Impact of age on the relationships of brown adipose tissue with sex and adiposity in humans.
OBJECTIVE
Brown adipose tissue (BAT) regulates energy homeostasis and fat mass in mammals and newborns and, most likely, in adult humans. Because BAT activity and BAT mass decline with age in humans, the impact of BAT on adiposity may decrease with aging. In the present study we addressed this hypothesis and further investigated the effect of age on the sex differences in BAT activity and BAT mass.


METHODS
Data from 260 subjects (98 with BAT and 162 study date-matched control subjects) who underwent (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) under thermoneutral conditions were analyzed. BAT activity and BAT mass were determined in the upper body.


RESULTS
BAT activity and BAT mass were higher in female (1.59 +/- 0.10 and 32 +/- 5 g vs. 1.02 +/- 0.10 and 18 +/- 4 g, both P < or = 0.0006) than in male subjects. In multivariate analyses, sex (P < 0.0001), age (P < 0.0001), and BMI (P = 0.0018) were associated independently with BAT activity. Interestingly, only in male subjects was there an interaction between BMI and age in determining BAT activity (P = 0.008) and BAT mass (P = 0.0002); BMI decreased with increasing BAT activity and BAT mass in the lowest age tertile (Spearman rank correlation coefficient r(s) = -0.38, P = 0.015 and r(s) = -0.37, P = 0.017, respectively), not in the higher age tertiles. Furthermore, BAT activity and mass differed between female and male subjects only in the upper two age tertiles (all P < or = 0.09).


CONCLUSIONS
Our data corroborate that, in general, BAT activity and BAT mass are elevated in female subjects and in younger people. Importantly, we provide novel evidence that the impact of BAT activity and BAT mass on adiposity appears to decline with aging only in male subjects. Furthermore, while BAT activity and BAT mass only moderately decline with increasing age in female subjects, a much stronger effect is found in male subjects.
Pfannenberg
Christina
C
Department of Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany.
Werner
Matthias K
MK
Ripkens
Sabine
S
Stef
Irina
I
Deckert
Annette
A
Schmadl
Maria
M
Reimold
Matthias
M
Häring
Hans-Ulrich
HU
Claussen
Claus D
CD
Stefan
Norbert
N
D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging* / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D002648:Child; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D012016:Reference Values; D012737:Sex Factors; D018709:Statistics, Nonparametric