Alzheimer disease (AD ) is an irreversible,progressive brain disease that slowly destroys memory and thinking skills . AD is the most common cause of dementia among older people above the age of 65 years. Dementia is loss of thinking, remembering and reasoning and affects behavioural abilities to such an extent that it interferes with persons daily life and activities.
The type 3 diabetes title has been proposed for AD which results from resistance to insulin in brain.Studies carried out has identified the possibility of a new form of diabetes after finding that insulin is produced in the brain as well as in pancreas. Insulin resistance and insulin like growth factor are key to development of AD.
Some researchers believe the connection between impaired glucose metabolism,faulty insulin signalling and AD is so strong that they refer AD as type 3 diabetes. Moreover pathological changes that occur in AD in brain, physically resemble those seen in pancreas and vasculature in type 2 diabetes.This suggest that either t2d or related features of metabolic syndrome bring about AD or that they are separate consequence of the same underlying cause .But whatever may be the reason.it is clear that insulin is a key factor.
Physical hallmark of AD--is-reduction in cerebral usage of glucose. Brain being just 2% of body weight,consumes 20% of body's glucose and oxygen.Any regional reduction in metabolism has dramatic effects.specifically this reduced fuel usage is localised in the regions of brain involved in memory processing and learning.
Some of the most relevant data supporting this concept have emerged from clinical studies demonstrating cognitive improvement and/or stabilisation of cognitive impairment in subjects with early AD following treatment with intra nasal insulin.