Boone Lindsey R, Brooks Patricia A, Niesen Melissa I, Ness Gene C
Department of Pathology, McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA.
J Lipids. 2011;2011:101242. doi: 10.1155/2011/101242. Epub 2011 Oct 5.
Background. Alterations in expression of hepatic genes that could contribute to resistance to dietary cholesterol were investigated in Sprague-Dawley rats, which are known to be resistant to the serum cholesterol raising action of dietary cholesterol. Methods. Microarray analysis was used to provide a comprehensive analysis of changes in hepatic gene expression in rats in response to dietary cholesterol. Changes were confirmed by RT-PCR analysis. Western blotting was employed to measure changes in hepatic cholesterol 7α hydroxylase protein. Results. Of the 28,000 genes examined using the Affymetrix rat microarray, relatively few were significantly altered. As expected, decreases were observed for several genes that encode enzymes of the cholesterol biosynthetic pathway. The largest decreases were seen for squalene epoxidase and lanosterol 14α demethylase (CYP 51A1). These changes were confirmed by quantitative RT-PCR. LDL receptor expression was not altered by dietary cholesterol. Critically, the expression of cholesterol 7α hydroxylase, which catalyzes the rate-limiting step in bile acid synthesis, was increased over 4-fold in livers of rats fed diets containing 1% cholesterol. In contrast, mice, which are not resistant to dietary cholesterol, exhibited lower hepatic cholesterol 7α hydroxylase (CYP7A1) protein levels, which were not increased in response to diets containing 2% cholesterol.
背景。在已知对膳食胆固醇升高血清胆固醇作用具有抗性的斯普拉格-道利大鼠中，研究了可能导致对膳食胆固醇产生抗性的肝脏基因表达变化。方法。采用微阵列分析对大鼠肝脏基因表达因膳食胆固醇而发生的变化进行全面分析。通过逆转录聚合酶链反应（RT-PCR）分析对变化进行确认。采用蛋白质免疫印迹法检测肝脏胆固醇7α羟化酶蛋白的变化。结果。使用Affymetrix大鼠微阵列检测的28000个基因中，只有相对较少的基因发生了显著改变。正如预期的那样，编码胆固醇生物合成途径中酶的几个基因表达下降。角鲨烯环氧化酶和羊毛甾醇14α脱甲基酶（CYP 51A1）的表达下降最为明显。这些变化通过定量RT-PCR得到了确认。膳食胆固醇未改变低密度脂蛋白受体的表达。关键的是，在喂食含1%胆固醇饲料的大鼠肝脏中，催化胆汁酸合成限速步骤的胆固醇7α羟化酶的表达增加了4倍多。相比之下，对膳食胆固醇不具有抗性的小鼠肝脏中胆固醇7α羟化酶（CYP7A1）蛋白水平较低，在喂食含2%胆固醇的饲料后其水平并未升高。
