Compounds in Cocoa Bean Shells May Reverse Obesity-Related Problems

Scientists may have discovered more reasons to love chocolate.

A new study by researchers at the University of Illinois suggests that three of the phenolic compounds found in cocoa bean shells have powerful effects on fat and immune cells in mice, potentially reversing the chronic inflammation and insulin resistance associated with obesity.

Food science professor Miguel Rebollo-Hernanz, assisted by Professor Elvira Gonzalez de Mejia, found that cocoa shells contained high concentrations of three useful bioactive chemicals also found in cocoa, green coffee and green tea: protocatechuic acid, epicatechin and procyanidin B2.

How was the study carried out?
Rebollo-Hernanz, the study's lead author, created a water-based extract containing these compounds and tested its effects on white fat cells called adipocytes and on immune cells called macrophages.

Using computer modelling and bioinformatics techniques, he also examined the impact of each of the phenolic compounds on the cells.

"The objectives of the study were to verify the effectiveness of the bioactive compounds in cocoa shells against macrophages, the inflammatory cells, in eliminating or reducing biomarkers of inflammation," says de Mejia, who is also director of nutritional sciences. "We wanted to see whether the phenolic compounds in the extract blocked or reduced the damage to the mitochondria of fat cells and prevented insulin resistance."

Similar to batteries in cells that burn fat and glucose to generate energy, mitochondria can be damaged when high levels of fat, glucose and inflammation occur in the body, de Mejia explains.

When the scientists treated adipocytes individually with the aqueous extract or the three phenolic compounds, the damaged mitochondria in the cells were repaired and less fat accumulated in the adipocytes, blocking inflammation and restoring the cells' insulin sensitivity, Rebollo-Hernanz explains.

When adipocytes accumulate too much fat, they promote the growth of macrophages. This starts a toxic cycle in which the adipocytes and macrophages interact, emitting toxins that inflame the fat tissue, de Mejia says.

Over time, this chronic inflammation reduces the cells' ability to absorb glucose, leading to insulin resistance and possibly type 2 diabetes, as blood glucose levels rise.

To recreate the inflammatory process that occurs in the body when macrophages and adipocytes begin their toxic dance, Rebollo-Hernanz grew adipocytes in a solution in which macrophages had been cultured.

"That's when we found that these inflammatory conditions in the solution increased oxidative damage" to the fat cells' mitochondria, he says.

He found that fewer mitochondria were present in the adipocytes that had grown in the solution and that the mitochondria that did exist in these cells were damaged.

When the scientists treated the adipocytes with the phenolic compounds in the extract, the adipocytes underwent a process called browning, in which they differentiated – that is, converted – from white adipocytes into another form called beige adipocytes.

Beige adipocytes are a specialised form of fat tissue with a greater number of mitochondria and increased fat-burning efficiency.

"We observed that the extract was able to maintain mitochondria and their function, modulate the inflammatory process and maintain the adipocytes' sensitivity to insulin," Rebollo-Hernanz says. "Assuming that these phenolic compounds are the main players in this extract, we can say that their consumption could prevent mitochondrial dysfunction in fat tissue."

Cocoa shell is a waste by-product generated when cocoa beans are roasted during chocolate production. About 700,000 tonnes of shells are thrown away every year, causing environmental contamination if they are not disposed of responsibly, de Mejia says.

In addition to giving cocoa producers another potential revenue stream, processing the shells in order to extract their nutrients would reduce the environmentally toxic substances currently generated by cocoa shell waste, de Mejia says.

Once extracted from cocoa bean shells, the phenolic compounds could be added to foods or drinks to boost the nutritional value of the products, she said.

The results were published in the journal Molecular Nutrition and Food Research.

University of Illinois at Urbana-Champaign.