Peptide YY_(3-36) inhibits morning, but not evening, food intake and decreases body weight in rhesus macaques

Peptide YY_(3-36) [PYY_(3-36)] is a hormone that is released after meal ingestion that is currently being investigated for the treatment of obesity; however, there are conflicting reports of the effects of PYY_(3-36) on energy balance in rodent models. To shed light on this controversy, we studied the effect of PYY_(3-36) on food intake and body weight in a nonhuman primate. Intravenous PYY_(3-36) infusions before a morning meal transiently suppressed the rate of food intake but did not suppress the evening meal or 24-h intake. Twice-daily or continuous intravenous PYY_(3-36) infusions to supraphysiological levels (levels that exceeded normal physiological levels) again suppressed the rate of feeding for the morning but not the evening meal. Twice-daily intravenous PYY _(3-36) infusions for 2 weeks significantly decreased body weight in all test animals (average weight loss 1.9%) without changing insulin response to glucose infusion. These results show that endogenous PYY_(3-36) may alter morning but not evening meal intake, and supraphysiological doses are required for effective suppression of food intake.