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Sample records for non-glucose induced insulin

  1. Changes in fetal mannose and other carbohydrates induced by a maternal insulin infusion in pregnant sheep

    PubMed Central

    2014-01-01

    Background The importance of non-glucose carbohydrates, especially mannose and inositol, for normal development is increasingly recognized. Whether pregnancies complicated by abnormal glucose transfer to the fetus also affect the regulation of non-glucose carbohydrates is unknown. In pregnant sheep, maternal insulin infusions were used to reduce glucose supply to the fetus for both short (2-wk) and long (8-wk) durations to test the hypothesis that a maternal insulin infusion would suppress fetal mannose and inositol concentrations. We also used direct fetal insulin infusions (1-wk hyperinsulinemic-isoglycemic clamp) to determine the relative importance of fetal glucose and insulin for regulating non-glucose carbohydrates. Results A maternal insulin infusion resulted in lower maternal (50%, P < 0.01) and fetal (35-45%, P < 0.01) mannose concentrations, which were highly correlated (r2 = 0.69, P < 0.01). A fetal insulin infusion resulted in a 50% reduction of fetal mannose (P < 0.05). Neither maternal nor fetal plasma inositol changed with exogenous insulin infusions. Additionally, maternal insulin infusion resulted in lower fetal sorbitol and fructose (P < 0.01). Conclusions Chronically decreased glucose supply to the fetus as well as fetal hyperinsulinemia both reduce fetal non-glucose carbohydrates. Given the role of these carbohydrates in protein glycosylation and lipid production, more research on their metabolism in pregnancies complicated by abnormal glucose metabolism is clearly warranted. PMID:24917928

  2. Paliperidone Induced Hypoglycemia by Increasing Insulin Secretion.

    PubMed

    Omi, Tsubasa; Riku, Keisen; Fukumoto, Motoyuki; Kanai, Koji; Omura, Yumi; Takada, Hiromune; Matunaga, Hidenori

    2016-01-01

    We report the case of a 41-year-old woman with schizophrenia who developed persistent hypoglycemia following paliperidone administration. After discontinuing paliperidone, the hypoglycemia resolved, but symptoms of diabetes emerged. Therefore, it appears that the hypoglycemia induced by paliperidone may mask symptoms of diabetes. Paliperidone may induce hypoglycemia by increasing insulin secretion. This report could help elucidate the relationship between atypical antipsychotics and glucose metabolism. PMID:27478670

  3. Paliperidone Induced Hypoglycemia by Increasing Insulin Secretion

    PubMed Central

    Riku, Keisen; Fukumoto, Motoyuki; Kanai, Koji; Omura, Yumi; Matunaga, Hidenori

    2016-01-01

    We report the case of a 41-year-old woman with schizophrenia who developed persistent hypoglycemia following paliperidone administration. After discontinuing paliperidone, the hypoglycemia resolved, but symptoms of diabetes emerged. Therefore, it appears that the hypoglycemia induced by paliperidone may mask symptoms of diabetes. Paliperidone may induce hypoglycemia by increasing insulin secretion. This report could help elucidate the relationship between atypical antipsychotics and glucose metabolism. PMID:27478670

  4. Insulin-induced cytokine production in macrophages causes insulin resistance in hepatocytes.

    PubMed

    Manowsky, Julia; Camargo, Rodolfo Gonzalez; Kipp, Anna P; Henkel, Janin; Püschel, Gerhard P

    2016-06-01

    Overweight and obesity are associated with hyperinsulinemia, insulin resistance, and a low-grade inflammation. Although hyperinsulinemia is generally thought to result from an attempt of the β-cell to compensate for insulin resistance, there is evidence that hyperinsulinaemia itself may contribute to the development of insulin resistance and possibly the low-grade inflammation. To test this hypothesis, U937 macrophages were exposed to insulin. In these cells, insulin induced expression of the proinflammatory cytokines IL-1β, IL-8, CCL2, and OSM. The insulin-elicited induction of IL-1β was independent of the presence of endotoxin and most likely mediated by an insulin-dependent activation of NF-κB. Supernatants of the insulin-treated U937 macrophages rendered primary cultures of rat hepatocytes insulin resistant; they attenuated the insulin-dependent induction of glucokinase by 50%. The cytokines contained in the supernatants of insulin-treated U937 macrophages activated ERK1/2 and IKKβ, resulting in an inhibitory serine phosphorylation of the insulin receptor substrate. In addition, STAT3 was activated and SOCS3 induced, further contributing to the interruption of the insulin receptor signal chain in hepatocytes. These results indicate that hyperinsulinemia per se might contribute to the low-grade inflammation prevailing in overweight and obese patients and thereby promote the development of insulin resistance particularly in the liver, because the insulin concentration in the portal circulation is much higher than in all other tissues. PMID:27094035

  5. Insulin-Inducible SMILE Inhibits Hepatic Gluconeogenesis.

    PubMed

    Lee, Ji-Min; Seo, Woo-Young; Han, Hye-Sook; Oh, Kyoung-Jin; Lee, Yong-Soo; Kim, Don-Kyu; Choi, Seri; Choi, Byeong Hun; Harris, Robert A; Lee, Chul-Ho; Koo, Seung-Hoi; Choi, Hueng-Sik

    2016-01-01

    The role of a glucagon/cAMP-dependent protein kinase-inducible coactivator PGC-1α signaling pathway is well characterized in hepatic gluconeogenesis. However, an opposing protein kinase B (PKB)/Akt-inducible corepressor signaling pathway is unknown. A previous report has demonstrated that small heterodimer partner-interacting leucine zipper protein (SMILE) regulates the nuclear receptors and transcriptional factors that control hepatic gluconeogenesis. Here, we show that hepatic SMILE expression was induced by feeding in normal mice but not in db/db and high-fat diet (HFD)-fed mice. Interestingly, SMILE expression was induced by insulin in mouse primary hepatocyte and liver. Hepatic SMILE expression was not altered by refeeding in liver-specific insulin receptor knockout (LIRKO) or PKB β-deficient (PKBβ(-/-)) mice. At the molecular level, SMILE inhibited hepatocyte nuclear factor 4-mediated transcriptional activity via direct competition with PGC-1α. Moreover, ablation of SMILE augmented gluconeogenesis and increased blood glucose levels in mice. Conversely, overexpression of SMILE reduced hepatic gluconeogenic gene expression and ameliorated hyperglycemia and glucose intolerance in db/db and HFD-fed mice. Therefore, SMILE is an insulin-inducible corepressor that suppresses hepatic gluconeogenesis. Small molecules that enhance SMILE expression would have potential for treating hyperglycemia in diabetes. PMID:26340929

  6. Methimazole-induced insulin autoimmune syndrome

    PubMed Central

    Jain, Nidhi; Savani, Malvi; Agarwal, Manyoo; Kadaria, Dipen

    2016-01-01

    Background: Hypoglycemia in a critical care setting is often multifactorial with iatrogenic insulin use, sulfonylurea (SU) use, sepsis, adrenal insufficiency and insulinoma among the common causes. Insulin autoimmune syndrome (IAS) is a rare cause of hypoglycemia characterized by the presence of insulin-binding autoantibodies to the sulfhydryl group-containing agents. We report a case of methimazole-induced IAS managed in the intensive care unit. Case presentation: A 76-year-old woman with a history of primary hyperthyroidism was sent from a nursing home for unresponsiveness. Vital signs were significant for hypotension (74/46) and low blood sugars. Fluid resuscitations with normal saline and 50% dextrose stabilized the blood pressure (BP) to 135/75 and her blood glucose to 264. Due to respiratory distress and septic appearance, she required emergency intubation. Nursing home medications were noted for methimazole and absence of any insulin or SU use. Empiric antibiotic treatment was started and fluid resuscitation was continued while home medications were held. Her laboratory values were significant for elevated creatinine, lactic acid, serum cortisol, C-peptide, and insulin. Her cultures, SU screen and computerized tomography (CT) scan were negative for significant findings. On day 2, in addition to 10% dextrose, octreotide was initiated for recurrent hypoglycemia. Her blood glucose (BG) continued to drop throughout the day for which she required glucagon support and a D20 infusion. By day 4, the rate of infusion was titrated up and her BG continued to drop to <60 mg/dl despite D20, octreotide and tube feeds with concentrated calories (1.5 cal/ml). Due to her declining health, her family endorsed palliative care and she was extubated. After day 11, her hypoglycemic episodes resolved and she remained endogenously euglycemic. Conclusions: IAS is associated with methimazole use due to formation of autoantibodies to insulin after its interaction with Sulfhydryl (SH

  7. Insulin-induced CARM1 upregulation facilitates hepatocyte proliferation

    SciTech Connect

    Yeom, Chul-gon; Kim, Dong-il; Park, Min-jung; Choi, Joo-hee; Jeong, Jieun; Wi, Anjin; Park, Whoashig; Han, Ho-jae; Park, Soo-hyun

    2015-06-05

    Previously, we reported that CARM1 undergoes ubiquitination-dependent degradation in renal podocytes. It was also reported that CARM1 is necessary for fasting-induced hepatic gluconeogenesis. Based on these reports, we hypothesized that treatment with insulin, a hormone typically present under the ‘fed’ condition, would inhibit gluconeogenesis via CARM1 degradation. HepG2 cells, AML-12 cells, and rat primary hepatocytes were treated with insulin to confirm CARM1 downregulation. Surprisingly, insulin treatment increased CARM1 expression in all cell types examined. Furthermore, treatment with insulin increased histone 3 methylation at arginine 17 and 26 in HepG2 cells. To elucidate the role of insulin-induced CARM1 upregulation, the HA-CARM1 plasmid was transfected into HepG2 cells. CARM1 overexpression did not increase the expression of lipogenic proteins generally increased by insulin signaling. Moreover, CARM1 knockdown did not influence insulin sensitivity. Insulin is known to facilitate hepatic proliferation. Like insulin, CARM1 overexpression increased CDK2 and CDK4 expression. In addition, CARM1 knockdown reduced the number of insulin-induced G2/M phase cells. Moreover, GFP-CARM1 overexpression increased the number of G2/M phase cells. Based on these results, we concluded that insulin-induced CARM1 upregulation facilitates hepatocyte proliferation. These observations indicate that CARM1 plays an important role in liver pathophysiology. - Highlights: • Insulin treatment increases CARM1 expression in hepatocytes. • CARM1 overexpression does not increase the expression of lipogenic proteins. • CARM1 knockdown does not influence insulin sensitivity. • Insulin-induced CARM1 upregulation facilitates hepatocyte proliferation.

  8. Leptin, skeletal muscle lipids, and lipid-induced insulin resistance.

    PubMed

    Dube, John J; Bhatt, Bankim A; Dedousis, Nikolas; Bonen, Arend; O'Doherty, Robert M

    2007-08-01

    Leptin-induced increases in insulin sensitivity are well established and may be related to the effects of leptin on lipid metabolism. However, the effects of leptin on the levels of lipid metabolites implicated in pathogenesis of insulin resistance and the effects of leptin on lipid-induced insulin resistance are unknown. The current study addressed in rats the effects of hyperleptinemia (HL) on insulin action and markers of skeletal muscle (SkM) lipid metabolism in the absence or presence of acute hyperlipidemia induced by an infusion of a lipid emulsion. Compared with controls (CONT), HL increased insulin sensitivity, as assessed by hyperinsulinemic-euglycemic clamp ( approximately 15%), and increased SkM Akt ( approximately 30%) and glycogen synthase kinase 3 alpha ( approximately 52%) phosphorylation. These improvements in insulin action were associated with decreased SkM triglycerides (TG; approximately 61%), elevated ceramides ( approximately 50%), and similar diacylglycerol (DAG) levels in HL compared with CONT. Acute hyperlipidemia in CONT decreased insulin sensitivity ( approximately 25%) and increased SkM DAG ( approximately 33%) and ceramide ( approximately 60%) levels. However, hyperlipidemia did not induce insulin resistance or SkM DAG and ceramide accumulation in HL. SkM total fatty acid transporter CD36, plasma membrane fatty acid binding protein, acetyl Co-A carboxylase phosphorylation, and fatty acid oxidation were similar in HL compared with CONT. However, HL decreased SkM protein kinase C theta (PKC theta), a kinase implicated in mediating the detrimental effects of lipids on insulin action. We conclude that increases in insulin sensitivity induced by HL are associated with decreased levels of SkM TG and PKC theta and increased SkM insulin signaling, but not with decreases in other lipid metabolites implicated in altering SkM insulin sensitivity (DAG and ceramide). Furthermore, insulin resistance induced by an acute lipid infusion is prevented by

  9. Xylitol prevents NEFA-induced insulin resistance in rats

    PubMed Central

    Kishore, P.; Kehlenbrink, S.; Hu, M.; Zhang, K.; Gutierrez-Juarez, R.; Koppaka, S.; El-Maghrabi, M. R.

    2013-01-01

    Aims/hypothesis Increased NEFA levels, characteristic of type 2 diabetes mellitus, contribute to skeletal muscle insulin resistance. While NEFA-induced insulin resistance was formerly attributed to decreased glycolysis, it is likely that glucose transport is the rate-limiting defect. Recently, the plant-derived sugar alcohol xylitol has been shown to have favourable metabolic effects in various animal models. Furthermore, its derivative xylulose 5-phosphate may prevent NEFA-induced suppression of glycolysis. We therefore examined whether and how xylitol might prevent NEFA-induced insulin resistance. Methods We examined the ability of xylitol to prevent NEFA-induced insulin resistance. Sustained ~1.5-fold elevations in NEFA levels were induced with Intralipid/heparin infusions during 5 h euglycaemic–hyperinsulinaemic clamp studies in 24 conscious non-diabetic Sprague-Dawley rats, with or without infusion of xylitol. Results Intralipid infusion reduced peripheral glucose uptake by ~25%, predominantly through suppression of glycogen synthesis. Co-infusion of xylitol prevented the NEFA-induced decreases in both glucose uptake and glycogen synthesis. Although glycolysis was increased by xylitol infusion alone, there was minimal NEFA-induced suppression of glycolysis, which was not affected by co-infusion of xylitol. Conclusions/interpretation We conclude that xylitol prevented NEFA-induced insulin resistance, with favourable effects on glycogen synthesis accompanying the improved insulin-mediated glucose uptake. This suggests that this pentose sweetener has beneficial insulin-sensitising effects. PMID:22460760

  10. Peroxiredoxin 4 improves insulin biosynthesis and glucose-induced insulin secretion in insulin-secreting INS-1E cells.

    PubMed

    Mehmeti, Ilir; Lortz, Stephan; Elsner, Matthias; Lenzen, Sigurd

    2014-09-26

    Oxidative folding of (pro)insulin is crucial for its assembly and biological function. This process takes place in the endoplasmic reticulum (ER) and is accomplished by protein disulfide isomerase and ER oxidoreductin 1β, generating stoichiometric amounts of hydrogen peroxide (H2O2) as byproduct. During insulin resistance in the prediabetic state, increased insulin biosynthesis can overwhelm the ER antioxidative and folding capacity, causing an imbalance in the ER redox homeostasis and oxidative stress. Peroxiredoxin 4 (Prdx4), an ER-specific antioxidative peroxidase can utilize luminal H2O2 as driving force for reoxidizing protein disulfide isomerase family members, thus efficiently contributing to disulfide bond formation. Here, we examined the functional significance of Prdx4 on β-cell function with emphasis on insulin content and secretion during stimulation with nutrient secretagogues. Overexpression of Prdx4 in glucose-responsive insulin-secreting INS-1E cells significantly metabolized luminal H2O2 and improved the glucose-induced insulin secretion, which was accompanied by the enhanced proinsulin mRNA transcription and insulin content. This β-cell beneficial effect was also observed upon stimulation with the nutrient insulin secretagogue combination of leucine plus glutamine, indicating that the effect is not restricted to glucose. However, knockdown of Prdx4 had no impact on H2O2 metabolism or β-cell function due to the fact that Prdx4 expression is negligibly low in pancreatic β-cells. Moreover, we provide evidence that the constitutively low expression of Prdx4 is highly susceptible to hyperoxidation in the presence of high glucose. Overall, these data suggest an important role of Prdx4 in maintaining insulin levels and improving the ER folding capacity also under conditions of a high insulin requirement. PMID:25122762

  11. Computational modeling and analysis of insulin induced eukaryotic translation initiation.

    PubMed

    Lequieu, Joshua; Chakrabarti, Anirikh; Nayak, Satyaprakash; Varner, Jeffrey D

    2011-11-01

    Insulin, the primary hormone regulating the level of glucose in the bloodstream, modulates a variety of cellular and enzymatic processes in normal and diseased cells. Insulin signals are processed by a complex network of biochemical interactions which ultimately induce gene expression programs or other processes such as translation initiation. Surprisingly, despite the wealth of literature on insulin signaling, the relative importance of the components linking insulin with translation initiation remains unclear. We addressed this question by developing and interrogating a family of mathematical models of insulin induced translation initiation. The insulin network was modeled using mass-action kinetics within an ordinary differential equation (ODE) framework. A family of model parameters was estimated, starting from an initial best fit parameter set, using 24 experimental data sets taken from literature. The residual between model simulations and each of the experimental constraints were simultaneously minimized using multiobjective optimization. Interrogation of the model population, using sensitivity and robustness analysis, identified an insulin-dependent switch that controlled translation initiation. Our analysis suggested that without insulin, a balance between the pro-initiation activity of the GTP-binding protein Rheb and anti-initiation activity of PTEN controlled basal initiation. On the other hand, in the presence of insulin a combination of PI3K and Rheb activity controlled inducible initiation, where PI3K was only critical in the presence of insulin. Other well known regulatory mechanisms governing insulin action, for example IRS-1 negative feedback, modulated the relative importance of PI3K and Rheb but did not fundamentally change the signal flow. PMID:22102801

  12. Effect of Naloxon on Counter Insulin Hormone Secretion in Insulin-Induced Hypoglycemia

    PubMed Central

    Ju, Yeong Shil; Kim, Sung Woon; Yang, In Myung; Kim, Jin Woo; Kim, Young Seol; Choi, Young Kil

    1987-01-01

    To investigate the normal physiologic role of endogenous opiates in glucose homeostasis and as a preliminary study for clarifying the association of endogenous opites with pathophysilogy of NIDDM, we obseved the changes in the secretion of counter-insulin hormones in response to insulin-induced hypoglycemia with or without naloxone. The results were as follows: Blood glucose was decreased significantly more rapidly with naloxone infusion than after insulin alone, which seems to play a role in the early responses of ACTH and GH.Not only was the more rapid response of ACTH and GH, but also the prolonged secretion of ACTH and Cortisol were observed after administration of insulin and naloxone. We concluded that endogenous opiates may be involved in the feedback regulation of secretion of ACTH and GH during hypoglycemia either at hypophysis or hypothalamus, and involved in glucose homeostasis via a certain direct mechanism other than regulation of counter hormone secretion. PMID:2856480

  13. Insulin Cannot Induce Adipogenic Differentiation in Primary Cardiac Cultures.

    PubMed

    Parameswaran, Sreejit; Sharma, Rajendra K

    2016-09-01

    Cardiac tissue contains a heterogeneous population of cardiomyocytes and nonmyocyte population especially fibroblasts. Fibroblast differentiation into adipogenic lineage is important for fat accumulation around the heart which is important in cardiac pathology. The differentiation in fibroblast has been observed both spontaneously and due to increased insulin stimulation. The present study aims to observe the effect of insulin in adipogenic differentiation of cardiac cells present in primary murine cardiomyocyte cultures. Oil Red O (ORO) staining has been used for observing the lipid accumulations formed due to adipogenic differentiation in murine cardiomyocyte cultures. The accumulated lipids were quantified by ORO assay and normalized using protein estimation. The lipid accumulation in cardiac cultures did not increase in presence of insulin. However, addition of other growth factors like insulin-like growth factor 1 and epidermal growth factor promoted adipogenic differentiation even in the presence of insulin and other inhibitory molecules such as vitamins. Lipid accumulation also increased in cells grown in media without insulin after an initial exposure to insulin-containing growth media. The current study adds to the existing knowledge that the insulin by itself cannot induce adipogenic induction in the cardiac cultures. The data have significance in the understanding of cardiovascular health especially in diabetic patients. PMID:27574386

  14. Metabolic acidosis-induced insulin resistance and cardiovascular risk.

    PubMed

    Souto, Gema; Donapetry, Cristóbal; Calviño, Jesús; Adeva, Maria M

    2011-08-01

    Microalbuminuria has been conclusively established as an independent cardiovascular risk factor, and there is evidence of an association between insulin resistance and microalbuminuria, the former preceding the latter in prospective studies. It has been demonstrated that even the slightest degree of metabolic acidosis produces insulin resistance in healthy humans. Many recent epidemiological studies link metabolic acidosis indicators with insulin resistance and systemic hypertension. The strongly acidogenic diet consumed in developed countries produces a lifetime acidotic state, exacerbated by excess body weight and aging, which may result in insulin resistance, metabolic syndrome, and type 2 diabetes, contributing to cardiovascular risk, along with genetic causes, lack of physical exercise, and other factors. Elevated fruits and vegetables consumption has been associated with lower diabetes incidence. Diseases featuring severe atheromatosis and elevated cardiovascular risk, such as diabetes mellitus and chronic kidney failure, are typically characterized by a chronic state of metabolic acidosis. Diabetic patients consume particularly acidogenic diets, and deficiency of insulin action generates ketone bodies, creating a baseline state of metabolic acidosis worsened by inadequate metabolic control, which creates a vicious circle by inducing insulin resistance. Even very slight levels of chronic kidney insufficiency are associated with increased cardiovascular risk, which may be explained at least in part by deficient acid excretory capacity of the kidney and consequent metabolic acidosis-induced insulin resistance. PMID:21352078

  15. Metabolic Acidosis-Induced Insulin Resistance and Cardiovascular Risk

    PubMed Central

    Souto, Gema; Donapetry, Cristóbal; Calviño, Jesús

    2011-01-01

    Abstract Microalbuminuria has been conclusively established as an independent cardiovascular risk factor, and there is evidence of an association between insulin resistance and microalbuminuria, the former preceding the latter in prospective studies. It has been demonstrated that even the slightest degree of metabolic acidosis produces insulin resistance in healthy humans. Many recent epidemiological studies link metabolic acidosis indicators with insulin resistance and systemic hypertension. The strongly acidogenic diet consumed in developed countries produces a lifetime acidotic state, exacerbated by excess body weight and aging, which may result in insulin resistance, metabolic syndrome, and type 2 diabetes, contributing to cardiovascular risk, along with genetic causes, lack of physical exercise, and other factors. Elevated fruits and vegetables consumption has been associated with lower diabetes incidence. Diseases featuring severe atheromatosis and elevated cardiovascular risk, such as diabetes mellitus and chronic kidney failure, are typically characterized by a chronic state of metabolic acidosis. Diabetic patients consume particularly acidogenic diets, and deficiency of insulin action generates ketone bodies, creating a baseline state of metabolic acidosisworsened by inadequate metabolic control, which creates a vicious circle by inducing insulin resistance. Even very slight levels of chronic kidney insufficiency are associated with increased cardiovascular risk, which may be explained at least in part by deficient acid excretory capacity of the kidney and consequent metabolic acidosis-induced insulin resistance. PMID:21352078

  16. 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

  17. Role of PTEN in TNFα induced insulin resistance

    SciTech Connect

    Bulger, David A.; Conley, Jermaine; Conner, Spencer H.; Majumdar, Gipsy; Solomon, Solomon S.

    2015-06-05

    Aims/hypothesis: PTEN may play a reversible role in TNFα induced insulin resistance, which has been linked to obesity-associated insulin resistance (IR). Methods: Western blots for PTEN and p-Akt were performed on H-411E liver cells incubated with insulin, TNFα, and in selected experiments VO-OHpic vanadium complex in the presence and absence of PTEN siRNA. Total PTEN was compared to β-actin loading control and p-Akt was compared to total Akt. Results: Western blot and Real Time RT-PCR experiments showed increased PTEN after TNFα treatment (p = 0.04); slightly decreased PTEN after insulin treatment; and slightly increased PTEN after insulin + TNFα treatment. PTEN siRNA markedly inhibited the TNFα-induced increase in PTEN (p < 0.01) without significantly changing the p-Akt levels. The vanadium complex, exhibiting insulin-like effects, also significantly prevented the TNFα-induced increase in PTEN. Combining insulin and VO-OHpic was additive, providing both proof of concept and insight into mechanism. Discussion: The PTEN increase due to TNFα treatment was reversible by both PTEN siRNA knockdown and VO-OHpic treatment. Thus, PTEN is identified as a potential new therapeutic target for reducing IR in Type 2 DM. - Highlights: • TNFα treatment induced a significant increase in PTEN in H-411E liver cells. • PTEN siRNA knockdown prevented this effect. • VO-OHpic (vanadium complex) treatment, like insulin, decreased PTEN protein levels. • Thus, PTEN is identified as a potential therapeutic target in DM Type 2.

  18. Insulin Resistance Induces Posttranslational Hepatic Sortilin 1 Degradation in Mice*

    PubMed Central

    Li, Jibiao; Matye, David J.; Li, Tiangang

    2015-01-01

    Insulin promotes hepatic apolipoprotein B100 (apoB100) degradation, whereas insulin resistance is a major cause of hepatic apoB100/triglyceride overproduction in type 2 diabetes. The cellular trafficking receptor sortilin 1 (Sort1) was recently identified to transport apoB100 to the lysosome for degradation in the liver and thus regulate plasma cholesterol and triglyceride levels. Genetic variation of SORT1 was strongly associated with cardiovascular disease risk in humans. The major goal of this study is to investigate the effect and molecular mechanism of insulin regulation of Sort1. Results showed that insulin induced Sort1 protein, but not mRNA, in AML12 cells. Treatment of PI3K or AKT inhibitors decreased Sort1 protein, whereas expression of constitutively active AKT induced Sort1 protein in AML12 cells. Consistently, hepatic Sort1 was down-regulated in diabetic mice, which was partially restored after the administration of the insulin sensitizer metformin. LC-MS/MS analysis further revealed that serine phosphorylation of Sort1 protein was required for insulin induction of Sort1 in a casein kinase 2-dependent manner and that inhibition of PI3K signaling or prevention of Sort1 phosphorylation accelerated proteasome-dependent Sort1 degradation. Administration of a PI3K inhibitor to mice decreased hepatic Sort1 protein and increased plasma cholesterol and triglyceride levels. Adenovirus-mediated overexpression of Sort1 in the liver prevented PI3K inhibitor-induced Sort1 down-regulation and decreased plasma triglyceride but had no effect on plasma cholesterol in mice. This study identified Sort1 as a novel target of insulin signaling and suggests that Sort1 may play a role in altered hepatic apoB100 metabolism in insulin-resistant conditions. PMID:25805502

  19. Inflammation-induced microvascular insulin resistance is an early event in diet-induced obesity

    PubMed Central

    Zhao, Lina; Fu, Zhuo; Wu, Jing; Aylor, Kevin W.; Barrett, Eugene J.; Cao, Wenhong

    2015-01-01

    Endothelial dysfunction and vascular insulin resistance usually coexist and chronic inflammation engenders both. In the present study, we investigate the temporal relationship between vascular insulin resistance and metabolic insulin resistance. We assessed insulin responses in all arterial segments, including aorta, distal saphenous artery and the microvasculature, as well as the metabolic insulin responses in muscle in rats fed on a high-fat diet (HFD) for various durations ranging from 3 days to 4 weeks with or without sodium salicylate treatment. Compared with controls, HFD feeding significantly blunted insulin-mediated Akt (protein kinase B) and eNOS [endothelial nitric oxide (NO) synthase] phosphorylation in aorta in 1 week, blunted vasodilatory response in small resistance vessel in 4 weeks and microvascular recruitment in as early as 3 days. Insulin-stimulated whole body glucose disposal did not begin to progressively decrease until after 1 week. Salicylate treatment fully inhibited vascular inflammation, prevented microvascular insulin resistance and significantly improved muscle metabolic responses to insulin. We conclude that microvascular insulin resistance is an early event in diet-induced obesity and insulin resistance and inflammation plays an essential role in this process. Our data suggest microvascular insulin resistance contributes to the development of metabolic insulin resistance in muscle and muscle microvasculature is a potential therapeutic target in the prevention and treatment of diabetes and its related complications. PMID:26265791

  20. Inflammation-induced microvascular insulin resistance is an early event in diet-induced obesity.

    PubMed

    Zhao, Lina; Fu, Zhuo; Wu, Jing; Aylor, Kevin W; Barrett, Eugene J; Cao, Wenhong; Liu, Zhenqi

    2015-12-01

    Endothelial dysfunction and vascular insulin resistance usually coexist and chronic inflammation engenders both. In the present study, we investigate the temporal relationship between vascular insulin resistance and metabolic insulin resistance. We assessed insulin responses in all arterial segments, including aorta, distal saphenous artery and the microvasculature, as well as the metabolic insulin responses in muscle in rats fed on a high-fat diet (HFD) for various durations ranging from 3 days to 4 weeks with or without sodium salicylate treatment. Compared with controls, HFD feeding significantly blunted insulin-mediated Akt (protein kinase B) and eNOS [endothelial nitric oxide (NO) synthase] phosphorylation in aorta in 1 week, blunted vasodilatory response in small resistance vessel in 4 weeks and microvascular recruitment in as early as 3 days. Insulin-stimulated whole body glucose disposal did not begin to progressively decrease until after 1 week. Salicylate treatment fully inhibited vascular inflammation, prevented microvascular insulin resistance and significantly improved muscle metabolic responses to insulin. We conclude that microvascular insulin resistance is an early event in diet-induced obesity and insulin resistance and inflammation plays an essential role in this process. Our data suggest microvascular insulin resistance contributes to the development of metabolic insulin resistance in muscle and muscle microvasculature is a potential therapeutic target in the prevention and treatment of diabetes and its related complications. PMID:26265791

  1. 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.

  2. A novel domain mediates insulin-induced proteasomal degradation of insulin receptor substrate 1 (IRS-1).

    PubMed

    Boura-Halfon, Sigalit; Shuster-Meiseles, Timor; Beck, Avital; Petrovich, Katia; Gurevitch, Diana; Ronen, Denise; Zick, Yehiel

    2010-11-01

    Insulin receptor substrate-1 (IRS-1) plays a pivotal role in insulin signaling, therefore its degradation is exquisitely regulated. Here, we show that insulin-stimulated degradation of IRS-1 requires the presence of a highly conserved Ser/Thr-rich domain that we named domain involved in degradation of IRS-1 (DIDI). DIDI (amino acids 386-430 of IRS-1) was identified by comparing the intracellular degradation rate of several truncated forms of IRS-1 transfected into CHO cells. The isolated DIDI domain underwent insulin-stimulated Ser/Thr phosphorylation, suggesting that it serves as a target for IRS-1 kinases. The effects of deletion of DIDI were studied in Fao rat hepatoma and in CHO cells expressing Myc-IRS-1(WT) or Myc-IRS-1(Δ386-430). Deletion of DIDI maintained the ability of IRS-1(Δ386-434) to undergo ubiquitination while rendering it insensitive to insulin-induced proteasomal degradation, which affected IRS-1(WT) (80% at 8 h). Consequently, IRS-1(Δ386-434) mediated insulin signaling (activation of Akt and glycogen synthesis) better than IRS-1(WT). IRS-1(Δ386-434) exhibited a significant greater preference for nuclear localization, compared with IRS-1(WT). Higher nuclear localization was also observed when cells expressing IRS-1(WT) were incubated with the proteasome inhibitor MG-132. The sequence of DIDI is conserved more than 93% across species, from fish to mammals, as opposed to approximately 40% homology of the entire IRS-1. These findings implicate DIDI as a novel, highly conserved domain of IRS-1, which mediates its cellular localization, rate of degradation, and biological activity, with a direct impact on insulin signal transduction. PMID:20843941

  3. Macrophage-secreted factors induce adipocyte inflammation and insulin resistance

    SciTech Connect

    Permana, Paska A. . E-mail: Paska.Permana@med.va.gov; Menge, Christopher; Reaven, Peter D.

    2006-03-10

    Macrophage infiltration into adipose tissue increases with obesity, a condition associated with low-grade inflammation and insulin resistance. We investigated the direct effects of macrophage-secreted factors on adipocyte inflammation and insulin resistance. 3T3-L1 adipocytes incubated with media conditioned by RAW264.7 macrophages (RAW-CM) showed dramatically increased transcription of several inflammation-related genes, greater nuclear factor kappa B (NF-{kappa}B) activity, and enhanced binding of U937 monocytes. All of these effects were prevented by co-incubation with pyrrolidinedithiocarbamate, an NF-{kappa}B inhibitor. Adipocytes incubated with RAW-CM also released more non-esterified fatty acids and this increased lipolysis was not suppressed by insulin. In addition, RAW-CM treatment decreased insulin-stimulated glucose uptake in adipocytes. Taken together, these results indicate that macrophage-secreted factors induce inflammatory responses and reduce insulin responsiveness in adipocytes. These effects of macrophage-secreted factors on adipocytes may contribute significantly to the systemic inflammation and insulin resistance associated with obesity.

  4. Recent advances in obesity-induced inflammation and insulin resistance.

    PubMed

    Tateya, Sanshiro; Kim, Francis; Tamori, Yoshikazu

    2013-01-01

    It has been demonstrated in rodents and humans that chronic inflammation characterized by macrophage infiltration occurs mainly in adipose tissue or liver during obesity, in which activation of immune cells is closely associated with insulin sensitivity. Macrophages can be classified as classically activated (M1) macrophages that support microbicidal activity or alternatively activated (M2) macrophages that support allergic and antiparasitic responses. In the context of insulin action, M2 macrophages sustain insulin sensitivity by secreting IL-4 and IL-10, while M1 macrophages induce insulin resistance through the secretion of proinflammatory cytokines, such as TNFα. Polarization of M1/M2 is controlled by various dynamic functions of other immune cells. It has been demonstrated that, in a lean state, TH2 cells, Treg cells, natural killer T cells, or eosinophils contribute to the M2 activation of macrophages by secreting IL-4 or IL-10. In contrast, obesity causes alteration of the constituent immune cells, in which TH1 cells, B cells, neutrophils, or mast cells induce M1 activation of macrophages by the elevated secretion of TNFα and IFNγ. Increased secretion of TNFα and free fatty acids from hypertrophied adipocytes also contributes to the M1 activation of macrophages. Since obesity-induced insulin resistance is established by macrophage infiltration and the activation of immune cells inside tissues, identification of the factors that regulate accumulation and the intracellular signaling cascades that define polarization of M1/M2 would be indispensable. Regulation of these factors would lead to the pharmacological inhibition of obesity-induced insulin resistance. In this review, we introduce molecular mechanisms relevant to the pathophysiology and review the most recent studies of clinical applications targeting chronic inflammation. PMID:23964268

  5. MondoA Senses Non-glucose Sugars

    PubMed Central

    Stoltzman, Carrie A.; Kaadige, Mohan R.; Peterson, Christopher W.; Ayer, Donald E.

    2011-01-01

    Glucose is required for cell growth and proliferation. The MondoA·Mlx transcription factor is glucose-responsive and accumulates in the nucleus by sensing glucose 6-phosphate. One direct and glucose-induced target of MondoA·Mlx complexes is thioredoxin-interacting protein (TXNIP). TXNIP is a potent negative regulator of glucose uptake, and hence its regulation by MondoA·Mlx triggers a feedback loop that restricts glucose uptake. This feedback loop is similar to the “hexose transport curb” first described almost 30 years ago. We show here that MondoA responds to the non-glucose hexoses, allose, 3-O-methylglucose, and glucosamine by accumulating in the nucleus and activating TXNIP transcription. The metabolic inhibitor 3-bromopyruvate blocks the transcriptional response to allose and 3-O-methylglucose, indicating that their metabolism, or a parallel pathway, is required to stimulate MondoA activity. Our dissection of the hexosamine biosynthetic pathway suggests that in addition to sensing glucose 6-phosphate, MondoA can also sense glucosamine 6-phosphate. Analysis of glucose uptake in wild-type, MondoA-null, or TXNIP-null murine embryonic fibroblasts indicates a role for the MondoA-TXNIP regulatory circuit in the hexose transport curb, although other redundant pathways also contribute. PMID:21908621

  6. Phosphate depletion impairs leucine-induced insulin secretion.

    PubMed

    Oh, H Y; Fadda, G Z; Smogorzewski, M; Liou, H H; Massry, S G

    1994-11-01

    Phosphate depletion (PD) in vivo causes a sundry of abnormalities in pancreatic islets including a rise in cytosolic calcium, low ATP content, reduced Ca2+ ATPase and Na(+)-K+ ATPase activity, and impaired insulin secretion in response to glucose or potassium. L-Leucine is a strong secretagogue that triggers insulin secretion by deamination to alpha-ketoisocaproic acid (KIC) and the subsequent metabolism of the latter to ATP and by the activation of glutamate dehydrogenase (GLDH), which acts on glutamate to generate alpha-ketoglutarate, the metabolism of which results in ATP production. The generation of ATP triggers events that lead to insulin secretion. It is not known whether PD impairs leucine-induced insulin secretion, and the cellular derangements that are involved in such an abnormality are not defined. These issues were studied in PD rats and in pair-weighed normal animals as controls. D-Leucine uptake by islets from PD rats is normal, but both leucine- and KIC-induced insulin secretions are impaired and the activity of branched-chain keto acid dehydrogenase, which facilitates the metabolism of KIC, is reduced. Both leucine and 2-aminobicyclo (2-2-1) haptene failed to stimulate GLDH and to augment the generation of alpha-ketoglutarate in the islets of PD rats. Also, the concentration of basal alpha-ketoglutarate was significantly higher in the islets of PD rats, suggesting that its metabolism is impaired. In addition, the activity of glutaminase is significantly reduced, an abnormality that would result in decreased production of glutamate, the substrate for GLDH. The data show that PD impairs leucine-induced insulin secretion.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7873737

  7. Insulin absorption and subcutaneous blood flow in normal subjects during insulin-induced hypoglycemia

    SciTech Connect

    Fernqvist-Forbes, E.; Linde, B.; Gunnarsson, R.

    1988-09-01

    We studied the effects of insulin-induced hypoglycemia on the absorption of 10 U /sup 125/I-labeled soluble human insulin injected sc in the thigh in 10 normal subjects. The disappearance of /sup 125/I from the injection site was followed by external gamma-counting. Subcutaneous blood flow (ATBF) was measured concomitantly with the 133Xe washout technique. The plasma glucose nadir (mean, 2.0 +/- 0.1 (+/- SE) mmol/L) occurred at 33 +/- 3 min and resulted in maximal arterial plasma epinephrine concentrations of approximately 6 nmol/L. From 30 min before to 60 min after the glucose nadir the (/sup 125/I)insulin absorption rate was depressed compared to that during normoglycemia. The first order disappearance rate constants were reduced by approximately 50% (P less than 0.01) during the first 30-min interval after the glucose nadir. During the same period ATBF increased by 100% (P less than 0.05). The results suggest that in normal subjects the absorption of soluble insulin from a sc depot is depressed in connection with hypoglycemia, despite considerably elevated ATBF.

  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. Insulin sensitizers prevent fine particulate matter-induced vascular insulin resistance and changes in endothelial progenitor cell homeostasis.

    PubMed

    Haberzettl, Petra; McCracken, James P; Bhatnagar, Aruni; Conklin, Daniel J

    2016-06-01

    Exposure to fine particular matter (PM2.5) increases the risk of developing cardiovascular disease and Type 2 diabetes. Because blood vessels are sensitive targets of air pollutant exposure, we examined the effects of concentrated ambient PM2.5 (CAP) on vascular insulin sensitivity and circulating levels of endothelial progenitor cells (EPCs), which reflect cardiovascular health. We found that CAP exposure for 9 days decreased insulin-stimulated Akt phosphorylation in the aorta of mice maintained on control diet. This change was accompanied by the induction of IL-1β and increases in the abundance of cleaved IL-18 and p10 subunit of Casp-1, consistent with the activation of the inflammasome pathway. CAP exposure also suppressed circulating levels of EPCs (Flk-1(+)/Sca-1(+) cells), while enhancing the bone marrow abundance of these cells. Although similar changes in vascular insulin signaling and EPC levels were observed in mice fed high-fat diet, CAP exposure did not exacerbate diet-induced changes in vascular insulin resistance or EPC homeostasis. Treatment with an insulin sensitizer, metformin or rosiglitazone, prevented CAP-induced vascular insulin resistance and NF-κB and inflammasome activation and restored peripheral blood and bone marrow EPC levels. These findings suggest that PM2.5 exposure induces diet-independent vascular insulin resistance and inflammation and prevents EPC mobilization, and that this EPC mobilization defect could be mediated by vascular insulin resistance. Impaired vascular insulin sensitivity may be an important mechanism underlying PM2.5-induced vascular injury, and pharmacological sensitization to insulin action could potentially prevent deficits in vascular repair and mitigate vascular inflammation due to exposure to elevated levels of ambient air pollution. PMID:27016579

  10. Reversal of diet-induced obesity and insulin resistance by inducible genetic ablation of GRK2.

    PubMed

    Vila-Bedmar, Rocio; Cruces-Sande, Marta; Lucas, Elisa; Willemen, Hanneke L D M; Heijnen, Cobi J; Kavelaars, Annemieke; Mayor, Federico; Murga, Cristina

    2015-07-21

    Insulin resistance is a common feature of obesity and predisposes individuals to various prevalent pathological conditions. G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor kinase 2 (GRK2) integrates several signal transduction pathways and is emerging as a physiologically relevant inhibitor of insulin signaling. GRK2 abundance is increased in humans with metabolic syndrome and in different murine models of insulin resistance. To support GRK2 as a potential drug target in type 2 diabetes and obesity, we investigated whether lowering GRK2 abundance reversed an ongoing systemic insulin-resistant phenotype, using a mouse model of tamoxifen-induced GRK2 ablation after high-fat diet-dependent obesity and insulin resistance. Tamoxifen-triggered GRK2 deletion impeded further body weight gain, normalized fasting glycemia, improved glucose tolerance, and was associated with preserved insulin sensitivity in skeletal muscle and liver, thereby maintaining whole-body glucose homeostasis. Moreover, when continued to be fed a high-fat diet, these animals displayed reduced fat mass and smaller adipocytes, were resistant to the development of liver steatosis, and showed reduced expression of proinflammatory markers in the liver. Our results indicate that GRK2 acts as a hub to control metabolic functions in different tissues, which is key to controlling insulin resistance development in vivo. These data suggest that inhibiting GRK2 could reverse an established insulin-resistant and obese phenotype, thereby putting forward this enzyme as a potential therapeutic target linking glucose homeostasis and regulation of adiposity. PMID:26198359

  11. Mammalian Tribbles homolog 3 impairs insulin action in skeletal muscle: role in glucose-induced insulin resistance

    PubMed Central

    Liu, Jiarong; Franklin, John L.; Messina, Joseph L.; Hill, Helliner S.; Moellering, Douglas R.; Walton, R. Grace; Martin, Mitchell; Garvey, W. Timothy

    2009-01-01

    Tribbles homolog 3 (TRIB3) was found to inhibit insulin-stimulated Akt phosphorylation and modulate gluconeogenesis in rodent liver. Currently, we examined a role for TRIB3 in skeletal muscle insulin resistance. Ten insulin-sensitive, ten insulin-resistant, and ten untreated type 2 diabetic (T2DM) patients were metabolically characterized by hyperinsulinemic euglycemic glucose clamps, and biopsies of vastus lateralis were obtained. Skeletal muscle samples were also collected from rodent models including streptozotocin (STZ)-induced diabetic rats, db/db mice, and Zucker fatty rats. Finally, L6 muscle cells were used to examine regulation of TRIB3 by glucose, and stable cell lines hyperexpressing TRIB3 were generated to identify mechanisms underlying TRIB3-induced insulin resistance. We found that 1) skeletal muscle TRIB3 protein levels are significantly elevated in T2DM patients; 2) muscle TRIB3 protein content is inversely correlated with glucose disposal rates and positively correlated with fasting glucose; 3) skeletal muscle TRIB3 protein levels are increased in STZ-diabetic rats, db/db mice, and Zucker fatty rats; 4) stable TRIB3 hyperexpression in muscle cells blocks insulin-stimulated glucose transport and glucose transporter 4 (GLUT4) translocation and impairs phosphorylation of Akt, ERK, and insulin receptor substrate-1 in insulin signal transduction; and 5) TRIB3 mRNA and protein levels are increased by high glucose concentrations, as well as by glucose deprivation in muscle cells. These data identify TRIB3 induction as a novel molecular mechanism in human insulin resistance and diabetes. TRIB3 acts as a nutrient sensor and could mediate the component of insulin resistance attributable to hyperglycemia (i.e., glucose toxicity) in diabetes. PMID:19996382

  12. Effects of diet-induced weight gain and turnout to pasture on insulin sensitivity in moderately insulin resistant horses.

    PubMed

    Lindåse, Sanna S; Nostell, Katarina E; Müller, Cecilia E; Jensen-Waern, Marianne; Bröjer, Johan T

    2016-03-01

    OBJECTIVE To quantify insulin sensitivity and monitor glucose, insulin, and lipid concentrations in a group of moderately insulin-resistant horses during induction of obesity by use of a forage diet supplemented with fat and during subsequent turnout to pasture. ANIMALS 9 adult Standardbred mares (11 to 20 years old). PROCEDURES Weight gain of horses was induced during 22 weeks by use of a forage diet supplemented with fat fed in gradually increasing amounts, followed by feeding of that fat-supplemented diet at 2.5 times the daily maintenance requirements. Horses were then turned out to pasture. Insulin sensitivity was measured with the euglycemic hyperinsulinemic clamp method before and after weight gain and after 4 weeks at pasture. Body weight, body condition score, and cresty neck score as well as fasting and postprandial concentrations of plasma insulin, plasma glucose, serum triglyceride, and serum nonesterified fatty acids were measured during the study. RESULTS Body weight typically increased by 10%, and body condition score (scale, 1 to 9) increased by > 1.5 from the start to the end of the weight-gain period. There was no difference in insulin sensitivity or metabolic clearance rate of insulin during the weight-gain period. Four weeks at pasture generally improved insulin sensitivity and metabolic clearance rate of insulin by 54% and 32%, respectively, but there was no change in body weight or body condition score. CONCLUSIONS AND CLINICAL RELEVANCE Findings indicated that dietary composition played a more important role than did short-term weight gain on alterations in insulin sensitivity of horses. PMID:26919602

  13. Aerosol Insulin Induces Regulatory CD8 γδ T Cells That Prevent Murine Insulin-dependent Diabetes

    PubMed Central

    Harrison, Leonard C.; Dempsey-Collier, Majella; Kramer, David R.; Takahashi, Kazuma

    1996-01-01

    Cellular immune hyporesponsiveness can be induced by the presentation of soluble protein antigens to mucosal surfaces. Most studies of mucosa-mediated tolerance have used the oral route of antigen delivery and few have examined autoantigens in natural models of autoimmune disease. Insulin is an autoantigen in humans and nonobese diabetic (NOD) mice with insulindependent diabetes mellitus (IDDM). When we administered insulin aerosol to NOD mice after the onset of subclinical disease, pancreatic islet pathology and diabetes incidence were both significantly reduced. Insulin-treated mice had increased circulating antibodies to insulin, absent splenocyte proliferation to the major epitope, insulin B chain amino acids 9–23, which was associated with increased IL-4 and particularly IL-10 secretion, and reduced proliferation to glutamic acid decarboxylase, another islet autoantigen. The ability of splenocytes from insulin-treated mice to suppress the adoptive transfer of diabetes to nondiabetic mice by T cells of diabetic mice was shown to be caused by small numbers of CD8 γδ T cells. These findings reveal a novel mechanism for suppressing cell-mediated autoimmune disease. Induction of regulatory CD8 γδ T cells by aerosol insulin is a therapeutic strategy with implications for the prevention of human IDDM. PMID:8976172

  14. 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.

  15. 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.

  16. Hippocampal memory processes are modulated by insulin and high-fat-induced insulin resistance

    PubMed Central

    McNay, Ewan C.; Ong, Cecilia T.; McCrimmon, Rory J.; Cresswell, James; Bogan, Jonathan S.; Sherwin, Robert S

    2010-01-01

    Insulin regulates glucose uptake and storage in peripheral tissues, and has been shown to act within the hypothalamus to acutely regulate food intake and metabolism. The machinery for transduction of insulin signaling is also present in other brain areas, particularly in the hippocampus, but a physiological role for brain insulin outside the hypothalamus has not been established. Recent studies suggest that insulin may be able to modulate cognitive functions including memory. Here we report that local delivery of insulin to the rat hippocampus enhances spatial memory, in a PI-3-kinase dependent manner, and that intrahippocampal insulin also increases local glycolytic metabolism. Selective blockade of endogenous intrahippocampal insulin signaling impairs memory performance. Further, a rodent model of type 2 diabetes mellitus produced by a high-fat diet impairs basal cognitive function and attenuates both cognitive and metabolic responses to hippocampal insulin administration. Our data demonstrate that insulin is required for optimal hippocampal memory processing. Insulin resistance within the telencephalon may underlie the cognitive deficits commonly reported to accompany type 2 diabetes. PMID:20176121

  17. Effect of Scoparia dulcis extract on insulin receptors in streptozotocin induced diabetic rats: studies on insulin binding to erythrocytes.

    PubMed

    Pari, Leelavinothan; Latha, Muniappan; Rao, Chippada Appa

    2004-01-01

    We investigated the insulin-receptor-binding effect of Scoparia dulcis plant extract in streptozotocin (STZ)-induced male Wistar rats, using circulating erythrocytes (ER) as a model system. An aqueous extract of S dulcis plant (SPEt) (200 mg/kg body weight) was administered orally. We measured blood levels of glucose and plasma insulin and the binding of insulin to cell-membrane ER receptors. Glibenclamide was used as standard reference drug. The mean specific binding of insulin to ER was significantly lower in diabetic control rats (DC) (55.0 +/- 2.8%) than in SPEt-treated (70.0 +/- 3.5%)- and glibenclamide-treated (65.0 +/- 3.3%) diabetic rats, resulting in a significant decrease in plasma insulin. Scatchard plot analysis demonstrated that the decrease in insulin binding was accounted for by a lower number of insulin receptor sites per cell in DC rats when compared with SPEt- and glibenclamide-treated rats. High-affinity (Kd1), low-affinity (Kd2), and kinetic analysis revealed an increase in the average receptor affinity in ER from SPEt and glibenclamide treated diabetic rats having 2.5 +/- 0.15 x 10(10) M(-1) (Kd1); 17.0 +/- 1.0 x 10(-8) M(-1) (Kd2), and 2.0 +/- 0.1 x 10(-10) M(-1) (Kd1); 12.3 +/- 0.9 x 10(-8) M(-1) (Kd2) compared with 1.0 +/- 0.08 x 10(-10) M(-1) (Kd1); 2.7 +/- 0.25 x 10(-8) M(-1) (Kd2) in DC rats. The results suggest an acute alteration in the number of insulin receptors on ER membranes in STZ-induced diabetic rats. Treatment with SPEt and glibenclamide significantly improved specific insulin binding, with receptor number and affinity binding (p < 0.001) reaching almost normal non-diabetic levels. The data presented here show that SPEt and glibenclamide increase total ER membrane insulin binding sites with a concomitant significant increase in plasma insulin. PMID:15803960

  18. Intranasal Insulin Prevents Anesthesia-Induced Spatial Learning and Memory Deficit in Mice

    PubMed Central

    Zhang, Yongli; Dai, Chun-ling; Chen, Yanxing; Iqbal, Khalid; Liu, Fei; Gong, Cheng-Xin

    2016-01-01

    Elderly individuals are at increased risk of cognitive decline after anesthesia. General anesthesia is believed to be a risk factor for Alzheimer’s disease (AD). At present, there is no treatment that can prevent anesthesia-induced postoperative cognitive dysfunction. Here, we treated mice with daily intranasal administration of insulin (1.75 U/day) for one week before anesthesia induced by intraperitoneal injection of propofol and maintained by inhalation of sevoflurane for 1 hr. We found that the insulin treatment prevented anesthesia-induced deficit in spatial learning and memory, as measured by Morris water maze task during 1–5 days after exposure to anesthesia. The insulin treatment also attenuated anesthesia-induced hyperphosphorylation of tau and promoted the expression of synaptic proteins and insulin signaling in the brain. These findings show a therapeutic potential of intranasal administration of insulin before surgery to reduce the risk of anesthesia-induced cognitive decline and AD. PMID:26879001

  19. Anesthesia with propofol induces insulin resistance systemically in skeletal and cardiac muscles and liver of rats

    SciTech Connect

    Yasuda, Yoshikazu; Fukushima, Yuji; Kaneki, Masao; Martyn, J.A. Jeevendra

    2013-02-01

    Highlights: ► Propofol, as a model anesthetic drug, induced whole body insulin resistance. ► Propofol anesthesia decreased glucose infusion rate to maintain euglycemia. ► Propofol decreased insulin-mediated glucose uptake in skeletal and cardiac muscles. ► Propofol increased hepatic glucose output confirming hepatic insulin resistance. -- Abstract: Hyperglycemia together with hepatic and muscle insulin resistance are common features in critically ill patients, and these changes are associated with enhanced inflammatory response, increased susceptibility to infection, muscle wasting, and worsened prognosis. Tight blood glucose control by intensive insulin treatment may reduce the morbidity and mortality in intensive care units. Although some anesthetics have been shown to cause insulin resistance, it remains unknown how and in which tissues insulin resistance is induced by anesthetics. Moreover, the effects of propofol, a clinically relevant intravenous anesthetic, also used in the intensive care unit for sedation, on insulin sensitivity have not yet been investigated. Euglycemic hyperinsulinemic clamp study was performed in rats anesthetized with propofol and conscious unrestrained rats. To evaluate glucose uptake in tissues and hepatic glucose output [{sup 3}H]glucose and 2-deoxy[{sup 14}C]glucose were infused during the clamp study. Anesthesia with propofol induced a marked whole-body insulin resistance compared with conscious rats, as reflected by significantly decreased glucose infusion rate to maintain euglycemia. Insulin-stimulated tissue glucose uptake was decreased in skeletal muscle and heart, and hepatic glucose output was increased in propofol anesthetized rats. Anesthesia with propofol induces systemic insulin resistance along with decreases in insulin-stimulated glucose uptake in skeletal and heart muscle and attenuation of the insulin-mediated suppression of hepatic glucose output in rats.

  20. Thyrotropin via cyclic AMP induces insulin receptor expression and insulin Co-stimulation of growth and amplifies insulin and insulin-like growth factor signaling pathways in dog thyroid epithelial cells.

    PubMed

    Burikhanov, R; Coulonval, K; Pirson, I; Lamy, F; Dumont, J E; Roger, P P

    1996-11-15

    Despite the similarity of their receptors and signal transduction pathways, insulin is regarded as a regulator of glucose, protein, and lipid metabolism, whereas insulin-like growth factors (IGF-I and IGF-II) mainly act as mitogenic hormones. In the dog thyroid primary culture model, the triggering of DNA synthesis by thyrotropin (TSH) through cAMP, or by cAMP-independent factors including epidermal growth factor, hepatocyte growth factor and phorbol esters, requires insulin or IGFs as comitogenic factors. In the present study, in TSH-treated cells, IGF-I receptors and insulin receptors were paradoxically equivalent in their capacity to elicit the comitogenic pathway, which, however, was mediated only by IGF-I receptors in dog thyroid cells stimulated by cAMP-independent mitogens. Moreover, prior cell exposure to TSH or forskolin increased their responsiveness to insulin, IGF-I, and IGF-II, as seen on DNA synthesis and activation of a common insulin/IGF signaling pathway. To understand these observations, binding characteristics and expression of insulin and IGF-I receptors were examined. To analyze IGF-I receptor characteristics, the unexpected interference of a huge presence of IGF-binding proteins at the cell membrane was avoided using labeled Long R3 IGF-I instead of IGF-I. Strikingly, TSH, through cAMP, time-dependently induced insulin binding and insulin receptor mRNA and protein accumulation without any effect on IGF-I receptors. These findings constitute a first example of an induction of insulin receptor gene expression by a cAMP-mediated hormone. In dog thyroid cells, this allows low physiological insulin concentrations to act as a comitogenic factor and might explain in part the enhanced responsiveness to IGFs in response to TSH. This raises the possibility that TSH-insulin interactions may play a role in the regulation of thyroid growth and function in vivo. PMID:8910605

  1. Go-6976 reverses hyperglycemia-induced insulin resistance independently of cPKC inhibition in adipocytes.

    PubMed

    Robinson, Katherine A; Hegyi, Krisztina; Hannun, Yusuf A; Buse, Maria G; Sethi, Jaswinder K

    2014-01-01

    Chronic hyperglycemia induces insulin resistance by mechanisms that are incompletely understood. One model of hyperglycemia-induced insulin resistance involves chronic preincubation of adipocytes in the presence of high glucose and low insulin concentrations. We have previously shown that the mTOR complex 1 (mTORC1) plays a partial role in the development of insulin resistance in this model. Here, we demonstrate that treatment with Go-6976, a widely used "specific" inhibitor of cPKCs, alleviates hyperglycemia-induced insulin resistance. However, the effects of mTOR inhibitor, rapamycin and Go-6976 were not additive and only rapamycin restored impaired insulin-stimulated AKT activation. Although, PKCα, (but not -β) was abundantly expressed in these adipocytes, our studies indicate cPKCs do not play a major role in causing insulin-resistance in this model. There was no evidence of changes in the expression or phosphorylation of PKCα, and PKCα knock-down did not prevent the reduction of insulin-stimulated glucose transport. This was also consistent with lack of IRS-1 phosphorylation on Ser-24 in hyperglycemia-induced insulin-resistant adipocytes. Treatment with Go-6976 did inhibit a component of the mTORC1 pathway, as evidenced by decreased phosphorylation of S6 ribosomal protein. Raptor knock-down enhanced the effect of insulin on glucose transport in insulin resistant adipocytes. Go-6976 had the same effect in control cells, but was ineffective in cells with Raptor knock-down. Taken together these findings suggest that Go-6976 exerts its effect in alleviating hyperglycemia-induced insulin-resistance independently of cPKC inhibition and may target components of the mTORC1 signaling pathway. PMID:25330241

  2. Fatty acid-induced NLRP3-PYCARD inflammasome activation interferes with insulin signaling

    PubMed Central

    Wen, Haitao; Gris, Denis; Lei, Yu; Jha, Sushmita; Zhang, Lu; Huang, Max Tze-Han; Brickey, Willie June; Ting, Jenny P.-Y.

    2014-01-01

    High-fat diet (HFD) and inflammation are key contributors to insulin resistance and type 2 diabetes (T2D). Interleukin (IL)-1β plays a role in insulin resistance; yet, how IL-1β is induced by fatty acid with HFD, and how this alters insulin signaling is unclear. We show that the saturated fatty acid, palmitate, but not unsaturated oleate, induces the activation of NLRP3-PYCARD inflammasome, causing caspase-1, IL-1β, and IL-18 production. This involves mitochondrial reactive oxygen species and the AMP-activated protein kinase and ULK1 autophagy signaling cascade. Inflammasome activation in hematopoietic cells impairs insulin signaling in several target tissues to reduce glucose tolerance and insulin sensitivity. Furthermore, IL-1β affects insulin sensitivity via TNF-independent and dependent pathways. These findings provide insights into the association of inflammation, diet and T2D. PMID:21478880

  3. Overexpression of uncoupling protein 3 in skeletal muscle protects against fat-induced insulin resistance

    PubMed Central

    Choi, Cheol Soo; Fillmore, Jonathan J.; Kim, Jason K.; Liu, Zhen-Xiang; Kim, Sheene; Collier, Emily F.; Kulkarni, Ameya; Distefano, Alberto; Hwang, Yu-Jin; Kahn, Mario; Chen, Yan; Yu, Chunli; Moore, Irene K.; Reznick, Richard M.; Higashimori, Takamasa; Shulman, Gerald I.

    2007-01-01

    Insulin resistance is a major factor in the pathogenesis of type 2 diabetes and is strongly associated with obesity. Increased concentrations of intracellular fatty acid metabolites have been postulated to interfere with insulin signaling by activation of a serine kinase cascade involving PKCθ in skeletal muscle. Uncoupling protein 3 (UCP3) has been postulated to dissipate the mitochondrial proton gradient and cause metabolic inefficiency. We therefore hypothesized that overexpression of UCP3 in skeletal muscle might protect against fat-induced insulin resistance in muscle by conversion of intramyocellular fat into thermal energy. Wild-type mice fed a high-fat diet were markedly insulin resistant, a result of defects in insulin-stimulated glucose uptake in skeletal muscle and hepatic insulin resistance. Insulin resistance in these tissues was associated with reduced insulin-stimulated insulin receptor substrate 1– (IRS-1–) and IRS-2–associated PI3K activity in muscle and liver, respectively. In contrast, UCP3-overexpressing mice were completely protected against fat-induced defects in insulin signaling and action in these tissues. Furthermore, these changes were associated with a lower membrane-to-cytosolic ratio of diacylglycerol and reduced PKCθ activity in whole-body fat–matched UCP3 transgenic mice. These results suggest that increasing mitochondrial uncoupling in skeletal muscle may be an excellent therapeutic target for type 2 diabetes mellitus. PMID:17571165

  4. Acute physical exercise reverses S-nitrosation of the insulin receptor, insulin receptor substrate 1 and protein kinase B/Akt in diet-induced obese Wistar rats

    PubMed Central

    Pauli, José R; Ropelle, Eduardo R; Cintra, Dennys E; Carvalho-Filho, Marco A; Moraes, Juliana C; De Souza, Cláudio T; Velloso, Lício A; Carvalheira, José B C; Saad, Mario J A

    2008-01-01

    Early evidence demonstrates that exogenous nitric oxide (NO) and the NO produced by inducible nitric oxide synthase (iNOS) can induce insulin resistance. Here, we investigated whether this insulin resistance, mediated by S-nitrosation of proteins involved in early steps of the insulin signal transduction pathway, could be reversed by acute physical exercise. Rats on a high-fat diet were subjected to swimming for two 3 h-long bouts, separated by a 45 min rest period. Two or 16 h after the exercise protocol the rats were killed and proteins from the insulin signalling pathway were analysed by immunoprecipitation and immunoblotting. We demonstrated that a high-fat diet led to an increase in the iNOS protein level and S-nitrosation of insulin receptor β (IRβ), insulin receptor substrate 1 (IRS1) and Akt. Interestingly, an acute bout of exercise reduced iNOS expression and S-nitrosation of proteins involved in the early steps of insulin action, and improved insulin sensitivity in diet-induced obesity rats. Furthermore, administration of GSNO (NO donor) prevents this improvement in insulin action and the use of an inhibitor of iNOS (l-N6-(1-iminoethyl)lysine; l-NIL) simulates the effects of exercise on insulin action, insulin signalling and S-nitrosation of IRβ, IRS1 and Akt. In summary, a single bout of exercise reverses insulin sensitivity in diet-induced obese rats by improving the insulin signalling pathway, in parallel with a decrease in iNOS expression and in the S-nitrosation of IR/IRS1/Akt. The decrease in iNOS protein expression in the muscle of diet-induced obese rats after an acute bout of exercise was accompanied by an increase in AMP-activated protein kinase (AMPK) activity. These results provide new insights into the mechanism by which exercise restores insulin sensitivity. PMID:17974582

  5. Long-term fatty liver-induced insulin resistance in orotic acid-induced nonalcoholic fatty liver rats.

    PubMed

    Han, Xiuqing; Liu, Chunhua; Xue, Yong; Wang, Jingfeng; Xue, Changhu; Yanagita, Teruyoshi; Gao, Xiang; Wang, Yuming

    2016-04-01

    We investigated whether fatty liver preceded insulin resistance or vice versa using a long-term orotic acid (OA)-induced nonalcoholic fatty liver disease (NAFLD) model without the confounding effects of obesity and hyperlipidemia and explored the role of the liver in insulin resistance. Male Wistar rats were fed with or without OA supplementation for 30, 60, and 90 days. The NAFLD group showed increased liver lipid at 30, 60, and 90 days; glucose intolerance was noted at 60 and 90 days. Furthermore, partial liver proteins and gene expressions related to upstream signaling of insulin were decreased. However, the liver glycogen content was elevated, and gluconeogenesis genes expressions were obviously decreased at 90 days. The occurrence of fatty liver preceded insulin resistance in OA-induced NAFLD without the interference of obesity and hyperlipidemia, and hepatic insulin resistance may not play a conclusive role in insulin resistance in this model. PMID:26775542

  6. Atorvastatin ameliorates endothelium-specific insulin resistance induced by high glucose combined with high insulin.

    PubMed

    Yang, Ou; Li, Jinliang; Chen, Haiyan; Li, Jie; Kong, Jian

    2016-09-01

    The aim of the present study was to establish an endothelial cell model of endothelium-specific insulin resistance to evaluate the effect of atorvastatin on insulin resistance-associated endothelial dysfunction and to identify the potential pathway responsible for its action. Cultured human umbilical vein endothelial cells (HUVECs) were pretreated with different concentrations of glucose with, or without, 10‑5 M insulin for 24 h, following which the cells were treated with atorvastatin. The tyrosine phosphorylation of insulin receptor (IR) and insulin receptor substrate-1 (IRS‑1), the production of nitric oxide (NO), the activity and phosphorylation level of endothelial NO synthase (eNOS) on serine1177, and the mRNA levels of endothelin‑1 (ET‑1) were assessed during the experimental procedure. Treatment of the HUVECs with 30 mM glucose and 10‑5 M insulin for 24 h impaired insulin signaling, with reductions in the tyrosine phosphorylation of IR and protein expression of IRS‑1 by almost 75 and 65%, respectively. This, in turn, decreased the activity and phosphorylation of eNOS on serine1177, and reduced the production of NO by almost 80%. By contrast, the mRNA levels of ET‑1 were upregulated. All these changes were ameliorated by atorvastatin. Taken together, these results demonstrated that high concentrations of glucose and insulin impaired insulin signaling leading to endothelial dysfunction, and that atorvastatin ameliorated these changes, acting primarily through the phosphatidylinositol 3-kinase/Akt/eNOS signaling pathway. PMID:27484094

  7. Importance of peripheral insulin levels for insulin-induced suppression of glucose production in depancreatized dogs.

    PubMed Central

    Giacca, A; Fisher, S J; Shi, Z Q; Gupta, R; Lickley, H L; Vranic, M

    1992-01-01

    It is generally believed that glucose production (GP) cannot be adequately suppressed in insulin-treated diabetes because the portal-peripheral insulin gradient is absent. To determine whether suppression of GP in diabetes depends on portal insulin levels, we performed 3-h glucose and specific activity clamps in moderately hyperglycemic (10 mM) depancreatized dogs, using three protocols: (a) 54 pmol.kg-1 bolus + 5.4 pmol.kg-1.min-1 portal insulin infusion (n = 7; peripheral insulin = 170 +/- 51 pM); (b) an equimolar peripheral infusion (n = 7; peripheral insulin = 294 +/- 28 pM, P < 0.001); and (c) a half-dose peripheral infusion (n = 7), which gave comparable (157 +/- 13 pM) insulinemia to that seen in protocol 1. Glucose production, use (GU) and cycling (GC) were measured using HPLC-purified 6-[3H]- and 2-[3H]glucose. Consistent with the higher peripheral insulinemia, peripheral infusion was more effective than equimolar portal infusion in increasing GU. Unexpectedly, it was also more potent in suppressing GP (73 +/- 7 vs. 55 +/- 7% suppression between 120 and 180 min, P < 0.001). At matched peripheral insulinemia (protocols 2 and 3), not only stimulation of GU, but also suppression of GP was the same (55 +/- 7 vs. 63 +/- 4%). In the diabetic dogs at 10 mM glucose, GC was threefold higher than normal but failed to decrease with insulin infusion by either route. Glycerol, alanine, FFA, and glucagon levels decreased proportionally to peripheral insulinemia. However, the decrease in glucagon was not significantly greater in protocol 2 than in 1 or 3. When we combined all protocols, we found a correlation between the decrements in glycerol and FFAs and the decrease in GP (r = 0.6, P < 0.01). In conclusion, when suprabasal insulin levels in the physiological postprandial range are provided to moderately hyperglycemic depancreatized dogs, suppression of GP appears to be more dependent on peripheral than portal insulin concentrations and may be mainly mediated by

  8. Insulin-induced localized lipoatrophy preceded by shingles (herpes zoster): a case report

    PubMed Central

    2014-01-01

    Introduction Localized involutional lipoatrophy of subcutaneous adipose tissue may develop due to subcutaneous injection of pharmaceutical preparations. The pathogenesis of this adverse drug reaction is unknown. The progression of localized involutional lipoatrophy ceases and occasionally it resolves after withdrawing the inducing agent. In case of localized involutional lipoatrophy due to subcutaneous insulin therapy, low-dose systemic corticosteroids may be curative despite ongoing insulin administration. Case presentation We report a recurrence of insulin-induced localized involutional lipoatrophy at the abdominal wall in a 57-year-old Caucasian woman with type-1 diabetes on continuous subcutaneous insulin infusion. The first episode of insulin-induced localized involutional lipoatrophy two years previously had been cured by oral prednisone. The recurrence was treated immediately with 10mg prednisone once daily for five months, and was cured thereafter. The insulin analog preparation (Humalog™) and the insulin pump equipment (Accu-Chek Spirit™) applied were the same during both episodes. Both episodes were preceded by a temporary disturbance of the immune balance (the first episode by vaccination, the second episode through shingles). Conclusions This case confirms that insulin-induced localized involutional lipoatrophy in type-1 diabetes can occur again, and can be cured by systemic corticosteroids. We suggest that temporary disturbance of the immune balance may trigger this transitory idiosyncratic reaction in a susceptible individual. PMID:24961832

  9. 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...

  10. Genetic variation in insulin-induced kinase signaling

    PubMed Central

    Wang, Isabel Xiaorong; Ramrattan, Girish; Cheung, Vivian G

    2015-01-01

    Individual differences in sensitivity to insulin contribute to disease susceptibility including diabetes and metabolic syndrome. Cellular responses to insulin are well studied. However, which steps in these response pathways differ across individuals remains largely unknown. Such knowledge is needed to guide more precise therapeutic interventions. Here, we studied insulin response and found extensive individual variation in the activation of key signaling factors, including ERK whose induction differs by more than 20-fold among our subjects. This variation in kinase activity is propagated to differences in downstream gene expression response to insulin. By genetic analysis, we identified cis-acting DNA variants that influence signaling response, which in turn affects downstream changes in gene expression and cellular phenotypes, such as protein translation and cell proliferation. These findings show that polymorphic differences in signal transduction contribute to individual variation in insulin response, and suggest kinase modulators as promising therapeutics for diseases characterized by insulin resistance. PMID:26202599

  11. Endogenous epinephrine protects against obesity induced insulin resistance.

    PubMed

    Ziegler, Michael G; Milic, Milos; Sun, Ping; Tang, Chih-Min; Elayan, Hamzeh; Bao, Xuping; Cheung, Wai Wilson; O'Connor, Daniel T

    2011-07-01

    Epinephrine (E) is a hormone released from the adrenal medulla in response to low blood sugar and other stresses. E and related β2-adrenergic agonists are used to treat asthma, but a side effect is high blood sugar. C57BL/6 mice prone to overfeeding induced type II diabetes had the PNMT gene knocked out to prevent E synthesis. These E deficient mice were very similar to control animals on a 14% fat diet. On a 40.6% fat diet they gained 20 to 33% more weight than control animals and increased their blood glucose response to a glucose tolerance test because they became resistant to insulin. Although the short term effect of β2-agonists such as E is to raise blood glucose, some long acting β2-agonists improve muscle glucose uptake. Endogenous E protects against overfeeding induced diabetes. Since adrenal E release can be impaired with aging and diabetes, endogenous E may help prevent adult onset diabetes. PMID:21354376

  12. Myotubes derived from human-induced pluripotent stem cells mirror in vivo insulin resistance

    PubMed Central

    Iovino, Salvatore; Burkart, Alison M.; Warren, Laura; Patti, Mary Elizabeth; Kahn, C. Ronald

    2016-01-01

    Induced pluripotent stem cells (iPS cells) represent a unique tool for the study of the pathophysiology of human disease, because these cells can be differentiated into multiple cell types in vitro and used to generate patient- and tissue-specific disease models. Given the critical role for skeletal muscle insulin resistance in whole-body glucose metabolism and type 2 diabetes, we have created a novel cellular model of human muscle insulin resistance by differentiating iPS cells from individuals with mutations in the insulin receptor (IR-Mut) into functional myotubes and characterizing their response to insulin in comparison with controls. Morphologically, IR-Mut cells differentiated normally, but had delayed expression of some muscle differentiation-related genes. Most importantly, whereas control iPS-derived myotubes exhibited in vitro responses similar to primary differentiated human myoblasts, IR-Mut myotubes demonstrated severe impairment in insulin signaling and insulin-stimulated 2-deoxyglucose uptake and glycogen synthesis. Transcriptional regulation was also perturbed in IR-Mut myotubes with reduced insulin-stimulated expression of metabolic and early growth response genes. Thus, iPS-derived myotubes from individuals with genetically determined insulin resistance demonstrate many of the defects observed in vivo in insulin-resistant skeletal muscle and provide a new model to analyze the molecular impact of muscle insulin resistance. PMID:26831110

  13. Edible Bird's Nest Prevents High Fat Diet-Induced Insulin Resistance in Rats

    PubMed Central

    Yida, Zhang; Imam, Mustapha Umar; Ismail, Maznah; Ooi, Der-Jiun; Sarega, Nadarajan; Azmi, Nur Hanisah; Ismail, Norsharina; Chan, Kim Wei; Hou, Zhiping; Yusuf, Norhayati Binti

    2015-01-01

    Edible bird's nest (EBN) is used traditionally in many parts of Asia to improve wellbeing, but there are limited studies on its efficacy. We explored the potential use of EBN for prevention of high fat diet- (HFD-) induced insulin resistance in rats. HFD was given to rats with or without simvastatin or EBN for 12 weeks. During the intervention period, weight measurements were recorded weekly. Blood samples were collected at the end of the intervention and oral glucose tolerance test conducted, after which the rats were sacrificed and their liver and adipose tissues collected for further studies. Serum adiponectin, leptin, F2-isoprostane, insulin, and lipid profile were estimated, and homeostatic model assessment of insulin resistance computed. Effects of the different interventions on transcriptional regulation of insulin signaling genes were also evaluated. The results showed that HFD worsened metabolic indices and induced insulin resistance partly through transcriptional regulation of the insulin signaling genes. Additionally, simvastatin was able to prevent hypercholesterolemia but promoted insulin resistance similar to HFD. EBN, on the other hand, prevented the worsening of metabolic indices and transcriptional changes in insulin signaling genes due to HFD. The results suggest that EBN may be used as functional food to prevent insulin resistance. PMID:26273674

  14. Edible Bird's Nest Prevents High Fat Diet-Induced Insulin Resistance in Rats.

    PubMed

    Yida, Zhang; Imam, Mustapha Umar; Ismail, Maznah; Ooi, Der-Jiun; Sarega, Nadarajan; Azmi, Nur Hanisah; Ismail, Norsharina; Chan, Kim Wei; Hou, Zhiping; Yusuf, Norhayati Binti

    2015-01-01

    Edible bird's nest (EBN) is used traditionally in many parts of Asia to improve wellbeing, but there are limited studies on its efficacy. We explored the potential use of EBN for prevention of high fat diet- (HFD-) induced insulin resistance in rats. HFD was given to rats with or without simvastatin or EBN for 12 weeks. During the intervention period, weight measurements were recorded weekly. Blood samples were collected at the end of the intervention and oral glucose tolerance test conducted, after which the rats were sacrificed and their liver and adipose tissues collected for further studies. Serum adiponectin, leptin, F2-isoprostane, insulin, and lipid profile were estimated, and homeostatic model assessment of insulin resistance computed. Effects of the different interventions on transcriptional regulation of insulin signaling genes were also evaluated. The results showed that HFD worsened metabolic indices and induced insulin resistance partly through transcriptional regulation of the insulin signaling genes. Additionally, simvastatin was able to prevent hypercholesterolemia but promoted insulin resistance similar to HFD. EBN, on the other hand, prevented the worsening of metabolic indices and transcriptional changes in insulin signaling genes due to HFD. The results suggest that EBN may be used as functional food to prevent insulin resistance. PMID:26273674

  15. Pharmacological TLR4 Inhibition Protects against Acute and Chronic Fat-Induced Insulin Resistance in Rats

    PubMed Central

    Zhang, Ning; Liang, Hanyu; Farese, Robert V.; Li, Ji

    2015-01-01

    Aims To evaluate whether pharmacological TLR4 inhibition protects against acute and chronic fat-induced insulin resistance in rats. Materials and Methods For the acute experiment, rats received a TLR4 inhibitor [TAK-242 or E5564 (2x5 mg/kg i.v. bolus)] or vehicle, and an 8-h Intralipid (20%, 8.5 mg/kg/min) or saline infusion, followed by a two-step hyperinsulinemic-euglycemic clamp. For the chronic experiment, rats were subcutaneously implanted with a slow-release pellet of TAK-242 (1.5 mg/d) or placebo. Rats then received a high fat diet (HFD) or a low fat control diet (LFD) for 10 weeks, followed by a two-step insulin clamp. Results Acute experiment; the lipid-induced reduction (18%) in insulin-stimulated glucose disposal (Rd) was attenuated by TAK-242 and E5564 (the effect of E5564 was more robust), suggesting improved peripheral insulin action. Insulin was able to suppress hepatic glucose production (HGP) in saline- but not lipid-treated rats. TAK-242, but not E5564, partially restored this effect, suggesting improved HGP. Chronic experiment; insulin-stimulated Rd was reduced ~30% by the HFD, but completely restored by TAK-242. Insulin could not suppress HGP in rats fed a HFD and TAK-242 had no effect on HGP. Conclusions Pharmacological TLR4 inhibition provides partial protection against acute and chronic fat-induced insulin resistance in vivo. PMID:26196892

  16. Short- and Longterm Glycemic Control of Streptozotocin-Induced Diabetic Rats Using Different Insulin Preparations

    PubMed Central

    Luippold, Gerd; Bedenik, Jessica; Voigt, Anke; Grempler, Rolf

    2016-01-01

    The chemical induction of diabetes with STZ has gained popularity because of the relative ease of rendering normal animals diabetic. Insulin substitution is required in STZ-rats in long-term studies to avoid ketoacidosis and consequently loss of animals. Aim of the present studies was to test different insulin preparations and different ways of administration in their ability to reduce blood glucose in STZ-induced diabetic rats. Single dosing of the long-acting insulin analogue glargine was able to dose-dependently reduce blood glucose over 4 h towards normoglycemia in STZ-treated rats. However, this effect was not sustained until 8 h post injection. A more sustained glucose-lowering effect was achieved using insulin-releasing implants. In STZ-rats, 1 insulin implant moderately lowered blood glucose levels 10 days after implantation, while 2 implants induced normoglycemia over the whole day. According to the glucose-lowering effect 1 as well as 2 insulin implants significantly reduced HbA1c measured after 26 days of implantation. In line with the improved glucose homeostasis due to the implants, urinary glucose excretion was also blunted in STZ-treated rats with 2 implants. Since diabetic nephropathy is one of the complications of longterm diabetes, renal function was characterized in the STZ-rat model. Increases in creatinine clearance and urinary albumin excretion resemble early signs of diabetic nephropathy. These functional abnormalities of the kidney could clearly be corrected with insulin-releasing implants 27 days after implantation. The data show that diabetic STZ-rats respond to exogenous insulin with regard to glucose levels as well as kidney parameters and a suitable dose of insulin implants for glucose control was established. This animal model together with the insulin dosing regimen is suitable to address diabetes-induced early diabetic nephropathy and also to study combination therapies with insulin for the treatment of type 1 diabetes. PMID:27253523

  17. Silymarin Induces Insulin Resistance through an Increase of Phosphatase and Tensin Homolog in Wistar Rats

    PubMed Central

    Cheng, Kai-Chun; Asakawa, Akihiro; Li, Ying-Xiao; Chung, Hsien-Hui; Amitani, Haruka; Ueki, Takatoshi; Cheng, Juei-Tang; Inui, Akio

    2014-01-01

    Background and aims Phosphatase and tensin homolog (PTEN) is a phosphoinositide phosphatase that regulates crucial cellular functions, including insulin signaling, lipid and glucose metabolism, as well as survival and apoptosis. Silymarin is the active ingredient in milk thistle and exerts numerous effects through the activation of PTEN. However, the effect of silymarin on the development of insulin resistance remains unknown. Methods Wistar rats fed fructose-rich chow or normal chow were administered oral silymarin to identify the development of insulin resistance using the homeostasis model assessment of insulin resistance and hyperinsulinemic- euglycemic clamping. Changes in PTEN expression in skeletal muscle and liver were compared using western blotting analysis. Further investigation was performed in L6 cells to check the expression of PTEN and insulin-related signals. PTEN deletion in L6 cells was achieved by small interfering ribonucleic acid transfection. Results Oral administration of silymarin at a dose of 200 mg/kg once daily induced insulin resistance in normal rats and enhanced insulin resistance in fructose-rich chow-fed rats. An increase of PTEN expression was observed in the skeletal muscle and liver of rats with insulin resistance. A decrease in the phosphorylation of Akt in L6 myotube cells, which was maintained in a high-glucose condition, was also observed. Treatment with silymarin aggravated high-glucose-induced insulin resistance. Deletion of PTEN in L6 cells reversed silymarin-induced impaired insulin signaling and glucose uptake. Conclusions Silymarin has the ability to disrupt insulin signaling through increased PTEN expression. Therefore, silymarin should be used carefully in type-2 diabetic patients. PMID:24404172

  18. Short- and Longterm Glycemic Control of Streptozotocin-Induced Diabetic Rats Using Different Insulin Preparations.

    PubMed

    Luippold, Gerd; Bedenik, Jessica; Voigt, Anke; Grempler, Rolf

    2016-01-01

    The chemical induction of diabetes with STZ has gained popularity because of the relative ease of rendering normal animals diabetic. Insulin substitution is required in STZ-rats in long-term studies to avoid ketoacidosis and consequently loss of animals. Aim of the present studies was to test different insulin preparations and different ways of administration in their ability to reduce blood glucose in STZ-induced diabetic rats. Single dosing of the long-acting insulin analogue glargine was able to dose-dependently reduce blood glucose over 4 h towards normoglycemia in STZ-treated rats. However, this effect was not sustained until 8 h post injection. A more sustained glucose-lowering effect was achieved using insulin-releasing implants. In STZ-rats, 1 insulin implant moderately lowered blood glucose levels 10 days after implantation, while 2 implants induced normoglycemia over the whole day. According to the glucose-lowering effect 1 as well as 2 insulin implants significantly reduced HbA1c measured after 26 days of implantation. In line with the improved glucose homeostasis due to the implants, urinary glucose excretion was also blunted in STZ-treated rats with 2 implants. Since diabetic nephropathy is one of the complications of longterm diabetes, renal function was characterized in the STZ-rat model. Increases in creatinine clearance and urinary albumin excretion resemble early signs of diabetic nephropathy. These functional abnormalities of the kidney could clearly be corrected with insulin-releasing implants 27 days after implantation. The data show that diabetic STZ-rats respond to exogenous insulin with regard to glucose levels as well as kidney parameters and a suitable dose of insulin implants for glucose control was established. This animal model together with the insulin dosing regimen is suitable to address diabetes-induced early diabetic nephropathy and also to study combination therapies with insulin for the treatment of type 1 diabetes. PMID:27253523

  19. Heterozygous caveolin-3 mice show increased susceptibility to palmitate-induced insulin resistance.

    PubMed

    Talukder, M A Hassan; Preda, Marilena; Ryzhova, Larisa; Prudovsky, Igor; Pinz, Ilka M

    2016-03-01

    Insulin resistance and diabetes are comorbidities of obesity and affect one in 10 adults in the United States. Despite the high prevalence, the mechanisms of cardiac insulin resistance in obesity are still unclear. We test the hypothesis that the insulin receptor localizes to caveolae and is regulated through binding to caveolin-3 (CAV3). We further test whether haploinsufficiency forCAV3 increases the susceptibility to high-fat-induced insulin resistance. We used in vivo and in vitro studies to determine the effect of palmitate exposure on global insulin resistance, contractile performance of the heart in vivo, glucose uptake in the heart, and on cellular signaling downstream of theIR We show that haploinsufficiency forCAV3 increases susceptibility to palmitate-induced global insulin resistance and causes cardiomyopathy. On the basis of fluorescence energy transfer (FRET) experiments, we show thatCAV3 andIRdirectly interact in cardiomyocytes. Palmitate impairs insulin signaling by a decrease in insulin-stimulated phosphorylation of Akt that corresponds to an 87% decrease in insulin-stimulated glucose uptake inHL-1 cardiomyocytes. Despite loss of Akt phosphorylation and lower glucose uptake, palmitate increased insulin-independent serine phosphorylation ofIRS-1 by 35%. In addition, we found lipid induced downregulation ofCD36, the fatty acid transporter associated with caveolae. This may explain the problem the diabetic heart is facing with the simultaneous impairment of glucose uptake and lipid transport. Thus, these findings suggest that loss ofCAV3 interferes with downstream insulin signaling and lipid uptake, implicatingCAV3 as a regulator of theIRand regulator of lipid uptake in the heart. PMID:27033451

  20. Umbelliferone attenuates unpredictable chronic mild stress induced-insulin resistance in rats.

    PubMed

    Su, Qiang; Tao, Weiwei; Wang, Hanqing; Chen, Yanyan; Huang, Huang; Chen, Gang

    2016-05-01

    The aim of this study was to investigate whether umbelliferone (Umb) could attenuate insulin resistance in unpredictable chronic mild stress (CUMS)-induced rats. Behavioral changes were evaluated through sucrose preference test (SPT), open-field test, forced swimming test, and tail suspension test (TST), suggesting that Umb (20 and 40 mg/kg) could effectively improve depression symptoms. Oral glucose tolerance test and serum insulin indicated that Umb attributed to the control of blood glucose levels. The phosphorylation of insulin receptor, insulin receptor substrate (IRS)-1, glycogen synthase kinase-3β, PI3K, and Akt was increased in Umb (20 and 40 mg/kg) treatment according to Western blot analysis. Taken together, the current results suggested the ameliorative effect of Umb against insulin resistance in the CUMS-induced rats. © 2016 IUBMB Life, 68(5):403-409, 2016. PMID:27027512

  1. JNK1 in hematopoietically derived cells contributes to diet-induced inflammation and insulin resistance without affecting obesity.

    PubMed

    Solinas, Giovanni; Vilcu, Cristian; Neels, Jaap G; Bandyopadhyay, Gautam K; Luo, Jun-Li; Naugler, Willscott; Grivennikov, Sergei; Wynshaw-Boris, Anthony; Scadeng, Miriam; Olefsky, Jerrold M; Karin, Michael

    2007-11-01

    Obesity-induced insulin resistance is a major factor in the etiology of type 2 diabetes, and Jun kinases (JNKs) are key negative regulators of insulin sensitivity in the obese state. Activation of JNKs (mainly JNK1) in insulin target cells results in phosphorylation of insulin receptor substrates (IRSs) at serine and threonine residues that inhibit insulin signaling. JNK1 activation is also required for accumulation of visceral fat. Here we used reciprocal adoptive transfer experiments to determine whether JNK1 in myeloid cells, such as macrophages, also contributes to insulin resistance and central adiposity. Our results show that deletion of Jnk1 in the nonhematopoietic compartment protects mice from high-fat diet (HFD)-induced insulin resistance, in part through decreased adiposity. By contrast, Jnk1 removal from hematopoietic cells has no effect on adiposity but confers protection against HFD-induced insulin resistance by decreasing obesity-induced inflammation. PMID:17983584

  2. Glucosamine induces REDD1 to suppress insulin action in retinal Müller cells.

    PubMed

    Moore, Joshua A; Miller, William P; Dennis, Michael D

    2016-05-01

    Resistance to insulin action is a key cause of diabetic complications, yet much remains unknown about the molecular mechanisms that contribute to the defect. Glucose-induced insulin resistance in peripheral tissues such as the retina is mediated in part by the hexosamine biosynthetic pathway (HBP). Glucosamine (GAM), a leading dietary supplement marketed to relieve the discomfort of osteoarthritis, is metabolized by the HBP, and in doing so bypasses the rate-limiting enzyme of the pathway. Thus, exogenous GAM consumption potentially exacerbates the resistance to insulin action observed with diabetes-induced hyperglycemia. In the present study, we evaluated the effect of GAM on insulin action in retinal Müller cells in culture. Addition of GAM to Müller cell culture repressed insulin-induced activation of the Akt/mTORC1 signaling pathway. However, the effect was not recapitulated by chemical inhibition to promote protein O-GlcNAcylation, nor was blockade of O-GlcNAcylation sufficient to prevent the effects of GAM. Instead, GAM induced ER stress and subsequent expression of the protein Regulated in DNA Damage and Development (REDD1), which was necessary for GAM to repress insulin-stimulated phosphorylation of Akt on Thr308. Overall, the findings support a model whereby GAM promotes ER stress in retinal Müller cells, resulting in elevated REDD1 expression and thus resistance to insulin action. PMID:26852666

  3. Inhibition of Carnitine Palmitoyltransferase-1 Activity Alleviates Insulin Resistance in Diet-Induced Obese Mice

    PubMed Central

    Keung, Wendy; Ussher, John R.; Jaswal, Jagdip S.; Raubenheimer, Monique; Lam, Victoria H.M.; Wagg, Cory S.; Lopaschuk, Gary D.

    2013-01-01

    Impaired skeletal muscle fatty acid oxidation has been suggested to contribute to insulin resistance and glucose intolerance. However, increasing muscle fatty acid oxidation may cause a reciprocal decrease in glucose oxidation, which might impair insulin sensitivity and glucose tolerance. We therefore investigated what effect inhibition of mitochondrial fatty acid uptake has on whole-body glucose tolerance and insulin sensitivity in obese insulin-resistant mice. C57BL/6 mice were fed a high-fat diet (60% calories from fat) for 12 weeks to develop insulin resistance. Subsequent treatment of mice for 4 weeks with the carnitine palmitoyltransferase-1 inhibitor, oxfenicine (150 mg/kg i.p. daily), resulted in improved whole-body glucose tolerance and insulin sensitivity. Exercise capacity was increased in oxfenicine-treated mice, which was accompanied by an increased respiratory exchange ratio. In the gastrocnemius muscle, oxfenicine increased pyruvate dehydrogenase activity, membrane GLUT4 content, and insulin-stimulated Akt phosphorylation. Intramyocellular levels of lipid intermediates, including ceramide, long-chain acyl CoA, and diacylglycerol, were also decreased. Our results demonstrate that inhibition of mitochondrial fatty acid uptake improves insulin sensitivity in diet-induced obese mice. This is associated with increased carbohydrate utilization and improved insulin signaling in the skeletal muscle, suggestive of an operating Randle Cycle in muscle. PMID:23139350

  4. Inhibition of carnitine palmitoyltransferase-1 activity alleviates insulin resistance in diet-induced obese mice.

    PubMed

    Keung, Wendy; Ussher, John R; Jaswal, Jagdip S; Raubenheimer, Monique; Lam, Victoria H M; Wagg, Cory S; Lopaschuk, Gary D

    2013-03-01

    Impaired skeletal muscle fatty acid oxidation has been suggested to contribute to insulin resistance and glucose intolerance. However, increasing muscle fatty acid oxidation may cause a reciprocal decrease in glucose oxidation, which might impair insulin sensitivity and glucose tolerance. We therefore investigated what effect inhibition of mitochondrial fatty acid uptake has on whole-body glucose tolerance and insulin sensitivity in obese insulin-resistant mice. C57BL/6 mice were fed a high-fat diet (60% calories from fat) for 12 weeks to develop insulin resistance. Subsequent treatment of mice for 4 weeks with the carnitine palmitoyltransferase-1 inhibitor, oxfenicine (150 mg/kg i.p. daily), resulted in improved whole-body glucose tolerance and insulin sensitivity. Exercise capacity was increased in oxfenicine-treated mice, which was accompanied by an increased respiratory exchange ratio. In the gastrocnemius muscle, oxfenicine increased pyruvate dehydrogenase activity, membrane GLUT4 content, and insulin-stimulated Akt phosphorylation. Intramyocellular levels of lipid intermediates, including ceramide, long-chain acyl CoA, and diacylglycerol, were also decreased. Our results demonstrate that inhibition of mitochondrial fatty acid uptake improves insulin sensitivity in diet-induced obese mice. This is associated with increased carbohydrate utilization and improved insulin signaling in the skeletal muscle, suggestive of an operating Randle Cycle in muscle. PMID:23139350

  5. PPARδ agonist attenuates alcohol-induced hepatic insulin resistance and improves liver injury and repair

    PubMed Central

    Pang, Maoyin; de la Monte, Suzanne M.; Longato, Lisa; Tong, Ming; He, Jiman; Chaudhry, Rajeeve; Duan, Kevin; Ouh, Jiyun; Wands, Jack R.

    2009-01-01

    Background/Aims Chronic ethanol exposure impairs liver regeneration due to inhibition of insulin signaling and oxidative injury. PPAR agonists function as insulin sensitizers and anti-inflammatory agents. We investigated whether treatment with a PPARδ agonist could restore hepatic insulin sensitivity, survival signaling, and regenerative responses vis-a-vis chronic ethanol feeding. Methods Adult rats were fed isocaloric liquid diets containing 0% or 37% ethanol, and administered a PPARδ agonist by i.p. injection. We used liver tissue to examine histopathology, gene expression, oxidative stress, insulin signaling, and regenerative responses to 2/3 hepatectomy. Results Chronic ethanol feeding caused insulin resistance, increased oxidative stress, lipid peroxidation, DNA damage, and hepatocellular injury in liver. These effects were associated with reduced insulin receptor binding and affinity, impaired survival signaling through PI3K/Akt/GSK3β, and reduced expression of insulin responsive genes mediating energy metabolism and tissue remodeling. PPARδ agonist treatment reduced ethanol-mediated hepatic injury, oxidative stress, lipid peroxidation, and insulin resistance, increased signaling through PI3K/Akt/GSK3β, and enhanced the regenerative response to partial hepatectomy. Conclusions PPARδ agonist administration may attenuate the severity of chronic ethanol-induced liver injury and ethanol’s adverse effects on the hepatic repair by restoring insulin responsiveness, even in the context of continued high-level ethanol consumption. PMID:19398227

  6. Odontella aurita-enriched diet prevents high fat diet-induced liver insulin resistance.

    PubMed

    Amine, Hamza; Benomar, Yacir; Haimeur, Adil; Messaouri, Hafida; Meskini, Nadia; Taouis, Mohammed

    2016-01-01

    The beneficial effect of polyunsaturated omega-3 fatty acid (w-3 FA) consumption regarding cardiovascular diseases, insulin resistance and inflammation has been widely reported. Fish oil is considered as the main source of commercialized w-3 FAs, and other alternative sources have been reported such as linseed or microalgae. However, despite numerous reports, the underlying mechanisms of action of w-3 FAs on insulin resistance are still not clearly established, especially those from microalgae. Here, we report that Odontella aurita, a microalga rich in w-3 FAs eicosapentaenoic acid, prevents high fat diet-induced insulin resistance and inflammation in the liver of Wistar rats. Indeed, a high fat diet (HFD) increased plasma insulin levels associated with the impairment of insulin receptor signaling and the up-regulation of toll-like receptor 4 (TLR4) expressions. Importantly, Odontella aurita-enriched HFD (HFOA) reduces body weight and plasma insulin levels and maintains normal insulin receptor expression and responsiveness. Furthermore, HFOA decreased TLR4 expression, JNK/p38 phosphorylation and pro-inflammatory factors. In conclusion, we demonstrate for the first time, to our knowledge, that diet supplementation with whole Ondontella aurita overcomes HFD-induced insulin resistance through the inhibition of TLR4/JNK/p38 MAP kinase signaling pathways. PMID:26459640

  7. Curcumin and docosahexaenoic acid block insulin-induced colon carcinoma cell proliferation.

    PubMed

    Fenton, Jenifer I; McCaskey, Sarah J

    2013-03-01

    Diets high in fish and curcumin are associated with a decreased risk of CRC. Insulin resistance and obesity are associated with increased CRC risk and higher reoccurrence rates. We utilized cell culture to determine if dietary compounds could reduce insulin-induced cell proliferation comparing the response in normal and metastatic colon epithelial cells. We treated model normal murine colon epithelial cells (YAMC) and adenocarcinoma cells (MC38) with docosahexaenoic acid (DHA) or curcumin alone and then co-treatments of the diet-derived compound and insulin were combined. Cell proliferation was stimulated with insulin (1 ug/mL) to model insulin resistance in obesity. Despite the presence of insulin, proliferation was reduced in the MC38 cells treated with 10 μM curcumin (p<0.001) and 50 μM DHA (p<0.001). Insulin stimulated MAPK and MEK phosphorylation was inhibited by DHA and curcumin in MC38 cancer cells. Here we show that curcumin and DHA can block insulin-induced colon cancer cell proliferation in vitro via a MEK mediated mechanism. PMID:23266210

  8. Hexane Extract of Orthosiphon stamineus Induces Insulin Expression and Prevents Glucotoxicity in INS-1 Cells

    PubMed Central

    Lee, Hae-Jung; Choi, Yoon-Jung; Park, So-Young; Kim, Jong-Yeon; Won, Kyu-Chang; Son, Jong-Keun

    2015-01-01

    Background Hyperglycemia, a characteristic feature of diabetes, induces glucotoxicity in pancreatic β-cells, resulting in further impairment of insulin secretion and worsening glycemic control. Thus, preservation of insulin secretory capacity is essential for the management of type 2 diabetes. In this study, we evaluated the ability of an Orthosiphon stamineus (OS) extract to prevent glucotoxicity in insulin-producing cells. Methods We measured insulin mRNA expression and glucose-stimulated insulin secretion (GSIS) in OS-treated INS-1 cells after exposure to a high glucose (HG; 30 mM) concentration. Results The hexane extract of OS elevated mRNA expression of insulin as well as pancreatic and duodenal homeobox-1 of INS-1 cells in a dose-dependent manner. The hexane OS extract also increased the levels of phosphorylated phosphatidylinositol 3-kinase (PI3K) in a concentration-dependent manner. Additionally, Akt phosphorylation was elevated by treatment with 100 and 200 µmol of the hexane OS extract. Three days of HG exposure suppressed insulin mRNA expression and GSIS; these expressions were restored by treatment with the hexane OS extract. HG elevated peroxide levels in the INS-1 cells. These levels were unaffected by OS treatment under both normal and hyperglycemic conditions. Conclusion Our results suggested that the hexane extract of OS elevates insulin mRNA expression and prevents glucotoxicity induced by a 3-day treatment with HG. This was associated with the activation of PI-3K and Akt. PMID:25729713

  9. Insulin-induced hypoglycemia activates the release of adrenocorticotropin predominantly via central and propranolol insensitive mechanisms.

    PubMed

    Jezová, D; Kvetnanský, R; Kovács, K; Oprsalová, Z; Vigas, M; Makara, G B

    1987-01-01

    The dynamic patterns of pituitary-adrenocortical and sympatho-adrenal hormone responses to insulin hypoglycemia as well as the relative importance of central vs. peripheral control of hypoglycemia-induced ACTH secretion were evaluated. In conscious rats bearing indwelling cannulae, the changes in hormone concentrations after insulin injection were dependent on the changes in blood glucose levels with respect to both time course and magnitude. ACTH, corticosterone, epinephrine, and norepinephrine levels were found to be maximal at 60 min after 2.5 IU kg-1 insulin injected ip, whereas earlier (20 min) but smaller increases were obtained in response to 0.5 IU kg-1 insulin injected iv. In rats 6-7 days after lesions of the medial basal hypothalamus (MBH), the rise of ACTH during insulin hypoglycemia was markedly inhibited and corticosterone levels were significantly reduced. Simultaneously, the hypoglycemia-induced increase in plasma epinephrine was unchanged and that in plasma norepinephrine was significantly enhanced in rats with the MBH destroyed. The beta-adrenoreceptor blocker propranolol did not inhibit ACTH and corticosterone responses to hypoglycemia in either sham-operated or MBH-lesioned animals. We conclude that the main factors triggering ACTH release during insulin-induced hypoglycemia are of central rather than peripheral origin. The high concentrations of circulating catecholamines occurring during insulin hypoglycemia are not responsible for pituitary-adrenocortical activation by direct, beta-adrenoreceptor mediated action at the pituitary level. PMID:3023036

  10. Euglycemic Infusion of Insulin Detemir Compared With Human Insulin Appears to Increase Direct Current Brain Potential Response and Reduces Food Intake While Inducing Similar Systemic Effects

    PubMed Central

    Hallschmid, Manfred; Jauch-Chara, Kamila; Korn, Oliver; Mölle, Matthias; Rasch, Björn; Born, Jan; Schultes, Bernd; Kern, Werner

    2010-01-01

    OBJECTIVE In the treatment of diabetic patients, the long-acting insulin analog insulin detemir is less prone to induce weight gain than other insulin formulations. Assuming that because of its pharmacologic properties, detemir displays stronger central nervous anorexigenic efficacy than human insulin, we compared acute effects of human insulin and detemir on electroencephalography (EEG) measures and food intake. RESEARCH DESIGN AND METHODS Frontocortical EEG direct current (DC) potentials were recorded in 15 healthy men during two hyperinsulinemic-euglycemic clamps that included an insulin bolus injection (human insulin, 17.75 mU/kg body wt; detemir, 90 mU/kg body wt) followed by a steady 90-min infusion (1.0 vs. 2.0 mU · kg−1 · min−1). A higher dosage was chosen for detemir to compensate for its delay in impact relative to human insulin and to elicit similar systemic effects. At 20 min after infusion, subjects were allowed to eat ad libitum from a test buffet. RESULTS Mean glucose infusions to maintain euglycemia (P > 0.93) and blood glucose concentrations (P > 0.34) did not differ between conditions. Detemir infusion induced a negative DC-potential shift, averaging −372.2 μV from 21 to 90 min that was not observed during human insulin infusion (146.5 μV, P = 0.02). Detemir, in comparison with human insulin, reduced subsequent food intake by 303 kcal (1,257 vs. 1,560, P < 0.04). CONCLUSIONS While inducing comparable peripheral effects, detemir exerts stronger acute effects on brain functions than human insulin and triggers a relative decrease in food consumption, suggesting an enhanced anorexigenic impact of detemir compared with human insulin on central nervous networks that control nutrient uptake. PMID:20068139

  11. Pid1 induces insulin resistance in both human and mouse skeletal muscle during obesity.

    PubMed

    Bonala, Sabeera; McFarlane, Craig; Ang, Jackie; Lim, Radiance; Lee, Marcus; Chua, Hillary; Lokireddy, Sudarsanareddy; Sreekanth, Patnam; Leow, Melvin Khee Shing; Meng, Khoo Chin; Shyong, Tai E; Lee, Yung Seng; Gluckman, Peter D; Sharma, Mridula; Kambadur, Ravi

    2013-09-01

    Obesity is associated with insulin resistance and abnormal peripheral tissue glucose uptake. However, the mechanisms that interfere with insulin signaling and glucose uptake in human skeletal muscle during obesity are not fully characterized. Using microarray, we have identified that the expression of Pid1 gene, which encodes for a protein that contains a phosphotyrosine-interacting domain, is increased in myoblasts established from overweight insulin-resistant individuals. Molecular analysis further validated that both Pid1 mRNA and protein levels are increased in cell culture models of insulin resistance. Consistent with these results, overexpression of phosphotyrosine interaction domain-containing protein 1 (PID1) in human myoblasts resulted in reduced insulin signaling and glucose uptake, whereas knockdown of PID1 enhanced glucose uptake and insulin signaling in human myoblasts and improved the insulin sensitivity following palmitate-, TNF-α-, or myostatin-induced insulin resistance in human myoblasts. Furthermore, the number of mitochondria in myoblasts that ectopically express PID1 was significantly reduced. In addition to overweight humans, we find that Pid1 levels are also increased in all 3 peripheral tissues (liver, skeletal muscle, and adipose tissue) in mouse models of diet-induced obesity and insulin resistance. An in silico search for regulators of Pid1 expression revealed the presence of nuclear factor-κB (NF-κB) binding sites in the Pid1 promoter. Luciferase reporter assays and chromatin immunoprecipitation studies confirmed that NF-κB is sufficient to transcriptionally up-regulate the Pid1 promoter. Furthermore, we find that myostatin up-regulates Pid1 expression via an NF-κB signaling mechanism. Collectively these results indicate that Pid1 is a potent intracellular inhibitor of insulin signaling pathway during obesity in humans and mice. PMID:23927930

  12. Insulin-induced hypoglycaemia is co-ordinately regulated by liver and muscle during acute and chronic insulin stimulation in rainbow trout (Oncorhynchus mykiss).

    PubMed

    Polakof, Sergio; Skiba-Cassy, Sandrine; Choubert, Georges; Panserat, Stéphane

    2010-05-01

    The relative glucose intolerance of carnivorous fish species is often proposed to be a result of poor peripheral insulin action or possibly insulin resistance. In the present study, data from aortic cannulated rainbow trout receiving bovine insulin (75 mIU kg(-1)) injections show for the first time their ability to clear glucose in a very efficient manner. In another set of experiments, mRNA transcripts and protein phosphorylation status of proteins controlling glycaemia and glucose-related metabolism were studied during both acute and chronic treatment with bovine insulin. Our results show that fasted rainbow trout are well adapted at the molecular level to respond to increases in circulating insulin levels, and that this hormone is able to potentially improve glucose distribution and uptake by peripheral tissues. After acute insulin administration we found that to counter-regulate the insulin-induced hypoglycaemia, trout metabolism is strongly modified. This short-term, efficient response to hypoglycaemia includes a rapid, coordinated response involving the reorganization of muscle and liver metabolism. During chronic insulin treatment some of the functions traditionally attributed to insulin actions in mammals were observed, including increased mRNA levels of glucose transporters and glycogen storage (primarily in the muscle) as well as decreased mRNA levels of enzymes involved in de novo glucose production (in the liver). Finally, we show that the rainbow trout demonstrates most of the classic metabolic adjustments employed by mammals to efficiently utilize glucose in the appropriate insulin context. PMID:20400628

  13. Inhibition of Src homology 2 domain-containing phosphatase 1 increases insulin sensitivity in high-fat diet-induced insulin-resistant mice.

    PubMed

    Krüger, Janine; Wellnhofer, Ernst; Meyborg, Heike; Stawowy, Philipp; Östman, Arne; Kintscher, Ulrich; Kappert, Kai

    2016-03-01

    Insulin resistance plays a crucial role in the development of type 2 diabetes. Insulin receptor signalling is antagonized and tightly controlled by protein tyrosine phosphatases (PTPs). However, the precise role of the PTP src homology 2 domain-containing phosphatase 1 (SHP-1) in insulin resistance has not been explored. Male C57BL/6J mice were fed a high-fat diet (HFD, 60% kcal from fat), to induce insulin resistance, or a low-fat diet (LFD, 10% kcal from fat) for 10 weeks. Afterwards, HFD-fed mice were pharmacologically treated with the SHP-1 (Ptpn6) inhibitor sodium stibogluconate and the broad spectrum pan-PTP inhibitor bis(maltolato)oxovanadium(IV) (BMOV). Both inhibitors ameliorated the metabolic phenotype, as evidenced by reduced body weight, improved insulin sensitivity and glucose tolerance, which was not due to altered PTP gene expression. In parallel, phosphorylation of the insulin receptor and of the insulin signalling key intermediate Akt was enhanced, and both PTP inhibitors and siRNA-mediated SHP-1 downregulation resulted in an increased glucose uptake in vitro. Finally, recombinant SHP-1 was capable of dephosphorylating the ligand-induced tyrosine-phosphorylated insulin receptor. These results indicate a central role of SHP-1 in insulin signalling during obesity, and SHP-1 inhibition as a potential therapeutic approach in metabolic diseases. PMID:27047746

  14. The effect of thyroidectomy and propylthiouracil-induced hypothyroidism on insulin secretion in male rats.

    PubMed

    Godini, A; Ghasemi, A; Karbalaei, N; Zahediasl, S

    2014-09-01

    Data available on thyroid dysfunction and insulin secretion are inconsistent. The aim of this study was to assess the effect of hypothyroidism on insulin secretion, in vivo and in vitro, in rats. Adult Wistar male rats were divided into 4 groups, the control, the propylthiouracyl (PTU)-treated hypothyroid, the surgically thyroidectomized, and the sham-operated thyroidectomized. After 5 weeks, intravenous glucose tolerance test (IVGTT) was performed and 3 weeks later pancreatic islets were isolated to assess glucose induced insulin secretion and insulin content. Fasting serum glucose and insulin levels did not differ between the groups, but serum glucose concentration during IVGTT in the PTU-induced hypothyroid group was significantly higher as compared to controls, throughout 5-60 min. The serum glucose concentration during IVGTT in the thyroidectomized rats was also significantly higher than in the sham-operated ones, except at 10 and 60 min. The area under the curve of the serum insulin was significantly lower during IVGTT in the PTU-treated (10,010 ± 1,380 pmol/l/60 min) and thyroidectomized (13,930 ± 2,786) groups vs. their comparable groups (19,150 ± 2,110), p<0.01 and (20,650 ± 1,601), p<0.05, respectively. In the PTU-treated, but not in thyroidectomized animals, insulin secretion in response to glucose 8.3 and 16.7 mM was significantly lower than their comparable group. The results show that PTU- and thyroidectomy-induced hypothyroidism leads to impaired glucose tolerance due to reduced glucose stimulated insulin secretion. Islets insulin secretion is positively correlated with serum T3 and T4 concentrations. PMID:24627102

  15. Effect of a p38 MAPK inhibitor on FFA-induced hepatic insulin resistance in vivo.

    PubMed

    Pereira, S; Yu, W Q; Moore, J; Mori, Y; Tsiani, E; Giacca, A

    2016-01-01

    The mechanisms whereby prolonged plasma free fatty acids elevation, as found in obesity, causes hepatic insulin resistance are not fully clarified. We herein investigated whether inhibition of p38 mitogen-activated protein kinase (MAPK) prevented hepatic insulin resistance following prolonged lipid infusion. Chronically cannulated rats were subdivided into one of four intravenous (i.v.) treatments that lasted 48 h: Saline (5.5 μl min(-1)), Intralipid plus heparin (IH, 20% Intralipid+20 U ml(-1) heparin; 5.5 μl min(-1)), IH+p38 MAPK inhibitor (SB239063) and SB239063 alone. During the last 2 h of treatment, a hyperinsulinemic (5 mU kg(-1) min(-1)) euglycemic clamp together with [3-(3)H] glucose methodology was carried out to distinguish hepatic from peripheral insulin sensitivity. We found that SB239063 prevented IH-induced hepatic insulin resistance, but not peripheral insulin resistance. SB239063 also prevented IH-induced phosphorylation of activating transcription factor 2 (ATF2), a marker of p38 MAPK activity, in the liver. Moreover, in another lipid infusion model in mice, SB239063 prevented hepatic but not peripheral insulin resistance caused by 48 h combined ethyloleate plus ethylpalmitate infusion. Our results suggest that inhibition of p38 MAPK may be a useful strategy in alleviating hepatic insulin resistance in obesity-associated disorders. PMID:27136448

  16. Brain insulin lowers circulating BCAA levels by inducing hepatic BCAA catabolism

    SciTech Connect

    Shin, Andrew C.; Fasshauer, Martin; Filatova, Nika; Grundell, Linus A.; Zielinski, Elizabeth; Zhou, Jianying; Scherer, Thomas; Lindtner, Claudia; White, Phillip J.; Lapworth, Amanda L.; Llkayeva, Olka; Knippschild, Uwe; Wolf, Anna M.; Scheja, Ludger; Grove, Kevin L.; Smith, Richard D.; Qian, Weijun; Lynch, Christopher J.; Newgard, Christopher B.; Buettner, Christoph

    2014-11-04

    Circulating branched-chain amino acid (BCAA) levels are elevated in obesity and diabetes and are a sensitive predictor for type 2 diabetes. Here we show in rats that insulin dose-dependently lowers plasma BCAA levels through induction of protein expression and activity of branched-chain alpha keto-acid dehydrogenase (BCKDH), the rate-limiting enzyme in the BCAA degradation pathway in the liver. Selective induction of hypothalamic insulin signaling in rats as well as inducible and lifelong genetic modulation of brain insulin receptor expression in mice both demonstrate that brain insulin signaling is a major regulator of BCAA metabolism by inducing hepatic BCKDH. Further, short-term overfeeding impairs the ability of brain insulin to lower circulating BCAA levels in rats. Chronic high-fat feeding in primates and obesity and/or type 2 diabetes in humans is associated with reduced BCKDH protein expression in liver, further supporting the concept that decreased hepatic BCKDH is a primary cause of increased plasma BCAA levels in insulin-resistant states. These findings demonstrate that neuroendocrine pathways control BCAA homeostasis and that hypothalamic insulin resistance can be a cause of impaired BCAA metabolism in obesity and diabetes.

  17. Nicotinamide induces differentiation of embryonic stem cells into insulin-secreting cells

    SciTech Connect

    Vaca, Pilar; Berna, Genoveva; Araujo, Raquel; Carneiro, Everardo M.; Bedoya, Francisco J.; Soria, Bernat; Martin, Franz

    2008-03-10

    The poly(ADP-ribose) polymerase (PARP) inhibitor, nicotinamide, induces differentiation and maturation of fetal pancreatic cells. In addition, we have previously reported evidence that nicotinamide increases the insulin content of cells differentiated from embryonic stem (ES) cells, but the possibility of nicotinamide acting as a differentiating agent on its own has never been completely explored. Islet cell differentiation was studied by: (i) X-gal staining after neomycin selection; (ii) BrdU studies; (iii) single and double immunohistochemistry for insulin, C-peptide and Glut-2; (iv) insulin and C-peptide content and secretion assays; and (v) transplantation of differentiated cells, under the kidney capsule, into streptozotocin (STZ)-diabetic mice. Here we show that undifferentiated mouse ES cells treated with nicotinamide: (i) showed an 80% decrease in cell proliferation; (ii) co-expressed insulin, C-peptide and Glut-2; (iii) had values of insulin and C-peptide corresponding to 10% of normal mouse islets; (iv) released insulin and C-peptide in response to stimulatory glucose concentrations; and (v) after transplantation into diabetic mice, normalized blood glucose levels over 7 weeks. Our data indicate that nicotinamide decreases ES cell proliferation and induces differentiation into insulin-secreting cells. Both aspects are very important when thinking about cell therapy for the treatment of diabetes based on ES cells.

  18. Unaltered Prion Pathogenesis in a Mouse Model of High-Fat Diet-Induced Insulin Resistance

    PubMed Central

    Zhu, Caihong; Schwarz, Petra; Abakumova, Irina; Aguzzi, Adriano

    2015-01-01

    Epidemiological, clinical, and experimental animal studies suggest a strong correlation between insulin resistance and Alzheimer’s disease. In fact, type-2 diabetes is considered an important risk factor of developing Alzheimer’s disease. In addition, impaired insulin signaling in the Alzheimer’s disease brain may promote Aβ production, impair Aβ clearance and induce tau hyperphosphorylation, thereby leading to deterioration of the disease. The pathological prion protein, PrPSc, deposits in the form of extracellular aggregates and leads to dementia, raising the question as to whether prion pathogenesis may also be affected by insulin resistance. We therefore established high-fat diet-induced insulin resistance in tga20 mice, which overexpress the prion protein. We then inoculated the insulin-resistant mice with prions. We found that insulin resistance in tga20 mice did not affect prion disease progression, PrPSc deposition, astrogliosis or microglial activation, and had no effect on survival. Our study demonstrates that in a mouse model, insulin resistance does not significantly contribute to prion pathogenesis. PMID:26658276

  19. Insulin inhibits cardiac contractility by inducing a Gi-biased β2-adrenergic signaling in hearts.

    PubMed

    Fu, Qin; Xu, Bing; Liu, Yongming; Parikh, Dippal; Li, Jing; Li, Ying; Zhang, Yuan; Riehle, Christian; Zhu, Yi; Rawlings, Tenley; Shi, Qian; Clark, Richard B; Chen, Xiongwen; Abel, E Dale; Xiang, Yang K

    2014-08-01

    Insulin and adrenergic stimulation are two divergent regulatory systems that may interact under certain pathophysiological circumstances. Here, we characterized a complex consisting of insulin receptor (IR) and β2-adrenergic receptor (β2AR) in the heart. The IR/β2AR complex undergoes dynamic dissociation under diverse conditions such as Langendorff perfusions of hearts with insulin or after euglycemic-hyperinsulinemic clamps in vivo. Activation of IR with insulin induces protein kinase A (PKA) and G-protein receptor kinase 2 (GRK2) phosphorylation of the β2AR, which promotes β2AR coupling to the inhibitory G-protein, Gi. The insulin-induced phosphorylation of β2AR is dependent on IRS1 and IRS2. After insulin pretreatment, the activated β2AR-Gi signaling effectively attenuates cAMP/PKA activity after β-adrenergic stimulation in cardiomyocytes and consequently inhibits PKA phosphorylation of phospholamban and contractile responses in myocytes in vitro and in Langendorff perfused hearts. These data indicate that increased IR signaling, as occurs in hyperinsulinemic states, may directly impair βAR-regulated cardiac contractility. This β2AR-dependent IR and βAR signaling cross-talk offers a molecular basis for the broad interaction between these signaling cascades in the heart and other tissues or organs that may contribute to the pathophysiology of metabolic and cardiovascular dysfunction in insulin-resistant states. PMID:24677713

  20. Effect of a p38 MAPK inhibitor on FFA-induced hepatic insulin resistance in vivo

    PubMed Central

    Pereira, S; Yu, W Q; Moore, J; Mori, Y; Tsiani, E; Giacca, A

    2016-01-01

    The mechanisms whereby prolonged plasma free fatty acids elevation, as found in obesity, causes hepatic insulin resistance are not fully clarified. We herein investigated whether inhibition of p38 mitogen-activated protein kinase (MAPK) prevented hepatic insulin resistance following prolonged lipid infusion. Chronically cannulated rats were subdivided into one of four intravenous (i.v.) treatments that lasted 48 h: Saline (5.5 μl min−1), Intralipid plus heparin (IH, 20% Intralipid+20 U ml−1 heparin; 5.5 μl min−1), IH+p38 MAPK inhibitor (SB239063) and SB239063 alone. During the last 2 h of treatment, a hyperinsulinemic (5 mU kg−1 min−1) euglycemic clamp together with [3-3H] glucose methodology was carried out to distinguish hepatic from peripheral insulin sensitivity. We found that SB239063 prevented IH-induced hepatic insulin resistance, but not peripheral insulin resistance. SB239063 also prevented IH-induced phosphorylation of activating transcription factor 2 (ATF2), a marker of p38 MAPK activity, in the liver. Moreover, in another lipid infusion model in mice, SB239063 prevented hepatic but not peripheral insulin resistance caused by 48 h combined ethyloleate plus ethylpalmitate infusion. Our results suggest that inhibition of p38 MAPK may be a useful strategy in alleviating hepatic insulin resistance in obesity-associated disorders. PMID:27136448

  1. Angiotensin-induced EGF receptor transactivation inhibits insulin signaling in C9 hepatic cells

    PubMed Central

    Arellano-Plancarte, Araceli; Hernandez-Aranda, Judith; Catt, Kevin J.; Olivares-Reyes, J. Alberto

    2014-01-01

    To investigate the potential interactions between the angiotensin II (Ang II) and insulin signaling systems, regulation of IRS-1 phosphorylation and insulin-induced Akt activation by Ang II were examined in clone 9 (C9) hepatocytes. In these cells, Ang II specifically inhibited activation of insulin-induced Akt Thr308 and its immediate downstream substrate GSK-3α/β in a time-dependent fashion, with ∼70% reduction at 15min. These inhibitory actions were associated with increased IRS-1 phosphorylation of Ser636/Ser639 that was prevented by selective blockade of EGFR tyrosine kinase activity with AG1478. Previous studies have shown that insulin-induced phosphorylation of IRS-1 on Ser636/Ser639 is mediated mainly by the PI3K/mTOR/S6K-1 sequence. Studies with specific inhibitors of PI3K (wortmannin) and mTOR (rapamycin) revealed that Ang II stimulates IRS-1 phosphorylation of Ser636/Ser639 via the PI3K/mTOR/S6K-1 pathway. Both inhibitors blocked the effect of Ang II on insulin-induced activation of Akt. Studies using the specific MEK inhibitor, PD98059, revealed that ERK1/2 activation also mediates Ang II-induced S6K-1 and IRS-1 phosphorylation, and the impairment of Akt Thr308 and GSK-3α/β phosphorylation. Further studies with selective inhibitors showed that PI3K activation was upstream of ERK, suggesting a new mechanism for Ang II-induced impairment of insulin signaling. These findings indicate that Ang II has a significant role in the development of insulin resistance by a mechanism that involves EGFR transactivation and the PI3K/ERK1/2/mTOR-S6K-1 pathway. PMID:19879250

  2. Photo-induced inhibition of insulin amyloid fibrillation on online laser measurement

    SciTech Connect

    Liu, Rui; Su, Rongxin; Qi, Wei; He, Zhimin

    2011-06-03

    Highlights: {yields} We compare the structures of insulin upon heating with or without laser irradiation. {yields} Laser irradiation inhibits insulin fibrillation and may be of insert for mechanistic disease studies. {yields} Online laser measurements should be carefully used in the study of amyloid proteins. -- Abstract: Protein aggregation and amyloid fibrillation can lead to several serious diseases and protein drugs ineffectiveness; thus, the detection and inhibition of these processes have been of great interest. In the present study, the inhibition of insulin amyloid fibrillation by laser irradiation was investigated using dynamic light scattering (DLS), transmission electron microscopy (TEM), far-UV circular dichroism (far-UV CD), and thioflavin T (ThT) fluorescence. During heat-induced aggregation, the size distribution of two insulin solutions obtained by online and offline dynamic light scattering were different. The laser-on insulin in the presence of 0.1 M NaCl exhibited fewer fibrils than the laser-off insulin, whereas no insulin fibril under laser irradiation was observed in the absence of 0.1 M NaCl for 45 h incubation. Moreover, our CD results showed that the laser-irradiated insulin solution maintained mainly an {alpha}-helical conformation, but the laser-off insulin solution formed bulk fibrils followed by a significant increase in {beta}-sheet content for 106 h incubation. These findings provide an inhibition method for insulin amyloid fibrillation using the laser irradiation and demonstrate that the online long-time laser measurements should be carefully used in the study of amyloid proteins because they may change the original results.

  3. Celastrol Protects against Antimycin A-Induced Insulin Resistance in Human Skeletal Muscle Cells.

    PubMed

    Abu Bakar, Mohamad Hafizi; Cheng, Kian-Kai; Sarmidi, Mohamad Roji; Yaakob, Harisun; Huri, Hasniza Zaman

    2015-01-01

    Mitochondrial dysfunction and inflammation are widely accepted as key hallmarks of obesity-induced skeletal muscle insulin resistance. The aim of the present study was to evaluate the functional roles of an anti-inflammatory compound, celastrol, in mitochondrial dysfunction and insulin resistance induced by antimycin A (AMA) in human skeletal muscle cells. We found that celastrol treatment improved insulin-stimulated glucose uptake activity of AMA-treated cells, apparently via PI3K/Akt pathways, with significant enhancement of mitochondrial activities. Furthermore, celastrol prevented increased levels of cellular oxidative damage where the production of several pro-inflammatory cytokines in cultures cells was greatly reduced. Celastrol significantly increased protein phosphorylation of insulin signaling cascades with amplified expression of AMPK protein and attenuated NF-κB and PKC θ activation in human skeletal muscle treated with AMA. The improvement of insulin signaling pathways by celastrol was also accompanied by augmented GLUT4 protein expression. Taken together, these results suggest that celastrol may be advocated for use as a potential therapeutic molecule to protect against mitochondrial dysfunction-induced insulin resistance in human skeletal muscle cells. PMID:25961164

  4. Myo1c binding to submembrane actin mediates insulin-induced tethering of GLUT4 vesicles

    PubMed Central

    Boguslavsky, Shlomit; Chiu, Tim; Foley, Kevin P.; Osorio-Fuentealba, Cesar; Antonescu, Costin N.; Bayer, K. Ulrich; Bilan, Philip J.; Klip, Amira

    2012-01-01

    GLUT4-containing vesicles cycle between the plasma membrane and intracellular compartments. Insulin promotes GLUT4 exocytosis by regulating GLUT4 vesicle arrival at the cell periphery and its subsequent tethering, docking, and fusion with the plasma membrane. The molecular machinery involved in GLUT4 vesicle tethering is unknown. We show here that Myo1c, an actin-based motor protein that associates with membranes and actin filaments, is required for insulin-induced vesicle tethering in muscle cells. Myo1c was found to associate with both mobile and tethered GLUT4 vesicles and to be required for vesicle capture in the total internal reflection fluorescence (TIRF) zone beneath the plasma membrane. Myo1c knockdown or overexpression of an actin binding–deficient Myo1c mutant abolished insulin-induced vesicle immobilization, increased GLUT4 vesicle velocity in the TIRF zone, and prevented their externalization. Conversely, Myo1c overexpression immobilized GLUT4 vesicles in the TIRF zone and promoted insulin-induced GLUT4 exposure to the extracellular milieu. Myo1c also contributed to insulin-dependent actin filament remodeling. Thus we propose that interaction of vesicular Myo1c with cortical actin filaments is required for insulin-mediated tethering of GLUT4 vesicles and for efficient GLUT4 surface delivery in muscle cells. PMID:22918957

  5. Myo1c binding to submembrane actin mediates insulin-induced tethering of GLUT4 vesicles.

    PubMed

    Boguslavsky, Shlomit; Chiu, Tim; Foley, Kevin P; Osorio-Fuentealba, Cesar; Antonescu, Costin N; Bayer, K Ulrich; Bilan, Philip J; Klip, Amira

    2012-10-01

    GLUT4-containing vesicles cycle between the plasma membrane and intracellular compartments. Insulin promotes GLUT4 exocytosis by regulating GLUT4 vesicle arrival at the cell periphery and its subsequent tethering, docking, and fusion with the plasma membrane. The molecular machinery involved in GLUT4 vesicle tethering is unknown. We show here that Myo1c, an actin-based motor protein that associates with membranes and actin filaments, is required for insulin-induced vesicle tethering in muscle cells. Myo1c was found to associate with both mobile and tethered GLUT4 vesicles and to be required for vesicle capture in the total internal reflection fluorescence (TIRF) zone beneath the plasma membrane. Myo1c knockdown or overexpression of an actin binding-deficient Myo1c mutant abolished insulin-induced vesicle immobilization, increased GLUT4 vesicle velocity in the TIRF zone, and prevented their externalization. Conversely, Myo1c overexpression immobilized GLUT4 vesicles in the TIRF zone and promoted insulin-induced GLUT4 exposure to the extracellular milieu. Myo1c also contributed to insulin-dependent actin filament remodeling. Thus we propose that interaction of vesicular Myo1c with cortical actin filaments is required for insulin-mediated tethering of GLUT4 vesicles and for efficient GLUT4 surface delivery in muscle cells. PMID:22918957

  6. Interleukin-1β mediates macrophage-induced impairment of insulin signaling in human primary adipocytes

    PubMed Central

    Gao, Dan; Madi, Mohamed; Ding, Cherlyn; Fok, Matthew; Steele, Thomas; Ford, Christopher; Hunter, Leif

    2014-01-01

    Adipose tissue expansion during obesity is associated with increased macrophage infiltration. Macrophage-derived factors significantly alter adipocyte function, inducing inflammatory responses and decreasing insulin sensitivity. Identification of the major factors that mediate detrimental effects of macrophages on adipocytes may offer potential therapeutic targets. IL-1β, a proinflammatory cytokine, is suggested to be involved in the development of insulin resistance. This study investigated the role of IL-1β in macrophage-adipocyte cross-talk, which affects insulin signaling in human adipocytes. Using macrophage-conditioned (MC) medium and human primary adipocytes, we examined the effect of IL-1β antagonism on the insulin signaling pathway. Gene expression profile and protein abundance of insulin signaling molecules were determined, as was the production of proinflammatory cytokine/chemokines. We also examined whether IL-1β mediates MC medium-induced alteration in adipocyte lipid storage. MC medium and IL-1β significantly reduced gene expression and protein abundance of insulin signaling molecules, including insulin receptor substrate-1, phosphoinositide 3-kinase p85α, and glucose transporter 4 and phosphorylation of Akt. In contrast, the expression and release of the proinflammatory markers, including IL-6, IL-8, monocyte chemotactic protein-1, and chemokine (C-C motif) ligand 5 by adipocytes were markedly increased. These changes were significantly reduced by blocking IL-1β activity, its receptor binding, or its production by macrophages. MC medium-inhibited expression of the adipogenic factors and -stimulated lipolysis was also blunted with IL-1β neutralization. We conclude that IL-1β mediates, at least in part, the effect of macrophages on insulin signaling and proinflammatory response in human adipocytes. Blocking IL-1β could be beneficial for preventing obesity-associated insulin resistance and inflammation in human adipose tissue. PMID:24918199

  7. Serpine1 Mediates Porphyromonas gingivalis Induced Insulin Secretion in the Pancreatic Beta Cell Line MIN6

    PubMed Central

    Bhat, Uppoor G.; Watanabe, Keiko

    2015-01-01

    Periodontitis is an inflammatory disease resulting in destruction of gingiva and alveolar bone caused by an exuberant host immunological response to periodontal pathogens. Results from a number of epidemiological studies indicate a close association between diabetes and periodontitis. Results from cross-sectional studies indicate that subjects with periodontitis have a higher odds ratio of developing insulin resistance (IR). However, the mechanisms by which periodontitis influences the development of diabetes are not known. Results from our previous studies using an animal model of periodontitis suggest that periodontitis accelerates the onset of hyperinsulinemia and IR. In addition, LPS from a periodontal pathogen, Porphyromonas gingivalis (Pg), stimulates Serpine1 expression in the pancreatic beta cell line MIN6. Based on these observations, we hypothesized that a periodontal pathogen induces hyperinsulinemia and Serpine1 may be involved in this process. To test this hypothesis, we co-incubated Pg with the pancreatic beta cell line MIN6 and measured the effect on insulin secretion by MIN6 cells. We further determined the involvement of Serpine1 in insulin secretion by downregulating Serpine1 expression. Our results indicated that Pg stimulated insulin secretion by approximately 3.0 fold under normoglycemic conditions. In a hyperglycemic state, Pg increased insulin secretion by 1.5 fold. Pg significantly upregulated expression of the Serpine1 gene and this was associated with increased secretion of insulin by MIN6 cells. However, cells with downregulated Serpine1 expression were resistant to Pg stimulated insulin secretion under normoglycemic conditions. We conclude that the periodontal pathogen, Pg, induced insulin secretion by MIN6 cells and this induction was, in part, Serpine1 dependent. Thus, Serpine1 may play a pivotal role in insulin secretion during the accelerated development of hyperinsulinemia and the resulting IR in the setting of periodontitis. PMID

  8. INSULIN INDUCED EPIDERMAL GROWTH FACTOR ACTIVATION IN VASCULAR SMOOTH MUSCLE CELLS IS ADAM-DEPENDENT

    PubMed Central

    Roztocil, Elisa; Nicholl, Suzanne M.; Davies, Mark G.

    2008-01-01

    Background With the rise in metabolic syndrome, understanding the role of insulin signaling within the cells of vasculature has become more important but yet remains poorly defined. The study examines the role of insulin actions on a pivotal cross-talk receptor, Epidermal Growth Factor Receptor (EGFR). EGFR is transactivated by both G-protein-coupled receptors and receptor linked tyrosine kinases and is key to many of their responses. Objective To determine the pathway of EGFR transactivation by insulin in human coronary smooth muscle cells (VSMC) Methods VSMC were cultured in vitro. Assays of EGFR phosphorylation were examined in response to insulin in the presence and absence of the plasmin inhibitors (e-aminocaproic acid and aprotinin) matrix metalloprotease (MMP) inhibitor GM6001, the ADAM (A Disintegrin And Metalloproteinase Domain) inhibitors TAPI-0 and TAPI-1, Heparin binding epidermal growth factor (HB-EGF) inhibitor, CRM197, HB-EGF inhibitory antibodies, EGF inhibitory antibodies and the EGFR inhibitor AG1478. Results Insulin induced time-dependent EGFR phosphorylation, which was inhibited by AG1478 in a concentration dependent manner. Application of the plasmin inhibitors did not block the response. EGFR phosphorylation by insulin was blocked by inhibition of MMP activity and the ligand HB-EGF. The presence of the ADAM inhibitors, TAPI-0 and TAPI-1 significantly decreased EGFR activation. EGFR phosphorylation by EGF was not interrupted by inhibition of plasmin, MMPs TAPIs, or HB-EGF. Direct blockade of the EGFR prevented activation by both insulin and EGF. Conclusion Insulin can induce transactivation of EGFR by an ADAM-mediated, HB-EGF dependent process. This is the first description of crosstalk via ADAM between insulin and EGFR in vascular SMC. Targeting a pivotal cross-talk receptor such as EGFR, which can be transactivated by both G-protein-coupled receptors and receptor tyrosine kinases is an attractive molecular target. PMID:18656632

  9. Effect of anaesthesia on insulin-induced hypoglycemia in rabbits.

    PubMed

    Haynes, F J; Cheema-Dhadli, S; Halperin, R M; Zettle, R; Robinson, L; Halperin, M L

    1988-12-01

    The aim of this study was to determine how anaesthetized rabbits survive much longer than awake rabbits after receiving an insulin overdose. Insulin appeared to act in both groups of rabbits because there was a prompt fall in circulating glucose, free fatty acids, and beta-hydroxybutyrate concentrations. Carbohydrate appeared to be the principal energy source for anaesthetized rabbits because their respiratory quotient approached unity. Although the fall in glycemia was similar in both groups of rabbits, the circulating lactate concentration rose only in the anaesthetized group. This rise in lactate in the initial 60 min after insulin was given could account for most of the fall in glycemia if the source of lactate was the glucose pool. The decline in hepatic glycogen was close to 100 mumol/g liver; this would account for about one-third of the total energy turnover and close to one-half of the measured glucose appearance in these anaesthetized rabbits. As judged from the rate of oxygen consumption, muscle glycogen seemed to supply two-thirds of the fuel to be oxidized in these rabbits. However, only one-third of the lactate released from muscle was first converted to glucose and the remainder was oxidized directly to CO2. Although insulin provided the metabolic setting for a rapid rate of glucose oxidation, this rate appeared to be diminished when the overall rate of oxygen consumption was lower during anaesthesia. PMID:3067835

  10. Insulin-induced phospho-oligosaccharide stimulates amino acid transport in isolated rat hepatocytes.

    PubMed Central

    Varela, I; Avila, M; Mato, J M; Hue, L

    1990-01-01

    The ability of the insulin-induced phospho-oligosaccharide to stimulate amino acid transport was studied in isolated rat hepatocytes. At low alpha-aminoisobutyric acid concentrations (0.1 mM), both 100 nM-insulin and 10 microM-phospho-oligosaccharide doubled amino acid uptake after 2 h of incubation. This stimulation was prevented by 0.1 mM-cycloheximide or 5 micrograms of actinomycin D/ml, indicating that the phospho-oligosaccharide, like insulin, was acting via the synthesis of a high-affinity transport component. The effects of the phospho-oligosaccharide and of insulin were blocked by Ins2P (2.5 mM), but not by myo-inositol, inositol hexaphosphoric acid or several monosaccharides such as mannose, glucosamine and galactose. Both the temporal effect on amino acid entry and the extent of stimulation of this process by the phospho-oligosaccharide indicate that this molecule mimics, and may mediate, some of the long-term actions of insulin. However, the effects of phospho-oligosaccharide and insulin were not exactly the same, since the effect of insulin, but not of the phospho-oligosaccharide, was additive with that of glucagon. PMID:2185744

  11. Neuropoietin Attenuates Adipogenesis and Induces Insulin Resistance in Adipocytes*

    PubMed Central

    White, Ursula A.; Stewart, William C.; Mynatt, Randall L.; Stephens, Jacqueline M.

    2008-01-01

    Recent findings have implicated gp130 receptor ligands, particularly ciliary neurotrophic factor (CNTF), as potential anti-obesity therapeutics. Neuropoietin (NP) is a recently discovered cytokine in the gp130 family that shares functional and structural features with CNTF and signals via the CNTF receptor tripartite complex comprised of CNTFRα, LIF receptor, and gp130. NP plays a role in the development of the nervous system, but the effects of NP on adipocytes have not been previously examined. Because CNTF exerts anti-obesogenic effects in adipocytes and NP shares the same receptor complex, we investigated the effects of NP on adipocyte development and insulin action. Using cultured 3T3-L1 adipocytes, we observed that NP has the ability to block adipogenesis in a dose- and time-dependent manner. We also observed that cultured adipocytes, as well as murine adipose tissue, are highly responsive to acute NP treatment. Rodents injected with NP had a substantial increase in STAT3 tyrosine phosphorylation and ERK 1 and 2 activation. We also observed the induction of SOCS-3 mRNA in 3T3-L1 adipocytes following NP treatment. Unlike CNTF, our studies have revealed that NP also substantially attenuates insulin-stimulated glucose uptake in 3T3-L1 adipocytes. In addition, NP blocks insulin action in adipose tissue in vivo. These observations are supported by data demonstrating that NP impairs insulin signaling via decreased activation of both IRS-1 and Akt. In summary, we have observed that both adipocytes in vitro and in vivo are highly responsive to NP, and this cytokine has the ability to affect insulin signaling in fat cells. These novel observations suggest that NP, unlike CNTF, may not be a viable obesity therapeutic. PMID:18562323

  12. Modulation of insulin/IGFs pathways by sirtuin-7 inhibition in drug-induced chemoreistance

    PubMed Central

    2014-01-01

    Background Insulin and insulin-like growth factors (IGFs) are key regulators of metabolism and growth. Recent evidences suggest a key role of these pathways in non-classical tissues and the metabolic pathways by which these hormones exert their effects in neoplasia is unclear. Aims To study insulin/IGFs pathways in drug sensitive and resistant cancer cells representing breast cancer (MCF-7), osteosarcoma (SaOS-2), and ovarian cancer (A2780) and to examine the effect of Sirtuin-7 (Sirt7) inhibition on insulin/IGFs pathways in MCF-7 cell line. Methods Drug resistant cells were generated by continuous incubation of parental cell lines with stepwise increases in Doxorubicin or Cisplatin over a period of 3 to 6 months. MCF-7 cells were transfected with cloned hairpin siRNA template for Sirt7 using the Amaxa GmbH transfection system. mRNA expression of Sirt7, INSR, IRS-1, IRS-2, IRS-4, IGF-1, IGF-2, MDR-1, MRP-1, BCRP was measured by qPCR and Sirt7 by standard Western blotting. FITC-insulin uptake was imaged with Leica Confocal Microscope. Results Insulin receptor (INSR), insulin receptor substrate-1 (IRS-1) were inhibited in drug-induced resistance, whereas IRS-2 was significantly induced in all the chemoresistant cells tested when compared to their parental counterparts. IGF-1 and IGF-2 were also upregulated in all the drug resistant cells tested. Sirt7 was significantly reduced in all chemoresistant cells tested. Knockdown of Sirt7 expression in human breast MCF-7 cell line by siRNA induced premature senescence-like phenotype and multi-drug resistance, suggesting that this gene may play an active role in regulating cancer cell response to stress. Suppression of Sirt7 selectively inhibited INSR and IRS-1, whereas it had minimal effect on that of IRS-2. Sirt7 suppression in MCF-7 also inhibited insulin uptake. Additionally, Sirt7 inhibition upregulated IGF-1, IGF-2 and IGFR expression. Conclusion Our data demonstrate that stress-induced Sirt7 inhibition significantly

  13. Hypoglycemic effect of aqueous shallot and garlic extracts in rats with fructose-induced insulin resistance.

    PubMed

    Jalal, Razieh; Bagheri, Sayyed Majid; Moghimi, Ali; Rasuli, Morteza Behnam

    2007-11-01

    The present study has been carried out to investigate the effect of aqueous extract of shallot (Allium ascalonicum) and garlic (Allium satium) on the fasting insulin resistance index (FIRI) and intraperitoneal glucose tolerance test (IPGTT) of fructose-induced insulin resistance rats. Male albino Wistar rats were fed either normal or high-fructose diet for a period of eight weeks. Fasting blood glucose level, fasting blood triglyceride level, FIRI, and the area under the glucose tolerance curve were significantly elevated in fructose-fed animals. Fructose-induced insulin resistance rats treated by aqueous shallot or garlic extract (500 mg/kg body weight/day, i.p.) for duration of eight weeks. Control animals only received normal saline (0.9%). The results showed that neither shallot nor garlic extracts significantly altered the FIRI and the IPGTT at the fourth week after treatment. The fasting blood glucose in fructose-induced insulin resistance animals has been significantly decreased in 8-week treated animals by both shallot and garlic extracts. Shallot extract administration, but not garlic extract, for a period of eight weeks can significantly improve the intraperitoneal glucose tolerance and diminish the FIRI. These results indicate that shallot and garlic extracts have a hypoglycemic influence on the fructose-induced insulin resistance animals and aqueous shallot extract is a stronger hypoglycemic agent than the garlic extract. PMID:18299719

  14. Myeloperoxidase Deletion Prevents High-Fat Diet–Induced Obesity and Insulin Resistance

    PubMed Central

    Wang, Qilong; Xie, Zhonglin; Zhang, Wencheng; Zhou, Jun; Wu, Yue; Zhang, Miao; Zhu, Huaiping

    2014-01-01

    Activation of myeloperoxidase (MPO), a heme protein primarily expressed in granules of neutrophils, is associated with the development of obesity. However, whether MPO mediates high-fat diet (HFD)-induced obesity and obesity-associated insulin resistance remains to be determined. Here, we found that consumption of an HFD resulted in neutrophil infiltration and enhanced MPO expression and activity in epididymal white adipose tissue, with an increase in body weight gain and impaired insulin signaling. MPO knockout (MPO−/−) mice were protected from HFD-enhanced body weight gain and insulin resistance. The MPO inhibitor 4-aminobenzoic acid hydrazide reduced peroxidase activity of neutrophils and prevented HFD-enhanced insulin resistance. MPO deficiency caused high body temperature via upregulation of uncoupling protein-1 and mitochondrial oxygen consumption in brown adipose tissue. Lack of MPO also attenuated HFD-induced macrophage infiltration and expression of proinflammatory cytokines. We conclude that activation of MPO in adipose tissue contributes to the development of obesity and obesity-associated insulin resistance. Inhibition of MPO may be a potential strategy for prevention and treatment of obesity and insulin resistance. PMID:25024373

  15. Paradoxical Acceleration of Dithiothreitol-Induced Aggregation of Insulin in the Presence of a Chaperone

    PubMed Central

    Bumagina, Zoya; Gurvits, Bella; Artemova, Natalya; Muranov, Konstantin; Kurganov, Boris

    2010-01-01

    The kinetics of dithiothreitol (DTT)-induced aggregation of human recombinant insulin and the effect of α-crystallin, a representative of the family of small heat shock proteins, on the aggregation process have been studied using dynamic light scattering technique. Analysis of the distribution of the particles by size measured in the course of aggregation showed that the initial stage of the aggregation process was the stage of formation of the start aggregates with a hydrodynamic radius (Rh) of about 90 nm. When studying the effect of α-crystallin on the rate of DTT-induced aggregation of insulin, it was demonstrated that low concentrations of α-crystallin dramatically accelerated the aggregation process, whereas high concentrations of α-crystallin suppressed insulin aggregation. In the present study, at the molar stoichiometric ratio (insulin:α-crystallin) less than 1:0.5, a pronounced accelerating effect of α-crystallin was observed; whereas a ratio exceeding the value of 1:0.6 caused suppression of insulin aggregation. The mechanisms underlying the dual effect of α-crystallin have been proposed. It is assumed that heterogeneous nucleation occurring on the surface of the α-crystallin particle plays the key role in the paradoxical acceleration of insulin aggregation by α-crystallin that may provide an alternative biologically significant pathway of the aggregation process. PMID:21151456

  16. Interference with Akt signaling pathway contributes curcumin-induced adipocyte insulin resistance.

    PubMed

    Zhang, Deling; Zhang, Yemin; Ye, Mao; Ding, Youming; Tang, Zhao; Li, Mingxin; Zhou, Yu; Wang, Changhua

    2016-07-01

    Previous study has shown that curcumin directly or indirectly suppresses insulin signaling in 3T3-L1 adipocytes. However, the underlying mechanism remains unclear. Here we experimentally demonstrate that curcumin inhibited the ubiquitin-proteasome system (UPS) function, activated autophagy, and reduced protein levels of protein kinase B (Akt) in a dose- and time-dependent manner in 3T3-L1 adipocytes, accompanied with attenuation of insulin-stimulated Akt phosphorylation, plasma membrane translocation of glucose transporter type 4 (GLUT4), and glucose uptake. These in vitro inhibitory effects of curcumin on Akt protein expression and insulin action were reversed by pharmacological and genetic inhibition of autophagy but not by inhibition of the UPS and caspases. In addition, Akt reduction in adipose tissues of mice treated with curcumin could be recovered by administration of autophagy inhibitor bafilomycin A1 (BFA). This new finding provides a novel mechanism by which curcumin induces insulin resistance in adipocytes. PMID:27113027

  17. Intermedin Restores Hyperhomocysteinemia-induced Macrophage Polarization and Improves Insulin Resistance in Mice.

    PubMed

    Pang, Yanli; Li, Yang; Lv, Ying; Sun, Lulu; Zhang, Songyang; Li, Yin; Wang, Yuhui; Liu, George; Xu, Ming-Jiang; Wang, Xian; Jiang, Changtao

    2016-06-01

    Hyperhomocysteinemia (HHcy) is a condition characterized by an abnormally high level of homocysteine, an inflammatory factor. This condition has been suggested to promote insulin resistance. To date, the underlying molecular mechanism remains largely unknown, and identifying novel therapeutic targets for HHcy-induced insulin resistance is of high priority. It is well known that intermedin (IMD), a calcitonin family peptide, exerts potent anti-inflammatory effects. In this study, the effects of IMD on HHcy-induced insulin resistance were investigated. Glucose tolerance and insulin tolerance tests were performed on mice treated with IMD by minipump implantation (318 ng/kg/h for 4 weeks) or adipocyte-specific IMD overexpression mice (Adipo-IMD transgenic mice). The expression of genes and proteins related to M1/M2 macrophages and endoplasmic reticulum stress (ERS) was evaluated in adipose tissues or cells. The expression of IMD was identified to be lower in the plasma and adipose tissues of HHcy mice. In both IMD treatment by minipump implantation and Adipo-IMD transgenic mice, IMD reversed HHcy-induced insulin resistance, as revealed by glucose tolerance and insulin tolerance tests. Further mechanistic study revealed that IMD reversed the Hcy-elevated ratio of M1/M2 macrophages by inhibiting AMP-activated protein kinase activity. Adipo-IMD transgenic mice displayed reduced ERS and lower inflammation in adipose tissues with HHcy. Soluble factors from Hcy-treated macrophages induced adipocyte ERS, which was reversed by IMD treatment. These findings revealed that IMD treatment restores the M1/M2 balance, inhibits chronic inflammation in adipose tissues, and improves systemic insulin sensitivity of HHcy mice. PMID:27080257

  18. Insulin nonattenuation of vasoactive agent-induced responses in mesangial cells from spontaneously hypertensive rats.

    PubMed

    Inishi, Y; Okuda, T; Arakawa, T; Yasuda, C; Ohara, M; Kurokawa, K

    1995-03-01

    We recently found that insulin attenuates intracellular calcium transients and cell contraction caused by vasoactive agents in cultured rat mesangial cells. Because altered glomerular function may be causally related to the evolution of hypertension, we examined in the present study the effects of insulin on the functions of mesangial cells derived from spontaneously hypertensive rats (SHR) of 4- and 8-weeks of age. Age-matched Wistar Kyoto rats (WKY) were used as controls. Intracellular calcium concentration ([Ca2+]i) was measured with Fura-2 method in suspended mesangial cells. Pretreatment of mesangial cells with 5 micrograms/ml insulin for 120 minutes did not affect basal [Ca2+]i in either WKY or SHR mesangial cells. However, insulin pretreatment significantly attenuated [Ca2+]i transients to vasoactive agents in WKY mesangial cells. In contrast, [Ca2+]i transients to these agents were not attenuated by insulin in SHR mesangial cells. Additionally, SHR mesangial cell contraction in response to angiotensin II (Ang II) was not altered by insulin, while WKY mesangial cell contraction to Ang II was, as in normal Wistar rats, significantly reduced by insulin. Since we previously showed the possibility that the attenuation of calcium signal by insulin is via insulin-like growth factor I (IGF-I) receptor, we also examined the effect of IGF-I. In contrast to WKY mesangial cells, IGF-I-induced attenuation of [Ca2+]i responses to platelet activating factor was absent in SHR mesangial cells. [125I]-IGF-I binding in SHR mesangial cells was not significantly different from that in WKY mesangial cells.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7752589

  19. Lipocalin-2 inhibits autophagy and induces insulin resistance in H9c2 cells.

    PubMed

    Chan, Yee Kwan; Sung, Hye Kyoung; Jahng, James Won Suk; Kim, Grace Ha Eun; Han, Meng; Sweeney, Gary

    2016-07-15

    Lipocalin-2 (Lcn2; also known as neutrophil gelatinase associated lipocalin, NGAL) levels are increased in obesity and diabetes and associate with insulin resistance. Correlations exist between Lcn2 levels and various forms or stages of heart failure. Insulin resistance and autophagy both play well-established roles in cardiomyopathy. However, little is known about the impact of Lcn2 on insulin signaling in cardiomyocytes. In this study, we treated H9c2 cells with recombinant Lcn2 for 1 h followed by dose- and time-dependent insulin treatment and found that Lcn2 attenuated insulin signaling assessed via phosphorylation of Akt and p70S6K. We used multiple assays to demonstrate that Lcn2 reduced autophagic flux. First, Lcn2 reduced pULK1 S555, increased pULK1 S757 and reduced LC3-II levels determined by Western blotting. We validated the use of DQ-BSA to assess autolysosomal protein degradation and this together with MagicRed cathepsin B assay indicated that Lcn2 reduced lysosomal degradative activity. Furthermore, we generated H9c2 cells stably expressing tandem fluorescent RFP/GFP-LC3 and this approach verified that Lcn2 decreased autophagic flux. We also created an autophagy-deficient H9c2 cell model by overexpressing a dominant-negative Atg5 mutant and found that reduced autophagy levels also induced insulin resistance. Adding rapamycin after Lcn2 could stimulate autophagy and recover insulin sensitivity. In conclusion, our study indicated that acute Lcn2 treatment caused insulin resistance and use of gain and loss of function approaches elucidated a causative link between autophagy inhibition and regulation of insulin sensitivity by Lcn2. PMID:27090568

  20. Imaging dynamic insulin release using a fluorescent zinc indicator for monitoring induced exocytotic release (ZIMIR).

    PubMed

    Li, Daliang; Chen, Shiuhwei; Bellomo, Elisa A; Tarasov, Andrei I; Kaut, Callan; Rutter, Guy A; Li, Wen-hong

    2011-12-27

    Current methods of monitoring insulin secretion lack the required spatial and temporal resolution to adequately map the dynamics of exocytosis of native insulin granules in intact cell populations in three dimensions. Exploiting the fact that insulin granules contain a high level of Zn(2+), and that Zn(2+) is coreleased with insulin during secretion, we have developed a fluorescent, cell surface-targeted zinc indicator for monitoring induced exocytotic release (ZIMIR). ZIMIR displayed a robust fluorescence enhancement on Zn(2+) chelation and bound Zn(2+) with high selectivity against Ca(2+) and Mg(2+). When added to cultured β cells or intact pancreatic islets at low micromolar concentrations, ZIMIR labeled cells rapidly, noninvasively, and stably, and it reliably reported changes in Zn(2+) concentration near the sites of granule fusion with high sensitivity that correlated well with membrane capacitance measurement. Fluorescence imaging of ZIMIR-labeled β cells followed the dynamics of exocytotic activity at subcellular resolution, even when using simple epifluorescence microscopy, and located the chief sites of insulin release to intercellular junctions. Moreover, ZIMIR imaging of intact rat islets revealed that Zn(2+)/insulin release occurred largely in small groups of adjacent β cells, with each forming a "secretory unit." Concurrent imaging of ZIMIR and Fura-2 showed that the amplitude of cytosolic Ca(2+) elevation did not necessarily correlate with insulin secretion activity, suggesting that events downstream of Ca(2+) signaling underlie the cell-cell heterogeneity in insulin release. In addition to studying stimulation-secretion coupling in cells with Zn(2+)-containing granules, ZIMIR may find applications in β-cell engineering and screening for molecules regulating insulin secretion on high-throughput platforms. PMID:22160693

  1. Beneficial effects of combined resveratrol and metformin therapy in treating diet-induced insulin resistance.

    PubMed

    Frendo-Cumbo, Scott; MacPherson, Rebecca E K; Wright, David C

    2016-08-01

    The polyphenol compound resveratrol (RSV) has attracted attention due to its reputed beneficial effects on insulin sensitivity. Our lab has previously identified protective effects of RSV against the development of type 2 diabetes in rats. These effects occurred in a manner similar to thiazolidinedione's (TZDs), a class of insulin sensitizing drugs. TZDs are commonly prescribed in combination with metformin (MET) and thus we sought to examine the combined effects of RSV and MET in treating insulin resistance. Male C57BL6 mice were fed a low- (LFD; 10% Kcal from fat) or high-fat diet (HFD; 60% Kcal from fat) for 9 weeks to induce glucose and insulin intolerance. HFD mice were then assigned to control (HFD), MET (231.28 ± 12.24 mg/kg/day), RSV (93.68 ± 3.51 mg/kg/day), or combined (COM; MET 232.01 ± 17.12 mg/kg/day and RSV 92.77 ± 6.92 mg/kg/day) treatment groups. Changes in glucose and insulin tolerance and tissue-specific insulin signaling were measured 4 weeks post-treatment. RSV or MET alone did not have beneficial effects on glucose tolerance, although MET significantly improved insulin tolerance compared to HFD Glucose and insulin tolerance were significantly improved in COM compared to HFD and this was mirrored by enhanced insulin-stimulated AKT phosphorylation in triceps muscle and inguinal subcutaneous adipose tissue in COM compared to HFD mice. Improvements with COM treatment were not explained by differences in body weight, adiposity, or markers of adipose tissue inflammation. In summary, this study provides evidence of beneficial effects of combined RSV and MET therapy in treating impairments in glucose homeostasis. PMID:27482073

  2. Aspirin-mediated acetylation induces structural alteration and aggregation of bovine pancreatic insulin.

    PubMed

    Yousefi, Reza; Taheri, Behnaz; Alavi, Parnian; Shahsavani, Mohammad Bagher; Asadi, Zahra; Ghahramani, Maryam; Niazi, Ali; Alavianmehr, Mohammad Mehdi; Moosavi-Movahedi, Ali Akbar

    2016-01-01

    The simple aggregation of insulin under various chemical and physical stresses is still an important challenge for both pharmaceutical production and clinical formulation. In the storage form, this protein is subjected to various chemical modifications which alter its physicochemical and aggregation properties. Aspirin (acetylsalicylic acid) which is the most widely used medicine worldwide has been indicated to acetylate a large number of proteins both in vitro and in vivo. In this study, as insulin treated with aspirin at 37°C, a significant level of acetylation was observed by flourescamine and o-phthalaldehyde assay. Also, different spectroscopic techniques, gel electrophoresis, and microscopic assessment were applied to compare the structural variation and aggregation/fibrillation propensity among acetylated and non-acetylated insulin samples. The results of spectroscopic assessments elucidate that acetylation induces insulin unfolding which is accompanied with the exposure of protein hydrophobic patches, a transition from alpha-helix to beta-sheet and increased propensity of the protein for aggregation. The kinetic studies propose that acetylation increases aggregation rate of insulin under both thermal and chemical stresses. Also, gel electrophoresis and dynamic light scattering experiments suggest that acetylation induces insulin oligomerization. Additionally, the results of Thioflavin T fluorescence study, Congo red absorption assessment, and microscopic analysis suggest that acetylation with aspirin enhances the process of insulin fibrillation. Overall, the increased susceptibility of acetylated insulin for aggregation may reflect the fact that this type of modification has significant structural destabilizing effect which finally makes the protein more vulnerable for pathogenic aggregation/fibrillation. PMID:25994118

  3. The Investigation of ADAMTS16 in Insulin-Induced Human Chondrosarcoma Cells

    PubMed Central

    Comertoglu, Ismail; Firat, Ridvan; Erdemli, Haci Kemal; Kursunlu, S. Fatih; Akyol, Sumeyya; Ugurcu, Veli; Altuntas, Aynur; Adam, Bahattin; Demircan, Kadir

    2015-01-01

    Abstract Objectives: A disintegrin-like metalloproteinase with thrombospondin motifs (ADAMTS) is a group of proteins that have enzymatic activity secreted by cells to the outside extracellular matrix. Insulin induces proteoglycan biosynthesis in chondrosarcoma chondrocytes. The purpose of the present in vitro study is to assess the time course effects of insulin on ADAMTS16 expression in OUMS-27 (human chondrosarcoma) cell line to examine whether insulin regulates ADAMTS16 expression as well as proteoglycan biosynthesis with multifaceted properties or not. Methods: Chondrosarcoma cells were cultured in Dulbecco's modified Eagle's medium having either 10 μg/mL insulin or not. While the experiment was going on, the medium containing insulin had been changed every other day. Cells were harvested at 1st, 3rd, 7th, and 11th days; subsequently, RNA and proteins were isolated in every experimental group according to their time interval. RNA expression of ADAMTS was estimated by quantitative real-time polymerase chain reaction (qRT-PCR) by using primers. Immunoreactive protein levels were encountered by the western blot protein detection technique by using proper anti-ADAMTS16 antibodies. Results: ADAMTS16 mRNA expression level of chondrosarcoma cells was found to be insignificantly decreased in chondrosarcoma cells induced by insulin detected by the qRT-PCR instrument. On the other hand, there was a gradual decrease in immune-reactant ADAMTS16 protein amount by the time course in insulin-treated cell groups when compared with control cells. Conclusion: It has been suggested that insulin might possibly regulate ADAMTS16 levels/activities in OUMS-27 chondrosarcoma cells taking a role in extracellular matrix turnover. PMID:26181853

  4. Regulation of recombinant human insulin-induced maturational events in Clarias batrachus (L.) oocytes in vitro.

    PubMed

    Hajra, Sudip; Das, Debabrata; Ghosh, Pritha; Pal, Soumojit; Nath, Poulomi; Maitra, Sudipta

    2016-04-01

    Regulation of insulin-mediated resumption of meiotic maturation in catfish oocytes was investigated. Insulin stimulation of post-vitellogenic oocytes promotes the synthesis of cyclin B, histone H1 kinase activation and a germinal vesicle breakdown (GVBD) response in a dose-dependent and duration-dependent manner. The PI3K inhibitor wortmannin abrogates recombinant human (rh)-insulin action on histone H1 kinase activation and meiotic G2-M1 transition in denuded and follicle-enclosed oocytes in vitro. While the translational inhibitor cycloheximide attenuates rh-insulin action, priming with transcriptional blocker actinomycin D prevents insulin-stimulated maturational response appreciably, albeit in low amounts. Compared with rh-insulin, human chorionic gonadotrophin (hCG) stimulation of follicle-enclosed oocytes in vitro triggers a sharp increase in 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DHP) secreted in the incubation medium at 12 h. Interestingly, the insulin, but not the hCG-induced, maturational response shows less susceptibility to steroidogenesis inhibitors, trilostane or dl-aminoglutethimide. In addition, priming with phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX) or cell-permeable dbcAMP or adenylyl cyclase activator forskolin reverses the action of insulin on meiotic G2-M1 transition. Conversely, the adenylyl cyclase inhibitor, SQ 22536, or PKA inhibitor H89 promotes the resumption of meiosis alone and further potentiates the GVBD response in the presence of rh-insulin. Furthermore, insulin-mediated meiotic maturation involves the down-regulation of endogenous protein kinase A (PKA) activity in a manner sensitive to PI3K activation, suggesting potential involvement of a cross-talk between cAMP/PKA and insulin-mediated signalling cascade in catfish oocytes in vitro. Taken together, these results suggest that rh-insulin regulation of the maturational response in C. batrachus oocytes involves down-regulation of PKA, synthesis of cyclin

  5. Insulin and hypoxia-inducible factor-1 cooperate in pancreatic cancer cells to increase cell viability

    PubMed Central

    ZHANG, DAPENG; CUI, LIHUA; LI, SHU SHUN; WANG, FENG

    2015-01-01

    The aim of the present study was to investigate whether interstitial insulin and cancer-induced hypoxia-inducible factor-1 (HIF-1) cooperate in pancreatic cancer cells. A population of 45 nude mice were divided into one intact control group and six pancreatic tumor-carrier groups. Pancreatic tumors were generated using HIF-1-positive wild-type MiaPaCa2 (wt-MiaPaCa2) pancreatic cancer cells in three groups of carriers and MiaPaCa2 cells transfected with small interfering RNA against HIF-1α (si-MiaPaCa2 cells) in the other three carrier groups. To vary the intrapancreatic insulin levels, tumor-carrying mice were subjected to one of the following conditions: i) Untreated, ii) single injection of the β-cell toxin streptozotosin prior to cancer cell transplantation and iii) daily injection of insulin following cancer cell transplantation. After 12 weeks, tumor viability was assessed by histological analysis. Western blotting of the tumor grafts was performed to determine the protein expression levels of insulin receptor (IR) and two downstream proteins, hexokinase-II (HK-II) and vascular endothelial growth factor (VEGF). Histologically, the greatest viability was observed in wt-MiaPaCa2 tumors with carriers that remained untreated. These tumors also exhibited greater IR expression than their si-MiaPaCa2 counterparts, indicating that HIF-1 is necessary for basal expression of IR. However, IR expression was increased in wt-MiaPaCa2 and si-MiaPaCa2 tumors when the carriers were treated with exogenous insulin. This indicates that the insulin-induced IR expression was independent of HIF-1. Notably, the insulin-induced IR expression was associated with increased HK-II and VEGF expression in wt-MiaPaCa2 tumors but not si-MiaPaC2 tumors. Therefore, the present study proposes that insulin and HIF-1 may cooperate to increase pancreatic cancer cell viability. Furthermore, the HIF-1 signaling pathway is required for insulin-induced HK-II and VEGF expression, as well as basal IR

  6. Identification of new biomarker candidates for glucocorticoid induced insulin resistance using literature mining

    PubMed Central

    2013-01-01

    Background Glucocorticoids are potent anti-inflammatory agents used for the treatment of diseases such as rheumatoid arthritis, asthma, inflammatory bowel disease and psoriasis. Unfortunately, usage is limited because of metabolic side-effects, e.g. insulin resistance, glucose intolerance and diabetes. To gain more insight into the mechanisms behind glucocorticoid induced insulin resistance, it is important to understand which genes play a role in the development of insulin resistance and which genes are affected by glucocorticoids. Medline abstracts contain many studies about insulin resistance and the molecular effects of glucocorticoids and thus are a good resource to study these effects. Results We developed CoPubGene a method to automatically identify gene-disease associations in Medline abstracts. We used this method to create a literature network of genes related to insulin resistance and to evaluate the importance of the genes in this network for glucocorticoid induced metabolic side effects and anti-inflammatory processes. With this approach we found several genes that already are considered markers of GC induced IR, such as phosphoenolpyruvate carboxykinase (PCK) and glucose-6-phosphatase, catalytic subunit (G6PC). In addition, we found genes involved in steroid synthesis that have not yet been recognized as mediators of GC induced IR. Conclusions With this approach we are able to construct a robust informative literature network of insulin resistance related genes that gave new insights to better understand the mechanisms behind GC induced IR. The method has been set up in a generic way so it can be applied to a wide variety of disease networks. PMID:23379763

  7. Effect of Glucocorticoid-Induced Insulin Resistance on Follicle Development and Ovulation1

    PubMed Central

    Hackbart, Katherine S.; Cunha, Pauline M.; Meyer, Rudelle K.; Wiltbank, Milo C.

    2013-01-01

    ABSTRACT Polycystic ovarian syndrome (PCOS) is characterized by hyperandrogenemia, polycystic ovaries, and menstrual disturbance and a clear association with insulin resistance. This research evaluated whether induction of insulin resistance, using dexamethasone (DEX), in a monovular animal model, the cow, could produce an ovarian phenotype similar to PCOS. In all of these experiments, DEX induced insulin resistance in cows as shown by increased glucose, insulin, and HOMA-IR (homeostasis model assessment of insulin resistance). Experiment 1: DEX induced anovulation (zero of five DEX vs. four of four control cows ovulated) and decreased circulating estradiol (E2). Experiment 2: Gonadotropin-releasing hormone (GnRH) was administered to determine pituitary and follicular responses during insulin resistance. GnRH induced a luteinizing hormone (LH) surge and ovulation in both DEX (seven of seven) and control (seven of seven) cows. Experiment 3: E2 was administered to determine hypothalamic responsiveness after induction of an E2 surge in DEX (eight of eight) and control (eight of eight) cows. An LH surge was induced in control (eight of eight) but not DEX (zero of eight) cows. All control (eight of eight) but only two of eight DEX cows ovulated within 60 h of E2 administration. Experiment 4: Short-term DEX was initiated 24 h after induced luteal regression to determine if DEX could acutely block ovulation before peak insulin resistance was induced, similar to progesterone (P4). All control (five of five), no P4-treated (zero of six), and 50% of DEX-treated (three of six) cows ovulated by 96 h after luteal regression. All anovular cows had reduced circulating E2. These data are consistent with DEX creating a lesion in hypothalamic positive feedback to E2 without altering pituitary responsiveness to GnRH or ovulatory responsiveness of follicles to LH. It remains to be determined if the considerable insulin resistance and the reduced follicular E2 production induced by DEX

  8. Effect of glucocorticoid-induced insulin resistance on follicle development and ovulation.

    PubMed

    Hackbart, Katherine S; Cunha, Pauline M; Meyer, Rudelle K; Wiltbank, Milo C

    2013-06-01

    Polycystic ovarian syndrome (PCOS) is characterized by hyperandrogenemia, polycystic ovaries, and menstrual disturbance and a clear association with insulin resistance. This research evaluated whether induction of insulin resistance, using dexamethasone (DEX), in a monovular animal model, the cow, could produce an ovarian phenotype similar to PCOS. In all of these experiments, DEX induced insulin resistance in cows as shown by increased glucose, insulin, and HOMA-IR (homeostasis model assessment of insulin resistance). Experiment 1: DEX induced anovulation (zero of five DEX vs. four of four control cows ovulated) and decreased circulating estradiol (E2). Experiment 2: Gonadotropin-releasing hormone (GnRH) was administered to determine pituitary and follicular responses during insulin resistance. GnRH induced a luteinizing hormone (LH) surge and ovulation in both DEX (seven of seven) and control (seven of seven) cows. Experiment 3: E2 was administered to determine hypothalamic responsiveness after induction of an E2 surge in DEX (eight of eight) and control (eight of eight) cows. An LH surge was induced in control (eight of eight) but not DEX (zero of eight) cows. All control (eight of eight) but only two of eight DEX cows ovulated within 60 h of E2 administration. Experiment 4: Short-term DEX was initiated 24 h after induced luteal regression to determine if DEX could acutely block ovulation before peak insulin resistance was induced, similar to progesterone (P4). All control (five of five), no P4-treated (zero of six), and 50% of DEX-treated (three of six) cows ovulated by 96 h after luteal regression. All anovular cows had reduced circulating E2. These data are consistent with DEX creating a lesion in hypothalamic positive feedback to E2 without altering pituitary responsiveness to GnRH or ovulatory responsiveness of follicles to LH. It remains to be determined if the considerable insulin resistance and the reduced follicular E2 production induced by DEX had any

  9. [Role of the NADH shuttle system in glucose-induced insulin secretion].

    PubMed

    Eto, K; Kadowaki, T

    1999-03-01

    To determine the role of the NADH shuttle system composed of the glycerol phosphate shuttle and malate-aspartate shuttle in glucose-induced insulin secretion from pancreatic beta cells, we have generated mice which lack mitochondrial glycerol-3 phosphate dehydrogenase (mGPDH), a rate-limiting enzyme of the glycerol phosphate shuttle. When both shuttles were halted in mGPDH-deficient islets treated with aminooxyacetate, an inhibitor of the malate-aspartate shuttle, glucose-induced insulin secretion was almost completely abrogated. Under these conditions, although the flux of glycolysis and supply of glucose-derived pyruvate into mitochondria were unaffected, glucose-induced increases in NAD(P)H autofluorescence, mitochondrial membrane potential, Ca2+ entry into mitochondria, and ATP content were severely attenuated. This study provides the first direct evidence that the NADH shuttle system is essential for coupling glycolysis with the activation of mitochondrial energy metabolism to trigger glucose-induced insulin secretion and thus revises the classical model for the metabolic signals of glucose-induced insulin secretion. PMID:10199125

  10. Deepure Tea Improves High Fat Diet-Induced Insulin Resistance and Nonalcoholic Fatty Liver Disease

    PubMed Central

    Deng, Jing-Na; Li, Juan; Mu, Hong-Na; Liu, Yu-Ying; Wang, Ming-Xia; Pan, Chun-Shui; Fan, Jing-Yu; Ye, Fei; Han, Jing-Yan

    2015-01-01

    This study was to explore the protective effects of Deepure tea against insulin resistance and hepatic steatosis and elucidate the potential underlying molecular mechanisms. C57BL/6 mice were fed with a high fat diet (HFD) for 8 weeks to induce the metabolic syndrome. In the Deepure tea group, HFD mice were administrated with Deepure tea at 160 mg/kg/day by gavage for 14 days. The mice in HFD group received water in the same way over the same period. The age-matched C57BL/6 mice fed with standard chow were used as normal control. Compared to the mice in HFD group, mice that received Deepure tea showed significantly reduced plasma insulin and improved insulin sensitivity. Deepure tea increased the expression of insulin receptor substrate 2 (IRS-2), which plays an important role in hepatic insulin signaling pathway. Deepure tea also led to a decrease in hepatic fatty acid synthesis and lipid accumulation, which were mediated by the downregulation of sterol regulatory element binding protein 1c (SREBP-1c), fatty acid synthesis (FAS), and acetyl-CoA carboxylase (ACC) proteins that are involved in liver lipogenesis. These results suggest that Deepure tea may be effective for protecting against insulin resistance and hepatic steatosis via modulating IRS-2 and downstream signaling SREBP-1c, FAS, and ACC. PMID:26504484

  11. Antidepressant-like Effect of Insulin in Streptozotocin-induced Type 2 Diabetes Mellitus Rats.

    PubMed

    Sestile, Caio C; Maraschin, Jhonatan C; Rangel, Marcel P; Cuman, Roberto K N; Audi, Elisabeth A

    2016-09-01

    This study evaluated the antidepressant-like effect of insulin compared to sertraline and a combination of insulin and sertraline in streptozotocin (STZ)-induced type 2 diabetes mellitus (T2DM) rats submitted to the forced swim test (FST). Male Wistar rats were daily treated for 21 days with insulin (1 or 2 IU/kg, i.p.), with the selective serotonin reuptake inhibitor (SSRI), sertraline (10 mg/kg, i.p.), or with a combination of insulin (1 or 2 IU/kg, i.p.) and sertraline (10 mg/kg, i.p.) and submitted to the FST. We also evaluated the water and food intake, urine volume and weight gain of the rats. Rats treated with STZ showed impaired glucose tolerance. Chronic treatment with sertraline showed an antidepressant-like effect in non-diabetic and diabetic rats. Furthermore, sertraline promoted lower weight gain in diabetic rats. Insulin reduced the immobility behaviour in T2DM rats with impaired glucose tolerance. In conclusion, our results showed that insulin has an antidepressant-like effect comparable to that of sertraline. Sertraline is effective as an antidepressant and reduces weight gain, which reinforces its superiority over other SSRIs in the treatment of major depression disorder in patients with T2DM. PMID:26857652

  12. Brain insulin lowers circulating BCAA levels by inducing hepatic BCAA catabolism

    PubMed Central

    Shin, Andrew C.; Fasshauer, Martin; Filatova, Nika; Grundell, Linus A.; Zielinski, Elizabeth; Zhou, Jian-Ying; Scherer, Thomas; Lindtner, Claudia; White, Phillip J.; Lapworth, Amanda L.; Ilkayeva, Olga; Knippschild, Uwe; Wolf, Anna M.; Scheja, Ludger; Grove, Kevin L.; Smith, Richard D.; Qian, Wei-Jun; Lynch, Christopher J.; Newgard, Christopher B.; Buettner, Christoph

    2014-01-01

    Summary Circulating branched-chain amino acid (BCAA) levels are elevated in obesity/diabetes and are a sensitive predictor for type 2 diabetes. Here we show in rats that insulin dose-dependently lowers plasma BCAA levels through induction of hepatic protein expression and activity of branched-chain α keto-acid dehydrogenase (BCKDH), the rate-limiting enzyme in the BCAA degradation pathway. Selective induction of hypothalamic insulin signaling in rats and genetic modulation of brain insulin receptors in mice demonstrate that brain insulin signaling is a major regulator of BCAA metabolism by inducing hepatic BCKDH. Short-term overfeeding impairs the ability of brain insulin to lower BCAAs in rats. High-fat feeding in non-human primates and obesity and/or diabetes in humans is associated with reduced BCKDH protein in liver. These findings support the concept that decreased hepatic BCKDH is a major cause of increased plasma BCAAs, and that hypothalamic insulin resistance may account for impaired BCAA metabolism in obesity and diabetes. PMID:25307860

  13. Histopathological nerve and skeletal muscle changes in rats subjected to persistent insulin-induced hypoglycemia

    PubMed Central

    Jensen, Vivi Flou Hjorth; Mølck, Anne-Marie; Heydenreich, Annette; Jensen, Karin Juul; Bertelsen, Line Olrik; Alifrangis, Lene; Andersen, Lene; Søeborg, Henrik; Chapman, Melissa; Lykkesfeldt, Jens; Bøgh, Ingrid Brück

    2015-01-01

    New insulin analogues with a longer duration of action and a flatter pharmacodynamic profile are developed to improve convenience and safety for diabetic patients. During the nonclinical development of such analogues, safety studies must be conducted in nondiabetic rats, which consequently are rendered chronically hypoglycemic. A rat comparator model using human insulin would be valuable, as it would enable differentiation between effects related to either persistent insulin-induced hypoglycemia (IIH) or a new analogue per se. Such a model could alleviate the need for an in-study-comparator and thereby reduce the number of animals used during development. Thus, the aims of the present study were i) to develop a preclinical animal model of persistent hypoglycemia in rats using human insulin infusion for four weeks and ii) to investigate histopathological changes in sciatic nerves and quadriceps femoris muscle tissue, as little is known about the response to persistent hypoglycemia in these tissues. Histopathologic changes in insulin-infused animals included axonal degeneration and myofibre degeneration. To our knowledge, this is the first study to show that persistent IIH provokes peripheral nerve and skeletal myofiber degeneration within the same animals. This suggests that the model can serve as a nonclinical comparator model during development of long-acting insulin analogues. PMID:26989298

  14. Assessment of benzene induced oxidative impairment in rat isolated pancreatic islets and effect on insulin secretion.

    PubMed

    Bahadar, Haji; Maqbool, Faheem; Mostafalou, Sara; Baeeri, Maryam; Rahimifard, Mahban; Navaei-Nigjeh, Mona; Abdollahi, Mohammad

    2015-05-01

    Benzene (C6H6) is an organic compound used in petrochemicals and numerous other industries. It is abundantly released to our environment as a chemical pollutant causing widespread human exposure. This study mainly focused on benzene induced toxicity on rat pancreatic islets with respect to oxidative damage, insulin secretion and glucokinase (GK) activity. Benzene was dissolved in corn oil and administered orally at doses 200, 400 and 800mg/kg/day, for 4 weeks. In rats, benzene significantly raised the concentration of plasma insulin. Also the effect of benzene on the release of glucose-induced insulin was pronounced in isolated islets. Benzene caused oxidative DNA damage and lipid peroxidation, and also reduced the cell viability and total thiols groups, in the islets of exposed rats. In conclusion, the current study revealed that pancreatic glucose metabolism is susceptible to benzene toxicity and the resultant oxidative stress could lead to functional abnormalities in the pancreas. PMID:25935538

  15. FFA-induced hepatic insulin resistance in vivo is mediated by PKCδ, NADPH oxidase, and oxidative stress.

    PubMed

    Pereira, Sandra; Park, Edward; Mori, Yusaku; Haber, C Andrew; Han, Ping; Uchida, Toyoyoshi; Stavar, Laura; Oprescu, Andrei I; Koulajian, Khajag; Ivovic, Alexander; Yu, Zhiwen; Li, Deling; Bowman, Thomas A; Dewald, Jay; El-Benna, Jamel; Brindley, David N; Gutierrez-Juarez, Roger; Lam, Tony K T; Najjar, Sonia M; McKay, Robert A; Bhanot, Sanjay; Fantus, I George; Giacca, Adria

    2014-07-01

    Fat-induced hepatic insulin resistance plays a key role in the pathogenesis of type 2 diabetes in obese individuals. Although PKC and inflammatory pathways have been implicated in fat-induced hepatic insulin resistance, the sequence of events leading to impaired insulin signaling is unknown. We used Wistar rats to investigate whether PKCδ and oxidative stress play causal roles in this process and whether this occurs via IKKβ- and JNK-dependent pathways. Rats received a 7-h infusion of Intralipid plus heparin (IH) to elevate circulating free fatty acids (FFA). During the last 2 h of the infusion, a hyperinsulinemic-euglycemic clamp with tracer was performed to assess hepatic and peripheral insulin sensitivity. An antioxidant, N-acetyl-L-cysteine (NAC), prevented IH-induced hepatic insulin resistance in parallel with prevention of decreased IκBα content, increased JNK phosphorylation (markers of IKKβ and JNK activation, respectively), increased serine phosphorylation of IRS-1 and IRS-2, and impaired insulin signaling in the liver without affecting IH-induced hepatic PKCδ activation. Furthermore, an antisense oligonucleotide against PKCδ prevented IH-induced phosphorylation of p47(phox) (marker of NADPH oxidase activation) and hepatic insulin resistance. Apocynin, an NADPH oxidase inhibitor, prevented IH-induced hepatic and peripheral insulin resistance similarly to NAC. These results demonstrate that PKCδ, NADPH oxidase, and oxidative stress play a causal role in FFA-induced hepatic insulin resistance in vivo and suggest that the pathway of FFA-induced hepatic insulin resistance is FFA → PKCδ → NADPH oxidase and oxidative stress → IKKβ/JNK → impaired hepatic insulin signaling. PMID:24824652

  16. FOXO1 Mediates Vitamin D Deficiency-induced Insulin Resistance in Skeletal Muscle

    PubMed Central

    Chen, Songcang; Villalta, Armando; Agrawal, Devendra K.

    2015-01-01

    Prospective epidemiological studies have consistently shown a relationship between vitamin D deficiency, insulin resistance, and type 2 diabetes mellitus (DM2). This is supported by recent trials showing that vitamin D supplementation in prediabetic or insulin-resistant patients with inadequate vitamin D levels improves insulin sensitivity. However, the molecular mechanisms underlying vitamin D deficiency-induced insulin resistance and DM2 remain unknown. Skeletal muscle insulin resistance is a primary defect in the majority of patients with DM2. While sustained activation of forkhead box O1 (FOXO1) in skeletal muscle causes insulin resistance, a relationship between vitamin D deficiency and FOXO1 activation in muscle is unknown. We generated skeletal muscle-specific vitamin D receptor (VDR)-null mice and discovered that these mice developed insulin resistance and glucose intolerance accompanied by increased expression and activity of FOXO1. We also found sustained FOXO1 activation in the skeletal muscle of global VDR-null mice. Treatment of C2C12 muscle cells with 1,25-dihydroxyvitamin D (VD3) reduced FOXO1 expression, nuclear translocation, and activity. The VD3-dependent suppression of FOXO1 activation disappeared by knockdown of VDR, indicating that it is VDR-dependent. Taken together, these results suggest that FOXO1 is a critical target mediating VDR-null signaling in skeletal muscle. The novel findings provide the conceptual support that persistent FOXO1 activation may be responsible for insulin resistance and impaired glucose metabolism in vitamin D signaling-deficient mice, as well as evidence for the utility of vitamin D supplementation for intervention in DM2. PMID:26462119

  17. Peroxisome Proliferator-Activated Receptor Agonist Treatment of Alcohol-Induced Hepatic Insulin Resistance

    PubMed Central

    de la Monte, Suzanne M.; Pang, Maoyin; Chaudhry, Rajeeve; Duan, Kevin; Longato, Lisa; Carter, Jade; Ouh, Jiyun; Wands, Jack R.

    2011-01-01

    Chronic ethanol exposure impairs insulin signaling in the liver. Peroxisome-proliferator activated receptor (PPAR) agonists function as insulin sensitizers and are used to treat type 2 diabetes mellitus. We examined the therapeutic effectiveness of PPAR agonists in reducing alcoholic hepatitis and hepatic insulin resistance in a model of chronic ethanol feeding. Adult male Long Evans rats were pair fed with isocaloric liquid diets containing 0% (control) or 37% ethanol (caloric content; 9.2% v/v) for 8 weeks. After 3 weeks on the diets, the rats were treated with vehicle, or a PPAR-α, PPAR-δ, or PPAR-γ agonist twice weekly by i.p. injection. Livers were harvested for histopathological, gene expression (RT-PCR), protein (Western and ELISA), and receptor binding studies. Ethanol-fed rats developed steatohepatitis with disordered hepatic chord architecture, increased hepatocellular apoptosis, reduced binding to the insulin, IGF-1, and IGF-2 receptors, and decreased expression of glyceraldehyde-3-phosphate dehydrogenase and aspartyl-(asparaginyl)-β-hydroxylase (mediates remodeling), which are regulated by insulin/IGF signaling. PPAR-α, PPAR-δ, or PPAR-γ agonist treatments reduced the severity of ethanol-mediated liver injury, including hepatic architectural disarray and steatosis. In addition, PPAR-δ and PPAR-γ agonists reduced insulin/IGF resistance and increased insulin/IGF-responsive gene expression. In conclusion, PPAR agonists may help reduce the severity of chronic ethanol-induced liver injury and insulin/IGF resistance, even in the context of continued high-level ethanol consumption. PMID:21426453

  18. Antigen Presentation and T-Cell Activation Are Critical for RBP4-Induced Insulin Resistance.

    PubMed

    Moraes-Vieira, Pedro M; Castoldi, Angela; Aryal, Pratik; Wellenstein, Kerry; Peroni, Odile D; Kahn, Barbara B

    2016-05-01

    Adipose tissue (AT) inflammation contributes to impaired insulin action, which is a major cause of type 2 diabetes. RBP4 is an adipocyte- and liver-derived protein with an important role in insulin resistance, metabolic syndrome, and AT inflammation. RBP4 elevation causes AT inflammation by activating innate immunity, which elicits an adaptive immune response. RBP4-overexpressing mice (RBP4-Ox) are insulin resistant and glucose intolerant and have increased AT macrophages and T-helper 1 cells. We show that high-fat diet-fed RBP4(-/-) mice have reduced AT inflammation and improved insulin sensitivity versus wild type. We also elucidate the mechanism for RBP4-induced macrophage antigen presentation and subsequent T-cell activation. In RBP4-Ox, AT macrophages display enhanced c-Jun N-terminal kinase, extracellular signal-related kinase, and p38 phosphorylation. Inhibition of these pathways and of NF-κB reduces activation of macrophages and CD4 T cells. MyD88 is an adaptor protein involved in proinflammatory signaling. In macrophages from MyD88(-/-) mice, RBP4 fails to stimulate secretion of tumor necrosis factor, IL-12, and IL-6 and CD4 T-cell activation. In vivo blockade of antigen presentation by treating RBP4-Ox mice with CTLA4-Ig, which blocks costimulation of T cells, is sufficient to reduce AT inflammation and improve insulin resistance. Thus, MyD88 and downstream mitogen-activated protein kinase and NF-κB pathways are necessary for RBP4-induced macrophage antigen presentation and subsequent T-cell activation. Also, blocking antigen presentation with CTLA4-Ig improves RBP4-induced insulin resistance and macrophage-induced T-cell activation. PMID:26936962

  19. Levocetirizine ameliorates high fructose diet-induced insulin resistance, vascular dysfunction and hepatic steatosis in rats.

    PubMed

    Shawky, Noha M; Shehatou, George S G; Abdel Rahim, Mona; Suddek, Ghada M; Gameil, Nariman M

    2014-10-01

    This study investigates the possible protective effects of levocetirizine against fructose-induced insulin resistance, hepatic steatosis and vascular dysfunction, in comparison to pioglitazone, a standard insulin sensitizer. Male Sprague Dawley rats (150-200 g) were divided into 4 groups. Three groups were fed on high fructose diets (HFD) containing 60% w/w fructose, while the fourth control group was fed on standard laboratory food for 8 weeks. AUCOGTT, AUCITT, fasting glucose, HOMA-IR, hepatic glutathione (GSH) and malondialdehyde (MDA) levels, serum total cholesterol, LDL-C, C-reactive protein (CRP) level and lactate dehydrogenase (LDH) activity and liver steatosis scores were significantly higher in HFD group compared to control group. Moreover, body weight gain, food intake, feeding efficiency, HOMA-β, Emax and pEC50 of acetylcholine-induced relaxations of aortic rings and hepatic superoxide dismutase (SOD) activity were significantly lower in HFD group than in control group. Treatment with levocetirizine caused significant decreases in AUCOGTT, AUCITT, HOMA-IR, hepatic GSH and MDA levels and serum CRP level and LDH activity and significant increases in hepatic SOD activity and HOMA-β when compared with the HFD group. Although levocetirizine failed to alter TC and LDL-C levels, it produced a significant increase in HDL-C level relative to control group. Levocetirizine was also able to improve acetylcholine-induced relaxations of aortic rings, indicating a protective effect against insulin resistance-induced endothelial damage comparable to that offered by pioglitazone. Moreover, levocetirizine substantially attenuated insulin resistance-associated liver macrovesicular steatosis. These findings demonstrate that levocetirizine ameliorates insulin resistance, improves glucose tolerance and attenuates insulin resistance-linked hepatic steatosis and vascular damage. PMID:25064340

  20. Insulin Suppresses Endotoxin-Induced Oxidative, Nitrosative, and Inflammatory Stress in Humans

    PubMed Central

    Dandona, Paresh; Ghanim, Husam; Bandyopadhyay, Arindam; Korzeniewski, Kelly; Ling Sia, Chang; Dhindsa, Sandeep; Chaudhuri, Ajay

    2010-01-01

    OBJECTIVE To investigate whether insulin reduces the magnitude of oxidative, nitrosative, and inflammatory stress and tissue damage responses induced by endotoxin (lipopolysaccharide [LPS]). RESEARCH DESIGN AND METHODS Nine normal subjects were injected intravenously with 2 ng/kg LPS prepared from Escherichia coli. Ten others were infused with insulin (2 units/h) for 6 h in addition to the LPS injection along with 100 ml/h of 5% dextrose to maintain normoglycemia. RESULTS LPS injection induced a rapid increase in plasma concentrations of nitric oxide metabolites, nitrite and nitrate (NOM), and thiobarbituric acid–reacting substances (TBARS), an increase in reactive oxygen species (ROS) generation by polymorphonuclear leukocytes (PMNLs), and marked increases in plasma free fatty acids, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), macrophage migration inhibition factor (MIF), C-reactive protein, resistin, visfatin, lipopolysaccharide binding protein (LBP), high mobility group-B1 (HMG-B1), and myoglobin concentrations. The coinfusion of insulin led to a total elimination of the increase in NOM, free fatty acids, and TBARS and a significant reduction in ROS generation by PMNLs and plasma MIF, visfatin, and myoglobin concentrations. Insulin did not affect TNF-α, MCP-1, IL-6, LBP, resistin, and HMG-B1 increases induced by the LPS. CONCLUSIONS Insulin reduces significantly several key mediators of oxidative, nitrosative, and inflammatory stress and tissue damage induced by LPS. These effects of insulin require further investigation for its potential use as anti-inflammatory therapy for endotoxemia. PMID:20699433

  1. SIRT1 attenuates high glucose-induced insulin resistance via reducing mitochondrial dysfunction in skeletal muscle cells.

    PubMed

    Zhang, Hao-Hao; Ma, Xiao-Jun; Wu, Li-Na; Zhao, Yan-Yan; Zhang, Peng-Yu; Zhang, Ying-Hui; Shao, Ming-Wei; Liu, Fei; Li, Fei; Qin, Gui-Jun

    2015-05-01

    Insulin resistance is often characterized as the most critical factor contributing to the development of type 2 diabetes mellitus (T2DM). Sustained high glucose is an important extracellular environment that induces insulin resistance. Acquired insulin resistance is associated with reduced insulin-stimulated mitochondrial activity as a result of increased mitochondrial dysfunction. Silent information regulator 1 (SIRT1) is one member of the SIRT2 (Sir2)-like family of proteins involved in glucose homeostasis and insulin secretion in mammals. Although SIRT1 has a therapeutic effect on metabolic deterioration in insulin resistance, it is still not clear how SIRT1 is involved in the development of insulin resistance. Here, we demonstrate that pcDNA3.1 vector-mediated overexpression of SIRT1 attenuates insulin resistance in the high glucose-induced insulin-resistant skeleton muscle cells. These beneficial effects were associated with ameliorated mitochondrial dysfunction. Further studies have demonstrated that SIRT1 restores mitochondrial complex I activity leading to decreased oxidative stress and mitochondrial dysfunction. Furthermore, SIRT1 significantly elevated the level of another SIRT which is named SIRT3, and SIRT3 siRNA-suppressed SIRT1-induced mitochondria complex activity increments. Taken together, these results showed that SIRT1 improves insulin sensitivity via the amelioration of mitochondrial dysfunction, and this is achieved through the SIRT1-SIRT3-mitochondrial complex I pathway. PMID:25710929

  2. Effects of Combination of Thiazolidinediones with Melatonin in Dexamethasone-induced Insulin Resistance in Mice

    PubMed Central

    Ghaisas, M. M.; Ahire, Y. S.; Dandawate, P. R.; Gandhi, S. P.; Mule, M.

    2011-01-01

    In type 2 Diabetes, oxidative stress plays an important role in development and aggregation of insulin resistance. In the present study, long term administration of the dexamethasone led to the development of insulin resistance in mice. The effect of thiazolidinediones pioglitazone and rosiglitazone, with melatonin on dexamethasone-induced insulin resistance was evaluated in mice. Insulin resistant mice were treated with combination of pioglitazone (10 mg/kg/day, p.o.) or rosiglitazone (5 mg/kg/day, p.o.) with melatonin 10 mg/kg/day p.o. from day 7 to day 22. In the biochemical parameters, the serum glucose, triglyceride levels were significantly lowered (P<0.05) in the combination groups as compared to dexamethasone treated group as well as with individual groups of pioglitazone, rosiglitazone, and melatonin. There was also, significant increased (P<0.05) in the body weight gain in combination treated groups as compared to dexamethasone as well as individual groups. The combination groups proved to be effective in normalizing the levels of superoxide dismutase, catalase, glutathione reductase and lipid peroxidation in liver homogenates may be due to antioxidant effects of melatonin and decreased hyperglycemia induced insulin resistance by thiazolidinediones. The glucose uptake in the isolated hemidiaphragm of mice was significantly increased in combination treated groups (PM and RM) than dexamethasone alone treated mice as well as individual (pioglitazone, rosiglitazone, melatonin) treated groups probably via increased in expression of GLUT-4 by melatonin and thiazolidinediones as well as increased in insulin sensitivity by thiazolidinediones. Hence, it can be concluded that combination of pioglitazone and rosiglitazone, thiazolidinediones, with melatonin may reduces the insulin resistance via decreased in oxidative stress and control on hyperglycemia. PMID:23112392

  3. Intranasal insulin prevents anesthesia-induced hyperphosphorylation of tau in 3xTg-AD mice

    PubMed Central

    Chen, Yanxing; Run, Xiaoqin; Liang, Zhihou; Zhao, Yang; Dai, Chun-ling; Iqbal, Khalid; Liu, Fei; Gong, Cheng-Xin

    2014-01-01

    Background: It is well documented that elderly individuals are at increased risk of cognitive decline after anesthesia. General anesthesia is believed to be a risk factor for Alzheimer’s disease (AD). Recent studies suggest that anesthesia may increase the risk for cognitive decline and AD through promoting abnormal hyperphosphorylation of tau, which is crucial to neurodegeneration seen in AD. Methods: We treated 3xTg-AD mice, a commonly used transgenic mouse model of AD, with daily intranasal administration of insulin (1.75 U/day) for one week. The insulin- and control-treated mice were then anesthetized with single intraperitoneal injection of propofol (250 mg/kg body weight). Tau phosphorylation and tau protein kinases and phosphatases in the brains of mice 30 min and 2 h after propofol injection were then investigated by using Western blots and immunohistochemistry. Results: Propofol strongly promoted hyperphosphorylation of tau at several AD-related phosphorylation sites. Intranasal administration of insulin attenuated propofol-induced hyperphosphorylation of tau, promoted brain insulin signaling, and led to up-regulation of protein phosphatase 2A, a major tau phosphatase in the brain. Intranasal insulin also resulted in down-regulation of several tau protein kinases, including cyclin-dependent protein kinase 5, calcium/calmodulin-dependent protein kinase II, and c-Jun N-terminal kinase. Conclusion: Our results demonstrate that pretreatment with intranasal insulin prevents AD-like tau hyperphosphorylation. These findings provide the first evidence supporting that intranasal insulin administration might be used for the prevention of anesthesia-induced cognitive decline and increased risk for AD and dementia. PMID:24910612

  4. Development of postglucoprivic insulin-induced suckling and feeding in rats.

    PubMed

    Williams, C L; Blass, E M

    1987-07-01

    Increased food or milk intake in response to insulin-induced hypoglycemia cannot be demonstrated in the rat until pups reach weaning age. However, when food and suckling are withheld from insulin-treated 5- to 25-day-old rats until their altered blood glucose levels return to normal, their rate of milk intake via suckling from their anesthetized dam is increased over saline-treated control pups. This postglucoprivic action of insulin could not be demonstrated in rats consuming wet mash until pups reached 25-30 days of age. Nonnutritive oral stimulation from dry suckling during the glucoprivic episode is sufficient to disrupt postglucoprivic suckling in 20-day-old rats. In contrast consuming a small quantity of wet mash became an effective inhibitor of postglucoprivic suckling only when pups reached 25 days of age. These data demonstrate the existence of an insulin-sensitive neural system for suckling and feeding in infant rats and point to the involvement of multiple and changing oral factors during development in insulin-induced postglucoprivic feeding. PMID:3300371

  5. NMR estimation of protective effect of insulin on mouse liver with epinephrine-induced metabolic lesions.

    PubMed

    Yushmanov, V E; Khristianovich, D S; Rozantseva, T V; Sibeldina, L A

    1991-08-01

    In order to study the effects of epinephrine and insulin on liver metabolism, measurements of cellular phosphates and intracellular pH by 31PNMR, of glycogen by 13C NMR and of lactate by 1H NMR were performed in freshly dissected mouse liver at 0-4 degrees C and in ethanolic liver extracts. The injection of epinephrine hydrochloride (0.1 mL of 0.1% solution i.p. per mouse) caused remarkable changes in liver metabolic profiles which were expressed most distinctly in 15-30 min and could not be attributed solely to epinephrine-induced hyperglycemia. Among these metabolic changes are falls in the levels of ATP and uridine diphosphate sugars by 60-70%, possibly related to glycogen depletion, and intracellular acidification by 0.5 units attributed to the release of protons during hydrolysis of ATP rather than to accumulation of lactate in anaerobic glycolysis. Insulin injected prior to epinephrine (4 units i.p.) markedly suppressed epinephrine-induced metabolic alterations, although the effect of the combination of insulin and epinephrine was not the sum of the separate effects of these hormones. The maximum protective effect of insulin was reached when insulin was injected 15 min prior to epinephrine. The results obtained demonstrate the applicability of NMR for evaluating the protective activity of modifiers at various extreme exposures. PMID:1931556

  6. Perfluorooctane sulfonate-induced insulin resistance is mediated by protein kinase B pathway.

    PubMed

    Qiu, Tianming; Chen, Min; Sun, Xiance; Cao, Jun; Feng, Chang; Li, Dandan; Wu, Wei; Jiang, Liping; Yao, Xiaofeng

    2016-09-01

    Perfluorooctane sulfonate (PFOS), a persistent organic pollutant, is blamed to be associated with the incidence of insulin resistance in the general human population. In this study, we found that PFOS inhibited the phosphorylation and activation of protein kinase B (AKT), a key mediator of cellular insulin sensitivity, in human hepatoma HepG2 cells. The mRNA level of the gluconeogenic gene PEPCK, a downstream target gene of AKT, was increased in PFOS-treated cells. Due to stimulated gluconeogenesis, insulin-stimulated glucose uptake was decreased in HepG2 cells. In our previous study, we found that PFOS disturbed autophagy in HepG2 cells. We proposed that PFOS could inhibit the activation of AKT through inhibiting mTORC2, a key regulator of autophagy. In this study, we found that the levels of triglyceride were increased in HepG2 cells. PFOS-induced accumulation of hepatic lipids also contributed to the inhibition of AKT. Eventually, the inhibition of AKT led to insulin resistance in PFOS-treated cells. Our data would provide new mechanistic insights into PFOS-induced hepatic insulin resistance. PMID:27363333

  7. Gut microbe-derived extracellular vesicles induce insulin resistance, thereby impairing glucose metabolism in skeletal muscle

    PubMed Central

    Choi, Youngwoo; Kwon, Yonghoon; Kim, Dae-Kyum; Jeon, Jinseong; Jang, Su Chul; Wang, Taejun; Ban, Minjee; Kim, Min-Hye; Jeon, Seong Gyu; Kim, Min-Sun; Choi, Cheol Soo; Jee, Young-Koo; Gho, Yong Song; Ryu, Sung Ho; Kim, Yoon-Keun

    2015-01-01

    Gut microbes might influence host metabolic homeostasis and contribute to the pathogenesis of type 2 diabetes (T2D), which is characterized by insulin resistance. Bacteria-derived extracellular vesicles (EVs) have been suggested to be important in the pathogenesis of diseases once believed to be non-infectious. Here, we hypothesize that gut microbe-derived EVs are important in the pathogenesis of T2D. In vivo administration of stool EVs from high fat diet (HFD)-fed mice induced insulin resistance and glucose intolerance compared to regular diet (RD)-fed mice. Metagenomic profiling of stool EVs by 16S ribosomal DNA sequencing revealed an increased amount of EVs derived from Pseudomonas panacis (phylum Proteobacteria) in HFD mice compared to RD mice. Interestingly, P. panacis EVs blocked the insulin signaling pathway in both skeletal muscle and adipose tissue. Moreover, isolated P. panacis EVs induced typical diabetic phenotypes, such as glucose intolerance after glucose administration or systemic insulin injection. Thus, gut microbe-derived EVs might be key players in the development of insulin resistance and impairment of glucose metabolism promoted by HFD. PMID:26510393

  8. Continuous administration of an elemental diet induces insulin resistance in neonatal pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We previously showed that total parenteral nutrition (TPN) compared to intermittent enteral feeding of a milk-based formula induces insulin resistance and hepatic steatosis in neonatal pigs. We hypothesized that intravenous (IV) feeding rather than the nature of the diet (elemental vs polymeric) or ...

  9. Palmitate induces insulin resistance without significant intracellular triglyceride accumulation in HepG2 cells.

    PubMed

    Lee, Jin-young; Cho, Hyang-Ki; Kwon, Young Hye

    2010-07-01

    Previous studies showed that increased release of free fatty acids from adipocytes leads to insulin resistance and triglyceride (TG) accumulation in the liver, which may progress into hepatic steatohepatitis. We and other investigators have previously reported that palmitate induces endoplasmic reticulum stress-mediated toxicity in several tissues. This work investigated whether palmitate could induce insulin resistance and steatosis in HepG2 cells. We treated cells with either saturated fatty acid (palmitate) or unsaturated fatty acid (oleate), and observed that palmitate significantly activated c-jun N-terminal kinase and inactivated protein kinase B. Both 4-phenylbutyric acid and glycerol significantly activated protein kinase B, confirming the involvement of endoplasmic reticulum stress in palmitate-mediated insulin resistance. Oleate, but not palmitate, significantly induced intracellular TG deposition and activated sterol regulatory element binding protein-1. Instead, diacylglycerol level and protein kinase C epsilon activity were significantly increased by palmitate, suggesting the possible role of diacylglycerol in palmitate-mediated lipotoxicity. Therefore, the present study clearly showed that palmitate impairs insulin resistance, but does not induce significant TG accumulation in HepG2 cells. PMID:20006364

  10. Insulin-induced Drosophila S6 kinase activation requires phosphoinositide 3-kinase and protein kinase B.

    PubMed Central

    Lizcano, Jose M; Alrubaie, Saif; Kieloch, Agnieszka; Deak, Maria; Leevers, Sally J; Alessi, Dario R

    2003-01-01

    An important mechanism by which insulin regulates cell growth and protein synthesis is through activation of the p70 ribosomal S6 protein kinase (S6K). In mammalian cells, insulin-induced PI3K (phosphoinositide 3-kinase) activation, generates the lipid second messenger PtdIns(3,4,5) P (3), which is thought to play a key role in triggering the activation of S6K. Although the major components of the insulin-signalling pathway are conserved in Drosophila, recent studies suggested that S6K activation does not require PI3K in this system. To investigate further the role of dPI3K (Drosophila PI3K) in dS6K (Drosophila S6K) activation, we examined the effect of two structurally distinct PI3K inhibitors on insulin-induced dS6K activation in Kc167 and S2 Drosophila cell lines. We found that both inhibitors prevented insulin-stimulated phosphorylation and activation of dS6K. To investigate further the role of the dPI3K pathway in regulating dS6K activation, we also used dsRNAi (double-stranded RNA-mediated interference) to decrease expression of dPI3K and the PtdIns(3,4,5) P (3) phosphatase dPTEN ( Drosophila phosphatase and tensin homologue deleted on chromosome 10) in Kc167 and S2 cells. Knock-down of dPI3K prevented dS6K activation, whereas knock-down of dPTEN, which would be expected to increase PtdIns(3,4,5) P (3) levels, stimulated dS6K activity. Moreover, when the expression of the dPI3K target, dPKB (Drosophila protein kinase B), was decreased to undetectable levels, we found that insulin could no longer trigger dS6K activation. This observation provides the first direct demonstration that dPKB is required for insulin-stimulated dS6K activation. We also present evidence that the amino-acid-induced activation of dS6K in the absence of insulin, thought to be mediated by dTOR (Drosophila target of rapamycin), which is unaffected by the inhibition of dPI3K by wortmannin. The results of the present study support the view that, in Drosophila cells, dPI3K and dPKB, as well d

  11. Insulin-induced activation of glycerol-3-phosphate acyltransferase by a chiro-inositol-containing insulin mediator is defective in adipocytes of insulin-resistant, type II diabetic, Goto-Kakizaki rats.

    PubMed Central

    Farese, R V; Standaert, M L; Yamada, K; Huang, L C; Zhang, C; Cooper, D R; Wang, Z; Yang, Y; Suzuki, S; Toyota, T

    1994-01-01

    Type II diabetic Goto-Kakizaki (GK) rats were insulin-resistant in euglycemic-hyperinsulinemic clamp studies. We therefore examined insulin signaling systems in control Wistar and diabetic GK rats. Glycerol-3-phosphate acyltransferase (G3PAT), which is activated by headgroup mediators released from glycosyl-phosphatidylinositol (GPI), was activated by insulin in intact and cell-free adipocyte preparations of control, but not diabetic, rats. A specific chiro-inositol-containing inositol phosphoglycan (IPG) mediator, prepared from beef liver, bypassed this defect and comparably activated G3PAT in cell-free adipocyte preparations of both diabetic GK and control rats. A myo-inositol-containing IPG mediator did not activate G3PAT. Relative to control adipocytes, labeling of GPI by [3H]glucosamine was diminished by 50% and insulin failed to stimulate GPI hydrolysis in GK adipocytes. In contrast to GPI-dependent G3PAT activation, insulin-stimulated hexose transport was intact in adipocytes and soleus and gastrocnemius muscles of the GK rat, as was insulin-induced activation of mitogen-activated protein kinase and protein kinase C. We conclude that (i) chiro-inositol-containing IPG mediator activates G3PAT during insulin action, (ii) diabetic GK rats have a defect in synthesizing or releasing functional chiro-inositol-containing IPG, and (iii) defective IPG-regulated intracellular glucose metabolism contributes importantly to insulin resistance in diabetic GK rats. PMID:7972005

  12. Insulin-induced redistribution of GLUT4 glucose carriers in the muscle fiber. In search of GLUT4 trafficking pathways.

    PubMed

    Zorzano, A; Muñoz, P; Camps, M; Mora, C; Testar, X; Palacín, M

    1996-01-01

    Insulin rapidly stimulates glucose transport in muscle fiber. This process controls the utilization of glucose in skeletal muscle, and it is deficient in various insulin-resistant states, such as non-insulin-dependent diabetes mellitus. The effect of insulin on muscle glucose transport is mainly due to the recruitment of GLUT4 glucose carriers to the cell surface of the muscle fiber. There is increasing evidence that the recruitment of GLUT4 carriers triggered by insulin affects selective domains of sarcolemma and transverse tubules. In contrast, GLUT1 is located mainly in sarcolemma and is absent in transverse tubules, and insulin does not alter its cellular distribution in muscle fiber. The differential distribution of GLUT1 and GLUT4 in the cell surface raises new questions regarding the precise endocytic and exocytic pathways that are functional in the muscle fiber. The current view of insulin-induced GLUT4 translocation is based mainly on studies performed in adipocytes. These studies have proposed the existence of intracellular compartments of GLUT4 that respond to insulin in a highly homogeneous manner. However, studies performed in skeletal muscle have identified insulin-sensitive as well as insulin-insensitive intracellular GLUT4-containing membranes. These data open a new perspective on the dynamics of intracellular GLUT4 compartments in insulin-sensitive cells. PMID:8529804

  13. 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

  14. Preadipocyte factor 1 induces pancreatic ductal cell differentiation into insulin-producing cells.

    PubMed

    Rhee, Marie; Lee, Seung-Hwan; Kim, Ji-Won; Ham, Dong-Sik; Park, Heon-Seok; Yang, Hae Kyung; Shin, Ju-Young; Cho, Jae-Hyoung; Kim, Young-Bum; Youn, Byung-Soo; Sul, Hei Sook; Yoon, Kun-Ho

    2016-01-01

    The preadipocyte factor 1 (Pref-1) is involved in the proliferation and differentiation of various precursor cells. However, the intracellular signaling pathways that control these processes and the role of Pref-1 in the pancreas remain poorly understood. Here, we showed that Pref-1 induces insulin synthesis and secretion via two independent pathways. The overexpression of Pref-1 activated MAPK signaling, which induced nucleocytoplasmic translocation of FOXO1 and PDX1 and led to the differentiation of human pancreatic ductal cells into β-like cells and an increase in insulin synthesis. Concurrently, Pref-1 activated Akt signaling and facilitated insulin secretion. A proteomics analysis identified the Rab43 GTPase-activating protein as a downstream target of Akt. A serial activation of both proteins induced various granular protein syntheses which led to enhanced glucose-stimulated insulin secretion. In a pancreatectomised diabetic animal model, exogenous Pref-1 improved glucose homeostasis by accelerating pancreatic ductal and β-cell regeneration after injury. These data establish a novel role for Pref-1, opening the possibility of applying this molecule to the treatment of diabetes. PMID:27044861

  15. ROS-mediated glucose metabolic reprogram induces insulin resistance in type 2 diabetes.

    PubMed

    Dong, Kelei; Ni, Hua; Wu, Meiling; Tang, Ziqing; Halim, Michael; Shi, Dongyun

    2016-08-01

    Oxidative stress is known to contribute to insulin resistance in diabetes, however the mechanism is not clear. Here we show that reactive oxygen species (ROS) could reprogram the glucose metabolism through upregulating the pentose pathway so as to induce insulin resistance in type 2 diabetes (T2DM). By using streptozotocin-high fat diet (STZ-HFD) induced T2DM in rats, we show that diabetic rats exhibited high level of oxidative stress accompanied with insulin resistance. Hypoxia inducible factor (HIF-1α) protein expression as well as its downstream target glucokinase (GK), were upregulated; The glycogen synthesis increased accordingly; However the glycolysis was inhibited as indicated by decreased phosphofructokinase-1 (PFK-1), pyruvate kinase (PK), phospho-PFK-2/PFK-2 (p-PFK-2/PFK-2) ratio, lactate dehydrogenase (LDH) and pyruvate dehydrogenase kinase (PDK); Pyruvate dehydrogenase (PDH) which promotes pyruvate to generate acetyl-CoA declined as well. While phospho-acetyl-CoA carboxylase/acetyl-CoA carboxylase (p-ACC/ACC) ratio increased, meaning that lipid beta-oxidation increased. The pentose pathway was activated as indicated by increased G6PD activity and NADPH level. Our results suggest that diabetic rats countervail ROS stress through increasing pentose pathway, and reprogram the energy metabolic pathway from glycolysis into lipid oxidation in order to compensate the ATP requirement of the body, which causes insulin resistance. PMID:27207834

  16. Preadipocyte factor 1 induces pancreatic ductal cell differentiation into insulin-producing cells

    PubMed Central

    Rhee, Marie; Lee, Seung-Hwan; Kim, Ji-Won; Ham, Dong-Sik; Park, Heon-Seok; Yang, Hae Kyung; Shin, Ju-Young; Cho, Jae-Hyoung; Kim, Young-Bum; Youn, Byung-Soo; Sul, Hei Sook; Yoon, Kun-Ho

    2016-01-01

    The preadipocyte factor 1 (Pref-1) is involved in the proliferation and differentiation of various precursor cells. However, the intracellular signaling pathways that control these processes and the role of Pref-1 in the pancreas remain poorly understood. Here, we showed that Pref-1 induces insulin synthesis and secretion via two independent pathways. The overexpression of Pref-1 activated MAPK signaling, which induced nucleocytoplasmic translocation of FOXO1 and PDX1 and led to the differentiation of human pancreatic ductal cells into β-like cells and an increase in insulin synthesis. Concurrently, Pref-1 activated Akt signaling and facilitated insulin secretion. A proteomics analysis identified the Rab43 GTPase-activating protein as a downstream target of Akt. A serial activation of both proteins induced various granular protein syntheses which led to enhanced glucose-stimulated insulin secretion. In a pancreatectomised diabetic animal model, exogenous Pref-1 improved glucose homeostasis by accelerating pancreatic ductal and β-cell regeneration after injury. These data establish a novel role for Pref-1, opening the possibility of applying this molecule to the treatment of diabetes. PMID:27044861

  17. Skeletal muscle salt inducible kinase 1 promotes insulin resistance in obesity

    PubMed Central

    Nixon, Mark; Stewart-Fitzgibbon, Randi; Fu, Jingqi; Akhmedov, Dmitry; Rajendran, Kavitha; Mendoza-Rodriguez, Maria G.; Rivera-Molina, Yisel A.; Gibson, Micah; Berglund, Eric D.; Justice, Nicholas J.; Berdeaux, Rebecca

    2015-01-01

    Objective Insulin resistance causes type 2 diabetes mellitus and hyperglycemia due to excessive hepatic glucose production and inadequate peripheral glucose uptake. Our objectives were to test the hypothesis that the proposed CREB/CRTC2 inhibitor salt inducible kinase 1 (SIK1) contributes to whole body glucose homeostasis in vivo by regulating hepatic transcription of gluconeogenic genes and also to identify novel SIK1 actions on glucose metabolism. Methods We created conditional (floxed) SIK1-knockout mice and studied glucose metabolism in animals with global, liver, adipose or skeletal muscle Sik1 deletion. We examined cAMP-dependent regulation of SIK1 and the consequences of SIK1 depletion on primary mouse hepatocytes. We probed metabolic phenotypes in tissue-specific SIK1 knockout mice fed high fat diet through hyperinsulinemic-euglycemic clamps and biochemical analysis of insulin signaling. Results SIK1 knockout mice are viable and largely normoglycemic on chow diet. On high fat diet, global SIK1 knockout animals are strikingly protected from glucose intolerance, with both increased plasma insulin and enhanced peripheral insulin sensitivity. Surprisingly, liver SIK1 is not required for regulation of CRTC2 and gluconeogenesis, despite contributions of SIK1 to hepatocyte CRTC2 and gluconeogenesis regulation ex vivo. Sik1 mRNA accumulates in skeletal muscle of obese high fat diet-fed mice, and knockout of SIK1 in skeletal muscle, but not liver or adipose tissue, improves insulin sensitivity and muscle glucose uptake on high fat diet. Conclusions SIK1 is dispensable for glycemic control on chow diet. SIK1 promotes insulin resistance on high fat diet by a cell-autonomous mechanism in skeletal muscle. Our study establishes SIK1 as a promising therapeutic target to improve skeletal muscle insulin sensitivity in obese individuals without deleterious effects on hepatic glucose production. PMID:26844205

  18. 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

  19. Glycogen overload by postexercise insulin administration abolished the exercise-induced increase in GLUT4 protein.

    PubMed

    Chou, Chia-Hau; Tsai, Yin-Lan; Hou, Chien-Wen; Lee, Hsing-Hao; Chang, Wei-Hsiang; Lin, Tzi-Wen; Hsu, Tung-Hsiung; Huang, Yi-Jen; Kuo, Chia-Hua

    2005-12-01

    To elucidate the role of muscle glycogen storage on regulation of GLUT4 protein expression and whole-body glucose tolerance, muscle glycogen level was manipulated by exercise and insulin administration. Sixty Sprague-Dawley rats were evenly separated into three groups: control (CON), immediately after exercise (EX0), and 16 h after exercise (EX16). Rats from each group were further divided into two groups: saline- and insulin-injected. The 2-day exercise protocol consisted of 2 bouts of 3-h swimming with 45-min rest for each day, which effectively depleted glycogen in both red gastrocnemius (RG) and plantaris muscles. EX0 rats were sacrificed immediately after the last bout of exercise on second day. CON and EX16 rats were intubated with 1 g/kg glucose solution following exercise and recovery for 16 h before muscle tissue collection. Insulin (0.5 microU/kg) or saline was injected daily at the time when glucose was intubated. Insulin injection elevated muscle glycogen levels substantially in both muscles above saline-injected group at CON and EX16. With previous day insulin injection, EX0 preserved greater amount of postexercise glycogen above their saline-injected control. In the saline-injected rats, EX16 significantly increased GLUT4 protein level above CON, concurrent with muscle glycogen supercompensation. Insulin injection for EX16 rats significantly enhanced muscle glycogen level above their saline-injected control, but the increases in muscle GLUT4 protein and whole-body glucose tolerance were attenuated. In conclusion, the new finding of the study was that glycogen overload by postexercise insulin administration significantly abolished the exercise-induced increases in GLUT4 protein and glucose tolerance. PMID:16319996

  20. GPR142 Controls Tryptophan-Induced Insulin and Incretin Hormone Secretion to Improve Glucose Metabolism

    PubMed Central

    Efanov, Alexander M.; Fang, Xiankang; Beavers, Lisa S.; Wang, Xuesong; Wang, Jingru; Gonzalez Valcarcel, Isabel C.; Ma, Tianwei

    2016-01-01

    GPR142, a putative amino acid receptor, is expressed in pancreatic islets and the gastrointestinal tract, but the ligand affinity and physiological role of this receptor remain obscure. In this study, we show that in addition to L-Tryptophan, GPR142 signaling is also activated by L-Phenylalanine but not by other naturally occurring amino acids. Furthermore, we show that Tryptophan and a synthetic GPR142 agonist increase insulin and incretin hormones and improve glucose disposal in mice in a GPR142-dependent manner. In contrast, Phenylalanine improves in vivo glucose disposal independently of GPR142. Noteworthy, refeeding-induced elevations in insulin and glucose-dependent insulinotropic polypeptide are blunted in Gpr142 null mice. In conclusion, these findings demonstrate GPR142 is a Tryptophan receptor critically required for insulin and incretin hormone regulation and suggest GPR142 agonists may be effective therapies that leverage amino acid sensing pathways for the treatment of type 2 diabetes. PMID:27322810

  1. Upregulation of myocellular DGAT1 augments triglyceride synthesis in skeletal muscle and protects against fat-induced insulin resistance

    PubMed Central

    Liu, Li; Zhang, Yiying; Chen, Nancy; Shi, Xiaojing; Tsang, Bonny; Yu, Yi-Hao

    2007-01-01

    Increased fat deposition in skeletal muscle is associated with insulin resistance. However, exercise increases both intramyocellular fat stores and insulin sensitivity, a phenomenon referred to as “the athlete’s paradox”. In this study, we provide evidence that augmenting triglyceride synthesis in skeletal muscle is intrinsically connected with increased insulin sensitivity. Exercise increased diacylglycerol (DAG) acyltransferase (DGAT) activity in skeletal muscle. Channeling fatty acid substrates into TG resulted in decreased DAG and ceramide levels. Transgenic overexpression of DGAT1 in mouse skeletal muscle replicated these findings and protected mice against high-fat diet–induced insulin resistance. Moreover, in isolated muscle, DGAT1 deficiency exacerbated insulin resistance caused by fatty acids, whereas DGAT1 overexpression mitigated the detrimental effect of fatty acids. The heightened insulin sensitivity in the transgenic mice was associated with attenuated fat-induced activation of DAG-responsive PKCs and the stress mediator JNK1. Consistent with these changes, serine phosphorylation of insulin receptor substrate 1 was reduced, and Akt activation and glucose 4 membrane translocation were increased. In conclusion, upregulation of DGAT1 in skeletal muscle is sufficient to recreate the athlete’s paradox and illustrates a mechanism of exercise-induced enhancement of muscle insulin sensitivity. Thus, increasing muscle DGAT activity may offer a new approach to prevent and treat insulin resistance and type 2 diabetes mellitus. PMID:17510710

  2. Reversal of tumor-induced biochemical abnormalities by insulin treatment in rats.

    PubMed

    Chance, W T; Muggia-Sullam, M; Chen, M H; Murphy, R F; Fischer, J E

    1986-08-01

    In F344 rats bearing transplantable 3-methylcholanthrene (CAS: 56-49-5)-induced sarcomas, plasma concentrations of immunoreactive insulin were decreased following the development of mild or severe anorexia. Plasma levels of immunoreactive glucagon and lactate were elevated in severely anorectic tumor-bearing (TB) rats, while plasma glucose concentrations remained normal. Both groups of TB rats exhibited decreased plasma levels of serine, glutamine, citrulline, and tryptophan and increased concentrations of alanine. Plasma levels of proline and phenylalanine were also elevated in the severely anorectic TB rats. In a second experiment, 7 daily treatments with insulin corrected the anorexia for 6 days and increased body weights of TB rats. Plasma concentrations of lactate and immunoreactive glucagon were decreased, and the abnormal plasma concentrations of glutamine, proline, analine, and phenylalanine were altered toward normal following the insulin treatments. Therefore, these data are consistent with insulin treatments benefiting the TB host by increasing feeding, increasing body weight, reducing tumor glycolysis and metabolism, reducing gluconeogenesis, and reducing host catabolism, while not stimulating tumor growth. Thus insulin therapy may have potential benefits in cancer treatment by shifting glucose metabolism toward the host and away from the tumor. PMID:3525958

  3. Hormones and Obesity: Changes in Insulin and Growth Hormone Secretion Following Surgically Induced Weight Loss

    PubMed Central

    Crockford, P. M.; Salmon, P. A.

    1970-01-01

    Ten obese patients were subjected to insulin tolerance tests (0.2 unit per kg. regular insulin intravenously) and/or treadmill exercise tolerance testing (2.6 m.p.h. at 11° angulation) before and after surgically induced weight reduction. Immunoreactive growth hormone (IRGH) responses returned to normal with weight reduction in all but one—a grossly obese woman studied relatively early in the postoperative period when still far from the ideal body weight. Five of these patients and two additional subjects had intravenous glucose tolerance tests (0.5 g. per kg.) before and after weight reduction. In all, there was a significant diminution in immunoreactive insulin (IRI) values, accompained by little or no change in the glucose disappearance rate (KG) and a significant improvement in insulin effectiveness as indicated by the calculated “insulinogenic index”. It was concluded that the abnormalities in IRGH and IRI secretion, as well as the insulin resistance in obesity, are probably secondary and not of primary importance in the etiology of this disorder. PMID:5430052

  4. Bezafibrate Improves Insulin Sensitivity and Metabolic Flexibility in STZ-Induced Diabetic Mice.

    PubMed

    Franko, Andras; Huypens, Peter; Neschen, Susanne; Irmler, Martin; Rozman, Jan; Rathkolb, Birgit; Neff, Frauke; Prehn, Cornelia; Dubois, Guillaume; Baumann, Martina; Massinger, Rebecca; Gradinger, Daniel; Przemeck, Gerhard K H; Repp, Birgit; Aichler, Michaela; Feuchtinger, Annette; Schommers, Philipp; Stöhr, Oliver; Sanchez-Lasheras, Carmen; Adamski, Jerzy; Peter, Andreas; Prokisch, Holger; Beckers, Johannes; Walch, Axel K; Fuchs, Helmut; Wolf, Eckhard; Schubert, Markus; Wiesner, Rudolf J; Hrabě de Angelis, Martin

    2016-09-01

    Bezafibrate (BEZ), a pan activator of peroxisome proliferator-activated receptors (PPARs), has been generally used to treat hyperlipidemia for decades. Clinical trials with type 2 diabetes patients indicated that BEZ also has beneficial effects on glucose metabolism, although the underlying mechanisms of these effects remain elusive. Even less is known about a potential role for BEZ in treating type 1 diabetes. Here we show that BEZ markedly improves hyperglycemia and glucose and insulin tolerance in mice with streptozotocin (STZ)-induced diabetes, an insulin-deficient mouse model of type 1 diabetes. BEZ treatment of STZ mice significantly suppressed the hepatic expression of genes that are annotated in inflammatory processes, whereas the expression of PPAR and insulin target gene transcripts was increased. Furthermore, BEZ-treated mice also exhibited improved metabolic flexibility as well as an enhanced mitochondrial mass and function in the liver. Finally, we show that the number of pancreatic islets and the area of insulin-positive cells tended to be higher in BEZ-treated mice. Our data suggest that BEZ may improve impaired glucose metabolism by augmenting hepatic mitochondrial performance, suppressing hepatic inflammatory pathways, and improving insulin sensitivity and metabolic flexibility. Thus, BEZ treatment might also be useful for patients with impaired glucose tolerance or diabetes. PMID:27284107

  5. Insulin Inhibits Low Oxygen-Induced ATP Release from Human Erythrocytes: Implication for Vascular Control

    PubMed Central

    Hanson, Madelyn S.; Ellsworth, Mary L.; Achilleus, David; Stephenson, Alan H.; Bowles, Elizabeth A.; Sridharan, Meera; Adderley, Shaquria; Sprague, Randy S.

    2010-01-01

    Objective ATP released from human erythrocytes in response to reduced oxygen tension (pO2) participates in the matching of oxygen (O2) supply with need in skeletal muscle by stimulating increases in blood flow to areas with increased O2 demand. Here we investigated the hypothesis that hyperinsulinemia inhibits ATP release from erythrocytes and impairs their ability to stimulate dilation of isolated arterioles exposed to decreased extra-luminal pO2. Methods Erythrocyte ATP release was stimulated pharmacologically (mastoparan 7) and physiologically (reduced pO2) in the absence or presence of insulin. We also examined the ability of isolated skeletal muscle arterioles perfused with buffer containing erythrocytes treated with insulin or its vehicle (saline) to dilate in response to decreased extra-luminal pO2. Results Insulin significantly attenuated mastoparan 7– and reduced pO2–induced ATP release. In vessels perfused with untreated erythrocytes, low extra-luminal pO2 resulted in an increase in vessel diameter. In contrast, when erythrocytes were treated with insulin, no vasodilation occurred. Conclusions These studies demonstrate that insulin inhibits ATP release from erythrocytes in response to reduced pO2 and impairs their ability to stimulate dilation of skeletal muscle arterioles. These results suggest that hyperinsulinemia could hinder the matching of O2 supply with need in skeletal muscle. PMID:19412833

  6. Angiotensin-converting enzyme inhibition increases glucose-induced insulin secretion in response to acute restraint.

    PubMed

    Schweizer, Júnia R O L; Miranda, Paulo A C; Fóscolo, Rodrigo B; Lemos, Joao P M; Paula, Luciano F; Silveira, Warley C; Santos, Robson A S; Pinheiro, Sérgio V B; Coimbra, Candido C; Ribeiro-Oliveira, Antônio

    2012-12-01

    There is increasing evidence suggesting involvement of the renin-angiotensin system (RAS) in carbohydrate metabolism and its response to stress. Thus, the aim of the present study was to evaluate the effects of chronic inhibition of the RAS on glucose and insulin levels during acute restraint stress. Male Holtzman rats were treated with 10 mg/kg per day enalapril solution or vehicle for 14 days. After 14 days, rats were divided into three experimental groups: enalapril + restraint (ER), vehicle + restraint (VR) and enalapril + saline (ES). Rats in the restraint groups were subjected to 30 min restraint stress, whereas rats in the ES groups were given saline infusion instead. Blood samples were collected at baseline and after 5, 10, 20 and 30 min restraint stress or saline infusion. After restraint, a hyperglycaemic response was observed in the ER and VR groups that peaked at 20 and 10 min, respectively (P < 0.05 compared with baseline). The area under the glucose curve was markedly increased in the ER and VR groups compared with that in the ES group (P < 0.05 for both). Importantly, restraint induced a marked increase in insulin secretion in the ER group compared with only a mild elevation in the VR group; insulin secretion in both groups peaked at 20 min (P < 0.05 compared with baseline). Analysis of the area under the insulin curve confirmed an increase in insulin secretion in the ER compared with the VR and ES groups (P < 0.05 for both). The results of the present study reinforce that the RAS is involved in modulating responses to stress and suggest that RAS inhibition with enalapril may increase glucose-induced insulin secretion in response to acute restraint. PMID:23734984

  7. Free fatty acid-induced PP2A hyperactivity selectively impairs hepatic insulin action on glucose metabolism.

    PubMed

    Galbo, Thomas; Olsen, Grith Skytte; Quistorff, Bjørn; Nishimura, Erica

    2011-01-01

    In type 2 Diabetes (T2D) free fatty acids (FFAs) in plasma are increased and hepatic insulin resistance is "selective", in the sense that the insulin-mediated decrease of glucose production is blunted while insulin's effect on stimulating lipogenesis is maintained. We investigated the molecular mechanisms underlying this pathogenic paradox. Primary rat hepatocytes were exposed to palmitate for twenty hours. To establish the physiological relevance of the in vitro findings, we also studied insulin-resistant Zucker Diabetic Fatty (ZDF) rats. While insulin-receptor phosphorylation was unaffected, activation of Akt and inactivation of the downstream targets Glycogen synthase kinase 3α (Gsk3α and Forkhead box O1 (FoxO1) was inhibited in palmitate-exposed cells. Accordingly, dose-response curves for insulin-mediated suppression of the FoxO1-induced gluconeogenic genes and for de novo glucose production were right shifted, and insulin-stimulated glucose oxidation and glycogen synthesis were impaired. In contrast, similar to findings in human T2D, the ability of insulin to induce triglyceride (TG) accumulation and transcription of the enzymes that catalyze de novo lipogenesis and TG assembly was unaffected. Insulin-induction of these genes could, however, be blocked by inhibition of the atypical PKCs (aPKCs). The activity of the Akt-inactivating Protein Phosphatase 2A (PP2A) was increased in the insulin-resistant cells. Furthermore, inhibition of PP2A by specific inhibitors increased insulin-stimulated activation of Akt and phosphorylation of FoxO1 and Gsk3α. Finally, PP2A mRNA levels were increased in liver, muscle and adipose tissue, while PP2A activity was increased in liver and muscle tissue in insulin-resistant ZDF rats. In conclusion, our findings indicate that FFAs may cause a selective impairment of insulin action upon hepatic glucose metabolism by increasing PP2A activity. PMID:22087313

  8. Insulin-induced tyrosine dephosphorylation of paxillin and focal adhesion kinase requires active phosphotyrosine phosphatase 1D.

    PubMed Central

    Ouwens, D M; Mikkers, H M; van der Zon, G C; Stein-Gerlach, M; Ullrich, A; Maassen, J A

    1996-01-01

    Insulin stimulation of fibroblasts rapidly induces the tyrosine dephosphorylation of proteins of 68 kDa and 125 kDa, in addition to the tyrosine phosphorylation of the insulin receptor beta-chain, insulin receptor substrates 1 and 2, and Shc. Using specific antibodies, the 68 kDa and 125 kDa proteins were identified as paxillin and focal adhesion kinase (pp125FAK) respectively. We have examined whether dephosphorylation of paxillin and pp125FAK requires interaction of the cells with the extracellular matrix. For this, cells were grown on poly(L-lysine) plates, and the tyrosine phosphorylation of pp125FAK and paxillin was increased by addition of lysophosphatidic acid. Under these conditions, insulin still induced the complete dephosphorylation of pp125FAK and paxillin, indicating that this process can occur independently of the interaction of integrins with extracellular matrix proteins. We also studied whether dephosphorylation of pp125FAK and paxillin results from the action of a phosphotyrosine phosphatase. It was found that phenylarsine oxide, a phosphotyrosine phosphatase inhibitor, prevented the insulin-induced dephosphorylation of pp125FAK and paxillin. Furthermore, this insulin-induced dephosphorylation was also impaired in cells expressing a dominant-negative mutant of phosphotyrosine phosphatase 1D (PTP 1D). Thus we have identified paxillin as a target for dephosphorylation by insulin. In addition, we have obtained evidence that the insulin-mediated dephosphorylation of paxillin and pp125FAK requires active PTP 1D. PMID:8809054

  9. [Differentiation of human amniotic mesenchymal stem cells into insulin-secreting cells induced by regenerating pancreatic extract].

    PubMed

    Zhang, Yanmei; Wang, Dianliang; Zeng, Hongyan; Wang, Lieming; Sun, Jinwei; Zhang, Zhen; Dong, Shasha

    2012-02-01

    In this study, the natural biological inducer, rat regenerating pancreatic extract (RPE), was used to induce human amniotic mesenchymal stem cells (hAMSCs) into insulin-secreting cells. We excised 60% of rat pancreas in order to stimulate pancreatic regeneration. RPE was extracted and used to induce hAMSCs at a final concentration of 20 microg/mL. The experiment methods used were as follows: morphological-identification, dithizone staining, immumofluorescence analysis, reverse transcription-PCR (RT-PCR) and insulin secretion stimulated by high glucose. The results show that the cell morphology of passge3 hAMSCs changed significantly after the induction of RPE, resulting in cluster shape after induction for 15 days. Dithizone staining showed that there were scarlet cell masses in RPE-treated culture. Immumofluorescence analysis indicated that induced cells were insulin-positive expression. RT-PCR showed the positive expression of human islet-related genes Pdx1 and insulin in the induced cells. The result of insulin secretion stimulated by high glucose indicated that insulin increasingly secreted and then kept stable with prolongation of high glucose stimulation. In conclusion, hAMSCs had the potential to differentiate into insulin-secreting cells induced by RPE in vitro. PMID:22667123

  10. Flow induced protein nucleation: Insulin oligomerization under shear.

    NASA Astrophysics Data System (ADS)

    Dexter, Andrew; Azadani, Ali; Sorci, Mirco; Belfort, Georges; Hirsa, Amir

    2007-11-01

    A large number of diseases are associated with protein aggregation and misfolding, such as Alzheimer's, Parkinson's and human prion diseases such as Creutzveld-Jakob disease. Characteristic of these diseases is the presence of amyloid fibrils and their precursors, oligomers and protofibrils. Considerable evidence exists that a shearing flow strongly influences amyloid formation both in vitro and in vivo. Furthermore, the stability of protein-based pharmaceuticals is essential for conventional therapeutic preparations and drug delivery systems. By studying the nucleation and growth of insulin fibrils in a well-defined flow system, we expect to identify the flow conditions that impact protein aggregation kinetics and which lead to protein destabilization. The present flow system consists of an annular region bounded by stationary inner and outer cylinders and is driven by rotation of the floor. Preliminary results indicate that a continuous shearing flow can accelerate the aggregation process. The interfacial shear viscosity was found to drastically increase during aggregation and appears to be a useful parameter to probe protein oligomerization and the effects of flow.

  11. Rescue of Obesity-Induced Infertility in Female Mice due to a Pituitary-Specific Knockout of the Insulin Receptor (IR)

    PubMed Central

    Brothers, Kathryn J.; Wu, Sheng; DiVall, Sara A.; Messmer, Marcus R.; Kahn, C. Ronald; Miller, Ryan S.; Radovick, Sally; Wondisford, Fredric E.; Wolfe, Andrew

    2010-01-01

    Summary Obesity is associated with insulin resistance in metabolic tissues such as adipose, liver, and muscle, but it is unclear whether non-classical target tissues, such as those of the reproductive axis, are also insulin resistant. To determine if the reproductive axis maintains insulin sensitivity in obesity in vivo, murine models of diet-induced obesity with and without intact insulin signaling in pituitary gonadotrophs were created. Diet-induced obese wild type female mice (WT DIO) were infertile and experienced a robust increase in luteinizing hormone (LH) after gonadotropin releasing hormone (GnRH) or insulin stimulation. By contrast, both lean and obese mice with a pituitary-specific knockout of the insulin receptor (PitIRKO) exhibited reproductive competency, indicating that insulin signaling in the pituitary is required for the reproductive impairment seen in diet-induced obesity and that the gonadotroph maintains insulin sensitivity in a setting of peripheral insulin resistance. PMID:20816095

  12. Malignant Drosophila tumors interrupt insulin signaling to induce cachexia-like wasting.

    PubMed

    Figueroa-Clarevega, Alejandra; Bilder, David

    2015-04-01

    Tumors kill patients not only through well-characterized perturbations to their local environment but also through poorly understood pathophysiological interactions with distant tissues. Here, we use a Drosophila tumor model to investigate the elusive mechanisms underlying such long-range interactions. Transplantation of tumors into adults induces robust wasting of adipose, muscle, and gonadal tissues that are distant from the tumor, phenotypes that resemble the cancer cachexia seen in human patients. Notably, malignant, but not benign, tumors induce peripheral wasting. We identify the insulin growth factor binding protein (IGFBP) homolog ImpL2, an antagonist of insulin signaling, as a secreted factor mediating wasting. ImpL2 is sufficient to drive tissue loss, and insulin activity is reduced in peripheral tissues of tumor-bearing hosts. Importantly, knocking down ImpL2, specifically in the tumor, ameliorates wasting phenotypes. We propose that the tumor-secreted IGFBP creates insulin resistance in distant tissues, thus driving a systemic wasting response. PMID:25850672

  13. Antipsychotic-induced insulin resistance and postprandial hormonal dysregulation independent of weight gain or psychiatric disease.

    PubMed

    Teff, Karen L; Rickels, Michael R; Grudziak, Joanna; Fuller, Carissa; Nguyen, Huong-Lan; Rickels, Karl

    2013-09-01

    Atypical antipsychotic (AAP) medications that have revolutionized the treatment of mental illness have become stigmatized by metabolic side effects, including obesity and diabetes. It remains controversial whether the defects are treatment induced or disease related. Although the mechanisms underlying these metabolic defects are not understood, it is assumed that the initiating pathophysiology is weight gain, secondary to centrally mediated increases in appetite. To determine if the AAPs have detrimental metabolic effects independent of weight gain or psychiatric disease, we administered olanzapine, aripiprazole, or placebo for 9 days to healthy subjects (n = 10, each group) under controlled in-patient conditions while maintaining activity levels. Prior to and after the interventions, we conducted a meal challenge and a euglycemic-hyperinsulinemic clamp to evaluate insulin sensitivity and glucose disposal. We found that olanzapine, an AAP highly associated with weight gain, causes significant elevations in postprandial insulin, glucagon-like peptide 1 (GLP-1), and glucagon coincident with insulin resistance compared with placebo. Aripiprazole, an AAP considered metabolically sparing, induces insulin resistance but has no effect on postprandial hormones. Importantly, the metabolic changes occur in the absence of weight gain, increases in food intake and hunger, or psychiatric disease, suggesting that AAPs exert direct effects on tissues independent of mechanisms regulating eating behavior. PMID:23835329

  14. Quantum dots induce charge-specific amyloid-like fibrillation of insulin at physiological conditions

    NASA Astrophysics Data System (ADS)

    Sukhanova, Alyona; Poly, Simon; Shemetov, Anton; Nabiev, Igor R.

    2012-10-01

    Agglomeration of some proteins may give rise to aggregates that have been identified as the main cause of amyloid diseases. For example, fibrillation of insulin is related to diabetes mellitus. Quantum dots (QDs) are of special interest as tagging agents for diagnostic and therapeutic studies due to their broad absorption spectra, narrow emission spectra, and high photostability. In this study, PEGylated CdSe/ZnS QDs have been shown to induce the formation of amyloid-like fibrils of human insulin under physiological conditions, this process being dependent on the variation of the surface charge of the nanoparticles (NPs) used. Circular dichroism (CD), protein secondary structure analysis, thioflavin T (ThT) fluorescence assay, and the dynamic light scattering (DLS) technique have been used for comparative analysis of different stages of the fibrillation process. In particular, insulin secondary structure remodelling accompanied by a considerable increase in the rate of amyloid fiber formation have been observed after insulin was mixed with PEGylated QDs. Nanoparticles may significantly influence the rate of protein fibrillation and induce new mechanisms of amyloid diseases, as well as offer opportunities for their treatment.

  15. Resveratrol prevents high-fructose corn syrup-induced vascular insulin resistance and dysfunction in rats.

    PubMed

    Babacanoglu, C; Yildirim, N; Sadi, G; Pektas, M B; Akar, F

    2013-10-01

    Dietary intake of fructose and sucrose can cause development of metabolic and cardiovascular disorders. The consequences of high-fructose corn syrup (HFCS), a commonly consumed form of fructose and glucose, have poorly been examined. Therefore, in this study, we investigated whether HFCS intake (10% and 20% beverages for 12 weeks) impacts vascular reactivity to insulin and endothelin-1 in conjunction with insulin receptor substrate-1(IRS-1), endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS) mRNA/proteins levels in aorta of rats. At challenge, we tested the effectiveness of resveratrol (28-30 mg/kg body weight/day) on outcomes of HFCS feeding. HFCS (20%) diet feeding increased plasma triglyceride, VLDL, cholesterol, insulin and glucose levels, but not body weights of rats. Impaired nitric oxide-mediated relaxation to insulin (10⁻⁹ to 3×10⁻⁶ M), and enhanced contraction to endothelin-1 (10⁻¹¹ to 10⁻⁸ M) were associated with decreased expression of IRS-1 and eNOS mRNA and protein, but increased expression of iNOS, in aortas of rats fed with HFCS. Resveratrol supplementation restored many features of HFCS-induced disturbances, probably by regulating eNOS and iNOS production. In conclusion, dietary HFCS causes vascular insulin resistance and endothelial dysfunction through attenuating IRS-1 and eNOS expressions as well as increasing iNOS in rats. Resveratrol has capability to recover HFCS-induced disturbances. PMID:23872130

  16. Western-style diet induces insulin insensitivity and hyperactivity in adolescent male rats.

    PubMed

    Marwitz, Shannon E; Woodie, Lauren N; Blythe, Sarah N

    2015-11-01

    The prevalence of obesity in children and adolescents has increased rapidly over the past 30 years, as has the incidence of attention deficit hyperactivity disorder (ADHD). In 2012, it was found that overweight children have a twofold higher chance of developing ADHD than their normal weight counterparts. Previous work has documented learning and memory impairments linked to consumption of an energy-dense diet in rats, but the relationship between diet and ADHD-like behaviors has yet to be explored using animal models. Therefore, the purpose of this study was to explore the role of diet in the etiology of attention and hyperactivity disorders using a rat model of diet-induced obesity. Male Sprague-Dawley rats were fed either a control diet or a Western-style diet (WSD) for ten weeks, and specific physiological and behavioral effects were examined. Tail blood samples were collected to measure fasting blood glucose and insulin levels in order to assess insulin insensitivity. Rats also performed several behavioral tasks, including the open field task, novel object recognition test, and attentional set-shifting task. Rats exposed to a WSD had significantly higher fasting insulin levels than controls, but both groups had similar glucose levels. The quantitative insulin sensitivity check index (QUICKI) indicated the development of insulin resistance in WSD rats. Performance in the open field test indicated that WSD induced pronounced hyperactivity and impulsivity. Further, control diet animals were able to discriminate between old and novel objects, but the WSD animals were significantly impaired in object recognition. However, regardless of dietary condition, rats were able to perform the attentional set-shifting paradigm. While WSD impaired episodic memory and induced hyperactivity, attentional set-shifting capabilities are unaffected. With the increasing prevalence of both obesity and ADHD, understanding the potential links between the two conditions is of clinical

  17. The effect of glucose concentration on insulin-induced 3T3-L1 adipose cell differentiation.

    PubMed

    Gagnon, A; Sorisky, A

    1998-03-01

    We examined the effect of glucose concentration on insulin-induced 3T3-L1 adipose cell differentiation. Oil Red O staining of neutral lipid, cellular triglyceride mass, and glycerol phosphate dehydrogenase (GPDH) activity, were greater in 3T3-L1 cells cultured at 5 mM vs. 25 mM glucose. GPDH activity was 2- to 4-fold higher at 5 mM vs. 25 mM glucose over a range of insulin concentrations (0.1 to 100 nM). Insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) was 1.7-fold greater, and insulin-stimulated phosphoinositide 3-kinase association with IRS-1 was 2.3-fold higher, at 5 mM vs. 25 mM glucose. These effects of glucose were not caused by alterations in IRS-1 mass or cell-surface insulin binding. In preadipose cells at 5 mM glucose, expression of the leukocyte antigen-related (LAR) protein tyrosine phosphatase (negative regulator of insulin signaling) was 63% of the level at 25 mM glucose. Our data demonstrate that glucose concentration affects insulin-induced 3T3-L1 adipose cell differentiation as well as differentiation-directed insulin signaling pathways. Alterations in LAR expression potentially may be involved in modulating these responses. PMID:9545023

  18. TNF-α Involvement in Insulin Resistance Induced by Experimental Scorpion Envenomation

    PubMed Central

    Ait-Lounis, Aouatef; Laraba-Djebari, Fatima

    2012-01-01

    Background Scorpion venom induces systemic inflammation characterized by an increase in cytokine release and chemokine production. There have been few experimental studies assessing the effects of scorpion venom on adipose tissue function in vivo. Methodology/Principal Findings To study the adipose tissue inflammation (ATI) induced by Androctonus australis hector (Aah) venom and to assess possible mechanisms of ATI, mice (n = 6, aged 1 month) were injected with Aah (0.45 mg/kg), toxic fraction of Aah (FTox-G50; 0.2 mg/kg) or saline solution (control). Inflammatory responses were evaluated by ELISA and cell sorting analyses in adipose tissue 45 minutes and 24 hours after injection. Quantitative real-time PCR was used to assess the regulation of genes implicated in glucose uptake. The titers of selected inflammatory cytokines (IL-1β, IL-6 and TNF-α) were also determined in sera and in insulin target tissues. The serum concentration of IL-1β rose 45 minutes after envenomation and returned to basal level after 24 hours. The pathophysiological effects of the venom after 24 hours mainly involved M1-proinflammatory macrophage infiltration in adipose tissue combined with high titers of IL-1β, IL-6 and TNF-α. Indeed, TNF-α was strongly induced in both adipose tissue and skeletal muscle. We studied the effects of Aah venom on genes implicated in insulin-stimulated glucose uptake. Insulin induced a significant increase in the expression of the mRNAs for hexokinase 2 and phosphatidylinositol 3-kinase in both skeletal muscle and adipose tissue in control mice; this upregulation was completely abolished after 24 hours in mice envenomed with Aah or FTox-G50. Conclusions/Significance Our findings suggest that Aah venom induces insulin resistance by mechanisms involving TNF-α-dependent Map4k4 kinase activation in the adipose tissue. PMID:22816003

  19. Polydatin supplementation ameliorates diet-induced development of insulin resistance and hepatic steatosis in rats.

    PubMed

    Zhang, Qi; Tan, Yingying; Zhang, Nan; Yao, Fanrong

    2015-01-01

    The pathophysiology of non-alcoholic fatty liver disease remains to be elucidated, and the currently available treatments are not entirely effective. Polydatin, a stilbenoid compound derived from the rhizome of Polygonum cuspidatum, has previously been demonstrated to possess hepatoprotective effects. The present study aimed to determine the effects of polydatin supplementation on hepatic fat accumulation and injury in rats fed a high-fat diet. In addition, the mechanisms underlying the protective effects of polydatin were examined. Male Sprague Dawley rats were randomly divided into four groups and received one of four treatment regimes for 12 weeks: Control diet, control diet supplemented with polydatin, high-fat diet, or high-fat diet supplemented with polydatin. Polydatin was supplemented in the drinking water at a concentration of 0.3% (wt/vol). The results of the present study showed that long-term high-fat feeding resulted in fatty liver in rats, which was manifested by excessive hepatic neutral fat accumulation and elevated plasma alanine aminotransferase and aspartate aminotransferase levels. Polydatin supplementation alleviated the hepatic pathological changes, and attenuated the insulin resistance, as shown by an improved homeostasis model assessment of basal insulin resistance values and a glucose tolerance test. Polydatin supplementation also corrected abnormal leptin and adiponectin levels. Specifically, polydatin supplementation enhanced insulin sensitivity in the liver, as shown by improved insulin receptor substrate 2 expression levels and Akt phosphorylation in the rat liver, following high-fat diet feeding. The results of the present study suggest that polydatin protects rats against high-fat feeding-induced insulin resistance and hepatic steatosis. Polydatin may be an effective hepatoprotective agent and a potential candidate for the prevention of fatty liver disease and insulin resistance. PMID:25333896

  20. Selective PPARγ modulator INT131 normalizes insulin signaling defects and improves bone mass in diet-induced obese mice

    PubMed Central

    Lee, Dae Ho; Huang, Hu; Choi, Kangduk; Mantzoros, Christos

    2012-01-01

    INT131 is a potent non-thiazolidinedione (TZD)-selective peroxisome proliferator-activated receptor-γ modulator being developed for the treatment of type 2 diabetes. In preclinical studies and a phase II clinical trial, INT131 has been shown to lower glucose levels and ameliorate insulin resistance without typical TZD side effects. To determine whether the insulin-sensitizing action of INT131 is mediated by effects on insulin-mediated glucose homeostasis and insulin signaling, high-fat diet-induced obese (DIO) insulin-resistant mice treated with INT131 were studied. INT131's effects on bone density were also investigated. Treatment with INT131 enhanced systemic insulin sensitivity, as revealed by lower insulin levels in the fasted state and an increase in the area above the curve during an insulin tolerance test. These effects were independent of changes in adiposity. Insulin-stimulated PI3K activity in skeletal muscle and adipose tissue of DIO mice was significantly reduced ∼50–65%, but this was restored completely by INT131 therapy. The INT131 effects on PI3K activity are most likely due to increased IRS-1 tyrosine phosphorylation. Concurrently, insulin-mediated Akt phosphorylation also increased after INT131 treatment in DIO mice. Importantly, INT131 therapy caused a significant increase in bone mineral density without alteration in circulating osteocalcin in these mice. These data suggest that a newly developed insulin-sensitizing agent, INT131, normalizes obesity-related defects in insulin action on PI3K signaling in insulin target tissues by a mechanism involved in glycemic control. If these data are confirmed in humans, INT131 could be used for treating type 2 diabetes without loss in bone mass. PMID:22215652

  1. Skeletal Muscle TRIB3 Mediates Glucose Toxicity in Diabetes and High- Fat Diet-Induced Insulin Resistance.

    PubMed

    Zhang, Wei; Wu, Mengrui; Kim, Teayoun; Jariwala, Ravi H; Garvey, W John; Luo, Nanlan; Kang, Minsung; Ma, Elizabeth; Tian, Ling; Steverson, Dennis; Yang, Qinglin; Fu, Yuchang; Garvey, W Timothy

    2016-08-01

    In the current study, we used muscle-specific TRIB3 overexpressing (MOE) and knockout (MKO) mice to determine whether TRIB3 mediates glucose-induced insulin resistance in diabetes and whether alterations in TRIB3 expression as a function of nutrient availability have a regulatory role in metabolism. In streptozotocin diabetic mice, TRIB3 MOE exacerbated, whereas MKO prevented, glucose-induced insulin resistance and impaired glucose oxidation and defects in insulin signal transduction compared with wild-type (WT) mice, indicating that glucose-induced insulin resistance was dependent on TRIB3. In response to a high-fat diet, TRIB3 MOE mice exhibited greater weight gain and worse insulin resistance in vivo compared with WT mice, coupled with decreased AKT phosphorylation, increased inflammation and oxidative stress, and upregulation of lipid metabolic genes coupled with downregulation of glucose metabolic genes in skeletal muscle. These effects were prevented in the TRIB3 MKO mice relative to WT mice. In conclusion, TRIB3 has a pathophysiological role in diabetes and a physiological role in metabolism. Glucose-induced insulin resistance and insulin resistance due to diet-induced obesity both depend on muscle TRIB3. Under physiological conditions, muscle TRIB3 also influences energy expenditure and substrate metabolism, indicating that the decrease and increase in muscle TRIB3 under fasting and nutrient excess, respectively, are critical for metabolic homeostasis. PMID:27207527

  2. Integrin-Linked Kinase in Muscle Is Necessary for the Development of Insulin Resistance in Diet-Induced Obese Mice.

    PubMed

    Kang, Li; Mokshagundam, Shilpa; Reuter, Bradley; Lark, Daniel S; Sneddon, Claire C; Hennayake, Chandani; Williams, Ashley S; Bracy, Deanna P; James, Freyja D; Pozzi, Ambra; Zent, Roy; Wasserman, David H

    2016-06-01

    Diet-induced muscle insulin resistance is associated with expansion of extracellular matrix (ECM) components, such as collagens, and the expression of collagen-binding integrin, α2β1. Integrins transduce signals from ECM via their cytoplasmic domains, which bind to intracellular integrin-binding proteins. The integrin-linked kinase (ILK)-PINCH-parvin (IPP) complex interacts with the cytoplasmic domain of β-integrin subunits and is critical for integrin signaling. In this study we defined the role of ILK, a key component of the IPP complex, in diet-induced muscle insulin resistance. Wild-type (ILK(lox/lox)) and muscle-specific ILK-deficient (ILK(lox/lox)HSAcre) mice were fed chow or a high-fat (HF) diet for 16 weeks. Body weight was not different between ILK(lox/lox) and ILK(lox/lox)HSAcre mice. However, HF-fed ILK(lox/lox)HSAcre mice had improved muscle insulin sensitivity relative to HF-fed ILK(lox/lox) mice, as shown by increased rates of glucose infusion, glucose disappearance, and muscle glucose uptake during a hyperinsulinemic-euglycemic clamp. Improved muscle insulin action in the HF-fed ILK(lox/lox)HSAcre mice was associated with increased insulin-stimulated phosphorylation of Akt and increased muscle capillarization. These results suggest that ILK expression in muscle is a critical component of diet-induced insulin resistance, which possibly acts by impairing insulin signaling and insulin perfusion through capillaries. PMID:27207548

  3. Probiotic supplementation prevents high-fat, overfeeding-induced insulin resistance in human subjects.

    PubMed

    Hulston, Carl J; Churnside, Amelia A; Venables, Michelle C

    2015-02-28

    The purpose of the present study was to determine whether probiotic supplementation (Lactobacillus casei Shirota (LcS)) prevents diet-induced insulin resistance in human subjects. A total of seventeen healthy subjects were randomised to either a probiotic (n 8) or a control (n 9) group. The probiotic group consumed a LcS-fermented milk drink twice daily for 4 weeks, whereas the control group received no supplementation. Subjects maintained their normal diet for the first 3 weeks of the study, after which they consumed a high-fat (65 % of energy), high-energy (50 % increase in energy intake) diet for 7 d. Whole-body insulin sensitivity was assessed by an oral glucose tolerance test conducted before and after overfeeding. Body mass increased by 0·6 (SE 0·2) kg in the control group (P< 0·05) and by 0·3 (SE 0·2) kg in the probiotic group (P>0·05). Fasting plasma glucose concentrations increased following 7 d of overeating (control group: 5·3 (SE 0·1) v. 5·6 (SE 0·2) mmol/l before and after overfeeding, respectively, P< 0·05), whereas fasting serum insulin concentrations were maintained in both groups. Glucose AUC values increased by 10 % (from 817 (SE 45) to 899 (SE 39) mmol/l per 120 min, P< 0·05) and whole-body insulin sensitivity decreased by 27 % (from 5·3 (SE 1·4) to 3·9 (SE 0·9), P< 0·05) in the control group, whereas normal insulin sensitivity was maintained in the probiotic group (4·4 (SE 0·8) and 4·5 (SE 0·9) before and after overeating, respectively (P>0·05). These results suggest that probiotic supplementation may be useful in the prevention of diet-induced metabolic diseases such as type 2 diabetes. PMID:25630516

  4. Probiotic supplementation prevents high-fat, overfeeding-induced, insulin resistance in humans

    PubMed Central

    Hulston, Carl J.; Churnside, Amelia A.; Venables, Michelle C.

    2015-01-01

    The purpose of this study was to determine whether probiotic supplementation (Lactobacillus casei Shirota [LcS]) prevents diet-induced insulin resistance in humans. Seventeen healthy individuals were randomised to probiotic (n = 8) or control (n = 9) groups. The probiotic group consumed an LcS-fermented milk drink twice daily for 4 weeks whereas the control group received no supplementation. Subjects maintained their normal diet for the first 3 weeks of the study, after which they consumed a high-fat (65% energy) high-energy (+50% kcal) diet for 7 days. Whole body insulin sensitivity was assessed via an oral glucose tolerance test conducted before and after overfeeding. Body mass increased by 0.6 ± 0.2 kg in the control group (p < 0.05) and 0.3 ± 0.2 kg in the probiotic group (p > 0.05). Fasting plasma glucose concentrations increased following 7 days of overeating (control group only; 5.3 ± 0.1 vs. 5.6 ± 0.2 mmol/L, p < 0.05) whereas fasting serum insulin concentrations were maintained in both groups. Glucose AUC increased by 10% (from 817 ± 45 to 899 ± 39 mmol/L/120 min, p < 0.05) and whole body insulin sensitivity decreased by 27% (from 5.3 ± 1.4 to 3.9 ± 0.9, p < 0.05) in the control group, whereas normal insulin sensitivity was maintained in the probiotic group (4.4 ± 0.8 and 4.5 ± 0.9 before and after overeating, respectively, p > 0.05). These results suggest that probiotic supplementation may be useful in the prevention of diet-induced metabolic diseases such as type II diabetes. PMID:25630516

  5. Association of Bactericidal Dysfunction of Paneth Cells in Streptozocin-Induced Diabetic Mice with Insulin Deficiency.

    PubMed

    Yu, Tao; Yang, Hong-Sheng; Lu, Xi-Ji; Xia, Zhong-Sheng; Ouyang, Hui; Shan, Ti-Dong; Huang, Can-Ze; Chen, Qi-Kui

    2016-01-01

    BACKGROUND Type 1 diabetes mellitus (T1DM) is associated with increased risks of enteric infection. Paneth cells constitute the first line of the gut defense. Little is known about the impact of T1DM on the bactericidal function of intestinal Paneth cells. MATERIAL AND METHODS A T1DM mouse model was induced by intraperitoneal injection of streptozocin. The analysis of intestinal microbiota and the mucosal bactericidal assay were conducted to evaluate intestinal innate defense. Numbers of Paneth cells and their expression of related antimicrobial peptides were analyzed. Expression of total insulin receptor (IR) mRNA and relative levels of IR-A/IR-B were analyzed. The primary mouse small intestinal crypt culture was used to analyze the effect of insulin and glucose on the expression of related antimicrobial peptides of Paneth cells. RESULTS In T1DM mice, bacterial loads were increased and there was an alteration in the composition of the intestinal microflora. Exogenous bacteria had better survival in the small bowel of the T1DM mice. The expression of Paneth cell-derived antimicrobial peptides was significantly decreased in the T1DM mice, although the number of Paneth cells was increased. Relative levels of IR-A/IR-B in Paneth cells of diabetic mice were elevated, but the total IR mRNA did not change. Insulin treatment restored the expression of antimicrobial peptides and normalized the microbiota in the gut of T1DM mice. Subsequently, in vitro culture assay demonstrated that insulin rather than glucose was essential for the optimal expression of Paneth cell-derived antimicrobial peptides. CONCLUSIONS The bactericidal function of intestinal Paneth cells was impaired in STZ-induced diabetic mice, resulting in the altered intestinal flora, and insulin was essential for the optimal expression of Paneth cell-derived antimicrobial peptides. PMID:27572949

  6. Insulin and insulin-like growth factor-1 induce pronounced hypertrophy of skeletal myofibers in tissue culture

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.; Karlisch, Patricia; Shansky, Janet

    1990-01-01

    Skeletal myofibers differentiated from primary avian myoblasts in tissue culture can be maintained in positive nitrogen balance in a serum-free medium for at least 6 to 7 days when embedded in a three dimensional collagen gel matrix. The myofibers are metabolically sensitive to physiological concentrations of insulin but these concentrations do not stimulate cell growth. Higher insulin concentrations stimulate both cell hyperplasia and myofiber hypertrophy. Cell growth results from a long term 42 percent increase in total protein synthesis and a 38 percent increase in protein degradation. Myofiber diameters increase by 71 to 98 percent after 6 to 7 days in insulin-containing medium. Insulin-like growth factor-1 but not insulin-like growth factor-2, at 250 ng/ml, is as effective as insulin in stimulating cell hyperplasia and myofiber hypertrophy. This model system provides a new method for studying the long-term anabolic effects of insulin and insulin-like growth factors on myofiber hypertrophy under defined tissue culture conditions.

  7. Regulation of insulin sensitivity, insulin production, and pancreatic β cell survival by angiotensin-(1-7) in a rat model of streptozotocin-induced diabetes mellitus.

    PubMed

    He, Junhua; Yang, Zhiming; Yang, Huiyu; Wang, Li; Wu, Huilu; Fan, Yunjuan; Wang, Wei; Fan, Xin; Li, Xing

    2015-02-01

    The aim of this study is to determine the antidiabetic activity of Ang-(1-7), an important component of the renin-angiotensin system, in a rat model of streptozotocin (STZ)-induced type 2 diabetes mellitus (DM). A total of 36 male Wistar rats were randomly divided into 3 groups: control group fed standard laboratory diet, DM group fed high-fat diet and injected with STZ, and Ang-(1-7) group receiving injection of STZ followed by Ang-(1-7) treatment. Body weight, blood glucose levels, fasting serum Ang II and insulin levels, and homeostasis model assessment of insulin resistance (HOMA-IR) were measured. The pancreas was collected for histological examination and gene expression analysis. Notably, the Ang-(1-7) group showed a significant decrease in fasting blood glucose and serum Ang II levels and HOMA-IR values and increase in fasting serum insulin levels. Pancreatic β cells in the control and Ang-(1-7) groups were normally distributed in the center of pancreatic islets with large clear nuclei. In contrast, pancreatic β cells in the DM group had a marked shrinkage of the cytoplasm and condensation of nuclear chromatin. Ang-(1-7) treatment significantly facilitated insulin production by β cells in diabetic rats. The DM-associated elevation of inducible nitric oxide synthase (iNOS), caspase-3, caspase-9, caspase-8, and Bax and reduction of Bcl-2 was significantly reversed by Ang-(1-7) treatment. Taken together, Ang-(1-7) protects against STZ-induced DM through improvement of insulin resistance, insulin secretion, and pancreatic β cell survival, which is associated with reduction of iNOS expression and alteration of the Bcl-2 family. PMID:25576844

  8. Lifestyle-induced metabolic inflexibility and accelerated ageing syndrome: insulin resistance, friend or foe?

    PubMed Central

    Nunn, Alistair VW; Bell, Jimmy D; Guy, Geoffrey W

    2009-01-01

    The metabolic syndrome may have its origins in thriftiness, insulin resistance and one of the most ancient of all signalling systems, redox. Thriftiness results from an evolutionarily-driven propensity to minimise energy expenditure. This has to be balanced with the need to resist the oxidative stress from cellular signalling and pathogen resistance, giving rise to something we call 'redox-thriftiness'. This is based on the notion that mitochondria may be able to both amplify membrane-derived redox growth signals as well as negatively regulate them, resulting in an increased ATP/ROS ratio. We suggest that 'redox-thriftiness' leads to insulin resistance, which has the effect of both protecting the individual cell from excessive growth/inflammatory stress, while ensuring energy is channelled to the brain, the immune system, and for storage. We also suggest that fine tuning of redox-thriftiness is achieved by hormetic (mild stress) signals that stimulate mitochondrial biogenesis and resistance to oxidative stress, which improves metabolic flexibility. However, in a non-hormetic environment with excessive calories, the protective nature of this system may lead to escalating insulin resistance and rising oxidative stress due to metabolic inflexibility and mitochondrial overload. Thus, the mitochondrially-associated resistance to oxidative stress (and metabolic flexibility) may determine insulin resistance. Genetically and environmentally determined mitochondrial function may define a 'tipping point' where protective insulin resistance tips over to inflammatory insulin resistance. Many hormetic factors may induce mild mitochondrial stress and biogenesis, including exercise, fasting, temperature extremes, unsaturated fats, polyphenols, alcohol, and even metformin and statins. Without hormesis, a proposed redox-thriftiness tipping point might lead to a feed forward insulin resistance cycle in the presence of excess calories. We therefore suggest that as oxidative stress

  9. High-fat diet induces hepatic insulin resistance and impairment of synaptic plasticity.

    PubMed

    Liu, Zhigang; Patil, Ishan Y; Jiang, Tianyi; Sancheti, Harsh; Walsh, John P; Stiles, Bangyan L; Yin, Fei; Cadenas, Enrique

    2015-01-01

    High-fat diet (HFD)-induced obesity is associated with insulin resistance, which may affect brain synaptic plasticity through impairment of insulin-sensitive processes underlying neuronal survival, learning, and memory. The experimental model consisted of 3 month-old C57BL/6J mice fed either a normal chow diet (control group) or a HFD (60% of calorie from fat; HFD group) for 12 weeks. This model was characterized as a function of time in terms of body weight, fasting blood glucose and insulin levels, HOMA-IR values, and plasma triglycerides. IRS-1/Akt pathway was assessed in primary hepatocytes and brain homogenates. The effect of HFD in brain was assessed by electrophysiology, input/output responses and long-term potentiation. HFD-fed mice exhibited a significant increase in body weight, higher fasting glucose- and insulin levels in plasma, lower glucose tolerance, and higher HOMA-IR values. In liver, HFD elicited (a) a significant decrease of insulin receptor substrate (IRS-1) phosphorylation on Tyr608 and increase of Ser307 phosphorylation, indicative of IRS-1 inactivation; (b) these changes were accompanied by inflammatory responses in terms of increases in the expression of NFκB and iNOS and activation of the MAP kinases p38 and JNK; (c) primary hepatocytes from mice fed a HFD showed decreased cellular oxygen consumption rates (indicative of mitochondrial functional impairment); this can be ascribed partly to a decreased expression of PGC1α and mitochondrial biogenesis. In brain, HFD feeding elicited (a) an inactivation of the IRS-1 and, consequentially, (b) a decreased expression and plasma membrane localization of the insulin-sensitive neuronal glucose transporters GLUT3/GLUT4; (c) a suppression of the ERK/CREB pathway, and (d) a substantial decrease in long-term potentiation in the CA1 region of hippocampus (indicative of impaired synaptic plasticity). It may be surmised that 12 weeks fed with HFD induce a systemic insulin resistance that impacts

  10. Urtica dioica modulates hippocampal insulin signaling and recognition memory deficit in streptozotocin induced diabetic mice.

    PubMed

    Patel, Sita Sharan; Gupta, Sahil; Udayabanu, Malairaman

    2016-06-01

    Diabetes mellitus has been associated with functional abnormalities in the hippocampus and performance of cognitive function. Urtica dioica (UD) has been used in the treatment of diabetes. In our previous report we observed that UD extract attenuate diabetes mediated associative and spatial memory dysfunction. The present study aimed to evaluate the effect of UD extract on mouse model of diabetes-induced recognition memory deficit and explore the possible mechanism behind it. Streptozotocin (STZ) (50 mg/kg, i.p. consecutively for 5 days) was used to induce diabetes followed by UD extract (50 mg/kg, oral) or rosiglitazone (ROSI) (5 mg/kg, oral) administration for 8 weeks. STZ induced diabetic mice showed significant decrease in hippocampal insulin signaling and translocation of glucose transporter type 4 (GLUT4) to neuronal membrane resulting in cognitive dysfunction and hypolocomotion. UD treatment effectively improved hippocampal insulin signaling, glucose tolerance and recognition memory performance in diabetic mice, which was comparable to ROSI. Further, diabetes mediated oxidative stress and inflammation was reversed by chronic UD or ROSI administration. UD leaves extract acts via insulin signaling pathway and might prove to be effective for the diabetes mediated central nervous system complications. PMID:26767366

  11. ATF7 ablation prevents diet-induced obesity and insulin resistance.

    PubMed

    Liu, Yang; Maekawa, Toshio; Yoshida, Keisuke; Furuse, Tamio; Kaneda, Hideki; Wakana, Shigeharu; Ishii, Shunsuke

    2016-09-16

    The activating transcription factor (ATF)2 family of transcription factors regulates a variety of metabolic processes, including adipogenesis and adaptive thermogenesis. ATF7 is a member of the ATF2 family, and mediates epigenetic changes induced by environmental stresses, such as social isolation and pathogen infection. However, the metabolic role of ATF7 remains unknown. The aim of the present study is to examine the role of ATF7 in metabolism using ATF7-dificeint mice. Atf7(-/-) mice exhibited lower body weight and resisted diet-induced obesity. Serum triglycerides, resistin, and adipose tissue mass were all significantly lower in ATF7-deficient mice. Fasting glucose levels and glucose tolerance were unaltered, but systemic insulin sensitivity was increased, by ablation of ATF7. Indirect calorimetry revealed that oxygen consumption by Atf7(-/-) mice was comparable to that of wild-type littermates on a standard chow diet, but increased energy expenditure was observed in Atf7(-/-) mice on a high-fat diet. Hence, ATF7 ablation may impair the development and function of adipose tissue and result in elevated energy expenditure in response to high-fat-feeding obesity and insulin resistance, indicating that ATF7 is a potential therapeutic target for diet-induced obesity and insulin resistance. PMID:27498002

  12. Decreased pituitary response to insulin-induced hypoglycaemia in young lean male patients with essential hypertension.

    PubMed

    Radikova, Z; Penesova, A; Cizmarova, E; Huckova, M; Kvetnansky, R; Vigas, M; Koska, J

    2006-07-01

    Essential hypertension is associated with changes in central catecholaminergic pathways which might also be reflected in the pituitary response to stress stimuli. The aim of this study was to determine whether the response of pituitary hormones, cortisol, plasma renin activity, aldosterone and catecholamines to insulin-induced hypoglycaemia is changed in hypertension. We studied 22 young lean male patients with newly diagnosed untreated essential hypertension and 19 healthy normotensive, age- and body mass index (BMI)-matched controls. All subjects underwent an insulin tolerance test (0.1 IU insulin/kg body weight intravenously) with blood sampling before and 15, 30, 45, 60 and 90 min after insulin administration. Increased baseline levels of norepinephrine (P<0.05), increased response of norepinephrine (P<0.001) and decreased response of growth hormone (P<0.001), prolactin (P<0.001), adrenocorticotropic hormone (P<0.05) and cortisol (P<0.001) were found in hypertensive patients when compared to normotensive controls. Increased norepinephrine levels and a decreased pituitary response to metabolic stress stimuli may represent another manifestation of chronically increased sympathetic tone in early hypertension. PMID:16617309

  13. Transgenic overexpression of VEGF-C induces weight gain and insulin resistance in mice.

    PubMed

    Karaman, Sinem; Hollmén, Maija; Yoon, Sun-Young; Alkan, H Furkan; Alitalo, Kari; Wolfrum, Christian; Detmar, Michael

    2016-01-01

    Obesity comprises great risks for human health, contributing to the development of other diseases such as metabolic syndrome, type 2 diabetes and cardiovascular disease. Previously, obese patients were found to have elevated serum levels of VEGF-C, which correlated with worsening of lipid parameters. We recently identified that neutralization of VEGF-C and -D in the subcutaneous adipose tissue during the development of obesity improves metabolic parameters and insulin sensitivity in mice. To test the hypothesis that VEGF-C plays a role in the promotion of the metabolic disease, we used K14-VEGF-C mice that overexpress human VEGF-C under control of the keratin-14 promoter in the skin and monitored metabolic parameters over time. K14-VEGF-C mice had high levels of VEGF-C in the subcutaneous adipose tissue and gained more weight than wildtype littermates, became insulin resistant and had increased ectopic lipid accumulation at 20 weeks of age on regular mouse chow. The metabolic differences persisted under high-fat diet induced obesity. These results indicate that elevated VEGF-C levels contribute to metabolic deterioration and the development of insulin resistance, and that blockade of VEGF-C in obesity represents a suitable approach to alleviate the development of insulin resistance. PMID:27511834

  14. Transgenic overexpression of VEGF-C induces weight gain and insulin resistance in mice

    PubMed Central

    Karaman, Sinem; Hollmén, Maija; Yoon, Sun-Young; Alkan, H. Furkan; Alitalo, Kari; Wolfrum, Christian; Detmar, Michael

    2016-01-01

    Obesity comprises great risks for human health, contributing to the development of other diseases such as metabolic syndrome, type 2 diabetes and cardiovascular disease. Previously, obese patients were found to have elevated serum levels of VEGF-C, which correlated with worsening of lipid parameters. We recently identified that neutralization of VEGF-C and -D in the subcutaneous adipose tissue during the development of obesity improves metabolic parameters and insulin sensitivity in mice. To test the hypothesis that VEGF-C plays a role in the promotion of the metabolic disease, we used K14-VEGF-C mice that overexpress human VEGF-C under control of the keratin-14 promoter in the skin and monitored metabolic parameters over time. K14-VEGF-C mice had high levels of VEGF-C in the subcutaneous adipose tissue and gained more weight than wildtype littermates, became insulin resistant and had increased ectopic lipid accumulation at 20 weeks of age on regular mouse chow. The metabolic differences persisted under high-fat diet induced obesity. These results indicate that elevated VEGF-C levels contribute to metabolic deterioration and the development of insulin resistance, and that blockade of VEGF-C in obesity represents a suitable approach to alleviate the development of insulin resistance. PMID:27511834

  15. Canavanine induces insulin release via activation of imidazoline I3 receptors.

    PubMed

    Yang, Ting-Ting; Niu, Ho-Shan; Chen, Li-Jen; Ku, Po-Ming; Lin, Kao-Chang; Cheng, Juei-Tang

    2015-03-01

    The aim of the present study was to identify the effect of canavanine on the imidazoline receptor because canavanine is a guanidinium derivative that has a similar structure to imidazoline receptor ligands. Transfected Chinese hamster ovary-K1 cells expressing imidazoline receptors (nischarin (NISCH)-CHO-K1 cells) were used to elucidate the direct effects of canavanine on imidazoline receptors. In addition, the imidazoline I3 receptor has been implicated in stimulation of insulin secretion from pancreatic β-cells. Wistar rats were used to investigate the effects of canavanine (0.1, 1 and 2.5 mg/kg, i.v.) on insulin secretion. In addition the a specific I3 receptor antagonist KU14R (4 or 8 mg/kg, i.v.) was used to block I3 receptors. Canavanine decreased blood glucose by increasing plasma insulin in rats. In addition, canavanine increased calcium influx into NISCH-CHO-K1 cells in a manner similar to agmatine, the endogenous ligand of imidazoline receptors. Moreover, KU12R dose-dependently attenuated canavanine-induced insulin secretion in HIT-T15 pancreatic β-cells and in the plasma of rats. The data suggest that canavanine is an agonist of I3 receptors both in vivo and in vitro. Thus, canavanine would be a useful tool in imidazoline receptor research. PMID:25482045

  16. Lactobacillus rhamnosus GG Reverses Insulin Resistance but Does Not Block Its Onset in Diet-Induced Obese Mice.

    PubMed

    Park, Kun-Young; Kim, Bobae; Hyun, Chang-Kee

    2015-05-01

    Recently, Lactobacillus rhamnosus GG (LGG) was shown to exert insulin-sensitizing and adiposity-reducing effects in high-fat (HF) diet-fed mice. In the present study, we observed that the effects were correlated with the extent of dysbiosis induced by HF diet feeding before LGG administration. LGG-treated mice were protected from HF diet-induced adiposity and/ or insulin resistance when LGG was treated after, not along with, HF diet feeding. Results indicate that, under HF dietary condition, supplemented LGG reverses insulin resistance, but does not block its onset. PMID:25433553

  17. Site-specific covalent modifications of human insulin by catechol estrogens: Reactivity and induced structural and functional changes

    PubMed Central

    Ku, Ming-Chun; Fang, Chieh-Ming; Cheng, Juei-Tang; Liang, Huei-Chen; Wang, Tzu-Fan; Wu, Chih-Hsing; Chen, Chiao-Chen; Tai, Jung-Hsiang; Chen, Shu-Hui

    2016-01-01

    Proteins, covalently modified by catechol estrogens (CEs), were identified recently from the blood serum of diabetic patients and referred to as estrogenized proteins. Estrogenization of circulating insulin may occur and affect its molecular functioning. Here, the chemical reactivity of CEs towards specific amino acid residues of proteins and the structural and functional changes induced by the estrogenization of insulin were studied using cyclic voltammetry, liquid chromatography-mass spectrometry, circular dichroism spectroscopy, molecular modeling, and bioassays. Our results indicate that CEs, namely, 2- and 4-hydroxyl estrogens, were thermodynamically and kinetically more reactive than the catechol moiety. Upon co-incubation, intact insulin formed a substantial number of adducts with one or multiple CEs via covalent conjugation at its Cys 7 in the A or B chain, as well as at His10 or Lys29 in the B chain. Such conjugation was coupled with the cleavage of inter-chain disulfide linkages. Estrogenization on these sites may block the receptor-binding pockets of insulin. Insulin signaling and glucose uptake levels were lower in MCF-7 cells treated with modified insulin than in cells treated with native insulin. Taken together, our findings demonstrate that insulin molecules are susceptible to active estrogenization, and that such modification may alter the action of insulin. PMID:27353345

  18. Site-specific covalent modifications of human insulin by catechol estrogens: Reactivity and induced structural and functional changes

    NASA Astrophysics Data System (ADS)

    Ku, Ming-Chun; Fang, Chieh-Ming; Cheng, Juei-Tang; Liang, Huei-Chen; Wang, Tzu-Fan; Wu, Chih-Hsing; Chen, Chiao-Chen; Tai, Jung-Hsiang; Chen, Shu-Hui

    2016-06-01

    Proteins, covalently modified by catechol estrogens (CEs), were identified recently from the blood serum of diabetic patients and referred to as estrogenized proteins. Estrogenization of circulating insulin may occur and affect its molecular functioning. Here, the chemical reactivity of CEs towards specific amino acid residues of proteins and the structural and functional changes induced by the estrogenization of insulin were studied using cyclic voltammetry, liquid chromatography-mass spectrometry, circular dichroism spectroscopy, molecular modeling, and bioassays. Our results indicate that CEs, namely, 2- and 4-hydroxyl estrogens, were thermodynamically and kinetically more reactive than the catechol moiety. Upon co-incubation, intact insulin formed a substantial number of adducts with one or multiple CEs via covalent conjugation at its Cys 7 in the A or B chain, as well as at His10 or Lys29 in the B chain. Such conjugation was coupled with the cleavage of inter-chain disulfide linkages. Estrogenization on these sites may block the receptor-binding pockets of insulin. Insulin signaling and glucose uptake levels were lower in MCF-7 cells treated with modified insulin than in cells treated with native insulin. Taken together, our findings demonstrate that insulin molecules are susceptible to active estrogenization, and that such modification may alter the action of insulin.

  19. Site-specific covalent modifications of human insulin by catechol estrogens: Reactivity and induced structural and functional changes.

    PubMed

    Ku, Ming-Chun; Fang, Chieh-Ming; Cheng, Juei-Tang; Liang, Huei-Chen; Wang, Tzu-Fan; Wu, Chih-Hsing; Chen, Chiao-Chen; Tai, Jung-Hsiang; Chen, Shu-Hui

    2016-01-01

    Proteins, covalently modified by catechol estrogens (CEs), were identified recently from the blood serum of diabetic patients and referred to as estrogenized proteins. Estrogenization of circulating insulin may occur and affect its molecular functioning. Here, the chemical reactivity of CEs towards specific amino acid residues of proteins and the structural and functional changes induced by the estrogenization of insulin were studied using cyclic voltammetry, liquid chromatography-mass spectrometry, circular dichroism spectroscopy, molecular modeling, and bioassays. Our results indicate that CEs, namely, 2- and 4-hydroxyl estrogens, were thermodynamically and kinetically more reactive than the catechol moiety. Upon co-incubation, intact insulin formed a substantial number of adducts with one or multiple CEs via covalent conjugation at its Cys 7 in the A or B chain, as well as at His10 or Lys29 in the B chain. Such conjugation was coupled with the cleavage of inter-chain disulfide linkages. Estrogenization on these sites may block the receptor-binding pockets of insulin. Insulin signaling and glucose uptake levels were lower in MCF-7 cells treated with modified insulin than in cells treated with native insulin. Taken together, our findings demonstrate that insulin molecules are susceptible to active estrogenization, and that such modification may alter the action of insulin. PMID:27353345

  20. Injecting engineered anti-inflammatory macrophages therapeutically induces white adipose tissue browning and improves diet-induced insulin resistance.

    PubMed

    Liu, Pu-Ste; Lin, Yi-Wei; Burton, Frank H; Wei, Li-Na

    2015-01-01

    We recently exploited a transgenic approach to coerce macrophage anti-inflammatory M2 polarization in vivo by lowering Receptor Interacting Protein 140 (RIP140) level in macrophages (mφRIP140KD), which induced browning of white adipose tissue (WAT). In vitro, conditioned medium from cultured adipose tissue macrophages (ATMs) of mφRIP140KD mice could trigger preadipocytes' differentiation into beige cells. Here we describe a cell therapy for treating high fat diet (HFD)-induced insulin resistance (IR). Injecting M2 ATMs retrieved from the WAT of mφRIP140KD mice into HFD-fed obese adult wild-type mice effectively triggers their WAT browning, reduces their pro-inflammatory responses, and improves their insulin sensitivity. These data provide a proof-of-concept that delivering engineered anti-inflammatory macrophages can trigger white fat browning, stimulate whole-body thermogenesis, and reduce obesity-associated IR. PMID:26167415

  1. Carnitine Palmitoyltransferase 1b Deficiency Protects Mice from Diet-Induced Insulin Resistance

    PubMed Central

    Kim, Teayoun; He, Lan; Johnson, Maria S.; Li, Yan; Zeng, Ling; Ding, Yishu; Long, Qinqiang; Moore, John F.; Sharer, Jon D.; Nagy, Tim R.; Young, Martin E.; Wood, Philip A.; Yang, Qinglin

    2014-01-01

    Background Carnitine Palmitoyl Transferase 1 (CPT1) is the rate-limiting enzyme governing long-chain fatty acid entry into mitochondria. CPT1 inhibitors have been developed and exhibited beneficial effects against type II diabetes in short-term preclinical animal studies. However, the long-term effects of treatment remain unclear and potential non-specific effects of these CPT1 inhibitors hamper in-depth understanding of the potential molecular mechanisms involved. Methods We investigated the effects of restricting the activity of the muscle isoform CPT1b in mice using heterozygous CPT1b deficient (Cpt1b+/−) and Wild Type (WT) mice fed with a High Fat Diet (HFD) for 22 weeks. Insulin sensitivity was assessed using Glucose Tolerance Test (GTT), insulin tolerance test and hyperinsulinemic euglycemic clamps. We also examined body weight/composition, tissue and systemic metabolism/energetic status, lipid profile, transcript analysis, and changes in insulin signaling pathways. Results We found that Cpt1b+/− mice were protected from HFD-induced insulin resistance compared to WT littermates. Cpt1b+/− mice exhibited elevated whole body glucose disposal rate and skeletal muscle glucose uptake. Furthermore, Cpt1b+/− skeletal muscle showed diminished ex vivo palmitate oxidative capacity by ~40% and augmented glucose oxidation capacity by ~50% without overt change in whole body energy metabolism. HFD feeding Cpt1b+/− but not WT mice exhibited well-maintained insulin signaling in skeletal muscle, heart, and liver. Conclusion The present study on a genetic model of CPT1b restriction supports the concept that partial CPT1b inhibition is a potential therapeutic strategy. PMID:25309812

  2. SIRT3 Deficiency Induces Endothelial Insulin Resistance and Blunts Endothelial-Dependent Vasorelaxation in Mice and Human with Obesity

    PubMed Central

    Yang, Lu; Zhang, Julei; Xing, Wenjuan; Zhang, Xing; Xu, Jie; Zhang, Haifeng; Chen, Li; Ning, Xiaona; Ji, Gang; Li, Jia; Zhao, Qingchuan; Gao, Feng

    2016-01-01

    Recent evidence implicates the critical role of Sirtuin 3 (SIRT3) in the development of many metabolic diseases, but the contribution of SIRT3 to vascular homeostasis remains largely unknown. The aim of this study was to investigate the role of SIRT3 in endothelial insulin resistance and vascular dysfunction in obesity. We found an impaired insulin-induced mesenteric vasorelaxation and concomitant reduced vascular SIRT3 expression in morbid obese human subjects compared with the non-obese subjects. Downregulation of SIRT3 in cultured human endothelial cells increased mitochondrial reactive oxygen species (mtROS) and impaired insulin signaling as evidenced by decreased phosphorylation of Akt and endothelial nitric oxide synthase and subsequent reduced nitric oxide (NO) release. In addition, obese mice induced by 24-week high-fat diet (HFD) displayed an impaired endothelium-dependent vasorelaxation to both insulin and acetylcholine, which was further exacerbated by the gene deletion of Sirt3. Scavenging of mtROS not only restored insulin-stimulated NO production in SIRT3 knockdown cells, but also improved insulin-induced vasorelaxation in SIRT3 knockout mice fed with HFD. Taken together, our findings suggest that SIRT3 positively regulates endothelial insulin sensitivity and show that SIRT3 deficiency and resultant increased mtROS contribute to vascular dysfunction in obesity. PMID:27000941

  3. SIRT3 Deficiency Induces Endothelial Insulin Resistance and Blunts Endothelial-Dependent Vasorelaxation in Mice and Human with Obesity.

    PubMed

    Yang, Lu; Zhang, Julei; Xing, Wenjuan; Zhang, Xing; Xu, Jie; Zhang, Haifeng; Chen, Li; Ning, Xiaona; Ji, Gang; Li, Jia; Zhao, Qingchuan; Gao, Feng

    2016-01-01

    Recent evidence implicates the critical role of Sirtuin 3 (SIRT3) in the development of many metabolic diseases, but the contribution of SIRT3 to vascular homeostasis remains largely unknown. The aim of this study was to investigate the role of SIRT3 in endothelial insulin resistance and vascular dysfunction in obesity. We found an impaired insulin-induced mesenteric vasorelaxation and concomitant reduced vascular SIRT3 expression in morbid obese human subjects compared with the non-obese subjects. Downregulation of SIRT3 in cultured human endothelial cells increased mitochondrial reactive oxygen species (mtROS) and impaired insulin signaling as evidenced by decreased phosphorylation of Akt and endothelial nitric oxide synthase and subsequent reduced nitric oxide (NO) release. In addition, obese mice induced by 24-week high-fat diet (HFD) displayed an impaired endothelium-dependent vasorelaxation to both insulin and acetylcholine, which was further exacerbated by the gene deletion of Sirt3. Scavenging of mtROS not only restored insulin-stimulated NO production in SIRT3 knockdown cells, but also improved insulin-induced vasorelaxation in SIRT3 knockout mice fed with HFD. Taken together, our findings suggest that SIRT3 positively regulates endothelial insulin sensitivity and show that SIRT3 deficiency and resultant increased mtROS contribute to vascular dysfunction in obesity. PMID:27000941

  4. Perfluorooctanoic acid exposure for 28 days affects glucose homeostasis and induces insulin hypersensitivity in mice

    NASA Astrophysics Data System (ADS)

    Yan, Shengmin; Zhang, Hongxia; Zheng, Fei; Sheng, Nan; Guo, Xuejiang; Dai, Jiayin

    2015-06-01

    Perfluoroalkyl acids (PFAAs) are widely used in many applications due to their unique physical and chemical characteristics. Because of the increasing prevalence of metabolic syndromes, including obesity, dyslipidemia and insulin resistance, concern has arisen about the roles of environmental pollutants in such diseases. Earlier epidemiologic studies showed a potential association between perfluorooctanoic acid (PFOA) and glucose metabolism, but how PFOA influences glucose homeostasis is still unknown. Here, we report on the modulation of the phosphatidylinositol 3-kinase-serine/threonine protein kinase (PI3K-AKT) signaling pathway in the livers of mice after 28 d of exposure to PFOA. Compared with normal mice, PFOA exposure significantly decreased the expression of the phosphatase and tensin homologue (PTEN) protein and affected the PI3K-AKT signaling pathway in the liver. Tolerance tests further indicated that PFOA exposure induced higher insulin sensitivity and glucose tolerance in mice. Biochemical analysis revealed that PFOA exposure reduced hepatic glycogen synthesis, which might be attributed to gluconeogenesis inhibition. The levels of several circulating proteins were altered after PFOA exposure, including proteins potentially related to diabetes and liver disease. Our results suggest that PFOA affected glucose metabolism and induced insulin hypersensitivity in mice.

  5. Decaffeinated green coffee bean extract attenuates diet-induced obesity and insulin resistance in mice.

    PubMed

    Song, Su Jin; Choi, Sena; Park, Taesun

    2014-01-01

    This study investigated whether decaffeinated green coffee bean extract prevents obesity and improves insulin resistance and elucidated its mechanism of action. Male C57BL/6N mice (N = 48) were divided into six dietary groups: chow diet, HFD, HFD-supplemented with 0.1%, 0.3%, and 0.9% decaffeinated green coffee bean extract, and 0.15% 5-caffeoylquinic acid. Based on the reduction in HFD-induced body weight gain and increments in plasma lipids, glucose, and insulin levels, the minimum effective dose of green coffee bean extract appears to be 0.3%. Green coffee bean extract resulted in downregulation of genes involved in WNT10b- and galanin-mediated adipogenesis and TLR4-mediated proinflammatory pathway and stimulation of GLUT4 translocation to the plasma membrane in white adipose tissue. Taken together, decaffeinated green coffee bean extract appeared to reverse HFD-induced fat accumulation and insulin resistance by downregulating the genes involved in adipogenesis and inflammation in visceral adipose tissue. PMID:24817902

  6. [Hypertriglyceridemia-induced pancreatitis treated with insulin in a nondiabetic patient].

    PubMed

    Park, Seon Young; Chung, Jin Ook; Cho, Dong Keun; Lee, Wan Sik; Kim, Hyun Soo; Choi, Sung-Kyu; Rew, Jong-Sun; Chung, Min Young

    2010-06-01

    Heparin and/or insulin stimulate lipoprotein lipase and are known to decrease serum triglyceride level. However, their efficacy in hypertriglyceridemia-induced acute pancreatitis in nondiabetic patients is not well documented. We report a case of hypertriglyceridemia-induced pancreatitis in 43-year-old nondiabetic woman in whom treatment with insulin was accompanied by reduction in serum triglyceride level and the resolution of pancreatitis. She presented to the emergency department with abdominal pain and biochemical evidence of acute pancreatitis. Her medical history was unremarkable. There was no history of alcohol consumption, and biliary imaging was not remarkable. Subsequent laboratory investigation revealed marked hypertriglyceridemia (1,951 mg/dL), impaired fasting glucose, and normal HbAlc level. The Ransons score and APATCH II score were 1 and 4. Abdominal CT showed diffuse enlargement of pancreas, peripancreatic fat infiltration, and multiple fluid collections around the pancreas. We treated the patient with the infusion of 5% dextrose and 1.5 unit/hr regular insulin to reduce serum triglyceride level. The level of serum triglyceride was decreased to 305 mg/dL on day 5. During the remainder of hospitalization, her clinical symptoms and laboratory values gradually improved. PMID:20571309

  7. Brain glycogen supercompensation in the mouse after recovery from insulin-induced hypoglycemia.

    PubMed

    Canada, Sarah E; Weaver, Staci A; Sharpe, Shannon N; Pederson, Bartholomew A

    2011-04-01

    Brain glycogen is proposed to function under both physiological and pathological conditions. Pharmacological elevation of this glucose polymer in brain is hypothesized to protect neurons against hypoglycemia-induced cell death. Elevation of brain glycogen levels due to prior hypoglycemia is postulated to contribute to the development of hypoglycemia-associated autonomic failure (HAAF) in insulin-treated diabetic patients. This latter mode of elevating glycogen levels is termed "supercompensation." We tested whether brain glycogen supercompensation occurs in healthy, conscious mice after recovery from insulin-induced acute or recurrent hypoglycemia. Blood glucose levels were lowered to less than 2.2 mmol/liter for 90 min by administration of insulin. Brain glucose levels decreased at least 80% and brain glycogen levels decreased approximately 50% after episodes of either acute or recurrent hypoglycemia. After these hypoglycemic episodes, mice were allowed access to food for 6 or 27 hr. After 6 hr, blood and brain glucose levels were restored but brain glycogen levels were elevated by 25% in mice that had been subjected to either acute or recurrent hypoglycemia compared with saline-treated controls. After a 27-hr recovery period, the concentration of brain glycogen had returned to baseline levels in mice previously subjected to either acute or recurrent hypoglycemia. We conclude that brain glycogen supercompensation occurs in healthy mice, but its functional significance remains to be established. PMID:21259334

  8. BRAIN GLYCOGEN SUPERCOMPENSATION IN THE MOUSE AFTER RECOVERY FROM INSULIN-INDUCED HYPOGLYCEMIA

    PubMed Central

    Canada, Sarah E.; Weaver, Staci A.; Sharpe, Shannon N.; Pederson, Bartholomew A.

    2010-01-01

    Brain glycogen is proposed to function in both physiological and pathological conditions. Pharmacological elevation of this glucose polymer in brain is hypothesized to protect neurons against hypoglycemia-induced cell death. Elevation of brain glycogen levels due to prior hypoglycemia is postulated to contribute to the development of hypoglycemia-associated autonomic failure (HAAF) in insulin-treated diabetic patients. This latter mode of elevating glycogen levels is termed “supercompensation”. We tested whether brain glycogen supercompensation occurs in healthy, conscious mice after recovery from insulin-induced acute or recurrent hypoglycemia. Blood glucose levels were lowered to less than 2.2 mmol/L for 90 min by administration of insulin. Brain glucose levels decreased at least 80% and brain glycogen levels decreased approximately 50% after episodes of either acute or recurrent hypoglycemia. Following these hypoglycemic episodes, mice were allowed access to food for 6 or 27 hrs. After 6 hrs, blood and brain glucose levels were restored while brain glycogen levels were elevated 25% in mice that were previously subjected to either acute or recurrent hypoglycemia as compared with saline-treated controls. Following a 27 hr recovery period, the concentration of brain glycogen had returned to baseline levels in mice previously subjected to either acute or recurrent hypoglycemia. We conclude that brain glycogen supercompensation occurs in healthy mice but its functional significance remains to be established. PMID:21259334

  9. Perfluorooctanoic acid exposure for 28 days affects glucose homeostasis and induces insulin hypersensitivity in mice

    PubMed Central

    Yan, Shengmin; Zhang, Hongxia; Zheng, Fei; Sheng, Nan; Guo, Xuejiang; Dai, Jiayin

    2015-01-01

    Perfluoroalkyl acids (PFAAs) are widely used in many applications due to their unique physical and chemical characteristics. Because of the increasing prevalence of metabolic syndromes, including obesity, dyslipidemia and insulin resistance, concern has arisen about the roles of environmental pollutants in such diseases. Earlier epidemiologic studies showed a potential association between perfluorooctanoic acid (PFOA) and glucose metabolism, but how PFOA influences glucose homeostasis is still unknown. Here, we report on the modulation of the phosphatidylinositol 3-kinase-serine/threonine protein kinase (PI3K-AKT) signaling pathway in the livers of mice after 28 d of exposure to PFOA. Compared with normal mice, PFOA exposure significantly decreased the expression of the phosphatase and tensin homologue (PTEN) protein and affected the PI3K-AKT signaling pathway in the liver. Tolerance tests further indicated that PFOA exposure induced higher insulin sensitivity and glucose tolerance in mice. Biochemical analysis revealed that PFOA exposure reduced hepatic glycogen synthesis, which might be attributed to gluconeogenesis inhibition. The levels of several circulating proteins were altered after PFOA exposure, including proteins potentially related to diabetes and liver disease. Our results suggest that PFOA affected glucose metabolism and induced insulin hypersensitivity in mice. PMID:26066376

  10. Decaffeinated Green Coffee Bean Extract Attenuates Diet-Induced Obesity and Insulin Resistance in Mice

    PubMed Central

    Song, Su Jin; Choi, Sena; Park, Taesun

    2014-01-01

    This study investigated whether decaffeinated green coffee bean extract prevents obesity and improves insulin resistance and elucidated its mechanism of action. Male C57BL/6N mice (N = 48) were divided into six dietary groups: chow diet, HFD, HFD-supplemented with 0.1%, 0.3%, and 0.9% decaffeinated green coffee bean extract, and 0.15% 5-caffeoylquinic acid. Based on the reduction in HFD-induced body weight gain and increments in plasma lipids, glucose, and insulin levels, the minimum effective dose of green coffee bean extract appears to be 0.3%. Green coffee bean extract resulted in downregulation of genes involved in WNT10b- and galanin-mediated adipogenesis and TLR4-mediated proinflammatory pathway and stimulation of GLUT4 translocation to the plasma membrane in white adipose tissue. Taken together, decaffeinated green coffee bean extract appeared to reverse HFD-induced fat accumulation and insulin resistance by downregulating the genes involved in adipogenesis and inflammation in visceral adipose tissue. PMID:24817902

  11. Biosimilar insulins.

    PubMed

    Heinemann, Lutz

    2012-08-01

    Until now most insulin used in developed countries is manufactured and distributed by a small number of multinational companies. Other pharmaceutical companies - many of these are located in countries such as India or China - are also able to manufacture insulin with modern biotechnological methods. Additionally, the patents for many insulin formulations have expired or are going to expire soon. This enables such companies to produce insulins and to apply for market approval of these as biosimilar insulins (BIs) in highly regulated markets such as the EU or the US. To understand the complexity of BIs' approval and usage, scientific and regulatory aspects have to be discussed. Differences in the manufacturing process (none of the insulin-manufacturing procedures are identical) result in the fact that all insulin that might become BIs differ from the originator insulin to some extent. The question is, have such differences in the structure of the insulin molecule and or the purity and so on clinically relevant consequences for the biological effects induced or not. The guidelines already in place in the EU for market approval require that the manufacturer demonstrates that his insulin has a safety and efficacy profile that is similar to that of the 'original' insulin formulation. Recently guidelines for biosimilars were issued in the US; however, these do not cover insulin. Although a challenging approval process for insulins to become BI might be regarded as a hurdle to keep companies out of certain markets, it is fair to say that the potential safety and efficacy issues surrounding BI are substantial and relevant, and do warrant a careful and evidence-driven approval process. Nevertheless, it is very likely that in the next years, BIs will come to the market also in highly regulated markets. PMID:22583127

  12. Preventing High Fat Diet-induced Obesity and Improving Insulin Sensitivity through Neuregulin 4 Gene Transfer

    PubMed Central

    Ma, Yongjie; Gao, Mingming; Liu, Dexi

    2016-01-01

    Neuregulin 4 (NRG4), an epidermal growth factor-like signaling molecule, plays an important role in cell-to-cell communication during tissue development. Its function to regulate energy metabolism has recently been reported. This current study was designed to assess the preventive and therapeutic effects of NRG4 overexpression on high fat diet (HFD)-induced obesity. Using the hydrodynamic gene transfer method, we demonstrate that Nrg4 gene transfer in mice suppressed the development of diet-induced obesity, but did not affect pre-existing adiposity and body weight in obese mice. Nrg4 gene transfer curbed HFD-induced hepatic steatosis by inhibiting lipogenesis and PPARγ-mediated lipid storage. Concurrently, overexpression of NRG4 reduced chronic inflammation in both preventive and treatment studies, evidenced by lower mRNA levels of macrophage marker genes including F4/80, Cd68, Cd11b, Cd11c, and macrophage chemokine Mcp1, resulting in improved insulin sensitivity. Collectively, these results demonstrate that overexpression of the Nrg4 gene by hydrodynamic gene delivery prevents HFD-induced weight gain and fatty liver, alleviates obesity-induced chronic inflammation and insulin resistance, and supports the health benefits of NRG4 in managing obesity and obesity-associated metabolic disorders. PMID:27184920

  13. Preventing High Fat Diet-induced Obesity and Improving Insulin Sensitivity through Neuregulin 4 Gene Transfer.

    PubMed

    Ma, Yongjie; Gao, Mingming; Liu, Dexi

    2016-01-01

    Neuregulin 4 (NRG4), an epidermal growth factor-like signaling molecule, plays an important role in cell-to-cell communication during tissue development. Its function to regulate energy metabolism has recently been reported. This current study was designed to assess the preventive and therapeutic effects of NRG4 overexpression on high fat diet (HFD)-induced obesity. Using the hydrodynamic gene transfer method, we demonstrate that Nrg4 gene transfer in mice suppressed the development of diet-induced obesity, but did not affect pre-existing adiposity and body weight in obese mice. Nrg4 gene transfer curbed HFD-induced hepatic steatosis by inhibiting lipogenesis and PPARγ-mediated lipid storage. Concurrently, overexpression of NRG4 reduced chronic inflammation in both preventive and treatment studies, evidenced by lower mRNA levels of macrophage marker genes including F4/80, Cd68, Cd11b, Cd11c, and macrophage chemokine Mcp1, resulting in improved insulin sensitivity. Collectively, these results demonstrate that overexpression of the Nrg4 gene by hydrodynamic gene delivery prevents HFD-induced weight gain and fatty liver, alleviates obesity-induced chronic inflammation and insulin resistance, and supports the health benefits of NRG4 in managing obesity and obesity-associated metabolic disorders. PMID:27184920

  14. Protein Fractions from Korean Mistletoe (Viscum Album coloratum) Extract Induce Insulin Secretion from Pancreatic Beta Cells

    PubMed Central

    Kim, Jong-Bae

    2014-01-01

    Mistletoe (Viscum Album coloratum) has been known as a medicinal plant in European and Asian countries. Recent data show that biological activity of mistletoe alleviates hypertension, heart disease, renal failure, and cancer development. In this study, we report the antidiabetic effect of Korean mistletoe extract (KME). KME treatments enhanced the insulin secretion from the pancreatic β-cell without any effects of cytotoxicity. PDX-1 and beta2/neuroD known as transcription factors that regulate the expression of insulin gene were upregulated by treatment of the KME protein fractions isolated by ion-exchange chromatography after ammonium sulfate precipitation. Furthermore, these KME protein fractions significantly lowered the blood glucose level and the volume of drinking water in alloxan induced hyperglycemic mice. Taken together with the findings, it provides new insight that KME might be served as a useful source for the development of medicinal reagent to reduce blood glucose level of type I diabetic patients. PMID:24959189

  15. Effect of insulin-induced hypoglycaemia on the central nervous system: evidence from experimental studies.

    PubMed

    Jensen, V F H; Bøgh, I B; Lykkesfeldt, J

    2014-03-01

    Insulin-induced hypoglycaemia (IIH) is a major acute complication in type 1 as well as in type 2 diabetes, particularly during intensive insulin therapy. The brain plays a central role in the counter-regulatory response by eliciting parasympathetic and sympathetic hormone responses to restore normoglycaemia. Brain glucose concentrations, being approximately 15-20% of the blood glucose concentration in humans, are rigorously maintained during hypoglycaemia through adaptions such as increased cerebral glucose transport, decreased cerebral glucose utilisation and, possibly, by using central nervous system glycogen as a glucose reserve. However, during sustained hypoglycaemia, the brain cannot maintain a sufficient glucose influx and, as the cerebral hypoglycaemia becomes severe, electroencephalogram changes, oxidative stress and regional neuronal death ensues. With particular focus on evidence from experimental studies on nondiabetic IIH, this review outlines the central mechanisms behind the counter-regulatory response to IIH, as well as cerebral adaption to avoid sequelae of cerebral neuroglycopaenia, including seizures and coma. PMID:24428753

  16. 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

  17. Insulin improves β-cell function in glucose-intolerant rat models induced by feeding a high-fat diet.

    PubMed

    Li, Hui-qing; Wang, Bao-ping; Deng, Xiu-Ling; Zhang, Jiao-yue; Wang, Yong-bo; Zheng, Juan; Xia, Wen-fang; Zeng, Tian-shu; Chen, Lu-lu

    2011-11-01

    Insulin therapy has been shown to contribute to extended glycemia remission in newly diagnosed patients with type 2 diabetes mellitus. This study investigated the effects of insulin treatment on pancreatic lipid content, and β-cell apoptosis and proliferation in glucose-intolerant rats to explore the protective role of insulin on β-cell function. A rat glucose-intolerant model was induced by streptozotocin and a high-fat diet. Plasma and pancreatic triglycerides, free fatty acids, and insulin were measured; and pancreatic β-cell cell apoptosis and proliferation were detected by a propidium iodide cell death assay and immunofluorescence for proliferating cell nuclear antigen. Relative β-cell area was determined by immunohistochemistry for insulin, whereas insulin production in pancreas was assessed by reverse transcriptase polymerase chain reaction. Islet β-cell secreting function was assessed by the index ΔI30/ΔG30. Glucose-intolerant rats had higher pancreatic lipid content, more islet β-cell apoptosis, lower β-cell proliferation, and reduced β-cell area in pancreas when compared with controls. Insulin therapy reduced blood glucose, inhibited pancreatic lipid accumulation and islet β-cell apoptosis, and increased β-cell proliferation and β-cell area in glucose-intolerant rats. Furthermore, impaired insulin secretion and insulin production in glucose-intolerant rats were improved by insulin therapy. Insulin can preserve β-cell function by protecting islets from glucotoxicity and lipotoxicity. It can also ameliorate β-cell area by enhancing β-cell proliferation and reducing β-cell apoptosis. PMID:21550078

  18. Role of Protein Farnesylation in Burn-Induced Metabolic Derangements and Insulin Resistance in Mouse Skeletal Muscle

    PubMed Central

    Tanaka, Tomokazu; Kramer, Joshua; Yu, Yong-Ming; Fischman, Alan J.; Martyn, J. A. Jeevendra; Tompkins, Ronald G.; Kaneki, Masao

    2015-01-01

    Objective Metabolic derangements, including insulin resistance and hyperlactatemia, are a major complication of major trauma (e.g., burn injury) and affect the prognosis of burn patients. Protein farnesylation, a posttranslational lipid modification of cysteine residues, has been emerging as a potential component of inflammatory response in sepsis. However, farnesylation has not yet been studied in major trauma. To study a role of farnesylation in burn-induced metabolic aberration, we examined the effects of farnesyltransferase (FTase) inhibitor, FTI-277, on burn-induced insulin resistance and metabolic alterations in mouse skeletal muscle. Methods A full thickness burn (30% total body surface area) was produced under anesthesia in male C57BL/6 mice at 8 weeks of age. After the mice were treated with FTI-277 (5 mg/kg/day, IP) or vehicle for 3 days, muscle insulin signaling, metabolic alterations and inflammatory gene expression were evaluated. Results Burn increased FTase expression and farnesylated proteins in mouse muscle compared with sham-burn at 3 days after burn. Simultaneously, insulin-stimulated phosphorylation of insulin receptor (IR), insulin receptor substrate (IRS)-1, Akt and GSK-3β was decreased. Protein expression of PTP-1B (a negative regulator of IR-IRS-1 signaling), PTEN (a negative regulator of Akt-mediated signaling), protein degradation and lactate release by muscle, and plasma lactate levels were increased by burn. Burn-induced impaired insulin signaling and metabolic dysfunction were associated with increased inflammatory gene expression. These burn-induced alterations were reversed or ameliorated by FTI-277. Conclusions Our data demonstrate that burn increased FTase expression and protein farnesylation along with insulin resistance, metabolic alterations and inflammatory response in mouse skeletal muscle, all of which were prevented by FTI-277 treatment. These results indicate that increased protein farnesylation plays a pivotal role in burn-induced

  19. Mechanisms of cinnamon extract-induced suppression of the intestinal overproduction of apolipoprotein B48-containing lipoproteins in insulin resistant high-fructose fed animals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We have reported previously that cinnamon extract (CE) prevents high-fructose (HF) feeding-induced whole-body insulin resistance by enhancing insulin signaling in skeletal muscle. In this study, we investigated whether intestinal apolipoprotein overproduction is inhibited by CE in this insulin-resis...

  20. Withaferin A protects against palmitic acid-induced endothelial insulin resistance and dysfunction through suppression of oxidative stress and inflammation

    PubMed Central

    Batumalaie, Kalaivani; Amin, Muhammad Arif; Murugan, Dharmani Devi; Sattar, Munavvar Zubaid Abdul; Abdullah, Nor Azizan

    2016-01-01

    Activation of inflammatory pathways via reactive oxygen species (ROS) by free fatty acids (FFA) in obesity gives rise to insulin resistance and endothelial dysfunction. Withaferin A (WA), possesses both antioxidant and anti-inflammatory properties and therefore would be a good strategy to suppress palmitic acid (PA)-induced oxidative stress and inflammation and hence, insulin resistance and dysfunction in the endothelium. Effect of WA on PA-induced insulin resistance in human umbilical vein endothelial cells (HUVECs) was determined by evaluating insulin signaling mechanisms whilst effect of this drug on PA-induced endothelial dysfunction was determined in acetylcholine-mediated relaxation in isolated rat aortic preparations. WA significantly inhibited ROS production and inflammation induced by PA. Furthermore, WA significantly decreased TNF-α and IL-6 production in endothelial cells by specifically suppressing IKKβ/NF-κβ phosphorylation. WA inhibited inflammation-stimulated IRS-1 serine phosphorylation and improved the impaired insulin PI3-K signaling, and restored the decreased nitric oxide (NO) production triggered by PA. WA also decreased endothelin-1 and plasminogen activator inhibitor type-1 levels, and restored the impaired endothelium-mediated vasodilation in isolated aortic preparations. These findings suggest that WA inhibited both ROS production and inflammation to restore impaired insulin resistance in cultured endothelial cells and improve endothelial dysfunction in rat aortic rings. PMID:27250532

  1. Withaferin A protects against palmitic acid-induced endothelial insulin resistance and dysfunction through suppression of oxidative stress and inflammation.

    PubMed

    Batumalaie, Kalaivani; Amin, Muhammad Arif; Murugan, Dharmani Devi; Sattar, Munavvar Zubaid Abdul; Abdullah, Nor Azizan

    2016-01-01

    Activation of inflammatory pathways via reactive oxygen species (ROS) by free fatty acids (FFA) in obesity gives rise to insulin resistance and endothelial dysfunction. Withaferin A (WA), possesses both antioxidant and anti-inflammatory properties and therefore would be a good strategy to suppress palmitic acid (PA)-induced oxidative stress and inflammation and hence, insulin resistance and dysfunction in the endothelium. Effect of WA on PA-induced insulin resistance in human umbilical vein endothelial cells (HUVECs) was determined by evaluating insulin signaling mechanisms whilst effect of this drug on PA-induced endothelial dysfunction was determined in acetylcholine-mediated relaxation in isolated rat aortic preparations. WA significantly inhibited ROS production and inflammation induced by PA. Furthermore, WA significantly decreased TNF-α and IL-6 production in endothelial cells by specifically suppressing IKKβ/NF-κβ phosphorylation. WA inhibited inflammation-stimulated IRS-1 serine phosphorylation and improved the impaired insulin PI3-K signaling, and restored the decreased nitric oxide (NO) production triggered by PA. WA also decreased endothelin-1 and plasminogen activator inhibitor type-1 levels, and restored the impaired endothelium-mediated vasodilation in isolated aortic preparations. These findings suggest that WA inhibited both ROS production and inflammation to restore impaired insulin resistance in cultured endothelial cells and improve endothelial dysfunction in rat aortic rings. PMID:27250532

  2. The Neuroprotective Role of Insulin Against MPP(+) -Induced Parkinson's Disease in Differentiated SH-SY5Y Cells.

    PubMed

    Ramalingam, Mahesh; Kim, Sung-Jin

    2016-04-01

    Parkinson's disease (PD) is a common chronic neurodegenerative disorder associated with aging that primarily caused by the death of dopaminergic neurons in the substantia nigra pars compacta (SN). Retinoic acid (RA)-differentiated human neuroblastoma SH-SY5Y cells (SH-SY5Y+RA) have been broadly utilized in studies of mechanisms of the pathogenesis underlying 1-Methyl-4-phenyl pyridinium (MPP(+) )-induced PD models. Here, we investigated the neuroprotective mechanisms of insulin on MPP(+) -induced neurotoxicity on SH-SY5Y+RA cells. Recent studies suggest that insulin has a protective effect against oxidative stress but not been elucidated for PD. In this study, pretreatment of insulin prevented the cell death in a dose dependent manner and lowered nitric oxide (NO) release, reactive oxygen species (ROS), and calcium ion (Ca(2+) ) influx induced by MPP(+) . Insulin also elevated tyrosine hydroxylase (TH) and insulin signaling pathways in dopaminergic neuron through activating PI3K/Akt/GSK-3 survival pathways which in turn inhibits MPP(+) -induced iNOS and ERK activation, and Bax to Bcl-2 ratio. These results suggest that insulin has a protective effect on MPP(+) -neurotoxicity in SH-SY5Y+RA cells. J. Cell. Biochem. 117: 917-926, 2016. © 2015 Wiley Periodicals, Inc. PMID:26364587

  3. Adrenomedullin 2 Improves Early Obesity-Induced Adipose Insulin Resistance by Inhibiting the Class II MHC in Adipocytes.

    PubMed

    Zhang, Song-Yang; Lv, Ying; Zhang, Heng; Gao, Song; Wang, Ting; Feng, Juan; Wang, Yuhui; Liu, George; Xu, Ming-Jiang; Wang, Xian; Jiang, Changtao

    2016-08-01

    MHC class II (MHCII) antigen presentation in adipocytes was reported to trigger early adipose inflammation and insulin resistance. However, the benefits of MHCII inhibition in adipocytes remain largely unknown. Here, we showed that human plasma polypeptide adrenomedullin 2 (ADM2) levels were negatively correlated with HOMA of insulin resistance in obese human. Adipose-specific human ADM2 transgenic (aADM2-tg) mice were generated. The aADM2-tg mice displayed improvements in high-fat diet-induced early adipose insulin resistance. This was associated with increased insulin signaling and decreased systemic inflammation. ADM2 dose-dependently inhibited CIITA-induced MHCII expression by increasing Blimp1 expression in a CRLR/RAMP1-cAMP-dependent manner in cultured adipocytes. Furthermore, ADM2 treatment restored the high-fat diet-induced early insulin resistance in adipose tissue, mainly via inhibition of adipocyte MHCII antigen presentation and CD4(+) T-cell activation. This study demonstrates that ADM2 is a promising candidate for the treatment of early obesity-induced insulin resistance. PMID:27207558

  4. Hydrogen peroxide induces activation of insulin signaling pathway via AMP-dependent kinase in podocytes

    SciTech Connect

    Piwkowska, Agnieszka; Rogacka, Dorota; Angielski, Stefan; Jankowski, Maciej

    2012-11-09

    Highlights: Black-Right-Pointing-Pointer H{sub 2}O{sub 2} activates the insulin signaling pathway and glucose uptake in podocytes. Black-Right-Pointing-Pointer H{sub 2}O{sub 2} induces time-dependent changes in AMPK phosphorylation. Black-Right-Pointing-Pointer H{sub 2}O{sub 2} enhances insulin signaling pathways via AMPK activation. Black-Right-Pointing-Pointer H{sub 2}O{sub 2} stimulation of glucose uptake is AMPK-dependent. -- Abstract: Podocytes are cells that form the glomerular filtration barrier in the kidney. Insulin signaling in podocytes is critical for normal kidney function. Insulin signaling is regulated by oxidative stress and intracellular energy levels. We cultured rat podocytes to investigate the effects of hydrogen peroxide (H{sub 2}O{sub 2}) on the phosphorylation of proximal and distal elements of insulin signaling. We also investigated H{sub 2}O{sub 2}-induced intracellular changes in the distribution of protein kinase B (Akt). Western blots showed that H{sub 2}O{sub 2} (100 {mu}M) induced rapid, transient phosphorylation of the insulin receptor (IR), the IR substrate-1 (IRS1), and Akt with peak activities at 5 min ({Delta} 183%, P < 0.05), 3 min ({Delta} 414%, P < 0.05), and 10 min ({Delta} 35%, P < 0.05), respectively. Immunostaining cells with an Akt-specific antibody showed increased intensity at the plasma membrane after treatment with H{sub 2}O{sub 2}>. Furthermore, H{sub 2}O{sub 2} inhibited phosphorylation of the phosphatase and tensin homologue (PTEN; peak activity at 10 min; {Delta} -32%, P < 0.05) and stimulated phosphorylation of the AMP-dependent kinase alpha subunit (AMPK{alpha}; 78% at 3 min and 244% at 10 min). The stimulation of AMPK was abolished with an AMPK inhibitor, Compound C (100 {mu}M, 2 h). Moreover, Compound C significantly reduced the effect of H{sub 2}O{sub 2} on IR phosphorylation by about 40% (from 2.07 {+-} 0.28 to 1.28 {+-} 0.12, P < 0.05). In addition, H{sub 2}O{sub 2} increased glucose uptake in podocytes

  5. Somatotropic, lactotropic and adrenocortical responses to insulin-induced hypoglycemia in patients with rheumatoid arthritis.

    PubMed

    Rovensky, Jozef; Bakosová, Jana; Koska, Juraj; Ksinantová, Lucia; Jezová, Daniela; Vigas, Milan

    2002-06-01

    Neuroendocrine mechanisms have been suggested to play an important role in the onset and progression of rheumatoid arthritis (RA). The aim of this study was to evaluate hypothalamic-pituitary functions in RA patients by measurement of hormone responses to insulin-induced hypoglycemia. Insulin-hypoglycemia (Actrapid HM 0.1 IU/kg, i.v. as a bolus) was induced in 17 male patients and in 11 age-, gender-, and weight-matched healthy subjects. Concentrations of growth hormone (GH), prolactin (PRL) and cortisol were analyzed in plasma. PRL release after thyreoliberin stimulation (TRH, 200 g, i.v.) was determined in 21 patients with active forms of RA and in 12 control subjects to evaluate pituitary lactotropic response. In RA patients, basal concentrations of glucose, GH, PRL, and cortisol were in the normal range and they were comparable to those in the control group. Stress of hypoglycemia induced significant elevation of GH, PRL, and cortisol concentrations in all groups. Cortisol responses to hypoglycemia were comparable in patients and in control subjects. GH release during hypoglycemia was increased (p < 0.05) and PRL response was attenuated (p < 0.05) in RA patients versus control subjects. After TRH administration, PRL response was the same in patients as in healthy subjects. In conclusion, the present study revealed an altered hypothalamic-pituitary function in patients with RA, namely, an enhanced somatotropic and reduced lactotropic activation in response to insulin-induced hypoglycemia. Basal hormone levels and cortisol release during hypoglycemia were similar to those in healthy subjects. PMID:12114282

  6. Palmitate-induced impairment of glucose-stimulated insulin secretion precedes mitochondrial dysfunction in mouse pancreatic islets.

    PubMed

    Barlow, Jonathan; Jensen, Verena Hirschberg; Jastroch, Martin; Affourtit, Charles

    2016-02-15

    It has been well established that excessive levels of glucose and palmitate lower glucose-stimulated insulin secretion (GSIS) by pancreatic β-cells. This β-cell 'glucolipotoxicity' is possibly mediated by mitochondrial dysfunction, but involvement of bioenergetic failure in the pathological mechanism is the subject of ongoing debate. We show in the present study that increased palmitate levels impair GSIS before altering mitochondrial function. We demonstrate that GSIS defects arise from increased insulin release under basal conditions in addition to decreased insulin secretion under glucose-stimulatory conditions. Real-time respiratory analysis of intact mouse pancreatic islets reveals that mitochondrial ATP synthesis is not involved in the mechanism by which basal insulin is elevated. Equally, mitochondrial lipid oxidation and production of reactive oxygen species (ROS) do not contribute to increased basal insulin secretion. Palmitate does not affect KCl-induced insulin release at a basal or stimulatory glucose level, but elevated basal insulin release is attenuated by palmitoleate and associates with increased intracellular calcium. These findings deepen our understanding of β-cell glucolipotoxicity and reveal that palmitate-induced GSIS impairment is disconnected from mitochondrial dysfunction, a notion that is important when targeting β-cells for the treatment of diabetes and when assessing islet function in human transplants. PMID:26621874

  7. Insulin-like growth factor binding protein-3 induces apoptosis in MCF7 breast cancer cells.

    PubMed

    Nickerson, T; Huynh, H; Pollak, M

    1997-08-28

    Insulin-like growth factors (IGFs) are known to have potent antiapoptotic activity. The antiestrogen ICI 182,780 (ICI) is a potent inhibitor of MCF7 human breast cancer cell growth and has recently been reported to act as an antiproliferative agent in part via upregulation of expression of insulin-like growth factor binding proteins (IGFBPs) -3 and -5, which attenuate the bioactivity of IGFs in many experimental systems. We show here that ICI and IGFBP-3 induce apoptosis in MCF7 cells. Treatment of MCF7 cells with 10 nM ICI or 36 nM recombinant human IGFBP. 3 for 72 hours increased apoptosis approximately 3.5-fold relative to control as quantitated by a cell death ELISA which measures DNA fragmentation. Long R3 IGF-I, an IGF-I analogue with greatly reduced affinity for IGFBPs yet similar affinity for IGF-I receptors, was a more potent inhibitor of IGFBP-3-induced and ICI-induced apoptosis than IGF-I. These results suggest that IGFBP-3 enhances apoptosis by reducing bioavailability of ligands for the IGF-I receptor and suggest that modulation of IGFBP-3 expression by ICI contributes to apoptosis induced by this compound. More generally, the data suggest that IGFBPs are regulators of apoptosis. PMID:9299428

  8. A single prior bout of exercise protects against palmitate-induced insulin resistance despite an increase in total ceramide content.

    PubMed

    Thrush, A Brianne; Harasim, Ewa; Chabowski, Adrian; Gulli, Roberto; Stefanyk, Leslie; Dyck, David J

    2011-05-01

    Ceramide accumulation has been implicated in the impairment of insulin-stimulated glucose transport in skeletal muscle following saturated fatty acid (FA) exposure. Importantly, a single bout of exercise can protect against acute lipid-induced insulin resistance. The mechanism by which exercise protects against lipid-induced insulin resistance is not completely known but may occur through a redirection of FA toward triacylglycerol (TAG) and away from ceramide and diacylglycerol (DAG). Therefore, in the current study, an in vitro preparation was used to examine whether a prior bout of exercise could confer protection against palmitate-induced insulin resistance and whether the pharmacological [50 μM fumonisin B(1) (FB1)] inhibition of ceramide synthesis in the presence of palmitate could mimic the protective effect of exercise. Soleus muscle of sedentary (SED), exercised (EX), and SED in the presence of FB1 (SED+FB1) were incubated with or without 2 mM palmitate for 4 h. This 2-mM palmitate exposure impaired insulin-stimulated glucose transport (-28%, P < 0.01) and significantly increased ceramide, DAG, and TAG accumulation in the SED group (P < 0.05). A single prior bout of exercise prevented the detrimental effects of palmitate on insulin signaling and caused a partial redistribution of FA toward TAG (P < 0.05). However, the net increase in ceramide content in response to palmitate exposure in the EX group was not different compared with SED, despite the maintenance of insulin sensitivity. The incubation of soleus from SED rats with FB1 (SED+FB1) prevented the detrimental effects of palmitate and caused a redirection of FA toward TAG accumulation (P < 0.05). Therefore, this research suggests that although inhibiting ceramide accumulation can prevent the detrimental effects of palmitate, a single prior bout of exercise appears to protect against palmitate-induced insulin resistance, which may be independent of changes in ceramide content. PMID:21325642

  9. Maternal Fructose Intake Induces Insulin Resistance and Oxidative Stress in Male, but Not Female, Offspring

    PubMed Central

    Rodríguez, Lourdes; Otero, Paola; Panadero, María I.; Rodrigo, Silvia; Álvarez-Millán, Juan J.; Bocos, Carlos

    2015-01-01

    Objective. Fructose intake from added sugars correlates with the epidemic rise in metabolic syndrome and cardiovascular diseases. However, consumption of beverages containing fructose is allowed during gestation. Recently, we found that an intake of fructose (10% wt/vol) throughout gestation produces an impaired fetal leptin signalling. Therefore, we have investigated whether maternal fructose intake produces subsequent changes in their progeny. Methods. Blood samples from fed and 24 h fasted female and male 90-day-old rats born from fructose-fed, glucose-fed, or control mothers were used. Results. After fasting, HOMA-IR and ISI (estimates of insulin sensitivity) were worse in male descendents from fructose-fed mothers in comparison to the other two groups, and these findings were also accompanied by a higher leptinemia. Interestingly, plasma AOPP and uricemia (oxidative stress markers) were augmented in male rats from fructose-fed mothers compared to the animals from control or glucose-fed mothers. In contrast, female rats did not show any differences in leptinemia between the three groups. Further, insulin sensitivity was significantly improved in fasted female rats from carbohydrate-fed mothers. In addition, plasma AOPP levels tended to be diminished in female rats from carbohydrate-fed mothers. Conclusion. Maternal fructose intake induces insulin resistance, hyperleptinemia, and plasma oxidative stress in male, but not female, progeny. PMID:25763281

  10. Maternal fructose intake induces insulin resistance and oxidative stress in male, but not female, offspring.

    PubMed

    Rodríguez, Lourdes; Otero, Paola; Panadero, María I; Rodrigo, Silvia; Álvarez-Millán, Juan J; Bocos, Carlos

    2015-01-01

    Objective. Fructose intake from added sugars correlates with the epidemic rise in metabolic syndrome and cardiovascular diseases. However, consumption of beverages containing fructose is allowed during gestation. Recently, we found that an intake of fructose (10% wt/vol) throughout gestation produces an impaired fetal leptin signalling. Therefore, we have investigated whether maternal fructose intake produces subsequent changes in their progeny. Methods. Blood samples from fed and 24 h fasted female and male 90-day-old rats born from fructose-fed, glucose-fed, or control mothers were used. Results. After fasting, HOMA-IR and ISI (estimates of insulin sensitivity) were worse in male descendents from fructose-fed mothers in comparison to the other two groups, and these findings were also accompanied by a higher leptinemia. Interestingly, plasma AOPP and uricemia (oxidative stress markers) were augmented in male rats from fructose-fed mothers compared to the animals from control or glucose-fed mothers. In contrast, female rats did not show any differences in leptinemia between the three groups. Further, insulin sensitivity was significantly improved in fasted female rats from carbohydrate-fed mothers. In addition, plasma AOPP levels tended to be diminished in female rats from carbohydrate-fed mothers. Conclusion. Maternal fructose intake induces insulin resistance, hyperleptinemia, and plasma oxidative stress in male, but not female, progeny. PMID:25763281

  11. Insulin Resistance Increases the Risk of Contrast-Induced Nephropathy in Patients Undergoing Elective Coronary Intervention.

    PubMed

    Li, Yueping; Liu, Yuyang; Shi, Dongmei; Yang, Lixia; Liang, Jing; Zhou, Yujie

    2016-02-01

    We assessed the influence of insulin resistance (IR) on the development of contrast-induced nephropathy (CIN) in patients (n = 719) undergoing elective percutaneous coronary intervention (PCI). Patients were divided into diabetes mellitus (DM = 242), nondiabetic IR (IR = 120), and nondiabetic insulin sensitivity (IS = 357) groups according to medical history and homeostasis model assessment insulin resistance index. Serum creatinine (SCr) and estimated glomerular filtration rate (eGFR) were measured before and 72 hours after PCI. There were no differences in SCr and eGFR among the groups before PCI; SCr increased and eGFR decreased significantly in the DM and IR groups post-PCI (P < .001). The incidence of CIN in the IR group was as high as in the DM group and were both significantly higher than in the IS group (6.7% vs 8.7% vs 2.2%, P < .05). Multivariate logistic regression analysis showed DM (odds ratio [OR] = 1.19, 95%CI = 1.08-1.510, P < .001), HOMA-IR (OR = 1.39, 95%CI = 1.23-1.58, P < 0.001), and eGFR (OR = 0.88, 95%CI = 0.84-0.92, P < .001) were independent risk factors in predicting CIN. Screening IR patients and taking appropriate prophylactic strategy before PCI may reduce the incidence of CIN. PMID:25843952

  12. Ribosomal protein mutations induce autophagy through S6 kinase inhibition of the insulin pathway.

    PubMed

    Heijnen, Harry F; van Wijk, Richard; Pereboom, Tamara C; Goos, Yvonne J; Seinen, Cor W; van Oirschot, Brigitte A; van Dooren, Rowie; Gastou, Marc; Giles, Rachel H; van Solinge, Wouter; Kuijpers, Taco W; Gazda, Hanna T; Bierings, Marc B; Da Costa, Lydie; MacInnes, Alyson W

    2014-01-01

    Mutations affecting the ribosome lead to several diseases known as ribosomopathies, with phenotypes that include growth defects, cytopenia, and bone marrow failure. Diamond-Blackfan anemia (DBA), for example, is a pure red cell aplasia linked to the mutation of ribosomal protein (RP) genes. Here we show the knock-down of the DBA-linked RPS19 gene induces the cellular self-digestion process of autophagy, a pathway critical for proper hematopoiesis. We also observe an increase of autophagy in cells derived from DBA patients, in CD34+ erythrocyte progenitor cells with RPS19 knock down, in the red blood cells of zebrafish embryos with RP-deficiency, and in cells from patients with Shwachman-Diamond syndrome (SDS). The loss of RPs in all these models results in a marked increase in S6 kinase phosphorylation that we find is triggered by an increase in reactive oxygen species (ROS). We show that this increase in S6 kinase phosphorylation inhibits the insulin pathway and AKT phosphorylation activity through a mechanism reminiscent of insulin resistance. While stimulating RP-deficient cells with insulin reduces autophagy, antioxidant treatment reduces S6 kinase phosphorylation, autophagy, and stabilization of the p53 tumor suppressor. Our data suggest that RP loss promotes the aberrant activation of both S6 kinase and p53 by increasing intracellular ROS levels. The deregulation of these signaling pathways is likely playing a major role in the pathophysiology of ribosomopathies. PMID:24875531

  13. Insulin-like growth factor I/somatomedin C: a potent inducer of oligodendrocyte development

    SciTech Connect

    McMorris, F.A.; Smith, T.M.; DeSalvo, S.; Furlanetto, R.W.

    1986-02-01

    Cell cultures established from cerebrum of 1-day-old rats were used to investigate hormonal regulation of the development of oligodendrocytes, which synthesize myelin in the central nervous system. The number of oligodendrocytes that developed was preferentially increased by insulin, or by insulin-like growth factor I (IGF-I), also known as somatomedin C. High concentrations of insulin were required for substantial induction of oligodendrocyte development, whereas only 3.3 ng of IGF-I per ml was needed for a 2-fold increase in oligodendrocyte numbers. At an IGF-I concentration of 100 ng/ml, oligodendrocyte numbers were increased 6-fold in cultures grown in the presence of 10% fetal bovine serum, or up to 60-fold in cultures maintained in serum-free medium. IGF-I produced less than a 2-fold increase in the number of nonoligodendroglial cells in the same cultures. Type I IGF receptors were identified on oligodendrocytes and on a putative oligodendrocyte precursor cell population identified by using mouse monoclonal antibody A2B5. Radioligand binding assays were done. These results indicate that IGF-I is a potent inducer of oligodendrocyte development and suggest a possible mechanism based on IGF deficiency for the hypomyelination that results from early postnatal malnutrition.

  14. A genetically engineered human pancreatic β cell line exhibiting glucose-inducible insulin secretion

    PubMed Central

    Ravassard, Philippe; Hazhouz, Yasmine; Pechberty, Séverine; Bricout-Neveu, Emilie; Armanet, Mathieu; Czernichow, Paul; Scharfmann, Raphael

    2011-01-01

    Despite intense efforts over the past 30 years, human pancreatic β cell lines have not been available. Here, we describe a robust technology for producing a functional human β cell line using targeted oncogenesis in human fetal tissue. Human fetal pancreatic buds were transduced with a lentiviral vector that expressed SV40LT under the control of the insulin promoter. The transduced buds were then grafted into SCID mice so that they could develop into mature pancreatic tissue. Upon differentiation, the newly formed SV40LT-expressing β cells proliferated and formed insulinomas. The resulting β cells were then transduced with human telomerase reverse transcriptase (hTERT), grafted into other SCID mice, and finally expanded in vitro to generate cell lines. One of these cell lines, EndoC-βH1, expressed many β cell–specific markers without any substantial expression of markers of other pancreatic cell types. The cells secreted insulin when stimulated by glucose or other insulin secretagogues, and cell transplantation reversed chemically induced diabetes in mice. These cells represent a unique tool for large-scale drug discovery and provide a preclinical model for cell replacement therapy in diabetes. This technology could be generalized to generate other human cell lines when the cell type–specific promoter is available. PMID:21865645

  15. TM-25659-Induced Activation of FGF21 Level Decreases Insulin Resistance and Inflammation in Skeletal Muscle via GCN2 Pathways.

    PubMed

    Jung, Jong Gab; Yi, Sang-A; Choi, Sung-E; Kang, Yup; Kim, Tae Ho; Jeon, Ja Young; Bae, Myung Ae; Ahn, Jin Hee; Jeong, Hana; Hwang, Eun Sook; Lee, Kwan-Woo

    2015-12-01

    The TAZ activator 2-butyl-5-methyl-6-(pyridine-3-yl)-3-[2'-(1H-tetrazole-5-yl)-biphenyl-4-ylmethyl]-3H-imidazo[4,5-b]pyridine] (TM-25659) inhibits adipocyte differentiation by interacting with peroxisome proliferator-activated receptor gamma. TM-25659 was previously shown to decrease weight gain in a high fat (HF) diet-induced obesity (DIO) mouse model. However, the fundamental mechanisms underlying the effects of TM-25659 remain unknown. Therefore, we investigated the effects of TM-25659 on skeletal muscle functions in C2 myotubes and C57BL/6J mice. We studied the molecular mechanisms underlying the contribution of TM-25659 to palmitate (PA)-induced insulin resistance in C2 myotubes. TM-25659 improved PA-induced insulin resistance and inflammation in C2 myotubes. In addition, TM-25659 increased FGF21 mRNA expression, protein levels, and FGF21 secretion in C2 myotubes via activation of GCN2 pathways (GCN2-phosphoeIF2α-ATF4 and FGF21). This beneficial effect of TM-25659 was diminished by FGF21 siRNA. C57BL/6J mice were fed a HF diet for 30 weeks. The HF-diet group was randomly divided into two groups for the next 14 days: the HF-diet and HF-diet + TM-25659 groups. The HF diet + TM-25659-treated mice showed improvements in their fasting blood glucose levels, insulin sensitivity, insulin-stimulated Akt phosphorylation, and inflammation, but neither body weight nor food intake was affected. The HF diet + TM-25659-treated mice also exhibited increased expression of both FGF21 mRNA and protein. These data indicate that TM-25659 may be beneficial for treating insulin resistance by inducing FGF21 in models of PA-induced insulin resistance and HF diet-induced insulin resistance. PMID:26537193

  16. TM-25659-Induced Activation of FGF21 Level Decreases Insulin Resistance and Inflammation in Skeletal Muscle via GCN2 Pathways

    PubMed Central

    Jung, Jong Gab; Yi, Sang-A; Choi, Sung-E; Kang, Yup; Kim, Tae Ho; Jeon, Ja Young; Bae, Myung Ae; Ahn, Jin Hee; Jeong, Hana; Hwang, Eun Sook; Lee, Kwan-Woo

    2015-01-01

    The TAZ activator 2-butyl-5-methyl-6-(pyridine-3-yl)-3-[2′-(1H-tetrazole-5-yl)-biphenyl-4-ylmethyl]-3H-imidazo[4,5-b]pyridine] (TM-25659) inhibits adipocyte differentiation by interacting with peroxisome proliferator-activated receptor gamma. TM-25659 was previously shown to decrease weight gain in a high fat (HF) diet-induced obesity (DIO) mouse model. However, the fundamental mechanisms underlying the effects of TM-25659 remain unknown. Therefore, we investigated the effects of TM-25659 on skeletal muscle functions in C2 myotubes and C57BL/6J mice. We studied the molecular mechanisms underlying the contribution of TM-25659 to palmitate (PA)-induced insulin resistance in C2 myotubes. TM-25659 improved PA-induced insulin resistance and inflammation in C2 myotubes. In addition, TM-25659 increased FGF21 mRNA expression, protein levels, and FGF21 secretion in C2 myotubes via activation of GCN2 pathways (GCN2-phosphoeIF2α-ATF4 and FGF21). This beneficial effect of TM-25659 was diminished by FGF21 siRNA. C57BL/6J mice were fed a HF diet for 30 weeks. The HF-diet group was randomly divided into two groups for the next 14 days: the HF-diet and HF-diet + TM-25659 groups. The HF diet + TM-25659-treated mice showed improvements in their fasting blood glucose levels, insulin sensitivity, insulin-stimulated Akt phosphorylation, and inflammation, but neither body weight nor food intake was affected. The HF diet + TM-25659-treated mice also exhibited increased expression of both FGF21 mRNA and protein. These data indicate that TM-25659 may be beneficial for treating insulin resistance by inducing FGF21 in models of PA-induced insulin resistance and HF diet-induced insulin resistance. PMID:26537193

  17. Morin attenuates hepatic insulin resistance in high-fat-diet-induced obese mice.

    PubMed

    Naowaboot, Jarinyaporn; Wannasiri, Supaporn; Pannangpetch, Patchareewan

    2016-06-01

    Morin is a natural bioflavonoid that exhibits antioxidant and anti-inflammatory properties. The present study was designed to evaluate the effect of morin on insulin resistance, oxidative stress, and inflammation in a high-fat-diet (HFD)-induced obese mice. Obesity was induced in ICR mice by feeding a HFD (60 % kcal from fat) for 12 weeks. After the first 6 weeks, obese mice were treated with morin (50 or 100 mg/kg/day) once daily for further 6 weeks. Blood glucose, lipid profile, insulin, leptin, adiponectin, and markers of oxidative stress and inflammation were then measured. Liver was excised, subjected to histopathology, glycogen determination, and gene and protein expression analysis. Morin administration reduced blood glucose, serum insulin, leptin, malondialdehyde, interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1) levels and increased serum adiponectin levels. Moreover, there was a reduction in serum lipid and liver triglyceride levels. Liver histology indicated that morin limited accumulation of lipid droplets. Interestingly, morin reduced expression of hepatic sterol regulatory element binding protein 1c (SREBP1c), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) and up-regulated hepatic carnitine palmitoyltransferase 1a (CPT1a) expression. Morin also stimulated glycogen storage and suppressed phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) protein expression. Furthermore, hepatic superoxide dismutase (SOD) and catalase (CAT) expression were increased after morin treatment. These findings indicate that morin has a positive effect in the HFD-induced obesity condition by suppressing lipogenesis, gluconeogenesis, inflammation, and oxidative stress activities. PMID:26976296

  18. Manganese supplementation protects against diet-induced diabetes in wild type mice by enhancing insulin secretion.

    PubMed

    Lee, Soh-Hyun; Jouihan, Hani A; Cooksey, Robert C; Jones, Deborah; Kim, Hyung J; Winge, Dennis R; McClain, Donald A

    2013-03-01

    Mitochondrial dysfunction is both a contributing mechanism and complication of diabetes, and oxidative stress contributes to that dysfunction. Mitochondrial manganese-superoxide dismutase (MnSOD) is a metalloenzyme that provides antioxidant protection. We have previously shown in a mouse model of hereditary iron overload that cytosolic iron levels affected mitochondrial manganese availability, MnSOD activity, and insulin secretion. We therefore sought to determine the metallation status of MnSOD in wild-type mice and whether altering that status affected β-cell function. 129/SvEVTac mice given supplemental manganese exhibited a 73% increase in hepatic MnSOD activity and increased metallation of MnSOD. To determine whether manganese supplementation offered glucose homeostasis under a situation of β-cell stress, we challenged C57BL/6J mice, which are more susceptible to diet-induced diabetes, with a high-fat diet for 12 weeks. Manganese was supplemented or not for the final 8 weeks on that diet, after which we examined glucose tolerance and the function of isolated islets. Liver mitochondria from manganese-injected C57BL/6J mice had similar increases in MnSOD activity (81%) and metallation as were seen in 129/SvEVTac mice. The manganese-treated group fed high fat had improved glucose tolerance (24% decrease in fasting glucose and 41% decrease in area under the glucose curve), comparable with mice on normal chow and increased serum insulin levels. Isolated islets from the manganese-treated group exhibited improved insulin secretion, decreased lipid peroxidation, and improved mitochondrial function. In conclusion, MnSOD metallation and activity can be augmented with manganese supplementation in normal mice on normal chow, and manganese treatment can increase insulin secretion to improve glucose tolerance under conditions of dietary stress. PMID:23372018

  19. Tectorigenin Attenuates Palmitate-Induced Endothelial Insulin Resistance via Targeting ROS-Associated Inflammation and IRS-1 Pathway

    PubMed Central

    Zhang, Dong-Yan; Gao, Xue-Jiao; Zhou, Ling; Qin, Xiao-Ying; Xie, Guo-Yong; Liu, Kang; Qin, Yong; Liu, Bao-Lin; Qin, Min-Jian

    2013-01-01

    Tectorigenin is a plant isoflavonoid originally isolated from the dried flower of Pueraria thomsonii Benth. Although its anti-inflammatory and anti-hyperglycosemia effects have been well documented, the effect of tectorigenin on endothelial dysfunction insulin resistance involved has not yet been reported. Herein, this study aims to investigate the action of tectorigenin on amelioration of insulin resistance in the endothelium. Palmitic acid (PA) was chosen as a stimulant to induce ROS production in endothelial cells and successfully established insulin resistance evidenced by the specific impairment of insulin PI3K signaling. Tectorigenin effectively inhibited the ability of PA to induce the production of reactive oxygen species and collapse of mitochondrial membrane potential. Moreover, tectorigenin presented strong inhibition effect on ROS-associated inflammation, as TNF-α and IL-6 production in endothelial cells was greatly reduced with suppression of IKKβ/NF-κB phosphorylation and JNK activation. Tectorigenin also can inhibit inflammation-stimulated IRS-1 serine phosphorylation and restore the impaired insulin PI3K signaling, leading to a decreased NO production. These results demonstrated its positive regulation of insulin action in the endothelium. Meanwhile, tectorigenin down-regulated endothelin-1 and vascular cell adhesion molecule-1 overexpression, and restored the loss of insulin-mediated vasodilation in rat aorta. These findings suggested that tectorigenin could inhibit ROS-associated inflammation and ameliorated endothelial dysfunction implicated in insulin resistance through regulating IRS-1 function. Tectorigenin might have potential to be applied for the management of cardiovascular diseases involved in diabetes and insulin resistance. PMID:23840461

  20. Insulin signalling mediates the response to male-induced harm in female Drosophila melanogaster.

    PubMed

    Sepil, Irem; Carazo, Pau; Perry, Jennifer C; Wigby, Stuart

    2016-01-01

    Genetic manipulations in nutrient-sensing pathways are known to both extend lifespan and modify responses to environmental stressors (e.g., starvation, oxidative and thermal stresses), suggesting that similar mechanisms regulate lifespan and stress resistance. However, despite being a key factor reducing female lifespan and affecting female fitness, male-induced harm has rarely been considered as a stressor mediated by nutrient sensing pathways. We explored whether a lifespan-extending manipulation also modifies female resistance to male-induced harm. To do so, we used long-lived female Drosophila melanogaster that had their insulin signalling pathway downregulated by genetically ablating the median neurosecretory cells (mNSC). We varied the level of exposure to males for control and ablated females and tested for interacting effects on female lifespan and fitness. As expected, we found that lifespan significantly declined with exposure to males. However, mNSC-ablated females maintained significantly increased lifespan across all male exposure treatments. Furthermore, lifespan extension and relative fitness of mNSC-ablated females were maximized under intermediate exposure to males, and minimized under low and high exposure to males. Overall, our results suggest that wild-type levels of insulin signalling reduce female susceptibility to male-induced harm under intense sexual conflict, and may also protect females when mating opportunities are sub-optimally low. PMID:27457757

  1. Liver lipid molecules induce PEPCK-C gene transcription and attenuate insulin action

    SciTech Connect

    Chen Guoxun

    2007-09-28

    Cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) plays key roles in gluconeogenesis, glyceroneogenesis, and cataplerosis. Experiments were designed to examine the effects of endogenous lipid molecules from rat livers on the expression of PEPCK-C gene in primary rat hepatocytes. The lipid extracts prepared from livers of Zucker fatty, lean, and Wistar rats induced the expression levels of PEPCK-C transcripts. Insulin-mediated reduction of PEPCK-C gene expression was attenuated by the same treatment. The lipid extracts induced the relative luciferase activity of reporter gene constructs that contain a 2.2-kb 5' promoter fragment of PEPCK-C gene, but not the construct that contains only the 3' untranslated region (UTR) of its mRNA. The estimated half life of PEPCK-C transcripts in the presence of the lipid extract is the same as that in the absence of it. My results demonstrate for the first time that endogenous lipid molecules induce PEPCK-C gene transcription and attenuate insulin action in liver.

  2. Insulin signalling mediates the response to male-induced harm in female Drosophila melanogaster

    PubMed Central

    Sepil, Irem; Carazo, Pau; Perry, Jennifer C.; Wigby, Stuart

    2016-01-01

    Genetic manipulations in nutrient-sensing pathways are known to both extend lifespan and modify responses to environmental stressors (e.g., starvation, oxidative and thermal stresses), suggesting that similar mechanisms regulate lifespan and stress resistance. However, despite being a key factor reducing female lifespan and affecting female fitness, male-induced harm has rarely been considered as a stressor mediated by nutrient sensing pathways. We explored whether a lifespan-extending manipulation also modifies female resistance to male-induced harm. To do so, we used long-lived female Drosophila melanogaster that had their insulin signalling pathway downregulated by genetically ablating the median neurosecretory cells (mNSC). We varied the level of exposure to males for control and ablated females and tested for interacting effects on female lifespan and fitness. As expected, we found that lifespan significantly declined with exposure to males. However, mNSC-ablated females maintained significantly increased lifespan across all male exposure treatments. Furthermore, lifespan extension and relative fitness of mNSC-ablated females were maximized under intermediate exposure to males, and minimized under low and high exposure to males. Overall, our results suggest that wild-type levels of insulin signalling reduce female susceptibility to male-induced harm under intense sexual conflict, and may also protect females when mating opportunities are sub-optimally low. PMID:27457757

  3. High fat diet-induced TGF-β/Gbb signaling provokes insulin resistance through the tribbles expression

    PubMed Central

    Hong, Seung-Hyun; Kang, Moonyoung; Lee, Kyu-Sun; Yu, Kweon

    2016-01-01

    Hyperglycemia, hyperlipidemia, and insulin resistance are hallmarks of obesity-induced type 2 diabetes, which is often caused by a high-fat diet (HFD). However, the molecular mechanisms underlying HFD-induced insulin resistance have not been elucidated in detail. In this study, we established a Drosophila model to investigate the molecular mechanisms of HFD-induced diabetes. HFD model flies recapitulate mammalian diabetic phenotypes including elevated triglyceride and circulating glucose levels, as well as insulin resistance. Expression of glass bottom boat (gbb), a Drosophila homolog of mammalian transforming growth factor-β (TGF-β), is elevated under HFD conditions. Furthermore, overexpression of gbb in the fat body produced obese and insulin-resistant phenotypes similar to those of HFD-fed flies, whereas inhibition of Gbb signaling significantly ameliorated HFD-induced metabolic phenotypes. We also discovered that tribbles, a negative regulator of AKT, is a target gene of Gbb signaling in the fat body. Overexpression of tribbles in flies in the fat body phenocopied the metabolic defects associated with HFD conditions or Gbb overexpression, whereas tribbles knockdown rescued these metabolic phenotypes. These results indicate that HFD-induced TGF-β/Gbb signaling provokes insulin resistance by increasing tribbles expression. PMID:27484164

  4. High fat diet-induced TGF-β/Gbb signaling provokes insulin resistance through the tribbles expression.

    PubMed

    Hong, Seung-Hyun; Kang, Moonyoung; Lee, Kyu-Sun; Yu, Kweon

    2016-01-01

    Hyperglycemia, hyperlipidemia, and insulin resistance are hallmarks of obesity-induced type 2 diabetes, which is often caused by a high-fat diet (HFD). However, the molecular mechanisms underlying HFD-induced insulin resistance have not been elucidated in detail. In this study, we established a Drosophila model to investigate the molecular mechanisms of HFD-induced diabetes. HFD model flies recapitulate mammalian diabetic phenotypes including elevated triglyceride and circulating glucose levels, as well as insulin resistance. Expression of glass bottom boat (gbb), a Drosophila homolog of mammalian transforming growth factor-β (TGF-β), is elevated under HFD conditions. Furthermore, overexpression of gbb in the fat body produced obese and insulin-resistant phenotypes similar to those of HFD-fed flies, whereas inhibition of Gbb signaling significantly ameliorated HFD-induced metabolic phenotypes. We also discovered that tribbles, a negative regulator of AKT, is a target gene of Gbb signaling in the fat body. Overexpression of tribbles in flies in the fat body phenocopied the metabolic defects associated with HFD conditions or Gbb overexpression, whereas tribbles knockdown rescued these metabolic phenotypes. These results indicate that HFD-induced TGF-β/Gbb signaling provokes insulin resistance by increasing tribbles expression. PMID:27484164

  5. Swimming improves high-fat induced insulin resistance by regulating lipid and energy metabolism and the insulin pathway in rats.

    PubMed

    Song, An; Wang, Chao; Ren, Luping; Zhao, Jiajun

    2014-06-01

    In this study, we aimed to determine the preventive and therapeutic effects of swimming on insulin resistance in high-fat-fed rats. Sprague-Dawley rats were divided into 4 groups and fed for 8 weeks as follows: i) the control (Con) group fed a control diet; ii) the high-fat (HF) group fed a high-fat diet; iii) the treatment (ST) group fed a high-fat diet and trained with swimming from the 4th week; and iv) the prevention (SP) group fed a high-fat diet and trained with swimming from the 1st week of the experiment. A hyperinsulinemic-euglycemic clamp was used to evaluate the insulin sensitivity of the rats. The ultrastructure of the liver cells was observed by electron microscopy. Hepatic lipid accumulation was observed by Oil Red O staining. Quantitative RT-PCR and western blot analysis were performed to detect the expression of proteins related to lipid metabolism, energy metabolism and insulin signaling transduction. After 8 weeks of feeding, compared with the Con group, the glucose infusion rate (GIR) was significantly decreased; a significant lipid accumulation was observed in the liver, while the ultrastructure of the liver cells was damaged in the HF group. Proteins related to lipid metabolism in the liver and skeletal muscle, including FAT and FABP were upregulated, while CPT1 and PPAR levels were downregulated in the HF group. The levels of the energy-metabolism-related molecules, AMPKα2, PGC1α, PGC1β and MFN2 were downregulated in skeletal muscle in the HF group. The expression levels of insulin signaling transduction molecules, INSR, IRS1, PI3K/p85, AKT2 and GLUT4, as well as the phosphorylation levels of INSR, IRS1, PI3K/p85 and AKT2 were lower in skeletal muscles in the HF rats. Compared with HF group, the GIR levels were significantly increased in the ST and SP groups. Lipid accumulation and damage to the ultrastructure of the liver cells were improved in both groups. The expression of molecules related to lipid metabolism in the liver and skeletal

  6. Involvement of PKC{alpha} in insulin-induced PKC{delta} expression: Importance of SP-1 and NF{kappa}B transcription factors

    SciTech Connect

    Horovitz-Fried, Miriam; Sampson, Sanford R. . E-mail: sampsos@mail.biu.ac.il

    2007-01-05

    Protein kinase C delta (PKC{delta}) is a key molecule in insulin signaling essential for insulin-induced glucose transport in skeletal muscle. Recent studies in our laboratory have shown that insulin rapidly stimulates PKC{delta} activity and increases PKC{delta} protein and RNA levels, and that the SP-1 transcription factor is involved in insulin-induced transcription of the PKC{delta} gene. Activation of SP-1 involves serine phosphorylation and translocation to the nucleus. In this study we examined the possibility that PKC{alpha} might be involved in serine phosphorylation and activation of SP-1. We found that insulin rapidly phosphorylates and translocates SP-1. In the cytoplasm, SP-1 was constitutively associated with PKC{alpha}, and insulin stimulation caused these proteins to dissociate. In contrast, in the nucleus insulin induced an increase in association between PKC{alpha} and SP-1. PKC{alpha} inhibition blocked insulin-induced serine phosphorylation of SP-1 and its association with PKC{alpha} in the nucleus. Inhibition of PKC{alpha} also reduced the insulin-induced increase in PKC{delta} RNA and protein in the cytoplasmic and nuclear fractions. We also attempted to determine if another transcription factor might be involved in regulation of PKC{delta} expression. We earlier showed that insulin did not affect nuclear NF{kappa}B levels. Inhibition of NF{kappa}B, however, increased insulin-induced increase in PKC{delta} RNA and protein in the cytoplasmic and nuclear fractions. Surprisingly, this inhibition reduced the insulin-induced increase in cytoplasmic and nuclear PKC{alpha} RNA and protein. Inhibition of PKC{delta} reduced I{kappa}B{alpha} phosphorylation as well as NF{kappa}B activation. Thus, PKC{alpha} regulates insulin-induced PKC{delta} expression levels and this regulation involves activation of SP-1 and NF{kappa}B.

  7. 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

  8. IRS1Ser³⁰⁷ phosphorylation does not mediate mTORC1-induced insulin resistance.

    PubMed

    Herrema, Hilde; Lee, Jaemin; Zhou, Yingjiang; Copps, Kyle D; White, Morris F; Ozcan, Umut

    2014-01-10

    Increased mammalian target of rapamycin complex 1 (mTORC1) activity has been suggested to play important roles in development of insulin resistance in obesity. mTORC1 hyperactivity also increases endoplasmic reticulum (ER) stress, which in turn contributes to development of insulin resistance and glucose intolerance. Increased IRS1 phosphorylation at Ser307 in vitro is correlated with mTORC1- and ER stress-induced insulin resistance. This phosphorylation site correlates strongly with impaired insulin receptor signaling in diabetic mice and humans. In contrast, evidence from knock-in mice suggests that phosphorylation of IRS1 at Ser307 is actually required to maintain insulin sensitivity. To study the involvement of IRS1(Ser307) phosphorylation in mTORC1-mediated glucose intolerance and insulin sensitivity in vivo, we investigated the effects of liver specific TSC1 depletion in IRS1(Ser307Ala) mice and controls. Our results demonstrate that blockade of IRS1(Ser307) phosphorylation in vivo does not prevent mTORC1-mediated glucose intolerance and insulin resistance. PMID:24333417

  9. Insulin-induced decrease in protein phosphorylation in rat adipocytes not explained by decreased A-kinase activity

    SciTech Connect

    Egan, J.J.; Greenberg, A.S.; Chang, M.K.; Londos, C.

    1987-05-01

    In isolated rat adipocytes, insulin inhibits lipolysis to a greater extent than would be predicted by the decrease in (-/+)cAMP activity ratio of cAMP-dependent protein kinase (A-kinase), from which it was speculated that insulin promotes the dephosphorylation of hormone-sensitive lipase. They have examined the phosphorylation state of cellular proteins under conditions of varying A-kinase activities in the presence and absence of insulin. Protein phosphorylation was determined by SDS-PAGE electrophoresis of extracts from /sup 32/P-loaded cells; glycerol and A-kinase activity ratios were measured in the cytosolic extracts from control, non-radioactive cells. Increased protein phosphorylation in general occurred over the same range of A-kinase activity ratios, 0.1-0.3, associated with increased glycerol release. The insulin-induced decrease in lipolysis was associated with a decrease in the /sup 32/P content of several proteins, an effect not explained by the modest reduction in A-kinase activity by insulin. This effect of insulin on protein phosphorylation was lost as the A-kinase activity ratios exceeded 0.5. The results suggest that insulin promotes the dephosphorylation of those adipocyte proteins which are subject to phosphorylation by A-kinase.

  10. Rosuvastatin Treatment Affects Both Basal and Glucose-Induced Insulin Secretion in INS-1 832/13 Cells.

    PubMed

    Salunkhe, Vishal A; Elvstam, Olof; Eliasson, Lena; Wendt, Anna

    2016-01-01

    Rosuvastatin is a member of the statin family. Like the other statins it is prescribed to lower cholesterol levels and thereby reduce the risk of cardiovascular events. Rosuvastatin lowers the cholesterol levels by inhibiting the key enzyme 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoA reductase) in the cholesterol producing mevalonate pathway. It has been recognized that apart from their beneficial lipid lowering effects, statins also exhibit diabetogenic properties. The molecular mechanisms behind these remain unresolved. To investigate the effects of rosuvastatin on insulin secretion, we treated INS-1 832/13 cells with varying doses (20 nM to 20 μM) of rosuvastatin for 48 h. At concentrations of 2 μM and above basal insulin secretion was significantly increased. Using diazoxide we could determine that rosuvastatin did not increase basal insulin secretion by corrupting the KATP channels. Glucose-induced insulin secretion on the other hand seemed to be affected differently at different rosuvastatin concentrations. Rosuvastatin treatment (20 μM) for 24-48 h inhibited voltage-gated Ca(2+) channels, which lead to reduced depolarization-induced exocytosis of insulin-containing granules. At lower concentrations of rosuvastatin (≤ 2 μM) the stimulus-secretion coupling pathway was intact downstream of the KATP channels as assessed by the patch clamp technique. However, a reduction in glucose-induced insulin secretion could be observed with rosuvastatin concentrations as low as 200 nM. The inhibitory effects of rosuvastatin on glucose-induced insulin secretion could be reversed with mevalonate, but not squalene, indicating that rosuvastatin affects insulin secretion through its effects on the mevalonate pathway, but not through the reduction of cholesterol biosynthesis. Taken together, these data suggest that rosuvastatin has the potential to increase basal insulin secretion and reduce glucose-induced insulin secretion. The latter is possibly an unavoidable

  11. Rosuvastatin Treatment Affects Both Basal and Glucose-Induced Insulin Secretion in INS-1 832/13 Cells

    PubMed Central

    Salunkhe, Vishal A.; Elvstam, Olof; Eliasson, Lena; Wendt, Anna

    2016-01-01

    Rosuvastatin is a member of the statin family. Like the other statins it is prescribed to lower cholesterol levels and thereby reduce the risk of cardiovascular events. Rosuvastatin lowers the cholesterol levels by inhibiting the key enzyme 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoA reductase) in the cholesterol producing mevalonate pathway. It has been recognized that apart from their beneficial lipid lowering effects, statins also exhibit diabetogenic properties. The molecular mechanisms behind these remain unresolved. To investigate the effects of rosuvastatin on insulin secretion, we treated INS-1 832/13 cells with varying doses (20 nM to 20 μM) of rosuvastatin for 48 h. At concentrations of 2 μM and above basal insulin secretion was significantly increased. Using diazoxide we could determine that rosuvastatin did not increase basal insulin secretion by corrupting the KATP channels. Glucose-induced insulin secretion on the other hand seemed to be affected differently at different rosuvastatin concentrations. Rosuvastatin treatment (20 μM) for 24–48 h inhibited voltage-gated Ca2+ channels, which lead to reduced depolarization-induced exocytosis of insulin-containing granules. At lower concentrations of rosuvastatin (≤ 2 μM) the stimulus-secretion coupling pathway was intact downstream of the KATP channels as assessed by the patch clamp technique. However, a reduction in glucose-induced insulin secretion could be observed with rosuvastatin concentrations as low as 200 nM. The inhibitory effects of rosuvastatin on glucose-induced insulin secretion could be reversed with mevalonate, but not squalene, indicating that rosuvastatin affects insulin secretion through its effects on the mevalonate pathway, but not through the reduction of cholesterol biosynthesis. Taken together, these data suggest that rosuvastatin has the potential to increase basal insulin secretion and reduce glucose-induced insulin secretion. The latter is possibly an unavoidable

  12. Interaction of myocardial insulin receptor and IGF receptor signaling in exercise-induced cardiac hypertrophy

    PubMed Central

    Ikeda, Hiroyuki; Shiojima, Ichiro; Ozasa, Yukako; Yoshida, Masashi; Holzenberger, Martin; Kahn, C Ronald; Walsh, Kenneth; Igarashi, Takashi; Abel, E Dale; Komuro, Issei

    2016-01-01

    Insulin-like growth factor-1 (IGF-1) signaling has recently been implicated in the development of cardiac hypertrophy after long-term endurance training, via mechanisms that may involve energetic stress. Given the potential overlap of insulin and IGF-1 signaling we sought to determine if both signaling pathways could contribute to exercise-induced cardiac hypertrophy following shorter-term exercise training. Studies were performed in mice with cardiac-specific IGF-1 receptor (IGF1R) knockout (CIGFRKO), mice with cardiac-specific insulin receptor (IR) knockout (CIRKO), CIGFRKO mice that lacked one IR allele in cardiomyocytes (IGFR−/−IR+/−), and CIRKO mice that lacked one IGF1R allele in cardiomyocytes (IGFR+/−IR−/−). Intravenous administration of IGF-1 or 75 hours of swimming over 4 weeks increased IGF1R tyrosine phosphorylation in the heart in control and CIRKO mice but not in CIGFRKO mice. Intriguingly, IR tyrosine phosphorylation in the heart was also increased following IGF-1 administration or exercise training in control and CIGFRKO mice but not in CIRKO mice. The extent of cardiac hypertrophy following exercise training in CIGFRKO and CIRKO mice was comparable to that in control mice. In contrast, exercise-induced cardiac hypertrophy was significantly attenuated in IGFR−/−IR+/− and IGFR+/−IR−/− mice. Thus, IGF-1 and exercise activates both IGF1R and IR in the heart, and IGF1R- and IR-mediated signals may serve redundant roles in the hypertrophic responses of the heart to exercise training. PMID:19744489

  13. The effect of oxytocin on the plasma glucagon response to insulin-induced hypoglycaemia in man.

    PubMed

    Page, S R; Ang, V T; Jackson, R; Nussey, S S

    1990-01-01

    The presence of the classical neurohypophyseal hormone oxytocin has recently been described in the human pancreas in considerably higher concentrations than those found in peripheral plasma. Evidence in animals and man suggests that oxytocin can directly stimulate the secretion of glucagon from pancreatic islets. In order to investigate a possible paracrine role for oxytocin in the regulation of glucagon secretion we have studied the effect of oxytocin on the plasma glucagon response to insulin-induced hypoglycaemia in 10 lean fasted male subjects. Intravenous insulin tests were performed in random order with or without oxytocin infusion (2 U bolus injection; 111 mU/min for 2 hours). Blood sugar nadir occurred at the onset of symptoms (time S) with no significant differences between oxytocin and saline infusions (saline S = 24 +/- 2.3 min; oxytocin S = 23.3 +/- 2.7 min). There was no significant change in peripheral plasma oxytocin concentrations during saline infusion. During the oxytocin infusion plasma oxytocin concentrations rose from 1.05 +/- 0.1 (mean +/- SEM) pmol/l to a peak of 632 +/- 179 pmol/l and remained elevated throughout the study. Peak plasma glucagon concentrations occurred at S + 10 mins with no significant differences in peak values (saline 200 +/- 26.3 pg/ml; oxytocin 207 +/- 23.6 pg/ml) between saline and oxytocin infusions. The data suggest that oxytocin at concentrations up to 6.3 X 10(-10) M has no effect on the decline or recovery of blood glucose concentrations or on the plasma glucagon response to insulin-induced hypoglycaemia. PMID:2210021

  14. Smad3 deficiency protects mice from obesity-induced podocyte injury that precedes insulin resistance.

    PubMed

    Sun, Yu B Y; Qu, Xinli; Howard, Victor; Dai, Lie; Jiang, Xiaoyun; Ren, Yi; Fu, Ping; Puelles, Victor G; Nikolic-Paterson, David J; Caruana, Georgina; Bertram, John F; Sleeman, Mark W; Li, Jinhua

    2015-08-01

    Signaling by TGF-β/Smad3 plays a key role in renal fibrosis. As obesity is one of the major risk factors of chronic and end-stage renal disease, we studied the role of Smad3 signaling in the pathogenesis of obesity-related renal disease. After switching to a high fat diet, the onset of Smad3 C-terminal phosphorylation, increase in albuminuria, and the early stages of peripheral and renal insulin resistance occurred at 1 day, and 4 and 8 weeks, respectively, in C57BL/6 mice. The loss of synaptopodin, a functional marker of podocytes, and phosphorylation of the Smad3 linker region (T179 and S213) appeared after 4 weeks of the high fat diet. This suggests a temporal pattern of Smad3 signaling activation leading to kidney injury and subsequent insulin resistance in the development of obesity-related renal disease. In vivo, Smad3 knockout attenuated the high fat diet-induced proteinuria, renal fibrosis, overall podocyte injury, and mitochondrial dysfunction in podocytes. In vitro palmitate caused a rapid activation of Smad3 in 30 min, loss of synaptopodin in 2 days, and impaired insulin signaling in 3 days in isolated mouse podocytes. Blockade of either Smad3 phosphorylation by SIS3 (a Smad3 inhibitor) or T179 phosphorylation by flavopiridol (a CDK9 inhibitor) prevented the palmitate-induced loss of synaptopodin and mitochondrial function in podocytes. Thus, Smad3 signaling plays essential roles in obesity-related renal disease and may be a novel therapeutic target. PMID:25945408

  15. Para-Tyrosine Supplementation Improves Insulin- and Liraglutide- Induced Vasorelaxation in Cholesterol-Fed Rats.

    PubMed

    Sélley, Eszter; Kun, Szilárd; Kürthy, Mária; Kovács, Tibor; Wittmann, István; Molnár, Gergo A

    2015-01-01

    Former data of our workgroup indicated that the accumulation of oxidized amino acids (meta- and ortho-tyrosine) due to oxidative stress may play an important role in the impaired insulininduced vasoactive properties of different arterial segments. There are evidences, that incorporation of these amino acids into cellular proteins leads to certain hormonal resistances, which might be restored by supplementation with the physiologic isoform, para-tyrosine. Rats in the control group were kept on a regular diet, rats in the cholesterol-fed group received high-fat diet, while the third group of rats received high-fat diet with para-tyrosine supplementation for 16 weeks. Plasma cholesterol level was significantly higher in the cholesterol-fed group, while the level of cholesterol in the cholesterol+para-tyrosine group did not differ significantly from that of the controls. Plasma level of insulin after glucose stimulation was decreased in the cholesterol-fed group, while that in the para-tyrosine supplemented group did not differ significantly from the controls. Vascular para-, meta- and ortho-tyrosine content was measured with HPLC. Elevated vascular meta-tyrosine/para-tyrosine ratio of cholesterol fed rats could be avoided by para-tyrosine supplementation. Vascular response of the thoracic aorta to insulin and liraglutide was assessed by a DMT multi-myograph. Cholesterol feeding resulted in vascular insulin-and liraglutide resistance, which was restored by para-tyrosine supplementation. Incorporation of the oxidative stress induced pathological tyrosine isoforms leads to vascular-hormone-resistances. We show that the physiological amino acid para-tyrosine is capable of restoring hypercholesterolemia-induced increased meta-tyrosine content of the vascular wall, thus attenuating functional vascular damage. PMID:26202368

  16. MicroRNA-29a induces insulin resistance by targeting PPARδ in skeletal muscle cells

    PubMed Central

    ZHOU, YUEHUA; GU, PINGQING; SHI, WEIJIE; LI, JINGYUN; HAO, QUN; CAO, XIAOMEI; LU, QIN; ZENG, YU

    2016-01-01

    Intrauterine growth retardation (IUGR) induces metabolic syndrome, which is often characterized by insulin resistance (IR), in adults. Previous research has shown that microRNAs (miRNAs or miRs) play a role in the target genes involved in this process, but the mechanisms remain unclear. In the present study, we examined miRNA profiles using samples of skeletal muscles from both IUGR and control rat offspring whose mothers were fed either a protein-restricted diet or a diet which involved normal amounts of protein during pregnancy, respectively. miR-29a was found to be upregulated in the skeletal muscles of IUGR offspring. The luciferase reporter assay confirmed the direct interaction between miR-29a and peroxisome proliferator-activated receptor δ (PPARδ). Overexpression of miR-29a in the skeletal muscle cell line C2C12 suppressed the expression of its target gene PPARδ, which, in turn, influenced the expression of its coactivator, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). Thus, PPARδ/PGC-1α-dependent signals together reduced insulin-dependent glucose uptake and adenosine triphosphate (ATP) production. Overexpression of miR-29a also caused a decrease in levels of glucose transporter 4 (GLUT4), the most important glucose transporter in skeletal muscle, which partially induced a decrease insulin-dependent glucose uptake. These findings provide evidence for a novel micro-RNA-mediated mechanism of PPARδ regulation, and we also noted the IR-promoting actions of miR-29a in skeletal muscles of IUGR. PMID:26936652

  17. Titanium dioxide nanoparticles increase plasma glucose via reactive oxygen species-induced insulin resistance in mice.

    PubMed

    Hu, Hailong; Guo, Qian; Wang, Changlin; Ma, Xiao; He, Hongjuan; Oh, Yuri; Feng, Yujie; Wu, Qiong; Gu, Ning

    2015-10-01

    There have been few reports about the possible toxic effects of titanium dioxide (TiO2 ) nanoparticles on the endocrine system. We explored the endocrine effects of oral administration to mice of anatase TiO2 nanoparticles (0, 64 and 320 mg kg(-1) body weight per day to control, low-dose and high-dose groups, respectively, 7 days per week for 14 weeks). TiO2 nanoparticles were characterized by scanning and transmission electron microscopy (TEM) and dynamic light scattering (DLS), and their physiological distribution was investigated by inductively coupled plasma. Biochemical analyzes included plasma glucose, insulin, heart blood triglycerides (TG), free fatty acid (FFA), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6 and reactive oxygen species (ROS)-related markers (total SOD, GSH and MDA). Phosphorylation of IRS1, Akt, JNK1, and p38 MAPK were analyzed by western blotting. Increased titanium levels were found in the liver, spleen, small intestine, kidney and pancreas. Biochemical analyzes showed that plasma glucose significantly increased whereas there was no difference in plasma insulin secretion. Increased ROS levels were found in serum and the liver, as evidenced by reduced total SOD activity and GSH level and increased MDA content. Western blotting showed that oral administration of TiO2 nanoparticles induced insulin resistance (IR) in mouse liver, shown by increased phosphorylation of IRS1 (Ser307) and reduced phosphorylation of Akt (Ser473). The pathway by which TiO2 nanoparticles increase ROS-induced IR were included in the inflammatory response and phosphokinase, as shown by increased serum levels of TNF-α and IL-6 and increased phosphorylation of JNK1 and p38 MAPK in liver. These results show that oral administration of TiO2 nanoparticles increases ROS, resulting in IR and increasing plasma glucose in mice. PMID:25826740

  18. Silymarin ameliorates fructose induced insulin resistance syndrome by reducing de novo hepatic lipogenesis in the rat.

    PubMed

    Prakash, Prem; Singh, Vishal; Jain, Manish; Rana, Minakshi; Khanna, Vivek; Barthwal, Manoj Kumar; Dikshit, Madhu

    2014-03-15

    High dietary fructose causes insulin resistance syndrome (IRS), primarily due to simultaneous induction of genes involved in glucose, lipid and mitochondrial oxidative metabolism. The present study evaluates effect of a hepatoprotective agent, silymarin (SYM) on fructose-induced metabolic abnormalities in the rat and also assessed the associated thrombotic complications. Wistar rats were kept on high fructose (HFr) diet throughout the 12-week study duration (9 weeks of HFr feeding and subsequently 3 weeks of HFr plus SYM oral administration [once daily]). SYM treatment significantly reduced the HFr diet-induced increase expression of peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α/β, peroxisome proliferator-activated receptor (PPAR)-α, forkhead box protein O1 (FOXO1), sterol regulatory element binding protein (SREBP)-1c, liver X receptor (LXR)-β, fatty acid synthase (FAS) and PPARγ genes in rat liver. SYM also reduced HFr diet mediated increase in plasma triglycerides (TG), non-esterified fatty acids (NEFA), uric acid, malondialdehyde (MDA), total nitrite and pro-inflammatory cytokines (C-reactive protein [CRP], interleukin-6 [IL-6], interferon-gamma [IFN-γ] and tumor necrosis factor [TNF]) levels. Moreover, SYM ameliorated HFr diet induced reduction in glucose utilization and endothelial dysfunction. Additionally, SYM significantly reduced platelet activation (adhesion and aggregation), prolonged ferric chloride-induced blood vessel occlusion time and protected against exacerbated myocardial ischemia reperfusion (MI-RP) injury. SYM treatment prevented HFr induced mRNA expression of hepatic PGC-1α/β and also its target transcription factors which was accompanied with recovery in insulin sensitivity and reduced propensity towards thrombotic complications and aggravated MI-RP injury. PMID:24486395

  19. N-Acetylneuraminic Acid Supplementation Prevents High Fat Diet-Induced Insulin Resistance in Rats through Transcriptional and Nontranscriptional Mechanisms

    PubMed Central

    Yida, Zhang; Imam, Mustapha Umar; Ismail, Maznah; Ismail, Norsharina; Azmi, Nur Hanisah; Wong, Waiteng; Altine Adamu, Hadiza; Md Zamri, Nur Diyana; Ideris, Aini; Abdullah, Maizaton Atmadini

    2015-01-01

    N-Acetylneuraminic acid (Neu5Ac) is a biomarker of cardiometabolic diseases. In the present study, we tested the hypothesis that dietary Neu5Ac may improve cardiometabolic indices. A high fat diet (HFD) + Neu5Ac (50 or 400 mg/kg BW/day) was fed to rats and compared with HFD + simvastatin (10 mg/kg BW/day) or HFD alone for 12 weeks. Weights and serum biochemicals (lipid profile, oral glucose tolerance test, leptin, adiponectin, and insulin) were measured, and mRNA levels of insulin signaling genes were determined. The results indicated that low and high doses of sialic acid (SA) improved metabolic indices, although only the oral glucose tolerance test, serum triglycerides, leptin, and adiponectin were significantly better than those in the HFD and HFD + simvastatin groups (P < 0.05). Furthermore, the results showed that only high-dose SA significantly affected the transcription of hepatic and adipose tissue insulin signaling genes. The data suggested that SA prevented HFD-induced insulin resistance in rats after 12 weeks of administration through nontranscriptionally mediated biochemical changes that may have differentially sialylated glycoprotein structures at a low dose. At higher doses, SA induced transcriptional regulation of insulin signaling genes. These effects suggest that low and high doses of SA may produce similar metabolic outcomes in relation to insulin sensitivity through multiple mechanisms. These findings are worth studying further. PMID:26688813

  20. N-Acetylneuraminic Acid Supplementation Prevents High Fat Diet-Induced Insulin Resistance in Rats through Transcriptional and Nontranscriptional Mechanisms.

    PubMed

    Yida, Zhang; Imam, Mustapha Umar; Ismail, Maznah; Ismail, Norsharina; Azmi, Nur Hanisah; Wong, Waiteng; Altine Adamu, Hadiza; Md Zamri, Nur Diyana; Ideris, Aini; Abdullah, Maizaton Atmadini

    2015-01-01

    N-Acetylneuraminic acid (Neu5Ac) is a biomarker of cardiometabolic diseases. In the present study, we tested the hypothesis that dietary Neu5Ac may improve cardiometabolic indices. A high fat diet (HFD) + Neu5Ac (50 or 400 mg/kg BW/day) was fed to rats and compared with HFD + simvastatin (10 mg/kg BW/day) or HFD alone for 12 weeks. Weights and serum biochemicals (lipid profile, oral glucose tolerance test, leptin, adiponectin, and insulin) were measured, and mRNA levels of insulin signaling genes were determined. The results indicated that low and high doses of sialic acid (SA) improved metabolic indices, although only the oral glucose tolerance test, serum triglycerides, leptin, and adiponectin were significantly better than those in the HFD and HFD + simvastatin groups (P < 0.05). Furthermore, the results showed that only high-dose SA significantly affected the transcription of hepatic and adipose tissue insulin signaling genes. The data suggested that SA prevented HFD-induced insulin resistance in rats after 12 weeks of administration through nontranscriptionally mediated biochemical changes that may have differentially sialylated glycoprotein structures at a low dose. At higher doses, SA induced transcriptional regulation of insulin signaling genes. These effects suggest that low and high doses of SA may produce similar metabolic outcomes in relation to insulin sensitivity through multiple mechanisms. These findings are worth studying further. PMID:26688813

  1. The protective effects of insulin and natural honey against hippocampal cell death in streptozotocin-induced diabetic rats.

    PubMed

    Jafari Anarkooli, Iraj; Barzegar Ganji, Hossein; Pourheidar, Maryam

    2014-01-01

    We investigated the effects of insulin and honey as antioxidants to prevent the hippocampal cell death in streptozotocin-induced diabetic rats. We selected sixty Wister rats (5 groups of 12 animals each), including the control group (C), and four diabetic groups (control (D) and 3 groups treated with insulin (I), honey (H), and insulin plus honey (I + H)). Diabetes was induced by streptozotocin injection (IP, 60 mg/kg). Six weeks after the induction of diabetes, the group I received insulin (3-4 U/kg/day, SC), group H received honey (5 mg/kg/day, IP), and group I + H received a combination of the above at the same dose. Groups C and D received normal saline. Two weeks after treatment, rats were sacrificed and the hippocampus was extracted. Neuronal cell death in the hippocampal region was examined using trypan blue assay, "H & E" staining, and TUNEL assay. Cell viability assessment showed significantly lower number of living cells in group D than in group C. Besides, the mean number of living cells was significantly higher in group I, H, and I + H compared to group D. Therefore, it can be concluded that the treatment of the diabetic rats with insulin, honey, and a combination of insulin and honey can prevent neuronal cell death in different hippocampal areas of the studied samples. PMID:24745031

  2. The Protective Effects of Insulin and Natural Honey against Hippocampal Cell Death in Streptozotocin-Induced Diabetic Rats

    PubMed Central

    Jafari Anarkooli, Iraj; Barzegar Ganji, Hossein; Pourheidar, Maryam

    2014-01-01

    We investigated the effects of insulin and honey as antioxidants to prevent the hippocampal cell death in streptozotocin-induced diabetic rats. We selected sixty Wister rats (5 groups of 12 animals each), including the control group (C), and four diabetic groups (control (D) and 3 groups treated with insulin (I), honey (H), and insulin plus honey (I + H)). Diabetes was induced by streptozotocin injection (IP, 60 mg/kg). Six weeks after the induction of diabetes, the group I received insulin (3-4 U/kg/day, SC), group H received honey (5 mg/kg/day, IP), and group I + H received a combination of the above at the same dose. Groups C and D received normal saline. Two weeks after treatment, rats were sacrificed and the hippocampus was extracted. Neuronal cell death in the hippocampal region was examined using trypan blue assay, “H & E” staining, and TUNEL assay. Cell viability assessment showed significantly lower number of living cells in group D than in group C. Besides, the mean number of living cells was significantly higher in group I, H, and I + H compared to group D. Therefore, it can be concluded that the treatment of the diabetic rats with insulin, honey, and a combination of insulin and honey can prevent neuronal cell death in different hippocampal areas of the studied samples. PMID:24745031

  3. Effect of simulated microgravity on endocrine response to insulin-induced hypoglycemia in physically fit men.

    PubMed

    Ksinantova, L; Koska, J; Kvetnansky, R; Marko, M; Hamar, D; Vigas, M

    2002-03-01

    Adaptation to microgravity is associated with alteration in some endocrine functions. In the present longitudinal study, the counterregulatory hormonal response to insulin-induced hypoglycemia (ITT, 0.1 IU/kg short acting insulin i. v.) was evaluated under simulated microgravity conditions in 15 physically fit subjects. ITT was performed at the beginning of the investigation, and again after completion of 6 weeks of endurance training and after a subsequent period of 4 days of head-down bed rest at a backward tilt of 6 degrees from the horizontal. Endurance training showed a significant increase in maximal aerobic capacity in previously well-trained subjects (increase by 12 %), as well as on attenuation of counterregulatory response of epinephrine to hypoglycemia. After 4 days of bed rest, basal concentrations of plasma norepinephrine was diminished (p < 0.002) and plasma renin activity was enhanced (p < 0.02). After bed rest, decreased responses of the two catecholamines (norepinephrine, p < 0.001; epinephrine, p < 0.001), growth hormone (p < 0.001), and cortisol (p < 0.05) were observed. Response of plasma renin activity after bed rest was increased (p < 0.01). This longitudinal study indicated that 4 days of bed rest in endurance-trained subjects induced increased response of PRA to hypoglycemia and attenuation of other counterregulatory neuroendocrine responses. PMID:11972306

  4. Effect of a polyphenol-rich extract from Aloe vera gel on experimentally induced insulin resistance in mice.

    PubMed

    Pérez, Yolanda Y; Jiménez-Ferrer, Enrique; Zamilpa, Alejandro; Hernández-Valencia, Marcelino; Alarcón-Aguilar, Francisco J; Tortoriello, Jaime; Román-Ramos, Rubén

    2007-01-01

    Insulin resistance, which precedes type 2 diabetes mellitus (T2DM), is a widespread pathology associated with the metabolic syndrome, myocardial ischemia, and hypertension. Finding an adequate treatment for this pathology is an important goal in medicine. The purpose of the present research was to investigate the effect of an extract from Aloe vera gel containing a high concentration of polyphenols on experimentally induced insulin resistance in mice. A polyphenol-rich Aloe vera extract (350 mg/kg) with known concentrations of aloin (181.7 mg/g) and aloe-emodin (3.6 mg/g) was administered orally for a period of 4 weeks to insulin resistant ICR mice. Pioglitazone (50 mg/kg) and bi-distilled water were used as positive and negative controls respectively. Body weight, food intake, and plasma concentrations of insulin and glucose were measured and insulin tolerance tests were performed. The insulin resistance value was calculated using the homeostasis model assessment for insulin resistance (HOMA-IR) formula. Results showed that the polyphenol-rich extract from Aloe vera was able to decrease significantly both body weight (p < 0.008) and blood glucose levels (p < 0.005) and to protect animals against unfavorable results on HOMA-IR, which was observed in the negative control group. The highest glucose levels during the insulin tolerance curve test were in the negative control group when compared to the Aloe vera extract and pioglitazone treated mice (p < 0.05). In conclusion, Aloe vera gel could be effective for the control of insulin resistance. PMID:18186589

  5. Low intensity exercise prevents disturbances in rat cardiac insulin signaling and endothelial nitric oxide synthase induced by high fructose diet.

    PubMed

    Stanišić, Jelena; Korićanac, Goran; Ćulafić, Tijana; Romić, Snježana; Stojiljković, Mojca; Kostić, Milan; Pantelić, Marija; Tepavčević, Snežana

    2016-01-15

    Increase in fructose consumption together with decrease in physical activity contributes to the development of metabolic syndrome and consequently cardiovascular diseases. The current study examined the preventive role of exercise on defects in cardiac insulin signaling and function of endothelial nitric oxide synthase (eNOS) in fructose fed rats. Male Wistar rats were divided into control, sedentary fructose (received 10% fructose for 9 weeks) and exercise fructose (additionally exposed to low intensity exercise) groups. Concentration of triglycerides, glucose, insulin and visceral adipose tissue weight were determined to estimate metabolic syndrome development. Expression and/or phosphorylation of cardiac insulin receptor (IR), insulin receptor substrate 1 (IRS1), tyrosine-specific protein phosphatase 1B (PTP1B), Akt, extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and eNOS were evaluated. Fructose overload increased visceral adipose tissue, insulin concentration and homeostasis model assessment index. Exercise managed to decrease visceral adiposity and insulin level and to increase insulin sensitivity. Fructose diet increased level of cardiac PTP1B and pIRS1 (Ser307), while levels of IR and ERK1/2, as well as pIRS1 (Tyr 632), pAkt (Ser473, Thr308) and pERK1/2 were decreased. These disturbances were accompanied by reduced phosphorylation of eNOS at Ser1177. Exercise managed to prevent most of the disturbances in insulin signaling caused by fructose diet (except phosphorylation of IRS1 at Tyr 632 and phosphorylation and protein expression of ERK1/2) and consequently restored function of eNOS. Low intensity exercise could be considered as efficient treatment of cardiac insulin resistance induced by fructose diet. PMID:26644274

  6. Insulin induced translocation of Na+/K+-ATPase is decreased in the heart of streptozotocin diabetic rats

    PubMed Central

    Rosta, Klara; Tulassay, Eszter; Enzsoly, Anna; Ronai, Katalin; Szantho, Ambrus; Pandics, Tamas; Fekete, Andrea; Mandl, Peter; Ver, Agota

    2009-01-01

    Aim: To investigate the effect of acute insulin administration on the subcellular localization of Na+/K+-ATPase isoforms in cardiac muscle of healthy and streptozotocin-induced diabetic rats. Methods: Membrane fractions were isolated with subcellular fractionation and with cell surface biotinylation technique. Na+/K+-ATPase subunit isoforms were analysed with ouabain binding assay and Western blotting. Enzyme activity was measured using 3-O-methylfluorescein-phosphatase activity. Results: In control rat heart muscle α1 isoform of Na+/K+ ATPase resides mainly in the plasma membrane fraction, while α2 isoform in the intracellular membrane pool. Diabetes decreased the abundance of α1 isoform (25 %, P<0.05) in plasma membrane and α2 isoform (50%, P<0.01) in the intracellular membrane fraction. When plasma membrane fractions were isolated by discontinuous sucrose gradients, insulin-stimulated translocation of α2- but not α1-subunits was detected. α1-Subunit translocation was only detectable by cell surface biotinylation technique. After insulin administration protein level of α2 increased by 3.3-fold, α1 by 1.37-fold and β1 by 1.51-fold (P<0.02) in the plasma membrane of control, and less than 1.92-fold (P<0.02), 1.19-fold (not significant) and 1.34-fold (P<0.02) in diabetes. The insulin-induced translocation was wortmannin sensitive. Conclusion: This study demonstrate that insulin influences the plasma membrane localization of Na+/K+-ATPase isoforms in the heart. α2 isoform translocation is the most vulnerable to the reduced insulin response in diabetes. α1 isoform also translocates in response to insulin treatment in healthy rat. Insulin mediates Na+/K+-ATPase α1- and α2-subunit translocation to the cardiac muscle plasma membrane via a PI3-kinase-dependent mechanism. PMID:19915586

  7. Mitochondrial dysfunction precedes depression of AMPK/AKT signaling in insulin resistance induced by high glucose in primary cortical neurons.

    PubMed

    Peng, Yunhua; Liu, Jing; Shi, Le; Tang, Ying; Gao, Dan; Long, Jiangang; Liu, Jiankang

    2016-06-01

    Recent studies have demonstrated brain insulin signaling impairment and mitochondrial dysfunction in diabetes. Hyperinsulinemia and hyperlipidemia arising from diabetes have been linked to neuronal insulin resistance, and hyperglycemia induces peripheral sensory neuronal impairment and mitochondrial dysfunction. However, how brain glucose at diabetic conditions elicits cortical neuronal insulin signaling impairment and mitochondrial dysfunction remains unknown. In the present study, we cultured primary cortical neurons with high glucose levels and investigated the neuronal mitochondrial function and insulin response. We found that mitochondrial function was declined in presence of 10 mmol/L glucose, prior to the depression of AKT signaling in primary cortical neurons. We further demonstrated that the cerebral cortex of db/db mice exhibited both insulin resistance and loss of mitochondrial complex components. Moreover, we found that adenosine monophosphate-activated protein kinase (AMPK) inactivation is involved in high glucose-induced mitochondrial dysfunction and insulin resistance in primary cortical neurons and neuroblastoma cells, as well as in cerebral cortex of db/db mice, and all these impairments can be rescued by mitochondrial activator, resveratrol. Taken together, our results extend the finding that high glucose (≥10 mmol/L) comparable to diabetic brain extracellular glucose level leads to neuronal mitochondrial dysfunction and resultant insulin resistance, and targeting mitochondria-AMPK signaling might be a promising strategy to protect against diabetes-related neuronal impairment in central nerves system. We found that high glucose (≥10 mmol/L), comparable to diabetic brain extracellular glucose level, leads to neuronal mitochondrial dysfunction and resultant insulin resistance in an AMPK-dependent manner, and targeting mitochondria-AMPK signaling might be a promising strategy to protect against diabetes-related neuronal impairment in central

  8. Resveratrol attenuates intermittent hypoxia-induced macrophage migration to visceral white adipose tissue and insulin resistance in male mice.

    PubMed

    Carreras, Alba; Zhang, Shelley X L; Almendros, Isaac; Wang, Yang; Peris, Eduard; Qiao, Zhuanhong; Gozal, David

    2015-02-01

    Chronic intermittent hypoxia during sleep (IH), as occurs in sleep apnea, promotes systemic insulin resistance. Resveratrol (Resv) has been reported to ameliorate high-fat diet-induced obesity, inflammation, and insulin resistance. To examine the effect of Resv on IH-induced metabolic dysfunction, male mice were subjected to IH or room air conditions for 8 weeks and treated with either Resv or vehicle (Veh). Fasting plasma levels of glucose, insulin, and leptin were obtained, homeostatic model assessment of insulin resistance index levels were calculated, and insulin sensitivity tests (phosphorylated AKT [also known as protein kinase B]/total AKT) were performed in 2 visceral white adipose tissue (VWAT) depots (epididymal [Epi] and mesenteric [Mes]) along with flow cytometry assessments for VWAT macrophages and phenotypes (M1 and M2). IH-Veh and IH-Resv mice showed initial reductions in food intake with later recovery, with resultant lower body weights after 8 weeks but with IH-Resv showing better increases in body weight vs IH-Veh. IH-Veh and IH-Resv mice exhibited lower fasting glucose levels, but only IH-Veh had increased homeostatic model assessment of insulin resistance index vs all 3 other groups. Leptin levels were preserved in IH-Veh but were significantly lower in IH-Resv. Reduced VWAT phosphorylated-AKT/AKT responses to insulin emerged in both Mes and Epi in IH-Veh but normalized in IH-Resv. Increases total macrophage counts and in M1 to M2 ratios occurred in IH-Veh Mes and Epi compared all other 3 groups. Thus, Resv ameliorates food intake and weight gain during IH exposures and markedly attenuates VWAT inflammation and insulin resistance, thereby providing a potentially useful adjunctive therapy for metabolic morbidity in the context of sleep apnea. PMID:25406018

  9. Genetic ablation of lymphocytes and cytokine signaling in nonobese diabetic mice prevents diet-induced obesity and insulin resistance.

    PubMed

    Friedline, Randall H; Ko, Hwi Jin; Jung, Dae Young; Lee, Yongjin; Bortell, Rita; Dagdeviren, Sezin; Patel, Payal R; Hu, Xiaodi; Inashima, Kunikazu; Kearns, Caitlyn; Tsitsilianos, Nicholas; Shafiq, Umber; Shultz, Leonard D; Lee, Ki Won; Greiner, Dale L; Kim, Jason K

    2016-03-01

    Obesity is characterized by a dysregulated immune system, which may causally associate with insulin resistance and type 2 diabetes. Despite widespread use of nonobese diabetic (NOD) mice, NOD with severe combined immunodeficiency (scid) mutation (SCID) mice, and SCID bearing a null mutation in the IL-2 common γ chain receptor (NSG) mice as animal models of human diseases including type 1 diabetes, the underlying metabolic effects of a genetically altered immune system are poorly understood. For this, we performed a comprehensive metabolic characterization of these mice fed chow or after 6 wk of a high-fat diet. We found that NOD mice had ∼50% less fat mass and were 2-fold more insulin sensitive, as measured by hyperinsulinemic-euglycemic clamp, than C57BL/6 wild-type mice. SCID mice were also more insulin sensitive with increased muscle glucose metabolism and resistant to diet-induced obesity due to increased energy expenditure (∼10%) and physical activity (∼40%) as measured by metabolic cages. NSG mice were completely protected from diet-induced obesity and insulin resistance with significant increases in glucose metabolism in peripheral organs. Our findings demonstrate an important role of genetic background, lymphocytes, and cytokine signaling in diet-induced obesity and insulin resistance. PMID:26644351

  10. Palmitate-induced inflammatory pathways in human adipose microvascular endothelial cells promote monocyte adhesion and impair insulin transcytosis.

    PubMed

    Pillon, Nicolas J; Azizi, Paymon M; Li, Yujin E; Liu, Jun; Wang, Changsen; Chan, Kenny L; Hopperton, Kathryn E; Bazinet, Richard P; Heit, Bryan; Bilan, Philip J; Lee, Warren L; Klip, Amira

    2015-07-01

    Obesity is associated with inflammation and immune cell recruitment to adipose tissue, muscle and intima of atherosclerotic blood vessels. Obesity and hyperlipidemia are also associated with tissue insulin resistance and can compromise insulin delivery to muscle. The muscle/fat microvascular endothelium mediates insulin delivery and facilitates monocyte transmigration, yet its contribution to the consequences of hyperlipidemia is poorly understood. Using primary endothelial cells from human adipose tissue microvasculature (HAMEC), we investigated the effects of physiological levels of fatty acids on endothelial inflammation and function. Expression of cytokines and adhesion molecules was measured by RT-qPCR. Signaling pathways were evaluated by pharmacological manipulation and immunoblotting. Surface expression of adhesion molecules was determined by immunohistochemistry. THP1 monocyte interaction with HAMEC was measured by cell adhesion and migration across transwells. Insulin transcytosis was measured by total internal reflection fluorescence microscopy. Palmitate, but not palmitoleate, elevated the expression of IL-6, IL-8, TLR2 (Toll-like receptor 2), and intercellular adhesion molecule 1 (ICAM-1). HAMEC had markedly low fatty acid uptake and oxidation, and CD36 inhibition did not reverse the palmitate-induced expression of adhesion molecules, suggesting that inflammation did not arise from palmitate uptake/metabolism. Instead, inhibition of TLR4 to NF-κB signaling blunted palmitate-induced ICAM-1 expression. Importantly, palmitate-induced surface expression of ICAM-1 promoted monocyte binding and transmigration. Conversely, palmitate reduced insulin transcytosis, an effect reversed by TLR4 inhibition. In summary, palmitate activates inflammatory pathways in primary microvascular endothelial cells, impairing insulin transport and increasing monocyte transmigration. This behavior may contribute in vivo to reduced tissue insulin action and enhanced tissue