Evidence of Brown Fat Activity in Constitutional Leanness

• Published in: The journal of clinical endocrinology and metabolism 2013-03, Vol.98 (3), p.1214-1218
• Main Authors: Pasanisi, Fabrizio, Pace, Leonardo, Fonti, Rosa, Marra, Maurizio, Sgambati, Donatella, De Caprio, Carmela, De Filippo, Emilia, Vaccaro, Andrea, Salvatore, Marco, Contaldo, Franco
• Format: Article
• Language: English
• Subjects: Adipose Tissue, Brown - diagnostic imaging; Adipose Tissue, Brown - metabolism; Adolescent; Adult; Anorexia Nervosa - diagnostic imaging; Anorexia Nervosa - metabolism; Biological and medical sciences; Body Mass Index; Body Temperature Regulation - physiology; Calorimetry, Indirect; Endocrinopathies; Feeding. Feeding behavior; Female; Fluorodeoxyglucose F18; Fundamental and applied biological sciences. Psychology; Humans; Linear Models; Medical sciences; Models, Biological; Positron-Emission Tomography; Thinness - diagnostic imaging; Thinness - metabolism; Tomography, X-Ray Computed; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vertebrates: endocrinology; Young Adult
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2012-2981

Background: Brown adipose tissue (BAT) was considered essentially nonexistent in adults until recent evidence obtained using 18-fluorodeoxyglucose (18-FDG) positron emission tomography/computed tomography. It seems to play a role in whole body metabolism, but it has not been evaluated in underweight conditions, such as in young females with constitutional leanness (CL) or anorexia nervosa (AN). Subjects and Methods: Thirty-eight subjects were evaluated from October 2011 to March 2012 : 7 CL (21.7 ± 3.6 y, body mass index [BMI] 16.2 ± 1.0 kg/m2), 7 AN (23.4 ± 4.5 y, BMI 15.5 ± 0.8), 3 of the 7 AN after stable refeeding (R-AN, 21.3 ± 1.5 y, BMI 18.8 ± 1.1), and 24 normal weight (NW) women (25.6 ± 3.9 y, BMI 22.2 ± 1.5). Fasting resting metabolic rate and respiratory quotient were measured by indirect calorimetry, body composition by bioimpedentiometry (only in CL, AN, and refed AN), and BAT activity by 18-FDG positron emission tomography/computed tomography scan, all in standardized conditions. Results: All CL (100%), none of the AN and refed AN (0%), and 3 of the 24 NW (12%) subjects showed FDG uptake. Average FDG maximum standardized uptake value was 11.4 + 6.7 g/mL in CL and 5.5 ± 1.2 g/mL (min 3.7, max 8.3) in the 3 NW subjects. In CL, the maximum standardized uptake value was directly correlated to resting metabolic rate, corrected for fat-free mass, and inversely correlated with respiratory quotient. Conclusion: BAT activity has been shown in CL in resting thermoneutral conditions and may exert a role against adipose tissue deposition.