Stomach have biological clock

University of Adelaide researchers have
discovered the first evidence that the nerves in
the stomach act as a circadian clock, limiting
food intake to specific times of the day. The discovery, published in The Journal of Neuroscience, could lead to new information about how the gut signals to our brains about
when we're full, and when to keep eating. In the University's Nerve-Gut Research
Laboratory, Dr Stephen Kentish investigated
how the nerves in the stomach respond to
stretch, which occurs as a consequence of food
intake, at three-hourly intervals across one day. "These nerves are responsible for letting the
brain know how much food we have eaten and
when to stop eating,” says Dr Kentish, who is
the lead author of the paper. "What we've found is that the nerves in the gut
are at their least sensitive at time periods
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. "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, signalling 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," he says. So far this discovery has been made in
laboratory studies, not in humans. "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," Dr
Kentish says. Study leader Associate Professor Amanda
Page says this research could lead to further
discoveries about how changes in people's
circadian clocks affect their eating habits. "We know that shift workers, for example, are
more prone to disruptions in sleep and eating
behaviour, leading to obesity and other health
problems.  We are now conducting further
research to see what kind of impact such
changes to the circadian rhythm will have on eating behaviour, and how the nerves in the
stomach react to those changes," Associate
Professor Page says. This study has been funded by the National
Health and Medical Research Council
(NHMRC).