Individuals with Prader-Willi syndrome (PWS) have a significant reduction in the number of oxytocin-producing neurons (42%) in the hypothalamic paraventricular nucleus. A number of animal studies and observations of humans show that lesions in this region can produce PWS-like symptoms. Given the evidence for potential oxytocin deficiency, we tested the effects of a course of intranasal oxytocin on PWS symptoms. Thirty individuals with PWS aged 12-30 years participated in an 18-week randomized double-blind placebo-controlled crossover trial. Participants received 8 weeks of oxytocin and 8 weeks of placebo with a minimum 2-week washout period. The first 11 participants received the following oxytocin doses: 24 IU (twice daily) B.I.D for participants 16 years and over and 18 IU B.I.D for participants 13-15 years. The dose was increased for the remaining 18 participants to 40 IU B.I.D for participants 16 years and over and 32 IU B.I.D for 13-15 years. Measures used to assess changes were standardized well-accepted measures, including the Developmental Behavior Checklist-Monitor, Parent, Teacher, and Adult; The Yale-Brown Obsessive Compulsive Scale; The Dykens Hyperphagia questionnaire; Reading The Mind in the Eyes Test; Epworth Sleepiness Scale and the Movie Stills. Oxytocin had little impact on any measure. The only significant difference found between the baseline, oxytocin, and placebo measures was an increase in temper outbursts (P = 0.023) with higher dose oxytocin. The lack of effect of oxytocin nasal spray may reflect the importance of endogenous release of oxytocin in response to exogenous oxytocin.

Our pilot study demonstrates that exenatide is well tolerated in PWS patients. It increases satiety independently of measured appetite hormones, exerting glucose lowering, and insulinotropic effects similarly in PWS and OBESE patients. Larger prospective studies should investigate whether chronic exenatide administration will reduce hyperphagia and overweight in PWS patients without side effects.

ObjectivePrader-Willi syndrome (PWS) is a leading genetic cause of obesity, characterized by hyperphagia, endocrine and developmental disorders. It is suggested that the intense hyperphagia could stem, in part, from impaired gut hormone signaling. Previous studies produced conflicting results, being confounded by differences in body composition between PWS and control subjects. Design Fasting and postprandial gut hormone responses were investigated in a cross-sectional cohort study including 10 adult PWS, 12 obese subjects matched for percentage body fat and central abdominal fat, and 10 healthy normal weight subjects. Methods PYY [total], PYY , GLP-1[active] and ghrelin [total] were measured by ELISA or radioimmunoassay. Body composition was assessed by dual energy X-ray absorptiometry. Visual analog scales were used to assess hunger and satiety. Results In contrast to lean subjects (p < 0.05), PWS and obese subjects were similarly insulin resistant and had similar insulin levels. Ghrelin[total] levels were significantly higher in PWS compared to obese subjects before and during the meal (p < 0.05). PYY meal responses were higher in PWS than in lean subjects (p = 0.01), but not significantly different to obese (p = 0.08), with an additional non-significant trend in PYY[total] levels. There were no significant differences in self-reported satiety between groups, however PWS subjects reported more hunger throughout (p = 0.003), and exhibited a markedly reduced mealinduced suppression of hunger (p = 0.01) compared to lean or obese subjects. Conclusions Compared to adiposity-matched control subjects, hyperphagia in PWS is not related to a lower postprandial GLP-1 or PYY response. Elevated ghrelin levels in PWS are consistent with increased hunger and are unrelated to insulin levels.

PWS subjects compared to adiposity-matched obese subjects demonstrate similar insulin resistance but increased low-grade inflammation. The dissociation of inflammation and central adiposity suggests that activation of innate immunity may be either a specific genetic feature of PWS or linked to the commonly associated obstructive sleep apnea syndrome, and might offer a treatment target to reduce cardiovascular disease.