Becoming more brain fit and following a lifestyle that is rich in mental and physical activity, has been shown to aid in protecting us from Alzheimer's disease.
Keeping active is one of the mainstays for maintaining health, both physically and mentally. The benefits of regular exercise for improved mood and cognition have been known for a while.
It has also been known that exercise stimulates the production of BDNF (brain derived neurotrophic factor) which assists in maintaining existing neurons as well as stimulating neurogenesis; the production of new neurons.
But what hasn't been known is the mechanism by which exercise protects the brain. In particular how exercise works in relation to memory changes associated with Alzheimer's disease. Researchers from the University of Nottingham, using mice models, have discovered that the stress hormone CRF (corticotrophic- releasing factor) works as a neuroprotector.
Now stress as you know, is not all bad. We need some stress in order to simply get out of bed in the morning and it helps to keep us mentally sharp and cognitively on our toes. Our stress response results in the release of stress hormones, which is normal.
However, being exposed to severe stress, especially if it is long lasting has been shown to be highly detrimental to the brain resulting in loss of memory and poorer function especially of the prefrontal cortex, (the area of the brain associated with planning, decision making, our working memory and paying attention) and the hippocampus (the area associated with learning and long term memory).
Severe chronic stress, which may manifest itself as anxiety or depression is considered a risk factor for cognitive decline and dementia. But what is actually going on here in the brain?
What the researchers noticed firstly was that people with Alzheimer's disease have been shown to have lower levels of the CRF hormone.
Using cognitively intact mice, they used an experimental drug to block the effect of CRF from being able to bind to its specific receptors (called CRF1) in the brain. The mice were then placed in a stressful situation, which here meant being placed in a new environment, not dissimilar to ourselves when we find ourselves fronting up to a new job. Except here the new environment was devoid of any stimulus. What happened was that the mice then exhibited what was noted as an abnormal stress response.
In other words the mice's brains showed less anxiety, but increased loss of behavioural function. Hence stress, if human brains work in the same way, results in poorer cognitive capability and potentially increases our risk of developing Alzheimer's. Keeping ourselves stimulated cognitively with mental challenges (something novel, with variety and ongoing stretch) helps to promote an active and useful stress response by triggering the CRF1 receptors.
Maintaining normal levels of CRF appears to be key here to helping the brain resist the potential adverse effects of stress.
In the same way the researchers also discovered that interrupting CRF from binding to its receptors leads to a block in how exercise normally stimulates memory. Using mice with Alzheimer's disease, they were able to show how moderate exercise then restored the levels of CRF to normal, thus providing the CRF system the ability to allow its memory enhancing effects to work.
The implication of this is that even in the presence of symptoms of Alzheimer's peoples are likely to gain significant benefit from undertaking a regular exercise program because it helps to modulates the negative effects of stress on the brain, and stimulates an individual's ability to cope better not only with life stresses themselves but also to help maintain their memory for longer.
Switching on the CRF1 receptor was shown to be crucial to build an increased number of synapses in response to the stimulus of exercise. Building more and strengthening existing synaptic connections in our brain, is the key to building cognitive reserve and maintaining healthy brain function for longer.
So there you have it. Living a life that is
full and varied keeps our brains fit by stimulating a normal stress response.
Your choice of lifestyle matters: Keeping
active, engaged and curious can help delay the onset of Alzheimer type
symptoms. In addition it appears that our stress
response and levels of CRF are what matters to maintain synaptic plasticity and
genesis which is necessary for learning and memory
Gillian A. Scullion, Katherine N. Hewitt and Marie-Christine Pardon (2013) Corticotropin-Releasing Factor Receptor 1 Activation During Exposure to Novelty Stress Protects Against Alzheimer's Disease-Like Cognitive Decline in AβPP/PS1 Mice Journal of Alzheimer's Disease DOI - 10.3233/JAD-122164