The neurobiology relating to the insatiable appetite observed in Prader-Willi
syndrome (PWS) has not been fully characterized. Two functional magnetic
resonance imaging (fMRI) scans were performed on each of three adults with PWS.
The scans were carried out pre- and post-treatment with the antiepileptic
topiramate, which had little effect on body weight and appetite in these
subjects. Subjects fasted overnight and drank a 75 g dextrose solution prior to
fMRI scans for measurement of brain activation levels during/after glucose
ingestion. Following glucose administration, there was a significant delay in
activation at the hypothalamus and other brain regions associated with satiety
compared with previous data on obese volunteers. These regions include the
insula ventromedial prefrontal cortex, and nucleus accumbens. Individuals with
PWS showed a mean latency of 24 min while in a previous study obese volunteers
had shown a latency of 15 min and lean volunteers a latency of 10 min in the
hypothalamus. Our results provide evidence towards a satiety dysfunction in the
central nervous system of PWS patients.
