The body’s ability to fight off food poisoning depends on the time of day, according to a new study from UT Southwestern Medical Center. The researchers found that levels of a natural antimicrobial compound increase during the day, when there is the greatest risk of exposure to toxic bacteria.
The experts report that the antimicrobial compound fluctuates on a circadian rhythm that is prompted by gut bacteria. The findings could eventually lead to the development of treatments and vaccines designed to maximize this immune response.
“This study shows that our immune systems are not turned on all the time, which is an unexpected result,” said study lead author Dr. John F. Brooks. “Our findings suggest that there are peak times in which the body is more primed to fight infections.”
Essentially, all animals follow circadian cycles that are aligned with daylight and darkness. These cycles are needed to help animals prepare for changes in their environment.
The researchers theorized that changes in antibacterial immunity may coincide with a circadian cycle. To investigate, they looked for rhythms in the expression of natural antimicrobial compounds produced in the gut of mice to fight off food poisoning.
The study revealed that one of these antimicrobial molecules, called regenerating islet-derived protein 3g (REG3G), was more abundant at night when the mice are most active. Levels of REG3G were much less abundant during the day, when mice are sleeping.
The researchers also found that in mice raised to have no gut bacteria, REG3G was essentially absent throughout both the day and the night.
The cycles of REG3G had significant consequences for the ability of mice to fight off infectious bacteria such as those that cause food poisoning.
When the researchers infected normal mice with bacteria, the animals had higher rates of death if they were exposed at sunset rather than at sunrise.
“These results make me think twice about waking up in the middle of the night and raiding the refrigerator,” said study co-author Dr. Lora Hooper. “It may be more dangerous to eat bacteria-laden potato salad when your gut defenses are lowest.”
The findings are published online in the journal Cell.