When I first started studying and researching diabetes and related conditions, it came to be as a bitter surprise to learn the vast impact of insulin resistance on nearly every system in the body, the brain being one of them.
On the face of it, Type 2 diabetes and Alzheimer’s disease are two chronic conditions with seemingly distinct pathologies and appear as exceedingly different diseases with no correlation, emerging research has uncovered a compelling link between the two, leading some experts to refer to Alzheimer’s as “type 3 diabetes.” In this blog post, we’ll dive into the intriguing connection between type 2 diabetes and Alzheimer’s disease, exploring the shared pathophysiology, risk factors, and implications for disease management.
Understanding Type 3 Diabetes:
The term “type 3 diabetes” was first proposed over a decade ago, and used to describe the association between insulin resistance, glucose dysregulation, and Alzheimer’s disease. While Alzheimer’s is traditionally characterized by neurodegeneration and the accumulation of beta-amyloid plaques and tau protein tangles in the brain resulting in the symptoms people are most familiar with, researchers have identified significant metabolic abnormalities in the brains of individuals with Alzheimer’s disease, reminiscent of those seen in type 2 diabetes
Shared Pathophysiology:
Both type 2 diabetes and Alzheimer’s disease are associated with insulin resistance, a condition in which cells become less responsive to the actions of insulin. In the brain, insulin plays a crucial role in regulating glucose metabolism, synaptic function, and neuronal survival. Insulin resistance disrupts these processes, impairing energy metabolism and contributing to neuronal dysfunction and cognitive decline.
Furthermore, dysregulation of glucose metabolism and impaired insulin signalling in the brain can lead to the accumulation of toxic beta-amyloid plaques and tau protein tangles, hallmark features of Alzheimer’s disease. Conversely, the presence of these pathological changes can exacerbate insulin resistance and further disrupt brain function, creating a vicious cycle of neurodegeneration and metabolic dysfunction in humans.
Risk Factors:
Several risk factors predispose individuals to both type 2 diabetes and Alzheimer’s disease, further supporting the concept of type 3 diabetes. Age is the most significant risk factor for both conditions, with advancing age associated with an increased risk of insulin resistance, cognitive decline, and Alzheimer’s disease.
Other common risk factors include obesity, physical inactivity, poor diet, hypertension, dyslipidaemia, and genetic predisposition. These factors contribute to systemic inflammation, oxidative stress, and vascular dysfunction, all of which play a role in the pathogenesis of both of the two diseases.
Implications for Disease Management:
Recognizing the link between type 2 diabetes and Alzheimer’s disease has significant implications for disease management and prevention. Strategies aimed at improving glycaemic control and insulin sensitivity may have potential benefits in reducing the risk of cognitive decline and progression of Alzheimer’s.
Lifestyle interventions, including regular exercise, a healthy diet, weight management, and cognitive stimulation, are essential components of a comprehensive approach to managing both type 2 diabetes and Alzheimer’s disease risk. These interventions target common underlying mechanisms such as insulin resistance, inflammation, and vascular dysfunction, promoting better metabolic and cognitive health.
The concept of Alzheimer’s disease as “type 3 diabetes” highlights the intricate link between metabolic dysfunction and neurodegeneration. Shared pathophysiology, risk factors, and therapeutic targets underscore the importance of adopting a holistic approach to managing both type 2 diabetes and Alzheimer’s disease risk.
References:
De la Monte, S. M., & Wands, J. R. (2008). Alzheimer’s disease is type 3 diabetes—evidence reviewed. Journal of diabetes science and technology, 2(6), 1101-1113.
Craft, S. (2009). The role of metabolic disorders in Alzheimer disease and vascular dementia: two roads converged. Archives of neurology, 66(3), 300-305.
Biessels, G. J., & Despa, F. (2018). Cognitive decline and dementia in diabetes mellitus: mechanisms and clinical implications. Nature Reviews Endocrinology, 14(10), 591-604.
Qiu, W. Q., & Folstein, M. F. (2006). Insulin, insulin-degrading enzyme and amyloid-β peptide in Alzheimer’s disease: review and hypothesis. Neurobiology of aging, 27(2), 190-198.