Antioxidant protection and lipid peroxidation in testes and different parts of epididymis in boars

Source and level of dietary iron influence semen quality by affecting inflammation, oxidative stress and iron utilization levels in boars

BACKGROUND

Boars fed a mixed form of inorganic and organic iron in excess of the NRC recommended levels still develop anemia, which suggested that the current level and form of iron supplementation in boar diets may be inappropriate. Therefore, 56 healthy Topeka E line boars aged 15-21 months were randomly divided into 5 groups: basal diet supplemented with 96 mg/kg ferrous sulfate (FeSO4) and 54 mg/kg glycine chelated iron (Gly-Fe, control); 80 mg/kg or 115 mg/kg Gly-Fe; 80 mg/kg or 115 mg/kg methionine hydroxyl analogue chelated iron (MHA-Fe, from Calimet-Fe) for 16 weeks. The effects of dietary iron supplementation with different sources and levels on semen quality in boars were investigated.

RESULTS

1) Serum Fe and hemoglobin concentrations were not affected by reduced dietary iron levels in the 80 mg/kg or 115 mg/kg Gly-Fe and MHA-Fe groups compared with the control group (P > 0.05). 2) Serum interleukin-6 (IL-6) and sperm malondialdehyde (MDA) levels in the 80 mg/kg or 115 mg/kg MHA-Fe groups were lower than those in the control group (P < 0.05), and higher serum superoxide dismutase levels and lower MDA levels in the 115 mg/kg MHA-Fe group (P < 0.05). 3) Boars in the 80 mg/kg or 115 mg/kg Gly-Fe and MHA-Fe groups had lower serum hepcidin (P < 0.01), ferritin (P < 0.05), and transferrin receptor (P < 0.01) concentrations, and boars in the 115 mg/kg MHA-Fe group had higher seminal plasma Fe concentrations compared with the control group. 4) Boars in the 80 mg/kg and 115 mg/kg MHA-Fe groups had lower abnormal sperm rate and in situ oscillating sperm ratio compared to the control group at weeks 12 and/or 16 of the trial. However, the effect of Gly-Fe on improving semen quality in boars was not evident. 5) Serum IL-6 level was positively correlated with hepcidin concentration (P < 0.05), which in turn was significantly positively correlated with abnormal sperm rate (P < 0.05). Furthermore, significant correlations were also found between indicators of iron status and oxidative stress and semen quality parameters.

CONCLUSIONS

Dietary supplementation with 80 mg/kg or 115 mg/kg MHA-Fe did not induce iron deficiency, but rather reduced serum inflammatory levels and hepcidin concentration, alleviated oxidative stress, increased body iron utilization, and improved semen quality in adult boars.

Monitoring of taurine dietary supplementation effect on parameters of Duroc boar ejaculate in summer season

The aim of this experiment was to find out whether the taurine supplementation in daily ration had an effect on quantity or quality of Duroc boar ejaculate. The experiment duration was from June to August, when it could assumed the possible occurrence of heat stress. For the study was chosen 12 Duroc boars of approximately the same age and condition. The control group of 6 Duroc boars was fed only by basic diet and the experimental group of 6 Duroc boars was fed by the same basic diet with supplementation of 15 g taurine/boar/day. Ejaculate was collected once a week by hand glowed technique. From ejaculate parameters were monitored volume of ejaculate, sperm concentration, total amount of sperm, morphologically abnormal sperm, taurine concentration and GSH/GSSH concentration. From microscopic analysis, results were statistically significant in motility in June and July (P<0.05). In biochemical results, a significant difference (P<0.05) has been found between the experimental groups in the concentrations of taurine as well as GSH/GSSG in ejaculate which indicates the effect of heat stress on boars during the experimental period.

Spirulina supplementation to the semen extender influences the quality and antioxidant parameters of chilled or cryopreserved Arabian stallion spermatozoa

The present study attempted to investigate the effect of various concentrations of spirulina platensis additions to the semen extender on Arabian stallion spermatozoa quality. Semen samples were collected with artificial vagina from five fertile stallions and diluted with an extender containing spirulina (2, 4, 6, and 8 mg/100 mL) or without spirulina (control). Aliquots of diluted semen were cooled (5°C, 90 min.) and frozen (-196°C, 7 d), then physical traits of thawed spermatozoa were examined. Furthermore, antioxidant activities of superoxide dismutase (SOD), glutathione reductase (GSR), total antioxidant capacity (TAC), and malondialdehyde (MDA) were measured in post-cooling and freezing spermatozoa. The results indicated that spirulina supplemented with the extender had no effect (P > 0.05) on sperm quality parameters and antioxidant activities after cooling. However, adding 6 mg spirulina/100 mL to the freezing extender improved (P < 0.05) the speed parameters and total motility percentage of frozen/thawed spermatozoa. Besides, supplementation of freezing extender with the previous level increased (P < 0.05) TAC, SOD and GSR concentrations/activities (0.86 ± 0.32 mM/L, 323.70 ± 12.81 U/mL, and 38.65 ± 1.90 U/mL, respectively) compared with the control (0.70 ± 0.25 mM/L, 165.80 ± 8.12 U/mL, and 25.70 ± 1.83 U/mL, respectively). While, lipid peroxidation of the frozen-thawed semen was reduced (P < 0.05, 17.97 ± 1.30 µmol/ L) compared with the control (29.39 ± 1.89 µmol/ L). Accordingly, the present results revealed that additions of 6 mg spirulina/100 mL to the freezing extender improved semen quality and reduced cryodamage of the Arabian stallion spermatozoa.

Porcine aldo-keto reductase 1C subfamily members AKR1C1 and AKR1C4: Substrate specificity, inhibitor sensitivity and activators

Most members of the aldo-keto reductase (AKR) 1 C subfamily are hydroxysteroid dehydrogenases (HSDs). Similarly to humans, four genes for AKR1C proteins (AKR1C1-AKR1C4) have been identified in the pig, which is a suitable species for biomedical research model of human diseases and optimal organ donor for xenotransplantation. Previous study suggested that, among the porcine AKR1Cs, AKR1C1 and AKR1C4 play important roles in steroid hormone metabolism in the reproductive tissues; however, their biological functions are still unknown. Herein, we report the biochemical properties of the two recombinant enzymes. Kinetic and product analyses of steroid specificity indicated that AKR1C1 is a multi-specific reductase, which acts as 3α-HSD for 3-keto-5β-dihydro-C₁₉/C₂₁-steroids, 3β-HSD for 3-keto-5α-dihydro-C₁₉-steroids including androstenone, 17β-HSD for 17-keto-C₁₉-steroids including estrone, and 20α-HSD for progesterone, showing K_m values of 0.5-11 µM. By contrast, AKR1C4 exhibited only 3α-HSD activity for 3-keto groups of 5α/β-dihydro-C₁₉-steroids, 5β-dihydro-C₂₁-steroids and bile acids (K_m: 1.0-1.9 µM). AKR1C1 and AKR1C4 also showed broad substrate specificity for nonsteroidal carbonyl compounds including endogenous 4-oxo-2-nonenal, 4-hydroxy-nonenal, acrolein, isocaproaldehyde, farnesal, isatin and methylglyoxal, of which 4-oxo-2-nonenal was reduced with the lowest K_m value of 0.9 µM. Moreover, AKR1C1 had the characteristic of reducing aliphatic ketones and all-trans-retinal. The enzymes were inhibited by flavonoids, synthetic estrogens, nonsteroidal anti-inflammatory drugs, triterpenoids and phenolphthalein, whereas only AKR1C4 was activated by bromosulfophthalein. These results suggest that AKR1C1 and AKR1C4 function as 3α/3β/17β/20α-HSD and 3α-HSD, respectively, in metabolism of steroid hormones and a sex pheromone androstenone, both of which also play roles in metabolism of nonsteroidal carbonyl compounds.

Physiological role of reactive oxygen species in testis and epididymal spermatozoa

The reactive oxygen species (ROS) play an important role in various aspects of male reproductive function, for spermatozoa to acquire the ability to fertilize. However, the increase in ROS generation, both due to internal and external factors, can induce oxidative stress, causing alterations in the structure and function of phospholipids and proteins. In the nucleus, ROS attack DNA, causing its fragmentation and activation of apoptosis, thus altering gene and protein expression. Accumulating evidence also reveals that endogenously produced ROS can act as second messengers in regulating cell signalling pathways and in the transduction of signals that are responsible for regulating spermatogonia self-renewal and proliferation. In the epididymis, they actively participate in the formation of disulphide bridges required for the final condensation of chromatin, as well as in the phosphorylation and dephosphorylation of proteins contained in the fibrous sheath of the flagellum, stimulating the activation of progressive motility in epididymal spermatozoa. In this review, the role of small amounts of ROS during spermatogenesis and epididymal sperm maturation was discussed.

Specific Activity of Superoxide Dismutase in Stallion Seminal Plasma Is Related to Sperm Cryotolerance

While the removal of seminal plasma is a routine practice prior to equine sperm cryopreservation, this fluid contains the main source of antioxidant enzymes able to scavenge these reactive oxygen species. Therefore, stallion seminal plasma components may have an impact on ejaculate freezability. Against this background, this study was designed to investigate whether the activities of the main stallion seminal plasma antioxidant enzymes are related to sperm cryotolerance. With this purpose, 16 ejaculates were collected from 14 healthy stallions, and each ejaculate was split into two aliquots. The first one was used to evaluate the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GSR) in seminal plasma. The second aliquot was extended and then processed for cryopreservation. Sperm motility and viability were evaluated before and after cryopreservation, and ejaculates were classified as of good (GFE) or poor freezability (PFE) based on total motile and viable spermatozoa at post-thaw. We observed that, while the specific activities of CAT, GPX, and GSR were similar between GFE and PFE, that of SOD was significantly (p < 0.05) higher in GFE than in PFE. We can thus conclude that, in stallions, the specific activity of SOD in the seminal plasma of a given ejaculate might be related to its freezability.

Effects of Fluoride on SOD and CAT in Testis and Epididymis of Mice

Oxidative damage has been implicated to be one of main mechanisms by which fluoride (F) induces toxic effects. Previous studies reported that F destroyed the epididymal structure of mouse and rabbit. Epididymis is the important place for sperm maturation. However, little is known about the effect of F on the oxidative stress status of epididymis. Therefore, the aim of the present study was to explore the changes in the activities and transcriptional levels of CuZn superoxide dismutase (CuZn-SOD, SOD1) and catalase (CAT), as well as the ultrastructure, in testis and epididymis of mice administrated with F. Sixty health Kunming mice were randomly divided into four groups. With one group untreated as controls, the others were treated with 25, 50, and 100 mg NaF/L in drinking water. After 10 weeks administration, mitochondrial ultrastructural changes in testis and epididymis were observed, including the incomplete membrane and the dissolved or disappeared cristae. Compared to the control group, the activities of both SOD1 and CAT in testis and epididymis were significantly reduced by 50 or 100 mg NaF exposure. In addition, the mRNA expressions of testicular SOD1 and CAT were also decreased significantly in 100 mg NaF/L group, while the SOD1 and CAT mRNA expressions in epididymides were significantly reduced in all F treatment groups. The above results suggest that in the presence of F, similar to testis, epididymis also loses the balance between oxidative stress and antioxidative defense, and perhaps more sensitive to F.

Effect of fish oil and vitamin E on sperm lipid peroxidation in dogs

The objective was to evaluate the effects of dietary fish oil (FO) and vitamin E (VE) supplementation on sperm sensitivity to lipid peroxidation (LP) in dogs. Using an incomplete replicate 3 × 3 Latin square design, five dogs were allocated into three groups. One of the squares was incomplete and had two dogs that were used with three treatments. The dogs were assigned to three different treatments, fed a control diet of balanced commercial food (control group; CG), control diet supplemented with 54 mg FO/kg body weight^0·75 per d (FO group; FG) and FO plus 400 mg VE per d (FO and VE group; FEG) for 60 d. Semen samples were collected on days 0 and 60 and divided into two halves, peroxidised and control, with or without ascorbate–Fe²⁺, respectively. LP was measured in both halves by chemiluminescence as counts per min/mg protein. Fatty acid profile was determined by GC. Data were analysed using the mixed procedure (SAS). On day 0, LP increased in all groups in the peroxidised samples (P < 0·05). However, on day 60 LP decreased in peroxidised samples of both the FG and FEG (P < 0·05), but there were no differences between the FG and FEG (P > 0·1). Additionally, on day 60 total n-3 was higher in the FG and FEG compared with the CG (P < 0·05). Supplementation with FO alone or together with VE decreased LP in peroxidised samples. These results could indicate a protective effect of n-3 on sperm. More studies are needed to understand the mechanism whereby FO and/or FO plus VE decrease LP in dogs’ sperm.