INS and type 2 diabetes mellitus: This study aimed to identify HbA1c thresholds associated with accelerated lipid-driven atherogenesis, quantify the mediating role of the triglyceride-to-HDL cholesterol ratio (TG/HDL-C)-a surrogate of insulin-resistance-related lipid metabolism-and assess the incremental predictive value of the Atherogenic Index of Plasma (AIP) within the clinically ambiguous "glycemic gray zone." A total of 271 adults with T2D not receiving lipid-lowering therapy were retrospectively grouped by HbA1c: good (<7.0%), moderate (7.0%-8.49%), and poor (≥8.5%) control.