With current research enlightening a link between Type II Diabetes and the development of Alzheimer’s Disease through many mechanisms and risk factors, the role of insulin in the pathologies of both conditions is becoming a hot topic in medicine. Type II Diabetes increases the risk factor of developing dementia by two, and according to a 2004 study, the risk of developing Type II Diabetes is higher in Alzheimer’s patients.[1] Since the risk of developing either disease goes both ways, it is important to explore the big picture ways each disease advances and their overlap.
Insulin is a hormone that is synthesized in the pancreas, and has long been associated with Type II Diabetes. In a healthy system, insulin is released from the pancreas following a rise in blood sugar levels (after eating), and can bind to insulin receptors on a variety of cells throughout our bodies including fat, liver, muscles and even brain cells. The cellular pathways initiated by insulin binding to its receptors are myriad: they can have downstream effects as different as sugar storage and cell growth, among others.[2]
However, since the discovery of insulin receptors in the brain, scientists have investigated many more functions of insulin. Fascinatingly, insulin has been shown to play a role in protection of neurons, aiding with neuronal growth and survival, improving verbal memory and selective attention in healthy humans (Vieira et al., 2017). Most pertaining to Alzheimer’s is the implication of insulin in gene expression related to long term memory.
This crazy, tiny hormone does so many things for our bodies! It is chilling to think about what happens when insulin signalling goes wrong. When these signalling pathways do not get initiated the way they are supposed to (by insulin), we say that the system is exhibiting insulin resistance.
Both Alzheimer’s Disease and Type II Diabetes display insulin resistance as a primary molecular mechanism that leads to their development and worsening, but it is difficult to decide what really causes insulin resistance, and therefore what causes either disease. Many potential starting points have been proposed and are plausible: it is almost as if insulin resistance is cyclical, and we are jumping on to the mechanistic wheel in the middle of the disease propagation regardless of where we start.
After briefly examining the overlap between Type II Diabetes and Alzheimer’s, serious questions must be asked of the current health care system and its ability to provide effective and accessible healthcare to those living with Type II Diabetes and Alzheimer’s. The inventors of synthetic insulin sold their patent for only one dollar, with the intention that everyone who should need the drug would have access to it. Unfortunately, their desire to make their insulin accessible and affordable is not a reality, with the price of insulin nearly tripling within ten years (2002 to 2013). At a standard price of 480$ per vial, each of the 30 million Americans experiencing diabetes can pay thousands of dollars per year to get enough insulin to survive. If insulin mediation and other treatments for Type II Diabetes might be effective treatments for Alzheimer’s, as Vieira’s review article suggests, then the disadvantaged population has increased by almost 6 million.[3] Further, if Type II Diabetes and Alzheimer’s both play roles in the development of the other, then effective and affordable education and management options for Type II Diabetes are necessary to reduce the risk of Alzheimer’s, a brutal and debilitating disease.
[1]Vieira MNN, Lima-Filho RAS, De Felice FG. 2017. Connecting Alzheimer’s disease to diabetes: Underlying mechanisms and potential therapeutic targets. Neuropharmacology 136(2018):160-171.Neurochem Artstract 1Neurochem Artstract 1
[2] Vieira MNN, Lima-Filho RAS, De Felice FG. 2017. Connecting Alzheimer’s disease to diabetes: Underlying mechanisms and potential therapeutic targets. Neuropharmacology 136(2018):160-171.
[3] https://www.alz.org/alzheimers-dementia/facts-figures
