Intestinal monoacylglycerol metabolism: developmental and nutritional regulation of monoacylglycerol lipase and monoacylglycerol acyltransferase.
Intestinal monoacylglycerol (MG) metabolism is well known to involve its anabolic reesterification to triacylglycerol (TG). We recently provided evidence for enterocyte MG hydrolysis and demonstrated expression of the monoacylglycerol lipase (MGL) gene in human intestinal Caco-2 cells and rodent small intestinal mucosa. Despite the large quantities of MG derived from dietary TG, the regulation of MG metabolism in the intestine has not been previously explored. In the present studies, we examined the mRNA expression, protein expression, and activities of the two known MG-metabolizing enzymes, MGL and MGAT2, in C57BL/6 mouse small intestine, as well as liver and adipose tissues, during development and under nutritional modifications. Results demonstrate that MG metabolism undergoes tissue-specific changes during development. Marked induction of small intestinal MGAT2 protein expression and activity were found during suckling. Moreover, while substantial levels of MGL protein and activity were detected in adult intestine, its regulation during ontogeny was complex, suggesting post-transcriptional regulation of expression. In addition, during the suckling period MG hydrolytic activity is likely to derive from carboxyl ester lipase rather than MGL. In contrast to intestinal MGL, liver MGL mRNA, protein and activity all increased 5-10-fold during development, suggesting that transcriptional regulation is the primary mechanism for hepatic MGL expression. Three weeks of high fat feeding (40% kcal) significantly induced MGL expression and activity in small intestine relative to low fat feeding (10% kcal), but little change was observed upon starvation, suggesting a role for MGL in dietary lipid assimilation following a high fat intake.
Chon
Su-Hyoun
SH
Department of Nutritional Sciences and the Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901.
Zhou
Yin Xiu
YX
Department of Nutritional Sciences and the Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901.
Dixon
Joseph L
JL
Department of Nutritional Sciences and the Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901.
Storch
Judith
J
Department of Nutritional Sciences and the Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901. Electronic address: storch@aesop.rutgers.edu.
D000217:Acyltransferases / Q000378:metabolism*; D000821:Animal Feed; D000818:Animals; D018507:Gene Expression Regulation, Developmental; D006868:Hydrolysis; D007413:Intestinal Mucosa / Q000378:metabolism*; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D008994:Monoacylglycerol Lipases / Q000737:chemistry*; D050178:Monoglycerides / Q000378:metabolism*; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D013997:Time Factors
D008055:Lipids; D050178:Monoglycerides; D000217:Acyltransferases; C021802:2-acylglycerol O-acyltransferase; D017351:N-Acetylglucosaminyltransferases; C063313:alpha-1,6-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase; D008994:Monoacylglycerol Lipases