Investigation of genes involved in anti-obesity and insulin sensitivity in the white adipose tissue

热量限制（CR）是已知的最简单的实验操作，可以延长寿命并延缓实验室啮齿动物与年龄相关的广泛病理生理变化。确切的潜在机制尚不清楚，但CR动物与长寿侏儒小鼠有许多共同特征，包括体型较小，血浆胰岛素和IGF-1水平较低，胰岛素敏感性较高。近年来，白色脂肪组织（WAT）被认为是一种内分泌器官，其功能障碍影响胰岛素敏感性、2型糖尿病的发病、并发症、衰老和寿命。为了阐明GH/IGF-1抑制作用与CR之间的关系，我们之前研究了野生型雄性（-/-）大鼠的生存和胰岛素敏感性，这些大鼠分别饲喂自由生长（AL）或30% CR，以及杂合转基因矮子大鼠（DF），它们携带反义GH转基因（抑制GH/IGF-1， tg/-），饲喂AL。与（-/-）AL大鼠相比，CR和DF都延长了中位和最长寿命10%，并提高了胰岛素敏感性。在本研究中，我们研究了CR和DF在白色脂肪组织中的影响，以阐明CR的有益作用的关键分子，包括更高的胰岛素敏感性。CR和DF都降低了血液中的胰岛素和瘦素水平，并增加了脂联素水平。在WAT中，CR和DF均降低瘦素mRNA水平，升高脂联素mRNA水平。用DNA芯片检测了CR大鼠和DF大鼠的25000多个基因，并与对照组（-/-）AL大鼠进行了比较。与AL（-/-）相比，CR和DF分别调节了672个（2.7%）和210个（0.84%）基因的表达。然而，在这些基因中，只有34个基因（0.1%）被CR和DF以相似的方式改变了表达，这表明CR和DF在WAT中独立调节基因的表达。特别是，CR增强了代谢相关基因的表达，而降低了细胞外基质、细胞骨架和炎症相关基因的表达。此外，利用Web工具对启动子进行分析发现，CR上调的某些基因的启动子具有SREBP结合位点。SREBP-1蛋白的Western blot结果显示，CR增加了WAT中SREBP-1蛋白水平，而DF没有增加。这些发现表明，SREBP-1至少在一定程度上以不依赖GH/ igf -1的方式调节WAT中cr相关基因的表达谱。SREBP-1可能是CR有益作用的关键参与者之一

Caloric restriction (CR) is the simplest experimental manipulation known to extend lifespan and to retard a broad spectrum of age-associated pathophysiological changes in laboratory rodents. The exact underlying mechanisms are still unknown, but CR animals share many characteristics with long-living dwarf mice, including smaller body size, lower plasma insulin and IGF-1 levels, and higher insulin sensitivity. Recently, white adipose tissue (WAT) has been recognized as an endocrine organ, and its dysfunction influences insulin sensitivity, onset of type 2 diabetes, its complications, aging and longevity. To clarify the relationship between the effects of GH/IGF-1 suppression and CR, we have previously examined the survival and insulin sensitivity of male wild type (-/-) rats fed either ad libitum (AL) or subjected to 30% CR, and heterozygous transgenic dwarf rats (DF) bearing an anti-sense GH transgene (suppression of GH/IGF-1, tg/-) fed ad AL. Both CR and DF extend the median and maxim … More um lifespan by 10% and enhance insulin sensitivity as compared with (-/-) AL rats. In the present study, we investigated the influences of CR and DF in white adipose tissue to clarify key molecules for the beneficial action of CR including higher insulin sensitivity. Both CR and DF reduced blood insulin and leptin levels, and increased adiponectin level. In WAT, both CR and DF decreased mRNA level of leptin, but increased that of adiponectin. Over 25,000 genes were examined using DNA chips in CR rats and DF rats, and compared with control (-/-) AL rats. CR and DF modulated the expression of 672 (2.7%) genes and 210 (0.84%) genes as compared with AL (-/-) rats, respectively. Among these genes, however, only 34 genes (0.1%) were altered the expressions by both CR and DF with the similar manner, suggesting that CR and DF independently regulate the expression of genes in WAT. Particularly, CR enhanced the expression of genes involved in metabolism but reduced that of genes involved in extracellular matrix, cytoskeleton and inflammation. In addition, promoter analysis using Web tool suggested that promoter of certain genes, which are up-regulated by CR, possesses SREBP binding site. Western blot for SREBP-1 indicated that CR increases protein level of SREBP-1 but DF dose not in WAT. These findings suggest that SREBP-1, at least in part, regulates the CR-associated gene expression profile in WAT in a GH/IGF-1-independent manner. SREBP-1 might be one of key players for the beneficial action of CR. Less