Cocoa confers life span extension in Drosophila melanogaster

Abstract

Cocoa is thought to be an excellent source of antioxidants. Here, we investigated the effects of cocoa supplementation on Drosophila melanogaster life span under different oxidative stress conditions. Our results illustrate that a moderate supplementation of cocoa under normoxia increases the average life span, whereas, at higher concentrations, average life span is normal. Under hyperoxia or in a Cu/Zn-superoxide dismutase–deficient background, cocoa exhibited a strong antioxidant activity, significantly increasing the average life span. Nevertheless, cocoa supplementation in a Mn-superoxide dismutase–deficient background enhanced an earlier mortality accompanied by a loss of climbing ability, indicating that cocoa may act as a pro-oxidant in mitochondria under conditions of extreme oxidative stress. Finally, we illustrate that cocoa also acts as a metal chelator in the presence of excess heavy metals, enhancing larval survival to the adult stage on copper or iron-supplemented medium. Taken together, our results document the antioxidative, pro-oxidative, and metal-chelating effects of cocoa on Drosophila melanogaster life span.

Introduction

Reactive oxygen species (ROS) are inevitable byproducts of aerobic respiration and are known to cause modifications to DNA bases, enhance lipid peroxidation, and result in loss of protein enzymatic activity [1], [2], [3]. Under the barrage of ROS, oxidative damage builds up over time and eventually causes a gradual loss of normal physiologic function, a process known as senescence [4]. Because of the severe consequences associated with oxidative damage, aerobic organisms have developed a diversity of antioxidant defense mechanisms. Nevertheless, even under normal physiologic conditions, ROS production transcends endogenous defenses over time and inflicts damage [5].

Diet-derived antioxidants play a major role in maintaining ROS homeostasis, with the combination of dietary antioxidants and endogenous defense enzymes resulting in a highly effective defense network against oxidative stress [6]. Cocoa and its products such as dark chocolate are known to be excellent sources of polyphenol and flavonoid antioxidants that may significantly contribute to the total antioxidant capacity of diet [7], [8], [9]. Other in vivo studies revealed that cocoa consumption increases the antioxidant capacity of serum and prevents lipid peroxidation and low-density lipoprotein oxidation [10], [11], [12]. Nevertheless, despite cocoa's antioxidative role in defense against ROS being well established, its contributions to longevity and aging have not been thoroughly investigated. The objectives of this study were to investigate the oxidative properties of cocoa and their effects on life span in Drosophila melanogaster. We hypothesize that cocoa supplementation has the potential to extend D melanogaster life span, particularly in the presence of stress-related oxidative damage. The relatively short life span of this model organism, the ability to control genetic background and experimental conditions, and, finally, the availability of different antioxidant-deficient transgenic lines should facilitate a further understanding of antioxidant contributions of dietary cocoa in defense against ROS and aging. Considering that the fruit fly has been used as a model for studies on human nutrition, the results of this study should provide useful insights into the potential roles of dietary cocoa in human longevity.