 "Exercise benefits brain, finds study on mice")
Physical activity is good for our brains. A wealth of science supports that idea. But precisely how exercise alters and improves the brain remains somewhat mysterious.
A new study with mice fills in one piece of that puzzle. It shows that, in rodents at least, strenuous exercise seems to beneficially change how certain genes work inside the brain. Though the study was in mice, and not people, there are encouraging hints that similar things may be going on inside our own skulls.
For years, scientists have known that the brains of animals and people who regularly exercise are different than the brains of those who are sedentary. Experiments in animals show that, for instance, exercise induces the creation of many new cells in the hippocampus, which is a part of the brain essential for memory and learning, and also improves the survival of those fragile, newborn neurons.
Researchers believe that exercise performs these feats at least in part by goosing the body's production of a substance called brain-derived neurotrophic factor, or BDNF, which is a protein that scientists sometimes refer to as "Miracle-Gro" for the brain. BDNF helps neurons to grow and remain vigorous and also strengthens the synapses that connect neurons, allowing the brain to function better. Low levels of BDNF have been associated with cognitive decline in both people and animals. Exercise increases levels of BDNF in brain tissue.
But scientists have not understood just what it is about exercise that prompts the brain to start pumping out additional BDNF.
So for the new study, which was published this month in the journal eLIFE, researchers with New York University's Langone Medical Centre and other institutions decided to microscopically examine and reverse engineer the steps that lead to a surge in BDNF after exercise.
They began by gathering healthy mice. Half of the animals were put into cages that contained running wheels. The others were housed without wheels. For a month, all of the animals were allowed to get on with their lives. Those living with wheels ran often, generally covering several miles a day, since mice like to run. The others remained sedentary. After four weeks, the scientists looked at brain tissue from the hippocampus of both groups of animals, checking for BDNF levels. As expected, the levels were much higher in the brains of the runners.
But then, to better understand why the runners had more BDNF, the researchers turned to the particular gene in the animals' DNA that is known to create BDNF. For some reason, the scientists realised, this gene was more active among the animals that exercised than those that did not.
Using sophisticated testing methods, the scientists soon learned why. In both groups of animals, the BDNF gene was partially covered with clusters of a particular type of molecule that binds to the gene, though in different amounts.
In the sedentary mice, these molecules swarmed so densely over the gene that they blocked signals that tell the gene to turn on. As a result, the BDNF genes of the sedentary animals were relatively muted, pumping out little BDNF.
But among the runners, the molecular blockade was much less effective. The molecules couldn't seem to cover and bind to the entire BDNF gene. So messages from the body continued to reach the gene and tell it to turn on and produce more BDNF.
Perhaps most remarkably, the researchers also found a particular substance in the runners' brains that fended off the action of these obstructionist molecules. The runners' brains contained high levels of ketones, which are a by-product of the breakdown of fat.
A new study with mice fills in one piece of that puzzle. It shows that, in rodents at least, strenuous exercise seems to beneficially change how certain genes work inside the brain. Though the study was in mice, and not people, there are encouraging hints that similar things may be going on inside our own skulls.
For years, scientists have known that the brains of animals and people who regularly exercise are different than the brains of those who are sedentary. Experiments in animals show that, for instance, exercise induces the creation of many new cells in the hippocampus, which is a part of the brain essential for memory and learning, and also improves the survival of those fragile, newborn neurons.
Researchers believe that exercise performs these feats at least in part by goosing the body's production of a substance called brain-derived neurotrophic factor, or BDNF, which is a protein that scientists sometimes refer to as "Miracle-Gro" for the brain. BDNF helps neurons to grow and remain vigorous and also strengthens the synapses that connect neurons, allowing the brain to function better. Low levels of BDNF have been associated with cognitive decline in both people and animals. Exercise increases levels of BDNF in brain tissue.
But scientists have not understood just what it is about exercise that prompts the brain to start pumping out additional BDNF.
So for the new study, which was published this month in the journal eLIFE, researchers with New York University's Langone Medical Centre and other institutions decided to microscopically examine and reverse engineer the steps that lead to a surge in BDNF after exercise.
They began by gathering healthy mice. Half of the animals were put into cages that contained running wheels. The others were housed without wheels. For a month, all of the animals were allowed to get on with their lives. Those living with wheels ran often, generally covering several miles a day, since mice like to run. The others remained sedentary. After four weeks, the scientists looked at brain tissue from the hippocampus of both groups of animals, checking for BDNF levels. As expected, the levels were much higher in the brains of the runners.
But then, to better understand why the runners had more BDNF, the researchers turned to the particular gene in the animals' DNA that is known to create BDNF. For some reason, the scientists realised, this gene was more active among the animals that exercised than those that did not.
Using sophisticated testing methods, the scientists soon learned why. In both groups of animals, the BDNF gene was partially covered with clusters of a particular type of molecule that binds to the gene, though in different amounts.
In the sedentary mice, these molecules swarmed so densely over the gene that they blocked signals that tell the gene to turn on. As a result, the BDNF genes of the sedentary animals were relatively muted, pumping out little BDNF.
But among the runners, the molecular blockade was much less effective. The molecules couldn't seem to cover and bind to the entire BDNF gene. So messages from the body continued to reach the gene and tell it to turn on and produce more BDNF.
Perhaps most remarkably, the researchers also found a particular substance in the runners' brains that fended off the action of these obstructionist molecules. The runners' brains contained high levels of ketones, which are a by-product of the breakdown of fat.
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