线粒体氧化磷酸化功能对成人脂肪细胞体积及脂肪酸代谢的影响

Obesity is increasing in an epidemic manner in most countries and constitutes a public health problem by enhancing the risk for cardiovascular disease and metabolic disorders such as type 2 diabetes. The factors determining fat mass in adult humans are not fully understood, but enlargement of cell size by increasing lipid storage in already developed fat cells (adipocytes) is thought to be most important. Cell size influences several aspects of adipocyte metabolism, and active mitochondrial is crucial for adipocyte function, including lipogenesis and lipolyis. Changes in mitochondrial oxidative capacity may explain some of the variations in the behavior of adipose tissue linked to obesity and related metabolic disorders. The aim of present study was to explore whether adipocyte mitochondrial function and content are associated with obesity, cell size and depots in non-diabetes adults. Omental and subcuteous adipose tissue samples are collected from non-diabetes patients. Using the property of large cells to come back up to the surface faster than small cells when they are mixed in aqueous solution, two populations of cells with different size are separated from each sample. For both large and small cells, mitochondria oxygen consumption rate (OCR), the abundance of mtDNA-encoded NADH dehydrogenase 1 genes (ND1/28S) and Citrate synthase (CS) activity and expression levels of HSL and CPT-1 are measured using a real-time quantitative PCR system, Clark-type oxygen electrode, spectrophotometrical method and western-blot et al. we plan to perform the assessment that whether mitochondrial function, mitochondrial abundance and lipid metabolism level are different in large and small adipocyte from the same/different depots, and whether these comparisons are confounded by the obesity status from whom the cells are obtained. We propose to detect some cell types that have rich mitochondria or have stronger ability to burn its own stored fat to produce energy or just produce heat with uncoupling, We hope that by collecting these preliminary data we can determine if there are potential differences that warrant future studies both into what might regulate mitochondrial function but also the downstream consequences of differences in function, which might provide new therapeutic target for pharmacological intervention in obesity.

脂肪细胞体积增大是成人肥胖症主要表现。目前认为线粒体功能障碍参与肥胖症的病理过程，但它和脂肪细胞脂质储积、体积增大之间的因果关系尚不清楚，特别是相同内环境下脂肪细胞体积差异较大，线粒体是否起了关键性的作用，目前无论在动物模型还是人体，国内外都未有相关的研究。本研究主要探讨不同肥胖度个体脂肪细胞线粒体氧化磷酸化功能对细胞体积和脂肪酸代谢水平的影响。目前课题组已能将脂肪细胞按照体积分组，分离获得足量有活性的线粒体进行氧消耗率测定以评估氧化磷酸化功能。下一步将比较不同肥胖度个体、大小脂肪细胞间线粒体DNA量、氧化磷酸化水平、三羧酸循环、脂肪酸代谢关键酶活性的差异，并通过前脂肪细胞诱导分化观察线粒体生成关键基因在不同肥胖度个体脂肪细胞分化过程中的表达情况。本研究结论可以明确线粒体在肥胖发生中的作用，为寻找线粒体功能强、易消耗能量的脂肪细胞提供线索，为更好的调控体脂分布、防治肥胖症提供新思路。

脂肪细胞体积增大是成人肥胖症主要表现。目前认为线粒体功能障碍参与肥胖症的病理过程，但它和脂肪细胞脂质储积、体积增大之间的因果关系尚不清楚，特别是相同内环境下脂肪细胞体积差异较大，线粒体是否起了关键性的作用，目前无论在动物模型还是人体，国内外都未有相关的研究。本研究主要探讨不同肥胖度个体脂肪细胞线粒体氧化磷酸化功能对细胞体积和脂肪酸代谢水平的影响。本项目研究结果显示肥胖患者较非肥胖者脂肪细胞线粒体功能（OCR和CS活性）差、脂肪分解（HSL酶活性）及脂肪酸代谢（CPT-1mRNA水平和酶活性）水平低。但同一个体中，不同体积、不同部位脂肪细胞线粒体功能无明显差异。不同肥胖度个体的前脂肪细胞在分化过程中线粒体生成的关键因子NRF-1\TFMA表达水平无明显差异，推测在体内环境中糖脂代谢紊乱、氧化应激、慢性炎症等过程导致了肥胖患者线粒体功能障碍，而线粒体的氧化磷酸化功能下降反过来又加重了细胞内的糖脂代谢紊乱和氧化应激。肥胖合并维生素D缺乏人群补充维生素D和钙剂不能改善肥胖相关代谢异常。本研究结论进一步明确了人体脂肪细胞线粒体氧化磷酸化功能在肥胖发生中的作用，为在人体内诱导生成线粒体功能强、易消耗能量的米色脂肪细胞提供实验基础，为更好的调控体脂分布、防治肥胖症提供新思路。