title: Prevalence, mass, and glucose-uptake activity of ¹⁸F-FDG-detected brown adipose tissue in humans living in a temperate zone of Italy.
abstract: BACKGROUND
  The ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG)-detected brown adipose tissue (BAT), is enhanced by cold stimulus and modulated by other factors that still have to be disentangled. We investigated the prevalence, mass, and glucose-uptake activity of ¹⁸F-FDG-detected BAT in a population of adults living in the temperate climatic zone of the Rome area.
  
  
  RESULTS
  We retrospectively analyzed 6454 patients who underwent ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) examinations. We found ¹⁸F-FDG BAT in 217 of the 6454 patients (3.36%). Some of them underwent more than one scan and the positive scans were 278 among 8004 (3.47%). The prevalence of patients with at least one positive scan was lower in men (1.77%; 56 of 3161) compared with women (4.88%; 161 of 3293). The BAT positive patients were most frequently younger, thinner and with lower plasma glucose levels compared with BAT negative patients. The amount of BAT in the defined region of interest, the activity of BAT and the number of positive sites of active BAT were similar in both sexes. The prevalence of patients with ¹⁸F-FDG positive PET/CT was highest in December-February, lower in March-May and September-November, and lowest in June-August and was positively correlated with night length and negatively correlated with ambient temperature. Changes in day length and variations of temperature, associated with the prevalence of positive BAT patients. Among the patients who had multiple scans, outdoor temperature was significantly lower and day length was shorter on the occasion when BAT was detected.
  
  
  CONCLUSIONS
  This study identifies day length, outdoor temperature, age, sex, BMI, and plasma glucose levels as major determinants of the prevalence, mass, and activity of ¹⁸F-FDG-detected BAT.
authors.affiliation: Section of Medical Pathophysiology, Food Science and Endocrinology, Department of Experimental Medicine, University of Rome "La Sapienza", Rome, Italy.
authors.forename: Agnese
authors.initials: A
authors.lastname: Persichetti
authors.forename: Rosa
authors.initials: R
authors.lastname: Sciuto
authors.forename: Sandra
authors.initials: S
authors.lastname: Rea
authors.forename: Sabrina
authors.initials: S
authors.lastname: Basciani
authors.forename: Carla
authors.initials: C
authors.lastname: Lubrano
authors.forename: Stefania
authors.initials: S
authors.lastname: Mariani
authors.forename: Salvatore
authors.initials: S
authors.lastname: Ulisse
authors.forename: Italo
authors.initials: I
authors.lastname: Nofroni
authors.forename: Carlo Ludovico
authors.initials: CL
authors.lastname: Maini
authors.forename: Lucio
authors.initials: L
authors.lastname: Gnessi
mesh_terms: D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000328:Adult; D000367:Age Factors; D001786:Blood Glucose / Q000032:analysis; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007558:Italy; D008297:Male; D017440:Photoperiod; D049268:Positron-Emission Tomography / Q000379:methods; D012189:Retrospective Studies; D012737:Sex Factors; D013696:Temperature; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D001786:Blood Glucose; D019788:Fluorodeoxyglucose F18; D005947:Glucose