Project description:To gain insight into the biological functions of the highly expressed GLP-1R in Brunnerâs glands, transcriptome analyses were conducted in male GLP-1R-/- and wild-type control mice. Analyses were performed 6 hours after a single s.c. dose of exendin-4 (1.0mg/kg s.c.), following 18 hours of two doses of exendin-4 (1.0 mg/kg s.c., administered at 0 and 9 hours), and in untreated controls. Brunnerâs glands were isolated by laser capture micro dissection and extracted total RNA was used for microarray profiling. A total of 18 samples consisting of laser captured microdissected Brunner's glands from individual male GLP-1R-/- and wild-type (CD-1) mice. Before the isolation of Brunner's glands, mice were dosed with exendin-4 for 6 and 18 hours. The extracted total RNA from Brunner's glands were compared by full transcriptome profiling.
Project description:To gain insight into the biological functions of the highly expressed GLP-1R in Brunner’s glands, transcriptome analyses were conducted in male GLP-1R-/- and wild-type control mice. Analyses were performed 6 hours after a single s.c. dose of exendin-4 (1.0mg/kg s.c.), following 18 hours of two doses of exendin-4 (1.0 mg/kg s.c., administered at 0 and 9 hours), and in untreated controls. Brunner’s glands were isolated by laser capture micro dissection and extracted total RNA was used for microarray profiling.
Project description:Gut intraepithelial lymphocytes (IELs) are one of the few immune cell populations in the body that expresses glucagon-like 1 receptors (GLP-1R). To test the potential effects of GLP-1 on gut IEL function, we performed bulk RNA-seq on gut IELs isolated from C57BL/6J mice treated with anti-CD3 and with or without exendin-4 for 3 hours.
Project description:Gut intraepithelial lymphocytes (IELs) are one of the few immune cell populations in the body that expresses glucagon-like 1 receptors (GLP-1R). To test the potential effects of GLP-1 on the gut microbiota through the gut IEL GLP-1R, we performed 16s rRNA seq on the DNA isolated from the fecal pellet of Lck-Cre; Glp1rfl/fl mice (Glp1rTcell-/-) or controls (Glp1rTcell+/+) fed a high-fat diet (HFD) for 12 weeks followed by 1 week of HFD plus semaglutide (10 ug/kg) or vehicle treatment. Fecal pellets from a group of age-matched, sex-matched control mice were included as a chow control group.
Project description:GLP-1 analogues, such as exendin-4, preserve functional β-cell mass in various model systems and are revolutionising management of type 2 diabetes. Yet, comparatively little is known about effectiveness in the face of severe β-cell depletion. Moreover, direct and sequential effects of exendin-4 on islet-specific gene expression over time in vivo are not well characterised. To address these issues and others, we have examined the time-dependent effects of exendin-4 treatment on β-cell mass regulation alongside accompanying changes in islet gene expression in vivo. Context-dependent actions were assessed by comparing effects on normal islets and also following massive toxigenetic β-cell ablation in pIns-MYCERTAM transgenic mice in vivo. Despite over 90% loss of β-cell mass, exendin-4 treatment normalised blood glucose and insulin levels in hyperglycaemic mice, though benefits rapidly waned on withdrawal of treatment. As exendin-4 did not arrest the decline in β-cell mass or turnover in this study, we could directly isolate effects on function of surviving β-cells. Improved glucose homeostasis was associated with dynamic changes in multiple islet genes and pathways in vivo favouring glucose-stimulated insulin secretion, such as Irs2, Pdx1, Sox4, glucokinase, and glycolysis pathway. Several key growth pathways and epigenetic regulators were also differentially expressed. Thus, even in the face of extensive β-cell loss exendin-4 can markedly improve hyperglycaemia by differential gene expression in surviving islet cells. Activation of MYCERTAM was achieved through administration of 1mg of 4 hydroxytamoxifen (4OHT; Sigma-Aldrich, St. Louis, MO) by daily intraperitoneal injection. To assess the effect of exendin-4 on MYCER-induced hyperglycaemia, mice were given either twice-daily subcutaneous (sc) injections of exendin-4 (50ug/kg dissolved in 5mls water), or equivalent volumes of water vehicle, starting 2 days prior to 4OHT injections. For microarray analyses parallel mouse experiments were set up using 8-12 week old pIns-MYCERTAM male mice either treated with 4OHT or vehicle (peanut oil) and exendin-4 or vehicle, as described, for 4, 8, 16, 32 and 72 hours (n=3 for each time point and for each of four conditions; 4OHT and exendin-4 treated, peanut oil and exendin-4 treated, 4OHT and water treated, peanut oil and water treated). !Sample_data_processing = After the quality control step, the following 8 samples out of 60 showing poor reproducibility were excluded from our further study: GSM930242, GSM930247, GSM930251, GSM930263, GSM930264, GSM930289, GSM930291, GSM930298.
Project description:Tirzepatide (LY3298176), a dual GIP and GLP-1 receptor agonist, has been shown to deliver enhanced glycemic control and superior weight loss compared to a selective GLP-1 receptor (GLP-1R) agonist in patients with type 2 diabetes mellitus. However, the mechanism by which tirzepatide improves efficacy and how GIP receptor (GIPR) agonism contributes to the therapy is not fully understood. Here, hyperinsulinemic-euglycemic clamp studies were used to show that tirzepatide is a highly effective insulin sensitizer, improving insulin sensitivity in obese mice to a greater extent than GLP-1R agonism. To determine if GIPR agonism contributes to the insulin sensitization, we compared the effect of tirzepatide in obese wild-type and Glp-1r null mice. In the absence of GLP-1R induced weight loss, tirzepatide improved systemic insulin sensitivity by enhancing glucose disposal in WAT. To corroborate these results, chronic treatment with a long-acting GIPR agonist (LAGIPRA) was also found to enhance insulin sensitivity by increasing insulin stimulated glucose uptake in WAT. Interestingly, the effect of tirzepatide and LAGIPRA on insulin sensitivity was associated with reduced branched chain amino and keto acids in the circulation. Whole-body insulin sensitization was associated with pronounced upregulation of genes associated with the catabolism of glucose, lipid and BCAAs in brown adipose tissue. Together, our studies show that tirzepatide improved insulin sensitivity in a weight-dependent and -independent manner. These results highlight how GIPR agonism contributes to the therapeutic profile of dual GIP and GLP-1 receptor agonism, offering mechanistic insights into the clinical efficacy of tirzepatide.
Project description:Glucagon and glucagon-like peptide-1 (GLP-1) are hormones involved in energy homeostasis. GLP-1 receptor (GLP-1R) agonism reduces food intake and delays gastric emptying, and glucagon receptor (GCGR) agonism increases energy expenditure by thermogenesis. BI 456906 is a subcutaneous, once-weekly injectable dual GLP-1R/GCGR agonist in development for the treatment of obesity or non-alcoholic steatohepatitis. Here we show that BI 456906 is a potent dual agonist with an extended half-life in human plasma. Key GLP-1R-mediated mechanisms of reduced food intake, delayed gastric emptying and improved glucose tolerance were confirmed in GLP-1R knockout mice. GCGR activity was confirmed by reduced plasma amino acids, increased hepatic expression of nicotinamide N-methyltransferase and increased energy expenditure. BI 456906 produced greater bodyweight reductions than maximally efficacious semaglutide doses and modulated gene expression, including genes involved in amino acid metabolism. BI 456906 is a potent dual agonist that produces bodyweight-lowering effects through both GLP-1R and GCGR agonism.
Project description:GLP-1 based diabetes drugs are effective to reduce hepatic lipid accumulation beyong glycemic control. As GLP-1 receptor (GLP-1R) is not expressed in hepatocytes, the mechanism behind the beneficial effects of GLP-1 based drugs on the liver remained elusive. Several studies have shown that the expression of hepatic fibroblast growth factor 21 (FGF21) can be stimulated by GLP-1-based drugs. Therefore, the present study aimed to assess such stimulation in mice and in mouse primary hepatocytes, determine whether hepatic FGF21 mediates functions of the GLP-1R agonist liraglutide, and to explore the potential mechanisms of liraglutide regulating the expression of FGF21. In high-fat diet induced obese mice, we observed hepatic and plasma FGF21 elevation, improved glucose disposal, and reduced plasma triglyceride levels by liraglutide treatment. Moreover, RNA-sequencing on the liver suggested that Fgf21 was the most upregulated gene after liraglutide treatment. In liver-specific FGF21 knock-out mice on high-fat and high-fructose diet, the body-weight gain attenuation and lipid homeostatic effects of liraglutide was lost or significantly reduced. These studies implied that hepatic FGF21 was the critical mediator of liraglutide-induced metabolic improvement.
Project description:GLP-1 analogues, such as exendin-4, preserve functional β-cell mass in various model systems and are revolutionising management of type 2 diabetes. Yet, comparatively little is known about effectiveness in the face of severe β-cell depletion. Moreover, direct and sequential effects of exendin-4 on islet-specific gene expression over time in vivo are not well characterised. To address these issues and others, we have examined the time-dependent effects of exendin-4 treatment on β-cell mass regulation alongside accompanying changes in islet gene expression in vivo. Context-dependent actions were assessed by comparing effects on normal islets and also following massive toxigenetic β-cell ablation in pIns-MYCERTAM transgenic mice in vivo. Despite over 90% loss of β-cell mass, exendin-4 treatment normalised blood glucose and insulin levels in hyperglycaemic mice, though benefits rapidly waned on withdrawal of treatment. As exendin-4 did not arrest the decline in β-cell mass or turnover in this study, we could directly isolate effects on function of surviving β-cells. Improved glucose homeostasis was associated with dynamic changes in multiple islet genes and pathways in vivo favouring glucose-stimulated insulin secretion, such as Irs2, Pdx1, Sox4, glucokinase, and glycolysis pathway. Several key growth pathways and epigenetic regulators were also differentially expressed. Thus, even in the face of extensive β-cell loss exendin-4 can markedly improve hyperglycaemia by differential gene expression in surviving islet cells.
Project description:Obesity is a chronic disease that contributes to the development of insulin resistance, type 2 diabetes (T2D), and cardiovascular risk. GIP receptor (GIPR) and GLP-1 receptor (GLP-1R) co-agonism provide an improved therapeutic profile in individuals with T2D and obesity when compared with selective GLP-1R agonism. While the metabolic benefits of GLP-1R agonism are established, whether GIPR activation impacts weight loss through peripheral mechanisms is yet to be fully defined. Here, we generated a mouse model of GIPR induction exclusively in the adipocyte. We show that GIPR induction in the fat cell protects mice from diet-induced obesity and triggers profound weight loss (~35%) in an obese setting. Adipose GIPR further increases lipid oxidation, thermogenesis and energy expenditure. Mechanistically, we demonstrate that GIPR induction activates SERCA-mediated futile calcium cycling in the adipocyte. GIPR activation further triggers a metabolic memory effect, which maintains weight loss after the transgene has been switched off, highlighting a unique aspect in adipocyte biology. Collectively, we present a mechanism of peripheral GIPR action in adipose tissue, which exerts beneficial metabolic effects on body weight and energy balance.