Scientists have found that our immune system benefits when we eat regular meals. The gastrointestinal system is closely connected to our immunity, and the consumption of food or anticipation of a regularly timed meal triggers the action of protective mechanisms in the gut. Using a rodent model, the researchers determined that eating initiates a cascade of gut hormone activity. This work may help us learn more about the importance of regular mealtimes, or help develop treatments for gut inflammation, which can be a symptom of serious diseases. The findings have been reported in Nature Immunology.
When food is eaten, it may introduce pathogens or nasty germs to the body. Food consumption causes intestinal nerves to release a hormone called vasoactive intestinal peptide (VIP), which triggers immune cell activity. Activation of VIP is a signal to immune cells called ILC3, which produce a molecule called interleukin-22 (IL-22).
"Food intake switches on VIP, which plays a critical role in alerting the gut’s army of ILC3 immune cells. In response, ILC3s secrete interleukin-22, which swings into protective action to defend against pathogens and maintain tissue integrity," said the research co-leader, Professor Gabrielle Belz of the Walter and Eliza Hall Institute. "We also showed that a deficiency in VIP limits the production of IL-22, which in turn negatively impacts the immune system's ability to prevent unwanted inflammation."
Cutting-edge imaging tools helped the scientists learn more about protective immunity in the gut. They obtained three-dimensional, high-resolution images that revealed how the close interactions between VIP hormone and ILC3 immune cells can protect gut health.
The researchers also learned that genes that are involved in the body's circadian clock help increase immunity when it's time for a meal. Immunity in the gut does not stay at the same level throughout the day; regular eating patterns and the circadian rhythm influence the fluctuation of gut immunity.
"We saw that gut immunity not only spikes with food intake. It also rises and falls due to inbuilt cellular machinery regulated by the circadian clock gene Bmal1, which appears to activate immune cells when eating is likely," said the co-leader of the research, Dr. Cyril Seillet of the Walter and Eliza Hall Institute. "While more work needs to be done to better understand this anticipatory mechanism, the results are very interesting and could help to explain why disruptions to circadian rhythms and regular eating patterns could increase chronic inflammation in the gut.
"The next steps of our research include gaining a molecular understanding of what properties of food are responsible for kickstarting the process of protective immunity," Seillet added. "For example, are there certain diets that drive a more protective response than others?"