Know Your Genes: DRD2 “The Dopamine Gene”

DRD2 gene: An introduction

DRD2 is a protein-coding gene that is located on chromosome 11.

The Dopamine Receptor Gene (DRD2) is associated with the synthesis of DRD2, which is the main receptor for all antipsychotic drugs.

The hormone Dopamine is a neurotransmitter and its secretion is increased during emotional upheavals.

From an evolutionary aspect, this hormone is released in response to some adverse condition, to prepare the body for a flight or fight response.

Under normal circumstances, when dopamine binds to DRD2 receptor, it should lower feelings of hunger and increase satiety.

Specific alleles of the DRD2 gene have been shown to be associated with a lower amount of DRD2 in the brain, which could lead to binge eating or overeating.

What is the function of dopamine receptors?

Before we look at the function of dopamine receptors, let’s understand what is dopamine.

Dopamine is a very important neurotransmitter and neurohormone in the body, which is responsible for enabling communication between nerve cells in the brain.

Dopamine is also linked with the brain's pleasure and reward system, and also controls movement.

Apart from this, dopamine also plays a role in memory and focus.

Dopamine receptors are important when we talk about certain neurological disorders like Parkinson’s disease.

Dopamine is produced by the substantia nigra in the brain( a part of the basal ganglia) which is responsible for controlling movement.

So, a steady flow of dopamine to these dopamine receptors ensures that controlled bodily movements occur normally.

But, when there is a decrease in dopamine reaching the receptors, movement, controlled movement and motor skills are affected, as we see in case of Parkinson’s disease.

The reverse of this happens in Tourette’s syndrome, where there is an excess of dopamine leading to excessive movements.

Dopamine receptors ensure adequate neurological signaling to allow dopamine to perform its functions and abnormal dopamine receptor signaling results in neuropsychiatric disorders.

These receptors are also the prime target of neurological drugs such as antipsychotics.

Types of Dopamine Receptors

There are 5 types of dopamine receptors – DRD1 to DRD5.

Dopamine Receptor 1 (DRD1)

It is a member of the D1-like receptor family and is the most abundant dopamine receptor found in the CNS.

The DRD1 receptor is found in the cortex, striatum and the limbic system of the brain, and the cardiovascular system.

It modulates the actions of dopamine receptor D2.

When dopamine binds to the DRD1 receptor, it regulates the growth and development of nerve cells in the brain and influences behavioral responses.

Dopamine Receptor 2(DRD2)

This receptor is a member of the D2-like receptor family and is found in many regions of the brain but has the highest concentration in the basal ganglia.

Since the basal ganglia comprise of structures responsible for motor control and learning, the DRD2 receptor mutations result in diseases such as schizophrenia or disorders like myoclonus dystonia.

Along with the DRD1 receptor, the DRD2 receptor reinforces the effects of drug abuse.

Dopamine Receptor 3 (DRD3)

This is a part of the D2-like receptor family-like Drd2 and is mainly present in two regions of the limbic system – the islands of Calleja and nucleus accumbens.

These two areas of the brain are primarily involved in reinforcing pleasure activities and emotions like addiction, laughter, etc.

It has been researched that mutations in this receptor can increase the susceptibility to a hereditary essential tremor 1, which is a type of movement disorder.

Dopamine Receptor 4 (DRD4)

It is also a member of the D2-like receptor family and is the receptor that is targeted by medications that are aimed at treating neurological disorders such as Parkinson’s and Schizophrenia.

This receptor is involved in motor coordination and exploratory behavior in humans.

A mutation in the DRD4 receptor can result in attention deficit hyperactivity disorder and dysfunction of the autonomic nervous system.

Dopamine receptor 5 (DRD5)

It is a member of the D1-like receptor family, just like DRD1.

These receptors are present in the limbic system of the brain and have a variety of functions such as long-term memory, smell, emotion, and behavior.

It has been shown that the D5 receptors have a higher affinity than the D1 receptors which means that they bind more easily to dopamine.

Dopamine receptor: What’s the genetic link?

Association with a tendency to overeat (binge eating disorder)

The SNP rs1800497 is also known as the Taq1A polymorphism of the dopamine D2 receptor(DRD2).

In a study conducted on obese people, Binge eating disorder and it was found that it was significantly associated with SNP rs1800497 and rs6277 that show enhanced or increased dopamine production.

The presence of the A1 allele is associated with reduced dopamine receptor availability in the brain thereby it was hypothesized that carrying this allele would increase the risk of emotional eating, especially in adolescents.

People with the T variant of the gene were found to be associated with increase in emotional eating behavior.

A recent study conducted on children found that T variant predisposes them to greater energy intake and higher risk of obesity.

Also, the presence of the T variant improves the speed of processing in individuals as compared to those who have the C variant.

The G allele of SNP rs4245150 of the DRD2 gene is associated with an increase in worry and anxiety.

Trait	SNP	Gene	Genotype	Risk
Perceptual speed	rs3758653	DRD4	CT	T variant is associated with better performance on processing speed
Anxiety	rs4245150	DRD2	TG	G variant associated with risk of anxiety

Association with language learning or bilingual ability

In a study conducted to determine linguistic language learning ability, people with the CC genotype were shown to be associated with better concatenative memory.

Another study conducted on older people, it was found that people with C variant had better associative memory.

A research was conducted to determine the genetic basis of bilingual ability, the T variant was found twice the amount among Spanish-English bilinguals than among only English speaking students.

Genotype (rs1800497)	Phenotype	Recommendation
CC	[Advantage] More likely to have higher amount of DRD2 in the brain [Advantage] Less likely to have binge eating disorder [Advantage] More likely to have better associative memory [Limitation] Less likely to be bilingual	Less likely to have binge eating disorder More likely to have better memory Including activities that improve memory will further enhance the ability
CT	Moderate amount of DRD2 in the brain with moderate binge eating behavior	More likely to have binge eating disorder Consciously avoid eating when in distress or when feeling low Store healthy snacks which will avoid unhealthy binge eating
TT	[Limitation] More likely to have lower amount of DRD2 in the brain [Limitation] More likely to have binge eating disorder [Limitation] More likely to have better associative memory [Advantage] More likely to be bilingual	More likely to have binge eating disorder Consciously avoid eating when in distress or when feeling low Store healthy snacks which will avoid unhealthy binge eating More likely to be bilingual Learn new languages and tap into your innate potential

Where are dopamine receptors in the brain?

The different types of D2-like receptors are found in different regions in the brain.

The D2 receptors are in high concentration in:

Basal ganglia –caudate, putamen regions
Nucleus accumbens
Ventral tegmental area
Substantia nigra
Amygdala
Hippocampus
Septal region
Thalamus
Cerebellum(in lobules IX and X)
Cerebral cortex

The D3 receptors are more limited in distribution and are found mainly in the nucleus accumbens of the limbic system.

However, less number of the D3 receptors are found in:

Substantia nigra
Septal regions
Ventral tegmental area
Cerebellum
Cerebral cortex

D4 receptors are the least in number in the brain and these are found in moderate levels in:

Substantia nigra
Hippocampus
Nucleus accumbens
Ventral tegmental area
Amygdala
Frontal cerebral cortex

What are the effective ways to stop overeating?

We often meet people in our social circles who are food-O-holics or are ‘foodies’ as they call themselves.

Most of these people struggle to control themselves when they see food or cannot prevent themselves from overeating.

But, on the other hand, we see some people who know exactly how much they want to eat and stop at a time when they feel they are full. These people avoid overeating.

While it may seem easy to prevent overeating, it is a habit that is difficult to break.

But, can one stop overeating?

Well, of course, you can! Here are a few effective ways to stop overeating:

Avoid distractions while you eat

these include watching TV or browsing through your phone, tablet or computer.

When you are distracted while eating, you tend to focus less on how much you are eating, often leading to excessive eating.

Eat low-calorie and high fiber foods

As these can make you feel full soon and yet you haven’t loaded up on excessive amounts of food or calories.

Including whole grains, salads, vegetables, fruits, etc., is a good way to increase the fiber content of your meals.

Don’t be too strict in avoiding foods

If you are seriously trying to avoid overeating, there are high chances that you have tried to keep food that you tend to indulge in away from you.

However, this behavior tends to backfire when you fall prey to the temptation and your problem of overeating is still unsolved.

Feel free to balance out the food items you eat and occasional indulgence will do no harm.

Avoid eating directly from packaged containers

When we eat chips from a packaged packet or munch on popcorn from a tub, we tend to binge eat on them without knowing the quantity we are consuming.

The best thing to do in such cases is getting out just the proportioned or measured amounts of food items onto the plate.

Eating regularly

Having a set routine for your three meal and snack-time is one of the time-tested methods to prevent overeating.

When you eat your meals regularly, your body knows how much it needs.

When you eat erratically or tend to skip meals, you feel more hungry due to a calorie deficit and this leads to overeating during the next meal.

Load up on protein foods

When you consume foods that are high in proteins such as a high protein breakfast, it tends to lower the hunger causing hormone ghrelin, thereby preventing overeating.

It is also a great idea to consume some yogurt in your breakfast for the same reason.

Eat slowly

It is often said that one must eat slowly and each meal should last a minimum of 20 minutes.

This is because this is the time needed by your stomach to convey to your brain that it is now full and that you need to stop eating.

However, in today’s lifestyle, people tend to eat really fast to save on time and get back to work.

This leads to unintentional overeating and we often don’t realize it.

Consume more water

There is no substitute for water.

Consuming more water throughout the day and keeping yourself hydrated also helps you feel less hungry, thereby preventing overeating during mealtimes.

Avoid falling into the diet-fad trap

Every now and then we come across diets that promise you weight loss and a healthy lifestyle.

But, these diets are not sustainable and people often fall back into their old lifestyles.

What are the natural remedies for anxiety?

We all feel anxious in our day to day lives, especially in today’s world where we all struggle for something or the other.

It is okay to suffer from anxiety once in a while but in many individuals, it becomes a chronic problem.

Anxiety which is chronic in form has detrimental effects on one’s mind and body and severely impacts the quality of one’s life.

While there are many medications in the market that help reduce or treat this condition, it is best to resort to some natural methods of doing so. Some of these are:

Getting adequate amounts of good quality sleep

Sleep is the best healer and medicine for our body for this is when our body relaxes completely.

People suffering from anxiety often find it difficult to get good sleep but they can use some tips to improve their sleep duration and quality.

When your mind and body have relaxed enough, you tend to feel the difference in your anxiety levels.

Avoid caffeine

Caffeine causes mental alertness, can make your mind active and can cause nervousness.

So, if you already suffer from anxiety, avoid caffeinated foods and drinks and resort to something more calming and soothing to both your mind and your body.

Avoid alcohol

Alcohol makes teleports you to another world, doesn’t it?

You feel comfortably numb or sedated and it gives you a sense of calmness.

But, the reality is that once the effect of alcohol starts to wear off, anxiety returns, and this time even more strong.

So, it is best to avoid resorting to alcohol and staying completely off it if you suffer from anxiety.

Avoid smoking

Just like alcohol, many people reach out for a puff when they are most stressed.

But, though the nicotine tends to offer you solace at that moment, in the long term, it tends to push you more towards developing an anxiety disorder.

Eat healthy food

Though quite a clichéd statement, eating healthy is actually beneficial for reducing your stress levels.

One must avoid foods that contain too much sugar, artificial sweeteners, flavors and colors, chemicals, dehydrating agents and preservatives.

All these affect one’s mood and temperament and can increase anxiety levels.

Meditation and deep breathing

The age-old art of meditation removes any negative and disturbing thoughts and helps instill a sense of calmness and peace of the mind.

However, it is easier said than done and this remedy often takes time but has repeatedly shown to reduce anxiety and people.

While slow, fast breathing is seen in cases of anxiety, practicing deep breathing while you meditate can help counter anxiety.

What is the travel gene?

What differentiates those homebodies who love to spend days on end at home and those that have this irking urge to undertake a holiday just a few days after they have returned from a long vacation?

Well, blame it on the DRD4-7R gene that is called as the ‘wanderlust gene’.

This gene codes for increased curiosity and restlessness and is present only in 20% of the population.

When proper history was taken while studying the gene, most people had a history of travel or will to travel.

This gene has also been linked to the first settlers in the continent of Africa who had the courage to migrate farther away from home, thereby spreading across the globe.

A mutant form of this DRD4 gene, the 7r makes people more likely to take risks, explore new places, new food, cultures, new ideas, drugs, and sexual opportunities.

Few scientists also link this DRD4 7r gene with migration.

A few scientists have also linked this behavior that is ‘out of control’ and hints at those people who wish to quit their high paying jobs for a few months of vacation, which is clearly irrational.

However, for a species as vast as humans in terms of genetics, it is unfair and rather difficult to pin down one particular gene for people who travel.

References:

“Nutrigenetics, fitness genetics, health genetics are all nascent but rapidly growing areas within human genetics. The information provided herein is based on preliminary scientific studies and it is to be read and understood in that context.”

Does your 23andme, Ancestry DNA, FTDNA raw data have DRD2 gene variant information?

CHIP Version	DRD2 SNPs
23andMe (Use your 23andme raw data to know your DRD2 Variant)
v1 23andme	Present
v2 23andme	Present
v3 23andme	Present
v4 23andme	Present
V5 23andme (current chip)	Present
AncestryDNA (Use your ancestry DNA raw data to know your DRD2 Variant)
v1 ancestry DNA	Present
V2 ancestry DNA (current chip)	Present
Family Tree DNA (Use your FTDNA raw data to know your DRD2 Variant)
OmniExpress microarray chip	Present

Know Your Genes: DRD2 “Dopamine Gene”