Effects of Hormone Replacement Therapy (HRT) on Gene Expression in the Amyloid Processing Pathway of Ovariectomized Rhesus Macaque Females Under an Obesogenic Diet

Abstract

Estrogens rapidly decline at the onset of menopause, putting women at higher risk of osteoporosis, obesity, and neurodegenerative diseases, including Alzheimer’s disease (AD). Estradiol hormone therapies (HT) have been suggested to limit these negative effects on women, with controversial findings as to their effectiveness. A study at OHSU recently found differentially expressed genes (DEGs) using RNAseq between ovariectomized/hysterectomized (OvH) old (range = 19.4–23.2 years) female rhesus macaques on HT and those on a placebo on chronic western style diet (WSD). The DEGs identified in the amyloid processing pathway of the amygdala were selected for validation using RT-qPCR because β-amyloid peptide (Aβ), made in the amyloid processing pathway, has a strong correlation with AD risk. The selected genes were: AKT3, APP, CAPN1, CAPNS1, CSNK2A1, CSNK2A2, MAPK1, MAPK14, MAPT, MARK1, NCSTN, PRKAR1A, PRKAR2A, PRKAR2B, and PRKCE. All the genes tested were found to be significantly downregulated (p <0.05) in the OvH-HT females. These genes were also tested in another set of old and young female rhesus macaques on a standard diet (SD) and were not differentially expressed using qPCR. Since the RNAseq analysis used a cutoff of 2.3logCPM to select genes, the qPCR tests confirming the DEGs at this level tells us 2.3logCPM is a valid cutoff to use in future RNAseq analysis. The genes in the amyloid processing pathway being significantly downregulated with HT suggests beneficial effects of the HT with WSD because this pathway regulates Aβ and accumulation of Aβ plaques in the brain are a hallmark of AD.