Scientists have discovered that a single gene forms a common link between type 2 diabetes and Alzheimer's disease, according to the City College of New York (CCNY).
This gene is present in many Alzheimer's disease cases and affects the insulin pathway, according to CCNY. Disruption of this pathway is a key feature of type 2 diabetes.
People with type 2 diabetes have an increased risk of dementia, according to lead researcher Professor Chris Li of CCNY. She states that the insulin pathways help keep the nervous system healthy and perform other metabolic functions.
Gene mutations block insulin pathway
The cause of Alzheimer's is still unknown. However, one criterion for diagnosing the disease is the presence of sticky plaques of amyloid protein in decimated portions of patients' brains. Mutations in the human amyloid precursor protein (APP) gene appear in hereditary Alzheimer's cases.
The researchers confirmed through studies with equivalent genes in worms that mutations in the APP gene slowed their development, suggesting it disrupted some metabolic pathway.
Further research uncovered that the equivalent APP gene was inhibiting the insulin pathway in these worms. This suggests that the human version of APP plays a role in both Alzheimer's and diabetes.
This discovery could help focus research and development of a treatment for both diseases.
Insulin resistance and dementia
Insulin resistance increases the risk of Alzheimer's disease and vascular dementia, a type of cognitive decline caused by damaged blood vessels in the brain, according to Mayo Clinic.
Mayo Clinic states that the link between Alzheimer's and type 2 diabetes may be caused by the complex ways that type 2 diabetes affects how the brain and other body tissues use glucose and respond to insulin.
Many cases of cognitive decline have brain changes seen in both Alzheimer's and vascular dementia. Some researchers hypothesize that each disease worsens the damage caused by the other, according to Mayo Clinic.