Calmodulin Kinases and Control of Skeletal Muscle Glucose Metabolism

 描述(由申请人提供)：2型糖尿病目前困扰着2580万美国人，每年给美国医疗保健系统造成超过2450亿美元的损失。它是一种以高血糖、高胰岛素血症和骨骼肌胰岛素抵抗为特征的疾病，骨骼肌是体内负责胰岛素介导的葡萄糖摄取的主要组织。尽管肌肉在维持血糖动态平衡方面很重要，但目前还没有针对独立于胰岛素的肌肉葡萄糖摄取的糖尿病药物治疗。抗阻运动/肌肉收缩活动刺激葡萄糖摄取进入肌肉；更重要的是，在2型糖尿病中，运动刺激肌肉葡萄糖摄取的能力仍然起作用。因此，针对运动/收缩介导的肌肉葡萄糖摄取的潜在机制是降低2型糖尿病患者血糖水平的有效策略。不幸的是，这些机制还没有被很好地理解。这项研究的长期目标是确定肌肉中调节胰岛素非依赖性葡萄糖摄取的分子、细胞或代谢机制，并测试针对这些机制是否有效地改善2型糖尿病患者的高血糖。最近的证据表明，钙激活的丝氨酸/苏氨酸激酶，钙/钙调蛋白依赖性蛋白激酶(CaMKK)是运动敏感、非胰岛素依赖的肌肉葡萄糖摄取的关键调节因子，提示CaMKK可能成为治疗2型糖尿病肌肉葡萄糖摄取受损的新靶点。不幸的是，CaMKK调节肌肉葡萄糖摄取能力的潜在机制(S)仍不清楚。本研究的具体目标是确定由CaMKK激活的细胞内信号蛋白(S)[即底物(S)]；确定CaMKK如何刺激肌肉对葡萄糖的利用；以及确定同时激活一个能量消耗过程是否对CaMKK介导的持续肌肉葡萄糖摄取是必要的。为了实现这些目标，将结合使用最先进的途径和方法，包括使用三磷酸腺苷类似物在肌肉中筛选新的CaMKK底物，体内肌肉基因转移/电穿孔以允许基因在小鼠肌肉中快速、瞬时表达，以及产生肌肉特异的CaMKK基因敲除小鼠。预计拟议的研究将阐明CaMKK刺激胰岛素敏感肌肉和胰岛素抵抗肌肉摄取葡萄糖的能力的细胞内机制(S)；这是开发旨在刺激骨骼肌摄取非胰岛素依赖的葡萄糖的2型糖尿病新疗法的关键第一步。

 DESCRIPTION (provided by applicant): Type 2 diabetes currently afflicts >25.8 million Americans and costs the US healthcare system over $245 billion/year. It is a disease characterized by hyperglycemia, hyperinsulinemia, and insulin resistance in skeletal muscle, the primary tissue responsible for insulin-mediated glucose uptake in the body. Despite the importance of muscle in maintaining blood glucose homeostasis, there are currently no pharmaceutical treatments for diabetes that target muscle glucose uptake independent of insulin. Resistance exercise/muscle contractile activity stimulates glucose uptake into muscle; and importantly in type 2 diabetes the ability of exercise to stimulate muscle glucose uptake remains functional. Thus, targeting the mechanisms underlying exercise/contraction-mediated muscle glucose uptake is an effective strategy for lowering blood glucose levels in type 2 diabetes. Unfortunately, these mechanisms are not well understood. The long-term goals of this research are to identify the molecular, cellular or metabolic mechanisms within muscle that regulate insulin-independent glucose uptake and to test whether targeting those mechanisms is effective at ameliorating hyperglycemia in type 2 diabetes. Recent evidence has now implicated the Ca2+-activated, serine/threonine kinase, Ca2+/calmodulin-dependent protein kinase kinase  (CaMKK) as a key regulator of exercise-sensitive, insulin-independent muscle glucose uptake, suggesting that CaMKK may be a promising new target for treating impaired muscle glucose uptake in type 2 diabetes. Unfortunately, the mechanism(s) underlying the ability of CaMKK to regulate muscle glucose uptake remains unclear. The specific objectives of this proposal are to identify the intracellular signaling protein(s) [i.e. substrate(s)] activated by CaMKK in muscle; to determine how CaMKK stimulates muscle glucose utilization; and to determine whether simultaneous activation of an energy consuming process is necessary for sustained CaMKK -mediated muscle glucose uptake. To achieve these objectives, a combination of state-of-the-art approaches and methodologies will be applied including use of an ATP analog to screen for novel CaMKK substrates in muscle, in vivo muscle gene transfer/electroporation to allow for the rapid, transient expression of genes in mouse muscle, and generation of a muscle-specific CaMKK knockout mouse. It is anticipated that the proposed research will elucidate the intracellular mechanism(s) governing the ability of CaMKK to stimulate glucose uptake in both insulin-sensitive and insulin-resistant muscle; a critical first step towards the development of new treatments for type 2 diabetes aimed at stimulating insulin-independent glucose uptake into skeletal muscle.