About 35 million people have Alzheimer’s; most of them require expensive, exhausting care. By 2050 that number is expected to triple. We still don’t really know what causes the disease or how it destroys the brain. There is no way to prevent it and no cure. Dealing with the epidemic will cost trillions.
There is growing evidence that Alzheimer’s is actually a late stage of another disease, type 2 diabetes. The link between the two has been noted for a few years and though it remains a hypothesis, the evidence is growing.
the same research also offers a way to reverse memory problems associated with diabetes – albeit in rats – which may hint at a new treatment for Alzheimer’s.
“Perhaps you should use Alzheimer’s drugs at the diabetes stage to prevent cognitive impairment in the first place,” says Ewan McNay from the University at Albany in New York.
At first glance that sounds like bad news. If the Alzheimer’s epidemic is scary, the type 2 diabetes one is truly terrifying. About 270 million people have type 2 diabetes already and their ranks are swelling rapidly – among them adolescents and young adults. If they are destined to progress to Alzheimer’s disease, the future looks bleak.
Or perhaps not. Type 2 diabetes is largely a lifestyle disease, caused by obesity, poor diet and lack of exercise. It can be prevented, alleviated and even cured by lifestyle changes, which holds out the hope that we could start to deal with Alzheimer’s in a similar way.
Experience tells us, of course, that exhorting people to eat better and exercise more often falls on deaf ears. But with obesity rates levelling off in some parts of the world and falling slightly in others, there is some evidence that the message is getting through.
If the link between diabetes and Alzheimer’s is firmed up, there will be even more reason to take heed – and even more reason to keep banging the public health drum. Good news comes in many guises. The possibility that Alzheimer’s is “just” diabetes is one of them.
Feeding animals a diet designed to give them type 2 diabetes leaves their brains riddled with insoluble plaques of a protein called beta-amyloid – one of the calling cards of Alzheimer’s. We also know that insulin plays a key role in memory. Taken together, the findings suggest that Alzheimer’s might be caused by a type of brain diabetes.
If that is the case, the memory problems that often accompany type 2 diabetes may in fact be early-stage Alzheimer’s rather than mere cognitive decline.
Although there is no definitive consensus on the exact causes of Alzheimer’s, we do know that brains get clogged with beta-amyloid plaques. One idea gaining ground is that it is not the plaques themselves that cause the symptoms, but their precursors – small, soluble clumps of beta-amyloid called oligomersMovie Camera. The insoluble plaques could actually be the brain’s way of trying to isolate the toxic oligomers.
For the last few years, organisations like the UK’s Alzheimer’s Society have been backing clinical trials to look for diabetes drugs that may have an effect on Alzheimer’s patients. “We’re saying that this may be not the only way to think about it,” says McNay.
The next step is to repeat the work, and if the results are corroborated, start looking for a drug that would do the same thing as the group’s modified antibodies, without having to inject the drug directly into the hippocampus. It will also be necessary to work out just how much amyloid the brain can safely do without, since low levels are important for memory formation.
“The work opens the door to inoculating the most at risk group, people with type 2 diabetes,” says Tres Thompson of the University of Texas at Dallas. There have been plenty of failed attempts to use antibodies to relieve Alzheimer’s in the past. “But these were all in people with advanced stages of the disease. Vaccinating people much earlier could give better results.”