Mealtime is dictated by the brain but also by an internal clock

Oct 25, 2006 14:23 GMT  ·  By

Researchers found that suprachiasmatic nucleus (SCN), a site in the brain that contains light entrained circadian clock (that dictate the life rhythm between day and night), regulates processes like cell division, reproductive cycles, sleep, and feeding. A second internal non neuronal circadian system - entrained by meal feeding - regulates metabolism and behavior.

French and German researchers have recently identifies a gene, called Period 2, crucial for the neural circadian clock, especially for anticipation of mealtime, according to daylight. When the brain daily schedules meal time, this resets the physiological timing of the internal organs, including the liver, in order to optimize the feeding process.

Recent researches revealed rhythmic clock gene expressions in many non-neural tissues such as liver. So, there is a functionally important internal circadian clock, outside the central nervous system, which reacts to food intake, not to light and is independent of the nervous system activity, but its molecular mechanism remains unknown.

Anticipatory periods of locomotor or gland activity and changes in body temperature optimize the organism in order to improve digestion and energy usage. The interaction between the two systems seems to be crucial for the capacity of organisms to synchronize their internal physiology. The French-German team has found the first evidence that just one gene mutation can let the mice without their neural circadian feeding clock.

This lack of meal anticipation at behavioral and physiological levels is specifically associated with a mutation in the Period 2 gene. But - interestingly enough - the non neuronal clock is not touched by the Period 2 mutation, so this gene does not affect the physiological coordination outside the central nervous system of the circadian feeding clock.

This genetic finding will eventually lead to the exact localization of the brain's center involved in food anticipation. Moreover, scientists are interested to see how this center inter-reacts with other brain regions responsible for other behaviors, like learning, memory, and the experience of pleasure. This is also expected to improve therapies against disorders provoked by disturbed circadian system, such as sleep problems, eating disorders, obesity, and depression.