Proliferation and function of fat cells of the obese in tissue: Fundamental research of the obesity

成熟的白色脂肪细胞（单室脂肪细胞）通常被认为处于终末分化，因此没有增殖能力。本实验室设计了一种新的方法，称为“天花板培养”，在体外培养单房脂肪细胞。在这样的培养条件下，脂肪细胞继续表现出脂质代谢的特定功能并广泛增殖。胞质内脂滴不抑制细胞分裂。单房脂肪细胞有两种增殖模式：“分室”细胞分裂，其中分裂细胞中的单个脂肪室被分解成多个液滴并均匀地分布在子细胞之间，而“保留室”细胞分裂，其中分裂细胞中的小室被最小程度地破坏，并由其中一个子细胞继承其形状，而另一个子细胞则得到只有少量细小的脂滴。这些发现表明，在体内的单房脂肪组织可能能够在某些条件下以这种模式增殖。根据这样的结果，在培养条件下检查了肥胖者的脂肪细胞。首先，胰岛素是一种脂肪生成因子，是肥胖的主要因素之一。因此，由胰岛素引起的脂肪细胞的“保腔”细胞分裂与肥胖者的高胰岛素血症是相容的。其次，肥胖者来源的大的单房脂肪细胞在培养条件下也能增殖，我们希望本研究所建立的培养体系对脂肪细胞生物学和肥胖发生机制的研究有一定的价值。

Mature white fat cells (unilocular fat cells) have generally been consifered to be in terminal differentiation and, hence, to have no proliferative ability. A new method, referred to as "ceiling culture", has been devised in our laboratory to culture unilocular fat cells in vitro. Under such culture conditions, the fat cells continue to exhibit specific functions of lipid metabolism and proliferate extensively. Intracytoplasmic lipid droplets did not inhibit division of the cells. There were two modes of proliferation of unilocular fat cells: "loculus-dividing" cell division, in which the single loculus of fat in the dividing cell was broken down into multiple droplets and distributed evenly between the daughter cells, and loculus-preserving" cell division, in which the loculus in the dividing cell was minimally broken down and inherited with its shape preserved by one of the daughter cells with the other getting only a small number of fine lipid droplets. Such findings suggest that unilocular fat tissue in vivo are probably capable of proliferation in such modes under some conditions. With such results, fat cells of the obese was examined under the culture condition. First, insulin which is a lipogenie factor is one of the major factors of obesity. Therefore, "loculus-preserving" cell division of fat cells by insulin is compatible with the hyperinsulinemia of the obese. Secondly, large unilocular fat cells derived from the obese could also proliferate under the culture condition.We hope that the culture system described here will be valuable in studies of the biology of fat cells and the mechanism of obesity.