Antioxidant Effects of Tryptophan on Selected Tissues in Diabetic Wistar Rats

Diabetes mellitus is associated with increased oxidative stress. Hyperglycaemia induces free radical generation and alters the antioxidant system in the body. This study explored the potential antioxidant activities of orally administered L‐tryptophan (TRP) on the levels of glycaemia, malondialdehyde (MDA) and glutathione peroxidise (GPx) in non‐diabetic (ND) and type 2 diabetic (T2D) male Wistar rats. Diabetes was induced by intraperitoneal injection of 120mg/kg of 10% alloxan in normal saline. At 18:30 every day for 21 days, TRP (125mg/kg body weight) was administered orally. At 08:00 every two days the glycaemia was measured and every day the intake of food and water recorded. At the end of treatment, MDA and GPx were measured in the homogenised tissues of liver and the brain. Glycaemic values were greater (p<0.01) in TD2 rats than in ND rats at all times studied and this parameter was not altered by the TRP administration. In ND rats, there were significant (p<0.05) reduction in GPx of liver and brain tissues. The TRP administration did not modify the GPx activity in liver tissue in ND rats, but raised (p<0.05) the levels in the brain tissues. In ND rats, MDA concentration was increased, while TRP administration significantly (p<0.05) lowered the MDA concentration in the brain tissue, there was no significant changes in MDA concentration in the liver tissue. There was increased food intake (g/day) in the treated T2D group (p<0.01). In conclusion, the oral administration of TRP increased the activity of GPx and reduced MDA concentration in the brain tissue, increased food intake in T2D rats, however, TRP administration did not alter the glycaemia level, liver GPx activity and liver MDA concentration.