Fasting and nutrient-stimulated plasma peptide-YY levels are elevated in critical illness and associated with feed intolerance: an observational, controlled study

Abstract

Introduction: Delayed gastric emptying and feed intolerance occur frequently in the critically ill. In these patients, gastric motor responses to nutrients are disturbed. Peptide YY (PYY) slows gastric emptying. The aim of this study was to determine fasting and nutrient-stimulated plasma PYY concentrations and their relationship to cholecystokinin (CCK) in critically ill patients.

Methods: Studies were performed in 19 unselected mechanically ventilated critically ill patients (12 males; 48 +/- 7 years old) in a randomised, single-blind fashion. Subjects received a 60-minute duodenal infusion of Ensure at either 1 or 2 kcal/minute. Blood samples were collected at baseline and at 20, 40, 60, and 180 minutes following commencement of the nutrient infusion for the measurement of plasma PYY and CCK concentrations (using radioimmunoassay). Patient data were compared to 24 healthy subjects (17 males; 43 +/- 2 years old).

Results: Fasting PYY concentration was higher in patients (P < 0.05), particularly in those with feed intolerance (P < 0.05). Plasma PYY concentrations were higher in patients during nutrient infusion (area under the curve [AUC] at 1 kcal/minute: 2,265 +/- 718 versus 1,125 +/- 138 pmol/l.min, P < 0.05; at 2 kcal/minute: 2,276 +/- 303 versus 1,378 +/- 210 pmol/l.min, P = 0.01) compared to healthy subjects. The magnitude of PYY elevation was greater in patients during the 1 kcal/minute infusion (AUC: 441 +/- 153 versus 186 +/- 58 pmol/l.min, P < 0.05), but not the 2 kcal/minute infusion. Fasting and nutrient-stimulated plasma CCK concentrations were higher in patients (P < 0.05). There was a relationship between plasma PYY and CCK concentrations during fasting (r = 0.52, P < 0.05) and nutrient infusion (r = 0.98, P < 0.0001).

Conclusion: In critical illness, both fasting and nutrient-stimulated plasma PYY concentrations are elevated, particularly in patients with feed intolerance, in conjunction with increased CCK concentrations.

Figure 1

Effects of critical illness on plasma PYY and CCK concentrations. Effects of critical illness on plasma (a) PYY and (b) CCK concentrations during fasting and duodenal nutrient infusions of 1 kcal/minute (ICU patients, n = 9; healthy subjects, n = 13) and 2 kcal/minute (ICU patients, n = 10; healthy subjects, n = 11) compared with healthy age- and gender-matched control group. ICU patients: closed diamond, solid line; healthy subjects: open circle, solid line. Fasting and nutrient-stimulated PYY and CCK concentrations were higher in patients compared with the healthy control group. *P < 0.05, **P < 0.001 versus healthy subjects. CCK, cholecystokinin; ICU, intensive care unit; PYY, peptide YY.

Figure 2

Plasma (a) PYY and (b) CCK concentrations during fasting and duodenal nutrient stimulation in feed-tolerant (n = 9) and feed-intolerant (n = 10) critically ill patients. Feed-tolerant patients: open diamond, solid line; feed-intolerant patients: closed square, solid line. Both fasting and nutrient-stimulated PYY and CCK concentrations were higher in patients with feed intolerance compared with feed-tolerant patients. *P < 0.05, **P < 0.001 versus feed-tolerant patients. CCK, cholecystokinin; PYY, peptide YY.

Figure 3

Relationship between plasma PYY and CCK concentrations during fasting and duodenal nutrient stimulation. Relationship between plasma PYY and CCK concentrations during (a) fasting and (b) duodenal nutrient stimulation (expressed as integrated plasma level [area under the curve from 0 to 180 minutes] in critical illness [n = 19]). There was a strong positive correlation between integrated PYY and CCK concentrations during both fasting (r = 0.52, P < 0.05) and nutrient stimulation (r = 0.98, P < 0.0001) in critically ill patients. CCK, cholecystokinin; PYY, peptide YY.