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Glutamine and the immune system
1Institute of Human Nutrition, University of Southampton, United Kingdom. pcc@soton.ac.uk
Insights
Glutamine is crucial for immune cell function and is depleted during illness and stress. Supplementing glutamine helps maintain immune function and may reduce infection risk in vulnerable patients.
Area of Science:
- Immunology
- Nutrition Science
- Cell Biology
Background:
- Glutamine is essential for immune cell proliferation, cytokine production, and macrophage phagocytosis.
- Immune function is impaired when glutamine levels decrease due to physiological stress like sepsis, injury, or overtraining.
Purpose of the Study:
- To investigate the role of glutamine in immune function and its potential therapeutic benefits.
- To explore the impact of glutamine supplementation on immune recovery and patient outcomes.
Main Methods:
- In vitro studies assessing lymphocyte and macrophage functions with glutamine and dipeptides.
- Analysis of plasma glutamine levels in various clinical conditions.
- Review of clinical data on glutamine supplementation in patients undergoing surgery, radiation, or bone marrow transplantation.
Main Results:
- Glutamine supports optimal immune cell function in vitro.
- Physiological stress significantly lowers plasma glutamine levels, potentially contributing to immunosuppression.
- Dietary glutamine enhances survival in animal models.
- Parenteral glutamine administration in patients improved outcomes, reducing infections and hospital stays, particularly after bone marrow transplantation.
Conclusions:
- Maintaining glutamine levels is vital for supporting immune function during critical illness and recovery.
- Glutamine supplementation offers a therapeutic strategy to mitigate immunosuppression and improve patient outcomes in high-risk populations.
Abstract:
Glutamine is utilised at a high rate by cells of the immune system in culture and is required to support optimal lymphocyte proliferation and production of cytokines by lymphocytes and macrophages. Macrophage-mediated phagocytosis is influenced by glutamine availability. Hydrolysable glutamine dipeptides can substitute for glutamine to support in vitro lymphocyte and macrophage functions. In man plasma and skeletal muscle glutamine levels are lowered by sepsis, injury, burns, surgery and endurance exercise and in the overtrained athlete. The lowered plasma glutamine concentrations are most likely the result of demand for glutamine (by the liver, kidney, gut and immune system) exceeding the supply (from the diet and from muscle). It has been suggested that the lowered plasma glutamine concentration contributes, at least in part, to the immunosuppression which accompanies such situations. Animal studies have shown that inclusion of glutamine in the diet increases survival to a bacterial challenge. Glutamine or its precursors has been provided, usually by the parenteral route, to patients following surgery, radiation treatment or bone marrow transplantation or suffering from injury. In most cases the intention was not to stimulate the immune system but rather to maintain nitrogen balance, muscle mass and/or gut integrity. Nevertheless, the maintenance of plasma glutamine concentrations in such a group of patients very much at risk of immunosuppression has the added benefit of maintaining immune function. Indeed, the provision of glutamine to patients following bone marrow transplantation resulted in a lower level of infection and a shorter stay in hospital than for patients receiving glutamine-free parenteral nutrition.