Integrative Multi-Omics-Informed Analysis Identifies Insulin Therapy-Associated Loci Implicated in Osteoarthritis...

Integrative genetic approaches can combine Mendelian randomization, variant annotation, pathway-level interpretation, and exploratory cellular measurements to investigate complex disease mechanisms. However, the relationship between genetic liability to insulin medication use and osteoarthritis (OA) remains incompletely characterized GWAS summary statistics for insulin medication use were obtained from the UK Biobank insulin medication-use dataset. Insulin therapy-associated SNPs were selected using a suggestive significance threshold (p < 5 × 10^-6) and clumped (r² < 0.001, 10,000 kb). Two-sample Mendelian randomization (MR) was performed using the inverse-variance weighted (IVW) method as the primary analysis, supplemented by MR-Egger, weighted median, simple mode, and weighted mode methods. Sensitivity analyses included Cochran's Q test, MR-Egger intercept, MR-PRESSO global test, and leave-one-out analysis. Insulin-associated genetic variants were functionally annotated using Ensembl VEP, ANNOVAR, FUMA, and Open Targets Genetics, and mapped genes were subjected to exploratory GO biological process and KEGG pathway enrichment analysis. A separate exploratory cellular experiment was performed in the immortalized human chondrocyte cell line TC28a2 using insulin treatment followed by Safranin O staining, RT-qPCR, western blotting, and ELISA. After SNP selection and harmonization, 56 instrument-outcome associations were retained, comprising 29 SNPs in the ukb-a-106 OA dataset and 27 SNPs in the ukb-b-14,486 OA dataset. IVW analysis suggested an association between genetic liability to insulin medication use and increased OA susceptibility (ukb-a-106: OR = 1.195, 95% CI = 1.062-1.344, p = 0.003; ukb-b-14,486: OR = 1.179, 95% CI = 1.066-1.305, p = 0.001). Sensitivity tests did not detect statistically significant heterogeneity or directional horizontal pleiotropy; however, indication-related genetic liability, correlated pleiotropy, and biologically plausible alternative pathways remain important concerns. Seven mapped genes were used for exploratory enrichment analysis. In a separate exploratory cellular experiment, insulin-treated TC28a2 cells under high-glucose conditions showed reduced proteoglycan staining, increased matrix-degrading and inflammatory markers, and reduced NRF2 protein expression. This study suggests an association between genetic liability to insulin medication use and OA susceptibility and provides exploratory functional-annotation and cellular observations for further investigation.