Correlation between sperm DNA methylation level and semen quality among 73 college students in Chongqing, China

Abstract

Objective To investigate the association of sperm DNA methylation level with routine semen parameters and sperm chromatin integrity. Methods A total of 73 male individuals who were sampled from our previously established cohort of the male reproductive health in Chongqing college students (MARHCS) study were recruited in this study. The routine semen parameters (semen volume, sperm density, total sperm count and sperm motility) and indicators of sperm chromatin integrity were detected and analyzed with computer-aided sperm analysis system (CASA) and sperm chromatin structure analysis (SCSA), respectively. ELISA was used to detect the sperm DNA 5mC content, which reflected the methylation level of sperm DNA. Meanwhile, age, BMI, abstinence time and lifestyle of the volunteers were collected through questionnaire survey. Multiple linear regression model was applied to explore the correlation of sperm DNA 5mC content with routine semen parameters and sperm chromatin integrity. The differences in percentages of different grade of sperm were compared in the high and low 5mC% groups (binary classification according to the median value of 5mC%). Results The semen routine parameters (median value) of the volunteers were as follows: semen volume was 4.18 mL, sperm density was 55.60×106/mL, total sperm count was 246.93×106, and sperm motility was 57.00%; Sperm chromatin was in structural integrity, with a median value of sperm DNA fragmentation index (DFI) and high DNA stainablity (HDS) of 10.99% and 3.39%, respectively. The median value of sperm DNA 5mC level was 2.63%. After adjustment for confounding factors, multiple linear regression analysis showed that sperm DNA 5mC level was negatively correlated with sperm density (β=-0.22, 95%CI: -0.36~-0.06, P=0.008) and total sperm count (β=-0.20, 95%CI: -0.33~-0.05, P=0.015), but no statistical correlations were observed in sperm DNA 5mC level with DFI and HDS (P>0.05). Meanwhile, there were no significant differences in the percentages of different grade of sperm (grade A~D) in the high 5mC group than the low 5mC group (P>0.05). Conclusion Elevated sperm DNA methylation level may be a biomarker for the decrease of sperm density and total sperm count, while is not correlated with indicators of sperm chromatin integrity.

Keywords

• sperm dna 5mc
• routine semen parameters
• sperm chromatin integrity
• correlation analysis