Molecular Metabolism最新文献

Maternal nutrition exerts profound, lasting effects on offspring metabolic health, yet the impact of maternal overconsumption of key nutrients such as branched-chain amino acid (BCAAs) remains poorly understood. Here, we show that intake of a BCAA-enriched isocaloric, protein content-matched diet throughout pregnancy and lactation induces hyperglycemia and altered circulating amino acid profiles in mouse dams, and programs lasting changes in offspring glucose homeostasis. Adult offspring of both sexes on a chow diet exhibited glucose intolerance. Male offspring showed fasting hyperglycemia despite normal adiposity, whereas females maintained normoglycemia via compensatory hyperinsulinemia. Under a postweaning high-fat diet challenge, offspring of BCAA-fed dams were protected from adiposity and hepatic steatosis, yet developed exacerbated hyperglycemia and glucose intolerance. Mechanistically, maternal BCAA overnutrition reprogrammed offspring energy substrate handling through enhanced white adipose tissue lipolysis and fatty acid oxidation, reduced hepatic fatty acid uptake, and increased hepatic oxidative and gluconeogenic capacity. Elevated hepatic PGC-1α served as a central integrator of oxidative and gluconeogenic pathways, uncoupling lipid and glucose metabolism. These findings identify excess maternal BCAA intake as a nutrient-specific driver of developmental programming that uncouples adiposity from glycemic control, highlighting amino acid-driven metabolic plasticity as a critical axis in intergenerational metabolic dysfunction.

Objective: Unimolecular triagonists drive substantial weight loss in patients with obesity by engaging the glucagon-like peptide 1 receptor (GLP-1R) and glucose dependent insulinotropic polypeptide receptor (GIPR) to reduce food intake (FI) and the hepatic glucagon receptor (GcgR) to enhance energy expenditure (EE). However, their development has been challenged by deleterious cardiovascular (CV) effects including increased heart rate (HR), elongated QTc, and arrhythmia mediated by GcgR agonism. GLP-1R mono-agonists on the other hand improve both obesity and CV outcomes with negligible effects on EE. We sought to imbue peptide GLP-1R agonists with an EE enhancing effect by combining them with ectopic GLP-1R expression and agonism in hepatocytes.

Methods: We used an adeno-associated virus (AAV) to induce the expression of a functional, liver-specific GLP-1R combined with traditional peptide agonist treatment to drive greater body weight loss via reduced energy intake and increased energy expenditure.

Results: Agonism of the ectopic GLP-1R with either semaglutide, a cAMP biased GLP-1R analogue (NNC5840), or a dual GLP-1R/GIPR agonist in wild-type (WT) diet induced obese (DIO) mice led to enhanced EE and improved weight loss compared to peptide agonist treatment alone.

Conclusions: This represents a novel mechanism for achieving poly-pharmacology to treat obesity.

Glucagon receptor (GCGR)-mediated thermogenesis is a key component for the next-generation of obesity therapeutics. Herein, we investigated the central and peripheral mechanism by which activation of the GCGR augments metabolic rate to promote weight loss. Chronic treatment of obese mice with a long-acting GCGR agonist (LAGCGRA) reduced body weight and fat mass at both room temperature and thermoneutrality. Metabolic cage studies highlight that whilst GCGR agonism induces a negative energy balance via effects on both sides of energy balance, weight loss is primarily due to augmented metabolic rate in obese mice. Mechanistically, we report for the first time that GCGR agonism recruits GABAergic signaling in the medial basal hypothalamus to promote uncoupling protein 1(UCP1)-dependent thermogenesis in adipose tissue, stimulate caloric expenditure, and drive a negative energy balance in obese mice. Our preclinical findings provide insight in to how multi-receptor agonists engaging the GCGR may function to improve the weight loss efficacy of anorectic agents. Collectively, our results point to a liver→brain→fat axis activated by GCGR agonism for weight loss in obesity. Future studies are required to validate our findings in the clinic.

Aims: Human adipose tissue is central to obesity-associated metabolic dysfunction. ANKRD53 is a human-specific, adipocyte-enriched ankyrin repeat scaffold protein with largely unknown function. We investigated its role in human adipocyte metabolism and the underlying mechanism.

Methods: RNA-seq analysis of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) from 236 individuals quantified ANKRD53 expression and its association with metabolic traits. In human primary adipocytes, we assessed lipolysis (free fatty acid and glycerol release) and mitochondrial respiration (oxygen consumption rate) after ANKRD53 overexpression or knockdown. An AAV was used to overexpress ANKRD53 in mouse inguinal white adipose tissue (iWAT). Protein interactors were identified by immunoprecipitation-mass spectrometry, and knockdown experiments confirmed a functional role of ACSL1.

Results: ANKRD53 expression in both adipose depots was markedly reduced in obesity and inversely correlated with BMI, adiposity measures, insulin resistance indices, and circulating triglycerides, while positively associated with adiponectin and HDL. In human adipocytes, ANKRD53 overexpression enhanced forskolin-stimulated lipolysis and mitochondrial respiration, whereas silencing impaired these processes. Adipose-targeted ANKRD53 overexpression in mice increased lipolysis in vivo. Mechanistically, ANKRD53 interacted with ACSL1 and promoted its mitochondrial localization, channeling lipolysis-derived FFAs into β-oxidation; silencing ACSL1 abrogated ANKRD53's effects.

Conclusions: ANKRD53 is reduced in obesity and coordinates lipolysis with mitochondrial oxidative metabolism in human adipocytes, promoting efficient use of lipolysis-derived FFAs via ACSL1. These findings establish ANKRD53 as a key regulator of adipocyte energy metabolism and a potential therapeutic target for improving metabolic health in obesity.

Purpose: Adipose tissue innervation is critical for regulating lipolysis, adipogenesis, and thermogenesis, yet the mechanisms that establish and maintain these neural networks remain poorly understood. Semaphorin 7A (Sema7A), a well-characterized axon guidance and neuroimmune signaling molecule that is highly expressed in adipose tissue. Sema7A regulates adipocyte metabolic processes, including lipid accumulation and thermogenic gene expression, via Integrin β1 signaling. However, its potential role in shaping adipose tissue innervation and coordinating neural-metabolic communication has not been explored.

Methods: In this study, we investigated a knockout of Sema7A in mice, and influences on adipose tissue innervation and metabolic regulation during postnatal development and in adulthood, both under baseline conditions and following cold exposure, a potent activator of sympathetic nerve activity and axonal remodeling in scWAT.

Results: Deletion of Sema7A increased adiposity at postnatal day 21, marked by enlarged subcutaneous and brown adipose depots and reduced lipolytic enzyme expression. Tyrosine hydroxylase-expressing (TH+), and calcitonin gene-related peptide-expressing (CGRP+) innervation was markedly reduced, indicating dysregulated neuro-adipose communication. Plexin C1, a receptor for Sema7A, was strongly expressed on subcutaneous adipose axons, suggesting direct signaling to support neuronal growth. In adulthood, Sema7A-deficient mice displayed normal metabolic responses to cold exposure but failed to mount the typical increase in sympathetic axon outgrowth within beige regions of scWAT.

Conclusions: Together, these findings identify Sema7A as a critical mediator of adipose neural development and remodeling, required for establishing and maintaining proper innervation and metabolic function.

Dietary sulfur amino acid restriction (SAAR) improves whole-body glucose homeostasis, elevates liver insulin action, and lowers liver triglycerides. These adaptations are associated with an increased expression of hepatic de novo serine synthesis enzymes, phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase 1 (PSAT1). This study tested the hypothesis that enhanced hepatic serine synthesis is necessary for glucose and lipid adaptations to SAAR. Hepatocyte-specific PSAT1 knockout (KO) mice and wild type (WT) littermates were fed a high-fat control or SAAR diet. In WT mice, SAAR increased liver PSAT1 protein (∼70-fold), serine concentration (∼2-fold), and ¹³C-serine (∼20-fold) following an intravenous infusion of [U-¹³C]glucose. The elevated liver serine and partitioning of circulating glucose to liver serine by SAAR were attenuated in KO mice. This was accompanied by a blunted improvement in glucose tolerance in KO mice fed a SAAR diet. Interestingly, SAAR decreased liver lysine lactoylation, a SAA-supported post-translational modification known to inhibit PHGDH enzymatic activity. This suggests dietary SAAR may increase serine synthesis, in part, by lowering lysine lactoylation. Beyond glucose metabolism, dietary SAAR reduced body weight, adiposity, and liver triglycerides similarly in WT and KO mice. Collectively, these results demonstrate that hepatic PSAT1 is necessary for glucose, but not lipid, adaptations to SAAR.

Survodutide is a novel GCG/GLP-1 receptor (GCGR/GLP-1R) dual agonist in clinical development for people with obesity and people with metabolic dysfunction-associated steatohepatitis (MASH). Preclinically, survodutide demonstrated body weight lowering efficacy through decreased energy intake and increased energy expenditure. Here, we investigated the central site of action of survodutide and provide further insights into its mechanism of action in reducing body weight. We assessed GCGR and GLP1R expression in human and mouse circumventricular organs (CVOS) and showed for the first time that GCGR is barely detectable in area postrema (AP) and arcuate nucleus of the hypothalamus (ARH) at the single cell level. In contrast, GLP1R is expressed in these tissues. Using a fluorophore labeled survodutide to visualize sites of action in the mouse brain, survodutide was observed to directly access the CVOs and adjacent hypothalamic and hindbrain nuclei, without evidence of uniformly crossing the blood-brain-barrier. In addition, c-Fos labeling showed that multiple nuclei associated with the control of food intake were activated by survodutide. Consistent with the hypothesis that the intake suppressive effects of survodutide are GLP-1R dependent, a long-acting GCGR agonist did not induce neuronal activation in satiety-mediating regions, nor reduced food intake but showed reduction in body weight. These data further support the dual mode of action of survodutide and its potential to provide clinical benefit for people with obesity and/or MASH.

Objectives: While glucagon raises blood glucose levels, it also promotes lipolysis and energy expenditure, and suppresses food intake and gastrointestinal motility, thereby resulting in weight loss. We previously reported that sodium-glucose cotransporter 1 (SGLT1) is highly expressed in pancreatic α cells. The present study aimed to investigate the effects of α-methyl d-glucopyranoside (αMG), an SGLT-specific substrate, on endogenous glucagon secretion and metabolic parameters in obese diabetic mice.

Methods: We injected αMG intraperitoneally daily into high fat, high sucrose diet (HFHSD)-fed mice and db/db mice, and measured metabolic parameters including plasma glucagon concentration. During the treatment with αMG, we evaluated various metabolic conditions, such as body weight, glucose tolerance and hepatic steatosis, in these mice. We also used SGLT1-specific inhibitor and liver-specific glucagon receptor knockout mice to elucidate the underlying mechanism.

Results: We showed that αMG stimulates endogenous glucagon secretion, and that chronic injection of αMG led to dramatic weight loss, improved glucose intolerance, and ameliorated hepatic steatosis, by reducing food intake and increasing energy expenditure and fat utilization, among obese diabetic mice. Interestingly amelioration of hepatic steatosis was abolished in liver-specific glucagon receptor knockout mice, but body weight reduction was not abolished. In addition, αMG, although to a modest extent, distinctly enhanced urinary glucose excretion.

Conclusions: These results in this study suggest that αMG stimulates endogenous glucagon secretion and may lead to a therapeutic strategy for obesity-associated metabolic diseases.