title: Active Brown Fat During18F-FDG PET/CT Imaging Defines a Patient Group with Characteristic Traits and an Increased Probability of Brown Fat Redetection.
abstract: Brown adipose tissue (BAT) provides a means of nonshivering thermogenesis. In humans, active BAT can be visualized by18F-FDG uptake as detected by PET combined with CT. The retrospective analysis of clinical scans is a valuable source to identify anthropometric parameters that influence BAT mass and activity and thus the potential efficacy of envisioned drugs targeting this tissue to treat metabolic disease.Methods:We analyzed 2,85418F-FDG PET/CT scans from 1,644 patients and identified 98 scans from 81 patients with active BAT. We quantified the volume of active BAT depots (mean values in mL ± SD: total BAT, 162 ± 183 [n= 98]; cervical, 40 ± 37 [n= 53]; supraclavicular, 66 ± 68 [n= 71]; paravertebral, 51 ± 53 [n= 69]; mediastinal, 43 ± 40 [n= 51]; subphrenic, 21 ± 21 [n= 29]). Because only active BAT is detectable by18F-FDG uptake, these numbers underestimate the total amount of BAT. Considering only 32 scans of the highest activity as categorized by a visual scoring strategy, we determined a mean total BAT volume of 308 ± 208 mL. In 30 BAT-positive patients with 3 or more repeated scans, we calculated a much higher mean probability to redetect active BAT (52% ± 25%) as compared with the overall prevalence of 4.9%. We calculated a BAT activity index (BFI) based on volume and intensity of individual BAT depots.Results:We detected higher total BFI in younger patients (P= 0.009), whereas sex, body mass index, height, mass, outdoor temperature, and blood parameters did not affect total or depot-specific BAT activity. Surprisingly, renal creatinine clearance as estimated from mass, age, and plasma creatinine was a significant predictor of BFI on the total (P= 0.005) as well as on the level of several individual depots. In summary, we detected a high amount of more than 300 mL of BAT tissue.Conclusion:BAT-positive patients represent a group with a higher than usual probability to activate BAT during a scan. Estimated renal creatinine clearance correlated with the extent of activated BAT in a given scan. These data imply an efficacy of drugs targeting BAT to treat metabolic disease that is at the same time higher and subject to a larger individual variation than previously assumed.
authors.affiliation: Department of Nuclear Medicine, Technical University of Munich, Munich, Germany c.gerngross@tum.de.
authors.forename: Carlos
authors.initials: C
authors.lastname: Gerngroß
authors.affiliation: Department of Nuclear Medicine, Technical University of Munich, Munich, Germany.
authors.forename: Johanna
authors.initials: J
authors.lastname: Schretter
authors.affiliation: Molecular Nutritional Medicine, ZIEL-Institute for Food & Health, Technical University of Munich, Freising, Germany; and.|Molecular Nutritional Medicine, Else Kröner-Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Klingenspor
authors.affiliation: Department of Nuclear Medicine, Technical University of Munich, Munich, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
authors.affiliation: Molecular Nutritional Medicine, ZIEL-Institute for Food & Health, Technical University of Munich, Freising, Germany; and.|Molecular Nutritional Medicine, Else Kröner-Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Fromme
mesh_terms: D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging* / Q000378:metabolism*; D000328:Adult; D017677:Age Distribution; D000375:Aging / Q000378:metabolism*; D015992:Body Mass Index; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008297:Male; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D014018:Tissue Distribution
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: FDG; brown adipose tissue; positron emission tomography