GSS and type 2 diabetes mellitus: The results showed that serum levels of nesfatin-1, GSH, SOD, ADPN and NAGL in T2DM were significantly decreased compared to either in prediabetes (P < 0.001) or in healthy controls (P < 0.001); in contrast, RBP levels in T2DM were significantly elevated (P < 0.001) compared to either in prediabetes or in healthy controls, and this significant elevation exhibited in the prediabetes vs. the healthy (P < 0.001).