Free radicals and antioxidants in fertility
Our primary ability to survive on this planet is our ability to breathe in oxygen (O2). Apart from producing carbon dioxide (CO2), breathing in oxygen creates a by-product known as reactive oxygen species (ROS). ROS are free radicals. A certain amount of ROS is needed for fertility, but too much ROS can stress the body, as a cellular level. When the balance between ROS and antioxidants is tipped towards an overabundance of ROS, oxidative stress occurs. Once the balance shifts these highly reactive radicals can start a chain reaction, like dominoes.
Their chief danger comes from the damage they can do when they react with important cellular components such as DNA in the sperm head or the cell membrane. Cells may function poorly or die (apoptosis). This causes a chain reaction, which can lead to the damage of tissues. To prevent free radical damage the body has a balancing system of antioxidants, such as vitamins C, E, beta-carotene and selenium.
These antioxidants are molecules that can safely interact with free radicals and terminate the chain reaction before vital molecules are damaged and also repair the damage done by ROS molecules. The body cannot manufacture these micronutrients so they must be supplied in the diet. This is especially true in older women who have low levels of antioxidants and high reactive oxygen species (ROS). This imbalance maybe a reason for poor egg quality and subsequent increase in birth defects.
Reactive Oxygen Species (ROS) appears to affect egg maturation, fertilization, luteal regression and shedding of the endometrial lining. Estimation of ROS levels in follicular fluid can be used as a marker for predicting the success of in vitro fertilization (IVF). Oxidative stress can affect female fertility potential in number of ways such as ovulation, fertilization, embryo development and implantation. Follicular fluid contains high levels of antioxidants, which protect eggs and sperm from oxidative damage. High levels of oxidants can damage the egg after its release from the ovary, the embryo and most importantly, sperm, which is very sensitive to oxidative stress.
Once damaged by excessive ROS, sperm are unable to repair the damage. When IUI or IVF is used, such damage may not be a cause of concern because the damage to the sperm plasma membrane ensures that fertilization cannot occur with a DNA-damaged sperm. However, when intracytoplasmic sperm injection (ICSI) is used, this natural selection barrier is bypassed and a sperm with damaged DNA may be directly injected into the egg, leading to a greater risk of the baby developing birth defects.
Inflammation or infection can increase levels of ROS from the male’s immune system via high levels of leukocytes (leukocytospermia) present in the semen. There are various markers that are used to test levels of oxidative stress, total antioxidant capacity (TAC), which is measured together with ROS to determine male fertility. A level of TAC-ROS below 30 is considered poor. Men who smoke have a low TAC-ROS score. In addition there is TAC plus lipoperoxidation (LPO), which is used to measure oxidative stress in women.
Unbalanced levels of ROS too can affect women. Some ROS is needed to help the uterus-lining shed to create a menstrual bleed, help with fertilization and implantation, however when levels become unbalanced and high, problems with fertility arise. Follicular fluid contains high concentrations of antioxidants, which balances ROS levels and protects eggs from ROS damage. High levels of ROS can damage the egg and its release from the follicle (ovulation) as well as damage the DNA in the sperm’s head. High levels of ROS are commonly seen in women with endometriosis, whilst low levels of antioxidants are seen in women with infertility. Women with low levels of ROS have a greater rate of their eggs reaching blastocyst.
Whilst levels of LPO and TAC are significantly lower in women who did not become pregnant than in those who did. Therefore, it’s now known that a minimum concentration of oxygen is necessary for the maturation of eggs, but not too much. Eggs can be damaged (fragmented) by ROS, as it creates a chain reaction that damages all cells unless there is enough antioxidants to counter balance it. Polyunsaturated fatty acids act as powerful antioxidants that can stop this chain reaction from occurring and egg damage. It’s been seen that the chain reaction brought on by high levels of ROS seem to travel along similar paths to acupuncture channels (meridians). It’s therefore possible that acupuncture may also act like a antioxidant and prevent cell damage.
Estimating ROS/antioxidant concentrations in the peritoneal and follicular fluid of women may help to predict fertility rates. During an IVF cycle, various mediums are used to reduce ROS exposure to embryos, which affects their development and subsequent pregnancy rates. However, levels of ROS are higher in vitro than inside the uterus. ROS level on day 1 in vitro (day after IVF fertilization) can be used as an important marker for early embryonic growth.
An increase in levels of ROS initiates an inflammatory response via cytokines along the lymphatic system. Modern research has shown that the chain reaction of ROS follows paths that are almost identical to acupuncture channels (meridians). This ties in with other research that has found the actual channels within the It’s therefore possible that acupuncture can act like an antioxidant and stop the chain reaction that too many free radicals pose.