Sperm mitochondrial DNA copy number in relation to semen quality: A cross-sectional study of 1164 potential sperm donors

Abstract

Objective: To investigate the association between mitochondrial DNA copy number (mtDNAcn) and semen quality.

Design: A cross-sectional study.

Setting: Hubei Province Human Sperm Bank of China (from April 2017 to July 2018).

Population: A total of 1164 healthy male sperm donors with 5739 specimens.

Main outcome measures: Real-time quantitative polymerase chain reaction (RT-PCR) was used to measure sperm mtDNAcn. We also determined semen volume, concentration and motility parameters (progressive motility, nonprogressive motility and immotility).

Methods: Mixed-effect models and general linear models were uses.

Results: After adjusting for relevant confounding factors, mixed-effect models revealed diminished sperm motility (progressive and total), concentration, and total count across the quartiles of mtDNAcn (all P < 0.05). Compared with men in the lowest quartile, men in the highest quartile of mtDNAcn had lower progressive sperm motility, total motility, concentration and total count of -8.9% (95% CI -12.7% to -5.0%), -8.0% (95% CI -11.6% to -4.4%), -42.8% (95% CI -47.7% to -37.4%), and - 44.3% (95% CI -50.1% to -37.7%), respectively. These inverse dose-response relationships were further confirmed in the cubic spline models, where mtDNAcn was modelled as a continuous variable.

Conclusions: We found that mtDNAcn was inversely associated with semen quality in a dose-dependent manner. Our results provide novel clues that sperm mtDNAcn may serve as a useful predictor of human semen characteristics.

Tweetable abstract: Sperm mitochondrial DNA copy number was markedly associated with diminished sperm motility (progressive and total), concentration and total count.

Keywords: mitochondrial DNA copy number; mitochondrial biomarkers; semen quality.