文章基本信息

标题：The use of stable isotope-labeled glycerol and oleic acid to differentiate the hepatic functions of DGAT1 and -2
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作者：Jenson Qi ; Wensheng Lang ; John G. Geisler 等
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：2012
卷号：53
期号：6
页码：1106-1116
DOI：10.1194/jlr.M020156
语种：English
出版社：American Society for Biochemistry and Molecular Biology
摘要：Diacylglycerol acyltransferase (DGAT) catalyzes the final step in triglyceride (TG) synthesis. There are two isoforms, DGAT1 and DGAT2, with distinct protein sequences and potentially different physiological functions. To date, the ability to determine clear functional differences between DGAT1 and DGAT2, especially with respect to hepatic TG synthesis, has been elusive. To dissect the roles of these two key enzymes, we pretreated HepG2 hepatoma cells with ¹³C₃-D₅-glycerol or ¹³C₁₈-oleic acid, and profiled the major isotope-labeled TG species by liquid chromatography tandem mass spectrometry. Selective DGAT1 and DGAT2 inhibitors demonstrated that ¹³C₃-D₅-glycerol-incorporated TG synthesis was mediated by DGAT2, not DGAT1. Conversely, ¹³C₁₈-oleoyl-incorporated TG synthesis was predominantly mediated by DGAT1. To trace hepatic TG synthesis and VLDL triglyceride (VLDL-TG) secretion in vivo, we administered D₅-glycerol to mice and measured plasma levels of D₅-glycerol-incorporated TG. Treatment with an antisense oligonucleotide (ASO) to DGAT2 led to a significant reduction in D₅-glycerol incorporation into VLDL-TG. In contrast, the DGAT2 ASO had no effect on the incorporation of exogenously administered ¹³C₁₈-oleic acid into VLDL-TG. Thus, our results indicate that DGAT1 and DGAT2 mediate distinct hepatic functions: DGAT2 is primarily responsible for incorporating endogenously synthesized FAs into TG, whereas DGAT1 plays a greater role in esterifying exogenous FAs to glycerol.
关键词：diacylglycerol acyltransferase ; triglyceride synthesis ; very low density lipoprotein triglyceride ; liquid chromatography tandem mass spectrometry ; ¹³C₃-D₅-glycerol ; ¹³C₁₈-oleic acid