Insulin resistance genetic susceptibility drives pulmonary arterial hypertension through monocyte metabolic reprogramming and immune dysregulation

Background Pulmonary arterial hypertension (PAH) is a progressive vasculopathy with significant mortality. Insulin resistance (IR), a central component of metabolic dysregulation, is an emerging risk factor in PAH, yet the specific cell types mediating its genetic risk and underlying molecular mechanisms remain elusive. Purpose This study aims to elucidate the role of IR genetic susceptibility in promoting PAH development through an integrated multi-omics approach. Methods We analyzed bulk RNA-seq (GSE113439: training, 15 PAH/11 controls; GSE15197: validation, 18 PAH/13 controls), single-cell RNA-seq (scRNA-seq) (GSE210248: 3 PAH/3 controls), and Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) GWAS data (ebi-a-GCST005179: 37037 Europeans). The scPagwas algorithm mapped HOMA-IR genetic associations to scRNA-seq to identify key cell types. Key cells were characterized for metabolism, cell-cell communication, heterogeneity/pseudotime trajectory, and transcriptional regulation. Key cell-specific gene modules were identified. Differentially expressed genes from bulk RNA-seq data were intersected with key cell-related and HOMA-IR-associated genes to derive candidates. Biomarkers were progressively identified through a multi-step procedure encompassing machine learning, expression level validation, and receiver operating characteristic analysis. A diagnostic nomogram was built. Functional enrichment, immune infiltration, regulatory networks, and drug prediction with molecular docking were performed. Results Monocytes showed the strongest genetic association with HOMA-IR. In PAH, they underwent metabolic reprogramming characterized by upregulation of oxidative phosphorylation and downregulation of pentose phosphate pathway, exhibited enhanced communication with several key cell types (including dendritic cells via IL1B-IL1R2, natural killer cells via HLA-E-KLRC1, and endothelial cells via CXCL8-ACKR1), and displayed skewed differentiation toward macrophage-like states. Multi-omics integration and machine learning identified ALDH9A1 and SPOP as consistently overexpressed diagnostic biomarkers. Their combined nomogram achieved powerful and reliable diagnostic power (AUC=0.949). Both genes were linked to RNA/polyamine metabolism and correlated with altered immune infiltration. Shared upstream regulators (JUN, SPI1; hsa-miR-765, -191-3p) were predicted. Paclitaxel and camptothecin were nominated as potential therapeutic agents. Conclusion This study identifies monocytes as the primary cell type mediating IR-related genetic risk in PAH, nominating ALDH9A1 and SPOP as key diagnostic biomarkers and therapeutic targets associated with metabolic pathways. These findings advance the understanding of PAH immunometabolic mechanisms.