Indoles Produced by the Gut Microbiome Increase Neurogenesis
There is good evidence for butyrate produced by the gut microbiome to increase neurogenesis via upregulation of BDNF. Here researchers show that indoles produced by gut microbes, via processing of tryptophan, also result in the outcome of increased neurogenesis. The balance of microbial species in the gut microbiome changes with age in ways that reduce this production of beneficial metabolites, as well as increasing the activity of harmful species that provoke the immune system into chronic inflammation. The combination of these issues may be as influential as physical activity on long-term health, judging from the benefits produced in animal models via transplantation of a youthful microbiome into old individuals.
The billions of microbes living in your gut could play a key role in supporting the formation of new nerve cells in the adult brain, with the potential to possibly prevent memory loss in old age and help to repair and renew nerve cells after injury. Researchers found that gut microbes that metabolise tryptophan - an essential amino acid - secrete small molecules called indoles, which stimulate the development of new brain cells in adults.
The team also demonstrated that the indole-mediated signals elicit key regulatory factors known to be important for the formation of new adult neurons in the hippocampus, an area of the brain also associated with memory and learning. Memory loss is a common sign of accelerated ageing and often an early sign of the Alzheimer's disease (AD).
"This finding is exciting because it provides a mechanistic explanation of how gut-brain communication is translated into brain cell renewal, through gut microbe produced molecules stimulating the formation of new nerve cells in the adult brain. These findings bring us closer to the possibility of novel treatment options to slow down memory loss, which is a common problem with ageing and neurodegenerative diseases. These include drugs to mimic the action of indoles to stimulate the production of new neurons in the hippocampus or to replace neurons damaged by stroke and spinal injury, as well as designing dietary intervention using food products enriched with indoles as a preventive measure to slow down ageing,"