Published on: September 28, 2014
by Fiona MacRae for The Daily Mail:
We all know that a good workout helps us relax. Now scientists have worked out why.
It seems that well-honed muscles stop a stress chemical from reaching the brain. The muscles filter out the dangerous substance, much like the liver removes poisons from the body.
The finding doesn’t just help explain why exercising makes us feel less stressed – it could also lead to new treatments for depression.
The Swedish researchers put two group of mice under stress by exposing them to loud bangs and flashing lights and waking them up at odd times.
After five weeks of this, the normal mice showed signs of depression, including loss of appetite.
However, the second group of GM mice remained healthy. These mice had genes that meant they were muscly, even without exercising. Further tests showed what is magical about muscle.
Muscly mice make more of protective proteins called KATs. These stop a stress chemical called kynurenine from travelling to the brain.
The researchers from Stockholm’s Karolinska Institute showed that normal mice quickly become depressed when given kynurenine.
But muscly mice were immune to the chemical. In fact, the amount of kynurenine in their blood never rose because the KAT enzymes in their bulging muscles quickly neutralised it.
Other experiments showed that normal mice made more of the protective KATs after regularly running on their wheel.
Importantly, people also made more KATs after just a few weeks of exercise.
Researcher Jorge Ruas said that by detoxifying the blood, muscle protects the brain said: ‘Well-trained muscle produces an enzyme that purges the body of harmful substances.
‘The muscle’s function is reminiscent of the kidney or liver.’
Writing in the journal Cell, Dr Ruas said the discovery paves the way for new and better treatments for depression, which affects up to one in five Britons as some point in their life.
Drugs that that works on the muscles, rather than the brain, should produce fewer side-effects.
Dr Ruas said: ‘Depression is a debilitating condition with a profound impact on quality of life for millions of people worldwide.
‘Depression is one the world’s leading causes of disease burden and time lived with disability and current anti-depressant treatments are insufficient.
‘Our work suggests that there is great therapeutic potential…in harnessing one of the many beneficial effects of exercise.’
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