A drug given to millions of people to treat their diabetes could alleviate anxiety, research suggests.
Tests on mice showed those given metformin showed less signs of anxiety-like behaviour.
Scientists believe the drug increases levels of serotonin, known as a feel-good chemical, in the brain.
Serotonin is produced in the brain and contributes to the feeling of happiness and relaxation, among other bodily functions.
Metformin used to treat diabetes was able to alleviate anxiety in a study on mice by increasing levels of the feel-good chemical in the brain, a study has shown
The team, led by Dr Bruno Guiard from Research Center on Animal Cognition in Toulouse, France, raised mice on a high fat diet.
They showed insulin resistance – a hallmark of type 2 diabetes – and depression symptoms including anxiety and despair.
Diabetics are known to be at an increased risk for disorders such as depression, thought to be due to having lower levels of serotonin.
WHAT IS METFORMIN?
Metformin is an oral antidiabetic drug for the treatment of diabetes.
Created by Bristol-Myers Squibb Company, Metformin is approved in the US and the UK as a treatment for type 2 diabetes.
It helps diabetics to respond normally to insulin. Like most diabetic drugs, the ultimate goals of Metformin are to lower blood sugar to a normal level and maintain this level.
Metformin helps the body to control blood sugar in several ways. The drug helps type 2 diabetics respond better to their own insulin, lower the amount of sugar created by the liver, and decreasing the amount of sugar absorbed by the intestines.
When taken alone, Metformin is unlikely to cause hypoglycemia or weight gain, but when taken in conjunction with insulin or a sulfonylurea both of these side effects are more likely.
Metformin contains the active ingredient metformin hydrochloride (or metformin hcl).
It is sold both under brand names, and also as a generic drug. Common brand names include Glucophage, Riomet and Fortamet.
The neurotransmitter, which affects mood, creates messages between nerve cells throughout the body, mostly influencing the brain.
It is created by the conversion of the amino acid tryptophan – a building block of protein – and an enzyme called tryptophan hydroxylase.
Tryptophan is one of the essential amino acids humans need. However, the body cannot synthesize it and so it has to be obtained from the diet.
Previous studies have found patients and rodents with type 2 diabetes have low levels of circulating tryptophan.
As well as this, tryptophans route to the brain where it converts to serotonin is blocked because of a build-up of a different amino acid (BCAAs).
The study showed metformin can curb the amino acids, called branched chained amino acids (BCAAs).
Writing in their paper, the researchers said metformin stimulated and improved the transmission of serotonin in the hippocampus.
The hippocampus is responsible for long term memory and emotional response, and its functions and size have been found to be altered in those with major depression.
The researchers achieved similar effects by reducing the amount of BCAAs in the diet.
Amino acids are essential for the body to function and BCAAs can only be obtained from food such as eggs, meat and dairy products.
As well as finding metformin may help, Dr Guiard and colleagues said the findings suggest a diet poor in BCAAs ‘could help relieve depressive symptoms’.
The relationship between diabetes and mental health disorders such as depression and anxiety aren’t fully understood and could trigger one another.
The stress of managing diabetes can cause feelings of depression. While depression can lead to poor lifestyle choices that lead to obesity, a cause of type 2 diabetes.
Anxiety disorders are the most common mental illness in the US, affecting 18.1 per cent of the adult population every year, according to Anxiety and Depression Association of America.
In the UK, general anxiety disorder is estimated to affect up to five per cent of the population, according to the NHS.
WHAT IS THE NEUROTRANSMITTER SEROTONIN AND WHAT DOES IT DO?
Serotonin, also known as 5-hydroxytryptamine, is a neurotransmitter – a chemical substance that transmits nerve impulses across the space between nerve cells or neurons – known as a synapse.
It plays an important part in the regulation of learning, mood, sleep and helps control blood vessels.
It has also been linked to anxiety, migraine, vomiting and appetite.
Serotonin is the chemical which can help with feelings of low-self esteem as well as a sense of not belonging.
As a neurotransmitter, once the first molecule makes its way across the synapse, the cell stops accepting any further chemicals or signals.
Once the process is completed, the remaining serotonin is reabsorbed into the original neuron.
Chemicals and tablets, such as Prozac, tackle depression by stopping the cell fromshutting off and not accepting any more serotonin.
By keeping the avenues open for more of the neurotransmitter to pass through, it increases the strength and duration of the signal.
This, at least theoretically, increases happiness.