Interrelation entre déficits métaboliques et neuropathologie associée à la maladie d'Alzheimer chez la souris 3xTg-AD
|Abstract:||Alzheimer’s disease (AD) is the neurodegenerative disorder underlying most dementia cases. About 15% of canadians over 65 years suffer from AD. With the aging of the population, AD cases are expected to increase in years to come. Unfortunately, no treatment is able to slow down the progression of the disease. For more than 99% of the cases, the cause of the disease remain undetermined. However, several risks factors have been identified, including Type 2 Diabetes (T2D) which doubles the risk of developing AD at a later age. Interestingly, metabolic changes such as impaired peripheral and central insulin signaling were also identified in AD patients. To study the interelation between AD and diabetes, we first studied the impact of the induction of AD on peripheral metabolism in an animal model, the 3xTg-AD mouse. We found that the generation of AD neuropathology was associated to glucose intolerance, which progressed with age and was more important in females than in males. Furthermore, glucose intolerance was linked to the accumulation to human beta-amyloid peptide (Aβ) in the pancreas of 3xTg-AD mice. Next, we fed the 3xTg-AD mice a high-fat diet to see the impact of exacerbating metabolic deficits on AD-like neuropathology. The high-fat diet aggravated glucose intolerance and was linked to a reduce pancreatic islets size and impaired insulin production in response to glucose injection. Futhermore, high-fat diet was associated to an increased soluble Aβ accumulation in mice cortex as well as a deteriorated memory function. Interestingly, Aβ accumulation and memory funciton were restored with a single insulin injection. We also observed an increased plasma Aβ 30 min following insulin injection, suggesting that the peptide might be cleared from the brain following insulin administration. Those results strengthen the evidences suggesting that insulin might be an interesting therapeutical tool in AD. However, results in human patients using intranasal insulin suggest that APOE4 carrier do not benefit from insulin. To study the effect of APOE genotype on central insulin response, we injected APOE3 and APOE4 mice with a single insulin injection, five min before sacrifice. We found that APOE4 genotype was linked to a more important cerebral insulin signaling following insulin administration. Also, more increased phosphorylation of tau protein was observe in APOE4 mice injected with insulin. In summary, those results highlight the presence of a vicious circle between AD and T2D. Insulin administration might be an interesting therapeutical tool in AD, although it’s effects are limited in APOE4 patients.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||24 April 2018|
|Collection:||Thèses et mémoires|
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