Gut microbes produce a chemical that enhances clotting in the arteries, increasing the risk of heart attack and stroke.

Stanley Hazen of the Cleveland Clinic in Ohio and his colleagues treated human platelets, which form blood clots, with a compound called TMAO. This is made in the body from a waste product of gut microbes, and has been linked to heart disease. The team found that TMAO made the platelets form artery-blocking clots faster. The researchers increased blood TMAO levels in mice by feeding them a diet that was rich in choline, a TMAO precursor, and found that the animals formed clots faster than did those with lower TMAO levels.

This effect was not seen in animals that lacked gut microbes or that were treated with antibiotics. When intestinal microbes from mice that produced high levels of TMAO were transplanted into mice with no gut microbes, the recipients' clotting risk increased. The results reveal a link between diet, gut microbes and heart-disease risk, the authors say.

Cell http://doi.org/bdb2 (2016)