HIV infection is associated with decreased thrombin generation.

BACKGROUND: Excess risk of cardiovascular disease occurs in effectively treated individuals with human immunodeficiency virus (HIV) infection. Although elevated plasma D-dimer levels are associated with increased morbidity and mortality, the impact of HIV infection on coagulation in vivo has not been well studied. METHODS: We measured D-dimers, antithrombin, endogenous thrombin potential (ETP; a functional measure of thrombin generation in vitro), thrombin/antithrombin complexes (TAT; a measure of thrombin generation in vivo), tissue factor, prothrombin fragment 1 + 2 (F1+2), and normalized APC sensitivity ratio (nAPCsr) in 199 HIV-positive men who were receiving antiretroviral therapy and had an undetectable HIV RNA level, in 79 HIV-positive untreated men, and in 39 uninfected controls. RESULTS: Median antithrombin levels were higher while the ETP was lower among HIV-infected adults (treated and untreated), compared with controls. There were few differences between coagulation markers in the 2 HIV groups. Compared with controls, the nAPCsr was lower in treated men and the TAT level was lower in untreated individuals. We observed little difference among measured levels of D-dimer, tissue factor, or F1+2 between HIV-infected individuals and controls. Antiretroviral therapy exposure was associated with a lower antithrombin level, a lower nAPCsr, and a lower ETP, while history of opportunistic infection was associated with a higher nAPCsr. CONCLUSIONS: HIV infection is associated with decreased thrombin generation, as measured by the ETP, and an increased antithrombin level. These data suggest that HIV infection may not be associated with increased propensity toward clotting, as has been suggested on the basis of isolated measures of D-dimer levels.

Novel Biomarkers of Cardiac Stress, Cardiovascular Dysfunction, and Outcomes in HIV-Infected Individuals.

OBJECTIVES: This study sought to determine whether biomarkers ST2, growth differentiation factor (GDF)-15, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and high-sensitivity troponin I are elevated in patients infected with human immunodeficiency virus (HIV) and are associated with cardiovascular dysfunction and all-cause mortality. BACKGROUND: HIV-infected patients have high rates of cardiovascular disease. Markers of myocardial stress may identify at-risk patients and provide additional prognostic information. METHODS: Biomarkers and echocardiograms were assessed in 332 HIV-infected patients and 50 age- and sex-matched control subjects. Left ventricular systolic dysfunction was defined as ejection fraction <50%, diastolic dysfunction (DD) as stage 1 or higher, and pulmonary hypertension as pulmonary artery systolic pressure ≥35 mm Hg. Mortality data were obtained from the National Death Index. RESULTS: Patients with HIV had a median age of 49 years, and 80% were male. Compared with control subjects, HIV-infected patients had higher adjusted percent estimates of all biomarkers except ST2 and interleukin-6. Among HIV-infected patients, 45% had DD; only ST2 was associated with DD (relative risk [RR]: 1.36; p = 0.047). Left ventricular systolic dysfunction was rare in this cohort (5%). Pulmonary hypertension was present in 27% of HIV-infected patients and was associated with GDF-15 (RR: 1.18; p = 0.04), NT-proBNP (RR: 1.18; p = 0.007), and cystatin C (RR: 1.54; p = 0.03). Thirty-eight deaths occurred among HIV-infected patients over a median of 6.1 years. In adjusted analysis, all-cause mortality was independently predicted by ST2 (hazard ratio [HR]: 2.04; p = 0.010), GDF-15 (HR: 1.42; p = 0.0054), high-sensitivity C-reactive protein (HR: 1.25; p = 0.023), and D-dimer (HR: 1.49; p = 0.029). Relationships were unchanged when analyses were restricted to virally suppressed HIV-infected patients receiving antiretroviral therapy. CONCLUSIONS: Among HIV-infected patients, ST2 and GDF-15 were associated with both cardiovascular dysfunction and all-cause mortality, and these variables may be useful at identifying those at risk for developing cardiovascular events and death.

Depletion of B-cells with rituximab improves endothelial function and reduces inflammation among individuals with rheumatoid arthritis.

BACKGROUND: Individuals with rheumatoid arthritis (RA) are at increased risk for cardiovascular disease, partly due to systemic inflammation and endothelial dysfunction. B-cells play an important pathogenic role in the inflammatory process that drives RA disease activity. Rituximab, a chimeric murine/human monoclonal antibody that depletes B-cells, is an effective therapy for RA. The purpose of this study was to determine whether B-cell depletion with rituximab reduces systemic inflammation and improves macrovascular (brachial artery flow-mediated dilation, FMD) and microvascular (reactive hyperemia) endothelial function in RA patients. METHODS AND RESULTS: RA patients received a single course of rituximab (1000 mg IV infusion at baseline and on day 15). FMD, reactive hyperemia, inflammatory markers, and clinical assessments were performed at baseline, week 12, and week 24. Twenty patients (95% female, median age 54 years) completed the study. Following treatment, FMD improved from a baseline of 4.5±0.4% to 6.4±0.6% at 12 weeks (mean±SE; P<0.0001), followed by a decline at week 24; a similar pattern was observed for hyperemic velocity. Significant decreases in RA disease scores, high-sensitivity C-reactive protein, erythrocyte sedimentation rate, and circulating CD19+ B-cells were sustained through week 24. Cholesterol and triglycerides became significantly although modestly elevated during the study. CONCLUSIONS: Depletion of B-cells with rituximab improved macrovascular and microvascular endothelial function and reduced systemic inflammation, despite modest elevation in lipids. Given these results, rituximab should be evaluated in the future for its possible role in reducing excess cardiovascular risk in RA. CLINICAL TRIAL REGISTRATION: URL http://ClinicalTrials.gov. Unique identifier: NCT00844714.

Increased levels of asymmetric dimethylarginine are associated with pulmonary arterial hypertension in HIV infection.

OBJECTIVE: To examine the relationship between asymmetric dimethylarginine (ADMA) and HIV-associated pulmonary arterial hypertension (PAH). DESIGN: HIV infection is an independent risk factor for PAH, but the underlying pathogenesis remains unclear. Chronic inflammation resulting in nitric oxide-mediated endothelial dysfunction is a key mechanism underlying other types of PAH. ADMA is an endogenous inhibitor of endothelial nitric oxide synthase. Among uninfected individuals, ADMA is associated with PAH and predicts disease-related mortality. METHODS: We measured ADMA, high sensitivity C-reactive protein, interleukin-6 (IL-6), D-dimer, and pulmonary artery systolic pressure (PASP) using echocardiography in HIV-infected individuals. Right heart catheterization (RHC) was performed in individuals with a PASP at least 30  mmHg. We performed multivariable analysis to identify factors associated with high PASP by echocardiogram and PAH by RHC. RESULTS: Among 214 HIV-infected individuals, the median age was 50 years, 82% were men, 71% were on antiretroviral therapy, and 4.2% carried a prior diagnosis of PAH. ADMA and IL-6 were associated with increased values of PASP following multivariable adjustment (7.2% per 0.1 µmol/l, P = 0.0049 and 3.9% per doubling, P = 0.027, respectively). In adjusted analysis among the 85 participants who underwent RHC, ADMA and IL-6 were associated with higher values of mean PAP (14.2% per 0.1 µmol/l, P = 0.0014 and 5.8% per doubling, P = 0.038, respectively). However, only ADMA was associated with PAH (prevalence ratio = 1.74, P = 0.029). CONCLUSION: Elevated levels of ADMA are independently associated with PAH among HIV-infected individuals. Our findings suggest that chronic HIV-associated inflammation leading to an accumulation of ADMA and subsequent nitric oxide-mediated endothelial dysfunction may represent a novel mechanism for HIV-associated PAH.

Elevated levels of asymmetric dimethylarginine are associated with lower CD4+ count and higher viral load in HIV-infected individuals.

OBJECTIVES: To compare asymmetric dimethylarginine (ADMA) among HIV-infected and uninfected individuals and to evaluate predictors of ADMA in HIV infection. BACKGROUND: HIV-infected individuals have high rates of atherosclerosis. Endothelial dysfunction is central to atherogenesis and is one possible mechanism underlying this increased cardiovascular risk. ADMA is an endogenous inhibitor of endothelial nitric oxide synthase. Among uninfected individuals, higher ADMA levels predict cardiovascular events and mortality. The association between HIV infection, HIV-related factors, and ADMA has not been well described. METHODS: We compared ADMA in 248 HIV-infected individuals and 50 uninfected controls. We performed multivariable analysis using traditional cardiovascular and HIV-specific factors as covariates to identify factors associated with ADMA. RESULTS: HIV-infected men were older, less often Caucasian, more hypertensive, and had lower HDL than uninfected men. The median duration of HIV infection was 13 years, median CD4+ count was 592 cells/µL, 76% had an undetectable viral load, and 76% were on antiretroviral therapy. ADMA levels were modestly higher in HIV-infected individuals than controls [median (IQR): 0.46 µM (0.41-0.52) vs. 0.44 µM (0.38-0.46), p = 0.019], but the association lost statistical significance after controlling for cardiovascular risk factors (+0.028 µM, p = 0.054). Lower CD4+ count and both detectable and higher viral load were independently associated with increased ADMA. CONCLUSIONS: ADMA levels were modestly elevated in the setting of HIV infection. Notably, a greater HIV-associated inflammatory burden, as evidenced by lower CD4+ counts and higher viral loads, was associated with increased ADMA levels. Our findings suggest that HIV infection impairs endothelial function and predisposes to atherosclerosis through chronic inflammation and subsequent accumulation of ADMA.