632   Increased Abdominal Visceral Fat Is Associated with Reduced Bone Density in HIV-Infected Men with Lipodystrophy.

J. S. Huang*^1,2, P. Rietschel¹, C. M. Hadigan^,2, D. I. Rosenthal¹, and S. Grinspoon¹.
¹Massachusetts Gen. Hosp. and²Children's Hosp, Boston.

Background:Reduced bone density has been reported recently in association with protease inhibitor (PI) therapy. However, bone density has not previously been characterized in relationship to fat distribution among HIV-infected patients with lipodystrophy.

Methods:We performed a cross-sectional, observational study in 3 different groups of men: HIV-positive men with lipodystrophy [N = 21], HIV-positive men without lipodystrophy [N = 20], and age-matched and BMI-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 (QCT) was used both to determine volumetric bone density of the spine and to quantify abdominal visceral fat. Dual-energy X-ray absorptiometry (DXA) was used to determine whole body composition and bone density. Statistical comparisons were performed according to lipodystrophy categorization and PI exposure.

Results:Men with HIV-associated lipodystrophy had reduced bone density compared with both HIV-infected non-lipodystrophic men [mean+S.D.: 132+29 vs. 154+30 mg K₂HPO₄/dL, P = 0.02] and HIV-negative controls [132+29 vs. 148+18 mg K₂HPO₄/dL, P = 0.04]. Bone density was significantly reduced in patients with HIV lipodystrophy independent of protease inhibitor use. In an analysis among all HIV-infected subjects, increased visceral abdominal fat area was associated with decreased bone density [ r = -0.50, P = 0.001]. The association between visceral fat and bone density remained significant after controlling for age, BMI, lowest body weight, PI use, and extremity fat in a multivariate regression model [P = 0.007]. Markers of bone turnover were not related to bone density or lipodystrophy status.

Conclusions:Bone density is reduced in association with increased visceral fat in HIV-infected men with lipodystrophy. The mechanisms of reduced bone density are not known in this population. Further studies are needed to determine whether increased marrow fat occurs in such patients and affects bone density.