title: Seasonal influence on stimulated BAT activity in prospective trials: a retrospective analysis of BAT visualized on 18F-FDG PET-CTs and 123I-mIBG SPECT-CTs.
abstract: Retrospective studies have shown that outdoor temperature influences the prevalence of detectable brown adipose tissue (BAT). Prospective studies use acute cold exposure to activate BAT. In prospective studies, BAT might be preconditioned in winter months leading to an increased BAT response to various stimuli. Therefore the aim of this study was to assess whether outdoor temperatures and other weather characteristics modulate the response of BAT to acute cold. To assess metabolic BAT activity and sympathetic outflow to BAT, 64 (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography-computed tomography (PET-CT) and 56 additional (123)I-meta-iodobenzylguanidine ((123)I-mIBG) single-photon emission computed tomography-CT (SPECT-CT) scans, respectively, of subjects participating in previously executed trials were retrospectively included. BAT activity was measured in subjects after an overnight fast, following 2 h of cold exposure (∼17°C). The average daytime outdoor temperatures and other weather characteristics were obtained from the Dutch Royal Weather Institute. Forty-nine subjects were BAT positive. One week prior to the scan, outdoor temperature was significantly lower in the BAT-positive group compared with the BAT-negative group. Higher outdoor temperatures on preceding days resulted in lower stimulated metabolic BAT activity and volume (all P < 0.01). Outdoor temperatures did not correlate with sympathetic outflow to BAT. In conclusion, outdoor temperatures influence metabolic BAT activity and volume, but not sympathetic outflow to BAT, in subjects exposed to acute cold. To improve the consistency of the findings of future BAT studies in humans and to exclude bias introduced by outdoor temperatures, these studies should be planned in periods of similar outdoor temperatures.
authors.affiliation: Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands; and l.bahler@amc.uva.nl.
authors.forename: Lonneke
authors.identifier: 0000-0002-7542-4655
authors.initials: L
authors.lastname: Bahler
authors.affiliation: Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands; and.
authors.forename: Jan W
authors.initials: JW
authors.lastname: Deelen
authors.affiliation: Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands; and.
authors.forename: Joost B
authors.initials: JB
authors.lastname: Hoekstra
authors.affiliation: Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands; and.
authors.forename: Frits
authors.initials: F
authors.lastname: Holleman
authors.affiliation: Department of Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Hein J
authors.initials: HJ
authors.lastname: Verberne
mesh_terms: D019797:3-Iodobenzylguanidine / Q000378:metabolism*; D002001:Adipose Tissue, Brown / Q000378:metabolism* / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003080:Cold Temperature; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods; D011446:Prospective Studies; D011877:Radionuclide Imaging / Q000379:methods; D019275:Radiopharmaceuticals / Q000378:metabolism; D012189:Retrospective Studies; D012621:Seasons; D013696:Temperature; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D019797:3-Iodobenzylguanidine
keywords: brown adipose tissue; outdoor temperature; preconditioning; recruitment; season