Effects of age on concentrations of plasma cholecystokinin, glucagon-like peptide 1, and peptide YY and their relation to appetite and pyloric motility

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Abstract
Background: Aging is associated with a decrease in appetite and a slowing of gastric emptying. The gastrointestinal hormones cholecystokinin (CCK), glucagon-like peptide 1 (GLP-1), and peptide YY (PYY) may mediate these changes. Objective: We investigated whether aging influenced the secretion of CCK, GLP-1, and PYY and their effects on appetite and pyloric motility. Design: Eight healthy older (65–80 y) and 7 younger (20–34 y) men received isoenergetic (12.1 kJ/min) intraduodenal infusions of lipid and glucose for 120 min on separate days. Plasma CCK, GLP-1, and PYY concentrations were measured. Results: Plasma CCK concentrations were higher in older than in younger subjects (P = 0.004) as a result of higher baseline values (4.7 ± 0.2 compared with 3.2 ± 0.2 pmol/L; P < 0.0001) and a greater rise during lipid infusion (increase from baseline: 7.1 ± 0.5 compared with 5.3 ± 0.6 pmol/L; P = 0.048). Plasma GLP-1 and PYY concentrations were not significantly different between groups. The decrease in hunger during intraduodenal lipid infusion was inversely related to the increase in CCK, GLP-1, and PYY in younger but not older subjects. During intraduodenal lipid infusion, the increase in isolated pyloric pressure wave (IPPW) frequency was positively related to GLP-1 and PYY and the increase in IPPW amplitude was positively related to CCK in older but not younger subjects, whereas the increase in IPPW amplitude and pyloric tone was negatively related to GLP-1 and PYY in younger subjects. Conclusions: Human aging is associated with increased CCK concentrations, which may contribute to the slowing of gastric emptying, mediated by increased pyloric motility. The role of increased plasma CCK concentrations in mediating the age-related decrease in appetite remains to be established.