Molecular Medicine of Clinical Implication of Obese Gene Product

(目的)探讨瘦素及其下游的解偶联蛋白3(UCP3)的病理生理学意义。(方法)对17例有肥胖家族史、体重指数(BMI)>30的日本肥胖者，采用直接测序法测定瘦素受体基因的所有外显子的结构。采用单链构象多态性和聚合酶链式反应-限制性片段长度多态性分析方法，对46例日本BMI&gt；30例和BMI&lt；25例瘦素受体基因多态性进行了检测。利用与小鼠UCP2基因的同源性，我们从大鼠骨骼肌中克隆了UCP3基因。我们检测了高脂饮食大鼠UCP3基因的表达。我们研究了吡格列酮对Wistar肥胖大鼠UCP3基因表达的影响。结果在日本病态肥胖者中发现了7个Leptin受体基因的多态性。非肥胖者和病态肥胖者的等位基因频率在所有的多态性上均无显著差异。在大鼠骨骼肌中克隆了UCP3基因。高脂饮食大鼠UCP3基因表达增加一倍。我们观察到UCP3基因在附睾脂肪中的表达显著增加了2.1倍，在腹膜后脂肪中增加了2.0倍，在棕色脂肪中增加了1.6倍。我们观察到在原代培养的大鼠白色脂肪细胞中，吡格列酮使UCP3基因表达显著增加。(讨论)大多数日本病态肥胖者的肥胖不能用瘦素受体基因多态性来解释。我们从大鼠骨骼肌中克隆了UCP3基因。我们证明了高脂饮食和噻唑烷类药物对UCP3基因表达的促进作用。

(Purpose) We examined pathophysiological significance of leptin, and uncoupling protein 3 (UCP3) which appears to be downstream of leptin.(Methods) We determined the structure of all exons of leptin receptor cDNA by direct sequencing in 17 Japanese obese subjects whose BMI is higher than 30 and who have family history of obesity. We determined allele frequency of polymorphisms of leptin receptor gene in 46 Japanese subjects with BMI > 30 and 64 subjects with BMI < 25 by SSCP and PCR-RFLP analyses. Using homology to mouse UCP2 cDNA, we cloned UCP3 cDNA from rat skeletal muscle. We examined UCP3 gene expression in rats fed high-fat diet. We investigated UCP3 gene expression in Wistar fatty rats treated with pioglitazone. We examined the UCP3 gene expression in primary mature adipocytes culture from rat epididymal fat.(Results) We identified 7 polymorphisms in leptin receptor gene in Japanese morbidly obese subjects. No significant difference of allele frequency was noted between nonobese and morbidly obese subjects in all polymorphisms. UCP3 cDNA was cloned in rat skeletal muscle. Two-fold elevation of UCP3 gene expression was observed in rats fed high-fat diet. We observed significant increase of UCP3 gene expression by 2.1-fold in the epididymal fat, by 2.0-fold in the retroperitoneal fat, and by 1.6-fold in the brown fat. We observed significant increase of UCP3 gene expression by pioglitazone from the concentration of 10^<-5>M in rat primary white adipocyte culture.(Discussion) Obesity in most of Japanese morbidy obese subjects can not be explained by leptin receptor gene polymorphisms. We cloned UCP3 cDNA from rat skeletal muscle. We demonstrated the increase of the UCP3 gene expression by high-fat diet feeding and by thiazolidines.