Gut-derived serotonin shown to negatively impact blood sugar

Coined the ‘happy hormone’, serotonin is associated with sleep regulation, wellbeing and metabolism. The gut produces 95% of the body’s serotonin, but not in the form that we associate with its existence in the brain.

A recent study has revealed how gut bacteria impact the normally feel-good chemical serotonin to negatively influence blood sugar levels. Specifically, the research investigated whether the gut microbiome influences glucose homeostasis through effects on gut-derived serotonin.

The team of researchers from Flinders University, the South Australian Health and Medical Research Institute (SAHMRI) and McMaster University in Canada demonstrated how bacteria living in the guts of mice communicate with cells producing serotonin to influence blood sugar levels in the host body. The findings are published in Proceedings of the National Academy of Sciences.

Professor Damien Keating, Head of Molecular and Cellular Physiology at Flinders University and Deputy Director of the Flinders Health and Medical Research Institute, said the study highlights the unanswered question about exactly how bacteria in the microbiome communicate to control glucose levels.

“We found that the microbiome worsens our metabolism by signalling to cells in the gut that produce serotonin. They drive up serotonin levels, which we previously showed to be increased in obese humans, and this rise in blood serotonin causes significant metabolic problems.

“The next step will be to understand exactly which bacteria do this, and how, in the hope that this could lead to new approaches to regulating blood sugar levels in humans,” he said.

The project is reported to be the first study to show how the microbiome, the bacteria that lives in the gut, effectively communicates with an organism to impact metabolism. If researchers can better understand which bacteria cause the signals to produce serotonin in the gut, treatments could one day be developed to reduce blood sugar levels, and this is a first step towards better understanding this process.

“This is an exciting revelation that can one day have direct implications for human health disorders such as diabetes, but much more research like this is required in the years to come,” Professor Keating said.

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