TitleThe effect of MGAT expression on cellular lipid metabolism
NameAhn, Kyong Jin (author), Storch, Judith (chair), Brasaemle, Dawn L (internal member), Igal, Ariel (internal member), Igal, R.Ariel (internal member), Rutgers University, Graduate School - New Brunswick,
Lipids in human nutrition,
DescriptionFollowing absorption into the enterocyte, free fatty acid (FFA) and sn-2-monoacylglycerol (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 expression promotes the rapid uptake of MG across the membrane by efficiently maintaining concentration gradients, or that the transmembrane lipid transport proteins are influenced by MGAT expression. The incorporation of absorbed MG into each lipid class was also significantly different between mock and MGAT expressing cells. More MG was incorporated into TG and DG in the MGAT transfected cells. In addition, the MGAT expressing cells showed higher percent incorporation into PL and lower percent incorporation into TG comparing to mock expressing cells. This difference in metabolic channeling suggests that diacylglycerol (DG) synthesized from MGAT pathway may not be equivalent with DG synthesized from G-3-P pathway, which is the ubiquitous metabolic pathway used to synthesize TG in most cells. We therefore suggest that MGAT expression may increase the net uptake of lipid into cells, and that the G-3-P and MGAT pathways may have different pools of DG which are metabolized to PL or TG.
NoteIncludes bibliographical references
Noteby Kyong Jin Ahn
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.