Multi-Omics Integration and Causal Inference Identify HSD17B1 as a Potential Nobiletin Target Linking Neurosteroid Metabolism to Alzheimer's Disease

Alzheimer's disease (AD) is characterized not only by neuronal dysfunction but also by profound remodeling of the brain microenvironment, including immune-glial activation and metabolic dysregulation. Increasing evidence also implicates neurosteroid-related pathways in AD and dementia. Nobiletin has shown neuroprotective effects in AD-related models, but its upstream human targets and mechanism-based translational relevance remain insufficiently defined. Here, we integrated multi-omics analyses, interpretable machine learning, causal inference, structural modeling, and experimental validation to identify candidate nobiletin-associated molecular nodes in AD. HSD17B1 consistently emerged as a central AD-associated candidate across multiple analytical layers and showed reproducible discriminatory performance in independent validation cohorts. SHAP analysis further identified HSD17B1 as a major contributor to the optimal predictive model, while Mendelian randomization supported a protective association between genetically increased HSD17B1 expression and AD risk. Immune infiltration, single-cell, and spatial transcriptomic analyses linked HSD17B1 to glia-associated remodeling and regionally heterogeneous expression patterns in AD. Molecular docking and molecular dynamics simulations supported the structural feasibility of nobiletin binding to HSD17B1, and in an Aβ1-42-induced SH-SY5Y cell model, nobiletin increased HSD17B1 expression at both the mRNA and protein levels. Together, these findings support HSD17B1 as an AD-associated and nobiletin-responsive candidate molecular node, highlight a potential connection between nobiletin and neurosteroid-related regulation, and provide an integrated framework for target prioritization and validation in AD.