INS and type 2 diabetes mellitus: The T2DM and PreDM groups were significantly older (p < 0.001 for both groups), and had significantly higher fasting plasma (fP) glucose (p < 0.001 for both groups), HbA1c (p < 0.001 for both groups), fasting serum (fS) insulin and HOMA-IR compared to the NG group.