Young women with cold-activated brown adipose tissue have higher bone mineral density and lower Pref-1 than women without brown adipose tissue: a study in women with anorexia nervosa, women recovered from anorexia nervosa, and normal-weight women

Abstract

Context: Anorexia nervosa (AN) is associated with depletion of body fat, loss of bone mineral density (BMD), and impaired thermogenesis. Brown adipose tissue (BAT) is lower in obese individuals and decreases during aging. Recent studies have suggested a link between BAT and bone metabolism.

Objective: Our objective was to investigate the presence and quantity of BAT in patients with AN, recovered AN (AN-R), and normal-weight controls and to study the relationship between BAT and BMD and body composition and investigate hormonal predictors of BAT.

Design and setting: This was a cross-sectional study at a clinical research center.

Patients: Patients included 15 women: five with AN (mean age 30 ± 6.3 yr), five AN-R, and five healthy nonobese controls of comparable age.

Main outcome measures: Cold-activated BAT was determined by fluorodeoxyglucose-positron emission tomography/computed tomography. BMD of total-body, spine, and hip, fat and lean mass was determined by dual-energy x-ray absorptiometry. Single-slice magnetic resonance imaging at L4 was done for abdominal fat compartments, and preadipocyte factor-1 (Pref-1), T₃, and T₄ were measured.

Results: Within the AN group, one of five; in the AN-R group, two of five; and in the healthy nonobese control group, four of five subjects were BAT positive. Subjects were divided into groups based on the presence (n = 7) or absence (n = 8) of BAT. Both groups were of comparable age and body mass index. Women with BAT had higher total-body BMD, higher T₃, and lower Pref-1 compared with women without BAT. There was a positive correlation between BAT and BMD that remained significant after controlling for disease status and body mass index.

Conclusion: Young women with AN have low cold-activated BAT, which may be due to impaired BAT thermogenesis. Young women with BAT have higher BMD and lower Pref-1 compared with women without BAT, suggesting that BAT may be involved in the regulation of stem cell differentiation into the bone lineage at the expense of adipogenesis.

Fig. 1.

A, FDG-PET image in a 27-yr-old HC subject (BMI = 21 kg/m², 95.9% IBW) showing increased FDG uptake along the neck and in the supraclavicular regions and axillae, which corresponded to BAT on the PET/CT. B, FDG-PET in a 28-yr-old subject with AN (BMI = 17.3 kg/m², 77% IBW) showing no evidence of BAT.

Fig. 2.

Regression analysis of BAT on lumbar spine BMD. There was a positive correlation BAT and lumbar spine BMD. Diamonds represent subjects with AN, squares AN-R, and triangles HC.