A Cocoa Peptide Protects Caenorhabditis elegans from Oxidative Stress and β-Amyloid Peptide Toxicity

Patricia Martorell,Salvador Genovés,Daniel Ramón,Beatriz Álvarez,Fernando Montón,Esther Bataller,Núria Gonzalez,Silvia Llopis,Pepa Ortiz,Prasun Datta

doi:10.1371/journal.pone.0063283

Abstract

BackgroundCocoa and cocoa-based products contain different compounds with beneficial properties for human health. Polyphenols are the most frequently studied, and display antioxidant properties. Moreover, protein content is a very interesting source of antioxidant bioactive peptides, which can be used therapeutically for the prevention of age-related diseases.Methodology/Principal FindingsA bioactive peptide, 13L (DNYDNSAGKWWVT), was obtained from a hydrolyzed cocoa by-product by chromatography. The in vitro inhibition of prolyl endopeptidase (PEP) was used as screening method to select the suitable fraction for peptide identification. Functional analysis of 13L peptide was achieved using the transgenic Caenorhabditis elegans strain CL4176 expressing the human Aβ1–42 peptide as a pre-clinical in vivo model for Alzheimer's disease. Among the peptides isolated, peptide 13L (1 µg/mL) showed the highest antioxidant activity (P≤0.001) in the wild-type strain (N2). Furthermore, 13L produced a significant delay in body paralysis in strain CL4176, especially in the 24–47 h period after Aβ1–42 peptide induction (P≤0.0001). This observation is in accordance with the reduction of Aβ deposits in CL4176 by western blot. Finally, transcriptomic analysis in wild-type nematodes treated with 13L revealed modulation of the proteosomal and synaptic functions as the main metabolic targets of the peptide.Conclusions/SignificanceThese findings suggest that the cocoa 13L peptide has antioxidant activity and may reduce Aβ deposition in a C. elegans model of Alzheimer's disease; and therefore has a putative therapeutic potential for prevention of age-related diseases. Further studies in murine models and humans will be essential to analyze the effectiveness of the 13L peptide in higher animals.

Highlights

Cocoa is the unprocessed bean from the plant Theobroma cacao
The present study has shown how a cocoa by-product, ‘‘Barquillo’’, exhibits antioxidant properties and the ability to reduce paralysis resulting from Ab1–42 peptide expression in a transgenic C. elegans strain
All the identified peptides in these fractions belonged to the 21 kDa seed protein from Theobroma cacao and, surprisingly, many of them were located in a region encoding trypsin inhibitor activity

Summary

Introduction

Cocoa is the unprocessed bean from the plant Theobroma cacao It originated in the rain forests of the Americas and was introduced to Europe in the 16th century. Numerous studies have shown that cocoa and cocoabased products contain many different substances with beneficial effects on human health [3], [4]. Cocoa polyphenols (mainly catechin, epicatechin and procyanidins) are the major antioxidant source in the cocoa bean as they are present in high concentrations. The literature [7] has described that compounds present in cocoa powder and chocolate exert several beneficial effects on the brain, improving cognition in animals and humans. The health-promoting properties of cocoa powder have mainly been attributed to their polyphenolic compounds. Cocoa and cocoa-based products contain different compounds with beneficial properties for human health. Protein content is a very interesting source of antioxidant bioactive peptides, which can be used therapeutically for the prevention of age-related diseases

Methods

Results

Conclusion