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.
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!
More Links You Should Know About
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, “M
ost 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.
Twin Mysteries
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.
I’m surprised no one has commented on this excellent post, as yet. Dementia runs in my family, unfortunately, and I hate to think that I could ever be burdened by Alzheimer’s and Type I simultaneously. Just think how complicated it would be to have to put one’s Type I diabetes completely in the care of someone else. UGH! Let’s hope researchers will soon find cures for both Type I AND Alzheimer’s.
very interesting post. The diabetes en alzheimer link has been doing the rounds since a few years. One of the things tied to this is that the brain produces insulin as well. Most articles differentiate between brain and blood insulin, but I have never been able to find whether the two are actually different (allbeit closely related) proteins or whether their production site names them.
Regardless, having had people suffer from alzheimer close to me and my family, my parents were in quite the state after I was diagnosed with type 1 and this hit the papers about a month later.
Because this was the early days and the main story was brain resistance to brain insulin, I sussed them by claiming it was more tied to type 2 diabetes (because also resistance) then type 1. Not necessarily the truth, but it covered it well enough for me as I was still adjusting to living with diabetes.
Now however, while nobody else in my family has either type 1 or 2 diabetes, I myself am wondering whether our genetic link would make them more likely to develop alzheimer.
This whole gene thing is great for understanding things, but it also adds worries.
Allison,
You really did a fantastic job on this article. The links are excellent.
This article should be shared widely in the Alzheimer’s and related dementia communities.
Bob DeMarco, Founder
Alzheimer’s Reading Room
My father’s mother’s family has a very strong history of Alzheimer’s (NOBODY has escaped it — then again, they very in-bred), and my mother’s father’s family has had individuals with geriatric senile dementia (which may or may not have been Alzheimer’s). It’s a very scary, very likely future for me and my sister, and I’ve been scared and concerned about recent episodes where I can picture an item or concept, but cannot recall either the word for it or words similar enough to it to bring me, or my audience-of-the-moment, to it.
Neither my father nor his sister, nor most of his family that I know of, has or had diabetes — they’ve been primarily hypoglycemic, though my grandmother did develop diet-controlled type 2 in her sixties, and heart and memory issues about a decade later. (Sixties has been the decade where most of that family began to develop memory and communication issues.)
I don’t know the full extent to which type 2 diabetes runs in my mother’s family, only that Mom was diagnosed in her late fifties, and her grandmother was being treated for it in her late seventies and early eighties, and didn’t start losing her shorter historical memory until her mid eighties. (Mom didn’t get that far; she died at age 77.)
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