Gut Bacteria Produce Heart-Brain Metabolite
Researchers identified indole-3-acetate (IAA), produced by gut bacteria from dietary tryptophan, as a key molecule regulating the 'gut-brain-heart' axis by controlling inflammation, supporting cardiovascular health, and influencing brain function. Scientists are investigating targeted diet and probiotic interventions to modulate IAA production for precision nutrition strategies.
- A recent screening of 206 human gut bacterial strains revealed that robust production of IAA is uncommon, with high-capacity output being confined to a few species, including *Blautia hydrogenotrophica* and *Intestinibacter bartlettii*. - The metabolite signals to the brain by activating the Aryl hydrocarbon receptor (AhR) in a specific group of hypothalamic cells called hypocretin (Hcrt) neurons. This action prevents the neurons from over-firing, which in turn blunts sympathetic nerve signals that can lead to heart muscle stiffening and diastolic dysfunction. - While beneficial in this context, high levels of IAA are considered a uremic toxin in patients with chronic kidney disease and have been linked to cardiovascular inflammation, fibrosis, and increased mortality. - Tryptophan, the precursor amino acid for IAA, is not produced by the body and must be obtained from dietary sources. Foods rich in tryptophan include poultry, meat, cheese, fish, eggs, soy products, pumpkin seeds, and chia seeds. - Lower levels of IAA have been observed not only in zebrafish models with hypertension but also in human patients with high blood pressure, suggesting IAA could serve as a potential biomarker for heart failure risk. - Though newly understood in the gut-brain-heart axis, IAA has been studied for decades as the most common and crucial plant hormone of the auxin class, where it regulates plant growth and development.
