Molecular Metabolism

White adipose tissue and pancreatic islets play central roles in the regulation of metabolic homeostasis. Although ectopic lipid accumulation is established as a driver of impaired insulin secretion, the acute contribution of adipocyte lipolysis to islet function remains poorly documented. Here, we investigated a mouse model with inducible adipocyte-specific deletion of both adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), which leads to defective adipocyte lipolysis. Despite preserved ex vivo islet function, these mice displayed a marked reduction in insulin secretion in response to stimulation of adipocyte {beta}3-adrenoceptors, as well as following glucose and arginine challenges. Mechanistically, we identified non-esterified fatty acids as critical mediators of lipolysis-driven insulin secretion, engaging pancreatic signaling of the free fatty acid receptors FFAR4 (a.k.a. GPR120) and FFAR1 (a.k.a. GPR40). The regulation of insulin secretion by adipocyte lipolysis was preserved in high-fat diet-induced obesity. These findings identify an underappreciated adipose-islet crosstalk that couples adipocyte lipolysis to insulin secretion and links lipid and glucose metabolism.

Adenosine is a widely distributed signaling molecule whose levels rise during conditions of metabolic stress, hypoxia, or inflammation. Adenosine is a homeostatic regulator of neuronal, cardiovascular, immune, and metabolic functions through activation of adenosine receptors. Here, we show that administration of adenosine rapidly elicits an immediate and pronounced excursion of glucose and non-esterified fatty acids (NEFA) in mice refed for four hours but is greatly attenuated in fasted mice. This adenosine-mediated postprandial response suggests that adenosine is a potent regulator of postprandial nutrient handling. Selective agonists and antagonists of A2A and A2B adenosine receptors demonstrate that activation of either is sufficient to evoke adenosines metabolic response, but both receptors must be inhibited simultaneously to abolish it. Adenosine strongly stimulates hepatic glucose production and adipose lipolysis, and this catabolic activity depends on sympathetic nerve activity as it requires autonomic signal transmission and is inhibited by blocking adrenergic receptors. Genetic ablation studies identify A2A and A2B receptors expressed on neurons, likely central neurons, as the primary site of action for mediating adenosines effects on whole-body metabolism. Collectively, these data demonstrate that acute adenosine administration promotes centrally mediated metabolic effects, particularly during the postprandial period. Rigorous dissection of signaling pathways shows that A2A and A2B receptors are individually sufficient and collectively necessary for adenosine-mediated glucose and fatty acid excursion.

ObjectiveG protein-coupled receptor 180 (GPR180) has been implicated in systemic energy metabolism, primarily in adipose tissue and the liver. Given impaired whole-body glucose tolerance following GPR180 dysfunction, we aimed to determine whether GPR180 regulates pancreatic {beta}-cell function. We investigated whether GPR180 contributes to {beta}-cell insulin secretion by modulating metabolic processes that couple glucose sensing to mitochondrial energy production. MethodsPhenotyping of whole-body (Gpr180 -/-) and {beta} cell-specific Gpr180 (bGpr180-KO) knockout mice was combined with gain- and loss-of-function studies in MIN6 cells. Glucose-stimulated insulin secretion, pancreatic endocrine architecture and identity, transcriptomic and metabolic profiles, as well as mitochondrial function were assessed using in vivo and in vitro approaches, including metabolic challenge tests, histology, RNA sequencing, targeted metabolomics, respirometry, and transmission electron microscopy. ResultsLoss of GPR180 impaired first-phase insulin secretion and glucose tolerance without affecting insulin sensitivity. These defects were {beta}-cell-autonomous, as confirmed in the bGpr180-KO mice and in MIN6 cells. Functional studies revealed that GPR180 regulates mitochondrial substrate utilization, anaplerotic support of the TCA cycle, and ATP generation without affecting glucose uptake or mitochondrial biogenesis. In particular, Gpr180-deficient {beta} cells showed mitochondrial membrane depolarization, reduced oxygen consumption, and endoplasmic reticulum remodeling, altering the local mitochondrial microenvironment. In vivo, Gpr180 deletion in {beta} cells led to downregulation of mitochondrial gene programs in islets, along with altered endocrine cell identity. ConclusionsGPR180 is a previously unrecognized regulator of pancreatic {beta}-cell metabolic competence and identity, linking defects in insulin secretion with alterations in mitochondrial function and endocrine cell identity. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=198 SRC="FIGDIR/small/720098v1_ufig1.gif" ALT="Figure 1"> View larger version (87K): org.highwire.dtl.DTLVardef@1a441ecorg.highwire.dtl.DTLVardef@e41e02org.highwire.dtl.DTLVardef@6e2212org.highwire.dtl.DTLVardef@7ee07a_HPS_FORMAT_FIGEXP M_FIG C_FIG

Central glucose-dependent insulinotropic polypeptide receptor (GIPR) signalling is required for the efficacy of GIP-based obesity therapeutics, yet how distinct subpopulations of GIPR neurons shape appetite remains undefined. Here we show that GIPR neurons in adjacent brainstem nuclei, the area postrema (AP) and nucleus tractus solitarius (NTS), exert opposing control over ingestion. We find GIPRAP neurons dampen post-ingestive satiation, permitting hyperphagia, whereas GIPRNTS neurons are anorectic. In line with this model, we show Gipr expression in AP, but not NTS, neurons is necessary for appetite suppression following GIPR antagonism. Additionally, we reveal that GIPR neurons in the AP and NTS occupy distinct gut-brain circuits, and are differentially sensitive to obesity-driven circuit remodelling. These data offer a framework for understanding how current GIPR agonist and antagonist strategies elicit weight loss.

Nutritional strategies to mitigate obesity and type 2 diabetes (T2D) have largely focused on dietary fat and carbohydrate composition, with less attention given to protein sources. While total dietary protein intake is recognized as an important modulator of energy balance and glucose metabolism, it remains unclear how the composition of dietary proteins can influence energy metabolism and body weight gain. Here, we investigated the metabolic effects of three distinct protein sources from meat (pork), dairy (casein) and plant (soy) on either a low-fat low sucrose (LFLS) or a high-fat high sucrose (HFHS) diet. While protein sources failed to influence metabolic homeostasis on LFLS, mice kept on the HFHS diet were distinctly impacted by the dietary protein sources. Pork and to a lesser extent soy protein feeding exacerbated obesity, glucose intolerance, and hepatic insulin resistance. Remarkably, livers of mice fed pork or soy protein on the HFHS diet were characterized by extensive microvesicular steatosis compared to the predominant macrovesicular steatosis in HFHS fed mice fed casein protein. Liver transcriptomic and metabolomic signatures in pork and soy protein fed mice were consistent with increased mitochondrial beta-oxidation. Intake of pork and soy proteins in HFHS fed mice lead to a striking reduction in hepatic acetyl CoA carboxylase 2 (ACC2) protein levels relative to casein fed HFHS mice. Pork and soy feeding raised carnitine exposure in the post-prandial period and we determined that exposure of hepatocytes to carnitine provokes downregulation of ACC2 and hepatic insulin resistance in the presence of palmitate:oleate and fructose. Collectively, these findings identify a novel mechanism by which dietary proteins modulate obesity and associated metabolic disturbances through a carnitine-mediated regulation of ACC2 protein and mitochondrial lipid handling in liver.

Hypoxia is a potent stressor and a major cause of {beta}-cell failure and loss after islet transplantation. Autophagy is a critical homeostatic mechanism that preserves organelle integrity and metabolic balance in cells under stress, but whether it supports {beta}-cell adaptation to sustained oxygen deprivation is unclear. Here, we used {beta}-cell-specific Atg5 knockout together with hypoxia and transplantation models, to demonstrate that autophagy is a major determinant of {beta}-cell survival during oxygen limitation and supports islet graft function. However, prolonged hypoxia suppressed autophagic flux, reduced lysosomal activity, and led to autophagosome accumulation, indicating failure of the lysosomal clearance pathway. This was accompanied by a marked reduction in transcription factor EB (TFEB) and its lysosomal target genes. Genetic and pharmacological activation of TFEB restored lysosomal gene expression and cathepsin B activity and improved {beta}-cell viability under hypoxia, implicating TFEB decline as a contributor to autophagy-lysosome dysfunction. Together, these findings outline a sequence in which autophagy initially safeguards {beta}-cells but becomes ineffective under sustained hypoxia as TFEB levels fall, identifying TFEB as a potential target to strengthen {beta}-cell resilience and survival in islet transplantation.

Adult zebrafish rapidly recover glucose homeostasis after {beta}-cell loss, but the cellular basis and regulatory mechanisms that enable this response remain unclear. Here we combine single-cell transcriptomics, single-cell chromatin accessibility profiling, paired multiome analysis and functional perturbation to define early pancreatic recovery after {beta}-cell ablation. We show that, during the first month after injury, insulin production is restored predominantly by sst1.1+ {delta}1-cells rather than by rapid reconstitution of canonical {beta}-cells. Following ablation, {delta}1-cells adopt a bihormonal hybrid state and induce metabolic, secretory and {beta}-cell-associated gene programs. Systematic comparison of chromatin accessibility across endocrine cell types reveals that these {delta}1-cells are uniquely close to {beta}-cells and exhibit open chromatin at {beta}-cell enhancers in the steady state. Moreover, hybrid-cell formation occurs without major chromatin remodeling, with {beta}-cell associated loci being already accessible in {delta}1-cells before {beta}-cell injury. A comparable permissive state is present in medaka but not in human {delta}-cells, suggesting that restricted insulin accessibility may represent a barrier to endocrine plasticity in the human pancreas. In zebrafish, {delta}1-cells also show evidence of metabolic remodeling after {beta}-cell loss, including rapid accumulation of neutral lipids. Finally, gene regulatory network analysis and perturbation identify meis1a/b as required regulators of {delta}1 hybrid-cell formation after {beta}-cell loss. Together, our results define pre-existing chromatin accessibility, metabolic remodeling and instructive transcriptional regulation as key features of early functional recovery after {beta}-cell loss in the adult zebrafish pancreas.

Cold-induced thermogenesis in brown adipose tissue (BAT) is essential for maintaining energy homeostasis, yet the Ca2+-dependent mechanisms underlying this process remain incompletely understood. Here, we identify Orai1, a component of the store-operated Ca2+ entry pathway, as a regulator of thermogenic activation in BAT. Using a brown adipocyte-specific Orai1 knockout mouse model, we demonstrate that cold exposure is associated with Orai1-dependent Ca2+ influx through a non-canonical mechanism. Orai1 deficiency leads to impaired cAMP-PKA signaling, reduces the expression of lipolytic enzymes and thermogenic genes, and diminished mitochondrial Ca2+ uptake and uncoupling. These defects culminate in cold intolerance, lipid accumulation, and decreased energy expenditure. Mechanistically, Orai1 facilitates Ca2+-dependent activation of adenylyl cyclase 3, linking membrane Ca2+ entry to cAMP production, and promotes mitochondrial remodeling and oxidative metabolism. These findings support a key role for Orai1 in coordinating Ca2+ entry to lipolytic and mitochondrial pathways in brown adipocytes and highlight its potential therapeutic target in metabolic diseases characterized by impaired energy metabolism. HIGHLIGHTSO_LIOrai1 mediates Ca2+ influx in brown adipocytes through a non-canonical, partially STIM1-independent mechanism. C_LIO_LIOrai1-mediated Ca2+ influx promotes both cAMP-PKA-driven lipolysis and mitochondrial oxidative activation. C_LIO_LIOrai1-dependent Ca2+ entry promotes cAMP-PKA signaling and lipolytic activation I nbrown adipocytes. C_LIO_LIOrai1 coordinates mitochondrial Ca2+ uptake to support thermogenic function in brown adipocytes. C_LI

ObjectiveThe aryl hydrocarbon receptor (AhR) pathway primarily mediates pollutant responses by activating xenobiotic metabolism enzymes like cytochrome P450 1A1 and 1A2 (CYP1A). Although AhR has also been implicated in systemic metabolic dysfunction and is inducible in pancreatic islets, its role in islet physiology remains unclear. MethodsWe analyzed a publicly available bulk human islet transcriptomic dataset to identify pathways associated with CYP1A1 expression. We also assessed islet responses to the pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and glucolipotoxicity (GLT) in vitro using two mouse models: a global Cyp1a1/1a2 double knockout (CypKO) model, which disrupts canonical AhR-CYP1A signaling in whole islets, and a {beta}-cell-specific Ahr knockout ({beta}AhrKO) model, which abolishes AhR signaling selectively in {beta}-cells. We then examined the role of {beta}-cell Ahr in early adaptation to high-fat diet (HFD) feeding in vivo. ResultsXenobiotic and nutrient metabolism pathways were enriched in donors with high CYP1A1 expression. Global Cyp1a1/1a2 deletion increased susceptibility of female mouse islets to TCDD-induced impairments in insulin secretion but had minimal effects on GLT responses in either sex. In contrast, {beta}-cell Ahr deletion did not affect islet responses to TCDD, but exacerbated GLT-induced islet dysfunction in male islets and increased baseline insulin secretion in both vehicle- and GLT-exposed female islets in vitro. Lastly, {beta}-cell Ahr deletion prevented adaptive HFD-induced hyperinsulinemia in both sexes in vivo. ConclusionIslet AhR signaling shapes responses to chemical and nutrient stressors in a context- and sex-dependent manner. While the canonical AhR-CYP1A axis supports female islet resilience to TCDD, {beta}-cell AhR signaling more broadly regulates nutrient stress responses in both sexes.

Obesity is one of the most prevalent diseases worldwide. Increasing thermogenesis to enhance energy expenditure has emerged as a promising therapeutic strategy. In an effort to identify new regulatory targets in thermogenic adipocytes, we found that SOX8 is correlated with obesity and serves as a novel marker of classical brown adipocytes in both humans and mice, upregulating during acute cold exposure. Functional studies further demonstrated that adipocyte-specific knockdown of SOX8 leads to obesity and metabolic dysfunction in mice. Mechanistically, SOX8 directly interacts with USP7 and stabilizes PGC-1 by reducing its K48-linked polyubiquitination. AAV-Rec2-mediated SOX8 overexpression initially enhanced energy expenditure, improved insulin sensitivity, and alleviated metabolic dysfunction in HFD-fed mice. However, prolonged SOX8 overexpression induced compensatory metabolic maladaptation, characterized by reduced energy expenditure, impaired glucose homeostasis, and mitochondrial structural disruption. These findings reveal a novel SOX8-USP7-PGC-1 regulatory axis in brown adipocytes, and reveal a previously unrecognized time-dependent effect of sustained thermogenic activation, highlighting SOX8 as a promising therapeutic target for obesity and metabolic syndrome.

Adipose tissue dysfunction drives obesity-associated insulin resistance, but whether expanding adipocyte lipid storage can improve metabolic health remains unclear. Here, we generated adipocyte-specific Pten knockout mice (PtenAKO) using Adipoq-Cre to determine how chronic Pten loss affects adipose tissue remodeling and systemic metabolism. PtenAKO mice exhibit increased adiposity and adipocyte hypertrophy under chow and high-fat diet feeding, yet showing lower blood glucose and insulin levels, enhanced insulin sensitivity, and reduced hepatic lipid accumulation during basal growth and diet-induced obesity without systemic metabolic deterioration. Despite lipid enrichment in brown adipose tissue, Pten-deficient adipocytes maintain UCP1 expression, OXPHOS protein abundance, and mitochondrial ultrastructure. Transcriptomic analysis of inguinal white adipose tissue reveals activation of adipogenesis, lipid metabolism, insulin response, oxidative phosphorylation, lipid storage, vascular and extracellular matrix pathways, together with suppression of immune and inflammatory programs. Mechanistically, Pten deficiency increases Cav1 expression, caveolae abundance, collagen expression, and extracellular matrix remodeling, suggesting coordinated structural adaptation to support adipocyte expansion. These findings demonstrate that adipocyte Pten deficiency promotes metabolically healthy adipose expansion by enhancing lipid storage capacity, preserving adipocyte function, and reducing inflammation.

Edible adipose tissue can enhance the sensory and nutritional qualities of cultivated and plant-based meats, yet efficient adipogenic differentiation remains a major bottleneck and synthetic PPAR{gamma} agonists are not approved for use in food production. Here, we report a natural compound screen in 3T3-L1 adipocytes that identifies magnolol and dicoumarol as enhancers of adipogenesis; this combination also robustly promotes lipid accumulation in primary porcine dedifferentiated fat cells and ovine preadipocytes. Transcriptomic analyses show that magnolol and dicoumarol induce adipogenesis in murine and porcine cell systems through canonical adipogenic pathways with a narrower transcriptional footprint than the potent PPAR{gamma} agonist rosiglitazone. These findings support the potential of naturally occurring compounds magnolol and dicoumarol as enhancers of adipogenesis for both mechanistic studies and food-relevant applications. More broadly, our findings establish a generalizable screening framework and identify small-molecule combinations that accelerate adipose tissue engineering across murine, porcine, and ovine culture systems.

Administration of ciliary neurotrophic factor (CNTF) reduces food intake and body weight in both humans and experimental animals, where it also ameliorates hyperglycemia, hyperinsulinemia, and dyslipidemia. To exert its anti-obesogenic and anti-diabetogenic effects, CNTF targets brain feeding centers as well as multiple peripheral organs inducing the phosphorylation of the transcription factor signal transducer and activator of transcription 3 (p-STAT3). However, data showing which peripheral cytotypes are specifically targeted by exogenous CNTF in vivo in metabolically relevant organs are currently lacking. Here, we first evaluated the gene expression levels of the subunits of the tripartite CNTF receptor (Cntfr) complex, i.e., the Cntfr, the leukemia inhibitory factor receptor {beta} (Lifr{beta}) and the glycoprotein 130 (gp130), by quantitative real-time PCR in metabolically relevant organs of adult male mice: gastrointestinal (GI) tract, pancreas, liver, visceral and subcutaneous white (WAT) and interscapular brown adipose tissue (iBAT), skeletal muscle and the sciatic nerve. We then quantified p-STAT3 by Western blotting in these organs after intraperitoneal administration of CNTF (0.3 mg/kg) or saline. Finally, we mapped CNTF-responsive cells by immunohistochemistry, followed by morphometric quantification and confocal microscopy in both CNTF- and saline-treated mice. Lifr{beta} and gp130 were ubiquitously detected across all the investigated organs; the Cntfr showed the highest expression levels in the skeletal muscle, sciatic nerve, and iBAT, whereas it was found to be expressed to a lesser extent in the other sites. Administration of CNTF led to a significant increase of p-STAT3/STAT3 protein ratio in all organs examined, except the duodenum, and induced a distinctive pattern of cell nuclear p-STAT3 immunoreactivity. Notably, along the analyzed GI tract CNTF induced nuclear STAT3 phosphorylation in neurons of the submucosal and myenteric plexuses of the enteric nervous system and in contractile cells of the muscularis externa, where the response peaked in the mesenteric gut and colon. In the pancreas, CNTF triggered a higher activation within the endocrine component compared to the exocrine parenchyma. In the liver, CNTF induced STAT3 phosphorylation not only in parenchymal cells but also in sinusoids and resident macrophages. The cytokine activated p-STAT3 in subcutaneous and visceral white adipocytes, but also in brown adipocytes, with a prominent response observed in the beige subcutaneous adipocytes; adipose resident macrophages and endothelial cells of numerous blood vessels were also CNTF-responsive. Lastly, in skeletal muscle, a major site for glucose/lipid utilization, CNTF induced widespread nuclear p-STAT3 immunoreactivity in muscle fibers and in connective and Schwann cells of the peripheral nerves, including the sciatic nerve, supplying the gastrocnemius. In conclusion, our data indicate that CNTF acts across diverse cytotypes within metabolically relevant organs and tissues, likely fostering its peripheral metabolic effects through this cellular heterogeneity.

Variants in the human PAX4 gene are associated with both monogenic and complex forms of diabetes, yet their pathogenic effects remain difficult to define in models that accurately mimic human islet architecture and neonatal metabolic transitions. Here, we created a porcine PAX4 loss-of-function model using CRISPR/Cas9 cytidine deaminase base editing to introduce a premature stop codon in the PAX4 coding sequence. PAX4 knockout piglets developed severe hyperglycemia within 24 hours of birth, followed by rapid postnatal clinical deterioration and uniform death by day 3. Biochemical analysis showed significant diabetic decompensation, including electrolyte imbalances, hyperosmolality, azotemia, dyslipidemia, and metabolic acidosis. Gross and histological examinations revealed notable pancreatic hypoplasia with preservation of exocrine tissue. Single-nucleus RNA sequencing and immunohistochemistry demonstrated an almost complete loss of insulin-and somatostatin-producing {beta}-and {delta}-cells, respectively, with relative preservation of glucagon-expressing -cells. Overall, these results establish PAX4 as a crucial factor in pancreatic endocrine development and postnatal glucose regulation in a large-animal model. This platform offers a human-relevant system for studying diabetes-associated PAX4 variants and for testing regenerative and gene-based therapies for insulin-deficient diabetes.

The intermittent energy restriction (iER) represents an effective dietary strategy for improving metabolic diseases including metabolic dysfunction-associated steatotic liver disease (MASLD) and type 2 diabetes mellitus (T2DM), yet the underlying mechanisms remain elusive. In this study, we integrated human clinical data, mouse models, and in vitro experiments to investigate the role of iER in modulating the gut-liver axis in comorbid MASLD and T2DM. We demonstrate that an iER diet improves hyperglycemia, hepatic steatosis and decreases the abundance of gut pathogen Klebsiella pneumoniae, which is strongly associated with reductions in blood endotoxin, lipopolysaccharide (LPS) levels, suggesting a potential role of K. pneumoniae-derived LPS in mediating effects of the iER on hepatometabolic improvements. We confirm that K. pneumoniae-derived LPS exacerbates lipid accumulation and inflammation using an in vitro model. Mechanistically, we reveal a core target of protein lysine acetylation (Kac), hydroxyacyl-CoA dehydrogenase -subunit (HADHA) Lys353 in the liver of db/db mice through a multi-omics analysis. The iER decreases HADHA-K353 acetylation and enhances its enzyme activity. A Kac-mimicking mutation (K353R) increases its enzyme activity and stability, blocks its binding to the inflammasome adaptor ASC, and alleviates lipid accumulation and inflammation in K. pneumoniae-derived LPS induced in vitro model. This study provides novel insights into the potential benefits of the iER in comorbid MASLD and T2DM.

Metabolites are emerging as signaling molecules that mediate cellular function, extending beyond their well-established roles in metabolic pathways. Members of the solute carrier (SLC) family mediate metabolite transport across cellular compartments, raising the possibility that these proteins may sense environmental stimuli and regulate cellular biological processes by triggering signaling cascades linked to metabolite transport. This study investigated the response of the SLC25A family, a unique set of inner mitochondrial membrane-localized transporters, to cold as an environmental stimulus in mediating metabolic reprogramming; and whether this reprogramming, driven by the metabolites transported by SLC25A proteins, subsequently promotes the activation of thermogenesis in brown adipocytes. After screening members of the SLC25A family for their responsiveness to cold stimuli and brown adipose tissue (BAT) activation, we found that Slc25a34 was robustly induced under these conditions. We further demonstrated that Slc25a34 mediates the transport of adenosine monophosphate (AMP), derived from de novo glucose synthesis, from mitochondria to the cytosol. This transport potentiates AMP-activated protein kinase (AMPK) signaling and glycolytic flux in brown adipocytes, both of which facilitate BAT thermogenesis during cold exposure. Intriguingly, cold exposure directly promoted the activation of peroxisome proliferator-activated receptor gamma (PPAR{gamma}), which transcriptionally upregulated Slc25a34 expression. More importantly, genetic ablation of Slc25a34 impaired BAT thermogenesis. Thus, our study reveals a novel cold-induced metabolite-sensing pathway, where Slc25a34-mediated AMP transport between mitochondria and the cytosol serves as a critical signal for activating BAT thermogenesis. These findings provide compelling evidence that metabolite transport across cellular compartments acts as a key driver of cellular physiology, thereby offering novel insights into metabolite-based therapeutic strategies for metabolic diseases. HighlightsO_LISlc25a34 is cold-responsive and transcriptionally regulated by PPAR{gamma}. C_LIO_LISlc25a34 functions specifically to mediate the mitochondrial-to-cytosolic transport of AMP in brown adipocytes. C_LIO_LIMitochondrially sequestered de novo synthesized AMP acts as a signaling reservoir, and its Slc25a34-mediated efflux to the cytosol activates AMPK and glycolysis, supporting BAT thermogenesis. C_LI

BackgroundVertical sleeve gastrectomy (VSG) improves glycaemic control in type 2 diabetes (T2D) through mechanisms that extend beyond weight loss. The interaction between glucocorticoid metabolism and inflammation in this context remains unclear. MethodsWe investigated the role of 11{beta}-hydroxysteroid dehydrogenase type 1 (11{beta}HSD1) in mediating the metabolic effects of VSG in humans and mice. Subcutaneous adipose tissue biopsies were collected before and 6 months after VSG. Parallel studies were conducted in lean and high-fat diet-fed mice undergoing VSG or sham surgery, alongside 11{beta}HSD1 knockout models. Glucose tolerance and expression of 11{beta}HSD1 and interleukin-6 (IL6) were assessed. Mechanistic interactions were examined in IL6-treated human hepatocytes. ResultsVSG reduced 11{beta}HSD1 and IL6 expression in human adipose tissue and improved insulin resistance. In lean mice, VSG improved glucose tolerance and downregulated both markers independently of weight loss. 11{beta}HSD1 knockout mice exhibited improved glucose tolerance despite increased adiposity, partially recapitulating the VSG phenotype. Both interventions reduced circulating and tissue IL6 levels. IL6 stimulation increased HSD11B1 expression in hepatocytes. Conclusions11{beta}HSD1 links glucocorticoid metabolism, inflammation, and glucose homeostasis following VSG. Targeting this pathway may offer a strategy to replicate key metabolic benefits of metabolic bariatric surgery.

Globin digest (GD), an acidic protease hydrolysate of hemoglobin, has been recognized for its anti-obesity and glucose-modulating effects; however, its direct anabolic potential in skeletal muscle remains uncharacterized. We evaluated the effects of GD and its constituent peptides on muscle hypertrophy and motor function using zebrafish, mice, and C2C12 myoblasts. Adult zebrafish administered GD (400 mg/kg BW/d) for 1 week showed significantly increased swimming distance (p < 0.05). Similarly, oral administration of GD (1 g/kg BW/d) to C57BL/6J mice for 4 weeks enhanced grip strength and rotarod performance, accompanied by a 1.5-fold increase in myofiber diameter and upregulation of fast-twitch Myh1 (1.9-fold) and Myh2 (1.8-fold) mRNA levels. In vitro, GD dose-dependently (1-100 g/mL) stimulated C2C12 differentiation and MyHC accumulation. Notably, GD did not merely serve as a nutritional nitrogen source; instead, it functioned as a signaling modulator via a specific "relay-like" peptide orchestration. Among six identified sequences, Peptides 3 (WTQR) and 5 (WGK) primarily initiated early-stage commitment by upregulating MyoD and Myf5, whereas Peptides 2 (VVYP) and 6 (FES) accelerated mid-stage maturation. This stage-specific synergy achieved robust myotube hypertrophy that exceeded the efficacy of individual components. These findings demonstrate that GD promotes skeletal muscle hypertrophy and motor function through direct myogenic signaling, establishing a novel foundation for precision sports nutrition to optimize muscle maintenance and physical performance. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/728339v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@1d19d5borg.highwire.dtl.DTLVardef@b1fcc4org.highwire.dtl.DTLVardef@149cc1eorg.highwire.dtl.DTLVardef@1f7ee3c_HPS_FORMAT_FIGEXP M_FIG C_FIG

GLP-1 receptor agonists (GLP-1 RAs) effectively reduce weight in obesity, although significant weight regain typically follows discontinuation. Here, in a randomized clinical trial (ChiCTR2200066014), we found that GLP-1 RA (semaglutide) and a high-fibre diet achieved similar 12-week weight reduction, but semaglutide recipients exhibited significantly higher weight rebound at the 14th week after intervention cessation. Shotgun metagenomic sequencing revealed that semaglutide aggravated the proinflammatory signature in the gut microbiome, which contrasted with high-fibre diet intervention. The microbiota transplanted from semaglutide-treated subjects to germ-free mice induced gut barrier dysfunction, systemic inflammation and an increase in the bacterial antigen load in the liver and adipose tissue, which activated the NF-{kappa}B pathway to drive lipid accumulation. Using a diet-induced obesity mouse model, we found that semaglutide exacerbated gut microbiome dysbiosis by weakening host immune surveillance of the gut microbiota through downregulating IFN-{gamma} to reduce antimicrobial peptides expression and delaying gut transit time to shift microbial metabolism from saccharolysis towards proteolysis. Crucially, combining semaglutide with dietary fibre in mice mitigated microbiome dysbiosis and attenuated weight regain post-cessation. These findings suggest that GLP-1 RA-exacerbated gut microbiome dysbiosis in obesity as a key mediator of post-treatment weight rebound and propose adjunctive fibre supplementation as a strategy to sustain weight loss.

Exercise training improves skeletal muscle insulin sensitivity, yet its effects on white adipose tissue remain incompletely understood. We investigated how adiposity and exercise training influence insulin-stimulated glucose uptake in skeletal muscle and abdominal subcutaneous adipose tissue (ASAT), alongside adaptations in gene expression and DNA-methylation. Ten monozygotic twin pairs discordant for BMI underwent [18F]FDG-PET/CT imaging of skeletal muscle (vastus lateralis, VL) and ASAT during a euglycemic-hyperinsulinaemic clamp before and after six months of exercise training. VL and ASAT biopsies were analyzed using mRNA-sequencing and reduced representation bisulfite sequencing. Exercise training improved whole-body and VL insulin sensitivity in leaner and heavier co-twins (p<0.05), without altering ASAT insulin sensitivity or body weight. Whole body adiposity exerted a stronger impact on ASAT molecular profiles than on skeletal muscle. At baseline, heavier co-twins displayed widespread ASAT transcriptional alterations enriched for inflammatory, proliferative and extracellular matrix pathways compared with leaner co-twins. In heavier co twins, exercise training attenuated inflammatory and proliferative signatures in ASAT and induced transcriptomic convergence with the leaner co twins. These changes were accompanied by marked shifts in transcription factor activity and context specific DNA methylation changes. In contrast, VL exhibited more modest transcriptomic and epigenetic responses relative to ASAT, particularly in heavier co-twins. In conclusion, six months of exercise training improved whole-body and VL insulin sensitivity while in ASAT many of the obesity associated transcriptomic programmes were reversed. These findings highlight adipose tissue as a major site of obesity- and exercise-responsive molecular plasticity and reveal tissue-specific regulatory mechanisms that contribute to the metabolic benefits of exercise training.