The clock mutant mouse, which is deficient in a central circadian regulator and displays disrupted circadian control, is associated not only with symptoms of the metabolic syndrome and diabetes, but also with increased sensitivity to the effects of exenatide on the regulation of food intake and weight loss.97 It is possible that effects of exenatide on glucose tolerance and appetite regulation could be associated with an improvement of sleep duration and quality in patients with disordered sleep, with or without diabetes. Here, CLOCK is linked to diabetes mellitus.