Sperm telomere length is associated with sperm nuclear DNA integrity and mitochondrial DNA abnormalities among healthy male college students in Chongqing, China

Abstract STUDY QUESTION Is sperm telomere length (STL) associated with sperm nuclear DNA damage and mitochondrial DNA abnormalities? SUMMARY ANSWER Sperm telomere length is related to sperm nuclear DNA integrity and mitochondrial DNA abnormalities in healthy young college students. WHAT IS KNOWN ALREADY Many studies have revealed the correlations between sperm genetic alterations in both the nucleus and mitochondria and sperm functionality, however, the possible associations between the telomere, an important component of chromosome, and conventional indicators of mitochondrial DNA and nuclear DNA changes have not been investigated. STUDY DESIGN, SIZE, DURATION A prospective cohort study, Male Reproductive Health in Chongqing College Students (MARHCS), was conducted from June 2013 to June 2015. We pooled data collected from the follow-up study in 2014 and a total of 444 participants were included. PARTICIPANTS/MATERIALS, SETTING, METHODS STL was measured by quantitative (Q)-PCR. Sperm nuclear DNA integrity was determined using sperm chromatin structure assay (SCSA) and comet assay. Mitochondrial DNA damage was assessed by mitochondrial DNA copy number (mtDNAcn) evaluated with Q-PCR, and mtDNA integrity was determined with long PCR. MAIN RESULTS AND THE ROLE OF CHANCE The univariable-linear regression analysis revealed that STL was significantly positively correlated with markers of sperm nuclear DNA damage including the DNA fragmentation index (DFI) and comet parameters (the percentage of DNA in the tail, tail length, comet length, and tail moment). Additionally, STL was also significantly positively correlated with mtDNAcn and significantly negatively correlated with mtDNA integrity. After adjustment for potential confounders, these relationships remained appreciable. Moreover, we investigated potential effects of biometric factors, including age, parental age at conception, and BMI on STL and found that STL was increased with paternal age at conception. LIMITATIONS, REASONS FOR CAUTION A mechanistic explanation of the correlation between STL, sperm nuclear DNA integrity, and mtDNA abnormalities cannot be provided with a cross-sectional study design, so well-designed longitudinal studies are still necessary. In addition, a single semen samples were provided and were not all obtained at the same time point, which may increase the intraindividual bias in this study. WIDER IMPLICATIONS OF THE FINDINGS The findings extend the literature including assessment of mitochondrial dysfunction, sperm nuclear DNA damage, and telomere length and provide new insights into the relevance of STL in male reproduction. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the National Natural Science Foundation of China (No. 82073590), the National Natural Science Foundation of China (No. 81903363), the National Natural Science Foundation of China (No. 82130097), and the National Key R&D Program of China (2022YFC2702900). The authors declare no conflicts of interest. TRIAL REGISTRATION NUMBER N/A.