A metabolic syndrome associated with atherosclerosis and cardiovascular disease has been described in HIV-positive individuals. In the present study we investigated whether HIV-positive individuals and CAD (coronary artery disease) patients have similarities in their vascular function and structure. In a case-control study, we compared measurements of carotid artery IMT (intima-media thickness) and brachial artery FMD (flow-mediated vasodilation) in HIV-positive individuals with age- and sex-matched controls with similar risk factors and patients with established CAD. Seventy-one HIV patients, age 42±13.9 years (91% male), were compared with 29 CAD patients and 25 controls. HIV patients had higher IMT than controls and similar IMT to CAD patients (0.64±0.2 compared with 0.55±0.05 and 0.66±0.08 mm respectively; F=4.2, P=0.01). Patients taking protease inhibitors had higher IMT (0.69±0.2 compared with 0.57±0.15 mm; P=0.01), blood pressure, cholesterol and triacylglycerols than those not taking protease inhibtors (P<0.05). In multiple regression analyses, increasing blood pressure (β: 0.37, P=0.001), glucose (β: 0.26, P=0.016), cholesterol (β: 0.24, P=0.033), duration of HIV disease (β: 0.33, P=0.008) and use of protease inhibitors (β: 0.27, P=0.04) were the most important determinants of IMT respectively. FMD was associated only with triacylglycerol measurements. Patients with HIV present arterial changes resembling those found in patients with atherosclerotic cardiovascular disease. These vascular changes are closely related to protease-inhibitor-induced changes of metabolic parameters. Thus intensive treatment of these metabolic parameters might retard atherosclerosis in HIV patients.

INTRODUCTION

The introduction of HAART (highly active antiretroviral therapy) dramatically reduced HIV-associated morbidity and mortality [1] prompting increasing concerns related to the chronic management of these patients. Metabolic alterations, namely dyslipidaemia, insulin resistance and lipodystrophy, are common side effects of HAART [2] and there is increasing concern that these changes will translate in the long-term into an increased incidence of cardiovascular atherosclerotic disease [3]. Indeed, the DAD (Data Collection on Adverse Events of Anti-HIV Drugs) Study Group [4] reported that HAART was associated with a 26% increase in the rate of myocardial infarction per year of exposure to antiretroviral drugs.

Careful cardiovascular evaluation in the course of HIV disease can identify changes early enough to intervene. In addition to the routine blood lipids and glucose measurements, it seems reasonable to estimate surrogate markers for atherosclerosis in HIV positive subjects. Endothelial function and carotid artery IMT (intima-media thickness) are surrogate markers commonly used in atherosclerotic patients and have been proven to be valuable for the prediction of acute ischaemic events [57]. Both endothelial function indices and carotid IMT have been shown to be abnormal in HIV patients compared with normal controls [8,9]. To date no study has been published comparing patients with HIV disease with patients with atherosclerotic heart disease. We hypothesized that these two groups of patients might have similarities in their vascular function and structure and therefore we designed a study to investigate the carotid artery IMT and the FMD (flow-mediated vasodilation) of the brachial artery, a reliable estimate of endothelial function, in HIV patients, subjects with proven CAD (coronary artery disease) and healthy individuals.

MATERIALS AND METHODS

Study population

We prospectively enrolled 71 HIV-positive patients (mean age 42±13.9 years, 91% male) attending a tertiary care centre with no previous medical history of CAD. Twenty-nine patients with angiographically documented CAD (positive control) and 25 subjects of similar age, sex and atherosclerotic risk factors to the HIV patients served as positive and control groups respectively. The HIV and control subjects had no history of cardiovascular disease, with normal physical examination and normal resting and exercise ECG. The presence of metabolic syndrome was assessed among the study groups according to the criteria proposed by the NCEP (National Cholesterol Education Program) ATP III (Adult Treatment Panel III) [10]. The creatinine clearance was calculated as a marker of renal function using the following formula: creatinine clearance={[140−age (years)]×weight (kg)]}/[72×serum creatine (mg/dl)] (multiplied by 0.85 for women). The study was approved by the hospital's scientific committee and all patients gave written informed consent. The research has been carried out in accordance with the Declaration of Helsinki (2000) of the World Medical Association.

Endothelial function

Endothelium-dependent FMD of the right brachial artery was determined in all patients. All subjects were studied in the morning, having abstained from alcohol, caffeine and food for 8 h prior to the study; all vasoactive medications were withheld for 48 h before the study. Optimal imaging of the brachial artery was obtained and a resting scan was recorded using an Echo-Doppler ultrasound system (Vivid 7; GE Medical systems) and a 10 MHz transducer. Reactive hyperaemia was then induced by inflation of a blood pressure cuff on the forearm at a pressure of 200 mmHg for 5 min and subsequent deflation; the brachial artery was scanned continuously 30 s before and 90 s after cuff deflation. All images were recorded on super VHS videotape for off-line analysis. Artery diameter measurements were made using electronic calipers from the anterior to the posterior m-line. FMD was calculated as the percentage increase in arterial diameter during hyperaemia as compared with the resting scan, as previously described [11]. Inter- and intra-observer variability of these measurements in our laboratory has been previously described [12]. At the end of the protocol, images were obtained again 4 min after sublingual nitroglycerin (0.4 mg) for measurement of nitrate-induced, endothelium-independent vasodilation.

Measurement of carotid atherosclerosis

B-mode ultrasonographic examination was performed in all patients using the same Echo-Doppler ultrasound. Scanning included left and right carotid arteries for the measurement of the IMT; all scans were performed by the same operator. The carotid artery image was focused in the far wall and two segments were identified on each side: the distal 1.0 cm of the common carotid proximal to the bifurcation and the carotid bulb [12]. The mean value of all four sites was used for analysis. All scans were digitally stored (Echopac; GE Medical Systems), and recorded on super VHS videotape for off-line analysis.

Statistical analysis

All variables are expressed as means±S.D. Skewed variables were log-transformed to normalize their distribution. Categorical data were compared by means of the χ2-test. Differences in IMT or FMD between the three study groups (HIV, CAD, healthy controls) were examined by full factorial ANOVA (General linear model) using as co-variables BMI (body mass index), smoking status, blood pressure (systolic or diastolic separately), cholesterol, triacylglycerols, serum glucose, creatinine clearance, use of β-blockers, diuretics, nitrates and statins. The interaction terms between the variable of the three study groups and the above co-variables were also examined. Using ANOVA, differences in IMT or FMD between the three study groups were also examined in a model including the presence of metabolic syndrome as a co-variable. The interaction term between the variable of the three study subgroups and metabolic syndrome was also examined. Post-hoc comparisons were performed with Bonferroni's correction. Differences in variables between patients with and without PIs (protease inhibitors), NRTIs (nucleoside reverse transcriptase inhibitors) and NNRTIs (non-nucleoside reverse transcriptase inhibitors) or between the above patient subgroups and controls were assessed by two-tailed unpaired t test. Using simple linear regression the association of IMT or FMD (dependent variables) with age, sex, BMI, atherosclerotic risk factors (blood pressure, smoking, serum cholesterol, triacylglycerols and glucose levels), presence of metabolic syndrome, creatinine clearance, duration of disease, minimum CD4 lymphocyte counts and maximum viral load, current viral load and current CD4 lymphocyte counts and duration of HAART was examined. Additionally, exposure to HAART, as well as a viral load of over 100;000 copies/ml for a period of more than 6 months or CD4 count <200 for 6 months were examined as dichotomous variables. Variables with a P value of <0.2 in univariate analysis or of major clinical significance (e.g. sex, BMI, blood pressure, glucose, cholesterol, triacylglycerols, smoking, pulse pressure) were entered in multiple regression models. All co-variables included in the final models were tested for interactions. The following variables were entered in the model separately to avoid co-linearity: (i) systolic, diastolic or mean blood pressure; (ii) use of HAART (any regimen), PI, NRTI or NNRTI; (iii) minimum CD4 or current CD4 lymphocyte counts, maximum viral load, current viral load or viral load >105 copies/ml for more than 6 months; (iv) disease duration or HAART duration; and (v) presence of metabolic syndrome or associated risk factors (glucose, cholesterol, triacylglycerols, blood pressure parameters).

Analysis was weighted for age. The associations between vascular indices and the clinical characteristics of the patient are presented by means of standardized regression coefficient (β). P<0.05 was considered to be the level of statistical significance. All statistical tests were two tailed. SPSS 11.5 software was used for statistical analysis.

RESULTS

Both control groups had similar age, sex, atherosclerotic risk factors, creatinine clearance, incidence of metabolic syndrome and use of statins to HIV patients (Table 1). The CAD group had a slightly higher mean age than the two other groups but this did not reach statistical significance. All diabetic patients were on oral antidiabetic treatment. The CAD patients were treated with a higher percentage of β-blockers than the other two groups (P<0.05) and four of them were receiving long-acting nitrates. The remaining medication was similar among HIV patients and control groups. Among HIV patients, those receiving PIs (n=37) had higher mean and diastolic blood pressure and higher levels of cholesterol, triacylglycerols and glucose compared with patients on other antiretrovirals or no treatment (see Table 1 for all comparisons; P<0.05). As a result, patients taking PIs had a higher incidence of metabolic syndrome than patients on other antiretrovirals or no treatment (P<0.05). Furthermore, patients receiving PIs had higher IMT (P=0.01) and similar FMD (P=0.07) values compared with patients on other antiretrovirals or no treatment. Patients receiving PIs had higher maximal viral load and incidence viral load >105 copies/ml for more than 6 months as well as a reduced minimum CD4 count compared with patients on other antiretrovirals or no treatment (P<0.05). However, the current CD4 count and viral load was similar between the two subgroups of HIV patients (Table 1; P=not significant).

Table 1
Clinical characteristics of the study groups

NMD, nitrate-mediated dilatation-brachial index, SBP, systolic blood pressure; DBP, diastolic blood pressure; MBP, mean blood pressure; N/A, not applicable. *P value for ANOVA between three groups; †P value for comparison between PI compared with non-PI; ‡P is not significant for HIV compared with normal controls.

CharacteristicHIV (n=71)CAD (n=29)CONTROLS (n=25)P*PI (n=37)No PI (n=34)P
Age (years) 42±13.9 46±5.7 40±5.6 0.1 44±12 40±13 0.1 
Males (n65 (91%) 24 (83%) 23 (92%) 0.2 32 (86%) 34 (97%) 0.24 
Cholesterol (mg/dl) 200±60 220±70 223±40 0.14 224±60* 175±48 <0.001 
Triacylglycerol (mg/dl) 200±154 137±70 182±100 0.11 256±166* 139±116 <0.001 
Glucose (mg/dl) 94±44 90±45 88±39 0.9 104±59* 83±112 <0.05 
Creatinine (mg/dl) 0.7±0.04 0.8±0.03 0.7±0.03 0.9 0.8±0.04 0.68±0.04 0.9 
Creatinine clearance (ml/min) 142±25 138±27 150±15 0.6 140±27 144±24 0.9 
BMI (kg/m224±3 28±4 25±3 0.9 24±3 24.5±3 0.8 
Smoking (n52 (73%) 24 (82%) 18 (72%) 0.7 26 (71%) 26 (76%) 0.7 
Hypertension (n14 (20%) 11 (37%) 6 (24%) 0.5 11 (32%) 3 (9%) <0.05 
Diabetes (n5 (7%) 4 (13%) 2 (8%) 0.6 4 (10%) 1 (3%) 0.19 
Hyperlipidaemia (n15 (21%) 6 (21%) 5 (20%) 0.9 11 (30.6%) 4 (11.8%) <0.05 
Metabolic syndrome (n13 (18%) 6 (21%) 5 (20%) 0.8 10 (27%) 3 (9%) 0.04 
Current CD4 (cells/ml) 443.6±246.2 N/A N/A  420.2±263.9 470.1±226.2 0.4 
Minimum CD4 (cells/ml) 232.2±152.4 N/A N/A  160.4±107.2 310.2±157.1 <0.001 
Duration CD4 <200 (months) 9.6±22.5 N/A N/A  9.8±24 9.5±21.5 0.9 
Current viral load (lg10) 2.94±1.4 N/A N/A  3.01±1.5 2.9±1.4 0.9 
Maximum viral load (lg10) 4.83±0.99 N/A N/A  5.1±0.89 4.5±1 <0.05 
Viral load >105×6 months 35 (49.3%) N/A N/A  25 (67.5%) 10 (29.4%) <0.001 
HIV medication (n       
 HAART 48 (68%) N/A N/A  N/A N/A  
 PI 37 (52%) N/A N/A  N/A N/A  
 NNRTI 33 (46%) N/A N/A  N/A N/A  
 NRTI 48 (68%) N/A N/A  N/A N/A  
SBP (mmHg) 117±20 117±16 120±9 0.8 120±25 115±13 0.1 
DBP (mmHg) 74±10 74±11 74±8 0.9 78±10* 71±9 <0.05 
MBP (mmHg) 88±12 89±11 89±7 0.9 92±13* 86±10 <0.05 
IMT (mm) 0.64±0.2 0.66±0.08 0.55±0.05 0.01 0.69±0.2* 0.57±0.15 <0.05 
NMD (%) 15.0±5.7 13.7±5.9 16.5±5.5 0.5 14.5±6.4 15.2±4.9 0.6 
FMD (%) 5.43±2.7 2.76±2.6 7.07±3.7 <0.001 5.34±3.2 5.5±2.3 0.8 
Medication        
 β-Blockers‡ 6 (8%) 25 (86%) 2 (8%) <0.001 5 (13%) 1 (3%) <0.05 
 Diuretics 8 (11%) 5 (17%) 4 (12%) 0.5 6 (16%) 2 (6%) <0.05 
 Nitrates 4 (13%) N/A N/A   
 Statins 9 (13%) 4 (14%) 3 (12%) 0.9 7 (19%) 2 (6%) <0.05 
CharacteristicHIV (n=71)CAD (n=29)CONTROLS (n=25)P*PI (n=37)No PI (n=34)P
Age (years) 42±13.9 46±5.7 40±5.6 0.1 44±12 40±13 0.1 
Males (n65 (91%) 24 (83%) 23 (92%) 0.2 32 (86%) 34 (97%) 0.24 
Cholesterol (mg/dl) 200±60 220±70 223±40 0.14 224±60* 175±48 <0.001 
Triacylglycerol (mg/dl) 200±154 137±70 182±100 0.11 256±166* 139±116 <0.001 
Glucose (mg/dl) 94±44 90±45 88±39 0.9 104±59* 83±112 <0.05 
Creatinine (mg/dl) 0.7±0.04 0.8±0.03 0.7±0.03 0.9 0.8±0.04 0.68±0.04 0.9 
Creatinine clearance (ml/min) 142±25 138±27 150±15 0.6 140±27 144±24 0.9 
BMI (kg/m224±3 28±4 25±3 0.9 24±3 24.5±3 0.8 
Smoking (n52 (73%) 24 (82%) 18 (72%) 0.7 26 (71%) 26 (76%) 0.7 
Hypertension (n14 (20%) 11 (37%) 6 (24%) 0.5 11 (32%) 3 (9%) <0.05 
Diabetes (n5 (7%) 4 (13%) 2 (8%) 0.6 4 (10%) 1 (3%) 0.19 
Hyperlipidaemia (n15 (21%) 6 (21%) 5 (20%) 0.9 11 (30.6%) 4 (11.8%) <0.05 
Metabolic syndrome (n13 (18%) 6 (21%) 5 (20%) 0.8 10 (27%) 3 (9%) 0.04 
Current CD4 (cells/ml) 443.6±246.2 N/A N/A  420.2±263.9 470.1±226.2 0.4 
Minimum CD4 (cells/ml) 232.2±152.4 N/A N/A  160.4±107.2 310.2±157.1 <0.001 
Duration CD4 <200 (months) 9.6±22.5 N/A N/A  9.8±24 9.5±21.5 0.9 
Current viral load (lg10) 2.94±1.4 N/A N/A  3.01±1.5 2.9±1.4 0.9 
Maximum viral load (lg10) 4.83±0.99 N/A N/A  5.1±0.89 4.5±1 <0.05 
Viral load >105×6 months 35 (49.3%) N/A N/A  25 (67.5%) 10 (29.4%) <0.001 
HIV medication (n       
 HAART 48 (68%) N/A N/A  N/A N/A  
 PI 37 (52%) N/A N/A  N/A N/A  
 NNRTI 33 (46%) N/A N/A  N/A N/A  
 NRTI 48 (68%) N/A N/A  N/A N/A  
SBP (mmHg) 117±20 117±16 120±9 0.8 120±25 115±13 0.1 
DBP (mmHg) 74±10 74±11 74±8 0.9 78±10* 71±9 <0.05 
MBP (mmHg) 88±12 89±11 89±7 0.9 92±13* 86±10 <0.05 
IMT (mm) 0.64±0.2 0.66±0.08 0.55±0.05 0.01 0.69±0.2* 0.57±0.15 <0.05 
NMD (%) 15.0±5.7 13.7±5.9 16.5±5.5 0.5 14.5±6.4 15.2±4.9 0.6 
FMD (%) 5.43±2.7 2.76±2.6 7.07±3.7 <0.001 5.34±3.2 5.5±2.3 0.8 
Medication        
 β-Blockers‡ 6 (8%) 25 (86%) 2 (8%) <0.001 5 (13%) 1 (3%) <0.05 
 Diuretics 8 (11%) 5 (17%) 4 (12%) 0.5 6 (16%) 2 (6%) <0.05 
 Nitrates 4 (13%) N/A N/A   
 Statins 9 (13%) 4 (14%) 3 (12%) 0.9 7 (19%) 2 (6%) <0.05 

Comparisons between HIV patients, CAD patients and healthy controls

By ANOVA, HIV patients had higher IMT than controls and a similar IMT to CAD patients (0.64±0.2 compared with 0.55±0.05 compared with 0.66±0.08 mm respectively; F=4.2, P=0.01, Table 1). However, this difference was driven by those patients treated with PIs (0.69±0.2 compared with 0.57±0.15 mm; P=0.01, Table 1) as patients not receiving PIs had similar IMT levels to those in controls (P=0.47). HIV patients had lower FMD than controls but higher FMD than CAD patients (5.4±2.8 compared with 7.1±3.7 compared with 2.8±2.6% respectively; F=11.7, P<0.01). NMD (nitrate-mediated dilatation-brachial index) values were similar among the study groups. Differences remained significant after adjustment for the use of statins, other medication or the presence of metabolic syndrome. Additionally, the interaction terms between the variable of the three study groups and use of medication or presence of metabolic syndrome were not significant (results not shown).

Determinants of vascular indices among HIV patients

In univariate regression analyses age, systolic, diastolic and mean blood pressure, serum glucose, cholesterol and triacylglycerol levels, creatinine clearance, duration of HIV infection, use of PIs and viral load >105 copies/ml for more than 6 months were associated with IMT (P<0.05 for all associations; Table 2). The presence of metabolic syndrome had a borderline association with IMT (β=0.24, P=0.049) and no association with FMD (β=0.043, P=0.68). Maximal viral load, current viral load, minimum CD4 count, CD4 count <200 for >6 months were not associated with IMT or FMD (P>0.2 for all associations).

Table 2
Linear regression models assessing the association of IMT and FMD with clinical characteristics in HIV patients

*The multivariate models are weighted for age. The following variables were entered in the model separately to avoid co-linearity: (i) SBP (systolic blood pressure), DBP (diastolic blood pressure) or MBP (mean blood pressure); (ii) use of HAART (any regimen) or the use of PI, NNRTI or NRTI; (iii) viral load >105 copies/ml for more than 6 months and current CD4; and (iv) disease duration or HAART duration.

IMTFMD
UnivariateMultivariate*UnivariateMultivariate
Characteristicβ coefficientPβ coefficientPβ coefficientPβ coefficientP
SBP 0.38 0.01 0.32 0.005 0.01 0.9   
DBP 0.45 <0.01 0.31 0.006 −0.009 0.9   
Pulse pressure 0.17 0.15   0.019 0.87   
MBP 0.46 <0.01 0.36 0.001 0.001 0.99   
Age 0.51 <0.01   −0.16 0.16   
Males 0.18 0.12   −0.04 0.7   
BMI 0.007 0.9   −0.08 0.5   
Cholesterol 0.32 0.008 0.23 0.037 0.03 0.77   
Triacylglycerol 0.24 0.043   0.37 0.006 0.36 0.003 
Glucose 0.37 0.002 0.25 0.02 −0.012 0.9   
Creatinine clearance −0.03 0.8   −0.012 0.9   
Smoking 0.19 0.12   −0.09 0.4   
Duration of disease 0.25 0.04 0.32 0.005 0.17 0.15   
HIV medication         
 HAART 0.17 0.14   −0.097 0.4   
 PI 0.28 0.018 0.27 0.04 −0.036 0.76   
 NNRTI 0.19 0.11   −0.038 0.75   
 NRTI 0.17 0.14   −0.13 0.26   
Duration of HAART 0.19 0.09   0.12 0.3   
Viral load >105×6 months 0.27 0.02 0.25 0.02 0.084 0.48   
Current CD4 0.17 0.14   0.11 0.19   
IMTFMD
UnivariateMultivariate*UnivariateMultivariate
Characteristicβ coefficientPβ coefficientPβ coefficientPβ coefficientP
SBP 0.38 0.01 0.32 0.005 0.01 0.9   
DBP 0.45 <0.01 0.31 0.006 −0.009 0.9   
Pulse pressure 0.17 0.15   0.019 0.87   
MBP 0.46 <0.01 0.36 0.001 0.001 0.99   
Age 0.51 <0.01   −0.16 0.16   
Males 0.18 0.12   −0.04 0.7   
BMI 0.007 0.9   −0.08 0.5   
Cholesterol 0.32 0.008 0.23 0.037 0.03 0.77   
Triacylglycerol 0.24 0.043   0.37 0.006 0.36 0.003 
Glucose 0.37 0.002 0.25 0.02 −0.012 0.9   
Creatinine clearance −0.03 0.8   −0.012 0.9   
Smoking 0.19 0.12   −0.09 0.4   
Duration of disease 0.25 0.04 0.32 0.005 0.17 0.15   
HIV medication         
 HAART 0.17 0.14   −0.097 0.4   
 PI 0.28 0.018 0.27 0.04 −0.036 0.76   
 NNRTI 0.19 0.11   −0.038 0.75   
 NRTI 0.17 0.14   −0.13 0.26   
Duration of HAART 0.19 0.09   0.12 0.3   
Viral load >105×6 months 0.27 0.02 0.25 0.02 0.084 0.48   
Current CD4 0.17 0.14   0.11 0.19   

In multivariate regression analysis, weighted for the effect of age, the most important determinants of increased IMT were serum glucose, cholesterol and blood pressure (mean, systolic or diastolic) levels, HIV duration, viral load >105 copies/ml for more than 6 months and use of PIs after adjustment for sex, BMI, pulse pressure, smoking status, triacylglycerols and duration of HAART (Table 2). In a similar model including the presence of metabolic syndrome instead of other associated risk factors (glucose, cholesterol, triacylglycerols, blood pressure parameters), the most important determinants of increased IMT were metabolic syndrome (β=0.29, P=0.01), use of PIs (β=0.24, P=0.046) and viral load >105 copies/ml for 6 months (β=0.23, P=0.049). In univariate and multivariate regression analysis (weighted for the effect of age), triacylglycerol levels were the most important determinants of decreased FMD (Table 2, P=0.002) after adjustment for sex, BMI, blood pressure (mean, systolic or diastolic separately), pulse pressure, smoking status, use of HAART (any regimen, PI, NRTI or NNRTI separately), duration of HAART or HIV disease (entered separately), viral load >105 copies/ml for more than 6 months. In a similar multivariable model, including metabolic syndrome instead of other associated risk factors (glucose, cholesterol, triacylglycerols, blood pressure parameters), the association between metabolic syndrome and FMD remained not significant (β=0.032, P=0.8).

DISCUSSION

Our case-controlled study compared functional and structural arterial changes between HIV patients, age- and sex-matched CAD patients and controls with similar atherosclerotic risk factors. Patients with HIV had similar IMT values to those observed in patients with CAD, and higher than those found in individuals with similar atherosclerotic risk factors. Components of the HIV disease such as treatment with PIs and duration of disease as well as components of the metabolic syndrome such as higher blood pressure, cholesterol and glucose levels determined independently increasing IMT values. Treatment with PIs was related to impaired metabolic parameters and a higher incidence of the metabolic syndrome compared with other antiretroviral treatment and thus may have contributed to increasing IMT values. Regarding FMD, HIV patients showed values between those of matched patients with CAD and healthy controls.

The present study confirms previous results evaluating IMT changes in HIV patients; however, none of the studies had examined patients with diagnosed CAD as controls. Although such comparisons are affected by significant confounding they may provide clinical insight. In a previously reported study, HIV-positive subjects had higher IMT values than age-matched controls, which also progressed rapidly after 1 year of follow-up [8]. In concordance with our findings this study found classical cardiovascular risk factors to be associated with increased IMT [8]; however, they also reported an association with low CD4 count, an index of immunodeficiency in HIV patients, that could not be verified in our patient population by univariate analysis. In addition, higher IMT values were observed in patients with viral load >105 copies/ml for more than 6 months, further suggesting a relationship between severity of the disease and vascular abnormalities.

Another recently performed study compared HIV patients with healthy controls as well as diabetic patients [13]; IMT was similar in HIV and diabetic patients but in addition to metabolic parameters, factors relating to HIV infection and antiretroviral medication use were also related to IMT [13]. The role of duration of disease and exposure to HAART needs further study. We found a significant positive association between increasing HIV duration and higher IMT weighted for the aging effect. Similarly a recent large case-controlled study emphasized the independent role of HIV duration as well as exposure to HAART in the development of higher IMT values [14]. In fact the study concluded that the vascular age of HIV individuals is 4–5 years more than age- and sex-matched controls [14]. Thus chronic inflammation during the course of the disease may cause the release of several cytokines and growth factors leading to functional and structural vascular changes in HIV patients. In support of this mechanism, we have observed an independent association between a viral load >105 copies/ml for more than 6 months, a marker of the intensity of the inflammatory process, and IMT values in our HIV patients. In the present study, we also found that exposure to PI treatment was related to increased IMT values independently of the examined metabolic parameters. Furthermore, in the present study patients receiving PIs had higher mean diastolic blood pressure and higher levels of cholesterol, triacylglycerols and glucose and thus a higher incidence of the metabolic syndrome compared with patients on other antiretroviral therapy or no treatment, in agreement with previous studies [2].

This finding suggests that PI treatment may contribute to the impairment of metabolic parameters in HIV patients leading to increasing IMT values. The significant adverse effects of antiretroviral treatment on cardiovascular indices have been reported in very young HIV patients without traditional risk factors; indeed in a study of 83 children under treatment, higher IMT values were noted in HIV-positive children compared with healthy children [15]. These observations further highlight that the importance of antiretroviral therapy cannot be ignored.

The finding that IMT values in HIV patients were comparable with those observed in CAD patients is of major concern. Measurement of IMT is useful in studying atherosclerosis; it is associated with the extent of coronary atherosclerosis [16] as well the occurrence of cardiovascular events [5,17,18]. Recently the value of using IMT as a predictor for cardiovascular events has been extended to younger patients, i.e less than 50 years of age [19]. Also IMT is a popular surrogate marker for the evaluation of various interventions for the retardation or even the regression of the atherosclerotic process [20]. It is reasonable to hypothesize that all applications of IMT in CAD patients can also be used in HIV patients for risk stratification and evaluation of anti-atherosclerotic therapies, but this hypothesis has yet to be proven.

The independent association of IMT with blood pressure measurements, serum glucose and cholesterol values or with the presence of metabolic syndrome in the present study highlights the significance of these parameters in the genesis of atherosclerosis in HIV individuals. Furthermore it underscores the necessity for intense treatment of these risk factors and metabolic syndrome, especially in patients with higher values of IMT.

Endothelial dysfunction appears to be an early step in the atherosclerotic process and may be present even in children with cardiovascular risk factors [11]. FMD of the brachial artery is a reliable estimate of endothelial function, and is commonly used in clinical studies since it is non-invasive, correlates with the endothelial function in the coronary arteries and can predict cardiovascular events in high risk populations [2124]. Endothelial dysfunction assessed by FMD was modest in our HIV patients, worse than in normal individuals and better compared with CAD patients. Endothelial dysfunction has been previously reported in HIV patients [9,13] and may be caused by the HIV infection itself as well being the result of the antiretroviral agents used to treat HIV. Infection with HIV is associated with a systemic inflammatory environment that could affect the vascular endothelium [25,26]. Moreover, infections with opportunistic pathogens in patients with advanced HIV disease may exacerbate endothelial damage [27]. From the available antiretroviral medications, specific PIs have been associated with metabolic changes that may lead to endothelial dysfunction [2,26], although a direct cytotoxic effect on endothelial cells has also been described [28,29]. Nevertheless, an association with either PIs or viral load and FMD was not found in the present study. Only triacylglycerol levels were an independent study predictor of decreased FMD in our HIV population, suggesting that intense treatment of elevated triacylglycerol levels might improve endothelial function in these patients. It is well known that hypertriglyceridaemia impairs endothelial function, whereas vasodilator function improves after lowering plasma triacylglycerols even without changes in confounding lipoproteins or insulin resistance [30]. Triacylglycerols may cause endothelial dysfunction through several mechanisms including enhancement of oxidative stress, reduction of high-density lipoprotein cholesterol, influence on LDL (low-density lipoprotein) size distribution, induction of cell adhesion molecule expression, direct effects of TRLs (triacylglycerol-rich lipoproteins) on the vessel wall and increase of fatty acids [30]. The triacylglycerols were the only independent determinant of FMD in our patients, probably because of the extensive use of PIs in the present study cohort (52%). We have previously shown, that the use of these drugs [2] is related a 2-fold higher incidence rate for hypertriglyceridaemia than for hypercholesterolaemia. Thus the use of PIs has a stronger association with elevated triacylglycerol levels than with other lipoprotein levels through mechanisms which are not fully defined and include a direct enhancement of the formation of VLDL (very LDL) lipoproteins [31] or reduction of LPL (lipoprotein lipase) activity [32]. LPL is an enzyme located at the capillary endothelial surface which hydrolyses triacylglycerols to make fatty acids available to cells [30,33]. Thus reduction of its activity by PIs may contribute to elevation of triacylglycerol levels and consequently to endothelial dysfunction as observed in the present study.

The lack of the assessment of oxidative stress and inflammatory markers such as C-reactive protein may be considered a limitation of the present study because oxidative stress and low-grade inflammation may contribute in the development of vascular changes. However, in the present study we have demonstrated an independent association between IMT and a viral load >105 copies/ml for more than 6 months which is a marker of the intensity of the inflammatory process in HIV patients.

In conclusion, patients with HIV present functional and structural arterial changes resembling those found in patients with atherosclerotic cardiovascular disease. Characteristics of the HIV infection itself, e.g. viral load treatment, duration of the disease, treatment with PIs as well as parameters of the metabolic syndrome, e.g. serum glucose, cholesterol and triacylglycerol values and blood pressure measurements, appear to influence the pathogenesis of these vascular changes. Therefore intensive treatment of such changes might be helpful in preventing or retarding the atherosclerotic process in HIV patients.

Abbreviations

     
  • BMI

    body mass index

  •  
  • CAD

    coronary artery disease

  •  
  • FMD

    flow-mediated vasodilation

  •  
  • HAART

    highly active antiretroviral therapy

  •  
  • IMT

    intima-media thickness

  •  
  • LDL

    low-density lipoprotein

  •  
  • LPL

    lipoprotein lipase

  •  
  • NRTI

    nucleoside reverse transcriptase inhibitor

  •  
  • NNRTI

    non-nucleoside reverse transcriptase inhibitor

  •  
  • PI

    protease inhibitor

References

References
1
Palella
 
F. J.
Delaney
 
K. M.
Moorman
 
A. C.
, et al 
Declining morbidity and mortality among patients with advanced human immunodeficiency virus infection. HIV Outpatient Study Investigators
N. Engl. J. Med.
1998
, vol. 
338
 (pg. 
853
-
861
)
2
Tsiodras
 
S.
Mantzoros
 
C.
Hammer
 
S.
Samore
 
M.
 
Effects of protease inhibitors on hyperglycemia, hyperlipidemia, and lipodystrophy: a 5-year cohort study
Arch. Intern. Med.
2000
, vol. 
160
 (pg. 
2050
-
2056
)
3
Leitner
 
J. M.
Pernerstorfer-Schoen
 
H.
Weiss
 
A.
Schindler
 
K.
Rieger
 
A.
Jilma
 
B.
 
Age and sex modulate metabolic and cardiovascular risk markers of patients after 1 year of highly active antiretroviral therapy (HAART)
Atherosclerosis
2006
, vol. 
187
 (pg. 
177
-
185
)
4
Friis-Moller
 
N.
Sabin
 
C. A.
Weber
 
R.
, et al 
Combination antiretroviral therapy and the risk of myocardial infarction
N. Engl. J. Med.
2003
, vol. 
349
 (pg. 
1993
-
2003
)
5
Bots
 
M. L.
Hoes
 
A. W.
Koudstaal
 
P. J.
Hofman
 
A.
Grobbee
 
D. E.
 
Common carotid intima-media thickness and risk of stroke and myocardial infarction: the Rotterdam Study
Circulation
1997
, vol. 
96
 (pg. 
1432
-
1437
)
6
Neunteufl
 
T.
Heher
 
S.
Katzenschlager
 
R.
, et al 
Late prognostic value of flow-mediated dilation in the brachial artery of patients with chest pain
Am. J. Cardiol.
2000
, vol. 
86
 (pg. 
207
-
210
)
7
Schachinger
 
V.
Britten
 
M. B.
Zeiher
 
A. M.
 
Prognostic impact of coronary vasodilator dysfunction on adverse long-term outcome of coronary heart disease
Circulation
2000
, vol. 
101
 (pg. 
1899
-
1906
)
8
Hsue
 
P. Y.
Lo
 
J. C.
Franklin
 
A.
, et al 
Progression of atherosclerosis as assessed by carotid intima-media thickness in patients with HIV infection
Circulation
2004
, vol. 
109
 (pg. 
1603
-
1608
)
9
Solages
 
A.
Vita
 
J. A.
Thornton
 
D. J.
, et al 
Endothelial function in HIV-infected persons
Clin. Infect. Dis.
2006
, vol. 
42
 (pg. 
1325
-
1332
)
10
Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults., Evaluation
Executive summary of the third report of The National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, And Treatment of High Blood Cholesterol In Adults (Adult Treatment Panel III)
JAMA, J. Am. Med. Assoc.
2001
, vol. 
285
 (pg. 
2486
-
2497
)
11
Celermajer
 
D. S.
Sorensen
 
K. E.
Gooch
 
V. M.
, et al 
Non-invasive detection of endothelial dysfunction in children and adults at risk of atherosclerosis
Lancet
1992
, vol. 
340
 (pg. 
1111
-
1115
)
12
Lekakis
 
J.
Papamichael
 
C.
Anastasiou
 
H.
, et al 
Endothelial dysfunction of conduit arteries in insulin-dependent diabetes mellitus without microalbuminuria
Cardiovasc. Res.
1997
, vol. 
34
 (pg. 
164
-
168
)
13
van Wijk
 
J. P.
de Koning
 
E. J.
Cabezas
 
M. C.
, et al 
Functional and structural markers of atherosclerosis in human immunodeficiency virus-infected patients
J. Am. Coll. Cardiol.
2006
, vol. 
47
 (pg. 
1117
-
1123
)
14
Lorenz
 
M. W.
Stephan
 
C.
Harmjanz
 
A.
, et al 
Both long-term HIV infection and highly active antiretroviral therapy are independent risk factors for early carotid atherosclerosis
Atherosclerosis
2007
, vol. 
196
 (pg. 
720
-
726
)
15
Charakida
 
M.
Donald
 
A. E.
Green
 
H.
, et al 
Early structural and functional changes of the vasculature in HIV-infected children: impact of disease and antiretroviral therapy
Circulation
2005
, vol. 
112
 (pg. 
103
-
109
)
16
Lekakis
 
J. P.
Papamichael
 
C. M.
Cimponeriu
 
A. T.
, et al 
Atherosclerotic changes of extracoronary arteries are associated with the extent of coronary atherosclerosis
Am. J. Cardiol.
2000
, vol. 
85
 (pg. 
949
-
952
)
17
Chambless
 
L. E.
Heiss
 
G.
Folsom
 
A. R.
, et al 
Association of coronary heart disease incidence with carotid arterial wall thickness and major risk factors: the Atherosclerosis Risk in Communities (ARIC) Study, 1987–1993
Am. J. Epidemiol.
1997
, vol. 
146
 (pg. 
483
-
494
)
18
O'Leary
 
D. H.
Polak
 
J. F.
Kronmal
 
R. A.
Manolio
 
T. A.
Burke
 
G. L.
Wolfson
 
S. K.
 
Carotid-artery intima and media thickness as a risk factor for myocardial infarction and stroke in older adults. Cardiovascular Health Study Collaborative Research Group
N. Engl. J. Med.
1999
, vol. 
340
 (pg. 
14
-
22
)
19
Lorenz
 
M. W.
von Kegler
 
S.
Steinmetz
 
H.
Markus
 
H. S.
Sitzer
 
M.
 
Carotid intima-media thickening indicates a higher vascular risk across a wide age range: prospective data from the Carotid Atherosclerosis Progression Study (CAPS)
Stroke
2006
, vol. 
37
 (pg. 
87
-
92
)
20
Stamatelopoulos
 
K. S.
Lekakis
 
J. P.
Poulakaki
 
N. A.
, et al 
Tamoxifen improves endothelial function and reduces carotid intima-media thickness in postmenopausal women
Am. Heart J.
2004
, vol. 
147
 (pg. 
1093
-
1099
)
21
Anderson
 
T. J.
Uehata
 
A.
Gerhard
 
M. D.
, et al 
Close relation of endothelial function in the human coronary and peripheral circulations
J. Am. Coll. Cardiol.
1995
, vol. 
26
 (pg. 
1235
-
1241
)
22
Corretti
 
M. C.
Anderson
 
T. J.
Benjamin
 
E. J.
, et al 
Guidelines for the ultrasound assessment of endothelial-dependent flow-mediated vasodilation of the brachial artery: a report of the International Brachial Artery Reactivity Task Force
J. Am. Coll. Cardiol.
2002
, vol. 
39
 (pg. 
257
-
265
)
23
Gokce
 
N.
Keaney
 
J. F.
Hunter
 
L. M.
, et al 
Predictive value of noninvasively determined endothelial dysfunction for long-term cardiovascular events in patients with peripheral vascular disease
J. Am. Coll. Cardiol.
2003
, vol. 
41
 (pg. 
1769
-
1775
)
24
Karatzis
 
E. N.
Ikonomidis
 
I.
Vamvakou
 
G. D.
, et al 
Long-term prognostic role of flow-mediated dilatation of the brachial artery after acute coronary syndromes without ST elevation
Am. J. Cardiol.
2006
, vol. 
98
 (pg. 
1424
-
1428
)
25
Lewis
 
W.
 
Atherosclerosis in AIDS: potential pathogenetic roles of antiretroviral therapy and HIV
J. Mol. Cell. Cardiol.
2000
, vol. 
32
 (pg. 
2115
-
2129
)
26
Tsiodras
 
S.
Kelesidis
 
T.
Mantzoros
 
C.
 
Mantzoros
 
C.
 
The HAART induced metabolic syndrome
Obesity and Diabetes
2006
NJ
Humana Press Totowa
(pg. 
403
-
426
)
27
Nieto
 
F. J.
 
Infective agents and cardiovascular disease
Semin. Vasc. Med.
2002
, vol. 
2
 (pg. 
401
-
415
)
28
Conklin
 
B. S.
Fu
 
W.
Lin
 
P. H.
Lumsden
 
A. B.
Yao
 
Q.
Chen
 
C.
 
HIV protease inhibitor ritonavir decreases endothelium-dependent vasorelaxation and increases superoxide in porcine arteries
Cardiovasc. Res.
2004
, vol. 
63
 (pg. 
168
-
175
)
29
Zhong
 
D. S.
Lu
 
X. H.
Conklin
 
B. S.
, et al 
HIV protease inhibitor ritonavir induces cytotoxicity of human endothelial cells
Arterioscler. Thromb. Vasc. Biol.
2002
, vol. 
22
 (pg. 
1560
-
1566
)
30
Capell
 
W. H.
DeSouza
 
C. A.
Poirier
 
P.
, et al 
Short-term triglyceride lowering with fenofibrate improves vasodilator function in subjects with hypertriglyceridemia
Arterioscler. Thromb. Vasc. Biol.
2003
, vol. 
23
 (pg. 
307
-
313
)
31
Purnell
 
J. Q.
Zambon
 
A.
Knopp
 
R. H.
, et al 
Effect of ritonavir on lipids and post-heparin lipase activities in normal subjects
Aids
2000
, vol. 
14
 (pg. 
51
-
57
)
32
Ranganathan
 
S.
Kern
 
P. A.
 
The HIV protease inhibitor saquinavir impairs lipid metabolism and glucose transport in cultured adipocytes
J. Endocrinol.
2002
, vol. 
172
 (pg. 
155
-
162
)
33
Eckel
 
R. H.
 
Lipoprotein lipase: a multifunctional enzyme relevant to common metabolic diseases
N. Engl. J. Med.
1989
, vol. 
320
 (pg. 
1060
-
1068
)