Plasma Glucagon-like Peptide-1 Levels Research Articles

Effect of sleeve gastrectomy, Roux-en-Y gastric bypass, and ileal transposition on myocardial ischaemia\u2013reperfusion injury in non-obese non-diabetic rats

Bariatric surgery (BS) improves outcomes in patients with myocardial infarction (MI). Here we tested the hypothesis that BS-mediated reduction in fatal MI could be attributed to its infarct-limiting effect. Wistar rats were randomized into five groups: control (CON), sham (SHAM), Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), and ileotransposition (IT). Ten weeks later, animals were subjected to 30-min myocardial ischemia plus 120-min reperfusion. Infarct size (IS) and no-reflow area were determined histochemically. Fasting plasma levels of glucagon-like peptide-1 (GLP-1), leptin, ghrelin, and insulin were measured using ELISA. Compared with SHAM, RYGB and SG reduced IS by 22% (p = 0.011) and 10% (p = 0.027), and no-reflow by 38% (p = 0.01) and 32% (p = 0.004), respectively. IT failed to reduce IS and no-reflow. GLP-1 level was increased in the SG and RYGB groups compared with CON. In both the SG and RYGB, leptin level was decreased compared with CON and SHAM. In the SG group, ghrelin level was lower than that in the CON and SHAM. Insulin levels were not different between groups. In conclusion, RYGB and SG increased myocardial tolerance to ischemia–reperfusion injury of non-obese, non-diabetic rats, and their infarct-limiting effect is associated with decreased leptin and ghrelin levels and increased GLP-1 level.

Regulation of peripheral expression of glucagon-like peptide 1 receptors in a rat streptozotocin-model of sporadic Alzheimer's disease.

Our previous research indicated incretin dysregulation in a rat model of sporadic Alzheimer's disease (sAD) induced by intracerebroventricular streptozotocin (STZ-icv) and improvement of cognitive decline following oral galactose-induced potentiation of endogenous glucagon-like peptide 1 (GLP-1). This study explored peripheral GLP-1 receptors (GLP-1R) in STZ-icv rats following the acute inhibition of cerebral GLP-1 signaling and additional acute oral galactose administration. 1 month following STZ-icv treatment, male Wistar rats were acutely icv-treated with GLP-1R antagonist Exendin9-39 (85ug/kg; /EXE-icv/) (Experiment I), and 1 hour after EXE-icv additionally with D-galactose (200mg/kg, single oral dose) (Experiment II). Total/active GLP-1 levels were analyzed in plasma and cerebrospinal fluid (CSF) by ELISA. GLP-1R distribution in paraffin embedded duodenal/mesenteric adipose tissue was examined using catalyzed deposition of fluorescent reporters, and analyzed by hierarchical mixed-effect modelling. Baseline plasma level of active GLP-1 was increased in STZ-icv group (vs controls) while EXE-icv treatment decreased it in the STZ-icv and increased in the control group. In CSF, EXE-icv induced a trend of GLP-1 increment both in STZ-icv and control group. Following acute oral galactose treatment, the same trend was observed in plasma of controls, but EXE-icv didn't exhibit a reduction in STZ-icv animals, and CSF level remained unchanged in both. The GLP-1R expression in periduodenal mesenteric adipose tissue of STZ-icv rats was increased following EXE-icv but decreased following additional acute oral galactose treatment. Acute galactose treatment unmasked the effect of EXE-icv on duodenal regulation of GLP-1 as lacteal GLP-1R signal was decreased both in STZ-icv and control group following EXE-icv. Our preliminary results support the existence of dysregulated GLP-1 brain-periphery axis in the STZ-icv rat model of sAD, and additionally indicate that incretin dysregulation is localized both in the brain and the peripheral tissues of STZ-icv rats, and that brain GLP-1 seems to be involved in regulation of the peripheral GLP-1R distribution. Funded by the Croatian Science Foundation (IP-2018-01-8938). Co-financed by the Scientific Centre of Excellence for Basic, Clinical and Translational Neuroscience (project "Experimental and clinical research of hypoxic-ischemic damage in perinatal and adult brain"; GA KK01.1.1.01.0007 funded by the European Union through the European Regional Development Fund).

Statins Mitigate Stress-Related Vascular Aging and Atherosclerosis in apoE-Deficient Mice Fed High Fat-Diet: The Role of Glucagon-Like Peptide-1/Adiponectin Axis.

ObjectivesExposure to chronic psychosocial stress is a risk factor for atherosclerotic cardiovascular diseases. Given that the 3-hydroxy-3-methylglutaryl-coenzyme reductase inhibitor statins prevent atherogenesis, we evaluated whether pitavastatin prevents chronic stress- and high fat diet-induced vascular senescence and atherogenesis in apolipoprotein E-deficient (ApoE–/–) mice, with a special focus on glucagon-like peptide-1 (GLP-1)/adiponectin (APN) axis.Methods and Results6-week-old ApoE–/– mice loaded a high-fat diet were randomly assigned into non-stress (n = 12) and stress (n = 13) groups for 12 weeks. Non-stress control mice were left undisturbed. Chronic stress accelerated high fat diet-induce arterial senescence and atherosclerotic plaque growth. The chronic stress lowered the levels of circulating GLP-1 as well as adipose and plasma APN. As compared with the stress alone mice, the pitavastatin-treated mice had reduced macrophage infiltration, elastin fragments, and increased plaque collagen volume, and lowered levels of osteopontin, toll-like receptor-2/-4, macrophage chemoattractant protein-1, C-X-C chemokine receptor-4, p47phox, p47phox, gp91phox, cathepsins S, p16, and p21, mRNAs and/or proteins. Pitavastatin increased plasma GLP-1 and APN levels and suppressed matrix metalloproteinase-2/-9 gene expressions and activities in the aortas. Finally, the protective effect of pitavastatin was abrogated by APN blocking.ConclusionThese findings suggested that the pitavastatin-mediated pleiotropic vasculoprotective effects are likely attributable, at least in part, to the elevation of GLP-1 and APN levels and the inhibition of diet-induced plaque inflammation, oxidative stress, and proteolysis in ApoE–/– mice received chronic stress conditions.

Plasma levels of ghrelin and GLP-1, but not leptin or amylin, respond to a psychosocial stressor in women and men

It is well known that stress elevates intake of total calories and shifts food preference toward unhealthy food choices. There is, however, little known on the physiological mechanisms that drive stress-induced hyperphagia. In order to better understand how to reduce stress eating, it is critical to identify mechanisms in humans that are points of convergence between stress and eating. The feeding-related hormones ghrelin, leptin, glucagon-like peptide-1 (GLP-1), and amylin are likely candidates. It was hypothesized that ghrelin, an orexigenic hormone, would increase in response to an acute laboratory stressor, but that leptin, GLP-1, and amylin (anorexigenic hormones) would decrease after stress. To this aim, participants (n = 47) came into the laboratory and had feeding-related hormones, salivary cortisol and α-amylase, and self-rated anxiety measured. Then they underwent either exposure to a stressor (n = 24), which reliably elevates measures of stress and energy intake, or a no-stress condition (n = 23). Feeding hormones, stress hormones, and self-rated anxiety were measured twice more after the stressor. Elevated self-rated anxiety and α-amylase confirmed the validity of the stressor. Furthermore, there was a time X condition interaction for both ghrelin and GLP-1. Ghrelin was significantly elevated after stress compared to baseline (p = .02) and there was a trend for GLP-1 to be higher in the stress condition over the no-stress condition immediately after the stressor (p = .07). Overall, ghrelin is the most likely candidate driving energy intake after stress in humans.

Emodin Attenuated the Kidney Damage of High-Fat-Diet Mice via the Upregulation of Glucagon-Like Peptide-1 Receptor.

Objective Secretion of glucagon-like peptide 1 (GLP-1) and its effect on target organs were impaired in individuals with obesity. However, its mechanism needs to be further studied. We aim to explore the roles of the receptor of GLP-1 (GLP-1R) involved in high-fat-diet- (HFD-) induced kidney damage improved by emodin. Methods Male C57bl/6 mice were fed with HFD diet and therapied by emodin. NRK-52E cells were cultured and treated with palmitic acid or low-density lipoprotein cholesterol (LDL-C). Emodin was used to remedy the NRK-52E cell damage. GW9662 was administrated to block the function of peroxisome proliferator-activated receptor γ (PPAR-γ). GLP-1 in the plasma was measured by ELISA. PPAR-γ and GLP-1R in the kidney and NRK-52E cells were detected by western blotting. The interaction between PPAR-γ protein and GLP-1R promoter regions was observed by chromatin immunoprecipitation (ChIP). Results Postprandial GLP-1 levels in plasma, as well as PPAR-γ and GLP-1R, decreased in kidney tissue of HFD mice, while they were reserved by emodin treatment. Although PPAR-γ and GLP-1R were not downregulated by LDL-C, they were suppressed by palmitic acid. Interestingly, GLP-1R mRNA was detected by PCR in the mixture pulled down with PPAR-γ antibody. Additionally, downregulation of PPAR-γ and GLP-1R by palmitic acid was remanded by emodin. Moreover, GW9662, an inhibitor of PPAR-γ, abolished the protective effect of emodin. Conclusion The kidney damage of HFD mice seems to be alleviated by emodin via the upregulation of GLP-1R in kidney tissue.

The relation between postprandial glucagon-like peptide-1 release and insulin sensitivity before and after bariatric surgery in humans with class II/III obesity.

Glucagon-like peptide-1 (GLP-1) receptor agonist treatment is beneficial for the human glucose metabolism, and GLP-1 secretion is greatly enhanced following Roux-en-Y gastric bypass (RYGB). To elucidate the relationship between GLP-1 concentrations and insulin sensitivity in subjects with class II/III obesity without diabetes and to assess the relation between GLP-1 and the improvements in glucose metabolism following RYGB. Clinical research facility in a university hospital. We recruited 35 patients scheduled for RYGB and assessed their plasma GLP-1, insulin, and glucose responses to a high-fat mixed meal. Basal and insulin-mediated glucose fluxes were determined during a 2-step hyperinsulinemic-euglycemic clamp with stable isotope-labeled tracers. Out of 35 subjects, 10 were studied both before surgery and at 1 year of follow-up. Plasma GLP-1 increased following the high-fat mixed meal. Postprandial GLP-1 excursions correlated positively with hepatic and peripheral insulin sensitivity, but not with body mass index. At 1 year after RYGB, participants had lost 24% ± 6% of their body weight. Plasma GLP-1, insulin, and glucose levels peaked earlier and higher after the mixed meal. The positive association between the postprandial GLP-1 response and peripheral insulin sensitivity persisted. Postprandial GLP-1 concentrations correlate with insulin sensitivity in subjects with class II/III obesity without diabetes before and 1 year after RYGB. Increased GLP-1 signaling in postbariatric patients may, directly or indirectly, contribute to the observed improvements in insulin sensitivity and metabolic health.

Obesity and Dietary Added Sugar Interact to Affect Postprandial GLP-1 and Its Relationship to Striatal Responses to Food Cues and Feeding Behavior.

It has been hypothesized that the incretin hormone, glucagon-like peptide-1 (GLP-1), decreases overeating by influencing mesolimbic brain regions that process food-cues, including the dorsal striatum. We previously showed that habitual added sugar intake was associated with lower glucose-induced circulating GLP-1 and a greater striatal response to high calorie food cues in lean individuals. Less is known about how dietary added sugar and obesity may interact to affect postprandial GLP-1 and its relationship to striatal responses to food cues and feeding behavior. The current study aimed to expand upon previous research by assessing how circulating GLP-1 and striatal food cue reactivity are affected by acute glucose consumption in participants with varied BMIs and amounts of habitual consumption of added sugar. This analysis included 72 participants from the Brain Response to Sugar Study who completed two study visits where they consumed either plain water or 75g glucose dissolved in water (order randomized; both drinks were flavored with non-caloric cherry flavoring) and underwent repeated blood sampling, a functional magnetic resonance imaging (fMRI) based food-cue task, and an ad-libitum buffet meal. Correlations between circulating GLP-1 levels, striatal food-cue reactivity, and food intake were assessed, and interactions between obesity and added sugar on GLP-1 and striatal responses were examined. An interaction between BMI and dietary added sugar was associated with reduced post-glucose GLP-1 secretion. Participants who were obese and consumed high levels of added sugar had the smallest increase in plasma GLP-1 levels. Glucose-induced GLP-1 secretion was correlated with lower dorsal striatal reactivity to high-calorie versus low-calorie food-cues, driven by an increase in reactivity to low calorie food-cues. The increase in dorsal striatal reactivity to low calorie food-cues was negatively correlated with sugar consumed at the buffet. These findings suggest that an interaction between obesity and dietary added sugar intake is associated with additive reductions in postprandial GLP-1 secretion. Additionally, the results suggest that changes to dorsal striatal food cue reactivity through a combination of dietary added sugar and obesity may affect food consumption.

Post-oral fat-induced satiation is mediated by endogenous CCK and GLP-1 in a fat self-administration mouse model

Triacylglycerol is the most abundant dietary lipid, and a strong stimulator of satiation. Absorption of triacylglycerol in the small intestine occurs in the form of free fatty acids and 2-monoacylglycerol, a process known to trigger not only the release of cholecystokinin (CCK) but also glucagon-like peptide 1 (GLP-1) and peptide YY (PYY). It remains controversial, however, whether endogenously released GLP-1 and PYY are required for fat-induced satiation. Using a self-administration model where mice are trained to self-administer Intralipid 30% intragastrically, we show that blocking the CCK1 receptors with intraperitoneal devazepide diminishes the post-oral satiation effect of ingested fat. Similarly, s.c. administration of a GLP-1 receptor antagonist with a prolonged half-life (Jant4-C16) also reduced the post-oral satiation effect of ingested fat. Importantly, coadministration of the GLP-1 antagonist together with devazepide increased fat self-infusions to a level equal to the combined blockade of each individual peptide action alone, indicating an additive effect of endogenous CCK and GLP-1 in fat satiation signaling. Blocking the PYY Y2 receptor did not further enhance the fat intake in devazepide-treated mice. Consistent with the above, we show that voluntary post-oral ingestion of fat increases CCK and GLP-1 plasma levels and is correlated positively with CCK and GLP-1 plasma concentrations. Taken together, our results support the role of endogenous GLP-1 in the regulation of fat intake and suggest that both CCK and GLP-1 are required for the fat satiation signaling.

GLP-1 is an independent predictor of long-term mortality in patients with myocardial infarction complicated by cardiogenic shock – a substudy of the IABP-SHOCK II trial

Abstract Background The incretin hormone Glucagon-like-peptide 1 (GLP-1) is a major stimulus for glucose dependent insulin secretion and holds cardioprotective efficacy. This has made the GLP-1 system a preferred target for diabetes therapy. Secretion of GLP-1 happens in response to nutritional but also inflammatory stimuli. Consequently, marked elevation of circulating GLP-1 levels were found in critically ill patients featuring marked association to markers of inflammation. Purpose Our study sought to investigate GLP-1 levels in patients with cardiogenic shock (CS) complicating myocardial infarction and a possible prognostic correlation to short- and long-term outcome. Methods We serially assessed circulating GLP-1 levels in a prospectively planned biomarker substudy in the IABP-SHOCK II trial. Blood samples were drawn during index PCI and at day 2. The blood was centrifuged immediately, and serum was frozen at −87°C. GLP-1 was measured with a standard ELISA-kit. All-cause mortality at short- (30 days), intermediate- (1 year) and long-term (6 years) follow-up was used for outcome assessment. Results In this study we found circulating GLP-1 to be markedly elevated in patients with myocardial infarction complicated by CS (n=172) at time of index PCI. Patients with fatal short-term outcome (n=70) exhibited higher GLP-1 levels (86 [45–130] pM) at ICU admission in comparison to patients with 30-day survival (48 [33–78] pM; p<0.001) (n=102). In repeated measures ANOVA the course of GLP-1 levels between baseline and day 2 showed a significant interaction between survivors and non-survivors (p=0.04). By univariate Cox-regression analysis GLP-1 levels >median were predictive of short- (hazard ratio [HR] 2.43; 95% confidence interval [CI] 1.50–3.94; p<0.001), intermediate- (HR 2.46; 95% CI 1.62–3.76; p<0.001) and long-term (HR 2.12; 95% CI 1.44–3.11; p<0.001) outcome. This association remained after multivariable correction (HR 2.01; 95% CI 1.37–3.07; p<0.001). In a landmark analysis we found a significant higher mortality in patients with GLP-1 levels >median from day 30 to 1 year (HR 2.56; 95% CI 1.08–6.09; p=0.03). In contrast, beyond 1 year up to 6 years no difference has been observed anymore (HR 1.02; 95% CI 0.41–2.58; p=0.96). Conclusions Elevated plasma levels of GLP-1 are an independent predictor for impaired prognosis in patients with myocardial infarction complicated by CS at short-, intermediate and long-term follow-up. In a landmark analysis this prognostic effect is sustained up to 1 year. The functional relevance of GLP-1 in this context is currently unknown and needs further investigations. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): German Research Foundation (DFG), German Heart Research Foundation

Expression of serotonin receptor HTR4 in glucagon-like peptide-1-positive enteroendocrine cells of the murine intestine.

Serotonin (5-hydroxytryptamine [5-HT]) synthesized and released in enterochromaffin (EC) cells participates in various functions in the gastrointestinal tract by acting on a diverse range of 5-HT receptors (HTRs) expressed on smooth muscle, enteric neurons, and epithelial cells. We previously observed that genes encoding HTR2A, HTR2B, and HTR4 are expressed in murine intestinal organoids, suggesting the expression of these HTRs in intestinal epithelial cells. The present study investigated the localization of these HTRs in the murine intestine by immunofluorescence staining. HTR2A, HTR2B, and HTR4 localized in individual solitary cells in the epithelium, while HTR2C was observed in the lamina propria. In the epithelium, HTR2A, HTR2B, and HTR4 colocalized with 5-HT, and HTR4 colocalized with glucagon-like peptide 1 (GLP-1) and peptide YY (PYY). Murine intestinal organoids show a colocalization pattern that is similar to in vivo HTR2A and HTR4 with 5-HT, GLP-1, and PYY. Intraperitoneal and intragastric administration of tegaserod, an HTR4 agonist, failed to alter plasma GLP-1 levels in fasted mice. However, intragastric but not intraperitoneal administration of tegaserod reduced dietary lipid-induced increases of plasma GLP-1 levels. This action of tegaserod was inhibited by co-administration of RS39604, an HTR4 antagonist. These results suggest that murine ileal GLP-1/PYY-producing enteroendocrine (EE) cells express HTR4, while 5-HT-producing EC cells express HTR2A, HTR2B, and HTR4. In addition, the observations regarding in vivo GLP-1 secretion suggest that HTR4 signaling in ileal EE cells suppresses dietary lipid-induced GLP-1 secretion. We thus propose that EC and EE cells may interact with each other through paracrine signaling mechanisms.

Dapagliflozin promotes beta cell regeneration by inducing pancreatic endocrine cell phenotype conversion in type 2 diabetic mice

BackgroundClinical trials and animal studies have shown that sodium-glucose co-transporter type 2 (SGLT2) inhibitors improve pancreatic beta cell function. Our study aimed to investigate the effect of dapagliflozin on islet morphology and cell phenotype, and explore the origin and possible reason of the regenerated beta cells. MethodsTwo diabetic mouse models, db/db mice and pancreatic alpha cell lineage-tracing (glucagon-β-gal) mice whose diabetes was induced by high fat diet combined with streptozotocin, were used. Mice were treated by daily intragastric administration of dapagliflozin (1 mg/kg) or vehicle for 6 weeks. The plasma insulin, glucagon and glucagon-like peptide-1 (GLP-1) were determined by using ELISA. The evaluation of islet morphology and cell phenotype was performed with immunofluorescence. Primary rodent islets and αTC1.9, a mouse alpha cell line, were incubated with dapagliflozin (0.25–25 μmol/L) or vehicle in the presence or absence of GLP-1 receptor antagonist for 24 h in regular or high glucose medium. The expression of specific markers and hormone levels were determined. ResultsTreatment with dapagliflozin significantly decreased blood glucose in the two diabetic models and upregulated plasma insulin and GLP-1 levels in db/db mice. The dapagliflozin treatment increased islet and beta cell numbers in the two diabetic mice. The beta cell proliferation as indicated by C-peptide and BrdU double-positive cells was boosted by dapagliflozin. The alpha to beta cell conversion, as evaluated by glucagon and insulin double-positive cells and confirmed by using alpha cell lineage-tracing, was facilitated by dapagliflozin. After the dapagliflozin treatment, some insulin-positive cells were located in the duct compartment or even co-localized with duct cell markers, suggestive of duct-derived beta cell neogenesis. In cultured primary rodent islets and αTC1.9 cells, dapagliflozin upregulated the expression of pancreatic endocrine progenitor and beta cell specific markers (including Pdx1) under high glucose condition. Moreover, dapagliflozin upregulated the expression of Pcsk1 (which encodes prohormone convertase 1/3, an important enzyme for processing proglucagon to GLP-1), and increased GLP-1 content and secretion in αTC1.9 cells. Importantly, the dapagliflozin-induced upregulation of Pdx1 expression was attenuated by GLP-1 receptor antagonist. ConclusionsExcept for glucose-lowering effect, dapagliflozin has extra protective effects on beta cells in type 2 diabetes. Dapagliflozin enhances beta cell self-replication, induces alpha to beta cell conversion, and promotes duct-derived beta cell neogenesis. The promoting effects of dapagliflozin on beta cell regeneration may be partially mediated via GLP-1 secreted from alpha cells.

A Protein/Lipid Preload Attenuates Glucose-Induced Endothelial Dysfunction in Individuals with Abnormal Glucose Tolerance.

Postprandial hyperglycemia interferes with vascular reactivity and is a strong predictor of cardiovascular disease. Macronutrient preloads reduce postprandial hyperglycemia in subjects with impaired glucose tolerance (IGT) or type 2 diabetes (T2D), but the effect on endothelial function is unknown. Therefore, we examined whether a protein/lipid preload can attenuate postprandial endothelial dysfunction by lowering plasma glucose responses in subjects with IGT/T2D. Endothelial function was assessed by the reactive hyperemia index (RHI) at fasting, 60 min and 120 min during two 75 g oral glucose tolerance tests (OGTTs) preceded by either water or a macronutrient preload (i.e., egg and parmesan cheese) in 22 volunteers with IGT/T2D. Plasma glucose, insulin, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), glucagon, free fatty acids, and amino acids were measured through each test. RHI negatively correlated with fasting plasma glucose. During the control OGTT, RHI decreased by 9% and its deterioration was associated with the rise in plasma glucose. The macronutrient preload attenuated the decline in RHI and markedly reduced postprandial glycemia. The beneficial effect of the macronutrient preload on RHI was proportional to the improvement in glucose tolerance and was associated with the increase in plasma GLP-1 and arginine levels. In conclusion, a protein/lipid macronutrient preload attenuates glucose-induced endothelial dysfunction in individuals with IGT/T2D by lowering plasma glucose excursions and by increasing GLP-1 and arginine levels, which are known regulators of the nitric oxide vasodilator system.

Exogenous supplement of glucagon like peptide-1 protects the heart against aortic banding induced myocardial fibrosis and dysfunction through inhibiting mTOR/p70S6K signaling and promoting autophagy

Mammalian target of rapamycin (mTOR) and a ribosomal protein S6 kinase (p70S6K) mediate tissue fibrosis and negatively regulate autophagy. This study aims to investigate whether glucagon-like peptide-1 (GLP-1) analog liraglutide protects the heart against aortic banding-induced cardiac fibrosis and dysfunction through inhibiting mTOR/p70S6K signaling and promoting autophagy activity. Male SD rats were randomly divided into four groups (n=6/each group): sham operated control; abdominal aortic constriction (AAC); liraglutide treatment during AAC (0.3mg/kg, injected subcutaneously twice daily); rapamycin treatment during AAC (0.2mg/kg/day, administered by gastric gavage). Relative to the animals with AAC on week 16, liraglutide treatment significantly reduced heart/body weight ratio, inhibited cardiomyocyte hypertrophy, and augmented plasma GLP-1 level and tissue GLP-1 receptor expression. Phosphorylation of mTOR/p70S6K, populations of myofibroblasts and synthesis of collagen I/III in the myocardium were simultaneously inhibited. Furthermore, autophagy regulating proteins: LC3-II/LC3-I ratio and Beclin-1 were upregulated, and p62 was downregulated by liraglutide. Compared with liraglutide group, treatment with rapamycin, a specific inhibitor of mTOR, compatibly augmented GLP-1 receptor level, inhibited phosphorylation of mTOR/p70S6K and expression of p62 as well as increased level of LC3-II/LC3-I ratio and Beclin-1, suggesting that there is an interaction between GLP-1 and mTOR/p70S6K signaling in the regulation of autophagy. In line with these modifications, treatment with liraglutide and rapamycin significantly reduced perivascular/interstitial fibrosis, and preserved systolic/diastolic function. These results suggest that the inhibitory effects of liraglutide on cardiac fibrosis and dysfunction are potentially mediated by inhibiting mTOR/p70S6K signaling and enhancing autophagy activity.

Glucagon receptor antagonism promotes the production of gut proglucagon-derived peptides in diabetic mice

Glucagon is an essential regulator of glucose homeostasis, particularly in type 2 diabetes (T2D). Blocking the glucagon receptor (GCGR) in diabetic animals and humans has been shown to alleviate hyperglycemia and increase circulating glucagon-like peptide-1 (GLP-1) levels. However, the origin of the upregulated GLP-1 remains to be clarified. Here, we administered high-fat diet + streptozotocin-induced T2D mice and diabetic db/db mice with REMD 2.59, a fully competitive antagonistic human GCGR monoclonal antibody (mAb) for 12 weeks. GCGR mAb treatment decreased fasting blood glucose levels and increased plasma GLP-1 levels in the T2D mice. In addition, GCGR mAb upregulated preproglucagon gene expression and the contents of gut proglucagon-derived peptides, particularly GLP-1, in the small intestine and colon. Notably, T2D mice treated with GCGR mAb displayed a higher L-cell density in the small intestine and colon, which was associated with increased numbers of LK-cells coexpressing GLP-1 and glucose-dependent insulinotropic polypeptide and reduced L-cell apoptosis. Furthermore, GCGR mAb treatment upregulated GLP-1 production in the pancreas, which was detected at lower levels than in the intestine. Collectively, these results suggest that GCGR mAb can increase intestinal GLP-1 production and L-cell number by enhancing LK-cell expansion and inhibiting L-cell apoptosis in T2D.

The insulinotropic and incretin response to feeding a milk based protein matrix in healthy young women

Abstract Independent of glucose, ingestion of protein evokes an insulinotropic response due to enterogastric incretin hormones and hyperaminoacidemia. The aim of this study was to characterise insulin and incretin secretion in healthy young women (age 22.0 ± 1.2 y, n = 8) following acute ingestion of a milk based protein matrix (MPM) containing casein, whey protein and whey protein hydrolysates with in vitro dipeptidyl peptidase IV (DPP-IV) inhibitory activity. Following ingestion of 0.33 g protein/kg body mass, plasma insulin, glucose, glucagon, total glucose-dependent insulinotropic polypeptide (GIP), active glucagon-like peptide-1 (GLP-1), DPP-IV activity and amino acids were measured over a 3 h period. These biomarkers were also determined following ingestion of an isocaloric maltodextrin drink (MALT) in order to estimate the equivalent glucose-dependent response. Ingestion of MPM evoked ~50% of the insulin response obtained with MALT without hyperglycaemia. Time-dependent changes in plasma GIP, GLP-1 and amino acid levels indicated these factors were probably regulators of insulin secretion on MPM ingestion.

1911-P: The Physiological Role of GLP-1 in Regulating Pancreatic Inflammation in a Sepsis Model

Patients who have diabetes mellitus (both type 1 and type 2) have increased susceptibility to sepsis. Among the hormones that are altered by sepsis, there is an increase in the glucoregulatory peptide glucagon-like peptide-1 (GLP-1), and in animal models there is a specific increase in pancreatic-produced GLP-1 vs. glucagon. While the function of GLP-1 during sepsis is unknown, GLP-1 agonists have recently been of interest as an anti-inflammatory agent. We hypothesized that GLP-1 increases are necessary for dampening pancreatic inflammatory responses to sepsis in lean and HFD-fed mice. To model sepsis, we administered 100ng/g lipopolysaccharide (LPS) to C57BL/6 mice who had been fed HFD or chow for 12 weeks. We found that compared to vehicle treatment, LPS significantly increased plasma levels of GLP-1 in both HFD and chow-fed mice, but plasma GLP-1 was significantly higher and plasma glucose was significantly lower in HFD compared to chow-fed mice. To determine whether GLP-1 specifically regulated pancreatic inflammation, 24 hours after LPS we used flow cytometry to isolate pancreatic immune cells from chow-fed mice devoid of GLP-1 (GcgΔNull) and wild type (WT) mice. In chow-fed mice, we found approximately 20% more CD45+ cells in WT LPS treated mice compared to vehicle, and a similar percentage of CD45+ cells in LPS treated GcgΔNull mice compared to WT. In contrast, LPS administration to HFD-fed GcgΔNull mice, resulted in increased F4/80 positive cells compared to WT mice. Taken together, these data suggest that Gcg peptides are necessary to blunt LPS-induced inflammation in the pancreas and that GLP-1 physiologically regulates tissue inflammation. Future studies will determine whether the increased GLP-1 in HFD-fed mice is due to an increased inflammatory state or a decreased effectiveness of GLP-1. Disclosure E.M. Davis: None. C. Hutch: None. K. Kim: None. B. Maerz: None. M. Lehrke: Research Support; Self; Boehringer Ingelheim International GmbH, Merck Sharp & Dohme Corp., Novo Nordisk A/S. Other Relationship; Self; Amgen, AstraZeneca, Boehringer Ingelheim International GmbH, Lilly Diabetes, Novo Nordisk A/S. D.A. Sandoval: Research Support; Self; MedImmune, Novo Nordisk A/S.

Glucagon receptor antagonist upregulates circulating GLP-1 level by promoting intestinal L-cell proliferation and GLP-1 production in type 2 diabetes

ObjectiveGlucagon receptor (GCGR) blockage improves glycemic control and increases circulating glucagon-like peptide-1 (GLP-1) level in diabetic animals and humans. The elevated GLP-1 has been reported to be involved in the...

The nuclear receptor FXR inhibits Glucagon-Like Peptide-1 secretion in response to microbiota-derived Short-Chain Fatty Acids

The gut microbiota participates in the control of energy homeostasis partly through fermentation of dietary fibers hence producing short-chain fatty acids (SCFAs), which in turn promote the secretion of the incretin Glucagon-Like Peptide-1 (GLP-1) by binding to the SCFA receptors FFAR2 and FFAR3 on enteroendocrine L-cells. We have previously shown that activation of the nuclear Farnesoid X Receptor (FXR) decreases the L-cell response to glucose. Here, we investigated whether FXR also regulates the SCFA-induced GLP-1 secretion. GLP-1 secretion in response to SCFAs was evaluated ex vivo in murine colonic biopsies and in colonoids of wild-type (WT) and FXR knock-out (KO) mice, in vitro in GLUTag and NCI-H716 L-cells activated with the synthetic FXR agonist GW4064 and in vivo in WT and FXR KO mice after prebiotic supplementation. SCFA-induced GLP-1 secretion was blunted in colonic biopsies from GW4064-treated mice and enhanced in FXR KO colonoids. In vitro FXR activation inhibited GLP-1 secretion in response to SCFAs and FFAR2 synthetic ligands, mainly by decreasing FFAR2 expression and downstream Gαq-signaling. FXR KO mice displayed elevated colonic FFAR2 mRNA levels and increased plasma GLP-1 levels upon local supply of SCFAs with prebiotic supplementation. Our results demonstrate that FXR activation decreases L-cell GLP-1 secretion in response to inulin-derived SCFA by reducing FFAR2 expression and signaling. Inactivation of intestinal FXR using bile acid sequestrants or synthetic antagonists in combination with prebiotic supplementation may be a promising therapeutic approach to boost the incretin axis in type 2 diabetes.

Effects and Mechanisms of Vagal Nerve Stimulation on Body Weight in Diet-Induced Obese Rats.

Vagal nerve stimulation (VNS) has recently been indicated as a novel method for treating obesity. However, the optimal stimulation parameters were unknown and mechanisms were poorly understood. The aim of this study was to investigate the effects of VNS on food intake and body weight in diet-induced obesity (DIO) rats and its possible mechanism involving autonomic functions and gut hormones. Ten control rats and 16 DIO rats were chronically implanted with one pair of electrodes in the subdiaphragmatic vagal nerve. VNS with different stimulation parameters and sham-VNS were performed in control rats. In a chronic study, 8 DIO rats were applied with VNS and another 8 DIO rats were treated with sham-VNS for 4weeks. Food intake, body weight, gastric emptying, heart rate variability (HRV), and gut hormones were evaluated. In DIO rats, the food intake (p < 0.001) and body weight (p < 0.001) were significantly decreased in the VNS group, compared with the sham-VNS group. VNS decreased the sympathovagal ratio (p = 0.003) and increased vagal activity (p = 0.032) assessed from the spectral analysis of HRV. It also increased plasma levels of glucagon-like peptide-1 (p = 0.012), polypeptide YY (p = 0.008), and pancreatic polypeptide (p = 0.008) in DIO rats. Physiologically, VNS delayed solid gastric emptying (p < 0.001) and increased gastric volume (p = 0.004). VNS with appropriate parameters reduced food intake and body weight by delaying gastric emptying mediated via the enhancement of vagal activity and release of anorexigenic hormones.

Влияние Roux-en-Y гастрошунтирования и продольной резекции желудка на метаболические и гормональные показатели и гипоталамический сигналинг у крыс с диабетом 2 типа

Bariatric surgery is widely used to correct the metabolic dysfunctions in type 2 diabetes mellitus (T2DM), but the mechanisms of its action are not fully understood. The aim of the work was to study the effect of Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) on the metabolic and hormonal parameters and on the expression of the hypothalamic genes encoding appetite-regulating factors and the components of signaling systems controlling an energy metabolism in male rats with T2DM without obesity. The T2DM was induced by a 20-week high-fat diet and treatment of rats with 20 mg/kg of streptozotocin (STZ) at the 12th week of the experiment. The operations were performed 3 weeks after STZ treatment. The glucose sensitivity and the hormonal parameters were evaluated at the 19th week, and the hypothalamic tissues were taken at the 20th week to evaluate the gene expression. In rats with T2DM, both operations reduced the food intake, decreased the postprandial glucose levels, normalized the leptin levels, and lowered the plasma ghrelin levels in T2DM. The SG, which, in comparison with RYGB, had a lesser effect on the glucose homeostasis and the ghrelin level, reduced the food intake more effectively and, unlike RYGB, restored the glucagon-like peptide-1 (GLP-1) level decreased in T2DM. The RYGB led to a decrease in the expression of orexigenic genes, encoding agouti-like peptide and ghrelin receptor, increased in T2DM, and to an increase in the expression of anorexigenic genes, encoding the MC3- and MC4-melanocortin, the 5-HT2C-serotonin and leptin receptors and pro-opiomelanocortin. The largest contribution to the effects of SG is made by a significant increase in the hypothalamic expression of the GLP-1 receptor gene, associated with an increase in the plasma GLP-1 level. Thus, the RYGB and SG can be effective to correct the metabolic and functional dysfunctions in non-obese T2DM, and the restoration of the balance between the hypothalamic orexigenic and anorexigenic pathways makes a significant contribution to these effects.