Postruminal supply of amino acids enhances ghrelin secretion and lipid metabolism in feed-deprived sheep.

Single amino acids (AA) feeding is gaining more attention for their functional roles beyond nutritional needs. This study aimed to describe the endocrine and metabolic responses to a single AA administration (at 10% of MP for maintenance) in 48 hr fasted sheep (n = 4) receiving, over continued 4 hr, a duodenal infusate of saline (control), glutamate (Glu), glutamine (Gln), lysine HCl (Lys), threonine (Thr), or valine (Val) in a 4 by 6 Youden square design with weekly intervals. Blood samples were collected at 0, 15, 30, 60, 120, 180, and 240 min relative to the infusion onset, and plasma AA, glucose, β-hydroxybutyric acid (BHBA), nonesterified fatty acids (NEFA), ghrelin, insulin, glucagon, and insulin-like growth factor 1 (IGF-1) concentrations were measured. The results showed that the duodenal supply of Glu, Gln, Lys, Thr, and Val enhanced ghrelin release. Administration of Glu, Gln, and Val declined plasma BHBA concentrations, whereas plasma NEFA levels were decreased with Gln and Thr. Insulin concentration was greater with Thr, glucagon levels were increased with Lys, Thr, Val, and Glu, whereas IGF-1 levels were enhanced with Gln, Lys, and Thr supply. Thus, selective AA feeding can positively adjust the endocrine status and counteract the feed restriction-induced lipid mobilization.