Brazilian study finds reduced bone protein levels in people with HIV

2 July 2003

Estimated reading time 2 minutes

HIV-positive patients have lower levels of a protein associated with bone density according to a small Brazilian study published in the July 4^th edition of AIDS.

Decreased bone density has been noted in HIV-positive individuals and it is thought that this is caused by HIV infection itself. It has also been suggested that treatment with protease inhibitors can reduce bone mineral density (see links to news stories below).

The Brazilian investigators wished to establish the impact of HIV infection on plasma levels of osteocalcin, a protein associated with bone formation.

Glossary

protein

A substance which forms the structure of most cells and enzymes.

osteoporosis

Bone disease characterised by a decrease in bone mineral density and bone mass, resulting in an increased risk of fracture (a broken bone).

matched

In a case-control study, a process to make the cases and the controls comparable with respect to extraneous factors. For example, each case is matched individually with a control subject on variables such as age, sex and HIV status.

reservoir

The ‘HIV reservoir’ is a group of cells that are infected with HIV but have not produced new HIV (latent stage of infection) for many months or years. Latent HIV reservoirs are established during the earliest stage of HIV infection. Although antiretroviral therapy can reduce the level of HIV in the blood to an undetectable level, latent reservoirs of HIV continue to survive (a phenomenon called residual inflammation). Latently infected cells may be reawakened to begin actively reproducing HIV virions if antiretroviral therapy is stopped.

bone mineral density (BMD)

The higher your bone mineral content, the denser your bones are. And the denser your bones, the stronger they are and the less likely they are to break. A bone density test uses X-rays to measure how many grams of calcium and other bone minerals are packed into a segment of bone. The bones that are most commonly tested are in the spine, hip and sometimes the forearm.

The study involved 69 antiretroviral naive HIV-positive patients, who had an average age of 33 years. The patients were divided into three groups according to their CD4 cell count (group 1 above 500 cells/mm³; group 2 500-200 cells/mm³; and, group 3 below 200 cells/mm³. The study involved 50 HIV-negative volunteers who were age and sex matched with the HIV-positive patients.

Reduced osteocalcin levels were present in 43.5% of the HIV-positive patients and 16% of the controls (odds ratio 4.04; 95% CI, 1.68 ? 9.96, p=0.0001).

Although the three groups of HIV-positive patients had significantly different CD4 cell counts and HIV viral loads (average 9,600 copies/mL in group 1; 31,000 copies in group 2; amd 160,000 copies in group 3), osteocalcin levels between the three groups of patients were not significantly different.

The investigators suggest that HIV infection in the cells of ?the bone marrow microenvironment could induce chronic T-cell activation and abnormal cytokine production? affecting bone formation.

Although the investigators are unclear about the clinical significance of their findings they suggest that ?it is conceivable that if these abnormalities [in osteocalcin] persist over time, they may well lead to clinically significant bone loss? They call for further studies ?be performed to assess the magnitude of bone and mineral alterations? in HIV-infected patients.