Interleukin-6 promoter polymorphisms and susceptibility to atrial fibrillation in elderly Han Chinese patients with essential hypertension

Genetic Factors Altering Immune Responses in Atrial Fibrillation: JACC Review Topic of the Week

Atrial fibrillation (AF) is the most common cardiac arrhythmia worldwide and is associated with a range of adverse clinical outcomes. Accumulating evidence points to inflammatory processes resulting from innate immune responses as a cornerstone in AF pathogenesis. Genetic and epigenetic factors affecting leukocytes have been identified as key modulators of the inflammatory response. Inherited variants in genes encoding proteins involved in the innate immune response have been associated with increased risk for AF recurrence and stroke in AF patients. Furthermore, acquired somatic mutations associated with clonal hematopoiesis of indeterminate potential, leukocyte telomere shortening, and epigenetic age acceleration contribute to increased AF risk. In individuals carrying clonal hematopoiesis of indeterminate potential, myocardial monocyte-derived macrophage shift toward a proinflammatory phenotype may precipitate AF. Further studies are needed to better understand the role of genetic regulation of the native immune response in atrial arrhythmogenesis and its therapeutic potential as a target for personalized medicine.

Arterial Hypertension and Interleukins: Potential Therapeutic Target or Future Diagnostic Marker?

Hypertension as a multifactorial pathology is one of the most important cardiovascular risk factors, affecting up to 30-40% of the general population. Complex immune responses are involved in the inflammatory mechanism of hypertension, with evidence pointing to increased inflammatory mediators even in prehypertensive patients. Increased vascular permeability, thrombogenesis, and fibrosis, effects that are associated with sustained hypertension, could be attributed to chronic inflammation. Chronic inflammation triggers endothelial dysfunction via increased production of ROS through proinflammatory cytokines. Increased serum level of proinflammatory cytokines such as IL-1β, IL-6, IL-8, IL-17, IL-23, TGFβ, and TNFα in hypertensive patients has been associated with either increased blood pressure values and/or end-organ damage. Moreover, some cytokines (i.e., IL-6) seem to determine a hypertensive response to angiotensin II, regardless of blood pressure values. Understanding hypertension as an inflammatory-based pathology gives way to new therapeutic targets. As such, conventional cardiovascular drugs (statins, calcium channels blockers, and ACEIs/ARBs) have shown additional anti-inflammatory effects that could be linked to their blood pressure lowering properties. Moreover, anti-inflammatory drugs (mycophenolate mofetil) have been shown to decrease blood pressure in hypertensive patients or prevent its development in normotensive individuals. Further research is needed to evaluate whether drugs targeting hypertensive-linked proinflammatory cytokines, such as monoclonal antibodies, could become a new therapeutic option in treating arterial hypertension.

Biomarkers of Atrial Fibrillation in Hypertension

Background:

Atrial fibrillation (AF) is the most frequently encountered cardiac arrhythmia globally and substantially increases the risk for thromboembolic disease. Albeit, 20% of all cases of AF remain undiagnosed. On the other hand, hypertension amplifies the risk for both AF occurrences through hemodynamic and non-hemodynamic mechanisms and cerebrovascular ischemia. Under this prism, prompt diagnosis of undetected AF in hypertensive patients is of pivotal importance.

Method:

We conducted a review of the literature for studies with biomarkers that could be used in AF diagnosis as well as in predicting the transition of paroxysmal AF to sustained AF, especially in hypertensive patients.

Results:

Potential biomarkers for AF can be broadly categorized into electrophysiological, morphological and molecular markers that reflect the underlying mechanisms of adverse atrial remodeling. We focused on P-wave duration and dispersion as electrophysiological markers, and left atrial (LA) and LA appendage size, atrial fibrosis, left ventricular hypertrophy and aortic stiffness as structural biomarkers, respectively. The heterogeneous group of molecular biomarkers of AF encompasses products of the neurohormonal cascade, including NT-pro BNP, BNP, MR-pro ANP, polymorphisms of the ACE and convertases such as corin and furin. In addition, soluble biomarkers of inflammation (i.e. CRP, IL-6) and fibrosis (i.e. TGF-1 and matrix metalloproteinases) were assessed for predicting AF.

Conclusion:

The reviewed individual biomarkers might be a valuable addition to current diagnostic tools but the ideal candidate is expected to combine multiple indices of atrial remodeling in order to effectively detect both AF and adverse characteristics of high risk patients with hypertension.

Genomics of Atrial Fibrillation

Atrial fibrillation (AF) is a common clinical arrhythmia that appears to be highly heritable, despite representing a complex interplay of several disease processes that generally do not manifest until later in life. In this manuscript, we will review the genetic basis of this complex trait established through studies of familial AF, linkage and candidate gene studies of common AF, genome wide association studies (GWAS) of common AF, and transcriptomic studies of AF. Since AF is associated with a five-fold increase in the risk of stroke, we also review the intersection of common genetic factors associated with both of these conditions. Similarly, we highlight the intersection of common genetic markers associated with some risk factors for AF, such as hypertension and obesity, and AF. Lastly, we describe a paradigm where genetic factors predispose to the risk of AF, but which may require additional stress and trigger factors in older age to allow for the clinical manifestation of AF.

Interleukin-6 and rs1800796 locus single nucleotide polymorphisms in response to hypoxia/reoxygenation in hepatocytes

Ischemia-reperfusion injury due to hypoxia/reoxygenation (H/R) is one of the main causes of liver damage during liver surgery. Donor interleukin-6 (IL-6) rs1800796 single nucleotide polymorphisms (SNPs) affect the metabolism of tacrolimus following liver transplantation-related hepatic H/R. This study investigated the response of IL-6 and its promoter polymorphisms to hepatic H/R in liver parenchymal cells. The association between IL-6 rs1800796 SNPs and IL‑6 expression was measured in 84 disease-free liver tissues using tissue microarrays and immunohistochemistry. Subsequently, LO2G, LO2C and NC-LO2 cells were successfully constructed via stable lentivirus-mediated transfection. The effects of IL-6 and its SNPs on the biological function of LO2 cells were examined using a cell model of H/R. Our results revealed that IL-6 was mainly expressed in hepatocytes. The intermediate IL-6 expression rate in genotype CC carriers was higher than that in genotype CG/GG carriers (P=0.006), which was subsequently verified at the IL-6 mRNA level (P=0.002). The concentrations of alanine aminotransferase in the LO2G cells were significantly higher than those in the LO2C cells following H/R for 6 h and H/R for 24 h (P<0.05). The viability of the LO2C cells was higher than that of the LO2G cells (P<0.05). Furthermore, the expression of IL-6 and its downstream molecules was significantly increased in the LO2C cells compared with the LO2G cells (P<0.05). Therefore, the sequence variants of rs1800796 SNPs (G→C) exhibit an increased IL-6 transcription efficiency in liver parenchymal cells. In addition, the increased expression of IL-6 protects the hepatocytes following hepatic H/R injury.

Association Between Interleukin-6 -572 C>G and -174 G>C Polymorphisms and Hypertension: A Meta-analysis of Case-control Studies

Whether hypertension is associated with -572 C>G or -174 G>C polymorphism in interleukin (IL)-6 genes still remains hazy and ambiguous.We conducted a meta-analysis to offer a more reliable and clearer evaluation about the association.Electronic literature databases including PubMed, Web of Science, EMBASE, Google Scholar, Chinese National Knowledge Infrastructure and Wanfang database were searched.The study included the following: evaluating associations between -572 C>G or -174 G>C polymorphism in IL-6 gene and hypertension; case-control design; essential information must be offered; precise diagnostic criteria of hypertension; and no language restriction.Patients who met the diagnostic criteria and controls without a history of hypertension were included. Interventions were not available.A quality assessment was conducted using Newcastle-Ottawa scale. Combined odds ratios with 95% confidence intervals were calculated in 5 genetic models. Sources of heterogeneity were explored by subgroup analysis, meta-regression, and Galbraith plots. Finally, test for publication bias was performed to prove the stabilization.Fifteen studies were finally included. Eleven articles were judged high-quality reports. Overall, the -572 C>G polymorphism was proved to be significantly associated with hypertension in 4 genetic models. Subgroup analysis based on ethnicity revealed significant associations in Asian population in recessive model and homozygote comparison. The association in Europeans and Mid-East required further confirmation. No significant association was observed between the -174 G>C polymorphism and hypertension under all of the genetic models.The limitations of the study were the following: restrictive number of eligible studies limited the extrapolation range in subgroup analysis; gene-environment factors could not be described due to lack of data; some relevant studies could not be included because of various reasons.Current researches supported the association between the development of hypertension and the -572 C>G rather than -174 G>C polymorphism. Future well designed epidemiological studies may evaluate the possible gene-environment interactions.

Serum YKL-40 is increased in patients with slow coronary flow

OBJECTIVES

There is accumulating evidence that inflammation plays a major role in the development of the slow coronary flow (SCF) phenomenon. YKL-40 has been suggested to be a potential biomarker of inflammation. In this study, we aimed to study YKL-40 as it relates to SCF.

MATERIALS AND METHODS

Patients who underwent coronary angiography before and had angiographically normal coronary arteries of varying coronary flow rates without any atherosclerotic lesion were enrolled in this study. Patients who had thrombolysis in myocardial infarction frame counts (TFC) above the normal cutoffs were considered to have SCF and those within normal limits were considered to have normal coronary flow (NCF). The YKL-40 levels and biochemical profiles of all patients were studied and analyzed.

RESULTS

There were 41 patients in the SCF group and 209 patients in the NCF group. Compared with the NCF patients, SCF patients had higher serum high-sensitivity C-reactive protein (hs-CRP) (P=0.0003) and YKL-40 (P=0.0007) levels. A positive correlation was detected between the YKL-40 levels and hs-CRP (r=0.7021, P<0.001), and the mean TFC (r=0.4038, P=0.0088) in SCF patients.

CONCLUSION

Our study showed that YKL-40 levels are higher and correlated positively with TFC and hs-CRP in SCF patients. This finding suggests that YKL-40 may be a useful marker and predictor for SCF.

In-hospital clinical outcomes of elderly patients (≥60 years) undergoing primary percutaneous coronary intervention

Elderly patients are at high risk of mortality when they present with ST-elevation myocardial infarction (STEMI). However, the clinical outcomes of this sub-group undergoing primary percutaneous coronary intervention (PPCI) have not been well established, despite recent advances in both devices and techniques. In the present retrospective cohort study from a Chinese single center, we assessed the clinical outcomes and predictors of mortality in elderly patients (≥60 years) underwent with PPCI. The primary endpoints were immediate angiographic success and in-hospital procedural success. The secondary endpoints were all-cause death in hospital. Between January 2011 and December 2013, a total of 184 consecutive patients with acute STEMI underwent PPCI were enrolled. 116 (63.04%) patients were in the elderly group. Despite the difference in lesion complexity between groups, the immediate angiographic success rate was similar (93.97% in the elderly group, and 94.12% in the non-elderly group, P=0.966). The procedural success rate were not significantly different between the two groups (90.52% in the elderly group, and 94.12% in the non-elderly group, P=0.389). However, in-hospital mortality was statistically higher in elderly group than in the non-elderly group (8.62% Vs 1.47%, P=0.048). The major causes of death were cardiac shock and malignant arrhythmias (ventricular tachycardia and fibrillation). Our results indicate that PPCI in the elderly is feasible and has a high likelihood of immediate angiographic and procedural success.

Interleukin-10 promotor -592A/C polymorphism is associated with slow coronary flow in Han Chinese

An accumulating body of evidence suggests that slow coronary flow (SCF) phenomenon seems to be an early-form of atherosclerosis and low-grade inflammation plays a major role in the atherosclerotic vascular processes. Interleukin (IL)-10 is a multifunctional cytokine involved in both innate and adaptive immune response. The aim of the present study is to investigate the association of IL-10 gene -592A/C polymorphism with SCF in Han Chinese. 250 patients who underwent coronary angiography and had angiographically normal coronary arteries of varying coronary flow rates without any atherosclerotic lesion were enrolled in this study. Patients who had thrombolysis in myocardial infarction frame counts (TFC) above the normal cutoffs were considered to have SCF and those within normal limits were considered to have normal coronary flow (NCF). The PCR-based restriction fragment length polymorphism (PCR-RFLP) technique was used to assess the genotypes frequencies. The distribution of the IL-10 -592A/C genotypes (AA, AC, and CC) was 46.34%, 41.46%, and 12.20% in the NCF group, and 66.51%, 28.71%, and 4.78% in SCF subjects, respectively (P = 0.0280). The frequency of the A allele in the SCF group was significantly higher than that in the NCF group (80.86% vs. 67.07%, P = 0.0054). Compared with the CC genotype, the AA genotype had increased risk of SCF in both unadjusted and adjusted analyses. In SCF patients, the average serum IL-10 levels in AA genotype were statistically lower than in AC + CC genotype (P = 0.0000). These findings suggest that IL-10 -592A/C polymorphism is associated with SCF and the A allele has increased risk for SCF in Han Chinese.

A functional single-nucleotide polymorphism in interleukin-6 promoter is associated with p wave dispersion in hypertensive subjects with atrial fibrillation

Inflammation has been shown to be implicated in the pathophysiology of atrial fibrillation (AF). Interleukin-6 (IL-6) is a pleiotropic cytokine, functions as a mediator of inflammatory response and has both pro-inflammatory and anti-inflammatory properties. Little is known about genetic factors of inflammation in the accompanying atrial electrical remodeling expressed by P wave dispersion (Pdisp). The aim of the present study is to evaluate the association of -634C/G polymorphism of IL-6 gene with Pdisp in Han Chinese hypertensive patients with AF. A total of 100 patients with essential hypertension (EH) were eligible for this study. Patients with paroxysmal AF (n=50) were allocated to the AF group, and 50 subjects without AF to the control group. The PCR-based restriction fragment length polymorphism (PCR-RFLP) technique was used to assess the genotypes frequencies. The distribution of the IL-6 -634C/G genotypes (CC, CG, and GG) was 68.00%, 28.00%, and 4.00% in the controls, and 44.00%, 40.00%, and 16.00% in AF subjects, respectively (P=0.0269). The frequency of the G allele in the AF group was significantly higher than that in the control group (36.00% vs 18.00%, P=0.0041). Compared to the wild type CC, the G allele carriers (CG + GG genotypes) had a 2.7045-fold increased risk of AF (odds ratio =2.7045, 95% confidence interval =1.1966-6.1126, P=0.0156). AF patients with the CG + GG genotype had longer Pdisp (P=0.0032) than did patients with the CC genotype. The longer Pdisp in the subjects with the CG + GG genotype was also found in the control group (P=0.0016). These findings support that IL-6 -634C/G polymorphism is associated with Pdisp and AF, suggesting an active implication of inflammation in the atrial electrophysiological remodeling predisposing to AF.

Association of Interleukin-10 promotor polymorphisms with atrial fibrillation in Han Chinese

There is an accumulating body of evidence indicating strong association between inflammation and the pathogenesis of atrial fibrillation (AF). IL-10 is a multifunctional anti-inflammatory cytokine that down-regulates cell-mediated immune responses and cytotoxic inflammatory responses. The aim of the present study is to investigate the association of IL-10 gene -592A/C polymorphism with AF in Han Chinese. 117 AF patients and 100 healthy volunteers were eligible for this study. The PCR-based restriction fragment length polymorphism (PCR-RFLP) technique was used to assess the genotypes frequencies. The distribution of the IL-10 -592A/C genotypes (AA, AC, and CC) was 55.00%, 35.00%, and 10.00% in the controls, and 71.79%, 23.08%, and 5.13% in AF subjects, respectively (p = 0.0335). The frequency of the A allele in the AF group was significantly higher than that in the control group (83.33% vs 72.50%, p = 0.0063). Compared with the CC genotype, the AA genotype had increased risk of AF in both unadjusted and adjusted analyses. The average serum IL-10 levels in AA genotype were statistically lower than in AC + CC genotype (p = 0.0000). These findings suggest that IL-10 -592A/C polymorphism is associated with AF and the A allele has increased risk for AF in Han Chinese.

Interleukin-6 genotypes and serum levels in Chinese Hui population

Interleukin-6 (IL-6) is a key pro-inflammatory cytokine involved in different physiologic and pathophysiologic processes, and circulating levels of IL-6 differ greatly between individuals. The Chinese Hui is one of the largest ethnic minorities, little is known about the distribution of IL-6 genetic variations and their effects on serum levels in Hui population. The aim of the present study is to determine the prevalence of -174G/C (rs1800795), -597G/A (rs1800797), and -634C/G (rs1800796) polymorphisms in the IL-6 gene promoter region and their association with IL-6 serum levels in the Ningxia Hui population. A total of 96 Hui subjects, (57 men and 39 women; mean age 49.65 ± 19.73 years) unrelated nationality residents in Ningxia Hui Autonomous Region were enrolled. Genotyping of the three polymorphisms were performed by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) combined with gel electrophoresis and then confirmed by direct sequencing. The -174G/C (97.92% GG, 2.08% GC, and 0% CC) and -597G/A (98.96% GG, 1.04% GA, and 0% AA) polymorphisms were rare. The frequencies of -634C/G genotypes CC, CG, and GG were found to be 54.17%, 40.62%, and 5.21%, respectively in total studied subjects, the derived allele frequencies for the C and G alleles were 74.48% and 25.52%. Increased IL-6 levels were correlated with the IL-6 -634G allele carriers (CG+GG genotypes). The results suggest that IL-6 -174G/C and -597G/A are rare but -634C/G is common in the Ningxia Hui population, and the -634G allele is associated with circulating levels of IL-6.

Interleukin-6 promotor polymorphisms and coronary vasospastic angina in Han Chinese

There is an accumulating body of evidence indicating association between inflammation and the pathogenesis of coronary vasospastic angina (CVA). Interleukin-6 (IL-6) is a pleiotropic cytokine, functions as a mediator of inflammatory response and has both pro-inflammatory and anti-inflammatory properties. The aim of the present study is to investigate the association of -634C/G polymorphism of IL-6 gene with CVA in Han Chinese. A total of 27 CVA patients and 232 healthy controls were eligible for this study. The PCR-based restriction fragment length polymorphism (PCR-RFLP) technique was used to assess the genotypes frequencies. The distribution of the IL-6 -634C/G genotypes (CC, CG, and GG) was 59.48%, 37.07%, and 3.45% in the controls, and 37.04%, 48.15%, and 14.81% in CVA group, respectively (P = 0.0080). The frequency of the G allele in the CVA group was significantly higher than that in the control group (38.89% vs 21.98%, P = 0.0057). Compared with the wild type CC, the G allele carriers (CG + GG genotypes) had increased risk of CVA in both unadjusted and adjusted analyses. These findings suggest that IL-6 -634C/G polymorphism is associated with CVA and the G allele is an independent risk for CVA in Han Chinese.

IL-24 gene polymorphisms are associated with cardiometabolic parameters and cardiovascular risk factors but not with premature coronary artery disease: the genetics of atherosclerotic disease Mexican study

Coronary artery disease (CAD) is a multifactorial and polygenic disorder that results from an excessive inflammatory response. We analyzed whether interleukin-24 (IL-24) gene polymorphisms are associated with premature CAD in a case-control association study. Four polymorphisms (rs1150253, rs1150256, rs1150258, and rs3762344) of the IL-24 gene were analyzed by 5' exonuclease TaqMan genotyping assays in a group of 952 patients with premature CAD, 284 individuals with subclinical atherosclerosis (SA), and 912 controls. The studied polymorphisms were not associated with the risk of premature CAD or SA (P>0.05). Under dominant models adjusted for age, sex, body mass index, and medication, the polymorphisms were associated with cardiometabolic parameters and cardiovascular risk factors. Three polymorphisms (rs1150253, rs1150256, and rs3762344) were associated with hypertension and increased levels of systolic blood pressure in controls. In SA, 2 polymorphisms (rs1150256 and rs3762344) were associated with type 2 diabetes mellitus, gamma-glutamyl transpeptidase (GGT), and alkaline phosphatase, whereas rs1150253 was associated with GGT and type 2 diabetes mellitus and rs1150258 with GGT and alkaline phosphatase. In premature CAD, the 4 polymorphisms were associated with total cholesterol >200 mg/dL, low-density lipoprotein cholesterol (LDL-C), and GGT, whereas rs1150256 was associated also with ApoA. On the other hand, rs1150258 was associated with ApoA, LDL-C >100 mg/dL, and apoB/apoA ratio, and rs3762344 with ApoA, apoB/apoA ratio, LDL-C >100 mg/dL, and total cholesterol. On the basis of single-nucleotide polymorphism functional prediction software, rs1150253 and rs1150258 polymorphisms seem to be functional. The 4 studied polymorphisms were in linkage disequilibrium and had a similar haplotype distribution in patients and controls. Our study demonstrates the association of IL-24 polymorphisms with metabolic and cardiovascular risk factors in individuals with premature CAD, SA, and controls.

Association of IL-6-174G > C and -572C > G polymorphisms with risk of young ischemic stroke patients

AIM

To investigate the association between interleukin-6 (IL-6) -174G>C and -572C>G polymorphisms and risk for ischemic stroke (IS) in young patients.

METHODS

We genotyped IL-6 -174G>C and -572C>G in a case-control study of 430 young IS patients and 461 control subjects. An unconditional multiple logistical regression model was used to calculate the effects of IL-6-174G>C and -572C>G polymorphisms on IS risk.

RESULTS

Higher body mass index, diabetes, hypertension, obesity, and smoking were associated with risk of ischemic stroke. Multivariate regression analyses showed that subjects carrying the -174CC genotype (OR=1.69, 95% CI=1.16-2.57) and C allele (OR=1.37, 95% CI=1.09-1.67) had a small but significant increased risk of IS. Similarly, those carrying the -572GG genotype (OR=2.12, 95% CI=1.18-3.82) and G allele (OR=1.43, 95% CI=1.14-1.83) had a moderate increased risk of IS. We found the -174G>C and -572C>G polymorphisms interact with hypertension and obesity.

CONCLUSION

Our results suggest that polymorphisms in IL-6-174G>C and -572C>G are associated with IS risk in young patients, and that these polymorphisms interact with hypertension, obesity and etiologic subtypes. These findings could be helpful in identifying individuals at increased risk for developing IS.

Angiotensin-converting enzyme gene 2350 G/A polymorphism and susceptibility to atrial fibrillation in Han Chinese patients with essential hypertension

OBJECTIVE

The angiotensin-converting enzyme gene is one of the most studied candidate genes related to atrial fibrillation. Among the polymorphisms of the angiotensin-converting enzyme gene, the 2350 G/A polymorphism (rs4343) is known to have the most significant effects on the plasma angiotensin-converting enzyme concentration. The aim of the present study was to investigate the association of the angiotensin-converting enzyme 2350 G/A polymorphism with atrial fibrillation in Han Chinese patients with essential hypertension.

METHODS

A total of 169 hypertensive patients were eligible for this study. Patients with atrial fibrillation (n = 75) were allocated to the atrial fibrillation group, and 94 subjects without atrial fibrillation were allocated to the control group. The PCR-based restriction fragment length polymorphism technique was used to assess the genotype frequencies.

RESULTS

The distributions of the angiotensin-converting enzyme 2350 G/A genotypes (GG, GA, and AA, respectively) were 40.43%, 41.49%, and 18.08% in the controls and 18.67%, 46.67%, and 34.66% in the atrial fibrillation subjects (p = 0.037). The frequency of the A allele in the atrial fibrillation group was significantly greater than in the control group (58.00% vs. 38.83%, p = 0.0007). Compared with the wild-type GG genotype, the GA and AA genotypes had an increased risk for atrial fibrillation. Additionally, atrial fibrillation patients with the AA genotype had greater left atrial dimensions than the patients with the GG or GA genotypes (p<0.01 and p<0.05, respectively).

CONCLUSIONS

The results obtained in this study indicate that the angiotensin-converting enzyme 2350 G/A polymorphism is associated with atrial fibrillation and that the A allele shows an increased risk for atrial fibrillation in Han Chinese patients with essential hypertension.

Atrial fibrillation: inflammation in disguise?

Atrial fibrillation is highly prevalent, and affected patients are at an increased risk of a number of complications, including heart failure and thrombo-embolism. Over the past years, there has been increasing interest in the role of inflammatory processes in atrial fibrillation, from the first occurrence of the arrhythmia to dreaded complications such as strokes or peripheral emboli. As the standard drug combination which aims at rate control and anticoagulation only offers partial protection against complications, newer agents are needed to optimize treatment. In this paper, we review recent knowledge regarding the impact of inflammation on the occurrence, recurrence, perpetuation and complications of the arrhythmia, as well as the role of anti-inflammatory therapies in the treatment for the disease.

Assessment of interleukin-1 gene cluster polymorphisms in lone atrial fibrillation: new insight into the role of inflammation in atrial fibrillation

BACKGROUND

Systemic inflammation is accepted as one of the pathophysiological mechanisms of atrial fibrillation (AF). The role of inflammation has been shown previously. Interleukin (IL) system is the main modulator of the inflammatory responses and genetic polymorphisms of IL-1 cluster genes are associated with increased risk for inflammatory diseases.

OBJECTIVES

To investigate the association between polymorphisms of IL-1 cluster genes and lone AF.

SUBJECTS AND METHODS

DNA samples were collected from 70 proven lone AF patients and 70 healthy subjects. Genomic DNA was typed for the variable number of the tandem repeat (VNTR) IL-1 receptor antagonist (RN) gene polymorphism, IL-1B -511 C > T(rs16944) promoter polymorphism, and +3953 C > T(rs1143634) polymorphism in exon 5 by polymerase chain reaction.

RESULTS

In lone AF group the frequency of IL-1RN2/2 and IL-1RN1/2 genotypes were higher than in the control group (7.2% vs 4.3% and 48.5% vs 22.8%, respectively; χ(2) = 14.1; P = 0.028). The frequency of allele 2 was significantly higher in the lone AF group (32.1% vs 15.7%; χ(2) = 10.7; P = 0.005). Allele and genotype distribution of IL-1B -511 C > T and +3953 C > T polymorphisms were not statistically different between the groups. C-reactive protein (CRP) levels were higher in lone AF patients compared to the control group (median = 1.25, interquartile range [IQR] = 0.85 vs median = 1.08, IQR 0.46 mg/L, respectively; P = 0.02). In multivariate regression analysis, presence of allele 2 of IL-1 VNTR polymorphism and elevated plasma high-sensitive-CRP levels were the independent predictors of lone AF.

CONCLUSION

Presence of allele 2 of VNTR polymorphism of IL-1RN gene may cause increased risk for lone AF probably due to the inadequate limitation of inflammatory reactions.