A combination of melatonin and moderate-intensity aerobic exercise improves pancreatic beta-cell function and glycemic homeostasis in type 2 diabetic model of animals

Nocturnal melatonin secretion is important for preservation of s-cell mass and function. Knowing that type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by hyperglycemia caused by the elevated resistance of peripheral tissues to insulin, reduction in pineal melatonin and disturbances of insulin secretion by pancreatic s-cells.  In this context, exercise is considered one of the most valuable non-pharmacological approaches for treatment of T2DM. Considering the beneficial role of melatonin on glycemic metabolism in physical exercise, we investigated the effects of moderate-intensity aerobic exercise plus melatonin on glycemic homeostasis, the morphology and architecture of pancreas in spontaneous T2DM animals [Goto-Kakizaki (GK) rats]. The results confirmed that melatonin alone reduced the mass of epididymal white adipose tissue (WAT); however, only the combination of melatonin and physical exercise significantly reduced caloric intake, body weight, WAT and improved glucose tolerance and insulin sensitivity in T2DM rats. This combination also reduced apoptosis of cells in pancreatic islets. We observed either melatonin or the combination was able to reduce insulinemia. However, only the combination improved the morphology of the pancreatic islets. Thus, we conclude that in GK rats, melatonin plays a crucial role in the functionality of the pancreas to improve insulin sensitivity of peripheral tissues and, consequently, to maintain the glucose homeostasis. In addition, the combination is more efficiency to improve glucose tolerance and integrity of pancreatic islets in GK rats than melatonin alone.