Fertility, Age and Eggs

Fertility Week is wrapping up for 2020! This year's theme is age. If you are a female heading north of 35 years you no doubt have heard that age is a factor that impacts fertility. As we age the production of high quality eggs (oocytes) reduces. While we can’t do much about our chronological age, let’s take a look at what underlying mechanisms impact egg quality with age and an effective strategy that may reduce the impact of ageing on fertility. 

Age and Oocyte Quality

As our oocytes divide, the chromosomes inside segregate but with age there are more errors in this process. An oocyte with an incorrect number of chromosomes is a condition known as aneuploidy. In most cases this oocyte if fertilised will not lead to an ongoing pregnancy. We are beginning to understand more about the mechanisms that contribute to this aneuploidy. 

Mitochondria Dysfunction
​Mitochondria are little bean shaped organelles are found in almost every cell. They are involved in energy production and important players in the ageing process.

As we learn more about these little energy factories (our mitochondria), it appears that the health of your mitochondria is a great indicator of the success of fertilisation and embryo development.

The decline in egg quality with ageing has been related to mitochondria. The ability of mitochondria to produce energy is crucial during the development of eggs (oocytes) and to allow for normal embryo growth and development.

In aged oocytes, metabolic activity and energy production are reduced. This may in turn impair processes such as cell division, embryo development and implantation. 

Telomere Shortening
Telomeres are essentially little caps on the end of our DNA that protect our chromosomes. While Each time our cells copy themselves, telomeres get a little shorter.

While telomeres shorten as we age, they can also shorten in response to stress, smoking, lack of exercise, daily alcohol consumption and a poor diet. Inflammation and oxidative stress are key processes that have been shown to shorten telomeres.

Telomere length in cumulus cells at the time of oocyte collection is predictive of highly competent oocytes and good-quality embryos. In women that experience IVF failure or recurrent miscarriage (Mania et al, 2014), or aneuploid embryos (Treff et al, 2011), oocyte telomeres have been found to be shorter.
 
Spindle Instability
During cell division, an internal cell skeleton (spindle) has the job of keeping chromosomes in place for accurate segregation. With advancing maternal age nearly 80% of oocytes have some abnormalities in spindle formation. The proteins in the cell that help ensure correct spindle formation change with age.
 
This process requires lots of energy. If our mitochondria are low in number or are not functioning well, it is likely that spindle formation will be impacted.

So What Can I Do?

There are strategies that we know that may slow down cellular ageing. In this post we are going to talk about the incredible benefits of exercise to put the brakes on ageing, and in some cases even turn back time.

Exercise opposes the detrimental effects of ageing. It enhances insulin sensitivity, reduces inflammation, dampens reactive oxygen species, and improves efficiency of our mitochondria.

Engaging in regular activity has also been shown to improve the activity of an enzyme that protects our telomeres, and in some cases may even increase telomere length! With the close connection between oocyte quality and telomere length who wouldn’t want to lengthen their telomeres for optimal fertility.

With discussions of age and fertility you may have heard of AMH. Anti-Mullerian Hormone or AMH is secreted from cells within antral follicles and has been used as a marker of ovarian reserve. While it may be useful in predicting pregnancy rates in older females, AMH does not appear to predict pregnancy rates in women <36 years.

Women who exercise more than two times per week have higher AMH levels than women not exercising (Maslow et al 2019). Another study supports the benefits of exercise on AMH levels, where women that are physically active have higher levels of AMH compared to inactive women. The increase in AMH levels was irrespective of age (Kiranmayee et al., 2017).

Exercise can also improve how your oocyte spindles function, chromosomes align and healthy cell division. In a mouse model of ageing, exercise improves both ovarian follicle reserve and oocyte quality (Faraci et al., 2018). Exercise maintained normal mitochondrial distribution and improved spindle and chromosome alignment. This means that in the mature oocyte, the chromosomes were organised properly inside the cell. 

The Next Steps

​Seek out the ideal exercise prescription for you. Your medical background, fertility journey to date and previous activity will all influence what type of exercise and how much is right to optimise your fertility!