SINGLE SKELETAL MUSCLE FIBER MECHANICS AND MYOSIN KINETICS IN HUMAN AGING

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 我们研究的总体长期目标是在分子水平上研究衰老如何改变人类骨骼肌功能。本次提交的目的是获得批准，对年轻（21-35岁，n=24）和老年（65-75岁，n=24）志愿者人群进行肌肉功能测量，以完成NIH K 01资助的两个目标。 1)目标（NIH K 01补助金的具体目标）： 肌肉质量和性能的减少，或肌肉减少症，降低了一个人执行日常任务的能力，增加了他们跌倒和跌倒相关伤害的风险。这种功能能力下降的一个关键预测因素是肌肉力量（力量x速度）的减少。虽然研究表明，单肌纤维力的产生和收缩速度随着年龄的增长而减少，但没有报道的研究已经检查了单纤维肌肉性能与年龄相关的递减的分子基础。我们已经开发了协议和技术平台，将正弦分析应用于人类骨骼肌纤维，允许检查年龄对肌球蛋白-肌动蛋白跨桥水平上的单个肌纤维动力学和结构的影响。我们的假设是，衰老通过抑制肌球蛋白动力学参数和减少肌球蛋白含量来降低收缩功能。我们将通过检查年轻和老年男性和女性大腿肌肉（股外侧肌）的单个骨骼肌纤维功能来验证这一假设。 2)涉及人类受试者的程序： 在佛蒙特大学综合临床研究中心（GCRC）或心脏康复中心的两次（年轻）或三次（老年）门诊访视期间，将进行以下程序： 肌肉力量测试-将使用多关节测力计在等长和等速条件下测试膝伸肌的收缩性能。 运动应激试验-在跑步机运动期间测量有氧运动能力。 身体成分分析-将通过双能X射线吸收法测量全身脂肪和无脂肪组织质量，以确定全身瘦组织质量和四肢肌肉质量。将通过计算机断层扫描测量大腿肌肉横截面积。 心电图-将进行静息心电图检查，以检测心脏病体征，并在运动试验期间对老年人进行静息心电图检查，以监测心脏功能。 血液样本-将采集血液样本，以测量标准血液化学、计数（CBC w/diff）和肝/肾/激素功能，并根据GCRC对接受肌肉活检程序的任何志愿者的要求确定凝血能力（PT/PTT）。 肌肉组织采集-将在利多卡因麻醉下对右大腿和左大腿（股外侧肌）进行经皮活检。 以下程序将由GCRC以外的志愿者执行： 问卷-将完成测量8个领域（包括身体功能、角色功能、身体疼痛、一般健康、活力、社会功能、心理健康和报告的健康转变）的医学结局简表问卷（MOS-SF-36）。 活动监测器-将一个小型加速度计连接到受试者的裤子上7天，以监测活动水平。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The overall, long-term goal of our research is to examine how aging alters skeletal muscle function in humans at the molecular level. The purpose of this submission is to obtain approval to perform muscle function measurements on a population of young (21-35 yrs old, n=24) and elderly (65-75 yrs old, n=24) volunteers in order to complete two goals of a funded NIH K01 grant. 1) Objectives (Specific Aims of the NIH K01 Grant): Age-related reductions in muscle mass and performance, or sarcopenia, decrease a person's ability to perform everyday tasks and increase their risk of falling and fall-related injuries. A key predictor of this decrease in functional capacity is a reduction in muscle power (force x velocity). Although studies have shown that single muscle fiber force production and contractile velocity are reduced with age, no reported study has examined the molecular basis of the age-related decrements in single fiber muscle performance. We have developed protocols and technological platforms to apply sinusoidal analysis to human skeletal muscle fibers that allow examination of the effect of age on single muscle fiber kinetics and structure at the level of the myosin-actin cross-bridge. Our hypothesis is that aging reduces contractile function by depressing myosin kinetic parameters and reducing myosin protein content. We will test this hypothesis by examining single skeletal muscle fiber function of the thigh muscle (vastus lateralis) in young and elderly men and women. 2) Procedures involving human subjects: The following procedures will be performed during two (young) or three (elderly) out-patient visits to the University of Vermont General Clinical Research Center (GCRC) or Cardiac Rehabilitation Center: Muscle Strength Testing - The contractile performance of the knee extensor muscles will be tested under isometric and isokinetic conditions using a multi-joint dynamometer. Exercise Stress Test - Aerobic exercise capacity will be measured during treadmill exercise. Body Composition Analysis - Whole body fat and fat-free tissue mass will be measured by dual energy x-ray absorptiometry to determine whole body lean tissue mass and appendicular muscle mass. Thigh muscle cross-sectional area will be measured by computed tomography. Electrocardiogram - Resting ECG will be performed to test for signs of heart disease and will be performed on the elderly during the exercise test to monitor cardiac function. Blood Samples - Blood samples will be taken to measure standard blood chemistry, counts (CBC w/diff), and liver/kidney/hormonal function and to determine clotting ability (PT/PTT) per the GCRC's requirement of any volunteer undergoing the muscle biopsy procedure. Muscle Tissue Collection - Percutaneous biopsies of the right and left thigh (vastus lateralis) will be performed under lidocaine anesthesia. The following procedures will be performed by volunteers outside of the GCRC: Questionnaires - A Medical Outcomes Short Form Questionnaire (MOS-SF-36) which measures 8 domains, including physical functioning, role functioning, bodily pain, general health, vitality, social functioning, mental health and reported health transition, will be completed. Activity monitor - A small accelerometer will be attached to the subject's waistband of their pants for 7 days to monitor activity level.