运动诱导的CD36蛋白转位及化学修饰对骨骼肌胰岛素敏感性的调控及机制研究

In recent years, the international trend of rehabilitation medicine is leaning towards health promotion and the role of exercise therapy in improving metabolic diseases has become a research focus in this area. In view of the close association of fatty acid metabolism with insulin resistance and type 2 diabetes, the potential role of Fatty Acids Translocase/CD36 (FAT/CD36) in prevention and treatment of insulin resistance has attracted more attention of researchers. Our previous study has demonstrated that sarcolemmal CD36 signaling might engage AMPK to coordinate FA uptake and oxidation. However, the regulative role of CD36 in exercise improving muscle insulin sensitivity remains unclear. Thus, this project intends to do further research on our previous results. Firstly, CD36 knockout mice and CD36 small RNA interference technology were used to investigate the role of CD36 gene in improving skeletal muscle insulin sensitivity on different levels. Then, the mechanism of exercise-induced CD36 intracellular trafficking and membrane translocation was further explored in skeletal muscle satellite cells and tissues of db/db mice. Finally, the possibility that CD36 traffic may be determined by CD36 chemical modification, a process that is regulated by exercise, was revealed by CD36 ubiquitination or palmitoylation sites mutant. This study will enrich the cellular and molecular mechanism in exercise improving muscle insulin resistance, which is useful to provide the theoretical basis to assess the clinical value of CD36 in therapeutic stratege of diabetes.

近年康复医学的国际趋势已转向健康促进，如何通过运动干预防治代谢性疾病成为研究热点。鉴于脂肪酸代谢与胰岛素抵抗和2型糖尿病的密切关系，脂肪酸转位酶（CD36）在糖尿病防治中的作用逐渐被关注。近期我们首次发现，CD36通过激活AMPK对脂肪酸代谢进行调控。然而运动是否亦能通过CD36及其相关机制在调控骨骼肌胰岛素敏感性中发挥重要作用，尚不清楚。本课题首先利用基因敲除小鼠和小RNA干扰技术，在不同层面探讨CD36在调控骨骼肌胰岛素敏感性中的作用；然后利用糖尿病小鼠骨骼肌卫星细胞及组织，探讨运动诱导的CD36蛋白转位及细胞膜定位对骨骼肌胰岛素敏感性的调控；最后藉CD36泛素化位点和棕榈酰化位点突变，进一步探讨运动诱导的CD36蛋白化学修饰与CD36转位及胰岛素敏感性调控的关系。预期成果将有助于完善运动调控骨骼肌胰岛素敏感性的细胞生物学机制，为评估CD36在糖尿病临床诊疗中的靶点价值提供依据。

近年来，康复医学的国际趋势已转向慢性病的防治，尤其是对糖尿病的运动干预。鉴于脂肪酸代谢与胰岛素敏感性和2型糖尿病的密切关系，脂肪酸转位酶（CD36）在糖尿病防治中的作用逐渐被关注。我们前期研究发现，CD36作为信号分子，而非脂肪酸转运载体，通过激活AMPK对脂肪酸代谢进行调控。然而运动是否亦能通过CD36及其相关机制在改善骨骼肌胰岛素敏感性中发挥重要作用，尚不清楚。本项目采用小RNA干扰技术和基因敲除小鼠，在不同层面探讨CD36在调控骨骼肌胰岛素敏感性中的作用及其作用机制。结果表明：（1）CD36基因缺乏能够降低胰岛素抵抗骨骼肌细胞活力、减少细胞增殖、S期细胞减少，促进细胞凋亡；（2）离体和在体实验均表明CD36基因缺乏能有效改善骨骼肌胰岛素敏感性；（3）运动能够通过提高CD36向细胞膜的转位能力，并提高CD36在细胞膜脂筏上的准确定位，诱导细胞核LKB1向细胞质转位，激活AMPK，从而对糖尿病小鼠的骨骼肌胰岛素敏感性进行调控；（4）运动诱导的CD36蛋白棕榈酰化修饰可能是调控糖尿病小鼠骨骼肌胰岛素敏感性的内在原因之一；（5）运动可能通过调控CD36与CD47的协同作用，改善骨骼肌胰岛素敏感性。该项目成果将有助于完善运动调控骨骼肌胰岛素敏感性的细胞生物学机制，为评估CD36在糖尿病防治上的靶点价值提供一定的理论依据。