AGING AND SKELETAL MUSCLE--NEW BODY COMPOSITION MODELS

骨骼肌是组织系统中最大的组成部分之一。 身体成分的水平，并参与许多生物过程。 老年人的虚弱、骨质疏松症和恶病质 获得性免疫缺陷综合征只是 哪块肌肉起着重要的作用。尽管骨骼与 肌肉对这么多急慢性疾病，所用的方法 对活体肌肉的估计仍然有限，研究不足。 越来越多的证据有力地表明，目前可用的大多数 测量肌肉质量的方法通常不准确或 在应用于选定的组时出现系统性错误。的来源 错误/偏见可能包括：1.未能解释肌肉的变化 随着年龄的增长而产生的成分(例如，减少肌肉含量 钾和肌酸-磷酸，细胞外的相对扩张 体液、改变纤维类型比例和肌肉内脂肪组织 2.对族裔模型/方法的调整不充分 (例如，纤维类型比例和肌肉中的白色和黑色差异 分布)。活体骨骼肌研究的重大进展 引入了全身计算机断层扫描(CT)和更多 最近，核磁共振(MR)成像。来自我们的试点研究 基于CT和其他方法的实验室证明了不准确和 大多数广泛使用的测量方法存在较大的系统误差 活体肌肉质量(例如，中子激活和CT肌肉估计(X 正/负SD)、27.5正/负8.4公斤和34.4正/负6.2公斤)不同 健康男性平均增加20.0%；人体测量手臂肌肉面积 老年妇女的测量未能发现显著意义(p&lt；0.05) 肌肉质量的减少。 拟议的研究计划的总体目标有两个：研究， 使用最先进的方法(例如，MR成像和光谱学， 肌肉活检、~(13)C-肌酐动力学和遗传标记的分析 种族混杂)生物的(组成、分布和功能) 不同年龄、性别和种族的骨骼肌，并应用这一点 信息对方法的开发将允许广泛的 调查人员估计并适当解释全身骨骼 从流行病学现场站到环境中的肌肉质量 研究实验室。这些假设将得到检验，并有明确的目标。 在240名健康的白人和黑人男性和女性中进行了这项研究 18年前。 这项研究将填补身体成分方法学的一个重要空白。 并提供关于特定种族变化的广泛新信息 随着年龄的增长发生在肌肉中。

Skeletal muscle is one of the largest components at the tissue-system level of body composition and is involved in many biological processes. Weakness and frailty in the elderly, osteoporosis, and the cachexia of acquired immunodeficiency syndrome are only a few of the conditions in which muscle plays an important role. Despite the relevance of skeletal muscle to so many acute and chronic conditions, the methods used to estimate muscle in vivo remain limited and understudied. Accumulating evidence strongly suggests that most presently available methods of measuring muscle mass are inaccurate in general or systematically in error when applied to selected groups. The sources of error/bias may include: 1. a failure to account for changes in muscle composition that occur with aging (e.g., decreasing muscle contents of potassium and creatine-phosphate, relative expansion of extracellular fluid, changing fiber-type proportions, and intramuscular adipose tissue deposition); and 2. inadequate adjustment of models/methods for ethnicity (e.g., white-black differences in fiber-type proportions and muscle distribution). A major advance in the study of skeletal muscle in vivo was the introduction of whole-body computerized tomography (CT) and more recently magnetic resonance (MR) imaging. Pilot studies from our laboratory based on CT and other methods demonstrate inaccuracies and large systematic errors in most of the widely used methods for measuring muscle mass in vivo (e.g., neutron activation and CT muscle estimates (X plus/minus SD), 27.5 plus/minus 8.4 kg & 34.4 plus/minus 6.2 kg) differed by an average of 20.0% in healthy men; and anthropometric arm muscle area measurements in elderly women failed to detect significant (p<0.05) reductions in muscle mass. The overall aim of the proposed research program is twofold: to study, using state-of-the-art methods (e.g., MR imaging and spectroscopy, analyses of muscle biopsies, 13C-creatinine kinetics, & genetic markers of racial admixture) the biology (composition, distribution, and function) of skeletal muscle across age, gender, and ethnic groups, and to apply this information to the development of methods that will allow a broad range of investigators to estimate and appropriately interpret whole-body skeletal muscle mass in settings that range from epidemiologic field stations to the research laboratory. The hypotheses will be tested and specific aims carried out in 240 healthy white and black men and women over the age of 18 yrs. This research will fill an important gap in body composition methodology and provide extensive new information on the ethnic-specific changes that occur in muscle with aging.