P1‐070: Development of an Improved Immunoassay for Detection of Sorla in Cells and Biological Samples

Abstract

phosphorylation of amyloid precursor protein (APP). When phosphorylated at threonine 668 (T668), APP undergoes conformational changes affecting its intracellular sorting and trafficking, which in turns impact proteolytic cleavage and increases A b production. The role of APP T668 phosphorylation and obesity in AD are not well understood and indicate a critical need to understand the mechanism(s) linking obesity and cognitive decline. Methods: Obesity is induced in C57Bl/6 mice using a high fat diet (54% kCal from fat) for 24 wk. APP and tau phosphorylation is examined from cortex lysates. Cortical neurons are prepared from E15 rat embryo and cultured in vitro for 7 days before insulin and/or IGF-I treatment. Results: Obese mice displayed significant cognitive impairment at 24 wk in parallel with the increased tau and T668-APP phosphorylation in the cortex. We previously reported that embryonic cortical neurons (eCN) develop neuronal IR with decreased insulin and IGF-I signaling following chronic insulin treatment. IGF-I treatment of eCN decreased T668-APP phosphorylation. Insulin also decreased APP phosphorylation but the effect was much weaker compared to IGF-I. Chronic treatment of eCN with insulin increased basal T668-APP phosphorylation. IGF-I was still able to reduce T668 phosphorylation after chronic insulin treatment; insulin itself was unable to reduce APP phosphorylation. These effect was reversed with the simultaneous treatment of chronic insulin with PI3-K inhibitor, suggesting chronic hyperactivation of Akt is responsible for IR-induced APP phosphorylation. Conclusions: Our results suggest IR-induced increases in T668 phosphorylation of APP as a possible link between obesity and cognitive impairment. Furthermore our data reveal a potential and beneficial effect of IGF-I signaling as a therapeutic target.