Plasma free fatty acids and albumin in metabolic disease

肥胖导致血浆游离脂肪酸（FFA）浓度升高，肝脏和骨骼肌FFA供应过量。由此产生的组织脂质积累增加了胰岛素抵抗、非酒精性脂肪肝（NAFLD）和2型糖尿病的风险。通过直接解决肝脏和肌肉中过量脂质摄取的问题，减少FFA供应的干预措施可能会治疗肥胖的这些合并症。白蛋白是循环中促进FFA从脂肪转运到其他组织的主要蛋白质。在评价预防胰岛素抵抗和代谢组织中脂质蓄积的潜在靶点时，初步实验表明，白蛋白敲除小鼠表现出血浆FFA降低、肝脂质降低和胰岛素敏感性改善。虽然靶向脂解以降低血浆FFA在临床前和临床研究中遇到了重大缺陷，但白蛋白是一个有前途的治疗靶点。虽然白蛋白是体内常见的蛋白质，但预期FFA与白蛋白结合的部分抑制仍具有良好的耐受性，因为即使先天性白蛋白缺乏症成人患者完全不存在白蛋白，通常也仅与轻度或完全不存在症状相关。此外，初步研究表明，FFA-白蛋白相互作用可以通过内源性代谢物调节，支持FFA-白蛋白结合可以用小分子抑制剂靶向的观点。然而，关键的知识差距仍然存在，必须解决开发白蛋白作为代谢性疾病的治疗靶点。通过减少FFA与白蛋白的结合来减少血浆FFA是否可以预防或治疗肥胖症中的代谢失调综合征，这一点尚未确定。据推测，减少血浆中白蛋白相关FFA的丰度将降低肥胖小鼠的NAFLD病理、肌内脂质和胰岛素抵抗的程度。如果这种方法是有效的，FFA-白蛋白相互作用的特异性抑制剂在未来可能是有益的。在Aim-1中，将通过评估胰岛素敏感性以及脂肪组织、肝脏和肌肉中的分子和生化反应，在肥胖小鼠模型中研究血浆FFA降低的影响。将通过小鼠白蛋白基因敲除实现血浆FFA降低。为了提供新发现的背景，将结果与表现出由钝性脂解（脂肪甘油三酯脂肪酶的脂肪组织特异性敲除）引起的血浆FFA降低的小鼠模型进行比较。在Aim-2中，将研究相同的小鼠系以评估禁食和运动期间的血糖调节，以评估对代谢应激源的耐受性。在Aim- 3中，将使用体外生化测定和分子对接评估来研究作为CFA-白蛋白结合潜在抑制剂的内源性小分子。阐明小分子对FFA-白蛋白结合的影响将为未来的治疗策略铺平道路。这些结果将增强对代谢疾病中脂质运输的科学理解，FFA-白蛋白结合可能成为NAFLD，胰岛素抵抗和2型糖尿病的治疗靶点。

Obesity leads to elevated plasma free fatty acid (FFA) concentration and excessive supply of FFA to the liver and skeletal muscle. The resulting tissue lipid accumulation increases risk for insulin resistance, non-alcoholic fatty liver disease (NAFLD), and type 2 diabetes. By directly addressing the problem of excessive lipid uptake in the liver and muscle, interventions that reduce FFA supply could potentially treat these comorbidities of obesity. Albumin is the primary protein in circulation that facilitates the transport of FFA from adipose to other tissues. In evaluating potential targets to prevent insulin resistance and lipid accumulation in metabolic tissues, preliminary experiments demonstrated that albumin knockout mice exhibit reduced plasma FFA, reduced hepatic lipids, and improved insulin sensitivity. While targeting lipolysis to reduce plasma FFA has encountered significant pitfalls in pre-clinical and clinical studies, albumin is a promising therapeutic target. While albumin is a common protein in the body, partial inhibition of FFA-binding to albumin is still expected to be well-tolerated, as even the complete absence of albumin in adults with congenital analbuminemia is typically associated with only mild or complete absence of symptoms. Furthermore, initial studies indicate that the FFA-albumin interaction can be modulated by endogenous metabolites, supporting the notion that FFA- albumin binding can be targeted with small molecule inhibitors. However, critical knowledge gaps remain that must be addressed to develop albumin as a therapeutic target for metabolic disease. It is not yet established if reducing plasma FFA by reducing its binding to albumin can prevent or treat the syndrome of metabolic dysregulation in obesity. It is hypothesized that reducing the abundance of albumin-associated FFA in plasma will decrease the degree of NAFLD pathology, intramuscular lipid, and insulin resistance in obese mice. If the approach is effective, specific inhibitors of FFA-albumin interaction may be beneficial in the future. In Aim-1, the effects of reduced plasma FFA will be studied in obese mouse models through assessment of insulin sensitivity, as well as molecular and biochemical responses in adipose tissue, liver, and muscle. Reduced plasma FFA will be achieved through albumin gene knockout in mice. To provide context for the novel findings, results will be compared to a mouse model that exhibits reduced plasma FFA resulting from blunted lipolysis (adipose tissue-specific knockout of adipose triglyceride lipase). In Aim-2 the same mouse lines will be studied to assess glycemic regulation during fasting and exercise, to assess tolerance to metabolic stressors. In Aim- 3, endogenous small molecules that are potential inhibitors of FFA-albumin binding will be studied using in vitro biochemical assays and molecular docking assessment. This elucidation of the impact of small molecules upon FFA-albumin binding will pave the way for future therapeutic strategies. The results will enhance scientific understanding of lipid trafficking in metabolic disease, and FFA-albumin binding may emerge as a therapeutic target for NAFLD, insulin resistance, and type 2 diabetes.