The functional genotype of glutathione S-transferase T1 gene is strongly associated with increased risk of idiopathic infertility in Russian men

Do GSTM1 and GSTT1 polymorphisms influence the risk of developing mitochondrial diseases in a Tunisian population?

Mitochondria play an essential role to supply the cell with metabolic energy in the form of adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS). As a consequence, they are also the primary source of cellular reactive oxygen species (ROS) which can cause oxidative damage of individual respiratory chain complexes. Indeed, affected OXPHOS subunits result in decreases in ATP production and increases in ROS formation which generate oxidative phosphorylation deficiency leading to mitochondrial dysfunctions. It has been suggested that ROS play a vital role in the pathogenesis of mitochondrial diseases. To the best of our knowledge, this is the first study which aimed to investigate the genetic variant effect of the antioxidant enzymes GSTM1 and GSTT1 on mitochondrial disease among a Tunisian population. In this report, 109 patients with mitochondrial disease and 154 healthy controls were genotyped by multiplex PCR amplification, and data were analyzed by SPSS v20 software. The results showed that GSTM1 null genotype was found to be associated with mitochondrial disease with a protective effect; however, no significant association of GSTT1 polymorphism with mitochondrial disease risk was revealed. But, interestingly, our findings highlight that GSTM1 active and GSTT1 null genotype combination increased by three fold the risk of developing mitochondrial disease with p _c  = 0.020, notably mitochondrial myopathy with p _c  = 0.046 and Leigh syndrome with p _c  = 0.042. In conclusion, this study suggests that GSTM1 active and GSTT1 null genotype combination might be a risk factor in developing mitochondrial disease.

Interactions between CYP2E1, GSTZ1 and GSTT1 polymorphisms and exposure to drinking water trihalomethanes and their association with semen quality

Trihalomethanes (THMs) have been reported to be associated with altered semen quality, and this association may be modified by inherited differences in cytochrome P450 (CYP2E1) and glutathione S-transferase (GSTZ1 and GSTT1), which metabolize THMs. We conducted a cross-sectional study to examine the interactions between CYP2E1, GSTZ1 and GSTT1 polymorphisms and exposure to THMs on semen quality among 401 men from the Reproductive Center of Tongji Hospital in Wuhan China. The baseline blood concentrations of four individual THMs, chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform (TBM), were measured as biomarkers of exposure to drinking water THMs. Genotypes were determined by real-time PCR, and semen-quality parameters were evaluated according to the World Health Organization guidelines. GSTT1 genotype significantly modified the association between exposure to Br-THMs (sum of BDCM, DBCM and TBM) and below-reference sperm motility (Pint=0.02). Men with above-median blood Br-THM levels had an increased odds ratio (OR) of below-reference sperm compared to men with below-median blood Br-THM levels (OR=2.15, 95% CI: 1.11, 4.19) in the GSTT1 null genotype only. In addition, we found that men with a TT of CYP2E1 rs 915,906 had higher blood TCM and TTHM (sum of TCM, BDCM, DBCM and TBM) concentrations than men with a CT/CC of CYP2E1 rs 915,906. Our results suggest that GSTT1 polymorphisms modify Br-THM exposure relation with semen quality, and CYP2E1 polymorphisms are associated with internal levels of exposure to THMs.

Association of polymorphisms in glutathione S-transferase genes (GSTM1, GSTT1, GSTP1) with idiopathic azoospermia or oligospermia in Sichuan, China

The reported effects of the glutathione S-transferase (GSTs) genes (GSTM1, GSTT1, and GSTP1) on male factor infertility have been inconsistent and even contradictory. Here, we conducted a case-control study to investigate the association between functionally important polymorphisms in GST genes and idiopathic male infertility. The study group consisted of 361 men with idiopathic azoospermia, 118 men with idiopathic oligospermia, and 234 age-matched healthy fertile male controls. Genomic DNA was extracted from the peripheral blood, and analyzed by polymerase chain reaction and restriction fragment length polymorphism analysis. There was a significant association between the GSTP1 variant genotype (Ile/Val + Val/Val) with idiopathic infertility risk (odds ratio [OR]: 1.53; 95% confidence interval [CI]: 1.11–2.11; P = 0.009). Similarly, a higher risk of infertility was noted in individuals carrying a genotype combination of GSTT1-null and GSTP1 (Ile/Val + Val/Val) (OR: 2.17; 95% CI: 1.43–3.31; P = 0.0002). These results suggest an increased risk of the GSTP1 variant genotype (Ile/Val + Val/Val) for developing male factor infertility. Our findings also underrate the significance of the effect of GSTM1 and/or GSTT1 (especially the former) in modulating the risk of male infertility in males from Sichuan, southwest China.

An association study of four candidate loci for human male fertility traits with male infertility

STUDY QUESTION

Are the four candidate loci (rs7867029, rs7174015, rs12870438 and rs724078) for human male fertility traits, identified in a genome-wide association study (GWAS) of a Hutterite population in the USA, associated with male infertility in a Japanese population?

SUMMARY ANSWER

rs7867029, rs7174015 and rs12870438 are significantly associated with the risk of male infertility in a Japanese population.

WHAT IS KNOWN ALREADY

Recently, a GWAS of a Hutterite population in the USA revealed that 41 single-nucleotide polymorphisms (SNPs) were significantly correlated with family size or birth rate. Of these, four SNPs (rs7867029, rs7174015, rs12870438 and rs724078) were found to be associated with semen parameters in ethnically diverse men from Chicago.

STUDY DESIGN, SIZE, DURATION

This is a case-control association study in a total of 917 Japanese subjects, including 791 fertile men, 76 patients with azoospermia and 50 patients with oligozoospermia.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Azoospermia was diagnosed on the basis of semen analysis (the absence of sperm in ejaculate), serum hormone levels and physical examinations. Oligozoospermia was defined as a sperm concentration of <20 × 10(6)/ml. We excluded patients with any known cause of infertility (i.e. obstructive azoospermia, varicocele, cryptorchidism, hypogonadotropic hypogonadism, karyotype abnormalities or complete deletion of AZF a, b or c). The SNPs rs7867029, rs7174015, rs12870438 and rs724078 were genotyped using DNA from peripheral blood samples and either restriction fragment length polymorphism PCR or TaqMan probes. Genetic associations between the four SNPs and male infertility were assessed using a logistic regression analysis under three different comparative models (additive, recessive or dominant).

MAIN RESULTS AND THE ROLE OF CHANCE

The genotypes of all four SNPs were in Hardy-Weinberg equilibrium in the fertile controls. The SNPs rs7867029 and rs7174015 are associated with oligozoospermia [rs7867029: odds ratio (OR) = 1.70, 95% confidence interval (CI) = 1.07-2.68, P = 0.024 (log-additive); rs7174015: OR = 6.52, 95% CI = 1.57-27.10, P = 0.0099 (dominant)] and rs12870438 is associated with azoospermia (OR = 10.90, 95% CI = 2.67-44.60, P = 0.00087 (recessive)] and oligozoospermia [OR = 8.54, 95% CI = 1.52-47.90, P = 0.015 (recessive)]. The association between rs7174015 and oligozoospermia under a dominant model and between rs12870438 and azoospermia under additive and recessive models remained after correction for multiple testing. There were no associations between rs724078 and azoospermia or oligozoospermia.

LIMITATIONS, REASONS FOR CAUTION

Even though the sample size of case subjects was not very large, we found that three SNPs were associated with the risk of male infertility in a Japanese population.

WIDER IMPLICATIONS OF THE FINDINGS

The three infertility-associated SNPs may be contributing to a quantitative reduction in spermatogenesis.

STUDY FUNDING/COMPETING INTERESTS

This study was supported in part by the Ministry of Health and Welfare of Japan (1013201) (to T.I.), Grant-in-Aids for Scientific Research (C) (23510242) (to A.Ta.) from the Japan Society for the Promotion of Science, the European Union (BMH4-CT96-0314) (to T. I.) and the Takeda Science Foundation (to A.Ta.). None of the authors has any competing interests to declare.

Joint effect of glutathione S-transferase genotypes and cigarette smoking on idiopathic male infertility

Inconsistent results of association studies investigated the role of glutathione S-transferase genes in idiopathic male infertility may be explained by ethnical differences in gene-gene and gene-environment interactions. In this study, we investigated a joint contribution of GSTM1, GSTT1 and GSTP1 gene polymorphisms and cigarette smoking to the risk of idiopathic infertility in Russian men. DNA samples from 203 infertile and 227 fertile men were genotyped by a multiplex polymerase chain reaction (GSTM1 and GSTT1 deletions) and PCR-restriction fragment length polymorphism (GSTP1 I105V) methods. The GSTP1 genotype 105IV was associated with increased risk of male infertility (OR = 1.50 95% CI 1.02-2.20 P = 0.04). Genotype combinations GSTP1 105II/GSTT1 del (G1), GSTM1 del/GSTT1 del (G2) and GSTM1 + /GSTT1 del (G3) were associated with decreased risk of male infertility (P ≤ 0.003), whereas a genotype combination GSTP1 105IV/GSTT1 + (G4) was associated with increased disease risk (P = 0.001). The genotype combinations G3 and G4 showed a significant association with infertility in smokers; however, nonsmokers carriers did show the disease risk. In conclusion, GSTM1, GSTT1 and GSTP1 genes are collectively involved in the development of idiopathic male infertility and their phenotypic effects on the disease risk are potentiated by cigarette smoking.

Synergism between the N-acetyltransferase 2 gene and oxidant exposure increases the risk of idiopathic male infertility

N-acetyltransferase (NAT2) is a phase-II xenobiotic-metabolizing enzyme participating in the detoxification of toxic arylamines, aromatic amines and hydrazines. The present study was designed to investigate whether two common single-nucleotide polymorphisms (SNP) of the NAT2 gene (481C>T, rs1799929; 590G>A, rs1799930) are associated with susceptibility to idiopathic male infertility and to assess if the risk is modified by oxidant and antioxidant exposures. A total 430 DNA samples (203 infertile patients and 227 fertile men) were genotyped for the polymorphisms by PCR and restriction fragment length polymorphism. No association was found between the NAT2 polymorphisms and idiopathic male infertility. However, gene-environment interaction analysis revealed that a low-acetylation genotype, 590GA, was significantly associated with increased disease risk in men who had environmental risk factors such as cigarette smoking (OR 1.71, 95% CI 1.02-2.87, P = 0.042), alcohol abuse (OR 2.14, 95% CI 1.08-4.27, P = 0.029) and low fruit/vegetable intake (OR 1.68, 95% CI 1.01-2.79, P = 0.04). This pilot study found, as far as is known for the first time, that the polymorphism 590G>A of NAT2 is a novel genetic marker for susceptibility to idiopathic male infertility, but the risk is potentiated by exposure to various environmental oxidants.

GSTM1 and GSTT1 null polymorphisms and male infertility risk: an updated meta-analysis encompassing 6934 subjects

Published data on the association between the GST genes polymorphisms and male infertility risk are inconclusive. We investigated GST genes polymorphisms in a large sample size case-control study, and conducted a literature-based meta-analysis of 6934 individuals. Our case-control study showed the GSTM1 null genotype was significantly associated with idiopathic oligozoospermia, while the null genotype of GSTT1 was significantly associated with normozoospermia and azoospermia. Additionally, significantly elevated GSTT1 expression levels were observed in present genotype compared with null genotype. In the meta-analysis, the null genotype of GSTM1 was associated with a significantly increased risk of male infertility. Furthermore, a stratification analysis showed that the risk of GSTM1 polymorphism was associated with male infertility in both Asian and Caucasian groups. Further studies of GSTM1 and GSTT1 with their biological functions are needed to understand the role of these genes in the development of male infertility.

Association of GSTM1 and GSTT1 genes with the susceptibility to male infertility: result from a meta-analysis

The deletion polymorphisms of the glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) genes were considered as candidates for genetic susceptibility factors of male infertility. Previous studies concerning the relationship between the null genotype of the two genes and male infertility have been reported in recent years. However, the results remain elusive. A meta-analysis was performed to estimate the relationship between the deletion polymorphism of the GSTM1 or GSTT1 gene, and male infertility in this study. Sixteen studies concerning the GSTM1 gene, including 2174 cases and 1861 controls, and 13 case-control studies on the GSTT1 gene with a total number of 1992 cases and 1617 controls were processed. The results showed that the null genotype of the GSTM1 gene was associated with male infertility in the overall populations (P=0.003, OR=1.40, 95%CI=1.12-1.75), especially in Caucasian (P=0.012, OR=1.50, 95%CI=1.09-2.07) as well as Chinese (P=0.001, OR=1.55, 95%CI=1.19-2.03). The null genotype of the GSTT1 gene was strongly related to male infertility only in Chinese (P=0.000, OR=1.70, 95%CI=1.34-2.14). These results indicated that the null genotype of the GSTM1 gene might contribute to the susceptibility of male infertility, whereas the null genotype of the GSTT1 gene may be a genetic susceptibility factor of male infertility for the Chinese.

Smoking status modifies the relation between CYP1A1*2C gene polymorphism and idiopathic male infertility: the importance of gene-environment interaction analysis for genetic studies of the disease

The study was designed to investigate the associations of polymorphisms Ile462Val and 3801T>C of the cytochrome P450 1A1 (CYP1A1) gene with idiopathic male infertility (IMI) and to assess the impact of smoking status on the relationship between the polymorphisms and the susceptibility to the disease. DNA samples from 203 patients with IMI and 227 fertile men were genotyped for the polymorphisms by a polymerase chain reaction and restriction fragment length polymorphism methods. We found for the first time that the increased risk of IMI in carriers of genotype 462Ile/Val of the CYP1A1 gene occurred only in smoker men (odds ratio [OR] = 1.91; 95% confidence interval [CI] 1.01-3.59), whereas nonsmoker men did not have the risk of infertility (OR = 1.58; 95% CI 0.66-3.76). The results of our study demonstrate that the analysis of gene-environment interactions is necessary to explain conflicting results of genetic studies of IMI and to improve our understanding of the mechanisms of the disease.

Null genotype of GSTM1 and GSTT1 may contribute to susceptibility to male infertility with impaired spermatogenesis in Chinese population

Glutathione-S-transferases (GSTs) play a protective role during spermatogenesis and GST genes may be involved in impaired spermatogenesis. A case-control study was performed to explore the association of genes GSTM1 and GSTT1, two members of GST gene family, with spermatogenesis impairment. The deletion polymorphism distribution of genes GSTM1 and GSTT1 was investigated in 353 patients with azoospermia or oligospermia and 201 fertile controls in Chinese population using multiplex PCR. As a result, the frequencies of null genotype of genes GSTM1 (67.4% versus 57.7%, p = 0.022, OR = 1.516, 95% CI = 1.001-2.168) and GSTT1 (61.8% versus 46.8%, p = 0.001, OR = 1.838, 95% CI = 1.295-2.610) in patients were significantly higher than those in controls. After stratifying patients, the frequencies of null genotype of gene GSTM1 in oligospermia (68.3% versus 57.7%, p = 0.027, OR = 1.580, 95% CI = 1.051-2.375) and GSTT1 in azoospermia (66.9% versus 46.8%, p < 0.001, OR = 2.299, 95% CI = 1.484-3.562) as well as oligospermia (57.9% versus 46.8%, p = 0.025, OR = 1.567, 95% CI = 1.057-2.322) were still significantly higher compared with controls. The results suggested that null genotypes of GSTM1 and GSTT1 are associated with spermatogenesis impairment and may contribute to susceptibility to spermatogenesis impairment and male infertility in Chinese population.

Glutathione S-transferases gene polymorphisms and risk of male idiopathic infertility: a systematic review and meta-analysis

The Glutathione S-transferases (GSTs) polymorphisms have been implicated in susceptibility to male idiopathic infertility, but study results are still controversial. To investigate the genetic associations between GSTs polymorphisms and risk of male idiopathic infertility, a systematic review and meta-analysis were performed. Meta-analysis was performed by pooling odds ratio (OR) with its corresponding 95 % confidence interval (95 % CI) form studies in electronic databases up to March 16, 2012. Glutathione S-transferase M 1 (GSTM1) null genotype, Glutathione S-transferase T 1 (GSTT1) null genotype, and dual null genotype of GSTM1/GSTT1 were analyzed independently. 14 eligible studies with a total of 1,845 idiopathic infertility males and 1,729 controls were included. There were 13 studies on GSTM1 polymorphism, 10 ones on GSTT1 polymorphism and 5 ones on GSTM1-GSTT1 interaction analysis. Meta-analyses of total relevant studies showed GSTM1 null genotype was significantly associated with an increased risk of male idiopathic infertility (OR = 1.40, 95 % CI 1.07-1.84, P OR = 0.015). The GSTM1-GSTT1 interaction analysis showed dual null genotype of GSTM1/GSTT1 was also significantly associated with increased risk of male idiopathic infertility (OR = 1.85, 95 % CI 1.07-3.21, P OR = 0.028). Subgroup analyses by ethnicity showed the associations above were still statistically significant in Caucasians (For GSTM1, OR = 1.51, 95 % CI 1.11-2.05, P OR = 0.009; For GSTM1/GSTT1, OR = 2.10, 95 % CI 1.51-2.91, P OR < 0.001). This meta-analysis suggests GSTM1 null genotype contributes to increased risk of male idiopathic infertility in Caucasians, and males with dual null genotype of GSTM1/GSTT1 are particularly susceptible to developing idiopathic infertility.

Association of the Glutathione S-transferases M1 and T1 polymorphism with male infertility: a meta-analysis

BACKGROUND

Genes of different pathways regulate spermatogenesis, and the complexity of the spermatogenic process indicates that polymorphisms or mutations in these genes could cause male infertility. Published data on the association between the GSTM1 and GSTT1 polymorphism and male infertility risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed.

METHODS

A total of 11 studies regarding GSTM1 and 9 studies regarding GSTT1 between 1999 and 2012 were identified through researching MEDLINE, EMBASE and the Chinese Biomedical Database. It was performed to obtain summary estimated odd ratios and 95 % confidence intervals of GSTM1 and GSTT1 for male infertility, with attention to study quality and publication bias.

RESULTS

Overall, a significant association was seen between GSTM1 (OR=1.20, 95 % CI=1.02-1.40, P(heterogeneity) =0.000, P=0.027) genotypes and male infertility. Significant associations were also observed in subgroups of Caucasian populations (OR=1.65, 95 %CI=1.16-2.34, P(heterogeneity) =0.006, P=0.005), but were not observed in Asian populations (OR=1.09, 95 % CI=0.72-1.65, P(heterogeneity) =0.054, P=0.697) when stratified by ethnicity. While there was no significant association was seen between GSTT1 (OR=1.00, 95 % CI=0.74-1.35, P(heterogeneity) =0.000, P=0.980) null genotypes and male infertility. Simultaneously, significant associations were not observed in subgroups of Caucasian populations (OR=0.94, 95 %CI=0.44-2.00, P(heterogeneity) =0.000, P=0.867) and Asian populations (OR=0.93, 95 % CI=0.46-1.87, P(heterogeneity) =0.002, P=0.838) when stratified by ethnicity.

CONCLUSION

Our results suggest the GSTM1 null genotype contributes to male infertility susceptibility, while GSTT1 gene polymorphisms are not associated with male infertility in our study.

The glutathione-S-transferase gene polymorphisms (GSTM1 and GSTT1) and idiopathic male infertility risk: a meta-analysis

Published data on the association between male infertility and the glutathione-S-transferase (GST) gene polymorphism are inclusive. To drive a more precise estimation, we performed a meta-analysis based on 1897 cases and 1785 controls from 15 published case-control studies. PubMed and CBMdisc literature research were conducted to identify all eligible studies investigating such a relationship. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of the association. In the overall analysis, the frequency of glutathione-S-transferase Mu-1 (GSTM1) null genotype was significantly associated with susceptibility to idiopathic male infertility. In further stratified analysis by sperm concentration of the case group, no significantly increased risk of azoospermia was found in either GSTM1 null or glutathione-S-transferase Theta-1 (GSTT1) null genotype. Compared with a significant relationship between GSTM1 null genotype and oligoasthenoteratozoospermia (OAT), GSTT1 null genotype was not associated with the OAT risk. Additionally, a subgroup analysis on ethnicity showed no notable association between the polymorphism and the risk of idiopathic male infertility in any of GSTM1 null and GSTT1 null genotype, neither in Asian nor in European populations. In conclusion, these results support that the GSTM1 null genotype mainly contributes to idiopathic male infertility susceptibility, particularly to OAT.

GSTM1 null genotype contributes to increased risk of male infertility: a meta-analysis

BACKGROUND

Many studies have investigated the association between Glutathione S-Transferase M 1 (GSTM1) null genotype and risk of male infertility, but the impact of GSTM1 null genotype on infertility risk is unclear owing to the obvious inconsistency among those studies. This study aimed to quantify the strength of association between GSTM1 null genotype and risk of male infertility.

METHODS

We searched the PubMed, Embase and Wangfang databases for studies investigating the association between GSTM1 null genotype and risk of male infertility. We estimated pooled odds ratio (OR) with its 95 % confidence interval (95 % CI) to assess this possible association.

RESULTS

Twelve case-control studies with 1, 589 infertility cases and 1, 537 controls were included. Meta-analysis of total 12 studies showed that GSTM1 null genotype was associated with increased risk of male infertility (OR = 1.34, 95%CI 1.02-1.77, P = 0.036). In subgroup analysis of Caucasians, there was also an obvious association between GSTM1 null genotype and increased risk of male infertility (OR = 1.51, 95%CI 1.11-2.05, P = 0.006). Sensitivity analyses by sequential omission of individual studies or omitting studies without high quality did not significantly alter the overall pooled OR. Cumulative meta-analysis further showed a trend of more obvious association as information accumulated. No evidence of publication bias was observed.

CONCLUSION

Meta-analyses of available data suggest that GSTM1 null genotype contributes to increased risk of male infertility.

Are glutathione S transferases involved in DNA damage signalling? Interactions with DNA damage and repair revealed from molecular epidemiology studies

Glutathione S-transferases (GSTs) are members of a multigene family of isoenzymes that are important in the control of oxidative stress and in phase II metabolism. Acting non-enzymically, GSTs can modulate signalling pathways of cell proliferation, cell differentiation and apoptosis. Using a molecular epidemiology approach, we have investigated a potential involvement of GSTs in DNA damage processing, specifically the modulation of DNA repair in a group of 388 healthy adult volunteers; 239 with at least 5 years of occupational exposure to asbestos, stone wool or glass fibre, and 149 reference subjects. We measured DNA damage in lymphocytes using the comet assay (alkaline single cell gel electrophoresis): strand breaks (SBs) and alkali-labile sites, oxidised pyrimidines with endonuclease III, and oxidised purines with formamidopyrimidine DNA glycosylase. We also measured GST activity in erythrocytes, and the capacity for base excision repair (BER) in a lymphocyte extract. Polymorphisms in genes encoding three GST isoenzymes were determined, namely deletion of GSTM1 and GSTT1 and single nucleotide polymorphism Ile105Val in GSTP1. Consumption of vegetables and wine correlated negatively with DNA damage and modulated BER. GST activity correlated with oxidised bases and with BER capacity, and differed depending on polymorphisms in GSTP1, GSTT1 and GSTM1. A significantly lower BER rate was associated with the homozygous GSTT1 deletion in all asbestos site subjects and in the corresponding reference group. Multifactorial analysis revealed effects of sex and exposure in GSTP1 Ile/Val heterozygotes but not in Ile/Ile homozygotes. These variants affected also SBs levels, mainly by interactions of GSTP1 genotype with exposure, with sex, and with smoking habit; and by an interaction between sex and smoking. Our results show that GST polymorphisms and GST activity can apparently influence DNA stability and repair of oxidised bases, suggesting a potential new role for these proteins in DNA damage processing via DNA damage signalling.

Polymorphisms of glutathione S-transferases M1, T1, P1 and A1 genes in the Tunisian population: an intra and interethnic comparative approach

Genetic polymorphisms in glutathione S-transferases (GSTs) genes might influence the detoxification activities of the enzymes predisposing individuals to cancer risk. Owing to the presence of these genetic variants, inter-individual and ethnic differences in GSTs detoxification capacity have been observed in various populations. Therefore, the present study was performed to determine the prevalence GSTM1 0/0, GSTT1 0/0, GSTP1 Ile(105)Val, and GSTA1 A/B polymorphisms in 154 healthy individuals from South Tunisia, and to compare them with those observed in North and Centre Tunisian populations and other ethnic groups. GSTM1 and GSTT1 polymorphisms were analyzed by a Multiplex-PCR approach, whereas GSTP1 and GSTA1 polymorphisms were examined by PCR-RFLP. The frequencies of GSTM10/0 and GSTT1 0/0 genotypes were 53.9% and 27.9%, respectively. The genotype distribution of GSTP1 was 47.4% (Ile/Ile), 40.9% (Ile/Val), and 11.7% (Val/Val). For GSTA1, the genotype distribution was 24.7% (A/A), 53.9% (A/B), and 21.4% (B/B). The combined genotypes distribution of GSTM1, GSTT1, GSTP1 and GSTA1 polymorphisms showed that thirty one of the 36 possible genotypes were present in our population; eight of them have a frequency greater than 5%. To the best of our knowledge, this is the first report of GSTs polymorphisms in South Tunisian population. Our findings demonstrate the impact of ethnicity and reveal a characteristic pattern for Tunisian population. The molecular studies in these enzymes provide basis for further epidemiological investigations in the population where these functional polymorphisms alter therapeutic response and act as susceptibility markers for various clinical conditions.

Male infertility and its causes in human

Infertility is one of the most serious social problems facing advanced nations. In general, approximate half of all cases of infertility are caused by factors related to the male partner. To date, various treatments have been developed for male infertility and are steadily producing results. However, there is no effective treatment for patients with nonobstructive azoospermia, in which there is an absence of mature sperm in the testes. Although evidence suggests that many patients with male infertility have a genetic predisposition to the condition, the cause has not been elucidated in the vast majority of cases. This paper discusses the environmental factors considered likely to be involved in male infertility and the genes that have been clearly shown to be involved in male infertility in humans, including our recent findings.