Infertility is one of the most important public health problems and affects the equal proportion of men and women (1). In sperm chromatin improvement, already, supplements have been used as complementary in spermatogenesis in men who have a sperm quality defect (2). For example, the role of vitamin E with its antioxidant effects on the development of normal spermatogenesis is important in normal sperm function (3). Improving the performance of the sperm and accessory glands makes it reasonable to use this vitamin or other antioxidants such as selenium (4). The antioxidant activity of glutathione peroxidase is strongly dependent on the presence of selenium in the active site of the enzyme. This enzyme is effective in preventing spermatic membrane lipid peroxidation and ultimately affects sperm function by improving sperm motility (5).
From another glance, in male infertility, epigenetic modifications may play a role in regulating and maintaining male germ cells (88-92). Therefore, epigenetic disorders are associated with disorders of regulation of DNA methylation in sperm cells (6, 7). Significant changes in the methylation level of sperm samples in infertile men lead to abortion in about 20% of the cases. This supports the idea that epigenetic disorders may be the reason for high incidence of abortion in humans (8). Sperms with proper quality are likely to have a stable genetic and epigenetic status and, as a result, provide sufficient epigenetic information for the growth and development of the embryo (9).
DNA methylation is catalyzed by a family of DNA methyltransferases (DNMTs). DNMT1 is one of the most abundant DNMTs in somatic cells and has a functional priority in semi methylated DNA strand. Therefore, it is thought as the main enzyme responsible for copying and maintaining the pattern of methylation after DNA replication (10). DNMT3A and DNMT3B are both excellent candidates for the formation of new methylation patterns (11).
One of the important intermediates in the transfer of methyl groups is folic acid, which plays a role in the synthesis of DNA, stability, integrity, and the main methyl donor in methylation and macromolecule production (12). Folic acid converts to 5-methyltetrahydrofolate, which acts in the transformation of homocysteine to methionine. Methionine is then metabolized to S- adenosyl methionine, which is a methyl donor in methylation and macromolecular synthesis (13).
In a study of the effects of folic acid and zinc sulfate on sperm quality, protamine content and acrosome integrity after varicocelectomy, both supplements together as oxidizing free radicals and inhibition of lipid peroxidation had the highest improvement on the variables (14). In men with high folate intake, lower frequency of different types of spermatic aneuploidy, such as Disomy 21 and X, was reported (15). In mice receiving folic acid-free diet for 36 weeks resulted in irreversible changes, suggesting that the long-term shortage of diet cause permanent genetic and epigenetic changes in the liver, which cannot be compensated from modification of the natural diet (16).
Given that folic acid consumption in spermatogenesis disorders is prescribed for antioxidant purposes, administration of this supplement has not been investigated with the approach to improve the status of sperm DNA methylation in patients with spermatogenesis disorders. Therefore, this study aimed to assess the improvement of sperm parameters and chromatin following the balance of methylation levels of the sperm genome by improving the global DNA methylation and transcription of methyltransferase gene such as DNMT1, DNMT3A, and DNMT3B after use of folic acid in men with severe spermatogenesis dysfunction.