Role of Gs-alpha in central regulation of energy and glucose metabolism

我们通过将具有围绕Gs-α外显子1的loxP重组位点的Gs-α floxed等位基因杂合子的雌性与具有巢蛋白启动子-cre重组酶转基因的雄性交配，产生了中枢神经系统中来自母体等位基因的Gs-α表达中断的小鼠（mBGsKO）。通过正反交产生在中枢神经系统中具有类似的父系等位基因（pBGsKO）上的Gs-α表达丧失的小鼠。pBGsKO小鼠具有正常的存活率和总体表型，对葡萄糖或能量代谢或血清脂质没有影响，如通过多种实验方法（体重和组成、器官重量、血清化学和激素、葡萄糖和胰岛素耐受性测试、代谢率和食物摄入测量）所确定的。相比之下，mBGsKO发展为重度肥胖伴糖尿病、重度胰岛素抵抗和高血糖症。5周后肥胖开始发展。研究正在进行中，以确定糖尿病和胰岛素抵抗的发病。在mBGsKO小鼠中的进一步研究表明，肥胖主要是能量消耗减少和与能量耗散相关的棕色脂肪组织基因（如解偶联蛋白1（UCP 1））表达减少的结果。我们假设mBGsKO小鼠可能缺乏黑皮质素系统刺激交感神经系统活动和能量消耗的能力。为了验证这一假设，急性食物摄入和能量消耗的反应，黑皮质素激动剂（MTII）进行了测量。在pBGsKO小鼠和对照之间没有差异，并且对MTII抑制mBGsKO小鼠食物摄入的能力几乎没有影响。然而，与对照相比，MTII刺激能量消耗的能力在mBGsKO小鼠中显著降低。总体而言，这些结果证实了中枢神经系统中的Gs-alpha通路是代谢的关键调节剂，并且小鼠（以及最有可能的Albright遗传性骨营养不良患者）中的母体Gs-alpha突变是由中枢神经系统中一个或多个位点中的Gs-alpha印迹引起的。我们目前正试图通过与具有更严格分布模式的cre转基因系交配以及原位杂交研究来定义这些位点，这些研究检查了母体和父体Gs-alpha突变小鼠系中枢神经系统中Gs-alpha mRNA的表达。

We generated mice with disruption of Gs-alpha expression from the maternal allele in the central nervous system (mBGsKO) by mating females heterozygous for a Gs-alpha floxed allele with loxP recombination sites surrounding Gs-alpha exon 1 to males with a nestin promoter-cre recombinase transgene. Mice with similar loss of Gs-alpha expression in the central nervous system on the paternal allele (pBGsKO) were generated with reciprocal crosses. pBGsKO mice had normal survival and overall phenotype with no effect on glucose or energy metabolism or serum lipids as determined by multiple experimental approaches (body weight and composition, organ weights, serum chemistries and hormones, glucose and insulin tolerance tests, metabolic rate and food intake measurements). In contrast, mBGsKO developed severe obesity with diabetes, severe insulin resistance, and hypertriglyceridemia. The obesity began to develop after 5 weeks. Studies are underway to determine the onset of diabetes and insulin resistance. Further studies in mBGsKO mice showed that the obesity was primarily the result of reduced energy expenditure and reduced expression of brown adipose tissue genes associated with energy dissipation, such as uncoupling protein 1 (UCP1). We hypothesized that mBGsKO mice may be defective the ability of the melanocortin system to stimulate sympathetic nervous system activity and energy expenditure. To test this hypothesis, acute food intake and energy expenditure responses to a melanocortin agonist (MTII) were measured. There were no differences between pBGsKO mice and controls, and there was little effect on the ability of MTII to inhibit food intake in mBGsKO mice. However, the ability of MTII to stimulate energy expenditure was markedly reduced in mBGsKO mice as compared to controls. Overall these results confirm that Gs-alpha pathways in the central nervous system are critical regulators of metabolism and that maternal Gs-alpha mutations in mice (and most likely Albright hereditary osteodystrophy patients) results from Gs-alpha imprinting in one or more site in the central nervous system. We are presently trying to define these sites through matings with cre transgenic lines with a more restrictive distribution pattern as well as in situ hybridization studies examining Gs-alpha mRNA expression in the central nervous system in maternal and paternal Gs-alpha mutant mouse lines.