Bioactive peptides from milk permeate: evaluation of their antioxidant activity in cellular models

This study aims to contribute to environmental sustainability by addressing the issue of waste generated by food companies. The goal is to enhance the value of such waste by exploring solutions that benefit both human health and the environment. In particular, this study focuses on investigating the antioxidant activity of bioactive peptides extracted from milk permeate, a by-product of yogurt production that is recovered and valorized instead of being discarded. Bioactive peptides are short amino acid sequences with beneficial properties for human health and well-being. They can occur naturally in foods, be produced through protein hydrolysis, during digestion or fermentation processes, or be synthesized. The first phase of this research involved the extraction and identification of peptides from milk permeate. Subsequently, selected peptides were synthesized in order to evaluate their potential antioxidant activity. This activity was investigated on two colorectal cell lines (Caco-2 and HCT116) and one hepatocellular cell line (HepG2), using tert-butyl hydroperoxide and acetaminophen as oxidative stress inducers. Some of the selected peptides demonstrated high antioxidant capacity at specific concentrations, effectively protecting the viability of cells from oxidative stress. The mechanism through which the peptides induced this antioxidant activity was investigated and we found that they are able to effectively stimulate the activity of the transcription factor Nrf2 leading to an increased expression of antioxidant proteins without influencing the glutathione levels. In conclusion, the results obtained indicate that these peptides have promising potential in combating oxidative stress and could be useful for example in case of inflammatory diseases of the gastrointestinal tract or in improving human health through specific applications in the nutraceutical field.