Genetic polymorphisms of interleukin-6 gene and susceptibility to coronary artery disease in Chinese population: Evidence based on 4582 subjects

Study of the rs1800795 polymorphism of the <i>IL6</i> gene to verify the clinical portrait of a patient with chronic heart failure: gender aspects

Background. Genetic studies in cardiology allow to identify predisposition and predict the course of multifactorial cardiovascular diseases by identifying the association of polymorphic loci of candidate genes with the clinical phenotype. One of these diseases associated with poor prognosis is chronic heart failure (CHF). Activation of pro-inflammatory cytokines is one of the key aspects of the development and progression of CHF. Aim. To identify the features of the clinical course of CHF of ischemic etiology in patients, taking into account the gender and genotype of the rs1800795 polymorphism of the IL6 gene. Materials and methods. Four hundred fourteen patients of both sexes with stable CHF of ischemic origin, aged 66.410.4 years, were included. Clinical characteristics of men and women of each genotype of the rs1800795 polymorphism of the IL6 gene were compared. Genotyping of the rs1800795 polymorphism of the IL6 gene was performed by real-time polymerase chain reaction. Results. In male patients with CHF, the frequency of allele C was higher than in the control group (p=0.04). Homozygous carriers of the C allele showed a greater risk of developing atrial fibrillation (p=0.021). In terms of biochemical parameters, in patients with a heterozygous genotype, compared with homozygotes for the G allele of the rs1800795 polymorphism of the IL6 gene, the levels of cholesterol, triglycerides (TG), cholesterol not associated with high-density lipoproteins (non-HDL-cholesterol) were higher (p=0.044, p=0.019, p=0.016). Patients with the CC genotype of the rs1800795 polymorphism of the IL6 gene females compared with men were more likely to have IIIIV functional class of CHF (p=0.001) and had a high heart rate (p=0.021). Male patients of the CG genotype were more likely to undergo coronary interventions (p=0.001). In women of the CG genotype, CHF was more often combined with DM (p=0.015), the level of non-HDL-cholesterol (p=0.04) was higher, and glomerular filtration rate was lower than in men (p=0.001). Comparison of the GG genotype revealed a higher incidence of chronic kidney disease in women (p=0.022). Women had significantly lower glomerular filtration rate (p=0.001), systolic blood pressure (p=0.004). The level of such biochemical parameters as cholesterol (p=0.001), TG (p=0.019), low-density lipoprotein cholesterol (p=0.002) was reduced, except for high non-HDL-cholesterol (p=0.001). There were more men with left ventricular ejection fraction 40% (p=0.009), women with left ventricular ejection fraction 50% (p=0.002). Conclusion. The identified phenotypic and gender differences create prerequisites for determining patient-oriented genetic risk, opening up new opportunities for preventing the progression and complications of CHF.

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.

The IL-6 rs1800795 and rs1800796 polymorphisms are associated with coronary artery disease risk

Studies examining the associations between the interleukin‐6 (IL‐6) rs1800795 and rs1800796 gene polymorphisms and risk of coronary artery disease (CAD) remain controversial. Our aim was to evaluate the accurately determine role of these two polymorphisms in CAD risk. PubMed, Embase, VIP, Wan fang and China National Knowledge Infrastructure databases were searched. The odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. The trial sequential analysis (TSA) was conducted, and bioinformatics tools were employed. A total of thirty‐seven articles were obtained. For the IL‐6 rs1800795 polymorphism, 9411 CAD patients and 3161 controls were included, 4720 patients with CAD, and 5000 controls were included for the IL‐6 rs1800796 polymorphism. In the pooled analysis, significant associations were only observed for the rs1800796 polymorphism (allelic: OR [95%CI] = 1.28 [1.13, 1.44], dominant: OR [95%CI] = 1.35 [1.17, 1.57], recessive: OR [95%CI] = 1.35 [1.18, 1.55], heterozygote: OR [95%CI] = 1.26 [1.15, 1.37], homozygote: OR [95%CI] = 1.62 [1.23, 2.13]). Significant associations were detected in the Asian and Mongoloid populations and ‘more than 500’ subgroup for the rs1800795 polymorphism. TSA confirmed the true‐positive results for the rs1800796 polymorphism. The bioinformatics analysis showed that the two polymorphisms played important roles in the gene transcription. The IL‐6 rs1800796 polymorphism is associated with an increased susceptibility to CAD and is a risk factor for CAD. The IL‐6 rs1800795 polymorphism is associated with an increased risk of CAD in Asians, particularly in Chinese, and a decreased risk of CAD in an African population is remarkably observed.

Interleukin 6 (rs1800795) gene polymorphism is associated with cardiovascular diseases: a meta-analysis of 74 studies with 86,229 subjects

Cardiovascular diseases (CVD) are group of complex and multifactorial pathologies, in which interleukin-6 (IL-6) gene polymorphisms have been associated with several components of the CVD. Thus, in this study, we thoroughly reviewed and meta-analyzed evidence on the association between the IL-6 (rs1800795) gene polymorphism and CVD. We systematically searched in the PubMed, Web of Sciences, and Scopus databases. The analyses were performed using five study groups based on (1) a combined pool of the overall populations, (2) the country of birth, (3) the continent of birth, (4) the diagnosis and (5) both location (country or continent) and diagnosis. The analysis included the allelic, homozygote, heterozygote, dominant and recessive models. The meta-analysis showed that -174G>C (rs1800795) is a risk factor for CVD (allelic: OR=1.06, CI 95%=1.02-1.10. Z p value <0.0001; homozygous: OR=1.11, CI 95%=1.03-1.19, Z p value= 0.002; heterozygous: OR=1.08, CI 95%=1.03-1.21, Z p value= 0.003; dominant: OR= 1.12, CI 95%= 1.07-1.18, Z p value= 0.001) and that this risk increases in the Chinese population. Additionally, we found that carriers of the C allele of 174G>C (rs1800795) polymorphism have an increase in the risk of coronary artery disease under the hereditary models assessed in the study. Using robust data, we found that IL-6 (rs1800795) -174G>C gene polymorphism is associated with CVD risk.

Association of Interleukin-6 Genetic Polymorphisms and Environment Factors Interactions with Coronary Artery Disease in a Chinese Han Population

OBJECTIVES

To investigate the influence of IL-6 single nucleotide polymorphisms (SNPs), additional gene-gene and gene-environment interactions on coronary artery disease (CAD) risk.

METHODS

A total of 751 participants (429 CAD patients and 322 controls) were recruited in this study. Logistic regression analysis was conducted to evaluate the association of IL-6 SNPs with CAD risk and generalized multifactor dimensionality reduction (GMDR) was performed to investigate the best interaction combinations for gene-gene and gene-environment interactions.

RESULTS

CAD risk is significantly higher in carriers of C allele of the rs1800795 polymorphism than those with GG genotype (CC + CG versus GG, adjusted OR (95%CI) = 2.07 (1.56-2.86), p < 0.001). GMDR analysis revealed rs1800795 was significantly interacted with tobacco smoking and alcohol drinking in two-locus model (p < 0.0010). Current smokers with CC or CG of rs1800795 genotype have the highest CAD risk, OR (95%CI) = 3.22 (2.45-3.94) and current drinkers with CC or CG of rs1800795 genotype have the highest CAD risk, OR (95%CI) = 3.17 (2.20-4.24).

CONCLUSION

The C allele of rs1800795 within IL-6 gene promoter, rs1800795-tobacco smoking and rs1800795-alcohol drinking interaction were all associated with increased CAD risk.

The -174 G>C Interleukin-6 Gene Polymorphism is Associated with Angiographic Progression of Coronary Artery Disease over a 4-Year Period

BACKGROUND

Inflammation is a key process underlying the clinical course of coronary artery disease (CAD). C-reactive protein (CRP) and interleukin-6 (IL-6) contribute to its pathophysiology and act as biomarkers. We sought to examine whether known single nucleotide polymorphisms (SNPs) impact CAD progression, reflecting increased inflammation.

METHODS

We retrospectively evaluated coronary angiographies of patients with established CAD who were re-investigated for stable/unstable angina after a time interval of >12 months. We defined progression of CAD as the emergence of a new plaque or a ≥20 % increase of a formerly non-significant lesion. We genotyped patients for the 1846 C>T CRP and -174 G>C IL-6 SNPs. The probability of CAD progression among the Mendelian randomization groups was evaluated using the Kaplan-Meier method. Data were analyzed using a Cox model that included relevant clinical factors.

RESULTS

A total of 157 patients were included. The serum levels of CRP and IL-6 differed significantly between genotypes. The genotype frequencies of IL-6 were consistent with Hardy-Weinberg equilibrium, whereas those for CRP were excluded from our conclusions. At 48 months, 83 patients (52.9 %) with the IL-6 C allele versus 74 (47.1 %) with the G allele exhibited CAD progression. Patients with the IL-6 C allele had a 52.8 % probability for progression versus 13.3 % for those with the G allele (p=0.005). The results were confirmed by multivariate analysis; dyslipidemia, family history, and IL-6 SNP emerged as significant factors.

CONCLUSION

Patients with established CAD who carried the -174 C allele of the IL-6 gene demonstrated an increased risk for the progression of coronary plaques over a four-year period. Further studies will be needed to validate these findings.