MODULATORS OF ALCOHOLIC LIPIDEMIA & STEATOSIS:KEY ROLE OF SCAVENGER RECEPTOR B I

描述（由申请人提供）：基本原理：肝脏清除率受体B类，I型受体（SRBI），一种高度糖基化的82 kDa蛋白，主要负责肝脏从高密度脂蛋白（HDL）摄取胆固醇酯，这一过程被称为逆向胆固醇转运（RCT）。PI的核心假设是，SRBI是迄今尚未被探索的慢性酒精诱导缺陷RCT的潜在靶点，这是由于相应的SRB1表达受损和/或翻译后修饰，这反过来可能影响其细胞内运输。最终的结果是酒精性高脂血症的同时发作。因此，阐明酒精对酒精性高脂血症患者SRB1功能和状态的影响具有重要的临床意义。同样，由于膳食甜菜碱对血浆和肝脏脂质具有显著的降低作用，因此研究甜菜碱是否通过调节SRB1的表达、翻译后修饰和功能来发挥其降血脂作用也同样重要。初步结果：PI有以下初步数据支持本提案：1。与对照组相比，酒精喂养大鼠肝细胞对正常高密度脂蛋白胆固醇的肝脏摄取减少了48% （p<0.05）。2. 乙醇下调肝脏SRB1基因表达51% （p<0.05）。3. 乙醇抑制SRB1肝相对糖基化率41% （p<0.05）。4. 乙醇的这些作用可以通过食用甜菜碱来减弱。基于这些数据和我们的新假设，我们希望实现以下具体目标：慢性乙醇和甜菜碱对SRB1和HDL协同作用在RCT调节中的可能作用及其与血浆脂质和脂蛋白、肝脏脂质和肝脏组织病理学的相关性。具体目标2。慢性乙醇和甜菜碱在SRB1表达的转录和转录后调控中的可能作用/s。具体目标3。慢性乙醇和甜菜碱在调节肝脏相对合成、糖基化速率和SRB1转运中的可能作用。因此，R21申请的主要重点将是确定SRB1作为慢性酒精暴露的新靶点的核心作用，并可能和逻辑上导致更详细的R01申请，研究SRB1在酒精性高脂血症发病机制中的新作用和功能。最后，测试膳食甜菜碱是否可以通过恢复正常的SRB1状态和功能来减轻乙醇的有害作用是治疗相关的。方法：我们将运用分子生物学、免疫组织化学和生化方法，利用体内动物模型和肝细胞系统来完成我们的特定目标。PI拥有强大的分子生物学和生物化学团队，在该提案的各个方面都具有专业知识。

DESCRIPTION (provided by applicant): Rationale: Hepatic Scavenger Receptor Class B, Type I receptor (SRBI), a highly glycosylated 82 kDa protein, is primarily responsible for hepatic cholesterol ester uptake from high density lipoproteins (HDL), a process termed Reverse Cholesterol Transport (RCT). PI's central hypothesis is that SRBI is a, hitherto unexplored, potential target for chronic alcohol-induced defective RCT that is due to corresponding impaired SRB1 expression and/or post-translational modifications, which in turn, could affect its intracellular trafficking. The net result would be the concomitant onset of alcoholic hyperlipidemia. Therefore, it is important and clinically relevant to delineate the actions of alcohol on SRB1 function and status in relation to alcoholic hyperlipidemia. Similarly, since dietary betaine has significant lowering effects on plasma and liver lipids, it is equally important to investigate whether betaine elicits its hypolipidemic actions by regulating the expression, post-translational modification and function of SRB1. Preliminary Results: PI has the following preliminary data in support of this proposal: 1. Liver uptake of cholesterol from normal HDL is decreased by 48% (p<0.05) when tested with hepatocytes from alcohol-fed rats compared to the control group. 2. Ethanol down regulates liver SRB1 gene expression by 51% (p<0.05). 3. Ethanol inhibits hepatic relative glycosylation rate of SRB1 by 41% (p<0.05). 4. These effects of ethanol are attenuated by dietary betaine. Based on these data and our novel hypotheses, we wish to accomplish the following specific aims: Specific Aim 1. Possible action/s of chronic ethanol and betaine on the synergistic functions of SRB1 and HDL in the regulation of RCT and correlation with plasma lipids & lipoproteins, liver lipids and liver histopathology. Specific Aim 2. Possible action/s of chronic ethanol and betaine in the transcriptional and post- transcriptional regulation of SRB1 expression. Specific Aim 3. Possible action/s of chronic ethanol and betaine in the regulation of hepatic relative synthetic & glycosylation rates and trafficking of SRB1. Thus, the major emphasis on this R21 grant application will be to establish a central role for SRB1 as a new target of chronic alcohol exposure and can potentially and logically lead to a more detailed R01 application on this novel role of SRB1 status and function in the pathogenesis of alcoholic hyperlipidemia. Finally, it is therapeutically pertinent to test whether dietary betaine can attenuate deleterious actions of ethanol by restoring the normal SRB1 status & function. Methods of Approach: We will accomplish our specific aims using an in vivo animal model & liver cell systems applying molecular biology, immuno-histochemistry and biochemical approaches. PI has a strong molecular biology & biochemical group with expertise in all aspects of this proposal. PUBLIC HEALTH RELEVANCE: It is goal of this exploratory grant application to establish that chronic ethanol exposure affects the cholesterol uptake function of SRB1, a specific receptor for HDL cholesterol leading to alcoholic steatosis. If so, it is clinically important to verify whether this defect is due to impaired SRB1 gene expression, its post-translational modification and its disposition.