Insulin and glucose regulation at rest and during flight in a Neotropical nectar-feeding bat

A tightly regulated glucose homeostasis is essential for nectar-feeding bats, to manage and avoid hyperglycemia. The role of insulin and the contribution of glycogen reserves during rest periods and the extent of its involvement in blood glucose homeostasis during exercise have not been described yet and was the main objective of this study. Bats ( Anoura caudifer ) were assigned to the following groups: (1) Water and Resting (WR): received water (0.25 mL) and rested for zero, 45 or 90 min; (2) Glucose and Resting (GR): fed with a glucose solution (5.4 g/Kbw) and rested for 45 or 90 min; (3) Glucose and Exercise (GE): fed with a glucose solution (5.4 g/Kbw) and were induced to fly for a total of 45 or 90 min. Oxidative stress and metabolic markers were analyzed in all groups. We also describe morphometric and stereological parameters in pancreas from WR bats. Blood glucose concentrations were increased 45 min after glucose intake in resting bats compared to bats forced to fly and also compared to resting bats which received no glucose. Blood glucose levels after 90 min were the same in all bats, returning to baseline levels in GR bats. Plasma insulin concentrations and liver and muscle glycogen content did not show any differences among groups. Our results provide evidence that insulin secretion seems to play a role on glucose regulation when bats are at rest and that the increased nitric oxide production in the kidneys found in GE90 may contribute to renal protection during exercise.