Effects of acute 3-h swimming exercise on insulin secretion capacity of pancreatic islets

This study was conducted to evaluate the influence of acute exercise on insulin secretion capacity and its underlying regulatory mechanisms in isolated pancreatic islets. Two groups of male C57BL/6J mice were assessed: a sedentary control group and a group that was subjected to a single 3-h (hour) period of swimming exercise. Immediately after the swimming exercise, an oral glucose tolerance test (OGTT) was performed and glucose-stimulated insulin secretion was assessed in isolated islets. The expression levels of proteins involved with insulin secretion were also examined in isolated islets. The areas under the curves (AUCs) for plasma insulin in the OGTT did not differ significantly between the control and exercise groups. However, the exercise group exhibited a significantly higher insulin secretion capacity of isolated islets relative to the control group (p < 0.05). Glucose transporter (GLUT)-2 protein, which is the predominant glucose transporter isoform in rodent pancreatic β cells, was expressed at a higher level in the exercise group relative to the control group (p = 0.05), but the expression of other proteins (i.e., markers of autophagy and intracellular Ca2+) were unchanged. These results indicate that the increased insulin secretion capacity following acute exercise is accompanied by increased GLUT-2 protein content.