Gut microbe transplants may help fight strokes linked with animal product consumption, finds study

21 Jun 2021 --- Gut microbiome interventions and plant-based diets could help reduce the incidence and severity of strokes, according to new research at Cleveland Clinic, US. Researchers found that trimethylamine N-oxide (TMAO), a byproduct of ingesting red meats and other animal products, plays a central role in connecting the gut microbiome and disease.

The study, now published in Cell Host & Microbe, finds that gut microbiome transplants could provide an answer to the incidence of strokes. Almost 800,000 people are affected by strokes each year, according to the Centers for Disease Control and Prevention. 

Dr. Stanley Hazen, chair of the Department of Cardiovascular & Metabolic Sciences and director of Cleveland Clinic’s Center for Microbiome & Human Health, comments that the results prove simple microbiome transplants could profoundly impact stroke severity. 

“In this study, we found that dietary choline and TMAO produced greater stroke size and severity, and poorer outcomes in animal models,” he says. “Remarkably, simply transplanting gut microbes capable of making TMAO was enough to cause a profound change in stroke severity.”

Microbiome transplants could hold the key to diminishing stroke severity, according to the research.A decade of research 
The findings build on previous discoveries by Dr. Hazen and his team, showing that elevated TMAO levels can lead to the development of cardiovascular disease (CVD).

Through clinical trials involving thousands of patients, the researchers have shown that blood levels of TMAO predict future risk of heart attack, stroke and death – findings replicated around the world. 

“This new study expands on these findings and for the first time provides proof that gut microbes in general – and through TMAO specifically – can directly impact stroke severity or post-stroke functional impairment,” asserts Dr. Hazen.

Targeting the CutC enzyme 
The team compared performance on various tasks before and after the occurrence of strokes, both in short and long-term tests.

They then compared brain damage in preclinical stroke models between those with elevated or reduced TMAO levels. Over time, those with higher levels of TMAO had more extensive brain damage and a greater degree of motor and functional cognitive deficits following a stroke.

Dietary changes that alter TMAO levels, such as eating less red meat and eggs, impact stroke severity. A core finding was that a gut microbe enzyme critical to TMAO production called CutC drove heightened stroke severity and worsened outcomes. 

“When we genetically silenced the gut microbe gene that encodes CutC, stroke severity significantly diminished,” explains Dr. Weifei Zhu, co-author of the study. Following a plant-based diet reduces the prevalence of TMAO and its relationship to brain damage, say the study authors. 

“Ongoing research is exploring this treatment approach, as well as the potential for dietary interventions to help reduce TMAO levels and stroke risk since both a Western diet and a diet rich in red meat are known to elevate TMAO levels. Switching to plant-based protein sources helps to lower TMAO.”

Vegan momentum 
The findings follow a steady torrent of research suggesting plant-based diets can impact brain health and cognitive decline. Last year, a study linked just two servings of red meat per week with a higher risk of CVD. This followed a controversial 2019 meta-analysis suggesting red meat is not linked to poor health. 

The connection between the Mediterranean diet and neurodegenerative disorders such as Alzheimer's disease has long been investigated. This year, researchers from the University of British Columbia found the diet can slow down the onset of Parkinson’s disease by up to 17 years in women and eight years in men.

These benefits, however, were also found in separate research to diminish when unhealthy processed or junk foods are consumed. 

Other research last year found evidence that animal-free diets can impact emotional well-being. A large-scale study observed participants on a vegan diet were more introverted than those on animal-based diets; however, no association was found with depressive episodes. 

By Louis Gore-Langton