Diabetes increases your risk of heart disease, stroke, and damage to blood vessels and nerves, but did you know that studies suggest it may also increase your risk of eventually developing Alzheimer’s disease and other forms of dementia?
And the damage to your brain may even start before you have diabetes…
Type 2 diabetes begins with spikes in levels of sugar in the blood, which trigger your body to produce higher amounts of insulin to process this sugar. At first the higher amounts of insulin can reduce blood sugar to normal (this stage is referred to as pre-diabetes) but eventually, as your body becomes increasingly resistant to the effect of insulin, blood sugar can no longer be controlled at normal levels, and you are diagnosed with diabetes.
Research is suggesting that these increased levels of insulin begin the process of damaging the inside of blood vessels and, in the brain, also stimulate formation of toxic proteins that damage brain cells. Researchers have discovered that the same protein that is formed in Alzheimer’s patients’ brains, is found in the brains of people with type 2 diabetes (T2D). T2D patients often experience a sharp decline in cognitive function and almost 70% of them eventually develop signs of Alzheimer’s or another dementia, according to www.alzheimers.net.
Melissa Schilling, professor at NYU, suggests that all patients with dementia or who are at risk of developing dementia should be tested for hyperinsulinemia (high insulin in the blood). She suggests that high insulin could be responsible for almost half of all cases of dementia. However, she recommends that further research needs to be done to verify her arguments and implications for treating Alzheimer’s. Her article: Unraveling Alzheimer's: Making Sense of the Relationship between Diabetes and Alzheimer's Disease was published in the Journal of Alzheimer's disease in Jan 2016. Click here for the full text.
Research points to the protein, amylin, that is co-secreted with insulin and, along with the beta-amyloid protein, it is thought to be important in the formation of amyloid plaques found in the brains of Alzheimer’s patients.
Another possibly important factor, may be levels of insulin-degrading enzyme (IDE), the enzyme that breaks down insulin, reducing levels once it’s finished its job. The presence of insulin stimulates increased activity of IDE, the enzyme that breaks down insulin. Lower insulin leads to less activity of this enzyme. IDE also breaks down amyloid proteins, but it favours breakdown of insulin.
It may be an imbalance between IDE, insulin and amyloid-beta production that ultimately is shown to be a major cause of dementia. Here are 4 suggested scenarios:
Severe lack of insulin (as in type 1, insulin dependant diabetes), could lead to less IDE activity, and subsequent decrease in breakdown of amyloid proteins that create plaques in the brains of dementia patients.
Lack of production of IDE itself would lead to increased levels of both insulin and beta-amyloid
Excessively high levels of insulin (and amylin, secreted along with it) in early stages of type 2 diabetes could lead to competition for insulin-degrading enzyme between insulin and amyloid. Since the enzyme favours insulin, this would result in less breakdown of amyloid and increased amounts available for formation of plaque in the brain
An individual could produce higher than normal amounts of amyloid proteins that outpace the ability of IDE to break it down.
You can see how both a lack of insulin and too much insulin could be a cause of dementias. Too little insulin-degrading enzyme or increased production of amyloid proteins could cause problems in people with normal production of insulin. These confusing scenarios could explain why researchers have not yet determined the causal relationship between diabetes and Alzheimer’s, despite reporting on the connection as far back as 2003!
This type of research is especially important, as the drugs currently available to treat Alzheimer’s offer only small improvements in symptoms and do not stop the progression of the disease, in spite of their high cost.
So, ask your doctor to screen for early signs of diabetes and aggressively treat it when discovered to keep your insulin levels in the normal range. Eat a healthy diet and exercise regularly, as these are also known to lower the risk of developing diabetes. It seems likely that these strategies will lower your chances of developing dementia years down the road.
References: MayoClinic.org; Alzheimers.net
