Physiological Effects of Dietary Amino Acids on Gut Health and Functions of Swine

Abstract

Gut health has significant implications for swine overall health status and nutrient utilization, due to its various functions including digestion and absorption of nutrients, secretion of mucins and immunoglobulins, and selective barrier protection against harmful antigens and pathogens. Both the basic anatomical structure of the gut (such as epithelial cells) and its luminal microbiota play important roles for maintaining gut health and functions. The interactions between epithelial cells and luminal microbiota have significant impact on host nutrition and health through the metabolism of dietary components. Amino acids, which are major nutrients for pigs, are not only obligatory for maintaining the intestinal mucosal mass and integrity, but also for supporting the growth of microorganisms in the gut. Dietary amino acids are the major fuel of the small intestinal mucosa. Particularly, glutamate, glutamine, and aspartate are the major oxidative fuel of the intestine. Emerging evidence shows that arginine activates the mTOR signaling pathway in the small intestine. Utilization of glycine by the small intestinal mucosa to synthesize glutathione is a very important physiological pathway, and the role of glycine as a powerful cytoprotectant has also been recognized. The major end products of methionine and cysteine metabolism are glutathione, homocysteine and taurine, which play important roles in the intestinal immune and anti-oxidative responses. Threonine is highly utilized by the gut and is particularly important for mucin synthesis and maintenance of gut barrier integrity. Moreover, either a deficiency or an excess of dietary threonine can reduce the synthesis of intestinal mucosal proteins and mucins in young pigs. Various new functions of amino acids on gut health and functions have been discovered in recent years. Thus, this review is to provide some up-to-date knowledge for industry application of dietary amino acids in order to enhance swine gut health and functions, and also it is to provide a comprehensive reference for further scientific research in this regard.

Effects of Gut Microbiome and Short-Chain Fatty Acids (SCFAs) on Finishing Weight of Meat Rabbits

“…Although asparagine is a non-essential amino acid, emerging evidence has demonstrated that it plays a key role in attenuating intestinal injury and improving the energy status of enterocytes, all of which are good for the health and growth of animals (Wang et al, 2015;Patra et al, 2019). Cysteine is able to regulate the antioxidant status and expression of anti-inflammatory genes in intestinal cells, which exert beneficial effects on body weight gain in pigs and chickens (Dilger and Baker, 2007;Yang and Liao, 2019). Arginine is a hub precursor for the synthesis of various important metabolic molecules, including NO and polyamines, exerting regulatory roles in the host's metabolic processes (Flynn et al, 2002).…”

Effects of reducing dietary crude protein concentration and supplementation with laminarin or zinc oxide on the faecal scores and colonic microbiota in newly weaned pigs

“…Previously, pigs offered wheat-based diets had reduced ileal, caecal and colonic lactobacilli, colonic bifidobacteria and increased faecal Enterobacteriaceae compared with pigs offered non-wheat-based diets (Garry, Fogarty, Curran, O'Connell, & O'Doherty, 2007;Weiss et al, 2016), suggesting high wheat diets may negatively affect the microbiota. Amino acids also contribute to the growth of the luminal microbiota (Yang & Liao, 2019); however, their role in the development and maintenance of a stable gut microbiota is not well understood. In vitro experiments found that the addition of glutamate, arginine, proline, glycine and serine promoted bacterial growth in human faeces (Smith & Macfarlane, 1998).…”

Composition of amino acids and related nitrogenous nutrients in feedstuffs for animal diets

“…These results indicate the unique importance of the former in improving the feed consumption, growth and health of animals (including companion animals). Furthermore, the simultaneous presence of a significant amount of glutathione [the major smallmolecular-weight antioxidant (Wu 2013)] with creatine and polyamines in animal-source feedstuffs protects the small intestine of animals from oxidative stress that often occurs under stressful conditions such as weaning, transportation, and heat stress (Wu 2018;Yang and Liao 2019). Finally, the inclusion of creatine in diets reduces the need for its endogenous synthesis of arginine, glycine and methionine due to a potent inhibition of renal arginine:glycine amidinotransferase expression (Brosnan and Brosnan 2007), thereby sparing these AAs for protein synthesis.…”