INS and Insulin resistance: Previous studies performed by our research group have shown that melatonin supplementation (10 mg/kg/day) in the same strain model of diabesity (ZDF rats) improved blood parameters related to glucose tolerance and insulin resistance, such as fasting blood glucose, insulin, insulin resistance index such as HOMA-IR, HOMA1-%B of the β-cell function and adiponectin levels, as well as leptin concentrations [10].