| Abstract: | Glutamine is synthetized in most tissue and accounts for two-thirds of the free amino acid pool in skeletal muscle. Glutamine is not only an interorgan nitrogen shuttle but a precursor of urinary ammonium, and a favorite fuel of the immune system and the gut (which uses ≠ 17 g of glutamine per day). Because they were designed at a time when glutamine was considered both unstable and non-essential, « tradtionalparenteral nutrition (PN) solutions are devoid of glutamine. Although « classicPN is able to maintain normal rates of glutamine turnover in healthy subjects or unstressed patients, classic PN solutions are unable to correct the precipitous depletion of glutamine pool that accompagnies catabolic illness. Glutamine becomes a « conditionally essentialamino acid in these situations. Replenishment of glutamine pool seems to stimulate protein synthesis, and improve nitrogen balance in catabolic patients. Supplementation of PN with glutamine-containing dipeptides or α-ketoglutarate (at doses of 15–50 g/d) is as effective as glutamine itself. The enteral route represents an attractive alternative for the supply of glutamine since : 1) glutamine is efficiently absorbed ; 2) nearly 50 % of enterally infused glutamine reaches systemic blood ; 3) glutamine residues present in a bound form in peptides seem to be bioavailable ; and 4) in addition to its protein anabolic effect, glutamine affects intestinal absorption and trophicity. |
