Differences in the seminal plasma proteome are associated with oxidative stress levels in men with normal semen parameters.

OBJECTIVE: To study the seminal plasma proteome in association with semen lipid peroxidation levels in men with normal semen parameters.
DESIGN: Cross-sectional study.
SETTING: University andrology and research laboratories. PATIENT(S): A total of 156 normozoospermic men. INTERVENTION(S): Seminal lipid peroxidation levels were assessed in individual samples through thiobarbituric acid reactive substances quantification. Subsequently, lipid peroxidation data were used to divide the samples into the experimental groups: low lipid peroxidation levels (control group, bottom 15%, n = 23) and high lipid peroxidation levels (study group, top 15%, n = 23). Seminal plasma proteins from these groups were pooled (four pools per group, with biological variation between the pools) and used for a shotgun proteomic analysis using a liquid chromatography-tandem mass spectrometry approach. Quantitative data were used for univariate (unpaired Student's t test) and multivariate (partial least-squares discriminant analysis, logistic regression, and discriminant analyses) statistical analyses. Significant proteins were also used for functional enrichment analysis. MAIN OUTCOME MEASURE(S): Seminal plasma protein profile and postgenomic pathways of seminal plasma are associated with seminal lipid peroxidation levels. RESULT(S): In total, 629 proteins were quantified in seminal plasma. Of these, 23 proteins were absent or underexpressed and 71 were exclusive or overexpressed in the study group. The main enriched functions in association with seminal lipid peroxidation were unsaturated fatty acids biosynthesis, oxidants and antioxidants activity, cellular response to heat stress, and immune response. Moreover, we suggested mucin-5B as a potential biomarker of semen oxidative stress. CONCLUSION(S): The seminal plasma proteome does reflect semen lipid peroxidation status and, thus, oxidative stress.