Monday, December 16, 2013
Researchers say they have uncovered the first evidence that nerves situated in the stomach follow a circadian rhythm and limit a person's food intake to certain times throughout the day. This is according to a study published in The Journal of Neuroscience.
Investigators from the University of Adelaide in Australia say their findings may lead to insight into how the stomach tells the brain we are hungry or full.
To reach their findings, the researchers analyzed 8-week-old mice to determine how nerves in the stomach respond to "stretch" - a process that occurs following food intake at 3-hourly intervals throughout the day.
According to Dr. Stephen Kentish, of the University of Adelaide's Nerve-Gut Research Laboratory, these nerves are responsible for telling the brain how much food a person has eaten, and when to stop eating.
Stomach nerves 'act as a clock' to coordinate food intake
But their study found that the nerves in the gut have minimal sensitivity during times of the day that are associated with being awake.
"This means more food can be consumed before we feel full at times of high activity, when more energy is required," Dr. Kentish explains.
"However, with a change in the day-night cycle to a period associated with sleeping, the nerves in the stomach become more sensitive to stretch, signaling fullness to the brain quicker and thus limiting food intake.
This variation repeats every 24 hours in a circadian manner, with the nerves acting as a clock to coordinate food intake with energy requirements."
Although this study was conducted in mice, the investigators believe the same process applies to the human body.
"Our theory is that the same variations in nerve responses exist in human stomachs, with the gut nerves being less sensitive to fullness during the day and more sensitive at night," says Dr. Kentish.
Further research into how circadian rhythm affects eating habits
The researchers say their findings could lead to to discoveries regarding how people's eating habits could be affected by changes in their circadian clock.
Associate Prof. Amanda Page, of the University of Adelaide and leader of the study, uses the example of shift workers, who are more likely to experience sleep disruptions and irregular eating habits.
Previous research has suggested that nurses who work long shifts, overtime or other adverse work schedules may be more prone to obesity.
The investigators say they are now conducting further research to see how changes to the circadian rhythm impacts eating behavior, and how the nerves in the stomach react to the changes.
Circadian Variation in Gastric Vagal Afferent Mechanosensitivity, doi: 10.1523/JNEUROSCI.3846-13.2013, Stephen J. Kentish, Claudine L. Frisby, David J. Kennaway, Gary A. Wittert, Amanda J. Page, published in The Journal of Neuroscience, 4 December 2013.
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