The intestine expresses pancreatic triacylglycerol lipase: regulation by dietary lipid

We identified the enzyme responsible for alkaline lipolysis in mucosa of ra t small intestine. RT-PCR was used to amplify a transcript that, by cloning and sequencing, is identical to pancreatic triacylglycerol lipase. In rats fed normal laboratory chow, pancreatic triacylglycerol lipase mRNA was det ected in all four quarters of the small intestine, with the first quarter e xpressing about three times as much of this transcript as was found in the more distal three-quarters combined. Both acutely and chronically administe red dietary fat were shown to regulate pancreatic triacylglycerol lipase mR NA expression and lipase activity. The synthesis of pancreatic triacylglyce rol lipase protein by the small intestine was demonstrated by in vivo radio labeling experiments using [S-35]methionine/cysteine followed by immunoprec ipitation with an anti-pancreatic triacylglycerol lipase antibody. Immunohi stochemical studies suggest that pancreatic triacylglycerol lipase protein expression is restricted to enterocytes throughout the small intestine. To our knowledge, this is the first report identifying rat small intestinal mu cosa as a site of pancreatic triacylglycerol lipase synthesis and the first demonstration of its modulation in the mucosa by dietary fat. We propose t hat pancreatic triacylglycerol lipase is used by the intestine to hydrolyze the mucosal triacylglycerol that is not transported in chylomicrons.