Gut microbiome

Gut microbiome: gut disease and brain hemorrhage

The University of Chicago team has discovered a "remarkable" link: patients suffering from hemorrhagic brain disease also have a severely disrupted gut microbiome. This work, published in the journal Nature Communications, provides a new illustration of this gut-brain axis, which has previously focused on neurological diseases. The study has implications for the treatment of cavernous angiomas, a rare vascular malformation of the brain, and potentially for other bleeding disorders of the brain.

 

The study shows that patients with this rare genetic disease that causes brain bleeding also have a different gut microbiome. The disease in question, cavernous angioma, is characterized by abnormalities in the blood vessels of the brain, strokes, seizures, and severe neurological complications. The disease is caused by a genetic mutation in the lesion - which can be hereditary or sporadic - and its severity and course vary greatly from patient to patient, with molecules produced by this bacterial imbalance causing the lesions in the brains of these patients. The study thus suggests a direct link between this important "gut disorder" and the brain.

This is the first link between the gut microbiome and neurovascular disease in humans

This has implications for all neurovascular diseases that may be similarly affected by an "abnormal" gut microbiome, said the Chicago-based team, international experts in the disease. They analyzed the gut microbiome of patients with cavernous angioma: Why did they do it? Lead author Issam Awad, M.D., director of neurovascular surgery at UChicago Medicine, was involved in an earlier study in mice that showed cells lining blood vessels in the brain respond to gut bacteria.

 

Can the microbiome promote brain damage? What was observed in mice also applies to these patients with cavernous angiomas. Analysis of stool samples from more than 120 patients with cavernous angiomas and comparison with samples from healthy controls revealed significantly higher levels of gram-negative bacteria and significantly lower levels of gram-positive bacteria.

A combination of three bacterial species distinguishes patients with cavernous angiomas from other patients

Essentially, the analysis identifies a "profoundly altered" bacterial community in these patients. "Patients with cerebral angiomas all have the same specific microbiome, whether they inherited the mutation or developed a sporadic lesion. This bacterial imbalance causes lipopolysaccharide (LPS) molecules to enter the brain through the bloodstream and attach to the wall of the cerebral vessels, leading to the development of lesions."

The microbiome is the cause of the lesion, not the result

The researchers conclude:

"By examining both bacterial combinations and biomarkers in the blood, we can assess the severity of the disease in individual patients," they say.

 

The researchers are also investigating whether the link between the microbiome and the brain can be applied to other diseases. Especially since they can detect the same genes and biomarkers involved in cerebral angiomas in the brains of very old people.