ELUCIDATION OF SIGNIFICANCE OF UCP3 IN DIABETES AND OBESITY USING TRANSGENIC MICE

能量代谢包括食物摄入量和能量消耗。它的失衡会导致糖尿病和肥胖症。骨骼肌是能量代谢的重要器官之一。虽然大约40%的全身能量消耗是由骨骼肌能量消耗来解释的，但其具体的分子机制仍有待阐明。我们鉴定了在骨骼肌中高表达的解偶联蛋白3(UCP3)。在本研究中，我们利用骨骼肌特异的UCP3过表达转基因小鼠，阐明了UCP3基因表达的调控机制，以及UCP3的功能意义。由于脂肪酸是过氧化物酶体增殖物激活受体(PPAR)的激动剂，PPAR似乎参与了UCP基因表达的调节。在本研究中，我们证明了在L6培养的骨骼肌细胞系中，ucp3基因的表达增加，而不是pparα…激动剂所致。More或PPARγ而不受PPARδ激动剂L-165041的影响，表明L6细胞中主要的PPAR是PPARδ，表明UCP3基因的表达是通过PPARδ调节的。由于体内骨骼肌中主要的PPAR是PPARδ，因此PPARδ参与了活体骨骼肌中UCP3基因的表达调控。UCP3在转基因小鼠骨骼肌中的表达水平是转基因小鼠最高表达品系的18倍和15倍。在正常饮食条件下，转基因小鼠与对照小鼠相比没有明显的表型。在高脂饮食条件下，转基因小鼠的体重比对照小鼠轻约15%。附睾白色脂肪组织的重量比对照小鼠轻约20%。由于其他组织的重量没有明显差异，体重的显著下降似乎是由于白色脂肪组织的重量减少。虽然转基因小鼠在摄食量和体温方面没有显著差异，但其耗氧量比对照鼠增加了约25%，表明体重的减轻是由于能量消耗的增加。与对照小鼠相比，转基因小鼠的葡萄糖耐量有所提高。在血糖谱、血脂谱和组织学上没有明显的表型。这些结果表明，在高脂饮食条件下，UCP3基因在生理范围内的表达增加是导致能量消耗增加和体重下降的原因。由于UCP3基因表达的诱导可以通过药物来实现，本研究建议将UCP3应用于肥胖和糖尿病的临床治疗。较少

Energy metabolism consists of food intake and energy consumption. Its imbalance leads to diabetes and obesity. Skeletal muscle is one of the vital organs of energy metabolism. Although approximately 40 % of energy consumption of whole body is explained by that of skeletal muscle, the detail of molecular mechanism remains to be elucidated. We identified uncoupling protein 3 (UCP3), which is highly expressed in the skeletal muscle. In the present study, we elucidated regulatory mechanism of UCP3 gene expression, and functional significance of UCP3 using skeletal muscle-specific UCP3-overexpressed transgenic mice.UCP3 gene expression is increased in the skeletal muscle in vivo by fatty acid. Since fatty acid is an agonist for peroxisome Proliferator-Activated Receptor (PPAR), PPAR appears to be involved in the regulation of UCP gene expression. In the present study, we demonstrated that UCP3 gene expression is increased in L6 cultured cell line of skeletal muscle not by agonists for PPARα … More or PPARγ but by PPARδ agonist, L-165041, and that major PPAR in L6 cells is PPARδ, indicating that UCP3 gene expression is regulated via PPARδ. Since major PPAR in skeletal muscle in vivo is PPARδ, PPARδ is involved in the regulation ofUCP3 gene expression in the skeletal muscle in vivo.We created skeletal muscle-specific UCP3-overexpressed transgenic mice. UCP3 is expressed in the skeletal muscle of transgenic mice at 18 fold levels in mRNA and 15 fold levels in protein of the line with the highest expression. Under normal chow, the transgenic mice show no obvious phenotype as compared with control mice. Under high fat diet, the body weight of the transgenic mice is approximately 15 % less than that of control mice. The weight of epididymal white adipose tissue is approximately 20 % less than that of control mice. Since there is no significant difference in weight of other tissues, the significant reduction of body weight appears to be due to the decrease of weight of white adipose tissue. Although there is no significant difference in food intake and in body temperature, oxygen consumption is approximately 25 % increased in the transgenic mice as compared with control mice, indicating that the reduction of body weight is due to increase of energy consumption. Glucose tolerance is improved in the transgenic mice as compared with control mice. There is no obvious phenotype it blood profile of sugar and lipid and in histology. These results indicate that under high-fat food, increase of energy consumption and decrease of body weight are caused by increase of UCP3 gene expression within physiologica range. Since the induction of UCP3 gene expression as such can be attainable by pharmacologic agents, the present study suggests clinical application of UCP3 for treatment of obesity and diabetes. Less