University of Illinois researchers found that portions of the coffee bean that often get discarded after roasting may have beneficial health effects. The researchers were interested in the potential of inflammation-fighting compounds found in the silverskin and husk of coffee beans, not only for their benefits in alleviating chronic disease but also in adding value to would-be “waste” products from the coffee processing industry. Findings from their recent study—published in Food and Chemical Toxicology through an article titled “Phenolic compounds from coffee by-products modulate adipogenesis-related inflammation, mitochondrial dysfunction, and insulin resistance in adipocytes, via insulin/PI3K/AKT signaling pathways”—showed that when fat cells of mice were treated with water-based extracts from coffee beans skins, two phenolic compounds, protocatechuic acid, and gallic acid, in particular, reduced fat-induced inflammation in the cells and improved glucose absorption and insulin sensitivity.

“In my lab we have studied bioactive compounds from different foods and have seen the benefits for the prevention of chronic diseases,” explained senior scientific investigator Elvira Gonzalez de Mejia, PhD, professor of food science in the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois. “This material from coffee beans is interesting mainly because of its composition. It’s been shown to be nontoxic. And these phenolics have a very high antioxidant capacity.”

The new results show promise for these bioactive compounds, when consumed as part of the diet, as a strategy for preventing obesity-related chronic illnesses, such as type 2 diabetes and cardiovascular disease.

In the current study, the researchers looked at two types of cells, macrophages and adipocytes, and the effect of the combined compounds from the extracts, as well as the individual pure phenolics, on adipogenesis—the production and metabolism of fat cells in the body—and the related hormones. They also looked at the effect on inflammatory pathways.

When obesity-related inflammation is present, the two types of cells work together—stuck in a loop—to increase oxidative stress and interfere with glucose uptake, worsening the situation. In order to block this loop and prevent chronic disease, the researchers’ goals are to eliminate or reduce as much inflammation as possible in order to allow glucose uptake to be facilitated, as well as to have healthy cells that will produce adequate insulin.

“We evaluated two extracts and five pure phenolics, and we observed that these phenolics, mainly protocatechuic acid, and gallic acid, were able to block this fat accumulation in adipocytes mainly by stimulating lipolysis, but also by generating ‘brown-like’ or ‘beige’ adipocytes,” noted lead study investigator Rebollo-Hernanz, a visiting scholar in de Mejia’s laboratory

Significantly, these “brown-like” cells are known as fat burners, and they contain more mitochondria, an important organelle in cells that turns nutrients into energy. In the study, the researchers observed that some phenolics were able to stimulate browning of the fat cells, increasing the content of mitochondria in adipocytes, or fat cells.

“Macrophages are present in the adipose tissue and when adipose tissue grows excessively, there are interactions that stimulate inflammation and oxidative stress,” Rebollo-Hernanz stated. “We saw that these phenolics were able to reduce and decrease the secretion of inflammatory factors, but also decrease oxidative stress.”

When macrophages interact with fat cells, the cells have fewer mitochondria. Having fewer mitochondria, they lose the capacity of burning lipids. Using these phenolics, the researchers found that this impact of macrophages on the fat cells was completely blocked. The fat cells maintained their function.

“The compounds we tested were able to inhibit inflammation in the macrophage. That means inhibiting many markers that produce inflammation to the adipocytes. Those were blocked,” de Mejia said. “Coming to the adipocytes themselves, we saw inhibition of different markers related to inflammation as well. The absorption of glucose was improved because the glucose transporters were present. And this went back and forth.

“Now we know that in the presence of these compounds we can reduce inflammation, reduce adipogenesis, and decrease the ‘loop’ that helps the two types of cells grow and develop bad compounds that will negatively affect the whole system,” she added.

During coffee processing, the bean is separated from the husk, the external outer layer of the bean. After the bean is roasted, the silverskin layer is separated. “It’s a huge environmental problem because when they separate this husk after processing, it usually stays in the field fermenting, growing mold, and causing problems,” de Mejia explained. Worldwide 1,160,000 tons of husk is left in fields per year, potentially causing contamination.

Additionally, 43,000 tons of silverskin is produced each year, which, de Mejia adds, may be easier to utilize because it stays with the bean as it is exported to different countries to be roasted.

“Once producers see the value, they will treat these materials as an ingredient instead of a waste,” de Mejia says. “It will require good collaboration between academic institutions, industry, and the public sector to solve this problem, but the market is there for these products.”

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