Effects of different long-chain fatty acids on lipid uptake and CD36 palmitoylation in small intestinal epithelial cells of mouse

To investigate the impacts of various long-chain fatty acids on fatty acid uptake and the palmitoylation of cluster of differentiation 36 (CD36) in mouse small intestinal epithelial cells.

In vitro, ModeK, the mouse intestinal epithelial cells, were subjected to treatment with various long-chain fatty acids, including saturated fatty acid palmitic acid (PA), polyunsaturated linoleic acid (LA) and monounsaturated oleic acid (OA). A comparison of the cellular lipid uptake was conducted by BODIPY staining. Additionally, immunofluorescence and Western blot techniques were employed to evaluate the membrane localization of CD36 and its palmitoylation status, and the palmitoylation inhibitor was utilized to appraise the necessity of CD36 palmitoylation for fatty acid uptake. In vivo experiments involved the acute oral administration to mice with different oils, including lard, soy oil and olive oil, which were rich in PA, LA and OA respectively. It aimed to examine lipid uptake in the mouse jejunum, blood triglyceride (TG) level, and the palmitoylation level of CD36.

The BODIPY staining results indicated that the average fluorescence intensity within ModeK cells subjected to treatment with LA and OA were significantly higher than that in cells treated with PA (P<0.0001). This finding suggested that LA and OA enhanced lipid uptake by intestinal epithelial cells. The immunofluorescence results demonstrated that, in comparison to PA, LA and OA resulted in a greater localization of CD36 on the plasma membrane. Synchronously, palmitoylation assay results further indicated that LA and OA significantly increased the palmitoylation level of CD36 on plasma membrane (P<0.05, P<0.001). Moreover, the palmitoylation inhibitor 2-bromopalmitate (2BP) reversed the promoting effect of LA and OA on lipid uptake by intestinal epithelial cells (P<0.001, P<0.0001). And the results of acute gavage in vivo showed that gavage of soy oil and olive oil significantly promoted lipid uptake by jejunal epithelial cells compared to gavage of lard (P<0.05, P<0.0001), as well as elevated blood triglyceride (TG) level and the palmitoylation level of CD36 in the plasma membrane fraction of jejunal tissue (P<0.05).

In comparison to PA, a long-chain saturated fatty acid, the long-chain unsaturated fatty acids LA and OA exhibit the ability to enhance lipid uptake in small intestinal epithelial cells, with OA demonstrating a more pronounced effect. And this enhancement may be attributed to the promotive palmitoylation and localization of CD36 on the plasma membrane, which is facilitated by long-chain unsaturated fatty acids.