- In a pilot study, functional MRI was used on 10 men with overweight or obesity to examine brain network dynamics while the subjects viewed images of high-calorie food or control images
- When participants viewed images of high-calorie food, a single dose of oxytocin reduced functional connectivity between the ventral tegmental area (VTA), a key hedonic brain region, and multiple other brain regions involved in processing food cues
- Specifically, administration of oxytocin resulted in attenuation of the functional connectivity of the VTA with the insula, oral somatosensory cortex, amygdala, hippocampus, operculum, middle temporal gyrus and primary visual cortex
- That effect was not detected when subjects viewed low-calorie food items, household objects or fixation stimuli
There is strong clinical evidence that dosing with oxytocin, a hypothalamic neurohormone, decreases food intake and body weight. Adding to this evidence, a randomized, placebo-controlled pilot trial by Elizabeth A. Lawson, MD, clinician in the Neuroendocrine Clinical Center at Massachusetts General Hospital, and colleagues, published in Obesity, showed that oxytocin significantly reduced hunger-driven caloric intake in men across the weight spectrum.
In a later study, published in Neuropsychopharmacology, that utilized functional MRI, Dr. Lawson and colleagues investigated the mechanism of oxytocin's anorexigenic effect. They found that subjects with obesity who viewed images of high-calorie foods demonstrated hypoactivation of the ventral tegmental area (VTA), the origin of the mesolimbic dopaminergic reward circuit. Other hedonic brain regions ("pleasure centers") that drive efforts to obtain desirable foods were also hypoactivated.
Building on that research, Dr. Lawson, Liya Kerem, MD, MSc, pediatric endocrinology fellow, Franziska Plessow, PhD, experimental psychologist in the Neuroendocrine Unit, and colleagues have become the first to show that oxytocin attenuates the functional connectivity between the VTA and other food motivation brain regions. Their report is published in the International Journal of Obesity.
The team recruited 10 men with overweight or obesity who participated in a randomized, double-blind, placebo-controlled crossover study of a single dose of intranasal oxytocin. Using functional MRI, the researchers examined connectivity between brain regions while the participants viewed images of high-calorie palatable food, low-calorie food, household objects or fixation stimuli.
Activation of Interconnected Brain Regions
When the participants viewed high-calorie food after using oxytocin, they exhibited significantly attenuated functional connectivity between the VTA and certain brain regions compared with the results after they used placebo. The brain regions identified (the insula, oral somatosensory cortex, amygdala, hippocampus, operculum, middle temporal gyrus and primary visual cortex) help process sensory, cognitive and emotional aspects of visual food cues.
When the participants viewed low-calorie food, household objects or fixation stimuli, there was no difference in functional connectivity between the VTA and the other brain regions when comparing oxytocin and placebo.
These findings offer a partial explanation of the anorexigenic effect of oxytocin. They are particularly relevant to individuals with obesity, because it has been proposed that hyperactivity of the dopaminergic reward circuit exacerbates overeating behavior in that population.
Future studies could examine whether oxytocin affects functional connectivity after subjects actually consume high-calorie food and whether its effects on caloric intake are sustained with long-term administration.