How do bears manage to make the type of diabetes they develop during their hibernation go away in the spring? American researchers believe they are one step closer to the answer.
People with diabetes have too much glucose, a form of sugar, in their blood. In the long term, this can lead to cardiovascular diseases, among other things. The hormone insulin plays an important role in the condition. This substance removes glucose – which enters our body through food – from the blood and transfers it to the body’s cells, where it serves as a source of energy. Diabetes occurs when this happens too little. This is possible because the body does not produce enough insulin (type 1 diabetes) or because it becomes less sensitive or resistant to it (type 2).
The vast majority of people with diabetes have the second variant. Worldwide, more than a million people die each year, while the number of patients is only increasing. It is not without reason that researchers eagerly look for new or improved treatments. A team of researchers from Washington State University in the USA hopes to find inspiration in nature. With bears, that is.
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The reason: bears develop a similar resistance to insulin during hibernation. This does not make the animals sick, but allows them to survive for months without food and water. When they eat again after waking up in the spring and the concentration of glucose in the blood rises, insulin sensitivity returns. A practical trick that can also restore sensitivity to insulin in humans, the researchers reason.
For that, it is necessary to understand exactly how the insulin resistance ‘on/off switch’ works in bears. To come up with an answer, the team put six grizzly bears in captivity at a university research center through an experiment. Adipose tissue and blood samples were taken from each animal during the ‘active’ season as well as during hibernation. The researchers did the same while disrupting the bears’ hibernation by regularly feeding them a sugary drink for two weeks.
They then combined the different samples with each other in the laboratory. This caused the necessary changes in the tissue, according to the research results published this week. Blood serum from disturbed hibernation in particular had a great effect on cultured cells from adipose tissue taken during ‘normal’ hibernation. These began to exhibit behavior similar to cells in the active season.
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Remarkably, only a few proteins were responsible for all the changes, the researchers concluded after an analysis. “There appear to be eight proteins that either independently or together regulate insulin resistance in hibernating bears,” said evolutionary geneticist Joanna Kelley, who contributed to the study.
These are proteins of which humans possess so-called homologues, she notes. In other words, for every protein there is a human counterpart that is descended from a common ancestor. “This means there may be a direct opportunity for translation to humans.”
Therefore, the team is focusing more research on the proteins’ precise role in turning insulin resistance on and off. In this way, they hope to discover possible treatments for human diabetes. Whether the latter actually happens remains to be seen, says Cees Tack, professor of medicine at Radboud University. Tack, whose own research focuses on treating diabetes in humans, doubts that the cause of all the changes can be traced back to eight proteins. “The samples that the team is studying only come from a small number of bears. It is too limited to come to firm conclusions.’
Furthermore, the road to possible applications in humans is very long, says Tack. “It is possible that these eight proteins play an important role, but how they do it is still completely unknown. In fact, we don’t even know the exact function of most of them in the body. A lot of further research is needed to map this out. After which it is still doubtful to what extent this can teach us anything about processes in the human body.’