Oral administration of a glutamine-enriched diet before or after endotoxinchallenge in aged rats has limited effects

Numerous studies indicate beneficial effects of glutamine (Gln) in many mod els of catabolic adult rats. No data were available for aged rats. The effe cts of oral L-Gln-enriched diet were tested in endotoxemic 24-mo old rats. First, rats received for 7 d (from d0 to d7) an oral diet supplemented with either L-Gln [1g/(kg.d)] or casein (Cas: isonitrogenous supply) prior to l ipopolysaccharide (LPS) challenge. The rats were then killed after 24 h foo d deprivation (from d7 to d8). Endotoxemia induced a catabolic response as shown by muscle glutamine depletion, hyperphenylalaninemia, small bowel atr ophy and impaired functionality and bacterial translocation. The Gln-enrich ed diet did not prevent muscle Gin depletion but significantly (P less than or equal to 0.05) enhanced plantaris protein content by 18% compared to th e Cas-LPS rats and reduced the plasma phenylalanine-to-tyrosine ratio (1.32 +/- 0.05 vs. 1.54 +/- 0.10, respectively, P less than or equal to 0.01). G ut translocation and histomorphology were unaffected by diet. However, Gin pretreatment reduced the fall in sucrase and glucoamylase activities in the ileum, respectively, by 55 and 63% vs. Cas supplementation (P less than or equal to 0.05). In a second study, after endotoxin challenge, healthy 24-m o-old rats were then food-deprived for 2 d (from d0 to d2), received a nonp urified diet for 4 d (from d2 to d6), and then Cas or L-Gln-supplemented di et for 7 d (from d6 to d13). No beneficial effects of Gin supplementation w ere observed except an increase of 50 and 56% in sucrase and glucoamylase a ctivities in the ileum of Gin-treated rats, (P less than or equal to 0.01 v s. healthy rats). In conclusion, the effects of L-Gln supplementation in ag ed endotoxemic rats were limited.