SFRP5 and type 2 diabetes mellitus: Increasing evidence shows that adipokine abnormalities are involved in OSA.8, 9, 10 As an adipokine, secreted frizzled-related protein 5 (Sfrp5) is highly expressed in white adipose tissue.11, 12, 13, 14 Sfrp5 is associated with IR, T2DM and coronary artery diseases, and even represents a potential therapeutic target for abnormal glucose homeostasis.11, 15, 16, 17, 18 In addition, Sfrp5 expression is down-regulated under conditions of oxidative stress,19 which are frequently present in OSA during sleeping because of intermittent hypoxia.20