Role of Gs-alpha in regulation of adipose tissue growth and function

Gs-α 在调节脂肪组织生长和功能中的作用

基本信息

批准号：
7593595
负责人：
Lee Weinstein
金额：
$ 18.43万
依托单位：
NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/7593595
关键词：
Adipocytes Adipose tissue Adrenergic Agents Alleles Body Temperature Brown Fat CCAAT-Enhancer-Binding Protein-beta Catecholamines Cells Cyclic AMP Diet Embryo Energy Metabolism Environment Exons Fatty acid glycerol esters Fibroblasts GTP-Binding Protein alpha Subunits, Gs Genes Genetic Recombination Growth Gs alpha mutations Human Hypoglycemia Hypoglycemic Agents In Vitro Insulin Resistance Insulin-Like Growth Factor I Lead Lipids Lipolysis Mediating Metabolic Activation Morbid Obesity Mus Muscle Normal Cell Obesity Pathway interactions Pattern Phenotype Production Regulation Relative (related person)Role Signal Pathway Site Sympathetic Nervous System Thermogenesis Tissues Transgenic Mice Urine Weight Gain adrenergic base beta-adrenergic receptor gene induction glucose tolerance improved in vivo insulin sensitivity lipid biosynthesis lipid metabolism programs recombinase uncoupling protein 1

项目摘要

We generated mice with Gs-alpha deficiency in adipose tissue (FGsKO mice) by repeated matings of aP2-cre recombinase transgenic mice with floxed Gs-alpha mice which have loxP recombination sites surrounding Gs-alpha exon 1. Results to date show that FGsKO mice had poor survival and decreased linear growth, particularly those mice in which Gs-alpha expression in adipose tissue was severely reduced. The cause of these effects are unclear, although insulin-like growth factor 1 (IGF1) levels were reduce by 50% in FGsKO mice. In this subset of mice, white adipose tissue (WAT) pads were very small. Fibroblasts from FGsKO embryos had significantly reduced adipogenic conversion in the presence of agents known to induce adipogenesis. These in vivo and in vitro results confirm that Gs-alpha is critical for normal adipogenesis. FGsKO mice which survived had also had reduced relative fat mass with smaller WAT pads and smaller adipocytes with less lipid content per cell. In contrast, the interscapular brown adipose tissue (BAT) pads were larger than normal and the cells had increased lipid stores with a more unilocular distribution. This histological pattern is consistent with reduced metabolic activation presumably due to an inability of the sympathetic nervous system to stimulate lipolysis via beta-adrenergic/Gs-alpha pathways. Consistent with this, the expression of PGC-1, uncoupling protein 1 (UCP1) and other genes associated with lipid metabolism were markedly reduced in BAT from FGsKO mice. FGsKO mice were hypoglycemic and hypoinsulinemic relative to controls and had improved glucose tolerance and insulin sensitivity on both regular and high-fat diets, consistent with their lean phenotype. Two forms of adaptive thermogenesis, cold- and diet-induced thermogenesis, are mediated by increased sympathetic nervous system activity. In FGsKO mice cold-induced thermogenesis is markedly impaired as FGsKO mice placed in a cold environment do not maintain their body temperature. This is consistent with the known role for BAT in cold-induced thermogenesis and the results in FGsKO mice that BAT fails to be activated by sympathetic stimulation despite the fact that their sympathetic activity, as determined by urine catecholamine levels, was markedly increased. In contrast, diet-induced thermogenesis is maintained and in fact greater than normal in FGsKO mice based upon the observations that FGsKO mice fail to gain weight on a high-fat diet and have markedly increase their energy expenditure on a high-fat diet. These results suggest that cold- and diet-induced thermogenesis can occur in separate tissues and we propose that muscle is the main site for diet-induced thermogenesis in these mice. Finally, these results as well as results in heterozygous FGsKO mice suggest that adipose tissue is not the site whereby germline Gs-alpha mutations on the maternal allele lead to severe obesity and insulin resistance.

我们通过将 aP2-cre 重组酶转基因小鼠与 floxed Gs-alpha 小鼠重复交配，产生了脂肪组织中 Gs-alpha 缺陷的小鼠（FGsKO 小鼠），floxed Gs-alpha 小鼠在 Gs-alpha 外显子 1 周围具有 loxP 重组位点。迄今为止的结果表明，FGsKO 小鼠存活率低且线性生长下降，尤其是那些脂肪组织中 Gs-α 表达严重降低的小鼠。尽管 FGsKO 小鼠中胰岛素样生长因子 1 (IGF1) 水平降低了 50%，但造成这些影响的原因尚不清楚。在这组小鼠中，白色脂肪组织（WAT）垫非常小。在已知诱导脂肪生成的试剂存在下，来自 FGsKO 胚胎的成纤维细胞显着降低了脂肪生成转化。这些体内和体外结果证实，Gs-α 对于正常脂肪生成至关重要。存活的 FGsKO 小鼠的相对脂肪量也减少了，WAT 垫更小，脂肪细胞也更小，每个细胞的脂质含量也更少。相比之下，肩胛间棕色脂肪组织（BAT）垫比正常细胞大，并且细胞的脂质储存增加，且分布更加单房。这种组织学模式与代谢激活减少相一致，可能是由于交感神经系统无法通过 β-肾上腺素能/Gs-α 途径刺激脂肪分解。与此相一致的是，FGsKO 小鼠的 BAT 中 PGC-1、解偶联蛋白 1 (UCP1) 和其他与脂质代谢相关的基因的表达显着降低。与对照组相比，FGsKO 小鼠出现低血糖和低胰岛素血症，并且在常规和高脂肪饮食中葡萄糖耐量和胰岛素敏感性均得到改善，这与它们的瘦表型一致。适应性产热的两种形式，寒冷和饮食诱导的产热，是由交感神经系统活动增加介导的。在 FGsKO 小鼠中，寒冷诱导的生热作用明显受损，因为置于寒冷环境中的 FGsKO 小鼠无法维持体温。这与 BAT 在冷诱导产热中的已知作用一致，并且 FGsKO 小鼠的结果表明，尽管根据尿液儿茶酚胺水平确定，BAT 的交感活性显着增加，但 BAT 未能被交感神经刺激激活。相比之下，基于FGsKO小鼠在高脂肪饮食中体重未增加并且在高脂肪饮食中能量消耗显着增加的观察结果，饮食诱导的生热作用在FGsKO小鼠中得以维持，并且实际上高于正常水平。这些结果表明，寒冷和饮食诱导的生热作用可以发生在不同的组织中，我们认为肌肉是这些小鼠中饮食诱导的生热作用的主要部位。最后，这些结果以及杂合 FGsKO 小鼠的结果表明，脂肪组织并不是母体等位基因上种系 Gs-α 突变导致严重肥胖和胰岛素抵抗的部位。