A receptor called ALK7 is vital to the regulation of body fat deposition and the release of insulin from beta-cells in the pancreas, researchers at the Swedish medical university Karolinska Institutet have found.
Insulin is a hormone required by cells in the body to absorb glucose from the blood, thereby providing them with energy. Obesity has been shown to increase the risk of developing diabetes, and as overweight becomes more prevalent in the human population, so do the cases of diabetes.
According to the scientists, the findings have implications for the development of treatments against diabetes and obesity.
"We have shown in animal studies that removing the ALK7 receptor improves insulin release by beta-cells in the pancreas, and at the same time decreases fat deposition in situations of high caloric intake", says Professor Carlos Ibanez, who lead the two studies that are now published as back-to-back papers in the PNAS.
"The well-known connections between diabetes and obesity make our combined findings quite exciting," Ibanez added.
The research group led by Carlos Ibanez studies how signaling by growth factors and their receptors regulate different physiological functions in the body.
They have recently investigated the functions of one of these receptors, called ALK7, using mutant mice (knock-out mice) lacking this receptor.
They found that in the absence of ALK7, mice developed abnormally high levels of insulin in the blood, which with age led to insulin resistance and liver steatosis, a pathological condition in which the liver enlarges and accumulates abnormally high levels of fat.
In the second study, the scientists found that mice lacking ALK7 accumulated less fat and gained less weight than their normal counterparts when fed on a high-fat diet.
They discovered that another growth factor called GDF3 could also signal via the ALK7 receptor, and that mice lacking GDF3 showed similar defects in fat deposition and weight gain as the ALK7 mutants. Intriguingly, however, mutant mice consumed equal amounts of food as their normal counterparts during the experiment.