SAN DIEGO — A synthetic nasal formulation of the hormone oxytocin may help reduce caloric intake in healthy men and may be particularly helpful in lowering the consumption of fatty foods, according to a new randomized, double-blind, placebo-controlled crossover study being presented at ENDO 2015.
Oxytocin nasal spray reportedly lowered the number of calories men consumed at a subsequent breakfast, regardless of whether they were normal weight or overweight. In addition, the researchers found that oxytocin improved metabolic measures, such as insulin sensitivity.
“There are studies in animals that show that oxytocin is an important regulator of food intake. Not much is known about oxytocin effects on appetite and food consumption in humans or whether we could target oxytocin pathways in order to treat obesity. We wanted to translate findings in animals to humans, and see whether oxytocin would have the same effects in reducing food intake,” said lead investigator Elizabeth Lawson, MD, MMSc, who is an assistant professor of medicine at Harvard Medical School in Boston.
An oxytocin nasal spray made by Novartis is approved in Europe but not in the United States. However, oxytocin is available in the U.S. as an intravenous or injectable drug (Pitocin) to induce labor.
For their study, Dr. Lawson and colleagues enrolled 25 healthy men with a mean age of 27 years, 13 of whom were at a healthy weight and 12 of whom were overweight or obese.
All the men were randomly assigned to self-administer a single dose of either oxytocin nasal spray (24 IU) or a placebo after fasting. The men received breakfast 60 minutes later, and they were allowed to select what they wanted from a menu, although each meal contained double portions. After the meal, the researchers measured how many calories each man consumed.
In a separate visit, the men repeated the experiment but received the opposite treatment (placebo or oxytocin) from the first visit. Dr. Lawson said there was no difference in how much food the men reported eating in the 3 days before each experiment. The researchers found that the men, on average, ate 122 fewer calories (P=.03) and 9 grams less fat (P=.03) at the meal after they received oxytocin nasal spray compared with placebo. 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.
“Our findings that a single dose of intranasal oxytocin reduces caloric intake, increases the use of fat as an energy source for the body and improves glucose homeostasis are encouraging. Oxytocin may represent a novel treatment for obesity and its complications. Further study will be important to see if oxytocin is effective and safe over time. The side effects, which included dizziness, drowsiness, nasal irritation and abdominal pain in our study, were not severe and did not differ after receiving oxytocin vs. placebo,” Dr. Lawson told Endocrinology Advisor.
For this investigation, the caloric content of the food consumed was measured and visual analogue scales were used to assess appetite. The researchers also conducted fasting blood draws and analyzed appetite-regulating hormones (leptin, ghrelin, and peptide YY), insulin and glucose before and after oxytocin or placebo. Oxytocin had no effect on self-reported appetite or on appetite-regulating hormones measured in their blood.
Dr. Lawson said at this time, it is not entirely clear how oxytocin affected caloric intake. In preclinical studies, oxytocin was involved in appetite-reducing pathways in the brain.
Because oxytocin has sex-specific effects, it also needs to be studied in women, according to Dr. Lawson. She said studies in the future will need to look at the use of oxytocin in both sexes for an extended treatment duration.
Additionally, she noted that oxytocin is a key modulator of food intake and energy metabolism. She said future studies will also need to investigate whether oxytocin pathways can be modulated to treat obesity and metabolic syndrome.
- Lawson EA et al. Abstract OR40-2. Presented at: The Endocrine Society’s 97th Annual Meeting & Expo (ENDO 2015); March 5-8, 2015; San Diego.