Melatonin Unlocks a Microbial Key in Obesity

A natural hormone in the body, melatonin has long been supplemented by frequent flyers to ease circadian rhythms into new time zones. A newer and potentially more valuable finding is its role in weight gain and metabolism. Indeed, melatonin reduces body weight, liver steatosis, and low-grade inflammation and improves insulin resistance in high fat diet (HFD)-fed mice.

This is huge, given the soaring obesity rates across the globe- numbers which have doubled since 1980.

Could these benefits be related to the gut microbes, also implicated in metabolic disease?

Pengfei Xu and colleagues from Beijing Normal University, Beijing, China published research addressing that question in the May 2017 issue of Journal of Pineal Research.

The study

Mice were randomly assigned to three groups in a light and climate controlled room at 12-hours light—12-hours dark cycle and 25±2°C, with free access to water and different diets. The melatonin treatment group (HFD+M) was fed an HFD with melatonin at 50 mg/kg body weight (BW) by gavage once daily for 10 weeks.

Blood and fecal samples were collected.

Results 

Amazingly, melatonin prevented HFD-induced obesity, liver steatosis, insulin resistance, and  low-grade inflammation. Through the gut microbiota profiling, results indicate that melatonin also produces significant change in gut microbiota composition, suggesting a potential mechanism by which melatonin reduces obesity and its related disorders:

• A decrease of the Firmicutes-to-Bacteroidetes ratio—a known obesity marker
• An increase in the number of mucin-degrading bacteria Akkermansia, linked with healthy mucosa.

The specific mechanism needs further research. In addition, it is unclear whether melatonin can alter gut microbiota under a normal diet.

From the article titled Melatonin prevents obesity through modulation of gut microbiota in mice, Pengfei Xu and colleagues concluded:

“In conclusion, our results show that melatonin treatment modulates the gut microbiota, promoting a decrease in the ratio of Firmicutes to Bacteroidetes and increasing the relative abundance of Akkermansia, while bringing the abundances of Alistipes, Anaerotruncus, and Desulfovibrionaceae back to normal levels, thereby providing beneficial effects against obesity, insulin resistance, liver steatosis, and low-grade inflammation in HFD-fed mice.”

This is exciting data. Even after loading up on airplane food, melatonin may interact with our microbes to prevent weight gain.