Regulation of Intestinal Bile Acid Absorption in Health and Cholesterol-Related Disorders

健康和胆固醇相关疾病中肠道胆汁酸吸收的调节

• 批准号: 10486535
• 负责人: Waddah A. Alrefai
• 金额: --
• 依托单位: JESSE BROWN VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-04-01 至 2026-09-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10486535
• 关键词: ASBT protein; Acids; Acylation; Acyltransferase; Address; Bile Acids; Binding Proteins; Biochemical; Biological Models; Bioluminescence; Cardiovascular Diseases; Carrier Proteins; Cell membrane; Cells; Chemistry; Cholesterol; Cholesterol Homeostasis; Cholestyramine; Cysteine; Data; Deterioration; Development; Diabetes Mellitus; Diet; Dietary Fatty Acid; Disease; Effectiveness; Eicosapentaenoic Acid; Enterohepatic Circulation; Enzymes; Equilibrium; Fatty Acids; Fatty acid glycerol esters; Fish Oils; General Population; Health; High Fat Diet; Homeostasis; Hospitalization; Human; Hyperlipidemia; Individual; Intestines; Knockout Mice; Label; Lead; Light; Link; Lipids; Liver; Liver Fibrosis; Mediating; Membrane; Membrane Lipids; Membrane Microdomains; Membrane Proteins; Metabolic; Metabolic Diseases; Metabolic dysfunction; Metabolic syndrome; Methods; Modality; Modeling; Molecular; Mus; Oleates; Omega-3 Fatty Acids; Palmitates; Pathway interactions; Patients; Plant Resins; Plasma; Play; Post-Translational Protein Processing; Prevalence; Prevention; Recommendation; Reducing diet; Regulation; Response Elements; Role; Saturated Fatty Acids; Small Intestines; Sterols; Testing; Therapeutic; Time; Transgenic Mice; Transgenic Organisms; Unsaturated Fatty Acids; Veterans; Wild Type Mouse; absorption; cardiovascular risk factor; cholesterol absorption; deacylation; dietary; ezetimibe; feeding; high risk; high risk population; hypercholesterolemia; in vitro Model; inhibitor; lipid metabolism; liver inflammation; liver injury; long chain fatty acid; mouse model; novel; patient population; posttranscriptional; response; thioester

The ileal apical sodium-dependent bile acid transporter (ASBT) is crucial for the enterohepatic circulation of bile acids and plays a key role in maintaining bile acid, lipid, and cholesterol balance. Emerging evidence suggests that ASBT is an attractive therapeutic approach to restore metabolic functions and lower plasma cholesterol. This is particularly important in light of recent findings indicating the need to lower cholesterol to very low levels in individuals with high risk for developing cardiovascular diseases (CVDs) such as the veterans. Achieving such stringent target remains challenging in many cases despite the use of cholesterol synthesis inhibitors and blockers of cholesterol absorption. In this regard, dietary fatty acids are known to influence metabolic functions as well as lipid and cholesterol homeostasis. A recent study showed that the effectiveness of ASBT inhibition in restoring normal metabolic functions depends on the types of fatty acids present in the diet. However, specific effects of different types of fatty acids on ASBT function are not fully understood. Our recent novel data using resin-assisted capture (Acyl-RAC) and click-chemistry based metabolic labeling approaches provided evidence that ASBT protein is subject to s-acylation, a reversible post-translational modification where fatty acids attach to cysteine residues of membrane proteins governing their membrane raft localization and function. We have shown that incorporation of the unsaturated fatty acid oleate or omega-3 fatty acid eicosapentaenoic acid (EPA) into ASBT was associated with a significant decrease in its function. We have previously demonstrated that ASBT is regulated by post-transcriptional mechanisms including its association with membrane lipid raft microdomains. Our preliminary findings showed that feeding a diet rich with fish oil decreased ASBT function and association with lipid rafts in mice. Thus, identifying mechanisms that target s-acylation could be beneficial in inhibiting ASBT function as well as restoring normal lipid and cholesterol homeostasis. ASBT activity and association with lipid rafts were increased in a transgenic mouse model (ISR2tg) with intestine- specific overactivation of the Sterol Response Elements Binding Protein (SREBP2). Our recent data demonstrated that ISR2tg mice develop hypercholesterolemia and severe hepatic inflammation and fibrosis when fed a high fat high cholesterol diet and blocking bile acid absorption by cholestyramine reduced the diet-induced liver injury. ASBT function and association with lipid rafts are increased in ISR2tg mice. Based on these data, our proposed studies will test the hypothesis that acylation is critical for ASBT function and association with lipid rafts and that intestine-specific mechanisms are involved in regulating ASBT acylation (Specific aim 1). Studies in Specific Aim 2 will elucidate mechanisms mediating the effects of omega-3 fatty acids on ASBT function and s-acylation in in vitro models including enteroids and will examine their effects on bile acid homeostasis as well as lipid and cholesterol metabolism in wildtype and ASBT knockout mice. To investigate the beneficial effects of blocking ASBT acylation, our studies will further utilize ISR2tg mice fed a high fat high cholesterol diet as a unique model to examine the effects of feeding dietary omega-3 poly unsaturated fatty acids on ASBT acylation and metabolic dysfunction (Specific Aim 2). Our findings represent a paradigm shift in our understanding of the link between fatty acids and bile acid homeostasis. The proposed studies are highly significant and are likely to unravel novel avenues pertaining to potential beneficial effects of blocking ASBT function and acylation in restoring metabolic functions and cholesterol homeostasis.

回肠顶端钠依赖性胆汁酸转运蛋白（ASBT）对于肠肝脏至关重要 胆汁酸的循环和在维持胆汁酸，脂质和胆固醇平衡中起关键作用。 新兴证据表明，ASBT是恢复代谢的一种有吸引力的治疗方法 功能和较低的血浆胆固醇。根据最近的发现，这一点尤其重要 表明需要将胆固醇降低到具有高风险的人的水平很低 发展心血管疾病（CVD），例如退伍军人。实现这种严格的目标 尽管使用胆固醇合成抑制剂，但在许多情况下仍然具有挑战性 吸收胆固醇的阻滞剂。在这方面，已知饮食脂肪酸会影响 代谢功能以及脂质和胆固醇稳态。最近的一项研究表明 ASBT抑制在恢复正常代谢功能方面的有效性取决于 饮食中存在的脂肪酸。但是，不同类型的脂肪酸对ASBT的特定影响 功能尚未完全理解。我们最近使用树脂辅助捕获（Acyl-rac）的新型数据 基于点击化学的代谢标记方法提供了证据表明ASBT蛋白是 受S酰基化的约束，这是一种可逆的翻译后修饰，其中脂肪酸附着在 膜蛋白的半胱氨酸残基控制其膜木筏定位和功能。 我们已经表明，掺入不饱和脂肪酸或omega-3脂肪酸 Eicosapentaenoic（EPA）进入ASBT与其功能显着降低有关。 我们以前已经证明，ASBT受到转录后机制的调节 包括其与膜脂质筏微区的关联。我们的初步发现显示 富含鱼油的饮食降低了ASBT功能，并与脂质筏相关 老鼠。因此，识别靶向S酰化的机制可能有益于抑制ASBT 功能以及恢复正常的脂质和胆固醇稳态。 ASBT活动和 在转基因小鼠模型（ISR2TG）中，与脂质筏的关联与肠道相关 固醇反应元件结合蛋白（SREBP2）的特异性过度激活。我们最近 数据表明，ISR2TG小鼠患有高胆固醇血症和严重的肝 喂养高脂肪高胆固醇饮食并阻止胆汁酸时的炎症和纤维化 胆碱胺吸收减少了饮食诱导的肝损伤。 ASBT功能和关联 ISR2TG小鼠中脂质筏的增加。基于这些数据，我们提出的研究将测试 假说酰化对于ASBT功能至关重要，并且与脂质筏相关，并且 肠道特异性机制参与调节ASBT酰基化（特定目标1）。研究 在特定目标中2将阐明介导omega-3脂肪酸对的机制 体外模型中的ASBT功能和S-酰基化，包括肠toid，并将检查其效果 在WildType和Asbt中的胆汁酸稳态以及脂质和胆固醇代谢 淘汰老鼠。为了研究阻断ASBT酰基化的有益作用，我们的研究将 进一步利用喂养高脂肪高胆固醇饮食的ISR2TG小鼠作为一种独特的模型来检查 喂食饮食omega-3多饱和脂肪酸对ASBT酰化和代谢的影响 功能障碍（特定目标2）。我们的发现代表了我们对 脂肪酸与胆汁酸稳态之间的联系。拟议的研究非常重要 并且可能会揭示与阻塞ASBT潜在有益作用有关的新型途径 恢复代谢功能和胆固醇稳态的功能和酰化。