Bone mineral metabolism and HIV-infection
Paul Blanchard, HIV i-Base
Alterations in bone mineral metabolism leading to osteopaenia and osteoporosis have been observed in HIV-infection. It remains unclear, however, to what extent HIV-infection itself, or various antiretrovirals might be contributing to such disturbances.
A recent report published in AIDS investigated the influence of HIV-infection on osteocalcin plasma levels in Brazilian patients. Santos and colleagues performed a cross sectional analysis on 69 patients with HIV-infection before the initiation of any antiretroviral therapy. Matched controls consisted of 50 age and sex matched healthy seronegative adults.
Although the role of osteocalcin in the bone metabolism is still unknown, it is a specific and sensitive marker for bone formation.
Overall, reduced osteocalcin plasma levels were present in 43.5% of HIV-infected patients and in 16% of healthy controls (p=0.0001; odds ratio 4.04; 95% confidence interval 1.68 – 9.69).
The study authors hypothesised that the direct interaction of HIV with cells of the bone marrow microenvironment could induce chronic T-cell activation and abnormal cytokine production affecting osteoclast and osteoblast function. They also suggest that the reduced osteocalcin levels seen in these patients may, over time, lead to clinically significant bone loss.
It now remains to determine the relative contributions of HIV-infection itself and antiretroviral drugs to the bone mineral abnormalities observed in HIV-infected patients. If the osteocalcin reduction induced by HIV-infection itself is of primary importance you would expect antiretroviral treatment to correct this and perhaps negate its effects. The reports of a number of research teams, however, suggest that bone mineral loss may actually be accelerated once antiretroviral treatment is initiated leading to suspicions that at least some antiretroviral agents may interfere directly with bone mineral metabolism.
Silva Santos Jr AC, Lopes Crisostomo LM, Olavarria V et al. Alterations in bone mineral metabolism in Brazilian HIV-infected patients. AIDS. 2003 Jul 4;17(10):1578-1580.