A postbiotic could reduce the risk of damage after a traumatic brain injury, such as a concussion. Mice that had traumatic brain injuries experienced less damage and performed better on cognitive tests if they were given a postbiotic 鈥� a byproduct produced when gut bacteria digest food 鈥� before injury. This suggests the postbiotic could be given preventatively to people who are particularly at risk of traumatic brain injuries, such as military personnel.聽
The gut microbiome is known to influence the brain, and vice versa. Research suggests it may help , which worldwide each year.聽
The molecule indole-3-propionic acid (IPA) is produced when gut bacteria break down tryptophan, an amino acid in food such as meat, fish and eggs. Previous studies have linked lower IPA to worse outcomes after , a rare type of stroke that causes bleeding in the brain, and in people with .
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Now, at the Air Force Medical University in Shaanxi, China, and his colleagues have measured it in blood samples from 106 people with traumatic brain injuries. They found that higher levels were associated with less swelling around brain lesions and better neurological outcomes six months later.聽
Next, the researchers 鈥� who didn鈥檛 respond to a request for an interview 鈥� induced a brain injury in mice that had been given either IPA or a control solution every day for two weeks. They found that the treated mice had less brain swelling, neuronal death and tissue damage than the control group three days later. They also performed better on tests of movement, learning and memory up to 14 days after their injury.
Traumatic brain injuries cause a series of neurological changes that occur in phases. One phase involves enzymes attacking mitochondrial membranes, causing them to disintegrate, which leads to oxidative damage. This then causes violently reactive compounds, which are usually sequestered inside mitochondria, to leak out, ultimately leading to neuroinflammation and cell death.
Through a series of imaging and cell experiments, the researchers found that IPA appeared to protect the mitochondria inside the mice鈥檚 astrocytes 鈥� cells that provide energy and support to neurons, but can become reactive and release inflammatory signals after an injury.聽
The team traced this protective effect to IPA activating the so-called aryl hydrocarbon receptor聽in astrocytes, preserving their mitochondria鈥檚 function, while also suppressing immune responses linked to inflammation.
鈥淭his new study significantly advances the field by identifying a detailed mechanism through which IPA preserves astrocytic mitochondrial [regulation] after traumatic brain injury,鈥� says at the University of Texas Medical Branch in Galveston, whose team in 1999.
But the mice were given IPA before their brain injury. 鈥淭his is prophylaxis, not therapy,鈥� says at the University of Wisconsin鈥揗adison. 鈥淣o one can pre-dose a car crash.鈥� He notes, however, that this approach could be explored in people at risk of repeated head impacts, such as contact-sport athletes or military personnel.
Two advantages of IPA, which isn鈥檛 yet available as a supplement, are that it is an inexpensive compound and can be taken orally, says Rey. However, doses may have to be tailored depending on the level of IPA a person already has from their microbiome, say Rey and at Houston Methodist Scholars in Texas. 鈥淧atients differ in injury severity and location, age, sex, diet, medications, antibiotics, intensive-care exposures and pre-existing microbiome composition,鈥� says Villapol.
Qu and his colleagues write in their paper that they are planning to further study the link between IPA and traumatic brain injury outcomes in people, and that future studies should test the effects of IPA administration after an injury.
Interdisciplinary Medicine
