Abstract
Context: In healthy females, serum levels of oxytocin (OT) decrease post-prandially, corresponding to increased satiety. OT response to a meal in anorexia nervosa (AN), a psychiatric disorder characterized by chronic food restriction despite low weight, is not well-defined. We aimed to determine the pattern of postprandial OT levels and impact of AN presentation [restriction only (AN-R) vs. restriction + binge-purge (AN-BP)] and weight. Methods: Eighty-two females with AN/atypical AN, mean age 23.4±0.4 (SEM) years and mean % expected body weight (EBW) 85.6±1.1%, were instructed to eat a 400-kcal standardized mixed meal. Serum OT was sampled fasting and 30, 60, and 120 minutes post-meal. Subjective appetite was evaluated using Visual Analogue Scales. Participants were grouped by AN presentation [62 AN-R (<1 binge/purge episode/week) vs. 20 AN-BP (≥1 binge/purge episode/week)], weight [42 lower-weight (<85 %EBW, AN-LW) vs. 40 higher-weight (≥85 %EBW, AN-HW)]. Results: Age differed between AN-R and AN-BP (21.8±0.7 vs. 28.4±2.3 years, respectively, p=0.04), but was similar between AN-LW and AN-HW groups (24.3±1.0 vs. 22.3±1.4 years, respectively, p=0.24). %EBW did not differ between AN-R and AN-BP (85.6±1.3 vs. 85.6±2.1 %, p=0.99) but was lower in AN-LW vs. AN-HW, as per design (78.1±0.7 vs. 93.6±1.1%, respectively, p<0.0001). Menstrual cycle status and oral contraceptive pill use did not differ between comparison groups (p≥0.62). Quantity of food consumed was similar across groups (p≥0.45). In the whole sample, mean OT levels decreased from fasting to 60 and 120 minutes after the meal (60 min p=0.003 and 120 min p=0.015). A decrease in OT levels from fasting to 60 and 120 min was comparable between AN-R and AN-BP (60 min p=0.98 and 120 min p=0.61). However, OT decrease from fasting to 120 min was greater in AN-HW than AN-LW (-123 ± 38.8 vs. -4.2 ± 44.7 pg/mL, respectively, p=0.03), with no significant between-group difference at 60 min (p=0.22). Furthermore, in AN-HW, there was a trend for an inverse association between the decrease in OT levels and the decrease in hunger ratings after the meal. Specifically, the lesser the postprandial reduction in OT, the greater was the postprandial reduction in hunger ratings (r(s)=-0.306, p=0.054). There were no correlations between OT levels and appetite in other groups. Conclusions: Females with AN/atypical AN show a decrease in OT levels after a meal, as established in healthy females, and %EBW but not AN presentation seems to play a role in peripheral OT levels after food intake in AN. Postprandial OT levels seem to be related to appetite in AN-HW only, suggesting a disconnect between OT secretion and appetite in AN-LW.