l-Glutamate nutrition and metabolism in swine

Abstract

L-Glutamate (Glu) has traditionally not been considered as a nutrient needed in diets for humans and other animals (including swine) due to the unsubstantiated assumption that animals can synthesize sufficient amounts of Glu to meet their needs. The lack of knowledge about Glu nutrition has contributed to suboptimal efficiency of global livestock production. Over the past 25 years, there has been growing interest in Glu metabolism in the pig, which is an agriculturally important species and also a useful model for studying human biology. Because of analytical advances in its analysis, Glu is now known to be a highly abundant free amino acid in milk and intracellular fluid, a major constituent of food and tissue proteins, and a key regulator of gene expression, cell signaling, and anti-oxidative reactions. Emerging evidence shows that dietary supplementation with 2% Glu maintains gut health and prevents intestinal dysfunction in weanling piglets, while enhancing their growth performance and survival. In addition, the inclusion of 2% Glu is required for dietary arginine to maximize the growth performance and feed efficiency in growing pigs, whereas dietary supplementation with 2% Glu reduces the loss of skeletal muscle mass in endotoxin-challenged pigs. Furthermore, supplementing 2% Glu to a corn- and soybean-meal-based diet promotes milk production by lactating sows. Thus, an adequate amount of dietary Glu as a quantitatively major nutrient is necessary to support maximum growth, development, and production performance of swine. These results also have important implications for improving the nutrition and health of humans and other animals.

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

“…Emerging findings have revealed the importance of NEAAs, such as glycine, proline, glutamate, glutamine and 4-hydroxyproline, in improving intestinal health and whole-body growth in animals (Fan et al 2019;Le Floch et al 2018;Li and Wu 2018;Wu et al 2019). We have shown that glycine, proline and glutamate are the first, second, and third most abundant AAs in animal tissues, respectively (Wu 2013), supporting the notion that mammals, birds and other vertebrates have particularly high requirements for these nutrients (Hou and Wu 2018b;Liu et al 2019;Meléndez-Hevia et al 2009;Wu et al 2014). Despite the immunological, nutritional and physiological importance of tryptophan, the content of this AA in feedstuffs was often not analyzed due to technical difficulties (e.g., Bryan 2018;Dozier et al 2003;Jamdar and Harikumar 2008;Ravindran et al 2005;Renna et al 2017;Shumo et al 2019).…”

The Roles of Dietary Glutamate in the Intestine

“…Glu is the most important fuel for intestinal tissue, it is involved in gut protein metabolism and is the precursor of different important molecules produced within the intestinal mucosa (2-oxoglutarate, L-alanine, ornithine, arginine, proline, glutathione, GABA) [22]. In the intestine, Glu is taken up from the lumen or is produced in the epithelium from glutamine through glutaminase activity.…”

Leucine alone or in combination with glutamic acid, but not with arginine, increases biceps femoris muscle and alters muscle AA transport and concentrations in fattening pigs

“…Supplementing 0.55% Leu to a low protein (CP = 16.9%) increases longissimus muscle protein synthesis in weanling pigs by inducing ribosomal protein S6 kinase 1 (S6K1) and eIF4E‐binding protein‐1 (4E‐BP1) activation (Yin, Kang, & Liu, ), indicating dietary supplementation with Leu is benefit for muscle development of pigs. Apart from Leu, the AAs arginine (Arg) and glutamic acid (Glu) also possess multiple functions in muscle growth of pigs (Wu et al, ; Hou & Wu, ). Previous studies showed dietary supplementation with 1% Arg improves carcass lean percentage (Tan et al, ) and increases mammalian target of the rapamycin (mTOR) activity in muscle of neonatal pigs (Yao et al, ).…”