634   Circulating Leptin and Lactate Levels Are Not Associated with Osteopenia in HIV-Infected Men.

S. Claxton, D. Demarco, W. G. Powderly, and K. E. Yarasheski.
Washington Univ. Sch. of Med., St. Louis, MO.

Background:Central fat accumulation, subcutaneous fat loss and osteopenia have been observed in people living with HIV and receiving HAART. Serum leptin is a marker of increased adiposity and has been recently recognized as a potent inhibitor of bone formation. Hyperlactatemia has been linked to osteopenia in some studies. We examined the relationship between serum leptin, blood lactate and bone mineral density (BMD) in HIV-infected individuals treated with PI-based HAART.

Methods:We measured serum leptin and blood lactate levels, adipose tissue distribution, and lumbar spine BMD [using dual-energy x-ray absorptiometry (DEXA)] in HIV-infected people before (n = 30) and 24 wk after replacing their protease inhibitor component of HAART with nevirapine (n = 15) or efavirenz (n = 3).

Results:Osteopenia was present at baseline in 43% of the subjects (WHO definition). Baseline leptin levels correlated with appendicular (r = 0.84; p < 0.0001), trunk (r = 0.81; p < 0.0001), whole-body fat mass (r = 0.86; p < 0.0001), and lumbar spine BMD t-score (r = 0.40; p = 0.03). Higher leptin levels were correlated with higher lumbar spine BMD t-scores. After the switch, whole-body fat was reduced (0.5+0.3kg), but proportionally more appendicular fat was lost. Lumbar spine BMD and leptin levels were not changed after the switch. Baseline lactate levels were elevated (>2.5 mM) in 30% of the subjects but not related to BMD t-scores. Blood lactate levels tended to decrease 24 wk after switching to a non-nucleoside RT inhibitor (1.9+0.2 to 1.5+0.1 mM; p = 0.059).

Conclusions:Despite increased trunk adiposity, the low lumbar spine BMD observed in this population does not appear to be mediated by serum leptin or associated with blood lactic acid concentrations. Switching to nevirapine or efavirenz did not improve lumbar spine BMD, central adiposity, or serum leptin, but blood lactic acid levels were reduced.