Correlation between sperm oxidative stress and sperm DNA damage in subfertile men

Abstract: ABSTRACT Background: Approximately 15 % of all couples in the Western countries experience infertility. Up to half of these cases are thought to solely or partly depend upon the male factor. In most cases male infertility is unexplained. During the last decade there has been a growing focus on sperm DNA damage as a cause of male infertility. Sperm chromatin structure assay (SCSA) is increasingly used to evaluate male fertility status as it determines sperm DNA damage. This DNA damage can originate from several sources, the major being oxidative stress, i.e excess of reactive oxygen species (ROS). Increased ROS may be a result of different factors, for instance chronic diseases, infections or lifestyle factors such as smoking and high body mass index (BMI). Despite this, sperm ROS is not tested for in routine infertility assessment. A new promising analysis for assessing sperm ROS production is the nitro blue tetrazolium assay (NBT). Objectives: The primary objective was to study the correlation between sperm oxidative stress assessed with NBT assay and sperm DNA fragmentation index (DFI) assessed with SCSA in subfertile men. Secondly, the objective was to correlate these parameters to BMI as well as to the level of serum testosterone. Method: The prospective study was conducted on a cohort of forty-seven subfertile men. To assess sperm quality the NBT assay, SCSA and World Health Organization (WHO) sperm analysis were performed. For all men testosterone, lutenizing hormone (LH) and BMI were measured. Result: There was a tendency to a correlation between NBT outcome and DFI (n = 39, r = 0.281, P = 0.084), however not statistically significant. Men with a BMI > 30 kg/m2 had an increased risk for having a DFI > 30% (OR = 8.6, P = 0.070) compared to the normal weighted men, although not statistically significant. Conclusion: There was a weak association between sperm oxidative stress and sperm DNA damage. A high BMI was correlated to an increased risk of DNA damage. Although non of these findings were statistically significant they show the same tendencies as previous reports. Sperm oxidative stress seems likely as a cause of male infertility and large scale clinical trials are warranted to further evaluate the NBT assay. The hope for the future is to be able to sort out the men with sperm oxidative stress caused infertility, who potentially would benefit from antioxidant strategies.