Ram semen deterioration by short-term exposure to high altitude is prevented by improvement of antioxidant status

Differential gene expression and gut microbiota composition in low-altitude and high-altitude goats

Previous studies have presented evidence suggesting that altitude exerts detrimental effects on reproductive processes, yet the underlying mechanism remains elusive. Our study employed two distinct goat breeds inhabiting low and high altitudes, and conducted a comparative analysis of mRNA profiles in testis tissues and the composition of gut microbiota. The results revealed a reduced testis size in high-altitude goats. RNA-seq analysis identified the presence of 214 differentially expressed genes (DEGs) in the testis. These DEGs resulted in a weakened immunosuppressive effect, ultimately impairing spermatogenesis in high-altitude goats. Additionally, 16S rDNA amplicon sequencing recognized statistically significant variations in the abundance of the genera Treponema, unidentified_Oscillospiraceae, Desulfovibrio, Butyricicoccus, Dorea, Parabacteroides between the two groups. The collective evidence demonstrated the gut and testis played a synergistic role in causing decreased fertility at high altitudes. Our research provides a theoretical basis for future investigations into the reproductive fitness of male goats.

Effects of L-carnitine Administration on Sperm and Sex Hormone Levels in a Male Wistar Rat Reproductive System Injury Model in a High-Altitude Hypobaric Hypoxic Environment

The plateau environment impacts male reproductive function, causing decreased sperm quality and testosterone levels. L-carnitine can improve the semen microenvironment. However, the role of L-carnitine in a high-altitude environment remains unclear. In our study, we investigated the effects of L-carnitine administration in a male Wistar rat reproductive system injury model in the context of a simulated high-altitude environment. Rats were randomly divided into a normal control group (group A1, A2-low dose and A3-high dose) and high-altitude model groups (group B, C-low dose and D-high dose) with 20 rats in each group. With the exception of the normal control group exposed to normoxic conditions, the other groups were maintained in a hypobaric oxygen chamber that simulated an altitude of 6000 m for 28 days. In the experimental period, the low-dose groups (A2 and C) were administered 50 mg/kg L-carnitine via intraperitoneal injection once a day, and the high-dose groups (A3 and D) were given 100 mg/kg. After the feeding period, blood samples were collected to assess blood gas, serum hormone levels and oxidative stress. Sperm from the epididymis were collected to analyse various sperm parameters. After obtaining the testicular tissue, the morphological and pathological changes were observed under a light microscope and transmission electron microscopy (TEM). The impact of the simulated high-altitude environment on the rat testis tissue is obvious. Specifically, a decreased testicular organ index and altered indices of arterial blood gas and serum sex hormone levels caused testicular tissue morphological damage, reduced sperm quality, increased sperm deformity rate and altered malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) concentrations. The results demonstrate that L-carnitine can be administered as a preventive intervention to reduce the reproductive damage caused by high-altitude hypobaric and hypoxic environments and improve semen quality in a rat model.

Fertility Impairment after Trekking at High Altitude: A Proof of Mechanisms on Redox and Metabolic Seminal Changes

Many authors described negative but reversible effects of high-altitude hypoxic exposure on animal and human fertility in terms of sperm concentration, function, and biochemical alterations. The aim of this study was to evaluate the acute and chronic effects of high-altitude exposure on classical sperm parameters, redox status, and membrane composition in a group of travellers. Five healthy Italian males, all lowlanders not accustomed to the altitude, were evaluated after 19 days-trekking through low, moderate, and high altitudes in the Himalayas. Sperm samples were collected before (Pre), 10 days after (Post), and 70 days after the end of the expedition (Follow-up). Sperm concentration, cholesterol and oxysterol membrane content, and redox status were measured. Hypoxic trek led to a significant reduction in sperm concentration (p < 0.001, η2p = 0.91), with a reduction from Pre to Post (71.33 ± 38.81 to 60.65 ± 34.63 × 106/mL) and a further reduction at Follow-up (to 37.13 ± 39.17 × 106/mL). The seminal volume was significantly affected by the hypoxic trek (p = 0.001, η2p = 0.75) with a significant reduction from Pre to Post (2.86 ± 0.75 to 1.68 ± 0.49 mL) and with partial recovery at Follow-up (to 2.46 ± 0.45 mL). Moreover, subjects had an increase in ROS production (+86%), and a decrease in antioxidant capacity (−37%) in the Post period with partial recovery at Follow-up. These results integrated the hormonal response on thyroid function, hypothalamus−pituitary−gonadal axis, and the prolactin/cortisol pathways previously reported. An uncontrolled ROS production, rather than a compromised antioxidant activity, was likely the cause of impaired sperm quality. The reduction in fertility status observed in this study may lie in an evolutionary Darwinian explanation, i.e., limiting reproduction due to the “adaptive disadvantage” offered by the combined stressors of high-altitude hypoxia and daily physical exercise.

Oxidative Stress and Fetal Growth Restriction Set Up Earlier in Undernourished Sheep Twin Pregnancies: Prevention with Antioxidant and Nutritional Supplementation

Hypoxemia and oxidative stress, resulting in intrauterine growth restriction (IUGR) in undernourished twin sheep pregnancies, has been described in near-term studies. Our aim was to evaluate if the counteractive effects of maternal nutritional or antioxidant supplementation on the fetal redox status were evident before the accelerated fetal growth phase. Forty twin-bearing ewes grazing on natural Patagonian prairie were randomly assigned to four groups (n = 10 each; P: control ewes consuming mainly natural pasture; P+A: pasture plus antioxidants; P+C: pasture plus concentrate; P+A+C: pasture plus antioxidants and concentrate). Daily herbal antioxidants were supplemented in a feedstuff concentrate as a premix from day 35 until day 100 of gestation, when fetal venous cord blood samples and biometric measurements were obtained via cesarean section. The fetuses from group P were clearly hypoxemic. An analysis of variance showed that maternal antioxidant supplementation showed a trend of increased PO2, SatHb, and Ht, effects not observed in P+C fetuses. Antioxidants decreased the fetal MDA concentration (p < 0.05). Fetal TAC was increased by the antioxidants and concentrate (p < 0.05). Antioxidant supplementation showed a trend to increase fetal body weight but not biometry. The results suggest that negative effects of oxidative stress occur earlier than the overt growth arrest, and the maternal administration of antioxidants may constitute a good nutritional strategy for the early prevention of IUGR.

Effects of Environmental and Pathological Hypoxia on Male Fertility

Male infertility is a widespread health problem affecting approximately 6%-8% of the male population, and hypoxia may be a causative factor. In mammals, two types of hypoxia are known, including environmental and pathological hypoxia. Studies looking at the effects of hypoxia on male infertility have linked both types of hypoxia to poor sperm quality and pregnancy outcomes. Hypoxia damages testicular seminiferous tubule directly, leading to the disorder of seminiferous epithelium and shedding of spermatogenic cells. Hypoxia can also disrupt the balance between oxidative phosphorylation and glycolysis of spermatogenic cells, resulting in impaired self-renewal and differentiation of spermatogonia, and failure of meiosis. In addition, hypoxia disrupts the secretion of reproductive hormones, causing spermatogenic arrest and erectile dysfunction. The possible mechanisms involved in hypoxia on male reproductive toxicity mainly include excessive ROS mediated oxidative stress, HIF-1α mediated germ cell apoptosis and proliferation inhibition, systematic inflammation and epigenetic changes. In this review, we discuss the correlations between hypoxia and male infertility based on epidemiological, clinical and animal studies and enumerate the hypoxic factors causing male infertility in detail. Demonstration of the causal association between hypoxia and male infertility will provide more options for the treatment of male infertility.

Supplementation of Underfed Twin-Bearing Ewes with Herbal Vitamins C and E: Impacts on Birth Weight, Postnatal Growth, and Pre-Weaning Survival of the Lambs

Twin-bearing pregnancies of sheep reared in harsh environmental conditions result in maternal undernutrition and feto-maternal oxidative stress, leading to intrauterine growth restriction (IUGR). We assessed the efficiency of supplementation with antioxidant herbal vitamins C and E alone or in combination with concentrate throughout gestation on pregnancy outcomes, pre-weaning growth, and survival of twin lambs from grazing ewes at the Magellan Steppe. Four groups (n = 30 each) of twin-bearing ewes received a base natural prairie (P) diet, supplemented with either herbal vitamins C 500 mg and E 350 IU per day (V) or concentrated food (S); groups were: P, P + V, P + S, and P + VS. Vitamins and concentrate were supplemented until parturition. At birth, lambs were weighed, and blood was drawn for total antioxidant capacity (TAC) evaluation. Lamb body weight (BW) and survival rate were evaluated at mid-lactation (60 days) and at weaning (120 days). Vitamin supplementation resulted in increased lamb birth weight and TAC, with a trend towards higher BW at weaning, while nutritional supplementation only had a positive effect on birth weight. Lamb survival was higher in both vitamin supplemented groups. In conclusion, supplementation with herbal vitamins C and E alone or in combination with concentrate food during pregnancy may constitute a good nutritional strategy for sheep reared in harsh environmental conditions.

Maternal Supplementation with Antioxidant Vitamins in Sheep Results in Increased Transfer to the Fetus and Improvement of Fetal Antioxidant Status and Development

Twinning and maternal nutritional restriction leads to fetal hypoxia, oxidative stress, and intrauterine growth restriction (IUGR) in near-term sheep pregnancies. Our aim was to determine the effect of oral supplementation of vitamins C and E in pregnant sheep on maternal and umbilical cord blood concentrations of vitamins C and E and the effects on fetal antioxidant status, growth, and placental efficiency. Sixteen single- and sixteen twin-bearing ewes, grazing natural Patagonian prairies, were selected after transrectal ultrasound at day 30 after mating. Half of ewes from each pregnancy rank were supplemented daily with vitamins C and E, administered orally, from 30 to 140 days of gestation, when maternal jugular and fetal venous cord blood samples were obtained during cesarean section. Fetuses were weighed and sexed. Placental weight in each fetus was also obtained. Blood plasma was harvested for measurements of maternal and fetal vitamins concentration and fetal antioxidant capacity. Maternal administration of vitamin C and E was associated with increased fetal cord levels of both vitamins, improved antioxidant status, and enhanced fetal growth in both singleton and twin pregnancies associated with increased placental efficiency. These results highlight the potential of vitamin C and E supplementation to reduce the impact of IUGR in both livestock and humans.

Hypoxia and Oxidative Stress Are Associated with Reduced Fetal Growth in Twin and Undernourished Sheep Pregnancies

Low birth weight has profound implications for perinatal mortality and morbidity in lambs, causing higher mortality and lower growth potential. Low birth weight, as a consequence of fetal growth restriction, occurs in undernourished and multiple pregnancies, where hypoxia and oxidative stress could play a critical role. Our aim was to establish the effects of nutritional deprivation and pregnancy rank on fetal growth, oxygenation, and oxidative status in sheep pregnancies under extensive Patagonian conditions. At 30 days after mating, single- and twin-bearing ewes were offered only natural pasture (undernutrition group) or natural pasture plus concentrate supplementation (well-nourished group). At day 140 of gestation, blood gases and redox status were evaluated in venous cord blood, and fetal biometric characteristics were obtained after cesarean section. Both maternal undernutrition and twinning led to decreased oxygen supply to the fetuses (p = 0.016 and p = 0.050, respectively), which was associated with decreased intrauterine growth (r = 0.446, p < 0.01). Moreover, twinning increased oxidative stress in cord blood (p < 0.05), which might also contribute to fetal growth restriction. These results reinforce the importance of maternal nutrition, especially for those ewes bearing multiples, and opens new possibilities for nutritional or antioxidant interventions for preventing fetal hypoxia and oxidative stress.