Glutamine

The most abundant amino acid in blood. An important energy source for the cells of the small intestine and for immune cells; significant for the gut barrier and the nitrogen metabolism of the liver.

What glutamine does in the body

Glutamine is made mainly in the muscles: the enzyme glutamine synthetase attaches ammonia to glutamate, using energy in the process. In this way toxic ammonia is bound and distributed via the blood as glutamine. The cells of the small intestinal lining and immune cells such as lymphocytes and macrophages use glutamine as a source of energy and as a nitrogen supplier for the building blocks of genetic material – they divide quickly and need both in large amounts. The kidneys split glutamine back into glutamate and ammonia; with the ammonia they excrete acid and so maintain the acid-base balance. Glutamine is also a precursor of glutamate, GABA and glutathione. In the brain it shuttles between support cells and nerve cells and helps to recycle the messenger glutamate.

Low glutamine – what happens in the body?

When consumption exceeds production, glutamine in the blood falls. The muscles then break down more protein to supply glutamine. The small intestinal cells renew themselves more slowly, and in studies the connections between them (tight junctions) became less tight when glutamine was lacking; immune cells multiply less well and less glutathione is produced. Low values occur under severe strain on the body – after surgery, injuries, burns and with severe infections –, with malnutrition, and in studies they have been measured after very long, intense endurance exercise. In such phases glutamine is considered conditionally essential, because the body cannot make enough itself.

High glutamine – what happens in the body?

High values often show that the body has to capture a lot of ammonia. If the liver cannot process ammonia into urea sufficiently – with impaired liver function or in inherited disorders of the urea cycle –, the muscles and brain bind more of it as glutamine. In the brain this happens in the support cells (astrocytes); if a lot of glutamine accumulates there, the cells draw in water and swell, which impairs concentration and alertness. This process has been described in hepatic encephalopathy. Temporarily higher values occur after protein-rich meals.

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