A team of scientists at Université Laval may have found out why regular exercise and living in a good environment can help protect against depression.
Their study, published in the journal Nature Communications, shows how these positive factors protect a part of the brain called the blood-brain barrier. This barrier helps keep harmful substances out of the brain, especially in areas related to mood and emotions.
In their study, the researchers used lab mice and exposed them to long-term social stress, which is one of the major causes of depression. When mice were allowed to exercise or live in a more enriched environment—with shelter, toys, and nesting materials—they were better protected from the harmful effects of stress on their brains.
The blood-brain barrier has different layers of defense made up of many types of cells. One important protein called claudin-5 acts like glue, keeping the cells tightly together.
Without this protein, the barrier becomes weak, and harmful molecules can enter the brain. This can lead to anxiety and depression. The team had already found that chronic stress lowers claudin-5 levels in mice and in the brains of people with depression.
To explore the protective effects of exercise and environment, the researchers divided the stressed mice into three groups. One group lived in a fun, enriched environment. Another had access to a wheel to run on. The third group didn’t get any special treatment. The results were striking.
Mice in the enriched and exercise groups kept most of their claudin-5 protein, while the control group lost about half. Also, the mice with better conditions showed fewer signs of anxiety and depression.
The researchers discovered that another protein, called Fgf2, played an important role in these results. Fgf2 levels were higher in the brains of the mice that were more resilient to stress.
To test if Fgf2 caused this resilience, the scientists increased or lowered Fgf2 levels using special viral tools. Mice with more Fgf2 didn’t show much stress, while those with less Fgf2 showed more anxiety and didn’t benefit much from exercise.
Even more exciting, the team found that Fgf2 may be useful as a biomarker for depression. Because the blood-brain barrier weakens during stress, Fgf2 can pass into the blood and be measured.
The team tested blood samples from about 100 people, some with depression and some without. They saw that people with more severe depression had higher Fgf2 levels in their blood. These levels also seemed linked to life factors like having a job or level of education.
This suggests Fgf2 might one day help doctors diagnose depression, choose treatments, or even detect other mental illnesses like schizophrenia. For now, the research shows how powerful exercise and a good environment can be for brain health, and how one small protein might offer big clues about our mental well-being.
If you care about health, please read studies that scientists find a core feature of depression and this metal in the brain strongly linked to depression.
For more health information, please see recent studies about drug for mental health that may harm the brain, and results showing this therapy more effective than ketamine in treating severe depression.
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