Cardiovascular disease is increased in HIV-infected patients. Cytokines such as osteoprotegerin are implicated in atherosclerosis. The aim of our study was to evaluate the role of osteoprotegerin in the development and progression of atherosclerosis in HIV infected subjects on suppressive antiretroviral treatment. We enrolled 76 patients; 35 HIV infected men on suppressive Highly Active Antiretroviral Therapy with Framingham score <10%; 21 HIV negative individuals matched for age, gender, and Framingham score, and 20 subjects with Framingham score >10% as control groups. HIV positive subjects underwent echocardiography, electrocardiography, and heart multidetector computed tomography, whereas in HIV negative subjects, tomography was only performed in case of any abnormalities either in echocardiography or electrocardiography. In HIV positive patients, computed tomography showed stenosis in 51.4% of the subjects. Osteoprotegerin plasma levels were higher in HIV-infected patients than those in healthy controls but lower than in HIV negative subjects with Framingham score >10%. Higher osteoprotegerin plasma levels were found in HIV positive patients with grade I stenosis than in patients with grade II/III stenosis. In conclusion, in HIV infected subjects with Framingham score <10%, osteoprotegerin plasma concentrations are associated with atherosclerosis, in particular at the early stage of the process.
Cardiovascular disease (CVD) is an emerging and significant cause of morbidity and mortality in HIV-infected patients [
The study protocol designed according to the Helsinki Declaration II was approved by the local ethics committee. All the patients gave written informed consent to participate.
We recruited 76 patients from the Department of Public Health and Infectious Disease and the Department of Cardiovascular, Respiratory, Nephrologic and Geriatric Sciences of “Sapienza” University of Rome (Italy). Thirty-five were HIV-infected men on Highly Active Antiretroviral Therapy (HAART) since 48 weeks with undetectable viremia (<37 copies/mL) and low cardiovascular diseases risk defined by a Framingham score <10%. Subjects with diagnosis of metabolic syndrome (waist circumference: men >102 cm and women >88 cm, triglycerides ≥150 mg/dL, HDL cholesterol: men <40 mg/dL and women <50 mg/dL, blood pressure: ≥130/85 mm Hg or use of medication for hypertension, and fasting glucose ≥100 mg/dL or use of medication for hyperglycemia) were excluded [
IL-6 was measured with an ELISA kit (eBioscience bender MedSystem, Inc Vienna, Austria). The detection limit of assay was 3.1 pg/mL. Osteoprotegerin were measured by ELISA kits (Biomedica Gruppe, Vienna Austria). The detection limit of assay was 0.12 pmol/L.
The severity of CVD was evaluated in 35 HIV+ patients using a low-dose prospectively ECG-triggered CT coronary angiography protocol with 64-slice multidetector MDCT scanner (Somatom Definition Siemens medical Solution, Forehheimen, Germany) [
Diagnostic flowchart. Picture showing the diagnostic approach to cardiovascular disease.
Continuous data were analyzed with Student’s
General characteristics of the study population are summarized in Table
Clinical characteristics.
HIV− |
HIV+ | HIV− | |
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Age (M |
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|
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Sex | 21 M, 0 F | 35 M, 0 F | 20 M, 0 F |
Smoke status ( |
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no | 15 (71%) | 20 (57.1%) | 6 (30%) |
yes | 6 (29%) | 15 (42.9%) | 14 (70%) |
CD4+ (mmc) (M |
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CD4+ % (M |
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|
|
CD4+ (mmc) nadir (M |
— |
|
— |
CD4+ % nadir (M |
— |
|
— |
HIV-RNA zenith (cp/mL) (M |
— |
|
— |
HIV-RNA (cp/mL) | <37 | <37 | <37 |
Lipid-lowering therapy | |||
no | 21 (100%) | 35 (100%) | 12 (60%) |
yes | 0 | 0 | 8 (40%) |
Systolic blood pressure (mmHg) |
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Diastolic blood pressure (mmHg) |
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|
Triglycerides (mg/dL) (M |
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Cholesterol Total (mg/dL) (M |
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Cholesterol HDL (mg/dL) (M |
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Cholesterol LDL (mg/dL) (M |
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Body mass index (kg/m2) (M |
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Framingham score |
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FS: Framingham score; M: mean; SD: standard deviation; HDL: high density lipoprotein; LDL: low density lipoprotein.
MDCT examination was successfully and safely performed in all patients. We observed stenosis in 18/35 (51.4%) and no stenosis in 17/35 (48.6%). In patients with stenosis, 5/18 (27.7%) had mild stenosis (i.e., grade I) and 13/18 (72.3%) had grade II stenosis. As expected, no one had grade III stenosis. Among patients with grade II stenosis, 8/13 (61.5%) had 1 vessel and 5/13 (38.5%) 2 vessels coronary disease. All the plaques detected were eccentric and in 10/13 (76.9%) were soft. 13/13 (100%) patients with grade II stenosis at CT underwent CA and 6 (46.1%) underwent a percutaneous coronary intervention with application of 16 drug-eluting stents (Biosensors, Biomatrix DES). Twenty HIV negative subjects with CVD had grade II/III stenosis at MDTC and underwent CA; 8 (40%) underwent a percutaneous coronary intervention with application of 16 drug-eluting stents. Twenty-one HIV negative subjects with Framingham score <10% did not perform MDTC because of the absence of modifications at the echocardiography stress test and ECG.
Osteoprotegerin (OPG) plasma levels were significantly higher in HIV-infected patients than in healthy controls but lower than those in HIV negative subject with CVD (mean ± SD: 5.79 ± 2.82 versus 3.6 ± 1.7 versus 8.6 ± 4.3 pmol/L; median: 5.6 versus 3.6 versus 7 pmol/L) (
OPG plasma levels. OPG plasma levels were higher in HIV-infected patients than in healthy controls but lower than those in HIV negative subject with Framingham score (FS) >10%. Horizontal bars represent median. Upper and lower whisker mean third quartile +1.5 (Inter Quartile Range, IQR) and first quartile −1.5 (IQR).
OPG and stenosis. OPG plasma levels in HIV positive patients with grade I stenosis versus patients with grade II stenosis. Horizontal bars represent median. Upper and lower whisker mean third quartile +1.5 (Inter Quartile Range, IQR) and first quartile −1.5 (IQR).
IL-6 plasma levels. IL-6 plasma levels were higher in HIV-infected patients than healthy controls but lower than those in HIV negative subject with Framingham Score (FS) >10%. Horizontal bars represent median. Upper and lower whisker mean third quartile +1.5 (Inter Quartile Range, IQR) and first quartile −1.5 (IQR).
HIV infected adults have higher risk of cardiovascular disease than the general population due to an accelerated atherosclerosis process [
In this study, we enrolled 35 HIV infected men on suppressed HAART by at least 48 weeks with Framingham score <10%, 21 HIV negative individuals matched for age, gender, and Framingham score and 20 subjects with Framingham score >10%. We observed an increased prevalence of coronary stenosis in HIV infected patients than in uninfected controls as suggested by the absence of any abnormalities either in echocardiography or ECG in the latter group.
Heart CT scan is an accurate instrument for noninvasive assessment of coronary arteries which can substantially contribute to the diagnosis and management of cardiovascular disease [
It is known that chemokines/cytokines including IL-6 and the OPG/RANK/RANKL system are involved in endothelial dysfunction leading to atherosclerosis development and progression. IL-6 and OPG plasma levels in HIV positive subjects were higher than those in healthy controls.
IL-6 is a proinflammatory and multifunctional cytokine which is secreted by many cell types such as macrophages, T lymphocytes and endothelial cells. Several reports have consistently shown that baseline levels of IL-6 are powerful predictor of cardiovascular events [
As already known, there is a link between residual HIV replication, inflammation, endothelial dysfunction, and atherosclerosis; residual viral replication, persistent viral expression, and the loss of immunoregulatory cells can induce immune activation and inflammation whose persistence may result in endothelial dysfunction, vascular damage, and atherosclerosis [
Furthermore, OPG/RANK/RANKL system, member of TNF superfamily mostly implicated in bone remodelling, is involved in immune and in vascular system. In fact, RANKL, expressed by osteoblast cells and their precursors, activates its receptor, RANK, expressed by osteoclast cells and their precursors, promoting osteoclasts formation, activation, and prolonging osteoclasts survival. The effects of RANKL are blocked by the secretory glycoprotein osteoprotegerin which acts as a decoy receptor for RANKL. Changes in RANKL/OPG ratio are critical in the pathogenesis of bone disease [
The relationship between bone and vascular disease is shown; in this contest OPG could be considered as a bridge from bone to vascular system [
In our study, we found higher OPG plasma levels in HIV positive subjects than in healthy control but lower than those in HIV negative subjects with Framingham score >10% suggesting association between OPG plasma levels and cardiovascular disease. The increased OPG plasma concentration found in HIV positive patients with low cardiovascular risk may suggest that OPG is implicated in the early phase of atherosclerosis development process. Surprisingly, in HIV positive subjects we found that patients with grade I stenosis had higher OPG values rather than patients with grade II stenosis. Instead, in HIV negative patients with severe stenosis OPG plasma levels were higher than in HIV positive men. These apparently conflicting findings could be explained by the different composition and stage of the plaques; in fact, in HIV negative subjects with Framingham score >10% the calcium concentration in the plaque was higher than in HIV positive patients in whom most of the plaques were soft. OPG is expressed in different cell types including endothelial cells and vascular smooth muscle cells which are represented more in soft plaques. In this setting, OPG may indirectly prevent calcification by protecting arterial smooth muscle cells from apoptosis and OPG inactivation may lead to increased calcification which is present in older plaques [
Whereas in the bone system, OPG is considered as a counter-regulatory mechanism to protect bone loss; in the vascular system increased, OPG plasma levels may indicate endothelial damage [
We showed that OPG plasma concentrations are associated with atherosclerosis in HIV infected subjects with a low Framingham score. OPG plasma measurement could be a useful and noninvasive tool in clinical practice in order to early discriminate subjects at risk of developing atherosclerosis.
The project described was supported by the Department of Public Health and Infectious Disease of “Sapienza” University of Rome.
None of the authors have any conflicts or potential conflicts of interest.