12 January - 20 June 2016

Gene expression affected upon single dose of high-polyphenol cocoa powder

A group of scientists have published a study investigating the changes in gene expression upon intake of cocoa powder, a substance known to be rich in polyphenols. The team includes scientists from the National Institute of Genomic Medicine in Mexico City, along with groups at Nestlé research centres in Switzerland and New Zealand.

A group of scientists have published a study investigating the changes in gene expression upon intake of cocoa powder, a substance known to be rich in polyphenols. The team includes scientists from the National Institute of Genomic Medicine in Mexico City, along with groups at Nestlé research centres in Switzerland and New Zealand. The study, published in the European Journal of Nutrition, used a randomized trial to measure the effect of cocoa intake on gene expression in peripheral mononuclear cells.

Polyphenols have been shown to be involved in defence against UV radiation and pathogen aggression. They may have a mitigating effect on many risk factors involved in chronic diseases, such as high blood pressure, inflammation, insulin resistance, and others related to oxidative stress. This reduction has shown to be through a down-regulation of inflammatory mediators, and a reduced expression of biomarkers in endothelial dysfunction in ex vivo studies. The main drawback with these previous experiments has been the use of cocoa polyphenols in concentrations far exceeding normal dietary levels. Additionally, none of the previous human-based studies have investigated the underlying mechanisms involved.

In the current study, Barrera-Reyes et al. used a double-blinded, randomized crossover trial. 20 healthy subjects were given a single dose of either cocoa powder containing high levels of polyphenols, or a placebo of maltodextrins. The dose of cocoa powder contained higher levels of polyphenols than conventional cocoa, but the group claimed the amount was still achievable through diet. The pill contained around 1.3g of a commercially available cocoa powder extract, and the placebo pill around 1.3g of partially hydrolysed maltodextrin. 2 hours after ingestion, blood samples were taken under fasting conditions. No other food could be consumed in this time. Metabolites, measured as circulating (-)-epicatechin, which are said to modulate the antioxidant capacity of plasma, were monitored. There was then a one week “washout” period, followed by the group that had consumed the cocoa powder in the preceding week consuming the placebo, and vice versa. Blood samples were again taken as previously.

The scientists noted that the metabolite profiles in each of the participants varied, but that ultimately the levels of circulating (-)-epicatechin metabolites in the plasma were raised in those that had consumed the cocoa powder. Those participants also saw a change in the expression of a group of 98 genes, compared with only 18 in the placebo-taking group. These genes were focused on networks involved in decreased ROS production, and modulation of Ca2+ and inflammatory responses. The research group mentions that “these pathways have been associated with the biological effects of other polyphenols and may contribute to the known benefits of cocoa consumption”. They also note that a larger scale trial would benefit the research further, along with a stronger focus on the short and long-term effects on gene expression.

Barrera-Reyes et al. concluded that “this study confirmed that changes in gene expression may occur after a single dose of polyphenols within a short period of time”.

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