Altitude can alter the mtDNA copy number and nDNA integrity in sperm

Mitochondria are factories for energy production and genetic alterations in mtDNA will directly impact OXPHOS function. The copy number of mtDNA (i.e., the number of mtDNA per spermatozoon) is one of the major mitochondrial genetic features. Besides mtDNA copy number, the change of either mtDNA or nDNA integrity is another important factor causing asthenospermia, or poor sperm motility in infertile men. In this study, we investigated the mtDNA copy number and the integrities of mtDNA and nDNA respectively in semen samples from different donors at 5,300 m altitudes.

Total DNA was extracted from semen samples from donors in two different altitudes. Quantitative PCR was performed to evaluate the mtDNA copy number. PCR amplification was used to examine the integrity of sperm mtDNA. Flow cytometry was carried out to investigate sperm nDNA integrity. All data were analyzed to show the statistical significance.

Sperm mtDNA copy number for those living at high altitude (5,300 m) for one month was significantly higher (P < 0.05) than for those at the lower altitude (1,400 m) or in donors who had been living at the 5,300 m altitude for 1 year. In addition, sperm mtDNA copy numbers were remarkably decreased (P < 0.05) in those who had lived at the greater altitude for 1 year compared to those who had lived there for one month. The ratio of nDNA integrity among the 10,000 sperms at high altitude for one month was significantly lower (P < 0.05) than that at the lower altitude (1,400 m) or at 5,300 m for 1 year, and the ratio of nDNA integrity sperms at high altitude for 1 year was increased, and higher than that for at the lower altitude (P < 0.05).

High altitude can alter the mtDNA copy number and nDNA integrity in the sperms.