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Dear Colleagues,

Glutamine is a non-essential amino acid that is derived from glutamate via the action of the enzyme glutamine synthetase in most cells and is the most common amino acid found in the blood. However, it is essential that this amino acid is present in rapidly dividing cells such as cells of the immune system and tumor cells, as the ability of these cells to synthesize glutamine is limited, and it effectively becomes an essential amino acid.

Glutamine can donate its carbon and nitrogen to ensure nucleotide, amino acid, and other macromolecule biosyntheses occur in the cell. It can also be used as a source of cellular energy. Glutamine is a gluconeogenic substrate in the kidney and can act as a non-toxic carrier of ammonia in body fluids.

This Special Issue of the International Journal of Molecular Sciences, “Glutamine: The Essential Non-Essential Amino Acid”, will focus on the role glutamine plays in normal and transformed cells, be it catabolized to supply cellular energy or anabolized for the creation of key biomolecules in the cell. Of interest is the role that glutamine plays in the regulation of gene transcription and the changes that occur in the cell when they start to rely on this amino acid to supply many of their needs. The results from these studies will help us to better understand the central role that this amino acid plays in cell and organ metabolism, and how disrupting its role in tumor cell biology may give rise to new therapeutic agents.

Dr. Terrence Piva
Guest Editor

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Keywords

glutamine
amino acids
mitochondria and TCA cycle
enzymes
nucleotide synthesis
cell and body metabolism
gene regulation
cellular transport
immune cell function
cell proliferation
transformed cells
enzyme inhibition

Published Papers (2 papers)

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Research

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11 pages, 1310 KiB

Open AccessArticle

Effects of Glutamine, Curcumin and Fish Bioactive Peptides Alone or in Combination on Intestinal Permeability in a Chronic-Restraint Stress Model

by Ludovic D. Langlois, Sarah Oddoux, Kanhia Aublé, Paul Violette, Pierre Déchelotte, Antoine Noël and Moïse Coëffier

Int. J. Mol. Sci. 2023, 24(8), 7220; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms24087220 - 13 Apr 2023

Cited by 1 | Viewed by 1676

Abstract

Irritable bowel syndrome (IBS), a multifactorial intestinal disorder, is often associated with a disruption in intestinal permeability as well as an increased expression of pro-inflammatory markers. The aim of this study was to first test the impact of treatment with glutamine (Gln), a food supplement containing natural curcumin extracts and polyunsaturated n-3 fatty acids (Cur); bioactive peptides from a fish protein hydrolysate (Ga); and a probiotic mixture containing Bacillus coagulans, Lactobacillus acidophilus, Lactobacillus gasseri and Lactobacillus helveticus. These compounds were tested alone on a stress-based IBS model, the chronic-restraint stress model (CRS). The combination of Gln, Cur and Ga (GCG) was also tested. Eight-week-old C57Bl/6 male mice were exposed to restraint stress for two hours every day for four days and received different compounds every day one week before and during the CRS procedure. Plasma corticosterone levels were measured as a marker of stress, and colonic permeability was evaluated ex vivo in Ussing chambers. Changes in the gene expression of tight junction proteins (occludin, claudin-1 and ZO 1) and inflammatory cytokines (IL1β, TNFα, CXCL1 and IL10) were assessed using RT-qPCR. The CRS model led to an increase in plasma corticosterone and an increase in colonic permeability compared with unstressed animals. No change in plasma corticosterone concentrations was observed in response to CRS with the different treatments (Gln, Cur, Ga or GCG). Stressed animals treated with Gln, Cur and Ga alone and in combination showed a decrease in colonic permeability when compared to the CRS group, while the probiotic mixture resulted in an opposite response. The Ga treatment induced an increase in the expression of the anti-inflammatory cytokine IL-10, and the GCG treatment was able to decrease the expression of CXCL1, suggesting the synergistic effect of the combined mixture. In conclusion, this study demonstrated that a combined administration of glutamine, a food supplement containing curcumin and polyunsaturated n-3 fatty acids, and bioactive peptides from a fish hydrolysate was able to reduce colonic hyperpermeability and reduce the inflammatory marker CXCL1 in a stress-based model of IBS and could be of interest to patients suffering from IBS. Full article

(This article belongs to the Special Issue Glutamine: An Essential Non-essential Amino Acid 2.0)

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Review

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15 pages, 1598 KiB

Open AccessReview

The Role of Glutamine Homeostasis in Emotional and Cognitive Functions

by Ji Hyeong Baek, Hyeongchan Park, Hyeju Kang, Rankyung Kim, Jae Soon Kang and Hyun Joon Kim

Int. J. Mol. Sci. 2024, 25(2), 1302; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms25021302 - 21 Jan 2024

Viewed by 911

Abstract

Glutamine (Gln), a non-essential amino acid, is synthesized de novo by glutamine synthetase (GS) in various organs. In the brain, GS is exclusively expressed in astrocytes under normal physiological conditions, producing Gln that takes part in glutamatergic neurotransmission through the glutamate (Glu)–Gln cycle. Because the Glu–Gln cycle and glutamatergic neurotransmission play a pivotal role in normal brain activity, maintaining Gln homeostasis in the brain is crucial. Recent findings indicated that a neuronal Gln deficiency in the medial prefrontal cortex in rodents led to depressive behaviors and mild cognitive impairment along with lower glutamatergic neurotransmission. In addition, exogenous Gln supplementation has been tested for its ability to overcome neuronal Gln deficiency and reverse abnormal behaviors induced by chronic immobilization stress (CIS). Although evidence is accumulating as to how Gln supplementation contributes to normalizing glutamatergic neurotransmission and the Glu–Gln cycle, there are few reviews on this. In this review, we summarize recent evidence demonstrating that Gln supplementation ameliorates CIS-induced deleterious changes, including an imbalance of the Glu–Gln cycle, suggesting that Gln homeostasis is important for emotional and cognitive functions. This is the first review of detailed mechanistic studies on the effects of Gln supplementation on emotional and cognitive functions. Full article

(This article belongs to the Special Issue Glutamine: An Essential Non-essential Amino Acid 2.0)

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