The relationship between Alzheimer's disease and diabetes: Type 3 diabetes?

Abstract

In recent years, Alzheimer's disease (AD) has been considered to be, in part, a neuroendocrine disorder, even referred to by some as type 3 diabetes. Insulin functions by controlling neurotransmitter release processes at the synapses and activating signaling pathways associated with learning and long-term memory. Novel research demonstrates that impaired insulin signaling may be implicated in AD. Post-mortem brain studies show that insulin expression is inversely proportional to the Braak stage of AD progression. It was also demonstrated that neurotoxins, coined amyloid beta-derived diffusible ligands (ADDLs), disrupt signal transduction at synapses, making the cell insulin resistant. ADDLs reduce plasticity of the synapse, potentiate synapse loss, contribute to oxidative damage, and cause AD-type tau hyperphosphorylation. Diabetes and AD have signs of increased oxidative stress in common, including advanced glycation end products (AGEs), when compared to normal subjects. Diabetic patients appear to have an increased risk for AD because AGEs accumulate in neurofibrillary tangles and amyloid plaques in AD brains. This research should encourage a more proactive approach to early diagnosis of diabetes and nutritional counseling for AD patients.