Indeed, our results revealed that GSH and SOD levels in the subgroup of T2DM or prediabetes with impaired β-cell insulin secretion were significantly low in comparison to the counterpart with normal insulin action; in addition, serum SOD levels in subgroup of IFG or IFG combined IGT displayed a marked reduction compared to the IGT subgroup. Here, SOD1 is linked to type 2 diabetes mellitus.