When you see news about diabetes being linked to "brain shrinkage," it can be tough to take that seriously and not smirk about the silliness of headlines.
But the links between diabetes and brain disease are more serious and substantial than many once thought, even just a few years ago when the media reported that a new type of diabetes — type 3 — had been discovered.
Now, this isn't to be confused with the type 3 reference some in the diabetes community have coined for caregivers, also known as "Type Awesomes"... No, this type 3 is a disease on its own that's specifically linked to Alzheimer's disease. The D-community has been slow to adopt Alzheimer's patients as PWDs-in-arms, but more and more research is coming out showing that there is a close connection between what's going on in our pancreas and what's going on in our brain.
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This connection was of special interest to me, because my father-in-law had Alzheimer's. That's right... had. He passed away from the disease just three short months after I met my husband and I never had the chance to meet him. For nearly four years, I thought the only thing my father-in-law and I had in common was our shared love of my husband.
But it turns out that might not be the case after all. And with September being World Alzheimer's Month and Sept. 21 tagged "Alzheimer's Action Day, " we thought this would be the perfect time to explore this issue more in-depth.
Alzheimer's As Diabetes
As one of the most common types of dementia affecting about 35 million globally, Alzeimer's involves the brain progressively losing brain cells causing memory loss and the degradation of mental function. The cause of Alzheimer's has always been a mystery, but researchers have associated it with the growth of plaques and tangles in the brain. However, plaques have also been found in elderly adults without Alzheimer's. Researchers have duked it out at medical conferences, never fully deducing what causes Alzheimer's. (Hey, we in the Diabetes Community know that "unknown cause" feeling!)
Now, some researchers are speculating that Alzheimer's is caused by insulin resistance and are declaring that Alzheimer's is its own form of diabetes.
Researchers have learned that high levels of insulin, triggered by the same poor diet that is connected with type 2 diabetes, can cause the brain to stop responding to the hormone. This "brain resistance" hinders the ability to think and create new memories, and ultimately leads to permanent damage and Alzheimer's.
Suzanne de la Monte, a neuropathologist at Brown University in Rhode Island, is one of the lead investigators on the connection between Alzheimer's and diabetes. In 2005, she introduced the moniker "type 3 diabetes" after noticing the effects insulin resistance had on rat brains. In the study, researchers gave rats a chemical that made them resistant to insulin. Immediately, they began displaying symptoms of Alzheimer's.
Researchers have also found that worms (yes, worms!) show a plausible, genetic link between diabetes and Alzheimer's. Shockingly enough, nematode worms are useful in studying possible effects in humans. These little creatures have shown that an Alzheimer's gene also plays a role in insulin production. Researchers still have a long way to go (we should hope so!), but more and more evidence is coming to light that we have far more in common with our Alzheimer's brethren than we might think.
Apparently, we should be thanking these medical rats and worms!
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If you already have diabetes, you might think you're off the hook. But that's not necessarily true. Researchers also found that PWDs over the age of 60 are twice as likely to have Alzheimer's. But researchers aren't sure why. They've just observed a strong correlation between people who have diabetes and those who get Alzheimer's. Perhaps a person's insulin resistance in the body eventually reaches the brain?
Just as high blood sugar damages the body, glucose (which can pass the blood brain barrier), it also damages the brain by hardening and narrowing the arteries in the brain, which can lead to vascular dementia. Researchers have also found that high blood sugar can prevent the body from breaking down the proteins which cause the plaques found in Alzheimer's. In addition, high blood sugar also damage brain cells from something called oxidative stress.
"The emerging information on Alzheimer's disease and glucose shows us that we do need to remain vigilant on blood sugar levels as we get older," Dr. David Geldmacher, a professor of neurology at the University of Alabama at Birmingham, told CNN.
All of these findings show a connection between diabetes and Alzheimer's, but researchers have yet to determine why this happens and what we can do about it.
Treating Alzheimer's with Diabetes Drugs
Another surprising connection between the two illnesses is that researchers have found success in treating Alzheimer's using diabetes drugs. A Canadian study on mice showed that the type 2 super-drug, metformin, can create new brain cells in a petri dish by causing the cells to divide. This was tested in the lab with both human cells and mouse cells, and then in mice, but not yet in people. Researchers believe this could help repair the brain from Alzheimer's. Metformin has already been shown in studies to help reduce the risk of some cancers (And another study in mice showed metformin can help delay the onset of Huntington's disease, too. Powerful little pills!)
A University of Washington study showed that taking insulin through the nasal cavity using a special device temporarily helped the memories of Alzheimer's patients. The study was very small — only 104 people — so there's a chance that this was, well, just chance. The lead researcher, Dr. Suzanne Craft, believes that an insulin-resistant brain needs more insulin, but without increasing insulin to the rest of the body. So don't start increasing Grandma's doses just yet!
Other researchers were quite optimistic, Dr. Craft told NBC News, "Most medications for Alzheimer's disease benefit relatively fewer patients. So, from that standpoint we were surprised by how many of the participants benefited!"
There are a few interesting theories out there in terms of prevention, too. At the recent annual meeting of the American Association of Diabetes Educators (AADE), Dr. Neal Barnard of the George Washington University School of Medicine gave a talk emphasizing a vegan diet for those with type 2 diabetes as a way to reduce the risk of Alzheimer's. The vegan diet provides an indirect method to reducing the risk, he said, and apparently the vegan diet often reduces cholesterol — important since other studies show lower cholesterol is associated with lower rates of Alzheimer's.
"It could just be that what's good for the heart is good for the brain as well," Barnard said in a news summary of his session.
Both Alzheimer's and diabetes are a mystery to the diabetes community. Only parts of them are fully understood, so it's no surprise that researchers are even less sure about the connection between Alzheimer's and diabetes and what the heck we can do about it.
But what is becoming more clear is that a connection does exist between these two chronic, incurable conditions. This is not good news of course, but the more researchers know the better...
And so, as it turns out, I might just have more in common with my father-in-law than I thought.