Microbial Messenger Calms Brain Signals to Protect the Heart

Gut microbes produce indole-3 acetic acid (IAA) from tryptophan, which acts on hypothalamic hypocretin neurons to restrain sympathetic signals to the heart. When IAA is low, these neurons overactivate, contributing to diastolic dysfunction and hypertension; in humans, hypertensive patients have lower IAA levels, especially women, suggesting IAA could be a biomarker and that diet, probiotics, or supplementation may help prevent or treat cardiovascular disease via the gut–brain–heart axis.