Arginine-enriched diet limits plasma and muscle glutamine depletion in head-injured rats

Abstract 

Objective

Injury is associated with a depletion in glutamine (GLN) pools, which may contribute to impairment of immune and nutritional statuses. Total parenteral nutrition enriched with arginine (ARG) is able to generate GLN in surgical patients. We hypothesized that this same concept may be applicable to enteral administration and could be extended to muscle GLN reserves. This study investigated the ability of an enteral formula enriched with ARG to restore the GLN pools in an experimental model of head injury.

Methods

Twenty-five male Sprague-Dawley rats were randomized into 4 groups: ad libitum access to food, head injury plus free access to nutrition, head injury plus standard enteral nutrition (Sondalis), and an immune-enhancing diet (IED). The two enteral diets were adjusted to be isocaloric (290 kcal·kg⁻¹·d⁻¹) and isonitrogenous (3.29 g·kg⁻¹·d⁻¹) and were delivered for 4 d (24 h/24 h). After sacrifice, plasma and muscle amino acids were determined.

Results

Head injury was associated with a large depletion of muscle and plasma GLN pools that were restored by IED administration but not by the standard diet. Moreover, the IED but not the standard diet improved or normalized ornithine and glutamate pools, suggesting that the modification of GLN pools is related to ARG administration.

Conclusion

In our model of head injury, our IED, a diet without free GLN, is efficient in restoring the plasma and muscle pools of GLN, probably due to its high ARG content.

Keywords: Immune enhancing diet, Trauma, Enteral nutrition, Ornithine, Glutamate

Abbreviations: AA, amino acid, AL, ad libitum, HI, head injury, GLN, glutamine, ARG, arginine, IED, immune enhancing diet, HIS, head-injury receiving Sondalis, HIC, head-injury receiving the IED, EDL, extensor digitorum longus