L-glutamine and transforming growth factor-α enhance recovery of monoacylglycerol acyltransferase and diacylglycerol acyltransferase activity in porcine postischemic ileum

Abstract

Recovery of the ability to digest and absorb lipids is essential to the maintenance of normal nutrition in infants with bowel damage. Two intrinsic microsomal enzymes, monoacylglycerol acyltransferase (MGAT) and diacylglycerol acyltransferase (DGAT), catalyze the major pathway for intestinal triacylglycerol biosynthesis. This study describes the effects of intestinal ischemia on epithelial DGAT and MGAT activities and their recovery in response to two luminal treatments: L-glutamine (Gin), the primary intestinal fuel, and transforming growth factor-α (TGF-α), a mitogenic hormone similar to epidermal growth factor present in breast milk. Ischemic damage and recovery were analyzed in mucosa from Thiry-Vella loops in the midileum of 7-wk-old pigs. Loops were subjected to 2-h occlusion of local mesenteric arteries, followed by 6 or 72 h of recovery in the presence of luminal glucose (control), Gln, or TGF-α. Ischemic tissue followed by 6-h recovery exhibited an approximate 50% decrease in both MGAT and DGAT activities compared with nonischemic loop tissue. At 72 h, MGAT and DGAT recovery in Gln plus TGF-α-treated loops was significantly greater than their corresponding 6-h peak damage levels (p < 0.05). From 6 to 72 h, MGAT increased 4-fold and DGAT increased 3.6-fold after Gln plus TGF-α treatment. With other treatments, MGAT and DGAT activities increased <2.5-fold from 6 to 72 h. This study shows that intestinal MGAT and DGAT activities decrease after ischemic damage, yet recover rapidly in bowel exposed to Gln and/or TGF-α. By stimulating the rate of recovery of the villi and lipid synthesizing enzymes, these treatments could improve the efficacy of enteral feeding in infants recovering from bowel damage.