Uncovering the Role of Ribosomal Protein L8 in Milk Fat Synthesis Mechanisms in Yak Mammary Epithelial Cells

Abstract

, RPL8, mTORC1, SREBP1 The fat content in yak milk is higher than that in dairy cows, but the molecular mechanisms responsible for milk fat synthesis in yaks are still unclear. This study examined the regulatory mechanism of milk fat synthesis in yak mammary epithelial cells (YMECs) by investigating the role of Ribosomal protein L8 (RPL8) in the mTORC1-SREBP1 signaling pathways. The results showed that over-expression or inhibition of RPL8 had a significant effect on triglyceride (TG) secretion, which also affected the sterol regulatory element-binding protein 1 (SREBP1) pathway. Similarly, the intervention of SREBP1 revealed that RPL8 promoted TG secretion through the SREBP1 pathway. Additionally, the study found that over-expression or inhibition of RPL8 regulated the signaling activity of the mammalian target of rapamycin complex 1 (mTORC1), which promoted the SREBP1 signaling pathway through mTORC1. Further examination by over-expressing or inhibiting SREBP1 or mTOR showed that mTOR promoted TG secretion through the mTORC1-SREBP1 signaling pathway. Moreover, YMECs treated with palmitic acid showed increased expression of RPL8, mTOR, and SREBP1, as well as increased TG secretion. Overall, the study’s findings provide insights into the underlying mechanisms of milk fat synthesis in yaks, and suggest that the RPL8 gene and mTORC1-SREBP1 signaling pathways could serve as potential genetic markers for milk fat synthesis in yak mammary glands.