TRNA-derived RNA fragments in the exosomes of bovine milk and colostrum

Abstract

RNA in milk exosomes can be absorbed in the mammalian gastrointestinal tract and plays an important regulatory function. tRNA-derived RNA fragments (tRFs) have recently been found to have important physiological functions. In the present study, we examine in detail the landscape of tRFs in bovine milk exosomes to provide a molecular basis for understanding these functional components of bovine milk. Total RNA was isolated from exosomes in bovine colostrum and mature milk. High-throughput RNA sequencing was used to characterize the profiles of the tRFs. A total of 602 distinct tRFs were identified from milk exosomes, most of which were expressed either specifically in colostrum or in mature milk exosomes. The tRF profiles of colostrum and mature milk exosomes differed significantly. The target genes of the differentially expressed tRFs were predicted and analyzed. The target mRNAs of the downregulated tRFs were enriched in the cAMP signaling pathway, whereas those of the upregulated tRFs were enriched in the insulin and FoxO signaling pathways. Preliminary research shows that tRF-Gly-CCC-026 inhibits the translation of IL7R by directly targeting its 3′-UTR. As RNAs in milk exosomes can be absorbed and function in recipient cells, these RNAs might act as novel regulatory nutrients for infant and adult consumers, which is a possibility that needs further study.