INS and type 2 diabetes mellitus: Among the promising therapeutic strategies, it was recently demonstrated that melatonin, as the main product of the pineal gland, is considered a broad-spectrum antioxidant, can be applied in pathological conditions such as T2DM, mainly for its regulatory effects on the expression of the glucose transporter gene type 4 (GLUT4), glucose homeostasis and insulin sensitivity (21–23).