Restoring Muribaculum intestinale-Derived Butyrate Mitigates Skeletal Muscle Loss in Cancer Cachexia

Muscle wasting in cancer cachexia patients is a major clinical challenge. Although reduced levels of short-chain fatty acids (SCFAs) in cachexia patients have been associated with muscle atrophy, their precise role remains unclear. Given that the gut microbiota is the primary source of SCFAs, modulating SCFA composition through probiotic supplementation has shown promise in preclinical studies of cancer cachexia. In this study, we aimed to elucidate the dysregulation of the gut microbiota in cachexia mice and investigate the potential protective effect of supplementation with the inulin diet, Muribaculum intestinale (MI) and sodium butyrate (NaB) against cachexia-induced muscle wasting.

We analysed the gut microbiota composition using 16S rRNA gene amplicon sequencing and measured SCFA levels to evaluate metabolic changes in faecal samples from cancer cachexia models. We identified the associations between the microbiota and metabolites and evaluated the impacts of MI (10⁸ CFU per mouse), NaB (50 mg/kg) and inulin diet on cancer cachexia models. The mechanism of NaB was elucidated by muscle RNA-Seq and confirmed by Western blotting, qPCR, ATP assays and other experimental approaches, revealing the effects of altered gut microbiota composition and metabolite levels on muscle metabolism in cachectic mouse models.

Faecal analysis in cachectic mice revealed a significant alteration in gut microbiota composition, particularly a reduction in Muribaculaceae (76.0%) and Muribaculum intestinale (82.0%). Direct supplementation with MI increased its abundance and butyrate level (p < 0.05), reducing muscle wasting in cachexia. Correlation analysis underscored a significant positive association between Muribaculaceae, Muribaculum intestinale and butyrate levels (p < 0.05). NaB also ameliorated muscle wasting, with RNA-Seq of muscle tissues showing a decrease in inflammatory factors and autophagy, downregulation of pyruvate dehydrogenase kinase 4 (Pdk4) expression (61.6%) and increased ATP content (25.5%), thereby playing a pivotal role in attenuating muscle degradation in cancer cachexia. Supplementation with inulin diet increased the levels of Muribaculaceae and Muribaculum intestinale (p < 0.05), also alleviating cachexia symptoms in mice.

In cachectic mouse models, Muribaculaceae and Muribaculum intestinale are reduced and exhibit a significant positive correlation with SCFA butyrate. Inulin or MI supplementation increased these bacteria, ameliorating cachexia. NaB attenuates muscle wasting through coordinated modulation of autophagy suppression, anti-inflammatory effects and metabolic reprogramming (including PDK4 downregulation and ATP elevation), collectively indicating the existence of a gut-muscle axis in cachexia progression. These findings underscore the potential of microbiota-targeted interventions in managing cancer cachexia and highlight the intricate interplay between gut microbiota and skeletal muscle health.