(AFP) – Throughout a 24-hour day, the functioning of our body varies. Deeply embedded in us, this biological clock is better and better known, to the point that some doctors now want to use it as a lever in the face of many diseases.
“There is a set of clocks in the body which are there to optimize its functioning: this is called the circadian system”, sums up Claude Gronfier, researcher at the National Institute of Health and of medical research (Inserm), a French public research organization dedicated to human health.
Their existence has been known for a long time. For several decades, research has shown that our organs are more or less active over the course of 24 hours; our intestine, our liver, our heart are inclined to work harder at certain times, regardless of the rhythm of meals or physical activity.
At the same time, research carried out on animals and then humans has shown that this rhythm was not only a response to the outside world, such as the succession of day and night. It is inscribed in our cells, starting with the neurons of the brain.
But if this research was already sufficiently advanced to earn a Nobel Prize in Medicine for three researchers in 2017, it has accelerated further in recent years to, in particular, show how this clock is found in the cells of our entire body.
“There are clocks in the liver, in the heart, in the lung, in the kidney, in the retina…”, lists Mr. Gronfier.
– Understanding pain –
And one does not stop noticing that these clocks have very varied effects. A study led by Claude Gronfier, published this summer in the journal Brain, thus suggests that the perception of pain varies in intensity over the course of 24 hours.
During this work, twelve men were isolated from virtually all external stimulation for almost a day and a half, and exposed every two hours to a heated probe. Their pain threshold varied systematically over time.
For the researcher, this is a crucial step towards a better understanding of pain. One day, he suggests, we might manage to better treat it by taking into account its fluctuations during the day.
The researcher joins a larger school. For some researchers and doctors, we now know these rhythms well enough to use them in the face of many diseases.
This is “chronotherapy” or “circadian medicine”. For its promoters, the applications would be very varied, from oncology to cardiology via neurology.
In Alzheimer’s or Parkinson’s diseases, for example, the disruption of the biological clock is well known. But we now realize that it often precedes the symptoms and might, therefore, be a preventable cause rather than a consequence.
– Clock disorder –
Nevertheless, in general, “we are still challenged to put into practice in the medical world this knowledge on the role of circadian clocks”, warned last year the researchers Ravi Allada and Joseph Bass, in an inventory published in the New England Journal of Medicine.
There is therefore a lack of techniques that would allow a doctor to easily diagnose a disruption of the biological clock and, therefore, to advise a patient in a targeted manner to change his rhythm of life in order to avoid health problems.
Other avenues risk colliding with reality, such as the idea, certainly defended with enthusiasm by Claude Gronfier, of taking into account the time of day to administer chemotherapy to a cancer patient.
“Let’s imagine that a trial shows that the treatment must be administered between 10 p.m. and 8 a.m.: that will cause small organizational problems”, the chemo being given under infusion at the hospital, warns with the AFP oncologist Pierre Saintigny.
“We already live in a world, at least in France, where the health system is on the verge of breaking up,” he continues. “You would really have to be very convincing to drastically change an organization where there is already enormous pressure.”
It is therefore not only necessary that an effect be proven, but that it “has a major impact on the response to treatment and the survival of patients”, concludes Mr. Saintigny, believing that studies are currently insufficient in this area.
