With sports against depression

Researchers are deciphering the antidepressant effects of physical training

Sport as a way out of depression: trained muscles inhibit depressive signaling © freeimages
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Exercise depression - how does it work? Swedish researchers have now found out in an animal experiment how physical activity against depression works: Special proteins in trained muscles render harmless certain signals of depression in the blood. These can no longer develop their negative effects in the brain, the scientists write in the journal "Cell". With this mechanism, new, milder therapeutic approaches should be possible.

Sport against depression - physical activity can protect against mental illness and return the smile to some affected people. This effect is scientifically proven, but what mechanisms underlie it was unclear. However, it was known that during physical activity, the amount of a protein called PGC-1α1 increases in the blood. Also positive effects on the muscles themselves were proven in previous studies.

Researchers led by Jorge Ruas of the Karolinska Institute in Stockholm have therefore investigated whether the protein could also be linked to the antidepressant effects of physical activity. They developed a genetically modified mouse breeding line, in which the animals form a lot of PGC-1α1 in their muscles even without training.

Stressed mice develop depression

These mice and a group of normal animals specifically exposed the researchers to stress: loud noises, flashing lights and shifting day-night rhythms made life difficult for them. It is well known that mice react to such stressful conditions as many people: they develop depressive symptoms. That's exactly what happened to the experimental animals - but only to the control group. The genetically modified animals with the extra PGC-1α1 in their muscles, on the other hand, showed no depressive symptoms.

Further research revealed that the genetically engineered mice also produced more of an enzyme called kynurenine aminotransferase (KAT) in their muscles due to the increased levels of PGC-1α1. This transforms a signal substance for stress, the kynurenine, into kynurenic acid - and this in turn is unable to pass from the blood to the brain. The signaling effect of kynurenine is thus effectively suppressed. display

Trained muscles stop the depression signal

The exact function of kynurenine in depression is still unknown, but it is clear that it is more prevalent in patients with mental disorders. The researchers could now show in the context of their study: If one gives this substance to normal mice, they develop depressive symptoms. But not so the genetically modified animals: they are immune to the effects of kynurenine, experiments showed. The researchers therefore come to the conclusion: The KAT enzyme in their muscles makes the "Depri-substance" harmless.

"At the beginning of our study, we actually expected that trained muscles release a substance that has a beneficial effect on the brain, " says Jorge Ruas. "Now, on the other hand, it has turned out that the muscles produce a substance that frees the body from harmful substances. So, trained muscles have a purifying function similar to kidney or liver. "The research results could pave the way for the development of entirely new treatment options for depression, the researcher hopes. In particular, the fact that no signals or drugs need to cross the blood-brain barrier in this mechanism is promising.

(Cell, 2014; doi: 10.1016 / j.cell.2014.07.051)

(Agudelo et al., Cell, 26.09.2014 - MVI)