INS and Insulin resistance: Chao et al. [45] compared insulin resistance across four non-genetic T2DM induction models in rats—fructose-rich diet, HFD/STZ, low-dose STZ, and nicotinamide + STZ injection—and concluded that the fructose-rich and HFD/STZ models were most effective at elevating HOMA-IR and showed the lowest responsiveness in the hyperinsulinemic euglycemic clamp test (the gold standard for assessing insulin sensitivity), confirming their ability to induce insulin resistance.