P-049 Sperm GSTM3: a potential molecular biomarker for sperm quality and male (in)fertility

Abstract

Abstract Study question Is sperm Glutathione S-transferase Mu 3 (GSTM3) associated to sperm physiological status and male (in)fertility? Summary answer GSTM3 is expressed in human sperm, and is associated to sperm quality and fertility, which suggests it as a potential molecular biomarker for male (in)fertility. What is known already GSTM3 is an antioxidant enzyme expressed in sperm cells that is essential for an appropriate mitochondrial function, plasma membrane stability and oxidative regulation. Previous evidence suggested sperm GSTM3 to be useful as an infertility prognosis and diagnosis tool in mammalian species. In humans, expression of sperm GSTM3 has been found to be altered in mitochondrial-impaired sperm and in sperm from patients with unilateral varicocele. However, neither has this enzyme been related to semen alterations nor has it been reported to be associated to male infertility. Study design, size, duration A total of 34 semen samples from healthy, fertile men and men referred for infertility evaluation were collected, analysed and subsequently cryopreserved. Samples were classified as fertile having normal sperm parameters (NSP; n = 10); infertile with asthenoteratozoospermia (AT; n = 8) or oligoasthenoteratozoospermia (OAT; n = 8); or with idiopathic infertility (n = 8). Finally, frozen-thawed sperm samples were assessed for DNA fragmentation, and the presence, localization and relative content of GSTM3. Protein expression of GSTM3 in sperm was compared between groupss. Participants/materials, setting, methods All samples were initially evaluated by conventional sperm analysis (ejaculate volume and pH, sperm concentration, motility and morphology). Protein expression profile of GSTM3 was determined through immunoblotting and immunolocalization assays. Sperm GSTM3 was quantified using an enzyme-linked immunosorbent assay. Spearman's rank-order correlation coefficients between GSTM3 levels and sperm quality parameters were calculated. Statistical differences between groups were determined by Kruskal-Wallis followed by Mann-Whitney U tests. Main results and the role of chance GSTM3 was found to be present in human sperm cells, and to be localized along the tail. Sperm GSTM3 was positively and significantly correlated with sperm quality parameters (concentration [Rs=0.51], morphology [Rs=0.42], total [Rs=0.60] and progressive motility [Rs=0.58]; P < 0.05). Sperm GSTM3 levels were compared between sperm quality groups (NSP, AT and OAT). Sperm GSTM3 levels were found to be significantly higher (P < 0.05) in men with NSP than in those with AT or OAT (62.1, 28.1 and 20.6 ng GSTM3/mg total protein, respectively). Finally, levels of GSTM3 in sperm were compared between fertile and infertile men. Whereas fertile and idiopathic infertile men showed similar sperm GSTM3 levels (63.7 vs. 60.0 ng GSTM3/mg total protein, respectively, P > 0.05), infertile men with an altered seminogram had significantly lower (P < 0.05) levels (24.4 ng GSTM3/mg total protein). Limitations, reasons for caution The limited sample size of the present study warrants further research and clinical trials with larger sample sets before implementing this biomarker as a molecular diagnostic tool in fertility clinics. Wider implications of the findings The use of sperm GSTM3 as a novel biomarker in fertility clinics may be translated into cost-effective, non-invasive, time-saving and accurate diagnosis of men (in)fertility. Trial registration number N/A