Even when isolated from light, our bodies have an internal clock that follows a 24-hour cycle – this is called the circadian rhythm.
These circadian fluctuations in our energy availability are tied to alternating light/dark and wake/sleep cycles. Disturbing this natural rhythm – as seen with nurses, pilots, subway drivers and other rotational shift workers – often carries significant long-term health costs.
Scientists have long thought that our daily internal timekeeping was linked to DNA and cyclical gene activity. But now, a new Nature study shows that our red blood cells can keep perfect time without any DNA.
Specifically, scientists have assumed that our bodies' natural 24-hour cycle was determined by the feedback loop involving transcription: the production of RNA from DNA.
To test this assumption, University of Cambridge researchers decided to examine red blood cells (RBCs) – which, unlike many cells in the body, don't have organelles and thus don't carry any DNA and are transcription-free.
They took RBCs from healthy people and incubated them in the dark and at body temperature. And they found that the enzymes that help regulate RBCs were controlling activity on a self-sustained 24-hour cycle.
Our RBCs carry within them, our biological circadian clock.
"The implications of this for health are manifold. We already know that disrupted clocks... are associated with metabolic disorders such as diabetes, mental health problems and even cancer," says study author Akhilesh Reddy. "By furthering our knowledge of how the 24-hour clock in cells works, we hope that the links... will be made clearer.”
Many scientific studies have found links between working irregular hours and a greater likelihood of developing diabetes, heart disease and obesity. Sleep disruption is also associated with mental illnesses such as depression and bipolar disorder.
A team of scientists said last year they had used experimental drugs being developed by Pfizer to reset body clocks of mice in a lab – opening up the possibility that drugs might in future be developed to restore rhythms to people whose body clocks have been messed up.
Relatedly, Reddy also authored another paper in the same journal that showed further evidence that this 24-hour cycle doesn’t depend on gene activity. They found the circadian cycle in green algae (Ostreococcus tauri) – even after their DNA were inactivated by darkness.
Image: Clocks by Leo Reynolds via Flickr