By awarding three american scientists – Jeffrey Hall, Michael Rosbach, and Michael Young for their work on the genes of the internal biological clock, the Nobel prize for Medicine in 2017 also brings a boost welcome to the work is often confidential, conducted in the field of chronotherapeutics
However, taking into account biological rhythms, including the circadian rhythm based on the alternation day-night, brings real perspective in human medicine, as evidenced by two recent examples. In Parkinson’s disease, an american team showed that exposure to twice-daily patients to a strong light improving sleep disturbances and reduced daytime sleepiness, near-constant in this pathology, also improving their general state. This effect may be a resynchronization of circadian rhythms, very disturbed in this disease. As another example, a team of lille has recently shown that the myocardial infarction after aortic valve surgery were less frequent when the intervention took place in the afternoon and not the morning, some of the adverse biological responses of the heart muscle dependent on the internal clock. Figaro Infographics what is the internal clock? “We see three times more myocardial infarction in the early morning than the rest of the time, because their occurrence is associated with variations in blood pressure that rises in the end of the night” professor Pierre Boutouyrie, cardiologist (HEGP, Paris, and Inserm) Present in each cell, this clock generates the physiological rhythms of approximately 24 hours (circadian). Still it is necessary that they are all synchronized. It is the role of the central clock and “donors of time” of which the main one is the light of the day, which, by the retina, stimulates a small area in the center of the brain, the nucleus suprachiamatique, true conductor of the time inside.
It is he who sends the “top” throughout the body by the autonomic nervous system and the secretion of cyclic hormones: melatonin, whose production by the pineal gland is maximal during the night, and cortisol, whose production by the adrenals begins to increase shortly before the awakening. Other synchronizers are also, as the alternation of rest/activity, time, meals, social life, physical exercise, etc. , total, 20% to 40% of biological molecules produced by the body will vary more or less according to a circadian rhythm. ” READ ALSO – waking too early disrupt the metabolism doctors have long found that certain disorders were also contingent upon the time of day.
“We see three times more myocardial infarction in the early morning than the rest of the time, because their occurrence is associated with variations in blood pressure that rises in the end of the night,” explains professor Pierre Boutouyrie, cardiologist (HEGP, Paris, and Inserm).
The pain in of inflammatory diseases, such as rheumatoid arthritis, are more acute at night. In occupational medicine, the long-term impact of the shift work or night work, disrupt the circadian cycle, that promotes the occurrence of cancers. The same is true for inflammatory diseases. “The immune system responds to on a circadian rhythm.
The number of lymphocytes or of macrophages varies according to the circadian rhythm, as is the ability of these cells to infiltrate the tissue or to produce molecules with anti-bacterial,” says researcher Hélène Duez (Inserm, IP-Lille).
Circadian rhythms: healing the key?When the internal clock is disturbed, it can try to resynchronize.
This is what is done in sleep disorders, by encouraging the patients to improve the timing of their internal clock by differences in light exposure day-and-night and cycle activity/rest more marked. Bright light therapy has antidepressant effects well-known.
In the severe psychiatric disorders, the intervention on the circadian rhythms can go further: the sleep deprivation is under control, at the hospital, has a powerful antidepressant effect, albeit transitory. ” ALSO READ – best tips to sleep well You could also try to rely on the changes in biological circadian to increase the effectiveness of treatments or reduce their toxicity.
But, to be active, a drug must reach its target in the right dose, after a series of transformations, mainly in the liver and the blood, of biological molecules, some of which have a circadian rhythm.
It is far from simple. Thus, corticosteroids are more effective and better tolerated in the morning, probably because of the rhythm of cortisol, including the peak secretion is between 7 and 9 o’clock. “It is known that antihypertensive drugs, such as the sartans, are more effective in the evening than in the morning, but we do not know very well why,” says the Pr Boutouyrie. A lot of nonsteroidal anti-inflammatory drugs are better tolerated in the evening.. .. It is the cancer that chronotherapeutics is the most promising, with interesting results, in particular in colorectal cancer.
But the goal – to customize the treatment to the characteristics of each sick – still requires much progress. . .