title: Evidence of brown fat activity in constitutional leanness.
abstract: 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).
  
  
  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/m(2)), 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.
  
  
  CONCLUSIONS
  BAT activity has been shown in CL in resting thermoneutral conditions and may exert a role against adipose tissue deposition.
authors: Federico II University of Naples, Department of Clinical Medicine and Surgery, Via Pansini 5, Naples, Italy. pasanisi@unina.it
authors: Fabrizio
authors: F
authors: Pasanisi
authors: Leonardo
authors: L
authors: Pace
authors: Rosa
authors: R
authors: Fonti
authors: Maurizio
authors: M
authors: Marra
authors: Donatella
authors: D
authors: Sgambati
authors: Carmela
authors: C
authors: De Caprio
authors: Emilia
authors: E
authors: De Filippo
authors: Andrea
authors: A
authors: Vaccaro
authors: Marco
authors: M
authors: Salvatore
authors: Franco
authors: F
authors: Contaldo
mesh_terms: D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000856:Anorexia Nervosa / Q000000981:diagnostic imaging / Q000378:metabolism*; D015992:Body Mass Index; D001833:Body Temperature Regulation / Q000502:physiology; D002153:Calorimetry, Indirect; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D016014:Linear Models; D008954:Models, Biological; D049268:Positron-Emission Tomography; D013851:Thinness / Q000000981:diagnostic imaging / Q000378:metabolism*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D019788:Fluorodeoxyglucose F18