Our study also indicated that the metformin treatment successfully enhances hippocampal neuron survival and promotes hippocampal-dependent learning and memory in the HFS diet-induced T2D rats by altering the expression of Ntrk2, Irs1, Gsk3b, Bcl2, Map2k1, and Grin1 genes. The gene discussed is IRS1; the disease is type 2 diabetes mellitus.