Fecal transplant from myostatin deletion pigs positively impacts the gut-muscle axis.

The host genome may influence the composition of the intestinal microbiota, and the intestinal microbiota has a significant effect on muscle growth and development. In this study, we found that the deletion of the myostatin (MSTN) gene positively regulates the expression of the intestinal tight junction-related genes TJP1 and OCLN through the myosin light-chain kinase/myosin light chain pathway. The intestinal structure of MSTN-/- pigs differed from wild-type, including by the presence of a thicker muscularis and longer plicae. Together, these changes affect the structure of intestinal microbiota. Mice transplanted with the intestinal microbiota of MSTN-/- pigs had myofibers with larger cross-sectional areas and higher fast-twitch glycolytic muscle mass. Microbes responsible for the production of short-chain fatty acids (SCFAs) were enriched in both the MSTN-/- pigs and recipient mice, and SCFAs levels were elevated in the colon contents. We also demonstrated that valeric acid stimulates type IIb myofiber growth by activating the Akt/mTOR pathway via G protein-coupled receptor 43 and ameliorates dexamethasone-induced muscle atrophy. This is the first study to identify the MSTN gene-gut microbiota-SCFA axis and its regulatory role in fast-twitch glycolytic muscle growth.

Dynamic changes in intestinal microbiota and metabolite composition of pre-weaned beef calves.

Gut microbes and their metabolites are essential for maintaining host health and production. The intestinal microflora of pre-weaned calves gradually tends to mature with growth and development and has high plasticity, but few studies have explored the dynamic changes of intestinal microbiota and metabolites in pre-weaned beef calves. In this study, we tracked the dynamics of faecal microbiota in 13 new-born calves by 16S rRNA gene sequencing and analysed changes in faecal amino acid levels using metabolomics. Calves were divided into the relatively high average daily gain group (HA) and the relatively low average daily gain group (LA) for comparison. The results demonstrated that the alpha diversity of the faecal microbiota increased with calf growth and development. The abundance of Porphyromonadaceae bacterium DJF B175 increased in the HA group, while that of Lactobacillus reuteri decreased. The results of the LEfSe analysis showed that the microbiota of faeces of HA calves at eight weeks of age was enriched with P. bacterium DJF B175, while Escherichia coli and L. reuteri were enriched in the microbiota of faeces of LA calves. Besides, the total amino acid concentration decreased significantly in the eighth week compared with that in the first week (P < 0.05). Overall, even under the same management conditions, microorganisms and their metabolites interact to play different dynamic regulatory roles. Our results provide new insights into changes in the gut microbiota and metabolites of pre-weaned calves.