• Leg blood flow response to the intra-femoral artery infusion of methacholine chloride [ Time Frame: Measured at Week 4 ] [ Designated as safety issue: Yes ]
  

• Insulin sensitivity measured by the hyperinsulinemic euglycemic clamp study [ Time Frame: Measured at Week 4 ] [ Designated as safety issue: Yes ]
  

Antiretroviral therapy for HIV, particularly with the use of PIs, is associated with an increased risk of heart attack. Specific cardiovascular side effects seen with the use of some PIs include insulin resistance, abnormal blood lipid levels, and endothelial dysfunction (abnormalities in the cells that line the inner surface of blood vessels). Past studies have shown that treatment with indinavir, an older PI, results in significant endothelial dysfunction, which may be the main cause for the increase in cardiovascular risk. Indinavir is now seldom used in clinical practice, and the newer PIs atazanavir and combination lopinavir/ritonavir now account for nearly 70% of total PI use in the United States. It is not known what effect these new PIs have on endothelial dysfunction. This study will compare the effects of atazanavir, lopinavir/ritonavir, and placebo on certain cardiovascular disease risk factors, including abnormal glucose metabolism and endothelial dysfunction, in healthy people without HIV.

Participation in this study will last 4 weeks. All participants will undergo initial assessments that will include various vascular and metabolic evaluations. Body weight, height, basal heart rate, and systolic and diastolic blood pressure will also be measured. Participants will then be assigned randomly to receive 4 weeks of treatment with 400 mg of atazanavir per day plus placebo, 400 mg/100 mg of lopinavir/ritonavir twice per day plus placebo, or placebos for both drugs per day. Upon completing the 4 weeks of treatment, participants will repeat the initial assessments.