Researchers from the University of Illinois at Urbana-Champaign and the Autonomous University of Madrid treated fat cells of mice with water-based extracts from coffee bean skins. The researchers found that the phenolic compounds, protocatechuic acid and gallic acid, reduced fat-induced inflammation and improved glucose absorption and insulin sensitivity.
The researchers suggest that adding these phenolic compounds to one's diet may work as a nutritional strategy for preventing obesity-related chronic conditions, such as Type 2 diabetes and cardiovascular disease.
Coffee by-products like the husk and silverskin are generated in large amounts during the harvesting and processing of green, or raw, coffee beans. These by-products contain significant amounts of antioxidants that can be recovered for use as value-added products. Previous studies show that the phenolic compounds in coffee by-products can increase insulin secretion by beta cells and protect the pancreas from oxidative stress.
However, the researchers noted that the anti-inflammatory effect of coffee by-products on adipocytes (fat cells) and their mechanism of action hadn't been detailed before.
The team tested the effect of five pure phenolics found in coffee husk and silverskin on adipocytes and immune response cells called macrophages. These two types of cells work together in a loop in obesity-related inflammation, which increases oxidative stress and interferes with glucose uptake.
"Macrophages are present in the adipose tissue and when adipose tissue grows excessively, there are interactions that stimulate inflammation and oxidative stress," explained lead author Miguel Rebollo-Hernanz, a visiting scholar at the Department of Food Science and Human Nutrition at Urbana-Champaign. Those interactions can decrease the number of mitochondria in fat cells, weakening a person's ability to burn fats.
The researchers found that protocatechuic acid and gallic acid were the most effective at blocking fat accumulation in adipocytes. Upon further analysis, they discovered that these compounds work by stimulating lipolysis – the breakdown of fats – and by generating "brown" or "beige" adipocytes. These cells are known as fat burners and contain a high number of mitochondria, the cell organelles that convert nutrients into energy.
Moreover, the researchers observed that interactions between macrophages and the fat cells were completely blocked with the phenolics.
"The compounds we tested were able to inhibit inflammation in the macrophage," said co-author Elvira Gonzalez de Mejia of Urbana-Champaign. She added that different inflammatory markers had been inhibited, and glucose uptake was improved due to the presence of glucose transporters. (Related: Food, herbs, and spices that can control blood sugar.)
"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," de Mejia said.
The researchers are optimistic that their findings will lead to new strategies for the prevention of Type 2 diabetes, cardiovascular disease and other chronic conditions linked to obesity and being overweight.
Previous studies have also shown that unroasted coffee beans are beneficial for people with or at risk of Type 2 diabetes. In a 2013 study, researchers found that the extract from these beans can help lower blood sugar levels.
The extract of green coffee beans is rich in chlorogenic acids, which have powerful antioxidant, anti-inflammatory and antihypertensive effects. The researchers wondered whether the extract has a positive effect on blood sugar levels.
They enlisted healthy male and female participants and gave them between 100 milligrams (mg) and 400 mg of the extract each day. All of the participants managed to lower their blood sugar levels, with those who took the highest dose experiencing the biggest improvements.
Learn more about the health benefits of green coffee beans at Superfoods.news.