Trait overview: Dopamine Metabolism (COMT)

Friday, April 24, 2020. Author Alex Auld

Trait overview: Dopamine Metabolism (COMT)

What is dopamine?

Dopamine is commonly referred to as the body’s ‘pleasure chemical’ due to its release in response to food, drugs, sex and rewarding social interactions.

It also plays a variety of other roles, including:

  • control of movement
  • motivation
  • regulation of fluid balance and blood pressure

Dopamine primarily functions as  a neurotransmitter (nerve signalling molecule) - it conveys electrical messages by moving between nerves (or neurons).

When a nerve is stimulated, dopamine is released from special storage chambers (synaptic vesicles) and travels across a gap called the synapse before binding to a receiving nerve. This is how a signal is passed along our central nervous system.

 

Dopamine, reward and motivation

Dopamine has earned its name as the body’s pleasure chemical through its role in reward learning – the process of associating pleasurable sensations with a particular stimulus (e.g. food, drugs, video games, exercise).

For example, when we experience pleasure the first time we eat chocolate, the brain associates the sight, smell, taste and texture of chocolate with a pleasurable experience, leading us to want to find and eat more of it. This is known in psychological terms as reinforcement.

Reward learning and reinforcement are mediated by a network of structures in the brain known as our reward system. Our reward system is particularly rich in dopaminergic neurons, which are activated in response to rewarding stimuli.

Dopamine and control of movement

Another area that is rich in dopaminergic neurons and therefore reliant on dopamine to communicate is the basal ganglia – a collection of interconnected structures within the brain that help to control movement.

The basal ganglia contain networks of both inhibitory and excitatory neurons. These help muscles to execute appropriate movements planned by the brain, while dampening down unwanted movements.

The influence of the basal ganglia on movement is highlighted by the fact that damage to its pathways can cause movement disorders, such as Parkinson’s disease.

 

Dopamine and control of blood pressure

In addition to acting as a neurotransmitter in our brain and central nervous system (CNS), dopamine acts as a hormone in wider tissues in the body. One of the major hormonal roles of dopamine is to regulate blood pressure and blood volume.

When dopamine circulating in the bloodstream binds to receptors on blood vessel walls, it causes them to dilate (a process called vasodilatation), leading to an increase in blood flow to target organs as well as a decrease in blood pressure.

Dopamine and kidney function

Dopamine is also produced by cells lining the tubules of our kidneys.

When dopamine binds to receptors in our kidneys, it increases the excretion of sodium ions into the urine. As more water and sodium ions are excreted into the urine, this results in a fall in blood volume and drop in blood pressure.

How is dopamine made?

Dopamine is made by:

  • Neurons in the brain and central nervous system   
  • Adrenal glands (located above the kidneys)
  • Specialised cells in the tubules of kidneys.

Like other neurotransmitters including adrenaline, dopamine is derived from the non-essential amino acid tyrosine.

Tyrosine is firstly converted into L-DOPA by the enzyme tyrosine hydroxylase (TH).  L-DOPA is then converted into dopamine by the enzyme DOPA decarboxylase

How does dopamine exert its effects in the body?

Dopamine works by binding to specialized dopamine receptors on the surfaces of neurons and other cells.

When dopamine binds to a dopamine receptor, it triggers a cascade of chemical reactions. These chemical cascades ultimately modify other key molecules (e.g. enzymes, ion channels, other neurotransmitter receptors), which are responsible for the effects of dopamine.

How is dopamine degraded?

To prevent dopamine constantly activating neurons once it has been released into the synapse, its broken down by a number of specialised enzymes:

  • COMT (catechol-O-methytransferase)
  • MAO (monoamine oxidase)
  • ALDH (aldehyde dehydrogenase)

Together these enzymes metabolize dopamine into a molecule called HVA (homovanillic acid).

If activity of these enzymes is low, this can result in increased levels of dopamine in the synapse and increased activation of dopaminergic neurons. This in turn can lead to increased susceptibility to stress and sleep disturbance.

On the other hand, if activity of these enzymes is high, levels of dopamine in the synapse will be low, giving rise to low activity of dopaminergic neurons and associated brain networks. This may lead to central fatigue and reduced motivation, especially in relation to performing exercise.

The dopamine metabolism (COMT) trait

The dopamine metabolism (COMT) trait focuses specifically on activity of the COMT enzyme, which is encoded by the COMT gene. Variants of this gene can result in reduced or increased activity of the enzyme, which in turn influences dopamine levels.

Based on the variants of the COMT gene you carry, FitnessGenes members are categorised into one of three trait bands: low, medium or high dopamine metabolism.

As well as increasing your susceptibility to stress and sleep disturbance, those grouped in the low dopamine metabolism band are more prone to anxiety during times of stress and are therefore regarded as ‘worriers’.

In contrast, although they may be more susceptible to central fatigue and reduced motivation, those categorised in the high dopamine metabolism band are regarded as ‘warriors’ due to their better ability to deal with psychological stress.

Discover your personal trait

Are you a ‘worrier’ or a ‘warrior’? Discover your personal dopamine metabolism (COMT) trait alongside 75+ other fitness related traits by unlocking your unique genetic code with FitnessGenes. 

Already have genetic data from providers including 23andMe or Ancestry.com? Receive same-day access to all traits with the FitnessGenes DNA Upload.

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