Protective effects of L-theanine and dihydromyricetin on reproductive function in male mice under heat stress

Heat stress can impair the male reproductive function. L-Theanine and dihydromyricetin have biological activities against heat stress; however, their effects on reproductive function in heat-stressed males are unclear. In this study, male mice were given L-theanine, dihydromyricetin, or a combination of both for 28 days, followed by 2 h of heat stress daily for 7 days. All interventions alleviated heat stress-induced testicular damage, improving the testicular organ index, sperm density, acrosome integrity, sperm deformity rate, and hormone levels. Treatment increased the antioxidant enzyme activity and decreased the markers of oxidative and inflammatory stress in the testes. A combination dose of 200 + 200 mg kg-1 d-1 showed the best protective effect. The potential mechanism involves the regulation of HSP27 and HSP70, which regulate the levels of reproductive hormones through the StAR/Cyp11a1/Hsd3b1/Cyp17a1/Hsd17b3 pathway, alleviate inflammation and oxidative stress through the P38/NF-κB/Nrf2/HO-1 pathway, and regulate the Bcl-2/Fas/Caspase3 apoptotic pathway. Overall, L-theanine and dihydromyricetin may play a protective role against heat stress-induced reproductive dysfunction, suggesting their potential use in heat stress-resistant foods.

Characteristics of Zn Content and Localization, Cu-Zn SOD, and MT Levels in the Tissues of Marginally Zn-Deficient Mice

Zinc (Zn) is an important trace element in the human body, and Zn deficiency affects the Zn content of major tissues. Marginal Zn deficiency is more common than severe Zn deficiency in humans. The objective of the present study was to compare the content and distribution of Zn and the change in the copper (Cu)-Zn superoxide dismutase (SOD) and metallothionein (MT) levels of soft tissues. Mice were fed with 30 mg/kg (control) or 10 mg/kg (marginally Zn-deficient, MZD) Zn diet for 35 days. We observed that only the Zn contents of serum, bones, and muscles in the control group were higher than those in the MZD group. Autometallography (AMG) was used as a method for staining Zn ions, and the semi-quantitative result indicated that the AMG products of the liver, duodenum, heart, lung, testes, and epididymis in the control group were higher than those in the MZD group. Furthermore, the contents of MT and the activities of Cu-Zn SOD in the testes, brain, duodenum, and liver were higher in the control group than those in the MZD group. However, the AMG products and the activities of Cu-Zn SOD of the kidney in the MZD group were more/higher than those in the control group. These results indicated that a change in the total Zn content of soft tissues may be not obvious and insensitive, and thus, more attention should be given to the distribution and localization of Zn ions. The functional indicators, MT and Cu-Zn SOD, are suitable biomarkers for evaluating zinc nutritional status. The brain, testes, duodenum, and liver are susceptive organs to Zn deficiency.

Zinc alleviates the heat stress of primary cultured hepatocytes of broiler embryos via enhancing the antioxidant ability and attenuating the heat shock responses

Zinc (Zn) has been shown to attenuate the adverse effects of heat stress on broilers, but the mechanisms involving this process remain unclear. We aimed to investigate possible protective mechanisms of Zn on primary cultured hepatocytes of broiler embryos subjected to heat stress. Three experiments were conducted. In Exp. 1, hepatocytes were treated with 0, 50, 100, 200, or 400 μmol/L added Zn as inorganic Zn sulfate (iZn) for 12, 24 or 48 h. In Exp. 2, cells were exposed to 40 °C (a normal temperature [NT]) and 44 °C (a high temperature [HT]) for 1, 2, 4, 6, or 8 h. In Exp. 3, cells were preincubated with 0 or 50 μmol/L Zn as iZn or organic Zn lysine chelate (oZn) for 8 h under NT, and then incubated with the same Zn treatments under NT or HT for 4 or 6 h. The biomarkers of antioxidative status and heat stress in cells were measured. The results in Exp. 1 indicated that 50 μmol/L Zn and 12 h incubation were the optimal conditions for increasing antioxidant ability of hepatocytes. In Exp. 2, the 4 or 6 h incubation under HT was effective in inducing heat shock responses of hepatocytes. In Exp. 3, HT elevated (P < 0.01) malondialdehyde content and expressions of heat shock protein 70 (HSP70) mRNA and protein, as well as HSP90 mRNA. However, Zn supplementation increased (P < 0.05) copper zinc superoxide dismutase (CuZnSOD) activity and metallothionein mRNA expression, and effectively decreased (P < 0.05) the expressions of HSP70 mRNA and protein, as well as HSP90 mRNA. Furthermore, oZn was more effective (P < 0.05) than iZn in enhancing CuZnSOD activity of hepatocytes under HT. It was concluded that Zn (especially oZn) could alleviate heat stress of broiler hepatocytes via enhancing their antioxidant ability and attenuating heat shock responses.

Chronic exposure to multi-metals on testicular toxicity in rats

Despite the availability of sufficient data on the effects of individual metal exposure on living organisms, a critical knowledge gap still exists in predicting effects of multi-metals particularly on the pituitary-testicular axis. Thus, the aim of the present study was to check the effects of individual or combined (binary and ternary) exposure to aluminum, copper, and zinc on (i) sperm and testosterone levels (ii) oxidative stress and (iii) structural changes in testis of male Wistar rats. Animals were exposed to aluminum, copper, and zinc either individually (20 mg/kg, orally, once, daily), binary (10 mg/kg each, orally, once daily) or in ternary combination (5 mg/kg, each, orally, once daily) for 24 weeks. The exposure to aluminum, copper individually and in combination led to a significant decrease in sperm counts and an increased oxidative stress compared to the control group. Exposure to zinc caused significant decrease in oxidative stress and an increase in different sperm variables. The exposure to zinc with aluminum or copper had no toxic effects on testis while concomitant exposure to aluminum, copper, and zinc produced more pronounced testicular injury. In summary, while co-exposure to zinc with aluminum or copper produced reproductive toxicity the co-exposure to all the three metals may lead to a significant testicular toxicity and these changes were related to increase in oxidative stress in rats.

Amelioration of heat stress-induced damage to testes and sperm quality

Heat stress (HS) occurs when temperatures exceed a physiological range, overwhelming compensatory mechanisms. Most mammalian testes are ∼4-5 °C cooler than core body temperature. Systemic HS or localized warming of the testes affects all types of testicular cells, although germ cells are more sensitive than either Sertoli or Leydig cells. Increased testicular temperature has deleterious effects on sperm motility, morphology and fertility, with effects related to extent and duration of the increase. The major consequence of HS on testis is destruction of germ cells by apoptosis, with pachytene spermatocytes, spermatids and epididymal sperm being the most susceptible. In addition to the involvement of various transcription factors, HS triggers production of reactive oxygen species (ROS), which cause apoptosis of germ cells and DNA damage. Effects of HS on testes can be placed in three categories: testicular cells, sperm quality, and ability of sperm to fertilize oocytes and support development. Various substances have been given to animals, or added to semen, in attempts to ameliorate heat stress-induced damage to testes and sperm. They have been divided into various groups according to their composition or activity, as follows: amino acids, antibiotics, antioxidant cocktails, enzyme inhibitors, hormones, minerals, naturally produced substances, phenolic compounds, traditional herbal medicines, and vitamins. Herein, we summarized those substances according to their actions to mitigate HS' three main mechanisms: oxidative stress, germ cell apoptosis, and sperm quality deterioration and testicular damage. The most promising approaches are to use substances that overcome these mechanisms, namely reducing testicular oxidative stress, reducing or preventing apoptosis and promoting recovery of testicular tissue and restoring sperm quality. Although some of these products have considerable promise, further studies are needed to clarify their ability to preserve or restore fertility following HS; these may include more advanced sperm analysis techniques, e.g. sperm epigenome or proteome, or direct assessment of fertilization and development, including in vitro fertilization or breeding data (either natural service or artificial insemination).

Seminal Plasma Analysis of Oxidative Stress in Different Genitourinary Topographical Regions Involved in Reproductive Tract Disorders Associated with Genital Heat Stress

The pathophysiological mechanisms responsible for male subfertility/infertility caused by or complicated by genital heat stress remains unclear in many respects. Because seminal plasma creates the environment for the proper functioning of spermatozoa, in this study, we verified the associations among standard spermiograms, seminal biochemical parameters (neutral alpha-glucosidase, fructose, and citric acid) and oxidative stress markers (total antioxidant capacity, catalase activity, superoxide dismutase activity, and malondialdehyde concentration) in distinct entities associated with male infertility with and without long-time exposure to local hyperthermia. We demonstrated that men exposed to prolonged environmental or clinically recognized local heat stress in adulthood may suffer from dysregulation of seminal antioxidant components, which can be directly associated with epididymal and prostate function. The comparative analysis of the studied parameters showed numerous correlations among all biochemical parameters (particularly neutral alpha-glucosidase) with low standard semen quality in almost all the investigated infertile groups. In light of the data obtained in this originally designed study, we conclude that more attention should be paid to the epididymis and accessory gland function in subfertile and infertile men exposed to genital heat stress, especially in the context of novel treatment algorithms (targeted therapies).

Antioxidant and Anti-Inflammatory Effects of Different Zinc Sources on Diquat-Induced Oxidant Stress in a Piglet Model

Zinc (Zn) plays a crucial role in reducing oxidative stress and diarrhea in postweanling piglets. This study is aimed at comparing the effects of zinc chelate of 2-hydroxy-4 methyl-thio butanoic acid (HMZn) and ZnSO₄ on the oxidative stress in weaned piglets. A total of 32 piglets were randomly divided into 4 treatments: CON: basal diet+80 mg/kg Zn as ZnSO₄; DIQ: basal diet+80 mg/kg Zn as ZnSO₄; HMZn: basal diet+200 mg/kg Zn as HMZn; and ZnSO₄: basal diet+200 mg/kg Zn as ZnSO₄. On day 15, the DIQ, HMZn, and ZnSO₄ groups were injected intraperitoneally with diquat except for the CON group. The trial lasted 21 days. The results showed that zinc sources did not influence the growth performance during the first 14 days. But HMZn increased activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and total antioxidant capacity (T-AOC) in serum (P < 0.05). After diquat injection, the fecal score was decreased in the HMZn group. Both HMZn and ZnSO₄ increased the activities of GPX and T-AOC in serum and the relative mRNA expressions of hepatic and renal Nrf2, SOD1, and GPX compared with the DIQ group (P < 0.05). Moreover, the relative mRNA expression of inflammatory factors in the small intestine, liver, and kidney was downregulated; the phosphorylation of NF-κB protein was inhibited in the HMZn group compared with the DIQ and ZnSO₄ groups (P < 0.05). In general, HMZn showed notable advantage over ZnSO₄ in reducing diarrhea and improving antioxidant and anti-inflammatory ability in piglets challenged with diquat.

Protective effects of zinc and N-acetyl-L-cysteine supplementation against cadmium induced erythrocyte cytotoxicity in Arbor Acres broiler chickens (Gallus gallus domesticus)

Cadmium (Cd) is one of the most toxic metals released into the environment. Here, we investigated the protective role of Zn²⁺ and/or N-acetyl-L-cysteine (NAC) against Cd cytotoxicity in the erythrocytes of Arbor Acres (AA) broiler chickens. Four hundred one-day-old AA chickens were divided into 12 groups for in vitro and in vivo studies. Zn²⁺ and/or NAC was given to the Cd exposed AA chickens to assess their protective roles. This was accomplished by investigating nuclear morphological abnormalities, oxidative stress (SOD, CAT, GPx, GSH and T-AOC), cell apoptosis, ROS accumulation and mitochondrial membrane potential (MMP). Results showed that Cd led to dose- and time-dependent cytotoxicity in the erythrocytes of AA chickens characterized by morphological abnormalities, nucleus damage, increased apoptosis rate and antioxidants depletion. Zn²⁺ or NAC significantly decreased the erythrocyte apoptosis, ROS production and mitochondrial membrane depolarization caused by Cd. SOD, CAT, GPx, GSH and T-AOC activities significantly decreased both in serum and erythrocytes of Cd exposed AA chickens. The supplementation with Zn²⁺ or NAC alleviated Cd induced oxidative stress through promoting SOD or GPx/GSH activities respectively. NAC presented a better role in reducing apoptosis, improving antioxidant activities more than Zn²⁺ in vitro. The combined use of Zn²⁺ and NAC enhanced cytoprotection in Cd exposed erythrocytes of AA chickens compared to Zn²⁺ or NAC alone. In conclusion, Zn²⁺ and NAC exerted remarkable protective roles in Cd exposed erythrocytes of AA chickens by inhibiting cell apoptosis and oxidative stress, and this provides a promising approach to antagonize Cd poisoning in poultry.