This study stratified early-stage T2DM patients (disease duration ≤5 years, fasting C-peptide >0.8 ng/mL) by baseline C-peptide levels, justified by its correlation with IR and unique advantages: 1) Resilience to β-cell functional heterogeneity; 2) Superior stability over HOMA-IR assays; 3) Methodological extensibility to insulin-treated populations. The gene discussed is INS; the disease is type 2 diabetes mellitus.