What Makes Your Body Tick

Ticking away inside almost all cells are tiny clocks composed of protein gears. Scientists have known that these molecular clocks govern the daily rhythms of life, from mealtimes and bedtimes to the rise and fall of hormone levels, body temperature and blood pressure. New research shows that circadian clocks, as the daily timekeepers are known, do more than just control day-to-day schedules. Such clocks, some scientists say, have the potential to play a role in nearly every biological function as diverse as cellular division and aging.

Some of the new insights come from studying the brain’s master clock, a pair of structures known as the suprachiasmatic nucleus, or SCN, that set the body’s daily rhythms. Other work, meanwhile, suggests that the SCN is not a single monolithic clock but more a set of interrelated nodes that help coordinate clocks throughout the body. And still other researchers have found that the SCN may not even be the ultimate arbiter of the body’s time, and that other organs control biological rhythms on their own without much, if any, help from the SCN.

Think of the SCN as the atomic clock in this network of ATM. Each body cell has its own clock, just as individual cash machines do. And periodically those peripheral clocks check in with a central timekeeper to stay synchronized.

The rhythm of the SCN is set mainly by light, as special cells in the retina relay a message to the brain when they sense daylight. The light cues affect the gears of the molecular clock inside the SCN’s neurons, which then somehow control the cells’ firing rates — the frequency at which neurons zip off electrical messages to other brain cells.
Bonnie - this shows the great importance of getting restful, unobtrusive sleep in a bedroom devoid of any light that may throw off your rhythm.

Scientists have also discovered that the SCN is actually a clock confederation with several different clusters, or nodes. The nodes form a relay team, passing electrical activity from one to another. "One node fires, then the second, third and so on, and then the whole thing is quiet for a few minutes,” researchers say in Journal of Biological Rhythms. Having independent nodes instead of one monolithic clock may make the brain clock more robust and allow it to adjust more quickly to environmental changes.

While many researchers continue to probe the mysteries of the brain clock, others think it gets too much credit for controlling circadian rhythms in the rest of the body. The liver, for instance, who's clock corresponds to mealtimes, works fine without much input from the SCN.

Whichever process is found to be the right one, the results have implications for our health. Many scientists think that one role for circadian clocks is to separate biological processes, such as digesting food and replicating DNA; multitasking such activities at the same time could lead to DNA damage. Having a more crisply defined circadian rhythm could help improve the efficiency of metabolism. A recent study in Cell Metabolism found that high serum triglycerides can be caused by a disrupted circadian rhythm.

Researchers are trying to sharpen circadian rhythms in mice by restricting feeding to certain times of day to see if it will have beneficial effects on health over the long-term. New data from studies of fruit flies also suggest that robust circadian rhythms are one key to a long and healthy life. These results indicate that circadian clocks may help control more than just daily rhythms of life. Researchers are confident that anything that messes up the phase of the clock probably affects aging and life span. After all, circadian rhythms tend to wind down in elderly people and rodents. Further research may suggest ways to reset the health and aging clock. And that, in turn, could underscore yet again the most important lesson of circadian clocks: that timing is everything.
Bonnie - this research correlates with other research showing that calorie restriction in mice increases lifespan dramatically. Eating optimal portions of real food at designated times, with plenty of time in between to digest, throw in the occasional fast/smart detox, along with an optimal sleep pattern, and you are doing your circadian rhythm good.

Excerpts taken from "Keeping Time," by Tina Hesman Saey for Science News