DETERMINANTS OF MAXIMAL O2 TRANSPORT

慢性病(慢性阻塞性肺病、心力衰竭、肾衰竭)的特点是运动能力降低。越来越多的证据表明，在这种情况下，骨骼肌的结构和功能可能存在内在的异常。本提案从当前周期继续努力，以更好地了解运动限制对健康和疾病的作用机制，特别是骨骼肌的作用。在PPG下已经开发的涉及肌肉O2运输分析的生理学方法(大和小肌肉质量运动、股动脉血流、血气采样、磁共振光谱测量细胞内P02、形态学评估扩散距离和毛细血管表面积)将与侧重于与肌肉对运动的血管生成反应相关的基因的分子水平研究相结合，因为毛细血管表面的数量似乎对O2运输限制至关重要。这一综合方法将应用于动物和人类研究，后者用于健康和慢性疾病(心力衰竭、慢性阻塞性肺疾病)。动物工作将使用在人类中不可能的机械干预来补充人类的实验，在这两个实验中，分子方法将应用于完整的生理系统。主要目标包括：1)将慢性疾病中基于氧气转运的运动限制与由于肌肉内在异常引起的运动限制分开；2)使用Cre/loxP靶向敲除策略以及血管内皮生长因子拮抗剂(如苏拉明、氯沙坦和卡托普利)确定血管生成是否必需的血管生成；3)确定在慢性病中通常增加血管内皮生长因子信息和蛋白质毛细血管的机制。我们的最终目标是在基因调控的水平上识别慢性疾病中肌肉氧转运的异常，以期最终进行基因靶向治疗。我们假设这些将集中地涉及肌肉对运动的血管生成反应。

Chronic diseases (COPD, heart failure, renal failure) are marked by reduced exercise capacity. There is increasing evidence that skeletal muscle structure and function may be intrinsically abnormal in such conditions. The present proposal continues work from the current cycle to better understand the mechanisms of exercise limitation in both health and disease, in particular the role of skeletal muscle. Physiological approaches already developed under the PPG involving muscle O2 transport analysis (large versus small muscle mass exercise, femoral blood flow, blood gas sampling, magnetic resonance spectroscopy to measure intracellular P02, morphology to assess diffusion distances and capillary surface area) will be combined with molecular-level studies focused on genes associated with muscle angiogenic responses to exercise, since the amount of capillary surface appears critical to O2 transport limitation. This integrated approach will be applied in both animal and human studies, the latter in both health and chronic disease (heart failure, chronic obstructive pulmonary disease). Animal work will use mechanistic interventions not possible in man to complement human experiments, and in both, the molecular approaches will be applied in intact physiological systems. Major goals include: 1) separating O2 transport-based exercise limitation from that due to intrinsic muscle abnormalities in chronic diseases; 2) determining if VEGF is essential to angiogenesis using Cre/loxP targeted knockout strategy, as well as VEGF antagonists such as Suramin, Losartan and Captopril; 3) defining the mechanisms that normally increase VEGF message and protein capillarity in chronic diseases. Our ultimate objective is to identify abnormalities of muscle O2 transport in chronic disease at the level of gene regulation, in the hope of eventual gene-targeted therapy. We hypothesize that these will centrally involve the muscle angiogenic response to exercise.