No evidence of circulating autoantibodies against osteoprotegerin in patients with celiac disease

AIM: To investigate risk factors for low bone mineral density (BMD) in celiac disease (CD) patients, focusing on circulating autoantibodies against osteoprotegerin (OPG). METHODS: Seventy asymptomatic CD adult patients on gluten-free diet (GFD) and harbouring persistent negative CD-related serology were recruited. Conventional risk factors for osteoporosis (e.g., age, sex, menopausal status, history of fractures, smoke, and body mass index) were checked and BMD was assessed by dual energy X ray absorptiometry. Serum calcium and parathyroid hormone (PTH) levels were evaluated. Thirty-eight patients underwent repeat duodenal biopsy. Serum samples from a selected sub-group of 30 patients, who were also typed for human leukocyte antigen (HLA) DQ2 and DQ8 haplotype, were incubated with homodimeric recombinant human OPG and tested by western blotting with an anti-OPG antibody after immunoprecipitation. RESULTS: Despite persistent negative CD-related serology and strict adherence to GFD, 49 out of the 70 (74%) patients displayed low BMD. Among these patients, 13 (24%) showed osteoporosis and 36 (76%) osteopenia. With the exception of age, conventional risk factors for osteoporosis did not differ between patients with normal and low BMD. Circulating serum calcium and PTH levels were normal in all patients. Duodenal mucosa healing was found in 31 (82%) out of 38 patients who underwent repeat duodenal biopsy with 20 (64%) still displaying low BMD. The remaining 7 patients had an incomplete normalization of duodenal mucosa with 6 (84%) showing low BMD. No evidence of circulating antibodies against OPG was found in the serum of 30 celiac patients who were tested for, independent of BMD, duodenal histology, and HLA status. CONCLUSION: If any, the role of circulating autoantibodies against OPG in the pathogenesis of bone derangement in patients with CD is not a major one