Circadian rhythm of glucose tolerance in laboratory mice

Abstract

Mice on a regular light-dark cycle were subjected, at 08.00, 13.00, 20.00 and 01.00 h, to the following assay procedures: Glucose tolerance in both fed and fasted animals; insulin sensitivity in fed animals; liver glycogen assay in fed animals. Feeding activity was also measured at these times. Glucose tolerance did not vary in the fasted groups but showed a single large increase with its peak at 01.00 h in the fed groups. Insulin sensitivity showed lower values in the evening than at other times and the liver showed a pattern of glycogen deposition from 13.00 to 01.00 h and release from 01.00 to 13.00 h. Mid-morning and mid-night peaks of feeding activity were observed. It is suggested that the high glucose tolerance at 01.00 h is due to the coincidence of high glycogen deposition and high insulin activity at this time and that the insulin sensitivity changes are closely related to the liver glycogen cycle. The effects of handling stress on grouped animals are reported and clearly indicate both the hyperglycaemic and the insulin-antagonistic responses to this stress. © 1970 Springer-Verlag.