Effect of rosiglitazone on amyloid precursor protein processing and Aβ clearance in streptozotocin-induced rat model of Alzheimer's disease.

Increasing evidence suggests that Alzheimer's disease (AD) is associated with diabetes. Rosiglitazone, a peroxisome proliferator-activated receptor γ (PPAR-γ) agonist and anti-diabetic agent, may improve symptoms of AD. However, the underlying therapeutic potential of it has not been fully elucidated. Rats were divided into four groups: control group, sham operated group, Streptozotocin (STZ) group, rosiglitazone (RGZ) group. Particularly, the STZ-induced rat model was established by intracerebroventricular injection (3 mg/kg) on the first and third day. The water maze behavioral test was performed to evaluate spatial reference learning and memory of the rats. Aβ1-40 and Aβ1-42 levels were measured by ELISA method. To determine APP-derived fragment, BACE1 and Aβ degrading enzymes levels, such as NEP and IDE, as well as Aβ transportation protein level, such as LRP1, RAGE, Abca1 and APOE, which were analyzed by Western blot. Immunohistochemistry was used to observe the change of Aβ1-40 and Aβ1-42 in hippocampus. Chronic treatment with RGZ could reduce the Aβ level and improved spatial memory performance in STZ-induced rat model. However, RGZ modified the expression of specific transport proteins monitoring Aβ clearance, such as ATP-binding cassette transporter 1 (ABCA1), lipoprotein receptor-related protein 1 (LRP1), and the advanced glycation end product-specific receptor (RAGE) rather than change levels of Aβ degrading enzymes, such as IDE and NEP, nor affect APP processing. As a potential therapeutic strategy, rosiglitazone might exert anti-AD effect not by alteration of APP processing pathway and Aβ degradation directly, but through promotion of Aβ clearance indeed.