Type 2 diabetes transmitted to others
Diabetes may be transferable between people, via a similar mechanism similar to that of mad cow disease, according to research from the University of Texas.
Professor Claudio Soto showed that a protein causes diabetes-like symptoms when transferred from diabetic mice to normal mice.
Diabetes is a chronic illness, characterised by abnormally high blood sugar levels. The World Health Organisation has calculated that diabetes affects 422 million people globally, and is responsible for approximately 1.6 million deaths a year.
Diabetes is associated with high levels of a protein called islet amyloid polypeptide, or IAPP. This protein is found naturally in the many parts of your body, including a group of cells in your pancreas called beta cells, but its exact relationship with diabetes hasn't been investigated until now.
But the work from Soto, published in the Journal of Experimental Medicine, suggests that IAPP is playing an unexpected role in the disease.
After you eat food, your blood sugar levels rise. In response, your beta cells release insulin into the blood to bring the blood’s sugar levels back down to normal. Prolonged high blood sugar levels are extremely harmful.
In diabetes, however, this process goes wrong. For a variety of reasons, type 1 diabetics lack beta cells, but in most cases of type 2 diabetes, risk factors like obesity leave the beta cells damaged and unable to release insulin.
Interestingly, over 90% of patients with type 2 diabetes have abnormally high amounts of IAPP in their beta cells. The levels are so high, in fact, that these proteins aggregate together to form clumps, which can build up before symptoms of the disease manifest.
But because no-one knew what IAPP did or why this build up happened, it has been largely ignored until now.
Soto showed that if you took small clumps of human IAPP and gave it to cultured human pancreases, those pancreases would develop IAPP clumps of their own.
They then genetically modified mice to possess human IAPP. When these mice were given IAPP bundles, their pancreases made their own IAPP clusters.
To their great surprise, however, healthy animals infected with the IAPP clumps went on to develop some of the symptoms of diabetes.
This is similar to what happens in mad cow disease - people ate beef containing damaged proteins, in this case, called prions. The infectious prions travelled to the brain where they passed the damage on to the person’s own prion proteins.
Furthermore, Alzheimer's disease, Parkinson's disease, and ALS, of ice bucket challenge fame, are all in some way caused by proteins grouping up abnormally, although scientists are still working out how. Nevertheless, the clumping of proteins causing disease isn’t a new hypothesis.
Despite the exciting findings in mice and the knowledge that some diseases can be spread through infectious proteins, the authors of the study are clear that there isn’t sufficient evidence to conclude that diabetes is transferable in humans. But they do believe this work merits further research.
Indeed, there are anecdotal stories of healthy people who’ve received organ donations from diabetics and have subsequently gone on to develop diabetes themselves.
So what does all of this actually mean for diabetes? The authors argue that their work demonstrates how diabetes might spread from cell to cell, within a body, rather than between them.
Nevertheless, they are still interested in studying whether diabetes can be transmitted via infectious IAPP proteins in humans. Even though this transmission is unlikely to be responsible for the majority of diabetes cases, their work could have important implications for organ donation, blood transfusions and the sharing of needles.