Plant-based diet is growingly recommended, although switching the source of proteins from animal to plant regimen requires metabolic adaptations. According to its pivotal function in bridging amino acids and glucose homeostasis, we investigated the role of liver GDH in short-term adaptation to plant versus animal dietary proteins keeping the same spectrum of macronutrients. Control and Hep-Glud1-/- mice lacking liver GDH were fed for 4 days with either animal- or plant-based diets. Hepatic GDH was upregulated in control mice eating animal proteins compared to mice under the plant regimen. Glycemia of ad libitum fed control mice were lower under plant-based regimen compared to animal-based diet; not further changed in Hep-Glud1-/- mice. After 6h of fasting, glycemia remained within the physiological range but mice under the plant-based diet engaged a more robust fasting response versus animal protein regimen. In Hep-Glud1-/- mice, exhibiting impaired endogenous glucose production evoked by amino acids, plant-based diet was associated with reduced plasma concentrations of gluconeogenic alanine and L-carnitine precursor lysine, underscoring limited fasting adaptation. Liver in situ high-resolution metabolomics revealed higher pyruvate levels in periportal regions of mice fed the animal-based diet and the knockout of liver GDH induced elevated aspartate, while urea production was impaired. This resulted in high plasma ammonia concentrations in Hep-Glud1-/- mice, causing severe hyperammonemia in GDH null mice under plant-based diet. These mice exhibited reduced voluntary physical activity, an effect absent in Hep-Glud1-/- mice under animal-based proteins. Overall, dietary source of proteins shapes energy partitioning according to the respective amino acid availability.
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.
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. GLP-1 receptor is expressed in ovaries and testes, potentially allowing a direct effect of SEMA. Testicular expression of this receptor was 4-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. 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.
Agonists of the lipid-sensing PPAR nuclear receptors, including PPARα, are being explored as therapies for metabolic disorders due to their roles in metabolic and anti-inflammatory processes. PPARα transcriptional programs have tissue-dependent features, yet there is a lack of genetic tools to study tissue-specific signaling activation without the addition of a systemic agonist. We aimed to investigate intestinal epithelial cell (IEC)-specific roles of PPARα signaling using a novel transgenic mouse that enables spatial and temporal control of Ppara overexpression. CAG-Ppara,-EGFP mice were bred to Villin-CreERT2 to establish the IEC-Ppara mouse, which was compared to littermate controls 2 weeks after tamoxifen exposure. IEC-Ppara mice had increased Ppara mRNA and PPARα protein in the intestinal epithelium. Transcriptional analysis of intestinal tissue from IEC-Ppara mice showed upregulation of PPARα target genes and functional enrichment for fatty acid catabolic processes. As expected, the enterocytes of IEC-Ppara mice were primed to absorb lipids following oral administration of an olive oil bolus. Unexpectedly, the enteroendocrine hormone Gip was among the most downregulated genes. GIP-positive cells were reduced in the intestines of IEC-Ppara mice and in mice treated with PPARα agonist WY-14643. Circulating GIP hormone was reduced in IEC-Ppara mice. GLP-1-positive cells and hormone were unchanged. Consistent with reduced GIP function, IEC-Ppara mice consumed more food. These findings reveal PPARα as a regulator of GIP and support a new framework in which PPARα signaling influences systemic energy balance via a gut hormone axis. This study could have future impact on understanding responses to therapies targeting PPAR or incretin signaling.
OBJECTIVE:Brain glucose sensing is critical for survival during hypoglycaemia, yet how glucose-sensing neurons access circulating glucose concentrations to maintain glucose homeostasis remains poorly understood. Here we tested the hypothesis that adult oligodendrogenesis in the median eminence (ME) is responsive to changes in blood glucose levels and contributes to hypothalamic glucose sensing through regulation of the blood-hypothalamus barrier. METHODS:We used glycemic challenges and hypoinsulinaemic clamp studies to identify the effect of systemic changes in glycaemia on hypothalamic oligodendrocyte lineage cells. We used conditional knockout mouse models to dissect the respective contributions of adult oligodendrogenesis and new myelin formation to glucose homeostasis in adult male mice. Analyses combined immunofluorescence, serial electron microscopy, whole-brain tissue clearing, and transcriptomic analyses. RESULTS:We found that adult oligodendrogenesis in the median eminence (ME) is modulated by changes in circulating glucose levels and rapidly upregulated by hypoglycaemia. Genetic blockade of new oligodendrocyte production in adult male mice impairs the regulation of glucose homeostasis, the integrity of the ME blood-hypothalamus barrier, and hypothalamic glucose sensing. Unexpectedly, functional integrity of adult-formed myelin is not required for the maintenance of glucose homeostasis. Instead, we show that blockade of adult oligodendrogenesis disrupts hypothalamic expression of A disintegrin and metallopeptidase with thrombospondin motifs 4 (ADAMTS4), a metallopeptidase whose brain expression is restricted to the oligodendrocyte lineage and whose ME expression requires ongoing adult oligodendrogenesis. We show that ADAMTS4 regulates hypothalamic perineuronal net deposition, vascular permeability and glucose sensing. Finally, we show that ME ADAMTS4 expression is regulated by changes in peripheral glycaemia and is dysregulated in diabetes, providing a mechanism by which ME oligodendrocytes contribute to the regulation of glucose homeostasis.
