Regulation of pancreas development and enzymatic gene expression by duodenal infusion of leucine and phenylalanine in dairy goats

Abstract

This study aimed to investigate the effect of a duodenal infusion of leucine and phenylalanine on pancreatic development and enzyme gene expression in dairy goats. Sixteen healthy yearling Guanzhong dairy goats of similar weights (29.7 ± 1.4 kg) had surgical duodenal intubation, and were used in a completely random design in this experimental. The animals were randomly divided into the 4 treatment groups, with 4 goats in each group: control, 3 g/d leucine (3 Leu), 9 g/d leucine (9 Leu) and 2 g/d phenylalanine (2 Phe), dissolved in and infused into the duodenum for 21 days. The goats were fed twice daily (0800 and 1800) with 350 g (dry matter) of total mixed rations, and were all slaughtered on the last day of the experimental period for pancreatic tissue sampling. The results showed that leucine and phenylalanine infusion did not affect pancreas weight or protein concentration (P > 0.05). However, 9 Leu treatment reduced pancreatic DNA concentration, and both 9 Leu and 2 Phe treatments increased the pancreatic protein:DNA ratio (P < 0.05). Leucine and phenylalanine infusions increased pancreatic amylase activity (P < 0.05), whereas had no effect on the total trypsin and lipase activities (P > 0.05). Treatment with 9 Leu and 2 Phe increased amylase mRNA levels (P < 0.05), and 2 Phe increased lipase mRNA levels (P < 0.05). Trypsin mRNA levels were unaffected by leucine and phenylalanine infusion (P > 0.05). The phosphorylation of eukaryotic translation initiation factor 4E-binding protein 1 was increased by leucine infusion (P < 0.05), but not by phenylalanine infusion (P > 0.05). Leucine infusion also increased the free leucine concentration in the pancreas (P < 0.05), and had no effect on glucose concentrations (P > 0.05). In conclusion, duodenal infusion of an appropriate amount of leucine and/or phenylalanine can effectively improve the expression and secretion of pancreatic amylase in goats, which is important for improving intestinal starch digestion in ruminant animals. The regulation of the pancreatic amylase expression by leucine and phenylalanine mainly occurs at the transcriptional and/or translational level in goats.