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Microbiome heart attack risk

Thu, 10th Mar 2016

Chris Smith

Signals produced by intestinal microbes can make strokes and heart attacksAn artists impression of red blood cells more likely, new research has shown.

According to Cleveland Clinic, Ohio, scientist Stanley Hazen and his colleagues, a breakdown product released when certain groups of bowel bacteria digest food nutrients increases the "stickiness" of blood, making the formation of a fatal clot or thrombus in an artery more likely.

Western diets rich in the chemicals choline, carnitine and phosphatidyl choline, which are found in foodstuffs like meat, fish and liver, lead to high blood levels of a substance called TMA-O or trimethylamine oxide.

This promotes the formation of atheroma, the fatty deposits that furr up arteries, and it also increases the activity of platelets, cells fragments that float in the blood and play a critical role in the coagulation system.

Experimental mice fed diets high in choline, the team found, showed higher blood levels of TMA-O and were more prone to developing lethal blood clots in arteries, but only if they had a normal population of bacteria in their intestines.

Animals reared without any bowel bugs, or mice dosed long-term with broad-spectrum antibiotics, were not susceptible in the same way. But a "trans-poosion" of bowel bacteria from a normal mouse into one of these "germ free" counterparts restored the dietary risk from choline.

To identify which bugs might be involved, the team used genetic techniques to compare the microbial activity in the animals' guts with their blood levels of TMA-O.

This enabled them to home in on eight common bacterial species that appear to do the bulk of the metabolism of choline into TMA that is then absorbed into the bloodstream, although how blood platelets sense and respond to TMA-O, or even why, isn't known yet.

Nevertheless, the results suggests that dietary - prebiotic - or other interventions to manipulate the levels of these microbes are likely to affect an individual's risk of heart disease and stroke.

As the team point out in their paper in Cell this week, the mainstay of current cardiac therapy is the use of anti-platelet drugs like aspirin, which prevent blood clots. While effective at saving lives, these drugs bring with them a significant risk of bleeding.

"Could manipulating gut microbes be a safer anti-platelet alternative?" they wonder.

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