Role of Antioxidants For Improvement of Semen Parameters
Semen analysis is important in the assessment of infertile couples. The quality of sperm is a measure of both the sperm's genetic integrity and its capacity for fertilizing an oocyte. Poor sperm quality has been associated with abnormal sperm motility, failure of sperm recognition of the zona pellucida and susceptibility to complete the processes of fertilization.
One in five infertile couples the problem lies solely in the male partner. It is estimated that one in 20 men has some sort of fertility problem with low numbers of sperm in his ejaculate. However, only about one in every 100 men has no sperm in his ejaculate.
Oxidative stress is one of the most common reason in the destruction of sperm quality and the adverse of male reproductive health. Reactive oxygen species (ROS) alter the integrity of spermatozoa DNA and result in DNA fragmentation. Free radicals also alter sperm function and structure, which impairs all semen parameters.
Mature spermatozoa are enclosed in a polyunsaturated lipid membrane, which is vulnerable to oxidation in the presence of ROS, and it is the destruction of this fatty membrane that results in impaired sperm morphology and motility. High levels of ROS are not only associated with idiopathic male infertility but are also implicated in impaired pre-implantation embryonic development and an increased rate of early pregnancy loss. The production of ROS is a physiological process in normal cell metabolism, including mitochondrial respiration. To some extent, low levels of ROS provide certain positive effects such as gene regulation, intracellular signaling and specific to sperm cells, enhancement of the ability to bind to the zona pellucida.
When this level of ROS is above the threshold, it causes damage to the sperms. Antioxidants that are naturally found in semen include vitamins E and C, folate, zinc, selenium, carnitine and carotenoids. These antioxidants act as free radical scavengers that help to overcome ROS. DNA integrity of the spermatozoa is one of the major determinants of normal fertilization and embryo growth in natural and assisted conception.
The location of mitochondria, in sperm mid piece is unique in as it is positioned at the site of maximum energy requirement. It has been well established that mitochondria make ATP by the coupling of respiration generated proton gradient with the proton-driven phosphorylation of ATP. It is associated with the inner mitochondrial membrane where highly mutagenic oxygen radicals are generated as by-product in the respiratory chain and leakage of these free radicals from the respiratory chain makes the mitochondria as a major intracellular source of ROS.
Sperm with DNA damage that fertilize oocyte are repaired by oocyte repair mechanisms before first round of replication, to prevent replication of damaged DNA. But if the damage is too extensive and especially accumulation of oxidative by-products like ethno-nucleosides can inhibit oocyte nucleotide excision repair mechanisms and thenby result in propagation of damaged DNA.
A few of the available antioxidants and their roles are described here
Coenzyme Q-10 is a non enzymatic antioxidant that is related to low-density lipoproteins and protects against per oxidative damage. Since it is an energy-promoting agent, it also enhances sperm motility. It is present in the mid-piece of sperms and recyclables vitamin E that preventing its pro-oxidant activity. It also acts a proton and electron carrier in electron transport chain and helps maintain cell membranes integrity and reduces the effect of reactive oxygen species in the sperm.
It is also known as ubiquinone because its found everywhere in the body and is known for its role in mitochondrial bioenergetics as electron and proton carrier. Studies demonstrated its presence in outer cellular membranes and in blood plasma. More recent data indicates that CoQ10 affects expression of genes involved in human cell signaling, metabolism and transport. Most CoQ10 deficiencies are due to autosomal recessive mutations, mitochondrial diseases, ageing-related oxidative stress and carcinogenesis. Some neurodegenerative disorders, diabetes, cancer, fibromyalgia, muscular and cardiovascular diseases have also been associated with CoQ10 deficiency.
Reduction in levels of CoQ10 is observed in sperm cells and seminal plasma of varicocele associated asthenozoospermia. Sperm cells characterized by low motility and abnormal morphology have low levels of CoQ10.Seminal plasma is rich in antioxidants that support, protect and nourish the sperm. The sperm have low levels of antioxidants and DNA repair enzymes and therefore are very dependent on the surrounding plasma. Spermatozoal membranes while being rich in polyunsaturated fatty acids are susceptible to oxygen damage from lipid peroxidation and abnormal spermatozoa.
Dietary sources of ubiquinone include fish, meat, whole grains and certain vegetables such as parsley and cage.
Coenzyme Q10 is known to cause gastrointestinal disorders, headache, insomnia, bleeding, skin rash, elevated liver enzymes at higher doses.
Carnitine is a water-soluble antioxidant mostly derived from the human diet that may play a role in sperm energy metabolism and provides the primary fuel for sperm motility. Spermatozoa exhibit increased L-carnitine and L-acetyl carnitine content during epididymal passage and acquisition of motility. Carnitines enhance the cellular energetics in mitochondria by facilitating the entry and utilization of free fatty acids within the mitochondria and also restore the phospholipid composition of mitochondrial membranes by decreasing fatty acid oxidation. carnitines protect sperm DNA and cell membranes from ROS-induced damage and apoptosis
A daily dose of 3 g given over a 3 or 4 month duration is significantly shown to improve patient's sperm motility from pre-treatment levels. Nausea, vomiting, abdominal pain, diarrhoea, body odor, seizures are some of its side effects.
The daily requirement of vitamin E (a-tocopherol) varies from 50 to 800 mg, depending on the intake of fruits, vegetables, tea or wine. Vitamin E is an important lipid soluble antioxidant molecule in the cell membrane. It is thought to interrupt lipid peroxidation and enhance the activity of various antioxidants that scavenge free radicals generated during the univalent reduction of molecular oxygen and during normal activity of oxidative enzymes. The results of in vitro experiments suggest that vitamin E may protect spermatozoa from oxidative damage and loss of motility as well as enhance the sperm performance in the hamster egg penetration assay. Vitamin E treatment decreased malondialdehyde (MDA) concentrations in spermatozoa down to normozoospermic levels, improving motility and the probability of achieving pregnancy.
Ascorbic Acid is water-soluble and a mid level ROS scavenger with high potency. It is found in concentrations 10-fold higher in seminal plasma than serum protecting human spermatozoa against endogenous oxidative damage by neutralizing hydroxyl, superoxide and hydrogen peroxide radical and preventing sperm agglutination. Vitamin C supplementation may minimize endogenous oxidative DNA damage, henceby reducing the risk of genetic defects, particularly in populations with low vitamin C levels (like in smokers). The hydrophilicity and lipophilicity of vitamins C and E may act synergistically to protect against peroxidative attack on spermatozoa.
Selenium (Se) may protect against oxidative sperm DNA damage and is required for normal testicular development, spermatogenesis, motility and function. The precise mechanism by which Se eliminates OS is not well-established. Se deficiency leads to impaired motility, breakage of the spermatozoal mid-piece and increased morphological abnormalities, mostly affecting the sperm head. The effectiveness of combined treatment with Se and vitamin E has been studied since Vitamin E works synergistically with Se as an antiperoxidant. A prospective, uncontrolled study reported that combined treatment significantly increased motility and mean seminal plasma glutathione peroxidase (GSHPx) activity.
Carotenoids work synergistically with Se and vitamin E and have a recommended dietary allowances value of 1000 mg per day. Another carotenoid of interest is lycopene – naturally derived from fruits and vegetables. Lycopene is found in high concentrations in the testes and seminal plasma, with lower levels in infertile men. A study reported that twice a day dose of 200 mg for 3 months resulted in a statistically significant improvement in sperm concentration of 66% of patients and motility of 53%.
Glutathione and N-acetyl cysteine:
Glutathione (GSH) is the most abundant reducing agent found in the body, protecting lipids, proteins and nucleic acids against oxidative damage. GSH combines with vitamin E and Se to form glutathione peroxidase, administration of 600 mg for 2 months by intramuscular injection in 20 infertile men significantly increased sperm motion characteristics, previously improved forward progression. GSH deficiency may render the midpiece unstable, resulting in defective morphology and motility. N-acetyl cysteine (NAC) replenishes GSH while scavenging free radicals and reducing ROS production in human ejaculate. NAC plays an important role in germ cell survival in human seminiferous tubules in vitro.
Pentoxifylline is a competitive nonselective phosphodiesterase inhibitor that raises intracellular cAMP and reduces inflammation by inhibiting TNF-a and leukotriene synthesis. Pentoxifylline has been shown to decrease ROS production reserve sperm motility in vitro and improve semen parameters in vivo. Orally administrated pentoxifylline had no effect at a low dosage, whereas a higher dosage increased sperm motility and some sperm motion parameters without altering sperm fertilizing ability.
Decreased amounts of LH production fail to initiate spermatogenesis that causing oligospermia due to secondary deficiency of testosterone. Such patients greatly benefit from a weekly dose of hCG because there is no endogenous production of hCG in male population.
Purified hCG is an effective substitute for LH since the structural homology between these two hormones which act through the same Leydig cell receptor.
A study shown that weekly injections of hCG administered in divided dose of 5000IU each week intramuscularly for four months, sperm count each month shown progressive increase in their number. Seventeen patients were in this group each of them had oligospermia as it was seen from their sperm count during the screening procedure. Progressive use of hCG in four month produces significant changes in the quantity of sperm count with initial average value of 25 million / ml rising to average 69 million / ml in four months. All of the 17 patients had normal levels of other hormone except one patient whose prolactin was elevated to 36ng / ml. Use of hCG in these patients mimics the effect of LH by binding to LH receptor which in turn activate the cyclic AMP cascade and finally resulting in the synthesis of testosterone which is primary hormone for the spermatogenesis. Thus hCG results in the increased level of testosterone which in turn potentiate the spermatogenesis.
• Oxidative stress plays an important role in male infertility
• Excessive production of reactive oxygen species, in particular hydrogen peroxide, can induce lipid peroxidation and DNA fragmentation and lead to sperm apoptosis
• Data on live births are available only for vitamin E and zinc
• A recent Cochrane analysis concluded that antioxidants may improve pregnancy and live birth rates in the context of assisted reproductive techniques.
• There is a need for well-designed and adequately powered randomized controlled trials investigating the impact of antioxidants on male infertility
Source by Johny Benfy