Folic acid mitigation of alcohol-induced sarcopenia via gut-muscle axis modulation

Alcohol-related muscle dysfunction is highly prevalent and substantially impairs the quality of life in individuals with alcohol use disorders. Chronic alcohol consumption-induced folic acid (FA) deficiency, potentially worsening alcohol-related diseases, and has been reported to FA exert protective effects on muscle health. However, the precise mechanisms by which FA may protect skeletal muscle via the gut-muscle axis in alcohol-induced sarcopenia remain insufficiently elucidated. This study aims to investigate whether FA can prevent alcohol-induced sarcopenia and to elucidate the underlying mechanisms of the gut-muscle axis.

In vivo, eight-week-old male C57BL/6 J mice were given a Lieber-DeCarli alcohol diet for 12 weeks and administered either FA (2.5 or 5 mg/kg) or idebenone (2.5 mg/kg). To further elucidate the role of the gut-muscle axis, we conducted in vivo myostatin (MSTN) manipulation and fecal microbiota transplantation (FMT) experiments. Evaluations included muscle mass and strength, histology, mitochondrial function, markers of oxidative stress and inflammation, gut microbiota, and serum metabolomics. In vitro, C2C12 myoblasts were treated with ethanol or indoxyl sulfate (IS) and then supplemented with FA to assess the mechanism of their action.

FA intervention effectively restored muscle mass and strength, reduced homocysteine levels, and improved mitochondrial function (P < 0.05). Mechanistically, FA downregulated MSTN signaling, resulting in decreased protein degradation and increased protein synthesis (P < 0.05). In vivo gain- and loss-of-function experiments, confirming MSTN's critical mediation of FA's protective effects. Concurrently, integrated multi-omic analysis identified that FA rebalanced the gut microbiota-metabolite network, with IS identified as a key gut-derived mediator. FMT from high-dose FA-treated donors replicated the muscle-protective effects, confirming the critical causal role of gut microbiota in FA's therapeutic efficacy. In vitro, FA (40 μM) improved mitochondrial membrane potential and increased the myotube fusion index while suppressing MSTN pathway activation (P < 0.05).

FA significantly attenuated alcoholic sarcopenia by modulating the gut-muscle axis. Specifically, FA corrected the dysregulation of the alcohol-Hcy axis, and enhanced mitochondrial function. Additionally, FA rebalanced to the intestinal microbiota-metabolite network and inhibited MSTN-mediated excessive protein degradation, collectively restoring muscle protein homeostasis.