Alpha-ketoglutarate ameliorates diabetes-associated skeletal muscle fibrosis by restoring TET2-dependent epigenetic remodeling in CD90 positive fibro-adipogenic progenitors.

OBJECTIVE: Fibro-adipogenic progenitor (FAP) dysfunction drives skeletal muscle fibrosis in type 2 diabetes mellitus (T2DM), yet the underlying metabolic-epigenetic mechanisms remain poorly understood. This study investigates how metabolite fluctuations regulate the cell fate of CD90+ FAPs in the diabetic skeletal muscles. METHODS AND RESULTS: Re-analysis of single-cell RNA sequencing data from human diabetic skeletal muscle, combined with immunofluorescence staining of biopsy specimens, revealed a significant expansion of CD90+ FAPs characterized by aberrant asymmetric cell division (ACD) associated polarity and a profibrotic phenotype. Using LC-MS, we identified a marked metabolic shift in insulin-resistant CD90+ FAPs, with reduced alpha-ketoglutarate (α-KG) and elevated L-2-hydroxyglutarate (L-2HG) levels. Reduced α-KG availability, together with competitive inhibition by accumulated L-2HG, suppresses TET2 activity and shifts DNA cytosine modification toward increased 5mC and decreased 5hmC. Specifically, epigenetic remodeling at the promoters of polarity-related genes-Pard3b, Pard6b, and Prkcz-was associated with activation of an ACD-related polarity program in CD90+ FAPs. This lineage bias promotes fibrogenic differentiation, ultimately exacerbating collagen accumulation and impairing muscle function. Dietary α-KG supplementation restored the α-KG/L-2HG ratio, restrained aberrant ACD-related polarity program, and effectively prevented or alleviated muscle fibrosis in T2DM mice. Conversely, TET2 knockdown attenuated the protective effects of α-KG on DNA hydroxymethylation and profibrotic activation of CD90+ FAPs, supporting a TET2-dependent mechanism underlying the epigenetic effects of α-KG. CONCLUSION: Our findings demonstrate that dysregulation of α-KG and L-2HG drives diabetic muscle fibrosis by disrupting TET2-dependent DNA hydroxymethylation and FAP division symmetry. Restoring this metabolic-epigenetic axis represents a promising therapeutic strategy for treating diabetic skeletal muscle fibrosis.