Bone Abstracts

Objectives: Impairment of bone mass accrual and alterations of bone metabolism is a common finding in HIV-infected youths. In particular, previous studies demonstrated higher bone formation and bone resorption rates in HIV-infected children and adolescents. Wnt ligands promote bone formation by stimulating osteoblast differentiation and their survival. Recent studies demonstrated that sclerostin (Scl) and dickkopf factor 1 (DKK-1), Wnt antagonists, are important negative regulators of bone formation. The aim of the study was to measure serum concentration of Scl and DKK-1 in young HIV-infected patients.

Methods: We studied 86 HIV-infected patients whose ages ranged from 5.7 to 27.9 years. Their mean CD4 number was 674 (S.D. 274) and their CD4% was 33.2 (9.5). Patients were all on highly active antiretroviral therapy (HAART), but seven who were naïve to antiretroviral treatment. Scl and DKK-1 were measured in serum by enzyme immunoassay. Bone mass was measured by dual-energy X-ray absorptiometry at the lumbar spine and in the whole skeleton. We also measured Scl and DKK-1 concentration in 105 healthy youths (age range 4.5–17.7 years). The values of young adult patients (>20 years) have been compared with published reference data.

Results: HIV-infected patients had lower than normal bone mineral density measurements (spine P<0.005, and whole skeleton P<0.03). Serum concentration of Scl of HIV-infected children and adolescents were lower than in controls (25.0 (11.5) vs 34.2 (16.3) pmol/l respectively; P=0.003). Similarly, DKK-1 concentration was lower in these patients than in controls (19.2 (12.5) vs 22.5 (14.1) pmol/l respectively; P=0.05). HIV-infected young adults showed both Scl and DKK-1 serum concentration (19.1 (12.1) and 15.6 (7.4) pmol/l respectively), lower than reference (P<0.001). The serum concentration of both analytes of patients naïve to antiretroviral treatment was not different from that of HAART-treated patients. No correlations were found between Scl, DKK-1 and bone mineral measurements.

Conclusion: Our data confirm the alteration of bone metabolism pathways in HIV-infected individuals, possibly leading to reduced bone mineral density. The increased concentration of Wnt antagonists is consistent with the increased bone formation markers observed in previous studies.