Obesity alters cells in ways that can lead to long-term health problems. Examples of obesity-induced cell changes include inflammation and damage to metabolic functions, such as the ability to use insulin and make energy.

Now, new research from the University of Illinois at Urbana-Champaign and other institutions has shown that extract of cocoa bean shells contains three compounds that could potentially reduce or prevent some of these cell changes.

Cocoa, green tea, and coffee also contain the same three compounds, which are protocatechuic acid, epicatechin, and procyanidin B2. A recent Molecular Nutrition & Food Research paper gives an account of the study and its findings. The three compounds are plant phenolics, a group that occurs throughout the plant kingdom. In recent years, scientists have become increasingly interested in the health properties of plant phenolics.

In obesity, white adipocytes, a type of fat cell, acquire too much fat and spur the growth of immune cells called macrophages. Interaction between the fat-laden adipocytes and the macrophages, in turn, promotes a state of persistent, or chronic, inflammation that accompanies obesity.

Eventually, the chronic inflammation reduces the ability of the cells to take in and convert glucose into energy. This impairment causes insulin resistance, which is a precursor to type 2 diabetes.

Phenols treat obesity-induced cell changes

A combination of too much fat, rising levels of glucose, and inflammation also damages mitochondria, the tiny powerhouses in cells that make energy by burning fat and glucose.

However, after studying these various obesity-related effects in fat and immune cells from mice, the researchers found that they could treat them with cocoa shell extract.

"We observed," says lead study author Miguel Rebollo-Hernanz, PhD, "that the extract was able to maintain the mitochondria and their function, modulating the inflammatory process and maintaining the adipocytes' sensitivity to insulin."

Rebollo-Hernanz is a visiting scholar in the Department of Food Science and Human Nutrition at the University of Illinois.

According to figures from the World Health Organization (WHO), there were more than 650 million people with obesity worldwide in 2016. WHO estimates also suggest that around 2.8 million deaths occur each year because of being overweight or having obesity. In addition, the proportion of people with obesity has nearly tripled in the 40 years leading up to 2016.

People with obesity have a higher risk of developing long-term diseases such as type 2 diabetes, cancer, and conditions that affect the heart and blood vessels. Previous studies have shown that as obesity progresses, fat accumulates, together with an increase in adipose tissue macrophages that promote "low-grade, chronic inflammation and dysregulated metabolism."

White fat cells turned fat-burning and beige

For the new study, Rebollo-Hernanz and colleagues wanted to find out whether targeting the interaction between adipocytes and macrophages with cocoa shell extract and its main phenolics could prevent the mitochondrial damage and insulin resistance that obesity can induce.

They ran several cell experiments and also used computer models and bioinformatics to analyze the molecular impact of each compound on the adipocyte-macrophage interactions.

In one set of experiments, the scientists got white adipocytes to grow in a culture containing macrophages. Rebollo-Hernanz says that they saw that the white adipocytes that grew in this way had fewer mitochondria and that the mitochondria that did grow were impaired.

However, he and his colleagues discovered that treating the cells with either cocoa shell extract or each of the three phenolics repaired damaged mitochondria and reduced fat accumulation in the cells.

On closer inspection, they found that adding the compounds to the culture caused the white adipocytes to turn into "beige adipocytes." Beige adipocytes differ from white ones in that they have many more mitochondria and are much more efficient at burning fat.

Should the findings also be true of human cells, the team sees potential in using cocoa shell extract as an additive to boost the nutritional value of foods and drinks. In addition to these nutritional benefits, the team highlights the potential environmental advantages of using cocoa shell extract to enhance nutrition.

Typically a waste product of the cocoa industry, cocoa bean shells can damage the environment if producers, who discard around 700,000 tons of them per year, do not dispose of the shells responsibly, notes professor Elvira Gonzalez de Mejia, a study co-author.

"Assuming that these phenolics were the main actors in this extract, we can say that consuming them could prevent mitochondrial dysfunction in adipose tissue."

—Miguel Rebollo-Hernanz, PhD