Plasma microRNAs (miRNAs), which exist in exosomal (EX) and non-exosomal free circulating (FC) fractions, can be utilized as blood biomarkers. To identify early indicators of carcass traits, we performed comprehensive analysis of plasma miRNAs separately on EX and FC fractions in Japanese Black cattle at 20, 25, and 30 months of age. We found a total of 1,071 miRNAs including 39 novel miRNA candidates, in which 345 and 358 miRNAs exhibited in measurable amounts in EX and FC fractions, respectively. Profiles of these miRNAs were similar at 20 and 25 months, but collectively different from those at 30 months. We identified 86 and 80 differentially existed miRNAs (DE-miRNAs) between 25 and 30 months in EX and FC fractions, respectively. Among the DE-miRNAs, we revealed significant correlations of bta-miR-150 (EX and FC), -30b-5p (EX), -423-3p (EX), and -222 (FC) with several carcass traits including marbling score. Interestingly, target genes of these DE-miRNAs were functionally enriched in KEGG pathways such as PI3-Akt and MAPK signaling pathways, suggesting their functional relevance to carcass quality and quantity traits. We clarified changes in plasma EX and FC miRNA profiles during the fattening period and identified several miRNAs having correlations with carcass traits. These results could support the utility of plasma miRNAs as potential early indicators of carcass traits in Japanese Black cattle.
Amolo et al. (Mon,) studied this question.