棕色脂肪细胞脂滴与线粒体锚定的功能与机制研究

白色脂肪组织的棕/米色化研究，为降低机体脂肪、减缓代谢疾病的发生发展提供新的解决思路和方法。但棕/米色脂肪细胞中参与脂质代谢的脂滴和线粒体，如何互作以促进脂肪酸运输、氧化及产热，仍需深入解析。我们通过纯化小鼠棕色脂肪和分化的棕/米色脂肪细胞的脂滴和线粒体，发现一类脂滴锚定线粒体（LDAM）。LDAM的形成，与胞浆线粒体（CM）的差异，物理接触是否促使脂肪酸直接从脂滴转运到线粒体，及它们对冷刺激的产热反应，对阐明白色脂肪棕/米色化至关重要。因此，我们计划将小鼠饲养在30度，23度和6度培养箱，纯化棕色脂肪的脂滴和线粒体，进行比较蛋白组学分析，找出两种线粒体的蛋白表达差异，筛选LDAM高表达蛋白。通过改变这些蛋白在棕/米色脂肪细胞和小鼠棕色脂肪中的表达，研究它们对LDAM形成及功能的调控。揭示LDAM形成的分子机制，特别是脂滴和线粒体间脂肪酸转运机制，为改善代谢类疾病提供很好的指导方向。

The studies of browning/beigeing of white adipose tissue have provided new insights and methods for reducing fat accumulation and the occurrence and development of metabolic diseases. However, how the contact between lipid droplets and mitochondria is involved in lipid metabolism in brown or beige adipocytes for fatty acid transport, oxidation and thermogenesis remains to be illustrated. Our previous study identified the lipid droplet-anchored mitochondria (LDAM) by purifying lipid droplets and mitochondria from mouse brown adipose tissue and from differentiated brown/beige adipocytes. The formation of LDAM, the differences between LDAM and cytoplasmic mitochondria (CM), the possibility of direct transport of fatty acids from lipid droplets to mitochondria through the physical contact, as well as the thermogenic response to cold stimuli are very important for understanding the browning/beigeing of white adipose tissue. Therefore, we plan to purify lipid droplets and mitochondria from mice that are housed in incubators at 30C, 23C, and 6C, perform a comparative proteomic analysis of these two organelles to find the differences of protein expression, and identify the highly expressed proteins in LDAM. Then we will utilize molecular genetic tools including CRISPER-Cas9, AAV, and transgenic to alter the expression and activity of selected proteins. The effects of these proteins on the formation and function of LDAM in brown/beige adipocytes and in mouse brown adipose tissue are going to be examined. Our preliminary results revealed that a lipid transport protein VPS13C was highly enriched in LDAM, thus, we will first study its function in LDAM. Revealing the molecular mechanisms of LDAM formation, especially the mechanism of fatty acid transport between lipid droplets to mitochondria, will provide a better direction for prevention and therapeutic treatment of the metabolic disorders such as obesity and diabetes.