Bacteroidota‐derived glycine lipids differentially regulate skeletal muscle mitochondrial adaptation during Western diet feeding in male Ldlr −/− mice

Abstract The Western diet (WD) is associated with skeletal muscle mitochondrial dysfunction, impaired oxidative metabolism, redox imbalance and inflammation. Emerging evidence suggests that gut microbiome‐derived metabolites contribute to host metabolic regulation, yet the role of Bacteroidota‐derived glycine lipids in skeletal muscle remains unknown. This study tested whether two structurally related bacterial glycine lipids, lipid 654 (L654) and lipid 1256 (L1256), regulate skeletal muscle mitochondrial remodelling in WD‐fed Ldlr −/− mice. Male Ldlr −/− mice were fed a normal chow or WD and administered L654, L1256 or vehicle control for 8 weeks. Skeletal muscle glycine lipid accumulation, mitochondrial respiration, mitochondrial biogenesis markers, mitophagy‐associated signalling, inflammatory and antioxidant proteins and muscle fibre cross‐sectional area were assessed. L1256, but not L654, accumulated in skeletal muscle. Functionally, L1256 selectively enhanced fatty acid‐supported mitochondrial respiration and increased respiratory control ratio. L1256 also increased peroxisome proliferator‐activated receptor gamma coactivator 1‐alpha (PGC‐1α), mitochondrial transcription factor A (TFAM) and electron transport chain complexes IV and V, suggesting enhanced oxidative mitochondrial remodelling. In parallel, L1256 altered markers associated with mitochondrial quality control signalling, increased nuclear factor erythroid 2‐related factor 2 (Nrf2), manganese superoxide dismutase (MnSOD) and glutathione peroxidase 4 (GPX4), suppressed nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) signalling and preserved muscle fibre cross‐sectional area. L654 upregulated mitochondrial biogenesis transcripts without altering protein abundance. These findings identify L1256 as a microbiome‐derived lipid retained within skeletal muscle that enhanced oxidative metabolism and preserved mitochondrial quality signalling under metabolic stress. The data suggest that tissue retention of bacterial lipids may be an important determinant of skeletal muscle mitochondrial adaptation. image Key points Western diet contributes to skeletal muscle mitochondrial dysfunction, impaired oxidative metabolism and chronic inflammation. Microbiome‐derived glycine lipids are bioactive molecules from Bacteroidota species, but their effects on skeletal muscle mitochondrial metabolism remain poorly understood. Bacteroidota‐derived glycine lipids produce distinct skeletal muscle responses in Western diet‐fed Ldlr − / − mice, where lipid 1256 accumulated in skeletal muscle and enhanced fatty acid‐supported respiration, whereas lipid 654 primarily induced transcriptional responses without detectable tissue accumulation. Lipid 1256 increased peroxisome proliferator‐activated receptor gamma coactivator 1‐alpha (PGC‐1α), mitochondrial transcription factor A (TFAM) and complexes IV and V of the electron transport chain together with restoration of Parkin, nuclear factor erythroid 2‐related factor 2 (Nrf2), manganese superoxide dismutase (MnSOD) and glutathione peroxidase 4 (GPX4) while reducing nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) and interleukin 6 (IL‐6) expression and preserving skeletal muscle cross‐sectional area. These findings suggest that gut microbiome‐derived glycine lipids are regulators of skeletal muscle mitochondrial metabolism, and that tissue retention of bacterial lipids influences mitochondrial oxidative remodelling during metabolic stress.