title: Presence of brown adipocytes in retroperitoneal fat from patients with benign adrenal tumors: relationship with outdoor temperature.
abstract: BACKGROUND
  Brown adipose tissue (BAT) is a metabolically highly active organ with increased thermogenic activity in rodents exposed to cold temperature. Recently its presence in the cervical adipose tissue of human adults and its association with a favorable metabolic phenotype have been reported.
  
  
  OBJECTIVE
  The objective of the study was to determine the prevalence of retroperitoneal BAT in human adults.
  
  
  METHODS
  This was an observational cohort study.
  
  
  METHODS
  The study was conducted at a tertiary referral hospital.
  
  
  METHODS
  Fifty-seven patients who underwent surgery for benign adrenal tumors were included in this study.
  
  
  METHODS
  Prevalence of retroperitoneal BAT adjacent to the removed adrenal tumor as determined by uncoupling protein 1 (UCP1) protein and mRNA expression was measured.
  
  
  RESULTS
  Using protein and mRNA expression analysis, we detected UCP1 protein in 26 of 57 patients (45.6%) as well as high mRNA expression of genes characteristic for brown adipocytes, independent of the adrenal tumor type. The presence of brown adipocytes within the retroperitoneal fat was associated with a significantly lower outdoor temperature during the month prior to surgery. Importantly, UCP1 expression on both mRNA and protein level was inversely correlated to outdoor temperature, whereas body mass index, sex, age, and diabetes status were not.
  
  
  CONCLUSIONS
  These findings suggest that human retroperitoneal adipose tissue can acquire a BAT phenotype, thereby adapting to environmental challenges. These adaptive processes might provide a valuable therapeutic target in the treatment of obesity and insulin resistance.
authors.affiliation: MD, PhD, Department of Medical and Clinical Genetics, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Medicinaregatan 9A, Box 440, SE-40530 Gothenburg, Sweden. sven.enerback@medgen.gu.se.
authors.forename: Matthias Johannes
authors.initials: MJ
authors.lastname: Betz
authors.forename: Marc
authors.initials: M
authors.lastname: Slawik
authors.forename: Martin E
authors.initials: ME
authors.lastname: Lidell
authors.forename: Andrea
authors.initials: A
authors.lastname: Osswald
authors.forename: Mikael
authors.initials: M
authors.lastname: Heglind
authors.forename: Daniel
authors.initials: D
authors.lastname: Nilsson
authors.forename: Urs Daniel
authors.initials: UD
authors.lastname: Lichtenauer
authors.forename: Brigitte
authors.initials: B
authors.lastname: Mauracher
authors.forename: Thomas
authors.initials: T
authors.lastname: Mussack
authors.forename: Felix
authors.initials: F
authors.lastname: Beuschlein
authors.forename: Sven
authors.initials: S
authors.lastname: Enerbäck
mesh_terms: D052437:Adipocytes, Brown / Q000378:metabolism*; D000310:Adrenal Gland Neoplasms / Q000378:metabolism* / Q000601:surgery; D000328:Adult; D000368:Aged; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D050152:Intra-Abdominal Fat / Q000378:metabolism* / Q000601:surgery; D007473:Ion Channels / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013696:Temperature; D000071246:Uncoupling Protein 2
chemical_list: D007473:Ion Channels; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D000071246:Uncoupling Protein 2