Tea polyphenols: prevention of cancer and optimizing health. Discussion 4.

Objective: To review and present the most distinct concepts on the association of reactive oxygen species (ROS) with male reproduction. Methods: The Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines were used to search PubMed, Medline, EMBASE, and the Cochrane electronic databases for studies investigating the role of oxidative stress (OS) on sperm function. Results: The literature search yielded 1857 studies, of which 1791 articles were excluded because of irrelevance of data, non-English language, non-human nature or because they were case reports or commentaries. All included studies were reviews (46), meta-analyses (one), original research studies (18) and guideline articles (one). The studies were published between 1984 and 2018. Under normal physiological conditions, ROS are vital for sperm maturation, hyperactivation, capacitation, acrosome reaction, as well as fertilisation. However, a number of endogenous and exogenous causes may induce supra-physiological levels of ROS resulting in lipid peroxidation, sperm DNA fragmentation and apoptosis, and consequently infertility. Several laboratory testing methods can be used in infertile men to diagnose OS. Treatment usually involves antioxidant supplementation and, when possible, elimination of the causative factor. Conclusion: OS is an important cause of male factor infertility. Its assessment provides essential information that can guide treatment strategies aimed at improving the male's reproductive potential. Abbreviations: bp: base-pair; CAT: catalase; LPO: lipid peroxidation; MDA: malondialdehyde; MiOXSYS: Male Infertility Oxidative System; mtDNA: mitochondrial DNA; NAD(PH): nicotinamide adenine dinucleotide (phosphate); NO: nitric oxide; 8-OHdG: 8-hydroxy-2'-deoxyguanosine; ORP: oxidation-reduction potential; OS: oxidative stress; PKA: protein kinase A; PLA2: phospholipase A2; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses; PUFA: poly-unsaturated fatty acid; ROS: reactive oxygen species; SOD: superoxide dismutase; TAC: total antioxidant capacity; TBA: thiobarbituric acid.

https://www.tandfonline.com/doi/pdf/10.1080/2090598X.2019.1599624

Oxidative stress and sperm function: A systematic review on evaluation and management

Infertility is a global health problem involving about 15% of couples. Approximately half of the infertility cases are related to male factors. The oxidative stress, which refers to an imbalance in levels of reactive oxygen species (ROS) and antioxidants, is one of the main causes of infertility in men. A small amount of ROS is necessary for the physiological function of sperm including the capacitation, hyperactivation and acrosomal reaction. However, high levels of ROS can cause infertility through not only by lipid peroxidation or DNA damage but inactivation of enzymes and oxidation of proteins in spermatozoa. Oxidative stress (OS) is mainly caused by factors associated with lifestyle. Besides, immature spermatozoa, inflammatory factors, genetic mutations and altering levels of sex hormones are other main source of ROS. Since OS occurs due to the lack of antioxidants and its side effects in semen, lifestyle changes and antioxidant regimens can be helpful therapeutic approaches to overcome this problem. The present study aimed to describe physiological ROS production, roles of genetic and epigenetic factors on the OS and male infertility with various mechanisms such as lipid peroxidation, DNA damage, and disorder of male hormone profile, inflammation, and varicocele. Finally, the roles of oral antioxidants and herbs were explained in coping with OS in male infertility.

Oxidative stress and male infertility: current knowledge of pathophysiology and role of antioxidant therapy in disease management

The body of evidence from the past three decades demonstrates that oxidative stress can be involved in several diseases. This study aims to summarise the current state of knowledge on the association between oxidative stress and the pathogenesis of some characteristic to the biological systems diseases and aging process. This review also presents the effect of physical activity on redox homeostasis. There is strong evidence from studies for participation of reactive oxygen and nitrogen species in pathogenesis of acute and chronic diseases based on animal models and human studies. Elevated levels of pro-oxidants and various markers of the oxidative stress and cells and tissues damage linked with pathogenesis of cancer, atherosclerosis, neurodegenerative diseases hypertension, diabetes mellitus, cardiovascular disease, atherosclerosis, reproductive system diseases, and aging were reported. Evidence confirmed that inflammation contributes widely to multiple chronic diseases and is closely linked with oxidative stress. Regular moderate physical activity regulates oxidative stress enhancing cellular antioxidant defence mechanisms, whereas acute exercise not preceded by training can alter cellular redox homeostasis towards higher level of oxidative stress. Future studies are needed to clarify the multifaceted effects of reactive oxygen/nitrogen species on cells and tissues and to continue study on the biochemical roles of antioxidants and physical activity in prevention of oxidative stress-related tissue injury.

Oxidative stress in biological systems and its relation with pathophysiological functions: the effect of physical activity on cellular redox homeostasis

This article addresses the importance of oxidative processes in both the generation of functional gametes and the aetiology of defective sperm function. Functionally, sperm capacitation is recognized as a redox-regulated process, wherein a low level of reactive oxygen species (ROS) generation is intimately involved in driving such events as the stimulation of tyrosine phosphorylation, the facilitation of cholesterol efflux and the promotion of cAMP generation. However, the continuous generation of ROS ultimately creates problems for spermatozoa because their unique physical architecture and unusual biochemical composition means that they are vulnerable to oxidative stress. As a consequence, they are heavily dependent on the antioxidant protection afforded by the fluids in the male and female reproductive tracts and, during the precarious process of insemination, seminal plasma. If this antioxidant protection should be compromised for any reason, then the spermatozoa experience pathological oxidative damage. In addition, situations may prevail that cause the spermatozoa to become exposed to high levels of ROS emanating either from other cells in the immediate vicinity (particularly neutrophils) or from the spermatozoa themselves. The environmental and lifestyle factors that promote ROS generation by the spermatozoa are reviewed in this article, as are the techniques that might be used in a diagnostic context to identify patients whose reproductive capacity is under oxidative threat. Understanding the strengths and weaknesses of ROS-monitoring methodologies is critical if we are to effectively identify those patients for whom treatment with antioxidants might be considered a rational management strategy.

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The Importance of Oxidative Stress in Determining the Functionality of Mammalian Spermatozoa: A Two-Edged Sword.

On the one hand, reactive oxygen species (ROS) are mandatory mediators for essential cellular functions including the function of germ cells (oocytes and spermatozoa) and thereby the fertilization process. However, the exposure of these cells to excessive levels of oxidative stress by too high levels of ROS or too low levels of antioxidative protection will render these cells dysfunctional thereby failing the fertilization process and causing couples to be infertile. Numerous causes are responsible for the delicate bodily redox system being out of balance and causing disease and infertility. Many of these causes are modifiable such as lifestyle factors like obesity, poor nutrition, heat stress, smoking, or alcohol abuse. Possible correctable measures include foremost lifestyle changes, but also supplementation with antioxidants to scavenge excessive ROS. However, this should only be done after careful examination of the patient and establishment of the individual bodily antioxidant needs. In addition, other corrective measures include sperm separation for assisted reproductive techniques. However, these techniques have to be carried out very carefully as they, if applied wrongly, bear risks of generating ROS damaging the germ cells and preventing fertilization.

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An Update on Oxidative Damage to Spermatozoa and Oocytes

Aspalathus linearis (rooibos tea) may improve sperm function owing to its antioxidant properties. To test this hypothesis, male rats were given 2% or 5% rooibos tea for 52 days. No significant alterations were observed in body and reproductive organs weight, serum antioxidant capacity and testosterone level. Seminiferous tubules displayed complete spermatogenesis. However, a significant (P < 0.05) decrease in tubule diameter and germinal epithelial height was observed. Epithelial height of caput epididymides showed a significant increase. Unfermented rooibos significantly enhanced sperm concentration, viability and motility. Fermented rooibos also significantly improved sperm vitality (P < 0.01), but caused a significant increase in spontaneous acrosome reaction (P < 0.05), whereas unfermented did not. Creatinine was significantly enhanced in all treated rats, consistent with significant higher kidney weights. Rooibos significantly reduced alanine transaminase level, while 2% fermented rooibos significantly decreased aspartate transaminase level (P < 0.01). In conclusion, treatment with rooibos improved sperm concentration, viability and motility, which might be attributed to its high level of antioxidants. However, prolonged exposure of rooibos might result in subtle structural changes in the male reproductive system and may induce acrosome reaction, which can impair fertility. Intake of large amounts of rooibos may also harm liver and kidney function.

In vivo effects of Aspalathus linearis (rooibos) on male rat reproductive functions.

Green tea is a popularly consumed beverage worldwide and contains polyphenols, whose antioxidant activities could improve sperm parameters and fertility thereof. We investigated the effect of green tea on the male rat reproductive system as well as its safety. Male Wistar rats were administered 2 and 5% aqueous extract of green tea for 52 days’ ad libitum, while the control group received tap water. Total polyphenol, flavanol, flavonol and soluble solids significantly increased in a concentration-dependent manner in vitro (P   0.05). Kidney weight, sperm concentration and vitality, spontaneous acrosome reaction increased (P   0.05). Histological sections of testis, epididymis, kidney and liver showed no conspicuous alteration. Diameter and epithelial height of seminiferous tubule decreased, while caudal epididymis epithelial height increased (P < 0.01). Consumption of green tea in the conditions used in the present study seems to be safe and improved sperm parameters. However, subtle structural changes observed in the decreased diameter and epithelial height of the seminiferous tubule and increased acrosome reaction needs further investigation.

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Green tea consumption increases sperm concentration and viability in male rats and is safe for reproductive, liver and kidney health.

Summary
Flavonoids are major compounds of Aspalathus linearis and Camellia sinensis. They are classified as endocrine disruptors and some have been shown to inhibit testosterone production. TM3 Leydig cell cultures were treated with 250–5000 μg mL−1 A. linearis (unfermented or fermented rooibos) or Camellia sinensis (green or black tea) for 24 h in the absence or presence of 6 mIU/200 μl human chorionic gonadotropin (hCG). Under nonstimulated conditions, all teas tend to decrease testosterone production (3.9–31.8%). However, under hCG-stimulation, a significant reduction in testosterone production was observed at all concentrations by both rooibos and tea (16.3–37.9%). MTT assay and phase contrast microscopy, revealed that at 250–1000 μg ml−1, both plants maintained the viability, proliferation and morphology of the cells, while 5000 μg ml−1 was cytotoxic to the cells (P < 0.05). In conclusion, the results here demonstrate the anti-androgenic property of A. linearis and C. sinensis.

Reduced testosterone production in TM3 Leydig cells treated with Aspalathus linearis (Rooibos) or Camellia sinensis (tea)

The effects of aqueous leaf extract of Moringa oleifera (MO) on human sperm functions and integrity was studied in vitro. Semen was obtained by masturbation after 3-5 days' abstinence from 34 healthy donors in Western Cape, South Africa. Liquefied semen was washed in human tubular fluid supplemented with 1% bovine serum albumin (HTF-BSA;1:5) with 10 min centrifugation at 300 g. Sperm suspensions were subsequently incubated with MO extract (0.625, 6.25, 62.5 and 625 µg/ml) for 1 hr, where HTF-BSA served as control. Sperm motility, vitality, DNA fragmentation, reactive oxygen species production, mitochondrial membrane potential, capacitation and acrosome reaction were assessed. Sperm motility, vitality, mitochondrial membrane potential and capacitation remained unchanged (p > .05). A dose-dependent decrease in sperm reactive oxygen species production (p < .0001), DNA fragmentation (p < .0001) and acrosome reaction (p < .001) was observed. An increase in the percentage of non-capacitated sperm (p < .01) was noted at 625 µg/ml. The antioxidant properties of MO actively maintained basic sperm functions, inhibited excess sperm free superoxide production and preserved acrosome reaction and DNA integrity. Further studies are needed to confirm the effect of aqueous MO leaf extract on fertility potential.

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Chinyerum S. Opuwari

Papers

An Update on Oxidative Damage to Spermatozoa and Oocytes

In vivo effects of Aspalathus linearis (rooibos) on male rat reproductive functions.

Green tea consumption increases sperm concentration and viability in male rats and is safe for reproductive, liver and kidney health.

Reduced testosterone production in TM3 Leydig cells treated with Aspalathus linearis (Rooibos) or Camellia sinensis (tea)

Aqueous leaf extract of Moringa oleifera reduced intracellular ROS production, DNA fragmentation and acrosome reaction in Human spermatozoa in vitro.