Increased abdominal visceral fat is associated with reduced bone density in HIV-infected men with lipodystrophy

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Abstract
To examine the relationship between bone density and changes in regional and whole body composition in HIV-infected men with and without lipodystrophy. Cross-sectional, observational study of HIV-infected men with and without lipodystrophy and matched HIV-negative controls. Tertiary care academic medical institution. A total of 59 men, belonging to three different groups: HIV-positive men with lipodystrophy (n = 21), HIV-positive men without lipodystrophy (n = 20), and age-matched and body mass index-matched HIV-negative controls (n = 18). Bone density, markers of bone turnover and indices of calcium metabolism were measured in all subjects. Quantitative computed tomography was used both to determine volumetric bone density of the spine and to quantify abdominal visceral fat. Dual energy X-ray absorptiometry was used to determine whole body composition and bone density. Statistical comparisons were performed according to lipodystrophy categorization and protease inhibitor exposure. Men with HIV-associated lipodystrophy had reduced lumbar spine bone density compared with both HIV-infected non-lipodystrophic men [mean ± SD, 132 ± 29 versus 154 ± 30 mg/cm3;P = 0.02] and HIV-negative controls [mean ± SD 132 ± 29 versus 148 ± 18) mg/cm3;P = 0.04]. Lumbar spine bone density was reduced significantly in HIV lipodystrophy patients independently of protease inhibitor use. In an analysis among all HIV-infected subjects, increased visceral abdominal fat area was associated with decreased lumbar spine bone density (r, −0.47;P = 0.002). The association between visceral fat and bone density remained significant (P = 0.007) after controlling for age, body mass index, lowest body weight, protease inhibitor use, and extremity fat in a multivariate regression model. Markers of bone turnover were not related to bone density or lipodystrophy status. Lumbar spine bone density is reduced in association with increased visceral fat in HIV-infected men with lipodystrophy. Further studies are needed to determine the mechanisms of osteopenia in HIV lipodystrophy and whether increased marrow fat occurs in such patients and affects bone density.