Function of the Myo-adipo Axis in Human Obesity and Type 2 Diabetes

描述（由申请人提供）： 肥胖和2型糖尿病（T2 D）的代谢功能障碍涉及多种组织的胰岛素抵抗。最近已经确定了脂肪组织产生和分泌的因子（称为脂肪因子）在代谢调节中的关键作用，这些因子可以诱导胰岛素抵抗或改善胰岛素敏感性。较少关注骨骼肌（肌因子）产生的因素，也可能影响胰岛素敏感性，以及影响脂肪组织（AT）的积累和功能。待检验的假设是：骨骼肌产生并释放因子（肌因子），这些因子可以以自体活动方式作用于肌肉，以增强或阻碍代谢和胰岛素作用，以及以内分泌方式作用，以影响AT代谢和蓄积。来自肥胖的2型糖尿病个体的肌肉产生更多的肌因子，其诱导胰岛素抵抗并刺激脂肪积累。 有3个具体目的：1）确定人骨骼肌产生和分泌GRO、IL-8和IL-15的能力，以及炎症和抗炎信号对这种产生的调节。2)建立这些特异性肌因子对骨骼肌葡萄糖代谢和胰岛素敏感性的自分泌作用，以及相关的信号通路。糖尿病患者的肌肉细胞对这些肌因子的作用是更敏感还是更不敏感？3)评价特定肌因子对脂肪细胞分化和凋亡、AT中血管生成和脂质代谢的影响，重点是潜在的储库（皮下vs内脏）差异以及肥胖和T2 D的影响。 该项目将完全在人类，其组织和来自这些组织的细胞中进行。胰岛素在骨骼肌中的作用将在肌肉组织和培养的肌肉细胞和脂肪组织中进行体内和体外研究。将获得肌肉和AT活检，用于评价GRO、IL-8和IL-15 mRNA和蛋白质的含量。来自活检的卫星细胞将在培养物中增殖并分化成肌管，以评估感兴趣的肌因子的肌肉特异性产生。肌管也将接受炎症和抗炎信号以及单个肌因子的治疗，以确定对这些因素的反应是否随糖尿病而变化。这些因子在肌管中的表达也将通过遗传手段来操纵。AT将保持在培养物中，用所提出的感兴趣的肌因子处理，然后是成熟脂肪细胞的脂肪形成和凋亡。AT也将用单独的肌因子治疗，以跟踪对血管生成的影响。 该项目的结果将提供肥胖和T2 D体内代谢功能障碍的分子机制，并确定治疗干预的可能靶点。

DESCRIPTION (provided by applicant): Metabolic dysfunction in obesity and type 2 diabetes (T2D) involves insulin resistance in multiple tissues. Recently key roles in metabolic regulation have been identified for factors produced by and secreted from adipose tissue (termed adipokines) that can either induce insulin resistance or improve insulin sensitivity. Less attention has been paid to factors produced by skeletal muscle (myokines) that could also influence insulin sensitivity, as well as impact adipose tissue (AT) accumulation and function. The hypothesis to be tested is: Skeletal muscle produces and releases factors (myokines) that can act in an autocine manner on muscle to augment or impede metabolism and insulin action as well as act in an endocrine manner to influence AT metabolism and accumulation. Muscle from obese type 2 diabetic individuals produces more of the myokines that induce insulin resistance and stimulate fat accumulation. There are 3 Specific Aims.1) Determine the ability of human skeletal muscle to produce and secrete GRO¿, IL-8, and IL-15 and regulation of this production by inflammatory and anti- inflammatory signals. 2) Establish the autocrine effects of these specific myokines on glucose metabolism and insulin sensitivity in skeletal muscle, and the signaling pathways involved. Are diabetic muscle cells more or less sensitive to the actions of these myokines? 3) Evaluate the effects of specific myokines on the differentiation and apoptosis of adipocytes, angiogenesis in AT, and lipid metabolism, with an emphasis on potential depot (subcutaneous vs visceral) differences and the impacts of obesity and T2D. This project will be performed totally in humans, their tissues and cells derived from those tissues. Insulin action in skeletal muscle will be studied both in vivo and in vitro in muscle tissue and cultured muscle cells and adipose tissue. Muscle and AT biopsies will be obtained for evaluation of the content of GRO¿, IL-8, and IL-15 mRNA and protein. Satellite cells from the biopsies will be propagated in culture and differentiated into myotubes to evaluate muscle specific production of the myokines of interest. Myotubes will also be treated with inflammatory and anti-inflammatory signals as well as individual myokines to determine if responsiveness to the factors varies with diabetes. Expression of the factors in myotubes will also be manipulated by genetic means. AT will be maintained in culture, treated with the proposed myokines of interest and both adipogenesis and apoptosis of mature adipocytes followed. AT will also be treated with individual myokines to follow effects on angiogenesis. Results from this project will provide molecular mechanisms for metabolic dysfunction seen in vivo in obesity and T2D and identify possible targets for therapeutic interventions.