title: Brown adipose tissue volume in healthy lean south Asian adults compared with white Caucasians: a prospective, case-controlled observational study.
abstract: BACKGROUND
  Individuals of south Asian origin have a very high risk of developing type 2 diabetes compared with white Caucasians. We aimed to assess volume and activity of brown adipose tissue (BAT), which is thought to have a role in energy metabolism by combusting fatty acids and glucose to produce heat and might contribute to the difference in incidence of type 2 diabetes between ethnic groups.
  
  
  METHODS
  We enrolled Dutch nationals with south Asian ancestry and matched Caucasian participants at The Rijnland Hospital (Leiderdorp, Netherlands). Eligible participants were healthy lean men aged 18-28 years, and we matched groups for BMI. We measured BAT volume and activity with cold-induced (18)F-fluorodeoxyglucose ((18)F-FDG) PET CT scans, and assessed resting energy expenditure, non-shivering thermogenesis, and serum parameters. This study is registered with the Netherlands Trial Register, number 2473.
  
  
  RESULTS
  Between March 1, 2013, and June 1, 2013, we enrolled 12 participants in each group; one Caucasian participant developed hyperventilation after (18)F-FDG administration, and was excluded from all cold-induced and BAT measurements. Compared with Caucasian participants, south Asian participants did not differ in age (mean 23.6 years [SD 2.8] for south Asians vs 24.6 years [2.8] for Caucasians) or BMI (21.5 kg/m(2) [2.0] vs 22.0 kg/m(2) [1.6]), but were shorter (1.74 m [0.06] vs 1.85 m [0.04]) and lighter (65.0 kg [8.5] vs 75.1 kg [7.2]). Thermoneutral resting energy expenditure was 1297 kcal per day (SD 123) in south Asian participants compared with 1689 kcal per day (193) in white Caucasian participants (difference -32%, p=0.0008). On cold exposure, shiver temperature of south Asians was 2.0°C higher than Caucasians (p=0.0067) and non-shivering thermogenesis was increased by 20% in white Caucasians (p<0.0001) but was not increased in south Asians. Although the maximum and mean standardised uptake values of (18)F-FDG in BAT did not differ between groups, total BAT volume was lower in south Asians (188 mL [SD 81]) than it was in Caucasians (287 mL [169]; difference -34%, p=0.04). Overall, BAT volume correlated positively with basal resting energy expenditure in all assessable individuals (β=0.44, p=0.04).
  
  
  CONCLUSIONS
  Lower resting energy expenditure, non-shivering thermogenesis, and BAT volumes in south Asian populations might underlie their high susceptibility to metabolic disturbances, such as obesity and type 2 diabetes. Development of strategies to increase BAT volume and activity might help prevent and treat such disorders, particularly in south Asian individuals.
  
  
  BACKGROUND
  Dutch Heart Foundation (2009T038) and Dutch Diabetes Research Foundation (2012.11.1500).
authors.affiliation: Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: Leontine E H
authors.initials: LE
authors.lastname: Bakker
authors.affiliation: Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, Netherlands. Electronic address: m.r.boon@lumc.nl.
authors.forename: Mariëtte R
authors.initials: MR
authors.lastname: Boon
authors.affiliation: Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: Rianne A D
authors.initials: RA
authors.lastname: van der Linden
authors.affiliation: Department of Nuclear Medicine, Rijnland Hospital, Leiderdorp, Netherlands.
authors.forename: Lenka Pereira
authors.initials: LP
authors.lastname: Arias-Bouda
authors.affiliation: Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: Jan B
authors.initials: JB
authors.lastname: van Klinken
authors.affiliation: Department of Nuclear Medicine, Rijnland Hospital, Leiderdorp, Netherlands.
authors.forename: Frits
authors.initials: F
authors.lastname: Smit
authors.affiliation: Department of Nuclear Medicine, Academic Medical Center, Amsterdam, Netherlands.
authors.forename: Hein J
authors.initials: HJ
authors.lastname: Verberne
authors.affiliation: Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, Netherlands; Department of Cardiology, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: J Wouter
authors.initials: JW
authors.lastname: Jukema
authors.affiliation: Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: Jouke T
authors.initials: JT
authors.lastname: Tamsma
authors.affiliation: Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, Netherlands; Department of Cardiology, Leiden University Medical Center, Leiden, Netherlands; TNO-Biosciences, Leiden, Netherlands.
authors.forename: Louis M
authors.initials: LM
authors.lastname: Havekes
authors.affiliation: Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, Maastricht, Netherlands.
authors.forename: Wouter D
authors.initials: WD
authors.lastname: van Marken Lichtenbelt
authors.affiliation: Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: Ingrid M
authors.initials: IM
authors.lastname: Jazet
authors.affiliation: Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: Patrick C N
authors.initials: PC
authors.lastname: Rensen
mesh_terms: D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging*; D050154:Adiposity; D000328:Adult; D044466:Asian People; D015992:Body Mass Index; D004198:Disease Susceptibility; D004734:Energy Metabolism; D006801:Humans; D008297:Male; D008659:Metabolic Diseases / Q000453:epidemiology; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D022722:Thermogenesis; D044465:White People