Exploration of the relationship between nicotinamide metabolism-related genes and osteoarthritis

Abstract

Objective·To explore the relationship between osteoarthritis and nicotinamide metabolism-related genes using bioinformatics analysis, and identify key genes with diagnostic value and therapeutic potential.Methods·By using "Osteoarthritis" as a search term, GSE12021, GSE55235, and GSE55457 were obtained from the GEO database, with GSE55457 being used as the validation set. After removing batch effects from the GSE12021 and GSE55235 datasets, the standardized combined dataset was obtained and used as the training dataset. Differentially expressed genes (DEGs) were identified from the training dataset. All nicotinamide metabolism-related genes (NMRGs) were obtained from the GeneCards and MSigDB databases. The intersection of DEGs and NMRGs was taken to obtain nicotinamide metabolism-related differentially expressed genes (NMRDEGs). Gene set enrichment analysis (GSEA) was performed on the training dataset, while gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) analysis were performed on NMRDEGs. Key genes were selected by using least absolute shrinkage and selection operator (LASSO) and support vector machine (SVM) analysis in NMRDEGs to build an osteoarthritis diagnosis model which was validated by using the GSE55457 dataset. Single sample gene set enrichment analysis (ssGSEA) was used to analyze the immune cell infiltration type. Interactions networks and drug molecule predictions were obtained for these key genes' mRNA with the DGIdb, ENCORI, and CHIPBase databases. siRNA was used to knock down the key genes in chondrocytes, and then real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of chondrogenesis-related genes.Results·Seven NMRDEGs, including NAMPT, TIPARP, were discovered. GO and KEGG analysis enriched some signaling pathways, such as nuclear factor-κB signaling pathway and positive regulation of interleukin-1-mediated signaling pathway. GSEA enriched pathways such as Hif1 Tfpathway and syndecan 1 pathway. Key genes NPAS2, TIPARP, and NAMPT were identified through LASSO and SVM analysis, and used to construct an osteoarthritis diagnostic model. The validated results showed that the diagnostic model had high accuracy. Immune infiltration analysis results obtained by ssGSEA showed significant differences (all P10, 19 transcription factors with upstream and downstream >7, and 27 RNA binding proteins with clusterNum >19. The results of RT-qPCR showed that knocking down key genes reduced the expression of chondrogenesis-related genes.Conclusion·Through bioinformatics analysis, key genes related to nicotinamide metabolism, NPAS2, TIPARP, and NAMPT, are discovered, and an osteoarthritis diagnostic model is constructed.

Keywords

• osteoarthritis
• nicotinamide metabolism
• bioinformatics
• diagnostic model
• nomogram