Dietary Leucine Supplementation Improves the Mucin Production in the Jejunal Mucosa of the Weaned Pigs Challenged by Porcine Rotavirus
September
Dietary Leucine Supplementation Improves the Mucin Production in the Jejunal Mucosa of the Weaned Pigs Challenged by Porcine Rotavirus
Xiangbing Mao 0 1 2
Minghui Liu 0 1 2
Jun Tang 0 1 2
Hao Chen 0 1 2
Daiwen Chen 0 1 2
Bing Yu 0 1 2
Jun He 0 1 2
Jie Yu 0 1 2
Ping Zheng 0 1 2
0 1 Animal Nutrition Institute, Sichuan Agricultural University , Ya'an, Sichuan , People's Republic of China, 2 Key Laboratory of Animal Disease-Resistance Nutrition, Ministry of Education , China, Ya'an, Sichuan , People's Republic of China
1 Funding: This study was financially supported by the grant from National Natural Science Foundation of China (31201812), the earmarked fund for the China Agriculture Research System (CARS-36), and the grant from the Science and Technology Support Program of Sichuan Province , 13ZC2237
2 Editor: Dipshikha Chakravortty, Indian Institute of Science , INDIA
The present study was mainly conducted to determine whether dietary leucine supplementation could attenuate the decrease of the mucin production in the jejunal mucosa of weaned pigs infected by porcine rotavirus (PRV). A total of 24 crossbred barrows weaned at 21 d of age were assigned randomly to 1 of 2 diets supplemented with 1.00% L-leucine or 0.68% L-alanine (isonitrogenous control) for 17 d. On day 11, all pigs were orally infused PRV or the sterile essential medium. During the first 10 d of trial, dietary leucine supplementation could improve the feed efficiency (P = 0.09). The ADG and feed efficiency were impaired by PRV infusion (P<0.05). PRV infusion also increased mean cumulative score of diarrhea, serum rotavirus antibody concentration and crypt depth of the jejunal mucosa (P<0.05), and decreased villus height: crypt depth (P = 0.07), goblet cell numbers (P<0.05), mucin 1 and 2 concentrations (P<0.05) and phosphorylated mTOR level (P<0.05) of the jejunal mucosa in weaned pigs. Dietary leucine supplementation could attenuate the effects of PRV infusion on feed efficiency (P = 0.09) and mean cumulative score of diarrhea (P = 0.09), and improve the effects of PRV infusion on villus height: crypt depth (P = 0.06), goblet cell numbers (P<0.05), mucin 1 (P = 0.08) and 2 (P = 0.07) concentrations and phosphorylated mTOR level (P = 0.08) of the jejunal mucosa in weaned pigs. These results suggest that dietary 1% leucine supplementation alleviated the decrease of mucin production and goblet cell numbers in the jejunal mucosa of weaned pigs challenged by PRV possibly via activation of the mTOR signaling.
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Competing Interests: The authors have declared
that no competing interests exist.
The mucosal barrier of intestine is the first defense line against the luminal hostile environment
[1]. The maintenance of intestinal mucosa function mainly depends on the mucosal barrier of
gastrointestinal tract that consists of non-specific barrier mechanisms, specific immunological
responses and intestinal microecology [2–5]. The mucin-type glycoproteins or mucins that are
mainly synthesized and secreted by the goblet cells in the intestinal mucosa are the important
component of non-specific barrier mechanisms [6].
Rotavirus is a kind of double-stranded RNA icosahedral RNA virus [7]. It is a major
pathogen inducing severe gastroenteritis and diarrhea in children and the other young animals [7,
8]. This could be due to rotavirus damaging the mucosal barrier of the proximal small intestine,
including the decrease of the mucin production and the goblet cell number [9–12].
Mucins, a kind of glycoproteins with molecular weights ranging from 0.5 to 20 MDa, consist
of the oligosaccharide chains and the protein core [13, 14]. The protein core of small-intestinal
mucins in pigs contains a lot of threonine that represents 28–35% of the total amino acid
residues [15]. Recent studies have shown that dietary leucine supplementation may decrease
serum threonine concentration of pigs [16], and do not affect the total tract apparent threonine
digestibility in pigs [17]. Additionally, as a functional amino acid, leucine may regulate protein
metabolism in intestines of pigs through the mTOR signaling pathway [16, 18, 19], and
stimulate the expression of some specific proteins in tissues and cells [20–23]. Leucine treatment
could also inhibit the autophagy via activating the mTOR signaling pathway, which affects the
cellular survival and function [24–25]. Thus, it is possible that dietary leucine supplementation
stimulated the mucin synthesis in the intestinal mucosa of pigs, and attenuated the effects of
rotavirus infection on the mucin production and the goblet cell number of intestinal mucosa.
However, these have not been determined.
Therefore, the present study was conducted to test the hypothesis that dietary leucine
supplementation could attenuate the decrease of the mucin production in the jejunal mucosa of
the weaned pigs infected by porcine rotavirus.
Materials and Methods
Animals and diets
The animal protocol for this study was approved by the Anima (...truncated)