**Background:** Alzheimer's disease (AD) is a common neurodegenerative disease with insidious onset, making early diagnosis difficult. Mitophagy, the selective autophagic removal of dysfunctional mitochondria, is crucial for neuronal health, and its dysfunction is implicated in AD. However, no study had systematically identified mitophagy-related diagnostic biomarkers for AD. This study aimed to screen mitophagy-related genes with diagnostic potential and construct a diagnostic prediction model.
**Methods:** The AD gene expression profile GSE63061 was downloaded from GEO. After normalization, protein-coding genes were extracted and compared with 137 mitophagy-related genes obtained from databases (Pathway Unification, GO, KEGG, MSigDB) and literature. Differentially expressed mitophagy-related genes (DE-MRGs) were identified using limma (|log2FC| >1, FDR <0.05, p<0.05). Functional enrichment (GO/KEGG), PPI network analysis (STRING, Cytoscape MCODE), and WGCNA (on GSE122063, 56 AD, 44 controls) were performed. Overlapping genes from PPI hub genes and WGCNA core modules were identified. Machine learning methods—univariate analysis, random forest, LASSO regression (λ=0.02, R²=0.80), and SVM classification—were used to select diagnostic markers. Multivariate logistic regression established the final diagnostic model. Model performance was evaluated by ROC curves (GSE122063 and GSE63061 as validation sets), nomogram, C-index, and calibration curves. Expression of key genes was validated in independent datasets (GSE63060, GSE5281), an AD cell model (SH-SY5Y + Aβ25-35, 25 μM), and peripheral blood from 10 AD patients and 10 healthy controls via RT-qPCR.
**Key Results:** From 114 overlapping mitophagy-related genes in GSE63061, 72 DE-MRGs were identified (63 upregulated, 9 downregulated). Top upregulated genes included UBC (logFC=3.90), UBB (logFC=3.58), TSPO (logFC=3.28); top downregulated included TOMM20 (logFC=-3.91), MAP1LC3B (logFC=-3.85), TOMM40 (logFC=-3.82). GO/KEGG enrichment showed involvement in autophagy, apoptosis, NF-κB signaling, ferroptosis, and neurological diseases. PPI analysis yielded 33 hub genes; WGCNA identified the turquoise module (576 genes) as most correlated with AD (r=-0.81, p=6e-08). Five overlapping genes (DNM1L, OPTN, PTGS2, TOMM20, VDAC1) were identified. Univariate analysis and random forest (accuracy 100% training, 73.3% test, F1=84.6%) selected OPTN, PTGS2, TOMM20, and VDAC1. LASSO and SVM (100% accuracy in both training and test sets, SVM-ROC AUC=100%) confirmed these four genes. Multivariate logistic regression yielded the diagnostic formula: y = 1.231 + 0.033×OPTN + 0.032×VDAC1 - 0.135×PTGS2 - 0.048×TOMM20. The model achieved AUC=0.965 in GSE122063 and AUC=0.806 in GSE63061. The nomogram (genes + age) had a C-index of 0.730, with good calibration. Individual gene AUCs in GSE63061 were: VDAC1=0.830, TOMM20=0.784, PTGS2=0.742, OPTN=0.726. GSEA showed these genes are involved in neurodegenerative disease pathways (PD, AD, HD, ALS), neural function, metabolism, and immune pathways. Validation in GSE5281 (brain tissue), GSE63060 (peripheral blood), AD cell model, and clinical blood samples confirmed consistent expression patterns: OPTN and VDAC1 upregulated, PTGS2 and TOMM20 downregulated in AD (all p<0.05).
**Clinical Implications:** This study provides a novel diagnostic prediction model based on four mitophagy-related genes (OPTN, PTGS2, TOMM20, VDAC1) that can be measured in peripheral blood, offering a non-invasive approach to aid early AD diagnosis. The consistent expression trends between brain tissue and peripheral blood support blood-based diagnostics. The model may help guide clinical decision-making and provide new therapeutic targets. However, limitations include lack of protein-level validation, absence of animal model confirmation, and the need for model updates as mitophagy gene databases expand.