Effects of supplementation with free glutamine and the dipeptide alanyl-glutamine on parameters of muscle damage and inflammation in rats submitted to prolonged exercise

In this study, we investigated the effect of the supplementation with the dipeptide L-alanyl-L-glutamine (DIP) and a solution containing L-glutamine and L-alanine on plasma levels markers of muscle damage and levels of pro-inflammatory cytokines and glutamine metabolism in rats submitted to prolonged exercise. Rats were submitted to sessions of swim training for 6 weeks. Twenty-one days prior to euthanasia, the animals were supplemented with DIP (n=8) (1.5 g.kg^-1), a solution of free L-glutamine (1 g.kg ^-1) and free L-alanine (0.61 g.kg^-1) (G&A, n=8) or water (control (CON), n=8). Animals were killed at rest before (R), after prolonged exercise (PE - 2 h of exercise). Plasma concentrations of glutamine, glutamate, tumour necrosis factor-α (TNF-α), prostaglandin E2 (PGE2) and activity of creatine kinase (CK), lactate dehydrogenase (LDH) and muscle concentrations of glutamine and glutamate were measured. The concentrations of plasma TNF-α, PGE2 and the activity of CK were lower in the G&A-R and DIP-R groups, compared to the CON-R. Glutamine in plasma ( p<0.04) and soleus muscle (p<0.001) was higher in the DIP-R and G&A-R groups relative to the CON-R group. G&A-PE and DIP-PE groups exhibited lower concentrations of plasma PGE2 ( p<0.05) and TNF-α (p<0.05), and higher concentrations of glutamine and glutamate in soleus (p<0.001) and gastrocnemius muscles ( p<0.05) relative to the CON-PE group. We concluded that supplementation with free L-glutamine and the dipeptide LL-alanyl-LL-glutamine represents an effective source of glutamine, which may attenuate inflammation biomarkers after periods of training and plasma levels of CK and the inflammatory response induced by prolonged exercise.