CTLA-4 +49 A/G polymorphism is associated with predisposition to type 1 diabetes in Iranians

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.

Association of CLTA-4 Gene Polymorphisms with Diabetes Mellitus: A Study Based on the Han Population of Northern China

OBJECTIVE

This study aimed to investigate the association of CLTA-4 gene polymorphism with Type 1 and 2 diabetes mellitus (DM) (T1DM and T2DM) in the Han population of northern China.

METHODS

A total of 234 Chinese Han DM patients and 187 non-diabetic subjects were included in the study. Two gene polymorphisms of the CLTA-4, including CTLA-4+49A/G (rs231775) and CTLA4-318C/T (rs5742909), were studied using polymerase chain reaction-restriction endonuclease fragment length polymorphism (PCR-RFLP) analysis. Chi-square analysis and Student's t-test were performed to determine the distribution of the gene polymorphism and alleles at the locus of CTLA4-318C/T and CTLA4+49A/G among T1DM and T2DM patients with or without diabetic ketosis (DK), diabetic nephropathy (DN) or autoantibodies (Ab).

RESULTS

Our results indicated that the distribution frequencies of genotypes and alleles at the CTLA-4+49A/G and CTLA4-318C/T loci of T1DM patients were not significantly different from those of the controls. However, the distribution frequencies of genotypes and alleles at the CTLA-4+49A/G loci of T2DM patients were significantly different from the controls (P=0.024 for genotypes and P=0.004 for A and G alleles). Besides, the A and G alleles at the CTLA4-318C/T loci of T2DM DK+ patients showed significantly different distribution frequencies compared to those of the T2DM DK patients (P=0.001).

CONCLUSION

Our data suggest that the gene polymorphisms of CTLA-4, including CTLA-4+49A/G and CTLA4-318C/T, are important predictors of DM. CTLA-4 may be a susceptibility gene for T2DM. Patients with T2DM carrying the T allele at the CTLA4-318 C/T locus are more predisposed to diabetic ketosis.

CTLA-4 (+49A/G) Polymorphism in Type 1 Diabetes Children of Sudanese Population

Background  Type 1 diabetes mellitus (T1DM) is an organ-specific T cell-mediated autoimmune disease, characterized by destruction of pancreatic islets. Cytotoxic lymphocyte antigen-4 ( CTLA-4 ) is a negative regulator of T cell proliferation, thus conferring susceptibility to autoimmunity.

Aims  This study aimed to investigate the association of CTLA-4 +49A/G (rs231775) polymorphism with a risk of T1DM in Sudanese children.

Methods  This a case–control study included 100 children with T1DM, referred to the pediatric clinic at referral pediatric teaching hospital in Gezira State-Sudan. Hundred unrelated healthy controls were recruited from departments in the same hospital. Genomic deoxyribonucleic acid (DNA) was extracted from Ethylenediaminetetraacetic Acid (EDTA)-preserved blood using QIAamp DNA Blood Mini Kit (QIAamp Blood) (QIAGEN; Valencia, CA). The polymerase chain reaction PCR restriction fragment length polymorphism (PCR-RFLP) and sequencing were applied for the CTLA-4 (+49A/G) genotyping. The changes accompanied the polymorphism were evaluated using relevant bioinformatics tools.

Results  The genotype and allele frequencies of the CTLA-4 (+49A/G) polymorphism were significantly different between the patients and controls ( p  = 0.00013 and 0.0002, respectively). In particular, the frequency of the G allele, GG homozygous genotype, and AG heterozygous genotype were significantly increased in patients than in controls ([28% versus 7%, odds ratio (OR) = 5.16, 95% confidence interval [CI] = 2.77–9.65, p  = 0.00] [12% versus 2%, OR = 6.68, CI = 1.46–30.69, p  = 0.01] [32% versus 10%, OR = 4.24, CI = 1.95–9.21, p  = 0.00], respectively). The presence of the G allele (homozygous) showed an influence on the signal peptide polarity, hydrophobicity, and α-helix propensity of the CTLA-protein.

Conclusion  The results further support the association of CTLA-4 (+49A/G) polymorphism and the risk of T1DM in our study population.

Association of CTLA-4 and CD28 Gene Polymorphisms with Type 1 Diabetes in South Indian Population

Each functional gene illustrates the complexity of genetic predisposition to disease; however, it is difficult to bring out these traits with reference to autoimmune diseases like type 1 diabetes (T1D). To find out the genetic contribution of CTLA-4 + 49A/G, CTLA-4 -318C/T and CD28 + 17T/C polymorphisms toward T1D, the present study was performed with 124 T1D patients, 54 siblings and 125 parents including 39 trios in South Indian population. The association and linkage of CTLA-4 + 49A/G, CTLA-4 -318C/T and CD28 + 17T/C polymorphisms with T1D were analyzed and transmission disequilibrium test was performed. CTLA-4 G allele carrying genotypes (GG+AG) showed a higher risk association and can be considered as susceptible to develop T1D among patients with age at diagnosis from 0 to 10 years as compared to siblings (OR = 2.9; p_c = 0.047) and parents (OR = 2.7; p_c = 0.036). On the other hand, a strong protection against the disease (age at diagnosis; 0-10 years) was observed with CTLA-4 + 49AA genotype (OR = 0.37; p_c = 0.036) and combined AA/CC genotype (OR = 0.31; p_c = 0.034) of CTLA-4 + 49A/G and CTLA-4 -318C/T polymorphisms. However, a significant association was not observed between CTLA-4 -318C/T and CD28 + 17T/C polymorphisms and T1D. This family-based study reports a strong association between possible genotypes of CTLA-4 gene polymorphism and T1D in South Indian population, particularly in younger individuals.

The Relationship between insulin variable number of tandem repeats (INS-VNTR) -23 A/T and cytotoxic Tlymphocyte associated protein-4 (CTLA-4) +49 A/G polymorphisms with islet autoantibodies in persons with diabetes

Background: Both genetic and environmental factors are important in pathogenesis of diabetes. Non HLA (Human Leukocyte Antigen) genes such as INS-VNTR and CTLA-4 in addition of HLA genes have influence on genetic susceptibility for diabetes mellitus. In this study the association of +49 A/G CTLA-4 and -23 A/T INS-VNTR polymorphisms with diabetes and their association with islet autoantibodies were investigated. Methods: Thirty four autoantibody positive adult persons with diabetes mellitus and 39 persons with Type 1diabetes mellitus (T1DM), 40 autoantibody negative Type 2 diabetes mellitus (T2DM) patients and 40 healthy controls were studied using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) technique. Results: The frequencies of -23 A/T INS-VNTR genotypes were not significantly different among study groups. It was shown that the distribution of the +49A/G CTLA-4 allele and genotype frequencies did not differ between T1DM patients, autoantibody positive adult patients and controls. With increasing CTLA-4 G allele and GG/AG genotypes, the frequency of Glutamic Acid Decarboxylase Autoantibody (GADA), Islet Cell Autoantibody (ICA) and Islet Antigen 2 Antibody (IA2A) positive patients were increased. Conclusion: Our results suggest that susceptibility allele A of -23A/T INS-VNTR does not have any role in the pathogenesis of diabetes in our patients and susceptibility allele G of +49 A/G CTLA-4 if not, has a small role in pathogenesis of diabetes in T1DM and autoantibody positive adult patients and in spite of significant increase in autoantibody negative T2DM group it does not have any role in disease pathogenesis.

Association study of IL2RA and CTLA4 Gene Variants with Type I Diabetes Mellitus in children in the northwest of Iran

Introduction: A variety of genetic predisposing factors and environmental factors are known to influence the pathogenesis of type-1 diabetes (T1D). This study intended to investigate the association of cytotoxic T-lymphocyte associated protein 4 (CTLA4) and interleukin 2 receptor subunit alpha (IL2RA) gene polymorphisms with type 1 diabetes in children of northwest of Iran. Methods: Genomic DNA was extracted by salting-out method. PCR amplification and direct sequencing methods were used for genotyping of CTLA4 (exon 1) and IL2RA (intron 1) genes in all patients and controls. SNPStats was used to calculate odds ratios (ORs), 95% confidence intervals (CIs), and p values. Results: In this study, the frequency of G allele and GG genotype of CTLA-4 (+49A/G) polymorphism in T1D patients were significantly different from those in the controls (26% vs. 11%, p = 0.006). Moreover, a significant difference was observed between patients and control group in the allele frequencies of the new SNP (chr2:203868145) that was identified in exon one of CTLA4 (14% vs. 3%, p = 0.006). The results showed that the GG homozygous genotype of +49 A>G was associated with increased glycemic level in T1D patients in the study population (95% CI = 10.47, p = 0.0067). However, no significant association was found between IL2RA (ss52580101C>A) polymorphism and T1D patients (2% vs. 4%, p = 0.41). Conclusion: The results further support the association of T1D with +49A>G SNP in the CTLA4 gene in the population of northwest of Iran. However, no significant relationship was observed between ss52580101C>A polymorphism of IL2RA gene and T1D in this study.

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.

Association of CTLA-4 gene 49A/G polymorphism with the incidence of type 1 diabetes mellitus in the Iranian Kurdish population

Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) has an inhibitory function on T cells and is critical for the induction of peripheral tolerance. CTLA-4 +49 G allele affects the CTLA-4 function and has been reported to be correlated with a higher risk of various autoimmune diseases including type 1 diabetes (T1D). The present study was conducted to investigate the association between the polymorphism of the CTLA-4 exon 1+49 A/G and susceptibility to TID and type 2 diabetes (T2D) in Kurds living in Iranian Kurdistan. The+49 A/G polymorphism was analyzed in 60 patients with T1D, 56 patients with T2D and 107 control subjects using PCR Single-strand Conformation Polymorphism (SSCP) and restriction fragment length polymorphism methods. All studied populations (T1D, T2D and Controls) were in Hardy-Weinberg equilibrium (p, 0.39, 0.94 and 0.89, respectively). Both+49 G allele (p = 0. 015, OR = 1.86) and +49 A/G genotype frequencies (p = 0. 012, OR = 2.31) were significantly higher in T1D patients than control. There was significant over-representation of the G allele in female T1D patients. No significant differences in +49 G allele and +49 A/G genotype frequencies were found between T2D and control subjects. SSCP analysis did not show new mutation in the amplified segment. The results of this study indicate that CTLA-4+49 A/G gene polymorphism confers genetic susceptibility to T1D but not T2D in the Kurdish population living in Iranian Kurdistan and women carrying the +49 G allele are at greater risk of getting T1D than men having the G allele.

Common variants on cytotoxic T lymphocyte antigen-4 polymorphisms contributes to type 1 diabetes susceptibility: evidence based on 58 studies

In the past decade, a number of case–control studies have been carried out to investigate the relationship between the CTLA4 gene polymorphisms and type 1 diabetes (T1D). However, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of all available studies dealing with the relationship between the CTLA4 polymorphism and T1D. In total, 58 association studies on two CTLA4 polymorphisms (G49A and C60T) and risk of T1D, including a total of 30,723 T1D cases and 45,254 controls were included. In a combined analysis, the summary per-allele odds ratio (OR) for T1D of the G49A and C60T polymorphism was 1.42 [95% confidence interval (CI): 1.31–1.53, P<10⁻⁵] and 1.23 (95% CI: 1.18–1.29, P<10⁻⁵), respectively. Significant results were also observed using dominant or recessive genetic model. In the subgroup analysis by ethnicity and sample size, significantly increased risks were also found for these polymorphisms. This meta-analysis demonstrated that the G49A and C60T polymorphism of CTLA4 is a risk factor associated with increased T1D susceptibility, but these associations vary in different ethnic populations.

Association of CTLA4 gene polymorphism (rs5742909) with cervical cancer: a meta-analysis

Previous studies suggested that CTLA4 polymorphism (rs5742909) is associated with susceptibility to cervical cancer. In the present study, we performed a meta-analysis to systematically summarize the possible association between rs5742909 and the risk for cervical cancer. We conducted a search of case–control studies on the associations of rs5742909 with susceptibility to cervical cancer in PubMed, EMBASE, ISI Web of Science, Cochrane Central Register of Controlled Trials, Wanfang database in China, and Chinese National Knowledge Infrastructure databases. We extracted the data from eligible studies for meta-analysis. The association of cervical cancer risk with rs5742909 was estimated by pooled odds ratios (ORs) and 95 % confidence intervals (95 % CIs). There were four studies on rs5742909 and cervical cancer in our meta-analysis. Our results suggested that both T allele frequency (OR = 1.63, 95 % CI 1.06-2.50; P = 0.03) and (TT + CT) genotype distribution (OR = 1.72, 95 % CI 1.07-2.77; P = 0.03) of the rs5742909 were associated with risk for cervical cancer. This meta-analysis suggests that rs5742909 is associated with the risk of cervical cancer. Well-designed studies with larger sample size and more ethnic groups are required to further validate the results.

CTLA-4 (+49A/G) polymorphism and type-1 diabetes in Turkish children

OBJECTIVE

To evaluate the contribution of cytotoxic T-Iymphocyte antigen-4(CTLA-4)+49A/G polymorphism to the susceptibility to type-1 diabetes (T1D) in Turkish children.

METHODS

A case-control study was designed to include 91 Turkish children with T1D and 99 healthy controls. CTLA-4 (+99A/G) gene polymorphism typing was done by PCR amplification followed by restriction fragment length polymorphism method.

RESULTS

The genotype and allele frequencies of the CTLA-4 (+99A/G)polymorphism in patients with T1D were not different from those in the controls (p>0.05). The allele frequency of G was 36.2% in patients with T1D,and 31.8% in controls (p>0.05). Additionally, this polymorphism was not associated with the clinical and laboratory characteristics of the patients with T1D (p>0.05).

CONCLUSIONS

Our case-control study suggests that the CTLA-4 (+99A/G) gene polymorphism is not associated with T1D in the Turkish population.

Association between the CTLA-4 +49A/G polymorphism and type 1 diabetes: a meta-analysis

BACKGROUND

+49A/G polymorphism of the cytotoxic T-lymphocyte-associated antigen-4 gene (CTLA-4) has been associated with type 1 diabetes (T1D). However, results were inconsistent. The aim of this study was to quantitatively summarize the evidence for CTLA-4 +49A/G polymorphism and T1D.

METHODS

Electronic search of PubMed was conducted to select studies. Case-control studies containing available genotype frequencies of CTLA-4 +49 were chosen, and the odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of this association.

RESULTS

49 case-control studies, including 8976 cases and 11012 controls, were identified. 8 studies were eliminated from the total 49 studies because of p<0.05 (p value for Hardy-Weinberg equilibrium in the control group) in these studies, which induce significant publication bias. The overall results suggested that the variant genotypes were highly associated (p<0.01) with T1D risk in all genetic models (additive model: OR 1.345, 95% CI 1.249-1.448, p<0.001; recessive model: OR 1.530, 95% CI 1.370-1.708, p<0.001; dominant model: OR 1.409, 95% CI 1.263-1.572 p<0.001). Similarly, in subgroup analyses for ethnicity (Caucasian, Asian), the results were positive.

CONCLUSION

This meta-analysis suggests that the CTLA-4 +49A/G polymorphism is highly associated (p<0.01) with increased risk of T1D, especially in Caucasians and Asians. To validate this association, further studies with more participants worldwide are needed to examine associations between this polymorphism and T1D. Otherwise, we found that the studies of Africans are rare. More studies in Africans are needed especially.

Association of cytotoxic T-lymphocyte associated antigen 4 gene polymorphism with type 1 diabetes mellitus: a meta-analysis

To evaluate the association between costimulatory molecule cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene polymorphism and type 1 diabetes mellitus(T1DM), sixty-three published studies before December, 2011 were included. Meta-analysis was performed for each genotype in a random/fixed effect model. The combined odds ratio (OR) with 95% confidence interval (95%CI) was calculated to estimate the strength of the association. Overall, significant correlation was noted between CTLA-4 gene polymorphism (i.e. +49A/G, CT60A/G in a per-allele model) and the risk of T1DM (for +49A/G: OR=1.47, 95%CI=1.36-1.60, P<0.001; for CT60A/G: OR=1.31, 95%CI=1.18-1.45, P<0.001). However, no significant association was noted between C(-318)T polymorphism and T1DM. In the subgroup analysis, for +49A/G and CT60A/G, the statistically significant associations were also demonstrated in diverse racial descents (Caucasian and Asian) and age of onset (<20 years and >20 years). In conclusion, our results suggest that CTLA-4 polymorphism contributes to the susceptibility of T1DM.

Association of CTLA-4 (+49A/G) gene polymorphism with type 1 diabetes mellitus in Egyptian children

OBJECTIVE

To investigate the distribution of cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) (+49 A/G) gene variants and the association of these variants with the clinical and laboratory findings in Egyptian children with Type-1 Diabetes (T1D).

METHODS

A case control study was done for 104 Egyptian children with T1D and 78 age and sex matched healthy control. CTLA-4 (+49 A/G) gene polymorphism typing was done by PCR amplification followed by restriction fragment length polymorphism (RFLP) method.

RESULTS

CTLA-4 G allele and GG homozygous genotype were significantly increased in T1D patients than in control group (P = 0.047, P = 0.048 respectively). There is no statistical difference between patient with optimal diabetic control (HbA1c < 8.5) and poor control (HbA1c ≥ 8.5) as regarding the CTLA-4 gene variant. The CTLA-4 GG genotype was statistically associated with younger age of patients (P = 0.027) and younger age of presentation (P = 0.036). Insignificant association was found between CTLA-4 alleles / genotypes and diabetic complications.

CONCLUSION

The CTLA-4 +49 GG homozygous genotype is associated with T1D in Egyptian children especially with younger age of onset and in younger patients, and not associated with grades of diabetic control or diabetic complication.

ctla-4 gene variations may influence cervical cancer susceptibility

BACKGROUND

CTLA-4 is the key player of the immune tolerance. Particular genotypes of ctla-4 have been reported to be associated with various diseases.

OBJECTIVE

We aimed to evaluate the role of four single nucleotide polymorphisms (SNPs) of ctla-4 gene in cervical cancer.

METHODS

55 patients and 110 healthy controls were genotyped for four polymorphic loci, three in promoter region; -1722(T/C), -1661(A/G), -318(C/T) and one in exon 1; +49(A/G) using PCR-ARMS and -RFLP methods.

RESULTS

At position -1661 the frequency of A/A homozygote and A allele were lower in patients than in controls. (P=0.01, P=0.035; respectively), while at position -318 the frequency of C/C homozygote and C allele were increased in patients (P=0.021, P=0.025; respectively). These significances, however, do not stand the Bonferroni correction suggesting that the effect of multiple comparisons should not be ignored. The haplotype analysis demonstrated 9 haplotypes, of which, 5 were observed in both groups with no significant different frequencies. The TGTA haplotype, however, was only observed in control group (9.54%, p=0.002) and the TGCG haplotype was only occurred in cervical cancer patients (6.48%, p=0.0003). The differences were still significant after Bonferroni correction.

CONCLUSION

As a conclusion TGTA haplotype as well as A allele at position -1661 might imply a protective role whereas TGCG haplotype as well as C allele at locus -318 might render susceptibility to cervical cancer. Investigation of ctla-4 gene variants in other ethnic populations will consolidate the findings of this study.

Association of PTPN22 C1858T and CTLA-4 A49G polymorphisms with Type 1 Diabetes in Croatians

In this case-control study the association between the PTPN22 1858T and CTLA-4 49G gene variants and T1D in Croatian population was examined. We found that distribution of PTPN22 C1858T and CTLA-4 A49G genotypes between T1D patient (n=102) and control (n=193) groups differ significantly (p<0.0001 and p=0.012, respectively). Moreover, although the risk alleles of both SNPs are distributed more frequently in patients, the significant difference is observed only for PTPN22 1858T allele (p<0.0001). This is therefore the first evidence that analyzed gene variants contribute to T1D pathogenesis in Croatian population.

Promoter region -318 C/ T and -1661 A/G CTLA-4 single nucleotide polymorphisms and type 1 diabetes in North Indians

Single nucleotide polymorphisms (SNPs) of the CTLA-4 gene have been associated with manifestation of type 1 diabetes in several populations. We assessed the association of five SNPs present in the CTLA-4 gene [-318C/T, -1661A/G and -1722C/T in the promoter region, +49A/G in exon 1 and CT60 in the 3' untranslated region (UTR) region] with type 1 diabetes in North Indian subjects. Genotyping was performed in the patients (n = 130) and the healthy control (n = 180) subjects by polymerase chain reaction-fragment length polymorphism analysis using MseI, BbvI, BstEII and NcoI restriction endonucleases for the -318, -1661, -1722, +49 and CT60 SNPs, respectively. The frequency of G alleles at -1661 locus was significantly higher in the patient group compared with the control subjects. Although the frequency of T alleles at -318 SNP was significantly higher in patients with type 1 diabetes compared with the controls, it did not remain significant after Bonferroni correction for the number of alleles tested. The frequencies of C/T alleles and genotypes at -1722C/T and G allele at +49A/G and CT60 SNPs were not significantly different between the patient and the control groups. Of the various possible haplotypes constructed using the five genetic loci tested (-318, -1661, -1722, +49, CT60), the frequency of 'TGTAG' haplotype was significantly higher in the patients when compared with the controls. The results of the present study indicate that the presence of G allele at -1661 locus at the CTLA-4 gene (IDDM12 locus) is associated with increased susceptibility to type 1 diabetes in North Indians, whereas A allele is protective.

Cytotoxic T lymphocyte antigen-4 promoter variants in breast cancer

CTLA4 is a coinhibitory molecule expressed mainly on activated T lymphocytes. To test the putative involvement of CTLA-4 in inhibitory state of immunity to breast cancer, we genotyped 283 patients and 245 healthy control subjects for -1722 T/C, -1661 A/G, and -318 C/T single nucleotide polymorphisms in the promoter region of the CTLA4 gene. There were no significant differences in genotype, allele, or haplotype frequencies in all three loci between patients and healthy controls. Moreover, the incidence of the most frequent haplotype combination (TAC/TAC, T -1722, A -1661, C -318) was only slightly higher among healthy controls than patients (68.4 vs. 64.8%, P = 0.2). This haplotype combination was associated with lower stages of the disease (P = 0.0007), however, and higher estrogen receptor (ER) expression in patients (P = 0.006). Association with tumor prognostic or predictive factors was also observed with certain genotypes: the -1661 AA genotype was associated with lesser lymph node (LN) involvement (P = 0.017) and higher ER expression (P = 0.004), and the -318 CC genotype with lesser LN involvement (P = 0.007). These results suggest that CTLA4 promoter variants participate in the progression of breast cancer rather than in its initial development.

Genetic association of type 1 diabetes in an Azerbaijanian population: the HLA-DQ, -DRB1*04, the insulin gene, and CTLA4

BACKGROUND

Little is known on the genetic susceptibility to type 1 diabetes mellitus (T1DM) in the nations of the former Soviet part of south-west Asia.

OBJECTIVE

The aim of the study was to characterize the genetic association of T1DM in the Azeri, the majority population of Azerbaijan.

SUBJECTS AND METHODS

One hundred and sixty patients with childhood-onset T1DM, and 271 healthy unrelated controls were compared in a case-control study. All declared themselves as Azeri. The human leukocyte antigen (HLA)-DQB1, -DQA1 alelles, of DRB1*04 subtypes, and of insulin gene and cytotoxic T-lymphocyte-associated protein 4 (CTLA4) single nucleotide polymorphisms were determined using polymerase chain reaction (PCR) techniques, the association was tested from cross-tabulations, and quantified using odds ratios (OR). In the non-HLA factors, analyses were also stratified according to the HLA-conferred risk.

RESULTS

Risk for T1DM was associated with presence of the HLA-DQB1*02-DQA1*05, OR = 6.6 [95% confidence interval (CI) 4.3-10], the HLA-DQB1*0302-DQA1*03, OR = 3.9 (95% CI 2.6-6.0), and an unexpectedly high risk was observed for DQB1*0304, OR = 10.9, but the very wide CI (CI 95% 2.4-49) prompts careful interpretation. A negative association with diabetes was observed for the DQB1*0602, 0503, 0301, and 0601 alleles, as well as the DRB1*0403 subtype. A strong protection was also associated with the less frequent variant of the insulin gene (OR of the phenotypic positivity was 0.28, CI 95% 0.17-0.46), while the CTLA4 +49 A/G transition was not associated with T1DM.

CONCLUSIONS

We bring the first report on both HLA, and non-HLA association of T1DM from the majority Azeri population of Azerbaijan.

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

AIMS

IL-18, a potent IFN-gamma-inducing cytokine, is capable of polarizing the immune response to a Th1 phenotype. Recent studies have demonstrated an association between single-nucleotide polymorphisms located at positions -607 (A/C) and -137 (C/G) in the promoter region of IL-18 gene and Type 1 diabetes. The aim of the present study was to determine whether the same polymorphisms of the gene were associated with Type 1 diabetes in Iranians.

METHODS

In 112 patients with Type 1 diabetes and 194 non-diabetic control subjects, these two single-nucleotide polymorphisms were analysed by sequence-specific PCR.

RESULTS

Allele and genotype frequencies of the IL-18 gene polymorphisms were similar in the whole group of Type 1 diabetic patients and controls. However, categorizing patients according to age at onset of diabetes revealed a significant difference in distribution of the genotypes at position -137 between patients with older age at onset (> 15 years) (GG 49%, GC 34%, CC 17%) and control subjects (GG 57.7%, GC 36.6%, CC 5.7%) (P = 0.027). Frequency of the C allele at position -137 was significantly higher in these patients than in controls (P = 0.038). Moreover, there was an association between -607AA/-137CC genotype combination and susceptibility to Type 1 diabetes in this subgroup of patients (pc = 0.027).

CONCLUSIONS

The results of this study show that polymorphisms of IL-18 promoter confer susceptibility to Type 1 diabetes in Iranian individuals with onset at older ages. Further investigations are necessary to clarify the effect of IL-18 variants on immune regulation.