Systems analysis of steroid induced osteonecrosis shows role for heme and vitamin D in pathogenesis

Abstract

ObjectiveFemoral Head Osteonecrosis (FHO) which includes Steroid-induced FHO (SFHO) is a debilitating disease. Though extensively studied the mechanisms have remained elusive. Hence systems analysis is carried out to identify a potential mechanism, biomarkers and therapeutic targets. DesignGene Set Enrichment Analysis (GSEA) and clustering analysis were performed on GEO data sets. A Cofactor-protein interaction network was generated and pathway analysis was performed. Followed by the generation of an integrated network model. Metabolic data were analyzed using MetaboAnalyst. ADMET analysis of steroids was carried out. ResultsSystems analyses based on GSEA, Pathway clustering and Cofactor gene network showed that the enriched pathways namely Steroid, Cholesterol, Vitamin D and heme metabolism could be regulated by Vitamin B6, B12, and heme cofactors. The integrated network model showed CYP450 genes which are critical for bioactivation of Vitamin D and clearing of xenobiotic steroid metabolites which are implicated in SFHO. Analysis of transcription factors and upstream kinome showed a role for HNF4A, SREBP and GSK3b in the pathogenesis. ADMET analysis identified CYP3A4 in SFHO associated steroid clearance. Vitamin D modulated genes CBS and CYP3A4 are downregulated in SFHO potentially due to deregulated vitamin D metabolism. GSEA analysis of steroid-treated osteoblasts and cartilage show enrichment of adipogenesis, cholesterol, xenobiotic metabolism, etc. ConclusionTaken together our analysis reveals the molecular signatures associated with the disease and identifies a critical role for vitamin D, B6, B12 and heme metabolism. Low B6, B12 modulate homocysteine levels and osteoclastogenesis, while compromised heme metabolism modulate CYP450s mediated steroid clearance, Vitamin D bioactivation and influence osteoblastogenesis. Thus steroids orchestrate the events that might influence disease pathogenesis by modulating bone remodeling and thrombosis. Furthermore, our work has implications for the protection of COVID-19 patients from osteonecrosis who underwent steroid therapy.