Human Energy and Body Weight Regulation Core

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Research highlights: 1. Brown adipose tissue continues to interest us as a potential source of increasing energy expenditure non-pharmacologically. In collaboration with Dr. Celi, we just completed studying 31 healthy volunteers in two overnight studies in the metabolic chamber, 12-hr environmental temperature randomized at 24 or 19 C. We found a 5-6% increase in 12-hr energy expenditure at 19 vs. 24 C which is comparable to our previously published finding in the day time. In order to explore the role of the brown adipose tissue we measured its activity by 18FDG-PET imaging. Although only 6 subjects showed visible brown adipose tissue activity at 19 C (as compare to none at 25 C), we hypothesis that the whole-body FDG uptake levels might be calculated to give us a metric of overall fuel utilization for heat generation, and thus better correlate with the individual changes in energy expenditure. We are in the process of analyzing this data and preparing a manuscript. 2. Resting energy expenditure may be reduced during weight loss in additional to the loss of fat-free mass and fat mass. In collaboration with Drs. Simchowitz and Celi, we are studying the potential role of thyroid hormone in contributing to the changes in resting energy expenditure during weight loss, using the repeated measurements of resting energy expenditure, body composition, and thyroid hormone levels at baseline and throughout the weight loss (up-to one year) in a group of (n=36) patients who are going through weight loss by life-style interventions with frequent follow-ups and repeated measurements. Preliminary analysis has shown trends in the changes in T3 levels and changes in resting energy expenditure in the early weight loss stage (one and three months), after controlling for the changes in fat and fat-free masses, but the association was not seen after 6 months. 3. The prevalence of overweight black women is higher than that of white women, and is associated with greater impairment in insulin-mediated glucose uptake. Exercise performance, which affects insulin sensitivity, contributes to a race difference in glucose utilization is being explored in 153 non-diabetic overweight women (63% black) in a cohort of patients by Dr. Cannon and our group (with Dr. Sumner). We found a statistical significant association between exercise capacity and insulin sensitivity index (as measured by IVGTT) in blacks but not in whites. We continue to analyze this data and to prepare the manuscript. 4. A lower core body temperature "set point" has been suggested to be a factor that could potentially predispose humans to develop obesity. Together with Drs. Yanovski and Skarulis, we tested the hypothesis that obese individuals might have lower core temperatures than those in normal-weight individuals. We did not, however, find a difference in mean daily or 24-hr time profiles of core temperature between 46 obese and 35 non-obese healthy volunteers (studied on the metabolic unit). We did find women to have a 0.23 C greater mean core temperature than men, which was similar to other previous studies. This study was published in AJCN. Services rendered (FY11 activities): 24-hr energy expenditure by whole-room respiratory chambers (244), resting energy expenditure by metabolic carts (371), exercise and physical function testing (86), experimental satiety test (139), body composition (404 Bod Pod, 390 DXA), objective physical activity monitoring (467 days), muscle biopsies (23), subcutaneous fat biopsies (88), and Health and Physical Exams (50).