Cold-activated brown adipose tissue is an independent predictor of higher bone mineral density in women

Abstract

SUMMARY

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 using 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 men, independent of age and body composition.

INTRODUCTION

Contrary to 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 (SUV)) were determined by ¹⁸F-Fluorodeoxyglugose ( ¹⁸F-FDG) Positron Emission Tomography (PET) after overnight mild cold exposure at 19°C and BMD by DXA.

RESULTS

Among 24 healthy adults (age 28±1 yr, F=10), BAT volumes were 82.4±99.5 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 in men. BAT volume correlated positively with total and spine BMD (r ²=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 was 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.