Non-canonical hepatic androgen receptor mediates glucagon sensitivity in female mice through the PGC1α/ERRα/mitochondria axis
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ABSTRACT: Glucagon has recently been found to modulate liver fat content, in addition to its role in regulating gluconeogenesis. However, the precise mechanisms by which glucagon signaling synchronizes glucose and lipid metabolism in the liver remain poorly understood. By employing chemical and genetic approaches, we demonstrate that inhibiting the androgen receptor (AR) impairs the ability of glucagon to stimulate gluconeogenesis and lipid catabolism in primary hepatocytes and female mice. Notably, AR expression in the liver of female mice is up to three times higher than that in their male littermates, accounting for the more pronounced response to glucagon in females. Mechanistically, hepatic AR promotes energy metabolism and enhances lipid breakdown for liver glucose production in response to glucagon treatment through the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α)/estrogen-related receptor alpha (ERRα)-mitochondria axis. Overall, our findings highlight the crucial role of hepatic AR in mediating glucagon signaling and the sexual dimorphism in hepatic glucagon sensitivity.
Project description:Glucagon has recently been found to modulate liver fat content, in addition to its role in regulating gluconeogenesis. However, the precise mechanisms by which glucagon signaling synchronizes glucose and lipid metabolism in the liver remain poorly understood. By employing chemical and genetic approaches, we demonstrate that inhibiting the androgen receptor (AR) impairs the ability of glucagon to stimulate gluconeogenesis and lipid catabolism in primary hepatocytes and female mice. Notably, AR expression in the liver of female mice is up to three times higher than that in their male littermates, accounting for the more pronounced response to glucagon in females. Mechanistically, hepatic AR promotes energy metabolism and enhances lipid breakdown for liver glucose production in response to glucagon treatment through the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α)/estrogen-related receptor alpha (ERRα)-mitochondria axis. Overall, our findings highlight the crucial role of hepatic AR in mediating glucagon signaling and the sexual dimorphism in hepatic glucagon sensitivity.
Project description:Glucagon is a key regulator of glucose homeostasis, amino acid catabolism, and lipid metabolism. Glucagon receptor knock-out (GcgrKO) mice have slightly reduced blood glucose levels whereas plasma levels of amino acids are vastly increased reflecting disruption of hepatic amino acid catabolism. To dissect the molecular mechanisms underlying this effect, RNA sequencing of livers from male GcgrKO mice and wild-type littermates were performed. The mice were 10 weeks of age and were subjected to a short-term fast of 4 h before anesthesia with 2.5% isoflurane.
Project description:Glucagon supports glucose homeostasis by stimulating hepatic gluconeogenesis, in part by promoting the uptake and conversion of amino acids into gluconeogenic precursors. Genetic disruption or pharmacologic inhibition of glucagon signaling results in elevated plasma amino acids and compensatory glucagon hypersecretion involving expansion of pancreatic a cell mass. Recent findings indicate that hyperaminoacidemia triggers pancreatic a cell proliferation via an mTOR-dependent pathway. We confirm and extend these findings by demonstrating that glucagon pathway blockade selectively increases expression of the sodium-coupled neutral amino acid transporter Slc38a5 in a subset of highly proliferative a cells and that Slc38a5 controls the pancreatic response to glucagon pathway blockade; most notably, mice deficient in Slc38a5 exhibit markedly decreased a cell hyperplasia to glucagon pathway blockade-induced hyperaminoacidemia. These results show that Slc38a5 is a key component of the feedback circuit between glucagon receptor signaling in the liver and amino-acid-dependent regulation of pancreatic a cell mass in mice.
Project description:Glucagon and insulin are counter-regulatory pancreatic hormones that precisely control blood glucose homeostasis1. Type 2 diabetes mellitus (T2DM) is characterized by inappropriately elevated blood glucagon2-5 levels as well as insufficient glucose stimulated insulin secretion (GSIS) by pancreatic ß-cells6. Early in the pathogenesis of T2DM, hyperglucagonemia is observable antecedent to ß-cell dysfunction7-9; and in mice, liver-specific activation of glucagon receptor-dependent signaling results in impaired GSIS10. However, the mechanistic relationship between hyperglucagonemia, hepatic glucagon action, and ß-cell dysfunction remains poorly understood. Here we show that glucagon action stimulates hepatic production of the neuropeptide kisspeptin1, which acts in an endocrine manner on ß-cells to suppress GSIS. In vivo glucagon administration acutely stimulates hepatic kisspeptin1 production, and kisspeptin1 is increased in livers from humans with T2DM and from mouse models of diabetes mellitus. Synthetic kisspeptin1 potently suppresses GSIS in vivo and in vitro from normal isolated islets, which express the kisspeptin1 receptor Kiss1R. Administration of a Kiss1R antagonist in diabetic Leprdb/db mice potently augments GSIS and reduces glycemia. Our observations indicate in the pathogenesis of T2DM an endocrine mechanism sequentially linking hyperglucagonemia via hepatic kisspeptin1 production to impaired insulin secretion. In addition, our findings suggest Kiss1R antagonism as a therapeutic avenue to improve ß-cell function in T2DM. Total RNA from L-Δprkar1a KO mice compared to control D-glucose mice
Project description:Long non-coding RNAs (lncRNAs) are emerging important epigenetic regulators in metabolic processes. Whether they contribute to the metabolic effects of vertical sleeve gastrectomy (VSG), one of the most effective treatments for sustainable weight loss and metabolic improvement, is unknown. Herein, we identified a hepatic lncRNA Gm19619, which was strongly repressed by VSG but highly up-regulated by diet-induced obesity and overnight-fasting in mice. Forced transcription of Gm19619 in the mouse liver significantly promoted hepatic gluconeogenesis with the elevated expression of G6pc and Pck1. In contrast, AAV-CasRx mediated knockdown of Gm19619 in HFD-fed mice significantly improved hepatic glucose and lipid metabolism. Mechanistically, Gm19619 was enriched along genomic regions encoding leptin receptor (Lepr) and the transcriptional factor Foxo1, as revealed in chromatin isolation by RNA purification (ChIRP) assay and was confirmed to modulate their transcription in the mouse liver. In conclusion, Gm19619 may enhance gluconeogenesis and lipid metabolism in the liver.
Project description:Long non-coding RNAs (lncRNAs) are emerging important epigenetic regulators in metabolic processes. Whether they contribute to the metabolic effects of vertical sleeve gastrectomy (VSG), one of the most effective treatments for sustainable weight loss and metabolic improvement, is unknown. Herein, we identified a hepatic lncRNA Gm19619, which was strongly repressed by VSG but highly up-regulated by diet-induced obesity and overnight-fasting in mice. Forced transcription of Gm19619 in the mouse liver significantly promoted hepatic gluconeogenesis with the elevated expression of G6pc and Pck1. In contrast, AAV-CasRx mediated knockdown of Gm19619 in HFD-fed mice significantly improved hepatic glucose and lipid metabolism. Mechanistically, Gm19619 was enriched along genomic regions encoding leptin receptor (Lepr) and the transcriptional factor Foxo1, as revealed in chromatin isolation by RNA purification (ChIRP) assay and was confirmed to modulate their transcription in the mouse liver. In conclusion, Gm19619 may enhance gluconeogenesis and lipid metabolism in the liver.
Project description:To investigate the role of the transient receptor potential channel vanilloid type 1 (TRPV1) channel in hepatic glucose metabolism, we performed proteomics analysis of the liver of C57Bl/6J (WT) and Trpv1 KO mice (n = 4 per group). Liver from Trpv1 KO mice showed significant proteomics changes consistent with enhanced glycogenolysis, as well as increased gluconeogenesis and inflammatory features.
Project description:Glucagon supports glucose homeostasis by stimulating hepatic gluconeogenesis, in part by promoting the uptake and conversion of amino acids into gluconeogenic precursors. Genetic disruption or pharmacologic inhibition of glucagon signaling results in elevated plasma amino acids, and compensatory glucagon hypersecretion involving expansion of pancreatic α-cell mass. Regulation of pancreatic α- and β-cell growth has drawn a lot of attention because of potential therapeutic implications. Recent findings indicate that hyperaminoacidemia triggers pancreatic α-cell proliferation via an mTOR-dependent pathway. We confirm and extend these findings by demonstrating that glucagon pathway blockade selectively increases expression of the sodium-coupled neutral amino acid transporter Slc38a5 in a subset of highly proliferative α-cells, and that Slc38a5 is critical for the pancreatic response to glucagon pathway blockade; most notably, mice deficient in Slc38a5 exhibit markedly decreased α-cell hyperplasia to glucagon pathway blockade-induced hyperaminoacidemia. These results show that Slc38a5 is a key component of the feedback circuit between glucagon receptor signaling in the liver and amino acid-dependent regulation of pancreatic α-cell mass in mice.
Project description:Glucagon is secreted from pancreatic α-cells, and hypersecretion (hyperglucagonemia) contributes to diabetic hyperglycemia. Molecular heterogeneity in hyperglucagonemia is poorly investigated. By screening human plasma by high-resolution-proteomics, we identified several glucagon variants among which proglucagon 1-61 (PG 1-61) appears to be the most abundant form. PG 1-61 was secreted in obese subjects before and as well after gastric bypass surgery with protein and fat as the main drivers for secretion before surgery, but glucose after. Studies in hepatocytes and in β-cells demonstrated that PG 1-61 dose-dependently increased levels of cAMP, through the glucagon receptor, and increased insulin secretion and protein levels of enzymes regulating glycogenolysis and gluconeogenesis. As a consequence, PG 1-61 increased blood glucose and plasma insulin and decreased plasma levels of amino acids in vivo. Glucagon variants, such as PG 1-61, may contribute to glucose regulation by stimulating hepatic glucose production and insulin secretion.
Project description:Mediator complex function as an integrative hub for transcriptional regulation. Here we show that Mediator subunit MED23 regulate glucose and lipid metabolism via FOXO1 in liver. Here, we have generated a liver-specific Med23-knockout (LMKO) mouse and found that Med23-deletion in liver improved glucose and lipid metabolism, as well as insulin responsiveness, and prevented diet-induced obesity. Mechanistically, MED23 participated in gluconeogenesis and cholesterol synthesis by interacting with FOXO1. Disruption of this interaction by hepatic Med23-deletion impaired the Mediator and RNAP II recruitment and partially reduced the expression of the FOXO1 target genes. Remarkably, acute hepatic Med23 knockdown in db/db mice significantly improved insulin sensitivity. Overall, our data revealed Mediator MED23 as a critical regulator of glucose and lipid metabolism, suggesting novel therapeutic strategies against metabolic diseases.