Regulation of pancreatic exocrine secretion in goats: differential effects of short‐ and long‐term duodenal phenylalanine treatment

Abstract

Four yearling goats (31.2 ± 2.5 kg), surgically fitted with common bile duct reentrant and duodenal catheter, were used in two 4 × 4 Latin square design experiments to investigate the effects of duodenal infusion of phenylalanine for different times on pancreatic exocrine secretion (PES). In experiment 1 (the long-term experiment), goats were duodenally infused with 0, 2, 4 or 8 g/day phenylalanine for 14 day. Pancreatic juice and jugular blood samples were collected over 1-h intervals for 6 h daily from day 11 to day 14 to encompass a 24-h day. In experiment 2 (the short-term experiment), goats were infused with phenylalanine for 10 h continuously at the same infusion rate as experiment 1 after feed deprivation for 24 h repeated every 10 day. Pancreatic juice and blood samples were collected at 0, 1, 2, 4, 6, 8 and 10 h of infusion. The volume and pH of pancreatic juice were measured, and a 5% subsample was composited and frozen until analysis of enzyme activities. Plasma was frozen until analysis of insulin and cholecystokinin (CCK). In experiment 1, pancreatic juice, α-amylase secretion and plasma CCK concentration responded quadratically (p < 0.05), with the top value observed at the 2 g/day phenylalanine. Trypsin secretion had a quadratic response (p < 0.05), with secretion increasing up to 4 g/day phenylalanine and decreasing thereafter. Phenylalanine linearly decreased pancreatic protein and lipase secretion (p < 0.05). The results of correlation analysis showed significant correlations (p < 0.05) between plasma CCK concentration and secretion of α-amylase and trypsin. However, the short-term phenylalanine infusion did not influence (p > 0.05) pancreatic juice, protein, α-amylase, lipase, trypsin secretion and plasma CCK concentration. These results indicate PES of ruminants is stimulated by phenylalanine and is potentially mediated by CCK in the long-term duodenal infusion treatment, but is not influenced by phenylalanine in the short-term duodenal infusion treatment.

Duodenal supply of glutamate and casein both improve intestinal starch digestion in cattle but by apparently different mechanisms1

“…Yet, hydrolysis of small-chain α-glycosides apparently increased 32% by NEAA compared with EAA (measured as a decrease in flow of ethanol-soluble starch to the ileum), which suggests that the hydrolytic capacity of bovine small intestine for small chain α-glycosides was appreciably increased in response to nonessential AA. Yu et al (2013) reported that duodenal infusion of Phe decreased pancreatic α-amylase secretions in goats. In the current experiment, small intestinal starch digestion was not different from the control when PTM was infused, and flows of ethanol-soluble starch were not different from the control when PTM alone was infused.…”

Leucine markedly regulates pancreatic exocrine secretion in goats

“…However, longterm leucine supplementation does not increase muscle mass in healthy elderly men (Verhoeven et al, 2009;Leenders et al, 2011). Our previous research also shows that duodenal infusion of phenylalanine for a short (10 h) or long period (14 days) has different effects on pancreatic exocrine secretion in goats (Yu et al, 2012). These results indicate that the acute regulating roles of leucine towards pancreatic exocrine secretion may differ from those of prolonged treatment.…”

“…In our recent report, duodenal infusion of phenylalanine for 14 days has been verified to be an effective regulating factor for pancreatic a-amylase secretion of goats (Yu et al, 2012). In rats, leucine not only decreases a-amylase mRNA expression (Hashimoto and Hara, 2004), but also stimulates pancreatic protein synthesis dependent on the mammalian target of rapamycin (mTOR) signalling pathway (Sans et al, 2006).…”

Effects of dietary leucine and phenylalanine on pancreas development, enzyme activity, and relative gene expression in milk-fed Holstein dairy calves

“…The milk fed to all the groups was made isonitrogenous by adding alanine (1.366, 0.391, 0.975, and 0 g/L of milk for control, leucine, phenylalanine, and mixed treatments, respectively). The doses of leucine and phenylalanine for the experimental groups were based on the results of Yu et al (2013) and Liu et al (2015). The milk was sampled weekly and stored at −20°C, and the samples were pooled.…”

“…Cholecystokinin can promote the synthesis of pancreatic amylase, trypsin, and trypsinogen, stimulate the release of these pancreatic enzymes, and enhance their activities. Duodenal infusions of phenylalanine (Yu et al, 2013) and leucine (Liu et al, 2015) play a role in regulating the secretion of pancreatic α-amylase.…”