title: Blunted metabolic responses to cold and insulin stimulation in brown adipose tissue of obese humans.
abstract: OBJECTIVE
  Inactive brown adipose tissue (BAT) may predispose to weight gain. This study was designed to measure metabolism in the BAT of obese humans, and to compare it to that in lean subjects. The impact of weight loss on BAT and the association of detectable BAT with various metabolic characteristics were also assessed.
  
  
  METHODS
  Using positron emission tomography (PET), cold- and insulin-stimulated glucose uptake and blood flow in the BAT of obese and lean humans were quantified. Further, cold-induced glucose uptake was measured in obese subjects before and after a 5-month conventional weight loss.
  
  
  RESULTS
  Mean responses in BAT glucose uptake rate to both cold and insulin stimulation were twice as large in lean as in obese subjects. Blood flow in BAT was also lower in obese subjects under cold conditions. The increase in cold-induced BAT glucose uptake rate after weight loss was not statistically significant. Subjects with cold-activated detectable BAT were leaner and had higher whole-body insulin sensitivity than BAT-negative subjects, irrespective of age and gender.
  
  
  CONCLUSIONS
  The effects of cold and insulin on BAT activity are severely blunted in obesity, and the presence of detectable BAT may contribute to a metabolically healthy status.
authors.affiliation: Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland.
authors.forename: Janne
authors.initials: J
authors.lastname: Orava
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nuutila
authors.forename: Tommi
authors.initials: T
authors.lastname: Noponen
authors.forename: Riitta
authors.initials: R
authors.lastname: Parkkola
authors.forename: Tapio
authors.initials: T
authors.lastname: Viljanen
authors.forename: Sven
authors.initials: S
authors.lastname: Enerbäck
authors.forename: Aila
authors.initials: A
authors.lastname: Rissanen
authors.forename: Kirsi H
authors.initials: KH
authors.lastname: Pietiläinen
authors.forename: Kirsi A
authors.initials: KA
authors.lastname: Virtanen
mesh_terms: D002001:Adipose Tissue, Brown / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D000328:Adult; D031204:Caloric Restriction; D003080:Cold Temperature; D005081:Exercise Therapy; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D013312:Stress, Physiological; D013851:Thinness / Q000378:metabolism; D061217:Weight Reduction Programs
chemical_list: D007328:Insulin; D005947:Glucose