Effects of peripheral administration of PYY3-36 on feed intake and plasma acyl-ghrelin levels in pigs.

These studies were designed to investigate the effects of i.v. administration of peptide YY3–36 (PYY3–36) on feed intake, acyl-ghrelin, and GH levels in castrated male pigs. Feed intake levels were evaluated during both ad libitum and fast-refed conditions, and plasma hormone responses were evaluated during fasting. During ad libitum feeding, i.v. injection of PYY3–36 (30 mg/kg body weight, BW) significantly reduced feed intake levels within 3 h post-treatment. In the fast-refed condition, both single bolus injection (30 mg/kg BW) and i.v. infusion (0$25 mg/kg BW per min) of PYY3–36 suppressed feed intake levels 1 h post-treatment. Duration of the elevation of plasma PYY levels induced by i.v. injection of porcine PYY3–36 in ad libitum-fed pigs was longer compared with the values of fasted or fast-refed pigs. In the infusion study, the elevation of plasma PYY levels was maintained throughout the infusion period and values were reduced less than half at 15 min after termination of infusion. These results showed that the anorexigenic short-term effect of PYY3–36 treatment corresponds to its half-life. However, i.v. PYY3–36 injection did not influence plasma acyl-ghrelin levels. On the other hand, single bolus injection of PYY3–36 increased plasma GH levels 30 min after treatment. Similar to previous findings in other mammalian species, the results of these studies show that PYY3–36 can reduce feed intake levels; in particular, the effect is potent and acute in pigs. Furthermore, basal plasma PYY levels were higher in ad libitum-fed pigs than in fasted pigs suggesting that circulating PYY3–36 levels influence satiety and contribute to the termination of feed intake in pigs.