The role of serum osteoprotegerin and receptor–activator of nuclear factor-κB ligand in metabolic bone disease of women after obesity surgery

Metabolic bone disease may appear as a complication of obesity surgery. Because an imbalance in the osteoprotegerin and receptor–activator of nuclear factor-κB ligand system may underlie osteoporosis, we aimed to study this system in humans in the metabolic bone disease occurring after obesity surgery. In this study we included sixty women with a mean age of 47 ± 10 years studied 7 ± 2 years after bariatric surgery. The variables studied were bone mineral density, β-isomer of C-terminal telopeptide of type I collagen cross-links (a bone resorption marker), the bone formation markers osteocalcin and N-terminal propeptide of procollagen 1, serum osteoprotegerin and receptor–activator of nuclear factor-κB ligand. Serum osteoprotegerin inversely correlated with the bone remodeling markers osteocalcin, β-isomer of C-terminal telopeptide of type I collagen cross-links and N-terminal propeptide of procollagen 1. The osteoprotegerin and receptor–activator of nuclear factor-κB ligand ratio also correlated inversely with serum parathormone and osteocalcin. Bone mineral density at the lumbar spine was associated with age (β = −0.235, P = 0.046), percentage of weight loss (β = 0.421, P = 0.001) and osteoprotegerin and receptor–activator of nuclear factor-κB ligand ratio (β = 0.259, P = 0.029) in stepwise multivariate analysis (R2 = 0.29, F = 7.49, P < 0.001). Bone mineral density at the hip site was associated only with percentage of weight loss (β = 0.464, P < 0.001) in stepwise multivariate regression (R2 = 0.21, F = 15.1, P < 0.001). These data show that the osteoprotegerin and receptor–activator of nuclear factor-κB ligand system is associated with bone markers and bone mineral density at the lumbar spine after obesity surgery.