The epidemic of obesity and metabolic syndrome is a major public health concern internationally. There is increasing knowledge and research in areas of appetite regulation and drivers of obesity but there is still a gap on how the interactomes are altered in a metabolically dysregulated human body. The human microbiome has been implicated in the pathogenesis of obesity. While the association of gut bacteriome dysbiosis is well described in obesity and metabolic syndrome, there is a lack of an integrative understanding about the roles of the non-bacterial microbiome (virome, mycobiome, and archaeome) in the pathogenesis and protection of obesity and metabolic syndrome. Accumulating studies have revealed that the non-bacterial microbes in the gut, including viruses/phages, fungi, and archaea, are profoundly altered in obesity, and impact host adiposity and physiology in nuanced manners. In this review, we aim to provide a comprehensive view on the role and the mechanisms of the gut virome, mycobiome, and archaeome in obesity. These insights will shed light on the translational value as well as the future research directions for harnessing the gut non-bacterial microbial entities in the therapeutics and prevention of metabolic diseases.

Introduction

The current understanding of interactions and crosstalk among essential organs remains incomplete, mainly due to the limitations of studies on the systemic mechanisms at play. The gut and the liver are essential for the functioning of the entire body, and their derived mediators circulate through blood or lymph, impacting other organs like the brain, heart, and kidneys.

Aim

This publication reviews gut-liver-derived mediators, which were tested and validated in vivo in humans and rodents, together with the current knowledge of their systemic effects on key vital organs.

Method

Original articles published up to February 2025, based on clinical trials or in vivo experimental models, were retrieved from PubMed and Web of Science.

Results

During this systematic analysis, 28 gut-liver-derived mediators were identified from 52 publications and classified into five distinct groups based on their molecular characteristics: (a) low molecular weight metabolites, (b) endotoxins, (c) hormones, (d) lipids and (e) proteins. Additionally, the mechanism of action for each of these molecules was specified, aimed at providing a mechanistic overview of their effects on the brain, heart, and kidneys.

Discussion

The diverse and occasionally conflicting impact of the identified mediators on comorbidities necessitates further investigations pinpointing key mechanisms influencing disease genesis and progression.

Conclusion

Our research shows the necessity of a thorough examination of these mediators, exploring their diagnostic and therapeutic potential in a holistic multi-organ setting, to elucidate inter-organ crosstalk.

Background

Gestational diabetes mellitus (GDM) is the most common metabolic disease during pregnancy and increases the prevalence of type 2 diabetes in both mothers and children. GDM management provides an opportunity to prevent and lower the global burden of diabetes across life. Molecular mechanisms underlying GDM are not completely understood. In this study, we explore the role of transforming growth factor beta (TGF-β) signaling in GDM, as this pathway reportedly affects pancreatic β-cell development, function, and proliferation.

Methods

We developed a GDM animal model. Serum circulating levels of TGF-β family ligands were measured in mice and human GDM. Pancreatic TGF-β signaling was investigated via gene and protein expression.

Results

Our GDM animal model recapitulates the main pathophysiological features of human GDM, including glucose intolerance, decreased insulin sensitivity and pancreatic β-cell malfunction. Islets from GDM mice showed impaired insulin secretion and content, altered ion channel activity, and decreased β-cell replication rate. This was accompanied by increased Smad2 signaling activation. Elevated serum activin-A and inhibin levels were found in mice and human GDM, suggesting their role as upstream signaling transducers of pancreatic Smad2 activation. Pharmacological inhibition of TGF-β/Activin-Smad2 signaling in mouse pancreatic islets resulted in improved pancreatic β-cell function and regeneration capacity.

Conclusions

Our data suggest that disruption of the pancreatic Smad2 pathway plays a critical role in the pathogenesis of GDM, contributing to abnormal glucose homeostasis and inadequate insulin secretion. Attenuation of this signaling pathway may represent a putative therapeutic target for GDM.

Background and aims

Fasting hypoglycemia has clinical implications for children with growth hormone (GH)-insensitivity syndrome. This study investigates the pathophysiology of juvenile hypoglycemia in a large animal model for GH receptor (GHR) deficiency (the GHR-KO pig) and elucidates mechanisms underlying the transition to normoglycemia in adulthood.

Methods

Insulin sensitivity was assessed in juvenile and adult GHR-KO pigs and wild-type (WT) controls via hyperinsulinemic-euglycemic clamp (HEC) tests. Glucose turnover was measured using D-[6,6-²H₂] glucose and ²H₂O. Clinical chemical and targeted metabolomics parameters in blood serum were correlated with qPCR and western blot analyses of liver and adipose tissue.

Results

GHR-KO pigs showed increased insulin sensitivity (p = 0.0019), especially at young age (M-value +34% vs. WT), insignificantly reduced insulin levels, and reduced endogenous glucose production (p = 0.0007), leading to fasting hypoglycemia with depleted liver glycogen, elevated β-hydroxybutyrate, but no increase in NEFA levels. Low hormone-sensitive lipase phosphorylation in adipose tissue suggested impaired lipolysis in young GHR-KO pigs. Metabolomics indicated enhanced fatty acid beta-oxidation and use of glucogenic amino acids, likely serving as compensatory pathways to maintain energy homeostasis. In adulthood, insulin sensitivity remained elevated but less pronounced (M-value +20%), while insulin levels were significantly reduced, enabling normoglycemia and improved NEFA availability. Increased fat mass, but not sex hormones, appeared key to this metabolic transition, as early castration had no effect.

Conclusions

Juvenile hypoglycemia in GH insensitivity results from excessive insulin sensitivity, reduced glucose production, and impaired lipolysis. Normoglycemia in adulthood emerges through increased adiposity and moderated insulin sensitivity, independently of sex hormones. These findings elucidate the age-dependent metabolic adaptations in GH insensitivity.

Due to significant risks of peripartum complications, pregnancies complicated by diabetes often require labor induction or augmentation with synthetic oxytocin. However, the efficacy of oxytocin is often compromised in diabetic pregnancies. Given that diabetes deregulates the body's circadian timekeeping system, our objective was to determine how time of day and the circadian clock gene, Bmal1, gate oxytocin efficacy. We compared oxytocin uterotonic efficacy in a smooth muscle-Bmal1 conditional knockout mouse (cKO), and a mouse model of food-induced gestational diabetes. We found that in wild-type mice, the oxytocin receptor is expressed in a time-of-day-dependent manner and is under the control of BMAL1. Both Bmal1 cKO and food-induced gestational diabetes mice, which presented with a downregulation of Bmal1 in the uterus, had decreased uterine contractility in response to oxytocin. To establish the translational value of these findings, we utilized an immortalized term human myometrial cell line. We determined that the time-of-day impacted oxytocin-induced myometrial contractility in vitro. Furthermore, we conducted a retrospective medical record analysis of 2,367 pregnant patients ≥39 weeks gestation undergoing induction of labor. We assessed the timing of labor induction and the impact of gestational diabetes mellitus on labor duration. Induction of labor in the morning compared to midnight was associated with a ∼1.5-hour and ∼7-hour shorter labor duration in controls and patients with gestational diabetes mellitus, respectively. In conclusion, circadian timing plays a key role in induction of labor and oxytocin responsiveness and should be considered when managing labor induction.

Mitochondrial dysfunction and declining energy production are hallmarks of aging, yet we lack a comprehensive systems-level view of ATP synthase (Complex V) activity across tissues, sex, and age. To overcome this, we leveraged a recently developed method to directly quantify complex V hydrolytic activity at scale in 32 tissues from young (10 weeks) and old (80 weeks) male and female mice. Our high-resolution atlas reveals several notable findings: 1) complex V activity differs markedly across tissues, with the highest levels seen in contractile organs such as the heart and striated muscles (quadriceps, hamstring, diaphragm, tongue); 2) sex influences complex V activity in a tissue-specific manner, with significant differences seen in the heart, liver, fat depots, pancreas, spleen, tongue, and cortex; 3) aging has a much larger impact than sex on complex V activity, with a greater number of age-dependent changes seen across tissues; 4) the directionality and magnitude of change in complex V activity across sex and age is variable and tissue dependent; 5) the expression of complex V related genes in human and mouse tissues across age shows only partial concordance with complex V activity, suggesting functional modulation by posttranscriptional mechanisms. This compendium of ATP synthase activity highlights organ-level variations in the mode and tempo of aging, affording an unprecedented view of the shared and divergent changes in ATP synthase function across sex and organ systems. Our data provide a valuable reference for comparative studies of mitochondrial adaptations across space and time, and in pathophysiological contexts.

Objectives

Soluble CD52 (sCD52) derived from activated CD4⁺ T cells regulates T cell immunity under autoimmune conditions; however, its role in obesity-associated chronic inflammation and glucose metabolism remains unclear. Therefore, we herein investigated the significance of CD52 in obesity.

Methods

CD52-knockout mice (KO) and their wild-type littermates were fed a high-fat diet (HFD) for 12 weeks and analyzed.

Results

sCD52 preferentially suppressed chronic liver inflammation and protected against impaired glucose tolerance and metabolic dysfunction-associated steatotic liver disease (MASLD) in obesity. No significant differences were observed in weight gain or energy metabolism in KO mice; however, glucose metabolism was impaired. A histological examination revealed more severe chronic inflammation and steatosis in KO mice, accompanied by changes in liver transcriptome profiles, but no significant differences in epididymal white adipose tissue (eWAT). In contrast, CD52 expression was significantly up-regulated in eWAT, with slightly higher levels in the liver and skeletal muscle in HFD-fed obese C57BL/6 mice than in chow-fed controls. sCD52 was released from the cultured eWAT of obese mice, but not lean mice, and circulating sCD52 levels were higher in obese mice. A re-analysis of a public single-nucleus RNA sequencing library revealed that increased CD52 in eWAT was linked to immune cells and adipocytes. T cell-derived purified sCD52 suppressed macrophage activation in vitro. In contrast, sCD52 was not secreted from 3T3-L1 adipocytes, although its protein levels increased with differentiation.

Conclusions

T cell-derived sCD52 mitigates the obesity-associated development of MASLD and glucose intolerance in mice.

The NLRP3 inflammasome is a key innate immune sensor that orchestrates inflammatory responses to diverse stress signals, including metabolic danger cues. Dysregulated NLRP3 activation has been implicated in chronic diseases such as type 2 diabetes, atherosclerosis, and neurodegeneration, underscoring the broad pathophysiological role of the NLRP3 pathway. In the context of obesity and its associated conditions, NLRP3 inhibition by VTX3232, an oral, selective, and brain-penetrant NLRP3 inhibitor, potently suppressed the release of proinflammatory cytokines (IL-1β, IL-18, IL-1α, IL-6, and TNF) from macrophages and microglia stimulated with metabolic stressors including palmitic acid and cholesterol crystals. Moreover, NLRP3 inhibition by VTX3232 also blocked NLRP3-driven insulin resistance in primary human hepatocytes and adipocytes while normalizing the acute phase response and FGF-21 secretion in hepatocytes under palmitic acid-induced inflammation. In vivo, NLRP3 inhibition by VTX3232 reduced systemic and tissue-specific inflammation in a mouse model of diet-induced obesity, reflected by decreased circulating inflammatory mediators, reduced hepatic inflammation, fewer crown-like structures in adipose tissue, and diminished hypothalamic gliosis. These anti-inflammatory effects were accompanied by improvements in body weight, food intake, and obesity-associated comorbidities such as hyperglycemia, hepatic steatosis, and markers of cardiovascular and renal disease. Notably, these effects were confined to the context of obesity, as no impact was observed in lean mice. When combined with glucagon-like peptide-1 receptor agonism by semaglutide, NLRP3 inhibition by VTX3232 yielded additive metabolic benefits, highlighting complementary mechanisms of action. Together, these findings reinforce the biological rationale for targeting NLRP3 in inflammatory conditions such as obesity, expand on the role of NLRP3 in metabolic inflammation, and underscore the importance of continued investigation into the NLRP3 pathway as a central node in cardiometabolic disease.

Background/Purpose

During exercise, myokine interleukin 6 (IL-6) plays a variety of metabolic roles including acting as a muscular energy sensor and liberating somatic energy stores. While the effects of IL-6 are relatively well-defined during exercise, its role in muscular metabolism during exercise recovery in humans has not been addressed.

Methods

To test whether myokine IL-6 allocates fat and glucose towards muscle, we conducted a randomized double-blind trial with 30 men (Age: 25.2 ± 3 yrs. BMI: 23.0 ± 1.5 kg/m2) where participants exercised at a moderate intensity for 2 h and received either tocilizumab to block IL-6 activity, or placebo. Continuous infusions of isotopically labeled palmitate, glucose, and glycerol paired with blood, breath, and muscle samples were used to measure muscle-specific metabolism.

Results

IL-6 blockade did not affect exercise performance, substrate utilization, or glucose, fatty acid and glycerol kinetics during exercise. During recovery, IL-6 blockade decreased the appearance of oral glucose and lowered the insulin response to a glucose drink. Despite this difference in glucose and insulin, the rate of post-exercise glycogen resynthesis before and after the ingestion of glucose was not altered between groups. Although IL-6 blockade did not affect lipolysis during exercise, it attenuated the accumulation of esterified oleate in muscle during recovery before the glucose drink was given. Furthermore, IL-6 blockade attenuated IL-1RA production in recovery but did not alter IL-10 secretion.

Conclusion

Together, these results imply that during recovery from moderate-intensity exercise, myokine IL-6 primarily regulates fatty acid metabolism within muscle and leaves glucose metabolism largely unaffected.

Aims

Low plasma high-density lipoprotein (HDL)-cholesterol levels are associated with increased risk of atherosclerotic cardiovascular disease (ASCVD), potentially reflecting impaired antiatherogenic HDL functions. These latter are strongly influenced by the HDL phospholipidome, which is frequently altered in ASCVD patients. Several studies reported that plasma levels of phosphatidylethanolamine (PE) species, particularly PE (36:5), were positively associated with ASCVD, but the underlying mechanisms remain unclear. Plasma PE (36:5) exists as eicosapentaenoic (EPA)-PE and arachidonic acid (ARA)-PE, with the latter predominating in ASCVD. This study investigated whether the association of PE (36:5) with ASCVD might result from an impairment of the antiatherogenic functions of HDL.

Methods and results

Total PE and PE (36:5) content of large HDL isolated from 86 women with metabolic syndrome was positively associated with carotid intima-media thickness in multivariate regression analysis adjusted for traditional risk factors. In TgCETP x Ldlr^−/− mice fed a high-cholesterol diet, the atherosclerotic plaque size was greater when reconstituted HDL (rHDL) containing ARA-PE was injected retro-orbitally, compared with injection of control rHDL containing only phosphatidylcholine (PC). In vitro, PE rHDL showed reduced cholesterol efflux capacity and impaired anti-inflammatory activity in THP-1 macrophages, together with diminished anti-oxidative activity against LDL oxidation compared to control rHDL. Strikingly, ARA-PE rHDL profoundly weakened of the HDL functions, while EPA-PE counteracted the ARA-PE-induced dysfunction and potentiated the functionality of rHDL.

Conclusions

This study reveals a causal link between PE species, particularly ARA-PE, and HDL dysfunction, contributing to atherosclerosis. EPA-PE can restore HDL function, supporting the therapeutic potential of EPA reducing ASCVD risk.

Metabolic flexibility, the capacity to adapt fuel utilization in response to nutrient availability, is essential for maintaining energy homeostasis and preventing metabolic disease. Here, we investigate the role of Ulk1 phosphorylation at serine 555 (S555), a site regulated by AMPK, in coordinating metabolic switching following short-term caloric restriction and fasting. Using Ulk1(S555A) global knock-in mice, we show loss of S555 phosphorylation impairs glucose oxidation in skeletal muscle and liver during short-term CR, despite improved glucose tolerance. Metabolomic, transcriptomic, and mitochondrial respiration analyses suggest a compensatory reliance on autophagy-derived amino acids in Ulk1(S555A) mice. These findings suggest Ulk1(S555) phosphorylation as a critical regulatory event linking nutrient stress to substrate switching. This work highlights an underappreciated role of Ulk1 in maintaining metabolic flexibility, with implications for metabolic dysfunction.

High-fat diet (HFD) promotes adipose tissue senescence, which in turn disrupts insulin-mediated glycemic homeostasis. The underlying mechanisms remain unclear. Through clinical survey data, animal models, and primary adipose-derived mesenchymal stem cells (ADSC), we investigated how dietary patterns influence adipocyte senescence. We found that elevated fatty acid levels enhance the interaction between the E3 ubiquitin ligase TRIP12 and Cyclin-dependent kinase 4 (CDK4) in ADSCs, triggering CDK4 ubiquitination and degradation. As a process associated with this disruption in cell cycle progression, cellular senescence may represent a key outcome. Consequently, senescent ADSC-derived mature adipocytes (ADSC-MA) exhibit impaired insulin-stimulated GLUT4 membrane translocation and reduced glucose uptake. In contrast, within an HFD setting, dietary fiber supplementation is associated with the reversal of cellular senescence. The gut microbiota–short-chain fatty acids (SCFAs) axis may be involved in the restoration of cell cycle progression and the amelioration of ADSC senescence, correlating with a partial recovery of glucose uptake capacity in ADSC-MAs. Our study highlights potential strategies to reverse cellular senescence and identifies promising therapeutic targets for impaired glucose tolerance.

Graphical abstract

Our study shows that an HFD increases circulating NEFAs. In this context, we demonstrate that NEFAs promote the binding of TRIP12 to CDK4 in ADSCs, leading to ubiquitination and subsequent degradation of CDK4. The loss of CDK4 disrupts the cell cycle and induces cellular senescence in ADSCs. Senescent ADSCs differentiate into dysfunctional MAs, which exhibit impaired insulin sensitivity and defective insulin-mediated GLUT4 membrane translocation. Consequently, glucose uptake in MAs is significantly diminished. It is thus plausible that this reduction contributes to the manifestation of impaired glucose tolerance at the systemic level. Dietary fiber supplementation alters the gut microbiota composition, increasing SCFAs production. These SCFAs act directly on ADSCs to restore CDK4 protein levels, rescue cell cycle progression, and reverse cellular senescence. This functional recovery of ADSCs suggests that targeting CDK4 restoration could represent a novel therapeutic strategy for HFD-related metabolic disorders.

Objectives

Small-molecule activators targeting the allosteric drug and metabolite (ADaM) site of AMPK enhance insulin-independent glucose uptake in skeletal muscle and lower glucose in preclinical models of hyperglycemia. The regulatory AMPKγ subunit plays a central role in energy sensing. While the skeletal muscle-selective γ3 isoform is essential for AMP/ZMP-induced glucose uptake, it is dispensable for ADaM site-binding activators. We hypothesized that the predominant γ1 isoform is required for ADaM site activator-stimulated glucose uptake in skeletal muscle.

Methods

Single-nucleus RNA sequencing (snRNA-seq) was performed on mouse and human skeletal muscle mapping AMPK subunit isoform distribution across resident cell types. To determine γ isoform-specific requirements for activator-stimulated glucose uptake, skeletal muscle-specific inducible AMPKγ1/γ3 double knockout (imγ1^−/−/γ3^−/−) and single knockout (imγ1^−/− and imγ3^−/−) mice were generated. Ex vivo glucose uptake was measured following treatment with AICAR (AMP-mimetic) or MK-8722 (ADaM site activator), and in vivo MK-8722-induced blood glucose lowering was assessed.

Results

snRNA-seq revealed distinct AMPK isoform distribution: γ1 was ubiquitously expressed, whereas γ3 was enriched in glycolytic myofibers in both mouse and human skeletal muscle. Ex vivo, glucose uptake stimulated by either AICAR or MK-8722 was severely blunted in imγ1^−/−/γ3^−/− muscle, and MK-8722-induced blood glucose lowering was significantly blunted in vivo. AICAR but not MK-8722-stimulated muscle glucose uptake was abolished in imγ3^−/−, whereas both activators fully retained effects on glucose uptake and glucose lowering in imγ1^−/− mice.

Conclusions

While γ1 predominates in stabilizing the AMPKα2β2γ1 complex, it is dispensable for AMPK activator-stimulated glucose uptake in skeletal muscle, whether mediated via the nucleotide-binding or ADaM site.

Biased agonism of the glucagon-like peptide-1/glucose-dependent insulinotropic polypeptide receptors (GLP-1R/GIPR) yields greater weight loss and better glycemic control than unbiased agonism in preclinical models. To evaluate whether biased agonism translates into improved efficacy for weight loss and glycemic control in clinical settings, we developed and characterized CT-388, a unimolecular peptide-based dual GLP-1R/GIPR agonist that is cAMP signal-biased at both receptors. In cell-based assays, CT-388 activated GLP-1R and GIPR with both having minimal receptor internalization vs their native ligands. CT-388 improved glycemic control in mice and monkeys, and reduced bodyweight, suppressed appetite, and improved metabolic dysfunction-associated steatohepatitis pathology in mice. In a phase 1, double-blind, randomized, placebo-controlled clinical study (NCT04838405) of CT-388 (subcutaneously administered single doses [0.5–7.5 mg] or 4 once-weekly doses [5–12 mg]) in otherwise healthy participants with overweight or obesity, CT-388 was generally well tolerated with a safety profile consistent with other incretin-based therapies; most treatment-emergent adverse events were mild or moderate. Glycemic parameters were improved during fasting conditions and an oral glucose tolerance test. The mean percent change in bodyweight from baseline to day 29 was −4.7% to −8.0% across CT-388 doses vs −0.5% with placebo. CT-388 pharmacokinetics supported once-weekly dosing. In conclusion, CT-388 demonstrated strong translatability from preclinical to clinical studies with consistent pharmacokinetics and pharmacodynamics across multiple species. In clinical settings, 4 weeks of CT-388 treatment produced clinically meaningful weight loss and improved glycemic control with favorable tolerability. These findings warrant further clinical evaluation of CT-388 for treating obesity and type 2 diabetes.

Type 2 diabetes and obesity impact billions of people and the global prevalence is only growing. Current treatment options, which include pharmacotherapy, e.g., GLP-1 receptor agonists (GLP-1RA) and bariatric surgical approaches have limitations. GLY-200 is an investigational clinical-stage oral non-absorbed polymeric drug designed to target proximal intestinal mucin and enhance its barrier function, emulating duodenal exclusion physiology for the treatment of diabetes and obesity. The efficacy of GLY-200 as a monotherapy and in combination with semaglutide, a leading GLP-1 receptor agonist (GLP-1RA) for obesity weight management was evaluated in diet-induced obesity (DIO) mice. Significant improvements in metabolic parameters were seen in mice treated with GLY-200 monotherapy. Moreover, an additive effect was observed when GLY-200 was combined with semaglutide, resulting in enhanced weight loss and metabolic improvements beyond those achieved with either treatment alone. GLY-200 showed promise as a weight maintenance drug, significantly blunting the weight rebound seen after GLP-1RA discontinuation. Phase 2a data from patients with type 2 diabetes (T2D) showed reductions in fasting and postprandial blood glucose, improved fasting lipid profiles, and progressive weight loss with GLY-200 treatment. These findings suggest that GLY-200, in combination with GLP-1RAs, holds promise as a novel therapeutic strategy for obesity, potentially offering a valuable approach for GLP-1RA dose reduction or weight maintenance following GLP-1RA discontinuation.

Insulin secretion from pancreatic β-cells is essential for maintaining glucose homeostasis and preventing type 2 diabetes, a condition closely associated with aging. Although previous studies in mice have shown that both basal and glucose-stimulated insulin secretion increase with age, the underlying mechanisms remained poorly understood. In this study, we identify protein kinase D (PKD) as a critical regulator of β-cell function during aging through its control of cellular senescence. Using β-cell–specific expression of dominant-negative PKDkd-EGFP and the selective PKD inhibitor CRT0066101, we demonstrate that inhibition of PKD activity in mature adult mice induced a senescent-like β-cell phenotype characterized by enlarged cell size and elevated β-galactosidase activity. These changes were associated with decreased expression of the antioxidant enzyme superoxide dismutase 2 and increased levels of reactive oxygen species. Surprisingly, despite promoting a senescent-like phenotype, PKD inhibition significantly improved glucose tolerance, enhanced glucose-stimulated insulin secretion, and protected against high-fat diet–induced glucose and insulin intolerance. These findings highlight the importance of PKD in preserving β-cell function under aging and metabolic stress conditions.

Electrogenic Na⁺/K⁺ ATPases (NKAs) control β-cell Ca²⁺ influx and insulin secretion by integrating the signal strength of stimulatory G protein (G_s)-coupled ligands (e.g., GLP-1, glucagon) and inhibitory G protein (G_i)-coupled ligands (e.g., somatostatin, epinephrine). However, there is a significant gap in our understanding of how specific NKA subunits contribute to β-cell function. Here, we demonstrate that the NKA β1-subunit (NKAβ1) is highly expressed and functional at the plasma membrane of mouse and human β-cells. β-cell-specific NKAβ1 knockout improves glucose tolerance and hepatic insulin sensitivity, coinciding with enhanced first- and second-phase glucose-stimulated insulin secretion (GSIS). Electrophysiological studies reveal that β-cell NKAβ1 enhances somatostatin-induced NKA currents, increases action potential afterhyperpolarization amplitude, and accelerates action potential frequency. Loss of NKAβ1 delays glucose-stimulated Ca²⁺ entry by impairing glycolysis-dependent NKA activation and reduces Na⁺ clearance efficiency during Ca²⁺ oscillations, resulting in prolonged silent phases. Thus, glycolytic stimulation of Na⁺ influx dictates silent phase duration via the kinetics of Na⁺ clearance by NKA, which is diminished in β-cells without NKAβ1. Furthermore, NKAβ1 differentially modulates β-cell G protein-coupled receptor (GPCR) signaling by attenuating G_i-GPCR effects and augmenting G_s-coupled GLP-1 receptor-mediated cAMP production and Ca²⁺ entry. β-cell NKAβ1 knockdown in human pseudoislets led to tonically elevated intracellular Ca²⁺ and increased insulin secretion. These findings establish NKAβ1-containing NKA complexes as critical regulators of β-cell electrical activity, Ca²⁺ oscillations, and secretory patterns, with direct consequences for systemic glucose homeostasis.

In rodent models of type 2 diabetes, a single intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1) induces sustained remission of hyperglycemia. Overactive agouti-related peptide (AgRP) neurons, located in the hypothalamic arcuate nucleus, are a hallmark of diabetic states, and their long-term inhibition has been linked to FGF1's antidiabetic effects. To investigate the underlying mechanism(s), we performed single-nucleus RNA sequencing of the mediobasal hypothalamus at Days 5 and 14 post-injection in wild-type and diabetic (Lep^ob/ob) mice treated with FGF1 or vehicle. We found that AgRP neurons from Lep^ob/ob mice form a transcriptionally distinct, hyperactive subpopulation. By Day 5, icv FGF1 induced a subset of these neurons to shift toward a less active, wild-type-like state, characterized by reduced activity-linked gene expression that persisted through Day 14. Spatial transcriptomics revealed that this FGF1-responsive AgRP subset is positioned dorsally within the arcuate nucleus. The transcriptional shift was accompanied by transcriptional processes indicative of increased GABAergic signaling, axonogenesis, and astrocyte–AgRP and oligodendrocyte–AgRP interactions. These glial inputs involve astrocytic neurexins and the perineuronal net (PNN) component phosphacan, suggesting both intrinsic and extrinsic mechanisms underlie FGF1-induced AgRP silencing. Combined with evidence that FGF1 increases PNN assembly in the arcuate nucleus, our findings reveal a cell-type–specific model for how FGF1 elicits long-term reprogramming of hypothalamic circuits to achieve diabetes remission.

Brown adipose tissue (BAT) dissipates energy as heat in response to β-adrenergic signaling induced by the sympathetic nervous system (SNS). While this pathway is essential for the cold-induced remodeling and metabolic activity of BAT, its role in developmental programming is unclear. Here, we show that brown adipocytes acquire thermogenic identity during embryogenesis independently of sympathetic innervation and β-adrenergic signaling. Genetic sympathectomy or disrupted β-adrenergic signaling had minimal effects on thermogenic gene expression or tissue morphology during either embryonic or postnatal BAT development in the absence of cold stress. Functional analyses revealed that the SNS is likely required for circulatory support of BAT activity during β-adrenergic stimulation but not for the development of the thermogenic capacity of BAT itself. These findings demonstrate that developmental and cold-responsive BAT remodeling are mechanistically distinct processes. Defining the molecular programs that drive BAT development may reveal new strategies to enhance BAT formation and function without relying on β-adrenergic stimulation.

Hypothalamic neurons expressing either POMC or AGRP sense nutritional state directly and indirectly and transmit these neuropeptide signals to other brain centres through the melanocortin 3 and 4 receptors. MC4R is primarily concerned with the control of appetite and energy expenditure while MC3R is more closely related to the control of linear growth and the timing of puberty. The role of MC3R in the long-term control of energy balance and body composition is less clear, particularly in humans. We have undertaken studies in humans, domestic dogs and mice with the goal of clarifying the relative impact of MC3R deficiency on energy balance, growth and sexual development. By studying three large consanguineously enriched cohorts, totalling approximately 300K people, we identified nine individuals who are homozygous for functionally null MC3R variants. The body mass index (BMI) of the homozygous MC3R variant carriers was not significantly different from that of age, sex and demographically matched controls, with six of the nine homozygotes having a BMI <30 kg/m².

We detected a canine MC3R missense variant (p.M320I) which is common in labrador retrievers and showed that this significantly impairs receptor signalling. Dogs homozygous for p.M320I were lighter and showed delayed pubertal development but were not significantly more obese than wild-type or heterozygous dogs. We also established that the lack of Mc3r delayed pubertal development in both male and female mice.

Finally, we studied growth and pubertal trajectories of individuals carrying rare loss-of-function MC3R variants and found that male carriers had delayed peak weight velocity and genital development but had no evidence for excess body fat compared to non-carriers.

Our results support MC3R having a conserved role across mammals in controlling growth and pubertal timing. While MC3R deficiency may influence linear growth and body composition, complete loss of MC3R does not result in a penetrant human obesity syndrome.

Background

C3 is highly expressed in human and rodent pancreatic islets, which secrete insulin to regulate blood glucose homeostasis. We have previously shown that cytosolic C3 protects pancreatic beta-cells from stress, by allowing cytoprotective autophagy, and that the same intracellular pool of C3 also protects beta-cells from cytokine-induced apoptosis.

Methods

We now generated a beta-cell specific C3 knockout mouse (beta-C3-KO) to test whether cell-intrinsic C3 is required for beta-cell function in a whole animal model. These mice were placed on high-fat diet (HFD), blood glucose and insulin measurements taken over time, and tissues examined at endpoint by qPCR and immunofluorescence.

Results

While no differences were found between in baseline metabolic performance when comparing floxed controls and beta-C3KO mice, significant differences were found when mice were put on high-fat diet (HFD). Beta-C3-KO mice gained more weight, exhibited higher fasting blood glucose and insulin levels, and showed signs of adipose tissue inflammation and insulin resistance. Consistent with previous results showing that C3 alleviates beta-cell stress, increased amounts of unprocessed pro-insulin were found in the circulation of HFD-fed beta-C3-KO mice, as well as in islets from these mice. Beta-C3-KO HFD mouse islets also had a higher proportion of insulin staining, and isolated islets released more insulin in vitro.

Conclusion

The interaction of increased insulin secretion and HFD leads to enhanced weight gain. Cell-intrinsic expression of C3 is important for optimal function of mouse pancreatic beta-cells under metabolic pressure in vivo.

Background

Tirzepatide, a single-molecule dual glucose-dependent insulinotropic polypeptide (GIP)/glucagon-like peptide-1 (GLP-1) receptor (R) agonist, has shown superiority in the reduction of blood glucose and body weight, above selective GLP-1R agonists, but the contribution of GIP to these effects remains incompletely understood.

Objectives

To characterize the preclinical and in-human effects of a long-acting GIPR agonist monotherapy in healthy participants and patients with type 2 diabetes (T2D).

Methods

A long-acting GIPR agonist (LY3537021) was characterized in vitro and in Long-Evans diet-induced obese rats and Wistar rats. Next, a phase 1, randomized, placebo-controlled, single ascending dose (SAD)/multiple ascending dose (MAD) study explored the safety, tolerability, pharmacokinetics, and pharmacodynamics of LY3537021 in healthy participants and participants with T2D in Singapore.

Results

In vitro, LY3537021 demonstrated potency greater than native GIP and selectivity for the GIPR. In vivo in rats, chronic treatment with LY3537021 resulted in weight loss and improved glycemic control during a glucose tolerance test. The phase 1 clinical study enrolled 85 healthy participants and patients with T2D (SAD, n = 47 [aged 25–64 years]; MAD, n = 38 [aged 25–69 years]; average baseline BMI was 25.9–27.0 kg/m² across the arms). During the MAD part, dose-dependent decreases in mean body weight were observed in all LY3537021 dose groups, regardless of T2D status, and persisted at 35 days after the last dose. For example, participants with T2D treated with 25 mg of LY3537021 lost a mean of 3.14 kg of body weight compared with 0.36 kg in the placebo group (p < 0.05) at day 57. Transient reductions in fasting glucose were observed in these participants, but the reductions were not sustained and not significantly different from placebo at day 29. The time to maximum observed drug concentrations varied across cohorts (8–96 h), and the half-life was estimated at approximately 12 days for non-T2D and T2D cohorts with the 25-mg dose, supporting once-weekly administration. There was no delay in gastric emptying following a single subcutaneous dose of 0.3–25 mg LY3537021. LY3537021 was well tolerated with infrequent gastrointestinal adverse events.

Conclusions

In vivo studies demonstrated that LY3537021 reduced body weight and improved glycemia during a glucose challenge in rats. The phase 1 study demonstrated that the long-acting GIPR agonist LY3537021 was well tolerated, induced weight loss, and improved glucose control in humans. These observations better define the therapeutic benefit of long-acting GIPR agonists and support a distinct contribution of GIP agonism to the benefits observed with multi-agonist peptides that act via the GIPR. Future studies are needed in more diverse populations and in cohorts with overweight/obesity to confirm these findings.

Diabetes is associated with compromised reproductive health; however, the cellular and molecular mechanisms underlying its impact on ovarian function remain largely unclear. In this study, we integrated single-cell RNA sequencing, DNA methylation profiling, and metabolomic analyses to comprehensively characterize the ovarian cellular landscape, epigenetic alterations, and metabolic reprogramming in diabetic female mice, with a focus on identifying diabetes-induced changes in ovarian cells. Our cell type-specific transcriptomic analysis revealed that dysregulated steroid hormone biosynthesis and impaired fatty acid metabolism are prominent features of diabetic ovarian dysfunction. Notably, key genes including Cyp11a1, Fshr, and Lhcgr exhibited reduced expression accompanied by increased DNA methylation levels in their gene regions within granulosa cells under diabetic conditions. Furthermore, disrupted granulosa cell differentiation was evident, leading to aberrant luteal cell formation and compromised luteal function. In parallel, metabolomic profiling revealed profound metabolic reprogramming in diabetic ovaries, with significant alterations in lipid metabolism pathways, including elevated unsaturated fatty acid and reduced glycerophospholipid metabolism. Taken together, these findings provide novel insights into the molecular pathways underlying ovarian dysfunction in the context of diabetes, thereby enhancing our understanding of folliculogenesis in metabolic disorders.

Internalisation of G protein-coupled receptors (GPCRs) can contribute to altered cellular responses by directing signalling from non-canonical locations, such as endosomes. If signalling processes are locally constrained, active receptors in different subcellular locations could produce different downstream effects. This phenomenon may be relevant to the optimal targeting of the glucagon-like peptide-1 receptor (GLP-1R), a type 2 diabetes and obesity target GPCR for which several ligands with varying internalisation tendency have been discovered. To investigate, we compared the signalling localisation effects of two prototypical GLP-1RAs with opposite signal bias and effects on GLP-1R trafficking: exendin-asp3 (ExD3), a full agonist that drives rapid internalisation, and exendin-phe1 (ExF1), which shows much slower internalisation. After using bioorthogonal labelling and fluorescent agonist conjugates to verify the divergent trafficking patterns of ExF1 and ExD3 in β-cell lines and primary pancreatic islets, we used live cell biosensors to monitor signalling at different subcellular locations. This revealed that cAMP/PKA/ERK signalling in β-cells is in fact distributed widely across the cell over short- (<5 min) and medium-term (up to 60 min) stimulation at pharmacological (>10 pM) concentrations, with no major differences in signal localisation that could be linked to internalised versus cell surface-bound GLP-1R. Moreover, washout experiments highlighted that, whilst fast-internalising ExD3 shows much greater accumulation and binding to GLP-1R in endosomes than slow-internalising ExF1, it is a rather inefficient driver of both cAMP production in β-cells and insulin secretion from perfused rat pancreata. These data provide a greater understanding of the cellular effects of biased GLP-1R agonism.

High-protein (HP) diets are widely adopted in Western societies for body-weight management; yet, they exacerbate senescence-associated metabolic deterioration, posing an unresolved pathophysiological conundrum. Here, we demonstrate that long-term HP intake mediates adipocyte-specific NAD⁺ depletion and mitochondrial dysfunction in white adipose tissue (WAT). Single-nucleus transcriptomic analyses revealed adipocyte-restricted senescence signatures in HP-fed mice. Mechanistically, HP intake triggers macrophage-specific upregulation of CD38 (a key NAD⁺ hydrolase), which depletes adipocyte NAD⁺ pools and thereby accelerates cellular senescence. Restoration of NAD⁺ levels, either via supplementation with NAD⁺ precursor or pharmacological inhibition of CD38 activity, alleviated the senescence-associated metabolic sequelae induced by HP diets. Our findings establish macrophage-adipocyte NAD⁺ crosstalk as a central axis linking dietary protein excess to WAT aging, providing actionable targets for the prevention and treatment of age-related metabolic disorders.

Background

Glucagon-like peptide-2 (GLP-2) reduces systemic and gut inflammation while preserving mucosal integrity. Preclinical and clinical reports implicate GLP-2 receptor (GLP-2R) agonism as a potential therapy for graft vs. host disease (GvHD).

Methods

Here we assessed whether enhanced vs. loss of GLP-2R signaling modifies gut injury and inflammation in experimental murine acute GvHD (aGvHD). Allogeneic hematopoietic cell transplantation (HCT) was performed using bone marrow and splenocytes from BALB/cJ donor mice to induce aGvHD in C57BL/6J recipients. Chimerism was determined by flow cytometry of immune cell compartments. Inflammation was assessed by measuring circulating cytokines and histological scoring of gut mucosal damage. GLP-2 responsivity was assessed using histology and gene expression analyses. The gut microbiome was assessed by 16S rRNA sequencing.

Results

Allogeneic chimerism was >90% in peripheral blood and in the gut epithelial compartment. Gut GLP-2R signaling was preserved following allogeneic bone marrow transplantation. Surprisingly, GLP-2R agonism using teduglutide did not reduce circulating cytokines, gut injury, immune cell infiltration or the severity of aGvHD. In contrast, transplant recipient Glp2r^−/− mice exhibited reduced survival, associated with increased bacteremia. Shifts in microbial species abundance with gain or loss of GLP-2R signaling were not correlated with aGvHD clinical outcomes.

Conclusions

Activation of GLP-2R signaling did not reduce the severity of experimental aGvHD, failing to replicate a previous study using an identical aGvHD protocol. Nevertheless, loss of GLP-2R signaling in transplant recipients decreased survival and increased bacteremia, implicating an essential role for endogenous GLP-2R signaling in maintaining barrier function in the context of immune-mediated gut epithelial injury.

Males and females have different physiological and reproductive demands and consequently exhibit widespread differences in metabolism and behavior. One of the most consistent differences across animals is that females store more body fat than males, a metabolic trait conserved from flies to humans. Given the central role of gut hormones in energy balance, we asked whether gut endocrine signaling underlies these sex differences. We therefore performed a multidimensional screen of enteroendocrine cell (EEC)-derived signaling across a broad panel of metabolic and behavioral traits in male and female Drosophila. Here, we uncover extensive sex-biased roles for EEC-derived signals – many of which are conserved in mammals – in energy storage, stress resistance, feeding, and sleep. We find that EEC-derived amidated peptide hormones sustain female-typical states, including elevated fat reserves, enhanced stress resilience, and protein-biased food choice. In contrast, the non-amidated peptide Allatostatin C (AstC) promotes male-like traits by stimulating energy mobilization, thereby antagonizing amidated-peptide function. Female guts contain more AstC-positive EECs. Disruption of peptide amidation by eliminating peptidylglycine α-hydroxylating monooxygenase – the enzyme required for maturation of most gut peptide hormones – abolished female-typical physiology and behavior, shifting females toward a male-like state. Among individual amidated peptides, Diuretic hormone 31 (Dh31) and Neuropeptide F (NPF) emerged as key mediators of female physiology. These findings establish gut hormone signaling as a determinant of sex-specific metabolic and behavioral states.

Obesity remains a major global health challenge, yet the brain-wide effects of hormones regulating appetite remain incompletely understood. Amylin, co-secreted with insulin by pancreatic β-cells, promotes satiation and is a promising therapeutic target for metabolic disorders. While its receptor distribution is well-characterized, its influence on large-scale neural dynamics is unknown. Here, resting-state fMRI was used to map time-resolved connectivity changes following peripheral amylin administration in wild-type (WT) and receptor activity-modifying protein 1/3 knockout (RAMP1/3 KO) mice. In WT animals, amylin triggered rapid and transient network reconfigurations, engaging canonical satiation hubs such as the area postrema and parabrachial nucleus, and extending to sensory-integrative areas including the inferior colliculus and insular cortex. Early hindbrain responses propagated to hypothalamic, thalamic, and mesolimbic circuits implicated in appetite and reward. These effects, along with amylin-driven modulation of large-scale networks and low-frequency oscillations, were absent in KO mice. The findings position amylin as a potent modulator of distributed brain circuits, offering a framework for targeted obesity treatments.

Objectives

Despite transformative advances in obesity pharmacotherapy, safely increasing energy expenditure remains a key unmet need. Exploiting thermogenic adipocytes represents a promising target given their capacity for significant catabolic activity. We previously showed that G protein-coupled receptor 3 (GPR3) can drive energy expenditure in brown and white mouse and human adipocytes. GPR3 is a unique GPCR because it displays high intrinsic activity and leads to constitutive cAMP signaling upon reaching the cell surface. Therefore, the transcriptional induction of GPR3 is analogous to ligand-binding activation of most GPCRs. Gpr3 expression is physiologically induced in thermogenic adipocytes by cold exposure, and mimicking this event through overexpression in mice is fully sufficient to increase energy expenditure and counteract metabolic disease. Yet the factors mediating physiological Gpr3 expression remain unknown.

Methods

Here, we apply ATAC-Seq to identify cold-induced promoter elements of Gpr3. We uncover a role for the estrogen-related receptors, ERRα and ERRγ, in the physiological transcriptional control of Gpr3 using adipose-specific double knock-out mice with and without adeno-associated virus (AAV)-mediated rescue.

Results

We show that ERRα directly binds the cold-induced promoter element of Gpr3 and that ERRα, ERRβ, and ERRγ each activate the Gpr3 promoter in vitro when co-transfected with PGC-1α. Adipocyte ERRα and ERRγ are required for the in vivo transcriptional induction of Gpr3 during cold exposure. Importantly, deficient Gpr3 cold-inducibility in adipose-specific ERRα and ERRγ KO mice is fully rescued by delivery of AAVs re-expressing either ERRα or ERRγ directly into brown adipose tissue.

Conclusions

ERRα and ERRγ are critical regulators of cold-induced transcription of Gpr3 and represent a targetable strategy for pharmacologically unlocking GPR3-induced energy expenditure.

Dietary glucose is a preferred source of energy, but it remains unknown how the mammalian brain rapidly detects and discriminates this sugar from other sweeteners, and whether this depends on nutritional environment and metabolic need. Our results show that signals generated by metabolism-dependent and -independent actions of oral glucose can each be recruited to guide nutrient choice. Further, glucose (or its non-metabolizable analog) evokes a discernible pattern of neural activity from calorie-matched fructose in the central gustatory system, and this is conditioned by diet. Although the brain responses and corresponding consummatory behaviors do not require sweet taste receptor input, the results indicate that the sweet receptor is important for integrating nutritional states with metabolic pathways in the taste system and ultimately guiding intake towards glucose-yielding substrates.

Objective

Adipocyte differentiation is critical for the metabolically protective expansion of adipose tissue. Impaired differentiation drives lipodystrophy and pathologic tissue remodeling, major contributors to cardiometabolic diseases. The differentiation process is governed by master transcription factors, including the pioneer factor C/EBPβ, which initiates the adipogenic program. Here, we sought to identify novel C/EBPβ-associated factors that regulate human adipocyte differentiation.

Methods

We used chromatin immunoprecipitation followed by selective isolation of chromatin-associated proteins (ChIP-SICAP) to identify proteins that interact with C/EBPβ on chromatin during human adipocyte differentiation. Candidate factors were assessed for their effects on differentiation, through conducting a CRISPR/Cas9-based knockout screen in human adipocyte precursor cells (hAPCs). The transcription factor CUX1 emerged as a top candidate. We performed gain- and loss-of-function studies in primary human and mouse adipocyte differentiation models, coupled with RNA-seq and ChIP-seq, to define CUX1-regulated genes and pathways. In vivo relevance was tested using adipocyte precursor–selective Cux1 knockout and lineage reporter mice.

Results

Loss of CUX1 impaired, whereas its overexpression enhanced, adipocyte differentiation in hAPCs. RNA-seq and ChIP-seq analyses revealed that CUX1 promotes the expression of key adipogenic genes, including PPARG in hAPCs. By contrast, CUX1 exerted the opposite effect in mouse adipocyte differentiation. Cux1 deletion enhanced, while CUX1 overexpression suppressed, differentiation in mouse APCs (mAPCs). CUX1 exhibited distinct chromatin-binding patterns and motif enrichment profiles in mouse versus human cells. In vivo, Cux1 deletion in APCs of mice increased de novo adipocyte formation during early stages of obesity development.

Conclusions

The transcription factor CUX1 regulates adipocyte differentiation in opposite directions in humans and mice, emphasizing the need for species-specific models in metabolic disease research,

Pancreatitis is a common cause of hospitalization that necessitates attentive clinical management. Affected individuals are at risk for pancreatic cancer due to aberrant signaling and empowered cell plasticity. Yet, molecular and cellular dynamics that govern epithelial cell behavior in response to inflammation remain largely elusive.

Here we found that inflammation induces Endoplasmic Reticulum-Associated Degradation protein (ERAD)-mediated downregulation of Niemann-Pick type C protein 1 (NPC1), which leads to the sequestration of free cholesterol within acinar cells’ lysosomes. Reducing intra-pancreatic cholesterol levels through genetic ablation of Acly ameliorates cerulein-induced pancreatitis, while pharmacological targeting of NPC1 exacerbates tissue damage.

Mechanistically, the accumulation of lysosomal cholesterol is sensed by the mechanistic Target of Rapamycin Complex 1 (mTORC1) that promotes metaplasia of pancreatic acinar cells, an event commonly associated to pancreatitis and tissue regeneration. Indeed, cholesterol supplementation or NPC1 inhibition facilitate acinar-to-ductal metaplasia (ADM) both ex vivo and in vivo, in an mTORC1-dependent manner.

These results identify a metabolic/signaling axis driving the reprogramming of pancreatic epithelial cells in response to inflammation. This hinges on a nutrient sensing paradigm, previously documented exclusively in pathological conditions.