Sezgin Gunes

Smoking and Male Infertility: An Evidence-Based Review.

Many studies have reported that the contents of cigarette smoke negatively affect sperm parameters, seminal plasma, and various other fertility factors. Nevertheless, the actual effect of smoking on male fertility is not clear. The effect of smoking on semen parameters is based on the well-established biological finding that smoking increases the presence of reactive oxygen species, thereby resulting in oxidative stress (OS). OS has devastating effects on sperm parameters, such as viability and morphology, and impairs sperm function, hence reducing male fertility. However, not all studies have come to the same conclusions. This review sheds light upon the arguable association between smoking and male fertility and also assesses the impact of non-smoking routes of tobacco consumption on male infertility. It also highlights the evidence that links smoking with male infertility, including newly emerging genetic and epigenetic data, and discusses the clinical implications thereof.

Spermatogenesis, DNA damage and DNA repair mechanisms in male infertility.

Spermatogenesis is a complex process of proliferation and differentiation during male germ cell development involving mitosis, meiosis and spermiogenesis. Endogenous and exogenous physical, chemical and biological sources modify the genome of spermatozoa. The genomic integrity and stability of the sperm is protected by DNA repair mechanisms. In the male germline cells, DNA repair mechanisms include nucleotide excision repair, base excision repair, DNA mismatch repair, double strand break repair and post-replication repair. Defects in repair mechanisms cause arrest of spermatogenesis and abnormal recombination, ultimately resulting in male infertility. This review focuses on molecular mechanisms of the DNA repair pathways, DNA repair defects and male infertility.

Polymorphisms of CYP1A1, GSTM1, GSTT1, and Prostate Cancer Risk in Turkish Population

Prostate cancer is the most common cancer among men in many countries. Although the etiology of prostate cancer largely is unknown, both genetic and environmental factors may be involved. Advanced age, androgen metabolism, and heredity-race have been reported to be possible risk factors. On the other hand, several studies indicate that genetic polymorphisms in biotransformation enzymes play a role in prostate cancer development. In this study, association of the prostate cancer risk with genotype frequencies of the Phase I (CYP1A1) and Phase II (GSTM1 and GSTT1) biotransformation enzymes was investigated in 321 Turkish individuals (152 prostate cancer patients and 169 age-matched male controls). The presence or absences of the GSTM1 and GSTT1 genes were determined by a PCR-based method. Genotypes of CYP1A1 were determined by MspI-RFLP. The prevalence of GSTM1 null genotype in the cases was 64 percent, compared to 31 percent in the control group, indicating a strong association (OR = 4.08, 95%CI = 2.50–6.69). No association was observed between either GSTT1 null genotype or CYP1A1 polymorphism and prostate cancer incidence. No statistically significant association was observed between smoking status of the patients and any of the polymorphisms studied. In conclusion, results of this study indicate that only the GSTM1 null genotype may play an important role as a risk factor for prostate cancer development in Turkish population.

Vitamin D receptor gene polymorphisms in patients with urolithiasis

Urolithiasis is a multifactorial disease, the onset and severity of which is influenced by both genetic and environmental factors. This study represents an investigation of the role of vitamin D receptor (VDR) gene polymorphisms (ApaI, BsmI, and TaqI) and combined genotypes in urolithiasis in a Turkish population. We studied 110 patients with urinary stones and 150 control subjects. The polymorphic regions were amplified using polymerase chain reaction, followed by digestion with restriction enzymes BsmI, ApaI, and TaqI, and analyzed electrophoretically. Genotype and allele frequencies were calculated, and the association with urolithiasis, family history, and recurrence of stone was investigated. Our data provide no evidence for an association between urolithiasis and VDR ApaI, BsmI, and TaqI genotypes. We also analyzed the effects of VDR ApaI, BsmI, and TaqI genotypes in combination; the “GTT” VDR haplotype, constructed from three adjacent restriction fragment length polymorphisms was overrepresented among the urolithiasis patients. However, no significant differences between heterozygous carriers (OR 1.302; 95% CI 0.527–3.215) and homozygous carriers (OR 3.39; 95% CI 0.719–15.985) were observed in our study population. A significant association was found only between the ApaI polymorphism and family history (P=0.017; χ2=5.657). Our data indicate that the VDR ApaI, BsmI, and TaqI polymorphisms do not confer a significant risk for urolithiasis.

The relationship between the presence of ADHD and certain candidate gene polymorphisms in a Turkish sample.

Due to the high heritability of attention-deficit hyperactivity disorder (ADHD), parents of children with ADHD appear to represent a good sample group for investigating the genetics of the disorder. The aim of this study was to investigate the association between ADHD and six polymorphisms in five candidate genes [5-HT2A (rs6311), NET1 (rs2242447), COMT (rs4818), NTF3 (rs6332), SNAP-25 (rs3746544) and (rs1051312)]. We included 228 parents of children diagnosed with ADHD and 109 healthy parents as the control group. The polymorphisms were genotyped using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) assays and analyzed using the chi-square test and the multinomial logit model. SNAP-25 (rs3746544) polymorphism was associated with loading for ADHD, while 5-HT2A (rs6311) and NET1 (rs2242447) polymorphisms were associated with ADHD. On the other hand, there was no significant association between the SNAP-25 (rs1051312), NTF3 (rs6332), or COMT (rs4818) gene polymorphisms and ADHD. In addition, we found that even if variation in the SNAP-25 gene alone does not affect the phenotype, it may nevertheless lead to the emergence of a clinical ADHD picture in the presence of other genetic factors. Our findings suggest that a combination of NET1 (rs2242447) and SNAP-25 (rs3746544) is a risk factor for ADHD. Problems associated with the noradrenergic and serotonergic systems and SNAP-25 may play a role, both alone and in interaction with one another, in the pathophysiological mechanisms of ADHD.

Hypermethylation of TWIST1 and NID2 in Tumor Tissues and Voided Urine in Urinary Bladder Cancer Patients

Bladder cancer like other cancers arises from the accumulation of many genetic and epigenetic changes that lead to the activation of proto-oncogenes or inactivation of tumor suppressor genes. We aimed to investigate the methylation patterns of Twist homolog 1 (TWIST1) and nidogen-2 (NID2) genes in bladder cancer. Fifty six histologically confirmed bladder tumor samples and paired 24 urine samples constituted the study group and was compared with 15 age- and gender-matched noncancerous individuals. DNA was purified from both tumor and urine samples. The methylation status of the two genes was analyzed by methylation-specific polymerase chain reaction (MSP) in both urinary bladder cell carcinoma samples and urine samples. Sensitivity and specificity values of the method were assessed and compared with the results of the cytology test. Methylation of TWIST1 and NID2 was detected in 98.2% and 96.4% of the tumor samples, and in 87.5% and 95.8% of the urine samples, respectively. The sensitivity of TWIST1 and NID2 genes (87.5% and 95.8% in urine samples, respectively), was higher compared with urine cytology (62.5%) for cancer detection. The sensitivity of any of the two genes was 88.8% (8/9) for low-grade cases. The sensitivity of urine cytology was 33.3% for the same low-grade cases. To be used in the early noninvasive diagnosis of bladder cancer, the combined methylation analysis of TWIST1 and NID2 genes may be a simple, noninvasive, sensitive, and specific method for detecting cancer cells in urine.

Effects of aging on the male reproductive system.

The study aims to discuss the effects of aging on the male reproductive system. A systematic review was performed using PubMed from 1980 to 2014. Aging is a natural process comprising of irreversible changes due to a myriad of endogenous and environmental factors at the level of all organs and systems. In modern life, as more couples choose to postpone having a child due to various socioeconomic reasons, research for understanding the effects of aging on the reproductive system has gained an increased importance. Paternal aging also causes genetic and epigenetic changes in spermatozoa, which impair male reproductive functions through their adverse effects on sperm quality and count as, well as, on sexual organs and the hypothalamic-pituitary-gonadal axis. Hormone production, spermatogenesis, and testes undergo changes as a man ages. These small changes lead to decrease in both the quality and quantity of spermatozoa. The offspring of older fathers show high prevalence of genetic abnormalities, childhood cancers, and several neuropsychiatric disorders. In addition, the latest advances in assisted reproductive techniques give older men a chance to have a child even with poor semen parameters. Further studies should investigate the onset of gonadal senesce and its effects on aging men.

The role of epigenetics in idiopathic male infertility.

Infertility is a complex disorder with multiple genetic and environmental causes. Although some specific mutations have been identified, other factors responsible for sperm defects remain largely unknown. Despite considerable efforts to identify the pathophysiology of the disease, we cannot explain the underlying mechanisms of approximately half of infertility cases. This study reviews current data on epigenetic regulation and idiopathic male infertility. Recent data have shown an association between epigenetic modifications and idiopathic infertility. In this regard, epigenetics has emerged as one of the promising research areas in understanding male infertility. Many studies have indicated that epigenetic modifications, including DNA methylation in imprinted and developmental genes, histone tail modifications and short non-coding RNAs in spermatozoa may have a role in idiopathic male infertility.

SOX4 expression levels in urothelial bladder carcinoma

High levels of SOX4 gene expression have been reported in a variety of human cancers. The protein may function in the apoptosis pathway, leading to cell death as well as to tumorigenesis. The aim of this study was to investigate the levels of SOX4 expression in bladder cancer. Urinary bladder tumor samples were obtained from 57 bladder cancer and 13 normal bladder biopsies. The levels of SOX4 expression in bladder cancer were determined by immunohistochemistry and real-time PCR. SOX4 gene expression was increased 2.2 times in bladder tumors as compared with normal tissue. The presence of protein was confirmed by immunostaining. There were significant differences between immunostaining of bladder tumors and normal bladder tissue (P=0.001). The present data suggest that SOX4 gene may have a role in bladder cancer tumorigenesis.

Lack of evidence for association between endothelial nitric oxide synthase gene polymorphism (glu298asp) with Behçet’s disease in the Turkish population

Endothelial nitric oxide synthase (eNOS) could be a candidate gene for Behçet’s disease (BD). This study investigated the relationship of the eNOS Glu298→Asp polymorphism with the presence and severity of BD in the Turkish population. Ninety-two patients with BD and 100 controls were studied. Analyses of Glu298Asp polymorphism in exon 7 of the eNOS gene were made by the polymerase chain reaction (PCR)-restriction fragment length polymorphism technique. The frequencies of the eNOS genotypes were similar for BD patients (GG:GT:TT=58.7%:38%:3.3%) and controls (59.2%:33.7%:7.1 %), P=0.335. No evidence of difference was found in the frequency of the T allele between BD patients (22.3%) and controls (24%), [OR=0.91, 95% CI (0.55–1.50), P=0.690]. Glu298→Asp polymorphism of the eNOS gene does not appear to be associated with the presence of BD in the Turkish population.