Metabolic effects of enteral versus parenteral alanyl-glutamine dipeptide administration in critically ill patients receiving enteral feeding:: A pilot study

Background: Glutamine (Gln) may become conditionally indispensable during critical illness. The short-term metabolic effects of enteral versus parenteral Gln supplementation are unknown in this clinical setting. Objectives: We studied metabolic effects of intravenous (IV) alanyl-Gln dipeptide (AG) supplementation and enteral (EN) AG supplementation on plasma Gln concentration, antioxidant status, plasma lymphocyte subset number, gut permeability and nitrogen balance in adult critically ill patients requiring tube feeding compared to a control group not receiving Gln supplementation. Methods: In a double-blind, pilot clinical trial, 44 medical and surgical ICU patients received identical Gln-free tube feedings 24 h/day and were randomized to either isonitrogenous control (n = 15), EN AG in = 15) or IV AG (n = 14) groups (AG). Twelve patients were discontinued from the study. The goat AG dose was 0.5 g/kg/day. Biochemical and metabolic end-points were measured at baseline and on day 9 (plasma Gin, antioxidant indices, Lymphocyte subsets; serum IGF-1 and IGF-binding protein-3; intestinal permeability). Nitrogen balance was determined between study days 6 and 8. Results: Illness severity indices, clinical demographics, enteral energy and nitrogen intake and major biochemical indices were similar between groups during study. Plasma Gin was higher in the IV AG (565 +/- 119 mu M, mean +/- SEM) vs the EN AG (411 +/- 27 mu M) group by day 9 (p = 0.039); however, subjects in the IV AG group received a higher dose of AG (IV AG 0.50 versus EN AG 0.32 +/- 0.02 g/kg/day; p < 0.001). EN AG subjects showed a significant increase in plasma a-tocopherol Levels over time and maintained plasma gamma-tocopherol concentrations. There were no differences between groups for plasma concentrations of vitamin C. glutathione, malondialdehyde (MDA), T-lymphocyte subsets, intestinal permeability or nitrogen balance. Conclusions: This study showed that alanyl-Gln administration by enteral or parenteral routes did not appear to affect antioxidant capacity or oxidative stress markers, T-Lymphocyte subset (CD-3, CD-4, CD-8) number, gut barrier function or whole-body protein metabolism compared to unsupplemented ICU patients requiring enteral tube feeding. Enteral. Gin appeared to maintain plasma tocopherol Levels in this pilot metabolic study. (c) 2007 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.