Organophosphate flame retardants and incident type 2 diabetes: Integrating population evidence, mechanistic insights, and effect modification by healthy lifestyle.

Higher exposure to organophosphate flame retardants (OPFRs) may contribute to type 2 diabetes mellitus (T2DM), but prospective evidence, lifestyle modification, and biological plausibility remain insufficiently characterized. We conducted a nested case-control study within the Henan Rural Cohort to evaluate associations between OPFRs exposure and incident T2DM. Cox models, WQS, QGC, BKMR, and an adaptive elastic-net-based environmental risk score were used to assess single and mixed OPFRs exposure. Baseline and trajectory-based healthy lifestyle scores were applied to evaluate joint effects, and signed Wald χ² decomposition quantified contributions of OPFRs and lifestyle domains. Mechanistic evidence was integrated from in vitro experiments and toxicogenomic analyses, including RNA-sequencing, network toxicology, molecular docking, and GEO re-analysis, to evaluate EGFR-related signaling and build an integrative adverse outcome pathway. Higher urinary OPFRs, particularly TPHP, were associated with increased T2DM risk, and OPFRs mixtures showed a linear dose-response relationship with T2DM risk. High OPFRs exposure combined with unhealthy or deteriorating lifestyle trajectories conferred the greatest risk, with OPFRs plus lifestyle explaining 55.36% of total model χ². In HepG2 cells, TPHP impaired glucose consumption and downregulated EGFR, whereas EGFR overexpression alleviated the TPHP-associated abnormal glucose consumption. EGFR overexpression was confirmed at both mRNA and protein levels. The p-AKT/total AKT results provided supportive evidence of AKT-related signaling changes, whereas total GLUT2 protein abundance was not significantly altered. Molecular docking supported potential TPHP-EGFR binding affinity of -8.5 kcal/mol, and GEO analyses provided external supportive evidence that EGFR expression tended to be higher in healthier lifestyle-related conditions. These findings suggest that mixed OPFRs exposure, dominated by TPHP, was associated with higher incident T2DM risk, partly attenuated by healthier lifestyle trajectories, supporting combined exposure-reduction and lifestyle-based prevention strategies.