A recent study suggests that two or more serious hits to the head within days of each other can interfere with the brain’s ability to use sugar to repair cells damaged by the injuries. According to Ohio State University scientists, in animal studies brain cells increase their energy use 6 days following a concussion to recover from the damage. Should a second injury occur before that surge of energy use begins, the brain loses its best chance to recover.
In the new research, which was presented at Neuorscience 2014, the scientists noted that even if the required glucose is present in the brain, faulty insulin signals in an injured brain do not allow cells to take up the sugar and use it.
A university news release reports that clinical signs indicate that two head injuries close together are dangerous and can also be potentially deadly. Yet, the science remains unclear, according to Zachary Weil, PhD, lead author, and assistant professor of neuroscience at Ohio State. Determining these details, he adds, could help in deciding when to return athletes to play or military members to service.
Weil goes on to point out in the release that, “Lots of data show that if two head injuries occur close together, it’s not like 1 plus 1. It’s more like 1 plus 10. So our goals are to understand what it is about injuries close together that makes us more vulnerable, and can we eventually use some sort of biological signal to tell when it’s safe to go back?”
Additionally, Weil explains that the discovery that insulin resistance plays a role in brain recovery post-injury could help outline the development of chronic traumatic encephalopathy (CTE), seen in professional athletes who have sustained multiple traumas to the head.
A link between defective insulin signals and Alzheimer’s disease has already been established, according to the release.
To this end, “With injury, the damaged cells are not able to use energy even though they need it and the glucose is there. It appears that’s because the signals are messed up. It’s the same thing seen in Alzheimer’s patients. Cells are chronically undernourished even though the sugar level might be high.”
During earlier animal studies, Weil and colleagues compared the impact of head injuries that occurred either 3 days or 20 days apart. Of all the animals, the mice injured 3 days apart had higher inflammation in the brain, more degeneration of axons, and issues learning how to navigate a maze and remembering the lessons they did manage to learn.
The release notes that mice with a single injury or head blows 20 days apart both exhibited a surge in brain energy use 6 days post-injury. The brains in mice injured 3 days apart never developed such a high level of glucose use.
“With the second injury, demands for energy might outstrip the ability of the damaged cells to actually use the energy,” Weil said.
During the follow-up work presented at the Society for Neuroscience, researchers investigated brain tissue in mice that had sustained no injury, one concussion, or two head injuries 24 hours apart. Once treating the tissue with insulin, the scientists then measured activation levels of a key protein in the insulin signaling process. In mice with no injury, the protein activation was heightened by the presence of insulin. However, the injured brains did not respond to the presence of insulin at all, the release says.
Weil states that this indicates traumatic brain injury induces insulin resistance in the brain, “So we need to work on finding ways to acutely increase insulin sensitivity rather than increasing the actual amount of insulin in the brain.”
Source(s): Medical News Today, Ohio State University
