Atazanavir use and carotid intima media thickness progression in HIV: potential influence of bilirubin

The physiology of bilirubin: health and disease equilibrium

Bilirubin has several physiological functions, both beneficial and harmful. In addition to reactive oxygen species-scavenging activities, bilirubin has potent immunosuppressive effects associated with long-term pathophysiological sequelae. It has been recently recognized as a hormone with endocrine actions and interconnected effects on various cellular signaling pathways. Current studies show that bilirubin also decreases adiposity and prevents metabolic and cardiovascular diseases. All in all, the physiological importance of bilirubin is only now coming to light, and strategies for increasing plasma bilirubin levels to combat chronic diseases are starting to be considered. This review discusses the beneficial effects of increasing plasma bilirubin, incorporates emerging areas of bilirubin biology, and provides key concepts to advance the field.

The regional pattern of abnormal cerebrovascular reactivity in HIV-infected, virally suppressed women

The purpose of this study was to assess whole brain and regional patterns of cerebrovascular reactivity (CVR) abnormalities in HIV-infected women using quantitative whole brain arterial spin labeling (ASL). We hypothesized that HIV-infected women would demonstrate decreased regional brain CVR despite viral suppression. This cross-sectional study recruited subjects from the Bay Area Women's Interagency Health Study (WIHS)-a cohort study designed to investigate the progression of HIV disease in women. In addition to conventional noncontrast cerebral MRI sequences, perfusion imaging was performed before and after the administration of intravenous acetazolamide. CVR was measured by comparing quantitative ASL brain perfusion before and after administration of intravenous acetazolamide. In order to validate and corroborate ASL-based whole brain and regional perfusion, phase-contrast (PC) imaging was also performed through the major neck vessels. FLAIR and susceptibility weighted sequences were performed to assess for white matter injury and microbleeds, respectively. Ten HIV-infected women and seven uninfected, age-matched controls were evaluated. Significant group differences were present in whole brain and regional CVR between HIV-infected and uninfected women. These regional differences were significant in the frontal lobe and basal ganglia. CVR measurements were not significantly impacted by the degree of white matter signal abnormality or presence of microbleeds. Despite complete viral suppression, dysfunction of the neurovascular unit persists in the HIV population. Given the lack of association between CVR and traditional imaging markers of small vessel disease, CVR quantification may provide an early biomarker of pre-morbid vascular disease.

Association Between Bilirubin, Atazanavir, and Cardiovascular Disease Events Among People Living With HIV Across the United States

OBJECTIVE

Bilirubin is an antioxidant that may suppress lipid oxidation. Elevated bilirubin is associated with decreased cardiovascular events in HIV-uninfected populations. We examined these associations in people living with HIV (PLWH).

METHODS

Potential myocardial infarctions (MIs) and strokes were centrally adjudicated. We examined MI types: type 1 MI (T1MI) from atherosclerotic plaque instability and type 2 MI (T2MI) in the setting of oxygen demand/supply mismatch such as sepsis. We used multivariable Cox regression analyses to determine associations between total bilirubin levels and outcomes adjusting for traditional and HIV-specific risk factors. To minimize confounding by hepatobiliary disease, we conducted analyses limited to bilirubin values <2.1 mg/dL; among those with fibrosis-4 values <3.25; and among everyone. We repeated analyses stratified by hepatitis C status and time-updated atazanavir use.

RESULTS

Among 25,816 PLWH, there were 392 T1MI and 356 T2MI during follow-up. Adjusted hazard ratios for the association of higher bilirubin levels with T1MI were not significant. Higher bilirubin levels were associated with T2MI. By contrast, among PLWH on atazanavir, higher bilirubin levels were associated with fewer T2MI (hazard ratio 0.56:0.33-1.00). Higher bilirubin levels among those on atazanavir were associated with fewer T1MI combined with ischemic stroke.

LIMITATIONS

Analyses were conducted with total rather than unconjugated bilirubin.

CONCLUSIONS

Among PLWH, higher bilirubin levels were associated with T2MI among some subgroups. However, among those on atazanavir, there was a protective association between bilirubin and T2MI. These findings demonstrate different associations between outcomes and elevated bilirubin due to diverse causes and the importance of distinguishing MI types.

Brief Report: Hyperbilirubinemia Is Associated With a Decreased Risk of Carotid Atherosclerosis in HIV-Infected Patients on Virological Suppression

OBJECTIVE

To investigate the association between total, direct, and indirect bilirubin and the presence of carotid lesions in a large sample of HIV-1-infected patients on virological suppression.

DESIGN

Retrospective study on adult HIV-1-infected patients, with a carotid ultrasound (CUS) examination performed between January 2008 and August 2016, with HIV-RNA <50 copies per milliliter at CUS and without previous cardiovascular events.

METHODS

Intima media thickness was measured in 4 segments: carotid common artery and bifurcation on the left and right sides. Carotid lesion was defined as an intima media thickness ≥1.5 mm in ≥1 region at CUS. Patients were classified as: normal if all bilirubin values before CUS were below the upper normal limit and with hyperbilirubinemia if ≥1 bilirubin value above upper normal limit before CUS was recorded. Multivariate logistic regression was used to determine whether hyperbilirubinemia showed association with the presence of ≥1 carotid lesion, after adjusting for confounding factors.

RESULTS

Overall, 903 patients were evaluated, 511 with ≥1 and 392 without carotid lesions. At multivariate analysis, total [adjusted odds ratio (95% confidence interval) 0.57 (0.36 to 0.90), P = 0.016] and indirect hyperbilirubinemia before CUS [adjusted odds ratio (95% confidence interval) 0.62 (0.40 to 0.97), P = 0.036] were associated with a lower risk of carotid lesions in addition to younger age, negative hepatitis C virus antibodies, higher nadir CD4, lower low-density lipoprotein cholesterol, higher high-density lipoprotein cholesterol, lower triglycerides, and no use of statin; no effect of atazanavir treatment on carotid lesions was detected.

CONCLUSIONS

In HIV-1-treated patients, total or indirect hyperbilirubinemia was likely associated with the absence of carotid lesions.

Induction of Mild Hyperbilirubinemia: Hype or Real Therapeutic Opportunity?

Observational epidemiological studies showed that mild hyperbilirubinemia has beneficial effects on the prevention of cardiovascular disease, type 2 diabetes mellitus, and metabolic syndrome. In mammals, bilirubin plays a major role as a potent antioxidant. Uridine 5'-diphospho-glucuronosyl transferase (UGT)1A1 variants coding for bilirubin UDP-glucuronosyl transferase resulting in mild hyperbilirubinemia (as in Gilbert syndrome (GS)) may confer a strong genetic advantage. Strategies to boost bioavailability of bilirubin or to mimic GS represent an attractive approach to prevent many oxidative stress and inflammation-mediated diseases. Even a tiny, micromolar increase in serum bilirubin concentrations substantially decreases the risk of oxidative stress-mediated diseases. There are several possible ways to achieve this, including lifestyle changes, changes in dietary patterns, regular physical activities, or use of chemical drug or of specific plant products either in the form of regular food items or nutraceuticals. Further basic and experimental research is required to fully uncover this promising therapeutic field.

Epidemiology of ischemic heart disease in HIV

PURPOSE OF REVIEW

The purpose of this review is to summarize and synthesize recent data on the risk of ischemic heart disease (IHD) in HIV-infected individuals.

RECENT FINDINGS

Recent studies in the field demonstrate an increasing impact of cardiovascular disease (CVD) on morbidity and mortality in HIV relative to AIDS-related diagnoses. Studies continue to support an approximately 1.5 to two-fold increased risk of IHD conferred by HIV, with specific risk varying by sex and virologic/immunologic status. Risk factors include both traditional CVD risk factors and novel, HIV-specific factors including inflammation and immune activation. Specific antiretroviral therapy (ART) drugs may increase CVD risk, yet the net effect of ART with viral suppression is beneficial with regard to CVD risk. Management of cardiovascular risk and prevention of CVD is complex, because current general population strategies target traditional CVD risk factors only. Extensive investigation is being directed at developing tailored CVD risk prediction algorithms and interventions to reduce CVD risk in HIV.

SUMMARY

Increased IHD risk is a significant clinical and public health challenge in HIV. The development and application of HIV-specific interventions to manage CVD risk factors and reduce CVD risk will improve the long-term health of this ageing population.

Subclinical cardiovascular disease in patients starting contemporary protease inhibitors

OBJECTIVES

The aim of the study was to assess changes in and factors associated with anatomical [carotid artery intima-media thickness (CIMT)] and functional (arterial stiffness) markers of subclinical cardiovascular disease progression in antiretroviral-naïve patients starting triple combination antiretroviral therapy containing contemporary protease inhibitors.

METHODS

This was a planned substudy of the ATADAR (Metabolic Effects of Atazanavir/Ritonavir Versus Darunavir/Ritonavir in Combination With Tenofovir/Emtricitabine in naïve HIV-1 Infected Patients) clinical trial (ClinicalTrials.gov identifier NCT01274780). ATADAR is a multicentre, randomized, open-label clinical trial comparing the effects of ritonavir-boosted atazanavir and darunavir, both with tenofovir/emtricitabine, in antiretroviral-naïve HIV-infected patients. Common CIMT and aortic augmentation index (AIx@75) were measured at baseline and after 12 months of follow-up. Antiretroviral treatment, traditional cardiovascular risk factors and HIV-related factors were assessed as potential predictors of CIMT and Aix@75 changes using linear regression analysis.

RESULTS

Thirty-three patients were included in this pilot study. While CIMT significantly increased in the pooled population [median (interquartile range (IQR)) 68 (-13, 128) μm; P = 0.0511], AIx@75 did not [median (IQR) 1 (-6, 5)%; P = 0.8964]. Patients on darunavir showed a trend to faster CIMT progression than those on atazanavir [median change (IQR) 117 (-2, 143) vs. -6 (-58, 89) μm, respectively; P = 0.0917]. However, after adjustment in the multivariate analysis, a higher baseline Framingham score was the only factor associated with CIMT progression (coefficient 16.02; 95% confidence interval -1.04, 33.08; P = 0.064). AIx@75 change was not associated with any baseline factor.

CONCLUSIONS

CIMT was a more sensitive marker of subclinical vascular disease progression than arterial stiffness in antiretroviral-naïve patients starting antiretroviral therapy with contemporary protease inhibitors. Classical risk factors but not antiretroviral therapy were associated with faster CIMT progression.

Conflicting effects of atazanavir therapy on atherosclerotic risk factors in stable HIV patients: A randomized trial of regimen switch to atazanavir

Bilirubin acts as a potent endogenous antioxidant, with higher concentrations associated with lower rates of CVD; the antiretroviral drug atazanavir (ATV) increases bilirubin levels but may also increase von Willebrand factor levels. We tested the hypothesis that increasing endogenous bilirubin using ATV would improve cardiometabolic risk factors and vascular function in older patients with HIV. Ninety participants were enrolled in two study protocols. In protocol 1, we evaluated markers of inflammation, thrombosis, and conduit artery endothelial function in subjects on non-ATV containing regimens. Participants were randomly assigned to continue baseline treatment or switch to an ATV-based regimen. Measurements were made at baseline and 28 days. In the protocol 2, we enrolled 30 subjects who received atazanavir for more than one year and were compared to the aim 1 protocol subjects at baseline. 60 subjects were enrolled in the first protocol (mean age 53, +/- 6 years), with 31 randomized to ATV and 29 continuing baseline treatment. Atazanavir significantly increased serum total bilirubin levels (p<0.001) and acutely but not chronically plasma total antioxidant capacity (p<0.001). An increase in von Willebrand Factor (p<0.001) and reduction in hs-CRP (p = 0.034) were noted. No changes were seen in either flow-mediated endothelium-dependent or vasodilation. In cross-sectional analysis (second protocol), similar findings were seen in the baseline attributes of non-atazanavir-based and long-term atazanavir users. Increasing serum bilirubin levels with atazanavir in subjects with HIV reduces hs-CRP, temporarily reduces oxidative stress, but increases von Willebrand Factor. Atazanavir does not improve endothelial function of conduit arteries.

Trial registration: ClinicalTrials.gov NCT03019783.

Cardiovascular outcomes among HIV-infected veterans receiving atazanavir

OBJECTIVE

Patients with HIV infection have an increased risk of cardiovascular disease compared with uninfected individuals. Antiretroviral therapy with atazanavir (ATV) delays progression of atherosclerosis markers; whether this reduces cardiovascular disease event risk compared with other antiretroviral regimens is currently unknown.

DESIGN

Population-based, noninterventional, historical cohort study conducted from 1 July 2003 through 31 December 2015.

SETTING

Veterans Health Administration hospitals and clinics throughout the United States.

PARTICIPANTS

Treatment-naive patients with HIV infection (N = 9500).

ANTIRETROVIRAL EXPOSURES

Initiating antiretroviral regimens containing ATV, other protease inhibitors, nonnucleoside reverse transcriptase inhibitors (NNRTIs), or integrase strand transfer inhibitors (INSTIs).

MAIN OUTCOME/EFFECT SIZE MEASURES

Incidence rates of myocardial infarction (MI), stroke, and all-cause mortality within each regimen. ATV versus other protease inhibitor, NNRTI, or INSTI covariate-adjusted hazard ratios by using Cox proportional hazards models and inverse probability of treatment weighting.

RESULTS

Incidence rates for MI, stroke, and all-cause mortality with ATV-containing regimens (5.2, 10.4, and 16.0 per 1000 patient-years, respectively) were lower than with regimens containing other protease inhibitors (10.2, 21.9, and 23.3 per 1000 patient-years), NNRTIs (7.5, 15.9, and 17.5 per 1000 patient-years), or INSTIs (13.0, 33.1, and 21.5 per 1000 patient-years). After inverse probability of treatment weighting, adjusted hazard ratios (95% confidence intervals) for MI, stroke, and all-cause mortality with ATV-containing regimens versus all non-ATV-containing regimens were 0.59 (0.41-0.84), 0.64 (0.50-0.81), and 0.90 (0.73-1.11), respectively.

CONCLUSION

Among treatment-naive HIV-infected patients in the Veterans Health Administration initiating ATV-containing regimens, risk of both MI and stroke were significantly lower than in those initiating regimens containing other protease inhibitors, NNRTIs, or INSTIs.

Atazanavir and Cardiovascular Risk Among Human Immunodeficiency Virus-Infected Patients: A Systematic Review

Introduction

Patients with human immunodeficiency virus (HIV) infection have an increased risk of cardiovascular disease (CVD). While viral suppression with antiretroviral therapy decreases CVD risk overall, several studies have suggested that certain antiretrovirals, particularly certain protease inhibitors, may be associated with an increased relative risk of CVD. In AIDS Clinical Trials Group 5260 s, ritonavir-boosted atazanavir (ATV) was associated with slower atherosclerosis progression compared to ritonavir-boosted darunavir and raltegravir, potentially due to hyperbilirubinemia. Although hyperbilirubinemia may lead to increased rates of treatment discontinuation, it may also contribute to a favorable cardiovascular (CV) profile for ATV. To fully elucidate the effect of ATV on CVD risk among HIV-infected patients, a systematic review of the literature was performed.

Methods

A systematic search of the PubMed and Embase databases was conducted on August 26, 2015, using terms to identify papers that discuss ATV, HIV, and CVD. Articles were limited to English-language publications of randomized-controlled or observational studies investigating adult humans. The primary outcome was the incidence of CVD. Articles describing surrogate markers of CVD were also included.

Results

Ten studies were included in this qualitative analysis: six reported CVD outcomes, two reported data on atherosclerosis as assessed by carotid intima-media thickness (cIMT), and two reported outcomes related to endothelial function. The studies reporting the incidence of myocardial infarction (MI) among HIV-infected patients showed that ATV (boosted and unboosted) was not associated with an increased risk of acute MI. Other CV endpoints were similarly unaffected by treatment with ATV. Compared with non-ATV-based regimens, ATV had beneficial effects on cIMT progression in the publications identified, with no apparent impact on endothelial function.

Conclusions

This analysis showed that there was no increased risk or occurrence of adverse CV events among HIV-infected patients receiving ATV. Markers of atherosclerosis were improved, suggesting a possible antioxidant effect of ATV, and endothelial function was not affected.

Funding

Bristol-Myers Squibb (article processing charges and medical writing support).

Electronic supplementary material

The online version of this article (doi:10.1007/s40121-016-0132-z) contains supplementary material, which is available to authorized users.