Insulin Resistance in the Brain may Link Alzheimer’s and Epilepsy
New research has shown that the process of insulin resistance in the brain affects both Alzheimer’s disease and epilepsy and may be a linking factor between the two diseases. The findings confirm clinical evidence that people with epilepsy are at greater risk of developing Alzheimer’s disease as they age. It is also not uncommon for people with Alzheimer’s disease to have seizures. Among the various factors that trigger epileptic seizures is low blood sugar (hypoglycemia).
Alzheimer’s disease is a complex, multifactorial neurodegenerative disease for which there is no cure and no known cause. Among the various hypotheses to explain its onset, the amyloid cascade stands out. That cascade involves depositing of beta-amyloid plaques in the brain as the initial and critical event that triggers a series of processes that culminate in neuronal death, synapse loss, and ultimately dementia.
The new research looks at another hypothesis to explain the onset of Alzheimer’s, which is that the process of cerebral insulin resistance leads to neuronal damage and defective synaptic plasticity in a brain area called the hippocampus. Brain insulin resistance could even increase the likelihood of neuroinflammation and neurodegeneration and trigger the production and accumulation of beta-amyloid and tau proteins in brain tissue.
It is worth noting that although patients with diabetes have a higher risk of Alzheimer’s, it is possible to have central insulin resistance without having type 1 or type 2 diabetes. According to this hypothesis, which is not yet a consensus among experts, Alzheimer’s would be due to a type of diabetes called type 3, which describes a state of insulin resistance in the brain.
To test the type 3 diabetes hypothesis, researchers treated animals with a substance known to induce insulin resistance and used previously to study diabetes and Alzheimer’s disease. Surprisingly, some of the animals began to show seizure-like symptoms after receiving a high-intensity sound stimulus. This study demonstrated that the process of insulin resistance has an effect not only on Alzheimer’s but also on epilepsy,” says Suélen Santos Alves, PhD student and first author of the study.