) is a multifunctional gp130 cytokine. Although OSM is produced in adipose tissue, it is not produced by adipocytes. OSM expression is significantly induced in adipose tissue from obese mice and humans. The OSM-specific receptor, OSM receptor β (OSMR), is expressed in adipocytes, but its function remains largely unknown. To better understand the effects of OSM in adipose tissue, we knocked down Osmr expression in adipocytes in vitro using siRNA. In vivo, we generated a mouse line lacking Osmr in adiponectin-expressing cells (OSMR(FKO) mice). The effects of OSM on gene expression were also assessed in vitro and in vivo OSM exerts proinflammatory effects on cultured adipocytes that are partially rescued by Osmr knockdown. Osm expression is significantly increased in adipose tissue T cells of high fat-fed mice. In addition, adipocyte Osmr expression is increased following high fat feeding. OSMR(FKO) mice exhibit increased insulin resistance and adipose tissue inflammation and have increased lean mass, femoral length, and bone volume. Also, OSMR(FKO) mice exhibit increased expression of Osm, the T cell markers Cd4 and Cd8, and the macrophage markers F4/80 and Cd11c Interestingly, the same proinflammatory genes induced by OSM in adipocytes are induced in the adipose tissue of the OSMR(FKO) mouse, suggesting that increased expression of proinflammatory genes in adipose tissue arises both from adipocytes and other cell types. These findings suggest that adipocyte OSMR signaling is involved in the regulation of adipose tissue homeostasis and that, in obesity, OSMR ablation may exacerbate insulin resistance by promoting adipose tissue inflammation. PMID:27325693

  16. Chronic Exposure to Aroclor 1254 Disrupts Glucose Homeostasis in Male Mice via Inhibition of the Insulin Receptor Signal Pathway.

    PubMed

    Zhang, Shiqi; Wu, Tian; Chen, Meng; Guo, Zhizhun; Yang, Zhibin; Zuo, Zhenghong; Wang, Chonggang

    2015-08-18

    Epidemiological studies demonstrate that polychlorinated biphenyls (PCBs) induce diabetes and insulin resistance. However, the development of diabetes caused by PCBs and its underlying mechanisms are still unclear. In the present study, male C57BL/6 mice were orally administered with Aroclor 1254 (0.5, 5, 50, and 500 μg/kg) once every 3 days for 60 days. The body weight and the fasting blood glucose levels were significantly elevated; the levels of serum insulin, resistin, tumor necrosis factor α (TNFα), and interleukin-6 (IL-6) increased, while glucagon levels decreased in the animals treated with Aroclor 1254. Pancreatic β-cell mass significantly increased, while α-cell mass was reduced. Aroclor 1254 inhibited the expression of the insulin receptor signaling cascade, including insulin receptor, insulin receptor substrate, phosphatidylinositol 3-kinase-Akt, and protein kinase B and glucose transporter 4, both in the skeletal muscle and the liver. The results suggested that chronic exposure to Aroclor 1254 disrupted glucose homeostasis and induced hyperinsulinemia. The significant elevation of serum resistin, TNFα and IL-6 indicated that obesity caused by Aroclor 1254 is associated with insulin resistance. The elevation of blood glucose levels could have been mainly as a result of insulin receptor signals pathway suppression in skeletal muscle and liver, and a decrease in pancreatic α-cells, accompanied by a reduction of serum glucagon levels, may play an important role in the development of type 2 diabetes.

  17. Insulin stimulates movement of sorting nexin 9 between cellular compartments: a putative role mediating cell surface receptor expression and insulin action.

    PubMed Central

    MaCaulay, S Lance; Stoichevska, Violet; Grusovin, Julian; Gough, Keith H; Castelli, Laura A; Ward, Colin W

    2003-01-01

    SNX9 (sorting nexin 9) is one member of a family of proteins implicated in protein trafficking. This family is characterized by a unique PX (Phox homology) domain that includes a proline-rich sequence and an upstream phospholipid binding domain. Many sorting nexins, including SNX9, also have a C-terminal coiled region. SNX9 additionally has an N-terminal SH3 (Src homology 3) domain. Here we have investigated the cellular localization of SNX9 and the potential role it plays in insulin action. SNX9 had a cytosolic and punctate distribution, consistent with endosomal and cytosolic localization, in 3T3L1 adipocytes. It was excluded from the nucleus. The SH3 domain was responsible, at least in part, for the membrane localization of SNX9, since expression of an SH3-domain-deleted GFP (green fluorescent protein)-SNX9 fusion protein in HEK293T cells rendered the protein cytosolic. Membrane localization may also be attributed in part to the PX domain, since in vitro phospholipid binding studies demonstrated SNX9 binding to polyphosphoinositides. Insulin induced movement of SNX9 to membrane fractions from the cytosol. A GST (glutathione S-transferase)-SNX9 fusion protein was associated with IGF1 (insulin-like growth factor 1) and insulin receptors in vitro. A GFP-SNX9 fusion protein, overexpressed in 3T3L1 adipocytes, co-immunoprecipitated with insulin receptors. Furthermore, overexpression of this GFP-SNX9 fusion protein in CHOT cells decreased insulin binding, consistent with a role for SNX9 in the trafficking of insulin receptors. Microinjection of 3T3L1 cells with an antibody against SNX9 inhibited stimulation by insulin of GLUT4 translocation. These results support the involvement of SNX9 in insulin action, via an influence on the processing/trafficking of insulin receptors. A secondary role in regulation of the cellular processing, transport and/or subcellular localization of GLUT4 is also suggested. PMID:12917015

  18. β-Cell deletion of Nr4a1 and Nr4a3 nuclear receptors impedes mitochondrial respiration and insulin secretion.

    PubMed

    Reynolds, Merrick S; Hancock, Chad R; Ray, Jason D; Kener, Kyle B; Draney, Carrie; Garland, Kevin; Hardman, Jeremy; Bikman, Benjamin T; Tessem, Jeffery S

    2016-07-01

    β-Cell insulin secretion is dependent on proper mitochondrial function. Various studies have clearly shown that the Nr4a family of orphan nuclear receptors is essential for fuel utilization and mitochondrial function in liver, muscle, and adipose. Previously, we have demonstrated that overexpression of Nr4a1 or Nr4a3 is sufficient to induce proliferation of pancreatic β-cells. In this study, we examined whether Nr4a expression impacts pancreatic β-cell mitochondrial function. Here, we show that β-cell mitochondrial respiration is dependent on the nuclear receptors Nr4a1 and Nr4a3. Mitochondrial respiration in permeabilized cells was significantly decreased in β-cells lacking Nr4a1 or Nr4a3. Furthermore, respiration rates of intact cells deficient for Nr4a1 or Nr4a3 in the presence of 16 mM glucose resulted in decreased glucose mediated oxygen consumption. Consistent with this reduction in respiration, a significant decrease in glucose-stimulated insulin secretion rates is observed with deletion of Nr4a1 or Nr4a3. Interestingly, the changes in respiration and insulin secretion occur without a reduction in mitochondrial content, suggesting decreased mitochondrial function. We establish that knockdown of Nr4a1 and Nr4a3 results in decreased expression of the mitochondrial dehydrogenase subunits Idh3g and Sdhb. We demonstrate that loss of Nr4a1 and Nr4a3 impedes production of ATP and ultimately inhibits glucose-stimulated insulin secretion. These data demonstrate for the first time that the orphan nuclear receptors Nr4a1 and Nr4a3 are critical for β-cell mitochondrial function and insulin secretion.

  19. β-Cell deletion of Nr4a1 and Nr4a3 nuclear receptors impedes mitochondrial respiration and insulin secretion.

    PubMed

    Reynolds, Merrick S; Hancock, Chad R; Ray, Jason D; Kener, Kyle B; Draney, Carrie; Garland, Kevin; Hardman, Jeremy; Bikman, Benjamin T; Tessem, Jeffery S

    2016-07-01

    β-Cell insulin secretion is dependent on proper mitochondrial function. Various studies have clearly shown that the Nr4a family of orphan nuclear receptors is essential for fuel utilization and mitochondrial function in liver, muscle, and adipose. Previously, we have demonstrated that overexpression of Nr4a1 or Nr4a3 is sufficient to induce proliferation of pancreatic β-cells. In this study, we examined whether Nr4a expression impacts pancreatic β-cell mitochondrial function. Here, we show that β-cell mitochondrial respiration is dependent on the nuclear receptors Nr4a1 and Nr4a3. Mitochondrial respiration in permeabilized cells was significantly decreased in β-cells lacking Nr4a1 or Nr4a3. Furthermore, respiration rates of intact cells deficient for Nr4a1 or Nr4a3 in the presence of 16 mM glucose resulted in decreased glucose mediated oxygen consumption. Consistent with this reduction in respiration, a significant decrease in glucose-stimulated insulin secretion rates is observed with deletion of Nr4a1 or Nr4a3. Interestingly, the changes in respiration and insulin secretion occur without a reduction in mitochondrial content, suggesting decreased mitochondrial function. We establish that knockdown of Nr4a1 and Nr4a3 results in decreased expression of the mitochondrial dehydrogenase subunits Idh3g and Sdhb. We demonstrate that loss of Nr4a1 and Nr4a3 impedes production of ATP and ultimately inhibits glucose-stimulated insulin secretion. These data demonstrate for the first time that the orphan nuclear receptors Nr4a1 and Nr4a3 are critical for β-cell mitochondrial function and insulin secretion. PMID:27221116

  20. Characterization of insulin-like growth factor I and insulin receptors on cultured bovine adrenal fasciculata cells. Role of these peptides on adrenal cell function

    SciTech Connect

    Penhoat, A.; Chatelain, P.G.; Jaillard, C.; Saez, J.M.

    1988-06-01

    We have characterized insulin-like growth factor I (IGF-I) and insulin receptors in cultured bovine adrenal cells by binding and cross-linking affinity experiments. At equilibrium the dissociation constant and the number of binding sites per cell for IGF-I were 1.4 +/- (SE) 0.3 x 10(-9) M and 19,200 +/- 2,100, respectively. Under reduction conditions, disuccinimidyl suberate cross-linked (/sup 125/I)iodo-IGF-I to one receptor complex with an Mr of 125,000. Adrenal cells also contain specific insulin receptors with an apparent dissociation constant (Kd) of 10(-9) M. Under reduction conditions (/sup 125/I)iodo-insulin binds to one band with an approximate Mr of 125,000. IGF-I and insulin at micromolar concentrations, but not at nanomolar concentrations, slightly stimulated DNA synthesis, but markedly potentiated the mitogenic action of fibroblast growth factor. Adrenal cells cultured in a serum-free medium containing transferrin, ascorbic acid, and insulin (5 micrograms/ml) maintained fairly constant angiotensin-II (A-II) receptor concentration per cell and increased cAMP release on response to ACTH and their steroidogenic response to both ACTH and A-II. When the cells were cultured in the same medium without insulin, the number of A-II receptors significantly decreased to 65% and the increased responsiveness was blunted. Treatment of such cells for 3 days with increasing concentrations of IGF-I (1-100 ng/ml) produced a 2- to 3-fold increase in A-II receptors and enhanced the cAMP response (3- to 4-fold) to ACTH and the steroidogenic response (4- to 6-fold) to ACTH and A-II. These effects were time and dose dependent (ED50 approximately equal to 10(-9) M). Insulin at micromolar concentrations produced an effect similar to that of IGF-I, but at nanomolar concentrations the effect was far less.

  1. Sustained Brown Fat Stimulation and Insulin Sensitization by a Humanized Bispecific Antibody Agonist for Fibroblast Growth Factor Receptor 1/βKlotho Complex

    PubMed Central

    Kolumam, Ganesh; Chen, Mark Z.; Tong, Raymond; Zavala-Solorio, Jose; Kates, Lance; van Bruggen, Nicholas; Ross, Jed; Wyatt, Shelby K.; Gandham, Vineela D.; Carano, Richard A.D.; Dunshee, Diana Ronai; Wu, Ai-Luen; Haley, Benjamin; Anderson, Keith; Warming, Søren; Rairdan, Xin Y.; Lewin-Koh, Nicholas; Zhang, Yingnan; Gutierrez, Johnny; Baruch, Amos; Gelzleichter, Thomas R.; Stevens, Dale; Rajan, Sharmila; Bainbridge, Travis W.; Vernes, Jean-Michel; Meng, Y. Gloria; Ziai, James; Soriano, Robert H.; Brauer, Matthew J.; Chen, Yongmei; Stawicki, Scott; Kim, Hok Seon; Comps-Agrar, Laëtitia; Luis, Elizabeth; Spiess, Christoph; Wu, Yan; Ernst, James A.; McGuinness, Owen P.; Peterson, Andrew S.; Sonoda, Junichiro

    2015-01-01

    Dissipating excess calories as heat through therapeutic stimulation of brown adipose tissues (BAT) has been proposed as a potential treatment for obesity-linked disorders. Here, we describe the generation of a humanized effector-less bispecific antibody that activates fibroblast growth factor receptor (FGFR) 1/βKlotho complex, a common receptor for FGF21 and FGF19. Using this molecule, we show that antibody-mediated activation of FGFR1/βKlotho complex in mice induces sustained energy expenditure in BAT, browning of white adipose tissue, weight loss, and improvements in obesity-associated metabolic derangements including insulin resistance, hyperglycemia, dyslipidemia and hepatosteatosis. In mice and cynomolgus monkeys, FGFR1/βKlotho activation increased serum high-molecular-weight adiponectin, which appears to contribute over time by enhancing the amplitude of the metabolic benefits. At the same time, insulin sensitization by FGFR1/βKlotho activation occurs even before the onset of weight loss in a manner that is independent of adiponectin. Together, selective activation of FGFR1/βKlotho complex with a long acting therapeutic antibody represents an attractive approach for the treatment of type 2 diabetes and other obesity-linked disorders through enhanced energy expenditure, insulin sensitization and induction of high-molecular-weight adiponectin. PMID:26288846

  2. GH Receptor Deficiency in Ecuadorian Adults Is Associated With Obesity and Enhanced Insulin Sensitivity

    PubMed Central

    Rosenbloom, Arlan L.; Balasubramanian, Priya; Teran, Enrique; Guevara-Aguirre, Marco; Guevara, Carolina; Procel, Patricio; Alfaras, Irene; De Cabo, Rafael; Di Biase, Stefano; Narvaez, Luis; Saavedra, Jannette

    2015-01-01

    Context: Ecuadorian subjects with GH receptor deficiency (GHRD) have not developed diabetes, despite obesity. Objective: We sought to determine the metabolic associations for this phenomenon. Design: Four studies were carried out: 1) glucose, lipid, adipocytokine concentrations; 2) metabolomics evaluation; 3) metabolic responses to a high-calorie meal; and 4) oral glucose tolerance tests. Setting: Clinical Research Institute in Quito, Ecuador. Subjects: Adults homozygous for the E180 splice mutation of the GH receptor (GHRD) were matched for age, gender, and body mass index with unaffected control relatives (C) as follows: study 1, 27 GHRD and 35 C; study 2, 10 GHRD and 10 C; study 3, seven GHRD and 11 C; and study 4, seven GHRD and seven C. Results: Although GHRD subjects had greater mean percentage body fat than controls, their fasting insulin, 2-hour blood glucose, and triglyceride levels were lower. The indicator of insulin sensitivity, homeostasis model of assessment 2%S, was greater (P < .0001), and the indicator of insulin resistance, homeostasis model of assessment 2-IR, was lower (P = .0025). Metabolomic differences between GHRD and control subjects were consistent with their differing insulin sensitivity, including postprandial decreases of branched-chain amino acids that were more pronounced in controls. High molecular weight and total adiponectin concentrations were greater in GHRD (P = .0004 and P = .0128, respectively), and leptin levels were lower (P = .02). Although approximately 65% the weight of controls, GHRD subjects consumed an identical high-calorie meal; nonetheless, their mean glucose concentrations were lower, with mean insulin levels one-third those of controls. Results of the 2-hour oral glucose tolerance test were similar. Main Outcome Measures: Measures of insulin sensitivity, adipocytokines, and energy metabolites. Conclusions: Without GH counter-regulation, GHRD is associated with insulin efficiency and obesity. Lower leptin levels

  3. The Drosophila HNF4 nuclear receptor promotes glucose-stimulated insulin secretion and mitochondrial function in adults

    PubMed Central

    Barry, William E; Thummel, Carl S

    2016-01-01

    Although mutations in HNF4A were identified as the cause of Maturity Onset Diabetes of the Young 1 (MODY1) two decades ago, the mechanisms by which this nuclear receptor regulates glucose homeostasis remain unclear. Here we report that loss of Drosophila HNF4 recapitulates hallmark symptoms of MODY1, including adult-onset hyperglycemia, glucose intolerance and impaired glucose-stimulated insulin secretion (GSIS). These defects are linked to a role for dHNF4 in promoting mitochondrial function as well as the expression of Hex-C, a homolog of the MODY2 gene Glucokinase. dHNF4 is required in the fat body and insulin-producing cells to maintain glucose homeostasis by supporting a developmental switch toward oxidative phosphorylation and GSIS at the transition to adulthood. These findings establish an animal model for MODY1 and define a developmental reprogramming of metabolism to support the energetic needs of the mature animal. DOI: http://dx.doi.org/10.7554/eLife.11183.001 PMID:27185732

  4. The Novel Functions of High-Molecular-Mass Complexes Containing Insulin Receptor Substrates in Mediation and Modulation of Insulin-Like Activities: Emerging Concept of Diverse Functions by IRS-Associated Proteins

    PubMed Central

    Hakuno, Fumihiko; Fukushima, Toshiaki; Yoneyama, Yosuke; Kamei, Hiroyasu; Ozoe, Atsufumi; Yoshihara, Hidehito; Yamanaka, Daisuke; Shibano, Takashi; Sone-Yonezawa, Meri; Yu, Bu-Chin; Chida, Kazuhiro; Takahashi, Shin-Ichiro

    2015-01-01

    Insulin-like peptides, such as insulin-like growth factors (IGFs) and insulin, induce a variety of bioactivities, such as growth, differentiation, survival, increased anabolism, and decreased catabolism in many cell types and in vivo. In general, IGFs or insulin bind to IGF-I receptor (IGF-IR) or insulin receptor (IR), activating the receptor tyrosine kinase. Insulin receptor substrates (IRSs) are known to be major substrates of receptor kinases, mediating IGF/insulin signals to direct bioactivities. Recently, we discovered that IRSs form high-molecular-mass complexes (referred to here as IRSomes) even without IGF/insulin stimulation. These complexes contain proteins (referred to here as IRSAPs; IRS-associated proteins), which modulate tyrosine phosphorylation of IRSs by receptor kinases, control IRS stability, and determine intracellular localization of IRSs. In addition, in these complexes, we found not only proteins that are involved in RNA metabolism but also RNAs themselves. Thus, IRSAPs possibly contribute to modulation of IGF/insulin bioactivities. Since it is established that disorder of modulation of insulin-like activities causes various age-related diseases including cancer, we could propose that the IRSome is an important target for treatment of these diseases. PMID:26074875

  5. Treating Diabetes Mellitus: Pharmacophore Based Designing of Potential Drugs from Gymnema sylvestre against Insulin Receptor Protein

    PubMed Central

    Hossain, Mohammad Uzzal; Khan, Md. Arif; Rakib-Uz-Zaman, S. M.; Ali, Mohammad Tuhin; Islam, Md. Saidul; Keya, Chaman Ara; Salimullah, Md.

    2016-01-01

    Diabetes mellitus (DM) is one of the most prevalent metabolic disorders which can affect the quality of life severely. Injectable insulin is currently being used to treat DM which is mainly associated with patient inconvenience. Small molecules that can act as insulin receptor (IR) agonist would be better alternatives to insulin injection. Herein, ten bioactive small compounds derived from Gymnema sylvestre (G. sylvestre) were chosen to determine their IR binding affinity and ADMET properties using a combined approach of molecular docking study and computational pharmacokinetic elucidation. Designing structural analogues were also performed for the compounds associated with toxicity and less IR affinity. Among the ten parent compounds, six were found to have significant pharmacokinetic properties with considerable binding affinity towards IR while four compounds were associated with toxicity and less IR affinity. Among the forty structural analogues, four compounds demonstrated considerably increased binding affinity towards IR and less toxicity compared with parent compounds. Finally, molecular interaction analysis revealed that six parent compounds and four analogues interact with the active site amino acids of IR. So this study would be a way to identify new therapeutics and alternatives to insulin for diabetic patients. PMID:27034931

  6. Insulin receptor regulates food intake through sulfakinin signaling in the red flour beetle, Tribolium castaneum.

    PubMed

    Lin, Xianyu; Yu, Na; Smagghe, Guy

    2016-06-01

    Insects obtain energy and nutrients via feeding to support growth and development. The insulin signaling pathway is involved in the regulation of feeding; however, the underlying mechanisms are not fully understood. Here, we show that insulin signaling regulates food intake via crosstalk with neuropeptide sulfakinin in the red flour beetle, Tribolium castaneum. Silencing of the insulin receptor (InR) decreased the food intake in the penultimate and final instar stages, leading to a decrease of weight gain and mortality during larval-pupal metamorphosis. Interestingly, the knockdown of InR co-occurred with an increased expression of sulfakinin (sk), a gene encoding neuropeptide SK functioning as a satiety signal. In parallel, double silencing of sk and InR eliminated the inhibitory effect on food intake as induced by silencing of InR and the larvae died as prepupae. In conclusion, this study shows, for the first time, that the insulin/InR signaling regulates food intake through the sulfakinin signaling pathway in the larval stages of this important model and pest insect, indicating a novel target for pest control. PMID:26972481

  7. P2Y₁ receptor-dependent diacylglycerol signaling microdomains in β cells promote insulin secretion.

    PubMed

    Wuttke, Anne; Idevall-Hagren, Olof; Tengholm, Anders

    2013-04-01

    Diacylglycerol (DAG) controls numerous cell functions by regulating the localization of C1-domain-containing proteins, including protein kinase C (PKC), but little is known about the spatiotemporal dynamics of the lipid. Here, we explored plasma membrane DAG dynamics in pancreatic β cells and determined whether DAG signaling is involved in secretagogue-induced pulsatile release of insulin. Single MIN6 cells, primary mouse β cells, and human β cells within intact islets were transfected with translocation biosensors for DAG, PKC activity, or insulin secretion and imaged with total internal reflection fluorescence microscopy. Muscarinic receptor stimulation triggered stable, homogenous DAG elevations, whereas glucose induced short-lived (7.1 ± 0.4 s) but high-amplitude elevations (up to 109 ± 10% fluorescence increase) in spatially confined membrane regions. The spiking was mimicked by membrane depolarization and suppressed after inhibition of exocytosis or of purinergic P2Y₁, but not P2X receptors, reflecting involvement of autocrine purinoceptor activation after exocytotic release of ATP. Each DAG spike caused local PKC activation with resulting dissociation of its substrate protein MARCKS from the plasma membrane. Inhibition of spiking reduced glucose-induced pulsatile insulin secretion. Thus, stimulus-specific DAG signaling patterns appear in the plasma membrane, including distinct microdomains, which have implications for the kinetic control of exocytosis and other membrane-associated processes.

  8. Inflammatory mediators and insulin resistance in obesity: role of nuclear receptor signaling in macrophages.

    PubMed

    Fuentes, Lucía; Roszer, Tamás; Ricote, Mercedes

    2010-01-01

    Visceral obesity is coupled to a general low-grade chronic inflammatory state characterized by macrophage activation and inflammatory cytokine production, leading to insulin resistance (IR). The balance between proinflammatory M1 and antiinflammatory M2 macrophage phenotypes within visceral adipose tissue appears to be crucially involved in the development of obesity-associated IR and consequent metabolic abnormalities. The ligand-dependent transcription factors peroxisome proliferator activated receptors (PPARs) have recently been implicated in the determination of the M1/M2 phenotype. Liver X receptors (LXRs), which form another subgroup of the nuclear receptor superfamily, are also important regulators of proinflammatory cytokine production in macrophages. Disregulation of macrophage-mediated inflammation by PPARs and LXRs therefore underlies the development of IR. This review summarizes the role of PPAR and LXR signaling in macrophages and current knowledge about the impact of these actions in the manifestation of IR and obesity comorbidities such as liver steatosis and diabetic osteopenia.

  9. A candidate targeting molecule of insulin-like growth factor-I receptor for gastrointestinal cancers

    PubMed Central

    Adachi, Yasushi; Yamamoto, Hiroyuki; Ohashi, Hirokazu; Endo, Takao; Carbone, David P; Imai, Kohzoh; Shinomura, Yasuhisa

    2010-01-01

    Advances in molecular research in cancer have brought new therapeutic strategies into clinical usage. One new group of targets is tyrosine kinase receptors, which can be treated by several strategies, including small molecule tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mAbs). Aberrant activation of growth factors/receptors and their signal pathways are required for malignant transformation and progression in gastrointestinal (GI) carcinomas. The concept of targeting specific carcinogenic receptors has been validated by successful clinical application of many new drugs. Type I insulin-like growth factor (IGF) receptor (IGF-IR) signaling potently stimulates tumor progression and cellular differentiation, and is a promising new molecular target in human malignancies. In this review, we focus on this promising therapeutic target, IGF-IR. The IGF/IGF-IR axis is an important modifier of tumor cell proliferation, survival, growth, and treatment sensitivity in many malignant diseases, including human GI cancers. Preclinical studies demonstrated that downregulation of IGF-IR signals reversed the neoplastic phenotype and sensitized cells to anticancer treatments. These results were mainly obtained through our strategy of adenoviruses expressing dominant negative IGF-IR (IGF-IR/dn) against gastrointestinal cancers, including esophagus, stomach, colon, and pancreas. We also summarize a variety of strategies to interrupt the IGFs/IGF-IR axis and their preclinical experiences. Several mAbs and TKIs targeting IGF-IR have entered clinical trials, and early results have suggested that these agents have generally acceptable safety profiles as single agents. We summarize the advantages and disadvantages of each strategy and discuss the merits/demerits of dual targeting of IGF-IR and other growth factor receptors, including Her2 and the insulin receptor, as well as other alternatives and possible drug combinations. Thus, IGF-IR might be a candidate for a molecular

  10. Role of the Insulin-Like Growth Factor Type 1 Receptor in the Pathogenesis of Diabetic Encephalopathy

    PubMed Central

    Zhang, Duo; Jiang, Shuang; Meng, Heng

    2015-01-01

    Defective cognitive function is common in patients with diabetes, suggesting that insulin normally exerts anabolic actions in neuron, namely, diabetic encephalopathy. However, because insulin can cross-activate the insulin-like growth factor type 1 receptor (IGF-1R), which also functions in most of tissues, such as muscle and bone, it has been difficult to establish the direct (IGF-1-independent) actions of insulin in the pathogenesis of diabetic encephalopathy. To overcome this problem, we examined insulin signaling and action in primary PC-12 cells engineered for conditional disruption of the IGF-1 receptor (ΔIGF-1R). The results showed that the lower glucose metabolism and high expression of IGF-1R occurred in the brain of the DE rat model. The results also showed the defect of IGF-1R could significantly improve the ability of glucose consumption and enhance sensitivity to insulin-induced IR and Akt phosphorylation in PC12 cells. And meanwhile, IGF-1R allele gene knockout (IGF-1Rneo) mice treated with HFD/STZ had better cognitive abilities than those of wild mice. Those results indicate that insulin exerts direct anabolic actions in neuron-like cells by activation of its cognate receptor and prove that IGF-1R plays an important role in the pathogenesis of diabetic encephalopathy. PMID:26089889

  11. Arg924X homozygous mutation in insulin receptor gene in a Tunisian patient with Donohue syndrome.

    PubMed

    Azzabi, Ons; Jilani, Houweyda; Rejeb, Imen; Siala, Nadia; Elaribi, Yasmina; Hizem, Syrine; Selmi, Ines; Halioui, Sonia; Lascols, Olivier; Jemaa, Lamia Ben; Maherzi, Ahmed

    2016-06-01

    Donohue syndrome (DS) is a rare and lethal autosomal recessive disease caused by mutations in the insulin receptor (INSR) gene, manifesting marked insulin resistance, severe growth retardation, hypertrichosis, and characteristic dysmorphic features. We describe a new case of Donohue syndrome born at 37 weeks' gestation of unrelated parents and presented with intra-uterine growth retardation, nipple hypertrophy, macropenis, distended abdomen, hirsutism and dysmorphic features. The clinical course showed failure to thrive, and episodes of alternating hypoglycemia and hyperglycemia. Laboratory tests revealed direct hyperbilirubinemia. The diagnosis of Donohue syndrome was established based on the above clinical characteristics and determination of the INSR mutation. He was found to have homozygous nonsense mutation c. 2270 C>T (Arg924X) at exon 14 of the INSR gene. He later developed enterocolitis and died at 3 months old. Prenatal diagnosis was performed for the family via chorionic villous biopsy. We try to explain gastrointestinal dysfunction seen in our patient. PMID:26974131

  12. The β2 Adrenergic Receptor Gln27Glu Polymorphism Affects Insulin Resistance in Patients with Heart Failure

    PubMed Central

    Vardeny, Orly; Detry, Michelle A.; Moran, John J.M.; Johnson, Maryl R.; Sweitzer, Nancy K.

    2009-01-01

    Insulin resistance is prevalent in heart failure (HF) patients, and beta2 adrenergic receptors (β2-AR) are involved in glucose homeostasis. We hypothesized that β2-AR Gln27Glu and Arg16Gly polymorphisms affect insulin resistance in HF patients and explored if effects of β2-AR polymorphisms on glucose handling are modified by choice of beta blocker. We studied 30 non-diabetic adults with HF and a history of systolic dysfunction, 15 on metoprolol succinate and 15 on carvedilol. We measured fasting glucose, insulin, and insulin resistance, and determined β2-AR genotypes at codons 27 and 16. The cohort was insulin resistant with a mean HOMA-IR score of 3.4 (95%CI 2.3-4.5, normal value=1.0). Patients with the Glu27Glu genotype exhibited higher insulin and HOMA-IR compared to individuals carrying a Gln allele (p=0.019). Patients taking carvedilol demonstrated lower insulin resistance if also carrying a wild type allele at codon 27 (fasting insulin 9.8±10.5 versus 20.5±2.1 for variant, p=0.072, HOMA-IR 2.4±2.7 versus 5.1±0.6, p=0.074, respectively); those on metoprolol succinate had high insulin resistance irrespective of genotype. The β2-AR Glu27Glu genotype may be associated with higher insulin concentrations and insulin resistance in patients with HF. Future studies are needed to confirm whether treatment with carvedilol may be associated with decreased insulin and insulin resistance in β2-AR codon 27 Gln carriers. PMID:19034036

  13. Mutation of tyrosine-141 inhibits insulin-promoted tyrosine phosphorylation and increased responsiveness of the human beta 2-adrenergic receptor.

    PubMed Central

    Valiquette, M; Parent, S; Loisel, T P; Bouvier, M

    1995-01-01

    The ability of insulin to promote phosphorylation of the human beta 2-adrenergic receptor (beta 2AR) was assessed in Chinese hamster fibroblasts transfected with beta 2AR cDNA. Phosphotyrosine residues were detected in purified beta 2AR using a polyclonal anti-phosphotyrosine antibody and by phosphoamino acid analysis following metabolic labelling with inorganic 32P. Treatment of the cells with insulin induced a 2.4-fold increase in the phosphotyrosine content of the receptor. The insulin-promoted phosphorylation of the beta 2AR was accompanied by an increase in the beta-adrenergic-stimulated adenyl cyclase activity. Substitution of a phenylalanine residue for tyrosine-141 completely prevented both the increased tyrosine phosphorylation and the enhanced responsiveness of the beta 2AR promoted by insulin treatment. Mutation of three other tyrosines located in the cytoplasmic domain of the receptor, tyrosine-366, tyrosine-350 and tyrosine-354, did not abolish the insulin-promoted tyrosine phosphorylation. Taken together, these results suggest that insulin promotes phosphorylation of the beta 2AR on tyrosine-141 and that such phosphorylation leads to a supersensitization of the receptor. Images PMID:8521811

  14. Robert Feulgen Prize Lecture 1993. The journey of the insulin receptor into the cell: from cellular biology to pathophysiology.

    PubMed

    Carpentier, J L

    1993-09-01

    The data that we have reviewed indicate that insulin binds to a specific cell-surface receptor. The complex then becomes involved in a series of steps which lead the insulin-receptor complex to be internalized and rapidly delivered to endosomes. From this sorting station, the hormone is targeted to lysosomes to be degraded while the receptor is recycled back to the cell surface. This sequence of events presents two degrees of ligand specificity: (a) The first step is ligand-dependent and requires insulin-induced receptor phosphorylation of specific tyrosine residues. It consists in the surface redistribution of the receptor from microvilli where it preferentially localizes in its unoccupied form. (b) The second step is more general and consists in the association with clathrin-coated pits which represents the internalization gate common to many receptors. This sequence of events participates in the regulation of the biological action of the hormone and can thus be implicated in the pathophysiology of diabetes mellitus and various extreme insulin resistance syndromes, including type A extreme insulin resistance, leprechaunism, and Rabson-Mendehall syndrome. Alterations of the internalization process can result either from intrinsic abnormalities of the receptor or from more general alteration of the plasma membrane or of the cell metabolism. Type I diabetes is an example of the latter possibility, since general impairment of endocytosis could contribute to extracellular matrix accumulation and to an increase in blood cholesterol. Thus, better characterization of the molecular and cellular biology of the insulin receptor and of its journey inside the cell definitely leads to better understanding of disease states, including diabetes.

  15. Robert Feulgen Prize Lecture 1993. The journey of the insulin receptor into the cell: from cellular biology to pathophysiology.

    PubMed

    Carpentier, J L

    1993-09-01

    The data that we have reviewed indicate that insulin binds to a specific cell-surface receptor. The complex then becomes involved in a series of steps which lead the insulin-receptor complex to be internalized and rapidly delivered to endosomes. From this sorting station, the hormone is targeted to lysosomes to be degraded while the receptor is recycled back to the cell surface. This sequence of events presents two degrees of ligand specificity: (a) The first step is ligand-dependent and requires insulin-induced receptor phosphorylation of specific tyrosine residues. It consists in the surface redistribution of the receptor from microvilli where it preferentially localizes in its unoccupied form. (b) The second step is more general and consists in the association with clathrin-coated pits which represents the internalization gate common to many receptors. This sequence of events participates in the regulation of the biological action of the hormone and can thus be implicated in the pathophysiology of diabetes mellitus and various extreme insulin resistance syndromes, including type A extreme insulin resistance, leprechaunism, and Rabson-Mendehall syndrome. Alterations of the internalization process can result either from intrinsic abnormalities of the receptor or from more general alteration of the plasma membrane or of the cell metabolism. Type I diabetes is an example of the latter possibility, since general impairment of endocytosis could contribute to extracellular matrix accumulation and to an increase in blood cholesterol. Thus, better characterization of the molecular and cellular biology of the insulin receptor and of its journey inside the cell definitely leads to better understanding of disease states, including diabetes. PMID:8244769

  16. Thyroid-stimulating hormone improves insulin sensitivity in skeletal muscle cells via cAMP/PKA/CREB pathway-dependent upregulation of insulin receptor substrate-1 expression.

    PubMed

    Moon, Min Kyong; Kang, Geun Hyung; Kim, Hwan Hee; Han, Sun Kyoung; Koo, Young Do; Cho, Sun Wook; Kim, Ye An; Oh, Byung-Chul; Park, Do Joon; Chung, Sung Soo; Park, Kyong Soo; Park, Young Joo

    2016-11-15

    Thyroid-stimulating hormone (TSH) receptor is expressed in extrathyroidal tissues such as hepatocytes, adipocytes, and skeletal muscle, which suggests a possible novel role of TSH in various metabolic processes in extrathyroidal tissues independent of thyroid hormones. We investigated whether TSH has any effects on glucose tolerance and insulin sensitivity in the skeletal muscle using diet-induced obesity (DIO) mouse models and rodent skeletal muscle cells. TSH improved glucose tolerance in DIO mice and this was associated with an improvement of skeletal muscle insulin sensitivity resulting from the increased expression of insulin receptor substrate (IRS)-1 protein and mRNA therein. TSH significantly increased both basal and insulin-stimulated glucose transport in rat L6 myotubes and increased the expression of IRS-1 protein and mRNA in these cells as well. TSH also stimulated Irs1 promoter activation; this stimulation was abolished by protein kinase A (PKA) inhibition using H89 or by mutation of the cAMP-response element site located at -1155 to -875 bp of the Irs1 promoter region, supporting a novel role of TSH activated-cAMP/PKA/CREB signaling in the regulation of Irs1 expression. In conclusion, TSH improves insulin sensitivity in skeletal muscle by increasing Irs1 gene expression. This regulatory effect is mediated by a PKA-CREB-dependent pathway.

  17. Introduction of exogenous growth hormone receptors augments growth hormone-responsive insulin biosynthesis in rat insulinoma cells

    SciTech Connect

    Billestrup, N.; Moeldrup, A.; Serup, P.; Nielsen, J.H. ); Mathews, L.S.; Norstedt, G. )

    1990-09-01

    The stimulation of insulin biosynthesis in the pancreatic insulinoma cell line RIN5-AH by growth hormone (GH) is initiated by GH binding to specific receptors. To determine whether the recently cloned rat hepatic GH receptor is able to mediate the insulinotropic effect of GH, the authors have transfected a GH receptor cDNA under the transcriptional control of the human metallothionein promoter into RIN5-AH cells. The transfected cells were found to exhibit an increased expression of GH receptors and to contain a specific GH receptor mRNA that was not expressed in the parent cell line. The expression of GH receptors in one clone (1.24) selected for detailed analysis was increased 2.6-fold compared to untransfected cells. The increased GH receptor expression was accompanied by an increased responsiveness to GH. Thus, the maximal GH-stimulated increase of insulin biosynthesis was 4.1-fold in 1.24 cells compared to 1.9-fold in the nontransfected RIN5-AH cells. The expression of the transfected receptor was stimulated 1.6- and 2.3-fold when cells were cultured in the presence of 25 or 50 {mu}M Zn{sup 2+} was associated with an increased magnitude of GH-stimulated insulin biosynthesis. A close stoichiometric relationship between the level of receptor expression and the level of GH-stimulated insulin biosynthesis was observed. They conclude from these results that the hepatic GH receptor is able to mediate the effect of GH on insulin biosynthesis in RIN5-AH cells.

  18. Chronic exposure to nicotine enhances insulin sensitivity through α7 nicotinic acetylcholine receptor-STAT3 pathway.

    PubMed

    Xu, Tian-Ying; Guo, Ling-Ling; Wang, Pei; Song, Jie; Le, Ying-Ying; Viollet, Benoit; Miao, Chao-Yu

    2012-01-01

    This study was to investigate the effect of nicotine on insulin sensitivity and explore the underlying mechanisms. Treatment of Sprague-Dawley rats with nicotine (3 mg/kg/day) for 6 weeks reduced 43% body weight gain and 65% blood insulin level, but had no effect on blood glucose level. Both insulin tolerance test and glucose tolerance test demonstrated that nicotine treatment enhanced insulin sensitivity. Pretreatment of rats with hexamethonium (20 mg/kg/day) to antagonize peripheral nicotinic receptors except for α7 nicotinic acetylcholine receptor (α7-nAChR) had no effect on the insulin sensitizing effect of nicotine. However, the insulin sensitizing effect but not the bodyweight reducing effect of nicotine was abrogated in α7-nAChR knockout mice. Further, chronic treatment with PNU-282987 (0.53 mg/kg/day), a selective α7-nAChR agonist, significantly enhanced insulin sensitivity without apparently modifying bodyweight not only in normal mice but also in AMP-activated kinase-α2 knockout mice, an animal model of insulin resistance with no sign of inflammation. Moreover, PNU-282987 treatment enhanced phosphorylation of signal transducer and activator of transcription 3 (STAT3) in skeletal muscle, adipose tissue and liver in normal mice. PNU-282987 treatment also increased glucose uptake by 25% in C2C12 myotubes and this effect was total abrogated by STAT3 inhibitor, S3I-201. All together, these findings demonstrated that nicotine enhanced insulin sensitivity in animals with or without insulin resistance, at least in part via stimulating α7-nAChR-STAT3 pathway independent of inflammation. Our results contribute not only to the understanding of the pharmacological effects of nicotine, but also to the identifying of new therapeutic targets against insulin resistance.

  19. Prostaglandin A2 enhances cellular insulin sensitivity via a mechanism that involves the orphan nuclear receptor NR4A3.

    PubMed

    Zhu, X; Walton, R G; Tian, L; Luo, N; Ho, S-R; Fu, Y; Garvey, W T

    2013-03-01

    We have previously reported that members of the NR4A family of orphan nuclear receptors can augment insulin's ability to stimulate glucose transport in adipocytes. In the current study, we endeavored to test for an insulin-sensitizing effect in muscle cells and to identify a potential transactivator. Lentiviral constructs were used to engineer both hyperexpression and shRNA silencing of NR4A3 in C2C12 myocytes. The NR4A3 hyper-expression construct led to a significant increase in glucose transport rates in the presence of maximal insulin while the NR4A3 knock-down exhibited a significant reduction in insulin-stimulated glucose transport rates. Consistently, insulin-mediated AKT phosphorylation was increased by NR4A3 hyperexpression and decreased following shRNA NR4A3 suppression. Then, we examined effects of prostaglandin A2 (PGA2) on insulin action and NR4A3 transactivation. PGA2 augmented insulin-stimulated glucose uptake in C2C12 myocytes and AKT phosphorylation after 12-h treatment, without significant effects on basal transport or basal AKT phosphorylation. More importantly, we demonstrated that PGA2 led to a greater improvement in insulin-stimulated glucose rates in NR4A3 overexpressing C2C12 myocytes, when compared with Lac-Z controls stimulated with insulin and PGA2. Moreover, the sensitizing effect of PGA2 was significantly diminished in NR4A3 knockdown myocytes compared to scramble controls. These results show for the first time that: (i) PGA2 augments insulin action in myocytes as manifested by enhanced stimulation of glucose transport and AKT phosphorylation; and (ii) the insulin sensitizing effect is dependent upon the orphan nuclear receptor NR4A3. PMID:23104421

  20. Sphingosine 1-phosphate counteracts insulin signaling in pancreatic β-cells via the sphingosine 1-phosphate receptor subtype 2.

    PubMed

    Japtok, Lukasz; Schmitz, Elisabeth I; Fayyaz, Susann; Krämer, Stephanie; Hsu, Leigh J; Kleuser, Burkhard

    2015-08-01

    Glucolipotoxic stress has been identified as a key player in the progression of pancreatic β-cell dysfunction contributing to insulin resistance and the development of type 2 diabetes mellitus (T2D). It has been suggested that bioactive lipid intermediates, formed under lipotoxic conditions, are involved in these processes. Here, we show that sphingosine 1-phosphate (S1P) levels are not only increased in palmitate-stimulated pancreatic β-cells but also regulate β-cell homeostasis in a divergent manner. Although S1P possesses a prosurvival effect in β-cells, an enhanced level of the sphingolipid antagonizes insulin-mediated cell growth and survival via the sphingosine 1-phosphate receptor subtype 2 (S1P2) followed by an inhibition of Akt-signaling. In an attempt to investigate the role of the S1P/S1P2 axis in vivo, the New Zealand obese (NZO) diabetic mouse model, characterized by β-cell loss under high-fat diet (HFD) conditions, was used. The occurrence of T2D was accompanied by an increase of plasma S1P levels. To examine whether S1P contributes to the morphologic changes of islets via S1P2, the receptor antagonist JTE-013 was administered. Most interestingly, JTE-013 rescued β-cell damage clearly indicating an important role of the S1P2 in β-cell homeostasis. Therefore, the present study provides a new therapeutic strategy to diminish β-cell dysfunction and the development of T2D. PMID:25911610

  1. Diabetic state, high plasma insulin and angiotensin II combine to augment endothelin-1-induced vasoconstriction via ETA receptors and ERK

    PubMed Central

    Kobayashi, T; Nogami, T; Taguchi, K; Matsumoto, T; Kamata, K

    2008-01-01

    Background and purpose: Mechanisms associated with the enhanced contractile response to endothelin-1 in hyperinsulinaemic diabetes have been examined using the rat aorta. Functions for angiotensin II, endothelin-1 receptor expression and extracellular signal-regulated kinase (ERK) have been investigated. Experimental approach: Streptozotocin-induced diabetic rats were infused with angiotensin II or, following insulin treatment, were treated with losartan, an angiotensin II receptor antagonist. Contractions of aortic strips with or without endothelium, in response to endothelin-1 and angiotensin II, were examined in vitro. Aortic ETA receptors and ERK/MEK expression were measured by western blotting. Key results: Insulin-treated diabetic rats exhibited increases in plasma insulin, angiotensin II and endothelin-1. The systolic blood pressure and endothelin-1-induced contractile responses in aortae in vitro were enhanced in insulin-treated diabetic rats and blunted by chronic losartan administration. LY294002 (phosphatidylinositol 3-kinase inhibitor) and/or PD98059 (MEK inhibitor) diminished the enhanced contractile response to endothelin-1 in aortae from insulin-treated diabetic rats. ETA and ETB receptors, ERK-1/2 and MEK-1/2 protein expression and endothelin-1-stimulated ERK phosphorylation were all increased in aortae from insulin-treated diabetic rats. Such increases were blunted by chronic losartan administration. Endothelin-1-induced contraction was significantly higher in aortae from angiotensin II-infused diabetic rats. angiotensin II-infusion increased ERK phosphorylation, but the expression of endothelin receptors and ERK/MEK proteins remained unchanged. Conclusions and implications: These results suggest that the combination of high plasma angiotensin II and insulin with a diabetic state induced enhancement of endothelin-1-induced vasoconstriction, ETA receptor expression and ERK expression/activity in the aorta. Losartan improved both the diabetes

  2. Oxidative stress-mediated, post-translational loss of MafA protein as a contributing mechanism to loss of insulin gene expression in glucotoxic beta cells.

    PubMed

    Harmon, Jamie S; Stein, Roland; Robertson, R Paul

    2005-03-25

    Glucose toxicity in pancreatic islet beta cells causes loss of insulin gene expression, content, and secretion due to loss of binding of transcription factors, most notably PDX-1 and RIPE-3b1 activator, to the promoter region of the insulin gene. Recently, RIPE-3b1 activator was cloned and identified as the mammalian homologue of avian MafA/Maf-L (MafA). This enabled us to carry out more extensive studies of the role of MafA in glucotoxicity than were hitherto possible. Northern analysis of glucotoxic HIT-T15 cells revealed normal amounts of MafA mRNA, but Western analysis demonstrated a 97 +/- 1% reduction in MafA protein (p < 0.0001). The proteasome is a likely site for MafA degradation as lactacystin, an irreversible proteasome inhibitor, caused an accumulation of MafA protein. Antioxidants have previously been shown to prevent the adverse effects of glucose toxicity on beta cell function both in vivo and in vitro. In the current study, chronic culturing of HIT-T15 cells with the antioxidant N-acetylcysteine (NAC) prevented loss of MafA protein (late passage = 18.9 +/- 10.4% of early passage, p < 0.001; late passage with NAC = 68.7 +/- 19.7% of early passage, p = not significant) and loss of DNA binding (late passage = 63.7 +/- 9% of early passage, p < 0.02; late passage with NAC = 116 +/- 10% of early passage, p = not significant). Additionally, transient transfection of PDX-1 or MafA cDNA into glucotoxic cells increased PDX-1 and MafA protein levels and individually increased insulin promoter activity (untreated = 34%, PDX-1 = 70%, MafA = 78%; percentage of activity of early passage cells), whereas the combined transfection of MafA and PDX-1 completely restored insulin promoter activity. This recovery of promoter activity following transient transfection had no effect on endogenous insulin mRNA. However, adenoviral infection of MafA and PDX-1 significantly increased endogenous insulin mRNA levels by 93% (121 +/- 9 versus 233 +/- 18 density light units; n = 5

  3. Oxidative stress-mediated, post-translational loss of MafA protein as a contributing mechanism to loss of insulin gene expression in glucotoxic beta cells.

    PubMed

    Harmon, Jamie S; Stein, Roland; Robertson, R Paul

    2005-03-25

    Glucose toxicity in pancreatic islet beta cells causes loss of insulin gene expression, content, and secretion due to loss of binding of transcription factors, most notably PDX-1 and RIPE-3b1 activator, to the promoter region of the insulin gene. Recently, RIPE-3b1 activator was cloned and identified as the mammalian homologue of avian MafA/Maf-L (MafA). This enabled us to carry out more extensive studies of the role of MafA in glucotoxicity than were hitherto possible. Northern analysis of glucotoxic HIT-T15 cells revealed normal amounts of MafA mRNA, but Western analysis demonstrated a 97 +/- 1% reduction in MafA protein (p < 0.0001). The proteasome is a likely site for MafA degradation as lactacystin, an irreversible proteasome inhibitor, caused an accumulation of MafA protein. Antioxidants have previously been shown to prevent the adverse effects of glucose toxicity on beta cell function both in vivo and in vitro. In the current study, chronic culturing of HIT-T15 cells with the antioxidant N-acetylcysteine (NAC) prevented loss of MafA protein (late passage = 18.9 +/- 10.4% of early passage, p < 0.001; late passage with NAC = 68.7 +/- 19.7% of early passage, p = not significant) and loss of DNA binding (late passage = 63.7 +/- 9% of early passage, p < 0.02; late passage with NAC = 116 +/- 10% of early passage, p = not significant). Additionally, transient transfection of PDX-1 or MafA cDNA into glucotoxic cells increased PDX-1 and MafA protein levels and individually increased insulin promoter activity (untreated = 34%, PDX-1 = 70%, MafA = 78%; percentage of activity of early passage cells), whereas the combined transfection of MafA and PDX-1 completely restored insulin promoter activity. This recovery of promoter activity following transient transfection had no effect on endogenous insulin mRNA. However, adenoviral infection of MafA and PDX-1 significantly increased endogenous insulin mRNA levels by 93% (121 +/- 9 versus 233 +/- 18 density light units; n = 5

  4. Loss of connexin36 channels alters beta-cell coupling, islet synchronization of glucose-induced Ca2+ and insulin oscillations, and basal insulin release.

    PubMed

    Ravier, Magalie A; Güldenagel, Martin; Charollais, Anne; Gjinovci, Asllan; Caille, Dorothée; Söhl, Goran; Wollheim, Claes B; Willecke, Klaus; Henquin, Jean-Claude; Meda, Paolo

    2005-06-01

    Normal insulin secretion requires the coordinated functioning of beta-cells within pancreatic islets. This coordination depends on a communications network that involves the interaction of beta-cells with extracellular signals and neighboring cells. In particular, adjacent beta-cells are coupled via channels made of connexin36 (Cx36). To assess the function of this protein, we investigated islets of transgenic mice in which the Cx36 gene was disrupted by homologous recombination. We observed that compared with wild-type and heterozygous littermates that expressed Cx36 and behaved as nontransgenic controls, mice homozygous for the Cx36 deletion (Cx36(-/-)) featured beta-cells devoid of gap junctions and failing to exchange microinjected Lucifer yellow. During glucose stimulation, islets of Cx36(-/-) mice did not display the regular oscillations of intracellular calcium concentrations ([Ca(2+)](i)) seen in controls due to the loss of cell-to-cell synchronization of [Ca(2+)](i) changes. The same islets did not release insulin in a pulsatile fashion, even though the overall output of the hormone in response to glucose stimulation was normal. However, under nonstimulatory conditions, islets lacking Cx36 showed increased basal release of insulin. These data show that Cx36-dependent signaling is essential for the proper functioning of beta-cells, particularly for the pulsatility of [Ca(2+)](i) and insulin secretion during glucose stimulation.

  5. Identification and Characterization of an Insulin-Like Receptor Involved in Crustacean Reproduction.

    PubMed

    Sharabi, O; Manor, R; Weil, S; Aflalo, E D; Lezer, Y; Levy, T; Aizen, J; Ventura, T; Mather, P B; Khalaila, I; Sagi, A

    2016-02-01

    Sexual differentiation and maintenance of masculinity in crustaceans has been suggested as being regulated by a single androgenic gland (AG) insulin-like peptide (IAG). However, downstream elements involved in the signaling cascade remain unknown. Here we identified and characterized a gene encoding an insulin-like receptor in the prawn Macrobrachium rosenbergii (Mr-IR), the first such gene detected in a decapod crustacean. In mining for IRs and other insulin signaling-related genes, we constructed a comprehensive M. rosenbergii transcriptomic library from multiple sources. In parallel we sequenced the complete Mr-IR cDNA, confirmed in the wide transcriptomic library. Mr-IR expression was detected in most tissues in both males and females, including the AG and gonads. To study Mr-IR function, we performed long-term RNA interference (RNAi) silencing in young male prawns. Although having no effect on growth, Mr-IR silencing advanced the appearance of a male-specific secondary trait. The most noted effects of Mr-IR silencing were hypertrophy of the AG and the associated increased production of Mr-IAG, with an unusual abundance of immature sperm cells being seen in the distal sperm duct. A ligand blot assay using de novo recombinant Mr-IAG confirmed the existence of a ligand-receptor interaction. Whereas these results suggest a role for Mr-IR in the regulation of the AG, we did not see any sexual shift after silencing of Mr-IR, as occurred when the ligand-encoding Mr-IAG gene was silenced. This suggests that sexual differentiation in crustaceans involve more than a single Mr-IAG receptor, emphasizing the complexity of sexual differentiation and maintenance. PMID:26677879

  6. TCF7L2 Polymorphism, Weight Loss and Proinsulin∶Insulin Ratio in the Diabetes Prevention Program

    PubMed Central

    McCaffery, Jeanne M.; Jablonski, Kathleen A.; Franks, Paul W.; Dagogo-Jack, Sam; Wing, Rena R.; Knowler, William C.; Delahanty, Linda; Dabelea, Dana; Hamman, Richard; Shuldiner, Alan R.; Florez, Jose C.

    2011-01-01

    Aims TCF7L2 variants have been associated with type 2 diabetes, body mass index (BMI), and deficits in proinsulin processing and insulin secretion. Here we sought to test whether these effects were apparent in high-risk individuals and modify treatment responses. Methods We examined the potential role of the TCF7L2 rs7903146 variant in predicting resistance to weight loss or a lack of improvement of proinsulin processing during 2.5-years of follow-up participants (N = 2,994) from the Diabetes Prevention Program (DPP), a randomized controlled trial designed to prevent or delay diabetes in high-risk adults. Results We observed no difference in the degree of weight loss by rs7903146 genotypes. However, the T allele (conferring higher risk of diabetes) at rs7903146 was associated with higher fasting proinsulin at baseline (P<0.001), higher baseline proinsulin∶insulin ratio (p<0.0001) and increased proinsulin∶insulin ratio over a median of 2.5 years of follow-up (P = 0.003). Effects were comparable across treatment arms. Conclusions The combination of a lack of impact of the TCF7L2 genotypes on the ability to lose weight, but the presence of a consistent effect on the proinsulin∶insulin ratio over the course of DPP, suggests that high-risk genotype carriers at this locus can successfully lose weight to counter diabetes risk despite persistent deficits in insulin production. PMID:21814547

  7. Novel Small Molecule Glucagon-Like Peptide-1 Receptor Agonist Stimulates Insulin Secretion in Rodents and From Human Islets

    PubMed Central

    Sloop, Kyle W.; Willard, Francis S.; Brenner, Martin B.; Ficorilli, James; Valasek, Kathleen; Showalter, Aaron D.; Farb, Thomas B.; Cao, Julia X.C.; Cox, Amy L.; Michael, M. Dodson; Gutierrez Sanfeliciano, Sonia Maria; Tebbe, Mark J.; Coghlan, Michael J.

    2010-01-01

    OBJECTIVE The clinical effectiveness of parenterally-administered glucagon-like peptide-1 (GLP-1) mimetics to improve glucose control in patients suffering from type 2 diabetes strongly supports discovery pursuits aimed at identifying and developing orally active, small molecule GLP-1 receptor agonists. The purpose of these studies was to identify and characterize novel nonpeptide agonists of the GLP-1 receptor. RESEARCH DESIGN AND METHODS Screening using cells expressing the GLP-1 receptor and insulin secretion assays with rodent and human islets were used to identify novel molecules. The intravenous glucose tolerance test (IVGTT) and hyperglycemic clamp characterized the insulinotropic effects of compounds in vivo. RESULTS Novel low molecular weight pyrimidine-based compounds that activate the GLP-1 receptor and stimulate glucose-dependent insulin secretion are described. These molecules induce GLP-1 receptor-mediated cAMP signaling in HEK293 cells expressing the GLP-1 receptor and increase insulin secretion from rodent islets in a dose-dependent manner. The compounds activate GLP-1 receptor signaling, both alone or in an additive fashion when combined with the endogenous GLP-1 peptide; however, these agonists do not compete with radiolabeled GLP-1 in receptor-binding assays. In vivo studies using the IVGTT and the hyperglycemic clamp in Sprague Dawley rats demonstrate increased insulin secretion in compound-treated animals. Further, perifusion assays with human islets isolated from a donor with type 2 diabetes show near-normalization of insulin secretion upon compound treatment. CONCLUSIONS These studies characterize the insulinotropic effects of an early-stage, small molecule GLP-1 receptor agonist and provide compelling evidence to support pharmaceutical optimization. PMID:20823098

  8. Low Oxygen Tension Modulates the Insulin-Like Growth Factor-1 or -2 Signaling via Both Insulin-Like Growth Factor-1 Receptor and Insulin Receptor to Maintain Stem Cell Identity in Placental Mesenchymal Stem Cells.

    PubMed

    Youssef, Amer; Han, Victor K M

    2016-03-01

    Placental mesenchymal stem cells (PMSCs) are readily available multipotent stem cells for potential use in regenerative therapies. For this purpose, PMSCs must be maintained in culture conditions that mimic the in vivo microenvironment. IGFs (IGF-1 and IGF-2) and oxygen tension are low in the placenta in early gestation and increase as pregnancy progresses. IGFs bind to two receptor tyrosine kinases, the IGF-1 receptor (IGF-1R) and the insulin receptor (IR), and their hybrid receptors. We hypothesized that IGF-1 and IGF-2 signal via distinct signaling pathways under low-oxygen tension to maintain PMSC multipotency. In preterm PMSCs, low-oxygen tension increased the expression of IGF-2 and reduced IGF-1. IGF-1 stimulated higher phosphorylation of IGF-1Rβ, ERK1/2, and AKT, which was maintained at steady lower levels by low oxygen tension. PMSC proliferation was increased by IGF-1 more than IGF-2,and was potentiated by low-oxygen tension. This IGF/low oxygen tension-mediated proliferation was receptor dependent because neutralization of the IGF-1R inhibited PMSC proliferation in the presence of IGF-1 and the IR in presence of IGF-2. These findings suggest that both IGF-1R and the IR can participate in mediating IGF signaling in maintaining PMSCs multipotency. We conclude that low-oxygen tension can modify the IGF-1 or IGF-2 signaling via the IGF-1R and IR in PMSCs.

  9. Receptors and growth-promoting effects of insulin and insulinlike growth factors on cells from bovine retinal capillaries and aorta.

    PubMed Central

    King, G L; Goodman, A D; Buzney, S; Moses, A; Kahn, C R

    1985-01-01

    It has been suggested that elevated levels of insulin or insulin-like growth factors (IGFs) play a role in the development of diabetic vascular complications. Previously, we have shown a differential response to insulin between vascular cells from retinal capillaries and large arteries with the former being much more insulin responsive. In the present study, we have characterized the receptors and the growth-promoting effect of insulinlike growth factor I (IGF-I) and multiplication-stimulating activity (MSA, an IGF-II) on endothelial cells and pericytes from calf retinal capillaries and on endothelial and smooth muscle cells from calf aorta. We found single and separate populations of high affinity receptors for IGF-I and MSA with respective affinity constants of 1 X 10(-9) M-1 and 10(-8) M-1 in all four cell types studied. Specific binding of IGF-I was between 7.2 and 7.9% per milligram of protein in endothelial cells and 9.1 and 10.4% in the vascular supporting cells. For 125I-MSA, retinal endothelial cells bound only 1.7-2.5%, whereas the aortic endothelial cells and the vascular supporting cells bound between 5.6 and 8.5% per milligram of protein. The specificity of the receptors for IGF-I and MSA differed, as insulin and MSA was able to compete with 125I-IGF-I for binding to the IGF-I receptors with 0.01-0.1, the potency of unlabeled IGF-I, whereas even 1 X 10(-6) M, insulin did not significantly compete with 125I-MSA for binding to the receptors for MSA. For growth-promoting effects, as measured by the incorporation of [3H]thymidine into DNA, confluent retinal endothelial cells responded to IGF-I and MSA by up to threefold increase in the rate of DNA synthesis, whereas confluent aortic endothelial cells did not respond at all. A similar differential of response to insulin between micro- and macrovascular endothelial cells was reported by us previously. In the retinal endothelium, insulin was more potent than IGF-I and IGF-I was more potent that MSA. In the

  10. Insulin-stimulated Na/sup +/ transport in a model renal epithelium: protein synthesis dependence and receptor interactions

    SciTech Connect

    Blazer-Yost, B.L.; Cox, M.

    1987-05-01

    The urinary bladder of the toad, Bufo marinus, is a well characterized model of the mammalian distal nephron. Porcine insulin (approx. 0.5-5.0 ..mu..M) stimulates net mucosal to serosal Na/sup +/ flux within 10 minutes of hormone addition. The response is maintained for at least 5 hr and is completely abolished by low doses (10..mu..M) of the epithelial Na/sup +/ channel blocker amiloride. Insulin-stimulated Na/sup +/ transport does not require new protein synthesis since it is actinomycin-D (10..mu..g/ml) insensitive. Also in 3 separate experiments in which epithelial cell proteins were examined by /sup 35/S-methionine labeling, 2-dimensional polyacrylamide gel electrophoresis/autoradiography, no insulin induced proteins were observed. Equimolar concentrations of purified porcine proinsulin and insulin (0.64..mu..M) stimulate Na/sup +/ transport to the same extent. Thus, the putative toad insulin receptor may have different affinity characteristics than those demonstrated for insulin and proinsulin in mammalian tissues. Alternatively, the natriferic action of insulin in toad urinary bladders may be mediated by occupancy of another receptor. Preliminary experiments indicating that nanomolar concentrations of IGF/sub 1/ stimulate Na/sup +/ transport in this tissue support the latter contention.

  11. Molecular docking studies of banana flower flavonoids as insulin receptor tyrosine kinase activators as a cure for diabetes mellitus

    PubMed Central

    Ganugapati, Jayasree; Baldwa, Aashish; Lalani, Sarfaraz

    2012-01-01

    Diabetes mellitus is a metabolic disorder caused due to insulin deficiency. Banana flower is a rich source of flavonoids that exhibit anti diabetic activity. Insulin receptor is a tetramer that belongs to a family of receptor tyrosine kinases. It contains two alpha subunits that form the extracellular domain and two beta subunits that constitute the intracellular tyrosine kinase domain. Insulin binds to the extracellular region of the receptor and causes conformational changes that lead to the activation of the tyrosine kinase. This leads to autophosphorylation, a step that is crucial in insulin signaling pathway. Hence, compounds that augment insulin receptor tyrosine kinase activity would be useful in the treatment of diabetes mellitus. The 3D structure of IR tyrosine kinase was obtained from PDB database. The list of flavonoids found in banana flower was obtained from USDA database. The structures of the flavonoids were obtained from NCBI Pubchem. Docking analysis of the flavonoids was performed using Autodock 4.0 and Autodock Vina. The results indicate that few of the flavonoids may be potential activators of IR tyrosine kinase. PMID:22493522

  12. Molecular docking studies of banana flower flavonoids as insulin receptor tyrosine kinase activators as a cure for diabetes mellitus.

    PubMed

    Ganugapati, Jayasree; Baldwa, Aashish; Lalani, Sarfaraz

    2012-01-01

    Diabetes mellitus is a metabolic disorder caused due to insulin deficiency. Banana flower is a rich source of flavonoids that exhibit anti diabetic activity. Insulin receptor is a tetramer that belongs to a family of receptor tyrosine kinases. It contains two alpha subunits that form the extracellular domain and two beta subunits that constitute the intracellular tyrosine kinase domain. Insulin binds to the extracellular region of the receptor and causes conformational changes that lead to the activation of the tyrosine kinase. This leads to autophosphorylation, a step that is crucial in insulin signaling pathway. Hence, compounds that augment insulin receptor tyrosine kinase activity would be useful in the treatment of diabetes mellitus. The 3D structure of IR tyrosine kinase was obtained from PDB database. The list of flavonoids found in banana flower was obtained from USDA database. The structures of the flavonoids were obtained from NCBI Pubchem. Docking analysis of the flavonoids was performed using Autodock 4.0 and Autodock Vina. The results indicate that few of the flavonoids may be potential activators of IR tyrosine kinase.

  13. The effects of maternal diabetes on expression of insulin-like growth factor-1 and insulin receptors in male developing rat hippocampus.

    PubMed

    Hami, Javad; Sadr-Nabavi, Ariane; Sankian, Mojtaba; Balali-Mood, Mehdi; Haghir, Hossein

    2013-01-01

    Diabetes during pregnancy causes neurodevelopmental and neurocognitive abnormalities in offspring. Insulin and insulin-like growth factor-1 (IGF-1) are important regulators of developmental and cognitive functions in the central nervous system. We examined the effects of maternal diabetes on insulin-like growth factor-1 receptor (IGF-1R) and insulin receptor (InsR) expression in the developing rat hippocampus. Female rats were maintained diabetic from a week before pregnancy through parturition and male offspring was killed at P0, P7, and P14. We found a significant bilateral upregulation of both IGF-1R and InsR transcripts in the hippocampus of pups born to diabetic mothers at P0, as compared to controls. However, at the same time point, the results of western blot analysis revealed only a slight change in their protein levels. At P7, there was a marked bilateral reduction in mRNA expression and protein levels of IGF-1R, although not of InsR in the diabetic group. We also found a downregulation in IGF1-R transcripts, especially in left hippocampus of the diabetic group at P14. Moreover, at the same time point, InsR expression was significantly decreased in both hippocampi of diabetic newborns. When compared with controls, we did not find any difference in hippocampal IGF-1R or InsR mRNA and protein levels in the insulin-treated group. The present study revealed that diabetes during pregnancy strongly influences the regulation of both IGF-1R and InsR in the right/left developing hippocampi. Furthermore, the rigid control of maternal glycaemia by insulin administration normalized these effects.

  14. Myeloid Cell-Restricted Insulin/IGF-1 Receptor Deficiency Protects against Skin Inflammation.

    PubMed

    Knuever, Jana; Willenborg, Sebastian; Ding, Xiaolei; Akyüz, Mehmet D; Partridge, Linda; Niessen, Carien M; Brüning, Jens C; Eming, Sabine A

    2015-12-01

    Myeloid cells are key regulators of tissue homeostasis and disease. Alterations in cell-autonomous insulin/IGF-1 signaling in myeloid cells have recently been implicated in the development of systemic inflammation and insulin-resistant diabetes mellitus type 2 (DM). Impaired wound healing and inflammatory skin diseases are frequent DM-associated skin pathologies, yet the underlying mechanisms are elusive. In this study, we investigated whether myeloid cell-restricted IR/IGF-1R signaling provides a pathophysiologic link between systemic insulin resistance and the development of cutaneous inflammation. Therefore, we generated mice lacking both the insulin and IGF-1 receptor in myeloid cells (IR/IGF-1R(MKO)). Whereas the kinetics of wound closure following acute skin injury was similar in control and IR/IGF-1R(MKO) mice, in two different conditions of dermatitis either induced by repetitive topical applications of the detergent SDS or by high-dose UV B radiation, IR/IGF-1R(MKO) mice were protected from inflammation, whereas controls developed severe skin dermatitis. Notably, whereas during the early phase in both inflammatory conditions the induction of epidermal proinflammatory cytokine expression was similar in control and IR/IGF-1R(MKO) mice, during the late stage, epidermal cytokine expression was sustained in controls but virtually abrogated in IR/IGF-1R(MKO) mice. This distinct kinetic of epidermal cytokine expression was paralleled by proinflammatory macrophage activation in controls and a noninflammatory phenotype in mutants. Collectively, our findings provide evidence for a proinflammatory IR/IGF-1R-dependent pathway in myeloid cells that plays a critical role in the dynamics of an epidermal-dermal cross-talk in cutaneous inflammatory responses, and may add to the mechanistic understanding of diseases associated with disturbances in myeloid cell IR/IGF-1R signaling, including DM. PMID:26519530

  15. Myeloid cell-restricted Insulin/IGF-1 receptor deficiency protects against skin inflammation

    PubMed Central

    Ding, Xiaolei; Akyüz, Mehmet D.; Partridge, Linda; Niessen, Carien M.; Brüning, Jens C.; Eming, Sabine A.

    2016-01-01

    Myeloid cells are key regulators of tissue homeostasis and disease. Alterations in cell-autonomous Insulin/IGF-1 signaling in myeloid cells have recently been implicated in the development of systemic inflammation and insulin-resistant diabetes mellitus type 2 (DM). Impaired wound healing and inflammatory skin diseases are frequent DM-associated skin pathologies, yet the underlying mechanisms are elusive. Here we investigated whether myeloid cell-restricted IR/IGF-1R signalling provides a pathophysiological link between systemic insulin resistance and the development of cutaneous inflammation. Therefore, we generated mice lacking both the Insulin and IGF-1 receptor in myeloid cells (IR/IGF-1RMKO). Whereas the kinetics of wound closure following acute skin injury was similar in control and IR/IGF-1RMKO mice, in two different conditions of dermatitis either induced by repetitive topical applications of the detergent SDS or by high-dose UVB radiation, IR/IGF-1RMKO mice were protected from inflammation, whereas controls developed severe skin dermatitis. Notably, whereas during the early phase in both inflammatory conditions the induction of epidermal pro-inflammatory cytokine expression was similar in control and IR/IGF-1RMKO mice, during the late stage, epidermal cytokine expression was sustained in controls, however virtually abrogated in IR/IGF-1RMKO mice. This distinct kinetic of epidermal cytokine expression was paralleled by pro-inflammatory macrophage activation in controls and a non-inflammatory phenotype in mutants. Collectively, our findings provide evidence for a pro-inflammatory IR/IGF-1R-dependent pathway in myeloid cells that plays a critical role in the dynamics of an epidermal-dermal crosstalk in cutaneous inflammatory responses, and may add to the mechanistic understanding of diseases associated with disturbances in myeloid cell IR/IGF-1R signaling including DM. PMID:26519530

  16. Autoradiographic visualization of insulin-like growth factor-II receptors in rat brain

    SciTech Connect

    Mendelsohn, L.G.; Kerchner, G.A.; Clemens, J.A.; Smith, M.C.

    1986-03-01

    The documented presence of IGF-II in brain and CSF prompted us to investigate the distribution of receptors for IGF-II in rat brain slices. Human /sup 125/-I-IGF-II (10 pM) was incubated for 16 hrs at 4/sup 0/C with slide-mounted rat brain slices in the absence and presence of unlabeled human IGF-II (67 nM) or human insulin (86 nM). Slides were washed, dried, and exposed to X-ray film for 4-7 days. The results showed dense labeling in the granular layers of the olfactory bulbs, deep layers of the cerebral cortex, pineal gland, anterior pituitary, hippocampus (pyramidal cells CA/sub 1/-CA/sub 2/ and dentate gyrus), and the granule cell layers of the cerebellum. Unlabeled IGF-II eliminated most of the binding of these brain regions while insulin produced only a minimal reduction in the amount of /sup 125/I-IGF-II bound. These results indicate that a specific neural receptor for IGS-II is uniquely distributed in rat brain tissue and supports the notion that this peptide might play an important role in normal neuronal functioning.

  17. Peroxisome proliferator-activated receptor gamma agonists as insulin sensitizers: from the discovery to recent progress.

    PubMed

    Cho, Nobuo; Momose, Yu

    2008-01-01

    An epidemic of metabolic diseases including type 2 diabetes and obesity is undermining the health of people living in industrialized societies. There is an urgent need to develop innovative therapeutics. The peroxisome proliferator-activated receptor gamma (PPARgamma) is one of the ligand-activated transcription factors in the nuclear hormone receptor superfamily and a pivotal regulator of glucose and lipid homeostasis. The discovery of PPARgamma as a target of multimodal insulin sensitizers, represented by thiazolidinediones (TZDs), has attracted remarkable scientific interest and had a great impact on the pharmaceutical industry. With the clinical success of the PPARgamma agonists, pioglitazone (Actos) and rosiglitazone (Avandia), development of novel and potent insulin-sensitizing agents with diverse clinical profiles has been accelerated. Currently, a number of PPARgamma agonists from different chemical classes and with varying pharmacological profiles are being developed. Despite quite a few obstacles to the development of PPAR-related drugs, PPARgamma-targeted agents still hold promise. There are new concepts and encouraging evidence emerging that suggest this class can yield improved anti-diabetic agents. This review covers the discovery of TZDs, provides an overview of PPARgamma including the significance of PPARgamma as a drug target, describes the current status of a wide variety of novel PPARgamma ligands including PPAR dual and pan agonists and selective PPARgamma modulators (SPPARgammaMs), and highlights new approaches for identifying agents targeting PPARgamma in the treatment of type 2 diabetes. PMID:19075761

  18. Extracellular vimentin interacts with insulin-like growth factor 1 receptor to promote axonal growth.

    PubMed

    Shigyo, Michiko; Kuboyama, Tomoharu; Sawai, Yusuke; Tada-Umezaki, Masahito; Tohda, Chihiro

    2015-01-01

    Vimentin, an intermediate filament protein, is generally recognised as an intracellular protein. Previously, we reported that vimentin was secreted from astrocytes and promoted axonal growth. The effect of extracellular vimentin in neurons was a new finding, but its signalling pathway was unknown. In this study, we aimed to determine the signalling mechanism of extracellular vimentin that facilitates axonal growth. We first identified insulin-like growth factor 1 receptor (IGF1R) as a receptor that is highly phosphorylated by vimentin stimulation. IGF1R blockades diminished vimentin- or IGF1-induced axonal growth in cultured cortical neurons. IGF1, IGF2 and insulin were not detected in the neuron culture medium after vimentin treatment. The combined drug affinity responsive target stability method and western blotting analysis showed that vimentin and IGF1 interacted with IGF1R directly. In addition, immunoprecipitation and western blotting analyses confirmed that recombinant IGF1R bound to vimentin. The results of a molecular dynamics simulation revealed that C-terminal residues (residue number 330-407) in vimentin are the most appropriate binding sites with IGF1R. Thus, extracellular vimentin may be a novel ligand of IGF1R that promotes axonal growth in a similar manner to IGF1. Our results provide novel findings regarding the role of extracellular vimentin and IGF1R in axonal growth. PMID:26170015

  19. Insulin-like Growth Factor Receptor Inhibitors: Baby or the Bathwater?

    PubMed Central

    2012-01-01

    The success of targeted therapies for cancer is undisputed; strong preclinical evidence has resulted in the approval of several new agents for cancer treatment. The type I insulin-like growth factor receptor (IGF1R) appeared to be one of these promising new targets. Substantial population and preclinical data have all pointed toward this pathway as an important regulator of tumor cell biology. Although early results from clinical trials that targeted the IGF1R showed some evidence of response, larger randomized phase III trials have not shown clear clinical benefit of targeting this pathway in combination with conventional strategies. These disappointing results have resulted in the discontinuation of several anti-IGF1R programs. However, the conduct of these trials has brought to the forefront several important factors that need to be considered in the conduct of future clinical trials. The need to develop biomarkers, a clearer understanding of insulin receptor function, and defining rational combination regimens all require further consideration. In this commentary, the current state of IGF1R inhibitors in cancer therapy is reviewed. PMID:22761272

  20. Highly specific role of the insulin receptor in breast cancer progression

    PubMed Central

    Rostoker, Ran; Abelson, Sagi; Bitton-Worms, Keren; Genkin, Inna; Ben-Shmuel, Sarit; Dakwar, Maria; Orr, Zila Shen; Caspi, Avishay; Tzukerman, Maty

    2015-01-01

    Accumulating evidence from clinical trials indicates that specific targeting of the IGF1 receptor (IGF1R) is not efficient as an anti-breast cancer treatment. One possible reason is that the mitogenic signals from the insulin receptor (IR) can be processed independently or as compensation to inhibition of the IGF1R. In this study, we highlight the role of the IR in mediating breast tumor progression in both WT mice and a hyperinsulinemic MKR mouse model by induction of Ir (Insr) or Igf1r knockdown (KD) in the mammary carcinoma Mvt-1 cell line. By using the specific IR antagonist-S961, we demonstrated that Igf1r-KD induces elevated responses by the IR to IGF1. On the other hand, Ir-KD cells generated significantly smaller tumors in the mammary fat pads of both WT and MKR mice, as opposed to control cells, where as the Igf1r-KD cells did not. The tumorigenic effects of insulin on the Mvt-1 cells were also demonstrated using microarray analysis, which indicates alteration of genes and signaling pathways involved in proliferation, the cell cycle, and apoptosis following insulin stimulation. In addition, the correlation between IR and the potential prognostic marker for aggressive breast cancer, CD24, was examined in the Ir-KD cells. Fluorescence-activated cell sorting (FACS) analysis revealed more than 60% reduction in CD24 expression in the Ir-KD cells when compared with the control cells. Our results also indicate that CD24-expressing cells can restore, at least in part, the tumorigenic capacity of Ir-KD cells. Taken together, our results highlight the mitogenic role of the IR in mammary tumor progression with a direct link to CD24 expression. PMID:25694511

  1. Comparative 2D NMR studies of human insulin and des-pentapeptide insulin: Sequential resonance assignment and implications for protein dynamics and receptor recognition

    SciTech Connect

    Hua, Qingxin ); Weiss, M.A. Massachusetts General Hospital, Boston, MA )

    1991-06-04

    The solution structure and dynamics of human insulin are ivestigated by 2D {sup 1}H NMR spectroscopy in reference to a previously analyzed analogue, des-pentapeptide (B26-B30) insulin. This spectroscopic comparison is of interest since (i) the structure of the C-terminal region of the B-chain has not been determined in the monomeric state and (ii) the role of this region in binding to the insulin receptor has been the subject of long-standing speculation. The present NMR studies are conducted in the presence of an organic cosolvent (20% acetic acid), under which conditions both proteins are monomeric and stably folded. Complete sequential assignment of human insulin is obtained and leads to the following conclusions. (1) The secondary structure of the insulin monomer (three {alpha}-helices and B-chain {beta}-turn) is similar to that observed in the 2-Zn crustal state. (2) The folding of DPI is essentially the same as the corresponding portion of intact insulin, in accord with the similarities between their respective crystal structues. (3) residues B24-B28 adopt an extended configuration in the monomer and pack against the hydrophobic core as in crystallographic dimers; residues B29 and B30 are largely disordered. (4) The insulin fold is shown to provide a model for collective motions in a protein with implications for the mechanism of protein-protein recognition. To their knowledge, this paper describes the first detailed analysis of a protein NMR spectrum under conditions of extensive conformational broadening.

  2. IGF-I, IGF-II, and Insulin Stimulate Different Gene Expression Responses through Binding to the IGF-I Receptor

    PubMed Central

    Versteyhe, Soetkin; Klaproth, Birgit; Borup, Rehannah; Palsgaard, Jane; Jensen, Maja; Gray, Steven G.; De Meyts, Pierre

    2013-01-01

    Insulin and the insulin-like growth factors (IGF)-I and -II are closely related peptides important for regulation of metabolism, growth, differentiation, and development. The IGFs exert their main effects through the IGF-I receptor. Although the insulin receptor is the main physiological receptor for insulin, this peptide hormone can also bind at higher concentrations to the IGF-I receptor and exert effects through it. We used microarray gene expression profiling to investigate the gene expression regulated by IGF-I, IGF-II, and insulin after stimulation of the IGF-I receptor. Fibroblasts from mice, knockout for IGF-II and the IGF-II/cation-independent mannose-6-phosphate receptor, and expressing functional IGF-I but no insulin receptors, were stimulated for 4 h with equipotent saturating concentrations of insulin, IGF-I, and IGF-II. Each ligand specifically regulated a group of transcripts that was not regulated by the other two ligands. Many of the functions and pathways these regulated genes were involved in, were consistent with the known biological effects of these ligands. The differences in gene expression might therefore account for some of the different biological effects of insulin, IGF-I, and IGF-II. This work adds to the evidence that not only the affinity of a ligand determines its biological response, but also its nature, even through the same receptor. PMID:23950756

  3. Probing Receptor Specificity by Sampling the Conformational Space of the Insulin-like Growth Factor II C-domain*

    PubMed Central

    Hexnerová, Rozálie; Křížková, Květoslava; Fábry, Milan; Sieglová, Irena; Kedrová, Kateřina; Collinsová, Michaela; Ullrichová, Pavlína; Srb, Pavel; Williams, Christopher; Crump, Matthew P.; Tošner, Zdeněk; Jiráček, Jiří; Veverka, Václav; Žáková, Lenka

    2016-01-01

    Insulin and insulin-like growth factors I and II are closely related protein hormones. Their distinct evolution has resulted in different yet overlapping biological functions with insulin becoming a key regulator of metabolism, whereas insulin-like growth factors (IGF)-I/II are major growth factors. Insulin and IGFs cross-bind with different affinities to closely related insulin receptor isoforms A and B (IR-A and IR-B) and insulin-like growth factor type I receptor (IGF-1R). Identification of structural determinants in IGFs and insulin that trigger their specific signaling pathways is of increasing importance in designing receptor-specific analogs with potential therapeutic applications. Here, we developed a straightforward protocol for production of recombinant IGF-II and prepared six IGF-II analogs with IGF-I-like mutations. All modified molecules exhibit significantly reduced affinity toward IR-A, particularly the analogs with a Pro-Gln insertion in the C-domain. Moreover, one of the analogs has enhanced binding affinity for IGF-1R due to a synergistic effect of the Pro-Gln insertion and S29N point mutation. Consequently, this analog has almost a 10-fold higher IGF-1R/IR-A binding specificity in comparison with native IGF-II. The established IGF-II purification protocol allowed for cost-effective isotope labeling required for a detailed NMR structural characterization of IGF-II analogs that revealed a link between the altered binding behavior of selected analogs and conformational rearrangement of their C-domains. PMID:27510031

  4. Insulin receptor autophosphorylation in BC/sub 3/H-1 whole cell assays is inhibited by the specific calmodulin inhibitors calmidazolium and W-7

    SciTech Connect

    Arnold, T.P.; Pollet, R.I.

    1987-05-01

    Recent reports suggest the involvement of Ca/sup + +/ and the Ca/sup + +/ binding protein calmodulin in the insulin stimulated receptor tyrosine kinase activity in cell free (adipocyte) phosphorylation systems. Working with the insulin-responsive well characterized muscle cell line BC/sub 3/H-1, they have investigated the effects of calmodulin antagonists on insulin receptor phosphorylation in cultured intact cells. BC/sub 3/H-1 myocytes were grown to confluency (10-12 days) then exposed to media containing /sup 32/P-orthophosphate for 24 hours (100 mCi/ml). Insulin treatment stimulated the phosphorylation of a 95K protein which is immunoprecipitable with antireceptor antibodies indicating insulin-induced phosphorylation of the insulin receptor beta subunit in vivo. This phosphorylation occurs rapidly within 30 minutes at physiologic insulin concentrations at 37/sup 0/C. Phosphorylation can also be stimulated by the B-10 anti-insulin receptor antibody (1:500). Pretreatment of cells for 30 min with 1uM calmidazolium (R24571) and 10nM W-7 (n-(6-AminoHexyl)-s-chloro-1-naphalenesulfonamide) each significantly inhibited insulin-stimulated phosphorylation. This would suggest that calmodulin may play a role in mediation of the insulin receptor tyrosine kinase activity in the BC/sub 3/H-1 myocyte.

  5. Insulin-like growth factor receptor 1b is required for zebrafish primordial germ cell migration and survival.

    PubMed

    Schlueter, Peter J; Sang, Xianpeng; Duan, Cunming; Wood, Antony W

    2007-05-01

    Insulin-like growth factor (IGF) signaling is a critical regulator of somatic growth during fetal and adult development, primarily through its stimulatory effects on cell proliferation and survival. IGF signaling is also required for development of the reproductive system, although its precise role in this regard remains unclear. We have hypothesized that IGF signaling is required for embryonic germline development, which requires the specification and proliferation of primordial germ cells (PGCs) in an extragonadal location, followed by directed migration to the genital ridges. We tested this hypothesis using loss-of-function studies in the zebrafish embryo, which possesses two functional copies of the Type-1 IGF receptor gene (igf1ra, igf1rb). Knockdown of IGF1Rb by morpholino oligonucleotides (MO) results in mismigration and elimination of primordial germ cells (PGCs), resulting in fewer PGCs colonizing the genital ridges. In contrast, knockdown of IGF1Ra has no effect on PGC migration or number despite inducing widespread somatic cell apoptosis. Ablation of both receptors, using combined MO injections or overexpression of a dominant-negative IGF1R, yields embryos with a PGC-deficient phenotype similar to IGF1Rb knockdown. TUNEL analyses revealed that mismigrated PGCs in IGF1Rb-deficient embryos are eliminated by apoptosis; overexpression of an antiapoptotic gene (Bcl2l) rescues ectopic PGCs from apoptosis but fails to rescue migration defects. Lastly, we show that suppression of IGF signaling leads to quantitative changes in the expression of genes encoding CXCL-family chemokine ligands and receptors involved in PGC migration. Collectively, these data suggest a novel role for IGF signaling in early germline development, potentially via cross-talk with chemokine signaling pathways. PMID:17362906

  6. Efficacy of anti-insulin-like growth factor I receptor monoclonal antibody cixutumumab in mesothelioma is highly correlated with insulin growth factor-I receptor sites/cell.

    PubMed

    Kalra, Neetu; Zhang, Jingli; Yu, Yunkai; Ho, Mitchell; Merino, Maria; Cao, Liang; Hassan, Raffit

    2012-11-01

    Insulin growth factor-I receptor (IGF-IR) is expressed in mesothelioma and therefore an attractive target for therapy. The antitumor activity of cixutumumab, a humanized monoclonal antibody to IGF-IR, in mesothelioma and relationship to IGF-IR expression was investigated using eight early passage tumor cells obtained from patients, nine established cell lines and an in vivo human mesothelioma tumor xenograft model. Although IGF-IR expression at the mRNA and protein level was present in all mesothelioma cells, using a quantitative ELISA immunoassay, there was considerable variability of IGF-IR expression ranging from 1 to 14 ng/mg of lysate. Using flow cytometry, the number of IGF-IR surface receptors varied from ≈ 2,000 to 50,000 sites/cell. Cells expressing >10,000 sites/cell had greater than 10% growth inhibition when treated with cixutumumab (100 μg/ml). Cixutumumab also induced antibody-dependent cell-mediated toxicity (>10% specific lysis) in cell lines, which had >20,000 IGF-IR sites/cell. Treatment with cixutumumab decreased phosphorylation of IGF-IR, Akt and Erk in cell lines, H226 and H28 having 24,000 and 51,000 IGF-IR sites/cell, respectively, but not in the cell line H2052 with 3,000 IGF-IR sites/cell. In vivo, cixutumumab treatment delayed growth of H226 mesothelioma tumor xenografts in mice and improved the overall survival of these mice compared to mice treated with saline (p < 0.004). Our results demonstrate that the antitumor efficacy of cixutumumab including inhibition of IGF-IR downstream signaling is highly correlated with IGF-IR sites/cell. A phase II clinical trial of cixutumumab is currently ongoing for the treatment of patients with mesothelioma.

  7. Recurrent Pregnancy Loss in Polycystic Ovary Syndrome: Role of Hyperhomocysteinemia and Insulin Resistance

    PubMed Central

    Rajani, Shweta; Sharma, Sunita; Kabir, Syed N.; Chakravarty, Baidyanath; Jana, Kuladip

    2013-01-01

    Recurrent pregnancy loss (RPL) in polycystic ovary syndrome (PCOS), which occurs in ∼50% of total pregnancies is a frequent obstetric complication. Among the several hypotheses, insulin resistance (IR), obesity and hyperhomocysteinemia (HHcy) play significant role/s in RPL. This study was conducted to assess the link between elevated levels of homocysteine and IR in PCOS-associated women with RPL in Kolkata, India. A retrospective study was conducted of one hundred and twenty six PCOS women (<30 years) who experienced two or more spontaneous abortions during the first trimester presenting to Institute of Reproductive Medicine (IRM) in Kolkata during the period of March 2008 through February 2011. One hundred and seventeen non-PCOS subjects with matching age range were randomly chosen as controls. Incidence of HHcy and IR was 70.63% (n = 89) and 56.34% (n = 71), respectively, in RPL-affected PCOS population which was significantly higher (p<0.04; p<0.0001) when compared to the non-PCOS set (HHcy: 57.26%; IR: 6.83%). Rates of miscarriage were significantly higher (p<0.008; p<0.03) in hyperhomocysteinemia-induced miscarriage when compared to the normohomocysteinemic segment (PCOS: 70.63% vs.29.36% & non-PCOS: 57.26% vs. 42.73%) along with the insulin resistant (p<0.04; p<0.0001) population (PCOS: 70.63% vs. 56.34% & non-PCOS: 57.26% vs. 6.83%) in both groups. A probabilistic causal model evaluated HHcy as the strongest plausible factor for diagnosis of RPL. A probability percentage of 43.32% in the cases of HHcy- mediated RPL suggests its increased tendency when compared to IR mediated miscarriage (37.29%), further supported by ROC-AUC (HHcy: 0.778vs. IR: 0.601) values. Greater susceptibility towards HHcy may increase the incidence for miscarriage in women in India and highlights the need to combat the condition in RPL control programs in the subcontinent. PMID:23700477

  8. Insulin Receptor Substrate Adaptor Proteins Mediate Prognostic Gene Expression Profiles in Breast Cancer

    PubMed Central

    Becker, Marc A.; Ibrahim, Yasir H.; Oh, Annabell S.; Fagan, Dedra H.; Byron, Sara A.; Sarver, Aaron L.; Lee, Adrian V.; Shaw, Leslie M.; Fan, Cheng; Perou, Charles M.; Yee, Douglas

    2016-01-01

    Therapies targeting the type I insulin-like growth factor receptor (IGF-1R) have not been developed with predictive biomarkers to identify tumors with receptor activation. We have previously shown that the insulin receptor substrate (IRS) adaptor proteins are necessary for linking IGF1R to downstream signaling pathways and the malignant phenotype in breast cancer cells. The purpose of this study was to identify gene expression profiles downstream of IGF1R and its two adaptor proteins. IRS-null breast cancer cells (T47D-YA) were engineered to express IRS-1 or IRS-2 alone and their ability to mediate IGF ligand-induced proliferation, motility, and gene expression determined. Global gene expression signatures reflecting IRS adaptor specific and primary vs. secondary ligand response were derived (Early IRS-1, Late IRS-1, Early IRS-2 and Late IRS-2) and functional pathway analysis examined. IRS isoforms mediated distinct gene expression profiles, functional pathways, and breast cancer subtype association. For example, IRS-1/2-induced TGFb2 expression and blockade of TGFb2 abrogated IGF-induced cell migration. In addition, the prognostic value of IRS proteins was significant in the luminal B breast tumor subtype. Univariate and multivariate analyses confirmed that IRS adaptor signatures correlated with poor outcome as measured by recurrence-free and overall survival. Thus, IRS adaptor protein expression is required for IGF ligand responses in breast cancer cells. IRS-specific gene signatures represent accurate surrogates of IGF activity and could predict response to anti-IGF therapy in breast cancer. PMID:26991655

  9. The G Protein-coupled Receptor P2Y14 Influences Insulin Release and Smooth Muscle Function in Mice*

    PubMed Central

    Meister, Jaroslawna; Le Duc, Diana; Ricken, Albert; Burkhardt, Ralph; Thiery, Joachim; Pfannkuche, Helga; Polte, Tobias; Grosse, Johannes; Schöneberg, Torsten; Schulz, Angela

    2014-01-01

    UDP sugars were identified as extracellular signaling molecules, assigning a new function to these compounds in addition to their well defined role in intracellular substrate metabolism and storage. Previously regarded as an orphan receptor, the G protein-coupled receptor P2Y14 (GPR105) was found to bind extracellular UDP and UDP sugars. Little is known about the physiological functions of this G protein-coupled receptor. To study its physiological role, we used a gene-deficient mouse strain expressing the bacterial LacZ reporter gene to monitor the physiological expression pattern of P2Y14. We found that P2Y14 is mainly expressed in pancreas and salivary glands and in subpopulations of smooth muscle cells of the gastrointestinal tract, blood vessels, lung, and uterus. Among other phenotypical differences, knock-out mice showed a significantly impaired glucose tolerance following oral and intraperitoneal glucose application. An unchanged insulin tolerance suggested altered pancreatic islet function. Transcriptome analysis of pancreatic islets showed that P2Y14 deficiency significantly changed expression of components involved in insulin secretion. Insulin secretion tests revealed a reduced insulin release from P2Y14-deficient islets, highlighting P2Y14 as a new modulator of proper insulin secretion. PMID:24993824

  10. Intranasal insulin protects against substantia nigra dopaminergic neuronal loss and alleviates motor deficits induced by 6-OHDA in rats.

    PubMed

    Pang, Y; Lin, S; Wright, C; Shen, J; Carter, K; Bhatt, A; Fan, L-W

    2016-03-24

    Protection of substantia nigra (SN) dopaminergic (DA) neurons by neurotrophic factors (NTFs) is one of the promising strategies in Parkinson's disease (PD) therapy. A major clinical challenge for NTF-based therapy is that NTFs need to be delivered into the brain via invasive means, which often shows limited delivery efficiency. The nose to brain pathway is a non-invasive brain drug delivery approach developed in recent years. Of particular interest is the finding that intranasal insulin improves cognitive functions in Alzheimer's patients. In vitro, insulin has been shown to protect neurons against various insults. Therefore, the current study was designed to test whether intranasal insulin could afford neuroprotection in the 6-hydroxydopamine (6-OHDA)-based rat PD model. 6-OHDA was injected into the right side of striatum to induce a progressive DA neuronal lesion in the ipsilateral SN pars compact (SNc). Recombinant human insulin was applied intranasally to rats starting from 24h post lesion, once per day, for 2 weeks. A battery of motor behavioral tests was conducted on day 8 and 15. The number of DA neurons in the SNc was estimated by stereological counting. Our results showed that 6-OHDA injection led to significant motor deficits and 53% of DA neuron loss in the ipsilateral side of injection. Treatment with insulin significantly ameliorated 6-OHDA-induced motor impairments, as shown by improved locomotor activity, tapered/ledged beam-walking performance, vibrissa-elicited forelimb-placing, initial steps, as well as methamphetamine-induced rotational behavior. Consistent with behavioral improvements, insulin treatment provided a potent protection of DA neurons in the SNc against 6-OHDA neurotoxicity, as shown by a 74.8% increase in tyrosine hydroxylase (TH)-positive neurons compared to the vehicle group. Intranasal insulin treatment did not affect body weight and blood glucose levels. In conclusion, our study showed that intranasal insulin provided strong

  11. Intranasal insulin protects against substantia nigra dopaminergic neuronal loss and alleviates motor deficits induced by 6-OHDA in rats.

    PubMed

    Pang, Y; Lin, S; Wright, C; Shen, J; Carter, K; Bhatt, A; Fan, L-W

    2016-03-24

    Protection of substantia nigra (SN) dopaminergic (DA) neurons by neurotrophic factors (NTFs) is one of the promising strategies in Parkinson's disease (PD) therapy. A major clinical challenge for NTF-based therapy is that NTFs need to be delivered into the brain via invasive means, which often shows limited delivery efficiency. The nose to brain pathway is a non-invasive brain drug delivery approach developed in recent years. Of particular interest is the finding that intranasal insulin improves cognitive functions in Alzheimer's patients. In vitro, insulin has been shown to protect neurons against various insults. Therefore, the current study was designed to test whether intranasal insulin could afford neuroprotection in the 6-hydroxydopamine (6-OHDA)-based rat PD model. 6-OHDA was injected into the right side of striatum to induce a progressive DA neuronal lesion in the ipsilateral SN pars compact (SNc). Recombinant human insulin was applied intranasally to rats starting from 24h post lesion, once per day, for 2 weeks. A battery of motor behavioral tests was conducted on day 8 and 15. The number of DA neurons in the SNc was estimated by stereological counting. Our results showed that 6-OHDA injection led to significant motor deficits and 53% of DA neuron loss in the ipsilateral side of injection. Treatment with insulin significantly ameliorated 6-OHDA-induced motor impairments, as shown by improved locomotor activity, tapered/ledged beam-walking performance, vibrissa-elicited forelimb-placing, initial steps, as well as methamphetamine-induced rotational behavior. Consistent with behavioral improvements, insulin treatment provided a potent protection of DA neurons in the SNc against 6-OHDA neurotoxicity, as shown by a 74.8% increase in tyrosine hydroxylase (TH)-positive neurons compared to the vehicle group. Intranasal insulin treatment did not affect body weight and blood glucose levels. In conclusion, our study showed that intranasal insulin provided strong

  12. Effects of meal composition on postprandial incretin, glucose and insulin responses after surgical and medical weight loss

    PubMed Central

    Brown, T. T.; Cheskin, L. J.; Choi, P.; Moran, T. H.; Peterson, L.; Matuk, R.; Steele, K. E.

    2015-01-01

    Summary Background Meal tolerance tests are frequently used to study dynamic incretin and insulin responses in the postprandial state; however, the optimal meal that is best tolerated and suited for hormonal response following surgical and medical weight loss has yet to be determined. Objective To evaluate the tolerability and effectiveness of different test meals in inducing detectable changes in markers of glucose metabolism in individuals who have undergone a weight loss intervention. Methods Six individuals who underwent surgical or medical weight loss (two Roux‐en‐Y gastric bypass, two sleeve gastrectomy and two medical weight loss) each completed three meal tolerance tests using liquid‐mixed, solid‐mixed and high‐fat test meals. The tolerability of each test meal, as determined by the total amount consumed and palatability, as well as fasting and meal‐stimulated glucagon‐like peptide, glucose‐dependent insulinotropic polypeptide, insulin and glucose were measured. Results Among the six individuals, the liquid‐mixed meal was better and more uniformly tolerated with a median meal completion rate of 99%. Among the four bariatric surgical patients, liquid‐mixed meal stimulated on average a higher glucagon‐like peptide (percent difference: 83.7, 89), insulin secretion (percent difference: 155.1, 158.7) and glucose‐dependent insulinotropic polypeptide (percent difference: 113.5, 34.3) compared with solid‐mixed and high‐fat meals. Conclusions The liquid‐mixed meal was better tolerated with higher incretin and insulin response compared with the high‐fat and solid‐mixed meals and is best suited for the evaluation of stimulated glucose homeostasis. PMID:27774253

  13. Activation of transmembrane bile acid receptor TGR5 stimulates insulin secretion in pancreatic {beta} cells

    SciTech Connect

    Kumar, Divya P.; Rajagopal, Senthilkumar; Mahavadi, Sunila; Mirshahi, Faridoddin; Grider, John R.; Murthy, Karnam S.; Sanyal, Arun J.

    2012-10-26

    Highlights: Black-Right-Pointing-Pointer G protein coupled receptor TGR5 is expressed in mouse and human islets. Black-Right-Pointing-Pointer TGR5 is coupled to activation of Gs and Ca{sup 2+} release via cAMP/Epac/PLC-{epsilon} pathway. Black-Right-Pointing-Pointer Activation of TGR5 by bile salts and selective ligands causes insulin secretion. Black-Right-Pointing-Pointer TGR5 could be a potential therapeutic target to treat diabetes. -- Abstract: Bile acids act as signaling molecules and stimulate the G protein coupled receptor, TGR5, in addition to nuclear farnesoid X receptor to regulate lipid, glucose and energy metabolism. Bile acid induced activation of TGR5 in the enteroendocrine cells promotes glucagon like peptide-1 (GLP-1) release, which has insulinotropic effect in the pancreatic {beta} cells. In the present study, we have identified the expression of TGR5 in pancreatic {beta} cell line MIN6 and also in mouse and human pancreatic islets. TGR5 selective ligands, oleanolic acid (OA) and INT-777 selectively activated G{alpha}{sub s} and caused an increase in intracellular cAMP and Ca{sup 2+}. OA and INT-777 also increased phosphoinositide (PI) hydrolysis and the increase was blocked by NF449 (a selective G{alpha}{sub s} inhibitor) or (U73122) (PI hydrolysis inhibitor). OA, INT-777 and lithocholic acid increased insulin release in MIN6 and human islets and the increase was inhibited by treatment with NF449, (U73122) or BAPTA-AM (chelator of calcium), but not with myristoylated PKI (PKA inhibitor), suggesting that the release is dependent on G{sub s}/cAMP/Ca{sup 2+} pathway. 8-pCPT-2 Prime -O-Me-cAMP, a cAMP analog, which activates Epac, but not PKA also stimulated PI hydrolysis. In conclusion, our study demonstrates that the TGR5 expressed in the pancreatic {beta} cells regulates insulin secretion and highlights the importance of ongoing therapeutic strategies targeting TGR5 in the control of glucose homeostasis.

  14. Interaction of growth hormone receptor/binding protein gene disruption and caloric restriction for insulin sensitivity and attenuated aging.

    PubMed

    Arum, Oge; Saleh, Jamal; Boparai, Ravneet; Turner, Jeremy; Kopchick, John; Khardori, Romesh; Bartke, Andrzej

    2014-01-01

    The correlation of physiological sensitivity to insulin ( vis-à-vis glycemic regulation) and longevity is extensively established, creating a justifiable gerontological interest on whether insulin sensitivity is causative, or even predictive, of some or all phenotypes of slowed senescence (including longevity). The growth hormone receptor/ binding protein gene-disrupted (GHR-KO) mouse is the most extensively investigated insulin-sensitive, attenuated aging model. It was reported that, in a manner divergent from similar mutants, GHR-KO mice fail to respond to caloric restriction (CR) by altering their insulin sensitivity. We hypothesized that maximized insulin responsiveness is what causes GHR-KO mice to exhibit a suppressed survivorship response to dietary (including caloric) restriction; and attempted to refute this hypothesis by assessing the effects of CR on GHR-KO mice for varied slow-aging-associated phenotypes. In contrast to previous reports, we found GHR-KO mice on CR to be less responsive than their ad libitum (A.L.) counterparts to the hypoglycemia-inducing effects of insulin. Further, CR had negligible effects on the metabolism or cognition of GHR-KO mice. Therefore, our data suggest that the effects of CR on the insulin sensitivity of GHR-KO mice do not concur with the effects of CR on the aging of GHR-KO mice. PMID:25789159

  15. Glucagon receptor antibody completely suppresses type 1 diabetes phenotype without insulin by disrupting a novel diabetogenic pathway

    PubMed Central

    Wang, May-Yun; Yan, Hai; Shi, Zhiqing; Evans, Matthew R.; Yu, Xinxin; Lee, Young; Chen, Shiuhwei; Williams, Annie; Philippe, Jacques; Roth, Michael G.; Unger, Roger H.

    2015-01-01

    Insulin monotherapy can neither maintain normoglycemia in type 1 diabetes (T1D) nor prevent the long-term damage indicated by elevated glycation products in blood, such as glycated hemoglobin (HbA1c). Here we find that hyperglycemia, when unaccompanied by an acute increase in insulin, enhances itself by paradoxically stimulating hyperglucagonemia. Raising glucose from 5 to 25 mM without insulin enhanced glucagon secretion ∼two- to fivefold in InR1-G9 α cells and ∼18-fold in perfused pancreata from insulin-deficient rats with T1D. Mice with T1D receiving insulin treatment paradoxically exhibited threefold higher plasma glucagon during hyperglycemic surges than during normoglycemic intervals. Blockade of glucagon action with mAb Ac, a glucagon receptor (GCGR) antagonizing antibody, maintained glucose below 100 mg/dL and HbA1c levels below 4% in insulin-deficient mice with T1D. In rodents with T1D, hyperglycemia stimulates glucagon secretion, up-regulating phosphoenolpyruvate carboxykinase and enhancing hyperglycemia. GCGR antagonism in mice with T1D normalizes glucose and HbA1c, even without insulin. PMID:25675519

  16. Loss of regular oscillatory insulin secretion in islet cell antibody positive non-diabetic subjects.

    PubMed

    Bingley, P J; Matthews, D R; Williams, A J; Bottazzo, G F; Gale, E A

    1992-01-01

    Basal insulin secretion was compared in nine islet-cell antibody positive, non-diabetic first-degree relatives of children with Type 1 (insulin-dependent) diabetes mellitus and nine normal control subjects matched for age, sex and weight. Acute insulin responses to a 25 g intravenous glucose tolerance test were similar in the two groups (243 (198-229) vs 329 (285-380) mU.l-1 x 10 min-1, mean (+/- SE), p = 0.25). Fasting plasma insulin was assayed in venous samples taken at one min intervals for 2 h. Time series analysis was used to demonstrate oscillatory patterns in plasma insulin. Autocorrelation showed that regular oscillatory activity was generally absent in the islet-cell antibody-positive group, whereas a regular 13 min cycle was shown in control subjects (p less than 0.0001). Fourier transformation did, however, show a 13 min spectral peak in the islet-cell antibody positive group, consistent with intermittent pulsatility. We conclude that overall oscillatory patterns of basal insulin secretion are altered in islet-cell antibody positive subjects even when the acute insulin response is within the normal range. PMID:1541379

  17. Identification and transcriptional modulation of the largemouth bass, Micropterus salmoides, vitellogenin receptor during oocyte development by insulin and sex steroids.

    PubMed

    Dominguez, Gustavo A; Quattro, Joseph M; Denslow, Nancy D; Kroll, Kevin J; Prucha, Melinda S; Porak, Wesley F; Grier, Harry J; Sabo-Attwood, Tara L

    2012-09-01

    Fish vitellogenin synthesized and released from the liver of oviparous animals is taken up into oocytes by the vitellogenin receptor. This is an essential process in providing nutrient yolk to developing embryos to ensure successful reproduction. Here we disclose the full length vtgr cDNA sequence for largemouth bass (LMB) that reveals greater than 90% sequence homology with other fish vtgr sequences. We classify LMB Vtgr as a member of the low density lipoprotein receptor superfamily based on conserved domains and categorize as the short variant that is devoid of the O-glycan segment. Phylogenetic analysis places LMB Vtgr sequence into a well-supported monophyletic group of fish Vtgr. Real-time PCR showed that the greatest levels of LMB vtgr mRNA expression occurred in previtellogenic ovarian tissues. In addition, we reveal the effects of insulin, 17beta-estradiol (E(2)), and 11-ketotestosterone (11-KT) in modulation of vtgr, esr, and ar mRNAs in previtellogenic oocytes. Insulin increased vtgr expression levels in follicles ex vivo while exposure to E(2) or 11-KT did not result in modulation of expression. However, both steroids were able to repress insulin-induced vtgr transcript levels. Coexposure with insulin and E(2) or of insulin and 11-KT increased ovarian esr2b and ar mRNA levels, respectively, which suggest a role for these nuclear receptors in insulin-mediated signaling pathways. These data provide the first evidence for the ordered stage-specific expression of LMB vtgr during the normal reproductive process and the hormonal influence of insulin and sex steroids on controlling vtgr transcript levels in ovarian tissues. PMID:22786822

  18. Identification and transcriptional modulation of the largemouth bass, Micropterus salmoides, vitellogenin receptor during oocyte development by insulin and sex steroids.

    PubMed

    Dominguez, Gustavo A; Quattro, Joseph M; Denslow, Nancy D; Kroll, Kevin J; Prucha, Melinda S; Porak, Wesley F; Grier, Harry J; Sabo-Attwood, Tara L

    2012-09-01

    Fish vitellogenin synthesized and released from the liver of oviparous animals is taken up into oocytes by the vitellogenin receptor. This is an essential process in providing nutrient yolk to developing embryos to ensure successful reproduction. Here we disclose the full length vtgr cDNA sequence for largemouth bass (LMB) that reveals greater than 90% sequence homology with other fish vtgr sequences. We classify LMB Vtgr as a member of the low density lipoprotein receptor superfamily based on conserved domains and categorize as the short variant that is devoid of the O-glycan segment. Phylogenetic analysis places LMB Vtgr sequence into a well-supported monophyletic group of fish Vtgr. Real-time PCR showed that the greatest levels of LMB vtgr mRNA expression occurred in previtellogenic ovarian tissues. In addition, we reveal the effects of insulin, 17beta-estradiol (E(2)), and 11-ketotestosterone (11-KT) in modulation of vtgr, esr, and ar mRNAs in previtellogenic oocytes. Insulin increased vtgr expression levels in follicles ex vivo while exposure to E(2) or 11-KT did not result in modulation of expression. However, both steroids were able to repress insulin-induced vtgr transcript levels. Coexposure with insulin and E(2) or of insulin and 11-KT increased ovarian esr2b and ar mRNA levels, respectively, which suggest a role for these nuclear receptors in insulin-mediated signaling pathways. These data provide the first evidence for the ordered stage-specific expression of LMB vtgr during the normal reproductive process and the hormonal influence of insulin and sex steroids on controlling vtgr transcript levels in ovarian tissues.

  19. Differential pathway coupling efficiency of the activated insulin receptor drives signaling selectivity by xmeta, an allosteric partial agonist antibody

    Technology Transfer Automated Retrieval System (TEKTRAN)

    XMetA, an anti-insulin receptor (IR) monoclonal antibody, is an allosteric partial agonist of the IR. We have previously reported that XMetA activates the “metabolic-biased” Akt kinase signaling pathway while having little or no effect on the “mitogenic” MAPK signaling pathwayof ERK 1/2. To inves...

  20. Acute treatment with XMetA activates hepatic insulin receptors and lowers blood glucose in normal mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It has been proposed that monoclonal antibodies may become therapeutics for metabolic diseases such as diabetes mellitus. We have previously characterized an allosteric monoclonal antibody to the human insulin receptor (IR), XMetA, that activated metabolic signaling leading to enhanced glucose tran...

  1. The role of insulin receptor substrate 2 in hypothalamic and β cell function

    PubMed Central

    Choudhury, Agharul I.; Heffron, Helen; Smith, Mark A.; Al-Qassab, Hind; Xu, Allison W.; Selman, Colin; Simmgen, Marcus; Clements, Melanie; Claret, Marc; MacColl, Gavin; Bedford, David C.; Hisadome, Kazunari; Diakonov, Ivan; Moosajee, Vazira; Bell, Jimmy D.; Speakman, John R.; Batterham, Rachel L.; Barsh, Gregory S.; Ashford, Michael L.J.; Withers, Dominic J.

    2005-01-01

    Insulin receptor substrate 2 (Irs2) plays complex roles in energy homeostasis. We generated mice lacking Irs2 in β cells and a population of hypothalamic neurons (RIPCreIrs2KO), in all neurons (NesCreIrs2KO), and in proopiomelanocortin neurons (POMCCreIrs2KO) to determine the role of Irs2 in the CNS and β cell. RIPCreIrs2KO mice displayed impaired glucose tolerance and reduced β cell mass. Overt diabetes did not ensue, because β cells escaping Cre-mediated recombination progressively populated islets. RIPCreIrs2KO and NesCreIrs2KO mice displayed hyperphagia, obesity, and increased body length, which suggests altered melanocortin action. POMCCreIrs2KO mice did not display this phenotype. RIPCreIrs2KO and NesCreIrs2KO mice retained leptin sensitivity, which suggests that CNS Irs2 pathways are not required for leptin action. NesCreIrs2KO and POMCCreIrs2KO mice did not display reduced β cell mass, but NesCreIrs2KO mice displayed mild abnormalities of glucose homeostasis. RIPCre neurons did not express POMC or neuropeptide Y. Insulin and a melanocortin agonist depolarized RIPCre neurons, whereas leptin was ineffective. Insulin hyperpolarized and leptin depolarized POMC neurons. Our findings demonstrate a critical role for IRS2 in β cell and hypothalamic function and provide insights into the role of RIPCre neurons, a distinct hypothalamic neuronal population, in growth and energy homeostasis. PMID:15841180

  2. Oleanolic acid supplement attenuates liquid fructose-induced adipose tissue insulin resistance through the insulin receptor substrate-1/phosphatidylinositol 3-kinase/Akt signaling pathway in rats

    SciTech Connect

    Li, Ying; Wang, Jianwei; Gu, Tieguang; Yamahara, Johji; Li, Yuhao

    2014-06-01

    Oleanolic acid, a triterpenoid contained in more than 1620 plants including various fruits and foodstuffs, has numerous metabolic effects, such as hepatoprotection. However, its underlying mechanisms remain poorly understood. Adipose tissue insulin resistance (Adipo-IR) may contribute to the development and progress of metabolic abnormalities through release of excessive free fatty acids from adipose tissue. This study investigated the effect of oleanolic acid on Adipo-IR. The results showed that supplement with oleanolic acid (25 mg/kg, once daily, by oral gavage) over 10 weeks attenuated liquid fructose-induced increase in plasma insulin concentration and the homeostasis model assessment of insulin resistance (HOMA-IR) index in rats. Simultaneously, oleanolic acid reversed the increase in the Adipo-IR index and plasma non-esterified fatty acid concentrations during the oral glucose tolerance test assessment. In white adipose tissue, oleanolic acid enhanced mRNA expression of the genes encoding insulin receptor, insulin receptor substrate (IRS)-1 and phosphatidylinositol 3-kinase. At the protein level, oleanolic acid upregulated total IRS-1 expression, suppressed the increased phosphorylated IRS-1 at serine-307, and restored the increased phosphorylated IRS-1 to total IRS-1 ratio. In contrast, phosphorylated Akt to total Akt ratio was increased. Furthermore, oleanolic acid reversed fructose-induced decrease in phosphorylated-Akt/Akt protein to plasma insulin concentration ratio. However, oleanolic acid did not affect IRS-2 mRNA expression. Therefore, these results suggest that oleanolic acid supplement ameliorates fructose-induced Adipo-IR in rats via the IRS-1/phosphatidylinositol 3-kinase/Akt pathway. Our findings may provide new insights into the mechanisms of metabolic actions of oleanolic acid. - Highlights: • Adipose insulin resistance (Adipo-IR) contributes to metabolic abnormalities. • We investigated the effect of oleanolic acid (OA) on adipo-IR in

  3. Insulin Receptor Expression and Activity in the Brains of Nondiabetic Sporadic Alzheimer's Disease Cases

    PubMed Central

    Ho, Lap; Yemul, Shrishailam; Knable, Lindsay; Katsel, Pavel; Zhao, Rudy; Haroutunian, Vahram; Pasinetti, Giulio Maria

    2012-01-01

    We investigated the contents of the insulin receptor-beta subunit (IRβ) and [Tyr1162/1163]-phosphorylated IRβ as surrogate indices of total IR content and IR activation in postmortem hippocampal formation brain specimens from nondiabetic sporadic Alzheimer's disease (AD) cases. We found no significant changes in the brain contents of total IRβ or [Tyr1162/1163]-phosphorylated IRβ, suggesting normal IR content and activation in the brains of nondiabetic sporadic AD cases. Moreover, total IRβ and [Tyr1162/1163]-phosphorylated IRβ levels in the hippocampal formation are not correlated with the severity of amyloid or tau-neuropathology. Exploring the regulation of glycogen synthase kinase 3 (GSK3) α/β, key IR-signaling components, we observed significantly lower levels of total GSK3 α/β in brain specimens from nondiabetic AD cases, suggesting that impaired IR signaling mechanisms might contribute to the onset and/or progression of AD dementia. Outcomes from our study support the development of insulin-sensitizing therapeutic strategies to stimulate downstream IR signaling in nondiabetic AD cases. PMID:22666619

  4. The human insulin receptor mRNA contains a functional internal ribosome entry segment

    PubMed Central

    Spriggs, Keith A.; Cobbold, Laura C.; Ridley, Simon H.; Coldwell, Mark; Bottley, Andrew; Bushell, Martin; Willis, Anne E.; Siddle, Kenneth

    2009-01-01

    Regulation of mRNA translation is an important mechanism determining the level of expression of proteins in eukaryotic cells. Translation is most commonly initiated by cap-dependent scanning, but many eukaryotic mRNAs contain internal ribosome entry segments (IRESs), providing an alternative means of initiation capable of independent regulation. Here, we show by using dicistronic luciferase reporter vectors that the 5′-UTR of the mRNA encoding human insulin receptor (hIR) contains a functional IRES. RNAi-mediated knockdown showed that the protein PTB was required for maximum IRES activity. Electrophoretic mobility shift assays confirmed that PTB1, PTB2 and nPTB, but not unr or PTB4, bound to hIR mRNA, and deletion mapping implicated a CCU motif 448 nt upstream of the initiator AUG in PTB binding. The IR-IRES was functional in a number of cell lines, and most active in cells of neuronal origin, as assessed by luciferase reporter assays. The IRES was more active in confluent than sub-confluent cells, but activity did not change during differentiation of 3T3-L1 fibroblasts to adipocytes. IRES activity was stimulated by insulin in sub-confluent cells. The IRES may function to maintain expression of IR protein in tissues such as the brain where mRNA translation by cap-dependent scanning is less effective. PMID:19654240

  5. Implications of Insulin-like Growth Factor 1 Receptor Activation in Lung Cancer

    PubMed Central

    Nurwidya, Fariz; Andarini, Sita; Takahashi, Fumiyuki; Syahruddin, Elisna; Takahashi, Kazuhisa

    2016-01-01

    Insulin-like growth factor 1 receptor (IGF1R) has been intensively investigated in many preclinical studies using cell lines and animal models, and the results have provided important knowledge to help improve the understanding of cancer biology. IGF1R is highly expressed in patients with lung cancer, and high levels of circulating insulin-like growth factor 1 (IGF1), the main ligand for IGF1R, increases the risk of developing lung malignancy in the future. Several phase I clinical trials have supported the potential use of an IGF1R-targeted strategy for cancer, including lung cancer. However, the negative results from phase III studies need further attention, especially in selecting patients with specific molecular signatures, who will gain benefits from IGF1R inhibitors with minimal side effects. This review will discuss the basic concept of IGF1R in lung cancer biology, such as epithelial-mesenchymal transition (EMT) induction and cancer stem cell (CSC) maintenance, and also the clinical implications of IGF1R for lung cancer patients, such as prognostic value and cancer therapy resistance. PMID:27418865

  6. Monomeric ß-amyloid interacts with type-1 insulin-like growth factor receptors to provide energy supply to neurons

    PubMed Central

    Giuffrida, Maria L.; Tomasello, Marianna F.; Pandini, Giuseppe; Caraci, Filippo; Battaglia, Giuseppe; Busceti, Carla; Di Pietro, Paola; Pappalardo, Giuseppe; Attanasio, Francesco; Chiechio, Santina; Bagnoli, Silvia; Nacmias, Benedetta; Sorbi, Sandro; Vigneri, Riccardo; Rizzarelli, Enrico; Nicoletti, Ferdinando; Copani, Agata

    2015-01-01

    ß-amyloid (Aß1−42) is produced by proteolytic cleavage of the transmembrane type-1 protein, amyloid precursor protein. Under pathological conditions, Aß1−42self-aggregates into oligomers, which cause synaptic dysfunction and neuronal loss, and are considered the culprit of Alzheimer's disease (AD). However, Aß1−42 is mainly monomeric at physiological concentrations, and the precise role of monomeric Aß1−42 in neuronal function is largely unknown. We report that the monomer of Aß1−42 activates type-1 insulin-like growth factor receptors and enhances glucose uptake in neurons and peripheral cells by promoting the translocation of the Glut3 glucose transporter from the cytosol to the plasma membrane. In neurons, activity-dependent glucose uptake was blunted after blocking endogenous Aß production, and re-established in the presence of cerebrospinal fluid Aß. APP-null neurons failed to enhance depolarization-stimulated glucose uptake unless exogenous monomeric Aß1−42 was added. These data suggest that Aß1−42 monomers were critical for maintaining neuronal glucose homeostasis. Accordingly, exogenous Aß1−42 monomers were able to rescue the low levels of glucose consumption observed in brain slices from AD mutant mice. PMID:26300732

  7. Loss of Pdk1-Foxo1 Signaling in Myeloid Cells Predisposes to Adipose Tissue Inflammation and Insulin Resistance

    PubMed Central

    Kawano, Yoshinaga; Nakae, Jun; Watanabe, Nobuyuki; Fujisaka, Shiho; Iskandar, Kristy; Sekioka, Risa; Hayashi, Yoshitake; Tobe, Kazuyuki; Kasuga, Masato; Noda, Tetsuo; Yoshimura, Akihiko; Onodera, Masafumi; Itoh, Hiroshi

    2012-01-01

    Chronic inflammation in adipose tissue contributes to obesity-related insulin resistance. The 3-phosphoinositide-dependent protein kinase 1 (Pdk1)/forkhead transcription factor (Foxo1) pathway is important in regulating glucose and energy homeostasis, but little is known about this pathway in adipose tissue macrophages (ATMs). To investigate this, we generated transgenic mice that carried macrophage/granulocyte-specific mutations, including a Pdk1 knockout (LysMPdk1−/−), a Pdk1 knockout with transactivation-defective Foxo1 (Δ256LysMPdk1−/−), a constitutively active nuclear (CN) Foxo1 (CNFoxo1LysM), or a transactivation-defective Foxo1 (Δ256Foxo1LysM). We analyzed glucose metabolism and gene expression in ATM populations isolated with fluorescence-activated cell sorting. The LysMPdk1−/− mice exhibited elevated M1 macrophages in adipose tissue and insulin resistance. Overexpression of transactivation-defective Foxo1 rescued these phenotypes. CNFoxo1LysM promoted transcription of the C-C motif chemokine receptor 2 (Ccr2) in ATMs and increased M1 macrophages in adipose tissue. On a high-fat diet, CNFoxo1LysM mice exhibited insulin resistance. Pdk1 deletion or Foxo1 activation in bone marrow–derived macrophages abolished insulin and interleukin-4 induction of genes involved in alternative macrophage activation. Thus, Pdk1 regulated macrophage infiltration by inhibiting Foxo1-induced Ccr2 expression. This shows that the macrophage Pdk1/Foxo1 pathway is important in regulating insulin sensitivity in vivo. PMID:22586579

  8. DOWNREGULATION OF HYPOTHALAMIC INSULIN RECEPTOR EXPRESSION ELICITS DEPRESSIVE-LIKE BEHAVIORS IN RATS

    PubMed Central

    Grillo, Claudia A.; Piroli, Gerardo G.; Kaigler, Kris F.; Wilson, Steven P.; Wilson, Marlene A.; Reagan, Lawrence P.

    2011-01-01

    Ongoing epidemiological studies estimate that greater than 60% of the adult US population may be categorized as either overweight or obese. There is a growing appreciation that the complications of obesity extend to the central nervous system (CNS) and may result in increased risk for neurological co-morbidities like depressive illness. One potential mechanistic mediator linking obesity and depressive illness is the adipocyte derived hormone leptin. We previously demonstrated that lentivirus-mediated downregulation of hypothalamic insulin receptors increases body weight, adiposity and plasma leptin levels, which is consistent with features of the metabolic syndrome. Using this novel model of obesity, we examined performance in the forced swim test (FST), the sucrose preference test and the elevated plus maze (EPM), approaches that are often used as measures of depressive-like and anxiety-like behaviors, in rats that received third ventricular injections of either an insulin receptor antisense lentivirus (hypo-IRAS) or a control lentivirus (hypo-Con). Hypo-IRAS rats exhibited significant increases in immobility time and corresponding decreases in active behaviors in the FST and exhibited anhedonia as measured by decreased sucrose intake compared to hypo-Con rats. Hypo-IRAS rats also exhibited increases in anxiety-like behaviors in the EPM. Plasma, hippocampal and amygdalar brain-derived neurotrophic factor (BDNF) levels were reduced in hypo-IRAS rats, suggesting that the obesity/hyperleptinemic phenotype may elicit this behavioral phenotype through modulation of neurotrophic factor expression. Collectively, these data support the hypothesis for an increased risk for mood disorders in obesity, which may be related to decreased expression of hippocampal and amygdalar BDNF. PMID:21458499

  9. Insulin binding properties of normal and transformed human epidermal cultured keratinocytes

    SciTech Connect

    Verrando, P.; Ortonne, J.P.

    1985-10-01

    Insulin binding to its receptors was studied in cultured normal and transformed (A431 line) human epidermal keratinocytes. The specific binding was a temperature-dependent, saturable process. Normal keratinocytes possess a mean value of about 80,000 receptors per cell. Fifteen hours exposure of the cells to insulin lowered their receptor number (about 65% loss in available sites); these reappeared when the hormone was removed from the culture medium. In the A431 epidermoid carcinoma cell line, there is a net decrease in insulin binding (84% of the initial bound/free hormone ratio in comparison with normal cells) essentially related to a loss in receptor affinity for insulin. Thus, cultured human keratinocytes which express insulin receptors may be a useful tool in understanding skin pathology related to insulin disorders.

  10. GLP-1 receptor agonism ameliorates hepatic VLDL overproduction and de novo lipogenesis in insulin resistance

    PubMed Central

    Taher, Jennifer; Baker, Christopher L.; Cuizon, Carmelle; Masoudpour, Hassan; Zhang, Rianna; Farr, Sarah; Naples, Mark; Bourdon, Celine; Pausova, Zdenka; Adeli, Khosrow

    2014-01-01

    Background/objectives Fasting dyslipidemia is commonly observed in insulin resistant states and mechanistically linked to hepatic overproduction of very low density lipoprotein (VLDL). Recently, the incretin hormone glucagon-like peptide-1 (GLP-1) has been implicated in ameliorating dyslipidemia associated with insulin resistance and reducing hepatic lipid stores. Given that hepatic VLDL production is a key determinant of circulating lipid levels, we investigated the role of both peripheral and central GLP-1 receptor (GLP-1R) agonism in regulation of VLDL production. Methods The fructose-fed Syrian golden hamster was employed as a model of diet-induced insulin resistance and VLDL overproduction. Hamsters were treated with the GLP-1R agonist exendin-4 by intraperitoneal (ip) injection for peripheral studies or by intracerebroventricular (ICV) administration into the 3rd ventricle for central studies. Peripheral studies were repeated in vagotomised hamsters. Results Short term (7–10 day) peripheral exendin-4 enhanced satiety and also prevented fructose-induced fasting dyslipidemia and hyperinsulinemia. These changes were accompanied by decreased fasting plasma glucose levels, reduced hepatic lipid content and decreased levels of VLDL-TG and -apoB100 in plasma. The observed changes in fasting dyslipidemia could be partially explained by reduced respiratory exchange ratio (RER) thereby indicating a switch in energy utilization from carbohydrate to lipid. Additionally, exendin-4 reduced mRNA markers associated with hepatic de novo lipogenesis and inflammation. Despite these observations, GLP-1R activity could not be detected in primary hamster hepatocytes, thus leading to the investigation of a potential brain–liver axis functioning to regulate lipid metabolism. Short term (4 day) central administration of exendin-4 decreased body weight and food consumption and further prevented fructose-induced hypertriglyceridemia. Additionally, the peripheral lipid

  11. Receptor for advanced glycation end products regulates adipocyte hypertrophy and insulin sensitivity in mice: involvement of Toll-like receptor 2.

    PubMed

    Monden, Masayo; Koyama, Hidenori; Otsuka, Yoshiko; Morioka, Tomoaki; Mori, Katsuhito; Shoji, Takuhito; Mima, Yohei; Motoyama, Koka; Fukumoto, Shinya; Shioi, Atsushi; Emoto, Masanori; Yamamoto, Yasuhiko; Yamamoto, Hiroshi; Nishizawa, Yoshiki; Kurajoh, Masafumi; Yamamoto, Tetsuya; Inaba, Masaaki

    2013-02-01

    Receptor for advanced glycation end products (RAGE) has been shown to be involved in adiposity as well as atherosclerosis even in nondiabetic conditions. In this study, we examined mechanisms underlying how RAGE regulates adiposity and insulin sensitivity. RAGE overexpression in 3T3-L1 preadipocytes using adenoviral gene transfer accelerated adipocyte hypertrophy, whereas inhibitions of RAGE by small interfering RNA significantly decrease adipocyte hypertrophy. Furthermore, double knockdown of high mobility group box-1 and S100b, both of which are RAGE ligands endogenously expressed in 3T3-L1 cells, also canceled RAGE-medicated adipocyte hypertrophy, implicating a fundamental role of ligands-RAGE ligation. Adipocyte hypertrophy induced by RAGE overexpression is associated with suppression of glucose transporter type 4 and adiponectin mRNA expression, attenuated insulin-stimulated glucose uptake, and insulin-stimulated signaling. Toll-like receptor (Tlr)2 mRNA, but not Tlr4 mRNA, is rapidly upregulated by RAGE overexpression, and inhibition of Tlr2 almost completely abrogates RAGE-mediated adipocyte hypertrophy. Finally, RAGE(-/-) mice exhibited significantly less body weight, epididymal fat weight, epididymal adipocyte size, higher serum adiponectin levels, and higher insulin sensitivity than wild-type mice. RAGE deficiency is associated with early suppression of Tlr2 mRNA expression in adipose tissues. Thus, RAGE appears to be involved in mouse adipocyte hypertrophy and insulin sensitivity, whereas Tlr2 regulation may partly play a role.

  12. Photoreceptor Ablation Initiates the Immediate Loss of Glutamate Receptors in Postsynaptic Bipolar Cells in Retina

    PubMed Central

    2015-01-01

    Structural changes underlying neurodegenerative diseases include dismantling of synapses, degradation of circuitry, and even massive rewiring. Our limited understanding of synapse dismantling stems from the inability to control the timing and extent of cell death. In this study, selective ablation of cone photoreceptors in live mouse retina and tracking of postsynaptic partners at the cone-to-ON cone bipolar cell synapse reveals that early reaction to cone loss involves rapid and local changes in postsynaptic glutamate receptor distribution. Glutamate receptors disappear with a time constant of 2 h. Furthermore, binding of glutamate receptors by agonists and antagonists is insufficient to rescue glutamate receptor loss, suggesting that receptor allocation depends on the physical presence of cones. These findings demonstrate that the initial step in synapse disassembly involves postsynaptic receptor loss rather than dendritic retraction, providing insight into the early stages of neurodegenerative disease. PMID:25673837

  13. Piceatannol, Natural Polyphenolic Stilbene, Inhibits Adipogenesis via Modulation of Mitotic Clonal Expansion and Insulin Receptor-dependent Insulin Signaling in Early Phase of Differentiation*

    PubMed Central

    Kwon, Jung Yeon; Seo, Sang Gwon; Heo, Yong-Seok; Yue, Shuhua; Cheng, Ji-Xin; Lee, Ki Won; Kim, Kee-Hong

    2012-01-01

    Piceatannol, a natural stilbene, is an analog and a metabolite of resveratrol. Despite a well documented health benefit of resveratrol in intervention of the development of obesity, the role of piceatannol in the development of adipose tissue and related diseases is unknown. Here, we sought to determine the function of piceatannol in adipogenesis and elucidate the underlying mechanism. We show that piceatannol inhibits adipogenesis of 3T3-L1 preadipocytes in a dose-dependent manner at noncytotoxic concentrations. This anti-adipogenic property of piceatannol was largely limited to the early event of adipogenesis. In the early phase of adipogenesis, piceatannol-treated preadipocytes displayed a delayed cell cycle entry into G2/M phase at 24 h after initiation of adipogenesis. Furthermore, the piceatannol-suppressed mitotic clonal expansion was accompanied by reduced activation of the insulin-signaling pathway. Piceatannol dose-dependently inhibited differentiation mixture-induced phosphorylation of insulin receptor (IR)/insulin receptor substrate-1 (IRS-1)/Akt pathway in the early phase of adipogenesis. Moreover, we showed that piceatannol is an inhibitor of IR kinase activity and phosphatidylinositol 3-kinase (PI3K). Our kinetics study of IR further identified a Km value for ATP of 57.8 μm and a Ki value for piceatannol of 28.9 μm. We also showed that piceatannol directly binds to IR and inhibits IR kinase activity in a mixed noncompetitive manner to ATP, through which piceatannol appears to inhibit adipogenesis. Taken together, our study reveals an anti-adipogenic function of piceatannol and highlights IR and its downstream insulin signaling as novel targets for piceatannol in the early phase of adipogenesis. PMID:22298784

  14. Proteomic analysis of the palmitate-induced myotube secretome reveals involvement of the annexin A1-formyl peptide receptor 2 (FPR2) pathway in insulin resistance.

    PubMed

    Yoon, Jong Hyuk; Kim, Dayea; Jang, Jin-Hyeok; Ghim, Jaewang; Park, Soyeon; Song, Parkyong; Kwon, Yonghoon; Kim, Jaeyoon; Hwang, Daehee; Bae, Yoe-Sik; Suh, Pann-Ghill; Berggren, Per-Olof; Ryu, Sung Ho

    2015-04-01

    Elevated levels of the free fatty acid palmitate are found in the plasma of obese patients and induce insulin resistance. Skeletal muscle secretes myokines as extracellular signaling mediators in response to pathophysiological conditions. Here, we identified and characterized the skeletal muscle secretome in response to palmitate-induced insulin resistance. Using a quantitative proteomic approach, we identified 36 secretory proteins modulated by palmitate-induced insulin resistance. Bioinformatics analysis revealed that palmitate-induced insulin resistance induced cellular stress and modulated secretory events. We found that the decrease in the level of annexin A1, a secretory protein, depended on palmitate, and that annexin A1 and its receptor, formyl peptide receptor 2 agonist, played a protective role in the palmitate-induced insulin resistance of L6 myotubes through PKC-θ modulation. In mice fed with a high-fat diet, treatment with the formyl peptide receptor 2 agonist improved systemic insulin sensitivity. Thus, we identified myokine candidates modulated by palmitate-induced insulin resistance and found that the annexin A1- formyl peptide receptor 2 pathway mediated the insulin resistance of skeletal muscle, as well as systemic insulin sensitivity. PMID:25616869

  15. A Novel Approach to Identify Two Distinct Receptor Binding Surfaces of Insulin-like Growth Factor II*S⃞

    PubMed Central

    Alvino, Clair L.; McNeil, Kerrie A.; Ong, Shee Chee; Delaine, Carlie; Booker, Grant W.; Wallace, John C.; Whittaker, Jonathan; Forbes, Briony E.

    2009-01-01

    Very little is known about the residues important for the interaction of insulin-like growth factor II (IGF-II) with the type 1 IGF receptor (IGF-1R) and the insulin receptor (IR). Insulin, to which IGF-II is homologous, is proposed to cross-link opposite halves of the IR dimer through two receptor binding surfaces, site 1 and site 2. In the present study we have analyzed the contribution of IGF-II residues equivalent to insulin's two binding surfaces toward the interaction of IGF-II with the IGF-1R and IR. Four “site 1” and six “site 2” analogues were produced and analyzed in terms of IGF-1R and IR binding and activation. The results show that Val43, Phe28, and Val14 (equivalent to site 1) are critical to IGF-1R and IR binding, whereas mutation to alanine of Gln18 affects only IGF-1R and not IR binding. Alanine substitutions at Glu12, Asp15, Phe19, Leu53, and Glu57 analogues resulted in significant (>2-fold) decreases in affinity for both the IGF-1R and IR. Furthermore, taking a novel approach using a monomeric, single-chain minimized IGF-1R we have defined a distinct second binding surface formed by Glu12, Phe19, Leu53, and Glu57 that potentially engages the IGF-1R at one or more of the FnIII domains. PMID:19139090

  16. Fatty acid represses insulin receptor gene expression by impairing HMGA1 through protein kinase C{epsilon}

    SciTech Connect

    Dey, Debleena; Bhattacharya, Anirban; Roy, SibSankar; Bhattacharya, Samir . E-mail: smrbhattacharya@gmail.com

    2007-06-01

    It is known that free fatty acid (FFA) contributes to the development of insulin resistance and type2 diabetes. However, the underlying mechanism in FFA-induced insulin resistance is still unclear. In the present investigation we have demonstrated that palmitate significantly (p < 0.001) inhibited insulin-stimulated phosphorylation of PDK1, the key insulin signaling molecule. Consequently, PDK1 phosphorylation of plasma membrane bound PKC{epsilon} was also inhibited. Surprisingly, phosphorylation of cytosolic PKC{epsilon} was greatly stimulated by palmitate; this was then translocated to the nuclear region and associated with the inhibition of insulin receptor (IR) gene transcription. A PKC{epsilon} translocation inhibitor peptide, {epsilon}V1, suppressed this inhibitory effect of palmitate, suggesting requirement of phospho-PKC{epsilon} migration to implement palmitate effect. Experimental evidences indicate that phospho-PKC{epsilon} adversely affected HMGA1. Since HMGA1 regulates IR promoter activity, expression of IR gene was impaired causing reduction of IR on cell surface and that compromises with insulin sensitivity.

  17. Reduced phosphorylation of brain insulin receptor substrate and Akt proteins in apolipoprotein-E4 targeted replacement mice.

    PubMed

    Ong, Qi-Rui; Chan, Elizabeth S; Lim, Mei-Li; Cole, Gregory M; Wong, Boon-Seng

    2014-01-17

    Human ApoE4 accelerates memory decline in ageing and in Alzheimer's disease. Although intranasal insulin can improve cognition, this has little effect in ApoE4 subjects. To understand this ApoE genotype-dependent effect, we examined brain insulin signaling in huApoE3 and huApoE4 targeted replacement (TR) mice. At 32 weeks, lower insulin receptor substrate 1 (IRS1) at S636/639 and Akt phosphorylation at T308 were detected in fasting huApoE4 TR mice as compared to fasting huApoE3 TR mice. These changes in fasting huApoE4 TR mice were linked to lower brain glucose content and have no effect on plasma glucose level. However, at 72 weeks of age, these early changes were accompanied by reduction in IRS2 expression, IRS1 phosphorylation at Y608, Akt phosphorylation at S473, and MAPK (p38 and p44/42) activation in the fasting huApoE4 TR mice. The lower brain glucose was significantly associated with higher brain insulin in the aged huApoE4 TR mice. These results show that ApoE4 reduces brain insulin signaling and glucose level leading to higher insulin content.

  18. Primary Hyperparathyroidism: The Influence of Bone Marrow Adipose Tissue on Bone Loss and of Osteocalcin on Insulin Resistance

    PubMed Central

    Mendonça, Maira L.; Batista, Sérgio L.; Nogueira-Barbosa, Marcello H.; Salmon, Carlos E.G.; de Paula, Francisco J.A.

    2016-01-01

    OBJECTIVES: Bone marrow adipose tissue has been associated with low bone mineral density. However, no data exist regarding marrow adipose tissue in primary hyperparathyroidism, a disorder associated with bone loss in conditions of high bone turnover. The objective of the present study was to investigate the relationship between marrow adipose tissue, bone mass and parathyroid hormone. The influence of osteocalcin on the homeostasis model assessment of insulin resistance was also evaluated. METHODS: This was a cross-sectional study conducted at a university hospital, involving 18 patients with primary hyperparathyroidism (PHPT) and 21 controls (CG). Bone mass was assessed by dual-energy x-ray absorptiometry and marrow adipose tissue was assessed by 1H magnetic resonance spectroscopy. The biochemical evaluation included the determination of parathyroid hormone, osteocalcin, glucose and insulin levels. RESULTS: A negative association was found between the bone mass at the 1/3 radius and parathyroid hormone levels (r = -0.69; p<0.01). Marrow adipose tissue was not significantly increased in patients (CG = 32.8±11.2% vs PHPT = 38.6±12%). The serum levels of osteocalcin were higher in patients (CG = 8.6±3.6 ng/mL vs PHPT = 36.5±38.4 ng/mL; p<0.005), but no associations were observed between osteocalcin and insulin or between insulin and both marrow adipose tissue and bone mass. CONCLUSION: These results suggest that the increment of adipogenesis in the bone marrow microenvironment under conditions of high bone turnover due to primary hyperparathyroidism is limited. Despite the increased serum levels of osteocalcin due to primary hyperparathyroidism, these patients tend to have impaired insulin sensitivity.

  19. Primary Hyperparathyroidism: The Influence of Bone Marrow Adipose Tissue on Bone Loss and of Osteocalcin on Insulin Resistance

    PubMed Central

    Mendonça, Maira L.; Batista, Sérgio L.; Nogueira-Barbosa, Marcello H.; Salmon, Carlos E.G.; de Paula, Francisco J.A.

    2016-01-01

    OBJECTIVES: Bone marrow adipose tissue has been associated with low bone mineral density. However, no data exist regarding marrow adipose tissue in primary hyperparathyroidism, a disorder associated with bone loss in conditions of high bone turnover. The objective of the present study was to investigate the relationship between marrow adipose tissue, bone mass and parathyroid hormone. The influence of osteocalcin on the homeostasis model assessment of insulin resistance was also evaluated. METHODS: This was a cross-sectional study conducted at a university hospital, involving 18 patients with primary hyperparathyroidism (PHPT) and 21 controls (CG). Bone mass was assessed by dual-energy x-ray absorptiometry and marrow adipose tissue was assessed by 1H magnetic resonance spectroscopy. The biochemical evaluation included the determination of parathyroid hormone, osteocalcin, glucose and insulin levels. RESULTS: A negative association was found between the bone mass at the 1/3 radius and parathyroid hormone levels (r = -0.69; p<0.01). Marrow adipose tissue was not significantly increased in patients (CG = 32.8±11.2% vs PHPT = 38.6±12%). The serum levels of osteocalcin were higher in patients (CG = 8.6±3.6 ng/mL vs PHPT = 36.5±38.4 ng/mL; p<0.005), but no associations were observed between osteocalcin and insulin or between insulin and both marrow adipose tissue and bone mass. CONCLUSION: These results suggest that the increment of adipogenesis in the bone marrow microenvironment under conditions of high bone turnover due to primary hyperparathyroidism is limited. Despite the increased serum levels of osteocalcin due to primary hyperparathyroidism, these patients tend to have impaired insulin sensitivity. PMID:27626477

  20. A novel, rapid, inhibitory effect of insulin on alpha1beta2gamma2s gamma-aminobutyric acid type A receptors.

    PubMed

    Williams, Daniel B

    2008-09-26

    In the CNS, GABA and insulin seem to contribute to similar processes, including neuronal survival; learning and reward; and energy balance and food intake. It is likely then that insulin and GABA may interact, perhaps at the GABA(A) receptor. One such interaction has already been described [Q. Wan, Z.G. Xiong, H.Y. Man, C.A. Ackerley, J. Braunton, W.Y. Lu, L.E. Becker, J.F. MacDonald, Y.T. Wang, Recruitment of functional GABA(A) receptors to postsynaptic domains by insulin, Nature 388 (1997) 686-690]; in it a micromolar concentration of insulin causes the insertion of GABA(A) receptors into the cell membrane, increasing GABA current. I have discovered another effect of insulin on GABA(A) currents. Using a receptor isoform, alpha(1)beta(2)gamma(2s) that is the likely main neuronal GABA(A) isoform expressed recombinantly in Xenopus oocytes, insulin inhibits GABA-induced current when applied simultaneously with low concentrations of GABA. Insulin will significantly inhibit currents induced by EC(30-50) concentrations of GABA by about 38%. Insulin is potent in this effect; IC(50) of insulin was found to be about 4.3 x 10(-10) M. The insulin effect on the GABA dose responses looked like that of an antagonist similar to bicuculline or beta-carbolines. However, an effect of phosphorylation on the GABA(A) receptor from the insulin receptor signal transduction pathway cannot yet be dismissed.

  1. Photoperiodic regulation of insulin receptor mRNA and intracellular insulin signaling in the arcuate nucleus of the Siberian hamster, Phodopus sungorus.

    PubMed

    Tups, Alexander; Helwig, Michael; Stöhr, Sigrid; Barrett, Perry; Mercer, Julian G; Klingenspor, Martin

    2006-09-01

    During the last 5 years it has been well established that photoperiod-induced changes in body weight in the seasonal hamster, Phodopus sungorus, are accompanied by a marked seasonal cycle in leptin sensitivity. In the present study, we investigated the possible involvement of insulin signaling in seasonal body weight regulation. We analyzed the expression pattern and relative intensity of insulin receptor (IR), phosphatidylinositol 3-kinase (PI3-kinase), and protein tyrosine phosphatase 1B (PTP1B) mRNAs by in situ hybridization in the brains of juvenile female hamsters acclimated to either long- (LD) or short-day length (SD) for 8 wk, with or without superimposed food deprivation for 48 h. Furthermore, the hypothalamic concentration and distribution of phospho-AKT, a marker of PI3-kinase activity was determined by immunoblotting and immunohistochemistry. Eight weeks of acclimation to SD led to a substantial downregulation of IR, PTP1B gene expression, and phospho-AKT concentration in this brain region, whereas PI3-kinase mRNA was unchanged. Food deprivation induced a decrease in PTP1B and a trend toward lowered IR gene expression in LD but not in SD. Additionally, a striking increase in PTP1B gene expression in the thalamus was observed after food deprivation in both photoperiods. The direction of change in neuronal insulin signaling contrasts to the central catabolic nature of this pathway described in other species. SD-induced reduction in insulin signaling may be due to decline in body fat stores mediated by enhanced central leptin sensitivity. Increased anorexigenic tone of leptin may overwrite central insulin signaling to prevent catabolic overdrive.

  2. Association between GRB2/Sos and insulin receptor substrate 1 is not sufficient for activation of extracellular signal-regulated kinases by interleukin-4: implications for Ras activation by insulin.

    PubMed

    Pruett, W; Yuan, Y; Rose, E; Batzer, A G; Harada, N; Skolnik, E Y

    1995-03-01

    Insulin receptor substrate 1 (IRS-1) mediates the activation of a variety of signaling pathways by the insulin and insulin-like growth factor 1 receptors by serving as a docking protein for signaling molecules with SH2 domains. We and others have shown that in response to insulin stimulation IRS-1 binds GRB2/Sos and have proposed that this interaction is important in mediating Ras activation by the insulin receptor. Recently, it has been shown that the interleukin (IL)-4 receptor also phosphorylates IRS-1 and an IRS-1-related molecule, 4PS. Unlike insulin, however, IL-4 fails to activate Ras, extracellular signal-regulated kinases (ERKs), or mitogen-activated protein kinases. We have reconstituted the IL-4 receptor into an insulin-responsive L6 myoblast cell line and have shown that IRS-1 is tyrosine phosphorylated to similar degrees in response to insulin and IL-4 stimulation in this cell line. In agreement with previous findings, IL-4 failed to activate the ERKs in this cell line or to stimulate DNA synthesis, whereas the same responses were activated by insulin. Surprisingly, IL-4's failure to activate ERKs was not due to a failure to stimulate the association of tyrosine-phosphorylated IRS-1 with GRB2/Sos; the amounts of GRB2/Sos associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. Moreover, the amounts of phosphatidylinositol 3-kinase activity associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. In contrast to insulin, however, IL-4 failed to induce tyrosine phosphorylation of Shc or association of Shc with GRB2. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Previous studies have indicated that activation of ERks in this cell line is dependent upon Ras since a dominant-negative Ras (Asn-17) blocks ERK activation by insulin. Our findings, taken in the context

  3. Venus Kinase Receptors at the Crossroads of Insulin Signaling: Their Role in Reproduction for Helminths and Insects

    PubMed Central

    Dissous, Colette

    2015-01-01

    Venus kinase receptors (VKRs) are invertebrate receptor tyrosine kinases (TKs) first discovered in the human parasite Schistosoma. They contain an extracellular Venus FlyTrap module similar to the ligand-binding domain of G protein-coupled receptors of class C and an intracellular TK domain similar to that of insulin receptors. VKRs are present from cnidarians to echinoderms. They were shown to be activated by amino-acids, to induce insulin-like intracellular pathways, and to be highly expressed in larvae and in gonads of helminths and insects. The function of VKR in gametogenesis was demonstrated in schistosomes by VKR silencing and recent studies in Aedes aegypti have confirmed the importance of VKR in mosquito egg formation. AaeVKR was shown to bind to ovary ecdysteroidogenic hormone and to activate the production of ecdysteroids by the ovary, independently of signaling mediated by insulin-like peptides. These new data confirm and specify the function of VKRs in the reproduction of helminths and insects and they open interesting perspectives for elucidating the role of VKRs in other models. VKR targeting would also provide opportunities for the control of parasites and various vector-borne infectious diseases. PMID:26284029

  4. Venus Kinase Receptors at the Crossroads of Insulin Signaling: Their Role in Reproduction for Helminths and Insects.

    PubMed

    Dissous, Colette

    2015-01-01

    Venus kinase receptors (VKRs) are invertebrate receptor tyrosine kinases (TKs) first discovered in the human parasite Schistosoma. They contain an extracellular Venus FlyTrap module similar to the ligand-binding domain of G protein-coupled receptors of class C and an intracellular TK domain similar to that of insulin receptors. VKRs are present from cnidarians to echinoderms. They were shown to be activated by amino-acids, to induce insulin-like intracellular pathways, and to be highly expressed in larvae and in gonads of helminths and insects. The function of VKR in gametogenesis was demonstrated in schistosomes by VKR silencing and recent studies in Aedes aegypti have confirmed the importance of VKR in mosquito egg formation. AaeVKR was shown to bind to ovary ecdysteroidogenic hormone and to activate the production of ecdysteroids by the ovary, independently of signaling mediated by insulin-like peptides. These new data confirm and specify the function of VKRs in the reproduction of helminths and insects and they open interesting perspectives for elucidating the role of VKRs in other models. VKR targeting would also provide opportunities for the control of parasites and various vector-borne infectious diseases.

  5. Effects of a 12-month moderate weight loss intervention on insulin sensitivity and inflammation status in nondiabetic overweight and obese subjects.

    PubMed

    Ho, T P; Zhao, X; Courville, A B; Linderman, J D; Smith, S; Sebring, N; Della Valle, D M; Fitzpatrick, B; Simchowitz, L; Celi, F S

    2015-04-01

    Weight loss intervention is the principal non-pharmacological method for prevention and treatment of type 2 diabetes. However, little is known whether it influences insulin sensitivity directly or via its anti-inflammatory effect. The aim of this study was to assess the independent role of changes in inflammation status and weight loss on insulin sensitivity in this population.Overweight and obese nondiabetic participants without co-morbidities underwent a one-year weight loss intervention focused on caloric restriction and behavioral support. Markers of inflammation, body composition, anthropometric para-meters, and insulin sensitivity were recorded at baseline, 6, and 12 months. Insulin sensitivity was assessed with frequently sampled intravenous glucose tolerance test and Minimal Model. Twenty-eight participants (F: 15, M: 13, age 39±5 years, BMI 33.2±4.6 kg/m(2)) completed the study, achieving 9.4±6.9% weight loss, which was predominantly fat mass (7.7±5.6 kg, p<0.0001). Dietary intervention resulted in significant decrease in leptin, leptin-to-adiponectin ratio, hs-CRP, and IL-6 (all p<0.02), and improvement in HOMA-IR and Insulin Sensitivity Index (SI) (both p<0.001). In response to weight loss IL-1β, IL-2, leptin, and resistin were significantly associated with insulin, sensitivity, whereas sICAM-1 had only marginal additive effect. Moderate weight loss in otherwise healthy overweight and obese individuals resulted in an improvement in insulin sensitivity and in the overall inflammation state; the latter played only a minimal independent role in modulating insulin sensitivity.

  6. Gender dimorphism in skeletal muscle leptin receptors, serum leptin and insulin sensitivity.

    PubMed

    Guerra, Borja; Fuentes, Teresa; Delgado-Guerra, Safira; Guadalupe-Grau, Amelia; Olmedillas, Hugo; Santana, Alfredo; Ponce-Gonzalez, Jesus Gustavo; Dorado, Cecilia; Calbet, José A L

    2008-01-01

    To determine if there is a gender dimorphism in the expression of leptin receptors (OB-R170, OB-R128 and OB-R98) and the protein suppressor of cytokine signaling 3 (SOCS3) in human skeletal muscle, the protein expression of OB-R, perilipin A, SOCS3 and alpha-tubulin was assessed by Western blot in muscle biopsies obtained from the m. vastus lateralis in thirty-four men (age = 27.1+/-6.8 yr) and thirty-three women (age = 26.7+/-6.7 yr). Basal serum insulin concentration and HOMA were similar in both genders. Serum leptin concentration was 3.4 times higher in women compared to men (P<0.05) and this difference remained significant after accounting for the differences in percentage of body fat or soluble leptin receptor. OB-R protein was 41% (OB-R170, P<0.05) and 163% (OB-R128, P<0.05) greater in women than men. There was no relationship between OB-R expression and the serum concentrations of leptin or 17beta-estradiol. In men, muscle OB-R128 protein was inversely related to serum free testosterone. In women, OB-R98 and OB-R128 were inversely related to total serum testosterone concentration, and OB-R128 to serum free testosterone concentration. SOCS3 protein expression was similar in men and women and was not related to OB-R. In women, there was an inverse relationship between the logarithm of free testosterone and SCOS3 protein content in skeletal muscle (r = -0.46, P<0.05). In summary, there is a gender dimorphism in skeletal muscle leptin receptors expression, which can be partly explained by the influence of testosterone. SOCS3 expression in skeletal muscle is not up-regulated in women, despite very high serum leptin concentrations compared to men. The circulating form of the leptin receptor can not be used as a surrogate measure of the amount of leptin receptors expressed in skeletal muscles.

  7. Insulin receptor substrate 1 is a substrate of the Pim protein kinases

    PubMed Central

    Song, Jin H.; Padi, Sathish K. R.; Luevano, Libia A.; Minden, Mark D.; DeAngelo, Daniel J.; Hardiman, Gary; Ball, Lauren E.; Warfel, Noel A.; Kraft, Andrew S.

    2016-01-01

    The Pim family of serine/threonine protein kinases (Pim 1, 2, and 3) contribute to cellular transformation by regulating glucose metabolism, protein synthesis, and mitochondrial oxidative phosphorylation. Drugs targeting the Pim protein kinases are being tested in phase I/II clinical trials for the treatment of hematopoietic malignancies. The goal of these studies was to identify Pim substrate(s) that could help define the pathway regulated by these enzymes and potentially serve as a biomarker of Pim activity. To identify novel substrates, bioinformatics analysis was carried out to identify proteins containing a consensus Pim phosphorylation site. This analysis identified the insulin receptor substrate 1 and 2 (IRS1/2) as potential Pim substrates. Experiments were carried out in tissue culture, animals, and human samples from phase I trials to validate this observation and define the biologic readout of this phosphorylation. Our study demonstrates in both malignant and normal cells using either genetic or pharmacological inhibition of the Pim kinases or overexpression of this family of enzymes that human IRS1S1101 and IRS2S1149 are Pim substrates. In xenograft tumor experiments and in a human phase I clinical trial, a pan-Pim inhibitor administered in vivo to animals or humans decreased IRS1S1101 phosphorylation in tumor tissues. This phosphorylation was shown to have effects on the half-life of the IRS family of proteins, suggesting a role in insulin or IGF signaling. These results demonstrate that IRS1S1101 is a novel substrate for the Pim kinases and provide a novel marker for evaluation of Pim inhibitor therapy. PMID:26956053

  8. Hydroxylamine enhances glucose uptake in C2C12 skeletal muscle cells through the activation of insulin receptor substrate 1.

    PubMed

    Kimura, Taro; Kato, Eisuke; Machikawa, Tsukasa; Kimura, Shunsuke; Katayama, Shinji; Kawabata, Jun

    2014-02-28

    Diabetes mellitus is a global disease, and the number of patients with it is increasing. Of various agents for treatment, those that directly act on muscle are currently attracting attention because muscle is one of the main tissues in the human body, and its metabolism is decreased in type II diabetes. In this study, we found that hydroxylamine (HA) enhances glucose uptake in C2C12 myotubes. Analysis of HA's mechanism revealed the involvement of IRS1, PI3K and Akt that is related to the insulin signaling pathway. Further investigation about the activation mechanism of insulin receptor or IRS1 by HA may provide a way to develop a novel anti-diabetic agent alternating to insulin.

  9. PCSK7 Genotype Modifies Effect of a Weight-Loss Diet on 2-Year Changes of Insulin Resistance: The POUNDS LOST Trial

    PubMed Central

    Huang, Tao; Huang, Jinyan; Qi, Qibin; Li, Yanping; Bray, George A.; Rood, Jennifer; Sacks, Frank M.

    2015-01-01

    OBJECTIVE A common variant rs236918 in the PCSK7 gene has the strongest association with iron homeostasis and is related to insulin resistance. Dietary carbohydrate (CHO) modulates the genetic effect on insulin resistance. We examined whether 2-year weight-loss diets modify the effect of PCSK7 genetic variants on changes in fasting insulin levels and insulin resistance in a randomized, controlled trial. RESEARCH DESIGN AND METHODS Data were analyzed in the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) trial, which is a randomized, controlled 2-year weight-loss trial using diets that differed in macronutrient proportions. PCSK7 rs236918 was genotyped in 730 overweight or obese adults (80% whites) in this trial. We assessed the progression in fasting insulin and glucose levels, and insulin resistance by genotypes. RESULTS During the 6-month weight-loss phase, the PCSK7 rs236918 G allele was significantly associated with greater decreases in fasting insulin levels in the high–dietary CHO group (P for interaction = 0.04), while the interaction for changes in HOMA-insulin resistance (HOMA-IR) (P for interaction = 0.06) did not reach significant levels in white subjects. The G allele was significantly associated with a greater decrease in fasting insulin levels and HOMA-IR in response to high dietary CHO levels (P = 0.02 and P = 0.03, respectively). From 6 months to 2 years (weight-regain phase), the interactions became attenuated due to the regaining of weight (P for interactions = 0.08 and 0.06, respectively). In addition, we observed similar and even stronger results in the whole-study samples from the trial. CONCLUSIONS Our data suggest that PCSK7 genotypes may interact with dietary CHO intake on changes in insulin sensitivity in the white Americans. PMID:25504030

  10. Phosphorylation in vitro of the 85 kDa subunit of phosphatidylinositol 3-kinase and its possible activation by insulin receptor tyrosine kinase.

    PubMed Central

    Hayashi, H; Miyake, N; Kanai, F; Shibasaki, F; Takenawa, T; Ebina, Y

    1991-01-01

    Insulin causes a dramatic and rapid increase in phosphatidylinositol 3-kinase activity in the anti-phosphotyrosine immunoprecipitates of cells overexpressing the human insulin receptor. This enzyme may therefore be a mediator of insulin signal transduction [Endemann, Yonezawa & Roth (1990) J. Biol. Chem. 265, 396-400; Ruderman, Kapeller, White & Cantley (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 1411-1415]. At least two questions remain to be elucidated. Firstly, does the insulin receptor tyrosine kinase phosphorylate phosphatidylinositol 3-kinase directly, or does it phosphorylate a protein associated with the 3-kinase? Second, if the enzyme is a direct substrate for the insulin receptor tyrosine kinase, does tyrosine phosphorylation of phosphatidylinositol 3-kinase by the kinase alter the specific enzyme activity, or does the amount of the tyrosine-phosphorylated form of the phosphatidylinositol 3-kinase increase, with no change in the specific activity? We report here evidence that the 85 kDa subunit of highly purified phosphatidylinositol 3-kinase is phosphorylated on the tyrosine residue by the activated normal insulin receptor in vitro, but not by a mutant insulin receptor which lacks tyrosine kinase activity. We found that an increase in enzyme activity was detected in response to insulin not only in the anti-phosphotyrosine immunoprecipitates of the cytosol, but also in the cytosolic fraction before immunoprecipitation. In addition, we partially separated the tyrosine-phosphorylated form from the unphosphorylated form of the enzyme, by using a f.p.l.c. Mono Q column. The insulin-stimulated phosphatidylinositol 3-kinase activity was mainly detected in the fraction containing almost all of the tyrosine-phosphorylated form. This result suggests that tyrosine phosphorylation of phosphatidylinositol 3-kinase by the insulin receptor kinase may increase the specific activity of the former enzyme in vivo. Images Fig. 1. Fig. 2. Fig. 4. PMID:1722393

  11. Enhanced insulin-receptor tyrosine kinase activity associated with chromosomal translocation (1;19) in a pre-B-cell leukemia line.

    PubMed

    Newman, J D; Harrison, L C; Eckardt, G S; Jack, I

    1992-02-01

    The gene for the insulin receptor has been assigned to chromosome 19 near the breakpoint of the translocation t(1;19) which occurs in 25% of pre-B-cell leukemias. Insulin receptors in a pre-B-cell leukemia cell line (ACV) with t(1;19) were found to have 2-fold higher affinity for insulin, 5-fold higher basal and insulin-stimulated beta sub-unit autophosphorylation, and 2-fold higher basal and 4-fold higher insulin-stimulated beta sub-unit kinase activity on the synthetic peptide poly(Glu,Tyr), compared to receptors in a B-cell line (ADD) with normal karyotype from the same patient. ACV cells had a novel 13-kb receptor mRNA species and expressed a DNA polymorphism localized to the tyrosine kinase domain of the receptor gene. These findings suggest that t(1;19) in the ACV cell may result in rearrangement of the insulin receptor gene and translation of a receptor with enhanced tyrosine kinase activity. PMID:1310491

  12. The comparison of insulin resistance frequency in patients with recurrent early pregnancy loss to normal individuals

    PubMed Central

    2012-01-01

    Background Patients with ≥ 3 recurrent spontaneous miscarriages are classified as having RSM. Polycystic ovary syndrome (PCOS) is associated with insulin resistance (IR). The purpose of this study is to evaluate the association of IR and RMS. Methods Present case- control prospective study was performed on 100 women in control group (with a history of at a live birth and no history of one more abortion) and study group (with a history of ≥ 3 RMS) who were not diabetes and PCOS. Two groups matched in base of age and body mass index. Blood was withdrawn from the case and control patients for the determination of the fasting blood glucose (FG), fasting insulin (FI) levels and ultrasonography was performed on all the patients. Results The observed differences between age, FG and FG to FI ratio levels in case and control groups were not significant (p > 0.05) but it was significant about fasting insulin (p = 0.0119). FI of < 20 μu/ml or ≥ 20 μu/ml in case and control group was significant (Chi-square: 4.083, p: 0.0433, odds ratio: 4.4386, CI95% = 1.1541 to 17.0701), whereas the difference between absolute and proportional frequency of patients with FG to FI ratio of < 4.5 and ≥ 4.5 in case and control groups was not significant (Chi-square: 2.374, p = 0.123). Conclusion Current study showed that in women with RPL, in Iranian race like Americans, frequency of insulin resistance in high, therefore there is a probability of the degree of insulin resistance in women with RPL. PMID:22405326

  13. Dysfunctionally phosphorylated type 1 insulin receptor substrate in neural-derived blood exosomes of preclinical Alzheimer's disease.

    PubMed

    Kapogiannis, Dimitrios; Boxer, Adam; Schwartz, Janice B; Abner, Erin L; Biragyn, Arya; Masharani, Umesh; Frassetto, Lynda; Petersen, Ronald C; Miller, Bruce L; Goetzl, Edward J

    2015-02-01

    Insulin resistance causes diminished glucose uptake in similar regions of the brain in Alzheimer's disease (AD) and type 2 diabetes mellitus (DM2). Brain tissue studies suggested that insulin resistance is caused by low insulin receptor signaling attributable to its abnormal association with more phospho (P)-serine-type 1 insulin receptor substrate (IRS-1) and less P-tyrosine-IRS-1. Plasma exosomes enriched for neural sources by immunoabsorption were obtained once from 26 patients with AD, 20 patients with DM2, 16 patients with frontotemporal dementia (FTD), and matched case control subjects. At 2 time points, they were obtained from 22 others when cognitively normal and 1 to 10 yr later when diagnosed with AD. Mean exosomal levels of extracted P-serine 312-IRS-1 and P-pan-tyrosine-IRS-1 by ELISA and the ratio of P-serine 312-IRS-1 to P-pan-tyrosine-IRS-1 (insulin resistance factor, R) for AD and DM2 and P-serine 312-IRS-1 and R for FTD were significantly different from those for case control subjects. The levels of R for AD were significantly higher than those for DM2 or FTD. Stepwise discriminant modeling showed correct classification of 100% of patients with AD, 97.5% of patients with DM2, and 84% of patients with FTD. In longitudinal studies of 22 patients with AD, exosomal levels of P-serine 312-IRS-1, P-pan-tyrosine-IRS-1, and R were significantly different 1 to 10 yr before and at the time of diagnosis compared with control subjects. Insulin resistance reflected in R values from this blood test is higher for patients with AD, DM2, and FTD than case control subjects; higher for patients with AD than patients with DM2 or FTD; and accurately predicts development of AD up to 10 yr prior to clinical onset. PMID:25342129

  14. Exercise and Weight Loss Improve Muscle Mitochondrial Respiration, Lipid Partitioning, and Insulin Sensitivity After Gastric Bypass Surgery

    PubMed Central

    Coen, Paul M.; Menshikova, Elizabeth V.; Distefano, Giovanna; Zheng, Donghai; Tanner, Charles J.; Standley, Robert A.; Helbling, Nicole L.; Dubis, Gabriel S.; Ritov, Vladimir B.; Xie, Hui; Desimone, Marisa E.; Smith, Steven R.; Stefanovic-Racic, Maja; Toledo, Frederico G.S.; Houmard, Joseph A.

    2015-01-01

    Both Roux-en-Y gastric bypass (RYGB) surgery and exercise can improve insulin sensitivity in individuals with severe obesity. However, the impact of RYGB with or without exercise on skeletal muscle mitochondria, intramyocellular lipids, and insulin sensitivity index (SI) is unknown. We conducted a randomized exercise trial in patients (n = 101) who underwent RYGB surgery and completed either a 6-month moderate exercise (EX) or a health education control (CON) intervention. SI was determined by intravenous glucose tolerance test. Mitochondrial respiration and intramyocellular triglyceride, sphingolipid, and diacylglycerol content were measured in vastus lateralis biopsy specimens. We found that EX provided additional improvements in SI and that only EX improved cardiorespiratory fitness, mitochondrial respiration and enzyme activities, and cardiolipin profile with no change in mitochondrial content. Muscle triglycerides were reduced in type I fibers in CON, and sphingolipids decreased in both groups, with EX showing a further reduction in a number of ceramide species. In conclusion, exercise superimposed on bariatric surgery–induced weight loss enhances mitochondrial respiration, induces cardiolipin remodeling, reduces specific sphingolipids, and provides additional improvements in insulin sensitivity. PMID:26293505

  15. Exercise and Weight Loss Improve Muscle Mitochondrial Respiration, Lipid Partitioning, and Insulin Sensitivity After Gastric Bypass Surgery.

    PubMed

    Coen, Paul M; Menshikova, Elizabeth V; Distefano, Giovanna; Zheng, Donghai; Tanner, Charles J; Standley, Robert A; Helbling, Nicole L; Dubis, Gabriel S; Ritov, Vladimir B; Xie, Hui; Desimone, Marisa E; Smith, Steven R; Stefanovic-Racic, Maja; Toledo, Frederico G S; Houmard, Joseph A; Goodpaster, Bret H

    2015-11-01

    Both Roux-en-Y gastric bypass (RYGB) surgery and exercise can improve insulin sensitivity in individuals with severe obesity. However, the impact of RYGB with or without exercise on skeletal muscle mitochondria, intramyocellular lipids, and insulin sensitivity index (SI) is unknown. We conducted a randomized exercise trial in patients (n = 101) who underwent RYGB surgery and completed either a 6-month moderate exercise (EX) or a health education control (CON) intervention. SI was determined by intravenous glucose tolerance test. Mitochondrial respiration and intramyocellular triglyceride, sphingolipid, and diacylglycerol content were measured in vastus lateralis biopsy specimens. We found that EX provided additional improvements in SI and that only EX improved cardiorespiratory fitness, mitochondrial respiration and enzyme activities, and cardiolipin profile with no change in mitochondrial content. Muscle triglycerides were reduced in type I fibers in CON, and sphingolipids decreased in both groups, with EX showing a further reduction in a number of ceramide species. In conclusion, exercise superimposed on bariatric surgery-induced weight loss enhances mitochondrial respiration, induces cardiolipin remodeling, reduces specific sphingolipids, and provides additional improvements in insulin sensitivity.

  16. Striatal dopamine D2/3 receptor availability increases after long-term bariatric surgery-induced weight loss.

    PubMed

    van der Zwaal, Esther M; de Weijer, Barbara A; van de Giessen, Elsmarieke M; Janssen, Ignace; Berends, Frits J; van de Laar, Arnold; Ackermans, Mariette T; Fliers, Eric; la Fleur, Susanne E; Booij, Jan; Serlie, Mireille J

    2016-07-01

    In several studies reduced striatal dopamine D2/3 receptor (D2/3R) availability was reported in obese subjects compared to lean controls. Whether this is a reversible phenomenon remained uncertain. We previously determined the short-term effect of Roux-en-Y gastric bypass surgery (RYGB) on striatal D2/3R availability (using [(123)I]IBZM SPECT) in 20 morbidly obese women. Striatal D2/3R availability was lower compared to controls at baseline, and remained unaltered after 6 weeks, despite significant weight loss. To determine whether long-term bariatric surgery-induced weight loss normalizes striatal D2/3R binding, we repeated striatal D2/3R binding measurements at least 2 years after RYGB in 14 subjects of the original cohort. In addition, we assessed long-term changes in body composition, eating behavior and fasting plasma levels of leptin, ghrelin, insulin and glucose. Mean body mass index declined from 46±7kg/m(2) to 32±6kg/m(2), which was accompanied by a significant increase in striatal D2/3R availability (p=0.031). Striatal D2/3R availability remained significantly reduced compared to the age-matched controls (BMI 22±2kg/m(2); p=0.01). Changes in striatal D2/3R availability did not correlate with changes in body weight/fat, insulin sensitivity, ghrelin or leptin levels. Scores on eating behavior questionnaires improved and changes in the General Food Craving Questionnaire-State showed a borderline significant correlation with changes in striatal D2/3R availability. These findings show that striatal D2/3R availability increases after long-term bariatric-surgery induced weight loss, suggesting that reduced D2/3R availability in obesity is a reversible phenomenon. PMID:27184782

  17. Cricket body size is altered by systemic RNAi against insulin signaling components and epidermal growth factor receptor.

    PubMed

    Dabour, Noha; Bando, Tetsuya; Nakamura, Taro; Miyawaki, Katsuyuki; Mito, Taro; Ohuchi, Hideyo; Noji, Sumihare

    2011-09-01

    A long-standing problem of developmental biology is how body size is determined. In Drosophila melanogaster, the insulin/insulin-like growth factor (I/IGF) and target of rapamycin (TOR) signaling pathways play important roles in this process. However, the detailed mechanisms by which insect body growth is regulated are not known. Therefore, we have attempted to utilize systemic nymphal RNA interference (nyRNAi) to knockdown expression of insulin signaling components including Insulin receptor (InR), Insulin receptor substrate (chico), Phosphatase and tensin homologue (Pten), Target of rapamycin (Tor), RPS6-p70-protein kinase (S6k), Forkhead box O (FoxO) and Epidermal growth factor receptor (Egfr) and observed the effects on body size in the Gryllus bimaculatus cricket. We found that crickets treated with double-stranded RNA (dsRNA) against Gryllus InR, chico, Tor, S6k and Egfr displayed smaller body sizes, while Gryllus FoxO nyRNAi-ed crickets exhibited larger than normal body sizes. Furthermore, RNAi against Gryllus chico and Tor displayed slow growth and RNAi against Gryllus chico displayed longer lifespan than control crickets. Since no significant difference in ability of food uptake was observed between the Gryllus chico(nyRNAi) nymphs and controls, we conclude that the adult cricket body size can be altered by knockdown of expressions of Gryllus InR, chico, Tor, S6k, FoxO and Egfr by systemic RNAi. Our results suggest that the cricket is a promising model to study mechanisms underlying controls of body size and life span with RNAi methods. PMID:21777227

  18. Increased Skeletal Muscle Capillarization After Aerobic Exercise Training and Weight Loss Improves Insulin Sensitivity in Adults With IGT

    PubMed Central

    Prior, Steven J.; Blumenthal, Jacob B.; Katzel, Leslie I.; Goldberg, Andrew P.; Ryan, Alice S.

    2014-01-01

    OBJECTIVE Transcapillary transport of insulin is one determinant of glucose uptake by skeletal muscle; thus, a reduction in capillary density (CD) may worsen insulin sensitivity. Skeletal muscle CD is lower in older adults with impaired glucose tolerance (IGT) compared with those with normal glucose tolerance and may be modifiable through aerobic exercise training and weight loss (AEX+WL). We tested the hypothesis that 6-month AEX+WL would increase CD to improve insulin sensitivity and glucose tolerance in older adults with IGT. RESEARCH DESIGN AND METHODS Sixteen sedentary, overweight-obese (BMI 27–35 kg/m2), older (63 ± 2 years) men and women with IGT underwent hyperinsulinemic-euglycemic clamps to measure insulin sensitivity, oral glucose tolerance tests, exercise and body composition testing, and vastus lateralis muscle biopsies to determine CD before and after 6-month AEX+WL. RESULTS Insulin sensitivity (M) and 120-min postprandial glucose (G120) correlated with CD at baseline (r = 0.58 and r = −0.60, respectively, P < 0.05). AEX+WL increased maximal oxygen consumption (VO2max) 18% (P = 0.02) and reduced weight and fat mass 8% (P < 0.02). CD increased 15% (264 ± 11 vs. 304 ± 14 capillaries/mm2, P = 0.01), M increased 21% (42.4 ± 4.0 vs. 51.4 ± 4.3 µmol/kg FFM/min, P < 0.05), and G120 decreased 16% (9.35 ± 0.5 vs. 7.85 ± 0.5 mmol/L, P = 0.008) after AEX+WL. Regression analyses showed that the AEX+WL-induced increase in CD independently predicted the increase in M (r = 0.74, P < 0.01) as well as the decrease in G120 (r = −0.55, P < 0.05). CONCLUSIONS Six-month AEX+WL increases skeletal muscle CD in older adults with IGT. This represents one mechanism by which AEX+WL improves insulin sensitivity in older adults with IGT. PMID:24595633

  19. Lack of the architectural factor HMGA1 causes insulin resistance and diabetes in humans and mice.

    PubMed

    Foti, Daniela; Chiefari, Eusebio; Fedele, Monica; Iuliano, Rodolfo; Brunetti, Leonardo; Paonessa, Francesco; Manfioletti, Guidalberto; Barbetti, Fabrizio; Brunetti, Arturo; Croce, Carlo M; Fusco, Alfredo; Brunetti, Antonio

    2005-07-01

    Type 2 diabetes mellitus is a widespread disease, affecting millions of people globally. Although genetics and environmental factors seem to have a role, the cause of this metabolic disorder is largely unknown. Here we report a genetic flaw that markedly reduced the intracellular expression of the high mobility group A1 (HMGA1) protein, and adversely affected insulin receptor expression in cells and tissues from four subjects with insulin resistance and type 2 diabetes. Restoration of HMGA1 protein expression in subjects' cells enhanced INSR gene transcription, and restored cell-surface insulin receptor protein expression and insulin-binding capacity. Loss of Hmga1 expression, induced in mice by disrupting the Hmga1 gene, considerably decreased insulin receptor expression in the major targets of insulin action, largely impaired insulin signaling and severely reduced insulin secretion, causing a phenotype characteristic of human type 2 diabetes. PMID:15924147

  20. The influence of exercise-induced oxidative stress on binding and degradation of 125I-insulin by the receptors on erythrocytes.

    PubMed

    Szcześniak, L; Karolkiewicz, J; Deskur, E; Rychlewski, T; Konys, L; Stankiewicz, K

    1998-09-01

    In the present work we investigated the influence of oxidative stress induced by strenuous exercise on the affinity of a specific insulin receptors on human erythrocytes. 13 male members of the national basketball staff performed a maximal treadmill exercise test. In the blood samples collected before and directly after the test acid-base equilibrium parameters, lactic acid concentrations, glucose and insulin serum levels as well as 125I-insulin binding and degradation by receptor on erythrocytes were measured. As markers of oxidative stress, plasma thiobarbituric acid-reactive substance levels (TBARS) and red blood cells glutathione content (GSH) were determined. After the exercise test TBARS levels increased significantly and GSH concentrations decreased indicating that oxidative stress occurred. Binding of 125I-insulin to the receptors on erythrocytes decreased significantly during the test, while there was only insignificant reduction in 125I-insulin degradation. Correlation analysis and multiple linear regression revealed that changes in insulin degradation by receptors on erythrocytes during exhaustive exercise are determined by oxidative stress, probably via oxidation of sulfhydryl groups of certain enzymes. The affinity of receptors for insulin seems to depend mainly on glucose concentrations.

  1. Effect on Insulin-Stimulated Release of D-Chiro-Inositol-Containing Inositolphosphoglycan Mediator during Weight Loss in Obese Women with and without Polycystic Ovary Syndrome

    PubMed Central

    Sistrun, Sakita N.; Morel, Kelley S.; Nestler, John E.

    2016-01-01

    Background. A deficiency of D-chiro-inositol-inositolphosphoglycan mediator (DCI-IPG) may contribute to insulin resistance in polycystic ovary syndrome (PCOS). Whether the relationship between impaired DCI-IPG release and insulin resistance is specific to PCOS rather than obesity is unknown. We assessed insulin-released DCI-IPG and its relationship to insulin sensitivity at baseline and after weight loss in obese women with and without PCOS. Methods. Obese PCOS (n = 16) and normal (n = 15) women underwent 8 weeks of a hypocaloric diet. The Matsuda index, area under the curve DCI-IPG (AUCDCI-IPG), AUCinsulin, and AUCDCI-IPG/AUCinsulin were measured during a 2 hr OGTT at baseline and 8 weeks. Results. PCOS women had lower AUCDCI-IPG/AUCinsulin at baseline and a significant relationship between AUCDCI-IPG/AUCinsulin and Matsuda index (p = 0.0003), which was not present in controls. Weight loss was similar between PCOS (−4.08 kg) and normal women (−4.29 kg, p = 0.6281). Weight loss in PCOS women did not change the relationship between AUCDCI-IPG/AUCinsulin and Matsuda index (p = 0.0100), and this relationship remained absent in control women. Conclusion. The association between AUCDCI-IPG/AUCinsulin and insulin sensitivity was only found in PCOS but not in normal women, and this relationship was unaffected by weight loss. DCI and its messenger may contribute to insulin resistance in PCOS independent of obesity. PMID:27721826

  2. Modulatory effect of insulin on T cell receptor mediated calcium signaling is blunted in long lasting type 1 diabetes mellitus.

    PubMed

    Demkow, Urszula; Winklewski, Paweł; Ciepiela, Olga; Popko, Katarzyna; Lipińska, Anna; Kucharska, Anna; Michalska, Beata; Wąsik, Maria

    2012-01-01

    Insulin significantly influences Ca(2+) signals evoked by various stimulants. In type 1 recent onset diabetes mellitus the proliferative response of T cells is significantly decreased. The number of clinical trials exploring the role of anti-CD3 monoclonal antibodies (mAb) as a therapeutic agent in recent onset diabetes mellitus type 1 is increasing last years. Therefore, a better understanding of the interplay between T cell receptor (TCR) dependent Ca(2+) increase, and insulin is of vital clinical significance. The aim of the study was to assess the effect of insulin on TCR evoked Ca(2+) responses in T lymphocytes obtained from healthy volunteers and patients suffering from long lasting diabetes mellitus type 1. Analysis was performed with use of the flow cytometer. We demonstrated that T cells ability to mobilize Ca(2+) was significantly reduced in long lasting diabetes mellitus type 1. Ca(2+) decrease achieved by the long term incubation with anti-CD3 mAb in T cells from healthy volunteers was restored by insulin. Strong interrelationship between baseline Ca(2+) level and plateau phase response to TCR stimulation was observed in the cytoplasm of cells pre-incubated with insulin from both healthy subjects and diabetic patients (r = 0.95, p < 0.0001 and r = 0.94, p < 0.0001, respectively). We postulate the existence of the interplay between TCR mediated activation and insulin. The TCR-insulin interplay is blunted in long lasting diabetes mellitus type 1. These observations may have an important implication for future therapeutic options in diabetes.

  3. Extension of Drosophila lifespan by cinnamon through a sex-specific dependence on the insulin receptor substrate chico.

    PubMed

    Schriner, Samuel E; Kuramada, Steven; Lopez, Terry E; Truong, Stephanie; Pham, Andrew; Jafari, Mahtab

    2014-12-01

    Cinnamon is a spice commonly used worldwide to flavor desserts, fruits, cereals, breads, and meats. Numerous health benefits have been attributed to its consumption, including the recent suggestion that it may decrease blood glucose levels in people with diabetes. Insulin signaling is an integral pathway regulating the lifespan of laboratory organisms, such as worms, flies, and mice. We posited that if cinnamon truly improved the clinical signs of diabetes in people that it would also act on insulin signaling in laboratory organisms and increase lifespan. We found that cinnamon did extend lifespan in the fruit fly, Drosophila melanogaster. However, it had no effect on the expression levels of the 3 aging-related Drosophila insulin-like peptides nor did it alter sugar, fat, or soluble protein levels, as would be predicted. In addition, cinnamon exhibited no protective effects in males against oxidative challenges. However, in females it did confer a protective effect against paraquat, but sensitized them to iron. Cinnamon provided no protective effect against desiccation and starvation in females, but sensitized males to both. Interestingly, cinnamon protected both sexes against cold, sensitized both to heat, and elevated HSP70 expression levels. We also found that cinnamon required the insulin receptor substrate to extend lifespan in males, but not females. We conclude that cinnamon does not extend lifespan by improving stress tolerance in general, though it does act, at least in part, through insulin signaling.

  4. Toll-like receptor 2 mediates high-fat diet-induced impairment of vasodilator actions of insulin

    PubMed Central

    Jang, Hyun-Ju; Kim, Hae-Suk; Hwang, Daniel H.; Quon, Michael J.

    2013-01-01

    Obesity is characterized by a chronic proinflammatory state that leads to endothelial dysfunction. Saturated fatty acids (SFA) stimulate Toll-like receptors (TLR) that promote metabolic insulin resistance. However, it is not known whether TLR2 mediates impairment of vascular actions of insulin in response to high-fat diet (HFD) to cause endothelial dysfunction. siRNA knockdown of TLR2 in primary endothelial cells opposed palmitate-stimulated expression of proinflammatory cytokines and splicing of X box protein 1 (XBP-1). Inhibition of unfolding protein response (UPR) reduced SFA-stimulated expression of TNFα. Thus, SFA stimulates UPR and proinflammatory response through activation of TLR2 in endothelial cells. Knockdown of TLR2 also opposed impairment of insulin-stimulated phosphorylation of eNOS and subsequent production of NO. Importantly, insulin-stimulated vasorelaxation of mesenteric arteries from TLR2 knockout mice was preserved even on HFD (in contrast with results from arteries examined in wild-type mice on HFD). We conclude that TLR2 in vascular endothelium mediates HFD-stimulated proinflammatory responses and UPR that accompany impairment of vasodilator actions of insulin, leading to endothelial dysfunction. These results are relevant to understanding the pathophysiology of the cardiovascular complications of diabetes and obesity. PMID:23531618

  5. Suppression of the Insulin Receptors in Adult Schistosoma japonicum Impacts on Parasite Growth and Development: Further Evidence of Vaccine Potential

    PubMed Central

    You, Hong; Gobert, Geoffrey N.; Cai, Pengfei; Mou, Rong; Nawaratna, Sujeevi; Fang, Guofu; Villinger, Francois; McManus, Donald P.

    2015-01-01

    To further investigate the importance of insulin signaling in the growth, development, sexual maturation and egg production of adult schistosomes, we have focused attention on the insulin receptors (SjIRs) of Schistosoma japonicum, which we have previously cloned and partially characterised. We now show, by Biolayer Interferometry, that human insulin can bind the L1 subdomain (insulin binding domain) of recombinant (r)SjIR1 and rSjIR2 (designated SjLD1 and SjLD2) produced using the Drosophila S2 protein expression system. We have then used RNA interference (RNAi) to knock down the expression of the SjIRs in adult S. japonicum in vitro and show that, in addition to their reduced transcription, the transcript levels of other important downstream genes within the insulin pathway, associated with glucose metabolism and schistosome fecundity, were also impacted substantially. Further, a significant decrease in glucose uptake was observed in the SjIR-knockdown worms compared with luciferase controls. In vaccine/challenge experiments, we found that rSjLD1 and rSjLD2 depressed female growth, intestinal granuloma density and faecal egg production in S. japonicum in mice presented with a low dose challenge infection. These data re-emphasize the potential of the SjIRs as veterinary transmission blocking vaccine candidates against zoonotic schistosomiasis japonica in China and the Philippines. PMID:25961574

  6. Peroxisome proliferator-activated receptor γ regulates genes involved in insulin/insulin-like growth factor signaling and lipid metabolism during adipogenesis through functionally distinct enhancer classes.

    PubMed

    Oger, Frédérik; Dubois-Chevalier, Julie; Gheeraert, Céline; Avner, Stéphane; Durand, Emmanuelle; Froguel, Philippe; Salbert, Gilles; Staels, Bart; Lefebvre, Philippe; Eeckhoute, Jérôme

    2014-01-10

    The nuclear receptor peroxisome proliferator-activated receptor (PPAR) is a transcription factor whose expression is induced during adipogenesis and that is required for the acquisition and control of mature adipocyte functions. Indeed, PPAR induces the expression of genes involved in lipid synthesis and storage through enhancers activated during adipocyte differentiation. Here, we show that PPAR also binds to enhancers already active in preadipocytes as evidenced by an active chromatin state including lower DNA methylation levels despite higher CpG content. These constitutive enhancers are linked to genes involved in the insulin/insulin-like growth factor signaling pathway that are transcriptionally induced during adipogenesis but to a lower extent than lipid metabolism genes, because of stronger basal expression levels in preadipocytes. This is consistent with the sequential involvement of hormonal sensitivity and lipid handling during adipocyte maturation and correlates with the chromatin structure dynamics at constitutive and activated enhancers. Interestingly, constitutive enhancers are evolutionary conserved and can be activated in other tissues, in contrast to enhancers controlling lipid handling genes whose activation is more restricted to adipocytes. Thus, PPAR utilizes both broadly active and cell type-specific enhancers to modulate the dynamic range of activation of genes involved in the adipogenic process.

  7. Peroxisome Proliferator-activated Receptor γ Regulates Genes Involved in Insulin/Insulin-like Growth Factor Signaling and Lipid Metabolism during Adipogenesis through Functionally Distinct Enhancer Classes*

    PubMed Central

    Oger, Frédérik; Dubois-Chevalier, Julie; Gheeraert, Céline; Avner, Stéphane; Durand, Emmanuelle; Froguel, Philippe; Salbert, Gilles; Staels, Bart; Lefebvre, Philippe; Eeckhoute, Jérôme

    2014-01-01

    The nuclear receptor peroxisome proliferator-activated receptor (PPAR) γ is a transcription factor whose expression is induced during adipogenesis and that is required for the acquisition and control of mature adipocyte functions. Indeed, PPARγ induces the expression of genes involved in lipid synthesis and storage through enhancers activated during adipocyte differentiation. Here, we show that PPARγ also binds to enhancers already active in preadipocytes as evidenced by an active chromatin state including lower DNA methylation levels despite higher CpG content. These constitutive enhancers are linked to genes involved in the insulin/insulin-like growth factor signaling pathway that are transcriptionally induced during adipogenesis but to a lower extent than lipid metabolism genes, because of stronger basal expression levels in preadipocytes. This is consistent with the sequential involvement of hormonal sensitivity and lipid handling during adipocyte maturation and correlates with the chromatin structure dynamics at constitutive and activated enhancers. Interestingly, constitutive enhancers are evolutionary conserved and can be activated in other tissues, in contrast to enhancers controlling lipid handling genes whose activation is more restricted to adipocytes. Thus, PPARγ utilizes both broadly active and cell type-specific enhancers to modulate the dynamic range of activation of genes involved in the adipogenic process. PMID:24288131

  8. Self-renewal of human embryonic stem cells requires insulin-like growth factor-1 receptor and ERBB2 receptor signaling

    PubMed Central

    Wang, Linlin; Schulz, Thomas C.; Sherrer, Eric S.; Dauphin, Derek S.; Shin, Soojung; Nelson, Angelique M.; Ware, Carol B.; Zhan, Mei; Song, Chao-Zhong; Chen, Xiaoji; Brimble, Sandii N.; McLean, Amanda; Galeano, Maria J.; Uhl, Elizabeth W.; D'Amour, Kevin A.; Chesnut, Jonathan D.; Rao, Mahendra S.

    2007-01-01

    Despite progress in developing defined conditions for human embryonic stem cell (hESC) cultures, little is known about the cell-surface receptors that are activated under conditions supportive of hESC self-renewal. A simultaneous interrogation of 42 receptor tyrosine kinases (RTKs) in hESCs following stimulation with mouse embryonic fibroblast (MEF) conditioned medium (CM) revealed rapid and prominent tyrosine phosphorylation of insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF1R); less prominent tyrosine phosphorylation of epidermal growth factor receptor (EGFR) family members, including ERBB2 and ERBB3; and trace phosphorylation of fibroblast growth factor receptors. Intense IGF1R and IR phosphorylation occurred in the absence of MEF conditioning (NCM) and was attributable to high concentrations of insulin in the proprietary KnockOut Serum Replacer (KSR). Inhibition of IGF1R using a blocking antibody or lentivirus-delivered shRNA reduced hESC self-renewal and promoted differentiation, while disruption of ERBB2 signaling with the selective inhibitor AG825 severely inhibited hESC proliferation and promoted apoptosis. A simple defined medium containing an IGF1 analog, heregulin-1β (a ligand for ERBB2/ERBB3), fibroblast growth factor-2 (FGF2), and activin A supported long-term growth of multiple hESC lines. These studies identify previously unappreciated RTKs that support hESC proliferation and self-renewal, and provide a rationally designed medium for the growth and maintenance of pluripotent hESCs. PMID:17761519

  9. Insulin-like growth factor-I receptor blockade by a specific tyrosine kinase inhibitor for human gastrointestinal carcinomas.

    PubMed

    Piao, Wenhua; Wang, Yu; Adachi, Yasushi; Yamamoto, Hiroyuki; Li, Rong; Imsumran, Arisa; Li, Hua; Maehata, Tadateru; Ii, Masanori; Arimura, Yoshiaki; Lee, Choon-Taek; Shinomura, Yasuhisa; Carbone, David P; Imai, Kohzoh

    2008-06-01

    Insulin-like growth factor-I receptor (IGF-IR) signaling is required for carcinogenicity and proliferation of gastrointestinal (GI) cancers. In this study, we sought to evaluate the effect of a new tyrosine kinase inhibitor of IGF-IR, NVP-AEW541, on the signal transduction and the progression of GI carcinomas. We assessed the effect of NVP-AEW541 on signal transduction, proliferation, survival, and migration in four GI cancer cells: colorectal adenocarcinoma HT29, pancreatic adenocarcinoma BxPC3, esophageal squamous cell carcinoma TE1, and hepatoma PLC/PRF/5. The effects of NVP-AEW541 alone and with chemotherapy were studied in vitro and in nude mouse xenografts. We also analyzed the effects of NVP-AEW541 on insulin signals and hybrid receptor formation between IGF-IR and insulin receptor. NVP-AEW541 blocked autophosphorylation of IGF-IR and both Akt and extracellular signal-regulated kinase activation by IGF but not by insulin. NVP-AEW541 suppressed proliferation and tumorigenicity in vitro in a dose-dependent manner in all cell lines. The drug inhibited tumor as a single agent and, when combined with stressors, up-regulated apoptosis in a dose-dependent fashion and inhibited mobility. NVP-AEW541 augmented the effects of chemotherapy on in vitro growth and induction of apoptosis. Moreover, the combination of NVP-AEW541 and chemotherapy was highly effective against tumors in mice. This compound did not influence hybrid receptor formation. Thus, NVP-AEW541 may have significant therapeutic utility in human GI carcinomas both alone and in combination with chemotherapy.

  10. Reduced Insulin Sensitivity Is Related to Less Endogenous Dopamine at D2/3 Receptors in the Ventral Striatum of Healthy Nonobese Humans

    PubMed Central

    Caravaggio, Fernando; Borlido, Carol; Hahn, Margaret; Feng, Zhe; Fervaha, Gagan; Gerretsen, Philip; Nakajima, Shinichiro; Plitman, Eric; Chung, Jun Ku; Iwata, Yusuke; Wilson, Alan; Remington, Gary

    2015-01-01

    Background: Food addiction is a debated topic in neuroscience. Evidence suggests diabetes is related to reduced basal dopamine levels in the nucleus accumbens, similar to persons with drug addiction. It is unknown whether insulin sensitivity is related to endogenous dopamine levels in the ventral striatum of humans. We examined this using the agonist dopamine D2/3 receptor radiotracer [11C]-(+)-PHNO and an acute dopamine depletion challenge. In a separate sample of healthy persons, we examined whether dopamine depletion could alter insulin sensitivity. Methods: Insulin sensitivity was estimated for each subject from fasting plasma glucose and insulin using the Homeostasis Model Assessment II. Eleven healthy nonobese and nondiabetic persons (3 female) provided a baseline [11C]-(+)-PHNO scan, 9 of which provided a scan under dopamine depletion, allowing estimates of endogenous dopamine at dopamine D2/3 receptor. Dopamine depletion was achieved via alpha-methyl-para-tyrosine (64mg/kg, P.O.). In 25 healthy persons (9 female), fasting plasma and glucose was acquired before and after dopamine depletion. Results: Endogenous dopamine at ventral striatum dopamine D2/3 receptor was positively correlated with insulin sensitivity (r(7)=.84, P=.005) and negatively correlated with insulin levels (r(7)=-.85, P=.004). Glucose levels were not correlated with endogenous dopamine at ventral striatum dopamine D2/3 receptor (r(7)=-.49, P=.18). Consistently, acute dopamine depletion in healthy persons significantly decreased insulin sensitivity (t(24)=2.82, P=.01), increased insulin levels (t(24)=-2.62, P=.01), and did not change glucose levels (t(24)=-0.93, P=.36). Conclusion: In healthy individuals, diminished insulin sensitivity is related to less endogenous dopamine at dopamine D2/3 receptor in the ventral striatum. Moreover, acute dopamine depletion reduces insulin sensitivity. These findings may have important implications for neuropsychiatric populations with metabolic

  11. Insulin like growth factor 2 regulation of aryl hydrocarbon receptor in MCF-7 breast cancer cells

    SciTech Connect

    Tomblin, Justin K.; Salisbury, Travis B.

    2014-01-17

    Highlights: •IGF-2 stimulates concurrent increases in AHR and CCND1 expression. •IGF-2 promotes the binding of AHR to the endogenous cyclin D1 promoter. •AHR knockdown inhibits IGF-2 stimulated increases in CCND1 mRNA and protein. •AHR knockdown inhibits IGF-2 stimulated increases in MCF-7 proliferation. -- Abstract: Insulin like growth factor (IGF)-1 and IGF-2 stimulate normal growth, development and breast cancer cell proliferation. Cyclin D1 (CCND1) promotes cell cycle by inhibiting retinoblastoma protein (RB1). The aryl hydrocarbon receptor (AHR) is a major xenobiotic receptor that also regulates cell cycle. The purpose of this study was to investigate whether IGF-2 promotes MCF-7 breast cancer proliferation by inducing AHR. Western blot and quantitative real time PCR (Q-PCR) analysis revealed that IGF-2 induced an approximately 2-fold increase (P < .001) in the expression of AHR and CCND1. Chromatin immunoprecipitation (ChIP), followed by Q-PCR indicated that IGF-2 promoted (P < .001) a 7-fold increase in AHR binding on the CCND1 promoter. AHR knockdown significantly (P < .001) inhibited IGF-2 stimulated increases in CCND1 mRNA and protein. AHR knockdown cells were less (P < .001) responsive to the proliferative effects of IGF-2 than control cells. Collectively, our findings have revealed a new regulatory mechanism by which IGF-2 induction of AHR promotes the expression of CCND1 and the proliferation of MCF-7 cells. This previously uncharacterized pathway could be important for the proliferation of IGF responsive cancer cells that also express AHR.

  12. Expression of insulin-like growth factor-1 receptor in keloid and hypertrophic scar

    PubMed Central

    Hu, Z-C; Tang, B; Guo, D; Zhang, J; Liang, Y-Y; Ma, D; Zhu, J-Y

    2014-01-01

    Background Keloid and hypertrophic scar (HS) are two pathological forms of excessive dermal fibrosis, which are due to aberrant wound-healing responses. Accumulating evidence suggests that aberrant activity of growth factors and increased numbers of growth factor receptors play an important role in the formation of pathological scar. Aim We examined the expression level of insulin-like growth factor-1 receptor (IGF-IR) in keloid, HS and normal skin. Methods IGF-IR expression was analyzed by immunohistochemistry, real-time PCR and western blotting on tissues and fibroblasts from 30 patients, comprising 10 patients with keloid and 20 with HS (10 with immature and 10 with mature HS), and from 10 age-matched and sex-matched healthy controls. Results Immunoreactivity to IGF-IR was found in dermal fibroblasts of keloid (90%), immature HS, (80%) and mature HS (30%), but not in normal skin. There was no statistically significant difference in immunoreactivity scores between keloid and immature HS, but there was a significant difference (P < 0.01) between mature and immature HS. Real-time PCR and western blot analysis confirmed that there was high expression of IGF-IR in keloid and immature HS fibroblasts, but not in mature HS or normal skin fibroblasts. IGF-IR was expressed in the overlying epidermis, and there was no significant difference between the groups. Conclusions IGF-IR may be involved in the pathogenesis of keloid and HS. Given that IGF-IR are predominantly expressed on dermal fibroblasts, targeting of IGF-IR in fibroblasts may be of benefit to prevent scarring. PMID:25154292

  13. Insulin-like growth factor-1 receptor acts as a growth regulator in synovial sarcoma.

    PubMed

    Friedrichs, N; Küchler, J; Endl, E; Koch, A; Czerwitzki, J; Wurst, P; Metzger, D; Schulte, J H; Holst, M I; Heukamp, L C; Larsson, O; Tanaka, S; Kawai, A; Wardelmann, E; Buettner, R; Pietsch, T; Hartmann, W

    2008-12-01

    Synovial sarcomas account for 5-10% of all soft tissue sarcomas and the majority of synovial sarcomas display characteristic t(X;18) translocations that result in enhanced transcription of the insulin-like growth factor-2 (IGF-2) gene. IGF-2 is an essential fetal mitogen involved in the pathogenesis of different tumours, leading to cellular proliferation and inhibition of apoptosis. Here we asked whether activation of IGF signalling is of functional importance in synovial sarcomas. We screened human synovial sarcomas for expression of IGF-2 and the phosphorylated IGF-1 receptor (IGF-1R), which mainly mediates the proliferative and anti-apoptotic effects of IGF-2. Since both the phosphatidylinositol 3'-kinase (PI3K)-AKT pathway and the MAPK signalling cascade are known to be involved in the transmission of IGF-1R signals, expression of phosphorylated (p)-AKT and p-p44/42 MAPK was additionally assessed. All tumours expressed IGF-2 and 78% showed an activated IGF-1R. All tumours were found to express p-AKT and 92% showed expression of activated p44/42 MAPK. To analyse the functional and potential therapeutic relevance of IGF-1R signalling, synovial sarcoma cell lines were treated with the IGF-1R inhibitor NVP-AEW541. Growth was impaired by the IGF-1R antagonist, which was consistently accompanied by a dose-dependent reduction of phosphorylation of AKT and p44/42 MAPK. Functionally, inhibition of the receptor led to increased apoptosis and diminished mitotic activity. Concurrent exposure of selected cells to NVP-AEW541 and conventional chemotherapeutic agents resulted in positive interactions. Finally, synovial sarcoma cell migration was found to be dependent on signals transmitted by the IGF-1R. In summary, our data show that the IGF-1R might represent a promising therapeutic target in synovial sarcomas.

  14. MicroRNA-494 inhibits proliferation and metastasis of osteosarcoma through repressing insulin receptor substrate-1

    PubMed Central

    Zhi, Xiaodong; Wu, Kai; Yu, Deshui; Wang, Yansong; Yu, Yang; Yan, Peng; Lv, Gang

    2016-01-01

    Despite microRNA-494 (miR-494) has a well-established role in many types of cancer; the biological function and potential mechanism of miR-494 in human osteosarcoma (OS) has not been elucidated. The aim of this study was therefore to investigate the role and underlying mechanism of miR-494 expression in osteosarcoma. Here, we found that miR-494 was significantly decreased in OS tissues and cell lines compared to the adjacent noncancerous bone tissues (P<0.01) and human normal osteoblast cells (NHOst) (P<0.05), respectively. Functional assays demonstrated that ectopic overexpression of miR-494 could significantly inhibit cell proliferation, colony formation, migration and invasion in vitro, as well as suppress tumor growth in nude mice model. Further integrative and functional studies suggested insulin receptor substrate 1 (IRS1) as a target gene of miR-494 in OS cells. IRS1 expression was upregulated, and inversely correlated with miR-494 expression in clinical OS tissues (r=-0.589, P=0.001). Moreover, downregulation of IRS1 had similar the inhibition effect on cell proliferation, colony formation, migration and invasion of miR-494 overexpression. Overexpresion of miR-494 obviously decreased AKT signal pathway activation. These findings suggested that miR-494 functioned as a tumor suppressor in OS, at least in part, by targeting IRS1. PMID:27648134

  15. MicroRNA-494 inhibits proliferation and metastasis of osteosarcoma through repressing insulin receptor substrate-1

    PubMed Central

    Zhi, Xiaodong; Wu, Kai; Yu, Deshui; Wang, Yansong; Yu, Yang; Yan, Peng; Lv, Gang

    2016-01-01

    Despite microRNA-494 (miR-494) has a well-established role in many types of cancer; the biological function and potential mechanism of miR-494 in human osteosarcoma (OS) has not been elucidated. The aim of this study was therefore to investigate the role and underlying mechanism of miR-494 expression in osteosarcoma. Here, we found that miR-494 was significantly decreased in OS tissues and cell lines compared to the adjacent noncancerous bone tissues (P<0.01) and human normal osteoblast cells (NHOst) (P<0.05), respectively. Functional assays demonstrated that ectopic overexpression of miR-494 could significantly inhibit cell proliferation, colony formation, migration and invasion in vitro, as well as suppress tumor growth in nude mice model. Further integrative and functional studies suggested insulin receptor substrate 1 (IRS1) as a target gene of miR-494 in OS cells. IRS1 expression was upregulated, and inversely correlated with miR-494 expression in clinical OS tissues (r=-0.589, P=0.001). Moreover, downregulation of IRS1 had similar the inhibition effect on cell proliferation, colony formation, migration and invasion of miR-494 overexpression. Overexpresion of miR-494 obviously decreased AKT signal pathway activation. These findings suggested that miR-494 functioned as a tumor suppressor in OS, at least in part, by targeting IRS1.

  16. MicroRNA-494 inhibits proliferation and metastasis of osteosarcoma through repressing insulin receptor substrate-1.

    PubMed

    Zhi, Xiaodong; Wu, Kai; Yu, Deshui; Wang, Yansong; Yu, Yang; Yan, Peng; Lv, Gang

    2016-01-01

    Despite microRNA-494 (miR-494) has a well-established role in many types of cancer; the biological function and potential mechanism of miR-494 in human osteosarcoma (OS) has not been elucidated. The aim of this study was therefore to investigate the role and underlying mechanism of miR-494 expression in osteosarcoma. Here, we found that miR-494 was significantly decreased in OS tissues and cell lines compared to the adjacent noncancerous bone tissues (P<0.01) and human normal osteoblast cells (NHOst) (P<0.05), respectively. Functional assays demonstrated that ectopic overexpression of miR-494 could significantly inhibit cell proliferation, colony formation, migration and invasion in vitro, as well as suppress tumor growth in nude mice model. Further integrative and functional studies suggested insulin receptor substrate 1 (IRS1) as a target gene of miR-494 in OS cells. IRS1 expression was upregulated, and inversely correlated with miR-494 expression in clinical OS tissues (r=-0.589, P=0.001). Moreover, downregulation of IRS1 had similar the inhibition effect on cell proliferation, colony formation, migration and invasion of miR-494 overexpression. Overexpresion of miR-494 obviously decreased AKT signal pathway activation. These findings suggested that miR-494 functioned as a tumor suppressor in OS, at least in part, by targeting IRS1. PMID:27648134

  17. Characterization of phorbol ester-stimulated serine phosphorylation of the human insulin receptor.

    PubMed Central

    Feener, E P; Shiba, T; Hu, K Q; Wilden, P A; White, M F; King, G L

    1994-01-01

    Phorbol 12-myristate 13-acetate (PMA)-stimulated phosphorylation of the human insulin receptor (IR) was characterized and compared in two cell types of different lineage: normal rat kidney epithelial (NRK) cells and Chinese hamster ovary (CHO) fibroblasts. PMA stimulation increased IR beta-subunit phosphorylation to 252 +/- 43 and 25- +/- 47% (+/- S.D.) of the unstimulated control in NRK and CHO cells respectively. Tryptic phosphopeptide analysis by Tricine/SDS/PAGE revealed significant differences in the PMA-stimulated phosphorylation of the IR in these two cell types. This phosphorylation of the IR was predominantly located in two tryptic phosphopeptides, and these phosphopeptides were absent in an IR mutant truncated by 43 C-terminal amino acids. The major PMA-stimulated tryptic phosphopeptide from in vivo-labelled CHO/IR was immunoprecipitated with an antibody against residues Ser1315 to Lys1329, and this precipitation was blocked with excess unlabelled peptide containing this sequence. Radiosequencing by manual Edman degradation revealed that this tryptic phosphopeptide was phosphorylated at Ser1315. This PMA-stimulated phosphorylation did not inhibit autophosphorylation of the IR in vivo. These results demonstrate that PMA-stimulated phosphorylation of the IR can exhibit significant differences when expressed in different cell types, and that Ser1315 is a major PMA-stimulated phosphorylation site on the human IR. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 PMID:7945263

  18. Targeting the Insulin-Like Growth Factor 1 Receptor in Ewing's Sarcoma: Reality and Expectations

    PubMed Central

    Olmos, David; Martins, Ana Sofia; Jones, Robin L.; Alam, Salma; Scurr, Michelle; Judson, Ian R.

    2011-01-01

    Ewing's sarcoma family of tumours comprises a group of very aggressive diseases that are potentially curable with multimodality treatment. Despite the undoubted success of current treatment, approximately 30% of patients will relapse and ultimately die of disease. The insulin-like growth factor 1 receptor (IGF-1R) has been implicated in the genesis, growth, proliferation, and the development of metastatic disease in Ewing's sarcoma. In addition, IGF1-R has been validated, both in vitro and in vivo, as a potential therapeutic target in Ewing's sarcoma. Phase I studies of IGF-1R monoclonal antibodies reported several radiological and clinical responses in Ewing's sarcoma patients, and initial reports of several Phase II studies suggest that about a fourth of the patients would benefit from IGF-1R monoclonal antibodies as single therapy, with approximately 10% of patients achieving objective responses. Furthermore, these therapies are well tolerated, and thus far severe toxicity has been rare. Other studies assessing IGF-1R monoclonal antibodies in combination with traditional cytotoxics or other targeted therapies are expected. Despite, the initial promising results, not all patients benefit from IGF-1R inhibition, and consequently, there is an urgent need for the identification of predictive markers of response. PMID:21647361

  19. Targeting the Insulin-like Growth Factor Receptor: Developing Biomarkers from Gene Expression Profiling

    PubMed Central

    Boone, David N.; Lee, Adrian V.

    2014-01-01

    Overwhelming evidence implicates insulin-like growth factor (IGF) signaling in the growth and survival of many types of human cancer cells. Numerous inhibitors of the IGF1 receptor (IGF1R) have been developed, and they displayed remarkable antineoplastic activity in preclinical models and promising success in early phase clinical trials. However, while responses have been observed in numerous cancer types, they have occurred in a minority of patients, and serious toxicities have been observed. Identifying patients likely to benefit from anti-IGF1R therapy requires further characterizing the role of IGF1 signaling in various stages of tumorigenesis in order to identify critical downstream factors that may be used as predictors of response, or to serve as novel therapeutic targets. Recent microarray analyses have begun to unravel expression “signatures” specific for IGF1 that correlate with poor breast cancer prognosis and with response to anti-IGF1R inhibitors. In this review we briefly discuss the history of the IGF1 family in neoplasia, how it is targeted, results from clinical trials, and the quest for biomarkers that will predict response to IGF1R-targeted therapy. PMID:22471706

  20. Protein kinase C activators selectively inhibit insulin-stimulated system A transport activity in skeletal muscle at a post-receptor level.

    PubMed Central

    Gumà, A; Camps, M; Palacín, M; Testar, X; Zorzano, A

    1990-01-01

    We have investigated the role of phorbol esters on different biological effects induced by insulin in muscle, such as activation of system A transport activity, glucose utilization and insulin receptor function. System A transport activity was measured by monitoring the uptake of the system A-specific analogue alpha-(methyl)aminoisobutyric acid (MeAIB), by intact rat extensor digitorum longus muscle. The addition of 12-O-tetradecanoylphorbol 13-acetate (TPA, 0.5 microM) for 60 or 180 min did not modify basal MeAIB uptake by muscle, suggesting that insulin signalling required to stimulate MeAIB transport does not involve protein kinase C activation. However, TPA added 30 min before insulin (100 nM) markedly inhibited insulin-stimulated MeAIB uptake. The addition of polymyxin B (0.1 mM) or H-7 (1 mM), protein kinase C inhibitors, alone or in combination with TPA leads to impairment of insulin-stimulated MeAIB uptake. This paradoxical pattern is incompatible with a unique action of Polymyxin B or H-7 on protein kinase C activity. Therefore these agents are not suitable tools with which to investigate whether a certain insulin effect is mediated by protein kinase C. TPA did not cause a generalized inhibition of insulin action. Thus both TPA and insulin increased 3-O-methylglucose uptake by muscle, and their effects were not additive. Furthermore, TPA did not modify insulin-stimulated lactate production by muscle. In keeping with this selective modification of insulin action, treatment of muscles with TPA did not modify insulin receptor binding or kinase activities. In conclusion, phorbol esters do not mimic insulin action on system A transport activity; however, they markedly inhibit insulin-stimulated amino acid transport, with no modification of insulin receptor function in rat skeletal muscle. It is suggested that protein kinase C activation causes a selective post-receptor modification on the biochemical pathway by which insulin activates system A amino acid

  1. Mechanisms of acetylcholine receptor loss in myasthenia gravis.

    PubMed Central

    Drachman, D B; Adams, R N; Stanley, E F; Pestronk, A

    1980-01-01

    The fundamental abnormality affecting the neuromuscular junctions of myasthenic patients is a reduction of available AChRs, due to an autoimmune attack directed against the receptors. Antibodies to AChR are present in most patients, and there is evidence that they have a predominant pathogenic role in the disease, aided by complement. The mechanism of antibody action involves acceleration of the rate of degradation of AChRs, attributable to cross-linking of the receptors. In addition, antibodies may block AChRs, and may participate in producing destructive changes, perhaps in conjunction with complement. The possibility that cell-mediated mechanisms may play a role in the autoimmune responses of some myasthenic patients remains to be explored. Although the target of the autoimmune attack in myasthenic patients is probably always the acetylcholine receptors, it is not yet clear which of these immune mechanisms are most important. It is likely that the relative role of each mechanism varies from patient to patient. One of the goals of future research will be to identify the relative importance of each of these mechanisms in the individual patient, and to tailor specific immunotherapeutic measures to the abnormalities found. PMID:6249894

  2. Free fatty acid receptor 1 (FFAR1/GPR40) signaling affects insulin secretion by enhancing mitochondrial respiration during palmitate exposure.

    PubMed

    Kristinsson, Hjalti; Bergsten, Peter; Sargsyan, Ernest

    2015-12-01

    Fatty acids affect insulin secretion via metabolism and FFAR1-mediated signaling. Recent reports indicate that these two pathways act synergistically. Still it remains unclear how they interrelate. Taking into account the key role of mitochondria in insulin secretion, we attempted to dissect the metabolic and FFAR1-mediated effects of fatty acids on mitochondrial function. One-hour culture of MIN6 cells with palmitate significantly enhanced mitochondrial respiration. Antagonism or silencing of FFAR1 prevented the palmitate-induced rise in respiration. On the other hand, in the absence of extracellular palmitate FFAR1 agonists caused a modest increase in respiration. Using an agonist of the M3 muscarinic acetylcholine receptor and PKC inhibitor we found that in the presence of the fatty acid mitochondrial respiration is regulated via Gαq protein-coupled receptor signaling. The increase in respiration in palmitate-treated cells was largely due to increased glucose utilization and oxidation. However, glucose utilization was not dependent on FFAR1 signaling. Collectively, these results indicate that mitochondrial respiration in palmitate-treated cells is enhanced via combined action of intracellular metabolism of the fatty acid and the Gαq-coupled FFAR1 signaling. Long-term palmitate exposure reduced ATP-coupling efficiency of mitochondria and deteriorated insulin secretion. The presence of the FFAR1 antagonist during culture did not improve ATP-coupling efficiency, however, it resulted in enhanced mitochondrial respiration and improved insulin secretion after culture. Taken together, our study demonstrates that during palmitate exposure, integrated actions of fatty acid metabolism and fatty acid-induced FFAR1 signaling on mitochondrial respiration underlie the synergistic action of the two pathways on insulin secretion.

  3. Nigella sativa Relieves the Altered Insulin Receptor Signaling in Streptozotocin-Induced Diabetic Rats Fed with a High-Fat Diet.

    PubMed

    Balbaa, Mahmoud; El-Zeftawy, Marwa; Ghareeb, Doaa; Taha, Nabil; Mandour, Abdel Wahab

    2016-01-01

    The black cumin (Nigella sativa) "NS" or the black seeds have many pharmacological activities such as antioxidant, anticarcinogenic, antihypertensive, and antidiabetic properties. In this work, streptozotocin-induced diabetic rats fed with a high-fat diet were treated daily with NS oil (NSO) in order to study the effect on the blood glucose, lipid profile, oxidative stress parameters, and the gene expression of some insulin receptor-induced signaling molecules. This treatment was combined also with some drugs (metformin and glimepiride) and the insulin receptor inhibitor I-OMe-AG538. The administration of NSO significantly induced the gene expression of insulin receptor compared to rats that did not receive NSO. Also, it upregulated the expression of insulin-like growth factor-1 and phosphoinositide-3 kinase, whereas the expression of ADAM-17 was downregulated. The expression of ADAM-17 is corroborated by the analysis of TIMP-3 content. In addition, the NSO significantly reduced blood glucose level, components of the lipid profile, oxidative stress parameters, serum insulin/insulin receptor ratio, and the tumor necrosis factor-α, confirming that NSO has an antidiabetic activity. Thus, the daily NSO treatment in our rat model indicates that NSO has a potential in the management of diabetes as well as improvement of insulin-induced signaling. PMID:27579151

  4. Nigella sativa Relieves the Altered Insulin Receptor Signaling in Streptozotocin-Induced Diabetic Rats Fed with a High-Fat Diet

    PubMed Central

    El-Zeftawy, Marwa; Taha, Nabil; Mandour, Abdel Wahab

    2016-01-01

    The black cumin (Nigella sativa) “NS” or the black seeds have many pharmacological activities such as antioxidant, anticarcinogenic, antihypertensive, and antidiabetic properties. In this work, streptozotocin-induced diabetic rats fed with a high-fat diet were treated daily with NS oil (NSO) in order to study the effect on the blood glucose, lipid profile, oxidative stress parameters, and the gene expression of some insulin receptor-induced signaling molecules. This treatment was combined also with some drugs (metformin and glimepiride) and the insulin receptor inhibitor I-OMe-AG538. The administration of NSO significantly induced the gene expression of insulin receptor compared to rats that did not receive NSO. Also, it upregulated the expression of insulin-like growth factor-1 and phosphoinositide-3 kinase, whereas the expression of ADAM-17 was downregulated. The expression of ADAM-17 is corroborated by the analysis of TIMP-3 content. In addition, the NSO significantly reduced blood glucose level, components of the lipid profile, oxidative stress parameters, serum insulin/insulin receptor ratio, and the tumor necrosis factor-α, confirming that NSO has an antidiabetic activity. Thus, the daily NSO treatment in our rat model indicates that NSO has a potential in the management of diabetes as well as improvement of insulin-induced signaling. PMID:27579151

  5. Metabolic syndrome and colorectal cancer: Is hyperinsulinemia/insulin receptor-mediated angiogenesis a critical process?☆

    PubMed Central

    Liu, Jane Jijun; Druta, Mihaela; Shibata, David; Coppola, Domenico; Boler, Ivette; Elahi, Abul; Reich, Richard R.; Siegel, Erin; Extermann, Martine

    2015-01-01

    Objective Components of metabolic syndrome (MS) have been individually linked to colorectal cancer risk and prognosis; however, an understanding of the dominant mechanisms is lacking. Materials and methods Twenty-one patients (10 MS; 11 non-MS) with resectable colorectal cancer were prospectively enrolled. Patients were classified for MS by the World Health Organization criteria and tested for circulating vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), insulin-like growth factor-1 (IGF-1), fasting insulin, and tumor expression of IGF-1 receptor (IGF-1R), insulin-receptor (IR) and receptor for advanced glycation end-products (RAGE). Circulating markers were re-tested 6 months after surgery. Results The MS group had significantly higher baseline and post-operative fasting insulin levels (p < 0.001 and 0.003). No differences were observed in circulating IL-6, VEGF, IGF-1 and free IGF-1. By immunohistochemistry (IHC), IGF-1R expression was significantly higher in tumor vs. normal tissues (p < 0.001) while IR expression showed no difference. Interestingly, 64% of tumors demonstrated high IR positivity in the vessels within or surrounding the tumor stroma, but not in the vessels away from the tumor. By reverse transcription polymerase chain reaction (RT-PCR), tumor IGF-1R over-expression (80%) was confirmed, but there was no difference between MS and non-MS patients. Tumor RAGE over-expression was found in 67% of patients and was equally distributed between the two groups. Conclusions Hyperinsulinemia was the only significant factor distinguishing patients with colorectal cancer who have MS. The preferential over-expression of IR in the peri-tumoral microvessels suggests that hyperinsulinemia might contribute to colorectal cancer growth by enhancing angiogenesis. PMID:24484717

  6. Clinical disorders associated with autoantibodies to the insulin receptor. Simulation by passive transfer of immunoglobulins to rats.

    PubMed Central

    Dons, R F; Havlik, R; Taylor, S I; Baird, K L; Chernick, S S; Gorden, P

    1983-01-01

    Patients with autoantibodies to the insulin receptor (Anti-R) may exhibit either fasting hypoglycemia or hyperglycemia and extreme insulin resistance. Occasionally, both these phenomena are observed in the same patient at different times in the clinical course. In an effort to understand what determines the patient's response to Anti-R, we developed an animal model of these clinical disorders by passive transfer of Anti-R IgG to rats. IgG fractions from the plasma of Anti-R patients and control subjects were prepared by affinity chromatography with staphylococcal protein A-Sepharose. Anti-R IgG, injected into fasting rats, induced severe and persistent hypoglycemia (plasma glucose 30-60 mg/dl). Rats injected with control IgG maintained a plasma glucose within the range of 75 (fasting) to 165 mg/dl (feeding). In comparison with the effects of insulin, the hypoglycemic response to Anti-R IgG had a slower onset (2-4 h) and lasted longer (8-24 h). Similar, dose-dependent hypoglycemic responses were observed in rats whether the Anti-R IgG was derived from an insulin-resistant or hypoglycemic patient. When Anti-R IgG was administered in sufficiently high doses for several days to fed rats, persistent hyperglycemia (plasma glucose 200-400 mg/dl) developed. Based on these in vivo and previous in vitro studies, we attribute the hypoglycemic response to an insulin-like effect of Anti-R, and the hyperglycemic response to a desensitization of host tissues to the effects of insulin, with more prolonged exposure to higher levels of Anti-R. PMID:6350362

  7. Impact of Oxidative Stress and Peroxisome Proliferator–Activated Receptor γ Coactivator-1α in Hepatic Insulin Resistance

    PubMed Central

    Kumashiro, Naoki; Tamura, Yoshifumi; Uchida, Toyoyoshi; Ogihara, Takeshi; Fujitani, Yoshio; Hirose, Takahisa; Mochizuki, Hideki; Kawamori, Ryuzo; Watada, Hirotaka

    2008-01-01

    OBJECTIVE—Recent studies identified accumulation of reactive oxygen species (ROS) as a common pathway causing insulin resistance. However, whether and how the reduction of ROS levels improves insulin resistance remains to be elucidated. The present study was designed to define this mechanism. RESEARCH DESIGN AND METHODS—We investigated the effect of overexpression of superoxide dismutase (SOD)1 in liver of obese diabetic model (db/db) mice by adenoviral injection. RESULTS—db/db mice had high ROS levels in liver. Overexpression of SOD1 in liver of db/db mice reduced hepatic ROS and blood glucose level. These changes were accompanied by improvement in insulin resistance and reduction of hepatic gene expression of phosphoenol-pyruvate carboxykinase and peroxisome proliferator–activated receptor γ coactivator-1α (PGC-1α), which is the main regulator of gluconeogenic genes. The inhibition of hepatic insulin resistance was accompanied by attenuation of phosphorylation of cAMP-responsive element-binding protein (CREB), which is a main regulator of PGC-1α expression, and attenuation of Jun NH2-terminal kinase (JNK) phosphorylation. Simultaneously, overexpression of SOD1 in db/db mice enhanced the inactivation of forkhead box class O1, another regulator of PGC-1α expression, without the changes of insulin-induced Akt phosphorylation in liver. In hepatocyte cell lines, ROS induced phosphorylation of JNK and CREB, and the latter, together with PGC-1α expression, was inhibited by a JNK inhibitor. CONCLUSIONS—Our results indicate that the reduction of ROS is a potential therapeutic target of liver insulin resistance, at least partly by the reduced expression of PGC-1α. PMID:18487450

  8. [Effect of chronic blockade of the opiodergic receptor on insulin resistance in a hyperandrogenic woman].

    PubMed

    Sir, T; López, G; Alba, F; Cipriano, A; Candía, M; Castillo, T; Devoto, L

    1994-04-01

    We report a woman with insulin resistance associated with hyperandrogenism and acanthosis nigricans (HAIR-AN syndrome) treated during 30 days with the prolonged action opioid antagonist Naltrexone. During its administration, decreases in basal blood glucose and serum insulin, insulin and glucose response to a glucose load and plasma testosterone were observed. These findings suggest that opioid activity could play a critical role in the physiopathology of hyperinsulinemia in hyperandrogenic women. PMID:7809540

  9. Structural and functional characterization of the human T lymphocyte receptor for insulin-like growth factor I in vitro.

    PubMed Central

    Tapson, V F; Boni-Schnetzler, M; Pilch, P F; Center, D M; Berman, J S

    1988-01-01

    Growth factor receptors for T lymphocytes, such as interleukin 2 and insulin, are present on activated but not resting T lymphocytes. We sought to determine if insulin-like growth factor I (IGF-I) could act as a growth factor for human T cells and to characterize its receptor on resting and activated cells. Recombinant IGF-I induced two separate functions. It was chemotactic for and increased incorporation of tritiated thymidine into both unactivated (resting) and mitogen-activated T cells. High-affinity 125I-IGF-I binding to human T cells was saturable with an apparent Kd of 1.2 +/- .6 X 10(-10) M for binding to activated T cells and 1.2 +/- .9 X 10(-10) for unactivated T cells. The calculated binding for activated cells was 330 +/- 90 and for resting cells 45 +/- 9 high-affinity receptor sites per cell. Affinity cross-linking of 125I-IGF-I to resting or activated T cells revealed a radioligand-receptor complex of 360,000 mol wt when analyzed by SDS-PAGE without reduction and complexes of 270,000 and 135,000 mol wt upon reduction; prior incubation with excess unlabeled IGF-I prevented formation of the 125I-IGF-I receptor complex. Our data suggest that both resting and activated T lymphocytes bear functional IGF-I receptors similar to those found in other tissues. These receptors may mediate T cell growth and chemotaxis. Images PMID:3262126

  10. Insulin resistance, polycystic ovary syndrome and metformin.

    PubMed

    Pugeat, M; Ducluzeau, P H

    1999-01-01

    Polycystic ovary syndrome (PCOS) is the most common disorder of ovarian function in premenopausal women. PCOS is characterised by chronic anovulation and androgen excess with clinical manifestation of irregular menstrual cycles, hirsutism and/or acne. Insulin resistance with resultant hyperinsulinaemia, irrespective of excess weight or frank obesity, has been reported in patients with PCOS, and, as insulin has a direct effect on ovarian androgen production in vitro, insulin resistance may play a crucial role in the physiopathology of PCOS. Although the molecular mechanism(s) of insulin resistance in PCOS is unclear, excessive insulin-independent serine phosphorylation of the beta subunit of the insulin receptor, as reported in some patients with PCOS, has been put forward as a new mechanism for insulin resistance. Insulin-sensitising agents have recently been investigated for their role in the short term treatment of insulin resistance in PCOS. Controlled studies have shown that metformin administration, by promoting bodyweight loss, can decrease fasting and stimulated plasma insulin levels. However, other studies have shown metformin 500 mg 3 times daily to decrease insulin secretion and to reduce ovarian production of 17alpha-hydroxyprogesterone with recovery of spontaneous or clomifene-induced ovulation, independently of weight loss. These findings suggest a new indication for metformin and present insulin-sensitising agents as a novel approach in the treatment of ovarian hyperandrogenism and abnormal ovulation in PCOS. They also suggest that long term administration of metformin might be helpful in treating insulin resistance, thus reducing risks of type 2 (non-insulin-dependent) diabetes and cardiovascular disease in these patients.

  11. Insulin-like Growth Factor-II (IGF-II) and IGF-II Analogs with Enhanced Insulin Receptor-a Binding Affinity Promote Neural Stem Cell Expansion*

    PubMed Central

    Ziegler, Amber N.; Chidambaram, Shravanthi; Forbes, Briony E.; Wood, Teresa L.; Levison, Steven W.

    2014-01-01

    The objective of this study was to employ genetically engineered IGF-II analogs to establish which receptor(s) mediate the stemness promoting actions of IGF-II on mouse subventricular zone neural precursors. Neural precursors from the subventricular zone were propagated in vitro in culture medium supplemented with IGF-II analogs. Cell growth and identity were analyzed using sphere generation and further analyzed by flow cytometry. F19A, an analog of IGF-II that does not bind the IGF-2R, stimulated an increase in the proportion of neural stem cells (NSCs) while decreasing the proportion of the later stage progenitors at a lower concentration than IGF-II. V43M, which binds to the IGF-2R with high affinity but which has low binding affinity to the IGF-1R and to the A isoform of the insulin receptor (IR-A) failed to promote NSC growth. The positive effects of F19A on NSC growth were unaltered by the addition of a functional blocking antibody to the IGF-1R. Altogether, these data lead to the conclusion that IGF-II promotes stemness of NSCs via the IR-A and not through activation of either the IGF-1R or the IGF-2R. PMID:24398690

  12. Immunohistochemical localization of transient receptor potential vanilloid type 1 and insulin receptor substrate 2 and their co-localization with liver-related neurons in the hypothalamus and brainstem

    PubMed Central

    Zsombok, Andrea; Gao, Hong; Miyata, Kayoko; Issa, Alexandra; Derbenev, Andrei V.

    2011-01-01

    The central nervous system plays an important role in the regulation of energy balance and glucose homeostasis mainly via controlling the autonomic output to the visceral organs. The autonomic output is regulated by hormones and nutrients to maintain adequate energy and glucose homeostasis. Insulin action is mediated via insulin receptors (IR) resulting in phosphorylation of insulin receptor substrates (IRS) inducing activation of downstream pathways. Furthermore, insulin enhances transient receptor potential vanilloid type 1 (TRPV1) mediated currents. Activation of the TRPV1 receptor increases excitatory neurotransmitter release in autonomic centers of the brain, thereby impacting energy and glucose homeostasis. The aim of this study is to determine co-expression of IRS2 and TRPV1 receptors in the paraventricular nucleus of the hypothalamus (PVN) and dorsal motor nucleus of the vagus (DMV) in the mouse brain as well as expression of IRS2 and TRPV1 receptors at liver-related preautonomic neurons pre-labeled with a trans-neural, viral tracer (PRV-152). The data indicate that IRS2 and TRPV1 receptors are present and co-express in the PVN and the DMV. A large portion (over 50%) of the liver-related preautonomic DMV and PVN neurons expresses IRS2. Moreover, the majority of liver-related DMV and PVN neurons also express TRPV1 receptors, suggesting that insulin and TRPV1 actions may affect liver-related preautonomic neurons. PMID:21620379

  13. Loss of striatal type 1 cannabinoid receptors is a key pathogenic factor in Huntington's disease.

    PubMed

    Blázquez, Cristina; Chiarlone, Anna; Sagredo, Onintza; Aguado, Tania; Pazos, M Ruth; Resel, Eva; Palazuelos, Javier; Julien, Boris; Salazar, María; Börner, Christine; Benito, Cristina; Carrasco, Carolina; Diez-Zaera, María; Paoletti, Paola; Díaz-Hernández, Miguel; Ruiz, Carolina; Sendtner, Michael; Lucas, José J; de Yébenes, Justo G; Marsicano, Giovanni; Monory, Krisztina; Lutz, Beat; Romero, Julián; Alberch, Jordi; Ginés, Silvia; Kraus, Jürgen; Fernández-Ruiz, Javier; Galve-Roperh, Ismael; Guzmán, Manuel

    2011-01-01

    Endocannabinoids act as neuromodulatory and neuroprotective cues by engaging type 1 cannabinoid receptors. These receptors are highly abundant in the basal ganglia and play a pivotal role in the control of motor behaviour. An early downregulation of type 1 cannabinoid receptors has been documented in the basal ganglia of patients with Huntington's disease and animal models. However, the pathophysiological impact of this loss of receptors in Huntington's disease is as yet unknown. Here, we generated a double-mutant mouse model that expresses human mutant huntingtin exon 1 in a type 1 cannabinoid receptor-null background, and found that receptor deletion aggravates the symptoms, neuropathology and molecular pathology of the disease. Moreover, pharmacological administration of the cannabinoid Δ(9)-tetrahydrocannabinol to mice expressing human mutant huntingtin exon 1 exerted a therapeutic effect and ameliorated those parameters. Experiments conducted in striatal cells show that the mutant huntingtin-dependent downregulation of the receptors involves the control of the type 1 cannabinoid receptor gene promoter by repressor element 1 silencing transcription factor and sensitizes cells to excitotoxic damage. We also provide in vitro and in vivo evidence that supports type 1 cannabinoid receptor control of striatal brain-derived neurotrophic factor expression and the decrease in brain-derived neurotrophic factor levels concomitant with type 1 cannabinoid receptor loss, which may contribute significantly to striatal damage in Huntington's disease. Altogether, these results support the notion that downregulation of type 1 cannabinoid receptors is a key pathogenic event in Huntington's disease, and suggest that activation of these receptors in patients with Huntington's disease may attenuate disease progression.

  14. Liver protein profiles in insulin receptor-knockout mice reveal novel molecules involved in the diabetes pathophysiology.

    PubMed

    Capuani, Barbara; Della-Morte, David; Donadel, Giulia; Caratelli, Sara; Bova, Luca; Pastore, Donatella; De Canio, Michele; D'Aguanno, Simona; Coppola, Andrea; Pacifici, Francesca; Arriga, Roberto; Bellia, Alfonso; Ferrelli, Francesca; Tesauro, Manfredi; Federici, Massimo; Neri, Anna; Bernardini, Sergio; Sbraccia, Paolo; Di Daniele, Nicola; Sconocchia, Giuseppe; Orlandi, Augusto; Urbani, Andrea; Lauro, Davide

    2015-05-01

    Liver has a principal role in glucose regulation and lipids homeostasis. It is under a complex control by substrates such as hormones, nutrients, and neuronal impulses. Insulin promotes glycogen synthesis, lipogenesis, and lipoprotein synthesis and inhibits gluconeogenesis, glycogenolysis, and VLDL secretion by modifying the expression and enzymatic activity of specific molecules. To understand the pathophysiological mechanisms leading to metabolic liver disease, we analyzed liver protein patterns expressed in a mouse model of diabetes by proteomic approaches. We used insulin receptor-knockout (IR(-/-)) and heterozygous (IR(+/-)) mice as a murine model of liver metabolic dysfunction associated with diabetic ketoacidosis and insulin resistance. We evaluated liver fatty acid levels by microscopic examination and protein expression profiles by orthogonal experimental strategies using protein 2-DE MALDI-TOF/TOF and peptic nLC-MS/MS shotgun profiling. Identified proteins were then loaded into Ingenuity Pathways Analysis to find possible molecular networks. Twenty-eight proteins identified by 2-DE analysis and 24 identified by nLC-MS/MS shotgun were differentially expressed among the three genotypes. Bioinformatic analysis revealed a central role of high-mobility group box 1/2 and huntigtin never reported before in association with metabolic and related liver disease. A different modulation of these proteins in both blood and hepatic tissue further suggests their role in these processes. These results provide new insight into pathophysiology of insulin resistance and hepatic steatosis and could be useful in identifying novel biomarkers to predict risk for diabetes and its complications.

  15. Insulin and IGF1 receptors are essential for XX and XY gonadal differentiation and adrenal development in mice.

    PubMed

    Pitetti, Jean-Luc; Calvel, Pierre; Romero, Yannick; Conne, Béatrice; Truong, Vy; Papaioannou, Marilena D; Schaad, Olivier; Docquier, Mylène; Herrera, Pedro Luis; Wilhelm, Dagmar; Nef, Serge

    2013-01-01

    Mouse sex determination provides an attractive model to study how regulatory genetic networks and signaling pathways control cell specification and cell fate decisions. This study characterizes in detail the essential role played by the insulin receptor (INSR) and the IGF type I receptor (IGF1R) in adrenogenital development and primary sex determination. Constitutive ablation of insulin/IGF signaling pathway led to reduced proliferation rate of somatic progenitor cells in both XX and XY gonads prior to sex determination together with the downregulation of hundreds of genes associated with the adrenal, testicular, and ovarian genetic programs. These findings indicate that prior to sex determination somatic progenitors in Insr;Igf1r mutant gonads are not lineage primed and thus incapable of upregulating/repressing the male and female genetic programs required for cell fate restriction. In consequence, embryos lacking functional insulin/IGF signaling exhibit (i) complete agenesis of the adrenal cortex, (ii) embryonic XY gonadal sex reversal, with a delay of Sry upregulation and the subsequent failure of the testicular genetic program, and (iii) a delay in ovarian differentiation so that Insr;Igf1r mutant gonads, irrespective of genetic sex, remained in an extended undifferentiated state, before the ovarian differentiation program ultimately is initiated at around E16.5.

  16. The aging brain. Changes in the neuronal insulin/insulin receptor signal transduction cascade trigger late-onset sporadic Alzheimer disease (SAD). A mini-review.

    PubMed

    Hoyer, Siegfried

    2002-07-01

    Aging of the brain has been demonstrated to be the main risk factor for late-onset sporadic AD what is in contrast to early-onset familial AD in which mutations predominate the pathology. Aging of the brain was found to be associated with a multitude of aberrancies from normal in morphological, cellular and molecular terms. Recent findings provide clear evidence that the function of the neuronal insulin/insulin receptor signal transduction cascade is of pivotal significance to maintain normal cerebral blood flow and oxidative energy metabolism, work of the endoplasmatic reticulum/Golgi apparatus and the cell cycle in terminally differentiated neurons no longer in the cell cycle. It has become evident that normal metabolism of both amyloid precursor protein and tau-protein is part of interactive processes controlled by the neuronal I/IR signal transduction cascade. In normal brain aging, the function of this cascade starts to fail compared to normal resulting in adverse effects in CBF/oxidative energy metabolism, work of the endoplasmatic reticulum/Golgi apparatus and cell cycle. The aberrancies may not be drastic, but multifold and permanently existing, inclusive the metabolism of APP and tau-protein. The amount of intraneuronally formed betaA4 may increase, and tau-protein may become hyperphosphorylated. These processes as a whole may increase the vulnerability of the aging brain and may facilitate the generation of late-onset sporadic AD. PMID:12111436

  17. Liver X Receptor (LXR) in yellow catfish Pelteobagrus fulvidraco: Molecular characterization, mRNA tissue expression and transcriptional regulation by insulin in vivo and in vitro.

    PubMed

    Pan, Ya-Xiong; Luo, Zhi; Zhuo, Mei-Qin; Hu, Wei; Wu, Kun; Shi, Xi; Xu, Yi-Huan

    2016-01-01

    Liver X Receptor (LXR) plays a pivotal role in metabolic regulation in mammals, but little is known about its function in fish. In this study, two lxra isoforms, namely lxra1 and lxra2, were isolated. Their molecular characterization, tissues distribution and transcriptional regulation by insulin in vivo and in vitro were determined. lxrα1 and lxrα2 cDNA covered 2775bp and 3093bp, encoding 446 and 515 amino acid residues, respectively. The protein sequence of yellow catfish lxra included characteristic feature of mammalian lxrs, including the DNA binding (DBD) (containing P-box), ligand binding (LBD) and activation function-2 (AF-2) domains, D-box, and D (hinge) region. Phylogenetic analysis revealed that yellow catfish lxra grouped with lxra of zebrafish but was distant from those of medaka and stickleback. lxrβ clades was absent in teleosts in phylogenetic tree, proving gene loss of lxrβ in teleosts during evolution. The two lxra isoforms (lxra1 and lxra2) mRNAs were ubiquitously expressed in 11 tested tissues. Compared to lxra2, lxra1 mRNA expression was predominant in all tested tissues. The expression of lxrα1 was the highest in testis, then in liver, and the lowest in other tissues. lxrα2 expression was the highest in liver, then in testis, and the lowest in ovary. Insulin significantly stimulated the mRNA expression of lxra1 in vitro and in vivo, while the expression of lxra2 remained unchanged after insulin treatment. The present study serves to increase our understanding into the function of lxra in fish. PMID:26342960

  18. Functional properties of an isolated. cap alpha beta. heterodimeric human placenta insulin-like growth factor 1 receptor complex

    SciTech Connect

    Feltz, S.M.; Swanson, M.L.; Wemmie, J.A.; Pessin, J.E.

    1988-05-03

    Treatment of human placenta membranes at pH 8.5 in the presence of 2.0 mM dithiothreitol (DTT) for 5 min, followed by the simultaneous removal of the DTT and pH adjustment of pH 7.6, resulted in the formation of a functional ..cap alpha beta.. heterodimeric insulin-like growth factor 1 (IGF-1) receptor complex from the native ..cap alpha../sub 2/..beta../sub 2/ heterotetrameric disulfide-linked state. The membrane-bound ..cap alpha beta.. heterodimeric complex displayed similar curvilinear /sup 125/I-IGF-1 equilibrium binding compared to the ..cap alpha../sub 2/..beta../sub 2/ heterotetrameric complex. /sup 125/I-IGF-1 binding to both the isolated ..cap alpha../sub 2/..beta../sub 2/ heterotetrameric and ..cap alpha beta.. heterodimeric complexes demonstrated a marked straightening of the Scatchard plots, compared to the placenta membrane-bound IGF-1 receptors, with a 2-fold increase in the high-affinity binding component. IGF-1 stimulation of IGF-1 receptor autophosphorylation indicated that the ligand-dependent activation of ..cap alpha beta.. heterodimeric protein kinase activity occurred concomitant with the reassociation into a covalent ..cap alpha../sub 2/..beta../sub 2/ heterotetrameric state. These data demonstrate that (i) a combination of alkaline pH and DTT treatment of human placenta membranes results in the formation of an ..cap alpha beta.. heterodimeric IGF-1 receptor complex, (ii) unlike the insulin receptor, high-affinity homogeneous IGF-1 binding occurs in both the ..cap alpha../sub 2/..beta../sub 2/ heterotetrameric and ..cap alpha beta.. heterodimeric complexes, and (iii) IGF-1-dependent autophosphorylation of the ..cap alpha beta.. heterodimeric IGF-1 receptor complex correlates wit an IGF-1 dependent covalent reassociation into an ..cap alpha../sub 2/..beta../sub 2/ heterotetrameric disulfide-linked state.

  19. Dietary approaches to stop hypertension influence on insulin receptor substrate-1gene expression: A randomized controlled clinical trial

    PubMed Central

    Kafeshani, Marzieh; Janghorbani, Mohsen; Salehi, Rasol; Kazemi, Mohammad; Entezari, Mohammad Hasan

    2015-01-01

    Background: Insulin receptor substrate (IRS) Type 1 is a main substrate for the insulin receptor, controls insulin signaling in skeletal muscle, adipose tissue, and the vascular, so it is an important candidate gene for insulin resistance (IR). We aimed to compare the effects of the Dietary Approaches to Stop Hypertension (DASH) and Usual Dietary Advices (UDA) on IRS1 gene expression in women at risk for cardiovascular disease. Materials and Methods: A randomized controlled clinical trial was performed in 44 women at risk for cardiovascular disease. Participants were randomly assigned to a UDA diet or the DASH diet. The DASH diet was rich in fruits, vegetables, whole grains, and low-fat dairy products and low in saturated fat, total fat, cholesterol, refined grains, and sweets, with a total of 2400 mg/day sodium. The UDA diet was a regular diet with healthy dietary advice. Gene expression was assessed by the real-time polymerase chain reaction at the first of study and after 12 weeks. Independent sample t-test and paired-samples t-test were used to compare means of all variables within and between two groups respectively. Results: IRS1 gene expression was increased in DASH group compared with UDA diet (P = 0.00). Weight and waist circumference decreased in DASH group significantly compared to the UDA group (P < 0.05) but the results between the two groups showed no significant difference. Conclusion: DASH diet increased IRS1 gene expression and probably has beneficial effects on IR risks. PMID:26759568

  20. Liquid fructose down-regulates liver insulin receptor substrate 2 and gluconeogenic enzymes by modifying nutrient sensing factors in rats.

    PubMed

    Rebollo, Alba; Roglans, Núria; Baena, Miguel; Padrosa, Anna; Sánchez, Rosa M; Merlos, Manuel; Alegret, Marta; Laguna, Juan C

    2014-02-01

    High consumption of fructose-sweetened beverages has been linked to a high prevalence of chronic metabolic diseases. We have previously shown that a short course of fructose supplementation as a liquid solution induces glucose intolerance in female rats. In the present work, we characterized the fructose-driven changes in the liver and the molecular pathways involved. To this end, female rats were supplemented or not with liquid fructose (10%, w/v) for 7 or 14 days. Glucose and pyruvate tolerance tests were performed, and the expression of genes related to insulin signaling, gluconeogenesis and nutrient sensing pathways was evaluated. Fructose-supplemented rats showed increased plasma glucose excursions in glucose and pyruvate tolerance tests and reduced hepatic expression of several genes related to insulin signaling, including insulin receptor substrate 2 (IRS-2). However, the expression of key gluconeogenic enzymes, glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, was reduced. These effects were caused by an inactivation of hepatic forkhead box O1 (FoxO1) due to an increase in its acetylation state driven by a reduced expression and activity of sirtuin 1 (SIRT1). Further contributing to FoxO1 inactivation, fructose consumption elevated liver expression of the spliced form of X-box-binding-protein-1 as a consequence of an increase in the activity of the mammalian target of rapamycin 1 and protein 38-mitogen activated protein kinase (p38-MAPK). Liquid fructose affects both insulin signaling (IRS-2 and FoxO1) and nutrient sensing pathways (p38-MAPK, mTOR and SIRT1), thus disrupting hepatic insulin signaling without increasing the expression of key gluconeogenic enzymes.

  1. Grb-IR: A SH2-Domain-Containing Protein that Binds to the Insulin Receptor and Inhibits Its Function

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Roth, Richard A.

    1995-10-01

    To identify potential signaling molecules involved in mediating insulin-induced biological responses, a yeast two-hybrid screen was performed with the cytoplasmic domain of the human insulin receptor (IR) as bait to trap high-affinity interacting proteins encoded by human liver or HeLa cDNA libraries. A SH2-domain-containing protein was identified that binds with high affinity in vitro to the autophosphorylated IR. The mRNA for this protein was found by Northern blot analyses to be highest in skeletal muscle and was also detected in fat by PCR. To study the role of this protein in insulin signaling, a full-length cDNA encoding this protein (called Grb-IR) was isolated and stably expressed in Chinese hamster ovary cells overexpressing the human IR. Insulin treatment of these cells resulted in the in situ formation of a complex of the IR and the 60-kDa Grb-IR. Although almost 75% of the Grb-IR protein was bound to the IR, it was only weakly tyrosine-phosphorylated. The formation of this complex appeared to inhibit the insulin-induced increase in tyrosine phosphorylation of two endogenous substrates, a 60-kDa GTPase-activating-protein-associated protein and, to a lesser extent, IR substrate 1. The subsequent association of this latter protein with phosphatidylinositol 3-kinase also appeared to be inhibited. These findings raise the possibility that Grb-IR is a SH2-domain-containing protein that directly complexes with the IR and serves to inhibit signaling or redirect the IR signaling pathway.

  2. A monoclonal anti-peptide antibody reacting with the insulin receptor beta-subunit. Characterization of the antibody and its epitope and use in immunoaffinity purification of intact receptors.

    PubMed Central

    Ganderton, R H; Stanley, K K; Field, C E; Coghlan, M P; Soos, M A; Siddle, K

    1992-01-01

    A mouse monoclonal antibody (CT-1) was prepared against the C-terminal peptide sequence of the human insulin receptor beta-subunit (KKNGRILTLPRSNPS). The antibody reacted with native human and rat insulin receptors in solution, whether or not insulin was bound and whether or not the receptor had undergone prior tyrosine autophosphorylation. The antibody also reacted specifically with the receptor beta-subunit on blots of SDS/polyacrylamide gels. Preincubation of soluble receptors with antibody increased the binding of 125I-insulin approx. 2-fold. The antibody did not affect insulin-stimulated autophosphorylation, but increased the basal autophosphorylation rate approx. 2-fold. The amino acid residues contributing to the epitope for CT-1 were defined by construction and screening of an epitope library. Oligonucleotides containing 23 random bases were synthesized and ligated into the vector pCL627, and the corresponding peptide sequences expressed as fusion proteins in Escherichia coli were screened by colony blotting. Reactive peptides were identified by sequencing the oligonucleotide inserts in plasmids purified from positive colonies. Six different positive sequences were found after 900,000 colonies had been screened, and the consensus epitope was identified as GRVLTLPRS. Phosphorylation of the threonine residue within this sequence (corresponding to the known phosphorylation site Thr-1348 in the insulin receptor) decreased the affinity of antibody binding approx. 100-fold, as measured by competition in an e.l.i.s.a. Antibody CT-1 was used for immunoaffinity isolation of insulin receptor from detergent-solubilized human placental or rat liver microsomal membranes. Highly purified receptor was obtained in 60% yield by binding to CT-1-Sepharose immunoadsorbent and specific elution with a solution of peptide corresponding to the known epitope. This approach to purification under very mild conditions may in principle be used with any protein for which an antibody is

  3. Expression of insulin-like factor 3 hormone-receptor system in the reproductive organs of male goats.

    PubMed

    Pitia, Ali Mohammed; Minagawa, Itaru; Uera, Naoto; Hamano, Koh-Ichi; Sugawara, Yasushi; Nagura, Yoshio; Hasegawa, Yoshihisa; Oyamada, Toshifumi; Sasada, Hiroshi; Kohsaka, Tetsuya

    2015-11-01

    Relaxin-like factor (RLF), generally known as insulin-like factor 3 (INSL3), is essential for testis descent during fetal development. However, its role in adult males is not fully understood. We investigate the function of INSL3 in male Saanen goats by identifying cell types expressing its receptor, relaxin/insulin-like family peptide receptor (RXFP)2 and by characterizing the developmental expression pattern of INSL3 and RXFP2 and the binding of INSL3 to target cells in the male reproductive system. A highly specific RXFP2 antibody that co-localizes with an anti-FLAG antibody in HEK-293 cells recognizes RXFP2-transcript-expressing cells in the testis. INSL3 and RXFP2 mRNA expression is upregulated in the testis, starting from puberty. INSL3 mRNA and protein expression has been detected in Leydig cells, whereas RXFP2 mRNA and protein localize to Leydig cells, to meiotic and post-meiotic germ cells and to the epithelium and smooth muscle of the cauda epididymis and vas deferens. INSL3 binds to all of these tissues and cell types, with the exception of Leydig cells, in a hormone-specific and saturable manner. These results provide evidence for a functional intra- and extra-testicular INSL3 ligand-receptor system in adult male goats.

  4. Expression of variant forms of insulin receptor substrate-1 identified in patients with noninsulin-dependent diabetes mellitus.

    PubMed

    Imai, Y; Philippe, N; Sesti, G; Accili, D; Taylor, S I

    1997-12-01

    Several polymorphisms have been identified in the amino acid sequence of human insulin receptor substrate-1 (IRS-1). Some of the variant sequences have been reported to be increased in prevalence among patients with noninsulin-dependent diabetes mellitus (NIDDM). This observation led to the hypothesis that these amino acid substitutions may impair the function of IRS-1, thereby causing the insulin resistance seen in patients with NIDDM. To address this question, we have designed studies to evaluate the effects of three variant sequences identified in our laboratory: Gly819-->Arg, Gly972-->Arg, and Arg1221-->Cys. We constructed four IRS-1 expression vectors for transfection in COS-7 cells: wild-type, single mutant (Gly819-->Arg), double mutant (Gly819-->Arg; Gly972-->Arg), and triple mutant (Gly819-->Arg; Gly972-->Arg; Arg1221-->Cys) IRS-1. The mutations did not alter the level of expression or the extent of insulin receptor-mediated tyrosine phosphorylation of recombinant IRS-1. Moreover, the mutations did not lead to a detectable impairment in the association of recombinant IRS-1 with important downstream effectors, including the p85 subunit of phosphatidylinositol 3-kinase and growth factor receptor-binding protein-2. We conclude that these amino acid substitutions do not appear to cause a major defect in the function of IRS-1, as judged by our assays. However, this type of assay probably lacks the sensitivity to detect subtle functional defects. In light of the suggestive associations observed in epidemiological studies, it is premature to totally discard the hypothesis that variant sequences of IRS-1 may contribute to the pathogenesis of NIDDM. Nevertheless, our studies cannot be interpreted as lending support to that hypothesis. PMID:9398740

  5. G(q/11) is involved in insulin-stimulated inositol phosphoglycan putative mediator generation in rat liver membranes: co-localization of G(q/11) with the insulin receptor in membrane vesicles.

    PubMed

    Sleight, S; Wilson, B A; Heimark, D B; Larner, J

    2002-07-12

    Insulin signaling to generate inositol phosphoglycans (IPGs) was demonstrated to occur via the participation of the heterotrimeric G-proteins G(q/11). IPGs were measured as two specific inositol markers, myo-inositol and chiro-inositol after strong acid hydrolysis. Insulin and Pasteurella multocida toxin (PMT) generated both myo-inositol and chiro-inositol IPGs in a dose-dependent manner. PMT has been shown to activate G(q) specifically. Insulin action was abrogated by pre-treatment with anti G(q/11) antibody. Western blotting demonstrated the enrichment of both insulin receptor beta subunit and G(q/11) in the liver membrane vesicles. Vesicles also contained clathrin, caveolin PLC beta 1 and PLC Delta. Immunogold staining revealed the co-localization of both insulin receptor beta subunit and G(q/11) in an approximate stochiometric ratio of 1:3. No vesicles were detected with either component alone. The present and considerable published data provide strong evidence for insulin signaling both via a tyrosine kinase cascade mechanism and via heterotrimeric G-protein interactions. PMID:12150987

  6. Loss of intestinal GATA4 prevents diet-induced obesity and promotes insulin sensitivity in mice

    PubMed Central

    Patankar, Jay V.; Chandak, Prakash G.; Obrowsky, Sascha; Pfeifer, Thomas; Diwoky, Clemens; Uellen, Andreas; Sattler, Wolfgang; Stollberger, Rudolf; Hoefler, Gerald; Heinemann, Akos; Battle, Michele; Duncan, Stephen; Kratky, Dagmar

    2011-01-01

    Transcriptional regulation of small intestinal gene expression controls plasma total cholesterol (TC) and triglyceride (TG) levels, which are major determinants of metabolic diseases. GATA4, a zinc finger domain transcription factor, is critical for jejunal identity, and intestinal GATA4 deficiency leads to a jejunoileal transition. Although intestinal GATA4 ablation is known to misregulate jejunal gene expression, its pathophysiological impact on various components of metabolic syndrome remains unknown. Here, we used intestine-specific GATA4 knockout (GATA4iKO) mice to dissect the contribution of GATA4 on obesity development. We challenged adult GATA4iKO mice and control littermates with a Western-type diet (WTD) for 20 wk. Our findings show that WTD-fed GATA4iKO mice are resistant to diet-induced obesity. Accordingly, plasma TG and TC levels are markedly decreased. Intestinal lipid absorption in GATA4iKO mice was strongly reduced, whereas luminal lipolysis was unaffected. GATA4iKO mice displayed a greater glucagon-like peptide-1 (GLP-1) release on normal chow and even after long-term challenge with WTD remained glucose sensitive. In summary, our findings show that the absence of intestinal GATA4 has a beneficial effect on decreasing intestinal lipid absorption causing resistance to hyperlipidemia and obesity. In addition, we show that increased GLP-1 release in GATA4iKO mice decreases the risk for development of insulin resistance. PMID:21177287

  7. Higher-Resolution Structure of the Human Insulin Receptor Ectodomain: Multi-Modal Inclusion of the Insert Domain.

    PubMed

    Croll, Tristan I; Smith, Brian J; Margetts, Mai B; Whittaker, Jonathan; Weiss, Michael A; Ward, Colin W; Lawrence, Michael C

    2016-03-01

    Insulin receptor (IR) signaling is critical to controlling nutrient uptake and metabolism. However, only a low-resolution (3.8 Å) structure currently exists for the IR ectodomain, with some segments ill-defined or unmodeled due to disorder. Here, we revise this structure using new diffraction data to 3.3 Å resolution that allow improved modeling of the N-linked glycans, the first and third fibronectin type III domains, and the insert domain. A novel haptic interactive molecular dynamics strategy was used to aid fitting to low-resolution electron density maps. The resulting model provides a foundation for investigation of structural transitions in IR upon ligand binding.

  8. Obesogenic memory can confer long-term increases in adipose tissue but not liver inflammation and insulin resistance after weight loss

    PubMed Central

    Schmitz, J.; Evers, N.; Awazawa, M.; Nicholls, H.T.; Brönneke, H.S.; Dietrich, A.; Mauer, J.; Blüher, M.; Brüning, J.C.

    2016-01-01

    Objective Obesity represents a major risk factor for the development of type 2 diabetes mellitus, atherosclerosis and certain cancer entities. Treatment of obesity is hindered by the long-term maintenance of initially reduced body weight, and it remains unclear whether all pathologies associated with obesity are fully reversible even upon successfully maintained weight loss. Methods We compared high fat diet-fed, weight reduced and lean mice in terms of body weight development, adipose tissue and liver insulin sensitivity as well as inflammatory gene expression. Moreover, we assessed similar parameters in a human cohort before and after bariatric surgery. Results Compared to lean animals, mice that demonstrated successful weight reduction showed increased weight gain following exposure to ad libitum control diet. However, pair-feeding weight-reduced mice with lean controls efficiently stabilized body weight, indicating that hyperphagia was the predominant cause for the observed weight regain. Additionally, whereas glucose tolerance improved rapidly after weight loss, systemic insulin resistance was retained and ameliorated only upon prolonged pair-feeding. Weight loss enhanced insulin action and resolved pro-inflammatory gene expression exclusively in the liver, whereas visceral adipose tissue displayed no significant improvement of metabolic and inflammatory parameters compared to obese mice. Similarly, bariatric surgery in humans (n = 55) resulted in massive weight reduction, improved hepatic inflammation and systemic glucose homeostasis, while adipose tissue inflammation remained unaffected and adipocyte-autonomous insulin action only exhibit minor improvements in a subgroup of patients (42%). Conclusions These results demonstrate that although sustained weight loss improves systemic glucose homeostasis, primarily through improved inflammation and insulin action in liver, a remarkable obesogenic memory can confer long-term increases in adipose tissue

  9. Chemokine-like receptor 1 deficiency does not affect the development of insulin resistance and nonalcoholic fatty liver disease in mice.

    PubMed

    Gruben, Nanda; Aparicio Vergara, Marcela; Kloosterhuis, Niels J; van der Molen, Henk; Stoelwinder, Stefan; Youssef, Sameh; de Bruin, Alain; Delsing, Dianne J; Kuivenhoven, Jan Albert; van de Sluis, Bart; Hofker, Marten H; Koonen, Debby P Y

    2014-01-01

    The adipokine chemerin and its receptor, chemokine-like receptor 1 (Cmklr1), are associated with insulin resistance and nonalcoholic fatty liver disease (NAFLD), which covers a broad spectrum of liver diseases, ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). It is possible that chemerin and/or Cmklr1 exert their effects on these disorders through inflammation, but so far the data have been controversial. To gain further insight into this matter, we studied the effect of whole-body Cmklr1 deficiency on insulin resistance and NAFLD. In view of the primary role of macrophages in hepatic inflammation, we also transplanted bone marrow from Cmklr1 knock-out (Cmklr1-/-) mice and wild type (WT) mice into low-density lipoprotein receptor knock-out (Ldlr-/-) mice, a mouse model for NASH. All mice were fed a high fat, high cholesterol diet containing 21% fat from milk butter and 0.2% cholesterol for 12 weeks. Insulin resistance was assessed by an oral glucose tolerance test, an insulin tolerance test, and by measurement of plasma glucose and insulin levels. Liver pathology was determined by measuring hepatic inflammation, fibrosis, lipid accumulation and the NAFLD activity score (NAS). Whole-body Cmklr1 deficiency did not affect body weight gain or food intake. In addition, we observed no differences between WT and Cmklr1-/- mice for hepatic inflammatory and fibrotic gene expression, immune cell infiltration, lipid accumulation or NAS. In line with this, we detected no differences in insulin resistance. In concordance with whole-body Cmklr1 deficiency, the absence of Cmklr1 in bone marrow-derived cells in Ldlr-/- mice did not affect their insulin resistance or liver pathology. Our results indicate that Cmklr1 is not involved in the pathogenesis of insulin resistance or NAFLD. Thus, we recommend that the associations reported between Cmklr1 and insulin resistance or NAFLD should be interpreted with caution.

  10. A novel unidirectional cross-talk from the insulin-like growth factor-I receptor to leptin receptor in human breast cancer cells.

    PubMed

    Ozbay, Tuba; Nahta, Rita

    2008-06-01

    Obesity is a major risk factor for the development and progression of breast cancer. Increased circulating levels of the obesity-associated hormones leptin and insulin-like growth factor-I (IGF-I) and overexpression of the leptin receptor (Ob-R) and IGF-I receptor (IGF-IR) have been detected in a majority of breast cancer cases and during obesity. Due to correlations between increased leptin, Ob-R, IGF-I, and IGF-IR in breast cancer, we hypothesized that molecular interactions may exist between these two signaling pathways. Coimmunoprecipitation and immunoblotting showed that IGF-IR and Ob-R interact in the breast cancer cell lines MDA-MB-231, MCF7, BT474, and SKBR3. Stimulation of cells with IGF-I promoted Ob-R phosphorylation, which was blocked by IGF-IR kinase inhibition. In addition, IGF-I activated downstream signaling molecules in the leptin receptor and IGF-IR pathways. In contrast to IGF-I, leptin did not induce phosphorylation of IGF-IR, indicating that receptor cross-signaling is unidirectional, occurring from IGF-IR to Ob-R. Our results show, for the first time, a novel interaction and cross-talk between the IGF-I and leptin receptors in human breast cancer cells.

  11. Multiple loss-of-function variants of taste receptors in modern humans.

    PubMed

    Fujikura, Kohei

    2015-01-01

    Despite recent advances in the knowledge of interindividual taste differences, the underlying genetic backgrounds have remained to be fully elucidated. Much of the taste variation among different mammalian species can be explained by pseudogenization of taste receptors. Here I investigated whether the most recent disruptions of taste receptor genes segregate with their intact forms in modern humans by analyzing 14 ethnically diverse populations. The results revealed an unprecedented prevalence of 25 segregating loss-of-function (LoF) taste receptor variants, identifying one of the most pronounced cases of functional population diversity in the human genome. LoF variant frequency in taste receptors (2.10%) was considerably higher than the overall LoF frequency in human genome (0.16%). In particular, molecular evolutionary rates of candidate sour (14.7%) and bitter (1.8%) receptors were far higher in humans than those of sweet (0.02%), salty (0.05%), and umami (0.17%) receptors compared with other carnivorous mammals, although not all of the taste receptors were identified. Many LoF variants are population-specific, some of which arose even after population differentiation, not before divergence of the modern and archaic human. I conclude that modern humans might have been losing some sour and bitter receptor genes because of high-frequency LoF variants. PMID:26307445

  12. Multiple loss-of-function variants of taste receptors in modern humans

    PubMed Central

    Fujikura, K.

    2015-01-01

    Despite recent advances in the knowledge of interindividual taste differences, the underlying genetic backgrounds have remained to be fully elucidated. Much of the taste variation among different mammalian species can be explained by pseudogenization of taste receptors. Here I investigated whether the most recent disruptions of taste receptor genes segregate with their intact forms in modern humans by analyzing 14 ethnically diverse populations. The results revealed an unprecedented prevalence of 25 segregating loss-of-function (LoF) taste receptor variants, identifying one of the most pronounced cases of functional population diversity in the human genome. LoF variant frequency in taste receptors (2.10%) was considerably higher than the overall LoF frequency in human genome (0.16%). In particular, molecular evolutionary rates of candidate sour (14.7%) and bitter (1.8%) receptors were far higher in humans than those of sweet (0.02%), salty (0.05%), and umami (0.17%) receptors compared with other carnivorous mammals, although not all of the taste receptors were identified. Many LoF variants are population-specific, some of which arose even after population differentiation, not before divergence of the modern and archaic human. I conclude that modern humans might have been losing some sour and bitter receptor genes because of high-frequency LoF variants. PMID:26307445

  13. Lower risk of hypoglycaemia and greater odds for weight loss with initiation of insulin detemir compared with insulin glargine in Turkish patients with type 2 diabetes mellitus: local results of a multinational observational study

    PubMed Central

    2014-01-01

    Background The purpose of this analysis is to evaluate the safety and effectiveness of insulin initiation with once-daily insulin detemir (IDet) or insulin glargine (IGlar) in real-life clinical practice in Turkish patients with type 2 diabetes mellitus (T2DM). Methods This was a 24-week multinational observational study of insulin initiation in patients with T2DM. Results The Turkish cohort (n = 2886) included 2395 patients treated with IDet and 491 with IGlar. The change in glycosylated haemoglobin (HbA1c) from the pre-insulin levels was -2.21% [95% confidence interval (CI) -2.32, -2.09] in the IDet group and -1.88% [95% CI -2.17, -1.59] in the IGlar group at the final visit. The incidence rate of minor hypoglycaemia increased in both groups from the pre-insulin to the final visit (+0.66 and +2.23 events per patient year in the IDet and IGlar groups, respectively). Weight change in the IDet group was -0.23 kg [95% CI -0.49, 0.02 kg], and +1.55 kg [95% CI 1.11, 2.00 kg] in the IGlar group. Regression analysis with adjustment for previously identified confounders (age, gender, duration of diabetes, body mass index, previous history of hypoglycaemia, microvascular disease, number and change in oral anti-diabetic drug therapy, HbA1c at baseline and insulin dose) identified an independent effect of insulin type (IDet versus IGlar) with a risk of at least one episode of hypoglycaemia (odds ratio (OR): 0.33 [95% CI 0.21, 0.52], p <0.0001), and weight loss ≥1 kg (OR: 1.75 [95% CI 1.18, 2.59], p = 0.005), but not on HbA1c (+0.05% [95% CI -0.15, 0.25%], p = 0.6). Conclusions Initiation of basal insulin analogues, IDet and IGlar, were associated with clinically significant glycaemic improvements. A lower risk of minor hypoglycaemia and greater odds of weight loss ≥1 kg was observed with IDet compared with IGlar. Trial registration NCT00825643 and NCT00740519 PMID:25048824

  14. Studies on the autophosphorylation of the insulin receptor from human placenta. Analysis of the sites phosphorylated by two-dimensional peptide mapping.

    PubMed Central

    Tavaré, J M; Denton, R M

    1988-01-01

    1. A partially purified preparation of human placental insulin receptors was incubated with [gamma-32P]ATP in the presence or absence of insulin. The 32P-labelled insulin-receptor beta-subunits were then isolated, cleaved with trypsin followed by protease V8 and the [32P]phosphopeptides generated were analysed by thin layer electrophoresis and chromatography. This approach revealed that insulin stimulates autophosphorylation of the insulin-receptor beta-subunit in vitro on at least seven tyrosine residues distributed among three distinct domains. 2. One domain (domain 2), containing tyrosine residues 1146, 1150 and 1151 was the most rapidly phosphorylated and could be recovered as mono-, di- and triphosphorylated peptides cleaved by trypsin at Arg-1143 and either Lys-1153 or Lys-1156. Multiple phosphorylation of this domain appears to partially inhibit the cleavage at Lys-1153 by trypsin. 3. In a second domain (domain 3) containing two phosphorylated tyrosine residues at positions 1316 and 1322 the tyrosines were phosphorylated more slowly than those in domain 2. This domain is close to the C-terminus of the beta-subunit polypeptide chain. 4. At least two further tyrosine residues appeared to be phosphorylated after those in domains 2 and 3. These residues probably residue within a domain lying in close proximity to the inner face of the plasma membrane containing tyrosines 953, 960 and 972, but conclusive evidence is still required. 5. The two-dimensional thin-layer analysis employed in this study to investigate insulin-receptor phosphorylation has several advantages over previous methods based on reverse-phase chromatography. It allows greater resolution of 32P-labelled tryptic peptides and, when coupled to radioautography, is considerably more sensitive. The approach can be readily adapted to study phosphorylation of the insulin receptor within intact cells. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. PMID:3166375

  15. Quasi-Steady-State Analysis based on Structural Modules and Timed Petri Net Predict System’s Dynamics: The Life Cycle of the Insulin Receptor

    PubMed Central

    Scheidel, Jennifer; Lindauer, Klaus; Ackermann, Jörg; Koch, Ina

    2015-01-01

    The insulin-dependent activation and recycling of the insulin receptor play an essential role in the regulation of the energy metabolism, leading to a special interest for pharmaceutical applications. Thus, the recycling of the insulin receptor has been intensively investigated, experimentally as well as theoretically. We developed a time-resolved, discrete model to describe stochastic dynamics and study the approximation of non-linear dynamics in the context of timed Petri nets. Additionally, using a graph-theoretical approach, we analyzed the structure of the regulatory system and demonstrated the close interrelation of structural network properties with the kinetic behavior. The transition invariants decomposed the model into overlapping subnetworks of various sizes, which represent basic functional modules. Moreover, we computed the quasi-steady states of these subnetworks and demonstrated that they are fundamental to understand the dynamic behavior of the system. The Petri net approach confirms the experimental results of insulin-stimulated degradation of the insulin receptor, which represents a common feature of insulin-resistant, hyperinsulinaemic states. PMID:26694479

  16. Quasi-Steady-State Analysis based on Structural Modules and Timed Petri Net Predict System's Dynamics: The Life Cycle of the Insulin Receptor.

    PubMed

    Scheidel, Jennifer; Lindauer, Klaus; Ackermann, Jörg; Koch, Ina

    2015-12-17

    The insulin-dependent activation and recycling of the insulin receptor play an essential role in the regulation of the energy metabolism, leading to a special interest for pharmaceutical applications. Thus, the recycling of the insulin receptor has been intensively investigated, experimentally as well as theoretically. We developed a time-resolved, discrete model to describe stochastic dynamics and study the approximation of non-linear dynamics in the context of timed Petri nets. Additionally, using a graph-theoretical approach, we analyzed the structure of the regulatory system and demonstrated the close interrelation of structural network properties with the kinetic behavior. The transition invariants decomposed the model into overlapping subnetworks of various sizes, which represent basic functional modules. Moreover, we computed the quasi-steady states of these subnetworks and demonstrated that they are fundamental to understand the dynamic behavior of the system. The Petri net approach confirms the experimental results of insulin-stimulated degradation of the insulin receptor, which represents a common feature of insulin-resistant, hyperinsulinaemic states.

  17. Quasi-Steady-State Analysis based on Structural Modules and Timed Petri Net Predict System's Dynamics: The Life Cycle of the Insulin Receptor.

    PubMed

    Scheidel, Jennifer; Lindauer, Klaus; Ackermann, Jörg; Koch, Ina

    2015-01-01

    The insulin-dependent activation and recycling of the insulin receptor play an essential role in the regulation of the energy metabolism, leading to a special interest for pharmaceutical applications. Thus, the recycling of the insulin receptor has been intensively investigated, experimentally as well as theoretically. We developed a time-resolved, discrete model to describe stochastic dynamics and study the approximation of non-linear dynamics in the context of timed Petri nets. Additionally, using a graph-theoretical approach, we analyzed the structure of the regulatory system and demonstrated the close interrelation of structural network properties with the kinetic behavior. The transition invariants decomposed the model into overlapping subnetworks of various sizes, which represent basic functional modules. Moreover, we computed the quasi-steady states of these subnetworks and demonstrated that they are fundamental to understand the dynamic behavior of the system. The Petri net approach confirms the experimental results of insulin-stimulated degradation of the insulin receptor, which represents a common feature of insulin-resistant, hyperinsulinaemic states. PMID:26694479

  18. A highly pleiotropic amino acid polymorphism in the Drosophila insulin receptor contributes to life-history adaptation

    PubMed Central

    Paaby, Annalise B.; Bergland, Alan O.; Behrman, Emily L.; Schmidt, Paul S.

    2016-01-01

    Finding the specific nucleotides that underlie adaptive variation is a major goal in evolutionary biology, but polygenic traits pose a challenge because the complex genotype–phenotype relationship can obscure the effects of individual alleles. However, natural selection working in large wild populations can shift allele frequencies and indicate functional regions of the genome. Previously, we showed that the two most common alleles of a complex amino acid insertion–deletion polymorphism in the Drosophila insulin receptor show independent, parallel clines in frequency across the North American and Australian continents. Here, we report that the cline is stable over at least a five-year period and that the polymorphism also demonstrates temporal shifts in allele frequency concurrent with seasonal change. We tested the alleles for effects on levels of insulin signaling, fecundity, development time, body size, stress tolerance, and life span. We find that the alleles are associated with predictable differences in these traits, consistent with patterns of Drosophila life-history variation across geography that likely reflect adaptation to the heterogeneous climatic environment. These results implicate insulin signaling as a major mediator of life-history adaptation in Drosophila, and suggest that life-history trade-offs can be explained by extensive pleiotropy at a single locus. PMID:25319083

  19. Comparative evaluation of the therapeutic effect of metformin monotherapy with metformin and acupuncture combined therapy on weight loss and insulin sensitivity in diabetic patients

    PubMed Central

    Firouzjaei, A; Li, G-C; Wang, N; Liu, W-X; Zhu, B-M

    2016-01-01

    Objective: Obesity induces insulin resistance (IR), the key etiologic defect of type 2 diabetes mellitus (T2DM). Therefore, an incidence of obesity-induced diabetes is expected to decrease if obesity is controlled. Although Metformin is currently one of the main treatment options for T2DM in obese patients, resulting in an average of 5% weight loss, adequate weight control in all patients cannot be achieved with Metformin alone. Thus, additional therapies with a weight loss effect, such as acupuncture, may improve the effectiveness of Metformin. Subjective: We designed this randomized clinical trial (RCT) to compare the effects of Metformin monotherapy with that of Metformin and acupuncture combined therapy on weight loss and insulin sensitivity among overweight/obese T2DM patients, to understand whether acupuncture plus Metformin is a better approach than Metformin only on treating diabetes. To understand whether acupuncture can be an insulin sensitizer and, if so, its therapeutic mechanism. Results: Our results show that Metformin and acupuncture combined therapy significantly improves body weight, body mass index (BMI), fasting blood sugar (FBS), fasting insulin (FINS), homeostasis model assessment (HOMA) index, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), leptin, adiponectin, glucagon-like peptide-1 (GLP-1), resistin, serotonin, free fatty acids (FFAs), triglyceride (TG), low-density lipoprotein cholesterol (LDLc), high-density lipoprotein cholesterol (HDLc) and ceramides. Conclusions: Consequently, Metformin and acupuncture combined therapy is more effective than Metformin only, proving that acupuncture is an insulin sensitizer and is able to improve insulin sensitivity possibly by reducing body weight and inflammation, while improving lipid metabolism and adipokines. As a result, electro-acupuncture (EA) might be useful in controlling the ongoing epidemics in obesity and T2DM. PMID:27136447

  20. Post-translational acquisition of ligand binding- and tyrosine kinase-domain function by the epidermal growth factor and insulin receptors.

    PubMed

    Lane, M D; Slieker, L J; Olson, T S; Martensen, T M

    1987-01-01

    The epidermal growth factor receptor (EGFR) and insulin receptor undergo slow post-translational modification by which they acquire hormone binding and tyrosine kinase (EGFR) function. The half-time for acquisition of EGF or insulin binding activity is 30-40 min and of tyrosine kinase activity (EGFR), is 10-15 min. Tunicamycin, an inhibitor of N-linked oligosaccharide addition, blocks acquisition of both EGF and insulin binding activity. With EGFR, activation precedes acquisition of resistance to endoglucosaminidase H (t1/2 approximately equal to 75 min), a medial Golgi event. Treatment of active high mannose receptor with endo H generates fully active aglyco-receptor; thus, core oligosaccharide addition is a prerequisite for activation, but not for EGF binding per se. EGFR is activated in and translocated from the endoplasmic reticulum (ER) slowly (t1/2 approximately equal to 75 min). Since translocation rate equals the rate for acquisition of endo H resistance, transit from the ER is rate limiting for EGFR maturation. Tunicamycin inhibits exit from the ER parallel to its effect on acquisition of binding activity. Insulin proreceptor, a 210 kDa high-mannose glycopolypeptide, acquires insulin binding function (t1/2 approximately equal to 45 min) then is proteolytically cleaved (t1/2 approximately equal to 3 hr) into subunits of the mature alpha 2 beta 2 receptor. Modification giving rise to insulin binding activity is due to a conformational change in the binding domain, since human autoimmune antibody recognizes only the active species, while rabbit polyclonal antibody recognizes all forms. Newly-translated EGF proreceptor lacks a functional tyrosine domain capable of autophosphorylation; 30-40 min after translation, while still in the ER, tyrosine kinase activity is acquired. Since the kinase domain is cytoplasmic, the receptor may become phosphorylated on tyrosine before reaching the plasma membrane. PMID:3305909

  1. Targeting the insulin-like growth factor-1 receptor to overcome bortezomib resistance in preclinical models of multiple myeloma.

    PubMed

    Kuhn, Deborah J; Berkova, Zuzana; Jones, Richard J; Woessner, Richard; Bjorklund, Chad C; Ma, Wencai; Davis, R Eric; Lin, Pei; Wang, Hua; Madden, Timothy L; Wei, Caimiao; Baladandayuthapani, Veerabhadran; Wang, Michael; Thomas, Sheeba K; Shah, Jatin J; Weber, Donna M; Orlowski, Robert Z

    2012-10-18

    Proteasome inhibition with bortezomib is a validated approach to the treatment of multiple myeloma, but drug resistance often emerges and limits its utility in the retreatment setting. To begin to identify some of the mechanisms involved, we developed bortezomib-resistant myeloma cell lines that, unlike previously reported models, showed no β5 subunit mutations. Instead, up-regulation of the insulin-like growth factor (IGF)-1 axis was identified, with increased autocrine and paracrine secretion of IGF-1, leading to increased activation of the IGF-1 receptor (IGF-1R). Exogenous IGF-1 reduced cellular sensitivity to bortezomib, whereas pharmacologic or small hairpin RNA-mediated IGF-1R suppression enhanced bortezomib sensitivity in cell lines and patient samples. In vitro studies with OSI-906, a clinically relevant dual IGF-1R and insulin receptor inhibitor, showed it acted synergistically with bortezomib, and potently resensitized bortezomib-resistant cell lines and patient samples to bortezomib. Importantly, OSI-906 in combination with bortezomib also overcame bortezomib resistance in an in vivo model of myeloma. Taken together, these data support the hypothesis that signaling through the IGF-1/IGF-1R axis contributes to acquired bortezomib resistance, and provide a rationale for combining bortezomib with IGF-1R inhibitors like OSI-906 to overcome or possibly prevent the emergence of bortezomib-refractory disease in the clinic. PMID:22932796

  2. Insulin-like growth factor-I receptor blockade reduces the invasiveness of gastrointestinal cancers via blocking production of matrilysin.

    PubMed

    Adachi, Yasushi; Li, Rong; Yamamoto, Hiroyuki; Min, Yongfen; Piao, Wenhua; Wang, Yu; Imsumran, Arisa; Li, Hua; Arimura, Yoshiaki; Lee, Choon-Taek; Imai, Kohzoh; Carbone, David P; Shinomura, Yasuhisa

    2009-08-01

    Insulin-like growth factor-I receptor (IGF-IR) signaling is required for carcinogenicity and proliferation of gastrointestinal (GI) cancers. We have previously shown significant therapeutic activity for recombinant adenoviruses expressing dominant-negative insulin-like growth factor-I receptor (IGF-IR/dn), including suppression of tumor invasion. In this study, we sought to evaluate the mechanism of inhibition of invasion and the relationship between IGF-IR and matrix metalloproteinase (MMP) activity in GI carcinomas. We analyzed the role of IGF-IR on invasion in three GI cancer cell lines, colorectal adenocarcinoma, HT29; pancreatic adenocarcinoma, BxPC3 and gastric adenocarcinoma, MKN45, using a modified Boyden chamber method and subcutaneous xenografts in nude mice. The impact of IGF-IR signaling on the expression of MMPs and the effects of blockade of matrilysin or IGF-IR on invasiveness were assessed using recombinant adenoviruses, a tyrosine kinase inhibitor NVP-AEW541 and antisense matrilysin. Invasive subcutaneous tumors expressed several MMPs. IGF-IR/dn reduced the expression of these MMPs but especially matrilysin (MMP-7). Insulin-like growth factor (IGF) stimulated secretion of matrilysin and IGF-IR/dn blocked IGF-mediated matrilysin induction in three GI cancers. Both IGF-IR/dn and inhibition of matrilysin reduced in vitro invasion to the same degree. NVP-AEW541 also reduced cancer cell invasion both in vitro and in murine xenograft tumors via suppression of matrilysin. Thus, blockade of IGF-IR is involved in the suppression of cancer cell invasion through downregulation of matrilysin. Strategies of targeting IGF-IR may have significant therapeutic utility to prevent invasion and progression of human GI carcinomas.

  3. Codon 972 polymorphism in the insulin receptor substrate-1 gene, obesity, and risk of noninsulin-dependent diabetes mellitus

    SciTech Connect

    Sigal, R.J.; Doria, A.; Warram, J.H.; Krolewski, A.S.

    1996-04-01

    Because of the role of insulin receptor substrate-1 in insulin action, the insulin receptor substrate-1 gene is a candidate gene for noninsulin-dependent diabetes mellitus (NIDDM). Modest associations between NIDDM and a GGG-AGG single base substitution (corresponding to a glycine-arginine amino acid substitution) in codon 972 of the gene have been found, but none reached statistical significance. To examine further how large a proportion of NIDDM cases could be caused by the mutation, we performed a stratified analysis combining the results from the 6 earlier studies and those from our panel of 192 unrelated NIDDM subjects and 104 healthy controls. In addition, we looked for a possibility that the codon 972 mutation plays a role only in the presence of certain conditions. Genomic DNA samples obtained from NIDDM cases and healthy controls were genotyped using a PCR-restriction fragment length polymorphism protocol modified for genomic DNA. The GGG{r_arrow}AGG substitution was found in 5.7% of the diabetic subjects (11 of 192) and 6.9% of the controls (7 of 104). The difference between groups was not statistically significant, and it was not different from the results of other studies. The Mantel-Haenszel summary odds ratio across all studies was 1.49 (P < 0.05; 95% confidence intervals, 1.01-2.2). This summary odds ratio is consistent with a small proportion of NIDDM cases ({approximately}3%) being caused by the mutation. Exploratory subgroup analyses on our panel suggested a clustering of NIDDM, the codon 972 mutation, and overweight, raising the hypothesis that the mutation may predispose to NIDDM only in the presence of excess body weight. 9 refs., 2 tabs.

  4. Abnormal glucose tolerance and insulin resistance in polycystic ovary syndrome amongst the Taiwanese population- not correlated with insulin receptor substrate-1 Gly972Arg/Ala513Pro polymorphism

    PubMed Central

    Lin, Ta-Chin; Yen, Jui-Mei; Gong, Kum-Bing; Kuo, Tsung-Cheng; Ku, Dong-Chi; Liang, Shu-Fen; Wu, Ming-Jiuan

    2006-01-01

    Background Insulin resistance and glucose dysmetabolism in polycystic ovary syndrome (PCOS) are related with the polymorphisms in the genes encoding the insulin receptor substrate (IRS) proteins, especially Gly972Arg/Ala513Pro polymorphism being reported to be associated with type-2 diabetes and PCOS. We intended to assess the prevalence of abnormal glucose tolerance (AGT) and insulin resistance in Taiwanese PCOS women. We also tried to assess whether the particular identity of Gly972Arg/Ala513Pro polymorphic alleles of the IRS-1 gene mutation can be used as an appropriate diagnostic indicator for PCOS. Methods We designed a prospective clinical study. Forty-seven Taiwanese Hoklo and Hakka women, diagnosed with PCOS were enrolled in this study as were forty-five healthy Hoklo and Hakka women as the control group. Insulin resistance was evaluated with fasting insulin, fasting glucose/insulin ratio, and homeostasis model assessment index for insulin resistance (HOMAIR). The genomic DNA of the subjects was amplified by PCR and digested by restriction fragmented length polymorphism (RFLP) with Bst N1 used for codon 972 and Dra III for codon 513. Results AGT was found in 46.8% of these PCOS patients and was significantly related to high insulin resistance rather than the low insulin resistance. Those patients with either insulin resistance or AGT comprised the majority of PCOS affected patients (AGT + fasting insulin ≥17: 83%, AGT + glucose/insulin ratio ≥6.5: 85.1%, AGT + HOMAIR ≥ 2: 87.2%, and AGT + HOMAIR ≥ 3.8: 72.3%). None of the tested samples revealed any polymorphism due to the absence of any Dra III recognition site or any Bst N1 recognition site in the amplified PCR fragment digested by restriction fragmented length polymorphism. Conclusion There is significantly high prevalence of AGT and insulin resistance in PCOS women, but Gly972Arg and Ala513Pro polymorphic alleles of IRS-1 are rare and are not associated with the elevated risk of PCOS amongst

  5. Serotonin 2B receptor: upregulated with age and hearing loss in mouse auditory system.

    PubMed

    Tadros, Sherif F; D'Souza, Mary; Zettel, Martha L; Zhu, XiaoXia; Lynch-Erhardt, Martha; Frisina, Robert D

    2007-07-01

    Serotonin (5-HT) is a monoamine neurotransmitter. Serotonin may modulate afferent fiber discharges in the cochlea, inferior colliculus (IC) and auditory cortex. Specific functions of serotonin are exerted upon its interaction with specific receptors; one of those receptors is the serotonin 2B receptor. The aim of this study was to investigate the differences in gene expression of serotonin 2B receptors with age in cochlea and IC, and the possible correlation between gene expression and functional hearing measurements in CBA/CaJ mice. Immunohistochemical examinations of protein expression of IC in mice of different age groups were also performed. Gene expression results showed that serotonin 2B receptor gene was upregulated with age in both cochlea and IC. A significant correlation between gene expression and functional hearing results was established. Immunohistochemical protein expression studies of IC showed more serotonin 2B receptor cells in old mice relative to young adult mice, particularly in the external nucleus. We conclude that serotonin 2B receptors may play a role in the pathogenesis of age-related hearing loss.

  6. Neuritin activates insulin receptor pathway to up-regulate Kv4.2-mediated transient outward K+ current in rat cerebellar granule neurons.

    PubMed

    Yao, Jin-Jing; Gao, Xiao-Fei; Chow, Chi-Wing; Zhan, Xiao-Qin; Hu, Chang-Long; Mei, Yan-Ai

    2012-11-30

    Neuritin is a new neurotrophic factor discovered in a screen to identify genes involved in activity-dependent synaptic plasticity. Neuritin also plays multiple roles in the process of neural development and synaptic plasticity. The receptors for binding neuritin and its downstream signaling effectors, however, remain unclear. Here, we report that neuritin specifically increases the densities of transient outward K(+) currents (I(A)) in rat cerebellar granule neurons (CGNs) in a time- and concentration-dependent manner. Neuritin-induced amplification of I(A) is mediated by increased mRNA and protein expression of Kv4.2, the main α-subunit of I(A). Exposure of CGNs to neuritin markedly induces phosphorylation of ERK (pERK), Akt (pAkt), and mammalian target of rapamycin (pmTOR). Neuritin-induced I(A) and increased expression of Kv4.2 are attenuated by ERK, Akt, or mTOR inhibitors. Unexpectedly, pharmacological blockade of insulin receptor, but not the insulin-like growth factor 1 receptor, abrogates the effect of neuritin on I(A) amplification and Kv4.2 induction. Indeed, neuritin activates downstream signaling effectors of the insulin receptor in CGNs and HeLa. Our data reveal, for the first time, an unanticipated role of the insulin receptor in previously unrecognized neuritin-mediated signaling. PMID:23066017

  7. Androgen receptors and experimental bone loss - an in vivo and in vitro study.

    PubMed

    Steffens, Joao Paulo; Coimbra, Leila Santana; Rossa, Carlos; Kantarci, Alpdogan; Van Dyke, Thomas E; Spolidorio, Luis Carlos

    2015-12-01

    Testosterone is a sex hormone that exhibits many functions beyond reproduction; one such function is the regulation of bone metabolism. The role played by androgen receptors during testosterone-mediated biological processes associated with bone metabolism is largely unknown. This study aims to use a periodontal disease model in vivo in order to assess the involvement of androgen receptors on microbial-induced inflammation and alveolar bone resorption in experimental bone loss. The impact of hormone deprivation was tested through both orchiectomy and chemical blockage of androgen receptor using flutamide (FLU). Additionally, the direct effect of exogenous testosterone, and the role of the androgen receptor, on osteoclastogenesis were investigated. Thirty male adult rats (n=10/group) were subjected to: 1-orchiectomy (OCX); 2-OCX sham surgery; or 3-OCX sham surgery plus FLU, four weeks before the induction of experimental bone loss. Ten OCX sham-operated rats were not subjected to experimental bone loss and served as healthy controls. The rats were euthanized two weeks later, so as to assess bone resorption and the production of inflammatory cytokines in the gingival tissue and serum. In order to study the in vitro impact of testosterone, osteoclasts were differentiated from RAW264.7 cells and testosterone was added at increasing concentrations. Both OCX and FLU increased bone resorption, but OCX alone was observed to increase osteoclast count. IL-1β production was increased only in the gingival tissue of OCX animals, whereas FLU-treated animals presented a decreased expression of IL-6. Testosterone reduced the osteoclast formation in a dose-dependent manner, and significantly impacted the production of TNF-α; FLU partially reversed these actions. When taken together, our results indicate that testosterone modulates experimental bone loss, and that this action is mediated, at least in part, via the androgen receptor.

  8. Massive losses of taste receptor genes in toothed and baleen whales.

    PubMed

    Feng, Ping; Zheng, Jinsong; Rossiter, Stephen J; Wang, Ding; Zhao, Huabin

    2014-05-06

    Taste receptor genes are functionally important in animals, with a surprising exception in the bottlenose dolphin, which shows extensive losses of sweet, umami, and bitter taste receptor genes. To examine the generality of taste gene loss, we examined seven toothed whales and five baleen whales and sequenced the complete repertoire of three sweet/umami (T1Rs) and ten bitter (T2Rs) taste receptor genes. We found all amplified T1Rs and T2Rs to be pseudogenes in all 12 whales, with a shared premature stop codon in 10 of the 13 genes, which demonstrated massive losses of taste receptor genes in the common ancestor of whales. Furthermore, we analyzed three genome sequences from two toothed whales and one baleen whale and found that the sour taste marker gene Pkd2l1 is a pseudogene, whereas the candidate salty taste receptor genes are intact and putatively functional. Additionally, we examined three genes that are responsible for taste signal transduction and found the relaxation of functional constraints on taste signaling pathways along the ancestral branch leading to whales. Together, our results strongly suggest extensive losses of sweet, umami, bitter, and sour tastes in whales, and the relaxation of taste function most likely arose in the common ancestor of whales between 36 and 53 Ma. Therefore, whales represent the first animal group to lack four of five primary tastes, probably driven by the marine environment with high concentration of sodium, the feeding behavior of swallowing prey whole, and the dietary switch from plants to meat in the whale ancestor.

  9. Clinical utility of insulin and insulin analogs

    PubMed Central

    Sanlioglu, Ahter D.; Altunbas, Hasan Ali; Balci, Mustafa Kemal; Griffith, Thomas S.; Sanlioglu, Salih

    2013-01-01

    Diabetes is a pandemic disease characterized by autoimmune, genetic and metabolic abnormalities. While insulin deficiency manifested as hyperglycemia is a common sequel of both Type-1 and Type-2 diabetes (T1DM and T2DM), it does not result from a single genetic defect—rather insulin deficiency results from the functional loss of pancreatic β cells due to multifactorial mechanisms. Since pancreatic β cells of patients with T1DM are destroyed by autoimmune reaction, these patients require daily insulin injections. Insulin resistance followed by β cell dysfunction and β cell loss is the characteristics of T2DM. Therefore, most patients with T2DM will require insulin treatment due to eventual loss of insulin secretion. Despite the evidence of early insulin treatment lowering macrovascular (coronary artery disease, peripheral arterial disease and stroke) and microvascular (diabetic nephropathy, neuropathy and retinopathy) complications of T2DM, controversy exists among physicians on how to initiate and intensify insulin therapy. The slow acting nature of regular human insulin makes its use ineffective in counteracting postprandial hyperglycemia. Instead, recombinant insulin analogs have been generated with a variable degree of specificity and action. Due to the metabolic variability among individuals, optimum blood glucose management is a formidable task to accomplish despite the presence of novel insulin analogs. In this article, we present a recent update on insulin analog structure and function with an overview of the evidence on the various insulin regimens clinically used to treat diabetes. PMID:23584214

  10. Effects of the antitumor drug OSI-906, a dual inhibitor of IGF-1 receptor and insulin receptor, on the glycemic control, β-cell functions, and β-cell proliferation in male mice.

    PubMed

    Shirakawa, Jun; Okuyama, Tomoko; Yoshida, Eiko; Shimizu, Mari; Horigome, Yuka; Tuno, Takayuki; Hayasaka, Moe; Abe, Shiori; Fuse, Masahiro; Togashi, Yu; Terauchi, Yasuo

    2014-06-01

    The IGF-1 receptor has become a therapeutic target for the treatment of cancer. The efficacy of OSI-906 (linstinib), a dual inhibitor of IGF-1 receptor and insulin receptor, for solid cancers has been examined in clinical trials. The effects of OSI-906, however, on the blood glucose levels and pancreatic β-cell functions have not yet been reported. We investigated the impact of OSI-906 on glycemic control, insulin secretion, β-cell mass, and β-cell proliferation in male mice. Oral administration of OSI-906 worsened glucose tolerance in a dose-dependent manner in the wild-type mice. OSI-906 at a dose equivalent to the clinical daily dose (7.5 mg/kg) transiently evoked glucose intolerance and hyperinsulinemia. Insulin receptor substrate (IRS)-2-deficient mice and mice with diet-induced obesity, both models of peripheral insulin resistance, exhibited more severe glucose intolerance after OSI-906 administration than glucokinase-haploinsufficient mice, a model of impaired insulin secretion. Phloridzin improved the hyperglycemia induced by OSI-906 in mice. In vitro, OSI-906 showed no effect on insulin secretion from isolated islets. After daily administration of OSI-906 for a week to mice, the β-cell mass and β-cell proliferation rate were significantly increased. The insulin signals in the β-cells were apparently unaffected in those mice. Taken together, the results suggest that OSI-906 could exacerbate diabetes, especially in patients with insulin resistance. On the other hand, the results suggest that the β-cell mass may expand in response to chemotherapy with this drug. PMID:24712877

  11. Effects of the antitumor drug OSI-906, a dual inhibitor of IGF-1 receptor and insulin receptor, on the glycemic control, β-cell functions, and β-cell proliferation in male mice.

    PubMed

    Shirakawa, Jun; Okuyama, Tomoko; Yoshida, Eiko; Shimizu, Mari; Horigome, Yuka; Tuno, Takayuki; Hayasaka, Moe; Abe, Shiori; Fuse, Masahiro; Togashi, Yu; Terauchi, Yasuo

    2014-06-01

    The IGF-1 receptor has become a therapeutic target for the treatment of cancer. The efficacy of OSI-906 (linstinib), a dual inhibitor of IGF-1 receptor and insulin receptor, for solid cancers has been examined in clinical trials. The effects of OSI-906, however, on the blood glucose levels and pancreatic β-cell functions have not yet been reported. We investigated the impact of OSI-906 on glycemic control, insulin secretion, β-cell mass, and β-cell proliferation in male mice. Oral administration of OSI-906 worsened glucose tolerance in a dose-dependent manner in the wild-type mice. OSI-906 at a dose equivalent to the clinical daily dose (7.5 mg/kg) transiently evoked glucose intolerance and hyperinsulinemia. Insulin receptor substrate (IRS)-2-deficient mice and mice with diet-induced obesity, both models of peripheral insulin resistance, exhibited more severe glucose intolerance after OSI-906 administration than glucokinase-haploinsufficient mice, a model of impaired insulin secretion. Phloridzin improved the hyperglycemia induced by OSI-906 in mice. In vitro, OSI-906 showed no effect on insulin secretion from isolated islets. After daily administration of OSI-906 for a week to mice, the β-cell mass and β-cell proliferation rate were significantly increased. The insulin signals in the β-cells were apparently unaffected in those mice. Taken together, the results suggest that OSI-906 could exacerbate diabetes, especially in patients with insulin resistance. On the other hand, the results suggest that the β-cell mass may expand in response to chemotherapy with this drug.

  12. Activation of the PI3K/Akt signal transduction pathway and increased levels of insulin receptor in protein repair-deficient mice.

    PubMed

    Farrar, Christine; Houser, Carolyn R; Clarke, Steven

    2005-02-01

    Protein L-isoaspartate (D-aspartate) O-methyltransferase is an enzyme that catalyses the repair of isoaspartyl damage in proteins. Mice lacking this enzyme (Pcmt1-/- mice) have a progressive increase in brain size compared with wild-type mice (Pcmt1+/+ mice), a phenotype that can be associated with alterations in the PI3K/Akt signal transduction pathway. Here we show that components of this pathway, including Akt, GSK3beta and PDK-1, are more highly phosphorylated in the brains of Pcmt1-/- mice, particularly in cells of the hippocampus, in comparison with Pcmt1+/+ mice. Examination of upstream elements of this pathway in the hippocampus revealed that Pcmt1-/- mice have increased activation of insulin-like growth factor-I (IGF-I) receptor and/or insulin receptor. Western blot analysis revealed an approximate 200% increase in insulin receptor protein levels and an approximate 50% increase in IGF-I receptor protein levels in the hippocampus of Pcmt1-/- mice. Higher levels of the insulin receptor protein were also found in other regions of the adult brain and in whole tissue extracts of brain, liver, heart and testes of both juvenile and adult Pcmt1-/- mice. There were no significant differences in plasma insulin levels for adult Pcmt1-/- mice during glucose tolerance tests. However, they did show higher peak levels of blood glucose, suggesting a mild impairment in glucose tolerance. We propose that Pcmt1-/- mice have altered regulation of the insulin pathway, possibly as a compensatory response to altered glucose uptake or metabolism or as an adaptive response to a general accumulation of isoaspartyl protein damage in the brain and other tissues.

  13. Nuclear receptors reverse McGarry's vicious cycle to insulin resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Several pathways and pathologies have been suggested as connections between obesity and diabetes, including inflammation of adipose and other tissues, toxic lipids, endoplasmic reticulum stress, and fatty liver. One specific proposal is that insulin resistance induces a vicious cycle in which hyperi...

  14. Ghrelin receptor regulates HFCS-induced adipose inflammation and insulin resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High fructose corn syrup (HFCS) is the most commonly used sweetener in the United States. Some studies show that HFCS consumption correlates with obesity and insulin resistance, while other studies are in disagreement. Owing to conflicting and insufficient scientific evidence, the safety of HFCS con...

  15. INS-1 cell glucose-stimulated insulin secretion is reduced by the downregulation of the 67 kDa laminin receptor.

    PubMed

    Sabra, Georges; Dubiel, Evan A; Kuehn, Carina; Khalfaoui, Taoufik; Beaulieu, Jean-François; Vermette, Patrick

    2015-12-01

    Understanding β cell-extracellular matrix (ECM) interactions can advance our knowledge of the mechanisms that control glucose homeostasis and improve culture methods used in islet transplantation for the treatment of diabetes. Laminin is the main constituent of the basement membrane and is involved in pancreatic β cell survival and function, even enhancing glucose-stimulated insulin secretion. Most of the studies on cell responses towards laminin have focused on integrin-mediated interactions, while much less attention has been paid on non-integrin receptors, such as the 67 kDa laminin receptor (67LR). The specificity of the receptor-ligand interaction through the adhesion of INS-1 cells (a rat insulinoma cell line) to CDPGYIGSR-, GRGDSPC- or CDPGYIGSR + GRGDSPC-covered surfaces was evaluated. Also, the effects of the 67LR knocking down over glucose-stimulated insulin secretion were investigated. Culture of the INS-1 cells on the bioactive surfaces was improved compared to the low-fouling carboxymethyl dextran (CMD) surfaces, while downregulation of the 67LR resulted in reduced cell adhesion to surfaces bearing the CDPGYIGSR peptide. Glucose-stimulated insulin secretion was hindered by downregulation of the 67LR, regardless of the biological motif available on the biomimetic surfaces on which the cells were cultured. This finding illustrates the importance of the 67LR in glucose-stimulated insulin secretion and points to a possible role of the 67LR in the mechanisms of insulin secretion.

  16. (Pro)renin receptor in skeletal muscle is involved in the development of insulin resistance associated with postinfarct heart failure in mice.

    PubMed

    Fukushima, Arata; Kinugawa, Shintaro; Takada, Shingo; Matsushima, Shouji; Sobirin, Mochamad Ali; Ono, Taisuke; Takahashi, Masashige; Suga, Tadashi; Homma, Tsuneaki; Masaki, Yoshihiro; Furihata, Takaaki; Kadoguchi, Tomoyasu; Yokota, Takashi; Okita, Koichi; Tsutsui, Hiroyuki

    2014-09-15

    We previously reported that insulin resistance was induced by the impairment of insulin signaling in the skeletal muscle from heart failure (HF) via NAD(P)H oxidase-dependent oxidative stress. (Pro)renin receptor [(P)RR] is involved in the activation of local renin-angiotensin system and subsequent oxidative stress. We thus examined whether (P)RR inhibitor, handle region peptide (HRP), could ameliorate insulin resistance in HF after myocardial infarction (MI) by improving oxidative stress and insulin signaling in the skeletal muscle. C57BL6J mice were divided into four groups: sham operated (Sham, n = 10), Sham treated with HRP (Sham+HRP, 0.1 mg·kg(-1)·day(-1), n = 10), MI operated (MI, n = 10), and MI treated with HRP (MI+HRP, 0.1 mg/kg/day, n = 10). After 4 wk, MI mice showed left ventricular dysfunction, which was not affected by HRP. (P)RR was upregulated in the skeletal muscle after MI (149% of sham, P < 0.05). The decrease in plasma glucose after insulin load was smaller in MI than in Sham (21 ± 2 vs. 44 ± 3%, P < 0.05), and was greater in MI+HRP (38 ± 2%, P < 0.05) than in MI. Insulin-stimulated serine phosphorylation of Akt and glucose transporter 4 translocation were decreased in the skeletal muscle from MI by 48 and 49% of Sham, both of which were ameliorated in MI+HRP. Superoxide production and NAD(P)H oxidase activities were increased in MI, which was inhibited in MI+HRP. HRP ameliorated insulin resistance associated with HF by improving insulin signaling via the inhibition of NAD(P)H oxidase-induced superoxide production in the skeletal muscle. The (P)RR pathway is involved in the development of insulin resistance, at least in part, via the impairment of insulin signaling in the skeletal muscle from HF.

  17. Exercise-Induced Weight Loss is More Effective than Dieting for Improving Adipokine Profile, Insulin Resistance, and Inflammation in Obese Men.

    PubMed

    Khoo, Joan; Dhamodaran, Subbiah; Chen, Dan-Dan; Yap, Siew-Yoon; Chen, Richard Yuan-Tud; Tian, Roger Ho-Heng

    2015-12-01

    The adipokines chemerin and adiponectin are reciprocally related in the pathogenesis of insulin resistance and inflammation in obesity. Weight loss increases adiponectin and reduces chemerin, insulin resistance, and inflammation, but the effects of caloric restriction and physical activity are difficult to separate in combined lifestyle modification. We compared effects of diet- or exercise-induced weight loss on chemerin, adiponectin, insulin resistance, and inflammation in obese men. Eighty abdominally obese Asian men (body mass index [BMI] ≥ 30 kg/m(2), waist circumference [WC] ≥ 90 cm, mean age 42.6 years) were randomized to reduce daily intake by ~500 kilocalories (n = 40) or perform moderate-intensity aerobic and resistance exercise (200-300 min/week) (n = 40) to increase energy expenditure by a similar amount for 24 weeks. The diet and exercise groups had similar decreases in energy deficit (-456 ± 338 vs. -455 ± 315 kcal/day), weight (-3.6 ± 3.4 vs. -3.3 ± 4.6 kg), and WC (-3.4 ± 4.4 vs. -3.6 ± 3.2 cm). The exercise group demonstrated greater reductions in fat mass (-3.9 ± 3.5 vs. -2.7 ± 5.3 kg), serum chemerin (-9.7 ± 11.1 vs. -4.3 ± 12.4 ng/ml), the inflammatory marker high-sensitivity C-reactive protein (-2.11 ± 3.13 vs. -1.49 ± 3.08 mg/L), and insulin resistance as measured by homeostatic model assessment (-2.45 ± 1.88 vs. -1.38 ± 3.77). Serum adiponectin increased only in the exercise group. Exercise-induced fat mass loss was more effective than dieting for improving adipokine profile, insulin resistance, and systemic inflammation in obese men, underscoring metabolic benefits of increased physical activity.

  18. The Amelioration of Hepatic Steatosis by Thyroid Hormone Receptor Agonists Is Insufficient to Restore Insulin Sensitivity in Ob/Ob Mice

    PubMed Central

    Cimini, Stephanie L.; Webb, Paul; Phillips, Kevin J.

    2015-01-01

    Thyroid hormone receptor (TR) agonists have been proposed as therapeutic agents to treat non-alcoholic fatty liver disease (NAFLD) and insulin resistance. We investigated the ability of the TR agonists GC-1 and KB2115 to reduce hepatic steatosis in ob/ob mice. Both compounds markedly reduced hepatic triglyceride levels and ameliorated hepatic steatosis. However, the amelioration of fatty liver was not sufficient to improve insulin sensitivity in these mice and reductions in hepatic triglycerides did not correlate with improvements in insulin sensitivity or glycemic control. Instead, the effects of TR activation on glycemia varied widely and were found to depend upon the time of treatment as well as the compound and dosage used. Lower doses of GC-1 were found to further impair glycemic control, while a higher dose of the same compound resulted in substantially improved glucose tolerance and insulin sensitivity, despite all doses being equally effective at reducing hepatic triglyceride levels. Improvements in glycemic control and insulin sensitivity were observed only in treatments that also increased body temperature, suggesting that the induction of thermogenesis may play a role in mediating these beneficial effects. These data illustrate that the relationship between TR activation and insulin sensitivity is complex and suggests that although TR agonists may have value in treating NAFLD, their effect on insulin sensitivity must also be considered. PMID:25849936

  19. Dual silencing of insulin-like growth factor-I receptor and epidermal growth factor receptor in colorectal cancer cells is associated with decreased proliferation and enhanced apoptosis.

    PubMed

    Kaulfuss, Silke; Burfeind, Peter; Gaedcke, Jochen; Scharf, Jens-Gerd

    2009-04-01

    Overexpression and activation of tyrosine kinase receptors are common features of colorectal cancer. Using the human colorectal cancer cell lines DLD-1 and Caco-2, we evaluated the role of the insulin-like growth factor-I (IGF-I) receptor (IGF-IR) and epidermal growth factor receptor (EGFR) in cellular functions of these cells. We used the small interfering RNA (siRNA) technology to specifically down-regulate IGF-IR and EGFR expression. Knockdown of IGF-IR and EGFR resulted in inhibition of cell proliferation of DLD-1 and Caco-2 cells. An increased rate of apoptosis was associated with siRNA-mediated silencing of IGF-IR and EGFR as assessed by activation of caspase-3/caspase-7. The combined knockdown of both EGFR and IGF-IR decreased cell proliferation and induced cell apoptosis more effectively than did silencing of either receptor alone. Comparable effects on cell proliferation and apoptosis were observed after single and combinational treatment of cells by the IGF-IR tyrosine kinase inhibitor NVP-AEW541 and/or the EGFR tyrosine kinase inhibitor erlotinib. Combined IGF-IR and EGFR silencing by either siRNAs or tyrosine kinase inhibitors diminished the phosphorylation of downstream signaling pathways AKT and extracellular signal-regulated kinase (ERK)-1/2 more effectively than did the single receptor knockdown. Single IGF-IR knockdown inhibited IGF-I-dependent phosphorylation of AKT but had no effect on IGF-I- or EGF-dependent phosphorylation of ERK1/2, indicating a role of EGFR in ligand-dependent ERK1/2 phosphorylation. The present data show that inhibition of the IGF-IR transduction cascade augments the antipoliferative and proapoptotic effects of EGFR inhibition in colorectal cancer cells. A clinical application of combination therapy targeting both EGFR and IGF-IR could be a promising therapeutic strategy.

  20. Green tea epigallocatechin gallate inhibits insulin stimulation of adipocyte glucose uptake via the 67-kilodalton laminin receptor and AMP-activated protein kinase pathways.

    PubMed

    Hsieh, Chi-Fen; Tsuei, Yi-Wei; Liu, Chi-Wei; Kao, Chung-Cheng; Shih, Li-Jane; Ho, Low-Tone; Wu, Liang-Yi; Wu, Chi-Peng; Tsai, Pei-Hua; Chang, Hsin-Huei; Ku, Hui-Chen; Kao, Yung-Hsi

    2010-10-01

    Insulin and (-)-epigallocatechin gallate (EGCG) are reported to regulate obesity and fat accumulation, respectively. This study investigated the pathways involved in EGCG modulation of insulin-stimulated glucose uptake in 3T3-L1 and C3H10T1/2 adipocytes. EGCG inhibited insulin stimulation of adipocyte glucose uptake in a dose- and time-dependent manner. The concentration of EGCG that decreased insulin-stimulated glucose uptake by 50-60% was approximately 5-10 µM for a period of 2 h. At 10 µM, EGCG and gallic acid were more effective than (-)-epicatechin, (-)-epigallocatechin, and (-)-epicatechin 3-gallate. We identified the EGCG receptor [also known as the 67-kDa laminin receptor (67LR)] in fat cells and extended the findings for this study to clarify whether EGCG-induced changes in insulin-stimulated glucose uptake in adipocytes could be mediated through the 67LR. Pretreatment of adipocytes with a 67LR antibody, but not normal rabbit immunoglobulin, prevented the effects of EGCG on insulin-increased glucose uptake. This suggests that the 67LR mediates the effect of EGCG on insulin-stimulated glucose uptake in adipocytes. Moreover, pretreatment with an AMP-activated protein kinase (AMPK) inhibitor, such as compound C, but not with a glutathione (GSH) activator, such as N-acetyl-L-cysteine (NAC), blocked the antiinsulin effect of EGCG on adipocyte glucose uptake. These data suggest that EGCG exerts its anti-insulin action on adipocyte glucose uptake via the AMPK, but not the GSH, pathway. The results of this study possibly support that EGCG mediates fat content.

  1. The insulin-like growth factor 1 receptor causes acquired resistance to erlotinib in lung cancer cells with the wild-type epidermal growth factor receptor.

    PubMed

    Suda, Kenichi; Mizuuchi, Hiroshi; Sato, Katsuaki; Takemoto, Toshiki; Iwasaki, Takuya; Mitsudomi, Tetsuya

    2014-08-15

    Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) therapy often provides a dramatic response in lung cancer patients with EGFR mutations. In addition, moderate clinical efficacy of the EGFR-TKI, erlotinib, has been shown in lung cancer patients with the wild-type EGFR. Numerous molecular mechanisms that cause acquired resistance to EGFR-TKIs have been identified in lung cancers with the EGFR mutations; however, few have been reported in lung cancers with the wild-type EGFR. We used H358 lung adenocarcinoma cells lacking EGFR mutations that showed modest sensitivity to erlotinib. The H358 cells acquired resistance to erlotinib via chronic exposure to the drug. The H358 erlotinib-resistant (ER) cells do not have a secondary EGFR mutation, neither MET gene amplification nor PTEN downregulation; these have been identified in lung cancers with the EGFR mutations. From comprehensive screening of receptor tyrosine kinase phosphorylation, we observed increased phosphorylation of insulin-like growth factor 1 receptor (IGF1R) in H358ER cells compared with parental H358 cells. H358ER cells responded to combined therapy with erlotinib and NVP-AEW541, an IGF1R-TKI. Our results indicate that IGF1R activation is a molecular mechanism that confers acquired resistance to erlotinib in lung cancers with the wild-type EGFR.

  2. Differential pathway coupling efficiency of the activated insulin receptor drives signaling selectivity by XMetA, an allosteric partial agonist antibody

    Technology Transfer Automated Retrieval System (TEKTRAN)

    XMetA, an anti-insulin receptor (IR) monoclonal antibody, is an allosteric partial agonist of the IR. We have previously reported that XMetA activates the “metabolic-biased” Akt kinase signaling pathway while having little or no effect on the “mitogenic” MAPK signaling pathwayof ERK 1/2. To inves...

  3. Ryanodine receptor type I and nicotinic acid adenine dinucleotide phosphate receptors mediate Ca2+ release from insulin-containing vesicles in living pancreatic beta-cells (MIN6).

    PubMed

    Mitchell, Kathryn J; Lai, F Anthony; Rutter, Guy A

    2003-03-28

    We have demonstrated recently (Mitchell, K. J., Pinton, P., Varadi, A., Tacchetti, C., Ainscow, E. K., Pozzan, T., Rizzuto, R., and Rutter, G. A. (2001) J. Cell Biol. 155, 41-51) that ryanodine receptors (RyR) are present on insulin-containing secretory vesicles. Here we show that pancreatic islets and derived beta-cell lines express type I and II, but not type III, RyRs. Purified by subcellular fractionation and membrane immuno-isolation, dense core secretory vesicles were found to possess a similar level of type I RyR immunoreactivity as Golgi/endoplasmic reticulum (ER) membranes but substantially less RyR II than the latter. Monitored in cells expressing appropriately targeted aequorins, dantrolene, an inhibitor of RyR I channels, elevated free Ca(2+) concentrations in the secretory vesicle compartment from 40.1 +/- 6.7 to 90.4 +/- 14.8 microm (n = 4, p < 0.01), while having no effect on ER Ca(2+) concentrations. Furthermore, nicotinic acid adenine dinucleotide phosphate (NAADP), a novel Ca(2+)-mobilizing agent, decreased dense core secretory vesicle but not ER free Ca(2+) concentrations in permeabilized MIN6 beta-cells, and flash photolysis of caged NAADP released Ca(2+) from a thapsigargin-insensitive Ca(2+) store in single MIN6 cells. Because dantrolene strongly inhibited glucose-stimulated insulin secretion (from 3.07 +/- 0.51-fold stimulation to no significant glucose effect; n = 3, p < 0.01), we conclude that RyR I-mediated Ca(2+)-induced Ca(2+) release from secretory vesicles, possibly potentiated by NAADP, is essential for the activation of insulin secretion.

  4. Increased oxidative stress and apoptosis in the hypothalamus of diabetic male mice in the insulin receptor substrate-2 knockout model

    PubMed Central

    Canelles, Sandra; Argente, Jesús; Barrios, Vicente

    2016-01-01

    ABSTRACT Insulin receptor substrate-2-deficient (IRS2−/−) mice are considered a good model to study the development of diabetes because IRS proteins mediate the pleiotropic effects of insulin-like growth factor-I (IGF-I) and insulin on metabolism, mitogenesis and cell survival. The hypothalamus might play a key role in the early onset of diabetes, owing to its involvement in the control of glucose homeostasis and energy balance. Because some inflammatory markers are elevated in the hypothalamus of diabetic IRS2−/− mice, our aim was to analyze whether the diabetes associated with the absence of IRS2 results in hypothalamic injury and to analyze the intracellular mechanisms involved. Only diabetic IRS2−/− mice showed increased cell death and activation of caspase-8 and -3 in the hypothalamus. Regulators of apoptosis such as FADD, Bcl-2, Bcl-xL and p53 were also increased, whereas p-IκB and c-FLIPL were decreased. This was accompanied by increased levels of Nox-4 and catalase, enzymes involved in oxidative stress. In summary, the hypothalamus of diabetic IRS2−/− mice showed an increase in oxidative stress and inflammatory markers that finally resulted in cell death via substantial activation of the extrinsic apoptotic pathway. Conversely, non-diabetic IRS2−/− mice did not show cell death in the hypothalamus, possibly owing to an increase in the levels of circulating IGF-I and in the enhanced hypothalamic IGF-IR phosphorylation that would lead to the stimulation of survival pathways. In conclusion, diabetes in IRS2-deficient male mice is associated with increased oxidative stress and apoptosis in the hypothalamus. PMID:27013528

  5. Increased oxidative stress and apoptosis in the hypothalamus of diabetic male mice in the insulin receptor substrate-2 knockout model.

    PubMed

    Baquedano, Eva; Burgos-Ramos, Emma; Canelles, Sandra; González-Rodríguez, Agueda; Chowen, Julie A; Argente, Jesús; Barrios, Vicente; Valverde, Angela M; Frago, Laura M

    2016-05-01

    Insulin receptor substrate-2-deficient (IRS2(-/-)) mice are considered a good model to study the development of diabetes because IRS proteins mediate the pleiotropic effects of insulin-like growth factor-I (IGF-I) and insulin on metabolism, mitogenesis and cell survival. The hypothalamus might play a key role in the early onset of diabetes, owing to its involvement in the control of glucose homeostasis and energy balance. Because some inflammatory markers are elevated in the hypothalamus of diabetic IRS2(-/-) mice, our aim was to analyze whether the diabetes associated with the absence of IRS2 results in hypothalamic injury and to analyze the intracellular mechanisms involved. Only diabetic IRS2(-/-) mice showed increased cell death and activation of caspase-8 and -3 in the hypothalamus. Regulators of apoptosis such as FADD, Bcl-2, Bcl-xL and p53 were also increased, whereas p-IκB and c-FLIPL were decreased. This was accompanied by increased levels of Nox-4 and catalase, enzymes involved in oxidative stress. In summary, the hypothalamus of diabetic IRS2(-/-) mice showed an increase in oxidative stress and inflammatory markers that finally resulted in cell death via substantial activation of the extrinsic apoptotic pathway. Conversely, non-diabetic IRS2(-/-) mice did not show cell death in the hypothalamus, possibly owing to an increase in the levels of circulating IGF-I and in the enhanced hypothalamic IGF-IR phosphorylation that would lead to the stimulation of survival pathways. In conclusion, diabetes in IRS2-deficient male mice is associated with increased oxidative stress and apoptosis in the hypothalamus. PMID:27013528

  6. Adiponectin and Adiponectin Receptor Gene Variants in Relation to Type 2 Diabetes and Insulin Resistance-Related Phenotypes

    PubMed Central

    Potapov, Viktor A.; Chistiakov, Dimitry A.; Dubinina, Anna; Shamkhalova, Minara S.; Shestakova, Marina V.; Nosikov, Valery V.

    2008-01-01

    BACKGROUND: Alterations in adiponectin-mediated pathways are known to be associated with glucose intolerance, insulin resistance (IR), obesity, and type 2 diabetes (T2D) mellitus. Genetic variations in adiponectin (ADIPOQ) and adiponectin 1 and 2 receptor (ADIPOR1 and ADIPOR2) could have effects on IR-related phenotypes and T2D. Here we examine whether the polymorphic markers rs2241766 (ADIPOQ), rs22753738 (ADIPOR1), rs11061971 and rs16928751 (both in ADIPOR2) are implicated in susceptibility to T2D in a Russian population. METHODS: The polymorphic markers were genotyped in 129 T2D patients, and 117 non-diabetic controls, by polymerase chain reaction (PCR) restriction fragment length polymorphism approach. In the subjects, biochemical characteristics including serum insulin, plasma glucose and serum lipids/lipoproteins were measured and compared for correlation with the genetic variations studied. RESULTS: Allele T of rs11061971 and allele A of rs16928751 showed association with higher risk of diabetes providing odds ratios (OR) of 2.05 (p = 0.0025) and 1.88 (p = 0.018), respectively. Haplotype A-G consisting of allele A of rs11061971 and allele G of rs16928751 was associated with reduced risk of T2D (OR = 0.59, pc = 0.0224). Compared to other variants, diabetic patients double homozygous for A/A of rs16928751 and G/G of rs16928751 had decreased homeostasis model assessment-insulin resistance (pc = 0.0375) and serum triglycerides (pc = 0.0285). CONCLUSIONS: The variants of ADIPOR2 confer susceptibility to T2D and are associated with some IR-related phenotypes in the Russian study population. PMID:18548168

  7. Increased oxidative stress and apoptosis in the hypothalamus of diabetic male mice in the insulin receptor substrate-2 knockout model.

    PubMed

    Baquedano, Eva; Burgos-Ramos, Emma; Canelles, Sandra; González-Rodríguez, Agueda; Chowen, Julie A; Argente, Jesús; Barrios, Vicente; Valverde, Angela M; Frago, Laura M

    2016-05-01

    Insulin receptor substrate-2-deficient (IRS2(-/-)) mice are considered a good model to study the development of diabetes because IRS proteins mediate the pleiotropic effects of insulin-like growth factor-I (IGF-I) and insulin on metabolism, mitogenesis and cell survival. The hypothalamus might play a key role in the early onset of diabetes, owing to its involvement in the control of glucose homeostasis and energy balance. Because some inflammatory markers are elevated in the hypothalamus of diabetic IRS2(-/-) mice, our aim was to analyze whether the diabetes associated with the absence of IRS2 results in hypothalamic injury and to analyze the intracellular mechanisms involved. Only diabetic IRS2(-/-) mice showed increased cell death and activation of caspase-8 and -3 in the hypothalamus. Regulators of apoptosis such as FADD, Bcl-2, Bcl-xL and p53 were also increased, whereas p-IκB and c-FLIPL were decreased. This was accompanied by increased levels of Nox-4 and catalase, enzymes involved in oxidative stress. In summary, the hypothalamus of diabetic IRS2(-/-) mice showed an increase in oxidative stress and inflammatory markers that finally resulted in cell death via substantial activation of the extrinsic apoptotic pathway. Conversely, non-diabetic IRS2(-/-) mice did not show cell death in the hypothalamus, possibly owing to an increase in the levels of circulating IGF-I and in the enhanced hypothalamic IGF-IR phosphorylation that would lead to the stimulation of survival pathways. In conclusion, diabetes in IRS2-deficient male mice is associated with increased oxidative stress and apoptosis in the hypothalamus.

  8. Moieties in antidiabetic drugs as a target of insulin receptors in association with common neurological disorders

    PubMed Central

    GUZMÁN, DAVID CALDERÓN; OLGUÍN, HUGO JUÁREZ; GARCÍA, ERNESTINA HERNÁNDEZ; HERRERA, MARIBEL ORTIZ; BRIZUELA, NORMA OSNAYA

    2016-01-01

    Insulin is a peptide that can be harmful with regards to neuroplasticity, neuroprotection and neuromodulation. Furthermore, the role of insulin highlights its relevance in the progress of diverse clinical disorders as well as in the mechanisms associated with certain pathogenesis and their evolution towards diabetes, obesity and neurodegenerative diseases. The precise molecular mechanisms by which these diseases are induced remain to be elucidated. The benefits in knowing/discovering these mechanisms in animal models and humans cannot be undermined. An in depth understanding of the principal risk factors leading to obesity and their management is vital in the implementation of early-life strategies of intervention and prevention, with a view to avoid adverse late-life outcomes. Therefore, the aim of the present study was to review their possible association with antidiabetic drugs. PMID:27073619

  9. Insulin-like growth factor 1 receptors in human breast tumour: localisation and quantification by histo-autoradiographic analysis.

    PubMed Central

    Jammes, H.; Peyrat, J. P.; Ban, E.; Vilain, M. O.; Haour, F.; Djiane, J.; Bonneterre, J.

    1992-01-01

    To assess the precise role of IGF1 in benign and malignant breast diseases, we analysed the tissular localisation, characterised, and quantified specific insulin-like growth factor 1 (IGF1) binding sites in these heterogenous tissues, using histo-autoradiographic analysis (HAA). The 125I-IGF1 binding was performed on frozen tissue sections and analysed using 3H Ultrofilm autoradiography coupled to computerised image analysis. Competitive binding experiments using unlabelled IGF1, IGF2 and insulin showed that the tissues exhibited typical type I IGF binding sites. This specificity was confirmed by the use of alpha IR-3 monoclonal antibody, as inhibitor of 125I-IGF1 binding. IGF1 binding sites were detected in 18 human primary breast cancers, 12 benign breast tumours and two normal breast tissues. Using HAA we found that the human breast carcinomas studied exhibit a specific and high binding capacity for 125I-IGF1 exclusively localised on the proliferative epithelial component. The 125I-IGF1 binding activity of benign breast tumours or normal breast tissue was significantly lower than in cancerous tissues. There was a significant correlation between IGF1-R concentrations detected with HAA and those detected with a classical biochemical method. Moreover, HAA could be useful in further detailing whether a tumour is IGF1-R positive or negative HAA appears to be a useful method for the detection of growth factor receptors, specially in small biopsy specimens. Images Figure 2 Figure 3 PMID:1323990

  10. The gut microbiota suppresses insulin-mediated fat accumulation via the short-chain fatty acid receptor GPR43

    PubMed Central

    Kimura, Ikuo; Ozawa, Kentaro; Inoue, Daisuke; Imamura, Takeshi; Kimura, Kumi; Maeda, Takeshi; Terasawa, Kazuya; Kashihara, Daiji; Hirano, Kanako; Tani, Taeko; Takahashi, Tomoyuki; Miyauchi, Satoshi; Shioi, Go; Inoue, Hiroshi; Tsujimoto, Gozoh

    2013-01-01

    The gut microbiota affects nutrient acquisition and energy regulation of the host, and can influence the development of obesity, insulin resistance, and diabetes. During feeding, gut microbes produce short-chain fatty acids, which are important energy sources for the host. Here we show that the short-chain fatty acid receptor GPR43 links the metabolic activity of the gut microbiota with host body energy homoeostasis. We demonstrate that GPR43-deficient mice are obese on a normal diet, whereas mice overexpressing GPR43 specifically in adipose tissue remain lean even when fed a high-fat diet. Raised under germ-free conditions or after treatment with antibiotics, both types of mice have a normal phenotype. We further show that short-chain fatty acid-mediated activation of GPR43 suppresses insulin signalling in adipocytes, which inhibits fat accumulation in adipose tissue and promotes the metabolism of unincorporated lipids and glucose in other tissues. These findings establish GPR43 as a sensor for excessive dietary energy, thereby controlling body energy utilization while maintaining metabolic homoeostasis. PMID:23652017

  11. Increased Soluble Leptin Receptor Levels in Morbidly Obese Patients With Insulin Resistance and Nonalcoholic Fatty Liver disease

    PubMed Central

    Medici, Valentina; Ali, Mohamed R.; Seo, Suk; Aoki, Christopher A.; Rossaro, Lorenzo; Kim, Kyoungmi; Fuller, Will D.; Vidovszky, Tamas J.; Smith, William; Jiang, Joy X.; Maganti, Kalyani; Havel, Peter J.; Kamboj, Amit; Ramsamooj, Rajendra; Török, Natalie J.

    2016-01-01

    The adipocyte hormone, leptin has been demonstrated to have profibrogenic actions in vitro and in animal models. However, no correlation was found between plasma leptin levels and fibrosis stage in humans. Thus, our aim was to study whether soluble leptin receptor (SLR) or free leptin index (FLI; calculated as the ratio of leptin to SLR), may correlate better with the features of metabolic syndrome and with the histological grade and stage of nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH). We studied a population (n = 104) of morbidly obese patients undergoing bariatric surgery. Data including BMI, type 2 diabetes mellitus, hypertension, and hyperlipidemia were obtained. Plasma fasting leptin and SLR, fasting glucose and insulin were measured, and homeostasis model of assessment insulin resistance (HOMAIR) index and FLI were calculated. All patients had intraoperative liver biopsies. Leptin levels correlated with the BMI. The multiple regression analysis indicated that increasing HOMA and decreasing FLI were predictors of steatosis in the liver (P < 0.0003). SLR levels were positively correlated with the presence of diabetes mellitus and the stage of fibrosis. In conclusion, increased SLR levels in morbidly obese patients with diabetes are correlated with the stage of liver fibrosis, and may reflect progressive liver disease. PMID:20448542

  12. Increased soluble leptin receptor levels in morbidly obese patients with insulin resistance and nonalcoholic fatty liver disease.

    PubMed

    Medici, Valentina; Ali, Mohamed R; Seo, Suk; Aoki, Christopher A; Rossaro, Lorenzo; Kim, Kyoungmi; Fuller, Will D; Vidovszky, Tamas J; Smith, William; Jiang, Joy X; Maganti, Kalyani; Havel, Peter J; Kamboj, Amit; Ramsamooj, Rajendra; Török, Natalie J

    2010-12-01

    The adipocyte hormone, leptin has been demonstrated to have profibrogenic actions in vitro and in animal models. However, no correlation was found between plasma leptin levels and fibrosis stage in humans. Thus, our aim was to study whether soluble leptin receptor (SLR) or free leptin index (FLI; calculated as the ratio of leptin to SLR), may correlate better with the features of metabolic syndrome and with the histological grade and stage of nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH). We studied a population (n = 104) of morbidly obese patients undergoing bariatric surgery. Data including BMI, type 2 diabetes mellitus, hypertension, and hyperlipidemia were obtained. Plasma fasting leptin and SLR, fasting glucose and insulin were measured, and homeostasis model of assessment insulin resistance (HOMA(IR)) index and FLI were calculated. All patients had intraoperative liver biopsies. Leptin levels correlated with the BMI. The multiple regression analysis indicated that increasing HOMA and decreasing FLI were predictors of steatosis in the liver (P < 0.0003). SLR levels were positively correlated with the presence of diabetes mellitus and the stage of fibrosis. In conclusion, increased SLR levels in morbidly obese patients with diabetes are correlated with the stage of liver fibrosis, and may reflect progressive liver disease. PMID:20448542

  13. The type 1 insulin-like growth factor receptor signalling system and targeted tyrosine kinase inhibition in cancer.

    PubMed

    Haisa, Minoru

    2013-04-01

    Type 1 insulin-like growth factor receptor (IGF1R) signalling plays a critical role in normal cell growth, and in cancer development and progression. IGF1R and the insulin-like growth factors 1 and 2 (IGF1 and IGF2) are involved in various aspects of the malignant phenotype, suggesting that IGF1R is a potential target for cancer therapy. IGF1R is particularly important in the establishment and maintenance of the transformed phenotype, in mediating proliferation, and for the survival of tumour cells with anchorage-independent growth. IGF1R also exerts antiapoptotic activity and has a substantial influence on the control of the cell and body size. This property enables transformed cells to form macroscopic tumours and to survive the process of detachment required for metastasis. Pharmaceutical companies are investigating molecules that target IGF1R, including specific low molecular weight tyrosine kinase inhibitors and monoclonal antibodies, both of which possess various advantages and display different activity profiles. This review article focuses on the preclinical and clinical development of low molecular weight IGF1R tyrosine kinase inhibitors. It is critical to pursue a thorough molecular analysis of the metabolic activity of IGF1R to avoid possible side-effects of its inhibition.

  14. The insulin-like growth factor 1 receptor (IGF1R) contributes to reduced size in dogs

    PubMed Central

    Hoopes, Barbara C.; Rimbault, Maud; Liebers, David; Ostrander, Elaine A.

    2012-01-01

    Domestic dog breeds have undergone intense selection for a variety of morphologic features, including size. Among small-dog breeds, defined as those averaging less than ~15 in. at the withers, there remains still considerable variation in body size. Yet essentially all such dogs are fixed for the same allele at the insulin-like growth factor 1 gene, which we and others previously found to be a size locus of large effect. In this study we sought to identify additional genes that contribute to tiny size in dogs using an association scan with the single nucleotide polymorphism (SNP) dataset CanMap, in which 915 purebred dogs were genotyped at 60,968 SNP markers. Our strongest association for tiny size (defined as breed-average height not more than 10 in. at the withers) was on canine chromosome 3 (p = 1.9 × 10−70). Fine mapping revealed a nonsynonymous SNP at chr3:44,706,389 that changes a highly conserved arginine at amino acid 204 to histidine in the insulin-like growth factor 1 receptor (IGF1R). This mutation is predicted to prevent formation of several hydrogen bonds within the cysteine-rich domain of the receptor’s ligand-binding extracellular subunit. Nine of 13 tiny dog breeds carry the mutation and many dogs are homozygous for it. This work underscores the central importance of the IGF1 pathway in controlling the tremendous size diversity of dogs. PMID:22903739

  15. Insulin enhances striatal dopamine release by activating cholinergic interneurons and thereby signals reward

    PubMed Central

    Stouffer, Melissa A.; Woods, Catherine A.; Patel, Jyoti C.; Lee, Christian R.; Witkovsky, Paul; Bao, Li; Machold, Robert P.; Jones, Kymry T.; de Vaca, Soledad Cabeza; Reith, Maarten E. A.; Carr, Kenneth D.; Rice, Margaret E.

    2015-01-01

    Insulin activates insulin receptors (InsRs) in the hypothalamus to signal satiety after a meal. However, the rising incidence of obesity, which results in chronically elevated insulin levels, implies that insulin may also act in brain centres that regulate motivation and reward. We report here that insulin can amplify action potential-dependent dopamine (DA) release in the nucleus accumbens (NAc) and caudate–putamen through an indirect mechanism that involves striatal cholinergic interneurons that express InsRs. Furthermore, two different chronic diet manipulations in rats, food restriction (FR) and an obesogenic (OB) diet, oppositely alter the sensitivity of striatal DA release to insulin, with enhanced responsiveness in FR, but loss of responsiveness in OB. Behavioural studies show that intact insulin levels in the NAc shell are necessary for acquisition of preference for the flavour of a paired glucose solution. Together, these data imply that striatal insulin signalling enhances DA release to influence food choices. PMID:26503322

  16. Insulin enhances striatal dopamine release by activating cholinergic interneurons and thereby signals reward.

    PubMed

    Stouffer, Melissa A; Woods, Catherine A; Patel, Jyoti C; Lee, Christian R; Witkovsky, Paul; Bao, Li; Machold, Robert P; Jones, Kymry T; de Vaca, Soledad Cabeza; Reith, Maarten E A; Carr, Kenneth D; Rice, Margaret E

    2015-01-01

    Insulin activates insulin receptors (InsRs) in the hypothalamus to signal satiety after a meal. However, the rising incidence of obesity, which results in chronically elevated insulin levels, implies that insulin may also act in brain centres that regulate motivation and reward. We report here that insulin can amplify action potential-dependent dopamine (DA) release in the nucleus accumbens (NAc) and caudate-putamen through an indirect mechanism that involves striatal cholinergic interneurons that express InsRs. Furthermore, two different chronic diet manipulations in rats, food restriction (FR) and an obesogenic (OB) diet, oppositely alter the sensitivity of striatal DA release to insulin, with enhanced responsiveness in FR, but loss of responsiveness in OB. Behavioural studies show that intact insulin levels in the NAc shell are necessary for acquisition of preference for the flavour of a paired glucose solution. Together, these data imply that striatal insulin signalling enhances DA release to influence food choices. PMID:26503322

  17. Insulin enhances striatal dopamine release by activating cholinergic interneurons and thereby signals reward.

    PubMed

    Stouffer, Melissa A; Woods, Catherine A; Patel, Jyoti C; Lee, Christian R; Witkovsky, Paul; Bao, Li; Machold, Robert P; Jones, Kymry T; de Vaca, Soledad Cabeza; Reith, Maarten E A; Carr, Kenneth D; Rice, Margaret E

    2015-10-27

    Insulin activates insulin receptors (InsRs) in the hypothalamus to signal satiety after a meal. However, the rising incidence of obesity, which results in chronically elevated insulin levels, implies that insulin may also act in brain centres that regulate motivation and reward. We report here that insulin can amplify action potential-dependent dopamine (DA) release in the nucleus accumbens (NAc) and caudate-putamen through an indirect mechanism that involves striatal cholinergic interneurons that express InsRs. Furthermore, two different chronic diet manipulations in rats, food restriction (FR) and an obesogenic (OB) diet, oppositely alter the sensitivity of striatal DA release to insulin, with enhanced responsiveness in FR, but loss of responsiveness in OB. Behavioural studies show that intact insulin levels in the NAc shell are necessary for acquisition of preference for the flavour of a paired glucose solution. Together, these data imply that striatal insulin signalling enhances DA release to influence food choices.

  18. C. elegans maximum velocity correlates with healthspan and is maintained in worms with an insulin receptor mutation.

    PubMed

    Hahm, Jeong-Hoon; Kim, Sunhee; DiLoreto, Race; Shi, Cheng; Lee, Seung-Jae V; Murphy, Coleen T; Nam, Hong Gil

    2015-01-01

    Ageing is marked by physical decline. Caenorhabditis elegans is a valuable model for identifying genetic regulatory mechanisms of ageing and longevity. Here we report a simple method to assess C. elegans' maximum physical ability based on the worms' maximum movement velocity. We show maximum velocity declines with age, correlates well with longevity, accurately reports movement ability and, if measured in mid-adulthood, is predictive of maximal lifespan. Contrary to recent findings, we observe that maximum velocity of worm with mutations in daf-2(e1370) insulin/IGF-1 signalling scales with lifespan. Because of increased odorant receptor expression, daf-2(e1370) mutants prefer food over exploration, causing previous on-food motility assays to underestimate movement ability and, thus, worm health. Finally, a disease-burden analysis of published data reveals that the daf-2(e1370) mutation improves quality of life, and therefore combines lifespan extension with various signs of an increased healthspan. PMID:26586186

  19. Loss of Dopamine D2 Receptors Increases Parvalbumin-Positive Interneurons in the Anterior Cingulate Cortex

    PubMed Central

    2015-01-01

    Disruption to dopamine homeostasis during brain development has been implicated in a variety of neuropsychiatric disorders, including depression and schizophrenia. Inappropriate expression or activity of GABAergic interneurons are common features of many of these disorders. We discovered a persistent upregulation of GAD67+ and parvalbumin+ neurons within the anterior cingulate cortex of dopamine D2 receptor knockout mice, while other GABAergic interneuron markers were unaffected. Interneuron distribution and number were not altered in the striatum or in the dopamine-poor somatosensory cortex. The changes were already present by postnatal day 14, indicating a developmental etiology. D2eGFP BAC transgenic mice demonstrated the presence of D2 receptor expression within a subset of parvalbumin-expressing cortical interneurons, suggesting the possibility of a direct cellular mechanism through which D2 receptor stimulation regulates interneuron differentiation or survival. D2 receptor knockout mice also exhibited decreased depressive-like behavior compared with wild-type controls in the tail suspension test. These data indicate that dopamine signaling modulates interneuron number and emotional behavior and that developmental D2 receptor loss or blockade could reveal a potential mechanism for the prodromal basis of neuropsychiatric disorders. PMID:25393953

  20. Variant in the 5' untranslated region of insulin-like growth factor 1 receptor is associated with susceptibility to mastitis in cattle.

    PubMed

    Sugimoto, Mayumi; Sugimoto, Yoshikazu

    2012-09-01

    Mastitis is a common infectious disease of the mammary gland and generates large losses in the dairy industry. By means of positional cloning and functional analysis techniques, we here show that insulin-like growth factor 1 receptor (IGF1R) can possibly mediate susceptibility to mastitis through autophagy. Scanning the whole genome of cows (Bos taurus) that were susceptible or resistant to mastitis in the half-sib families revealed that susceptible cows had a relatively long stretch of cytosine residues (C stretch) in the 5' untranslated region of IGF1R. The forebrain embryonic zinc finger-like (FEZL) transcription factor, which was previously identified as a factor controlling mastitis resistance in the same half-sib families, bound the C stretch of IGF1R. The susceptible type of FEZL with a glycine stretch containing 13 glycines (13G) and the longer C stretch of IGF1R together enhanced expression of IGF1R. Enhancing IGF1R inhibited autophagy in response to Streptococcus agalactiae invasion of mammary epithelial cells, whereas treatment with rapamycin, a known inducer of autophagy, rescued it. Cows carrying the variant combination of 13GFEZL might be more susceptible to mastitis as the result of impaired autophagy. Our results suggest that IGF1R could control innate immunity in mammals and serve as a potential tool for preventing mastitis.

  1. Variant in the 5' untranslated region of insulin-like growth factor 1 receptor is associated with susceptibility to mastitis in cattle.

    PubMed

    Sugimoto, Mayumi; Sugimoto, Yoshikazu

    2012-09-01

    Mastitis is a common infectious disease of the mammary gland and generates large losses in the dairy industry. By means of positional cloning and functional analysis techniques, we here show that insulin-like growth factor 1 receptor (IGF1R) can possibly mediate susceptibility to mastitis through autophagy. Scanning the whole genome of cows (Bos taurus) that were susceptible or resistant to mastitis in the half-sib families revealed that susceptible cows had a relatively long stretch of cytosine residues (C stretch) in the 5' untranslated region of IGF1R. The forebrain embryonic zinc finger-like (FEZL) transcription factor, which was previously identified as a factor controlling mastitis resistance in the same half-sib families, bound the C stretch of IGF1R. The susceptible type of FEZL with a glycine stretch containing 13 glycines (13G) and the longer C stretch of IGF1R together enhanced expression of IGF1R. Enhancing IGF1R inhibited autophagy in response to Streptococcus agalactiae invasion of mammary epithelial cells, whereas treatment with rapamycin, a known inducer of autophagy, rescued it. Cows carrying the variant combination of 13GFEZL might be more susceptible to mastitis as the result of impaired autophagy. Our results suggest that IGF1R could control innate immunity in mammals and serve as a potential tool for preventing mastitis. PMID:22973545

  2. Molecular predictors of sensitivity to the insulin-like growth factor 1 receptor inhibitor Figitumumab (CP-751,871).

    PubMed

    Pavlicek, Adam; Lira, Maruja E; Lee, Nathan V; Ching, Keith A; Ye, Jingjing; Cao, Joan; Garza, Scott J; Hook, Kenneth E; Ozeck, Mark; Shi, Stephanie T; Yuan, Jing; Zheng, Xianxian; Rejto, Paul A; Kan, Julie L C; Christensen, James G

    2013-12-01

    Figitumumab (CP-751,871), a potent and fully human monoclonal anti-insulin-like growth factor 1 receptor (IGF1R) antibody, has been investigated in clinical trials of several solid tumors. To identify biomarkers of sensitivity and resistance to figitumumab, its in vitro antiproliferative activity was analyzed in a panel of 93 cancer cell lines by combining in vitro screens with extensive molecular profiling of genomic aberrations. Overall response was bimodal and the majority of cell lines were resistant to figitumumab. Nine of 15 sensitive cell lines were derived from colon cancers. Correlations between genomic characteristics of cancer cell lines with figitumumab antiproliferative activity revealed that components of the IGF pathway, including IRS2 (insulin receptor substrate 2) and IGFBP5 (IGF-binding protein 5), played a pivotal role in determining the sensitivity of tumors to single-agent figitumumab. Tissue-specific differences among the top predictive genes highlight the need for tumor-specific patient selection strategies. For the first time, we report that alteration or expression of the MYB oncogene is associated with sensitivity to IGF1R inhibitors. MYB is dysregulated in hematologic and epithelial tumors, and IGF1R inhibition may represent a novel therapeutic opportunity. Although growth inhibitory activity with single-agent figitumumab was relatively rare, nine combinations comprising figitumumab plus chemotherapeutic agents or other targeted agents exhibited properties of synergy. Inhibitors of the ERBB family were frequently synergistic and potential biomarkers of drug synergy were identified. Several biomarkers of antiproliferative activity of figitumumab both alone and in combination with other therapies may inform the design of clinical trials evaluating IGF1R inhibitors. PMID:24107449

  3. Overexpression of human