Glutamine and intestinal barrier function

Abstract

The intestinal barrier integrity is essential for the absorption of nutrients and health in humans and animals. Dysfunction of the mucosal barrier is associated with increased gut permeability and development of multiple gastrointestinal diseases. Recent studies highlighted a critical role for glutamine, which had been traditionally considered as a nutritionally non-essential amino acid, in activating the mammalian target of rapamycin cell signaling in enterocytes. In addition, glutamine has been reported to enhance intestinal and whole-body growth, to promote enterocyte proliferation and survival, and to regulate intestinal barrier function in injury, infection, weaning stress, and other catabolic conditions. Mechanistically, these effects were mediated by maintaining the intracellular redox status and regulating expression of genes associated with various signaling pathways. Furthermore, glutamine stimulates growth of the small intestinal mucosa in young animals and also enhances ion transport by the gut in neonates and adults. Growing evidence supports the notion that glutamine is a nutritionally essential amino acid for neonates and a conditionally essential amino acid for adults. Thus, as a functional amino acid with multiple key physiological roles, glutamine holds great promise in protecting the gut from atrophy and injury under various stress conditions in mammals and other animals.

Immune response in Eimeria sp. and E. coli challenged broilers supplemented with amino acids

“…Potential regulatory activities of functional amino acids must be included in determining the nutritional requirements of broilers (Wang et al 2015). However, the optimal levels that facilitate the expression of these activities are still not clear.…”

“…Glutamine (Gln) is considered an essential amino acid in certain species under inflammatory conditions (Newsholme 2001, Wang et al 2015. The role of this amino acid is well recognised as the main fuel for the intestinal mucosa and immune cells (Calder 1995, Wu andMorris 1998).…”

Oxygen metabolism and barrier regulation in the intestinal mucosa

“…As alluded to above, ATP and its associated creatine/phosphocreatine buffering system are metabolites of paramount importance, as exemplified by HIF transactivation of creatine transport and creatine kinase enzymes (37). Glutamine is also a fundamental component of mucosal cell metabolism and promotes barrier maintenance by transcriptional regulation of proteins involved in cell proliferation, differentiation, apoptosis, autophagy, protein turnover, antioxidant activity, and immunity (61). Other metabolites have demonstrated roles in barrier restoration and maintenance (62), including arginine and tyrosine through focal adhesion kinase-dependent signaling mechanisms (63)(64)(65), polyamines biosynthesized from ornithine (66,67), n-3 and n-6 fatty acids (68,69), vitamin D (70,71), and zinc (72).…”

Probiotics as regulators of inflammation: A review

“…A number of different natural health products will help repair a hyperpermeable epithelial barrier, including glutamine [8], quercetin, zinc [9] (e.g., zinc carnosine [10]) and different herbal medicines, but undoubtedly the most studied product is probiotics.…”