Epigenetics and the stress response

Recent studies have looked further into the regulation of gene expression in the central nervous system (CNS) during stress. Epigenetic changes have an influence on the expression of genes. Mechanisms that influence epigenetic changes include DNA methylation, histone modifications and microRNA activity. These mechanisms can influence the way we adapt to stress and stressors. The Limbic-hypothalamic-pituitary-adrenal axis (LHPA) is the circuit of the body responsible for the regulation, ignition and restriction of a stress response. Genetic testing and clinical studies have uncovered a variety of mechanisms that give us a close look into exactly how our genes affect us.

Any potential threat that endangers our integrity or function, immediately triggers a stress response. This is a naturally occurring reaction, meant to aid us in escaping dangerous situations. Think about a small mouse in the wild. When threatened, mechanisms in the body activate to aid in it’s escape. This is also known as the fight or flight response. The LHPA system is essential  in coordinating both rapid and long-term behavioural, psychological and molecular responses to stress. Stress has been shown to alter the neurotransmission and synaptic plasticity in the brain. These affected areas of the brain include the prefrontal cortex, hippocampus and amygdala. Stressors that are long lasting and persistent can lead to a change in stress response, as well as the structure and function of the brain. 

DNA methylation and gene expression

It is suggested that stress causes DNA changes in the brain and can lead to an array of neurological issues. Histone and gene methylation help cells to determine gene expression, by activating or deactivating a gene. Epigenetic changes are related to synaptic plasticity, memory and cognitive processes. It is also related to determining stress-related phenotypes and adaptations to stress.

Dietary Stress and the Epigenome

Dietary stress on the body can also have a huge effect on the expression of genes. The Dutch Famine of 1944 is an extreme example of this. Whilst the Germans created supply blockades into Holland, food became extremely scarce. The average calorie intake prior to the famine was around 2000 calories per day. During the famine, calorie consumption decreased to around 600 calories a day. The study was conducted by looking at pregnancies during this time. Children who were born during the famine had a much lower than average birth weight. This would be expected. What surprised scientists was that years after the famine ended, these children gave birth to underweight children as well. They were also far more predisposed to the development of Schizophrenia. 

This study is particularly interesting to note, as it illustrates the clear genetic connection we have to our parents and forefathers. Something like extended periods of famine can affect generations to come. Thus, it is important that we understand the environmental conditions we find ourselves in, and how it affects the children we eventually bring into the world.

Summary

The world is far from completely understanding exactly what dictates gene expression, and all factors that contribute to gene expression. From what we do know, studies suggest the link between environment, behaviour and gene expression to be closely related. It is important to take these factors into account when looking at a patient and the status of their health. These factors can play a significant role, as well as come to surface much later on in life. Epigenetics is an emerging field of science and has the potential to change the understanding and treatment of disease.