Peptide YY induces characteristic meal patterns of aged mice.

BACKGROUND & AIM: Changes in eating behavior occur in the elderly due to oral and swallowing dysfunctions. We aimed to clarify the difference between basal meal patterns of young and aged mice in relation to appetite regulating hormones. METHODS: Thirty two of young (7-week-old) and aged (23-25-month-old) C57BL/6 male mice were acclimated to a single housing and then transferred to a highly sensitive automated feeding monitoring device. Feeding behavior was monitored from the onset of the dark phase after habituation to the device. Plasma peptide YY (PYY) levels were assessed under the several feeding status or after treatment of PYY. PYY and its receptor (NPY Y2 receptor, Y2R) antagonist were intraperitoneally administered 30min before the monitoring. RESULTS: Although the basal 24-h meal amounts did not differ by age, the total meal time and frequency of minimum feeding activity (bout) were significantly increased and the average bout size and time per bout were significantly decreased in aged mice. PYY dynamics were abnormal and the temporal reduction in food intake by exogenous PYY was more prominent in aged mice than in young mice. PYY administration to young mice induced aged-like meal patterns, and Y2R antagonist administration to aged mice induced young-like meal patterns. CONCLUSIONS: Aged mice exhibited characteristic meal patterns probably due to PYY metabolism dysfunction and/or enhanced PYY-Y2R signaling, suggesting a novel method for assessing eating difficulties in aged animals and a potential target for the remedy.