Rats die earlier than humans: study

Washington, Apr 7 (UNI) A rat that grows teeth and bone in one-eighth the time of a human lives faster and dies younger.

A New York University dental professor has discovered a biological clock linking tooth growth to other metabolic processes.

This clock or biological rhythm controls many metabolic functions and is based on the circadian rhythm, which is a roughly 24-hour cycle that is important in determining sleeping and feeding patterns, cell regeneration, and other biological processes in mammals.

The newly discovered rhythm, like the circadian rhythm, originates in the hypothalamus, a region of the brain that functions as the main control center for the autonomic nervous system. But unlike the circadian rhythm, this clock varies from one organism to another, operating on shorter time intervals for small mammals, and longer ones for larger animals. For example, rats have a one-day interval, chimpanzees six, and humans eight.

Reporting his findings at the 37th Annual meeting of the American Association for Dental Research, Dr Bromage said, "The same biological rhythm that controls incremental tooth and bone growth also affects bone and body size and many metabolic processes, including heart and respiration rates." "In fact, the rhythm affects an organism's overall pace of life, and its life span. So, a rat that grows teeth and bone in one-eighth the time of a human also lives faster and dies younger," the Science daily quoted Dr Bromage as saying.

NYU dental professor Dr Timothy Bromage discovered the rhythm while observing incremental growth lines in tooth enamel, which appear much like the annual rings on a tree. He also observed a related pattern of incremental growth in skeletal bone tissue -- the first time such an incremental rhythm has ever been observed in bone.

Future research will also assess whether growth rhythms can be linked to variations in human behaviour.

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