BAT Transcriptomics in DIO Vehicle or Cotadutide Mice
Ontology highlight
ABSTRACT: Early drivers of Type 2 diabetes mellitus (T2D) include ectopic fat accumulation, especially in the liver, that significantly impairs insulin sensitivity. In a T2D setting, GLP-1R/GCGR dual agonists have been shown to reduce glycaemia, body weight and hepatic steatosis. We utilized cotadutide, a well characterized GLP-1R/GCGR dual-agonist, to demonstrate improved insulin sensitivity during hyperinsulinemic euglycemic clamp following sub-chronic dosing in male, diet-induced obese mice. Cotadutide or GCGR monoagonist treatment resulted in specific increased brown adipose tissue (BAT) insulin-stimulated glucose uptake, while GLP-1R monoagonist only showed a weak effect. BAT from cotadutide treated mice had induction of UCP-1 protein, increased mitochondrial area and a transcriptomic profile of increased fat oxidation and mitochondrial activity. Thus, GLP-1R/GCGR dual agonism provides multimodal efficacy to decrease hepatic steatosis and consequently improve insulin sensitivity, in concert with recovery of endogenous β-cell function and reduced insulin demand. This substantiates GLP-1R/GCGR dual-agonism as a novel and effective T2D treatment.
Project description:Early drivers of Type 2 diabetes mellitus (T2D) include ectopic fat accumulation, especially in the liver, that significantly impairs insulin sensitivity. In a T2D setting, GLP-1R/GCGR dual agonists have been shown to reduce glycaemia, body weight and hepatic steatosis. We utilized cotadutide, a well characterized GLP-1R/GCGR dual-agonist, to demonstrate improved insulin sensitivity during hyperinsulinemic euglycemic clamp following sub-chronic dosing in male, diet-induced obese mice. Phosphoproteomic analyses of insulin stimulated liver from cotadutide treated diet-induced obese (DIO) mice identified novel phosphorylation sites on key insulin signalling pathway proteins associated with improved insulin sensitivity. Cotadutide or GCGR monoagonist treatment also resulted in specific increased brown adipose tissue (BAT) insulin-stimulated glucose uptake, while GLP-1R monoagonist only showed a weak effect. BAT from cotadutide treated mice had induction of UCP-1 protein, increased mitochondrial area and a transcriptomic profile of increased fat oxidation and mitochondrial activity. Finally, the cotadutide-induced improvement in insulin sensitivity was associated with reduced insulin secretion from isolated pancreatic islet β-cells indicating reduced insulin secretory demand. Thus, GLP-1R/GCGR dual agonism provides multimodal efficacy to decrease hepatic steatosis and consequently improve insulin sensitivity, in concert with recovery of endogenous β-cell function and reduced insulin demand. This substantiates GLP-1R/GCGR dual-agonism as a novel and effective T2D treatment
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: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: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.
Project description:Agonists and antagonists of the glucose-dependent insulinotropic polypeptide receptor (GIPR) enhance body weight loss induced by glucagon-like peptide-1 receptor (GLP-1R) agonism. But while GIPR agonism decreases body weight and food intake in a GLP-1R-independent manner via GABAergic GIPR+ neurons, it remains unclear whether GIPR antagonism affects energy metabolism via a similar mechanism. Here we show that the body weight and food intake reducing effects of GIPR antagonism vanish in mice with global loss of either Gipr or Glp-1r but are preserved in mice with loss of Gipr in either GABAergic or peripheral neurons. RNA-sequencing shows opposing effects of GIPR agonism and antagonism in the hindbrain, with antagonism, but not agonism, mimicking GLP-1R signaling, and with GIPR antagonism and GLP-1R agonism both regulating gene programs implicated in synaptic plasticity. Collectively, we show that GIPR agonism and antagonism decrease body weight via different mechanisms, with GIPR antagonism, unlike agonism, depending on functional GLP-1R signaling.
Project description:Tirzepatide, a glucose-dependent insulinotropic polypeptide/glucagon-like peptide 1 receptor (GIPR/GLP-1R) agonist, has, in clinical trials, demonstrated greater reductions in glucose, body weight and triglyceride levels compared with selective GLP-1R agonists in people with type 2 diabetes (T2D). However, cellular mechanisms by which GIPR agonism may contribute to these improved efficacy outcomes have not been fully defined. Using human adipocyte and mouse models, we investigated how long-acting GIPR agonists regulate fasted and fed adipocyte functions in the presence and absence of insulin to model post-prandial and post-absorptive states. Transcriptional profiling of human adipocytes demonstrated differential gene, pathway, and upstream regulation by GIP indicative of modulation of both carbohydrate and lipid metabolism. In functional assays, GIPR agonism enhanced insulin signaling, augmented glucose uptake, and increased the conversion of glucose to glycerol in a cooperative manner with insulin. GIPR agonists increased lipolysis in the absence of insulin, an effect that was fully suppressed when co-administered with insulin. In diet-induced obese mice treated with a long-acting GIPR agonist, circulating triglyceride levels were reduced during oral lipid challenge and lipoprotein-derived fatty acid uptake into adipose tissue was increased. Our findings support a model for long-acting GIPR agonists to modulate both fasted and fed adipose tissue function differentially, by cooperating with insulin to augment glucose and lipid clearance in the fed state, while enhancing lipid release when insulin levels are reduced in the fasted state. This novel paradigm illustrates key mechanisms by which GIPR/GLP-1R agonists such as tirzepatide likely regulate adipocyte function to enhance weight loss as well as improve glucose and lipid metabolism in T2D.
Project description:Increased liver de novo lipogenesis (DNL) is a hallmark of nonalcoholic steatohepatitis (NASH). A key enzyme controlling DNL upregulated in NASH is ATP citrate lyase (ACLY). In mice, inhibition of ACLY reduces liver steatosis, ballooning and fibrosis and inhibits activation of hepatic stellate cells. Glucagon like peptide-1 receptor (GLP-1R) agonists lower body mass, insulin resistance and steatosis without improving fibrosis. Here, we find that combining an inhibitor of liver ACLY, bempedoic acid, and the GLP-1R agonist liraglutide reduces liver steatosis, hepatocellular ballooning, and hepatic fibrosis in a mouse model of NASH. Liver RNA analyses revealed additive downregulation of pathways that are predictive of NASH resolution, reductions in the expression of prognostically significant genes compared to clinical NASH samples, and a predicted gene signature profile that supports fibrosis resolution. These findings support further investigation of this combinatorial therapy to treat obesity, insulin resistance, hypercholesterolemia, steatohepatitis, and fibrosis in people with NASH.
Project description:Increased liver de novo lipogenesis (DNL) is a hallmark of nonalcoholic steatohepatitis (NASH). A key enzyme controlling DNL upregulated in NASH is ATP citrate lyase (ACLY). In mice, inhibition of ACLY reduces liver steatosis, ballooning and fibrosis and inhibits activation of hepatic stellate cells. Glucagon like peptide-1 receptor (GLP-1R) agonists lower body mass, insulin resistance and steatosis without improving fibrosis. Here, we find that combining an inhibitor of liver ACLY, bempedoic acid, and the GLP-1R agonist liraglutide reduces liver steatosis, hepatocellular ballooning, and hepatic fibrosis in a mouse model of NASH. Liver RNA analyses revealed additive downregulation of pathways that are predictive of NASH resolution, reductions in the expression of prognostically significant genes compared to clinical NASH samples, and a predicted gene signature profile that supports fibrosis resolution. These findings support further investigation of this combinatorial therapy to treat obesity, insulin resistance, hypercholesterolemia, steatohepatitis, and fibrosis in people with NASH.
Project description:Combinatorial therapies are under intense investigation for the development of more efficient anti-obesity drugs, however little is known about how they act in brain to produce enhanced satiety and weight loss. Here we used a multidisciplinary strategy to decipher the central mechanisms engaged downstream from the co-administration of GLP-1R and CCK1R agonists, an efficient combination therapy in obese rodents. The nucleus of the solitary tract (NTS) contained one of the few neuronal populations synergistically activated in response to GLP-1R and CCK1R co-agonism. None of the previously categorized NTS neuronal subpopulations relevant to feeding behaviour were synergistically activated. However, using PhosphoTRAP, we obtained the molecular signature of NTS and ARH neurons synergistically regulated by the GLP-1R and CCK1R co-agonism and identified NTS/AP Calcrl+ neurons and ARH Adcyap1r1+ neurons as targets of this treatment. Collectively these studies advance our understanding of the central mechanisms involved in the synergistic appetite- and weight-suppressive effect of a combinatorial therapy.
Project description:Glucagon-like peptide-1 (GLP-1) is an incretin hormone that potentiates glucose stimulated insulin secretion. GLP-1 is classically produced by gut L cells; however, under certain circumstances alpha-cells can express the prohormone convertase required for proglucagon processing to GLP-1, prohormone convertase 1/3 (PC1/3), and can produce GLP-1. However, the mechanisms through which this occurs are poorly defined. Understanding the mechanisms by which alpha-cell PC1/3 expression can be activated may reveal new targets for diabetes treatment. Here, we demonstrate that the GLP-1 receptor (GLP-1R) agonist, liraglutide, increases alpha-cell GLP-1 expression in a beta cell GLP-1R-dependent manner. We demonstrate that this effect of liraglutide is translationally relevant in human islets through application of a new scRNA-sequencing technology, DART-seq. We find that the effect of liraglutide to increase alpha-cell PC1/3 mRNA expression occurs in a sub-cluster of alpha-cells and is associated with increased expression of other beta-cell-like genes, which we confirm by IHC. Finally, we find that the effect of liraglutide to increase bi-hormonal insulin+ glucagon+ cells is mediated by the beta-cell GLP-1R in mice. Together, our data validate a new high-sensitivity method for scRNA-sequencing in human islets and identify a novel GLP-1 mediated pathway regulating human alpha-cell function.