Microbiota-gut-muscle axis shapes fish muscle texture by regulating collagen synthesis

Background: Increasing studies have emphasized the communication network between the gut microbiome and host organs, revealing that such interactions significantly influence host physiological performances. However, whether a gut-muscle axis exists to regulate muscle quality in animal production is unknown. Results: In two independent cohorts, the muscle hardness of tilapia subjected to a long-term faba bean diet exhibited significant inter-individual variation. RNA-Seq analyses of the high-hardness (H) and low-hardness (L) groups pointed to collagen-based extracellular matrix as a possible factor driving muscle hardness development. Transplantation of gut microbiota from the H donor resulted in enhanced collagen synthesis in gnotobiotic zebrafish. Muscular collagen deposition was featured with an increased abundance of gut Cetobacterium. Gnotobiotic models colonized with live C. somerae exhibited enhanced collagen synthesis. Integrated analyses of microbiome function, bacterial genome, and metabolic profiles identified acetate as a key effector of C. somerae. Acetate incubation upregulated collagen I expression in TGF-β-activated fibroblasts in an acetylation-dependent manner. Mechanistically, acetate promoted the acetylation of SMAD2/3, enhancing its nuclear transport and stability, which ultimately increased collagen expression. An acetate-supplemented feeding experiment corroborated these findings. Conclusion: The comprehensive results provided evidences that gut microbes regulated tilapia muscle texture through SMAD2/3 acetylation-driven collagen synthesis. This study expands our understanding of the multifaceted role of the gut-muscle axis in muscle physiology. Furthermore, our findings highlight that targeting gut microbiota and the downstream collagen synthesis pathway could be promising for manipulating muscle quality in animal production.