Bacterial imbalance in the gut after a stroke may worsen brain inflammation

The unexpected link between gut microbes and brain recovery after stroke attracted the attention of researchers at Uthealth Houston in Houston, providing new insights into some patients suffering from more severe inflammation and worse outcomes.

When a stroke strikes, it triggers a range of changes, including destroying the delicate balance of gut bacteria. According to the discovery of Natural Communications published on February 19, this imbalance may deprive the brain of key protective compounds that usually help regulate inflammation.

The study identified a key protein called aryl hydrocarbon receptor (AHR), which acts as a molecular sensor that responds to compounds in human and gut bacteria. After the stroke, the researchers found a huge shift in this chemical balance—the levels of beneficial bacteria-derived compounds decreased, while the potentially harmful compounds produced by the body increased.

“This study examines how substances from human and gut bacteria affect post-stroke inflammation,” said senior author Dr. Bhanu Priya Ganesh. “They found that changes in gut bacteria after a stroke lead to a decrease in beneficial substances and an increase in harmful substances. This suggests that restoring these beneficial substances from gut bacteria can help reduce inflammation after stroke.”

When examining the brain tissue of stroke patients, researchers found that AHR levels in microglia are elevated, which are the brain’s resident immune cells that coordinate inflammatory responses. When they supplemented elderly mice with beneficial bacterial compounds after inducing stroke, the animals showed reduced brain damage and better neurological function.

These findings are consistent with the growing evidence linking gut health to brain function. Previous preclinical Uthealth Houston, animal model studies showed that stroke and neurodegenerative diseases produce systemic responses, in which the intestinal microbiome plays a key role, and aging can worsen stroke-induced malnutrition.

The researchers used traditional mice and specially sterile mice lacking gut bacteria to point out how these bacterial compounds affect brain inflammation. Without beneficial bacterial compounds, immune cells in the brain show altered inflammatory responses and increased markers of damage.

The study also suggests that aging can worsen the bacterial imbalance after stroke, which may partly explain why older people often experience poorer results. Current stroke treatments focus primarily on disrupting blood flow through clots or mechanically removed, but due to timing limitations and other limitations, these options can be used in less than 10% of patients.

“Our recent animal model studies have shown that new treatment options can be focused on intestinal connections, thus providing potential ways to improve post-stroke recovery and reduce brain damage,” Ganesh said.

The timing of these bacterial changes may provide a broader window for interventions that may help patients who are not eligible for current treatment.

The first author is Pedram Peesh, resident of the Department of Neurosurgery of Vivian L. Smith, Smith, McGovern Medical School, PhD, MBA. Louise McCullough, MD, PhD, Professor, Roy M.

The study was supported by the Huffington Foundation and the National Institutes of Health.

These findings represent understanding the complex relationship between gut health and brain recovery, possibly pointing to future areas of diet, probiotics, or metabolites as research on stroke recovery.