ABSTRACT
Stearic acid (C18:0, SA) is a saturated long-chain fatty acid (LCFA) that has a prominent function in lactating dairy cows. It is obtained primarily from the diet and is stored in the form of triacylglycerol (TAG) molecules. The transmembrane glycoprotein cluster of differentiation 36 (CD36) is also known as fatty acid translocase, but whether SA promotes lipid synthesis through CD36 and FAK/mTORC1 signaling is unknown. In this study, we examined the function and mechanism of CD36-mediated SA-induced lipid synthesis in bovine mammary epithelial cells (BMECs). SA-enriched supplements enhanced lipid synthesis and the FAK/mTORC1 pathway in BMECs. SA-induced lipid synthesis, FAK/mTORC1 signaling, and the expression of lipogenic genes were impaired by anti-CD36 and the CD36-specific inhibitor SSO, whereas overexpression of CD36 effected the opposite results. Inhibition of FAK/mTORC1 by TAE226/Rapamycin attenuated SA-induced TAG synthesis, inactivated FAK/mTORC1 signaling, and downregulated the lipogenic genes PPARG, CD36, ACSL1, SCD, GPAT4, LIPIN1, and DGAT1 at the mRNA and protein levels in BMECs. By coimmunoprecipitation and yeast two-hybrid screen, CD36 interacted directly with Fyn but not Lyn, and Fyn bound directly to FAK; FAK also interacted directly with TSC2. CD36 linked FAK through Fyn, and FAK coupled mTORC1 through TSC2 to form the CD36/Fyn/FAK/mTORC1 signaling axis. Thus, stearic acid promotes lipogenesis through CD36 and Fyn/FAK/mTORC1 signaling in BMECs. Our findings provide novel insights into the underlying molecular mechanisms by which LCFA supplements promote lipid synthesis in BMECs.
Subject(s)
Lactation , Lipogenesis , Female , Cattle , Animals , Lipogenesis/genetics , Mechanistic Target of Rapamycin Complex 1/metabolism , Mammary Glands, Animal/metabolism , Stearic Acids/pharmacology , Fatty Acids/metabolism , Epithelial Cells/metabolismABSTRACT
Cistanche deserticola is a traditional and precious Chinese herbal medicine, known as "desert ginseng", with anti-inflammatory, anti-oxidant, improving immunity, nourishing the kidneys and other pharmacological effects. Its chemical components mainly include phenylethanol glycosides, iridoids, polysaccharides and volatile components, among which polysaccharides have received extensive attention due to their biological activities such as regulating immune activity, anti-aging, anti-spleen deficiency and antitumor. In recent years, a large number of research have been carried out on the extraction and isolation, chemical structure analysis and biological activity of Cistanche deserticola polysaccharides. The methods of polysaccharide extraction mainly include traditional extraction method, ultrasonic assisted method, microwave assisted method and enzyme assisted method, etc. The extracted polysaccharides were analyzed by chemical methods including methylation, acid hydrolysis and Smith degradation and spectroscopy methods such as NMR and IR. A variety of polysaccharides with new structures were obtained, and some polysaccharides with known structures were also investigated for their biological activities and their structure-activity relationships. However, the relationship between polysaccharides structure and their biological activities is still unclear due to the large number of polysaccharide components, their complex structures and the lack of systematic research and analysis on them. It is expected that the subsequent study of polysaccharide structure and active conformational relationship will be highly valuable for the application of Cistanche deserticola in pharmaceutical sciences and health food.