Diabetes mellitus (DM) is a health condition in which the body does not produce enough insulin (a hormone responsible for blood sugar regulation in the body) or cannot effectively use it, resulting in abnormally high blood sugar (glucose) levels. Generally, three types of diabetes are known:
- Type 1 diabetes (T1DM) is an autoimmune disorder in which the body attacks its insulin-producing beta cells in the endocrine part of the pancreas, causing them to lose the ability to make insulin. Consequently, the blood sugar level becomes too high.
- Type 2 diabetes (T2DM) is a chronic condition in which the body cells become resistant to insulin and do not use it well or the pancreas cannot produce it adequately to keep up with the demand.
- Gestational diabetes (GDM) occurs during pregnancy, and blood sugar levels are abnormally high during this period.
Some researchers have proposed the term “type 3 diabetes” for describing Alzheimer’s disease. According to them, a type of insulin resistance and insulin-growth factor dysfunction that occurs specifically in the brain cause amyloid plaques, inflammation, and oxidative stress in the brain triggering the disease. Some scientists also use this term when people with type 2 diabetes are diagnosed with Alzheimer’s.
“Type 3 Diabetes” is not universally acknowledged by the medical community as a clinical diagnosis. Its classification is highly controversial, and the American Diabetes Association and other major health organizations do not consider it a type of diabetes.
This condition is not to be confused with type 3c diabetes mellitus (also known as T3cDM and pancreatogenic diabetes). Type 3c may result due to pancreatitis and is entirely different from Alzheimer’s.
Causes of type 3 diabetes
In a review published in 2008, the authors conclude that “type 3 diabetes” precisely describes Alzheimer’s disease as a form of diabetes that impacts the brain. According to them, Alzheimer’s is a neuroendocrine disorder characterized by decreased insulin and insulin-like growth factor (IGF) signaling. It can also cause oxidative stress and inflammation in the brain. Besides, the authors note that while obesity and type 2 diabetes may contribute to the development of dementia, they are not sufficient causes in and of themselves.
A more recent study, however, reveals that an insulin-degrading enzyme may cause type 2 diabetes to progress to type 3 diabetes by shifting metabolic pathways. This mechanism may result in oxidative stress and beta-amyloid buildup in the brain, both of which are symptoms of Alzheimer’s.
Another study stated that people with type 2 diabetes might be about 60% more likely to develop Alzheimer’s or any other type of dementia, suggesting type 2 to be one of the risk factors.
Potential risk factors for type 3 diabetes, as mentioned in a recent study, include:
- Family history
- Genetics
- Birth weight
- Ethnicity and race
- Lack of physical activity
- Stress
- A diet high in calories, sugars, and fats and low in fiber
Inheritance of the APOE-ε4 gene is one of the most substantial risk factors for Alzheimer’s disease. Research has also suggested a stronger association between diabetes and Alzheimer’s-associated amyloid pathology among the carriers of the APOE-ε4 gene, implying that this gene can increase an individual’s risk of the condition.
Symptoms of type 3 diabetes
Since “type 3 diabetes” is not officially classified as diabetes, medical practitioners do not use it as a diagnostic term. Its symptoms are similar to dementia which include:
- Memory loss that impacts daily lives
- Trouble carrying out familiar tasks
- Frequently misplacing things
- Changes in mood and personality
- Confusion about time or location
- Poor judgment
- Withdrawal from work or social activities
Diagnosis and treatment
No specific test can diagnose type 3 diabetes. However, doctors can diagnose Alzheimer’s via brain imaging, neurophysiological tests, and neurological examination.
There is no specific treatment for type 3 diabetes, but distinct treatment options are available for people with pre-type 2 diabetes, type 2 diabetes, and Alzheimer’s.
Currently, Alzheimer’s has no treatment, and the available medication can temporarily treat its symptoms or slow its progression. In case a person has both Alzheimer’s disease and type 2 diabetes, treating the latter is essential to help slow dementia progression.
References
1. De la Monte, S.M. and Wands, J.R., 2008. Alzheimer’s disease is type 3 diabetes—evidence reviewed. Journal of diabetes science and technology, 2(6), pp.1101-1113. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769828/
2. Mittal, K., Mani, R.J. and Katare, D.P., 2016. Type 3 diabetes: cross talk between differentially regulated proteins of type 2 diabetes mellitus and Alzheimer’s disease. Scientific reports, 6(1), pp.1-8. https://www.nature.com/articles/srep25589
3. Chatterjee, Saion, Sanne AE Peters, Mark Woodward, Silvia Mejia Arango, G. David Batty, Nigel Beckett, Alexa Beiser et al. “Type 2 diabetes as a risk factor for dementia in women compared with men: a pooled analysis of 2.3 million people comprising more than 100,000 cases of dementia.” Diabetes care 39, no. 2 (2016): 300-307. https://diabetesjournals.org/care/article/39/2/300/37175/Type-2-Diabetes-as-a-Risk-Factor-for-Dementia-in
4. Nguyen, T.T., Ta, Q.T.H., Nguyen, T.K.O., Nguyen, T.T.D. and Van Giau, V., 2020. Type 3 diabetes and its role implications in Alzheimer’s disease. International journal of molecular sciences, 21(9), p.3165. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7246646/
5. Zhao, N., Liu, C.C., Van Ingelgom, A.J., Martens, Y.A., Linares, C., Knight, J.A., Painter, M.M., Sullivan, P.M. and Bu, G., 2017. Apolipoprotein E4 impairs neuronal insulin signaling by trapping insulin receptor in the endosomes. Neuron, 96(1), pp.115-129. https://www.cell.com/neuron/fulltext/S0896-6273(17)30791-2
