Gut microbiota-derived 7-KDCA protects against diabetic sarcopenia by interrupting the NLRP1-ferroptosis crosstalk in myotubes

Abstract Type 2 diabetes mellitus (T2DM) accompanied by sarcopenia is an emerging clinical challenge in aging populations, yet the treatment options remain scarce. Recent advances in metabolomics have revealed that gut microbial bile acids function as essential players in muscle mass and function. The aim of the present study was to assess whether 7-ketodeoxycholic acid (7-KDCA), a secondary bile acid, can ameliorate muscle atrophy and physical exercise impairment in a diabetic mouse model of sarcopenia. Untargeted and targeted metabolomics showed that the fecal and serum levels of 7-KDCA were significantly downregulated in T2DM mice. This decrease was also observed in T2DM patients with sarcopenia, and the contents of 7-KDCA were positively associated with the skeletal muscle index (SMI) and skeletal muscle density (SMD) in enrolled patients. Administration of 7-KDCA ameliorated glucose intolerance, attenuated muscle atrophy, restored muscle function, enhanced exercise capacity, and improved intestinal permeability in T2DM mice. 7-KDCA facilitated the differentiation and protein synthesis, as well as glucose uptake, in cultured C2C12 myotubes. The abundance of Bifidobacterium pseudolongum ( B. pseudolongum ) and Lactobacillus murinus ( L. murinus ), two key bacteria for 7-KDCA production, was diminished in T2DM mice and patients. Intestinal colonization of B. pseudolongum and L. Murinus showed similar effects as 7-KDCA. RNA sequencing and experimental analysis revealed that 7-KDCA inhibited NLRP1 inflammasome activation to suppress ferroptosis in myotubes since a potent NLRP1 agonist, muramyl dipeptide (MDP), and a ferroptosis inducer, Erastin, minimized the benefits of 7-KDCA. These findings highlight the therapeutic potential of 7-KDCA and its-generated B. pseudolongum and L. Murinus in alleviating diabetes-related muscle atrophy. Targeting 7-KDCA/NLRP1/ferroptosis axis offers a promising therapeutic strategy for metabolic disorders and sarcopenia.