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Journal of Lipid Research, Vol. 49, 1762-1769, August 2008
Copyright © 2008 by American Society for Biochemistry and Molecular Biology

Metabolism of apical versus basolateral sn-2-monoacylglycerol and fatty acids in rodent small intestine^*

Judith Storch¹, Yin Xiu Zhou and William S. Lagakos

Department of Nutritional Sciences and Rutgers Center for Lipid Research, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901

^* This work was supported by National Institutes of Health Grant DK-38389 and the Busch Biomedical Research Fund.

Published, JLR Papers in Press, April 17, 2008.

¹ To whom correspondence should be addressed. e-mail: storch{at}aesop.rutgers.edu

The metabolic fates of radiolabeled sn-2-monoacylglycerol (MG) and oleate (FA) in rat and mouse intestine, added in vivo to the apical (AP) surface in bile salt micelles, or to the basolateral (BL) surface via albumin-bound solution, were examined. Mucosal lipid products were quantified, and the results demonstrate a dramatic difference in the esterification patterns for both MG and FA, depending upon their site of entry into the enterocyte. For both lipids, the ratio of triacylglycerol to phospholipid (TG:PL) formed was approximately 10-fold higher for delivery at the AP relative to the BL surface. Further, a 3-fold higher level of FA oxidation was found for BL compared with AP substrate delivery. Incorporation of FA into individual PL species was also significantly different, with >2-fold greater incorporation into phosphatidylethanolamine (PE) and a 3-fold decrease in the phosphatidylcholine:PE ratio for AP- compared with BL-added lipid. Overnight fasting increased the TG:PL incorporation ratio for both AP and BL lipid addition, suggesting that metabolic compartmentation is a physiologically regulated phenomenon. These results support the existence of separate pools of TG and glycerolipid intermediates in the intestinal epithelial cell, and underscore the importance of substrate trafficking in the regulation of enterocyte lipid metabolism.

Supplementary key words fatty acid • enterocyte • epithelial cell • lipid metabolism • oxidation • triacylglycerol • phospholipid

Abbreviations: ACS, acyl CoA synthetase; AP, apical; BL, basolateral; DG, diacylglycerol; DGAT, diacylglycerol acyltransferase; ER, endoplasmic reticulum; FABP, fatty acid binding protein; G3P, glycerol-3-phosphate; IFABP, intestinal FABP; LFABP, liver FABP; MG, monoacylglycerol; PC, phosphatidylcholine; PE, phosphatidylethanolamine; PL, phospholipid; TC, taurocholate; TG, triacylglycerol

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