부산대학교 도서관

Grazing alters skeletal muscle physiological properties in cattle. We hypothesized that changes in circulating microRNA (c-miRNA) levels are attributed to release and/or uptake of exosomal miRNA at adipose and liver tissues. In this study, to determine grazing-induced mRNA and miRNA transcriptomic changes at those tissues, we conducted microarray analyses in biceps femoris muscle (BF), subcutaneous fat (ScF), and liver tissues of Japanese Shorthorn steers. Three steers (aged 20–22 mo) were allocated to each of grazing and housed groups; grazing steers were fed on pasture for 3 months from middle of May, when the other steers were housed and fed in a free-stall barn with grass harvested every morning. The samples were collected at 3 mo of grazing period, with surgical biopsy in case of solid tissues. Plasma exosomes (pEX) were prepared from the blood samples, using ultracentrifugation. Total RNAs were prepared from the tissues and pooled within each tissue, and finally applied to both mRNA and miRNA expression microarray analyses. The number of changed genes was the highest in BF (52 increased and 1088 decreased genes). On the other hand, the number of genes showing more than 2-fold increase (INC) and decrease (DEC) compared to the housed was the highest in ScF and the lowest in liver. Especially in ScF, we observed 169 INC and 249 DEC genes, indicating dominance of DEC genes over INC genes in ScF of the grazing steers. Using the list of INC and DEC genes, we conducted gene ontology analyses and extracted the term ‘extracellular exosome’ from the DEC genes in ScF, as a term associated with changes in ScF of the grazing steers. This was coincident with greater number of the decreased miRNAs than the increased in pEX. These results suggest an association of grazing-induced changes in c-miRNAs with ScF transcriptome in the steers.