Diabetes and Alzheimer's disease

Pancreatic extract infected mice with diabetes

Daria Spasskaya, N+1

Researchers from the University of Texas Medical School (Houston, USA) have shown that amyloid protein is involved in the pathogenesis of type 2 diabetes. This protein forms clusters in pancreatic cells similar to those formed in the brain in Alzheimer's disease, and eventually destroys insulin-producing cells. Injection of these amyloid structures into the abdominal cavity of mice led to the development of diabetes symptoms. Thus, diabetes can have a lot in common with prion diseases, in which protein is an infectious agent. The scientific article was published in The Journal of Experimental Medicine.

Amyloid proteins are proteins capable of forming very stable structures due to the specific laying of the polypeptide chain. Normally, such proteins perform some function, but with an increase in concentration, they can begin to change their conformation, aggregate and form so-called amyloid fibrils. This process occurs in some diseases, which are generally called amyloidosis. For example, amyloid plaques accumulate in the brains of patients with Alzheimer's, Parkinson's and Huntington's diseases, aggregates can accumulate in other organs.

Special cases of amyloidosis are prion diseases, in which amyloid proteins in the body begin to aggregate not by themselves, but as a result of infection. The fact is that amyloid proteins have the ability to "spoil" proteins of their type, that is, to force normally functioning proteins to aggregate. Thus, amyloid proteins can act as infectious agents – in these cases they are called prions. For some amyloidoses, it has been shown that the development of the disease occurs due to infection with prions. This includes, for example, Kuru cannibal disease and mad cow disease.

In type 2 diabetes, clusters of the amyloid protein IAPP (islet amyloid polypeptide) are also formed in the cells of the pancreas. IAPP plaques are probably the cause of the death of insulin-producing β-cells in the pancreas. This leads to the development of insulin deficiency at a certain stage of the disease.

As a rule, type 2 diabetes develops against the background of obesity and a sedentary lifestyle, but the molecular mechanism of its occurrence is not entirely clear. Scientists have suggested that the IAPP protein is involved in the pathogenesis of diabetes, and it is its amyloid transformation that can lead to the development of symptoms of the disease. In this case, IAPP can serve as an infectious agent that "carries" diabetes.

The authors tested their hypothesis on transgenic mice producing human IAPP models of the development of type 2 diabetes. By 12 months of life, these mice form plaques in the pancreas and develop diabetes. Scientists prepared an extract of the pancreas of old mice and injected it into the abdominal cavity of young mice who had no symptoms of the disease yet. As a result, clusters of IAPPS formed very quickly in the pancreas of young mice and the level of glucose in the blood rose. If IAPP aggregates were previously removed from the extract using antibodies, no such effect was observed.

Treatment with an extract from diseased mice of beta cells of the pancreas of healthy people also led to the formation of plaques.

To confirm that IAPP is the cause of the disease, the scientists made an amyloid solution that contained nothing but protein, and repeated the experiment, both on mice and on human cells. The effect was the same – the appearance of plaques and symptoms of diabetes in young mice. At the same time, no pathological changes were observed in other organs except the pancreas. 

Thus, the authors of the work showed that the ingestion of amyloid protein into the body from the outside caused the development of the disease. Of course, it is unlikely that diabetes can be contracted in the usual ways. Prion diseases are generally not so easy to get infected – for example, to get infected with a chicken, you had to eat the patient's brain. Nevertheless, the literature describes cases when the development of diabetes occurred after blood transfusion or organ transplantation. Perhaps diabetes should also be included in the list of diseases for which donors are checked.

Earlier we wrote how mice were cured of diabetes by injecting fibroblast growth factor into the brain. 

Portal "Eternal youth" http://vechnayamolodost.ru  29.08.2017