title: 17β-Estradiol regulates insulin-degrading enzyme expression via an ERβ/PI3-K pathway in hippocampus: relevance to Alzheimer's prevention.
abstract: Insulin-degrading enzyme (IDE), an enzyme that primarily degrades insulin, has recently been demonstrated to play a significant role in the catabolism of amyloid β (Aβ) protein in the brain. Reduced IDE expression and/or activity have been associated with the etiology and development of Alzheimer's disease (AD). Using three model systems, the present investigation provides the first documentation indicating that estrogen robustly regulates the expression of IDE in normal, menopausal and early-stage AD brains. In vitro analyses in primary cultures of rat hippocampal neurons revealed that 17β-estradiol (17β-E2) increased IDE in both mRNA and protein levels in a time-dependent manner. Further pharmacological analyses indicated that 17β-E2-induced IDE expression was dependent upon estrogen receptor (ER) β and required activation of phosphatidylinositol 3-kinase (PI3-K). In vivo analyses in adult female rats revealed a brain region-specific responsive profile. Ovariectomy (OVX) induced a significant decline in IDE expression in the hippocampus, which was prevented by 17β-E2. Neither OVX nor 17β-E2 affected IDE expression in the cerebellum. In vivo analyses in triple transgenic AD (3xTg-AD) female mice revealed an inverse correlation between the age-related increase in Aβ load and the decrease in IDE expression in the hippocampal formation. Treatment with 17β-E2 attenuated Aβ accumulation/plaque formation and elevated hippocampal IDE expression in 12-month-old 3xTg-AD OVX mice. Collectively, these findings indicate that 17β-E2 regulates IDE expression in a brain region-specific manner and such a regulatory role in the hippocampus, mediated by an ERβ/PI3-K pathway, could serve as a direct mechanism underlying estrogen-mediated preventative effect against AD when initiated at the onset of menopause.
authors.affiliation: Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, 1985 Zonal Avenue, Los Angeles, CA 90033, USA. liqinz@usc.edu
authors.forename: Liqin
authors.initials: L
authors.lastname: Zhao
authors.forename: Jia
authors.initials: J
authors.lastname: Yao
authors.forename: Zisu
authors.initials: Z
authors.lastname: Mao
authors.forename: Shuhua
authors.initials: S
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Roberta Diaz
authors.initials: RD
authors.lastname: Brinton
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism / Q000517:prevention & control; D016229:Amyloid beta-Peptides / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D004958:Estradiol / Q000494:pharmacology*; D047629:Estrogen Receptor beta / Q000378:metabolism*; D005260:Female; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D007339:Insulysin / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010052:Ovariectomy; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D016229:Amyloid beta-Peptides; D047629:Estrogen Receptor beta; D004958:Estradiol; D019869:Phosphatidylinositol 3-Kinases; D007339:Insulysin