Cold-activated brown adipose tissue is an independent predictor of higher bone mineral density in women.
In animals, defective brown adipogenesis leads to bone loss. Whether brown adipose tissue (BAT) mass relates to bone mineral density (BMD) in humans is unclear. We determined the relationship between BAT mass and BMD by cold-stimulated positron-emission tomography (PET) and dual-energy X-ray absorptiometry (DXA) in healthy volunteers. Higher BAT mass was associated with higher BMD in healthy women, but not in men, independent of age and body composition.


BACKGROUND
Contrary to the traditional belief that BAT is present only in infants, recent studies revealed significant depots of BAT present in adult humans. In animals, defective brown adipogenesis leads to bone loss. While white adipose tissue mass is a known determinant of BMD in humans, the relationship between BAT and BMD in humans is unclear. We thus examined the relationship between BAT and BMD in healthy adults.


METHODS
BAT volume (ml) and activity (standard uptake value) were determined by 18F-fluorodeoxyglucose PET after overnight mild cold exposure at 19 °C, and BMD was determined by DXA.


RESULTS
Among 24 healthy adults (age 28±1 years, F=10), BAT volumes were 82.4±99.5 ml in women and 49.7±54.5 ml in men. Women manifested significantly higher BAT activity, by 9.4±8.1% (p=0.03), than men. BAT volume correlated positively with total and spine BMD (r2=0.40 and 0.49, respectively, p<0.02) in women and remained a significant predictor after adjustment for age, fat, and lean body mass (p<0.05). Total and spine BMD were higher in women who harbored visually detectable BAT on PET images than those without by 11±2% (p=0.02) and 22±2% (p<0.01), respectively. No associations were observed between BAT parameters and BMD in men.


CONCLUSIONS
This study demonstrated higher BMD among healthy women with more abundant BAT, independent of age and other body compositional parameters. This was not observed in men. The data suggest that brown adipogenesis may be physiologically related to modulation of bone density.
Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bldg 10, CRC, 10 Center Drive, Bethesda, MD, USA. pcylee@gmail.com
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P
Lee
R J
RJ
Brychta
M T
MT
Collins
J
J
Linderman
S
S
Smith
P
P
Herscovitch
C
C
Millo
K Y
KY
Chen
F S
FS
Celi
D015502:Absorptiometry, Photon; D050156:Adipogenesis / Q000502:physiology; D002001:Adipose Tissue, Brown / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D000328:Adult; D001823:Body Composition / Q000502:physiology; D015519:Bone Density / Q000502:physiology*; D003080:Cold Temperature; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012727:Sex Characteristics; D055815:Young Adult
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18