Botham K M, Maldonado E N, Chico Y, Zheng X, Avella M, Ochoa B
Department of Physiology, University of the Basque Country, Medical School, Bilbao, Spain.
Biochim Biophys Acta. 2001 Dec 30;1534(2-3):96-109. doi: 10.1016/s1388-1981(01)00177-9.
The effect of chylomicron remnants derived from fish oil (rich in n-3 polyunsaturated fatty acids) or corn oil (rich in n-6 polyunsaturated fatty acids) on the formation and hydrolysis of cholesteryl esters in cultured rat hepatocytes was investigated. Hepatocytes were incubated with or without fish or corn oil chylomicron remnants (0.25-0.75 mM triacylglycerol), and the activity of acyl-CoA:cholesterol acyltranferase (ACAT) and cholesteryl ester hydrolases in the cytosol (cCEH) and endoplasmic reticulum (erCEH), and the expression of mRNA for ACAT1, ACAT2 and cCEH, and of enzyme protein for erCEH was determined. Addition of either type of remnants to hepatocyte cultures resulted in a decreased activity of erCEH, cCEH (after 6 and 19 h incubation), and of ACAT (after 6 h only). Hepatocyte levels of mRNA encoding ACAT1 and ACAT2 were not affected by either type of chylomicron remnants after 6 h of incubation, while ACAT2 mRNA levels were down-regulated by fish oil remnants as compared with corn oil remnants, and also with control cells in the long term (19 h). In contrast, cCEH mRNA levels were down-regulated by chylomicron remnants derived from corn oil but not fish oil. The expression of erCEH protein was induced in response to the inhibitory effect of both types of remnants on the activity of the enzyme, with corn oil remnants having a significantly greater effect. These findings demonstrate that dietary polyunsaturated fatty acids when delivered to hepatocytes in chylomicron remnants regulate the activity of the enzymes governing the intracellular cholesteryl ester balance, and suggest that dietary n-3 and n-6 polyunsaturated fatty acids or a metabolite thereof have differential effects on the expression of their genes at the mRNA and post-transcriptional levels.
研究了源自鱼油（富含n-3多不饱和脂肪酸）或玉米油（富含n-6多不饱和脂肪酸）的乳糜微粒残粒对培养的大鼠肝细胞中胆固醇酯形成和水解的影响。将肝细胞与有或没有鱼油或玉米油乳糜微粒残粒（0.25 - 0.75 mM三酰甘油）一起孵育，然后测定胞质溶胶（cCEH）和内质网（erCEH）中酰基辅酶A：胆固醇酰基转移酶（ACAT）和胆固醇酯水解酶的活性，以及ACAT1、ACAT2和cCEH的mRNA表达，还有erCEH的酶蛋白表达。向肝细胞培养物中添加任何一种残粒均导致erCEH、cCEH（孵育6小时和19小时后）以及ACAT（仅在6小时后）的活性降低。孵育6小时后，两种类型的乳糜微粒残粒均未影响肝细胞中编码ACAT1和ACAT2的mRNA水平，而与玉米油残粒相比，鱼油残粒使ACAT2 mRNA水平下调，长期（19小时）与对照细胞相比也是如此。相反，玉米油衍生的乳糜微粒残粒下调了cCEH mRNA水平，而鱼油衍生的则没有。两种类型的残粒对该酶活性的抑制作用诱导了erCEH蛋白的表达，玉米油残粒的作用明显更大。这些发现表明，当以乳糜微粒残粒形式递送至肝细胞时，膳食多不饱和脂肪酸调节控制细胞内胆固醇酯平衡的酶的活性，并表明膳食n-3和n-6多不饱和脂肪酸或其代谢产物在mRNA和转录后水平对其基因表达具有不同影响。
