Effects of Maillard reaction products from glucose-lysine model systems on oxidative stress markers and against oxidative induction by hydrogen peroxide in Caco-2 cells

The ability of Mail lard reaction products (MRP) from glucose-lysine (GL) model systems to counteract oxidative stress induced by H2O2 was studied in Caco-2 cells, evaluating the effect of heating time. GL mixtures were heated at 100 degrees C for 15, 60 or 90 min and partly characterized by measuring pH, free lysine and UV-visible spectra. The well-known antioxidant properties of MRP generated were shown in vitro and also ex-vivo, by incubating the Caco-2 cells for 3 h with the isolate samples (1 mg.m(-1)). Afterwards, the effects of the combined presence of samples and H2O2 (0.5 mmol.l(-1)) were tested. Changes in cell viability, lipid peroxidation and antioxidant enzymes activity (catalase, superoxide dismutase, glutathione peroxidase) were evaluated. The GL samples did not exert cytotoxic effects, and also significant reductions of the lipid peroxide levels were observed, with a positive influence of heating time. Significant inverse correlations were observed between cellular lipid peroxidation and antioxidant enzyme activities. Incubation of cells with GL mixtures together with H2O2 also lowered lipid peroxides and maintained antioxidant enzyme activity levels, although cell damage evoked by H2O2 was only partially restored. The ability of MRP to reduce the lipid peroxidation is for the first time shown to be related with their capability to activate the antioxidant enzyme activity.