DIETARY FAT REGULATION OF HEPATIC GENE EXPRESSION

膳食脂肪对肝基因表达的调节

基本信息

批准号：
3244555
负责人：
DONALD B JUMP
金额：
$ 15.31万
依托单位：
MICHIGAN STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
1991
资助国家：
美国
起止时间：
1991-08-01 至 1995-07-31
项目状态：
已结题

项目摘要

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.

膳食多不饱和脂肪酸（PUFA），特别是那些富含 20 和 22 碳 (n-3) 脂肪酸，具有多种独特的代谢作用，包括抑制 VLDL、抑制胆固醇合成和某些生长的调节癌。 PUFA 的一个特别有趣的特征是它们调节与脂质有关的多个基因表达的能力代谢，包括脂肪酸合酶、葡萄糖-6-磷酸脱氢酶和载脂蛋白。我们最近报道了PUFA 抑制脂肪酸合酶 (FAS) 和 S14 的表达蛋白质，一种假定的脂肪生成相关蛋白质。 PUFA 抑制通过减少肝细胞 mRNA 来表达 FAS 和 S14 基因通过抑制基因转录来达到水平。这些研究表明膳食脂肪可能是肝脏疾病的重要介质核水平的基因表达。我们建议PUFA抑制通过干扰FAS和S14基因的正常转录对这两种情况有效的内分泌信号机制基因（即 T3 或胰岛素）或 PUFA 通过独特的作用起作用控制这些转录的反式作用因子基因。为了验证这一假设，进行了以下研究建议：1）表征体内（大鼠）和体外（小鼠）肝细胞）FAS 和 S14 基因转录的调节膳食饱和脂肪酸、单饱和脂肪酸、二饱和脂肪酸和多烯脂肪酸； 2) 确定特定的 PUFA 调节的顺式作用元件使用广泛表征的控制 S14 基因转录大鼠肝脏S14染色质结构模型。为了证实在体内研究，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PUFA调节的反式作用对照组和 PUFA 喂养大鼠的因子、肝核提取物将检查对 DNA-蛋白质相互作用的具体影响在 S14 和 FAS 基因的调控区域内使用建立体外转录起始和凝胶转移分析。从这些研究中获得的信息将是具有重要的生物医学重要性，因为阐明 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药物，并提供深入了解开发抑制剂的新方法其可能具有作为抗肥胖剂的效用。最后，它不是期望 PUFA 基因控制机制可能是不合理的超越脂肪生成并可以解释其他代谢行为多不饱和脂肪酸。