soy beans

University of Illinois scientist Elvira de Mejia has discovered that soybeans with a certain protein profile inhibit lipid accumulation in fat cells. The discovery will in the future make it possible to create high-yielding cultivars that contain the ‘slimming’ trait for soybean farmers to grow in their fields. “This is exciting research because it could lead to the development of nutraceuticals to fight obesity,” she says. Credit: University of Illinois

U. ILLINOIS (US)—A certain type of soy protein is gaining ground and in the future may be instrumental in helping people reduce inflammation and lose weight.

“We found that soybeans rich in beta-conglycinins limit lipid accumulation in fat cells by inhibiting an enzyme called fatty acid synthase,” says Elvira de Meja, associate professor of food science and human nutrition at the University of Illinois.

“What’s more, we have identified the specific peptides (digested proteins) that do this, and we are now beginning to understand the mechanism behind it. This is exciting research because it could lead to the development of nutraceuticals to fight obesity.”

The most important factor influencing a soy cultivar’s healthful effects is the proportion in which they occur, de Mejia says. The soy contains, among others, two types of protein: glycinins and beta-conglycinins.

De Mejia’s study was the first to establish the anti-inflammatory properties of soy high in this type of protein. “The peptides fight inflammation by blocking key enzymes in the body’s immune response.”

Soy that is low in glycinins and high in beta-conglycinins is preferred for its ability to inhibit lipid accumulation and inflammation.

“Using the latest molecular marker-assisted breeding techniques, soybeans with the right composition can be tagged and later identified using a simple leaf tissue sample,” she says.

“This would make it possible to create high-yielding cultivars that contained the ‘slimming’ trait for soybean farmers to grow in their fields.”

In earlier research, de Mejia discovered that that administration of soy protein caused weight loss in laboratory rats, but she wanted to know exactly why it happened.

She incubated human fat cells in the lab, treated them with soy hydrolysates from 15 soy genotypes containing varying amounts of beta-conglycinin, and then measured the amount of fat that accumulated.

“As we increased the concentration of beta-conglycinin, we saw more inhibition of lipids and less accumulation of fat. Further testing showed that this occurred because fatty acid synthase, an enzyme responsible for synthesizing lipids, had been suppressed.

“We also found that fat cells exposed to digests made from the ‘slimming’ soybeans increased the synthesis of adiponectin, a hormone that enhances insulin sensitivity and fat metabolism,” she says.

She then compared the activity of beta-conglycinins with glycinins and found that hydrolysates from beta-conglycinins inhibited almost 50 percent of lipid accumulation in the fat cells. Glycinins did not inhibit lipid accumulation at all, she says.

In a separate study, her team identified specific soy peptides that inhibit fatty acid synthase, and they were able to learn exactly how it happens.

de Mejia and her colleagues are now taking their research a step further by performing human trials with soy milk that is high in beta-conglycinins.

“For years we’ve known that soy protein is a good source of essential amino acids. Soy helps us maintain muscle mass, and its peptides make people feel full so they don’t eat as much,” she explains.

“Now it appears that products made from soybeans selected for this particular protein profile may also help limit fat accumulation. Food manufacturers will be able to create soy products targeted at consumers who are trying to maintain their ideal weight,” she says.

The first study appeared in a recent issue of Molecular Nutrition and Food Research. The second study appears in the current issue of FEBS Journal.

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