The Bacterial Microbiome and Vascular Brain Disease

A big leap ahead for science this week:  for the first time ever, scientists from a variety of major universities (University of Chicago, the University of California San Diego, Children’s Hospital of Philadelphia/University of Pennsylvania, etc.) have directly connected specific alterations in gut bacteria to a neurovascular disease:  “This is the first demonstration of a sensitive and specific diagnostic microbiome in a human neurovascular disease.”[i]

The disease they studied specifically is called carvernous angioma (CA), which had I never heard of, as it is quite rare.  I checked it out on the UCLA website to learn more:  “A cavernous angioma is a blood vessel abnormality characterized by large, adjacent capillaries with little or no intervening brain. The blood flow through these vessels is slow. Cavernous angiomas can occur anywhere in the central nervous system. The disease occurs in 0.4 percent of the population, and 18.7 percent of these patients have multiple lesions.”  The symptoms can include seizures, headaches, hemorrhages, compression of the surrounding brain tissue, weakness, numbness, double vision, visual disturbances or language difficulties.

While this particular bit of research is on a rare condition, the lessons learned from it will likely have vast implications for a number of “brain diseases.”  They chose carvernous angioma because there was already a strong animal model, which suggested that there was a distinct association between the development of this illness and an altered gut biome.  Did this same gut-brain association exist in humans?If so, says the senior author, from the University of Chicago, “”The implications of that were very big…”[ii]  Remember that other vascular brain diseases include stroke, various kinds of stenosis,  aneurysms, and so forth.  So we are talking help/treatment for a lot of people before devastating illness strikes.  (I wonder too, if this won’t also apply to vascular dementia?)

The scientists sampled fecal samples from more than 100 people with CA and these were compared with 250 samples from non-affected controls.  There was a clear and distinct difference:  those with CA had a predominance of gram-negative bacteria, no matter where they were from, regardless of the number of lesions they have, regardless of how often lesions appear.  In fact, the researchers were able to identify the 3 species that made all the difference and could completely reliably be used to identify those with CA from those without:  “Those with greater amounts of a gram negative species called Odoribacter splanchnicus, lower numbers of gram positives Faecalibacterium prausnitzii and Bifidobacterium adolescentis.”

Lipopolysaccharides (LPS), metabolites produced by bacteria, seems to drive the formation of these brain lesions.  The data also suggest that “…microbiome and inflammation together drive CA disease severity…” which, of course, makes sense since the more aberrant the microbiome, the more severe the disease

The question then becomes, of course, can a regimen be constructed – perhaps a combination of diet, probiotics, prebiotics and potentially antibiotics of some sort – that can stop such a process in its tracks, now that science knows the exact culprits?  I’m watching and waiting for that next step because the implications for so many diseases is absolutely vast.

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[i] Polster, SP, et. al. Permissive microbiome characterizes human subjects with a neurovascular disease carvernous angioma.  Nature Communications. 2020;11:2.  https://doi.org/10.1038/s41467-020-16436-w

[ii] https://www.sciencealert.com/scientists-made-a-significant-discovery-linking-gut-bacteria-with-neurovascular-disease