The effect of different macronutrient infusions on appetite, ghrelin and peptide YY in parenterally fed patients

Background & aims Patients receiving parenteral nutrition (PN) still feel hungry despite adequate provision of calories intravenously. It is not known whether PN or its constituent macronutrients acutely affect appetite and to what degree this may be mediated by ghrelin and peptide YY (PYY). Methods Six medically stable patients (four men) with intestinal failure receiving PN received an isocaloric 200 kcal infusion on three separate occasions following a 12 h fast. The infusions consisted of either carbohydrate (10% dextrose), fat (10% intralipid) or mixed protein/carbohydrate (PN). Changes in ghrelin and peptide YY levels and changes in subjective symptoms of hunger, satiety and nausea during each macronutrient infusion were assessed. Results None of the three infusions acutely affected subjective symptoms of hunger, satiety and nausea (P>0.05 ANOVA). Ghrelin levels decreased significantly during dextrose [−19.1 (−35.9, −12.4), regression coefficient (95% CI), P<0.001] and parenteral nutrition infusions [−18.2 (−26.8, −9.6), P<0.001]. Lipid infusion had no effect on ghrelin levels but led to a significant decrease in PYY [−0.076 (−0.0123, −0.028), P=0.004]. Dextrose and PN infusion had no significant effect on PYY levels. Conclusions Dextrose and PN infusions decrease ghrelin levels. Lipid infusion does not affect ghrelin levels but in contrast to oral nutrients leads to a significant decrease in PYY. Despite these changes, in patients receiving PN, macronutrient infusions do no acutely affect appetite.