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A laboratory study explains how muscle cells may ‘speak’ to brain cells during exercise. Image credit: WayUp Productions/Getty Images.
  • Researchers investigated the cellular mechanisms behind how exercise improves cognition.
  • They found that contracting muscle cells release chemical signals that increase neuronal growth and firing.
  • They also found that support cells known as astrocytes prevent neurons exposed to chemical signals from muscle cells from excessive electrical signaling.
  • Further studies are needed to see whether these findings apply to humans.

Exercise is key for maintaining physical and mental health. Studies show that it positively affects health even if started later in life.

Some suggest that exercise improves cognition by inducing long-term changes in the hippocampus, such as increased volume and an increased rate of neuronal formation. How exactly exercise changes the hippocampus, however, remains unknown.

Understanding more about how exercise increases hippocampal size and function could allow researchers to reverse-engineer treatments for cognitive conditions such as dementia.

Recently, researchers conducted a series of in vitro experiments — experiments in cell cultures — to understand how exercise changes hippocampal cells.

They found that chemical signals from contracting muscle cells caused hippocampal cells to grow and fire more electrical signals. They also found that support cells known as astrocytes regulate neuronal growth and activity for optimum brain function.

“The implications support prior findings from other studies, which is that exercise, including muscle-strengthening exercises such as resistance training, can have a positive impact on brain function,” Ryan Glatt, senior brain health coach and director of the FitBrain Program at Pacific Neuroscience Institute in Santa Monica, CA, not involved in the study, told Medical News Today.

The study was published in Neuroscience.

For the study, the researchers isolated small muscle precursor-cell samples from mice and grew them in Petri dishes. Once they matured, they began to contract and release chemical signals into the cell culture.

The team then added the chemicals that had contained the mature muscle cell culture to another dish containing hippocampal neurons and astrocytes.

They used immunofluorescence and calcium imaging to track cell growth, as well as multi-electrode arrays to record neuronal activity.

In the end, they found that exposure to chemical signals from the muscle cells increased quantities of hippocampal neurons and astrocytes by 1.4 and 4.4 times.

The addition of muscle cell cultures also accelerated the creation of mature hippocampal neuronal networks – cells that fire synchronously.

The researchers next sought to explore how astrocytes affect the mixture. To do so, they observed the effects of removing astrocytes from cell cultures containing hippocampal cells and mature muscle cells.

In doing so, they noted that the neurons fired even more electrical signals, suggesting that astrocytes may help moderate and coordinate activation patterns between neurons.

From further tests, the researchers found that muscle contractions were necessary for the observed changes in hippocampal cultures.

When muscle cells were prevented from contracting, hippocampal cells no longer exhibited the same levels of neuronal firing, although synchronous firing was unaffected.

The researchers noted that this means muscle contractions- or exercise- release factors that stationary cells do not.

They concluded that their findings provide new insights into how exercise may support hippocampal function.

MNT asked Dr. Rong Zhang, a neurologist at UT Southwestern’s O’Donnell Brain Institute, not involved in the study, how exercise may reduce dementia risk.

He noted that whether this is the case still needs to be tested in large clinical trials and that further research should investigate underlying molecular mechanisms as well.

Meanwhile, Dr. Bennett noted that prior research shows that exercise reduces dementia risk by:

MNT also spoke with Dr. Romnesh de Souza, a consultant neurologist and interventional neurologist at Health City Cayman Islands, not involved in the study.

He said:

“Regular aerobic exercise for 20 to 30 minutes per day which can be achieved by walking, power walking, swimming or using an exercise bike. Target a heart rate of 70% of your maximum heart rate. To estimate your maximum age-related heart rate, subtract your age from 220. This practice has been shown to reduce dementia by 30-35%.”

“This was an in vitro study in rodents, using cell culture. It will take further study to see if these findings are applicable in people,” cautioned Dr. Zhang, commenting on the study.

Dr. Lauren Bennett, director of neuropsychology at the Pickup Family Neurosciences Institute at Hoag Memorial Hospital Presbyterian, not involved in the study, added that the research “was only conducted for a short period of time, and it is not clear whether the findings would be the same over a longer period of time.”

Nevertheless, “the outcomes of this study provide further evidence of the importance of exercise, at any point in life, in supporting hippocampal plasticity to combat hippocampal atrophy, which is a hallmark of Alzheimer’s disease,” noted Dr. Bennett.

“Down the road, studies like this could play a pivotal role in helping us optimize exercise regimens to support cognitive health,” she explained.

Dr de Souza added that the findings may also aid the development of new treatments for cognitive impairment.

“These findings show that in the future there is the potential to ‘reverse engineer treatments to recapitulate pro-cognitive effects of exercise in the absence of physical activity.’ What is also exciting is whether this can be used to reverse or halt the progression of cognitive decline in patients with dementia,” he said.