Selected adipose tissue hormones, bone metabolism, osteoprotegerin and receptor activator of nuclear factor-kB ligand in postmenopausal obese women

Abstract

Introduction: It has been suggested that changes in the production of adipose tissue hormones in obese postmenopausal women might affect their bone status. The aim of this study was to determine whether obese postmenopausal women exhibited any relationship between serum levels of LP, ADIPO, RES, VISF, APE and bone metabolism markers (OC and CTx), OPG, sRANKL, the OPG/sRANKL ratio as well as BMD.

Material and methods: 80 postmenopausal women (60 obese and 20 healthy) underwent BMD measurement using dual-energy X-ray absorptiometry (DXA) at lumbar spine L2-L4. Serum levels of selected adipose tissue hormones, OC, CTx, OPG and its soluble ligand, sRANKL, were assessed by ELISA.

Results: Obese postmenopausal women demonstrated a significant increase in body mass, BMI and WHR associated with significant increases in LP and RES levels, a decrease in ADIPO concentration, suppression of OC, CTx, OPG and sRANKL and an increase in the OPG/sRANKL ratio and BMD. BMI correlated positively with BMD, LP, RES, OPG and the OPG/sRANKL ratio, whereas in the case of ADIPO, OC, CTx, sRANKL the relationship was negative. WHR was positively correlated with the OPG/sRANKL ratio, and negatively with ADIPO and APE. A positive correlation was found between BMD and LP, APE and the OPG/sRANKL ratio, while the correlation between BMD and ADIPO, CTx, sRANKL was negative. Significant positive correlations were also revealed between OC, CTx and ADIPO; OPG and ADIPO; sRANKL and ADIPO, RES; the OPG/sRANKL ratio and LP. OC correlated negatively with LP, RES, VISF, APE; CTx with LP, VISF, APE; OPG with LP; sRANKL with LP and APE; the OPG/sRANKL ratio with VISF. ADIPO was an independent predictor of OC, OPG and sRANKL, while LP turned out to be an independent predictor of CTx, OPG, sRANKL and the OPG/sRANKL ratio.

Conclusions: Obesity in postmenopausal women can lead to changes in BMD, circulating levels of bone markers, OPG, sRANKL and/or the OPG/sRANKL ratio; these changes are associated with alterations in the concentrations of adipose tissue hormones under investigation. The relationships between bone status indicators and adipose tissue hormones, especially LP and ADIPO, seem to suggest that changes in these hormones observed in obese postmenopausal women might have a protective effect on bone tissue, most probably via a shift in the OPG/sRANKL ratio towards a functional excess of OPG.