Male fertility is reduced by chronic intermittent hypoxia mimicking sleep apnea in mice

Abstract

Study objectives: Obstructive sleep apnea (OSA) is characterized by intermittent hypoxia and oxidative stress. However, it is unknown whether intermittent hypoxia mimicking OSA modifies male fertility. We tested the hypothesis that male fertility is reduced by chronic intermittent hypoxia mimicking OSA in a mouse model.

Design: Case-control comparison in a murine model.

Setting: University research laboratory.

Participants: Eighteen F1 (C57BL/6xCBA) male mice.

Interventions: Mice were subjected to a pattern of periodic hypoxia (20 sec at 5% O2 followed by 40 sec of room air) 6 h/day for 60 days or normoxia. After this period, mice performed a mating trial to determine effective fertility by assessing the number of pregnant females and fetuses.

Measurements and results: After euthanasia, oxidative stress in testes was assessed by measuring the expression of glutathione peroxidase 1 (Gpx1) and superoxide dismutase-1 (Sod1) by reverse-transcription polymerase chain reaction. Sperm motility was determined by Integrated Semen Analysis System (ISAS). Intermittent hypoxia significantly increased testicular oxidative stress, showing a reduction in the expression of Gpx1 and Sod1 by 38.9% and 34.4%, respectively, as compared with normoxia (P < 0.05). Progressive sperm motility was significantly reduced from 27.0 ± 6.4% in normoxia to 12.8 ± 1.8% in the intermittent hypoxia group (P = 0.04). The proportion of pregnant females and number of fetuses per mating was significantly lower in the intermittent hypoxia group (0.33 ± 0.10 and 2.45 ± 0.73, respectively) than in normoxic controls (0.72 ± 0.16 and 5.80 ± 1.24, respectively).

Conclusions: These results suggest that the intermittent hypoxia associated with obstructive sleep apnea (OSA) could induce fertility reduction in male patients with this sleep breathing disorder.

Keywords: hypoxia; male fertility; obstructive sleep apnea; oxidative stress.

Figure 1

Time course of arterial oxygen saturation (SaO₂) (top) and testicular oxygen partial pressure (PtO₂) (bottom). Baseline SaO₂ value, represented by the open circle (94.9 ± 1.9%), was similar to maximal values (95.4 ± 0.1%) and significantly different from the minima of 62.3 ± 3.5% (P < 0.001). Testicular PtO₂ oscillated from 11.1 ± 1.6 mmHg (similar to baseline value: 11.7 ± 1.4, represented by the open square) down to 3.6 ± 1.5 mmHg (P < 0.001).

Figure 2

Relative gene expression of antioxidant enzymes glutathione peroxidase 1 (Gpx1) and superoxide dismutase-1 (Sod1) of young (top) and middle-aged mice (bottom). Gpx1 and Sod1 expression in young mice subjected to 30-day intermittent hypoxia was reduced by 37% and 57%, respectively (P < 0.05). In middle-aged mice subjected to 60-day intermittent hypoxia the reduction was 39% and 34%, respectively (P < 0.05). IH, intermittent hypoxia; mRNA, messenger RNA; N, normoxia.

Figure 3

Progressive sperm motility (%) of young (top) and middle-aged mice (bottom). Progressive sperm motility in young mice was decreased after intermittent hypoxia from 31.5 ± 3.5% in normoxia to 22.9 ± 1.8% in the 30-day intermittent hypoxia group (P < 0.04). In middle-aged mice, progressive sperm motility was reduced from 27.0 ± 6.4% in controls to 12.8 ± 1.8% in the 60-day intermittent hypoxia group (P = 0.04). N, normoxia; IH, intermittent hypoxia.

Figure 4

Pregnant females per mating (%) (top), average of fetuses per mating (middle), and copulatory plugs per male (bottom) after the mating trial. The number of pregnant females per mating was higher (P = 0.04) in the control group (0.72 ± 0.16) in comparison with the intermittent hypoxia group (0.33 ± 0.10). The number of fetuses per mating was reduced in the intermittent hypoxia group (2.45 ± 0.73) in comparison with controls (5.80 ± 1.24) (P = 0.025). No differences were found in the number of copulatory plugs per female: 0.62 ± 0.16 in normoxia and 0.70 ± 0.09 in intermittent hypoxia group. N, normoxia; IH, intermittent hypoxia.