Molecular mechanism of valine and its metabolite in improving triglyceride synthesis of porcine intestinal epithelial cells

An insufficient energy supply to intestinal epithelial cells decreases production performance in weaned piglets. Triglycerides are the main energy source for intestinal epithelial cells in piglets. The present study aimed to investigate the effects and mechanisms of valine supplementation on triglyceride synthesis in porcine intestinal epithelial (IPEC-J2) cells. Valine supplementation in the medium significantly increased the content of triglycerides, fat droplets, and long-chain fatty acids (C17:0, C18:0, C20:0, C18:1, C20:1, and C22:1) (P < 0.05). Valine metabolite (3-hydroxyisobutyrate [3-HIB]) concentration increased significantly in the valine-supplemented group (P < 0.05). Silencing of the 3-HIB synthase enzyme 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) in IPEC-J2 cells significantly reduced the triglyceride concentration and lipid droplet synthesis. Further studies found that 3-HIB supplementation in the medium significantly increased the concentration of triglycerides, lipid droplets, and unsaturated fatty acids (C16:1, C18:1, C18:2, C18:3, C20:3, C20:4, and C20:5) (P < 0.05) by upregulating the expression of proteins involved in fatty acid transport (CD36) and fatty acid binding protein 3 (FABP3) or triglyceride synthesis (DGAT1) (P < 0.05), indicating that 3-HIB mediates valine-enhanced triglyceride synthesis in IPEC-J2 cells. In conclusion, our results demonstrated that valine enhanced triglyceride synthesis in IPEC-J2 cells via increasing the 3-HIB concentration, which may promote fatty acid transport via upregulation of proteins related to fatty acid transporter. These findings provide new insights into the mechanisms through which valine participates in lipid metabolism.