Basic Science and Pathogenesis

This work aims to elucidate the mechanisms underlying insomnia-induced Alzheimer's disease (AD) in a sex- and ApoE genotype-dependent manner to predict treatment responsiveness. Sex-based differences contribute to AD, with a higher prevalence among females. Additionally, there are known associations between ApoE genotype and sex in AD prognosis. Furthermore, sleep disorders are a risk factor for AD development and are more common in females than males. This work demonstrates pathway interactions that link insomnia, sex, and ApoE genotype that will facilitate a more targeted approach to treat a specific patient population.

EMR/EHR data was accessed through The All of Us Research Program. The Religious Orders Study/Memory and Aging Program (ROSMAP) human brain transcriptomics and snRNA-sequencing data was utilized for mapping hub genes and key regulators related to AD and brain cell-specific gene expression profiles. Dual orexin receptor antagonists (DORA) were tested in cultured neurons from male and female mice that expressed the human ApoE4 allele (knock-in at the 5xFAD background). Neuronal activity was measured with the Microelectrode Array system from Axion Biosystems.

AllofUS EMR/EHR data mining showed that insomnia was associated with increased risk of development of AD-related Dementias (ADRD) in females, but not males. Insomnia was associated with increased risks of developing mild cognitive impairment (MCI) in both sexes. ROSMAP transcriptomic analysis identified orexin receptor 1 (HCRTR1), a gene dysregulated in insomnia, as a key driver in the AD brain network. Expression of HCRTR1 increased in neuronal clusters of ApoE4+ female MCI/AD brains compared to ApoE4 male counterparts. This sex difference was not seen in ApoE3+ MCI/AD brains. Neuronal and microglial co-culture studies demonstrated that HCRTR1 inhibition with DORA promoted neuronal activities in ApoE4+ female brain cells, but not males.

There are many factors that increase an individual's risk for developing AD, including insomnia, sex, and ApoE genotype. Here we have identified a pathway that may contribute to the interplay among these factors in AD pathogenesis. This study could facilitate a better understanding of sex- and ApoE-specific treatment responsiveness, which guide future precision-medicine guided therapeutic development in AD.