Adequate insulin production and protection of beta islet cells in the pancreas are both recognised to be important in the prevention of T2D.
Monomeric cocoa catechins were found to stimulate insulin production in the pancreatic beta cells of rats. Additionally, these compounds, also known as flavanols, helped protect against death of these cells when exposed to high doses of fat, discovered the team led by researchers from Brigham Young University (BYU), Utah.
The catechins exerted their effect by increasing mitochondrial respiration in the cells, which in turn raises the production of adenosine triphosphate (ATP) – the molecule that transports energy within the cells.
"What happens is it's protecting the cells, it's increasing their ability to deal with oxidative stress," explained lead researcher, Professor Jeffery Tessem from BYU. "The epicatechin monomers are making the mitochondria in the beta cells stronger, which produces more ATP (a cell's energy source), which then results in more insulin being released."
The findings may have applications in the fight against the growing epidemic of T2D.
"These results will help us get closer to using these compounds more effectively in foods or supplements to maintain normal blood glucose control and potentially even delay or prevent the onset of type-2 diabetes," said study co-author Professor Andrew Neilson, from Virginia Tech.
Small molecule effect
The researchers found that only the smaller molecules in cocoa extract – ‘monomeric’ catechins had the effect of increasing insulin production. The larger ‘oligomeric’ and ‘polymeric’ procyanidins and the whole cocoa extract actually slightly decreased insulin production.
Previous research has shown that the catechin monomer fraction of cocoa extract has the highest bioavailability when taken orally. Combined with the findings from this study that the monomeric flavanols are the most bioactive compounds, “suggests great potential for translation from in vitro cell culture to in vivo efficacy in animals and humans,” wrote the researchers.
Although the larger molecules’ (the oligomeric and polymeric procyanidins) influence on beta cell function is neutral or slightly negative, some animal studies have suggested these fractions of the cocoa extract may be metabolised by gut bacteria to bioavailable compounds.
Further studies are ongoing to investigate the impact of these larger cocoa flavanols in vivo.
Unfortunately, the beneficial effect on insulin production is likely to be obtained only from cocoa extract and not from eating chocolate bars, caution the researchers.
"You probably have to eat a lot of cocoa, and you probably don't want it to have a lot of sugar in it," said Tessem. "It's the compound in cocoa you're after."
As such, the next step will be to look at ways of extracting the monomeric catechins from cocoa, enhancing the quantity produced and then investigate its potential use as a treatment for diabetes patients, suggested the researchers.
Source: Journal of Nutritional Biochemistry
Volume 49, Pages 30-41, doi: 10.1016/j.jnutbio.2017.07.015
“Monomeric cocoa catechins enhance β-cell function by increasing mitochondrial respiration”
Authors: Thomas J. Rowley IV, Andrew P Neilson, Jeffery S Tessem et al.