Vitamin D receptor gene polymorphism and osteoporosis in the Turkish population

Osteoporosis is one of the most important medical problems facing the aging population. It is defined as a decrease in the bone mass leading to an unacceptably high risk of fractures. Osteoporosis is a multifactorial disease. It is well established that genetic factors are involved in the pathogenesis of osteoporosis. Polymorphism of the vitamin D receptor (VDR) gene has been reported to play a major role in variations for genetic regulation of bone mass. Its role within various ethnic populations is not clear. The purpose of this project was to determine the frequencies of VDR genotypes in Turkey. Three polymorphisms of the VDR gene were analyzed using the polymerase chain reaction-restriction fragment length polymorphism technique. The sample for our study was comprised of postmenopausal women in Turkey, 100 of whom were diagnosed with osteoporosis. They were compared with 146 healthy controls. BsmI genotype frequencies in Turks resemble Caucasians rather than Asians, and Taq genotype frequencies in Turks neither resemble Caucasians nor Asians. The genotype frequencies of VDR were not statistically different between patients with osteoporosis and the control group. Among VDR haplotypes, bbAATT and bbTtAa are more frequent in the osteoporosis group than the control group.     

Vitamin D receptor polymorphisms and prostate cancer risk in Brazilian men

Vitamin D seems to be an important determinant of prostate cancer risk and inherited polymorphisms in the 3'untranslated region of the vitamin D receptor (VDR) gene have been associated with the risk and progression of prostate cancer in some populations. We therefore studied VDR gene polymorphisms, as detected by Apal and Taql restriction fragments, in multiethnic Brazilian men (165 patients and 200 controls) for association with prostate cancer risk and parameters of disease severity (serum PSA, Gleason score and tumor stage). No statistical correlations were found. The unique ethnical background of Brazilian subjects, characterized by an extensive racial mixture of European, African-American and Native American, might have blunted any ethnic-specific significance of VDR polymorphisms. Further investigations of the associations between VDR and other genetic or environmental factors are warranted.     

Association of Vitamin D receptor gene variations with Gastric cancer risk in Kashmiri population

Molecular Biology Reports - Vitamin D receptor (VDR) mediates cellular processes like cell cycle arrest and apoptosis which effect cancer susceptibility. VDR single nucleotide polymorphisms (SNPs)...     

Vitamin D receptor gene polymorphisms in relation to Vitamin D related disease states

The role in skeletal metabolism of the steroid hormone Vitamin D and its nuclear receptor (VDR) is well known. In addition, however, Vitamin D is also involved in a wide variety of other biological processes including modulation of the immune response and regulation of cell proliferation and differentiation. Variations in the Vitamin D endocrine system have thus been linked to several diseases, including osteoarthritis, diabetes, cancer, cardiovascular disease and tuberculosis. Evidence to support this pleiotropic character of Vitamin D has included epidemiological studies on circulating Vitamin D hormone levels, but also genetic epidemiological studies. Genetic studies provide excellent opportunities to link molecular insights with epidemiological data and have therefore gained much interest. DNA sequence variations which occur frequently in the population are referred to as "polymorphisms" and are usually suspected of having only modest and subtle effects. Recent studies have indicated many polymorphisms to exist in the VDR gene, but the influence of VDR gene polymorphisms on VDR protein function are largely unknown. Sofar, three adjacent restriction fragment length polymorphisms (RFLP) for BsmI, ApaI and TaqI, respectively, at the 3' end of the VDR gene have been the most frequently studied sofar. But because these polymorphisms are probably non-functional, linkage disequilibrium (LD) with one or more truly functional polymorphisms elsewhere in the VDR gene is assumed to explain the associations observed. Research is therefore focussed on documenting additional polymorphisms across the VDR gene to verify this hypothesis, and on trying to understand the functional consequences of the variations. Substantial progress has been made including the discovery of novel polymorphisms in the large promoter region of the VDR gene. Eventually, results of this research will deepen our understanding of variability in the Vitamin D endocrine system and might find applications in risk-assessment of disease and in predicting response-to-treatment.     

Vitamin D receptor polymorphisms as markers in prostate cancer

Polymorphisms in the vitamin D receptor (VDR) gene have been analyzed in several studies for an association with prostate cancer (PCA) and odds ratios (OR) > or = 3 have been observed in study populations from North America. We studied three polymorphisms in the VDR gene (poly-A microsatellite, TaqI and FokI RFLPs) in 105 controls and 132 sporadic PCA cases from France and in a collection of families from Germany and France. The polymorphisms near the 3' end of the gene were in linkage disequilibrium with an almost complete coincidence of the short poly-A alleles and t (presence of the restriction site) of the TaqI polymorphism, (contingency tables, P<0.0001). An association was found by logistic regression for the poly-A between PCA and the heterozygous genotype (S/L; S < 17, L > or = 17, OR=0.44, 95% confidence interval, CI=0.198-0.966, P=0.041). OR was lower in patients < or = 70 years old and patients with a Gleason score > or = 6. The Tt genotype of the TaqI RFLP also showed an association with PCA (OR=0.5, CI=0.27-0.92, P=0.026). This association was also stronger for patients < or = 70 years old (OR=0.31, CI=0.15-0.63, P=0.001). The risk alleles were S and t alleles as indicated by the OR of the homozygotes, although these were not significant. The FokI RFLP at the 5' end of the gene did not reveal any association (P>0.7). While some association studies differ between Europe and North America, our present findings with the VDR gene agree with those from North America, indicating a weak but general role of the VDR in PCA susceptibility.     

Association of vitamin D receptor FokI and ApaI polymorphisms with lung cancer risk in Tunisian population

Many studies reported that Vitamin D Receptor (VDR) gene polymorphisms might influence the cancer risk due to their antiproliferative, antiangiogenic, and apoptotic effects. The aim of this study was to explore the genetic association of VDR polymorphisms with lung cancer risk in Tunisian population. The genotype and haplotype frequencies of four VDR polymorphisms, FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232) and TaqI (rs731236) were studied using polymerase chain reaction and restriction fragment length polymorphism analysis in 240 patients with lung cancer and 280 healthy controls. The distribution of genotype frequencies differed significantly between lung cancer subjects and controls (FokI P _adj  = 0.002; ApaI P _adj  = 0.013). Haplotype analyses revealed a significant association between G-A-C and A-C-T haplotypes and lung cancer risk (P _corr  = 0.0128, P _corr  = 0.008). When patients were stratified according to gender, age, and smoking, significant associations were detected with FokI and TaqI polymorphisms. We found a lack of association between BsmI, TaqI polymorphisms and lung cancer risk (P > 0.05). Only, the attributable proportion due to interaction and the synergic index for interaction between ApaI polymorphism and smoking were statistically significant (P _adj  = 0.74, 95 % CI = 0.38–1.20) and (P _adj  = 0.63, 95 % CI = 0.05–1.21), respectively. Both the additive interaction measures suggested the existence of a biological interaction between SNP ApaI, but not FokI, and smoking. The multiplicative interaction measure was not statistically significant (P > 0.05). This is the first study in Tunisia, which suggested that VDR FokI and ApaI polymorphisms might be risk factors for lung cancer development.     

Vitamin D receptor gene polymorphisms and susceptibility of hand osteoarthritis in Finnish women

We examined whether polymorphisms of the vitamin D receptor (VDR) gene was associated with individual risk of hand osteoarthritis (OA). Radiographs of both hands of 295 dentists and of 248 teachers were examined and classified for the presence of OA using reference images. The VDR ApaI and TaqI genotypes were determined by PCR-based methods. No association was observed between the VDR polymorphisms and the odds of overall hand OA. However, the carriers of the VDR t allele or At haplotype were at almost half the odds of symmetrical hand OA (odds ratio [OR] = 0.60, 95% confidence interval [CI] = 0.38-0.94 and OR = 0.59, 95% CI = 0.38-0.93, respectively) compared with the carriers of the T allele and of the non-At haplotype, respectively. Increased odds of this disease, on the contrary, was observed for women with two copies of the VDR a allele (OR = 1.93, 95% CI = 1.99-3.70) compared with women with the AA genotype. Conversely, the VDR a allele carriage was associated with a tendency of lowered odds of osteophyte (OR = 0.51, 95% CI = 0.25-1.03). When the genotype data were used to construct haplotypes, the VDR AaTt joint genotype appeared to pose a remarkably lower odds (OR = 0.26, 95% CI = 0.08-0.91) of osteophyte compared with the AAtt joint genotype. As a novel finding we observed a joint effect of a low calcium intake and VDR polymorphisms on symmetrical OA; the OR was 2.64 (95% CI = 1.29-5.40) for carriers of the aT haplotype with low daily calcium intake compared with non-carriers of the haplotype with high daily calcium intake. Our results suggest that VDR gene polymorphisms play a role in the etiology of symmetrical hand OA. Moreover, the association between the VDR gene and OA may be modified by calcium intake.     

Vitamin D receptor gene polymorphisms and susceptibility of hand osteoarthritis in Finnish women

We examined whether polymorphisms of the vitamin D receptor (VDR) gene was associated with individual risk of hand osteoarthritis (OA). Radiographs of both hands of 295 dentists and of 248 teachers were examined and classified for the presence of OA using reference images. The VDR ApaI and TaqI genotypes were determined by PCR-based methods. No association was observed between the VDR polymorphisms and the odds of overall hand OA. However, the carriers of the VDR t allele or At haplotype were at almost half the odds of symmetrical hand OA (odds ratio [OR] = 0.60, 95% confidence interval [CI] = 0.38–0.94 and OR = 0.59, 95% CI = 0.38–0.93, respectively) compared with the carriers of the T allele and of the non-At haplotype, respectively. Increased odds of this disease, on the contrary, was observed for women with two copies of the VDR a allele (OR = 1.93, 95% CI = 1.99–3.70) compared with women with the AA genotype. Conversely, the VDR a allele carriage was associated with a tendency of lowered odds of osteophyte (OR = 0.51, 95% CI = 0.25–1.03). When the genotype data were used to construct haplotypes, the VDR AaTt joint genotype appeared to pose a remarkably lower odds (OR = 0.26, 95% CI = 0.08–0.91) of osteophyte compared with the AAtt joint genotype. As a novel finding we observed a joint effect of a low calcium intake and VDR polymorphisms on symmetrical OA; the OR was 2.64 (95% CI = 1.29–5.40) for carriers of the aT haplotype with low daily calcium intake compared with non-carriers of the haplotype with high daily calcium intake. Our results suggest that VDR gene polymorphisms play a role in the etiology of symmetrical hand OA. Moreover, the association between the VDR gene and OA may be modified by calcium intake.     

Association of gene polymorphisms in prolactin and its receptor with breast cancer risk in Taiwanese women

Given the essential role of prolactin (PRL) and its receptor (PRLR) in breast tumorigenesis, we investigated whether single nucleotide polymorphisms (SNPs) in the PRL and PRLR genes were associated with breast cancer in Taiwanese women. A total of 160 breast cancer patients and 336 unrelated control Taiwanese women were enrolled in this study. Three SNPs (rs1341238, rs2244502 and rs3756824) in the PRL gene and one SNP (rs10941235) in the PRLR gene were genotyped using allele-specific polymerase chain reaction and DNA sequencing. We showed that the PRLR SNP rs10941235 was associated with breast cancer (P < 0.05) and its genotype frequencies in the breast cancer group were significantly associated (P < 0.05) with the levels of cancer antigen 15-3, a serum biomarker of breast cancer. The PRL SNP rs3756824 was significantly associated with breast cancer metastasis (P < 0.05). These findings suggest that the polymorphism rs10941235 in the PRLR gene is associated with breast cancer and cancer antigen 15-3 levels in Taiwanese women.     

Vitamin D receptor gene BsmI polymorphisms in Thai patients with systemic lupus erythematosus

The immunomodulatory role of 1,25-dihydroxyvitamin D3 is well known. An association between vitamin D receptor (VDR) gene BsmI polymorphisms and systemic lupus erythematosus (SLE) has been reported. To examine the characteristics of VDR gene BsmI polymorphisms in patients with SLE and the relationship of polymorphisms to the susceptibility and clinical manifestations of SLE, VDR genotypings of 101 Thai patients with SLE and 194 healthy controls were performed based on polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The relationship between VDR gene BsmI polymorphisms and clinical manifestations of SLE was evaluated. The distribution of VDR genotyping in patients with SLE was 1.9% for BB (non-excisable allele homozygote), 21.78% for Bb (heterozygote), and 76.23% for bb (excisable allele homozygote). The distribution of VDR genotyping in the control group was 1.03% for BB, 15.98% for Bb, and 82.99% for bb. There was no statistically significant difference between the two groups (p = 0.357). The allelic distribution of B and b was similar within the groups (p = 0.173). The relationship between VDR genotype and clinical manifestation or laboratory profiles of SLE also cannot be statistically demonstrated. In conclusion, we cannot verify any association between VDR gene BsmI polymorphism and SLE. A larger study examining other VDR gene polymorphisms is proposed.     

Vitamin D receptor gene BsmI, FokI, ApaI and TaqI polymorphisms and the risk of systemic lupus erythematosus

Recently, several studies have demonstrated the role of vitamin D receptor (VDR) polymorphisms in the development of systemic lupus erythematosus (SLE); however, these results are inconsistent between different cohorts. Therefore, we studied the prevalence of the VDR FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232) and TaqI (rs731236) genotypes and alleles in SLE patients (n = 258) and healthy individuals (n = 545) in a Polish population. We did not observe significant differences for either the VDR FokI, BsmI, ApaI and TaqI genotype and allele frequencies in patients with SLE and healthy individuals. However, the frequency of the VDR F/F and F/f genotypes of FokI was statistically different between patients with renal disease and patients without this symptom OR = 3.228 (1.534–6.792, p = 0.0014), p _corr = 0.0476)]. There was no association of the studied VDR BsmI, ApaI and TaqI polymorphisms with clinical manifestations and laboratory profiles in patients with SLE. Our study indicates that the studied VDR FokI variant might increase the risk of some clinical presentations in patients with SLE.     

Tumor necrosis factor alpha and beta and interferon gamma gene polymorphisms in Turkish breast cancer patients

Cytokine genes are important for researching cancer predisposition to cancers that elicit anti-tumor immune response. In this study, we investigated the association between breast cancer and tumor necrosis factor alpha (TNF-α) -308 (G>A), TNF-β +252 (A>G), and interferon gamma (IFN-γ) +874 (T>A) gene polymorphisms in a Turkish population. This study involved 204 female breast cancer patients and 204 healthy female controls. Genomic DNA was extracted from EDTA-preserved peripheral venous blood of patients and controls by a salting-out method and analyzed by polymerase chain reaction, allele-specific oligonucleotide polymerase chain reaction, and restriction fragment length polymorphism. TNF-α -308 genotype was found to have no effect on breast cancer susceptibility. However, there were statistically significant differences between the genotype frequencies of patients and controls for TNF-β polymorphism (p?=?0.016) and the allele and genotype frequencies for the IFN-γ polymorphism (p?=?0.0312 and p?=?0.001, respectively). In the composite genotype analysis, the TNF-α/β GAAG composite genotype (p?=?0.0424), the TNF-α/IFN-γ GGTT and GATT composite genotypes (p?=?0.0296 and p?=?0.0129, respectively), the TNF-β/IFN-γ AGTT composite genotype (p?=?0.0003), and the TNF-α/β/IFN-γ GGAGTT and GAAGTT composite genotypes (p?=?0.0437 and p?=?0.0038, respectively) were estimated to have a protective effect against breast cancer. However, the TNF-α/IFN-γ GGTA composite genotype is a risk factor for breast cancer (p?=?0.0156). In conclusion, TNF-β +252GG genotype was found more frequent in Turkish breast cancer patients than controls and IFN-γ TA+AA genotypes were estimated to increase breast cancer risk significantly in Turkish population.     

Vitamin D receptor polymorphisms in hypertensive disorders of pregnancy

Hypertension is the most common medical disorder in pregnancy, and a leading cause of maternal and neonatal morbidity and mortality. Vitamin D endocrine system has important influence on immune modulation and endothelial function, which play a role in preeclampsia (PE) and gestational hypertension (GH). Vitamin D receptor (VDR) is present in a large variety of cell types, including placental cells. We examined whether there is an association between VDR polymorphisms (FokI, ApaI and BsmI) with PE or with GH. Restriction fragment length polymorphism techniques were used to genotype 529 pregnant (154 with GH, 162 with PE, and 213 healthy pregnant—HP). VDR haplotype frequencies were inferred using the PHASE 2.1 program. We found similar genotype distributions for the three VDR polymorphisms in both PE and GH groups compared with the HP group (all P?>?0.05). In parallel with these findings, the VDR haplotype frequency distribution was similar in both PE and GH groups compared with the HP group (all P?>?0.05). Our results showing no significant association between VDR polymorphisms or haplotypes with PE or GH suggest that genetic variations in VDR do not predispose to hypertensive disorders of pregnancy.     

Vitamin D status and vitamin D receptor gene polymorphisms and susceptibility to type 1 diabetes in Egyptian children

Background

Type 1 diabetes mellitus (T1DM) is recognized as a T-cell-mediated autoimmune disease. Vitamin D compounds are known to suppress T-cell activation by binding to vitamin D receptor (VDR); and thus, VDR gene polymorphisms may be related to T-cell-mediated autoimmune diseases. The aim of this study was to investigate the association between vitamin D status and VDR gene polymorphisms and T1DM.

Materials and methods

One hundred and twenty patients with T1DM and one hundred and twenty controls were enrolled in the study. VDR gene BsmI, FokI, ApaI and TaqI polymorphisms were determined using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Serum 25-hydroxyvitamin D (25(OH)D) was determined using ELISA.

Result

Serum 25(OH)D levels revealed a vitamin D deficiency or insufficiency in 75% of the patients. The mean levels of vitamin D were significantly lower in patients as compared to their controls (P = < 0.001). VDR BsmI Bb and bb genotypes and VDR FokI Ff and ff genotypes were associated with increased risk of T1DM (OR = 2.3, 95% CI = 1.3–4.2, P = 0.005; OR = 2.2, 95% CI = 1.1–4.7, P = 0.04; OR = 1.8, 95% CI = 1.03–3.04, P = 0.04; OR = 4.03, 95% CI = 1.2–13.1, P = 0.01 respectively), while the VDR ApaI and TaqI polymorphisms were not.

Conclusion

Our study indicated that vitamin D deficiency and VDR BsmI and FokI polymorphisms were associated with T1DM in Egyptian children.     

Meta-analysis of vitamin D receptor gene polymorphisms and benign prostatic hyperplasia risk

The association between vitamin D receptor (VDR) gene polymorphisms and risk of benign prostatic hyperplasia (BPH) has been investigated in numerous publications, but published results remain inconclusive. Hence, we conducted this meta-analysis to derive a more precise conclusion. Four polymorphisms (Taq-I, Bsm-I, Apa-I, and Fok-I) of the VDR gene with risk of BPH from six case–control studies and one cohort study involving 2,248 individuals were identified from PubMed and China National Knowledge Internet databases up to November 20, 2013 (updated on March 5, 2014). After data extraction, the meta-analysis was performed using Comprehensive Meta-Analysis software. All four VDR polymorphisms were not associated with the risk of BPH [Taq-I: OR 0.61, 95 % CI (0.38–1.24) for tt vs. TT; Bsm-I: OR 1.27, 95 % CI (0.96–1.69) for bb vs. BB; Apa-I: OR 1.26, 95 % CI (0.64–2.46) for aa vs. AA; Fok-I: OR 0.95, 95 % CI (0.60–1.50) for ff vs. FF]. Subgroup analysis according to ethnicity for Taq-I polymorphism also showed that the polymorphism was not associated with risk of BPH for either Caucasians [OR 0.74, 95 % CI (0.31–1.78) for tt vs. TT] or Asians [OR 0.35, 95 % CI (0.11–1.11) for tt vs. TT]. However, results of this meta-analysis should be treated with caution because this meta-analysis has several limitations. We propose to conduct a high-quality study with large sample size to further identify the association between VDR gene polymorphisms and BPH susceptibility.     

RAD51 polymorphisms and breast cancer risk

Breast cancer (BC) is one of the most common causes of death among women, and second in Iran. The objectives of this study were to determine the frequency of RAD51 G/C polymorphism in patients with breast cancer. We evaluated these polymorphisms and effects on the breast cancer risk association in a Iranian sporadic population-based case?Ccontrol study of 294 breast cancer cases and 315 controls using a PCR?CRFLP-based assay. Analyses of affected and controls show that homozygote genotype RAD51 GG has the highest frequency in both groups (33.3 in patients and 41.4 in control group). Genotype RAD51 GG most risk factor were in our population: [CC/GC odds ratio, 0.364 (95?% confidence interval; CI, 0.168?C0.788) p?=?0.009, CC/GG odds ratio, 0.828 (95?% CI, 0.411?C1.668) p?=?0.596], GG/GC odds ratio, 2.276 (95?% CI, 1.497?C3.460) p?=?0.001]. There was a significant association of breast cancer risk with RAD51 GG and CC polymorphism.     

Vitamin D receptor polymorphisms in hypocalcemic vitamin D-resistant rickets carriers

BACKGROUND/AIMS: Hypocalcemic vitamin D-resistant rickets (HVDRR) is a rare autosomal recessive disorder characterized by severe rickets, hypocalcemia, secondary hyperparathyroidism, elevated levels of 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], and occasionally, alopecia. In most cases, the disease is associated with mutations in the gene of the vitamin D receptor (VDR), the mediator of 1,25(OH)(2)D(3) action. The apparently healthy HVDRR heterozygotes express both normal and mutant VDR alleles, and they present higher levels of 1,25(OH)(2)D(3) than their respective controls. Because VDR function, except for the disease-causative mutations, might be influenced by the presence of certain polymorphisms, we investigated the distribution of four common VDR polymorphisms--BsmI, ApaI, TaqI and FokI--in HVDRR carriers compared with their respective controls. METHODS: Sixty-seven relatives of 2 HVDRR patients, all members of an extended Greek kindred, were included in the study. VDR allelic polymorphisms were assessed by restriction fragment length polymorphisms after specific polymerase chain reaction amplification. RESULTS: The distribution of genotypic and allelic frequencies differed between HVDRR carriers and their respective controls regarding BsmI and TaqI polymorphisms. The bb genotype and the T allele (presence of BsmI and absence of TaqI polymorphisms) were less frequent in the HVDRR carrier group than in the control group in a statistically significant manner (p = 0.029 and p = 0.025, respectively). CONCLUSIONS: Our findings showed that the apparently healthy HVDRR carriers present a different distribution of BsmI and TaqI VDR polymorphisms than their controls, suggesting that further investigation of the HVDRR carrier population may elucidate the implication of VDR alleles in VDR function and the vitamin D endocrine system.     

Methyl-CpG binding domain 1 gene polymorphisms and lung cancer risk in a Chinese population

Polymorphisms of the methyl-CpG binding domain 1 (MBD1) gene may influence MBD1 activity on gene expression profiles, thereby modulating individual susceptibility to lung cancer. To test this hypothesis, we investigated the associations of four MBD1 polymorphisms and lung cancer risk in a Chinese population. Single locus analysis revealed significant associations between two polymorphisms (rs125555 and rs140689) and lung cancer risk (p=0.011 and p=0.005, respectively). Since the two polymorphisms were in linkage disequilibrium, further haplotype analyses were performed and revealed a significant association with lung cancer (global test p-value=0.0041). Our results suggested that MBD1 polymorphisms might be involved in the development of lung cancer. Validation of these findings in larger studies of other populations is needed.     

Association between vitamin D receptor gene polymorphisms and type 1 diabetes mellitus in Iranian population

Type 1 diabetes mellitus (T1DM) is one of the T-cell mediated autoimmune diseases and vitamin D suppresses activation of T-cell and has immunomodulatory effects. In this study the association between four vitamin D receptor (VDR) gene polymorphisms, at positions FokI, BsmI, ApaI and TaqI, and susceptibility to T1DM was investigated. We assessed 87 Iranian patients with T1DM and one hundred healthy controls with no history of diabetes or other autoimmune diseases. Our results demonstrated that genotypes frequency of the TaqI VDR polymorphism differed significantly between T1DM patients and controls, TT genotype and T allele was more frequent in healthy controls compared with TIDM patients (P = 0.003; OR = 0.51, 95% CI = 0.31–0.84). Therefore, allele t is the risk-allele for developing TIDM in this study. No significant association was observed between others VDR SNPs and disease susceptibility. In conclusion, our case-control study indicated that the VDR TaqI polymorphism is associated with TIDM in Iranian population.