A synthetic nasal formulation of the hormone
oxytocin reduced caloric intake in healthy men,
particularly consumption of fatty foods, after a
single treatment, a new study finds. The results, to
be presented at The Endocrine Society's 97th annual
meeting in San Diego, confirm those of animal
studies showing oxytocin reduces food intake.
Oxytocin nasal spray reportedly lowered the number
of calories men consumed at a subsequent breakfast
whether they were normal weight or overweight. In
addition, the researchers found that oxytocin
improved metabolic measures, such as insulin
sensitivity, which is the body's ability to
successfully clear glucose (sugar) from the
bloodstream.
The oxytocin nasal spray (made by Novartis) is
approved in Europe but not in the U.S. other than in
clinical trials. Oxytocin is available in the U.S.
as an intravenous or injectable drug (Pitocin) to
induce labor.
Elizabeth Lawson, MD, MMSc, assistant professor of
medicine at Harvard Medical School, Boston, and her
colleagues enrolled 25 healthy men into the study,
which received funding from the National Institutes
of Health and a Massachusetts General Hospital
Claflin Distinguished Scholar Award (to Lawson).
The participants had an average age of 27. Thirteen
of the men had a healthy weight, and the other 12
were overweight or obese. The men were randomly
assigned to self-administer a single dose (24
International Units, or IU) of either oxytocin nasal
spray or a placebo (dummy drug) after fasting. All
were unaware which treatment they received.
One hour later, the men received breakfast, which
they picked out from a menu. Each meal contained
double portions. After the meal, the researchers
measured how many calories each man ate.
In a separate visit, the men repeated the experiment
but received the opposite treatment (placebo or
oxytocin) from the first visit. According to the
investigators, there was no difference in how much
food the men reported eating in the three days
before each experiment.
On average, the men ate 122 fewer calories and 9
grams less fat at the meal after they received
oxytocin nasal spray compared with placebo, the
study data showed. Oxytocin also reportedly
increased the use of body fat as a fuel for energy.
There were no serious side effects and no difference
in side effects between oxytocin and placebo,
according to Lawson.
Oxytocin had no effect on self-reported appetite or
on appetite-regulating hormones measured in their
blood, the researchers discovered. Therefore, how
oxytocin affected caloric intake is unclear, Lawson
said.
In preclinical studies, oxytocin was involved in
appetite-reducing pathways in the brain.
Because oxytocin has sex-specific effects, it needs
to be studied in women, as well as in both sexes for
an extended treatment duration, she said.
See also:
Unexpected side
effect of the love hormone oxytocin (2015/04/08)
For more information
Endocrine Society
Harvard Medical School
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