Type 2 Diabetes (T2D) is a complex disease that has increased in prevalence in the last years affecting over 530 million people around the world. T2D increases mortality and morbidity by different mechanisms. As a complex disease, it is caused by many genetic changes and, consequently, T2D genetics has been analyzed from different points of view and using different strategies. Most studies have focused on inherited Single Nucleotide Variants (SNVs) present in genomic DNA, while other types of genetic variants have received less attention.

The aim of the present review is to examine the limitations of the studies conducted to date, and the importance of non-SNVs and non-germinal variants in the genetics of this disease. In this way, structural variants, mobile elements and tandem repeats have a crucial role in T2D. In addition, variations in mitochondrial DNA and somatic variations have been shown to play an important role in metabolic alterations that may lead to the development of T2D.

Time-restricted feeding (TRF) is proposed as a relevant strategy to counteract obesity and metabolic disorders; however, the therapeutic efficacy of more pragmatic intermittent TRF (iTRF) regimens remains undefined. Herein, daily and intermittent TRF significantly improved whole-body physiology, promoted key hallmarks of energy restriction, and induced coordinated transcriptional and lipidomic remodeling in male mice with chronic metabolic dysfunction previously established by prolonged high-fat, high-cholesterol, high-fructose feeding. These effects were summarized using three composite scores capturing physiological/metabolic, energy restriction, and lipidic responses, which consistently separated daily and intermittent TRF regimens from ad libitum-fed mice. Lipidomic profiling identified a subset of hepatic lipids associated with systemic health, pointing to lipid remodeling, particularly at the endoplasmic reticulum, as a potential feature of the TRF response. Notably, TRF failed to histologically improve hepatic steatosis, ballooning, or inflammation, and its overall benefits were clearly inferior to dietary normalization to standard chow diet. Altogether, these data (i) demonstrate that intermittent TRF recapitulates the beneficial effects in advanced metabolic disease, (ii) provides translational support for flexible TRF strategies, and (iii) highlights the need to integrate TRF with additional therapeutic strategies.

Mitochondrial calcium signaling, particularly its glucagon-mediated oscillatory dynamics, plays a pivotal role in regulating hepatic metabolism and is known to be disrupted in steatotic liver disease. We recently identified the mitochondrial Na⁺/Ca²⁺exchanger NCLX as a key mediator of glucagon-induced mitochondrial calcium oscillations, essential for proper gluconeogenic function. Here, using hepatocyte-specific NCLX knockout (cKO) mice, we demonstrate that NCLX is critical for intrahepatic lipolysis and fatty acid oxidation (FAO); its loss impairs glucagon-stimulated lipid droplet catabolism and blunts FAO. Mechanistically, we find that NCLX deficiency disrupts allosteric activation of lipolytic enzymes and increases CPT1 sensitivity to malonyl-CoA-mediated inhibition, resulting in defective lipolysis and FAO. We further show that glucagon regulates hepatic NCLX via cAMP/PKA-dependent phosphorylation at NCLX Ser258. Notably, PDE2A acts as a negative regulator of this pathway by degrading mitochondrial cAMP. Hepatic mitochondrial PDE2A abundance and cAMP-degrading activity are elevated in HFD, and in vivo BAY 60-7550 treatment suppresses mitochondrial cAMP degradation and augments PKA signaling in steatotic livers. Pharmacologic inhibition of PDE2A with BAY 60-7550 enhances NCLX phosphorylation, restores mitochondrial calcium efflux and oscillations, and stimulates FAO in an NCLX-dependent manner. Importantly, we uncover that cAMP/PKA-dependent phosphorylation of NCLX at Ser258 is suppressed in human steatotic livers, and that pharmacologic inhibition of PDE2A ameliorates hepatic FAO and steatosis in both dietary and genetic MASLD models. Collectively, our findings establish the glucagon–PDE2A–PKA–NCLX signaling axis as a key metabolic rheostat integrating mitochondrial calcium dynamics with lipid homeostasis, providing a promising therapeutic target for MASLD.

Background

Diabetic cardiomyopathy (DCM) is a prevalent and severe cardiovascular complication of diabetes mellitus, characterized by progressive cardiac dysfunction and pathological remodeling driven by myocardial metabolic disturbances. However, the underlying molecular mechanisms remain incompletely elucidated.

Methods

A type 2 DCM mouse model was established by feeding C57BL/6 mice a high-fat diet combined with streptozotocin injections. Cardiomyocyte-specific TRIM47 knockdown was achieved via AAV9-mediated delivery of a cardiomyocyte-specific cTnT promoter-driven shRNA. In vitro, primary neonatal mouse ventricular cardiomyocytes (NMCMs) were treated with palmitic acid (PA) to model cardiomyocyte injury.

Results

TRIM47 was significantly upregulated in diabetic hearts. Cardiomyocyte-specific TRIM47 knockdown improved left ventricular ejection fraction and fractional shortening, attenuated chamber dilation, and reduced heart weight-to-tibia length ratio. TRIM47 silencing attenuated cardiomyocyte hypertrophy, interstitial fibrosis, and cardiomyocyte apoptosis, alongside reduced myocardial inflammatory cytokine levels (TNF-α, IL-6, IL-1β). Furthermore, TRIM47 knockdown alleviated myocardial lipid accumulation and reduced triglyceride levels, accompanied by downregulation of the fatty acid translocase CD36. In vitro, PA-treated NMCMs exhibited elevated TRIM47 expression, and its knockdown mitigated PA-induced cardiomyocyte injury, inflammation, apoptosis, and lipid deposition. Mechanistically, the m6A reader YTHDF3 was upregulated under PA conditions and directly bound to m6A-modified TRIM47 mRNA, enhancing its stability. Rescue experiments demonstrated that YTHDF3 overexpression exacerbated PA-induced cardiomyocyte injury, whereas concurrent TRIM47 knockdown largely reversed these deleterious effects.

Conclusions

Our results revealed that TRIM47 may contribute to the progression of DCM by promoting abnormal cardiac lipid metabolism, exacerbating inflammation and apoptosis, and these effects are partially mediated through the upstream m6A reader YTHDF3.

Background

Semaglutide (SEMA), a glucagon-like peptide-1 (GLP-1) analogue approved for treatment of obesity, is now one of the most used anti-obesity pharmacotherapeutic agents worldwide. The effects of SEMA on body weight, appetite, and adiposity are well established. Moreover, sex differences in these effects are clearly emerging. Metabolism and reproduction are intimately intertwined; yet, whether and how these blockbuster drugs affect the reproductive system of males and females is poorly understood. To address this gap, we investigated the impact of chronic SEMA treatment on gonads and circulating reproductive hormones in diet-induced obese male and female rats.

Methods and Results

GLP-1 receptor is expressed in ovaries and testes, potentially allowing a direct effect of SEMA. Testicular expression of this receptor was 4.7-fold higher than in ovaries, supporting a potential male bias for potency of the drug effect. To disambiguate the direct effect of the drug from potential downstream effects of weight loss, and ensuing improvements in metabolism produced by the drug, we also evaluated pair-fed (PF) controls. After 4 weeks of treatment, PF and SEMA males displayed improvements in reproductive measures like sperm motility and mucus penetration parameters. Morphological analysis of male and female gonads largely suggested increased fertility. In males, changes in germinal epithelium and seminiferous tubules were detected. In females, increased folliculogenesis was identified in both SEMA and PF rats. Structural changes in the gonads were accompanied by changes in circulating gonadal hormones in a sex-specific manner. In males, SEMA attenuated the weight-loss-induced reduction in all androgens measured. In females, levels of progesterone, pregnenolone, and estradiol were reduced in a treatment specific manner. Pituitary hormones were also affected in both sexes.

Conclusions

Altogether, this study highlights broad SEMA-specific, as well as weight loss induced but rescued by SEMA, effects at transcriptional, functional, and systemic levels on the reproductive systems of males and females.

Loss-of-function variants of GPR75 are associated with protection against obesity in humans; however, the mechanisms through which GPR75 regulates whole-body energy homeostasis remain incompletely understood. Here, we generated Gpr75 global knockout (GKO) mice and performed comprehensive metabolic phenotyping under chow and high-fat diet (HFD) conditions. Despite high expression of GPR75 in the brain, male GKO mice exhibited unchanged food intake during the period when body weights began to diverge. Instead, GPR75 deficiency resulted in reduced whole-body energy expenditure and an elevated respiratory exchange ratio, indicating decreased fat utilization. Notably, male, but not female, GKO mice displayed markedly impaired intestinal lipid absorption, reduced chylomicron output, and increased fecal lipid excretion, consistent with limited dietary lipid assimilation under HFD feeding.

To define the tissue-specific contributions of GPR75, we next examined hepatocyte-, intestinal epithelial-, endothelial/hematopoietic-, and AgRP neuron-specific Gpr75 knockout mice. Deletion of Gpr75 in hepatocytes (Alb-Cre), intestinal epithelium (Vil-Cre), or endothelial/hematopoietic lineages (Tie2-Cre) did not reproduce the pronounced protection against HFD-induced weight gain observed in GKO mice. In contrast, AgRP neuron-specific deletion reduced body weight by approximately 10%–12% in male and female mice and decreased white adipose depot mass by 27%–50%, establishing AgRP neurons as a specific neuronal population through which GPR75 contributes to body-weight regulation. However, the magnitude of this phenotype remained substantially smaller than that observed in global GPR75-deicient mice.

Together, our findings demonstrate that GPR75 regulates diet-induced obesity through both central and peripheral mechanisms. AgRP-neuronal GPR75 contributes to body-weight regulation in both sexes, whereas global GPR75 deficiency additionally impairs intestinal lipid assimilation in males through a mechanism not recapitulated by deletion in the tested peripheral cell populations. These complementary effects likely contribute to the pronounced resistance to diet-induced obesity and hepatic steatosis observed in global GPR75-deficient mice and further support GPR75 as a therapeutic target for obesity and associated metabolic liver disease.

Background

Contracting skeletal muscle releases interleukin-6 (IL-6) which is primarily cleared by the liver. The tissue-specific regulation of IL-6 and soluble IL-6 receptor (sIL-6R) kinetics remains, however, poorly understood. To characterize tissue-specific IL-6 and sIL-6R exchange during exercise, we combined simultaneous arteriovenous measurements across the contracting leg, splanchnic region, and the brain with, or without, pharmacological IL-6 receptor (IL-6R) blockade.

Methods

Thirty young, well-trained men were randomized in a double-blind, placebo-controlled design to receive either tocilizumab (IL-6R blockade) or placebo before performing moderate-intensity cycling exercise. Net tissue flux of IL-6 and sIL-6R was determined from arteriovenous concentration differences across the femoral, hepatic, and internal jugular circulation.

Results

During exercise, leg IL-6 release increased with both placebo and IL-6R blockade but was significantly augmented by IL-6R blockade, suggesting a potential role for autocrine regulation of local IL-6 release. Under control conditions, the splanchnic bed was the predominant site of IL-6 clearance; however, IL-6R blockade shifted splanchnic IL-6 net balance from uptake to release. In addition, the exercising leg was identified as the source of circulating sIL-6R during exercise, whereas no consistent sIL-6R exchange occurred across the splanchnic bed or brain.

Conclusions

These findings suggest a potential role for IL-6 signaling in the autocrine regulation of IL-6 release from the contracting leg during exercise. Furthermore, exercise increases leg-derived sIL-6R, thereby contributing to increased circulating sIL-6R concentrations, while receptor-mediated splanchnic clearance appears to be a major determinant of systemic IL-6 availability during exercise in humans.

Clinical trial registration number

Clinicaltrials.gov (NCT06334653).

Objectives

The pregnane X receptor (Pxr; Nr1i2) plays a role in metabolic regulation. However, its contribution to systemic energy homeostasis under physiological conditions remains unclear. Here, we investigated the metabolic consequences of Nr1i2 deficiency in chow-fed mice.

Methods

Phenotyping was performed in adult whole-body Nr1i2 knockout (Nr1i2^−/−) chow-fed mice and their wild-type littermates. Body composition, metabolic parameters, skeletal muscle mass and myofiber size were assessed. Ileal gene expression, circulating Fgf15 levels, and bile acid composition were analyzed. Intestinal-specific Nr1i2^−/− mice were generated to evaluate the contribution of intestinal Pxr signaling. Mechanistic studies were conducted in HT29 cells and mouse ileal organoids.

Results

Chow-fed Nr1i2^−/− mice displayed a lean phenotype with reduced adiposity, improved insulin sensitivity, and increased skeletal muscle mass and myofiber size compared with wild-type mice. This phenotype was associated with strong induction of ileal Fgf15 gene expression and elevated circulating Fgf15 levels. Intestinal-specific Nr1i2 deletion did not reproduce the metabolic or muscular phenotype, indicating that intestinal Pxr loss alone is insufficient. Nr1i2 deficiency was associated with remodeling of the hepatic bile acid pathway and enrichment of specific taurine-conjugated and 6α-hydroxylated bile acids in the ileum. In vitro, these bile acids enhanced FGF19 expression through FXR-related canonical and non-canonical mechanisms, supporting a mechanistic link between bile acid remodeling and increased Fgf15/19 signaling.

Conclusions

These findings provide the first evidence that, under standard dietary conditions, loss of Pxr induces a lean phenotype, promotes reduced adiposity together with remodeling of bile acid pool, increased Fgf15 production and enhanced skeletal muscle mass.

Background

β-klotho (KLB), the obligate co-receptor for fibroblast growth factor (FGF) 19 and 21 signalling, has emerged as a therapeutic target for metabolic disease. Current understanding of KLB function is based largely on germline knockout mouse models, where developmental abnormalities obscure its function in adult physiology. Here, we used somatic hepatocyte-specific gene editing in adult mice to define hepatic KLB function.

Methods

Hepatocyte-specific KLB deficiency was induced by retro-orbital delivery of adeno-associated virus particles containing guide RNAs targeting Klb in adult male mice expressing Cas9 in the liver. Following transduction, mice were maintained on a 4-week chow diet or a 12-week high-fat diet, prior to comprehensive metabolic and biochemical phenotyping.

Results

Adult-onset hepatic KLB deficiency did not alter body weight or composition, indicating that reduced bodyweight in germline models reflects developmental effects. In line with previous studies, KLB deficiency resulted in derepressed bile acid synthesis, elevated faecal bile acid excretion, and a shift towards a more hydrophobic bile acid pool. Importantly, we also uncovered a role for hepatic KLB in regulating lipid homeostasis. Chow-fed KLB-deficient mice exhibited reduced circulating very-low-density lipoprotein levels (VLDL) with marked hepatic triglyceride accumulation, suggesting altered VLDL metabolism as a potential mechanism driving steatosis.

Conclusions

Using an adult-onset liver-specific knockout model, we disentangled KLB function from developmental confounders and established KLB as a critical regulator of adult lipid and lipoprotein homeostasis. Our study redefines the physiological role of KLB in hepatic metabolism and has important implications for the interpretation of FGF19/KLB-directed therapies for metabolic diseases.

The molecular circadian clock coordinates cellular and systemic metabolism across the day, yet how it integrates with energy-sensing pathways in human skeletal muscle remains incompletely understood. AMP-activated protein kinase (AMPK) functions as a cellular energy sensor and has been implicated in circadian regulation; however, its role in coupling clock components to metabolic programming in human muscle has not been established.

Here, we investigated the interaction between AMPK signaling and the circadian machinery in primary human myotubes, focusing on the downstream clock components NPAS2 and DBP. Silencing of the AMPKα subunit altered core clock gene expression, increasing CRY1 and CRY2 while reducing NPAS2 and DBP expression, with rhythmicity preserved. To determine the functional relevance of these changes, we examined metabolic phenotypes following siRNA-mediated silencing of NPAS2. NPAS2 knockdown reduced basal oxidative metabolism, decreased abundance of electron transport chain subunits, and increased β-oxidation flux, while maximal mitochondrial respiratory capacity remained intact. These alterations occurred independently of canonical AMPK–ACC signaling but were associated with reduced HIF1A expression. In contrast, DBP silencing reduced glucose oxidation but did not recapitulate the broader metabolic remodeling observed with NPAS2 knockdown.

Together, these findings identify NPAS2 as a downstream mediator linking AMPK-dependent circadian signaling to skeletal muscle metabolic regulation. Disruption of this axis alters substrate utilization and impairs mitochondrial function, revealing a mechanism by which circadian clock components contribute to metabolic regulation in human skeletal muscle.

Chronic inflammation in white adipose tissue (WAT) contributes to obesity-associated insulin resistance. Plasmalogens, ether phospholipids synthesized in peroxisomes, have been implicated in immune regulation. GNPAT (glyceronephosphate O-acyltransferase) is a peroxisomal enzyme that catalyzes the first and rate-limiting step of plasmalogen biosynthesis. Here, we show that dietary supplementation with alkyl glycerol (AG), a plasmalogen precursor, improves insulin sensitivity and reduces adipose inflammation in high-fat diet (HFD)-fed mice, independent of changes in body weight or invariant natural killer T cell activation. AG treatment reduced M1-like macrophage infiltration and proinflammatory gene expression in WAT without altering M2 macrophage polarization. Furthermore, AG supplementation restored levels of docosahexaenoic acid-enriched plasmalogen species that were reduced by HFD. In contrast, Gnpat⁺/⁻ mice displayed impaired plasmalogen biosynthesis, elevated M1 polarization, and exacerbated insulin resistance upon HFD feeding. Mechanistically, GNPAT overexpression in macrophages inhibited protein kinase C delta (PKCδ) activation and downstream signal transducer and activator of transcription 1 (STAT1) signaling, attenuating lipopolysaccharide-induced inflammation. In vivo studies showed that AG supplementation reduced diacylglycerol accumulation, suggesting that altered lipid flux contributes to the modulation of PKCδ signaling observed in macrophages. Of translational relevance, GNPAT expression was decreased in the visceral adipose tissue of humans with type 2 diabetes. These findings establish GNPAT-driven plasmalogen biosynthesis as a key modulator of adipose immune homeostasis via suppression of PKCδ–STAT1 signaling. Thus, enhancing plasmalogen levels may have therapeutic potential for obesity-related metabolic disorders.