Two isozymes for human acyl-coenzyme A:diacylglycerol acyltransferase (DGAT), DGAT1 and DGAT2, were independently expressed in DGAT-deficient Saccharomyces cerevisiae to establish DGAT1-and DGAT2-S. cerevisiae. The selectivity of DGAT inhibitors of natural origin towards the isozymes was assessed in enzyme assays using the microsomal fractions prepared from DGAT1-and DGAT2-S. cerevisiae. Amidepsines and xanthohumol inhibited DGAT1 and DGAT2 with similar potency, whereas roselipins were found to inhibit DGAT2 selectively. Keywords: acyl-CoA:diacylglycerol acyltransferase; amidepsine; DGAT; isozyme; roselipin; triacylglycerol; xanthohumol INTRODUCTION Triacylglycerol (TG) is the major energy-storage form of long-chain fatty acids in animals. 1,2 TG synthesis is important in many biological processes, including intestinal fat absorption, fat storage in adipocytes and energy metabolism in muscle, but excessive accumulation of TG in adipocytes as a result of a fat-rich diet or sedentary lifestyle causes obesity.Acyl-coenzyme A (CoA):diacylglycerol acyltransferase (DGAT, EC2.3.1.20) is a membrane-bound enzyme that catalyzes TG formation by acyl esterifications of diacylglycerol. Two biological pathways for TG synthesis, the glycerol phosphate pathway and the monoacylglycerol pathway, have been reported. These pathways form diacylglycerol (DG), which in turn is acylated by DGAT to form TG. 3 Recent molecular biological studies have revealed the existence of two different DGAT isozymes, DGAT1 and DGAT2, 4-6 in mammals, and extensive studies including biological experiments and knockout mice have shown that these isozymes have different functions in mammals. 7-13 Increased DGAT2 activity in the liver causes hepatic steatosis, whereas DGAT1 plays a role in very low-density lipoprotein (VLDL) synthesis in the liver and increases plasma VLDL concentration. Furthermore, newborn DGAT2-deficient mice die within hours of birth, whereas DGAT1-deficient mice are viable and have a modest reduction in tissue TG. Therefore, it is important to determine the selectivity of inhibitors towards the two DGAT isozymes for developing them as pharmaceutical drugs.Our research group conducted an enzyme assay involving rat liver microsomes to discover several DGAT inhibitors from natural sources,

Static fermentation of amidepsine-producing fungus Humicola sp. FO-2942 led to the production of six new amidepsines, including a new type of glycosylated congener. Non-glycosylated amidepsine J inhibited both human diacylglycerol acyltransferases 1 (DGAT1) and DGAT2 with the same IC 50 value of 40 lM, whereas glycosylated amidepsines F to I showed very weak inhibitory activity against DGAT1 and DGAT2.

. FO-2942. -Static fermentation of amidepsine-producing fungus Humicola sp. FO-2942 leads to the production of new amidepsines of type (I). The non-glycosylated amidepsine (Ia) inhibits both human diacylglycerol acyltransferases 1 (DGAT-1) and DGAT-2 with the same IC50 value, whereas the glycosylated amidepsines (Ib) and (Ic) show very weak inhibitory activity against the same acyltransferases. -(INOKOSHI, J.; TAKAGI, Y.; UCHIDA, R.; MASUMA, R.; OMURA, S.; TOMODA*, H.; J. Antibiot. 63 (2010) 1, 9-16; Grad. Sch. Pharm. Sci., Kitasato Univ., Minato, Tokyo 108, Japan; Eng.) -H. Haber