DIETARY FAT REGULATION OF HEPATIC GENE EXPRESSION

膳食多不饱和脂肪酸(PUFA)，尤其是 富含20碳和22碳(n-3)脂肪酸，有几种独特的 代谢作用包括抑制极低密度脂蛋白、抑制 胆固醇的合成和某些生长的调节 癌症。PUFA的一个特别耐人寻味的特点是他们的 调节几个与脂质有关的基因表达的能力 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，PUFA 抑制脂肪酸合成酶和S14的表达 蛋白质，一种可能与脂肪生成相关的蛋白质。多不饱和脂肪酸被抑制 肝细胞基因Fas和S14基因表达下调 通过抑制基因转录的水平。这些研究 提示膳食脂肪可能是肝脏的重要介质 在核水平上的基因表达。我们认为多不饱和脂肪酸可以抑制 干扰正常的Fas和S14基因转录 对这两种疾病起作用的内分泌信号机制 基因(如T3或胰岛素)或多不饱和脂肪酸通过独特的 控制这些基因转录的反式作用因子 基因。为了验证这一假设，以下研究包括 建议：1)表征体内(在大鼠)和体外(在 肝细胞)对Fas和S14基因转录的调节 膳食饱和、单、双饱和和多烯脂肪酸； 2)确定特定的PUFA调节的顺式作用元件 利用广泛鉴定的基因控制S14基因转录 大鼠肝脏S14染色质结构模型。为了证实内幕 体内研究，S14-CAT(SL4-氯霉素乙酰转移酶)和 Fas-CAT融合基因将用于转染培养的 肝细胞。3)识别特定的多不饱和脂肪酸调节的反式作用 对照组和饲喂多不饱和脂肪酸大鼠肝细胞核提取液的影响因素 将检查对DNA-蛋白质相互作用的具体影响 在S14和Fas基因的调节区内使用 体外转录起始和凝胶漂移的建立 分析。从这些研究中获得的信息将包括 重大的生物医学重要性，因为阐明了 多不饱和脂肪酸调控基因表达的分子机制 编码参与脂质合成的蛋白质可能会允许 开发潜在的降血脂药物，以及提供 一种开发缓蚀剂的新方法的洞察 它可能会被用作抗肥胖剂。最后，它不是 不合理地期望多不饱和脂肪酸基因控制机制可能 超越了脂肪生成，可以解释其他新陈代谢行为 多不饱和脂肪酸。

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.