February 5, 2014
Environment, Lifestyle Factors Determines Changes In Pain Sensitivity
Ranjini Raghunath for redOrbit.com - Your Universe Online
The way you react to pain keeps changing throughout your lifetime, influenced by lifestyle and environmental factors, a new study carried out by researchers at King’s College London suggests.
The study identified genetic changes that determine how different people – even identical twins -- react to pain differently. The results from the study could help scientists understand how pain sensitivity differs in individuals, and develop new ways to treat and manage chronic pain by switching on or off certain genes.
Our genes control many of our traits: how we look, what we like to eat, even whether we are nice to others. But some traits such as sensitivity to pain are only partly influenced by our original genetic make-up. Throughout one’s life, outside factors may also create changes in a person’s genetic make-up by switching certain genes on or off – a fact that forms the basis for a field of study called epigenetics.
Epigenetics refers to the study of changes in genes that happen due to outside factors. The addition of a methyl group to one of the molecules that make up DNA – a process called DNA methylation -- is one change, for instance, that is caused both by genetic and environmental factors. Earlier studies have shown that differences in DNA methylation may influence how identical twins react to and develop diseases ranging from diabetes to schizophrenia.
In the current study, researchers compared 25 pairs of identical twins’ tolerance levels to pain from heat. Participants in the study had a heat probe placed on their arm and were asked to push a button when it became painful for them, so that the researchers could determine their tolerance levels.
What the researchers found was that some of the participants didn’t have the same tolerance levels as their twin brother or sister – surprising, considering identical twins have the same genetic make-up. The differences in the way they reacted to pain must therefore come from changes created by their environment or lifestyle, the researchers inferred.
The researchers then examined the participants’ DNA sequences to identify the genes which underpinned these differences in pain tolerance.
Chemical changes, particularly in DNA methylation, were found to be different in the structure of nine genes between tolerance-mismatched twins. There were significant changes in a specific gene that controls the production of a membrane protein called TRPA1. TRPA1 has previously been linked to skin irritation, colds and pain sensitivity, and is the target of painkillers such as paracetamol.
The study is the first to show that the TRPA1 gene is influenced by external and not just hereditary factors. The study is also the first to carry out an in-depth analysis of epigenetic influences on pain tolerance, the authors wrote.
“Epigenetic switching is like a dimmer switch for gene expression. This landmark study shows how identical twins, when combined with the latest technology to look at millions of epigenetic signals, can be used to find the small chemical switches in our genes that make us all unique – and in this case respond to pain differently,” Tim Spector, senior author and genetic epidemiologist at King’s College London, said in a statement.
The study was published online today in the journal Nature Communications.