Peptides derived from eggshell membrane improve antioxidant enzyme activity and glutathione synthesis against oxidative damage in Caco-2 cells

Excess reactive oxygen species (ROS) cause oxidative stress that is associated with the development of oxidative damage and chronic inflammation. The objective of this study was to evaluate the bioactivity of eggshell membrane (ESM) peptides digested with Alcalase and Protease S (AL-PS) at the cellular level. Effects were tested for inhibition of lipid and protein oxidation, synthesis of glutathione (GSH), and cellular antioxidant enzyme activity in H2O2-stimulated Caco-2 cells. AL-PS and its ultrafiltered fraction AL-PS-I (MWCO <5 kDa) significantly suppressed the formation of H2O2-induced malondialdehyde (MDA) and protein carbonyl derivatives. AL-PS and AL-PS-I also increased glutathione peroxidase (GPx), glutathione S transferase (GST), and glutathione reductase (GR) activity. The peptides also elevated cellular GSH levels via up-regulation of gamma-glutamylcysteine synthetase (gamma-GCS) activity and its mRNA expression. This study confirms that ESM peptides are able to reduce intestinal oxidative stress and thus validates their use as a valuable source material of ESM waste. (C) 2014 Elsevier Ltd. All rights reserved.