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. Author manuscript; available in PMC: 2013 Sep 9.
Published in final edited form as: Antivir Ther. 2011 Dec 14;17(3):485–493. doi: 10.3851/IMP1990

Sex differences in urinary biomarkers of vascular and endothelial function in HIV-infected persons receiving antiretroviral therapy

Michael S Boger 1, Aihua Bian 2, Ayumi Shintani 2, Ginger L Milne 3, Jason D Morrow 3,*, Husamettin Erdem 4, Valerie Mitchell 4, David W Haas 4, Todd Hulgan 4
PMCID: PMC3766979  NIHMSID: NIHMS444270  PMID: 22293574

Abstract

Background

Cardiovascular disease (CVD) risk can be underestimated in HIV-infected patients receiving antiretroviral therapy (ART). Novel CVD risk markers in this population are needed. We hypothesized that eicosanoid metabolite production is increased with metabolic complications of ART. Our objective was to determine relationships between urine eicosanoids and traditional CVD risk factors in a cohort of HIV-infected persons receiving ART.

Methods

Cross-sectional analysis of 107 individuals from a prospective cohort study with urine eicosanoids (isoprostane [15-F2t-IsoP], prostaglandin-E metabolite [PGE-M], thromboxane metabolite [11dTxB2], prostacyclin metabolite [PGI-M]) determined by gas or liquid chromatography-mass spectrometry.

Results

15-F2t-IsoP was higher (p=0.003), 11dTxB2 tended to be higher (p=0.07), and PGE-M was lower (p=0.003) in females than in males. The overall median Framingham score was 4 (IQR 1 – 7). In multivariable analyses adjusting for age, CD4+ T-cells, smoking status, nonsteroidal anti-inflammatory use, aspirin use, and body mass index (BMI), associations included: higher 15-F2t-IsoP with female sex (p=0.004) and current smoking (p=0.04), lower PGE-M with female sex (p=0.005) and higher BMI (p=0.03), higher 11dTxB2 with increasing age (p=0.02) and current smoking (p=0.04), lower 11dTxB2 with higher BMI (p=0.02), and higher PGI-M with current smoking (p=0.04).

Conclusions

In this pilot study of predominantly virologically suppressed HIV-infected individuals on ART, there were sex-specific differences in urinary eicosanoids, with females having more risk-associated parameters despite low Framingham score. Eicosanoids might be useful CVD biomarkers in ART-treated, HIV-infected patients. Future studies should examine eicosanoids while assessing effects of specific ART regimens and targeted interventions on CVD outcomes.

INTRODUCTION

Antiretroviral therapy (ART) greatly reduces mortality from HIV infection, but may increase cardiovascular disease (CVD) risk[1]. Traditional Framingham prediction might underestimate this risk in HIV-infected persons on ART[2]. Thus, novel biomarkers need to be studied as a means to better assess CVD in HIV infection. Chronic HIV infection induces inflammation[3], and increased cardiovascular events were observed when previously suppressive ART was interrupted[4]. Treating HIV infection can improve endothelial function[5]. Eicosanoids, products of arachidonic acid (AA) metabolism (Figure 1), are involved in oxidant stress, inflammation, and endothelial function, all of which are important in atherosclerosis and CVD[6].

Figure 1.

Figure 1

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Synthesis and physiologic activities of the eicosanoids. 15-F2t-IsoP, 15-F2t-isoprostane-F2α COX, cyclooxygenase; PGE-M, 11-α-hydroxyl-9,15-dioxo-2,3,4,5-tetranor-prostane-1,20-dioic acid (prostaglandin-E metabolite); PGI-M, 2,3-dinor-6-keto-PGF1α(prostacyclin metabolite); 11dTxB2, 11-dehydro-thromboxane B2 (thromboxane metabolite).

Membrane phospholipids are converted to AA during vascular stress. In the presence of free radicals, AA undergoes cyclooxygenase-independent autoxidation to F2-isoprostanes (F2-IsoPs), causing vasoconstriction, platelet aggregation, and oxidative tissue damage. A major isoprostane is 15-F2t-isoprostane-F2α (15-F2t-IsoP). AA is metabolized in a cyclooxygenase-dependent pathway to prostaglandin H2. Prostaglandin E2, produced by vascular smooth muscle cells, causes vasodilation or vasoconstriction and/or vascular smooth muscle proliferation. The primary prostaglandin E2 urinary metabolite is 11-α-hydroxy-9,15-dioxo-2,3,4,5-tetranorprostane-1,20-dioic acid (PGE-M). In platelets, prostaglandin H2 is converted to thromboxane A2, causing vasoconstriction, platelet activation, and chemotaxis. The major urinary metabolite used to assess thromboxane A2 production is 11-dehydro-thromboxane B2 (11dTxB2). Prostacyclin, produced by vascular endothelial cells, causes vasodilation and inhibits platelet aggregation and vascular smooth muscle proliferation. The major urinary metabolite used to assess prostacyclin production is 2,3-dinor-6-keto-PGF1α (PGI-M). With the exception of 15-F2t IsoP[7], parent eicosanoids (Figure 1, bold) are unstable in and cannot be reliably assayed from plasma. Prostaglandin metabolites (Figure 1, boxes), as well as15-F2t-IsoP, are stable in urine and accurate indices of endogenous production. Urinary assays for these metabolites are precise and highly accurate[8–10].

In HIV-negative populations, urine 15-F2t-IsoP correlates with several traditional CVD risk factors[11] and surrogate measures, including flow-mediated dilation (FMD) and carotid intima media thickness (IMT)[12, 13]. Cigarette smoking is associated with higher 15-F2t-IsoP, 11dTxB2, PGI-M, and PGE-M[14–17]. Aspirin reduces 11dTxB2 synthesis, and other nonsteroidal anti-inflammatory drugs (NSAIDs) can reduce PGI-M synthesis[14, 18]. Eicosanoids other than 15-F2t-IsoP and 11dTxB2 have not been evaluated for CVD risk assessment, and no urinary eicosanoids have been studied among HIV-infected individuals.

We hypothesize that eicosanoid urinary metabolite synthesis increases during metabolic complications of ART and may be useful for assessing CVD risk in this setting. We characterize eicosanoid metabolites in a pilot study of HIV-1-infected individuals, most with fully suppressed HIV-1 RNA, on ART and correlate them with body mass index (BMI) and traditional CVD risk factors.

METHODS

Study Design

Data are from a prospective cohort study of chronically HIV-infected individuals enrolled at the Comprehensive Care Center in Nashville, TN, USA from June 2005 to July 2007. The cohort was established to assess the contribution of oxidant stress to the pathogenesis of ART-related toxicities, including metabolic and neurologic complications.

Study Population

Cohort inclusion criteria were described previously[19] and included age ≥18 years, current ART including ≥2 nucleoside reverse transcriptase inhibitors (NRTIs) for ≥24 consecutive weeks, and plasma HIV-1 RNA <10,000 copies/mL within 180 days of enrolment. Exclusion criteria included active diabetes mellitus not diet-controlled and documented or reported history of myocardial infarction (MI). The study was approved by the Vanderbilt University Institutional Review Board, and all participants provided written informed consent. Human experimentation guidelines of the US Department of Health and Human Services were followed. Ethical standards were in accordance with the Helsinki Declaration of 1975 as revised in 1983.

Data Collection

Current ART, smoking status, and self-reported use of anti-inflammatory and antioxidant drugs were assessed, and waist circumference, waist-to-hip ratio, and BMI were measured. Serum was obtained for highly-sensitive C-reactive protein (hsCRP) and lipids, determined using standard assays at a commercial reference laboratory (Laboratory Corporation of America, Birmingham, AL, USA). The most recent HIV-1 RNA and CD4+ T-cell determinations (performed at the same commercial laboratory) within 3 months of the above measures were obtained from the medical record. Clean-catch urine samples were collected, and 3 mL aliquots of urine were stored at −80 °C until analysis. Urinary 15-F2t-IsoP, 11dTxB2, and PGI-M were measured using gas chromatography-negative ion chemical ionization mass spectrometry employing stable isotope dilution methodology, as described elsewhere[7, 8, 10, 20]. PGE-M was measured by liquid chromatography-mass spectroscopy, as previously described[9].

Statistical Analyses

Characteristics of study participants are presented using the median (IQR) for continuous variables, and frequencies and proportions for categorical variables. Spearman’s correlation was used to assess associations between urinary eicosanoids and serum lipids, BMI, waist circumference, waist-to-hip ratio, Framingham score, age, CD4+ T-cells, and hsCRP. The Wilcoxon rank-sum test was used to compare the distribution of urinary eicosanoids by sex, race, smoking status, detectable versus undetectable viral load, antiretroviral therapy, and use of NSAIDs or aspirin. Fisher’s exact test was used to test the independence of categorical variables. Multivariable linear regression analysis was performed to assess associations of each urinary eicosanoid with sex, adjusting for six risk factors: age, CD4+ T-cells, smoking status, NSAID use, aspirin use, and BMI. In addition, interaction analysis was conducted to assess whether sex modified the effect of the above six risk factors on urinary eicosanoids by adding the cross-product of those risk factors and sex individually. Separate models for each urinary eicosanoid adjusting for these covariates assessed associations with serum lipids and Framingham score. 15-F2t-IsoP, 11dTxB2, PGI-M, PGE-M and hsCRP were natural log-transformed to provide normality in the regression residuals. Exponential of the regression coefficients were then computed, indicating the fold change in the urine eicosanoid of interest by one interquartile increase in the corresponding covariate. Adjustment was not made for multiple comparisons. Analyses were performed using Stata IC version 10.0 (Stata Corporation, College Station, TX, USA) and R software (R Foundation for Statistical Computing, Vienna, Austria).

RESULTS

Clinical Characteristics

Baseline characteristics of the 107 study participants are shown in Table 1. The median CD4+ T-cell and plasma HIV-1 RNA values were 502 cells/mm3 [IQR 329–738] and 50 copies/ml (range 50–9285), respectively. A total of 70 (65%) individuals had undetectable HIV-1 RNA (<50 copies/ml). Overall median age was 46 years (IQR 41–51), and in females was 48 years (IQR 40–52). In total, 26 (24%) patients reported daily aspirin use, 50 (47%) reported regular NSAID use, and 57 (53%) were current smokers. Two (8%) of the females were taking oestrogen. Seventeen (16%) patients were co-infected with hepatitis C. A total of 63 (59%) individuals were receiving protease inhibitor (PI)-containing ART and 41 (38%) patients non-nucleoside reverse transcriptase inhibitor (NNRTI)-containing ART. The median BMI was 25 kg/m2 (IQR 23–28), and females had a higher BMI of 27 kg/m2 (IQR 24–31) than males at 25 kg/m2 (IQR 23–27; p=0.03).

Table 1.

Characteristics of study participants.

Parameter Overall (n=107) Males (n=81) Females (n=26) p-value
Median age, years (IQR) 46 (41 – 51) 46 (42 – 51) 48 (40 – 52) 0.91
Sex
  Female, n (%) 26 (24) -- -- --
Male, n (%) 81 (76) -- -- --
Race
  Non-White, n (%) 45 (42) 32 (40) 13 (50) --
  White, n (%) 62 (58) 49 (60) 13 (50) 0.35
Current smoker, n (%) 57 (53) 40 (49) 17 (65) 0.15
Current daily aspirin use, n (%) 26 (24) 23 (28) 3 (12) 0.08
Current NSAID use, n (%) 50 (47) 36 (44) 14 (54) 0.40
Hepatitis C coinfection, n (%) 17 (16) 10 (12) 7 (27) 0.08
Median CD4+ T-cells, cells/mm3 (IQR) 502 (329 – 738) 502 (345 – 702) 507 (315 – 870) 0.96
Median HIV RNA, copies/ml (range) 50 (50 – 9285) 50 (50 – 9285) 50 (50 – 3495) 0.51
HIV RNA < 50 copies/ml, n (%) 70 (65) 50 (62) 20 (77) 0.24
Median hsCRP, mg/l (IQR) 2.9 (0.7 – 5.3) 2.2 (0.7 – 5.0) 4.2 (1.1 – 7.5) 0.19
Median BMI, kg/m2 (IQR) 25 (23 – 28) 25 (23 – 27) 27 (24 – 31) 0.03
Median total cholesterola, mg/dl (IQR) 193 (161 – 222) 190 (159 – 231) 194 (165 – 213) 0.49
Median LDL cholesterola, mg/dl (IQR) 98 (73 – 126) 100 (78 –123) 96 (68 – 127) 0.73
Median non-HDL cholesterola,mg/dl (IQR) 143 (116 – 176) 144 (117 – 182) 137 (115 – 153) 0.18
Median HDL cholesterola, mg/dl (IQR) 47 (40 – 53) 46 (39 – 51) 50 (45 – 60) 0.01
Median triglyceridesa, mg/dl (IQR) 179 (121 – 308) 193 (123 – 371) 144 (108 – 225) 0.06
Median Framingham scorea (IQR) 4 (1 – 7) 4 (1.8 – 6.2) 3.5 (−1.5 – 7) 0.61
NRTI, n (%) 107 (100) 81 (100) 26 (100) 1.00
NNRTI, n (%) 41 (38) 32 (39) 9 (35) 0.66
PI, n (%) 63 (59) 47 (58) 16 (62) 0.75
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a

Sample size was smaller than total number due to missing data (sample size ranged from 89–106 total individuals, of which 74–80 were males and 21– 26 were females).

NSAID = nonsteroidal anti-inflammatory drug, hsCRP = highly sensitive c-reactive protein, BMI = body mass index, LDL = low-density lipoprotein, HDL = high-density lipoprotein, NTRI = nucleoside reverse transcriptase inhibitor, NNRTI = non-nucleoside reverse transcriptase inhibitor, PI = protease inhibitor.

Median serum lipids included non-high-density lipoprotein (non-HDL) cholesterol 143 mg/dl (IQR 116–176), HDL cholesterol 47 mg/dl (IQR 40–53), and triglycerides 179 mg/dl (IQR 121–308). Only 89 individuals had low-density lipoprotein cholesterol available, and therefore analyses were performed using non-HDL cholesterol. Females had higher HDL cholesterol (50 mg/dl [IQR 45–60]) than males (46 mg/dl [IQR 39–51], p=0.01), and there was a trend toward females having lower triglycerides (p=0.06). Median hsCRP was 2.9 mg/l (IQR 0.7–5.3), indicating intermediate CVD risk (10–20% risk of CVD over 10 years) according to cutoffs derived from non-HIV-infected populations[21]. Higher hsCRP correlated with higher BMI (Spearman’s rho=0.27, p=0.005). We have previously published data regarding associations between hsCRP and metabolic parameters in this cohort[19]. The median Framingham score was 4 (IQR 1–7) overall, 4 (IQR 1.8–6.2) in males and 3.5 (IQR −1.5–7) in females, corresponding to a 10-year CVD risk <5%[22]. Patients taking abacavir (ABC) had higher Framingham risk scores compared to those who were not (7 [IQR 4–9] versus 3 [IQR 1–5]; p=0.004], but there were no other differences according to ART.

Urinary Eicosanoids and Measures of CVD Risk

Median 15-F2t-IsoP was higher in females (2.46 ng/mg Cr [IQR 1.93–4.44]) than males (1.98 ng/mg Cr [IQR 1.28–2.40]; p=0.003), as has been shown in HIV-negative cohort studies[23, 24]. Overall median 15-F2t-IsoP was higher (2.12 ng/mg Cr [IQR 1.33–2.64]) than in studies of HIV-negative healthy individuals (1.86 ng/mg Cr [IQR 1.25–2.62])[7, 25]. We found that 15-F2t-IsoP was increased in current smokers (2.25 ng/mg Cr [IQR 1.49–3.64]) compared with non-smokers (1.77 ng/mg Cr [IQR 1.23–2.30]; p=0.005). There was no association between 15-F2t-IsoP and HIV-1 RNA. Higher 15-F2t-IsoP was associated with elevated 11dTxB2 and PGI-M (rho=0.20, p=0.04 for both). Persons on ABC (1.54 ng/mg Cr [IQR 1.22–2.12] versus 2.24 ng/mg Cr [IQR 1.47–3.17]; p=0.001) or lopinavir (LPV; 1.77 ng/mg Cr [IQR 1.23–2.38] versus 2.19 ng/mg Cr [IQR 1.42–2.89]; p=0.05) had lower 15-F2t-IsoP than individuals who were not. 15-F2t-IsoP did not differ according to the use of other ART. In multivariable analysis (Figure 2A), higher 15-F2t-IsoP was associated with female sex (β=1.51; 95% CI 1.15, 1.99; p=0.004) and current smoking (β=1.27; 95% CI 1.01, 1.59; p=0.04). In interaction analyses, the association between 15-F2t-IsoP and current smoking was significant in females only (p=0.04), but was not modified by sex (p=0.22 for interaction).

Figure 2.

Figure 2

Figure 2

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Multivariable analysis of 15-F2t-isoprostane-F2αand prostaglandin-E metabolite. (A) 15-F2t-isoprostane-F2α(15-F2t-IsoP). (B) 11-α-hydroxyl-9,15-dioxo-2,3,4,5-tetranor-prostane-1,20-dioic acid (PGE-M; prostaglandin-E metabolite). Data are exponentials of regression coefficients (95% CI). The association between sex and each urinary eicosanoid was assessed using linear regression, adjusting for age, CD4+ T-cells, smoking status, non-steroidal anti-inflammatory drug (NSAID) use, aspirin (ASA) use, and body mass index (BMI, overall). In addition, interaction analysis (adding cross-product of sex and each covariate individually) was conducted to assess whether sex modified the effects of the covariates (male and female). The outcome variables (urinary eicosanoids) were natural log-transformed to provide normality in the regression residuals. Exponentials of regression coefficients were then computed, which indicates the fold change in the urine eicosanoid of interest by one interquartile increase in the corresponding covariate.

Median PGE-M was significantly lower in females (4.57 ng/mg Cr [IQR 2.11–7.63]) than males (8.27 ng/mg Cr [IQR 5.23–12.44]; p=0.003), particularly in three females reporting regular aspirin use (0.93 ng/mg Cr [IQR 0.57–1.50]) compared to females who did not (5.09 ng/mg Cr [IQR 3.08–10.63]; p=0.01). PGE-M was lower in our study in both sexes when compared with healthy HIV-negative populations[9, 24, 26]. PGE-M did not differ according to use of specific ART. Lower PGE-M was associated with higher BMI (rho=−0.34, p<0.001) and higher HIV-1 RNA (rho=−0.22, p=0.03). In multivariable analysis (Figure 2B), lower PGE-M was associated with female sex (β=0.55; 95% CI 0.37, 0.83; p=0.005) and higher BMI (β=0.83; 95% CI: 0.70, 0.98; p=0.03). The association between BMI and PGE-M was seen in males only (p<0.001) and was modified by sex (interaction p=0.04). Lower PGE-M was associated with aspirin use in females only (p<0.001), and this association was also modified by sex (interaction p<0.001).

Median 11dTxB2 tended to be higher in females (0.38 ng/mg Cr [IQR 0.24–0.53]) than males (0.29 ng/mg Cr [IQR 0.19–0.40]; p=0.07) and in current smokers (0.37 ng/mg Cr [IQR 0.22–0.47]) than non-smokers (0.27 ng/mg Cr [IQR 0.19–0.40]; p=0.06). Overall 11dTxB2 in our study population (0.32 ng/mg Cr [IQR 0.19–0.45]) was similar to published results for HIV-negative individuals (0.31 ng/mg Cr [IQR 0.23–0.44])[8, 27]. In multivariable analysis, higher 11dTxB2 was associated with increasing age (β=1.23; 95% CI 1.04, 1.45; p=0.02) and current smoking (β=1.35; 95% CI 1.02, 1.79; p=0.04), higher 11dTxB2 tended to be associated with female sex (p=0.07), and lower 11dTxB2 was associated with higher BMI (β=0.84; 95% CI 0.73, 0.97; p=0.02). In males, higher 11dTxB2 was associated with older age (p=0.02) and current smoking (p=0.02), and lower 11dTxB2 tended to be associated with higher BMI (p=0.06).

PGI-M did not differ according to sex. The overall median PGI-M was 0.13 ng/mg Cr [IQR 0.08–0.22] in our study, similar to that reported in HIV-negative individuals[10, 28, 29]. We found that PGI-M was higher in current smokers (0.17 ng/mg Cr [IQR 0.09–0.27]) than nonsmokers (0.11 ng/mg Cr [IQR 0.07–0.16]; p=0.02). PGI-M did not differ according to use of specific ART. There was no association between PGI-M and HIV-1 RNA. In multivariable analysis, higher PGI-M was associated with current smoking (β=1.41; 95% CI 1.02, 1.95; p=0.04).

In separate multivariable models for each urinary eicosanoid adjusting for age, sex, CD4+ T-cells, smoking, NSAID use, aspirin use, and BMI, there were no associations between any of the eicosanoids and Framingham score or serum lipids.

DISCUSSION

Data for eicosanoids in HIV-negative populations and animal models suggest potential utility for CVD risk prediction. Persons with coronary artery disease had higher urinary 15-F2t IsoP than controls, which correlated with the number of CVD risk factors and was positively associated with hsCRP[11]. Urinary F2-IsoPs, measured by ELISA, were higher in those with elevated carotid IMT and increased step-wise with the number of diseased coronary arteries on coronary angiography[12]. The odds ratio for a composite outcome of myocardial infarction, stroke or cardiovascular death increased with each quartile of urinary 11dTxB2[30].

The most important finding of this study is that, among virologically suppressed persons with HIV infection, low CVD risk by Framingham score, and intermediate CVD risk by hsCRP, females had higher urinary 15-F2t-IsoP and 11dTxB2 – eicosanoids with negative effects on endothelial function, inflammation, and oxidative tissue damage – than males. Furthermore, PGE-M, which may counteract these adverse effects, was lower in females. Consistent with data in HIV-negative populations, smoking and use of aspirin and NSAIDs affected several eicosanoids, often in sex-specific ways. Our group previously reported higher plasma F2-IsoP in HIV-infected females[31]. To our knowledge, this is the first study to describe urinary eicosanoid patterns in HIV-infected individuals and to report higher urine 15-F2t-IsoP in HIV-infected females.

The sex differences in our results are provocative. Females had higher urine 15-F2t-IsoP and 11dTxB2, vasoconstrictive eicosanoids stimulating platelet aggregation, and lower urine PGE-M, which tends to have beneficial vasodilatory properties. There were notable sex differences in associations between CVD risk modifiers and several urine eicosanoids, including interactions between sex, BMI, aspirin use, and PGE-M. A previous study found that HIV-infected females had higher hsCRP, a marker of future acute coronary events[21], than HIV-negative females[32]. We did not find correlations between urine eicosanoids and hsCRP, although the number of females in our study was small.

To our knowledge, we are the first to report an association between PGE-M and BMI. PGE-M has variable effects on vascular tone, depending on the target tissue and prostanoid receptor stimulated[33]. We also found that lower 11dTxB2 was associated with higher BMI, an unexpected finding given the association between thromboxane-dependent platelet activation and CVD risk factors[30]. In HIV-negative women, 11dTxB2 was higher in those who were obese[34]. Gender-specific differences may account for the discrepancy between the results of that study and ours: our patient population was predominantly male, with a lower BMI, and the negative association between 11dTxB2 and BMI was seen only in males in our subgroup analysis.

HIV infection may be associated with premature menopause. One study found a median (IQR) age of onset of 46 years [IQR 39–49] in HIV-infected females[35]. Thus, the majority of females in our study might have been postmenopausal. Previous studies suggest that oestrogen can be associated with more favourable eicosanoid profiles. In post-menopausal females, plasma thromboxane B2 and vascular impedance, measured by carotid Doppler, were reduced after starting hormone replacement therapy[36]. Another study found an increased urinary PGI-M-to- 11dTxB2 ratio with hormone replacement therapy[37]. None of our study participants were receiving hormone replacement therapy; loss of some beneficial effects of oestrogen on inflammation and endothelial function could explain, at least in part, the gender differences in our results. Although there were fewer females than males in our study, the associations in females were robust.

Higher BMI is associated with the metabolic syndrome and CVD[38], and oxidant stress appears to play an important role in this process. Urinary 8-isoprostane increased with each quintile of BMI in HIV-negative individuals[39], and higher plasma F2-IsoPs were associated with elevated BMI in HIV-infected persons[31]. In HIV-infected females, Glesby et al.[40] found that higher plasma F2-IsoPs were associated with higher BMI and waist circumference. We did not find an association between urinary 15-F2t-IsoP and BMI. However, our sample size was smaller than prior studies, and, unlike Glesby et al.[40], only 24% of our study participants were female.

Published data regarding the effect of PIs on eicosanoids are limited. In a mouse model, zidovudine (ZDV), but not indinavir, increased plasma 15-F2t-IsoP[41]. In the present study, we found that urine 15-F2t-IsoP was lower in persons receiving LPV, but not affected by other PIs. Recent data showed that use of ABC was associated with MI, and that individuals taking ABC had elevated hsCRP compared to other NRTIs[42]. By contrast, another study found that hsCRP did not significantly differ according to ABC use[43]. We also found no difference in hsCRP according to ABC use[19], although Framingham risk scores were higher in persons treated with ABC. Urine 15-F2t-IsoP, however, was lower in those receiving ABC (n=29). Interestingly, Gerschenson et al.[44] found that plasma F2-IsoP was reduced after switching from stavudine to tenofovir (TDF). In our study, 15-F2t-IsoP did not differ by use of other NRTIs, including TDF. These results must be interpreted with caution given the small number of persons taking individual ART in our study and the cross-sectional design, which precludes our ability to study effects of cumulative ART exposure. It is intriguing that two ART drugs previously associated with MI were associated with lower urine 15-F2t-IsoP. This suggests that excess MI risk observed with ABC and/or LPV exposure – if true – is not primarily mediated through lipid peroxidation, but further study is needed to confirm these findings. We previously saw no association between PIs or ABC and plasma F2-IsoPs[31, 45]; associations in the present study might differ from prior work owing to differences in underlying CVD risk and ART regimens.

Our study did not assess surrogate measures of CVD, including IMT and FMD. In an HIV-negative population undergoing coronary angiography, higher urine 15-F2t-IsoP correlated with and was an independent predictor of higher IMT[12]. In children with hyperlipidaemia, higher urine 15-F2t-IsoP correlated with higher IMT and FMD and was an independent predictor of both[13]. In adults with diabetes and hypertension, there was a negative correlation between plasma 8-isoprostane and FMD[46]. In another study, higher 11dTxB2 and lower prostacyclin-to-thromboxane ratio correlated with higher IMT[47]. Studies are needed in HIV-infected individuals to define the relationship between urinary eicosanoids and surrogate CVD measures in this patient population. This pilot study has other limitations. There was no HIV-negative control group, and all of the individuals in our study were receiving ART, precluding our ability to evaluate differences in HIV-negative persons or those with ongoing HIV viral replication, which may be associated with a proinflammatory state. We did not assess for insulin resistance, which may affect hsCRP and, possibly, eicosanoids[48, 49].

In summary, among predominantly virologically suppressed HIV-1-infected persons on ART, low CVD risk by Framingham score and moderate CVD risk by hsCRP, females had higher proinflammatory eicosanoids and lower PGE-M than males. These results highlight the potential importance of AA metabolism in the pathogenesis of metabolic complications of ART and suggest that urinary eicosanoids might be useful for assessing metabolic complications and CVD risk in HIV-infected patients on ART with virologic suppression. Larger studies are needed to replicate our findings, determine associations between urinary eicosanoids, specific ART regimens, and CVD outcome measures, and to explore these biomarkers as surrogate measures in studies of potential therapeutic interventions.

ACKNOWLEDGEMENTS

Sources of funding. Primary funding support was provided by NIH/NCCAM Career Development Award K23 AT002508 (TH), the Vanderbilt CTSA grant RR024975 from NCRR/NIH, the Vanderbilt Meharry Center for AIDS Research (AI54999), NIH GM15431 (GLM), the Vanderbilt Multidisciplinary Clinical Research Center grant AR056116-03 (AB), and the Vanderbilt Diabetes Research and Training Center grant DK020593-33 (AS). Additional support was provided by the Tennessee Valley VA Clinical Research Center of Excellence program (TH). There was no influence of the funding source on the analysis and reporting of the results.

DWH has received research grants from Bavarian Nordic, Boehringer-Ingelheim, Bristol-Myers Squibb, Gilead Sciences, Merck, Tanox and Tibotec, and is on Scientific Advisory Boards for GlaxoSmithKline and Tibotec. TH has received research support from Merck.

Footnotes

DISCLOSURE STATEMENT

All other authors declare no competing interests.

Some of these data were previously presented at the XVII International AIDS Conference, 6 August 2008, Mexico City, Mexico (abstract number WEAB0105) and at the 10th International Workshop on Adverse Drug Reactions and Lipodystrophy in HIV, 7 November 2008, London, UK (abstract number ADRLH-147).

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