The role of GSTM1, GSTT1, GSTP1, and OGG1 polymorphisms in type 2 diabetes mellitus risk: a case-control study in a Turkish population

The aim of the present study was to investigate the role of some polymorphisms in GSTs (GSTM1, GSTT1 and GSTP1) which are very important protective mechanisms against oxidative stress and in OGG1 gene which is important in DNA repair, against the risk of type 2 diabetes mellitus (T2DM). 127 T2DM and 127 control subjects were included in the study. DNA was extracted from whole blood. Analyses of GSTM1 and GSTT1 gene polymorphisms were performed by allele specific PCR and those of GSTP1 Ile105Val and OGG1 Ser326Cys by PCR-RFLP. Our data showed that GSTM1 null genotype frequency had a 2-6 times statistically significant increase in a patient group (OR=3.841, 95% CI=2.280-6.469, p<0.001) but no significance with GSTT1 null/positive and GSTP1 Ile105Val genotypes was observed. When T2DM patients with OGG1 Ser326Cys polymorphism were compared with patients with a wild genotype, a 2-3 times statistically significant increase has been observed (OR 1.858, 95% CI=1.099-3.141, p=0.021). The combined effect of GSTM1 null and OGG1 variant genotype frequencies has shown to be statistically significant. Similarly, the risk of T2DM was statistically increased with GSTM1 null (OR=3.841, 95% CI=2.28-6.469), GSTT1 null+GSTP1 (H+M) (OR=4.118, 95% CI=1.327-12.778) and GSTM1 null+OGG1 (H+M) (OR=3.322, 95% CI=1.898-5.816) and GSTT1 null+OGG1 (H+M) (OR=2.179, 95% CI=1.083-4.386) as compared to the control group. According to our study results, it has been observed that the combined evaluation of GSTM1-GSTT1-GSTP1 and OGG1 Ser326Cys gene polymorphisms can be used as candidate genes in the etiology of T2DM, especially in the development of T2DM.     

Association of glutathione S-transferase M1/T1 polymorphisms with susceptibility to vitiligo

Background

Some studies suggested that Glutathione S-transferases M1/T1(GSTM1/T1) null polymorphisms may be associated with the risk of vitiligo.

Aims

The purpose of this study is to further evaluate the association between GSTM1/T1 null polymorphisms and the susceptibility to vitiligo.

Methods

We carried out a retrieval of studies in the databases. Odds ratios (OR) and 95% confidence intervals (95% CIs) were used to assess the strength of this association. We analyzed the data using Stata 11.0.

Results

Six case–control studies including 1358 cases and 1673 controls were included in this meta-analysis. Our overall results showed the GSTM1 or GSTT1 null polymorphism was associated with vitiligo (GSTM1:OR = 1.59, 95% CI: 1.21–2.08, P = 0.001; GSTT1: OR = 1.30, 95% CI: 1.12–1.51, P = 0.001). In the subgroup analysis, the GSTM1 null polymorphism might be a genetic risk factor to vitiligo in East Asian (OR = 1.71, 95% CI: 1.12–2.63, P = 0.014) but not in the Mediterranean, however individuals with the GSTT1 null polymorphism in the Mediterranean (OR = 1.76, 95% CI: 1.15–2.71, P = 0.010) but not in East Asian have a greater predisposition to vitiligo. In addition there was also a significant trend toward an association with the combination of the GSTM1 null and GSTT1 null in either East Asians or Mediterraneans.

Conclusion

The GSTM1/T1 null polymorphisms may be associated with vitiligo. More studies are needed to confirm this conclusion.     

Glutathione S-Transferase M1, T1, P1 Genotypes and Risk for Development of Colorectal Cancer

The glutathione S-transferase (GST) supergene family is an important part of cellular enzyme defense against endogenous and exogenous chemicals, many of which have carcinogenic potential. The present investigation was conducted to detect a possible association between polymorphisms at the GSTM1, GSTT1, and GSTP1 genes and the interaction with cigarette smoking and colorectal cancer incidence. We examined 181 patients with colorectal cancer and 204 controls. DNA was extracted from whole blood, and the GSTM1, GSTT1, and GSTP1 polymorphisms were determined using a real-time polymerase chain reaction and fluorescence resonance energy transfer with a Light-Cycler instrument. Associations between specific genotypes and the development of colorectal cancer were examined by use of logistic regression analysis to calculate odds ratios (OR) and 95% confidence intervals (CI). The GSTM1 polymorphism was associated with an increased risk of developing colorectal cancer (OR = 1.62, 95% CI: 1.06–2.46). Also the risk of colorectal cancer associated with the GSTT1 null genotype was 1.64 (95% CI: 1.10–2.59). Statistically no differences were found between patients with colorectal cancer and control groups for the GSTP1 Ile/Ile, Ile/Val and Val/Val genotypes. In addition, the frequencies of the GSTM1 and GSTT1 deletion genotypes differed significantly between the cases and controls for current smokers; the GSTT1 null genotype especially is associated with a greater risk of colorectal cancer (OR = 2.44, 95% CI: 1.24–4.81). The GSTM1 and GSTT1 deletions were associated with an increased risk of developing a transverse or rectal tumor (OR = 1.86, 95% CI: 1.15–3.00; OR = 1.70, 95% CI: 1.02–2.84; respectively). The glutathione S-transferase polymorphisms were not associated with risk in patients stratified by age. The risk of colorectal cancer increased as putative high-risk genotypes increased for the combined genotypes of GSTM1 null, GSTT1 null, and either GSTP1 valine heterozygosity or GSTP1 valine homozygosity (OR = 2.69, 95% CI: 1.02–7.11). In conclusion, the results obtained in this study clearly suggest that those susceptibility factors related to different GST polymorphic enzymes are predisposing for colorectal cancer.     

Glutathione S-transferase M1, T1 and P1 genetic polymorphisms, cigarette smoking and gastric cancer risk

Glutathione S-transferases (GSTs) belong to a superfamily of detoxification enzymes that provide critical defences against a large variety of chemical carcinogens and environmental toxicants. GSTs are present in most epithelial tissues of the human gastrointestinal tract. We investigated associations between genetic variability in specific GST genes (GSTM1, GSTT1 and GSTP1), the interaction with cigarette smoking and susceptibility to gastric cancer. The GSTM1, GSTT1 and GSTP1 polymorphisms were determined using real-time polymerase chain reaction (PCR) and fluorescence resonance energy transfer with Light Cycler Instrument. The study included 70 patients with gastric cancer and 204 controls. Associations between specific genotypes and the development of gastric cancer were examined by use of logistic regression to calculate odds ratios (OR) and 95% confidence intervals (CI). The GSTM1 homozygous null genotype was associated with an increased risk of developing gastric cancer (OR = 1.73; 95% CI = 1.10-3.04). GSTT1 homozygous null genotype and GSTP1 genotypes were not associated with the risk of gastric cancer. Also there was no difference between cases and controls in the frequency of val-105 and ile-105 alleles (p = 0.07). After grouping according to smoking status, GSTM1 null genotype was associated with an increased gastric cancer risk for smokers (OR = 2.15; 95% CI, 1.02-4.52). There were no significant differences in the distributions of any of the other GST gene combinations. Our findings suggest that the GSTM1 null genotype may be associated with an increased susceptibility to gastric cancer.     

Null genotype of glutathione S-transferase M1 is associated with senile cataract susceptibility in non-smoker females

In the present study, we investigated whether the polymorphisms of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) genes are risk factors of cataract among Iranian population in a molecular epidemiological way. Blood samples from 150 subjects with cataract (72 male; 78 female) and 150 age- and sex-matched healthy persons were collected. Both patient and control groups were unrelated Iranian Muslims. Using PCR-based method, the genotypes were determined. The null GSTM1 genotype was associated with a 2.38-fold increase in the risk of developing cataract (OR=2.38; 95% CI=1.46-3.89; P = 0.0003). After stratification by sex of subjects, the association was apparent only among women (OR=3.20; 95% CI=1.58-6.52; P = 0.0007). The GSTT1 null genotype was associated with a 1.10-fold increased risk of developing cataract, but this association was not statistically significant. After stratification by sex of subjects, same results were obtained. Female patients with null genotype for GSTM1 and no history of smoking had a 3.45-fold increased cataract risk (P < 0.05), whereas females who were null for GSTM1 and having history of smoking were not at increased risk of cataract.     

Glutathione S transferase M1 andT1 genotypes and susceptibility to smoking related larynx cancer

Susceptibility to smoking related larynx cancer has been suggested to be associated with genetically determined differences in the ability to detoxify carcinogens present in tobacco smoke. The genetic polymorphisms of glutathione S-transferases, involved in the metabolic inactivation of, for example, tobacco derived carcinogens, have been recognized as potential risk modifiers in various environmentally induced malignancies, including larynx cancer. We employed PCR-based methods to determine the distribution of the GSTM 1 and G STT1 null genotypes in 171 larynx cancer patients and 180 controls to examine further their potential role in individual susceptibility to this neoplasm. The GSTM 1 null genotype was found in 49 1 % of the cases and 57 7 % of the controls and the GSTT1 null genotype in 17 5 % of the cases and 21 7 % of the controls, respectively. Larynx cancer risk associated with the lack of GST M 1 (OR = 0 7; 95 % CI: 0 5-1 1) or GSTT1 (OR = 0 8; 95 % CI: 0 5-1 3) was not significantly affected by age, smoking status, or cancer progression. Although this study thus suggests no role for the G STM 1 and GSTT1 gene polymorphisms in individual susceptibility to smoking-related larynx cancer, due to its relatively small sample size more data are required before any definite conclusions can be drawn.     

Glutathione S transferase M1 andT1 genotypes and susceptibility to smoking related larynx cancer

Susceptibility to smoking related larynx cancer has been suggested to be associated with genetically determined differences in the ability to detoxify carcinogens present in tobacco smoke. The genetic polymorphisms of glutathione S-transferases, involved in the metabolic inactivation of, for example, tobacco derived carcinogens, have been recognized as potential risk modifiers in various environmentally induced malignancies, including larynx cancer. We employed PCR-based methods to determine the distribution of the GSTM 1 and G STT1 null genotypes in 171 larynx cancer patients and 180 controls to examine further their potential role in individual susceptibility to this neoplasm. The GSTM 1 null genotype was found in 49 1 % of the cases and 57 7 % of the controls and the GSTT1 null genotype in 17 5 % of the cases and 21 7 % of the controls, respectively. Larynx cancer risk associated with the lack of GST M 1 (OR = 0 7; 95 % CI: 0 5-1 1) or GSTT1 (OR = 0 8; 95 % CI: 0 5-1 3) was not significantly affected by age, smoking status, or cancer progression. Although this study thus suggests no role for the G STM 1 and GSTT1 gene polymorphisms in individual susceptibility to smoking-related larynx cancer, due to its relatively small sample size more data are required before any definite conclusions can be drawn.     

Glutathione S-transferase gene polymorphisms in Turkish patients with diabetes mellitus

Glutathione S-transferases (GSTs) are enzymes involved in the metabolism of many disease-causing electrophilic substrates and protect the cells against oxidative stress. In the present study, we investigated the GSTM1, GSTT1 and GSTP1 gene polymorphisms in diabetic patients and healthy individuals and searched whether polymorphisms in GST genes are associated with diabetes mellitus (DM) in the Turkish population. The study population consisted of 98 unrelated healthy individuals and 98 patients with DM. Genotyping of GSTM1, GSTT1 and GSTP1 genes was performed using real time polymerase chain reaction with a Light Cycler instrument. Patients had a higher frequency of the GSTM1 null genotype than the control group (Odds ratios, OR = 3.7; 95% confidence intervals, CI = 2.05-6.70). However, there was no significant difference in the frequencies of the GSTT1 and GSTP1 gene polymorphisms between the patients and control group. The combined analysis of these three GST genotypes showed a further DM risk increase (OR = 5.7, 95% CI = 1.51-31.07). This is the first study to determine the association of diabetes with GST gene polymorphism in the Turkish population. These results show that GSTM1 null genotype may play a significant role in the aetiopathogeneses of DM and the GSTM1 gene may be a useful marker in the prediction of DM susceptibility of the Turkish population.     

Relation of glutathione S-transferase T1, M1 and P1 genotypes and breast cancer risk

The aim of this study was to investigate associations between genetic variability in specific Glutathione S-transferases (GST) genes (GSTM1, GSTT1 and GSTP1) and susceptibility to breast cancer. Genotypes of blood specimen DNA were determined for 65 women with incident cases of breast cancer and 108 control subjects. Associations between specific genotypes and the development of breast cancer were examined by the use of logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Neither GSTT1 nor GSTM1 homozygous null genotype was associated with a significant increased risk of developing breast cancer. The presence of valine alleles compared to isoleucine alleles in codon 105 in GSTP1 did not increase the risk of breast cancer development. The risk of breast cancer associated with a combined GSTT1 and GSTM1 null genotype was 3.37 (95% CI = 0.76-2.95, p = 0.115). The only significant association between increased risk of breast cancer development and GSTs polymorphisms was found when GSTT1 null, GSTM1 null and the presence of valine in GSTP1 in codon 105 were combined (p < 0.048, OR = 3.75, 95% CI = 1.01-13.90). Our findings suggest that combined genetic variability in members of the GST gene family may be associated with an increased susceptibility to breast cancer.     

Association of glutathione S-transferase polymorphisms (GSTM1 and GSTT1) with primary open-angle glaucoma: An evidence-based meta-analysis

Studies investigating the associations between glutathione S-transferase (GST) genetic polymorphisms and primary open-angle glaucoma (POAG) have reported controversial results. Therefore, a meta-analysis was performed to clarify the effects of GSTM1 and GSTT1 polymorphisms on POAG risk. Published literatures from PubMed, EMBASE, ISI Web of Science and CBM databases were retrieved. All studies evaluating the association between GSTM1/GSTT1 polymorphisms and POAG were included. Pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using fixed- or random-effects model. Eleven studies on GSTM1 (1339 cases and 1412 controls) and seven studies on GSTT1 (958 cases, 1003 controls) were included. Overall analysis showed that the association between GSTM1 and GSTT1 null genotype and POAG risk is not statistically significant. Subgroup analyses showed that the null genotype of GSTM1 increased the risk of POAG in Asians. In GSTM1–GSTT1 interaction analysis, individuals with dual null genotype were associated with a significantly increased risk of POAG when compared with the dual present genotype. In conclusion, the present meta-analysis suggested that GSTM1 null genotypes are associated with increased POAG risk in Asian populations but not in Caucasian and mixed populations. Dual null genotype of GSTM1/GSTT1 is associated with increased risk of POAG. Given the limited sample size, the finding on GST polymorphisms needs further investigation.     

Association of genetic polymorphisms in glutathione S-transferases and susceptibility to head and neck cancer

Polymorphism in glutathione S-transferase (GST) genes (GSTM1, GSTT1 and GSTP1) and interaction with environmental factors such as tobacco (smoking or chewing) and alcohol on susceptibility to head and neck squamous cell carcinoma (HNSCC) was studied in a case-control study. The study group consisted of 175 patients suffering from HNSCC and 200 age matched healthy controls. Statistical analysis showed an increase in risk to HNSCC in the patients with null genotype of GSTM1 (OR: 2.02; 95% CI: 1.32-3.10; P=0.001) or GSTT1 (OR: 1.66; 95% CI: 1.02-2.69; P=0.04), though the risk was not found to be significant when adjusted for age, sex, smoking, tobacco chewing or alcohol use by multivariate logistic regression model. Our data further showed that combination of deletion genotypes of GST (GSTM1 and GSTT1) confer an even higher risk of HNSCC. Interestingly, GSTP1 wild type genotype in combination with GSTM1 null or GSTT1 null genotype increased susceptibility for HNSCC (OR: 2.49 and 2.75, respectively). Likewise a much greater risk for HNSCC was observed in the patients carrying a genotype combination of GSTM1 null, GSTT1 null and GSTP1 (Ile/Ile) (OR: 4.47; 95% CI: 1.62-12.31; P=0.002). Our data have further provided evidence that tobacco chewing and alcohol consumption are the important risk factors for HNSCC. The interaction between tobacco chewing and null genotype of GSTM1 or GSTT1 resulted in about 3.5- and 2.2-fold increase in the risk respectively in the patients when compared to those not chewing tobacco. Alcohol use resulted in more than 4-fold increase in the risk in the patients with null genotype of GSTM1 as compared to those who are non-drinkers. Alcohol consumption also increased the risk (approx. 3-fold) in the cases with null genotype of GSTT1, though the association was not found to be significant when compared to non-drinkers. Our data have provided evidence that GST polymorphism modifies the susceptibility to HNSCC and have further demonstrated importance of gene-environment interaction in modulating the risk to HNSCC.     

Impact of glutathione transferase M1, T1, and P1 gene polymorphisms in the genetic susceptibility of North Indian population to renal cell carcinoma

In this study, we investigated the association of GSTP1, GSTM1, and GSTP1 genetic variants with renal cell carcinoma (RCC) among North Indian patients. The difference in frequency of the GSTT1 null genotype between cases and control subjects was statistically significant (active ver. null, odds ratio [OR]=0.368; confidence intervals [CI] 95%=0.243-0.557, p=0.001). The differences in the frequency of GSTP1 genotypes were statistically significant (AA ver. AG/GG, OR=1.879; CI 95%=0.355-0.797, p=0.002). Higher allelic frequency of the GSTP1 G allele was associated with RCC cases (G ver. A allele, OR=1.534; 95% CI=1.159-2.030, p=0.003). The gene-gene interaction in terms of three-way combination of GSTM1 null, GSTT1 null, and GSTP1 (AG/GG) resulted in 4.5-fold increase in RCC risk (OR=4.452; 95% CI=2.220-9.294). Similarly, our study revealed that GST polymorphism might be a vital determinant of advancement to higher pathological stages and histological grades of RCC. Our findings suggest that genetic variability in members of the GST gene family may be associated with an increased susceptibility to RCC and its progression.     

Null genotypes of GSTM1 and GSTT1 contribute to increased risk of diabetes mellitus: A meta-analysis

Diabetes mellitus (DM) is a common disease which results from various causes including genetic and environmental factors. Glutathione S-Transferase M1 (GSTM1) and Glutathione S-Transferase T1 (GSTT1) genes are polymorphic in human and the null genotypes lead to the absence of enzyme function. Many studies assessed the associations between GSTM1/GSTT1 null genotypes and DM risk but reported conflicting results. In order to get a more precise estimate of the associations of GSTM1/GSTT1 null genotypes with DM risk, we performed this meta-analysis. Published literature from PubMed, Embase and China Biology Medicine (CBM) databases was searched for eligible studies. Pooled odds ratios (OR) and corresponding 95% confidence intervals (95%CI) were calculated using a fixed- or random-effects model. 11 publications (a total of 2577 cases and 4572 controls) were finally included into this meta-analysis. Meta-analyses indicated that null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 were all associated with increased risk of DM (GSTM1: OR _{random-effects} = 1.60, 95%CI 1.10–2.34, P_OR = 0.014; GSTT1: OR _{random-effects} = 1.47, 95%CI 1.12–1.92, P_OR = 0.005; GSTM1–GSTT1: OR _{fixed-effects} = 1.83, 95%CI 1.30–2.59, P_OR = 0.001). Subgroup by ethnicity suggested significant associations between null genotypes of GSTM1 and GSTT1 and DM risk among Asians (GSTM1: OR _{random-effects} = 1.77, 95%CI 1.24–2.53, P_OR = 0.002; GSTT1: OR _{random-effects} = 1.58, 95%CI 1.09–2.27, P_OR = 0.015). This meta-analysis suggests null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 are all associated with increased risk of DM, and null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 are potential biomarkers of DM.     

Polymorphisms of cytochrome P450 1A1, glutathione s-transferases M1 and T1 genes in Ouangolodougou (Northern Ivory Coast)

In this study, the frequencies of CYP1A1, GSTM1, and GSTT1 gene polymorphisms were determined in 133 healthy individuals from Ouangolodougou, a small rural town situated in the north of the Ivory Coast. As appeared in several published studies, ethnic differences in these frequencies have been found to play an important role in the metabolism of a relevant number of human carcinogens. In the studied sample, the frequencies of Ile/Ile (wild type), Ile/Val (heterozygous variant), and Val/Val (homozygous variant) CYP1A1 genotypes were 0.271, 0.692, and 0.037, respectively. Frequencies of GSTM1 and GSTT1 null genotypes were 0.361 and 0.331, respectively. No significant differences were noted between men and women. In contrast to published data for Africans, CYP1A1 *Val Allele frequency (0.383) was significantly high (p < 0.001) in this specific population. For the GSTT1 null genotype, no differences were found between the studied and other African populations, the contrary to what occurred for the GSTM1 null genotype in relation to Gambia and Egypt.     

GSTM1 and GSTT1 gene polymorphisms as major risk factors for bronchopulmonary dysplasia in a Chinese Han population

Bronchopulmonary dysphasia (BPD) is a complex multifactorial disease with an obvious genetic predisposition. Oxidative stress plays an important role in its pathogenesis. Glutathione S-transferases (GSTs) detoxify metabolites produced by oxidative stress within the cell and protect the cells against injury. In the present study, the hypothesis that polymorphisms in the GSTM1 and GSTT1 genes are associated with BPD in Chinese Han infants was examined. Sixty infants with BPD and 100 gestational age and birth weight-matched preterm infants without BPD were recruited. Genotyping for GSTM1 and GSTT1 was performed by multiplex polymerase chain reaction (PCR). The GSTM1 null genotype was more prevalent in BPD infants (65.0%) than in the control subjects (48.0%), which yielded higher risk towards BPD (odds ratio (OR): 2.012, 95% confidence interval (CI) = 1.040–3.892, p = 0.037). There was no statistically significant association of GSTT1 genotype with BPD (OR: 1.691, 95% CI = 0.884–3.236, p = 0.111), although the frequency of GSTT1 null genotype was higher among the BPD subjects (60.0%) than in the control patients (47.0%). GSTM1 and GSTT1 double null genotype was also higher in BPD group (38.3%) than in controls (21.0%) with a higher risk towards BPD (OR: 2.338, 95%CI = 1.151–4.751, p = 0.017). The results suggest that null genotypes of GSTM1 and GSTT1 genes may contribute to the development of BPD in our Chinese Han population.     

西藏登山队员谷胱甘肽硫转移酶基因多态性与低氧反应敏感性关系的研究

目的：考察西藏登山队员谷胱甘肽硫转移酶（GSTs）基因多态性与高原低氧反应敏感性之间的关系。方法：采用高原-平原对照法,通过多重PCR和PCR—RFLP技术检测西藏登山队员和平原汉族人群体内谷胱甘肽硫转移酶基因多态性。结果：GSTT1缺失基因型频率在西藏登山队员和平原汉族人群中有显著性差异（P〈0．05）,OR=1．86（95％CI=101～3．39）;GSTP1-105变异基因型频率差异非常显蓍（P〈0．01）,OR=2．19（95％CI=1．16～4．13）．其等位基因A和G在两组人群中有显著性差异（P〈0．01）。而GSTM1缺失基因型无显著性差异（P〉0．05）,OR=0．78（95％CI=0．43～1．42）。结论：GSTT1和GSTP1-105基因型可能与高原低氧反应敏感性有关。     

Glutathione S-transferase M1, T1, and P1 genotypes and breast cancer risk: a study in a Portuguese population

Glutathione S-transferases are a superfamily of multifunctional enzymes that play a key role in Phase II metabolism, detoxifying therapeutic drugs, and various carcinogens by conjugation with glutathione. We undertook a case-control study in Central-Eastern Portuguese population to evaluate the association of null genotype in GSTM1 and GSTT1 along with the polymorphism in GSTP1 (A/G) and susceptibility to breast cancer. The population sample consisted of 85 patients with histological diagnosis of breast cancer and 102 healthy women. Genomic DNA was extracted from blood samples, and genotyping analyses were performed by PCR-based methods. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by unconditional logistic regression. We found a increased breast cancer risk associated with GSTM1 null genotype (OR = 3.597; 95% CI = 1.849-6.999; P = 0.0001) and GSTT1 (OR = 2.592; 95% CI = 1.432-4.690; P = 0.002), but the presence of valine alleles compared to isoleucine alleles in codon 105 in GSTP1 did not increase the risk of breast cancer development. The two-way combination of GSTM1 and GTTT1 null genotypes resulted in 8-fold increase for breast cancer risk (OR = 8.287; 95% CI = 3.124-21.980; P = 0.0001) and the three-way combination of GSTP1 105AA/AG and null genotypes for both GSTM1 and GSTT1 resulted in 5-fold increase for breast cancer risk (OR = 5.040; 95% CI = 1.392-18.248; P = 0.016). Our results suggest that GSTM1 and GSTT1 null genotype alone, both combined or combined with GSTP1 valine alleles, are associated with higher susceptibility to breast cancer development.     

Absence of association between GSTM1 and GSTT1 polymorphisms and melanoma susceptibility: a meta-analysis

Glutathione S-transferases (GSTs) are a family of multifunctional enzymes that are involved in the metabolism of many xenobiotics, including a wide range of environmental carcinogens. The null genotypes GSTM1 and GSTT1 have been implicated in the development of carcinogenesis. We conducted a meta-analysis to examine the association of GSTM1 and GSTT1 homozygous deletion polymorphisms with melanoma risk. In total, 8 relevant studies were identified in searches of the PubMed and Embase databases: 8 investigated GSTM1 (1349 cases and 1560 controls) and 5 GSTT1 (977 cases and 1060 controls). Fixed- and random-effects models were used to assess the summary odds ratios (ORs). No significant association of the GSTM1 and GSTT1 polymorphisms or the GSTM1-GSTT1 interaction on the risk of melanoma was observed (for GSTM1: OR=1.09; 95% confidence interval, 0.94-1.27; and for GSTT1: OR=0.95; 95% confidence interval, 0.76-1.19). Similarly, no significant association was found in a subgroup analysis of hair color. These results indicate that the GSTM1 and GSTT1 polymorphisms may not be a risk factor for developing melanoma.     

Glutathione S-Transferase M1 (GSTM1) and T1 (GSTT1) Null Polymorphisms and the Risk of Hypertension: A Meta-Analysis

Background

Some studies have recently focused on the association between glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) null polymorphisms and hypertension; however, results have been inconsistent.

Objective

In order to drive a more precise estimation, the present systematic review and meta-analysis is performed to investigate the relationship between the GSTM1 and GSTT1 null polymorphisms and hypertension.

Methods

Eligible articles were identified by a search of several bibliographic databases for the period up to August 17, 2013. Odds ratios were pooled using either fixed-effects or random-effects models.

Results

Regarding the GSTM1 null/present genotype, 14 case—control studies were eligible (2773 hypertension cases and 3189 controls). The meta-analysis revealed that it might present a small increased risk for hypertension, although the effect was not statistically significant (odd ratio (OR) = 1.16, 95% confidence interval (CI): 0.96, 1.40; P = 0.002, I2 = 59.8%). Further subgroup analysis by ethnicity and control source suggested that the association was still not significant. Thirteen case—control studies were eligible for GSTT1 (2497 hypertension cases and 3078 controls). No statistically significant association was observed between the GSTT1 null genotype and hypertension risk (OR = 1.14, 95% CI: 0.85, 1.53; P = 0.000, I2 = 80.3%). Furthermore, stratification by ethnicity and control source indicated no association between the GSTT1 null genotype and hypertension risk. We further confirmed the association by sensitivity analysis. No publication bias was detected.

Conclusion

This meta-analysis suggests that the GSTM1 and GSTT1 null polymorphisms are not associated with the risk of hypertension. Future large well-designed epidemiological studies with individual information, lifestyle factors, and environmental factors are warranted to validate the present findings.     

No contribution of GSTM1 and GSTT1 null genotypes to the risk of neutropenia due to benzene exposure in Southeastern Brazil

Exposure to benzene has been associated with haematological diseases such as neutropenia (NEB) and acute myeloid leukaemia (AML). We tested whether the null genotypes of the GSTM1 and GSTT1 genes, involved in benzene inactivation, altered the risk for NEB in southeastern Brazil. Genomic DNA from 55 NEB patients and 330 controls was analysed by multiplex-polymerase chain reaction. The frequency of the GSTM1, GSTT1 and combined null genotypes was similar in patients and controls (GSTM1, 27.3% vs. 38.8%, p = 0.16; GSTT1, 25.5% vs. 19.7%, p = 0.24; GSTM1/GSTT1, 12.7% vs. 6.7%, p = 0.26; respectively). The distribution of genotype classes in NEB patients was similar to normal controls, suggesting that GSTM1 and GSTT1 null genotypes make no specific contribution to the risk of NEB. As the GSTM1 and GSTT1 null genotypes were previously associated with increased risk for AML in Brazil and elsewhere, we hypothesise that different thresholds of chemical exposure relative to distinct GSTM1 and GSTT1 genotypes may determine whether AML or NEB manifests in benzene exposed individuals from southeastern Brazil. Although indicative, our results still require support by prospective and large scale epidemiological studies, with rigorous assessment of daily chemical exposures and control of the possible contribution of other polymorphic genes involved in benzene metabolism.