ALCAT1在糖尿病肾病病理进程中调控线粒体自噬功能的机制研究

It is extremely important to identify novel interventions to halt the development of diabetic nephropathy (DN). A number of studies showed autophagy dysfunction play an important role in DN progression. ALCAT1 is a lysocardiolipin acyltransferase that catalyzes pathological cardiolipin remodeling in several aging-related diseases. We investigated a role for ALCAT1 in the development of NAFLD. We showed that the onset of diet-induced NAFLD caused autophagic arrest in hepatocytes, leading to mitochondrial dysfunction. In contrast, targeted deletion of ALCAT1 in mice prevented the onset of NAFLD. ALCAT1 deficiency also restored mitophagy, mitochondrial architecture. In support of a causative role of the enzyme in a mitochondrial etiology of the disease, hepatic ALCAT1 expression was significantly up-regulated in mouse models of NAFLD. We also found targeted deletion of ALCAT1 in diabetic mice prevented the development of DN. Mitochondrial dysfunction served as the common link for several key pathogenic pathways in DN. Therefore, whether ALCAT1 cause DN pathological progression by affecting mitophagy? Based on previous works, using targeted deletion of ALCAT1 mice, primary mouse proximal tubules cell isolation, culture and ALCAT1 overexpression technique, the study want to advance our understanding of a regulatory role of ALCAT1 in mitophagy function in diabetes and elucide the underlying molecular mechanisms. This study aim to elucidate the control of ALCAT1 on mitophagy is the pathogenesis of DN pathological progression. The completion of this study could extend our understanding of the pathogenesis of DN, and provide a new target for DN therapy, which has important theoretical significance.

阻止糖尿病肾病（DN）进展，改善预后，已成为一项重要的公共问题。大量文献指出自噬功能障碍在DN病理进程中起重要作用。但具体机制不清。我们近期研究发现心磷脂酰基转移酶1（ALCAT1）在脂肪肝小鼠肝脏中表达上调，肝细胞中线粒体自噬阻滞。而ALCAT1基因敲除阻止了脂肪肝发生，修复了线粒体自噬功能障碍，减轻了线粒体形态异常。在糖尿病模型中，ALCAT1敲除同样减轻了DN病理损伤。线粒体功能障碍是几个主要参与DN发生途径的共同环节。那么，线粒体自噬障碍是否是引发DN病理进程的始动因素？本课题拟在前期研究基础上，采用ALCAT1敲除和高表达技术，系统研究糖尿病状态下，ALCAT1对原代肾小管上皮细胞线粒体自噬功能的影响，并对其中的分子学机制进行探讨。旨在阐明ALCAT1对线粒体自噬功能的调控是DN病理进程的始动机制。这些研究可以拓展对DN发病机制的认识，为DN治疗提供新的靶点，具有重要的理论意义。

细胞线粒体功能障碍，是几个主要参与糖尿病肾病（Diabetic Nephropathy，DN ）发生途径的共同环节。线粒体形态正常转化依靠线粒体自噬完成。心磷脂酰基转移酶1（Lysocardiolipin acyltransferase 1，ALCAT1）是一种赖氨酸二脂蛋白酰基转移酶，在一些与衰老相关的疾病中催化病理性心磷脂重塑，使心磷脂在线粒体呼吸链传递过程中的功能发生变化，从而导致活性氧（reactive oxygen species, ROS)产物增多，氧化应激增强，最终出现线粒体功能障碍。本研究利用STZ诱导制造了糖尿病小鼠模型，并分离了糖尿病小鼠肾脏原代肾小管上皮细胞，对高糖状态下的线粒体自噬功能进行了研究，并对其中的分子机制进行探讨。本研究发现STZ诱导的野生型糖尿病小鼠肾脏组织出现纤维化，肾小球基底膜增厚，肾小管空泡变性，同时存在线粒体自噬功能亢进，线粒体结构功能障碍，AKT，ERK增殖相关通道表达增强，同时线粒体氧化呼吸链解偶联异常，氧化应激增强。相反，ALCAT1基因敲除减轻了糖尿病小鼠由于高糖毒性导致的肾脏纤维化，缓解了线粒体自噬功能亢进和线粒体功能障碍，ALCAT1基因敲除还改善了高糖毒性所导致的线粒体结构异常，减少了线粒体DNA（mtDNA）的突变，减轻了氧化应激，从而减缓了DN的病理进程。本研究提示ALCAT1缺失减缓了高糖毒性导致的线粒体自噬亢进和线粒体功能障碍，ALCAT1在DN的线粒体病因中具有重要作用，是DN病理进程的重要始动因素。本研究将DN，ALCAT1表达与线粒体功能障碍联系起来，为DN治疗寻找新的靶点提供了实验室依据。