Do microbial-gut-muscle mediated by SCFAs, microbial-gut-brain axis mediated by insulin simultaneously regulate yak IMF deposition?

Ruminant rumen plays an important role in the digestibility of cellulose, hemicellulose, starch and fat. In this study, the yaks under graze and stall feeding were chosen as the models of different rumen bacteria and intramuscular fat (IMF). The characteristics of IMF deposition, serum indexes in yaks were detected; the bacteria, metabolites in rumen was explored by 16S rRNA sequencing technology, untargeted metabolomics based on liquid chromatography-mass spectrometer and gas chromatography, respectively; the transcriptome of longissimus thoracis was identified by RNA-Sequencing analysis. Based on above results, a hypothesis that yak IMF deposition is regulated by the combined action of microbiome-gut-brain and muscle axis was proposed. The short-chain fatty acids (SCFAs) and neurotransmitters precursors like acetylcholine produced in yak rumen promoted insulin secretion via central nervous system. These insulin resulted in the high expression of SREBF1 gene by gut-brain axis; SCFAs can directly arrive to muscular tissue via blood circulation system, then activated the expression of PPARγ gene by gut-muscle axis. The expression of lipogenesis gene SCD , FABP3 , CPT1 , FASN and ACC2 was accordingly up-regulated. This study firstly introduce the theory of microbiome-gut-brain/muscle axis into the study of ruminant, and comprehensively expounded the regulatory mechanism of yak IMF deposition. • Microbial-gut-muscle and brain axis in livestock were verified for the frist time. • The insulin secretion via CNS was increased under the regulation of gut-brain axis mediated by SCFAs and neurotransmitters from the microbial fermentation in yaks rumen. • SCFAs also directly arrive to muscular tissue by blood circulation system via gut-muscle axis. • The up-regulated expression of lipogenesis gene PPARγ , SREBF1 , SCD , FABP3 , CPT1 , FASN and ACC2 promotes IMF fat deposition in yaks. • Microbial-gut-muscle and brain axis also regulate the fatty acids composition in yak IMF. [ABSTRACT FROM AUTHOR]