Body clock: 'Rush hour' transformation discovered
A pair of "rush hours" every day rapidly change the way tissues throughout the body work, scientists have discovered, the BBC reports.
The animal study, in Proceedings of the National Academy of Sciences, monitored the function of cells, in 12 tissues, through the day.
It found large shifts in activity just before dawn and dusk.
Experts said the findings could help time medication to hit sweet-spots in the body clock.
The body's internal clock is known to drive huge changes - it alters alertness, mood, physical strength and even the risk of a heart attack in a daily rhythm.
A team at the University of Pennsylvania investigated the impact of the time of day on the way DNA functions in experiments on mice.
Every two hours they looked at samples from the kidney, liver, lung, adrenal gland, aorta, brainstem, cerebellum, brown fat, white fat, heart, hypothalamus, lung and skeletal muscle.
They showed that 43% of genes, sections of DNA, involved in protein manufacture altered their activity throughout the day.
Different genes had different activity patterns in different tissues so the research team conservatively estimate that more than half of genes would show daily fluctuations if every tissues type was sampled.
The liver was the most dynamic with 3,186 genes showing a daily pattern compared with just 642 in the hypothalamus.
Two major windows of activity were observed in the study - dawn and dusk.
It is already known that some drugs work better at certain times of the day.
Heart disease is driven by artery-clogging cholesterol, which is mostly made in the liver at night. Taking statins in the evening makes them more effective.
The researchers said 56 of the top 100 selling drugs and nearly half of the World Health Organization's list of essential medicines acted on genes which were now known to have this daily oscillation.
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