Objectives: The high incidence of bone disease and the increasing evidence of Crohn's disease (CD) bone decline in corticosteroid users and nonusers suggest that bone metabolism is affected by inflammatory process. The aim of the study was to compare serum levels of proinflammatory cytokines, markers of bone turnover and regulatory molecules of osteoclast biogenesis, receptor activator of nuclear factor kappaB-ligand (RANKL) and osteoprotegerin (OPG), between naïve and long-standing CD patients.
Methods: The study included 95 CD patients, 15 of them with newly diagnosed and previously untreated CD. The spine and hip bone mineral density was measured by dual-energy X-ray absorptiometry. Biochemical markers were determined by immunoassay.
Results: Osteopenia was recorded at diagnosis in 53% of naïve patients and osteoporosis was found in 26% of long-standing CD patients. The newly diagnosed patients showed correlation between TNF-alpha and soluble RANKL (sRANKL) (r=0.5; P=0.04), and this positive relationship characterized the study population as a whole (r=0.3; P=0.003). Analysis of the OPG and sRANKL relationship showed absence of correlation in patients with healthy skeleton, whereas an inverse correlation was found in those with osteopenia (r=-0.31; P=0.033) and osteoporosis (r=-0.48; P=0.028). In naïve patients with reduced T score, the correlation between sRANKL and OPG was highly inverse (r=-0.8; P=0.02) and these patients were characterized by lower BMI, significantly higher level of proinflammatory cytokines, elevated C-reactive protein, and increased activity of free sRANKL and OPG.
Conclusion: Bone disease that accompanies CD at diagnosis suggests that bone metabolism is affected by the underlying inflammatory process per se, as probably confirmed by our finding of the central proinflammatory cytokine TNF-alpha being strongly associated with the osteoclastogenic mediator RANKL, and inversely with bone density.