G6PD and diabetes mellitus: It can be assumed that the increased expression of the CTH, ANPEP, and G6PD genes in T2D samples compared with non-diabetic ones appear to be adaptive and aimed at replenishing glutathione deficiency in beta cells of diabetics: CTH and ANPEP supply amino acids such as L-cysteine (CTH and ANPEP) and glycine (ANPEP) for de novo biosynthesis of GSH, whereas G6PD generates NADPH for the reduction of GSSG to GSH.