In FY16, we made steady progresses in the following areas. 1. Our ongoing clinical protocol titled Energy expenditure responses to a range of environmental temperatures around the thermal neutral zone (12-DK-0097, NCT01568671) was designed to improve our understanding of dynamic regulation of energy expenditure in response to subtle changes in environmental temperature. In particular, we are interested in studying the capacity of (facultative) cold-induced thermogenesis in humans, defined as an increase in energy expenditure (EE or heat production) to a changed environmental temperature. Combined with the ongoing research on brown adipose tissue (BAT) and its role in non-shivering thermogenesis (NST) in our and other labs, such clinical research is generating substantial interests in the field of energy metabolism and obesity. We measure resting energy expenditure in a 5-hour period in the room calorimeter with randomized environmental temperature ranging between 16C and 31C, in 10-13 consecutive days (a 2-week inpatient protocol). We also carefully measure potential shivering by surface electromyography (EMG), acceleration, and heart rate, skin and core body temperatures, and stress responses by blood and urinary markers, while controlling for physical activity, clothing, posture, and dietary intake. To date, we successfully studied fifteen (15) healthy lean male volunteers as our normative control group and eight (8) healthy obese male volunteers matched for age and race/ethnicity. In FY2016, we opened the protocol to the rest of three cohorts, and studied six (6) lean female volunteers, three (3) older lean male volunteers, and three (3) young lean African-American male volunteers under a shortened (7-10 day) protocol design. Preliminary data analyses showed that we could reproduce the resting EE in the thermal neutral zone (TNZ) within 4% coefficient of variation, detect the slope and the maximum capacity of cold-induced thermogenesis, all of which are helping us to understand the parameters that define the dynamic human thermobiology to a range of environmental temperatures that have not been available currently. 2. For the protocol 13-DK-0200, NCT01950520, we use a pharmacologic approach to dissect the mechanism of NST. Since the principal physiologic stimulus to BAT (and possibly muscle) NST is via sympathetic nervous system, we hypothesize that, by careful measurements of NST and using -adrenergic drugs that differ in receptor specificity and agonist/antagonist properties, we will gain better understanding of the regulation of human NST and resting EE. To date, we studied six (16) healthy subjects to date to successfully complete the first phase (Cohort 1), and are in the data analysis phase of the research. Began at FY15, we worked closely with Dr. Aaron Cypess of our Branch on the dose response of a 3-adrenergic agonists to stimulate human BAT and energy expenditure. As the primary endpoint, the efficacy of mirabegron was compared with placebo, and as a secondary endpoint, with cold exposure, which has already been shown can activate human BAT. Interim data show that when compared with placebo, a one-time, oral dose of mirabegron (200 mg) profoundly stimulated BAT thermogenesis, white adipose tissue lipolysis, and whole-body energy expenditure. Using the paradigm under our current protocol, with the advanced technology available at our lab, we added an arm to this study to explore the effects of mirabegron on BAT activity in more depth (Cohort 3). In FY16, we successfully studied thirteen (13) healthy lean male volunteers, evaluated the effects of mirabegron on BAT activity at various dosages 0 mg, 50 mg, and 200 mg compared to cold exposure (20 deg C with a colling vest). We are just completing the last study this month and are in the data analysis stage. 3. With the focus on human BAT in our protocols, we worked closely with an international consensus group of clinical researchers from the US, Finland, Netherlands, and Sweden through FY16. We published the first brown adipose acquisition and reporting criteria in imaging studies (BARCIST 1.0) which establishes minimal requirements for conducting FDG PET/CT experiments on human BAT, data analysis and publication of results. This is the first best-practice recommendation in this area, as we hope this will enhance comparability across experiments for the future. 4. We published three high-impact papers from close collaborations with Dr. Kevin Hall's group on the topic of energy expenditure and substrate utilizations. One was a follow-up study we help conducted using resting metabolic carts in the Biggest Loser cohort (15-DK-0192, NCT02544009) that we studied 5 years ago. We found that, even with 70% of weight regain, the resting EE was still about 700 kcal/day below the baseline, which suggest the existence of metabolic adaptation in extreme weight loss. With data from the Carbohydrate vs. fat study (09-DK-0081, NCT00846040), we carefully compared chamber results and found carbohydrate restriction led to sustained increases in fat oxidation and loss of about 50 g/day of body fat, fat oxidation was unchanged by fat restriction, leading to about 90 g/day of fat loss, which was significantly greater than carbohydrate restriction. In another multi-center study (with Columbia University NY Obesity Center, Pennington Biomedical Research Center, and Florida Hospital Translational Research Institute for Metabolism and Diabetes), we initialized a multi-chamber study for the first time in this research area (NCT01967563). We found that the isocaloric ketogenic diet was not accompanied by increased body fat loss but was associated with relatively small increases (50-150 kcal/day) in EE. These data challenge the current hype of low-carb dieting, at least to the metabolic benefits.
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