Metabolism

Background: Sodium-glucose cotransporter-2 (SGLT2) inhibitors reduce cardiovascular mortality and chronic kidney disease (CKD) progression in cardiovascular-kidney-metabolic (CKM) syndrome, but this benefit derives primarily from reductions in heart failure and cardiovascular mortality rather than in atherothrombotic events. Sotagliflozin, which inhibits both intestinal SGLT1 and renal SGLT2, is the only drug in this class shown to lower rates of myocardial infarction and stroke in CKD. However, its mechanism remains unclear, and its effectiveness in non-diabetic CKD has not been studied. We hypothesized that dual SGLT1/2 inhibition reprograms systemic substrate utilization toward fatty acid oxidation, which may partially account for this protective effect. Methods: CKD was induced in male low-density lipoprotein receptor-deficient mice by 5/6 nephrectomy. Sham and CKD mice received a high-fat diet and drinking water containing sotagliflozin, empagliflozin, or vehicle for 16 weeks, at doses that produced equivalent fractional excretion of glucose. We quantified atherosclerosis en face and in the aortic sinus. Indirect calorimetry, echocardiography, hepatic RNA sequencing, plasma acylcarnitine profiling, and in vivo deuterium labeling of palmitate were performed. Results: At matched levels of glucosuria and plasma total cholesterol, sotagliflozin decreased body mass, atherosclerosis burden, triglycerides, and TNF- more than empagliflozin, and raised postprandial total GLP-1 approximately 3-fold, while both drugs similarly improved albuminuria and diastolic function. Sotagliflozin increased energy expenditure independent of body mass and lowered respiratory exchange ratio despite compensatory hyperphagia. Sotagliflozin reduced hepatic lipogenic genes and de novo lipogenic flux, while increasing {beta}-oxidation and ketogenesis; empagliflozin only activated the oxidative pathway. Conclusions: In experimental CKM syndrome, dual SGLT1/2 inhibition reduces atherosclerosis and metabolic syndrome more effectively than selective SGLT2 inhibition and is associated with reprogramming of hepatic lipid metabolism. These results suggest that sotagliflozin could be an attractive candidate for mitigating atherosclerotic risk in non-diabetic CKD.

Adult obesity, including morbid obesity, has reached epidemic proportions worldwide. Yet, the current genetic models based on BMI-associated common variants identified through genome-wide association studies (GWAS) explain only a modest fraction of BMI variability. Contribution of rare and low-frequency variants to polygenic obesity remains incompletely defined. Leveraging whole-exome sequences of 1138 adults spanning normal-weight, overweight, obese and morbidly obese (MO) categories from Kuwait and Qatar, we catalogued cohort-specific rare and low-frequency deleterious variants differentiating MO individuals from normal-weight individuals. Cross-cohort comparisons identified 147 risk variants seen in [≥]2 MO individuals from one cohort and in [≥]1 MO individual from the other; among these, 27 variants occurred in [≥]2 MO individuals from each cohort. The risk genes were enriched in obesity-related pathways and tissues, with most harbouring GWAS variants associated primarily with obesity traits followed by metabolic and brain-related traits. Duodenal tissue expression data exhibited significant dysregulation of key risk genes in MO individuals. Variants from the 147-list and 27-list occurred in 87% and 49% of MO individuals, respectively; MO-variant burden correlated positively with BMI (r=0.30 and r=0.31, respectively) across the overweight-obese-MO categories. Combinations of a finite set of low-frequency coding variants substantially shape the continuum of polygenic obesity.

The extracellular matrix (ECM) of adipose tissue regulates metabolic homeostasis, yet how ECM composition drives adipose dysfunction in obesity remains only partially defined. Multi-omics profiling of visceral adipose tissue identified the multidomain ECM protein SVEP1 as a candidate regulator of adipose remodeling; SVEP1 was elevated in obese human adipose tissue and correlated with insulin resistance and systemic inflammation, and interaction analysis predicted associations with ECM proteins, integrins, and cytoskeletal regulators. On a chow diet, Svep1 heterozygous (Svep1+/-) mice gained less weight with lower fasting glucose, and their adipocytes showed enhanced lipolysis and AMPK activation. On a high-fat diet, Svep1+/- mice exhibited attenuated adiposity, improved glucose tolerance and insulin sensitivity, and fewer adipose macrophages with a shift away from a pro-inflammatory profile, alongside downregulation of inflammatory, lipid-metabolic, and ECM-remodeling pathways. Decellularized Svep1+/- matrix altered macrophage adhesion and phenotype relative to Svep1+/+ matrix, identifying SVEP1 as a matrix-borne mediator coupling adipose remodeling to immune activation and metabolic impairment. Together, these findings position the adipose ECM as an active driver of immunometabolic dysfunction and nominate SVEP1 and its receptor network as candidate targets in obesity.

Arteries are among the first tissues to exhibit age-related dysfunction, yet the metabolic mechanisms driving vascular senescence remain poorly understood. Here, analysis of human aortic transcriptomic data identified HCAR1, encoding the lactate receptor GPR81, as one of the genes most significantly downregulated with age. We therefore investigated whether age-associated loss of GPR81 contributes to cellular senescence within the vessel wall. Senescent human endothelial cells and vascular smooth muscle cells accumulated neutral and oxidized lipids and exhibited increased labile iron and ferroptosis. Silencing GPR81 in early-passage cells recapitulated this metabolic phenotype together with multiple hallmarks of cellular senescence. Moreover, endothelial-specific deletion of GPR81 in young mice was sufficient to induce senescent cell accumulation, impaired lipid homeostasis, endothelial dysfunction, and elastin disorganization. Conversely, pharmacological activation of GPR81 with the agonist CHBA restored fatty acid metabolism, promoted glycolytic reprogramming, and attenuated ferroptotic stress and senescence-associated phenotypes. In lamin A knock-in (LAKI) progeroid mice, CHBA reduced arterial lipid accumulation and cellular senescence, shifted vascular cell composition toward a youthful state, improved endothelial integrity, and restored extracellular matrix homeostasis. Together, these findings identify age-associated loss of GPR81 as a driver of vascular metabolic dysfunction and cellular senescence and establish pharmacological GPR81 activation as a promising therapeutic strategy for preserving vascular homeostasis and mitigating age-associated cardiovascular disease.

Glucagon-like peptide-1 (GLP-1) receptor agonists produce less weight loss in people with type 2 diabetes than without, and higher compensatory doses are limited by gastrointestinal adverse events and lean-mass loss--leaving patients with obesity, type 2 diabetes, and metabolic dysfunction-associated steatohepatitis (MASH) inadequately treated. We tested whether linafexor, a pulsatile farnesoid X receptor (FXR) agonist, could augment the weight-loss efficacy of low-dose semaglutide in this population while preserving tolerability. In this multicenter, randomized, double-blind, placebo-controlled, phase 2 trial, 62 adults with obesity (body-mass index, 30-45 kg/m2), treatment-naive type 2 diabetes, and MASH (MRI-PDFF [≥]10%) were assigned to linafexor (4 mg orally once daily) or placebo, each with semaglutide (0.5 mg once weekly), for 16 weeks. The primary outcome was the percentage change in body weight at week 16. Adding linafexor more than doubled weight loss (-6.17% vs. -2.91%; treatment difference, -3.26%; 95% CI, -5.35 to -1.18; P=0.003), and more participants achieved at least 5% weight loss (53.3% vs. 28.1%; P=0.046). Consistent with this, combination therapy further reduced visceral adipose tissue (treatment difference, -13.85 cm2; P=0.035), the liver enzymes alanine aminotransferase and {gamma}-glutamyl transferase, and serum bile acids, whose changes correlated with weight and liver-enzyme improvements--associations absent with monotherapy. Gastrointestinal adverse events were comparable (23.3% vs. 18.8%), with no treatment-related serious adverse events or discontinuations. Thus, in a population with blunted GLP-1 responses, adding linafexor to low-dose semaglutide enhanced weight loss and improved body composition and hepatic measures while preserving tolerability--a dose-sparing, mechanism-complementary strategy (ClinicalTrials.gov number, NCT06492330).

Background & Aims: Childhood obesity is a complex, heterogeneous disease. Children with obesity are often grouped into metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO) phenotypes, although this classification may oversimplify the underlying metabolic diversity. We aimed to characterise the metabolic profiles associated with the conventional MHO/MUO classification and to identify data-driven metabolic profiles in 267 children and adolescents with obesity. Methods: In this cross-sectional study, we used serum 1H-NMR spectroscopy to quantify lipoproteins, glycoproteins, low-molecular-weight metabolites, and lipid fractions. Univariate comparisons and partial least squares discriminant analysis (PLS-DA) were used to characterise NMR-derived variables associated with MHO and MUO groups. We applied unsupervised k-means clustering based on principal component scores to identify data-driven metabolic profiles independent of the predefined clinical phenotypes. Results: Forty-one NMR-derived variables differed between MUO and MHO (FDR q-value < 0.05), predominantly in the triglyceride-rich lipoprotein and glycoprotein profiles, of which 31 were elevated in MUO. PLS-DA discriminated between MHO and MUO (AUC = 0.84, Q2 = 0.33; permutation p < 0.001). Unsupervised clustering identified two data-driven metabotypes that only partially overlapped with the clinical phenotypes: 27% of children with MHO clustered within the adverse metabolic profile (Cluster 2), characterised by a triglyceride-rich and inflammation-associated profile, whereas 41% of children with MUO were assigned to the comparatively favourable profile (Cluster 1). Clustering further revealed additional differences in lipoprotein subclasses and lipid composition that the MHO/MUO classification did not capture. Conclusions: The conventional MHO/MUO classification captures an important component of metabolic variation in childhood obesity but does not fully capture cardiometabolic heterogeneity. Quantitative 1H-NMR metabolomics identified putative metabotypes characterised by differences in lipoprotein composition and cholesterol distribution beyond clinical phenotypes. These findings support the potential value of metabolomic profiling to refine cardiometabolic risk stratification in children with obesity; however, the relevance of these data-driven metabotypes requires confirmation in independent cohorts and longitudinal follow-up studies.

Visceral white adipose tissue (vAT) is more susceptible than subcutaneous white adipose tissue (scAT) to obesity-associated metaflammation, but the metabolic pathways accompanying this depot specific transition remain incompletely defined. We profiled vAT and scAT from mice fed a control diet or a 60% kcal high-fat diet (HFD) for 1 or 8 weeks. Untargeted metabolomics was integrated with targeted endocannabinoid quantification, gene expression and promoter associated chromatin analyses, adipocyte and stromal vascular fraction (SVF) measurements, cross-omics correlation analysis, and cell-culture perturbations. After 1 week, HFD induced relatively few metabolic changes, although vAT showed early alterations associated with sphingomyelin metabolism. By week 8, both depots exhibited extensive but distinct metabolic remodeling. The KEGG retrograde endocannabinoid-signaling pathway was the highest-ranked enriched pathway in vAT, with arachidonoylglycerol (2AG) among the most strongly altered metabolites. Targeted analysis confirmed selective 2AG accumulation in vAT, accompanied by coordinated changes in genes and promoter-associated chromatin marks related to endocannabinoid synthesis, degradation and receptor expression. Cellular fractionation localized excess 2AG predominantly to vAT adipocytes, whereas Cnr2 was enriched in the SVF and induced by HFD specifically in vAT. Cross omics integration further revealed a denser and predominantly inverse transcript metabolite association network in vAT than in scAT. Using macrophage adipocyte co-culture and secretome profiling, we demonstrated that cannabinoid stimulation shifts activated macrophage outputs away from pro-inflammatory cytokines (Il1b, Ccl2) toward extracellular matrix (ECM) proteoglycan remodeling and intercellular signaling.

The hypothalamus is a central regulator of glucose and energy homeostasis, with arcuate nucleus (ARC) neurons orchestrating these processes. Agouti-related peptide (AgRP) and pro-opiomelanocortin (POMC) neurons integrate metabolic cues to control feeding behavior and systemic metabolism. Among these cues, fatty acids (FA) have emerged as key modulators of ARC neuronal activity. While neuronal sensing of circulating FA has begun to be defined, the contribution of FA derived from endogenous lipid stores to ARC neuron function and energy homeostasis remains largely unexplored. We recently identified lipid droplets (LD) as regulated FA reservoirs that control FA availability and metabolism in orexigenic AgRP neurons, thereby modulating their activity and regulating feeding. This prompted us to investigate whether LD-derived FA similarly regulate POMC neuron function. To this end, we targeted adipose triglyceride lipase (ATGL), which catalyzes the first committed step of LD lipolysis, in POMC neurons. We show that LD are present in POMC neurons under basal conditions both in vitro and in vivo, and that pharmacological or genetic inhibition of ATGL increases LD abundance. ATGL deficiency enhances spontaneous firing of POMC neurons and leads to reduced body weight, fat and lean mass in males, but not females. Consistent with enhanced glucose metabolism, ATGL loss lowers glycemia and insulinemia and increases carbohydrate utilization in chow-fed males. In contrast, ATGL deficiency does not alter metabolic adaptations to cold exposure, fasting or diet-induced obesity in either sex. Collectively, these findings establish ATGL-dependent LD lipolysis in POMC neurons as a previously unrecognized, sex-dependent regulator of energy homeostasis.

Pathogenic adipose tissue remodeling promotes metabolic disease in obesity, but the mechanisms that establish this unhealthy tissue state remain poorly understood. Here, we show that obesity drives SOX4-dependent reprogramming of mesenchymal stromal cells (MSCs) into cancer-associated fibroblast-like (CAF-like) cells that promote adipose tissue dysfunction. TGF{beta} signaling is elevated in obesity and activates SOX4 in mouse and human MSCs, inducing their conversion to a CAF-like state. In mice, MSC-specific SOX4 activation induces the CAF-like program and exacerbates adipose tissue inflammation and glucose intolerance, whereas Sox4 deletion attenuates inflammation and improves glucose homeostasis during obesity. We further identify the growth factor Midkine (MDK) as a SOX4-regulated paracrine effector produced by CAF-like cells. MDK inhibition in obese mice reduces adipose tissue inflammation and improves metabolic function. Together, these findings define a TGF{beta}-SOX4-MDK stromal signaling axis that drives pathological adipose tissue remodeling in obesity and highlight this pathway as a potential therapeutic target for improving metabolic health.

Peroxisome proliferator-activated receptor (PPAR) is a nuclear receptor that plays a central role in metabolic adaptation by regulating gene expression programs involved in lipid utilization and energy homeostasis. Although the hepatic functions of PPAR and its target genes are well characterized, less is known about its transcriptional activity in extrahepatic tissues. Pemafibrate (K-877), a selective PPAR modulator (SPPARM), is a high-affinity PPAR ligand with improved potency and selectivity compared with conventional fibrates. Here, we investigated pemafibrate-induced tissue-specific transcriptional responses comparing wild type and whole-body PPAR-deficient littermate mice. Twelve-week-old male PPAR+/+ and PPAR-/- mice were treated daily with pemafibrate (0.1 mg/kg) or vehicle by oral gavage for 14 days. We performed genome-wide transcriptomic analyses in the liver, jejunum, kidney, soleus muscle, and BAT. Pemafibrate-induced transcriptional changes were entirely dependent on PPAR, as no differentially expressed genes were detected in PPAR-/- mice. The magnitude and nature of the response were tissue-specific, with the strongest transcriptional effects observed in the liver and jejunum, whereas the kidney, soleus muscle, and BAT showed limited responses. In the liver, pemafibrate primarily induced the expression of genes involved in fatty acid metabolism, mitochondrial function, and energy production. In the jejunum, pemafibrate activated lipid metabolic programs together with tissue-specific pathways related to cellular homeostasis. Collectively, our findings show that pemafibrate is a highly selective PPAR activator with a preferential transcriptional activity in the liver and intestine after oral administration. This study provides a resource for defining tissue-specific PPAR-responsive gene networks and expands our understanding of PPAR functions beyond the liver.

Background: Macrophage foam cell formation is a central event in atherosclerosis. Although protein ubiquitination is increasingly recognized as a regulator of macrophage lipid handling, whether deubiquitinating enzymes directly control lipid uptake and metabolic remodeling during atherogenesis remains unclear. Methods and Results: Here, transcriptomic profiling identified ubiquitin-specific protease 20 (USP20) as a previously unrecognized regulator of macrophage foam cell formation. Genetic and pharmacological studies demonstrated that USP20 promoted macrophage lipid accumulation and foam cell formation, whereas macrophage-specific Usp20 deficiency markedly attenuated atherosclerotic lesion formation, lipid deposition, and macrophage accumulation in mice. To elucidate the underlying mechanism, integrative analysis of USP20-interacting proteins and proteomic alterations in Usp20-deficient macrophages identified fatty acid-binding protein 5 (FABP5) as a substrate of USP20. Mechanistically, USP20 interacted with FABP5 and stabilized its protein abundance by preventing ubiquitin-dependent proteasomal degradation. Consequently, USP20-mediated stabilization of FABP5 enhanced PPAR{gamma} occupancy at the Cd36 promoter, thereby increasing Cd36 transcription, ox-LDL uptake, and foam cell formation. Accordingly, Fabp5 knockdown abolished USP20-induced CD36 expression, ox-LDL uptake, and foam cell formation, whereas pharmacological activation of PPAR{gamma} restored CD36 expression in Fabp5-deficient macrophages. Finally, macrophage-targeted delivery of the USP20 inhibitor GSK2643943A markedly reduced atherosclerotic burden without evident systemic toxicity, supporting the therapeutic potential of targeting USP20 in atherosclerosis. Conclusions: USP20 promotes macrophage foam cell formation by stabilizing FABP5 and enhancing PPAR{gamma}-dependent Cd36 transcription. Targeting the USP20-FABP5-PPAR{gamma}-CD36 axis may represent a therapeutic strategy to limit macrophage lipid accumulation, metabolic dysfunction, and atherosclerosis progression.

Obesity-associated insulin resistance is driven in part by adipose tissue dysfunction and oxidative stress, yet the role of extracellular mechanisms in modulating insulin signaling remains poorly understood. Here, we show that extracellular Glutathione Peroxidase 3 (GPX3) enhances adipocyte insulin sensitivity and functionalities independent of its canonical peroxidase function. GPX3, a secreted selenoprotein highly expressed in white adipose tissue (WAT), is suppressed in obesity, but whether it actively regulates insulin sensitivity had not been established. We find that WAT GPX3 expression closely mirrors insulin receptor (InsR) expression across a broad range of metabolic parameters in humans and increases dynamically following weight loss. Prolonged therapeutic selenium supplementation in diet-induced obese mice selectively suppressed epididymal WAT oxidative damage, restored GPX3 and InsR expression, and enhanced insulin-stimulated AKT phosphorylation, improving oral glucose tolerance. Mechanistically, recombinant GPX3 extracellularly administered at physiological concentrations induced InsR expression across multiple adipocyte models, including pre-adipocytes, epididymal WAT explants, and adipocyte organoids, by promoting binding of the transcription factor Specificity Protein 1 (SP1) to the Insr promoter, while knockdown of GPX3 completely blocks SVF adipogenesis. These effects rely on the structural integrity, rather than selenocysteine-dependent activity. Thus, we identify a GPX3-SP1-InsR signaling axis in adipose tissue insulin sensitivity, suggesting GPX3 is a novel paracrine mediator of metabolic health and a potential therapeutic target to reinstate WAT insulin sensitivity in obesity and type 2 diabetes.

Ether glycerophospholipids (ether lipids) are a subclass of glycerophospholipids that are synthesized at the peroxisome and constitute nearly 20% of the total phospholipid content in metazoans. Biochemically, ether lipids have an alkyl chain attached by an ether bond at the sn-1 position of the glycerol backbone (alkyl-ether) primarily containing choline or ethanolamine head groups. Some ether lipids contain a cis bond adjacent to the ether linkage (alkenyl-ether) and are commonly referred to as plasmalogens. While the importance of ether lipids in humans is clear, highlighted by the severity of inherited peroxisomal disorders caused by ether lipid deficiency, the molecular roles of these lipids remain poorly understood. Here, we identify a link between ether lipid metabolism, peroxisome degradation, and oxygen availability. We find Fatty acyl-CoA-reductase 1 (FAR1), the rate-limiting enzyme in peroxisomal ether lipid metabolism, acts as a peroxisome receptor necessary for peroxisome degradation when oxygen is limiting. Hypoxia increases choline ether lipid abundance, promotes autophagy activation, and peroxisome degradation. Mechanistically, FAR1 binds ATG8-family protein LC3B and is necessary and sufficient to control peroxisome degradation under hypoxia. FAR1s enzymatic function as well as its capacity to bind LC3B is necessary to degrade peroxisomes under hypoxia. Similarly, loss of multiple components of peroxisomal ether lipid metabolism blocks peroxisome degradation under hypoxia in cells and in vivo. In mouse models of chronic HIF activation, Far1 is a direct HIF target gene and is necessary for peroxisome degradation in this setting. Increasing ether lipids using ether lipid precursors activates autophagy and promotes autophagy-dependent cardioprotection against ischemic injury. This work reveals FAR1 as a critical regulator of peroxisome homeostasis in the setting of oxygen limitation.

Enhanced excitability of output neurons in the olfactory bulb (OB) has been linked to regulation of energy homeostasis. The mechanism by which the olfactory system can drive metabolic state while processing odor information remains elusive yet must depend upon integration and relay to the rest of the brain. Herein, we screened brain-wide neuronal ensembles that preferentially engaged during odor stimulation (referred to as ODORTRAP) utilizing FOSTRAP activity mapping. Mice were exposed to the odor isopropyl tiglate (IPT), a preferred ligand for the olfactory receptor 160, previously shown to be vulnerable to diet-induced obesity. Odor activation resulted in elevated labelling in the olfactory bulb (ODORTRAP) (p < 0.001), as well as in higher olfactory cortices including anterior olfactory nucleus, piriform cortex, and cortical amygdala (p < 0.05). Interestingly, IPT differentially recruited hypothalamic feeding areas, namely the arcuate (ARC), dorsomedial (DMH) and lateral (LH) hypothalamus (p < 0.001), while the ventromedial hypothalamic nucleus and the suprachiasmatic nucleus exhibited no change in ODORTRAP activity (p > 0.05). In mice that were maintained on moderately high-fat (MHF) diets, we discovered that obesity re-models the activation pattern across the brain. Obese mice exhibited loss of ODORTRAP activity in the ARC (p < 0.0001), whereas in the DMH and LH increased baseline activity that obscured any odor-linked neural activity. While IPT activated the nucleus accumbens and medial septum in control mice (p < 0.01), obese mice demonstrated no changes in ODORTRAP activity (p > 0.05). Our study identifies key brain regions linking chemosensation and metabolic state, specifically demonstrating alteration in activity in hypothalamic domains upon obesogenic diet.

Obesity is associated with hypothalamic inflammation, leptin resistance and increased cardiometabolic risk, but the neuroimmune signals linking nutrient excess to these outcomes remain incompletely defined. Here we show that diet-induced obesity is accompanied by local complement activation in the mouse hypothalamus, leading to C3a generation that signals through C3a receptor (C3aR) on leptin receptor (ObRb)-expressing neurons and blunts leptin signaling. Deletion of C3aR in ObRb-expressing neurons preserves leptin responsiveness, reduces food intake and weight gain, and improves glucose homeostasis during dietary challenge. Systemic pharmacological C3aR targeting induces weight loss and improves leptin responsiveness in established obesity. Genetic or pharmacological C3aR targeting also attenuates obesity-associated diastolic dysfunction and myocardial fibrosis; pair-feeding experiments reveal an additional component of cardiac protection beyond reduced weight gain, associated with lower cardiac sympathetic innervation. In humans, circulating complement activation markers are elevated in obesity and decline after bariatric surgery. Together, our findings identify C3aR signaling in ObRb-expressing neurons as a neuroimmune pathway contributing to hypothalamic leptin resistance and obesity-associated cardiac remodeling, highlighting complement signaling as a potential therapeutic target in cardiometabolic disease.

Energy homeostasis and motivated behaviours are tightly interconnected processes coordinated by peripheral metabolic signals and central reward circuits. Among these signals, circulating triglycerides (TG) have emerged as neuromodulators of mesolimbic dopamine functions and reward processing. However, whether TG directly regulate the activity of defined neuronal populations within the nucleus accumbens (NAc) during appetitive behaviours remains unknown. Here, we investigated how central TG availability shapes the in vivo activity of NAc dopamine D2 receptor-expressing spiny projection neurons (D2R-SPNs) across distinct nutritional and metabolic states. Using in vivo fiber photometry in Drd2-Cre mice, we monitored D2R-SPN Ca2+ dynamics during appetitive Pavlovian conditioning and refeeding. D2R-SPNs progressively developed robust responses to a reward-predictive conditioned stimulus (CS+) over the course of learning, while their activity during reward consumption remained stable. Acute elevation of central TG levels through carotid infusion did not alter D2R-SPN activity or behavioural performance in lean chow-fed mice, irrespective of whether they were fed or food-restricted. In contrast, in mice exposed to a high-fat diet (HFD), central TG delivery suppressed cue-evoked D2R-SPN activity in food-restricted animals without affecting reward consumption or behavioural outputs. Likewise, TG significantly reduced refeeding-evoked D2R-SPN activation in fasted HFD-mice, while leaving novelty-induced neuronal responses unchanged. Together, these findings demonstrate that obesogenic conditions reveal a metabolic state-dependent sensitivity of accumbal D2R-SPNs to circulating lipids. This work identifies TG as context-dependent modulators of D2R-SPN function and uncovers a mechanism through which dietary history interacts with current metabolic state to reshape the neural encoding of reward-predictive cues and food-directed behaviours.

Background: Early postoperative weight loss may help predict later outcomes, but its reliability for longer-term weight loss and regain remains unclear. We assessed whether the percentage total weight loss (%TWL) 3 months after metabolic/bariatric surgery predicted later %TWL weight change/regain. Methods: This retrospective observational cohort study included 216 patients from a prospectively pre-recruited multicentre bariatric surgery cohort who underwent sleeve gastrectomy or Roux-en-Y gastric bypass and had 3-month %TWL and at least one later outcome. Linear regression assessed associations between 3-month %TWL and later %TWL plus weight change/regain outcomes. Adjusted incremental R2 quantified the additional variance explained by 3-month %TWL. Secondary procedure-stratified, diabetes-stratified, and baseline BMI comparator analyses are reported in the Supplementary Material. Results: Greater 3-month %TWL was associated with higher 1-year and 2-year %TWL in adjusted models (both p < 0.001) but not longer-term %TWL (p = 0.078). Incremental R2 was 38.23% for 1-year, 11.75% for 2-year %TWL and 2.25% for long-term %TWL. Greater 3-month %TWL was also associated with greater recurrent weight gain from 1 to 2 years and from 1 year to long-term follow-up. In secondary analyses, findings were broadly consistent across procedure and diabetes subgroups, while 3-month %TWL explained more additional variance in 1-year %TWL than baseline BMI Conclusion: 3-month %TWL predicted 1-year and 2-year outcomes but not longer-term %TWL, supporting its value as an early marker of postoperative weight trajectory. Heterogeneity in recurrent weight stability may contribute to weaker long-term prediction and warrants further study to determine whether early weight-loss patterns can identify patients requiring closer long-term weight management support.

Introduction: Adipose tissue fibrosis has been associated with metabolic dysfunction-associated steatotic liver disease (MASLD) and suboptimal weight loss after bariatric surgery. The objective was to characterize changes in adipose tissue fibrosis and extracellular matrix (ECM) components in adipose tissues from two abdominal fat compartments, subcutaneous and omental, in response to bariatric surgery; and determine the effect of weight loss on the association between adipose tissue fibrosis and MASLD feature changes with weight loss. Methods: Liver and adipose tissue biopsy samples were obtained before and after weight loss from patients who underwent two-stage bariatric surgery. Adipose tissue pericellular fibrosis was evaluated histologically with picrosirius red staining for collagen quantification and normalized to adipocyte count per microscope field. Transcript levels of ECM remodeling and inflammatory genes were measured by RNA sequencing in subcutaneous adipose tissue pre- and post-surgery. Results: At baseline, adipose tissue pericellular fibrosis did not associate with MASLD features, metabolic dysfunction-associated steatohepatitis or hepatic fibrosis in patients with severe obesity. Changes in liver histology after surgery were unrelated to changes in adipose tissue fibrosis. Transcripts for most genes involved in ECM remodeling and inflammation were downregulated in subcutaneous fat one year after bariatric surgery. Omental, but not subcutaneous, adipose tissue fibrosis decreased after surgery when adjusted for cell number (mean {+/-} SD: 0.41 {+/-} 0.12 vs 0.32 {+/-} 0.08 {micro}m2/cell, p<0.005). Higher subcutaneous adipose tissue fibrosis correlated with reduced weight loss (estimate {+/-} SE: -2.04 {+/-} 0.99, p<0.05) and BMI loss (-0.73 {+/-} 0.35, p<0.05), while increased omental adipose tissue fibrosis after weight loss was associated with worsening hepatic fibrosis (0.31 {+/-} 0.14, p<0.05). Conclusion: In individuals with severe obesity undergoing bariatric surgery, adipose tissue fibrosis is poorly correlated with MASLD features. Notably, pericellular fibrosis in subcutaneous abdominal, but not omental, adipose tissue was associated with a reduced weight-loss response to surgery.

Objectives: The bile acid nuclear receptor Farnesoid X Receptor (FXR, NR1H4) is a major regulator of metabolism and energy homeostasis in peripheral organs. It modulates bile acid, glucose, and lipid metabolism, as well as fat mass and body weight. However, FXR is also expressed in the brain, particularly in the hypothalamus, a key center for the regulation of energy homeostasis. Although one study has demonstrated a role for brain FXR activation in energy balance, its specific hypothalamic role is still unknown. Here, we examined the role of FXR in the mediobasal hypothalamus in the regulation of energy balance. Methods: We used a genetic approach combined with metabolic phenotyping to determine the effect of FXR invalidation in the mediobasal hypothalamus on metabolic parameters involved in the central regulation of energy homeostasis. Results: Our results demonstrate that hypothalamic FXR deficiency induces a positive energy balance, resulting in a reduction in energy expenditure due to alterations in glucose metabolism accompanied by structural changes in white adipose tissues. Conclusion: This study uncovers a previously unrecognized role for hypothalamic FXR in the central homeostatic control of energy balance, providing new insights into its contribution to peripheral glucose metabolism and adipose tissue structural remodeling.

Metabolic dysfunction-associated steatotic liver disease (MASLD) and steatohepatitis (MASH) arise, in part, from excessive free fatty acid flux from adipose tissue to the liver. Activin E (ActE, encoded by INHBE) suppresses adipocyte lipolysis through the type I receptor ALK7 (ACVR1C). Loss-of-function variants in INHBE and ACVR1C reduce waist-to-hip ratio in humans, yet genetic knockouts in mice produce insulin resistance and hepatic steatosis, suggesting discrepancies between human and mouse biology. We identify GDF3, a TGF-{beta} superfamily ligand upregulated in obese adipose tissue, as the principal endogenous antagonist of ActE/ALK7 signaling. Human transcriptomic datasets reveal coordinated dysregulation: hepatic INHBE expression and circulating ActE protein are elevated in obesity, while adipose ACVR1C is downregulated and GDF3 is reciprocally upregulated. Using ALK7-selective reporter assays, we show GDF3 inhibits ActE-driven SMAD2/3 signaling as a competitive antagonist rather than the weak agonist previously proposed. ActE suppressed beta-adrenergic-stimulated lipolysis in mouse and human adipocytes and primary human adipose tissue; GDF3 overexpression abolished this effect. In diet-induced obese mice, inducible Gdf3 deletion reduced adipose lipolysis, resolved hepatic steatosis and fibrosis, and improved insulin sensitivity, benefits abolished by Inhbe knockdown, confirming dependence on ActE signaling. Predicted loss-of-function variants in INHBE show only nominal, WHR-dependent associations with type 2 diabetes risk, potentially confounded by hematological effects on HbA1c. Gdf3 deficiency synergized with the clinical-stage anti-activin receptor antibody Bimagrumab to amplify fat-mass loss and improve glucose homeostasis in multiple MASH models. These findings establish GDF3 as an endogenous antagonist of ActE-ALK7 signaling and nominate GDF3 inhibition as a therapeutic strategy for MASLD/MASH.