Objective
Weight is an important determinant of bone mineral density (BMD). Several lines of evidence have suggested that the effects of weight on BMD may be mediated by hormonal factors, with the principal candidates being serum insulin, sex hormone, and adipocytokine. Adiponectin and its receptors are expressed in human osteoblasts. Recent evidences support the primitive roles of adiponectin in bone metabolism. Recombinant adiponectin induced receptor activator of NF-κB ligand (RANKL) and inhibited osteoprotegerin (OPG) mRNA expression in osteoblasts. Thus, the aim of this study was to investigate the relationship between serum adiponectin levels with circulating OPG/RANKL system in human being.
Methods
Subjects were eighty men aged 42~70 (mean age, 54.5 yr). Serum levels of adiponectin, OPG, and RANKL were measured by ELISA. Serum levels of total testosterone, estradiol, and biochemical markers of bone turnover were measured by standard methods. Bone mineral density (BMD) at lumbar spine and femoral neck were measured by dual energy x-ray absorptiometry.
Results
Serum adiponectin levels were negatively correlated to weight, waist circumference, waist to hip ratio, and body mass index. Although serum adiponectin levels were not significantly correlated to fasting insulin and femoral neck BMD, but here was a weak trend in it. Serum adiponectin levels were not correlated with serum OPG and RANKL levels, either in the presence or absence of weight, fasting insulin, and femoral neck BMD.
Conclusion
We observed that the serum adiponectin levels were not associated with circulating OPG/RANKL system in middle-aged men. The biologic roles of adiponectin in bone metabolism still need further clarification.
