The endocannabinoid (EC) system is a complex network comprising endogenous ligands, enzymes responsible for their synthesis and degradation, and various receptors (including CB1 and CB2). Present in many peripheral tissues, including skeletal muscle, EC system is now recognized to influence key physiological processes such as insulin sensitivity, mitochondrial metabolism, protein homeostasis and muscle development. Alterations in this system are associated with a variety of pathologies, including obesity, type 2 diabetes, sarcopenia, cachexia and muscle dystrophies. In this context, cannabidiol (CBD), a phytocannabinoid devoid of psychoactive properties, is attracting growing interest as a potential therapeutic agent. This article provides an analysis of the mechanisms by which the EC system, and more specifically the CB1 receptor, influences skeletal muscle development and function, while exploring emerging data on the potential benefits of CBD in various pathological conditions affecting skeletal muscle.

Graphical abstract

ECS composition and regulation: The endocannabinoid system (ECS) is composed of endogenous ligands (AEA, 2-AG), enzymes for their synthesis or degradation, and receptors (e.g., CB1, CB2). It also includes exogenous molecules like cannabidiol (CBD) produced from Cannabis sativa. Widely expressed in peripheral tissues such, the ECS plays a central role in the regulation of key skeletal muscle physiological processes, including insulin sensitivity, mitochondrial metabolism, protein homeostasis and skeletal muscle development. Dysregulation of this system is associated with the development of metabolic and muscular disorders, such as obesity, type 2 diabetes, sarcopenia, cachexia and muscular dystrophies. In this context, CBD, a non-psychoactive phytocannabinoid, has emerged as a potential therapeutic agent capable of modulating ECS activity, thereby contributing to the restoration of skeletal muscle function and homeostasis. ECS: endocannabinoid system, AEA: anandamine, 2-AG: 2-arachidonoyl glycerol, CB1/2: cannabinoid receptor type 1/2, CBD: cannabidiol.

Glycosylation encompasses a broad spectrum of post-translational modifications (PTMs) that shape protein stability, spatial organization, and function. Traditionally, it is classified into two major categories: complex glycosylation within the secretory pathway — including N-glycosylation, mucin-type O-glycosylation, glycosaminoglycans (GAGs), and glycolipids — which generate structurally stable and long-lived modifications; and O-GlcNAcylation, a highly dynamic modification of nucleocytoplasmic and mitochondrial proteins that rapidly responds to metabolic and environmental cues. While this dichotomous framework has guided our understanding of glycan biology, emerging evidence now reveals that glycosylations are functionally interconnected through shared metabolic substrates, and regulatory circuits.

Here, we revisit this classical classification and integrate it into a modern, systems-level view of glycosylation. We highlight the nucleotide sugar UDP-N-acetylglucosamine (UDP-GlcNAc) as a metabolic node reflecting cellular nutrient status and fuelling both complex glycan synthesis and O-GlcNAcylation. UDP-GlcNAc pool fluctuations drive coordinated remodeling across glycosylation pathways, and dysregulation of this hub is associated with diverse human diseases. We discuss how O-GlcNAcylation functions as a supplementary regulatory PTM, modulating glycosylation-related enzymes and proteins through both direct effects on their interactions, stability, localisation and activity, and via broader transcriptional and epigenetic programs, thereby dynamically controlling otherwise stable glycosylation processes. Examples from metabolic, cardiovascular, neurological diseases, cancer and congenital disorders of glycosylation (CDGs) illustrate how perturbations in one glycosylation pathway propagate through the glycosylation network, reshaping cellular identity and disease trajectories. We support a paradigm in which glycosylation operates as an integrated regulatory framework linking metabolism, signaling, and extracellular architecture, providing new perspectives for disease stratification and therapeutic intervention.

Background/Objective

Glycogen storage disease type I (GSD I) is an autosomal recessive inborn error of carbohydrate metabolism. Patients with GSD type Ia and Ib exhibit overlapping and distinct symptoms and complications. Notably, GSD Ia patients show more severe hypertriglyceridemia and higher risk of hepatic tumors than GSD Ib patients.

Methods

Given the liver's pivotal role in these processes, this study utilized hepatocyte-specific CRISPR/Cas9-mediated somatic gene editing to explore the pathophysiological and biochemical adaptations in hepatic GSD Ia and Ib side-by-side. Additionally, hepatic histology, transcriptomics, and proteomics analysis was performed.

Results

Compared to controls, hepatic GSD Ia and Ib mice showed hepatomegaly, fasting hypoglycemia, hyperlactatemia, and increased uric acid in plasma, which was somewhat more pronounced in GSD Ia than Ib. Both GSD I subtypes showed similar reductions in hepatic acetyl-CoA precursor pool enrichment and increases in de novo biosynthesis of hepatic stearate and oleate. Interestingly, only GSD Ia mice showed mildly elevated plasma triglyceride and hepatic phosphate sugars. Metabolic changes were reflected at the transcriptomic and proteomic levels, with largely similar responses between GSD Ia and Ib livers. Moreover, altered mRNAs and protein levels related to nucleotide-binding oligomerization domain (NOD) signaling pathways, infection and inflammation, liver disease, and chemical carcinogenesis were somewhat more pronounced in hepatic GSD Ia than in GSD Ib mice.

Conclusions

Overall, the metabolic disturbance was more severe in hepatocyte-specific GSD Ia than in GSD Ib mice, consistent with the clinical phenotype in patients. The metabolic disorders and specific metabolites, genes, and proteins identified in this study provided new insights into the pathophysiological and biochemical phenotypes of GSD I subtypes in the liver.

Metabolic liver disease arises due to dysregulated signaling between hepatocytes and non-parenchymal cells (NPCs). Through parallel RNA sequencing screens in diet-induced and genetic mouse models, backdropped by human transcriptomic data, we identified latent TGFβ binding protein-3 (LTBP3) – a regulator of TGFβ secretion – as a novel contributor to metabolic liver disease pathogenesis. GalNAc-conjugated Ltbp3 ASO reduced hepatic triglyceride accumulation in diet-induced metabolic liver disease mouse models, which was phenocopied in mice lacking hepatocyte TGFβ activity, but surprisingly not in hepatocyte-specific Ltbp3 knockout mice. This discordance prompted evaluation as to whether GalNAc-based tools are hepatocyte-specific. In fact, we found that GalNAc-Ltbp3 ASO also targeted multiple NPC populations, reducing intrahepatic TGFβ activity, culminating to lowered lipid content by increased proteasomal degradation of the key lipogenic enzyme Acetyl-CoA-Carboxylase 1 (ACC1) in hepatocytes. These data reveal a previously unrecognized NPC-hepatocyte axis to regulate lipogenesis in metabolic liver disease.

Background

Adiponectin is a key regulator of glucose and lipid metabolism that improves insulin sensitivity and promotes mitochondrial fatty acid oxidation via ADIPOR1 and ADIPOR2. Ovarian lipid accumulation contributes to metabolic reproductive disorders such as polycystic ovary syndrome (PCOS), yet current hormone-based therapies have limited efficacy and potential adverse effects. We evaluated whether placenta-derived mesenchymal stem cells (PDMSCs) mitigate ovarian lipotoxicity by restoring adiponectin signaling.

Methods

A thioacetamide (TAA) induced rat model of metabolic dysfunction with ovarian lipotoxicity was treated by intravenous transplantation of PDMSCs (2 × 10⁶) cells. Hepatic and ovarian phenotypes were assessed four weeks after transplantation. In parallel, PDMSCs were cocultured with TAA-treated granulosa and primary theca cells, with or without siRNA-mediated knockdown of ADIPOR1 and/or ADIPOR2.

Results

PDMSCs transplantation improved systemic insulin resistance and dyslipidemia and partially restored hepatic and ovarian architecture. PDMSCs treatment increased circulating and ovarian ADIPONECTIN levels and upregulated Adipor1/2 in ovarian tissue, accompanied by activation of the ADIPOR1/2/Fatty acid driven axis and enhanced mitochondrial fatty acid oxidation. These changes were associated with reduced ovarian lipid accumulation and improved endocrine homeostasis, including normalization of anti-Müllerian hormone (AMH), estradiol, and androgen levels, preservation of the primordial follicle pool, and induction of BMP15 expression. In vitro ADIPOR1/2 silencing abrogated these protective effects, supporting a requirement for adiponectin receptor signaling.

Conclusions

PDMSCs ameliorate systemic and ovarian metabolic dysfunction in a TAA-induced model, consistent with adiponectin, ADIPOR1/2 dependent mitochondrial metabolic reprogramming. PDMSCs restore both metabolic and reproductive competence in the context of hepatic-ovarian metabolic crosstalk. These findings support PDMSC-based therapy as a mechanistically informed, multi-target strategy for the treatment of PCOS and metabolic-associated ovarian dysfunction.

Pancreatic islets undergo coordinated cellular remodeling during obesity-induced insulin resistance. However, longitudinal changes across endocrine and non-endocrine compartments remain largely unexplored. We present a comprehensive high-resolution atlas using longitudinal single-cell RNA sequencing (scRNA-seq) and single-cell ATAC sequencing (scATAC-seq) on islets from C57BL/6 mice subjected to high-fat diet (HFD) feeding for 8, 16, and 24 weeks, along with age-matched controls on regular chow (RC). We mapped dynamic changes in islet cell composition and transcriptional states. Trajectory inference indicated diversification of beta-cell programs into adaptive and inflammatory states under HFD. Progression of insulin resistance induced shrinkage and transcriptional remodeling of glucagon-secreting alpha-cells, marked by upregulation of genes related to intracellular transport and oxidative stress, accompanied by the emergence of a polyhormonal alpha-cell subpopulation. Similarly, we identified delta-cell subpopulations exhibiting beta-like transcriptional signatures and polyhormonal identity under nutritional stress, suggesting adaptive delta-cell plasticity that may partially compensate for beta-cell loss during insulin resistance.

The islet microenvironment exhibited robust expansion of proinflammatory M1 macrophages, reaching a plateau by 16 weeks of HFD, indicating niche saturation. Cell–cell communication analyses revealed disruption of key signaling pathways within endocrine and between endocrine and non-endocrine cells under HFD conditions. Notably, CCL27a–chemokine receptor signaling between beta-cells and M1 macrophages was significantly reduced in HFD islets, likely driven by reduced Ccl27a expression and chromatin accessibility in a distinct beta cell subpopulation, which we further validated using INS-1 cells exposed to HFD-like conditions. Comparative analysis with scRNA seq of human islets confirmed conserved stress signatures. Furthermore, genetic variants at the CCL27 locus were associated with increased T2D risk and HOMA-IR in human populations, establishing a novel link between beta-cell stress and systemic inflammation. This resource provides a hierarchical framework for understanding islet failure and identifies potential therapeutic nodes for type 2 diabetes.

High-intensity exercise triggers a coordinated activation of metabolic, endocrine, and immune pathways, yet the mechanisms integrating these responses remain incompletely understood. Interleukin-6 (IL-6), released during exercise, has been proposed as a systemic signal linking skeletal muscle activity to whole-body stress responses. We tested whether exercise-induced IL-6 is required for full sympathoadrenal activation and immune cell mobilization during intense exercise in humans.

Healthy young men received the IL-6 receptor (IL-6R) antibody tocilizumab prior to high-intensity interval exercise. IL-6R blockade reduced circulating epinephrine by ∼50%, lowered plasma glucose levels, and attenuated lactate accumulation, resulting in a smaller decline in blood pH. Immune cell mobilization was selectively impaired, with reduced recruitment of lymphocytes, CD8⁺ T cells, CD56ˆbright natural killer (NK) cells, monocytes, neutrophils, and dendritic cells, while CD4⁺ T cells, CD56ˆdim NK cells, and B cells were unaffected. Although upstream hypothalamic-pituitary-adrenal (HPA)-axis hormones corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) were unchanged, adrenocorticotropic hormone (ACTH) was significantly reduced and associated with pH and catecholamine responses in the control condition. A lower lactate-to-pyruvate ratio during IL-6R blockade suggests enhanced pyruvate oxidation as a potential upstream mechanism.

These findings position IL-6 as an integrative metabolic signal that mediates organ crosstalk and amplifies the HPA and sympathoadrenal response during high-intensity exercise. By linking skeletal muscle metabolic stress to endocrine activation, glucose regulation, and immune cell mobilization, IL-6 appears to coordinate the complex systemic fight-or-flight response to intense physical exertion.

Objectives

After bariatric surgery, many individuals experience debilitating bouts of hypoglycemia, termed post-bariatric hypoglycemia (PBH). Our mouse model of vertical sleeve gastrectomy (VSG) mimics key aspects of PBH in humans. As glucagon is a key element of the counterregulatory hormonal response to hypoglycemia, the objective of this manuscript is to understand if glucagon responses and sensitivity are altered after VSG in mice.

Methods

Mice underwent sham or VSG surgery. We measured glucagon responses to insulin-induced hypoglycemia and mixed meal tolerance tests. We then measured glucose and insulin responses to different doses of exogenous glucagon in fed and fasted states. Lastly, we performed in vitro experiments to examine glucagon responses to glucose and amino acids.

Results

Postprandial glucagon levels were elevated in mice after VSG, but glucose responses to low doses of exogenous glucagon were blunted in the fasted and postprandial state. Administration of low dose glucagon in the fed state led to hypoglycemia in some VSG mice in parallel with stimulation of insulin release. This effect was partially prevented by pretreatment with the GLP-1 receptor antagonist exendin9-39. In islets isolated from VSG mice, glucagon release in response to high glucose was suppressed, but glucagon responses to alanine and high glucose were not different compared to sham controls.

Conclusions

Altogether, our data suggest both glucagon responses, and sensitivity to exogenous glucagon are altered by VSG. The glucagon dysregulation was not observed in isolated islets suggesting gut signaling may be critical in driving glucagon responses after VSG.

Background

Intestinal lipid absorption and chylomicron secretion are essential for systemic lipid homeostasis, yet the regulatory mechanisms coordinating lipoprotein assembly and ER export remain poorly understood. UFMylation is a newly identified ubiquitin-like modification pathway that plays critical roles in endoplasmic reticulum (ER)-related cellular activities such as protein quality control, ER-associated degradation (ERAD) and ER-phagy. However, its role in intestinal lipid transport and systemic lipid homeostasis is completely unclear.

Methods

To elucidate the role of UFMylation in intestinal lipid metabolism, we generated intestinal epithelial cell (IEC)-specific knockout mouse model of Ufbp1, a key component of the UFMylation pathway, and a double knockout model of Ufbp1 and IRE1α, one of the three signaling branches of Unfolded Protein response (UPR). After observing lipid droplet accumulation in the intestinal tissue of Ufbp1 and IRE1α double knockout mice, we further examined lipid metabolism in Ufbp1 knockout mice under high-fat diet. Finally, we used C2BBe1, a subclone of Caco-2 cell, as a cell model to investigate the role of UFMylation in Coat Protein Complex II (COPII)-mediated lipid transport in enterocytes.

Results

We serendipitously found that the combination of Ufbp1 and IRE1α deficiencies led to dramatic accumulation of lipid droplets in the enterocytes, thereby impairing enterocyte function and causing significant growth retardation. Furthermore, we found that Ufbp1 IEC-specific knockout mice were highly resistant to high-fat diet-induced hyperlipidemia. On the molecular level, we found that the components of the UFMylation pathway interacted with COPII complex and regulates the recruitment of COPII coat to ER-located lipoprotein.

Conclusions

Our findings have established that the UFMylation pathway is a novel mediator of enterocyte lipid transport and a key partner of COPII-mediated trafficking.

A bidirectional relationship exists between metabolic dysfunction-associated steatotic liver disease (MASLD) and its progressive inflammatory form, metabolic dysfunction-associated steatohepatitis (MASH), and sarcopenia, with each worsening the prevalence and prognosis of the other. Hepatokines have recently been shown to affect skeletal muscle metabolism and function, both in the context of MASLD and wasting diseases. We here explored the possibility of targeting hepatokines to counteract MASLD-induced sarcopenia. Integrating mouse and human liver transcriptomics with muscle proteomics from MCD- and GAN-diet induced murine MASH models with sarcopenia, we identified three MASH-induced hepatokines, namely LCN2, LGALS3 and OPN. These hepatokines were elevated in the circulation of mouse MASH models with sarcopenia and in sarcopenic patients with advanced chronic liver disease. C2C12 myotubes treated with liver-secreted proteins as well as recombinant LCN2 and LGALS3 exhibited atrophy. Stable isotope tracing and mitochondrial respiration showed that liver-secreted proteins altered mitochondrial metabolism in C2C12 myotubes, which was recapitulated in primary human myotubes. Human 3D skeletal muscle organoids treated with recombinant proteins exhibited functional impairment. Virus-mediated knockdown of LCN2 in liver of mice with MASH improved muscle function and myotube size, whereas virus-mediated overexpression of LCN2 in the liver aggravated MASH-induced myotube atrophy. Targeting hepatokines may therefore be a feasible future therapeutic strategy against sarcopenia.

Introduction

Overexpression of anti-apoptotic protein BCL-2 and hypermethylation are hallmarks of acute lymphoblastic leukemia (ALL) and can be pharmacologically addressed by venetoclax (VEN) and hypomethylating agents (HMA) such as azacytidine (AZA) or decitabine (DEC). Combined VEN and HMA application was recently successfully implemented into the clinical treatment regimen of acute myeloid leukemia but has so far not been investigated in ALL.

Methods

We therefore analyzed the anti-leukemic potential of VEN + HMA in four ALL cell lines and identified potential modes of synergy to overcome mono-drug-induced resistance using proliferation, metabolism, methylation and apoptotic protein expression assays. Single cell RNAseq of a VEN-treated PDX model was used to gain deeper insights into metabolic reprograming.

Results

All substances influenced proliferation and induced apoptosis in a subset of cell lines. Combined VEN and HMA application resulted in significantly reduced metabolic activity. In contrast, no synergistic effects were observed regarding the BCL-2 protein and methyltransferase expression or global methylation. Single cell RNAseq revealed that VEN interferes with both main energy supply routes, oxidative phosphorylation as well as glycolysis, to impede the cells’ metabolism and mitochondrial activity. The addition of HMA, especially DEC, increased anti-metabolic effects, leading to a strong reduction of respiration, ATP production and proton leakage. AZA-induced metabolic suppression and overall anti-leukemic activity alone and in combination with VEN was generally weaker compared to DEC.

Conclusion

Altogether, we herein demonstrate that combined VEN and HMA application acts synergistically and significantly reduces the leukemic burden in ALL cell lines via impairment of tumor cell metabolism and mitochondrial function.

Objectives

Glucokinase Regulatory Protein (GKRP) controls the activity of Glucokinase (GCK) to regulate liver glucose uptake and storage. Coding variants in GCKR, the gene encoding GKRP, strongly associate with fatty liver disease, hypertriglyceridemia, and hypercholesterolemia. Here, we sought to investigate the mechanisms by which a common GKRP variant affects hepatic lipid and cholesterol metabolism.

Methods

We developed mouse models to examine how the human GKRP P446L variant influences liver and systemic metabolism. Endogenous Gckr expression was ablated in adult mouse hepatocytes, together with re-expression of either human GKRP P446L or the reference GKRP protein. We assessed body weight, adiposity, systemic glucose homeostasis, and hepatic metabolites in mice expressing reference GKRP or GKRP P446L under multiple metabolic conditions. To determine whether the effects of GKRP P446L may result from reduced GCK activity, we analyzed mice with liver-specific deletion of Gck.

Results

Hepatic expression of GKRP P446L decreased GKRP and GCK protein levels and elevated serum cholesterol. Hepatic deletion of Gck in mice recapitulated several effects of GKRP P446L, including increased hepatic cholesterol and triglyceride content. The elevated cholesterol was associated with increased cholesterogenic gene expression and cholesterol synthesis. Hepatic expression of an alternative hexokinase (HKII) normalized the effects of GCK-deficiency, suggesting that impaired glucose phosphorylation underlies the phenotype.

Conclusions

The GKRP P446L variant reduced GKRP protein abundance, and diminished GCK activity while increasing cholesterol levels. Loss of GCK elevated cholesterol and hepatic triglyceride levels. Collectively, these findings demonstrate that GCK suppresses hepatic cholesterol synthesis and lipid accumulation, suggesting that reduced GCK activity underlies the metabolic abnormalities associated with the GKRP P446L variant.

Prenatal metabolic adversity, including fetal growth restriction (FR), programs long-term alterations in systemic and neural insulin sensitivity, yet its impact on insulin signaling within reward-circuit plasticity across development remains poorly understood. Using a rodent model of gestational FR, we examined how early metabolic stress alters insulin regulation of mesolimbic reward circuits using in vivo chronoamperometry to measure nucleus accumbens (NAc) dopamine (DA) release during palatable food exposure, with and without peripheral insulin. We assessed longitudinal consumption behavior and conducted transcriptomic profiling (RNA-Seq) at birth (P0), weaning (P21), and adulthood (P90) following saline or insulin administration. FR blunted immediate NAc DA release in response to palatable food, a deficit specifically reversed by peripheral insulin, indicating altered insulin sensitivity of mesolimbic reward circuits. FR animals also display accelerated initial palatable food consumption. Transcriptomic analysis revealed that FR reprograms the NAc's molecular response to insulin. Across development and sex, only 2–9% of insulin-responsive genes overlap between FR and controls. FR generated condition-specific and frequently inverted transcriptional signatures, affecting genes linked to synaptic plasticity (Cplx3, Rab3b) and neurodevelopment (Ccn3). These findings demonstrate that prenatal adversity reconfigures the NAc by altering its molecular and neurochemical responsiveness to insulin. This developmental reprogramming reveals how early metabolic stress reshapes insulin sensitivity within reward circuitry, a mechanism that may contribute to both metabolic and psychiatric disease vulnerability.

Objectives

RNASET2 is a lysosomal RNase whose enzymatic function is required for early events in lipotoxicity. However, the endogenous RNA substrates of RNASET2 that modulate lipid-induced cell death are not known. The purpose of this study was to identify RNASET2 substrates that impact lipotoxic stress.

Methods

RNA sequencing was used to identify RNAs that increase in abundance in human cells upon RNASET2 knockdown, and actinomycin D assays were used to show that RNASET2 impacted decay rates of these RNAs. We tested for the presence of these RNAs in immunoisolated lysosomes and determined the contribution of the lysosomal membrane transporter SIDT2 in delivery of these RNAs to the lysosome. A role for these RNAs in lipotoxic cell death was directly tested in loss- and gain of function analysis.

Results

RNASET2 knockdown increased steady-state abundance of UCHL3, PFN2 and PRDX3 mRNAs and prolonged their decay rate, leading to increased protein expression. These mRNAs were delivered to the lysosomal lumen by the lysosomal membrane transporter SIDT2 that mediates RNautophagy. While UCHL3 and PFN2 have not previously been implicated in lipotoxic responses, expression of these proteins protected against lipid-induced cell death.

Conclusions

Our study identified specific mRNA substrates of RNASET2 and uncovered a previously unexplored function for lysosomes and RNautophagy in regulation of the response to metabolic stress. Moreover, we demonstrated that RNautophagy selectively regulates turnover of specific endogenous RNAs and thereby impacts regulation of gene expression.

Chronic choline insufficiency reprograms hepatic metabolism and drives insulin resistance independent of obesity. While complete choline deficiency causes liver injury, the metabolic consequences of sustained, suboptimal intake, observed in ∼90% of US adults, remain poorly defined. Here, we used integrated lipidomic, metabolomic, and transcriptomic profiling to determine how graded choline intake (0.5, 1.4, or 6.3 g/kg) regulates hepatic metabolism during a control (Con) or high-fat (HF) diet-induced obesity regimen. Under Con diets, low choline intake induced a distinct metabolic state characterized by remodeled hepatic lipid architecture, particularly within triglyceride and glycerolipid species, without altering bulk triglyceride accumulation. Mechanistically, low choline disrupted phospholipid balance and induced a coordinated, sex-dependent transcriptional response, identifying ethanolamine-phosphate phospho-lyase (ETNPPL) and the fatty acid transporter CD36 as top choline-responsive genes. These metabolic effects were unique to the Con low choline group, as a high-fat diet masked all choline-dependent variations. Specifically, ETNPPL protein abundance increased under low choline Con conditions in males but not females. Functionally, this sustained restriction led to progressive hyperglycemia and insulin resistance exclusively in male mice, whereas females remained metabolically protected. Together, these findings demonstrate that chronic choline restriction remodels hepatic lipid metabolism in the absence of obesity and define a CD36–ETNPPL axis linking choline availability to sex-specific insulin resistance.

Objectives

Statins (HMG-CoA reductase inhibitors) are associated with myopathy, yet the precise in vivo mechanisms underlying this association remain unclear. Emerging evidence implicates a deficiency of geranylgeranyl pyrophosphate (GGPP), a key downstream isoprenoid metabolite of the mevalonate pathway. We employed novel muscle-specific genetic mouse models to elucidate the roles of GGPP and Rab geranylgeranyl transferase β (RabGGT-β) in the development of myopathy.

Methods

Using doxycycline-inducible Cre-LoxP technology, we generated three skeletal muscle-specific knockout (KO) models: Hmgcr-DimKO, Rabggtb-DimKO, and combined Hmgcr/Rabggtb-DimKO mice. The severity of myopathy was evaluated based on serum creatine kinase levels and histological examination. Mitochondrial mass and function were rigorously quantified. Prenylation deficit in Rabggtb-DimKO mice was confirmed via subcellular fractionation. To validate GGPP's involvement, rescue experiments were conducted using its precursor, geranylgeraniol (GGOH).

Results

Hmgcr KO resulted in pronounced myopathy, marked by an early reduction in mitochondria-rich myosin heavy chain (MyHC) type I and IIa muscle fibers, followed by a later reduction in mitochondria-poor glycolytic MyHC type IIb muscle fibers, and these changes were reversed by GGOH administration. Rabggtb-DimKO mice developed myopathy later than Hmgcr-DimKO mice; however, in Hmgcr/Rabggtb-DimKO mice, myopathy was dramatically accelerated and more severe. Across all models, mitochondrial dysfunction emerged early—preceding clinical signs of myopathy—consistent with a causal relationship.

Conclusions

Our findings demonstrate that myopathy induced by HMGCR deficiency is primarily driven by GGPP depletion in a mouse model. Furthermore, impaired RabGGT-β-mediated protein geranylgeranylation represents a critical downstream mechanism that aggravates the myopathic phenotype. Early mitochondrial abnormalities may contribute to the pathogenesis of myopathy due to disruption of the mevalonate pathway.

Introduction

Phthalates are widely used as plasticizers in consumer products and are suspected to be metabolism-disrupting chemicals. Di-isononyl phthalate (DINP) is commonly recognized as less hazardous substitute for more studied di(2-ethylhexyl) phthalate (DEHP).

Materials and methods

The effects of DINP on hepatic lipid metabolism were studied using C57BL/6J mice with diet-induced obesity, and human HepaRG and C3A cell lines. The mice were orally exposed to 0, 1.5, 15 or 150 mg/kg bw/d DINP for 20 weeks, followed by assessment of glucose and insulin tolerance, hepatic histology, transcriptome and metabolome. The cells were exposed to DINP and its metabolites, followed by measurement of mitochondrial function and nuclear receptor activation.

Results

The highest dose of DINP decreased hepatic lipid droplets and slightly attenuated weight gain and glucose tolerance of the mice. DINP exposure elevated acylcarnitine levels, indicating altered fatty acid beta-oxidation, which was accompanied by enrichment in mitochondrial and peroxisomal lipid metabolism pathways at transcriptomics level. In vitro, monoisononyl phthalate (MINP), the primary metabolite of DINP, increased mitochondrial respiration and beta-oxidation in presence of long-chain fatty acids. DINP metabolites activated peroxisome proliferator-activated receptors (PPARs) of both mouse and human, with an activation profile partially distinct from DEHP.

Conclusions

Our findings indicate that DINP remodels hepatic lipid metabolism through its active metabolites via PPARs at high doses, with additional modes of action at lower exposure levels. Due to species-specific differences in nuclear receptor activation potencies, the adverse or potentially beneficial nature of these effects in humans remains ambiguous.

Background

White adipose tissue (WAT) plays a central role in maintaining systemic metabolic homeostasis by buffering lipid flux throughout the body. Impairment of this lipid-buffering capacity is a hallmark of obesity and has also been observed during chronic viral infection. Such dysfunction is closely associated with ectopic fat accumulation, particularly in the liver.

Objectives

We hypothesized that the coexistence of obesity and chronic viral infection exacerbates WAT dysfunction, thereby promoting liver pathology. However, the specific response of obese WAT to chronic viral infection – and its downstream impact on liver health – remains to be explored.

Methods

To investigate this interaction, we employed a model of chronic viral infection in mice using lymphocytic choriomeningitis virus (LCMV) clone 13.

Results

In obese hosts, chronic infection caused sustained WAT depletion and progressive weight loss, accompanied by a reduction of Tim-4⁺ eWAT-resident macrophages and features reminiscent of lipodystrophy and aggravated metabolic dysfunction-associated steatotic liver disease (MASLD). Depletion of CD8⁺ T cells, the key mediators of LCMV-driven weight loss in lean mice, only modestly attenuated weight loss and did not ameliorate liver pathology in obese mice. Likewise, therapeutic interventions including TNF-α blockade and glycemic control with metformin did not reverse infection-induced weight loss; moreover, TNF-α blockade failed to improve liver pathology.

Conclusions

Collectively, these findings reveal a previously unrecognized crosstalk between WAT and the liver in infection-driven MASLD, highlight distinct responses in WAT of obese mice compared to their lean counterpart, and underscore the increased susceptibility to virus-induced metabolic complications in obesity.

Adaptive thermogenesis requires coordinated activation of mitochondrial oxidation and metabolic remodeling, yet the signals driving this coordination are incompletely understood. Here, we show that cold exposure and β3-adrenergic receptor (β3-AR) stimulation upregulate the high-affinity copper (Cu) importer CTR1 and promote Cu accumulation in thermogenic adipose tissues. Adipocyte-specific Ctr1 knockout (ACKO) mice exhibit markedly reduced energy expenditure and develop severe hypothermia during acute cold challenge. Proteomic analysis of brown adipose tissue (BAT) from ACKO mice reveals coordinated suppression of oxidative phosphorylation and thermogenic metabolic programs, accompanied by attenuation of lipolytic pathways. Cu deficiency also impairs cold- and β3-AR-induced lipolytic activation, including reduced HSL phosphorylation and lipid clearance in both BAT and inguinal white adipose tissue (iWAT). Although BAT-specific Ctr1 deletion (BCKO) leaves acute β3-adrenergic responses largely intact, these mice still exhibit cold intolerance, indicating that BAT Cu homeostasis is critical for sustaining thermogenic capacity during cold challenge. Treatment with the Cu ionophore elesclomol partially restores mitochondrial oxidative capacity and improves cold tolerance in ACKO mice. Together, these findings identify CTR1-dependent Cu import as an inducible component of the β3-adrenergic thermogenic program and establish intracellular Cu availability as a key determinant of thermogenic capacity during adaptive thermogenesis.

Background

The β cells in the pancreatic endocrine islets preferentially secrete insulin in specific subdomains of the plasma membrane adjacent to the vasculature (i.e., hot spots). Impaired insulin secretion and β -cell dysfunction are central features of Type-2 Diabetes, yet the cytoskeletal machinery that supports directional secretion and secretory hot spots remains incompletely defined. KIF21A is a plus-end-directed kinesin-4 motor protein that anchors microtubule plus ends to the cell cortex. However, the role of KIF21A in pancreatic islet endocrine cells and potential link to type 2 diabetes (T2D) remain unexplored.

Methods

KIF21A mRNA and protein levels were analyzed using bulk RNA-seq and single-cell RNA-seq data using proteomics databases. Kif21a protein distribution was assessed by immunofluorescence in isolated mouse islets using super-resolution microscopy. Likewise, immunostaining of insulin, glucagon, somatostatin, laminin, and detyrosinated tubulin is also performed.

Results

We show that KIF21A is downregulated in T2D human islets at both the mRNA (RNA-seq) and protein (quantitative proteomics) levels. We also demonstrate cell-type-specific enrichment of Kif21a protein (δ > α > β) in intact islets, confirming the hierarchy suggested by single-cell transcriptomics. We also show that within each endocrine lineage, Kif21a protein shows pronounced cell-to-cell heterogeneity, consistent with endocrine sub-states and functional specialization. And most importantly, we show that implicating Kif21a is spatially enriched at the rosettes and laminin-rich interfaces at vasculature-oriented secretion sites (hot spots), where microtubule anchoring is expected to shape targeted granule delivery.

Conclusions

KIF21A is a T2D-associated gene with cell-type-specific and heterogeneous expression in islet endocrine cells. KIF21A may have a cortical microtubule-anchoring function and may contribute to the directed granule delivery to the vasculature for regulated hormone secretion.

Glucagon-like peptide-1 receptor (GLP-1R) agonists such as semaglutide are highly effective treatments for obesity, yet the mechanisms by which they reduce food intake remain incompletely understood. Because taste plays a critical role in guiding food intake, several clinical studies have investigated whether GLP-1R agonists alter taste function, but these reports have yielded conflicting results. Here, we systematically tested the effects of chronic semaglutide treatment on taste responsivity in diet-induced obese mice. Mice were evaluated using brief-access gustometer tests to assess responses to sweet, bitter, sour, salty, and fatty tastants. Chronic semaglutide treatment produced robust weight loss but did not alter lick rates for any tastant, indicating intact taste-driven orosensory evaluation across modalities. Psychophysical analysis using a broad range of sucrose concentrations revealed similar concentration-response functions and comparable EC50 values between vehicle- and semaglutide-treated mice, demonstrating unchanged sweet taste sensitivity. However, semaglutide modestly increased total licking and trial initiation for sucrose, suggesting enhanced behavioral engagement rather than altered taste perception. Consistent with the behavioral findings on taste, semaglutide did not affect the abundance of taste receptor cell subtypes in the circumvallate papillae or the expression of genes involved in taste receptor signaling and neurotransmission. Together, these results indicate that chronic semaglutide does not detectably impair peripheral taste function in mice under our experimental conditions. Instead, GLP-1R agonists likely influence ingestive behavior through mechanisms independent of taste signaling, potentially involving alterations in motivational processes.