Study of Niacin on Endothelial Function in HIV-infected Subjects With Low High Density Lipoprotein Cholesterol Levels

Low high density lipoprotein (HDL) and a lipid pattern consistent with atherogenic dyslipidemia are also common in the human immunodeficiency virus (HIV)infected population and is likely due, in large part, to the chronic inflammatory effect of HIV infection per se. While highly active antiretroviral therapy (HAART) and the resultant reconstitution of the immune system might be expected to lead to improvement in this lipid profile, studies from our own research as well as others clearly demonstrate that such therapy fails to fully correct the low HDL pattern. This coronary artery disease (CAD) risk in the HIV population is then further compounded by the dyslipidemic effects of various protease inhibitors and other antiretroviral medications used to treat HIV.

Endothelial dysfunction is an early marker of atherosclerosis that can be determined non-invasively utilizing assessment of flow-mediated vasodilation (FMD) of the brachial artery, which may be analogous to blood flow through coronary arteries. Using this novel technology and HIV as a model of a chronic inflammatory state, we propose to determine if increasing HDL in subjects with low HDL but no LDL elevation may have potential beneficial effects. Our overall hypothesis for this pilot project is that increasing HDL levels in HIV-infected subjects with low HDL by the use of extended-release niacin over a 12 week period will lead to an identifiable improvement in endothelial function.

Specific Aim 1. To compare endothelial function, measured by flow-mediated vasodilation (FMD) of the brachial artery, among HIV-1 infected individuals with low high density lipoprotein (HDL) before and after treatment with extended-release niacin (Niaspan ®)

• Conduct a prospective randomized 12-week clinical trial on HIV-1 infected individuals with low HDL and normal low density lipoprotein levels who plan to continue their current anti-retroviral regimens
• Subjects will be randomized to either a treatment or control arm
• Subjects randomized to the treatment arm will receive extended-release niacin (Niaspan ®) starting at 500 mg per night and titrated to a maximum tolerated dose (not exceeding 1500 mg per night)
• Assess changes in FMD of the brachial artery using high-resolution ultrasound from baseline to week 12 (Total of 2 FMD assessments)
• Correlate changes in HDL with changes in FMD

Hypothesis to be tested:

Use of extended-release niacin will improve FMD among HIV-1 infected individuals with low HDL

• Following 12 weeks of therapy, subjects treated with extended-release niacin will show a 8% improvement in FMD compared to controls
• There will be a positive correlation between changes in HDL with changes in FMD

Specific Aim 2. To evaluate changes in lipid parameters, insulin sensitivity and cardiovascular risk markers with changes in FMD among the treatment and control arms

• Assess and compare changes in non-HDL lipid and lipoprotein parameters with changes in FMD among the two arms
• Assess and compare changes in insulin sensitivity by homeostasis model assessment (HOMA) with changes in FMD among the two arms
• Assess and compare changes in cardiovascular risk markers such as adhesion molecules and C-reactive protein with changes in FMD among the two arms

Hypothesis to be tested:

There will be a correlation between improvements in lipid, insulin sensitivity and cardiovascular risk markers and FMD in the extended niacin treatment arm

SIGNIFICANCE and RATIONALE: Low HDL cholesterol levels elevate CAD risk independent of low density lipoprotein (LDL) cholesterol levels. In association with high triglyceride levels and with small LDL particle size, low HDL is part of the syndrome of atherogenic dyslipidemia. This form of dyslipidemia is characteristic of the underlying dyslipidemia found in HIV-infected subjects, likely represents the consequences of chronic inflammatory changes due to HIV, and contributes substantively to the CAD risk in this population even without the added risk from dyslipidemic antiretroviral medications. Primary CAD preventive modalities may be warranted for patients in the HIV population as well as in the general population who manifest this type of dyslipidemia. Niacin is currently the best medication available to elevate HDL cholesterol levels. Thus, using the novel technique of assessing flow-mediated dilatation of the brachial artery, a pilot project is proposed to assess whether the use of extended release niacin will lead to short term improvement in endothelial function. If successful, this study may lay the foundation for further studies into the potential use of niacin for prevention of CAD in patients who are particularly at risk for CAD due to low HDL cholesterol levels.