DIETARY FAT REGULATION OF HEPATIC GENE EXPRESSION

膳食多不饱和脂肪酸（PUFA），尤其是 富含20-和22-碳（n-3）脂肪酸，有几个独特的 代谢 作用包括抑制VLDL，抑制 胆固醇合成，和 调节某些 癌 PUFA的一个特别有趣的特征是它们的 调节参与脂质代谢的几种基因表达的能力 代谢包括脂肪酸合成酶、葡萄糖-6-磷酸 脱氢酶和载脂蛋白。 我们最近报道说， 抑制脂肪酸合成酶（FAS）和S14的表达 蛋白质，一种假定的脂肪生成相关蛋白质。 PUFA抑制 通过降低肝细胞mRNA表达FAS和S14基因 通过抑制基因转录水平。 这些研究 提示膳食脂肪可能是肝损害的重要介质 基因在细胞核水平的表达。 我们建议PUFA抑制 干扰FAS和S14基因的正常转录 内分泌信号机制，这是有效的，这两个 基因（即T3或胰岛素）或PUFA通过独特的 控制这些转录的反式作用因子 基因. 为了验证这一假设，以下研究是 提议：1）表征体内（大鼠）和体外（ FAS和S14基因转录的调控 膳食饱和、单饱和、双饱和和多烯脂肪酸; 2)为了鉴定特定的PUFA调节的顺式作用元件， 控制S14基因转录，使用广泛表征的 大鼠肝S14染色质结构模型。 以证实 体内研究，S14-CAT（S14-氯霉素乙酰转移酶）和 FAS-CAT融合基因将被用于检测培养的 肝细胞3)为了确定特定的PUFA调节的反式作用， 因子，对照组和PUFA喂养大鼠的肝核提取物 将检查对DNA-蛋白质相互作用的特定影响 在S14和FAS基因的调控区域内， 建立体外转录起始和凝胶迁移 分析. 从这些研究中获得的信息将是 重要的生物医学意义，因为阐明了 PUFA控制基因表达的分子机制 编码参与脂质合成的蛋白质可能允许 开发潜在的降血脂剂，以及提供 深入了解开发抑制剂的新方法 其可用作抗肥胖剂。 最后， 不合理的期望，PUFA的基因控制机制可能 并能解释其他代谢作用 的PUFA。

Dietary polyunsaturated fatty acids (PUFA), particularly those rich in 20- and 22-carbon (n-3) fatty acids, have several unique metabolic effects including suppression of VLDL, inhibition of cholesterol synthesis, and modulation of growth of certain carcinomas. A particularly intriguing feature of PUFA is their ability to regulate expression of several genes involved in lipid metabolism including fatty acid synthase, glucose-6-phosphate dehydrogenase and apo-lipoprotein. We recently reported that PUFA suppressed the expression of fatty acid synthase (FAS) and the S14 protein, a putative lipogenesis-related protein. PUFA inhibited FAS and S14 gene expression by reducing hepatic cellular mRNA levels through inhibition of gene transcription. These studies suggest dietary fats may represent important mediators of hepatic gene expression at the nuclear level. We propose that PUFA inhibit FAS and S14 gene transcription by interfering with the normal endocrine signalling mechanisms which are operative for these two genes (i.e. T3 or insulin) or that PUFA act through unique trans-acting factors which control the transcription of these genes. In order to test this hypothesis, the following studies are proposed: 1) To characterize the in vivo (in rats) and in vitro (in hepatocytes) regulation of FAS and S14 gene transcription by dietary saturated, mono-, di-saturated and polyenic fatty acids; 2) To identify specific PUFA-regulated cis-acting elements which control S14 gene transcription using the extensively characterized rat liver S14 chromatin structure model. To corroborate the in vivo studies, S14-CAT (Sl4-chloramphenicol acetyl transferase) and FAS-CAT fusion genes will be used to transfect cultured hepatocytes. 3) To identify specific PUFA-regulated trans-acting factors, hepatic nuclear extracts from control and PUFA fed rats will be examined for specific effects on DNA-protein interactions within the regulatory regions of the S14 and FAS genes using established in vitro transcription initiation and gel shift analysis. The information gained from These studies will be of significant biomedical importance because elucidation of the molecular mechanisms by which PUFA control the expression of genes coding for proteins involved in lipid synthesis may allow for the development of potential hypolipemic agents, as well as provide insight into a novel approach for the development of inhibitors which may have utility as anti-obesity agents. Finally, it is not unreasonable to expect that the PUFA mechanism of gene control may extend beyond lipogenesis and could explain other metabolic actions of PUFA.