Body Composition & REE Responses to Bariatric Surgeries

描述(由申请人提供)： 严重肥胖者大幅和持续减肥后，身体成分和静息能量消耗(REE)的性质是一些重要的悬而未决的问题。实验室人群非常适合研究这些问题，因为：他们的肥胖程度很少被研究，这使我们能够测试和扩大现有知识的适用范围；他们将经历大规模的体重下降；体重下降可能持续很长一段时间，从而允许器官和组织质量的适应和脂肪重新分配发生；外科干预通过不同程度的限制和吸收不良实现其效果，提供了一个机会来确定这个维度是否以及如何影响身体组成和生热。在通常的负能量平衡条件下，超重和中度肥胖者的体重减轻的组成通常是70%-80%的脂肪和20%-30%的瘦组织，然而，极端肥胖者的体重减轻的组成可能不同。我们将使用先进的身体组成模型和测量方法来分析体重快速和大幅变化的实验室患者的体重组成。利用MRI，我们将描述组织和器官水平的身体成分变化和脂肪组织的分布，从而使我们能够解决具有生物学和临床重要性的问题，包括身体成分变化对REE的影响。其具体目的是：1)确定不同类型减肥手术患者体重变化的临床重要组成部分：脂肪质量及其分布和非脂肪质量(FFM)；包括基线和手术后两个时间点的骨密度(BMD)、骨骼肌和特定器官，以及这些指标是否与手术类型有关；2)测量手术后REE的变化并确定其与手术类型、身体成分变化及其在随访中的持续时间的关系。二次研究问题涉及心脏结构和功能、心理功能以及与大规模减肥相关的激素(生长激素、瘦素、胰岛素)水平的变化。经同意，来自哥伦比亚大学威尔康奈尔分校和匹兹堡大学的符合条件的实验室患者将接受以下测量的一些组合：用氚稀释的全身水分(脂肪和FFM)、溴化钠示踪剂的细胞外水分、BodPod的身体密度、全身MRI(脂肪组织及其分布；骨骼肌肉质量；肝、肾、心脏和大脑的质量)、双能X射线吸收法(髋骨密度、全身脂肪、FFM和骨矿含量)和REE。受试者将是非洲裔美国人和高加索人女性和男性(n=106；50%(35&gt；BMI kg/m2&lt；45)将在手术前以及一年和两年后接受MRI检查；50%(45&gt；BMI/m2&lt；60)将仅在手术后接受MRI检查)平均分布在纽约和匹兹堡两个地点，并平均分布在3种外科手术中：胃束带；胆胰管转流和十二指肠转流术；以及Roux-en-Y胃搭桥术。

DESCRIPTION (provided by applicant): Important unanswered questions surround the nature of body composition and resting energy expenditure (REE) after substantial and sustained weight loss by severely obese persons. The LABS population is well suited for the study of these questions in that: they are of a degree of fatness rarely studied, which allows us to test and extend the range of applicability of current knowledge; they will undergo massive weight loss; the weight loss is likely to be sustained over a long period of time thereby allowing for adaptations of organ and tissue mass and fat redistribution to occur; the surgical interventions achieve their effects by different degrees of restriction and malabsorption, providing an opportunity to determine whether and how this dimension affects body composition and thermogenesis. The composition of weight loss under usual negative energy balance conditions in overweight and moderately obese persons is typically 70-80% fat and 20-30% lean tissues, however it is likely that the composition of weight loss in extremely obese persons may be different. We will analyze the composition of body weight in LABS patients undergoing rapid and large changes in weight using advanced body composition models and measurement methods. Using MRI, we will describe body composition changes at the tissue and organ level and adipose tissue distribution allowing us to address questions of biological and clinical importance including the body composition changes influences on REE. The Specific Aims are to: 1) identify the clinically important components of weight change in persons undergoing different types of bariatric surgery on fat mass and its distribution, and on fat-free mass (FFM); including bone mineral density (BMD), skeletal muscle, and specific organs at baseline and two time-points post surgery, and whether these are related to the type of surgery; 2) measure the change in REE following surgery induced weight loss and determine its relation to type of surgery, to changes in body composition compartments, and its duration over the follow-up. Secondary research questions relate to changes in cardiac structure and function, psychological functioning, and hormonal (ghrelin, leptin, insulin) levels associated with massive weight loss. Consenting, eligible LABS patients from Columbia University-Weill Cornell and the University of Pittsburgh will undergo some combination of the following measures: total body water by deuterium dilution (fat and FFM), extracellular water by sodium bromide tracer, body density by the BodPod, whole-body MRI (adipose tissue and its distribution; skeletal muscle mass; mass of liver, kidneys, heart, and brain), dual energy-X-ray absorptiometry (hip BMD, total body fat, FFM, and bone mineral content), and REE. Subjects will be African-American and Caucasian women and men (n=106; 50 percent (35>BMI kg/m2<45) will undergo MRI studies before surgery and one and two years later; 50 percent (45>BMI kg/m2<60) will have MRI only post surgery) equally distributed between the New York and Pittsburgh sites, and equally distributed across 3 surgical procedures: gastric banding; biliary pancreatic diversion and duodenal switch; and Roux-en-Y gastric bypass.