Association of IL-18 promoter polymorphisms with predisposition to Type 1 diabetes

Single-nucleotide polymorphisms as important risk factors of diabetes among Middle East population

Diabetes is a chronic metabolic disorder that leads to the dysfunction of various tissues and organs, including eyes, kidneys, and cardiovascular system. According to the World Health Organization, diabetes prevalence is 8.8% globally among whom about 90% of cases are type 2 diabetes. There are not any significant clinical manifestations in the primary stages of diabetes. Therefore, screening can be an efficient way to reduce the diabetic complications. Over the recent decades, the prevalence of diabetes has increased alarmingly among the Middle East population, which has imposed exorbitant costs on the health care system in this region. Given that the genetic changes are among the important risk factors associated with predisposing people to diabetes, we examined the role of single-nucleotide polymorphisms (SNPs) in the pathogenesis of diabetes among Middle East population. In the present review, we assessed the molecular pathology of diabetes in the Middle East population that paves the way for introducing an efficient SNP-based diagnostic panel for diabetes screening among the Middle East population. Since, the Middle East has a population of 370 million people; the current review can be a reliable model for the introduction of SNP-based diagnostic panels in other populations and countries around the world.

Immune Response and Lipid Metabolism Gene Polymorphisms Are Associated with the Risk of Obesity in Middle-Aged and Elderly Patients

More than two billion people around the world are overweight or obese. Even in apparently healthy people, obesity has a potent effect on their quality of life. Experimental data indicate the role of infectious agents in systemic inflammation, revealing a correlation between the dietary habits of people with obesity and the level of systemic inflammation mediators, serum lipid concentration, and hormonal and immune status. This study aimed to determine the association of immune response and lipid metabolism gene polymorphisms with the risk of obesity. This study included 560 Caucasian participants living in Western Siberia (Russian Federation). A total of 52 polymorphic sites in 20 genes were analyzed using the 5′ TaqMan nuclease assay. Four risk-associated polymorphic variants were discovered—two variants in immune response genes (IL6R rs2229238, OR = 1.92, 95% CI = 1.36–2.7, p = 0.0002 in the dominant model; IL18 rs1946518, OR = 1.45, 95% CI = 1.03–2.04, p = 0.033 in the over-dominant model) and two variants in lipid metabolism genes (LPA rs10455872, OR = 1.86, 95% CI = 1.07–3.21, p = 0.026 in the log-additive model; LEPR rs1137100, OR = 2.88, 95% CI = 1.52–5.46, p = 0.001 in the recessive model). Thus, polymorphisms in immune response and lipid metabolism genes are potentially associated with the modification of obesity risk in the Caucasian population.

Association between IL-18 and IL-6 gene polymorphisms and the risk of T1D in Egyptian children

Purpose

To test the involvement between IL-18 and IL-6 genetic polymorphisms and susceptibility to Type 1 diabetes (T1D).

Methods

Single nucleotide polymorphisms (SNPs) at positions -607A/C and - 137G/C in IL-18 promoter region were examined by sequence specific primers-polymerase chain reaction (SSP-PCR) and position -174G/C in promoter region of IL-6 gene which analyzed by Mutagenically Separated PCR (MS-PCR) in 104 T1D participants and 114 controls.

Results

IL-18 -137GC and -137CC genotypes and -137C allele were significantly decreased in T1D subjects (P < 0.05), while -137GG genotype was insignificantly increased as compared to controls. A significant decrease was detected in haplotype -137C/-607C frequency in T1D participants compared with controls (OR = 0.04, P < 0.001). There was significant association between IL-18 -607 of (CC, AC and AA genotypes) in age at diagnosis, glycated hemoglobin (HbA1c) and higher body mass index (BMI) (P < 0.05).

Conclusion

This study demonstrated that IL-18 gene promoter polymorphisms might be associated with susceptibility to T1D in Egyptian children. Individuals carrying CC genotype at position -137 of IL-18 promoter may be at a low risk of T1D progression. Additionally, the susceptible combination of IL-18 and IL-6 cytokine genes associated with T1D highlight their risk toward the disease.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-021-00763-w.

Role of IL-18 Gene Promoter Polymorphisms, Serum IL-18 Levels, and Risk of Hepatitis B Virus-related Liver Disease in the Guangxi Zhuang Population: a Retrospective Case-Control Study

BACKGROUND

The aim of this study was to assess the relationship between IL-18 gene polymorphisms and HBV-related diseases and whether these polymorphisms influence its expression in the Guangxi Zhuang population.

MATERIALS AND METHODS

We enrolled 129 chronic HBV infected (CHB) patients, 86 HBV-related liver cirrhosis (LC) patients and 160 healthy controls in our study. Polymerase chain reaction-restriction fragment length polymorphism methods were used to detect IL-18 gene -607C/A, -137G/C polymorphisms, and an ELISA kit was employed to determine serum IL-18 levels.

RESULTS

No correlation was found between the -607C/A polymorphism and risk of HBV-related disease. For the -137G/C polymorphism, the GC genotype and C allele were associated with a significantly lower risk of CHB (95%CI: 0.32-0.95, p=0.034 and 95%CI: 0.35-0.91, p=0.018) and HBV-related LC (95%CI: 0.24-0.89, p=0.022 and 95%CI: 0.28-0.90, p=0.021). A similar decreased risk was also found with the A-607C-137 haplotype. With respect to IL-18 expression, it was significantly lower in both patient groups, but no association was noted between the two polymorphisms in the IL-18 gene and its expression.

CONCLUSIONS

Our study indicated that the -137C allele in the IL-18 gene may be a protective factor for HBV-related disease, and serum IL-18 level may be inversely associated with CHB and HBV-related LC.

The interleukin-18 gene promoter -607 A/C polymorphism contributes to non-small-cell lung cancer risk in a Chinese population

The purpose of the present study was to determine the relationship between interleukin-18 (IL-18) -607 A/C polymorphism and the risk of non-small-cell lung cancer (NSCLC) and its impact on the serum IL-18 level. The genotyping of IL-18 -607 A/C polymorphism was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results showed that the AA/AC genotype distribution in NSCLC patients was significantly higher than that of healthy controls (P=0.02). However, no significant differences were found between the two subgroups when stratified by clinical characteristics. Furthermore, serum IL-18 levels were found to be significantly higher in the NSCLC patients than in the controls (P=0.01) as detected by enzyme-linked immunosorbent assay analysis. There was no correlation between serum IL-18 levels and different genotypes. In conclusion, these findings suggest that IL-18 -607 A/C polymorphism increases the risk of NSCLC in the Chinese population, and this polymorphism could not functionally affect the IL-18 levels.

Association between Genetic Variants and Diabetes Mellitus in Iranian Populations: A Systematic Review of Observational Studies

INTRODUCTION

Diabetes mellitus as the most prevalent metabolic disease is a multifactorial disease which is influenced by environmental and genetic factors. In this systematic review, we assessed the association between genetic variants and diabetes/its complications in studies with Iranian populations.

METHODS

Google Scholar, PubMed, Scopus, and Persian web databases were systematically searched up to January 2014. The search terms were "gene," "polymorphism," "diabetes," and "diabetic complications"; nephropathy, retinopathy, neuropathy, foot ulcer, and CAD (coronary artery diseases); and Persian equivalents. Animal studies, letters to editor, and in vitro studies were excluded.

RESULTS

Out of overall 3029 eligible articles, 88 articles were included. We found significant association between CTLA-4, IL-18, VDR, TAP2, IL-12, and CD4 genes and T1DM, HNFα and MODY, haptoglobin, paraoxonase, leptin, TCF7L2, calreticulin, ERα, PPAR-γ2, CXCL5, calpain-10, IRS-1 and 2, GSTM1, KCNJ11, eNOS, VDR, INSR, ACE, apoA-I, apo E, adiponectin, PTPN1, CETP, AT1R, resistin, MMP-3, BChE K, AT2R, SUMO4, IL-10, VEGF, MTHFR, and GSTM1 with T2DM or its complications.

DISCUSSION

We found some controversial results due to heterogeneity in ethnicity and genetic background. We thought genome wide association studies on large number of samples will be helpful in identifying diabetes susceptible genes as an alternative to studying individual candidate genes in Iranian populations.

Interleukin-18 promoter -607 C/A and -137 G/C polymorphisms and susceptibility to type 1 diabetes: A meta-analysis

OBJECTIVE

The aim of this study was to determine whether the functional interleukin-18 (IL-18) promoter -607 C/A (rs1946518) and -137 G/C (rs187238) polymorphisms are associated with susceptibility to type 1 diabetes (TID).

METHODS

A meta-analysis was conducted to assess the associations between the IL-18 -607 C/A and -137 G/C polymorphisms and T1D in overall and by ethnic group.

RESULTS

A total of 6075 cases and 5744 controls from ten studies were considered in this meta-analysis. In all study subjects, the meta-analysis showed no association between T1D and the IL-18 -607 C allele (OR=1.083, 95% CI=0.930-1.260, p=0.307). However, stratification by ethnicity indicated an association between the IL-18 -607 C allele and T1D in Asians (OR=1.506, 95% CI=1.172-1.936, p=0.001), but not in Europeans (OR=0.988, 95% CI=0.808-1.209, p=0.907). Analysis using recessive and dominant models and homozygote contrast showed the same -607 C allele pattern in Asians and Europeans. Meta-analysis of the IL-18 -137 G/C polymorphism showed no association between T1D and the IL-18 -137 G allele in all study subjects (OR=1.066, 95% CI=0.926-1.2289, p=0.375). Stratification by ethnicity indicated no association between the IL-18 -137 G allele and T1D in Europeans and Asians (OR=1.021, 95% CI=0.961-1.085, p=0.504; OR=0.851, 95% CI=0.5821-1.245, p=0.406).

CONCLUSIONS

Our meta-analysis demonstrates that the IL-18 -607 C/A polymorphism may be associated with susceptibility to T1D in Asians, but not in Europeans.

Elevated levels of serum IL-12 and IL-18 are associated with lower frequencies of CD4(+)CD25 (high)FOXP3 (+) regulatory t cells in young patients with type 1 diabetes

Type 1 diabetes is thought to involve chronic inflammation, which is manifested by the activation and expression of different inflammatory mediators. IL-12 and IL-18 are two cytokines that have been shown to exert strong proinflammatory activity and have been implicated in the pathogenesis of type 1 diabetes in mice and humans. The overproduction of proinflammatory mediators is controlled by specialized T cell subset, namely regulatory T cells that express FOXP3 transcription factor. Since IL-12 and IL-18 mediate inflammatory response and Tregs exhibit anti-inflammatory potential, we aimed to examine their reciprocal relationship in patients with type 1 diabetes. The study group consisted of 47 children diagnosed with type 1 diabetes and 28 healthy individuals. Serum levels of IL-12 and IL-18 were measured by ELISA, and the peripheral blood CD4⁺CD25^high FOXP3⁺ regulatory T cell frequencies were analyzed by flow cytometry. Patients with type 1 diabetes had a decreased percentage of circulating CD4⁺CD25^highFOXP3⁺ Tregs in comparison to their healthy counterparts. In addition, they produced more IL-12 and IL-18 than children from the control group. Concentrations of these cytokines positively correlated with one another, as well as with CRP and HbA1c. Moreover, the negative association between IL-12, IL-18, CRP serum levels, and the frequency of regulatory CD4⁺CD25^highFOXP3⁺ Tregs was observed. IL-12 and IL-18 may have direct or indirect impact on regulatory T cell subset, which may contribute to their reduced frequency in peripheral blood of patients with type 1 diabetes mellitus.

IL-18 gene polymorphisms in aphthous stomatitis vs. Behçet's disease in a cohort of Egyptian patients

OBJECTIVE

A clinical investigation of the potential correlation of two single-nucleotide polymorphisms at -137 (G/C) and -607 (C/A) in the promoter region of the IL-18 gene, with the susceptibility to aphthous stomatitis and Behçet's disease.

PATIENT AND METHODS

This study included 80 aphthous stomatitis patients and 80 patients with Behçet's disease. Eighty healthy subjects were enrolled as a control group. IL-18 single-nucleotide polymorphisms at -607 and -137 regions were analyzed using polymerase chain reaction-restriction fragment length polymorphism analysis.

RESULTS

The genotype and allele distributions of the two regions did not differ significantly between patients with aphthous stomatitis and controls. The genotype and allele distributions at -607 were significantly different between patients with Behçet's disease [CC (P = 0.044), C allele (P = 0.043), A allele (P = 0.043)], and controls. The frequency of the GG genotype at position -137 in patients with Behçet's disease was associated only with a higher rate of ocular manifestations (OR= 1.4, CI= 0.76-2.7, P = 0.031).

CONCLUSION

IL-18 gene polymorphisms were not associated with any susceptibility to aphthous stomatitis, while a positive association was found with patients with Behçet's disease regarding -607 promoter site. Moreover, patients with Behçet's disease carrying the GG genotype at position -137 had a higher risk of developing ocular manifestations.

Association of the interleukin-18 -137 C/G, -607 A/C polymorphisms with type 1 diabetes: A meta-analysis

Published data on the association between interleukin (IL)-18 gene polymorphisms (-137 C/G, -607 A/C) and type 1 diabetes (T1D) risk are inconclusive. To obtain a more precise estimation of the association between the IL-18 gene polymorphisms and T1D, a meta-analysis was performed. A total of 11 studies including 5,945 cases and 6,404 controls were included in the analysis of the association between -137 C/G and T1D risk. No significant association between -137 C/G and T1D risk was observed in the total population [C vs. G: odds ratio (OR)=1.02, 95% confidence interval (CI)=0.87-1.20; CC + CG vs. GG: OR=1.05, 95% CI=0.87-1.25; CC vs. CG + GG: OR=0.96, 95% CI=0.68-1.36]. No significant association was identified in the stratified analysis for all the genetic models in the European population. Concerning -607 A/C, 10 studies involving 3,048 patients and 3,377 controls were included in this meta-analysis. When all the studies were pooled, the results showed no evidence for a significant association between IL-18 -607 A/C polymorphism and T1D risk (A vs. C: OR=0.93, 95% CI=0.81-1.06; AA + AC vs. CC: OR=0.99, 95% CI=0.89-1.10; AA vs. AC + CC: OR=0.81, 95% CI=0.60-1.09). In addition, similar results were obtained in the subgroup analysis based on ethnicity. In summary, the present meta-analysis suggests a lack of association between the two polymorphisms (-137 C/G, -607 A/C) in the IL-18 gene and T1D. Due to the limitation of the number of the studies, the conclusions drawn should be considered with caution. Larger scale primary studies are required to evaluate the association between IL-18 gene polymorphisms and T1D.

Effector and regulatory T cell subsets in diabetes-associated inflammation. Is there a connection with ST2/IL-33 axis? Perspective

Type 1 diabetes (DM1) is a chronic inflammatory disease, which when progresses leads to the development of late vascular complications. The disease involves impairments in regulatory and effector subsets of T lymphocytes, which suppress and maintain inflammatory response, respectively. ST2/IL-33 pathway is involved in T-cell-mediated immune response and might regulate the inflammatory process in several diseases. This review presents the latest research findings regarding effector and regulatory T cell subsets in the context of inflammation accompanying DM1 with particular focus on the ST2/IL-33 network and its possible association with T cell-mediated immunity.

Polymorphisms in the IL-18 and IL-12B genes and their association with the clinical outcome in Croatian patients with Type 1 diabetes

Genetic variants of IL-18 and IL-12B may be important in immunoregulatory abnormalities, observed in the patients with Type 1 diabetes mellitus (T1DM), that contribute to individual differences in response to a treatment. Therefore, we examined the significance of IL-18-137G/C, IL-18-607C/A, and IL-12B A/C polymorphisms in Croatians (187 patients, 236 controls), not only as factors that contribute to susceptibility to T1DM, but also as determinants of the clinical presentation of disease. The polymorphism screening has been performed using PCR sequence-specific primers (IL-18) or PCR-RFLP (IL-12B) approach. Results were evaluated by GraphPad Prism and Sigma Stat 3.5, Arlequin software and calculator for Hardy-Weinberg equilibrium. The genotype, allele and haplotype distribution were not statistically different between the patients and control subjects. The clinical parameter analysis revealed that patients with minor alleles at each locus, IL-18-137C/-607A, were significantly younger at T1DM onset than carriers of major alleles, IL-18-137G/-607C (20 vs 23.5 years). Moreover, the concomitant presence of minor alleles not only of IL-18 but also of IL-12B, is associated with the risk of disease progression even at younger age. These patients developed diabetes at 16 years of age, what is significantly earlier (p=0.044) compared to 25.5 years of age in patients with common alleles IL-18-137G/-607C/IL-12B A. Furthermore, combined genotype analysis of IL-18 and IL-12B has pointed out that patients with CC/AA/AA genotype have the worst glucose control based on HbA1c (8.7%, range 6.8-13.1%). In conclusion, susceptibility to T1DM in Croatians is not strongly associated with IL-18-137/-607 and IL-12B polymorphisms. These SNPs are associated with the higher risk of earlier disease development and might be implicated in the effectiveness of glycemic control.

Lack of association of interleukin-18 gene promoter -607 A/C polymorphism with susceptibility to autoimmune diseases: a meta-analysis

OBJECTIVE

Published data on the association between interleukin (IL)-18 gene promoter -607 A/C polymorphism and autoimmune diseases risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed.

METHODS

A total of 17 studies, including six studies on type 1 diabetes (T1D), four on rheumatoid arthritis (RA), five on systemic lupus erythematosus (SLE), three on Crohn's Disease (CD) and three on ulcerative colitis (UC), were available for the meta-analysis. Meta-analysis was performed for genotypes A/A (recessive effect), genotypes A/A + A/C (dominant effect), and A allele in fixed or random-effects models.

RESULTS

Overall, no significantly elevated autoimmune diseases risk was found in all genetic models when all studies were pooled into the meta-analysis. The overall odds ratios (ORs) and 95% confidence intervals (CIs) for A-allele were T1D (OR = 0.938, 95% CI = 0.757-1.162), RA (OR = 0.759, 95% CI = 0.540-1.067), SLE (OR = 0.858, 95% CI = 0.609-1.208), CD (OR = 1.159, 95% CI = 0.975-1.379) and UC (OR = 1.170, 95% CI = 0.977-1.402), respectively. In the subgroup analysis by ethnicity, there was still no significant association detected in all genetic models.

CONCLUSIONS

To date, there is still not enough evidence to indicate the association of IL-18 gene promoter -607 A/C polymorphism and the development of autoimmune diseases.

Interleukin-18 promoter polymorphisms and risk of Parkinson's disease in a Han Chinese population

The etiology of sporadic Parkinson's disease (PD) is not well established. Interleukin-18 (IL-18), a member of pro-inflammatory cytokines, might influence the risk of sporadic PD occurrence and development. In this study, two DNA polymorphisms at interleukin (IL)-18 promoter, -607C/A (rs1946518) and -137G/C (rs187238), were examined in sporadic PD patients in a Han Chinese population with 290 sporadic PD patients and 200 healthy controls. Direct sequencing was performed in 10% of the samples to validate the genotyping results. The results revealed that for -607C/A polymorphisms, there were significant differences in genotype distribution between PD and control in the total sample (P=0.017) and between LOPD and healthy-matched controls subgroup (P=0.011). For -137G/C polymorphisms, there were no significant differences in genotype distribution and gender and age-related differences between PD and control in the total sample (P=0.610). Results in this study revealed that the IL-18 607C/A polymorphism is a risk factor for sporadic LOPD in Han Chinese population, while IL-18 137G/C polymorphism is not a risk factor for sporadic PD in the Han Chinese population.

Association of polymorphisms in the IL-18 and IL-12 genes with susceptibility to Type 1 diabetes in Turkish patients

BACKGROUND

Recent studies have indicated that polymorphisms of the interleukin-18 (IL-18) and interleukin- 12 (IL-12) genes are associated with the development of Type 1 diabetes mellitus (T1DM) in some populations, but not all.

AIM

The present study was designed to examine the roles of polymorphisms in the IL-18 promoter and IL-12p40 with respect to susceptibility to T1DM in Turkish patients.

SUBJECTS AND METHODS

Ninety-one patients with T1DM and 87 unrelated healthy subjects were included in the study. The IL-18 polymorphisms at positions -607 and -137 were detected by a sequence-specific PCR method. The single nucleotide polymorphism in the IL-12p40 3' untranslated region (3'-UTR) at position +1188 was analyzed by the PCR-restriction fragment length polymorphism (RFPL) method.

RESULTS

The allelic and genotypic frequencies of the IL-18 and IL-12p40 polymorphisms did not differ significantly between subjects with T1DM and the controls (p>0.05). However, diabetic patients with the -137 (CC) genotype showed a younger onset age compared to patients with the -137 (GG) genotype (p=0.02). In addition, patients with the -607 (CC) genotype had higher levels of glycated hemoglobin (HbA1c) than patients with the -607 (AC) genotype (p=0.004). Furthermore, patients with the IL-12p40 (AC) genotype had higher HbA(1c) levels than patients with the IL-12p40 (AA) genotype (p=0.01).

CONCLUSIONS

The results of the present study show that the IL- 18 and IL-12p40 polymorphisms may have some effect on the onset age and deterioration of glycemic control in Turkish patients with T1DM.

Association between IL-18 gene polymorphisms and biopsy-proven giant cell arteritis

INTRODUCTION

The objective was to investigate the potential implication of the IL18 gene promoter polymorphisms in the susceptibility to giant-cell arteritis (GCA).

METHODS

In total, 212 patients diagnosed with biopsy-proven GCA were included in this study. DNA from patients and matched controls was obtained from peripheral blood. Samples were genotyped for the IL18-137 G>C (rs187238), the IL18-607 C>A (rs1946518), and the IL18-1297 T>C (rs360719) gene polymorphisms with polymerase chain reaction, by using a predesigned TaqMan allele discrimination assay.

RESULTS

No significant association between the IL18-137 G>C polymorphism and GCA was found. However, the IL18 -607 allele A was significantly increased in GCA patients compared with controls (47.8% versus 40.9% in patients and controls respectively; P = 0.02; OR, 1.32; 95% CI, 1.04 to 1.69). It was due to an increased frequency of homozygosity for the IL18 -607 A/A genotype in patients with GCA (20.4%) compared with controls (13.4%) (IL18 -607 A/A versus IL18 -607 A/C plus IL18 -607 C/C genotypes: P = 0.04; OR, 1.59; 95% CI, 1.02 to 2.46). Also, the IL18-1297 allele C was significantly increased in GCA patients (30.7%) compared with controls (23.0%) (P = 0.003; OR, 1.48; 95% CI, 1.13 to 1.95). In this regard, an increased susceptibility to GCA was observed in individuals carrying the IL18-1297 C/C or the IL18-1297 C/T genotypes compared with those carrying the IL18-1297 T/T genotype (IL18-1297 C/C plus IL18-1297 T/C versus IL18-1297 T/T genotype in GCA patients compared with controls: P = 0.005; OR, 1.61; 95% CI, 1.15 to 2.25). We also found an additive effect of the IL18 -1297 and -607 polymorphisms with TLR4 Asp299Gly polymorphism. The OR for GCA was 1.95 for combinations of genotypes with one or two risk alleles, whereas carriers of three or more risk alleles have an OR of 3.7.

CONCLUSIONS

Our results show for the first time an implication of IL18 gene-promoter polymorphisms in the susceptibility to biopsy-proven GCA. In addition, an additive effect between the associated IL18 and TLR4 genetic variants was observed.

Association of IL-18 promoter polymorphism with liver disease severity in HCV-infected patients

INTRODUCTION

Interleukin (IL)-18 plays an important dual role in Th1 polarization and viral clearance, as well as in the development of liver fibrosis. Single-nucleotide promoter polymorphisms influence the transcription of IL-18 mRNA. Promoter polymorphisms are linked to delayed virus clearance and disease susceptibility in many diseases. However, there is no information about their role in hepatitis C virus (HCV) infection.

AIM

To investigate the association between -607 or -137 polymorphism with susceptibility and severity of HCV infection.

PATIENTS AND METHODS

Two hundred and four serologically proven patients with chronic HCV infection and 350 matched healthy controls were included in this study. Patients were segregated in 2 groups: group A with mild liver disease and group B with severe liver disease on the basis of histological activity index (HAI </=5 or >5) and hepatic fibrosis score (</=2 or >2). IL-18 promoter genotyping was performed with sequence-specific primers.

RESULTS

There was no significant difference in the frequencies of -607 and -137 allelic distribution in patients and controls. The -607 A/A allele was more common in group A patients with mild liver disease than in patients with severe liver disease on the basis of HAI (38.6% vs. 21%, P = 0.05; odds ratio [OR] = 0.424, confidence interval [CI] = 0.233-0.773; R (2) = 0.631) and stage of fibrosis (38.7% vs. 16.7%, P = 0.008; OR = 0282, CI = 0.134-0.596; R (2) = 0.434).

CONCLUSIONS

IL-18 promoter polymorphism at -607 position with A/A allele is a potential protective marker, as it is associated with milder liver disease in patients with chronic HCV infection.

Head and neck squamous cell carcinoma is not associated with interleukin-18 promoter gene polymorphisms: a case–control study

Objective:

To investigate the association of two functional single nucleotide polymorphisms in the promoter region of the interleukin-18 gene, at positions −607 and −137, with head and neck squamous cell carcinoma.

Design:

Genomic deoxyribonucleic acid was extracted, by the salting-out method, from peripheral blood leukocytes. Single nucleotide polymorphisms of the interleukin-18 gene at positions −607 (cytosine/adenine) and −137 (guanine/cytosine) were analysed by sequence-specific polymerase chain reaction.

Subjects:

One hundred and eleven patients (86 men and 25 women; mean age 56.7±13.7 years) and 212 regional controls (165 men and 47 women; mean age 53.3±12.2 years) were studied. Control subjects comprised healthy volunteers or cancer-free individuals presenting with otolaryngological disease. The diagnosis of squamous cell carcinoma was confirmed histopathologically. Various clinical parameters were collected at diagnosis, including tumour site, tumour size, lymph node involvement, distant metastasis and stage.

Results:

There was no significant association between the allele, genotype or haplotype frequencies of the two single nucleotide polymorphisms of the interleukin-18 promoter and the head and neck squamous cell carcinoma susceptibility or clinical parameters at diagnosis.

Conclusion:

Interleukin-18 polymorphisms at positions −607 and −137 did not confer susceptibility to head and neck squamous cell carcinoma in southern Iranian patients.

T cell cytokine gene polymorphisms in canine diabetes mellitus

Insulin-deficiency diabetes in dogs shares some similarities with human latent autoimmune diabetes of adults (LADA). Canine diabetes is likely to have a complex pathogenesis with multiple genes contributing to overall susceptibility and/or disease progression. An association has previously been shown between canine diabetes and MHC class II genes, although other genes are also likely to contribute to the genetic risk. Potential diabetes susceptibility genes include immuno-regulatory TH1/TH2 cytokines such as IFNgamma, IL-12, IL-4 and IL-10. We screened these candidate genes for single nucleotide polymorphisms (SNPs) in a range of different dog breeds using dHPLC analysis and DNA sequencing. Thirty-eight of the SNPs were genotyped in crossbreed dogs and seven other breed groups (Labrador Retriever, West Highland White Terrier, Collie, Schnauzer, Cairn Terrier, Samoyed and Cavalier King Charles Spaniel), which demonstrated substantial intra-breed differences in allele frequencies. When SNPs were examined for an association with diabetes by case:control analysis significant associations were observed for IL-4 in three breeds, the Collie, Cairn Terrier and Schnauzer and for IL-10 in the Cavalier King Charles Spaniel. These results suggest that canine cytokine genes regulating the TH1/TH2 immune balance might play a contributory role in determining susceptibility to diabetes in some breeds.

Association of interleukin-18 polymorphisms and plasma level with the outcome of chronic HCV infection

Hepatitis C virus (HCV) infection is the main cause of chronic liver disease throughout the world, and may progress to cirrhosis and hepatocellular carcinoma (HCC). Immunological factors, especially cytokines and some host genetic variations, rather than direct HCV action, seem to play an important role in the pathogenesis of HCV infection. Elevated levels of interleukin-18 (IL-18) were described previously for chronically (HCV)-infected patients. This study is aimed at investigating IL-18 promoter polymorphisms (-607C/A and -137G/C) in HCV-infected patients with different disease severities (chronic hepatitis C, liver cirrhosis and HCC) and establishing an association between these polymorphisms and IL-18 plasma concentration with the outcome of chronic HCV infection. The carriage of at least one C allele at position -607 (CC + CA) was associated with a higher risk of cirrhosis and HCC (P = 0.032). Compared with controls, HCV-infected patients had significantly higher levels of IL-18 (P = 0.0001) that correlate with disease severity (P = 0.01, P = 0.001, P = 0.0006, respectively). In conclusion, we supposed a possible implication of IL-18 promoter polymorphisms in the pathogenesis of chronic HCV infection.

Genetic polymorphisms in susceptibility to Type 1 Diabetes

Type 1 Diabetes is a serious complex disease caused by several environmental and genetic factors. It is one of most common childhood diseases, requires life-long treatment, and is associated with increased mortality, mainly due to complications that occur later in life. More than three decades of genetic studies have identified several genetic disease variants and a longer list of putative associated genetic loci. These findings have greatly increased our understanding of the genetic background of T1D and have encouraged the development of genetic tools for mapping complex diseases. Here we review the wealth of data on T1D and discuss the major genetic polymorphisms involved in the disease. We place some putative genetic risk factors in perspective and look at those still to be detected.

Association of interleukin-18 gene polymorphism (-607A/A genotype) with susceptibility to chronic hepatitis B virus infection

Polymorphisms in the gene promoter can lead to different levels of cytokine expression and let some individuals have unique immune responses. Therefore, the association of single nucleotide polymorphism of interleukin (IL)-18 promoter region in chronic hepatitis B virus (HBV) infection was examined. The results demonstrated the significant involvement of genotype A/A at position -607 in patients (n = 140) when compared with healthy individuals (n = 140) [OR (95% CI) = 2.62 (1.36-5.09), P(c)= 0.009]. The frequencies of -607A/A, C/A, C/C genotypes were 27.86%, 48.57% and 23.57% in chronic HBV patients and 12.80%, 59.30% and 27.90% in healthy controls, respectively. No significant association at the position -137 was found between the two groups. The frequencies of -607A/-137G haplotype homozygosity were higher in the chronic HBV patients (17.14%) than in the controls (8.57%) [OR (95% CI) = 2.21 (1-4.93), P = 0.05], although this was not statistically significant when corrected for multiple comparison (P(c)= 0.40). In conclusion, this study proposes that A/A genotype at position -607 in IL-18 gene can be used as a new genetic maker in Thai population for predicting chronic hepatitis B development.

Analysis of Candidate Susceptibility Genes in Canine Diabetes

Canine diabetes is a complex genetic disease of unknown aetiology. It affects 0.005-1.5% of the canine population and shows a clear breed predisposition with the Samoyed being at high risk and the Boxer being at low risk of developing the disease. Canine diabetes is considered to be a disease homologue for human type 1 diabetes (T1D). It results in insulin deficiency as a consequence of autoimmune destruction of islet beta-cells in the pancreas and is believed to be mediated by Th1 cytokines (IFNgamma, TNFalpha, and IL-2). A number of genes have been associated with type 1 diabetes in humans, including the human leukocyte antigen region, the insulin variable number tandem repeat, PTPN22, CTLA4, IL-4, and IL-13. As yet, these genes have not been evaluated in canine diabetes. In this study, 483 cases of canine diabetes and 869 controls of known breed were analyzed for association with IFNgamma, IGF2, IL-10, IL-12beta, IL-6, insulin, PTPN22, RANTES, IL-4, IL-1alpha and TNFalpha. Minor allele frequencies were determined for these genes in each breed. These data were used for comparative analyses in a case-control study, and clear associations with diabetes were identified in some breeds with certain alleles of candidate genes. Some associations were with increased susceptibility to the disease (IFNgamma, IL-10, IL-12beta, IL-6, insulin, PTPN22, IL-4, and TNFalpha), whereas others were protective (IL-4, PTPN22, IL-6, insulin, IGF2, TNFalpha). This study demonstrates that a number of the candidate genes previously associated with human T1D also appear to be associated with canine diabetes and identifies an IL-10 haplotype which is associated with diabetes in the Cavalier King Charles Spaniel. This suggests that canine diabetes is an excellent comparative and spontaneously occurring disease model of human T1D.

IL-18 gene promoter ?137C/G and ?607C/A polymorphisms in Chinese Han children with type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is a heterogeneous autoimmune disease, and both environmental and genetic factors play a role in its pathogenesis. Interleukin (IL)-18 is a potent pro-inflammatory cytokine capable of inducing interferon-gamma production that is associated with the development of T1DM. The gene for IL-18 is located on chromosome 11q22.2-q22.3 and has been reported to be associated with a susceptibility to T1DM. To test the putative involvement between IL-18 gene polymorphism and predisposition to T1DM, we conducted a case-control study in Chinese Han children. The single nucleotide polymorphisms at position -607(C/A) and -137(C/G) in the promoter region of the IL-18 gene were analysed by sequence-specific primers-polymerase chain reaction in 118 patients with T1DM and 150 healthy controls. (1) The allele frequency of -607A was 41.2% and 53.0%, respectively, in patients and in control subjects (P = 0.01), but the allele frequency of -137C/G was not statistically significant (P = 0.37). (2) The distribution of CC genotype at position -607 was significantly different between patients and normal controls (P = 0.03), while the distribution of AA genotype in patients was significantly lower than that in the controls (P = 0.03). (3) Furthermore, there was a significant increase in haplotype (-137C/-607G) and genotype combination (-137GG/ -607CC) in patients compared with controls (P = 0.03 and P = 0.04, respectively). The results of this study show that IL-18 gene promoter polymorphisms confer susceptibility to T1DM in Chinese Han children. Moreover, subjects carrying AA genotype at position -607 of the promoter of IL-18 gene may be a low risk of T1DM development.

Interleukin-18 genetics and inflammatory disease susceptibility

IL18 was mapped to 11q22.2-22.3 in 1998. Owing to interleukin (IL)-18's important and novel role in immunomodulation, the gene itself has been subject to scrutiny, with the aim of discovering variants that may impact on disease susceptibility and/or progression. Despite being sequenced numerous times in different populations, no non-synonymous variants have been found. However, a number of polymorphisms within the proximal promoter have been verified that may interfere with transcription-factor-binding sites. Much of the subsequent association analyses have centred on these variants, but have yielded no consistent results, despite numerous different study populations being genotyped. IL18 has recently been resequenced in its entirety, enabling the tagging-single-nucleotide polymorphism (tSNP) methodology to be adopted. This approach has yielded interesting results, with genetic variation being shown to affect protein levels, and risk. This review aims to compile and reflect on the association data of interest published to date, with a focus on the diseases related to aberrant inflammatory control.

Interleukin-18 gene promoter polymorphisms and recurrent spontaneous abortion

BACKGROUND

IL-18 is a multifunctional cytokine capable of inducing either Th1 or Th2 polarization depending on the immunologic milieu. IL-18 is detected at the materno-fetal interface very soon in early pregnancy. Two polymorphisms in the promoter region of the IL-18 gene at positions of -607 and -137 appear to have functional impacts.

OBJECTIVE

This study attempts to evaluate the frequency of these two polymorphisms in the IL-18 gene promoter in patients with recurrent spontaneous abortion (RSA) and normal pregnant women.

SUBJECTS AND METHODS

One hundred and two RSA patients and 103 healthy pregnant women were enrolled in this study. Single nucleotide polymorphisms of the IL-18 gene at positions -607 (C/A) and -137 (G/C) were analyzed by the sequence-specific PCR method.

RESULTS

There was no significant association between the allele, genotype, and haplotype frequencies of the two single nucleotide polymorphisms (SNPs) in the IL-18 gene promoter and RSA.

CONCLUSION

The results of this study showed that IL-18 gene promoter polymorphisms at positions -607 and -137 did not confer susceptibility to RSA in southern Iranian patients.