Association of interleukin-6 circulating levels with coronary artery disease: a meta-analysis implementing mendelian randomization approach

Interleukin-6 trans-signaling induced laminin switch contributes to reduced trans-endothelial migration of granulocytic cells

BACKGROUND AND AIMS

Laminins are essential components of the endothelial basement membrane, which predominantly contains LN421 and LN521 isoforms. Regulation of laminin expression under pathophysiological conditions is largely unknown. In this study, we aimed to investigate the role of IL-6 in regulating endothelial laminin profile and characterize the impact of altered laminin composition on the phenotype, inflammatory response, and function of endothelial cells (ECs).

METHODS

HUVECs and HAECs were used for in vitro experiments. Trans-well migration experiments were performed using leukocytes isolated from peripheral blood of healthy donors. The BiKE cohort was used to assess expression of laminins in atherosclerotic plaques and healthy vessels. Gene and protein expression was analyzed using Microarray/qPCR and proximity extension assay, ELISA, immunostaining or immunoblotting techniques, respectively.

RESULTS

Stimulation of ECs with IL-6+sIL-6R, but not IL-6 alone, reduces expression of laminin α4 (LAMA4) and increases laminin α5 (LAMA5) expression at the mRNA and protein levels. In addition, IL-6+sIL-6R stimulation of ECs differentially regulates the release of several proteins including CXCL8 and CXCL10, which collectively were predicted to inhibit granulocyte transmigration. Experimentally, we demonstrated that granulocyte migration is inhibited across ECs pre-treated with IL-6+sIL-6R. In addition, granulocyte migration across ECs cultured on LN521 was significantly lower compared to LN421. In human atherosclerotic plaques, expression of endothelial LAMA4 and LAMA5 is significantly lower compared to control vessels. Moreover, LAMA5-to-LAMA4 expression ratio was negatively correlated with granulocytic cell markers (CD177 and myeloperoxidase (MPO)) and positively correlated with T-lymphocyte marker CD3.

CONCLUSIONS

We showed that expression of endothelial laminin alpha chains is regulated by IL-6 trans-signaling and contributes to inhibition of trans-endothelial migration of granulocytic cells. Further, expression of laminin alpha chains is altered in human atherosclerotic plaques and is related to intra-plaque abundance of leukocyte subpopulations.

Inflammatory Activity in Patients with Obstructive and Non-obstructive Coronary Artery Disease

Aim. To study the levels of pro-inflammatory biomarkers  in patients with obstructive  and non-obstructive coronary  artery disease (CAD), to identify possible differences  for diagnosing the degree of coronary  obstruction.

Material and methods. The observational  study included two groups of patients: with non-obstructive (main group,  coronary artery stenosis <50%; n=30) and obstructive  (comparison group,  hemodynamically significant  coronary  artery stenosis according to the results of coronary  angiography; n=30) CAD.  The levels of interleukin-1β (IL-1β) and interleukin 6 (IL-6) were measured in plasma using enzyme  immunoassay.

Results. IL-6  levels were significantly higher in patients with obstructive  CAD  (p=0.006) than in patients with non-obstructive CAD.  There were no significant  differences  in the level of IL-1β in both groups  (p=0.482). When  constructing the ROC  curve,  the threshold  value of IL-6  was  26.060 pg/ml. At the level of IL-6  less than this value, CAD  was diagnosed with hemodynamically insignificant stenoses of the coronary  arteries.

Conclusion. The results of this study confirm that in patients with different types of coronary  artery lesions, there are differences  in the activity of the inflammation process in the arterial wall. IL-6  was higher in the obstructive  lesion group,  and IL-1β levels did not differ between groups.  Thus, it can be assumed  that hemodynamically significant  obstruction  of the coronary  arteries develops  as a result of highly  active inflammation of the vascular wall. Given the presence of a proven biological  basis and the available data on the effectiveness of monoclonal antibodies to IL-1β, one cannot exclude their possible benefit in a cohort of patients with CAD  and hemodynamically insignificant stenoses.

IL6 gene polymorphism association with calcific aortic valve stenosis and influence on serum levels of interleukin-6

Aortic valve stenosis is the most frequent valve disease in developed countries and its prevalence will increase with population aging. There is still no pharmaceutical treatment nor biomarker to determine the susceptibility to develop aortic stenosis. Therefore, we analyzed the association of polymorphisms in risk loci with calcific aortic stenosis. Patients with aortic valve disease were genotyped for PALMD rs6702619, LPA rs10455872, and IL6 rs1800795 polymorphisms and circulating levels of interleukin-6 (IL-6) were measured. Calcium content of leaflets obtained in valve replacement surgeries was determined by micro-computed tomography. In the genotyping of 578 individuals, we found significant association between PALMD and IL6 polymorphisms and aortic stenosis in patients with tricuspid aortic valve, independently of other potentially confounding variables such as age and dyslipidemia. There was no association of these polymorphisms with valve calcium content, but this value correlated with the mean aortic pressure gradient (r = 0.44; P < 0.001). The CC genotype of IL6 polymorphism was associated with higher levels of serum IL-6 compared to other genotypes (23.5 vs. 10.5 pg/ml, respectively; P = 0.029). Therefore, patients carrying the CC genotype of IL6 rs1800795 polymorphism present higher levels of circulating IL-6 and this could contribute to the severity of the aortic valve stenosis. Our results agree with the identification of IL6 as a locus risk for stenosis and also with the intervention of this cytokine in aortic valve calcification. A more exhaustive follow-up of those patients carrying risk genotypes is therefore recommended.

The "Common Soil Hypothesis" Revisited-Risk Factors for Type 2 Diabetes and Cardiovascular Disease

The prevalence and the incidence of type 2 diabetes (T2D), representing >90% of all cases of diabetes, are increasing rapidly worldwide. Identification of individuals at high risk of developing diabetes is of great importance, as early interventions might delay or even prevent full-blown disease. T2D is a complex disease caused by multiple genetic variants in interaction with lifestyle and environmental factors. Cardiovascular disease (CVD) is the major cause of morbidity and mortality. Detailed understanding of molecular mechanisms underlying in CVD events is still largely missing. Several risk factors are shared between T2D and CVD, including obesity, insulin resistance, dyslipidemia, and hyperglycemia. CVD can precede the development of T2D, and T2D is a major risk factor for CVD, suggesting that both conditions have common genetic and environmental antecedents and that they share “common soil”. We analyzed the relationship between the risk factors for T2D and CVD based on genetics and population-based studies with emphasis on Mendelian randomization studies.

Association of interleukin 6 -174 G/C polymorphism with coronary artery disease and circulating IL-6 levels: a systematic review and meta-analysis

INTRODUCTION

Circulating IL-6 levels and at least one polymorphic form of IL6 gene (IL6 -174 G/C, rs1800795) have been shown to be independently associated with coronary artery disease (CAD) by several investigators. Despite more than 12 published meta-analyses on this subject, association of -174 G/C with CAD, especially amongst distinct ancestral population groups remain unclear. We, therefore, conducted a systematic review and an updated meta-analysis to comprehensively ascertain the association of IL6 -174 G/C with CAD and circulating IL-6 levels.

MATERIALS AND METHODS

Relevant case-control/cohort studies investigating association of -174 G/C with CAD and circulating IL-6 levels were identified following a comprehensive online search. Association status for CAD was determined for the pooled sample, as well as separately for major ancestral subgroups. Association status for circulating IL-6 levels was assessed for the pooled sample, as well as separately for CAD cases and CAD free controls. Study-level odds ratios (OR) and 95% confidence intervals (CI) were pooled using random/fixed-effects model.

RESULTS

Quantitative synthesis for the CAD endpoint was performed using 55 separate qualifying studies with a collective sample size of 51,213 (19,160 cases/32,053 controls). Pooled association of -174 G/C with CAD was found to be statistically significant through dominant (OR 1.15; 95% CI 1.05-1.25, p = 0.002) as well as allelic genetic model comparisons (OR 1.13, 95% CI 1.06-1.21, p = 0.0003). This effect was largely driven by Asian and Asian Indian ancestral subgroups, which also showed significant association with CAD in both genetic model comparisons (OR range 1.29-1.53, p value range ≤ 0.02). Other ancestral subgroups failed to show any meaningful association. Circulating IL-6 levels were found to be significantly higher amongst the 'C' allele carriers in the pooled sample (Standard mean difference, SMD 0.11, 95% CI 0.01-0.22 pg/ml, p = 0.009) as well as in the CAD free control subgroup (SMD 0.10, 95% CI 0.02-0.17 pg/ml, p = 0.009), though not in the CAD case subgroup (SMD 0.17, 95% CI = - 0.02 to 0.37, p = 0.12).

CONCLUSIONS

The present systematic review and meta-analysis demonstrate an overall association between IL6 -174 G/C polymorphism and CAD, which seems to be mainly driven by Asian and Asian Indian ancestral subgroups. Upregulation of plasma IL-6 levels in the 'C' allele carriers seems to be at least partly responsible for this observed association. This warrants further investigations with large, structured case-control studies especially amongst Asian and Asian Indian ancestral groups.

Inflammatory Markers in Cardiovascular Disease; Lessons Learned and Future Perspectives

BACKGROUND

Cardiovascular disease (CVD) still remains the leading cause of morbidity and mortality worldwide. It is now established that inflammation plays a crucial role in atherosclerosis and atherothrombosis, and thus, it is closely linked to cardiovascular disease.

OBJECTIVE

The aim of the present review is to summarize and critically appraise the most relevant evidence regarding the potential use of inflammatory markers in the field of CVD.

METHODS

We conducted a comprehensive research of the relevant literature, searching MEDLINE from its inception until November 2018, primarily for meta-analyses, randomized controlled trials and observational studies.

RESULTS

Established markers of inflammation, mainly C-reactive protein, have yielded significant results both for primary and secondary prevention of CVD. Newer markers, such as lipoprotein-associated phospholipase A2, lectin-like oxidized low-density lipoprotein receptor-1, cytokines, myeloperoxidase, cell adhesion molecules, matrix metalloproteinases, and the CD40/CD40 ligand system, have been largely evaluated in human studies, enrolling both individuals from the general population and patients with established CVD. Some markers have yielded conflicting results; however, others are now recognized not only as promising biomarkers of CVD, but also as potential therapeutic targets, establishing the role of anti-inflammatory and pleiotropic drugs in CVD.

CONCLUSION

There is significant evidence regarding the role of consolidated and novel inflammatory markers in the field of diagnosis and prognosis of CVD. However, multimarker model assessment, validation of cut-off values and cost-effectiveness analyses are required in order for those markers to be integrated into daily clinical practice.

Correlation between soluble receptor for advanced glycation end products levels and coronary artery disease in postmenopausal nondiabetic women

BACKGROUND

The established cardiovascular risk factors cannot explain the overall risk of coronary artery disease (CAD), especially in women. Therefore, there is a growing need for the assessment of novel biomarkers to identify women at risk. The receptor for advanced glycation end products (RAGE) and its interaction with the advanced glycation end product (AGE) ligand have been associated with atherogenesis. The soluble fraction of RAGE (sRAGE) antagonizes RAGE signaling and exerts an antiatherogenic effect.

AIM

The study aim was to explore the association between plasma levels of sRAGE and CAD in nondiabetic postmenopausal women.

METHODS

This case-control study included 110 nondiabetic postmenopausal women who were enrolled in two groups. Group I included 55 angiographically proven CAD subjects with > 50% stenosis in at least one of the major coronary arteries and Group II included 55 healthy control women who did not have CAD or had < 50% stenosis of the coronary arteries. Stenosis was confirmed by invasive angiography. Plasma sRAGE was determined by an enzyme-linked immunosorbent assay.

RESULTS

We observed significantly lower plasma sRAGE concentrations in subjects with CAD vs healthy controls (P < 0.05). Univariate and multivariate logistic regression analysis also revealed a significant correlation between plasma sRAGE levels and CAD (P = 0.01). Multivariate odds ratios for CAD revealed that subjects with sRAGE concentrations below 225 pg/mL (lowest quartile) had a 6-fold increase in CAD prevalence independent of other risk factors.

CONCLUSION

Our findings indicated that low sRAGE levels were independently associated with CAD in nondiabetic postmenopausal women. Risk assessment of CAD in postmenopausal women can be improved by including sRAGE along with other risk factors.

IL-6 as a Mediator of the Association Between Traditional Risk Factors and Future Myocardial Infarction: A Nested Case-Control Study

[Figure: see text].

Single-Cell Immune Profiling in Coronary Artery Disease: The Role of State-of-the-Art Immunophenotyping With Mass Cytometry in the Diagnosis of Atherosclerosis

Coronary artery disease remains the leading cause of death globally and is a major burden to every health system in the world. There have been significant improvements in risk modification, treatments, and mortality; however, our ability to detect asymptomatic disease for early intervention remains limited. Recent discoveries regarding the inflammatory nature of atherosclerosis have prompted investigation into new methods of diagnosis and treatment of coronary artery disease. This article reviews some of the highlights of the important developments in cardioimmunology and summarizes the clinical evidence linking the immune system and atherosclerosis. It provides an overview of the major serological biomarkers that have been associated with atherosclerosis, noting the limitations of these markers attributable to low specificity, and then contrasts these serological markers with the circulating immune cell subtypes that have been found to be altered in coronary artery disease. This review then outlines the technique of mass cytometry and its ability to provide high-dimensional single-cell data and explores how this high-resolution quantification of specific immune cell subpopulations may assist in the diagnosis of early atherosclerosis in combination with other complimentary techniques such as single-cell RNA sequencing. We propose that this improved specificity has the potential to transform the detection of coronary artery disease in its early phases, facilitating targeted preventative approaches in the precision medicine era.

Predictive Value of Blood Interleukin-6 Level in Patients with Acute Coronary Syndrome: A Meta-analysis

OBJECTIVE

Conflicting results have been reported on the association between blood level of interleukin-6 and adverse outcomes in patients with acute coronary syndrome (ACS). The current meta-analysis aimed to evaluate the predictive utility of elevated blood interleukin-6 level in patients with ACS.

METHODS

A systematically literature search was performed using PubMed and Embase databases up to December 31, 2019. Observational studies or post hoc analysis of randomized controlled trials investigating the values of blood interleukin-6 level for predicting major adverse cardiovascular events (MACE including death, re-infarction, revascularization, angina, heart failure, malignant arrhythmia, or stroke), all-cause mortality or cardiovascular mortality in ACS patients were eligible. The predictive values were summarized by pooling the multivariable-adjusted risk ratio (RR) and 95% confidence intervals (CI) for the highest versus lowest category of interleukin-6 level.

RESULTS

Thirteen studies enrolling 30,289 patients with ACS were included. When comparing the highest with lowest category of interleukin-6 level, the pooled RR was 1.29 (95% CI 1.12-1.48) for MACE, 1.50 (95% CI 1.35-1.67) for all-cause mortality, and 1.55 (95% CI 1.06-2.28) for cardiovascular mortality, respectively. Moreover, the predictive values of interleukin-6 level on MACE were consistently found in different study designs, subtypes of patients, sample sizes, follow-up duration, and cutoff value of interleukin-6 elevation subgroups.

CONCLUSION

Increased blood level of interleukin-6may be independently associated with higher risk of MACE, cardiovascular and all-cause mortality in patients with ACS. Measurement of blood interleukin-6 level has potential to improve risk stratification of ACS.

Usefulness of Certain Protein Biomarkers for Prediction of Coronary Heart Disease

Identification of biomarkers can help monitor and prevent cardiovascular disease (CVD) risk. We performed an exploratory analysis to identify potential biomarkers for coronary heart disease (CHD) in participants from the Life Conditions, Stress, and Health study. A total of 1,007 participants (50% women), randomly selected from the general population, were followed for incident CHD at 8 and 13 years of follow-up. Plasma levels of 184 CVD-related biomarkers were measured in samples collected at baseline in 86 cases with CHD and 184 age- and sex-matched controls by proximity extension assay. Biomarker levels were presented as normalized protein expression values (log 2 scale). After adjusting for confounding factors, 6 biomarkers showed significant association with incident CHD at 13 years. In a sensitivity analysis, this association remained significant at 8 years for 3 biomarkers; collagen α-1(I) chain (COL1A1), bone morphogenetic protein-6 (BMP-6), and interleukin-6 receptor α chain (IL-6Rα). When entering these biomarkers in the full adjustment model simultaneously, their association with incident CHD at 13 years remained significant, hazards ratio being 0.671, 0.335, and 2.854, respectively per unit increase in normalized protein expression values. Subjects with low COL1A1, low BMP-6, and high IL-6Rα levels had a hazards ratio of 5.097 for incident CHD risk (p = 0.019), compared with those without. In conclusion, we identified COL1A1, BMP-6 and IL-6Rα as biomarkers for incident CHD over a long-term follow-up in this exploratory analysis. For COL1A1 and BMP-6 this has not been previously reported. Further studies are needed to confirm our findings and establish their clinical relevance.

Cardiovascular safety of tocilizumab: A systematic review and network meta-analysis

OBJECTIVES

Our objective was to compare the cardiovascular safety of tocilizumab and other biological disease-modifying antirheumatic drugs (bDMARD) in rheumatoid arthritis using a network meta-analysis (NMA).

METHODS

A systematic literature search through May 2018 identified randomized controlled trials (RCT) or observational studies (cohort only) reporting cardiovascular outcomes of tocilizumab (TCZ) and/or abatacept (ABA) and/or rituximab (RTX) and/or tumor necrosis factor inhibitors (TNFi) in rheumatoid arthritis patients. The composite primary outcome was the rate of major adverse cardiovascular outcomes (MACE, myocardial infarction (MI), peripheral artery disease (PAD) and cardiac heart failure (CHF)).

RESULTS

19 studies were included in the NMA, including 11 RCTs and 8 cohort studies. We found less events with RTX (5.41 [1.70;17.26]. We found no difference between TCZ and other treatments. Concerning MI, we found no difference between TCZ and csDMARD (4.23 [0.22;80.64]), no difference between TCZ and TNFi (2.00 [0.18;21.84]). There was no difference between TCZ and csDMARD (1.51[0.02;103.50] and between TCZ and TNFi (1.00 [0.06;15.85]) for stroke event. With cohorts and RCT NMA, we found no difference between TCZ and other treatments for MACE (0.66 [0.42;1.03] with ABA, 1.04 [0.60;1.81] with RTX, 0.78[0.53;1.16] and 0.91 [0.54;1.51] with csDMARD), but the risk of myocardial infarction was lower with TCZ compared to ABA (0.67 [0.47;0.97]). We lacked data to compare TCZ and other bDMARD for stoke and MI. Not enough data was available to perform a NMA for CHF and PAD.

CONCLUSIONS

Despite an increase in cholesterol levels, TCZ has safe cardiovascular outcomes compared to other bDMARD.

Association of Chlamydia trachomatis, C. pneumoniae, and IL-6 and IL-8 Gene Alterations With Heart Diseases

Atherosclerosis is a progressive disease characterized by chronic inflammation of the arterial walls, associated with genetic and infectious factors. The present study investigated the involvement of Chlamydia trachomatis and Chlamydia pneumoniae infections and immunological markers (C-reactive protein, CRP, TNF-α, IL-6, IL-8, and IL-10) in the process of atherosclerosis. The evaluation included 159 patients for surgical revascularization (CAD) and 71 patients for surgical heart valve disease (HVD) at three hospitals in Belém, Brazil. The control group (CG) comprised 300 healthy individuals. Blood samples collected before surgery were used for antibodies detection (enzyme immunoassay), CRP (immunoturbidimetry) and IL-6 levels (enzyme immunoassay). Tissue fragments (atheroma plaque, heart valve and ascending aorta) were collected during surgery and subjected to qPCR for detection of bacterial DNA. Promoter region polymorphisms of each marker and relative quantification of TNF-α, IL-8, and IL-10 gene expression were performed. Demography and social information were similar to the general population involved with both diseases. Antibody prevalence to C. trachomatis was 30.6, 20.3, and 36.7% (in the CAD, HVD, and CG, respectively) and to C. pneumoniae was 83.6, 84.5, and 80.3% (in the CAD, HVD, and CG, respectively). C. trachomatis cryptic plasmid DNA was detected in 7.4% of the samples. Frequency of IL6−174G>C polymorphism was higher in CAD and HVD than in CG regardless of previous exposure to Chlamydia. Previous C. trachomatis infection showed involvement in HVD and CAD. Significant association between disease and previous C. pneumoniae infection was found only among HVD. GG genotype of IL6−174G>C is apparently a risk factor for heart disease, whereas AT genotype of IL8−251A>T was mainly involved in valvulopathies, including patients with prior exposure to C. pneumoniae.

Clinical utility of circulating interleukin-6 concentrations in the detection of functionally relevant coronary artery disease

BACKGROUND

Inflammation plays a major role in the pathogenesis of coronary artery disease (CAD).

METHODS

We hypothesized, that quantifying inflammation by measuring circulating interleukin-6 concentrations help in the diagnosis and/or prediction of functionally relevant CAD. Among consecutive patients with symptoms suggestive of CAD, functionally relevant CAD was adjudicated in two domains: first, diagnosis according to myocardial perfusion single photon emission tomography (MPI-SPECT) and coronary angiography; second, cardiovascular death and all-cause death during 2-years follow-up. Adjudication was done blinded to the interleukin-6 concentrations.

RESULTS

Among 1553 patients, symptoms were adjudicated to be causally related to CAD in 43% (665/1553). Interleukin-6 concentrations were higher in patients with functionally relevant CAD as compared to those without (1.56 pg/mL versus 1.30 pg/mL, p < 0.001), but overall had only low-to-modest diagnostic accuracy (area under the curve [AUC]: 0.57, 95%CI 0.55-0.61) and were no independent predictor of functionally relevant CAD after multivariable adjustment (p = 0.068). Interleukin-6 concentrations had moderate-to-high accuracy in the prediction of cardiovascular death (AUC 0.75, 95%CI 0.69-0.82) and all-cause death (AUC 0.72, 95%CI 0.66-0.78) at 2-years, and remained a significant predictor after multivariable adjustment (p < 0.001). Compared to patients with interleukin-6 concentrations below the median (1.41 pg/mL), patients with concentrations above the median had a significantly higher cumulative incidence of cardiovascular death (1% vs. 4%, log-rank p < 0.001) and all-cause death (2% vs. 8%, log-rank p < 0.001) at 2 years.

CONCLUSION

Interleukin-6 concentrations are strong and independent predictors of cardiovascular death and all-cause death.

Activation of non-canonical WNT signaling in human visceral adipose tissue contributes to local and systemic inflammation

The accumulation of visceral adiposity is strongly associated with systemic inflammation and increased cardiometabolic risk. WNT5A, a non-canonical WNT ligand, has been shown to promote adipose tissue inflammation and insulin resistance in animal studies. Among other non-canonical pathways, WNT5A activates planar cell polarity (PCP) signaling. The current study investigated the potential contribution of non-canonical WNT5A/PCP signaling to visceral adipose tissue (VAT) inflammation and associated metabolic dysfunction in individuals with obesity. VAT and subcutaneous adipose tissue (SAT) samples obtained from subjects undergoing bariatric surgery were analyzed by qRT-PCR for expression of WNT/PCP genes. In vitro experiments were conducted with preadipocytes isolated from VAT and SAT biopsies. The expression of 23 out of 33 PCP genes was enriched in VAT compared to SAT. Strong positive expression correlations of individual PCP genes were observed in VAT. WNT5A expression in VAT, but not in SAT, correlated with indexes of JNK signaling activity, IL6, waist-to-hip ratio and hsCRP. In vitro, WNT5A promoted the expression of IL6 in human preadipocytes. In conclusion, elevated non-canonical WNT5A signaling in VAT contributes to the exacerbated IL-6 production in this depot and the low-grade systemic inflammation typically associated with visceral adiposity.

Interleukin-1beta may act on hepatocytes to boost plasma homocysteine - The increased cardiovascular risk associated with elevated homocysteine may be mediated by this cytokine

The results of multi-center trials of B vitamin supplementation reveal that, whereas moderately elevated homocysteine predicts increased risk for coronary disease, it does not play a mediating role in this regard. This essay proposes that interleukin-1beta can act on hepatocytes to suppress expression of the hepatocyte-specific forms of methionine adenosyltransferase; this in turn can be expected to decrease hepatic activity of cystathionine-β-synthase, leading to an increase in plasma homocysteine. It is further proposed that interleukin-1beta (IL-1β) is a true mediating risk factor for cardiovascular disease, and that elevated homocysteine predicts coronary disease because it can serve as a marker for increased IL-1β activity. Potent statin therapy may decrease IL-1β production by suppressing inflammasome activation - thereby accounting for the marked protection from cardiovascular events observed in the classic JUPITER study, in which the enrolled subjects had low-normal Low Density Lipoprotein cholesterol but elevated C-reactive protein.

Elevated serum interleukin-6 is predictive of coronary artery disease in intermediate risk overweight patients referred for coronary angiography

BACKGROUND

Interleukin-6 (IL-6) plays a central role in atherosclerosis and inflammation. It may improve risk prediction in patients at intermediate cardiovascular risk.

OBJECTIVE

To analyze the impact of serum IL-6 in predicting early angiographic coronary artery disease in patients at intermediate cardiovascular risk with chest pain.

METHODS

In a cross-sectional study, patients referred for coronary angiography due to suspected coronary artery disease (CAD) were included. Coronary artery disease was defined as the presence of at least 30% stenosis in one or more coronary artery. Severity of CAD was classified by the anatomic burden score. Performance of serum IL-6 assay was compared with ACC/AHA atherosclerotic cardiovascular disease (ASCVD) risk score and hs-CRP through receiver operating characteristic (ROC) curves.

RESULTS

We have included 48 patients with a mean 10-year ASCVD risk of 10.0 ± 6.8%. The prevalence of CAD was 72.9%. The presence of CAD was associated with higher mean levels of IL-6 (p = 0.025). Patients with CAD had significantly more overweight than subjects without CAD. In 27% of patients, IL-6 was >1.0 pg/mL and 100% of these patients had CAD, while only 64% in those with IL-6 <1.0 pg/mL, corresponding to a positive predictive value of 100% (p = 0.015). The area under the receiver operating characteristic (ROC) curve of IL-6, hs-CRP and ASCVD were respectively 0.72, 0.60 and 0.54. Intermediate risk patients with IL-6 >1.0 pg/mL were further reclassified into ASCVD high risk due to the presence of coronary lesions.

CONCLUSION

In intermediate risk patients referred for coronary angiography, a serum IL-6 level above 1 pg/mL is predictive of significant CAD. IL-6 determination may be useful to reclassify ASCVD intermediate risk patients into higher risk categories.

C-Reactive Protein Identifies Low-Risk Metabolically Healthy Obese Persons: The European Prospective Investigation of Cancer-Norfolk Prospective Population Study

BACKGROUND

Conflicting data exist about the cardiovascular risk of metabolically healthy obese persons. The prognostic value of C-reactive protein (CRP) in this intriguing group is unknown. We assessed the association between CRP levels and the risk of coronary heart disease (CHD) in metabolically healthy persons with abdominal obesity.

METHODS AND RESULTS

In the European Prospective Investigation of Cancer-Norfolk prospective cohort, CRP levels and information on metabolic syndrome criteria were available for 7279 participants, of whom 825 (11%) developed CHD during a follow-up period of 10.9±1.8 years. There was a trend toward a higher multivariable-adjusted hazard ratio for CHD in metabolically healthy obese participants with CRP levels >2 mg/L compared with <2 mg/L (hazard ratio 1.59, 95% CI 0.97-2.62, P=0.066). Metabolically unhealthy obese participants had significantly higher CHD risk compared with metabolically healthy obese participants with CRP levels <2 mg/L (hazard ratio 1.88, 95% CI 1.20-2.94, P=0.006). Most important, we found that the risk of CHD among metabolically healthy obese persons with CRP levels <2 mg/L was comparable to that of metabolically healthy nonobese persons (hazard ratio 0.91, 95% CI 0.60-1.39, P=0.674).

CONCLUSIONS

Among metabolically healthy obese persons, low CRP levels were associated with a CHD risk comparable to that of metabolically healthy nonobese persons. CRP appears to be an easy and widely available method for identifying a low-risk subpopulation among metabolically healthy obese persons.

Circulating interleukin-10 levels and human papilloma virus and Epstein-Barr virus-associated cancers: evidence from a Mendelian randomization meta-analysis based on 11,170 subjects

Recent studies have showed interleukin 10 (IL-10) is a critical cytokine that determines antiviral immune response and is related to virus-associated cancers. However, whether genetically elevated circulating IL-10 levels are associated with the risk of human papilloma virus and Epstein–Barr virus-associated cancers (HEACs) is still unclear. Mendelian randomization method was implemented to meta-analyze available observational studies by employing IL-10 three variants (−592C>A, −819C>T, and −1082A>G) as instruments. A total of 24 articles encompassing 11,170 subjects were ultimately eligible for the meta-analysis. Overall, there was a significant association between IL-10 promoter variant −1082A>G and HEACs under allelic and dominant models (both P<0.01). Subgroup analysis by cancer type indicated that the risk estimate of −1082A>G was significant for nasopharyngeal cancer under allelic, homozygous genotypic and dominant models (all P<0.001). Moreover by ethnicity, carriers of −1082G allele had a 74% increased risk for nasopharyngeal cancer in Asians under dominant model (odds ratio [OR] =1.737; 95% confidence interval [CI]: 1.280–2.358; P<0.001). In further Mendelian randomization analysis, the predicted OR for 10 pg/mL increment in IL-10 levels was 1.14 (95% CI: 1.01–16.99) in HEACs. Our findings provided strong evidence for a critical role of genetically elevated circulating IL-10 levels in the development of HEACs, especially in Asian population and for nasopharyngeal cancer.

A Causal Role of Genetically Elevated Circulating Interleukin-10 in the Development of Digestive Cancers: Evidence from Mendelian Randomization Analysis Based on 29,307 Subjects

Recent studies have observed a high level of circulating interleukin-10 (IL-10) in patients with digestive cancers, yet whether elevated IL-10 is causally associated with digestive cancers so far remained unresolved. We therefore meta-analyzed available observational studies with Mendelian randomization method to explore this causal association by employing IL-10 gene 3 variants (-592C>A, -819C>T, and -1082A>G) as instruments. Data were available from 52 articles encompassing 29,307 subjects. Subgroup analysis by cancer type indicated that -1082A>G was associated with increased risk of gastric cancer (odds ratio [OR] = 1.19; 95% confidence interval [CI]: 1.05-1.35; P = 0.006), and the association was reinforced for intestinal type gastric cancer (OR = 1.26; 95%CI: 1.09-1.44; P = 0.001). By ethnicity, risk estimate for -1082G allele carriers was increased by 21% for digestive cancers in East Asians (95%CI: 1.05-1.40; P = 0.009). As for the genotype-phenotype association, carriers of -1082G allele had an overall 20.21 pg/mL higher IL-10 level than those with -1082AA genotype (P = 0.023). In further Mendelian randomization analysis, the predicted OR for 10 pg/mL increment in IL-10 was 1.14 (95%CI: 1.01-16.99) in gastric cancer. Our findings provided evidence for a causal role of genetically elevated IL-10 in the development of gastric cancer, especially in East Asians and for intestinal type gastric cancer.

Mendelian randomization studies: a review of the approaches used and the quality of reporting

BACKGROUND

Mendelian randomization (MR) studies investigate the effect of genetic variation in levels of an exposure on an outcome, thereby using genetic variation as an instrumental variable (IV). We provide a meta-epidemiological overview of the methodological approaches used in MR studies, and evaluate the discussion of MR assumptions and reporting of statistical methods.

METHODS

We searched PubMed, Medline, Embase and Web of Science for MR studies up to December 2013. We assessed (i) the MR approach used; (ii) whether the plausibility of MR assumptions was discussed; and (iii) whether the statistical methods used were reported adequately.

RESULTS

Of 99 studies using data from one study population, 32 used genetic information as a proxy for the exposure without further estimation, 44 performed a formal IV analysis, 7 compared the observed with the expected genotype-outcome association, and 1 used both the latter two approaches. The 80 studies using data from multiple study populations used many different approaches to combine the data; 52 of these studies used some form of IV analysis; 44% of studies discussed the plausibility of all three MR assumptions in their study. Statistical methods used for IV analysis were insufficiently described in 14% of studies.

CONCLUSIONS

Most MR studies either use the genotype as a proxy for exposure without further estimation or perform an IV analysis. The discussion of underlying assumptions and reporting of statistical methods for IV analysis are frequently insufficient. Studies using data from multiple study populations are further complicated by the combination of data or estimates. We provide a checklist for the reporting of MR studies.

Circulating cholesteryl ester transfer protein and coronary heart disease: mendelian randomization meta-analysis

BACKGROUND

The cholesteryl ester transfer protein (CETP) plays a central role in reverse cholesterol transport. Currently, it remains unresolved whether circulating CETP is causally associated with coronary heart disease (CHD). We aimed to investigate this causal association using CETP gene rs708272 polymorphism as an instrument in a Mendelian randomization meta-analysis.

METHODS AND RESULTS

We searched PubMed and EMBASE before May 2014. Data and study quality were assessed in duplicate. Thirty-four articles (17 813 CHD patients and 22 203 controls) were qualified. Overall analyses revealed a significant association of rs708272-B1 allele with a reduced CHD risk compared with B2 allele under allelic (odds ratio and 95% confidence interval: 0.87 and 0.82-0.92; P<0.001), homozygous genotypic (0.74 and 0.66-0.83; P<0.001), and dominant (0.87 and 0.80-0.94; P<0.001) models. Carriers of rs708272-B1B1 genotype (weighted mean difference and 95% confidence interval: -0.21 and -0.41 to 0.00 μg/dL; P=0.052) or B1 allele (-0.15 and -0.30 to 0.00 μg/dL; P=0.056) had a marginally lower circulating CETP level compared with B2B2 genotype carriers. In Mendelian randomization analysis, there was a 25% (odds ratio and 95% confidence interval: 0.75 and 0.19-0.91) and a 17% (0.83 and 0.41-0.96) significantly reduced risk of CHD by a reduction of 0.2 μg/mL in circulating CETP for the comparison of B1B1 genotype and B1 allele with B2B2 genotype, respectively. There were low probabilities of publication bias.

CONCLUSIONS

Our findings demonstrate that the long-term genetically reduced circulating CETP might be causally associated with the low risk of CHD.

Plasma IL-5 concentration and subclinical carotid atherosclerosis

Objective

Genetic variants robustly associated with coronary artery disease were reported in the vicinity of the interleukin (IL)-5 locus, and animal studies suggested a protective role for IL-5 in atherosclerosis. Therefore, we set this work to explore IL-5 as a plasma biomarker for early subclinical atherosclerosis, as determined by measures of baseline severity and change over time of carotid intima-media thickness (cIMT).

Methods

We used biobank and databases of IMPROVE, a large European prospective cohort study of high-risk individuals (n = 3534) free of clinically overt cardiovascular disease at enrollment, in whom composite and segment-specific measures of cIMT were recorded at baseline and after 15 and 30 months. IL-5 was measured with an immunoassay in plasma samples taken at baseline.

Results

IL-5 levels were lower in women than in men, lower in the South than in North of Europe, and showed positive correlations with most established risk factors. IL-5 showed significant inverse relationships with cIMT change over time in the common carotid segment in women, but no significant relationships to baseline cIMT in either men or women.

Conclusions

Our results suggest that IL-5 may be part of protective mechanisms operating in early atherosclerosis, at least in women. However, the relationships are weak and whereas IL-5 has been proposed as a potential molecular target to treat allergies, it is difficult to envisage such a scenario in coronary artery disease.

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Genetic and animal studies suggested a protective role for IL-5 in atherosclerosis.

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We studied plasma IL-5 relationships to baseline and change over time in carotid IMT.

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Significant relationships of IL-5 and cIMT were time, segment and gender specific.

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High plasma IL-5 was related to slow progression of IMT in common carotid in women.

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In general, IL-5 does not seem useful as biomarker for coronary artery disease.

Association of cholesteryl ester transfer protein (CETP) gene polymorphism, high density lipoprotein cholesterol and risk of coronary artery disease: a meta-analysis using a Mendelian randomization approach

BACKGROUND

Recent randomized controlled trials have challenged the concept that increased high density lipoprotein cholesterol (HDL-C) levels are associated with coronary artery disease (CAD) risk reduction. The causal role of HDL-C in the development of atherosclerosis remains unclear. To increase precision and to minimize residual confounding, we exploited the cholesteryl ester transfer protein (CETP)-TaqIB polymorphism as an instrument based on Mendelian randomization.

METHODS

The Mendelian randomization analysis was performed by two steps. First, we conducted a meta-analysis of 47 studies, including 23,928 cases and 27,068 controls, to quantify the relationship between the TaqIB polymorphism and the CAD risk. Next, the association between the TaqIB polymorphism and HDL-C was assessed among 5,929 Caucasians. We further employed Mendelian randomization to evaluate the causal effect of HDL-C on CAD based on the findings from the meta-analysis.

RESULTS

The overall comparison of the B2 allele with the B1 allele yielded a significant risk reduction of CAD (P < 0.0001; OR = 0.88; 95% CI: 0.84-0.92) with substantial between-study heterogeneity (I² = 55.2%; P(heterogeneity) <0.0001). The result was not materially changed after excluding the Hardy-Weinberg Equilibrium (HWE)-violation studies. Compared with B1B1 homozygotes, Caucasian carriers of the B2 allele had a 0.25 mmol/L increase in HDL-C level (95% CI: 0.20-0.31; P <0.0001; I² = 0; P(heterogeneity) =0.87). However, a 1 standard deviation (SD) elevation in HDL-C levels due to the TaqIB polymorphism, was marginal associated with CAD risk (OR =0.79; 95% CI: 0.54-1.03; P =0.08).

CONCLUSIONS

Taken together, our results lend support to the concept that increased HDL-C cannot be translated into a reduction in CAD risk.

Increased intake of carbohydrates from sources with a higher glycemic index and lower consumption of whole grains during puberty are prospectively associated with higher IL-6 concentrations in younger adulthood among healthy individuals

Chronic low-grade inflammation represents a likely intermediary in the relation between carbohydrate nutrition and both type 2 diabetes and cardiovascular disease. This study assessed the prospective association between carbohydrate quantity and quality [dietary glycemic index (GI), glycemic load (GL), and added sugar, fiber, and whole-grain intake] during puberty, a potentially critical period for later disease, and low-grade inflammation in younger adulthood. The analysis was based on 205 participants (113 girls and 92 boys) from the DONALD (Dortmund Nutritional and Anthropometric Longitudinally Designed) study with at least 2 3-d weighed dietary records during puberty (girls: 9-14 y, boys: 10-15 y) and blood samples in younger adulthood (18-36 y). Multivariable linear regression models were used to analyze the associations between carbohydrate nutrition and circulating concentrations of pro- and anti-inflammatory immune mediators [high-sensitivity C-reactive protein (hs-CRP), interleukin (IL) 6, IL-18, and adiponectin]. A higher intake of carbohydrates during puberty (P-trend = 0.005), particularly from higher-GI food sources (P-trend = 0.01), was prospectively related to higher concentrations of IL-6 in younger adulthood, independently of baseline BMI and early life, socioeconomic, and other nutritional factors. Furthermore, a higher dietary GL (P-trend = 0.002) and a lower intake of whole grains (P-trend = 0.01) were independently associated with higher IL-6 concentrations in adults. Dietary GI and added sugar and fiber intakes were not independently associated with IL-6 (P-trend ≥ 0.09). Carbohydrate nutrition during puberty was not independently related to hs-CRP, IL-18, and adiponectin concentrations (all P-trend > 0.1). During puberty, a higher intake of carbohydrates from higher-GI food sources and lower whole-grain consumption prospectively predict greater IL-6 concentrations in young adulthood. These data support the hypothesis that diet during puberty influences later inflammation and metabolic dysfunction.

Genetic and environmental influences on the prospective correlation between systemic inflammation and coronary heart disease death in male twins

OBJECTIVE

Because of lack of evidence, we aimed to examine to what degree low-grade systemic inflammation and coronary heart disease (CHD) death shared common genetic and environmental substrates.

APPROACH AND RESULTS

From the 41-year prospective National Heart, Lung, and Blood Institute Twin Study, we included 950 middle-aged male twins at baseline (1969-1973). Low-grade systemic inflammation was measured with plasma levels of interleukin-6 (IL-6) and C-reactive protein. Univariate and bivariate structural equation models were used, adjusted for a risk score for CHD death. The score-adjusted heritability was 19% for IL-6, 27% for C-reactive protein, and 22% for CHD death. The positive phenotypic correlation of IL-6 with CHD death (radjusted=0.27; 95% confidence interval [CI], 0.08-0.43) was driven by additive genetic factors (contribution [relative contribution], 0.30 [111%]) but attenuated by unique environment (-0.03 [-11%]). The genetic correlation between IL-6 and CHD death was 0.74 (95% CI, 0.21-1.00), whereas the unique environmental correlation was -0.05 (95% CI, -0.35 to 0.25). The proportion of genetic variance for CHD death shared with that for IL-6 was 74%. The phenotypic correlation of C-reactive protein with CHD death (radjusted=0.10; 95% CI, -0.02 to 0.22) was explained by additive genetic factors (0.20 [149%]) but was attenuated by the unique environment (-0.09 [-49%]). The genetic correlation of C-reactive protein with CHD death was 0.63 (95% CI, -0.07 to 1.00), whereas the unique environmental correlation was -0.07 (95% CI, -0.29 to 0.17).

CONCLUSIONS

Low-grade systemic inflammation, measured by IL-6, and long-term CHD death share moderate genetic substrates that augment both traits.

The association of four common polymorphisms from four candidate genes (COX-1, COX-2, ITGA2B, ITGA2) with aspirin insensitivity: a meta-analysis

OBJECTIVE

Evidence is mounting suggesting that a strong genetic component underlies aspirin insensitivity. To generate more information, we aimed to evaluate the association of four common polymorphisms (rs3842787, rs20417, rs201184269, rs1126643) from four candidate genes (COX-1, COX-2, ITGA2B, ITGA2) with aspirin insensitivity via a meta-analysis.

METHODS AND RESULTS

In total, there were 4 (353/595), 6 (344/698), 10 (588/878) and 7 (209/676) articles (patients/controls) qualified for rs3842787, rs20417, rs20118426 and rs1126643, respectively. The data were extracted in duplicate and analyzed by STATA software (Version 11.2). The risk estimate was expressed as odds ratio (OR) and 95% confidence interval (95% CI). Analyses of the full data set indicated significant associations of rs20417 (OR; 95% CI; P: 1.86; 1.44-2.41; <0.0005) and rs1126643 (2.37; 1.44-3.89; 0.001) with aspirin insensitivity under allelic model. In subgroup analyses, the risk estimate for rs1126643 was greatly potentiated among patients with aspirin semi-resistance relative to those with aspirin resistance, especially under dominant model (aspirin semi-resistance: 5.44; 1.42-20.83; 0.013 versus aspirin resistance: 1.96; 1.07-3.6; 0.03). Further grouping articles by ethnicity observed a stronger prediction of all, but rs20417, examined polymorphisms for aspirin insensitivity in Chinese than in Caucasians. Finally, meta-regression analyses observed that the differences in percentage of coronary artery disease (P = 0.034) and averaged platelet numbers (P = 0.012) between two groups explained a large part of heterogeneity for rs20417 and rs1126643, respectively.

CONCLUSION

Our findings provide strong evidence that COX-2 and ITGA2 genetic defects might increase the risk of having aspirin insensitivity, especially for aspirin semi-resistance and in Chinese populations.

Increased basal and alum-induced interleukin-6 levels in geriatric patients are associated with cardiovascular morbidity

BACKGROUND/AIM OF THE STUDY

Low-grade systemic inflammation was suggested to participate to the decline of physiological functions and increased vulnerability encountered in older patients. Geriatric syndromes encompass various features such as functional dependence, polymorbidity, depression and malnutrition. There is a strong prevalence of cardiovascular diseases and related risk factors and chronic cytomegalovirus infections in the geriatric population. As these underlying conditions were proposed to influence the inflammatory state, the aim of this study was to assess their potential contribution to the association of geriatric syndromes with inflammatory parameters.

METHODOLOGY

We recruited 100 subjects in the general population or hospitalized for chronic medical conditions (age, 23-96 years). We collected information on clinical status (medical history, ongoing comorbidities, treatments and geriatric scales), biological parameters (hematological tests, cytomegalovirus serology) and cytokines production (basal and alum-induced interleukin (IL)-1β and IL-6 levels). Using stepwise backward multivariate analyses, we defined which set of clinical and biological variables could be predictive for increased inflammatory markers.

PRINCIPAL FINDINGS

We confirmed the age-associated increase of circulating IL-6 levels. In contrast to geriatric scales, we found history of cardiovascular diseases to be strongly associated for this parameter as for high IL-6 production upon ex vivo stimulation with alum.

CONCLUSIONS

Association between low-grade inflammation and geriatric conditions could be linked to underlying cardiovascular diseases.

An interactive association of advanced glycation end-product receptor gene four common polymorphisms with coronary artery disease in northeastern Han Chinese

Background

Growing evidence indicates that advanced glycation end-product receptor (RAGE) might play a contributory role in the pathogenesis of coronary artery disease (CAD). To shed some light from a genetic perspective, we sought to investigate the interactive association of RAGE gene four common polymorphisms (rs1800625 or T-429C, rs1800624 or T-374A, rs2070600 or Gly82Ser, and rs184003 or G1704A) with the risk of developing CAD in a large northeastern Han Chinese population.

Methodology/Principal Findings

This was a hospital-based case-control study incorporating 1142 patients diagnosed with CAD and 1106 age- and gender-matched controls. All individuals were angiographically confirmed. Risk estimates were expressed as odds ratio (OR) and 95% confidence interval (CI). Overall there were significant differences in the genotype and allele distributions of rs1800625 and rs184003, even after the Bonferroni correction. Logistic regression analyses indicated that rs1800625 and rs184003 were associated with significant risk of CAD under both additive (OR = 1.20 and 1.23; 95% CI: 1.06–1.37 and 1.06–1.42; P = 0.006 and 0.008) and recessive (OR = 1.75 and 2.39; 95% CI: 1.28–2.40 and 1.47–3.87; P<0.001 and <0.001) models after adjusting for confounders. In haplotype analyses, haplotypes C-T-G-G and T-A-G-T (alleles in order of rs1800625, rs1800624, rs2070600 and rs184003), overrepresented in patients, were associated with 52% (95% CI: 1.19–1.87; P = 0.0052) and 63% (95% CI: 1.14–2.34; P = 0.0075) significant increases in adjusted risk for CAD. Further interactive analyses identified an overall best multifactor dimensionality reduction (MDR) model including rs1800625 and rs184003. This model had a maximal testing accuracy of 0.6856 and a cross-validation consistency of 10 out of 10 (P = 0.0016). The validity of this model was substantiated by classical Logistic regression analysis.

Conclusions

Our findings provided strong evidence for the potentially contributory roles of RAGE multiple genetic polymorphisms, especially in the context of locus-to-locus interaction, in the pathogenesis of CAD among northeastern Han Chinese.

Association of four genetic polymorphisms of AGER and its circulating forms with coronary artery disease: a meta-analysis

Background

Considerable efforts have been devoted to evaluating the association of the receptor for advanced glycation end-products (gene AGER and protein: RAGE) genetic variants to coronary artery disease (CAD); the results, however, are often irreproducible. To generate more information, we sought to explore four common polymorphisms of AGER and its circulating forms associated with the risk of CAD via a meta-analysis.

Methodology/Principal Findings

Articles were identified by searching PubMed, EMBASE, Wanfang and CNKI databases before March 2013. Qualified articles had case-control designs and investigated AGER four polymorphisms (T-429C, T-374A, Gly82Ser, G1704A) or circulating soluble RAGE (sRAGE) or endogenous secretory RAGE (esRAGE) levels associated with CAD. Twenty-seven articles involving 39 independent groups fulfilled the predefined criteria. Overall, no significance was observed for all examined polymorphisms under allelic and dominant models. When restricting groups to CAD patients with diabetes mellitus or renal disease, deviations of risk estimates from the unity were stronger than overall estimates for all polymorphisms except for G1704A due to limited available studies. For example, under dominant model, having -429C allele increased the odds of developing CAD in diabetic patients by 1.22-fold (95% confidence interval (95% CI) 0.99–1.51; P = 0.06; I² = 6.7%) compared with that of overall estimate of 1.15-fold (95% CI: 0.97–1.36; P = 0.111; I² = 18.0%). Circulating sRAGE levels were non-significantly lower in CAD patients than in controls, whereas this reduction was totally and significantly reversed in CAD patients with diabetes mellitus (weighted mean difference: 185.71 pg/ml; 95% CI: 106.82 to 264.61 pg/ml). Circulating esRAGE levels were remarkably lower in CAD patients, as well as in subgroups with or without diabetes mellitus and without renal disease.

Conclusions

Our findings demonstrated that association of AGER genetic polymorphisms with CAD was potentiated in patients with diabetes mellitus or renal disease. Practically, circulating esRAGE might be a powerful negative predictor for the development of CAD.

The interleukin-6 -147 g/c polymorphism is associated with increased risk of coronary artery disease in young South African Indian men

BACKGROUND

Interleukin-6 (IL-6) is a proinflammatory cytokine involved in the pathogenesis of chronic inflammatory diseases such as coronary artery disease (CAD). The -174 IL-6 G/C promoter polymorphism influences mRNA levels and protein expression and is implicated in CAD. The Indian population in South Africa, unlike the black community, has a high prevalence of premature CAD. This polymorphism has not been fully explored in this population. The present study assessed the -174 IL-6 G/C polymorphism in young Indian patients with angiographically documented CAD and compared them with age- and gender-matched Indian and black control subjects.

METHODS

Polymorphic variants were assessed by polymerase chain reaction-restriction fragment length polymorphism, and IL-6 levels were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The -174 IL-6 C allele was found with a higher frequency (23%) in the total Indian group compared to 2% in the black participants [P<0.0001, odds ratio (OR)=0.05, 95% confidence interval (CI) 0.018-0.14). The difference in frequency was more pronounced when Indian controls were compared to black controls (29% vs. 2%, respectively) (P<0.0001, OR=0.05, 95% CI 0.02-0.17). A significant association between the -174 IL-6 G allele and CAD was found in Indian patients compared to Indian controls (84% in cases vs. 71% in Indian controls; P=0.043, OR=0.47 95% CI 0.23-0.95). Levels of IL-6 in circulation were higher in black controls (6.62±0.63 pg/mL) compared to Indian controls (2.51±0.57 pg/mL) and CAD patients (1.46±0.36 pg/mL) (P<0.0001). Levels of IL-6 were higher in all groups with homozygous -174 IL-6 C alleles, but only significant in the healthy Indian control group (GG 3.73±0.94 pg/mL vs. GC/CC 0.89±0.5 pg/mL, P=0.0001).

CONCLUSION

The presence of the IL-6 -174 G allele influences levels of IL-6 and increases the risk of CAD in South African Indians.