title: Differences in Sympathetic Nervous Stimulation of Brown Adipose Tissue Between the Young and Old, and the Lean and Obese.
abstract: Brown adipose tissue (BAT) could facilitate weight loss by increasing energy expenditure. Cold is a potent stimulator of BAT, activating BAT primarily through the sympathetic nervous system (SNS). Older or overweight individuals have less metabolic BAT activity than the lean and young, but the role of the SNS in this decline is unknown. We aimed to determine whether this lower metabolic BAT activity in older or overweight individuals can be explained by a lower SNS response to cold.
  
  
  METHODS
  This was a prospective observational study. We included 10 young obese, 11 old lean, and 14 young lean healthy men. All subjects underwent (18)F-FDG PET/CT and (123)I-meta-iodobenzylguanidine ((123)I-mIBG) SPECT/CT after an overnight fast and 2 h of cold exposure. Metabolic BAT activity was expressed as volume and as SUVmax of (18)F-FDG. BAT SNS activity was expressed as volume and as the ratio between (123)I-mIBG uptake in BAT and a reference region (SQUVmax of (123)I-mIBG).
  
  
  RESULTS
  SUVmax, BAT volume, and SQUVmax were significantly different between young and old (SUVmax, 7.9 [range, 4.2-17.3] vs. 2.9 [range, 0.0-4.0]; volume, 124.8 [range, 10.9-338.8] vs. 3.4 [range, 0.0-10.9]; and SQUVmax, 2.7 [range, 1.9-4.7] vs. 0.0 [range, 0.0-2.2], respectively) (all P < 0.01) but not between lean and obese (SUVmax, 7.9 [range, 4.2-17.3] vs. 4.0 [range, 0.0-13.5] [P = 0.69]; volume, 124.8 [range, 10.9-338.8] vs. 11.8 [range, 0.0-190.2] [P = 0.64]; and SQUVmax, 2.7 [range, 1.9-4.7] vs. 1.7 [range, 0-3.5] [P = 0.69], respectively). We found a strong positive correlation between BAT activity measured with (18)F-FDG and (123)I-mIBG in the whole group of BAT-positive subjects (ρ = 0.82, P < 0.01).
  
  
  CONCLUSIONS
  Both sympathetic drive and BAT activity are lower in older but not in obese men.
authors.affiliation: Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands l.bahler@amc.uva.nl.
authors.forename: Lonneke
authors.initials: L
authors.lastname: Bahler
authors.affiliation: Department of Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Hein J
authors.initials: HJ
authors.lastname: Verberne
authors.affiliation: Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Wanda M
authors.initials: WM
authors.lastname: Admiraal
authors.affiliation: Laboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, Academic Medical Center, Amsterdam, The Netherlands; and.
authors.forename: Wim J
authors.initials: WJ
authors.lastname: Stok
authors.affiliation: Department of Endocrinology and Metabolism, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Maarten R
authors.initials: MR
authors.lastname: Soeters
authors.affiliation: Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Joost B
authors.initials: JB
authors.lastname: Hoekstra
authors.affiliation: Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Frits
authors.initials: F
authors.lastname: Holleman
mesh_terms: D019797:3-Iodobenzylguanidine; D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging / Q000254:growth & development* / Q000294:innervation*; D000328:Adult; D000375:Aging / Q000502:physiology; D001835:Body Weight; D003080:Cold Temperature; D004734:Energy Metabolism; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology*; D050177:Overweight / Q000473:pathology / Q000503:physiopathology; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D013564:Sympathetic Nervous System / Q000000981:diagnostic imaging / Q000502:physiology* / Q000503:physiopathology*; D055105:Waist Circumference; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D019797:3-Iodobenzylguanidine
keywords: 123I-mIBG SPECT/CT; 18F-FDG PET/CT; age; brown adipose tissue; obesity