Glutamine is a non-essential amino acid, also called Levoglutamide. Glutamine can release ammonia in its side chain to form urea (for excretion by the kidneys) and purines (essential for nucleic acid synthesis). Glutamine is a substrate for producing both the excitatory and inhibitory neurotransmitters, namely glutamate and GABA(gamma-Aminobutyric acid). Glutamine is an essential amino acid during the catabolic states of metabolism. L-glutamine is used as a dietary supplement, also to treat deficiency imbalances and symptoms. Glutamine metabolises to form glutamate, nucleotides, amino acids, proteins and sugars.
There are two forms of L-glutamine called exogenous and endogenous glutamate. It has a significant role in the growth, function and regeneration of gastrointestinal cells. The glutamine concentration is generally sustained from dietary intake and synthesised from endogenous glutamate. The glutamine role for nutritional requirement during trauma, infection, catabolic illness is different from a healthy individual, as the glutamine concentration decreases and the concentration of Glutamine in tissues increases during the catabolic disease states, regarding it as a ‘conditionally essential amino acid’. Glutamine is used by rapidly dividing cells like lymphocytes, erythrocytes, and fibroblasts.
L-Glutamine and Cancer
L-Glutamine is used as a radioprotective drug, as the data from a clinical study showed that the pelvic radiation for treating prostate cancer leading to notable acute and post-acute changes in the structure and composition of the vesical lamina propria and epithelium were prevented by the use of Glutamine as a nutritional supplement.
In clinical Glutamine served to reduce the radiation-induced severe diarrhoea as it is observed that the placebo group that is not treated with Glutamine has grade 3-4 diarrhoea, whereas the experimental group with oral Glutamine (15 g) was administered three times daily did not have grade 3-4 diahrea, unlike the placebo group.
Another study showed that oral or topical Glutamine has visibly reduced painful ulceration and mucosal symptoms affiliated with chemotherapy and radiation in the head and neck region, oesophagus, stomach and small intestine for cancer patients.
Animal and human studies showed that intake of Glutamine supplement benefits the cancer patient helping in recovery as glutamine depletion occurs because the tumour behaves as a “glutamine trap” and the cytokine-mediation changes in the glutamine metabolism pathway in the tissues.
The cancer cells are always in high demand for Glutamine; thus, glutamine metabolism is profoundly regulated to maintain the cell proliferation and cellular biosynthesis for the growth of the tumour. Thus the machinery that governs the glutamine metabolism pathway like SLC1A5/ASCT2 that is controlled by c-myc or E2F is highly expressed in triple-negative breast cancer patients.
Animal and Human in-vivo Xenografted solid tumour studies showed that the use of Glutamine, avicin(inhibited ribonucleotide biosynthesis) and DON(glutamine analogue) had shown cytotoxic activity, supporting the treatment of myeloid leukaemia if glucose with the combination mentioned above is used.
Other therapeutic uses of Glutamine
A study showed that Glutamine could maintain intestinal tissue integrity by regulating erythrocyte proliferation and maintaining tight-junction protein, acts as an anti-inflammatory agent by interfering with NF-κB and STAT signalling pathways, protecting against cellular stress and apoptosis.
Glutamine is an immune nutrient, as the study shows that Glutamine reduced the inflammation, rate of infection, hospital stay and mortality, and improved immune function, specifically the cell-mediated immunity and developed gut barrier function.
In 2017, FDA()Food and Drug Administration) has approved L-Glutamine as medication for sickle cell anaemia.
Glutamine is a part of TPN(Total Parenteral Nutrition); a study observation told that the patients in need of TPN trauma, malignancies showed beneficial recovery. They are administered <0.35 g/kg/day intravenously or <0.5 g/kg/day enterally. The data also showed that Glutamine had improved the outcomes in burn-injury patients reducing mortality and hospital stay without any signs of clinical risk.
Risk factors and side effects
Long term usage of Glutamine in high dosage(~40 g/d) adverse effects are observed on biochemical pathways and cellular functions like impaired distribution of amino acids in the tissue and their absorption in gut and kidneys, alteration of endogenous synthesis of Glutamine increasing ammonia and glutamate production, manifesting immunomodulating properties.
Side effects include nausea, vomiting, joint pains.
Cancer patients are advised to avoid glutamine intake without talking to the medical professional.
People suffering from kidney diseases and liver and brain swelling are advised to avoid glutamine supplementation.