The investigators demonstrate a role for the circadian clock proteins, Bmal1 and Clock, in regulating the day-to-day levels of glucose in the blood. Suppressing the action of these molecules eliminates the diurnal variation in glucose and triglyceride levels. In addition, they found that a mutated Clock gene protected mice from diabetes induced by a high-fat diet. Together these findings represent the first molecular insight into how timing of what we eat via the clock can influence metabolism. The findings appear in the November 2 issue of the online journal PLoS Biology.
The master molecular clock in mammals is located in the brain in an area called the suprachiasmatic nucleus, clusters of neurons in the hypothalamus. Many of our basic functions, including regulating body temperature and hormone levels, vary throughout the day and night. Some of these changes may relate to being asleep or awake and on the job, but others are under the control of a biochemical timepiece that sets and resets daily.
Over the last several years, researchers have begun to appreciate that the molecular components of the clock exist in most, if not all, tissues of the body. Some years ago, a team led by senior author Garret FitzGerald, MD, Chairman of Penn's Department of Pharmacology, discovered a molecular clock in the heart and blood vessels and described for the first time how the master clock in the brain could use a hormone to control such a peripheral clock.