Métabolisme de la glutamine in vivo chez l'homme : implications pour la nutrition artificielle

[Metabolic problems and nutrition in burns]

Metabolic changes with burns patients are enormous. The loss of skin substance and the necessity of its reconstruction are at the origin of this exceptional situation. In this context of major aggression with important metabolic alteration the nutritional needs are considerable. To assure a tissue reconstruction, nutrition is as important as the fight against infection. The authors make the point on the quantity needs and the quality needs. They raise up the perspectives concerning immunonutriments and note the importance of enteral administration. As a conclusion, they insist on the fundamental role of the clinical aspect, in the survey of nutritional state.

Amino acid metabolism during total parenteral nutrition in healthy volunteers: evaluation of a new amino acid solution

The aim of this study was to determine the metabolism and the tolerance of a new amino acid (AA) solution administered under conditions mimicking cyclical parenteral nutrition (PN) in humans. Eight healthy volunteers received peripheral PN for 10 h providing 10.5 mg N x kg(-1) x h(-1) and 2.0 kcal x kg(-1) x h(-1) (glucose-to-lipids ratio: 70/30%). For adaptation, a non-protein energy intake was increased progressively for 90 min; thereafter, AA infusion was started and maintained at a constant rate for 10 h. Plasma and urine concentrations of all the AAs were measured before, during and after the PN. For each given AA, the relation between plasma variations at the steady-state and infusion rate, plasma clearance (Cl), renal clearance (Clr), re-absorption rate (Reab) and, retention rate (Reten) were determined. The nitrogen balance (DeltaN) was calculated during the PN period. The results are presented as means+/-sem. All plasma AA concentrations decreased during the starting period of non-protein energy intake. The plasma AA concentrations reached a steady-state within 3 h upon AA infusion, except for glycine and lysine (6 h). At the steady state, the plasma concentrations of the infused AAs were closely correlated to their infusion rate (y= -18.3+1.5x, r(2)=0.92). The plasma glutamine concentration was maintained during the PN, which indicates that the solution might stimulate the de novo synthesis of this AA. When the PN was stopped, plasma levels of the AAs decreased, most of them returning to their basal levels, or significantly below for lysine (P<0.05), alanine (P<0.05), proline (P<0.01) and glutamine (P<0.05). No volunteer showed any adverse effect during the infusion period. DeltaN was: 0.8+/-0.5 gN/10 h. Metabolic characteristics for essential AAs were: Cl<0.5 l min(-1), Clr <1.5 ml x min(-1) Reab >or= 99%, Reten >or=99% and for non-essential AAs: Cl <0.6 l x min(-1) except aspartate (2.8+/-0.3 l x min(-1)), Clr < 3 ml x min(-1) except glycine (6.8+/-0.7), aspartate (8.2+/-3.5) and histidine (8.8+/-1.3); Reab >or= 98% except glycine (95+/-1), aspartate (94+/-2) and histidine (94+/-1), Reten >or=97% except histidine (94+/-1), glycine (95+/-3). These results indicate that in healthy subjects, the amounts of AAs provided by the new solution were well balanced for an intravenous administration, and so were well utilized without excessive urinary excretion. The present study provides useful metabolic parameters for a further evaluation in disease.

[Protein requirements in children during states of stress. Committee on Nutrition of the French Society of Pediatrics]

Acute and chronic stress conditions affecting critically ill children are characterized by severe protein breakdown and growth failure. This paper describes the disorders of protein metabolism, and gives recommendations for protein and energy intakes during stress conditions in children.

Can a glutamate-enriched diet counteract glutamine depletion in endotoxemic rats?

The study evaluated whether a glutamate-enriched diet would restore glutamine tissue pools and maintain tissue trophicity in endotoxemic rats. For this purpose, young male Sprague-Dawley rats received an intraperitoneal injection of lipopolysaccharide (LPS) from Escherichia coli at 3 mg/kg body weight. After 24 hours of food deprivation, the rats were enterally refed for 48 hours using Osmolite enriched with glutamate at 4 g/kg/d (LPS-Glu group, n = 7) or glycine isonitrogenous to glutamate (LPS-Gly group, n = 7). A control group (healthy group, n = 7) had free access to a standard rodent diet. Tissue weights and protein contents were significantly lower in both LPS-treated groups than in the healthy group. No plasma or tissue accumulation of glutamate was observed except in the liver. Glutamine concentrations were increased in the jejunum, liver, and plasma in the LPS-Glu group versus the other two groups (P < 0.05). Conversely, they were depleted in muscles of the endotoxemic groups versus the healthy group (P < 0.05). Villus height was significantly greater in the LPS-Glu group than in the LPS-Gly group in the jejunum (P < 0.05), but not in the ileum. In conclusion, a glutamate-enriched diet administered enterally to endotoxemic rats can counteract glutamine depletion in the splanchnic area but not in muscles. In addition, glutamate displayed a trophic effect restricted to the jejunum.

[Malnutrition and immunodeficiency in children]

Our knowledge on relationships between nutrition, immunity and infection has much progressed. Malnutrition affects all three defence mechanisms: unspecific immunity, cellular immunity and humoral immunity. Any kind of nutriment is concerned: nitrogen-caloric nutriments, trace elements, vitamins. Restoration and maintenance of a good nutritional status have become imperative in order to stop the vicious cercle of malnutrition-infection in infants and children.

[Caloric and nitrogen intake during pre- and post-operative periods. method and duration]

Preoperative nutritional support is analysed from 7 prospective studies. Clinical benefits from nutrient intake and duration are not demonstrable. In one study, preoperative long-chain triglycerides infusions are associated with more postoperative complications. Postoperative nutrition is analysed from 20 articles. No one considers the clinical benefit with regard to quantitative and qualitative intakes.