The trillions of microorganisms in the human gastrointestinal tract, the gut microbiome, has a powerful influence on many different parts of the body. While many links have been found between the gut microbiome and various diseases, scientists are now beginning to decipher the effects that certain gut microbes have on specific aspects of human health. One gut microbe in particular, Limosilactobacillus reuteri has many impacts; it is known to help maintain normal gut transit, boost the anti-inflammatory effects of the immune system, promote wound healing, and prevent bone loss in animal models of osteoporosis. This microbe also contributes to normal social behavior in mice. Oxytocin was thought to be related to biochemical signaling that links L. reuteri and social behavior. Scientists have now investigated that link, and the findings have been reported in the journal Gut Microbes.
“L. reuteri is one ...bacteria that can affect more than one organ in the body,” said co-corresponding study author Dr. Sara Di Rienzi, an assistant professor of molecular virology and microbiology at Baylor College of Medicine.
Oxytocin is primarily generated in a region of the brain known as the hypothalamus, and it is known to be related to social behavior, and the regulation of feeding, among other effects.
“Given that other brain-produced hormones also are made in the gut, we tested the novel idea that oxytocin itself was also produced in the intestinal epithelium where L. reuteri typically resides," said first study author Dr. Heather Danhof, an assistant professor of molecular virology and microbiology at Baylor.
The investigators analyzed the expression of genes in cells that line the gut, the intestinal epithelium, and found that various species including mice and humans express oxytocin genes in those cells. With fluorescence microscopy, the researchers were able to see that oxytocin gene expression in human intestinal organoids, which are simplified, three-dimensional models that can be grown in culture and mimic the physiology of the human gut.
“Finally, a big moment was when we visualized oxytocin in human intestinal tissue samples, demonstrating oxytocin as an intestinal hormone,” noted Di Rienzi.
The scientists also determined how the release of oxytocin from human intestinal tissue or organoids was influenced by L. reuteri. The bacterium is able to trigger the release of a hormone called secretin from enteroendocrine cells in the intestine, causing another type of cell in the intestine called enterocytes to release oxytocin, explained Danhhof.
The researchers have revealed that oxytocin can be generated in the gut, and discovered a novel way that a gut microbe affects oxytocin release in the gut. Now they want to find out whether these findings can open up new treatment options for autism spectrum disorders, and help us gain a better understanding of how social behavior, oxytocin production in the gut, and the brain are connected.
“We are excited about these findings,” said co-corresponding study author Dr. Robert Britton, professor of molecular virology and microbiology and member of the Dan L Duncan Comprehensive Cancer Center at Baylor.
Sources: Baylor College of Medicine, Gut Microbes
