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. 2009 Jan 19;11(3):333–341. doi: 10.1038/aja.2008.27

Genetic polymorphisms in glutathione S-transferase T1 affect the surgical outcome of varicocelectomies in infertile patients

Kentaro Ichioka 1, Kanji Nagahama 1, Kazutoshi Okubo 1, Takeshi Soda 1, Osamu Ogawa 1,*, Hiroyuki Nishiyama 1
PMCID: PMC3735287  PMID: 19151739

Abstract

Glutathione S-transferases (GSTs), superoxide dismutase 2 (SOD2) and NAD(P)H:quinone oxidoreductase 1 (NQO1) are anti-oxidant enzyme genes. Polymorphisms of GSTs, SOD2 and NQO1 have been reported to influence individual susceptibility to various diseases. In an earlier study, we obtained preliminary findings that a subset of glutathione S-transferase T1 (GSTT1)-wt patients with varicocele may exhibit good response to varicocelectomy. In this study, we extended the earlier study to determine the distribution of genotype of each gene in the infertile population and to evaluate whether polymorphism of these genes affects the results of surgical treatment of varicocele. We analyzed 72 infertile varicocele patients, 202 infertile patients without varicocele and 101 male controls. Genotypes of GSTs were determined by polymerase chain reaction (PCR). Genotyping of SOD2 and NQO1 was performed using the PCR-restriction fragment length polymorphism (PCR-RFLP) method. A significantly better response to varicocelectomy was found in patients with the GSTT1-wt genotype (63.2%) and NQO1-Ser/Ser genotype (80.0%) than in those with GSTT1-null genotype (35.3%) and NQO1-Pro/Pro or NQO1-Pro/Ser genotype (45.2%), respectively. The frequencies of glutathione S-transferase M1/T1, SOD2 and NQO1 genotypes did not differ significantly among the varicocele patients, idiopathic infertile patients and male controls. GSTT1 genotype is associated with improvement of semen parameters after varicocelectomy. As the number of patients with NQO1-Ser/Ser genotype was not sufficient to reach definite conclusions, the association of NQO1 genotype with varicocelectomy requires further investigation.

Keywords: genetic polymorphism, GSTM1, GSTT1, male infertility, NQO1, SOD2, varicocele testis

Introduction

The most common and correctable known risk factor for male infertility is varicocele. Varicoceles are found in approximately 40% of infertile men, whereas the incidence in the general male population is approximately 15%1, 2, 3. Surgical correction of varicocele in infertile men has been shown to improve semen parameters3, 4, 5. However, not all men with varicocele are infertile, and not all infertile patients with varicocele show an improvement in seminal findings following surgical repair. Thus, a clinically important issue is the preoperative determination of which subset of patients, among all infertile men with varicocele, will respond to varicocelectomy.

Reactive oxygen species (ROS) are groups of free radicals that have deleterious effects on many organs. In varicocele patients, ROS production is enhanced6, 7, and oxidative stress is present in spermatic vein blood and seminal plasma8, 9, 10. Varicocele treatment can significantly improve sperm parameters, by decreasing ROS concentration and increasing antioxidant capacity, and these effects lead to improved sperm parameters finally11. Oxidative stress results from an imbalance between the production and reduction of ROS, and several types of anti-oxidant enzyme genes are associated with the removal of ROS.

The glutathione S-transferases (GSTs) are a family of cytosolic or microsomal enzymes12 that play important roles in the detoxification of products resulting from oxidative damage and exposure to some carcinogens13. Four classes of cytosolic GSTs have been identified in mammals, including the alpha, pi, theta and mu classes. Two human GST isoenzymes—the mu class enzyme, glutathione S-transferase M1 (GSTM1), and the theta class enzyme, glutathione S-transferase T1 (GSTT1)—have been shown to be polymorphic. In both cases, a gene deletion is responsible for the existence of a null allele. Individuals who are homozygous with respect to a given null allele lack that specific enzyme function. About half of all the individuals from various racial groups lack GST activity14.

Superoxide dismutase 2 (SOD2) is the only known superoxide scavenger in the mitochondria. Several nucleotide polymorphisms in the SOD2 gene have been reported, one of which is the alanine (Ala)-to-valine (Val) polymorphism at codon 16 in exon 2 (rs4880 at double-strand single-nucleotide polymorphism [dbSNP]). The Ala-to-Val substitution may affect the mitochondrial targeting rate of SOD2, which is responsible for mitochondrial damage and a decrease in the activity of this enzyme15.

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a cytosolic enzyme that induces two-electron reduction of quinoid compounds to hydroquinones, a less toxic form, thus avoiding free radical formation. A sequence variant at position 609 (C-to-T, proline [Pro]-to serine [Ser], rs1800566 at dbSNP) in the NQO1 gene encodes for an enzyme with reduced quinone reductase activity, which has been hypothesized to affect cancer susceptibility16, 17.

These polymorphisms of GSTs, SOD2 and NQO1 have been reported to influence individual susceptibility to various diseases, including malignancy18, 19, 20, 21, 22, 23, 24, 25, although the relationship between polymorphisms and male infertility remains to be elucidated26, 27. We therefore speculated that individual susceptibility to varicocele-induced ROS may depend on one or more of these genetic polymorphisms and that the outcome of varicocelectomy may be influenced by an individual's genetic susceptibility to ROS. In our earlier study, we obtained preliminary findings that a subset of GSTT1-wt patients with varicocele showed good responses to varicocelectomy28. However, the number of patients in that study was not sufficient to yield definitive conclusions. We therefore extended the earlier study and analysed a larger number of clinical samples to determine the distribution of genotypes for the GSTM1, GSTT1, SOD2 and NQO1 genes in the infertile population and to evaluate whether polymorphisms of these genes affect the results of varicocele surgical treatment.

Materials and methods

Subjects

Seventy-two male patients with clinical varicocele, 202 infertile patients without varicocele and 101 male controls at the Kyoto University Hospital and Akita University Hospital were enrolled in this study. All patients had the same ethnic and geographical origin. Male infertility was diagnosed on the basis of the results from at least two semen analyses, according to published criteria29. Patients with azoospermia were excluded from this study. Chromosomal analysis of peripheral blood was performed using a G-banding method in patients with severe oligozoospermia (≤ 5 million sperm per mL), and patients with a chromosomal abnormality were excluded from this study. A varicocele testis was identified on physical examination. The control group consisted of healthy volunteers and patients from the same clinics who had a benign urological disease. This study was approved by the Institutional Review Board of Kyoto University Hospital (Kyoto, Japan). Written informed consent was obtained from all patients.

Varicocelectomy and postoperative evaluation

Seventy-two patients with clinical varicocele underwent varicocelectomy. All varicocelectomies were performed using an inguinal approach under microscopic magnification, according to a method reported earlier30. At least two semen analyses were performed at 3, 6, 9 or 12 months postoperatively. A positive response to varicocele repair was defined as a 100% increase in the concentration of total motile sperm (sperm concentration × motile fraction) in the postoperative study.

DNA extraction, amplification and GSTM1/GSTT1/SOD2/NQO1 polymorphism genotyping

Genomic DNA was extracted from blood samples by one of two methods: samples were processed using a QIAamp Blood Kit (QIAGEN, Hilden, Germany) or by the standard method, involving a proteinase K digestion followed by phenol-chloroform extraction.

Multiplex polymerase chain reaction (PCR) was performed to detect the presence or absence of GSTM1 and GSTT1 genes, as described31. Individuals with homozygous null alleles lack the respective enzyme function, whereas individuals with two wild-type alleles and heterozygotes with one active and one inactive allele were classified as one group having enzyme function. The primer sequences were 5′-GAACTCCCTGAAAAGCTAAAGC-3′ and 5′-GTTGGGCTCAAATATACGGTGG-3′ for GSTM1, and 5′-TTCCTTACTGGTCCTCACATCTC-3′ and 5′-TCACCGGATCATGGCCAGCA-3′ for GSTT1. As an internal positive control for successful PCR, the β-globin gene was amplified with the primers 5′-CAACTTCATCCACGTTCACC-3′ and 5′-GAAGAGCCAAGGACAGTTAC-3′. The PCR conditions were 10 min at 95 °C for one cycle, and 60 s at 95°C, 60 s at 58°C and 90 s at 72°C for 35 cycles. GSTM1 and GSTT1 wild or null genotypes were indicated by the presence or absence of a 215 bp band and a 480 bp band, respectively. The genotypes of GSTM1 and GSTT1 were not scored if the PCR product from the internal reference β-globin gene (268 bp) was not evident.

We also analysed single-nucleotide polymorphisms (SNPs) of SOD2 and NQO1. The SNP of SOD2 is a C-to-T conversion in exon 2 that substitutes a Val for an Ala in the signal peptide at codon 9 (Ala16Val). The SNP of NQO1 is a C-to-T conversion that substitutes a Ser for a Pro at codon 187 (Pro187Ser). To determine SOD2 and NQO1 genotypes, DNA was amplified by PCR and genotyped by restriction analysis, as described24, 32. The PCR primers used were 5′-ACCAGCAGGCAGCTGGCGCCGG-3′ and 5′-GCGTTGATGTGAGGTTCCAG-3′ for the Ala16Val SOD2 polymorphism, and 5′-TCCTCAGAGTGGCATTCTGC-3′ and 5′-TCTCCTCATCCTGTACCTCT-3′ for the Pro187Ser NQO1 polymorphism. The PCR conditions for SOD2 were 10 min at 95°C for one cycle, 30 s at 95°C, 30 s at 55°C and 60 s at 72°C for 35 cycles, and 5 min at 72°C for one cycle. For NQO1, the PCR proceeded for 10 min at 95°C for one cycle, 30 s at 95°C, 30 s at 58°C and 45 s at 72°C for 35 cycles, and 5 min at 72°C for one cycle. Each PCR product was digested with NaeI for the Ala16Val SOD2 polymorphism and with HinfI for the Pro187Ser NQO1 polymorphism. DNA samples, together with those that were examined earlier, served as quality controls and were concomitantly digested. For the Ala16Val SOD2 polymorphism, restriction fragments were 106 and 21 bp for the Ala allele, and 127 bp for the Val allele. For the Pro187Ser NQO1 polymorphism, restriction fragments were 195 and 35 bp for the Pro allele, and 151, 44 and 35 bp for the Ser allele.

Statistical methods

The distribution of each genotype was analysed with the χ2 test. Differences in clinical parameters among subgroups were examined with the Mann-Whitney U test and the χ2 test. Comparison of the distribution of responders and non-responders was performed with the χ2 test. Odds ratios in the combination groups were calculated using logistic regression analysis. P < 0.05 was considered significant.

Results

Patient background and outcome of varicocelectomy

We evaluated the clinical characteristics of 72 patients who underwent a varicocelectomy. In the preoperative evaluation, 40 (55.6%) and 57 (79.2%) of the patients had oligozoospermia and asthenozoospermia, respectively. Patient background factors are shown stratified by genotype in Table 1. There were no significant differences among genotype subgroups with regard to age, preoperative or postoperative seminal parameters, or the distribution of varicocele grades. Positive responses to varicocele repair, based on motile sperm concentrations, were observed in 36 (50%) out of 72 patients. Preoperative and postoperative seminal parameters in the responder and non-responder subgroups are shown in Table 2.

Table 1. Background characteristics of patients stratified by GSTM1/T1, SOD2 and NQO1 genotypes (mean ± SD).

  Age (years) Grade of varicocele
 Preoperative semen parameters
 Postoperative semen parameters
G1 G2 G3 Concentration (×106) Motility (%) Concentration (×106) Motility (%)
Overall (n = 72) 33.3 ±4.7 17 32 23 22.8 ±21.6 34.1 ±21.6 31.7 ±32.6 43.7 ±21.4
GSTM1                
  Null (n = 45) 33.1 ±4.9 9 23 13 21.1 ±20.4 35.9 ± 23.6 35.2 ± 36.5 43.6 ± 23.0
  Wt (n = 27) 33.6 ±4.4 8 9 10 25.6 ± 23.7 31.0 ±18.0 25.9 ± 24.2 44.0 ± 19.0
GSTT1                
  Null (n = 34) 33.6 ±5.2 10 16 8 26.1 ±26.2 31.4 ±18.6 31.8 ±37.7 44.1 ±21.9
  Wt (n = 38) 32.9 ± 4.2 7 16 15 19.8 ±16.3 36.4 ± 24.0 31.6 ±27.7 43.4 ±21.3
MnSOD                
  Ala/Ala+Ala/Val (n = 13) 33.8 ±4.4 2 5 6 17.2 ±16.8 39.9 ±27.1 37.2 ± 35.5 48.5 ± 22.4
  Val/Val (n = 59) 33.1 ±4.8 15 27 17 24.0 ± 22.5 32.8 ± 20.3 30.5 ±32.1 42.7 ±21.3
NQO1                
  Pro/Pro+Pro/Ser (n = 59) 33.5 ±4.7 15 28 19 23.1 ±22.0 35.5 ± 22.5 30.5 ± 33.4 44.8 ±21.8
  Ser/Ser (n = 10) 31.9 ±4.8 2 4 4 20.4 ± 20.2 25.0 ± 12.6 39.3 ± 27.5 37.5 ± 19.0
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Abbreviations: Ala, alanine; GSTM1, glutathione S-transferase M1; GSTT1, glutathione S-transferase T1; NQO1, NAD(P)H:quinone oxidoreductase; Pro, proline; Ser, serine; Val, valine.

Table 2. Background characteristics and pre- and postoperative seminal parameters for patients in the responder and non-responder subgroups (mean ± SD).

  Overall (n = 72) Responder (n = 36) Non-responder (n = 36) P-value
Age (year) 33.3 ±4.7 33.3 ±4.3 33.2 ±5.1 NS
Grade of varicocele (N)        
  G1 17 6 11  
  G2 32 16 16 NS
  G3 23 14 9  
Preoperative semen parameters
  Concentration (×106) 22.8 ±21.6 17.8 ±17.5 27.7 ± 24.3 NS
  Motility (%) 34.1 ±21.6 31.4 ±19.8 36.7 ± 23.3 NS
Postoperative semen parameters
  Concentration (×106) 31.7 ±32.6 46.3 ± 37.5 17.1 ± 17.7 < 0.001
  Motility (%) 43.7 ±21.4 50.8 ± 20.5 36.7 ± 20.2 0.0061
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Abbreviation: NS, not significant.

The rates of response to varicocelectomy were also examined in each genotype using motile sperm concentration (Table 3). A significantly higher response rate was observed in patients with the GSTT1-wt genotype (63.2%) and the NQO1-Ser/Ser genotype (80.0%), compared with the GSTT1-null genotype (35.3%) and the NQO1-Pro/Pro or NQO1-Pro/Ser genotype (45.2%).

Table 3. The response rates for varicocelectomy in each genotype and in combination subgroups of GSTM1/T1 and GSTT1/NQO1 genotypes.

  Response rate P-value Odds ratio (95% CI)
Genotype
  Over all 50.0% (36/72)    
  GSTM1
    null 51.1% (23/45) NS NS
    wt 48.1% (13/27)    
  GSTT1
    null 35.3% (12/34) 0.018 3.14(1.20–8.24)
    wt 63.2% (24/38)    
  MnSOD
    Ala/Ala+Ala/Val 61.5% (8/13) NS NS
    Val/Va 47.5% (28/59)    
  NQO1
    Pro/Pro+Pro/Ser 45.2% (28/62) 0.041 NS
    Ser/Ser 80.0% (8/10)    
Combination groups
  GSTT1-wt/GSTM1-wt 66.7% (8/12)    
  GSTT1-null/GSTM1-wt and GSTT1-wt/GSTM1-null 51.2% (21/41) NS NS
  GSTT1 -null/GSTM1 -null 36.8% (7/19)    
  GSTT1-wt/NQO1-Ser/Ser 88.9% (8/9)    
  GSTT1-null/NQO1-Ser/Ser and GSTT1-wt/NQO1-Pro/Pro or -Pro/Ser 53.3% (16/30) NS NS
  GSTT 1-null/NQO1-Pro/Pro or -Pro/Ser 36.4% (12/33)    
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Abbreviations: Ala, alanine; CI, confidence interval; GSTM1, glutathione S-transferase M1; GSTT1, glutathione S-transferase T1; NQO1, NAD(P)H:quinone oxidoreductase; NS, not significant; Pro, proline; Ser, serine; Val, valine.

Predictive values in combined subgroups

The response rates of the groups with combinations of GSTT1 and GSTM1 genotypes, and of GSTT1 and NQO1 genotypes were analysed (Table 3). A higher response rate was observed in the GSTT1-wt/M1-wt group (75%) than in the groups with combinations of other GSTT1/M1 genotypes, although the differences were not statistically significant. A favourable response rate was also noted in the GSTT1-wt/NQO1-Ser/Ser group (88.9%), compared with the groups having combinations of other GSTT1/NQO1 genotypes, although the differences were not statistically significant.

Comparison of the distribution of each genotype in the controls, the overall group of infertile patients and the varicocele patients

Genotypes for four genes—GSTM1, GSTT1, SOD2 and NQO1—were analysed using 101 male controls and 274 infertile patients, which included 72 patients with varicocele. Mean ages were 47.2, 33.2 and 34.9 years for controls, the total group of infertile patients and the infertile varicocele patients, respectively. As shown in Table 4, none of the frequencies of the genotypes were significantly different between either the controls and the overall group of infertile patients, or between the controls and the infertile varicocele patients.

Table 4. The frequencies of each genotype in the controls and the subgroups of infertile patients.

Genotype Controls (n = 101) Infertile patients
Overall (n = 274) vs. controls Varicocele patients (n = 72) vs. controls
GSTM1
  Null 52.5% (53) 58.0% (159)   62.5% (45)  
  wt 47.5% (48) 42.0% (115) NS 37.5% (27) NS
GSTT1
  Null 50.5% (51) 46.0% (126)   47.2% (34)  
  Wt 49.5% (50) 54.0% (148) NS 52.8% (38) NS
MnSOD
  Ala/Ala 2.0% (2) 0.7% (2)   0.0% (0)  
  Ala/Val 14.8% (15) 21.2% (58) NS 18.1% (13) NS
  Val/Val 83.2% (84) 78.1% (214)   81.9% (59)  
NQO1
  Pro/Pro 36.6% (37) 39.1% (107)   34.7% (25)  
  Pro/Ser 45.6% (46) 44.5% (122) NS 51.4% (37) NS
  Ser/Ser 17.8% (18) 16.4% (45)   13.9% (10)  
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Abbreviations: Ala, alanine; GSTM1, glutathione S-transferase M1; GSTT1, glutathione S-transferase T1; NQO1, NAD(P)H:quinone oxidoreductase; NS, not significant; Pro, proline; Ser, serine; Val, valine.

Discussion

Varicocelectomy has become such a widely used treatment that by 1990 a series of 50 observational studies had been conducted that altogether showed an improvement in semen quality in 57% of men33. On the other hand, several reports have shown no benefit from varicocele surgery34, 35, 36. This subject is still controversial, but the current consensus seems to be that not all men with varicocele are infertile, and not all infertile patients with varicocele show an improvement in seminal findings after surgical repair. Thus, one clinically important issue regarding varicocele is preoperative recognition of who will respond to surgical treatment. Several studies have shown that ROS production is enhanced in varicocele patients6, 7, and that oxidative stress is present in spermatic vein blood and seminal plasma8, 9, 10. Oxidative stress results from an imbalance between the production and reduction of ROS. Thus, the spermatogenesis in patients with an impaired ability to reduce ROS may be strongly influenced by varicocele. Our preliminary study found that a subset of GSTT1-wt patients with varicocele may show good responses to surgical repair. This report suggested that genetic susceptibility to ROS might be associated with varicocele-induced infertility28.

In the earlier study, GSTT1-wt patients showed a good response to varicocelectomy, and response rates among groups with combinations of GSTM1 and GSTT1 genotypes were significantly different28. In this study, we extended the earlier study and confirmed these findings, although response rates among combined groups did not differ significantly. Genotyping of GSTT1 may aid in the decision-making process while selecting treatment options for infertile varicocele patients. GSTs play an important role in detoxifying products of oxidative damage12, 13. No earlier study has examined the relationships between GSTT1 genotypes and male infertility, and the molecular mechanisms and effects of GSTT1 on testicular function is unknown. However, patients with a GSTT1-wt genotype have a greater ability to reduce ROS, and they may recover more effectively from accumulated ROS damage after varicocelectomy. Additionally, a poor response to varicocelectomy has been reported to be related to severe and irreversible testicular damage37. Thus, in our study, the poor response to varicocelectomy in patients with a GSTT1-null genotype may be because of the severe testicular damage that occurred before varicocele repair.

NQO1 has the potential to detoxify quinones that are found in cigarette smoke and in ambient air38, acting as a phase II enzyme in the pathways of xenobiotic metabolism. Phase II enzymes catalyse the conversion of quinones to hydroquinones, which are readily excreted by the body. However, the Pro-to-Ser substitution in NQO1 is associated with a loss of enzyme function because of protein instability16, 17. In our study, patients with an NQO1-Ser/Ser genotype showed a better response to surgical repair. Our findings suggest that quinone-containing substances may be related to the aetiology of varicocele-induced infertility. However, the NQO1-Ser/Ser genotype is rare, and only 17.8% of the control group showed this genotype in the present study. In the varicocele subgroups, only 10 patients were categorized in this genotype. Our findings regarding the effects of the NQO1 genotype on varicocele-induced infertility thus require further investigation.

We showed that genotypes of GSTT1 were signifi-cantly associated with postoperative improvement in a patient's concentration of motile sperm. Generally, two major end-points were used in earlier studies. One is the improvement of motile sperm concentrations, which we also used in this study. The other is that the improved levels of sperm parameters are sufficiently within the reference range defined by the WHO. In this study, the genotype of each gene was not significantly related to this end-point (data not shown), possibly because the number of patients in this study was too small to elicit statistically significant results regarding the frequency of patients whose seminal findings increased into the WHO reference range. However, it is still important to note that varicocelectomy improves motile sperm concentrations, because this factor influences patients' decisions regarding assisted reproductive techniques (ART) options, and men with semen variables lower than the WHO reference range may still be fertile in this modern ART era.

Individuals with GSTM1-null, GSTT1-null, SOD2-Val/Val and NQO1-Ser/Ser genotypes may have altered tissue protection from exogenous and endogenous oxidants. The frequencies of these genotypes differ among races. The frequencies of the GSTM1-null, GSTT1-null, SOD2-Val/Val and NQO1-Ser/Ser genotypes in Asians have been reported to be 42.5%–51.3%, 51.0%–54.0%, 73.9%–75.1% and 12.7%–20.3%, respectively, whereas those in Caucasians are 45.0%–52.3%, 13%–15.7%, 21.4%–25.4% and 2.6%–4.4%, respectively19, 20, 21, 22, 23, 24, 25, 38, 39, 40, 41. In our series, the GSTM1-null, GSTT1-null, SOD2-Val/Val and NQO1-Ser/Ser genotypes were found in 52.7%, 49.8%, 83.2% and 17.8% of the controls, respectively, which are consistent with those observed earlier in Asian populations. We checked for the existence of genetic polymorphisms in the GSTM1, GSTT1, SOD2 and NQO1 genes in the overall group of male infertile patients. In our study, the frequencies of these polymorphic genotypes in the overall group of infertile male patients were not different from those in male controls, suggesting that the GSTM1, GSTT1, SOD2 and NQO1 genes are not related to the risk of male infertility. Aydemir et al.42 reported that the frequency of increased oxidative damage for sperm and seminal plasma in the male population with idiopathic infertility is higher in patients with a GSTM1-null genotype, although no significant differences were found in the distribution of the GSTM1 variant genotype between idiopathic infertile subjects and fertile subjects. Chen et al.27 reported that the frequency of sperm mitochondrial DNA damage in infertility patients with varicocele is higher in those with a GSTM1-null genotype, although the frequency of the GSTM1-null genotype did not differ between the varicocele group and the controls.

In conclusion, the rate of response to varicocelec-tomy was significantly higher in patients with a GSTT1-wt genotype. Characterization of the genetic profiles of patients is of great interest in defining optimal candidates for varicocelectomy. Further research with larger studies is needed to confirm the findings of our study.

Acknowledgments

We are indebted to many physicians and urologists at the Kyoto University Hospital and Akita University Medical Center (Akita, Japan) for providing samples and clinical information. We also thank Itsuko Fujiwara, Tomoko Matsushita and Chie Hagihara for technical assistance. This work was supported by grants from the Ministry of Education, Culture, Sports, Science and Technology of Japan, and from the Smoking Research Foundation of Japan.

References

  1. Jarow JP, Coburn M, Sigman M. Incidence of varicoceles in men with primary and secondary infertility. Urology. 1996;47:73–6. doi: 10.1016/s0090-4295(99)80385-9. [DOI] [PubMed] [Google Scholar]
  2. Witt MA, Lipshultz LI. Varicocele: a progressive or static lesion. Urology. 1993;42:541–3. doi: 10.1016/0090-4295(93)90268-f. [DOI] [PubMed] [Google Scholar]
  3. Jarow JP, Sharlip ID, Belker AM, Lipshultz LI, Sigman M, et al. Male Infertility Best Practice Policy Committee of the American Urological Association Inc. Best practice policies for male infertility. J Urol. 2002;167:2138–44. [PubMed] [Google Scholar]
  4. Schlesinger MM, Wilets IF, Nagler HM. Treatment outcomes after varicocelectomy: a critical analysis. Urol Clin North Am. 1994;21:517–29. [PubMed] [Google Scholar]
  5. Madgar I, Weissenberg R, Lunenfeld B, Karasik A, Goldwasser B. Controlled trial of high spermatic vein ligation for varicocele in infertile men. Fertil Steril. 1995;63:120–4. doi: 10.1016/s0015-0282(16)57306-3. [DOI] [PubMed] [Google Scholar]
  6. Barbieri ER, Hidalgo ME, Venegas A, Smith R, Lissi EA. Varicocele-associated decrease in antioxidant defenses. J Andorol. 1999;20:713–7. [PubMed] [Google Scholar]
  7. Hendin BN, Kolettis PN, Sharma RK, Thomas AJ, Jr, Agarwal A. Varicocele is associated with elevated spermatozoal reactive oxygen species production and diminished seminal plasma antioxidant capacity. J Urol. 1999;161:1831–4. [PubMed] [Google Scholar]
  8. Mitropoulos D, Deliconstantinos G, Zervas A, Villiotou V, Dimopoulos C, et al. Nitric oxide synthase and xanthine oxidase activities in the spermatic vein of patients with varicocole: a potential role for nitric oxide and peroxynitrite in sperm dysfunction. J Urol. 1996;156:1952–8. [PubMed] [Google Scholar]
  9. Romeo C, Lentile R, Santoro G, Impellizzeri P, Turiaco N, et al. Nitric oxide production is increased in the spermatic veins of adolescents with left idiopathic varicocele. J Pediatr Surg. 2001;36:389–93. doi: 10.1053/jpsu.2001.20724. [DOI] [PubMed] [Google Scholar]
  10. Allamaneni SSR, Naughton CK, Sharma RK, Thomas AJ, Agarwal A. Increased seminal reactive oxygen species levels in patients with varicoceles correlate with varicocele grade but not with testis size. Fertil Steril. 2004;82:1684–6. doi: 10.1016/j.fertnstert.2004.04.071. [DOI] [PubMed] [Google Scholar]
  11. Mostafa T, Anis TH, El-Nashar A, Imam H, Othman IA. Varicocelectomy reduces reactive oxygen species levels and increases antioxidant activity of seminal plasma from infertile men with varicocele. Int J Androl. 2001;24:261–5. doi: 10.1046/j.1365-2605.2001.00296.x. [DOI] [PubMed] [Google Scholar]
  12. Hayes JD, Pulford DJ. The glutathione S-transferase supergene family: regulation of GST and the contribution of the isoenzymes to cancer chemoprotection and drug resistance. Crit Rev Biochem Mol Biol. 1995;30:445–600. doi: 10.3109/10409239509083491. [DOI] [PubMed] [Google Scholar]
  13. Smith G, Stanley LA, Sim E, Strange RC, Wolf CR. Metabolic polymorphisms and cancer susceptibility. Cancer Surv. 1995;25:27–65. [PubMed] [Google Scholar]
  14. Board P, Coggan M, Johnston P, Ross V, Suzuki T, et al. Genetic heterogeneity of the human glutathione transferases: a complex of gene families. Pharmacol Ther. 1990;48:357–69. doi: 10.1016/0163-7258(90)90054-6. [DOI] [PubMed] [Google Scholar]
  15. Shimoda-Matsubayashi S, Matsumine H, Kobayashi T, Nakagawa-Hattori Y, Shimizu Y, et al. Structural dimorphism in the mitochondrial targeting sequence in the human superoxide dismutase 2 gene: a predictive evidence for conformational change to influence mitochondrial transport and a study of allelic association in Parkinson's disease. Biochem Biophys Res Commun. 1996;226:561–5. doi: 10.1006/bbrc.1996.1394. [DOI] [PubMed] [Google Scholar]
  16. Traver RD, Horikoshi T, Danenberg KD, Stadlbauer TH, Danenberg PV, et al. NAD(P)H:quinone oxidoreductase gene expression in human colon carcinoma cells: characterization of a mutation which modulates DT-diaphorase activity and mitomycin sensitivity. Cancer Res. 1992;52:797–802. [PubMed] [Google Scholar]
  17. Ross D, Traver RD, Siegel D, Kuehl BL, Misra V, et al. A polymorphism in NAD(P)H:quinone oxidoreductase (NQO1): relationship of a homozygous mutation at position 609 of the NQO1 cDNA to NQO1 activity. Br J Cancer. 1996;74:995–6. doi: 10.1038/bjc.1996.477. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Chen H, Sandler DP, Taylor JA, Shore DL, Liu E, et al. Increased risk for myelodysplastic syndromes in individuals with glutathione transferase theta 1 (GSTT1) gene defect. Lancet. 1996;347:295–7. doi: 10.1016/s0140-6736(96)90468-7. [DOI] [PubMed] [Google Scholar]
  19. Rebbeck TR. Molecular epidemiology of the human glutathione S-transferase genotypes GSTM1 and GSTT1 in cancer susceptibility. Cancer Epidemiol Biomarkers Prev. 1997;6:733–43. [PubMed] [Google Scholar]
  20. Ambrosone CB, Freudenheim JL, Thompson PA, Bowman E, Vena JE, et al. Manganese superoxide dismutase (MnSOD) genetic polymorphisms, dietary antioxidants, and risk of breast cancer. Cancer Res. 1999;59:602–6. [PubMed] [Google Scholar]
  21. Murata M, Watanabe M, Yamanaka M, Kubota Y, Ito H, et al. Genetic polymorphisms in cytochrome P450 (CYP) 1A1, CYP1A2, CYP2E1, glutathione S-transferase (GST) M1 and GSTT1 and susceptibility to prostate cancer in the Japanese population. Cancer Lett. 2001;165:171–7. doi: 10.1016/s0304-3835(01)00398-6. [DOI] [PubMed] [Google Scholar]
  22. Cai Q, Shu XO, Wen W, Cheng JR, Dai Q, et al. Genetic polymorphism in the manganese superoxide dismutase gene, antioxidant intake, and breast cancer risk: results from the Shanghai Breast Cancer Study. Breast Cancer Res. 2004;6:R647–55. doi: 10.1186/bcr929. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Li H, Kantoff PW, Giovannucci E, Leitzmann MF, Gaziano JM, et al. Manganese superoxide dismutase polymorphism, prediagnostic antioxidant status, and risk of clinical significant prostate cancer. Cancer Res. 2005;65:2498–504. doi: 10.1158/0008-5472.CAN-04-3535. [DOI] [PubMed] [Google Scholar]
  24. Niwa Y, Hirose K, Nakanishi T, Nawa A, Kuzuya K, et al. Association of the NAD(P)H:quinone oxidoreductase C609T polymorphism and the risk of cervical cancer in Japanese subjects. Gynecol Oncol. 2005;96:423–9. doi: 10.1016/j.ygyno.2004.10.015. [DOI] [PubMed] [Google Scholar]
  25. Eguchi-Ishimae M, Eguchi M, Ishii E, Knight D, Sadakane Y, et al. The association of a distinctive allele of NAD(P)H:quinone oxidoreductase with pediatric acute lymphoblastic leukemias with MLL fusion genes in Japan. Haematologica. 2005;90:1511–5. [PubMed] [Google Scholar]
  26. Pajarinen J, Savolainen V, Perola M, Penttilä A, Karhunen PJ. Glutathione S-transferase-M1 'null' genotype and alcohol-induced disorders of human spermatogenesis. Int J Androl. 1996;19:155–63. doi: 10.1111/j.1365-2605.1996.tb00456.x. [DOI] [PubMed] [Google Scholar]
  27. Chen SS, Chang LS, Chen HW, Wei YH. Polymorphisms of glutathione S-transferase M1 and male infertility in Taiwanese patients with varicocele. Hum Reprod. 2002;17:718–25. doi: 10.1093/humrep/17.3.718. [DOI] [PubMed] [Google Scholar]
  28. Okubo K, Nagahama K, Kamoto T, Okuno H, Ogawa O, et al. GSTT1 and GSTM1 polymorphisms are associated with improvement in seminal findings after varicocelectomy. Fertil Steril. 2005;83:1579–80. doi: 10.1016/j.fertnstert.2004.11.057. [DOI] [PubMed] [Google Scholar]
  29. World Health Organization . New York: Cambridge University Press; 1992. WHO Laboratory Manual for the Examination of Human Semen and Semen–Cervical Mucus Interaction; p. p4. [Google Scholar]
  30. Okuno H, Nakamura E, Onishi H, Shichiri Y, Kakehi Y, et al. Clinical significance of varicocelectomy for male infertility. Jpn J Fertil Steril. 2000;45:333–7. [Google Scholar]
  31. Arand M, Mühlbauer R, Hengstler J, Jäger E, Fuchs J, et al. A multiplex polymerase chain reaction protocol for the simultaneous analysis of the glutathione S-transferase GSTM1 and GSTT1 polymorphisms. Anal Biochem. 1996;236:184–6. doi: 10.1006/abio.1996.0153. [DOI] [PubMed] [Google Scholar]
  32. Ichimura Y, Habuchi T, Tsuchiya N, Wang L, Oyama C, et al. Increased risk of bladder cancer associated with a glutathione peroxidase 1 codon 198 variant. J Urol. 2004;172:728–32. doi: 10.1097/01.ju.0000130942.40597.9d. [DOI] [PubMed] [Google Scholar]
  33. Mordel N, Mor-Yosef S, Margalioth EF, Simon A, Menashe M, et al. Spermatic vein ligation as treatment for male infertility: justification by post-operative semen improvement and pregnancy rates. J Reprod Med. 1990;35:123–7. [PubMed] [Google Scholar]
  34. Nieschlag E, Hertle L, Fischedick A, Abshagen K, Behre HM. Update on treatment of varicocele: counseling as effective as occlusion of the vena spermatica. Hum Reprod. 1998;13:2147–50. doi: 10.1093/humrep/13.8.2147. [DOI] [PubMed] [Google Scholar]
  35. Grasso M, Lania M, Castelli M, Galli L, Franzoso F, et al. Lowgrade left varicocele in patients over 30 years old: the effect of spermatic vein ligation on fertility. BJU Int. 2000;85:305–7. doi: 10.1046/j.1464-410x.2000.00437.x. [DOI] [PubMed] [Google Scholar]
  36. Evers JL, Collins JA. Assessment of efficacy of varicocele repair for male subfertility: a systematic review. Lancet. 2003;361:1849–52. doi: 10.1016/S0140-6736(03)13503-9. [DOI] [PubMed] [Google Scholar]
  37. Marks JL, McMahon R, Lipshultz LI. Predictive parameters of successful varicocele repair. J Urol. 1986;136:609–12. doi: 10.1016/s0022-5347(17)44990-1. [DOI] [PubMed] [Google Scholar]
  38. Joseph P, Jaiswal AK. NAD(P)H:quinone oxidoreductase 1 (DT diaphorase) specifically prevents the formation of benzo[a]pyrene quinone-DNA adducts generated by cytochrome P4501A1 and P450 reductase. Proc Nat Acad Sci USA. 1994;91:8413–7. doi: 10.1073/pnas.91.18.8413. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Kelsey KT, Ross D, Traver RD, Christiani DC, Zuo ZF, et al. Ethnic variation in the prevalence of a common NAD(P)H:quinone oxidoreductase polymorphism and its implications for anti-cancer chemotherapy. Br J Cancer. 1997;76:852–4. doi: 10.1038/bjc.1997.474. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. Brans R, Dickel H, Bruckner T, Coenraads PJ, Heesen M, et al. MnSOD polymorphisms in sensitized patients with delayed-type hypersensitivity reactions to the chemical allergen para-phenylene diamine: a case-control study. Toxicology. 2005;212:148–54. doi: 10.1016/j.tox.2005.04.008. [DOI] [PubMed] [Google Scholar]
  41. Mitrou PN, Watson MA, Loktionov AS, Cardwell C, Gunter MJ, et al. Role of NQO1 C609T and EPHX1 gene polymorphisms in the association of smoking and alcohol with sporadic distal colorectal adenomas: results from the UKFSS study. Carcinogenesis. 2007;28:875–82. doi: 10.1093/carcin/bgl194. [DOI] [PubMed] [Google Scholar]
  42. Aydemir B, Onaran I, Kiziler AR, Alici B, Akyolcu MC. Increased oxidative damage of sperm and seminal plasma in men with idiopathic infertility is higher in patients with glutathione S-transferase Mu-1 null genotype. Asian J Androl. 2007;9:108–15. doi: 10.1111/j.1745-7262.2007.00237.x. [DOI] [PubMed] [Google Scholar]

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