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What’s in your guts might influence how your brain
responds to food, alcohol and cigarettes, claimed
Dr. Tony Goldstone, head of the
psychoneuroendocrinology research group at Imperial
College London, based at the Hammersmith Hospital in
London, U.K., at an NIH psychoneuroendocrinology
scientific interest group lecture in the Clinical
Center.
Several gut hormones, including ghrelin, PYY, GLP-1,
and insulin influence the brain’s response to food,
he explained. These hormones send signals to areas
of the brain responsible for eating and addictive
behaviours.
“When you’re hungry, you’re liable to find
high-energy foods more appealing,” said Goldstone.
An empty stomach produces ghrelin, referred to as
the hunger hormone. Ghrelin signals the brain to
feel hunger.
After a person eats, the intestines produce hormones
such as GLP-1 and PYY that ease the sensation of
hunger.
In several studies, Goldstone has observed that when
volunteers were shown photos of hamburgers, pizza,
cake and other high-energy dense foods on an empty
stomach, activity increased in the areas in the
brain that respond to reward.
The opposite happened when patients were full.
Reward centers were less active when the volunteers
viewed photos of high-energy foods.
The effects of fasting could be mimicked by giving
injections of the hormone ghrelin.
He also studied patients who have had gastric bypass
surgery, a procedure for obesity in which parts of
the stomach and intestines are reconnected so that
food bypasses most of the stomach and the first part
of the small bowel.
After the surgery, Goldstone said, patients respond
less to photos of high-energy foods than do patients
with obesity who have not had surgery, or after a
different type of surgery called gastric banding.
The appeal of high-energy foods declines after
gastric bypass surgery, as does the associated
activation of the brain reward system, while the
appeal of low-energy foods, such as vegetables,
stays the same.
In fact, the intestines of patients who have had
gastric bypass surgery produce more GLP-1, a hormone
that reduces blood sugar and causes a reduction in
appetite, and PYY, a hormone that also reduces
appetite.
The changes in these hormones are in part
responsible for the beneficial effects of this
surgery and appear also to explain these healthy
changes in food reward.
In addition to altering how the brain responds to
pictures of food, nutritional state might also
influence other addictive behaviours, including how
people respond to money and stress, how impulsive
they are or the risks they take.
In one study, Goldstone’s team told healthy
volunteers they could win money if they pressed a
button at a correct time.
When volunteers had not eaten overnight and were
hungry, their brain’s reward centers showed more
activity while they were anticipating winning money
than when they were full.
This study also found that when volunteers were
shown unpleasant photos that produced discomfort,
their brains were more responsive if they hadn’t
eaten.
“Food intake suppresses the brain’s responsiveness
to unpleasant images,” he explained.
“We have also seen this happen after gastric bypass
surgery, suggesting that changes in gut hormone may
be responsible for this effect.”
In animal studies, the gut hormones GLP-1 and
ghrelin have been shown to “modify reward behaviours
to almost any drug tested.”
Currently, Goldstone is studying patients who are
trying to lose weight and others who have recently
quit drinking alcohol or smoking cigarettes, as part
of the Gut Hormones in Addiction study.
“We are investigating whether manipulation of these
GLP-1 and ghrelin hormones can reduce craving and
brain responses to food, alcohol or cigarettes, as
well as unpleasant images.”
He hopes to publish his findings soon.
“These gut hormones are targets towards treating
obesity, but also may be effective in preventing
cravings and reducing consumption and relapse in
populations such as alcoholics and smokers,” he
concluded.
See also
Effects of smoking and its abstinence on dietary
intake and appetite (2016/09/12)
Link...
Hormone ghrelin increases the sex drive (2015-05-15)
Link...
For more information
Imperial College London
Department of Medicine - Research
Link...
The
Gut Hormones in Addiction study
Link...
U.S.
National Institutes of Health
Link...
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