title: Metabolism of sn-1(3)-Monoacylglycerol and sn-2-Monoacylglycerol in Caecal Enterocytes and Hepatocytes of Brown Trout (Salmo trutta).
abstract: sn-2-Monoacylglycerol (2-MAG) and sn-1(3)-monoacylglycerol [1(3)-MAG] are important but yet little studied intermediates in lipid metabolism. The current study compared the metabolic fate of 2-MAG and 1(3)-MAG in isolated caecal enterocytes and hepatocytes of brown trout (Salmo trutta). 1(3)-Oleoyl [9,10-3H(N)]-glycerol and 2-Oleoyl [9,10-3H(N)]-glycerol were prepared by pancreatic lipase digestion of triolein [9,10-3H(N)]. The 1(3)-MAG and 2-MAG were efficiently absorbed by enterocytes and hepatocytes at similar rates. The 2-MAG was quickly resynthesized into TAG through the monoacylglycerol acyltransferase (EC: 2.3.1.22, MGAT) pathway in both tissues, whereas 1(3)-MAG was processed into TAG and phospholipids at a much slower rate, suggesting 2-MAG was the preferred substrates for MGAT. Further analysis showed that 1(3)-MAG was synthesized into 1,3-DAG, but there were no accumulation of 1,3-DAG in either enterocytes or hepatocytes, which contrasts that of mammalian studies. Some of the 1(3)-MAG may be acylated to 1,2(2,3)-DAG and then utilized for TAG synthesis. Alternatively, 1(3)-MAG can be hydrolyzed to free fatty acid and glycerol, and re-synthesized into TAG through the glycerol-3-phosphate (Gro-3-P) pathway. The overall data suggested that the limiting step of the intracellular 1(3)-MAG metabolism is the conversion of 1(3)-MAG itself.
authors.affiliation: Department of Biology, Norwegian University of Science and Technology, 7491, Trondheim, Norway. keshuai.li@ntnu.no.
authors.forename: Keshuai
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Biology, Norwegian University of Science and Technology, 7491, Trondheim, Norway.|Institute of Marine Research, Bergen, Norway.
authors.forename: Rolf Erik
authors.initials: RE
authors.lastname: Olsen
mesh_terms: D065567:Absorption, Physiological; D000818:Animals; D053898:Biosynthetic Pathways; D002432:Cecum / Q000166:cytology / Q000378:metabolism; D020895:Enterocytes / Q000737:chemistry / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism; D006868:Hydrolysis; D008049:Lipase / Q000378:metabolism; D050178:Monoglycerides / Q000378:metabolism*; D013379:Substrate Specificity; D014337:Trout / Q000378:metabolism*
chemical_list: D050178:Monoglycerides; D008049:Lipase
keywords: Fish nutrition; Lipid metabolism; Thin layer chromatography; Triglyceride synthesis