Role of Membrane Modifications in the Bioactivities of Conjugated Linoleic Acids

膜修饰在共轭亚油酸生物活性中的作用

• 批准号: 8727969
• 负责人: PAPASANI V SUBBAIAH
• 金额: --
• 依托单位: JESSE BROWN VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8727969
• 关键词: Adipocytes; Adipose tissue; Adverse effects; Affect; Animals; Atherosclerosis; Binding Proteins; Biochemical; Biological; Cell membrane; Cells; Clinical Trials; Conflict (Psychology); Conjugated Linoleic Acids; Cultured Cells; Dairy Products; Data; Development; Diabetes Mellitus; Diet; Disease; Endoplasmic Reticulum; Environment; Exhibits; Fatty Acids; Fatty Liver; Gene Targeting; Genes; Genetic Transcription; Goals; Health; Health care facility; Heart Diseases; Heat shock proteins; Hepatocyte; Human; In Vitro; Inflammation; Insulin; Insulin Receptor; Insulin Resistance; Insulin Signaling Pathway; Isomerism; Lead; Ligands; Linoleic Acids; Lipids; Liver; Malignant Neoplasms; Meat; Membrane; Modification; Molecular; Mus; Muscle Cells; Nutraceutical; Obesity; Omega-3 Fatty Acids; Phospholipids; Positioning Attribute; Prevalence; Property; Proteins; Rattus; Receptor Signaling; Regulatory Element; Reporting; Risk Factors; Role; Ruminants; Signal Pathway; Signaling Protein; Species Specificity; Sterols; Structure; Subcellular Fractions; Testing; Tissues; Veterans; Work; base; biological adaptation to stress; endoplasmic reticulum stress; glucose uptake; glycogenesis; in vivo; insulin sensitivity; lipid biosynthesis; lipid metabolism; novel; obesity prevention; obesity treatment; protein expression; protein function; public health relevance; receptor; stress protein; transcription factor

DESCRIPTION (provided by applicant): The major goal of this proposal is to investigate the mechanism of action of conjugated linoleic acids (CLA), the naturally occurring isomers of linoleic acid (LA), which have several unique physicochemical properties and biological activities. The two major CLA isomers in the dairy products and meats, namely cis 9 trans 11 CLA, and trans 10 cis 12 CLA, have several isomer-specific and species-specific beneficial effects, including anti-cancer and anti-obesity effects. However, they are also known to cause undesirable effects such as insulin resistance and fatty liver in certain species but not others. Despite extensive studies, the mechanism of action of CLA is largely unknown. In this proposal, we will test the novel hypothesis that the CLA act through modification of the membrane structure, especially the raft domains of the plasma membrane, and the micro environment of the endoplasmic reticulum (ER). We will first determine the incorporation profiles of different CLA isomers into membranes of cultured hepatocytes, adipocytes, and myocytes of human and mouse origins. These studies will determine to what extent specific CLA isomers modify the lipid and fatty acid composition of the raft domains and the ER, and whether there is a tissue- and species- specificity in the incorporation profiles and membrane composition changes. We will also investigate the effect of the presence of CLA at the sn-1 position of phospholipids on the properties of the membranes, since our preliminary studies show that unlike LA, the CLA are preferentially incorporated into the sn-1 position of cellular phospholipids. We will next compare the in vivo incorporation profiles of dietary CLA in mice and rats, since these two animal species respond very differently to CLA, especially with regard to insulin resistance and fatty liver development. The effect of CLA on the distribution of raft-associated proteins will be investigated in cultured cells, as well as in primary adipocytes and hepatocytes from mice and rats. The function of raft associated proteins, specifically those involved in the insulin receptor signaling pathway will be studied following the CLA enrichment and insulin stimulation of the cells in vitro. In addition, the effectof CLA enrichment of cell membranes on glucose uptake, glycogenesis, and lipogenesis will be assessed. These studies should show whether the isomer- specific effects of CLA on insulin resistance are due to their modification of membrane structure. Finally, we will test the hypothesis that specific CLA species induce ER stress, and consequently promote the development of fatty liver and insulin resistance. We propose that the previously reported effects of CLA on the transcription of various genes involved in lipid metabolism and inflammation are due to the altered membrane composition of ER, which in turn affects the activation of transcription factors including sterol regulatory element binding proteins (SREBPs), the master regulators of lipid metabolism. The effect of various CLA isomers on ER lipid composition and the induction of ER stress proteins will be correlated with the activation of the SREBPs and the expression of their target genes. The results from all these studies should lead to a better understanding of the isomer-specific, tissue-specific, and species-specific actions of CLA, and to a more rational use of these nutraceutical agents for treatment or prevention of obesity, diabetes and other diseases.

描述(由申请人提供)： 这项建议的主要目的是研究共轭亚油酸(CLA)的作用机制，共轭亚油酸是亚油酸(LA)的天然异构体，具有几种独特的物理化学性质和生物活性。乳制品和肉类中的两种主要共轭亚油酸异构体，即顺9反11共轭亚油酸和反10顺12共轭亚油酸，具有多种异构体特异性和物种特异性的有益作用，包括抗癌和抗肥胖作用。然而，众所周知，它们也会在某些物种中引起不良影响，如胰岛素抵抗和脂肪肝，但在其他物种中则不会。尽管有广泛的研究，但共轭亚油酸的作用机制在很大程度上是未知的。在这个提议中，我们将检验这一新的假设，即CLA通过改变膜结构，特别是质膜的RAFT结构域和内质网(ER)的微环境来发挥作用。我们将首先确定不同CLA异构体对人和小鼠来源的培养肝细胞、脂肪细胞和肌细胞膜的掺入情况。这些研究将确定特定的CLA异构体在多大程度上改变RAFT结构域和内质网的脂肪和脂肪酸组成，以及在掺入谱和膜组成变化中是否存在组织和物种特异性。我们还将研究CLA在磷脂sn-1位的存在对膜性能的影响，因为我们的初步研究表明，与LA不同，CLA优先结合到细胞磷脂的sn-1位。接下来，我们将比较小鼠和大鼠饮食中共轭亚油酸的体内掺入情况，因为这两种动物对共轭亚油酸的反应非常不同，特别是在胰岛素抵抗和脂肪肝发展方面。此外，还将研究共轭亚油酸对RAFT相关蛋白在培养细胞中分布的影响。 与小鼠和大鼠的原代脂肪细胞和肝细胞一样。RAFT相关蛋白的功能，特别是那些参与胰岛素受体信号通路的蛋白，将在细胞体外CLA浓缩和胰岛素刺激后进行研究。此外，还将评估细胞膜上共轭亚油酸的增加对葡萄糖摄取、糖生成和脂肪生成的影响。这些研究应该表明，共轭亚油酸对胰岛素抵抗的异构体特异性作用是否源于它们对膜结构的改变。最后，我们将验证这一假说，即特定的CLA物种诱导ER应激，从而促进脂肪肝和胰岛素抵抗的发展。我们认为，CLA对多种参与脂代谢和炎症的基因转录的影响是由于内质网膜成分的改变，进而影响转录因子的激活，包括类固醇调节元件结合蛋白(SREBPs)，它是脂代谢的主要调节因子。不同CLA异构体对ER脂组成的影响和ER应激蛋白的诱导将与SREBPs的激活及其靶基因的表达有关。所有这些研究的结果应该有助于更好地理解CLA的异构体特异性、组织特异性和物种特异性的作用，并更合理地使用这些营养制剂来治疗或预防肥胖、糖尿病和其他疾病。