The effect of MGAT expression on cellular lipid metabolism

Abstract

OF THE THESIS THE EFFECT OF MGAT EXPRESSION ON CELLULAR LIPID METABOLISM by KYONG JIN AHN Thesis Director: Judith Storch, PhD Following absorption into the enterocyte, free fatty acid (FFA) and sn-2monoacylglycerol (sn-2-MG), the major hydrolysis products of dietary lipids, are reconstituted to triacylglycerol (TG) by the monoacylglycerol acyltransferase (MGAT) pathway, which is the primary TG synthesis pathway in the postprandial condition. Nevertheless, the precise function and contribution of the MGAT pathway to lipid synthesis are not fully understood. Therefore in this study, we examined the effect of MGAT expression on cellular lipid metabolism. Although the Caco-2 cell line, which is derived from human colorectal cancer cells, is the most relevant in vitro model to examine the influence of hMGAT2 expression on lipid metabolism in the enterocyte, we could not obtain any definitive metabolism data caused by MGAT expression due to their inconsistent transfection efficiency. Thus we transiently expressed hMGAT2 in CHO-K1 cells, which are relatively easier to transfect, and these cells were then used to study the metabolism of radiolabeled FFA or sn-2-MG. Empty vector-transfected (mock) and MGAT-transfected cells, which were incubated with FA, showed the increased net uptake as a function of time, and both groups metabolized most of absorbed FA to phospholipid (PL). Between the two groups, there were no significant differences. In contrast, MGAT expressing cells which were incubated with MG, absorbed remarkably higher amounts of lipid relative to mock-transfected cells. This suggests that MGAT