Model Of Diet-induced Insulin Resistance Research Articles

234-OR: Succinate Potentiates Insulin Secretion through SUCNR1

Here, we examined the role of succinate, a metabolite that acts by engaging the succinate receptor 1 (SUCNR1), in regulating insulin secretion by β-cells. We found that glucose increases SUCNR1 expression in β-cells and that activating SUCNR1 with either extracellular succinate or a synthetic agonist boosts glucose-stimulated insulin secretion through the Gq and PKC signaling pathways. Also, we identified that SUCNR1 is essential for preserving insulin secretion in a diet-induced insulin-resistance model. Mice with β-cell-specific SUCNR1 deficiency had impaired glucose tolerance and reduced insulin secretion when fed a high-fat diet, without changes in β-cell mass or insulin sensitivity. To investigate the physiological significance of succinate as a secretagogue in humans, we studied the potential connection between circulating succinate levels and β-cell function in response to oral and intravenous glucose challenges in a cohort of patients with impaired glucose tolerance (IGT). These patients were characterized by presenting hyperinsulinemia during both oral and intravenous glucose tests, compared to normal glucose tolerance (NGT) individuals. Moreover, succinate levels were elevated in IGT patients in response to these challenges compared to NGT patients, whereas circulating GLP-1 levels during the tests were not different between groups. Remarkably, we found that circulating succinate levels are positively correlated with insulin secretion potentiation during intravenous glucose administration, indicating that this system is activated by high glucose levels and partially regulated by the β-cell in an autocrine fashion. These findings suggest that succinate may act as a hormone, potentiating insulin secretion in humans through SUCNR1- a compensatory mechanism particularly relevant in the hyperinsulinemia elicited by insulin resistance. Our work sheds new light on the role of the succinate-SUCNR1 axis as a potential therapeutic target for improving insulin secretion in metabolic disorders. Disclosure J.Sabadell-basallote: None. J.J.Vendrell: None. S.Fernandez-veledo: None. B.D.Astiarraga: None. M.Ejarque: None. M.Repollés-de-dalmau: None. F.X.Sureda: None. D.F.De jesus: None. C.Núñez roa: None. A.Mari: Consultant; Eli Lilly and Company. R.Kulkarni: Advisory Panel; Novo Nordisk, Inversago, Biomea Fusion, Inc., REDD Pharma, Research Support; Inversago. Funding Spanish Ministry of Science and Innovation (SAF2015-65019-R, RTI2018-093919-B-100); Instituto de Salud Carlos III (FI18/00151, CP10/00438, CPII16/00008); Spanish Biomedical Research Center in Diabetes and Associated Metabolic Disorders (CB07708/0012); Catalan Association of Diabetes (PV21039S)

Low-fat dairy consumption improves intestinal immune function more than high-fat dairy in a diet-induced swine model of insulin resistance.

To understand the effects of consuming high-fat and low-fat dairy products on postprandial cardiometabolic risk factors and intestinal immune function, we used an established low birthweight (LBW) swine model of diet-induced insulin resistance. LBW piglets were randomized to consume one of the 3 experimental high fat diets and were fed for a total of 7weeks: (1) Control high fat (LBW-CHF), (2) CHF diet supplemented with 3 servings of high-fat dairy (LBW-HFDairy) and (3) CHF diet supplemented with 3 servings of low-fat dairy (LBW-LFDairy). As comparison groups, normal birthweight (NBW) piglets were fed a CHF (NBW-CHF) or standard pig grower diet (NBW-Chow). At 11weeks of age, all piglets underwent an established modified oral glucose and fat tolerance test. At 12weeks of age, piglets were euthanized and ex vivo cytokine production by cells isolated from mesenteric lymph node (MLN) stimulated with mitogens was assessed. Dairy consumption did not modulate postprandial plasma lipid, inflammatory markers and glucose concentrations. A lower production of IL-2 and TNF-α after pokeweed mitogen (PWM) stimulation was observed in LBW-CHF vs NBW-Chow (P < 0.05), suggesting impaired MLN T cell function. While feeding high-fat dairy had minimal effects, feeding low-fat dairy significantly improved the production of IL-2 and TNF-α after PWM stimulation (P < 0.05). Irrespective of fat content, dairy had a neutral effect on postprandial cardiometabolic risk factors. Low-fat dairy products improved intestinal T cell function to a greater extent than high-fat dairy in this swine model of obesity and insulin resistance.

Effect of High-Fat and Low-Fat Dairy Products on Cardiometabolic Risk Factors and Immune Function in a Low Birthweight Swine Model of Diet-Induced Insulin Resistance.

Although dairy intake has been shown to have a neutral or some beneficial effect on major cardiometabolic risk factors, the impact of dairy, and especially dairy fat, on immune function remains to be investigated. To understand the effect of consuming dairy fat on cardiometabolic risk factors and immune function, we used an established low birthweight (LBW) swine model of diet-induced insulin resistance to compare high-fat and low-fat dairy products to a control high-fat diet (CHF). LBW piglets were randomized to consume one of the 3 experimental HF diets: (1) CHF, (2) CHF diet supplemented with 3 servings/day of high-fat dairy (HFDairy) and (3) CHF diet supplemented with 3 servings/day of low-fat dairy (LFDairy). As comparison groups, normal birthweight (NBW) piglets were fed a CHF (NBW-CHF) or standard pig grower diet (NBW-Chow). A total of 35 pigs completed the study and were fed for a total of 7 weeks, including 1 week of CHF transition diet. At 12 weeks of age, piglets were euthanized. Fasting blood and tissue samples were collected. Ex vivo cytokine production by peripheral blood mononuclear cells (PBMCs) stimulated with pokeweed (PWM), phytohemagglutinin (PHA) and phorbol myristate acetate-ionomycin (PMA-I) were assessed. As expected, LBW-CHF piglets showed early signs of insulin resistance (HOMA-IR, P model = 0.08). Feeding high-fat dairy products improved fasting plasma glucose concentrations more than low-fat dairy compared to LBW-CHF (P < 0.05). Irrespective of fat content, dairy consumption had neutral effect on fasting lipid profile. We have also observed lower production of IL-2 after PWM and PHA stimulation as well as lower production of TNF-α and IFN-γ after PWM stimulation in LBW-CHF than in NBW-Chow (all, P < 0.05), suggesting impaired T cell and antigen presenting cell function. While feeding high-fat dairy had minimal effect on immune function, feeding low-fat dairy significantly improved the production of IL-2, TNF-α and IFN-γ after PWM stimulation, IL-2 and IFN-γ after PHA stimulation as well as TNF-α after PMA-I stimulation compared to LBW-CHF (all, P < 0.05). These data provide novel insights into the role of dairy consumption in counteracting some obesity-related cardiometabolic and immune perturbations.

Endothelial Notch signaling controls insulin transport in muscle.

The role of the endothelium is not just limited to acting as an inert barrier for facilitating blood transport. Endothelial cells (ECs), through expression of a repertoire of angiocrine molecules, regulate metabolic demands in an organ‐specific manner. Insulin flux across the endothelium to muscle cells is a rate‐limiting process influencing insulin‐mediated lowering of blood glucose. Here, we demonstrate that Notch signaling in ECs regulates insulin transport to muscle. Notch signaling activity was higher in ECs isolated from obese mice compared to non‐obese. Sustained Notch signaling in ECs lowered insulin sensitivity and increased blood glucose levels. On the contrary, EC‐specific inhibition of Notch signaling increased insulin sensitivity and improved glucose tolerance and glucose uptake in muscle in a high‐fat diet‐induced insulin resistance model. This was associated with increased transcription of Cav1, Cav2, and Cavin1, higher number of caveolae in ECs, and insulin uptake rates, as well as increased microvessel density. These data imply that Notch signaling in the endothelium actively controls insulin sensitivity and glucose homeostasis and may therefore represent a therapeutic target for diabetes.

Liver-specific insulin receptor isoform A expression enhances hepatic glucose uptake and ameliorates liver steatosis in a mouse model of diet-induced obesity.

ABSTRACTAmong the main complications associated with obesity are insulin resistance and altered glucose and lipid metabolism within the liver. It has previously been described that insulin receptor isoform A (IRA) favors glucose uptake and glycogen storage in hepatocytes compared with isoform B (IRB), improving glucose homeostasis in mice lacking liver insulin receptor. Thus, we hypothesized that IRA could also improve glucose and lipid metabolism in a mouse model of high-fat-diet-induced obesity. We addressed the role of insulin receptor isoforms in glucose and lipid metabolism in vivo. We expressed IRA or IRB specifically in the liver by using adeno-associated viruses (AAVs) in a mouse model of diet-induced insulin resistance and obesity. IRA, but not IRB, expression induced increased glucose uptake in the liver and muscle, improving insulin tolerance. Regarding lipid metabolism, we found that AAV-mediated IRA expression also ameliorated hepatic steatosis by decreasing the expression of Fasn, Pgc1a, Acaca and Dgat2 and increasing Scd-1 expression. Taken together, our results further unravel the role of insulin receptor isoforms in hepatic glucose and lipid metabolism in an insulin-resistant scenario. Our data strongly suggest that IRA is more efficient than IRB at favoring hepatic glucose uptake, improving insulin tolerance and ameliorating hepatic steatosis. Therefore, we conclude that a gene therapy approach for hepatic IRA expression could be a safe and promising tool for the regulation of hepatic glucose consumption and lipid metabolism, two key processes in the development of non-alcoholic fatty liver disease associated with obesity.This article has an associated First Person interview with the first author of the paper.

Effects of vitamin D on insulin resistance and myosteatosis in diet-induced obese mice.

Epidemiological studies pointed out to a strong association between vitamin D deficiency and type 2 diabetes prevalence. However, the role of vitamin D supplementation in the skeletal muscle, a tissue that play a crucial role in the maintenance of glucose homeostasis, has been scarcely investigated so far. On this basis, this study aimed to evaluate the effect of vitamin D supplementation in a murine model of diet-induced insulin resistance with particular attention to the effects evoked on the skeletal muscle. Male C57BL/6J mice (n = 40) were fed with a control or a High Fat-High Sugar (HFHS) diet for 4 months. Subsets of animals were treated for 2 months with vitamin D (7 μg·kg-1, i.p. three times/week). HFHS diet induced body weight increase, hyperglycemia and impaired glucose tolerance. HFHS animals showed an impaired insulin signaling and a marked fat accumulation in the skeletal muscle. Vitamin D reduced body weight and improved systemic glucose tolerance. In addition, vitamin D restored the impaired muscle insulin signaling and reverted myosteatosis evoked by the diet. These effects were associated to decreased activation of NF-κB and lower levels of TNF-alpha. Consistently, a significantly decreased activation of the SCAP/SREBP lipogenic pathway and lower levels of CML protein adducts and RAGE expression were observed in skeletal muscle of animals treated with vitamin D.Collectively, these data indicate that vitamin D-induced selective inhibition of signaling pathways (including NF-κB, SCAP/SREBP and CML/RAGE cascades) within the skeletal muscle significantly contributed to the beneficial effects of vitamin D supplementation against diet-induced metabolic derangements.

Study of In Vivo Glucose Metabolism in High-fat Diet-fed Mice Using Oral Glucose Tolerance Test (OGTT) and Insulin Tolerance Test (ITT).

Obesity represents the most important single risk factor in the pathogenesis of type 2 diabetes, a disease which is characterized by a resistance to insulin-stimulated glucose uptake and a gross decompensation of systemic glucose metabolism. Despite considerable progress in the understanding of glucose metabolism, the molecular mechanisms of its regulation in health and disease remain under-investigated, while novel approaches to prevent and treat diabetes are urgently needed. Diet derived glucose stimulates the pancreatic secretion of insulin, which serves as the principal regulator of cellular anabolic processes during the fed-state and thus balances blood glucose levels to maintain systemic energy status. Chronic overfeeding triggers meta-inflammation, which leads to alterations in peripheral insulin receptor-associated signaling and thus reduces the sensitivity to insulin-mediated glucose disposal. These events ultimately result in elevated fasting glucose and insulin levels as well as a reduction in glucose tolerance, which in turn serve as important indicators of insulin resistance. Here, we present a protocol for the generation and metabolic characterization of high-fat diet (HFD)-fed mice as a frequently used model of diet-induced insulin resistance. We illustrate in detail the oral glucose tolerance test (OGTT), which monitors the peripheral disposal of an orally administered glucose load and insulin secretion over time. Additionally, we present a protocol for the insulin tolerance test (ITT) to monitor whole-body insulin action. Together, these methods and their downstream applications represent powerful tools to characterize the general metabolic phenotype of mice as well as to specifically assess alterations in glucose metabolism. They may be especially useful in the broad research field of insulin resistance, diabetes and obesity to provide a better understanding of pathogenesis as well as to test the effects of therapeutic interventions.

Upregulation of Glutaredoxin-1 Activates Microglia and Promotes Neurodegeneration: Implications for Parkinson's Disease.

Neuroinflammation and redox dysfunction are recognized factors in Parkinson's disease (PD) pathogenesis, and diabetes is implicated as a potentially predisposing condition. Remarkably, upregulation of glutaredoxin-1 (Grx1) is implicated in regulation of inflammatory responses in various disease contexts, including diabetes. In this study, we investigated the potential impact of Grx1 upregulation in the central nervous system on dopaminergic (DA) viability. Increased GLRX copy number in PD patients was associated with earlier PD onset, and Grx1 levels correlated with levels of proinflammatory tumor necrosis factor-alpha (TNF-α) in mouse and human brain samples, prompting mechanistic in vitro studies. Grx1 content/activity in microglia was upregulated by lipopolysaccharide (LPS), or TNF-α, treatment. Adenoviral overexpression of Grx1, matching the extent of induction by LPS, increased microglial activation; Grx1 silencing diminished activation. Selective inhibitors/probes of nuclear factor κB (NF-κB) activation revealed glrx1 induction to be mediated by the Nurr1/NF-κB axis. Upregulation of Grx1 in microglia corresponded to increased death of neuronal cells in coculture. With a mouse diabetes model of diet-induced insulin resistance, we found upregulation of Grx1 in brain was associated with DA loss (decreased tyrosine hydroxylase [TH]; diminished TH-positive striatal axonal terminals); these effects were not seen with Grx1-knockout mice. Our results indicate that Grx1 upregulation promotes neuroinflammation and consequent neuronal cell death in vitro, and synergizes with proinflammatory insults to promote DA loss in vivo. Our findings also suggest a genetic link between elevated Grx1 and PD development. In vitro and in vivo data suggest Grx1 upregulation promotes neurotoxic neuroinflammation, potentially contributing to PD. Antioxid. Redox Signal. 25, 967-982.

Experimental type II diabetes and related models of impaired glucose metabolism differentially regulate glucose transporters at the proximal tubule brush border membrane.

What is the central question of this study? Although SGLT2 inhibitors represent a promising treatment for patients suffering from diabetic nephropathy, the influence of metabolic disruption on the expression and function of glucose transporters is largely unknown. What is the main finding and its importance? In vivo models of metabolic disruption (Goto-Kakizaki typeII diabetic rat and junk-food diet) demonstrate increased expression of SGLT1, SGLT2 and GLUT2 in the proximal tubule brush border. In the typeII diabetic model, this is accompanied by increased SGLT- and GLUT-mediated glucose uptake. A fasted model of metabolic disruption (high-fat diet) demonstrated increased GLUT2 expression only. The differential alterations of glucose transporters in response to varying metabolic stress offer insight into the therapeutic value of inhibitors. SGLT2 inhibitors are now in clinical use to reduce hyperglycaemia in typeII diabetes. However, renal glucose reabsorption across the brush border membrane (BBM) is not completely understood in diabetes. Increased consumption of a Western diet is strongly linked to typeII diabetes. This study aimed to investigate the adaptations that occur in renal glucose transporters in response to experimental models of diet-induced insulin resistance. The study used Goto-Kakizaki typeII diabetic rats and normal rats rendered insulin resistant using junk-food or high-fat diets. Levels of protein kinaseC-βI (PKC-βI), GLUT2, SGLT1 and SGLT2 were determined by Western blotting of purified renal BBM. GLUT- and SGLT-mediated d-[(3) H]glucose uptake by BBM vesicles was measured in the presence and absence of the SGLT inhibitor phlorizin. GLUT- and SGLT-mediated glucose transport was elevated in typeII diabetic rats, accompanied by increased expression of GLUT2, its upstream regulator PKC-βI and SGLT1 protein. Junk-food and high-fat diet feeding also caused higher membrane expression of GLUT2 and its upstream regulator PKC-βI. However, the junk-food diet also increased SGLT1 and SGLT2 levels at the proximal tubule BBM. Glucose reabsorption across the proximal tubule BBM, via GLUT2, SGLT1 and SGLT2, is not solely dependent on glycaemic status, but is also influenced by diet-induced changes in glucose metabolism. We conclude that different metabolic disturbances result in complex adaptations in renal glucose transporter protein levels and function.

Coenzyme Q10 Supplementation Prevents Iron Overload While Improving Glycaemic Control and Antioxidant Protection in Insulin-Resistant Psammomys obesus.

This study investigated the anti-diabetic preventive activity of coenzyme Q10 (CoQ10) in a murine model of diet-induced insulin resistance (IR), Psammomys obesus (Po). IR was induced by feeding a standard laboratory diet (SD). CoQ10 oil suspension was orally administered at 10mg/kg body weight (BW)/day along with SD for 9months. Anthropometric parameters, namely, total body weight gain (BWG) and the relative weight of white adipose tissue (WAT) were determined. Blood glucose, insulin, quantitative insulin sensitivity check index (QUICKI), total antioxidant status (TAS), iron, malondialdehyde (MDA) and nitrite (NO2 (-)) were evaluated. NO2 (-) level was also assessed in peripheral blood mononuclear cells (PBMCs) culture supernatants. Our results show that CoQ10 supplementation significantly improved blood glucose, insulin, QUICKI, TAS, iron and MDA, but influenced neither NO2 (-) levels nor the anthropometric parameters. These findings support the hypothesis that CoQ10 would exert an anti-diabetic activity by improving both glycaemic control and antioxidant protection. The most marked effect of CoQ10 observed in this study concerns the regulation of iron levels, which may carry significant preventive importance.

Retinol as a cofactor for PKCδ-mediated impairment of insulin sensitivity in a mouse model of diet-induced obesity.

We previously defined that the mitochondria-localized PKCδ signaling complex stimulates the conversion of pyruvate to acetyl-coenzyme A by the pyruvate dehydrogenase complex. We demonstrated in vitro and ex vivo that retinol supplementation enhances ATP synthesis in the presence of the PKCδ signalosome. Here, we tested in vivo if a persistent oversupply of retinol would further impair glucose metabolism in a mouse model of diet-induced insulin resistance. We crossed mice overexpressing human retinol-binding protein (hRBP) under the muscle creatine kinase (MCK) promoter (MCKhRBP) with the PKCδ(-/-) strain to generate mice with a different status of the PKCδ signalosome and retinoid levels. Mice with a functional PKCδ signalosome and elevated retinoid levels (PKCδ(+/+)hRBP) developed the most advanced stage of insulin resistance. In contrast, elevation of retinoid levels in mice with inactive PKCδ did not affect remarkably their metabolism, resulting in phenotypic similarity between PKCδ(-/-)hRBP and PKCδ(-/-) mice. Therefore, in addition to the well-defined role of PKCδ in the etiology of metabolic syndrome, we present a novel PKCδ signaling pathway that requires retinol as a metabolic cofactor and is involved in the regulation of fuel utilization in mitochondria. The distinct role in whole-body energy homeostasis establishes the PKCδ signalosome as a promising target for therapeutic intervention in metabolic disorders.

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

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

MicroRNA-29 fine-tunes the expression of key FOXA2-activated lipid metabolism genes and is dysregulated in animal models of insulin resistance and diabetes.

MicroRNAs (miRNAs) have emerged as biomarkers of metabolic status, etiological factors in complex disease, and promising drug targets. Recent reports suggest that miRNAs are critical regulators of pathways underlying the pathophysiology of type 2 diabetes. In this study, we demonstrate by deep sequencing and real-time quantitative PCR that hepatic levels of Foxa2 mRNA and miR-29 are elevated in a mouse model of diet-induced insulin resistance. We also show that Foxa2 and miR-29 are significantly upregulated in the livers of Zucker diabetic fatty (fa/fa) rats and that the levels of both returned to normal upon treatment with the insulin-sensitizing agent pioglitazone. We present evidence that miR-29 expression in human hepatoma cells is controlled in part by FOXA2, which is known to play a critical role in hepatic energy homeostasis. Moreover, we demonstrate that miR-29 fine-tunes FOXA2-mediated activation of key lipid metabolism genes, including PPARGC1A, HMGCS2, and ABHD5. These results suggest that miR-29 is an important regulatory factor in normal metabolism and may represent a novel therapeutic target in type 2 diabetes and related metabolic syndromes.

Comparative Effects of the Renin–Angiotensin System Blockers on Nonalcoholic Fatty Liver Disease and Insulin Resistance in C57Bl/6 Mice

The activation of the renin-angiotensin system (RAS) has been related to various aspects of metabolic syndrome. The current study evaluated the effects of RAS blockers in a model of diet-induced insulin resistance (IR) and nonalcoholic fatty liver disease (NAFLD). Male C57BL/6 mice were fed a standard chow (SC; 10% lipids, n=15) diet or a high-fat (HF; 50% lipids, n=60) diet for 8 weeks and then treated with aliskiren (HF-A; 50 mg/kg per day, n=15), enalapril (HF-E; 30 mg/kg per day, n=15), or losartan (HF-L; 10 mg/kg per day, n=15) for an additional 6 weeks. We assessed glucose and lipid metabolism, hepatic histopathology, the expression profile of genes and proteins affecting hepatic gluconeogenesis, RAS and insulin signaling, and lipid beta-oxidation and accumulation. The differences between the groups were tested via analysis of variance (ANOVA) and the post hoc Holm-Sidak test. All treatments restored the up-regulation of hepatic RAS. The enalapril treatment, but not aliskiren or losartan, was effective in improving leptin, glucose intolerance, IR, hepatic steatosis, and triglycerides and in preventing increased hepatic protein levels of phosphoenolpyruvate carboxykinase (PEPCK), glucose 6-phosphatase (G6Pase), and glucose transporter-2 (GLUT-2). Furthermore, enalapril improved the response to the deleterious effects of the HF diet by upregulating signal transduction through the insulin receptor substrate (IRS) 1/protein kinase B (Akt) pathway, as well as downregulating the protein levels and mRNA expression of peroxisome proliferator-activated receptor-γ (PPARγ), sterol regulatory element-binding protein-1c (SREBP-1c), and fatty acid synthase (FAS). Enalapril was the most successful treatment in protecting against hepatic IR and NAFLD by enhancing hepatic insulin action, leptin, and gluconeogenesis and by reducing the lipogenic pathway and lipid accumulation in the liver.

Grape-Seed Procyanidins Prevent the Cafeteria-Diet-Induced Decrease of Glucagon-Like Peptide-1 Production

Grape-seed procyanidin extract (GSPE) has been reported to improve insulin resistance in cafeteria rats. Because glucagon-like peptide-1 (GLP-1) is involved in glucose homeostasis, the preventive effects of GSPE on GLP-1 production, secretion, and elimination were evaluated in a model of diet-induced insulin resistance. Rats were fed a cafeteria diet for 12 weeks, and 25 mg of GSPE/kg of body weight was administered concomitantly. Vehicle-treated cafeteria-fed rats and chow-fed rats were used as controls. The cafeteria diet decreased active GLP-1 plasma levels, which is attributed to a decreased intestinal GLP-1 production, linked to reduced colonic enteroendocrine cell populations. Such effects were prevented by GSPE. In the same context, GSPE avoided the decrease on intestinal dipeptidyl-peptidase 4 (DPP4) activity and modulated the gene expression of GLP-1 and its receptor in the hypothalamus. In conclusion, the preventive treatment with GSPE abrogates the effects of the cafeteria diet on intestinal GLP-1 production and DPP4 activity.

Erratum

Acta PhysiologicaVolume 208, Issue 1 p. 136-136 ErratumFree Access Erratum This article corrects the following: The hexosamine biosynthetic pathway can mediate myocardial apoptosis in a rat model of diet-induced insulin resistance U. Rajamani, D. Joseph, S. Roux, M. F. Essop, Volume 202Issue 2Acta Physiologica pages: 151-157 First Published online: April 19, 2011 First published: 12 April 2013 https://doi.org/10.1111/apha.12069AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat The hexosamine biosynthetic pathway can mediate myocardial apoptosis in a rat model of diet-induced insulin resistance. Rajamani U, Joseph D, Roux S, Essop MF For the above article, some of the values in Table 1 were incorrectly published. Here is the correct Table and associated text. Table 1. Values are expressed as mean ± SEM (n = 6 rats per experimental group) Control Insulin resistance Number of rats 6 6 Gender Male Male Body weight (g) 505.00 ± 13.27 557.17 ± 8.48aa P < 0.05. Glucose (mmol per L) 6.03 ± 0.20 8.22 ± 0.65aa P < 0.05. Insulin (μU) 32.62 ± 5.15 57.88 ± 9.96aa P < 0.05. HOMA–IR 8.80 ± 1.45 22.04 ± 5.64aa P < 0.05. a P < 0.05. First paragraph of results section Rats consuming the high-fat diet displayed a moderate increase in body weight (9.36%, P < 0.05 vs. controls) (Table 1). Fasting insulin and glucose plasma levels were significantly increased in response to the high-fat feeding regimen vs. matched controls, that is, 57.88 vs. 32.62 μU and 8.22 vs. 6.03 mmol/L respectively. High-fat feeding markedly increased the HOMA–IR (P < 0.05 vs. control) demonstrating insulin resistance (Table 1). Reference Rajamani, U., Joseph, D., Roux, S. & Essop, M.F. 2011. The hexosamine biosynthetic pathway can mediate myocardial apoptosis in a rat model of diet-induced insulin resistance. Acta Physiol (Oxf) 202, 151– 157. doi: 10.1111/j.1748-1716.2011.02275.x. Wiley Online LibraryCASPubMedWeb of Science®Google Scholar Volume208, Issue1May 2013Pages 136-136 ReferencesRelatedInformation

Regulation of Intestinal Chylomicron Production by Glucagon-Like Peptides

Apolipoprotein B48 (apoB48)-containing triglyceride-rich lipoproteins are atherogenic and therefore it is important to understand factors that regulate their metabolism in the intestine. Insulin resistant states are associated with increased intestinal output of apo B48, but the mechanistic studies explaining this overproduction have relied heavily on models of diet-induced insulin resistance. There is evidence that glucagon-like peptide (GLP) secretion is diminished in insulin resistant and diabetic states, which may have implications for postprandial lipid secretion. This review presents a survey of studies on GLPs and intestinal lipoprotein metabolism, along with some insights into the net physiological significance of GLP action in postprandial lipoprotein metabolism. Studies with GLP-1 receptor agonists and dipeptidyl peptidase-IV inhibitors have indicated that GLP-1 in pharmacological and physiological doses can inhibit intestinal TRL production. On the other hand, GLP-2 has an acute stimulatory effect on intestinal apoB48 secretion. Modulating GLP action may serve as a strategy to improve postprandial dyslipidemia in insulin resistant states.

16 Weeks of Diabetogenic Diet are Sufficient To Induce Cardiac Hypertrophy and Fibrosis in a Murine Model of Diet-Induced Insulin Resistance and Cardiomyopathy

16 Weeks of Diabetogenic Diet are Sufficient To Induce Cardiac Hypertrophy and Fibrosis in a Murine Model of Diet-Induced Insulin Resistance and Cardiomyopathy

Metformin, but not Diet-Induced Weight Loss, Decreases Myocardial Fibrosis in a Murine Model of Diet-Induced Insulin Resistance and Cardiomyopathy

Metformin, but not Diet-Induced Weight Loss, Decreases Myocardial Fibrosis in a Murine Model of Diet-Induced Insulin Resistance and Cardiomyopathy

Cafeteria diet intake for fourteen weeks can cause obesity and insulin resistance in Wistar rats

OBJECTIVE: Obesity is a strong predictor of some kinds of diseases. High intake of high-fat foods contributes significantly to the growth of the obese population globally. The aim of this study was to verify if consumption of a cafeteria diet for fourteen weeks could increase white fat mass, body weight and skeletal muscle mass and promote insulin resistance in male Wistar rats. METHODS: Twenty animals were divided into two groups: control and obese. Both were fed standard chow and water ad libitum. Additionally, a cafeteria diet consisting of bacon, bologna sausage, sandwich cookies and soft drink was given to the obese group. RESULTS: The obese group was significantly heavier (p&lt;0.0001) than controls from the second week until the end of the cafeteria-diet intervention. Absolute and relative fat mass, liver weight and Lee Index increased significantly (p&lt;0.05) in the obese group. Furthermore, the obese group had lower (p&lt;0.05) insulin sensitivity than the control group. CONCLUSION: In conclusion, fourteen weeks of cafeteria diet promoted a progressive increase of fat mass and insulin resistance. Therefore, this is a great and inexpensive diet-induced insulin resistance model.