The ancient clock that rules our lives – and determines our health

October 5, 2017 by Russell Foster, The Conversation
Credit: Vadim Sadovski/Shutterstock

Our lives are ruled by time; we use time to tell us what to do. But the alarm clock that wakes us in the morning or the wristwatch that tells us we are late for supper are unnatural clocks. Our biology answers to a profoundly more ancient beat that probably started to tick early in the evolution of all life.

Embedded within the genes of us, and almost all life on earth, are the instructions for a biological clock that marks the passage of around 24 hours. Biological clocks or "circadian clocks" help time our , alertness, mood, physical strength, blood pressure and much more.

Under normal conditions, we experience a 24-hour pattern of light and dark, and our circadian uses this signal to align biological time to the day and night. The clock is then used to anticipate the differing demands of the 24-hour day and fine-tune physiology and behaviour in advance of the changing conditions. Body temperature drops, blood pressure decreases, cognitive performance drops and tiredness increases in anticipation of going to bed. While before dawn, metabolism is geared-up in anticipation of increased activity when we wake.

A also stops everything happening at the same time, ensuring that biological processes occur in the appropriate sequence. For cells to work properly they need the right materials in the right place at the right time.

Thousands of genes have to be switched on and off in order and in harmony. Proteins, enzymes, fats, carbohydrates, hormones, nucleic acids and other compounds have to be absorbed, broken down, metabolised and produced in a precise time window. Energy has to be obtained and then allocated to growth, reproduction, metabolism, locomotion and cellular repair.

All of these processes, and many others, take energy and all have to be timed to the correct time of the day. Without a clock, our biology would be in chaos.

The pioneering research of Jeffrey Hall, Michael Rosbash and Michael Young – awarded the 2017 Nobel Prize in Physiology or Medicine earlier this week – provided our first clear understanding of how a ticks in any organism; in this case, a fruit fly.

How the clock works

At the heart of the clock is a "negative feedback loop" which consists of the following sequence of events. The produce messages that are translated into proteins. The proteins then interact to form complexes and move from the cytoplasm of the cell into the nucleus and then inhibit their own genes. These inhibitory clock protein complexes are then broken down and the clock genes are then once more free to make more messages and fresh protein – and the cycle continues day after day.

This negative feedback loop generates a near 24-hour rhythm of protein production and degradation that drives the internal biological day.

Based on the findings of Hall, Rosbash and Young in the fruit fly, very similar clock genes were then discovered in mice, humans and many other animals. So the biological clocks that "tick" in us are broadly similar to the clocks found in insects, worms, fish and birds.

We now know that the morning and evening preferences of individuals who describe themselves as either "larks" or "owls" also appear to be related to small changes in some of these clock genes that either speed up or slow down our .

Do not disturb

An understanding of how circadian clocks work and the central role they play in our biology has led to advances in many areas, not least an appreciation that when circadian rhythms are disrupted our overall health and well-being can be severely affected.

Shift workers try to sleep during the day, but sleep is usually shorter and of poorer quality than when sleep occurs at night because, although desperately tired, the circadian system is instructing the body that it should be awake. They then work during the night at a time when the circadian system has prepared the body for sleep, and alertness and performance are low. In effect, they work when they are sleepy and sleep when they are not.

Short-term circadian rhythm disruption can have a big negative impact on memory, problem solving, emotional responses and attention. And years of night-shift work has been shown to increase the risk of heart disease, infection, cancer, type 2 diabetes and obesity. So we ignore our circadian rhythms at our peril.

Circadian rhythm disruption is also a feature shared by some of the most challenging diseases of our time. Sufferers of mental illnesses such as schizophrenia, bipolar disorder and depression; neurological conditions like Alzheimer's, stroke and multiple sclerosis; developmental disorders such as autism; and serious disorders of the eye (including the development of cataracts) all exhibit circadian-rhythm disruption.

The future of circadian rhythms research is to understand how this disruption comes about, and, based on this knowledge, develop new drugs and treatments that will help us regulate internal across the health spectrum. We truly live in exciting times.

Explore further: The Latest: Nobel winner Young: Body clocks are the future

Related Stories

The Latest: Nobel winner Young: Body clocks are the future

October 2, 2017
The Latest on the Nobel Prize in Physiology or Medicine (all times local):

Scientists are unraveling the mystery of your body's clock – and soon may be able to reset it

September 18, 2017
For people who don't get sleepy until 2 a.m., the buzz of an alarm clock can feel mighty oppressive.

Cells in the retina light the way to treating jet lag

April 18, 2017
Researchers have found a new group of cells in the retina that directly affect the biological clock by sending signals to a region of the brain which regulates our daily (circadian) rhythms. This new understanding of how ...

Gut bacteria have own circadian clock

August 8, 2016
The circadian rhythm, or circadian clock, is an internal mechanism that drives the 24-hour cycles that tell our bodies when to sleep, wake and eat — and now, new research has found that bacteria living within the gut ...

ZeitZeiger: Computer tells the time according to your body clock

February 27, 2017
A computer method called ZeitZeiger that uses a sample of blood to accurately predict circadian time - the time of day according to a person's body clock - is described in new research published in the open access journal ...

Recommended for you

Scientists produce human intestinal lining that re-creates living tissue inside organ-chip

February 16, 2018
Investigators have demonstrated how cells of a human intestinal lining created outside an individual's body mirror living tissue when placed inside microengineered Intestine-Chips, opening the door to personalized testing ...

Data wave hits health care

February 16, 2018
Technology used by Facebook, Google and Amazon to turn spoken language into text, recognize faces and target advertising could help doctors fight one of the deadliest infections in American hospitals.

Researcher explains how statistics, neuroscience improve anesthesiology

February 16, 2018
It's intuitive that anesthesia operates in the brain, but the standard protocol among anesthesiologists when monitoring and dosing patients during surgery is to rely on indirect signs of arousal like movement, and changes ...

Team reports progress in pursuit of sickle cell cure

February 16, 2018
Scientists have successfully used gene editing to repair 20 to 40 percent of stem and progenitor cells taken from the peripheral blood of patients with sickle cell disease, according to Rice University bioengineer Gang Bao.

Appetite-controlling molecule could prevent 'rebound' weight gain after dieting

February 15, 2018
Scientists have revealed how mice control their appetite when under stress such as cold temperatures and starvation, according to a new study by Monash University and St Vincent's Institute in Melbourne. The results shed ...

First study of radiation exposure in human gut Organ Chip device offers hope for better radioprotective drugs

February 14, 2018
Chernobyl. Three Mile Island. Fukushima. Accidents at nuclear power plants can potentially cause massive destruction and expose workers and civilians to dangerous levels of radiation that lead to cancerous genetic mutations ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.