SOD1 and type 2 diabetes mellitus: In addition, our qPCR results revealed that the mRNA expression levels of catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) were significantly down-regulated in the testis of T2DM group when compared to control group (Fig. 4), and metformin and ICA treatment both partially restored the mRNA expression levels of CAT, GPx and SOD in the testis of diabetic rats (Fig. 4).