To the Editor:
Metabolic abnormalities such as hypercholesterolemia, hypertriglyceridemia, and hyperglycemia in HIV-infected individuals receiving highly active antiretroviral therapy (HAART) have been increasingly reported in recent years,1,2 leading to an increased risk of cardiovascular diseases.3,4 Therefore, the identification of additional surrogate markers of cardiovascular risk in this population is mandatory. Some reports have found a possible correlation between hyperhomocysteinemia and cardiovascular risk,5 and homocysteine levels are increased in HIV-infected subjects receiving protease inhibitor (PI)-based HAART compared with healthy controls.6 The increased plasma homocysteine level is a sensitive marker of folate and/or vitamin B12 deficiency in the general population,7 and a recent report confirms this correlation in HIV-positive subjects.8
The aims of our study were to compare plasma homocysteine levels between HIV-infected subjects, treated or naive for HAART, and healthy controls and to evaluate the correlations between hyperhomocysteinemia and folate and vitamin B12 levels.
A cross-sectional study was conducted in 298 consecutive individuals. All the subjects were <50 years old and did not have any other cardiovascular risk factor such as previous cardiovascular events and/or procedures, diabetes, blood hypertension, or alcohol abuse.
Plasma homocysteine concentrations were measured by a validated high-performance liquid chromatography method (Eureka srl, Laboratory Division, Chiaravalle, Italy). Blood samples were collected in sterile ethylenediaminetetraacetic acid (EDTA) tubes, maintained at 4°C, and processed within 2 hours. Plasma homocysteine normal values were <12.8 μmol/L for male subjects and <11.5 μmol/L for female subjects. Serum folate and vitamin B12 concentrations were measured by direct chemoluminescent competitive dosage (normal values: 3.1-17.5 ng/mL of folate and 197-866 pg/mL of vitamin B12).
Differences between groups were evaluated by χ2 and Wilcoxon tests. Predictors of hyperhomocysteinemia were evaluated by multivariable logistic regression analysis. Variables included in the model were gender, age, the presence of low folate and vitamin B12 levels, and patient group. The SAS 8.2 statistical software package (Cary, NC) was used for all the analyses.
Three groups of patients were identified: group 1 (G1), healthy controls (n = 54); G2, HIV-infected HAART-naive subjects (n = 83); and G3, HIV-infected subjects receiving stable HAART for ≥6 months with an HIV RNA level <50 copies/mL (n = 161). Table 1 shows demographic and clinical characteristics of these groups. G3 subjects had higher triglyceride levels than G1 and G2 subjects. Mean plasma homocysteine levels were higher and folate levels were lower in G3 subjects compared with G1 and G2 subjects. In the whole cohort, 79 (26.5%) subjects had hyperhomocysteinemia: 10 in G1 (12.7%), 17 in G2 (21.5%), and 52 in G3 (65.8%) (P = 0.004). Patients with hyperhomocysteinemia were older (43 vs. 40 years; P = 0.004); 34 of them (43%) had low folate levels (G1: n = 2 [3.7%], G2: n = 6 [7.2%], and G3: n = 27 [16.8%]; P = 0.02).
Multivariate analysis showed that predictors of hyperhomocysteinemia were older age (odds ratio [OR] = 1.35, 95% confidence interval [CI]: 1.05 to 1.72; P = 0.016 for each additional 5 years) and low folate levels (OR = 4.53, 95% CI: 2.45 to 8.37; P < 0.001 compared with normal); no correlation with group was found (G2: OR = 1.05, 95% CI: 0.93 to 1.20, P = 0.14 vs. GI; G3: OR = 1.59, 95% CI: 0.71 to 3.57; P = 0.26 vs. G1).
To date, a few studies have evaluated plasma homocysteine levels in HIV-positive individuals,6,7,9 showing a prevalence between 12.3% and 35%;6,9 in our cohort, the prevalence was intermediate (26.5%). These differences might be attributable to several factors such as the number of subjects included, dietary habits, exposure to different antiretroviral drugs, and genetic diversity. Furthermore, the studies of Bernasconi et al6 and of Uccelli et al8 included small numbers of subjects and did not consider antiretroviral-naive subjects, and the study of Bernasconi et al6 did not evaluate folate levels.
We found a statistical correlation between hyperhomocysteinemia and reduced plasma folate levels. This finding may have relevant clinical implications, because a supplementary treatment with folate-vitamin B12 complex might be effective in reducing homocysteine levels.10 The impact of this treatment on the reduction of cardiovascular events has not been definitively demonstrated, however, and data in HIV-positive subjects are still lacking.5
The main limitations of the present study are its cross-sectional design and the quite limited number of individuals included, reducing the possible impact of chronic HIV infection and HAART in the development of hyperhomocysteinemia. In our study, hyperhomocysteinemia was statistically associated with older age and with a deficiency in folate levels, whereas no statistical correlation was found with HIV infection itself, HAART exposure, or gender. Further studies are needed to evaluate the use of folate supplementation in subjects with hyperhomocysteinemia, especially in those with a high cardiovascular risk. In HIV-positive individuals, however, other variables associated with this increased risk, such as smoking habit, exercise, blood pressure, and lipid abnormalities, must be frequently evaluated and eventually corrected.
Marco Bongiovanni, MD*
Maddalena Casana, MD*
Massimo Pisacreta, MD†
Federica Tordato, MD*
Paola Cicconi, MD*
Umberto Russo, MD‡
Roberto Ranieri, MD*
Antonella d'Arminio Monforte, MD*
Teresa Bini, MD*
*Clinic of Infectious Diseases, São Paolo Hospital, University of Milan, Milan, Italy
†Vascular Surgery Unit, Sacco Hospital, Milan, Italy
‡Hematology Unit, Sacco Hospital, Milan, Italy
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