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

Background: Aging is associated with a decrease in appetite and a slowing o f gastric emptying. The gastrointestinal hormones cholecystokinin (CCK), gl ucagon-like peptide 1 (GLP-1), and peptide YY (PYY) may mediate these chang es. Objective: We investigated whether aging influenced the secretion of CCK, G LP-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 m easured. Results: Plasma CCK concentrations were higher in older than in younger sub jects (P = 0.004) as a result of higher baseline values (4.7 +/- 0.2 compar ed with 3.2 +/- 0.2 pmol/L; P < 0.0001) and a greater rise during lipid inf usion (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 di fferent between groups. The decrease in hunger during intraduodenal lipid i nfusion was inversely related to the increase in CCK, GLP-1, and PYY in you nger but not older subjects. During intraduodenal lipid infusion, the incre ase in isolated pyloric pressure wave (IPPW) frequency was positively relat ed to GLP-1 and PYY and the increase in IPPW amplitude was positively relat ed to CCK in older but not younger subjects, whereas the increase in IPPW a mplitude and pyloric tone was negatively related to GLP-1 and PYY in younge r subjects. Conclusions: Human aging is associated with increased CCK concentrations, w hich may contribute to the slowing of gastric emptying, mediated by increas ed pyloric motility. The role of increased plasma CCK concentrations in med iating the age-related decrease in appetite remains to be established.