“You will see that after a good night’s sleep you will feel better”. A popular wisdom that could hide truths at a molecular biological level. At night, in fact, the genes that regulate immunity work harder as well as those that supervise the cellular repair mechanisms. It is one of the many pieces of evidence that emerge from a study conducted at the Polytechnic University of Lausanne which appeared on the pages of Science, a research conducted on a database made up of 16,000 samples of human messenger RNA obtained from 914 donors. The paper is quite technical, but its implications are worth trying to understand. The first, as he explains Lorenzo Talamanca, first author of the research, is that this is the first time that the expressions of the genes that make up the biological clock in different human tissues have been studied. “Until now the most complete data related to mouse models, something was known about some tissues – such as muscles or skin – but in humans the molecular activity of the circadian rhythm was not characterized”, explains the biophysicist.
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What is the biological clock
Most of the mammals that inhabit the earth have a rhythm of life that develops around 24 hours, with the alternation of light and dark. Circadian rhythms (from the Latin circa diem, approximately one day) regulate a large variety of metabolic, physiological and behavioral mechanisms. Genetics has made it possible to identify a dozen genes which in mammals are responsible for the circadian oscillations of the whole organism: a few genes which, however, influence thousands of other genes which are expressed at the level of individual tissues. The endogenous circadian oscillators are then continuously synchronized with the 24-hour period of the Earth’s rotation, thanks to the effects of external signals such as light and temperature. A mechanism still poorly defined in humans and which only in recent years has begun to be considered also in its clinical implications with promising results.
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Women have more rhythm
The research conducted by Talamanca has revealed a greater rhythmicity in female fabrics. “For example, the liver of women seems to metabolize drugs more in the morning, this data indicates that for women taking the therapies at a certain time could be more important than for men”, explains the researcher. Another difference is that in the activity of the adrenal glands which in women seems to fluctuate more than in men; this surplus of rhythms in the adrenal glands could be the cause of the more marked oscillations in women in general. The indications that come from the data analyzed at the Lausanne Polytechnic do not have an immediate clinical significance but contribute to the understanding of some evidence, such as that chemotherapy can have a greater effect when administered in the afternoon than in the morning.
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Age differences
The researchers also wanted to see what happens when tissues age. Does the clock always strike with the same intensity or not? “It would seem so, but what changes is the body’s ability to receive signals. This means, for example, that almost all tissues lose part of their rhythms; however, some organs such as the liver, colon and pituitary switch from 24-hour rhythms to 12-hour rhythms. A possible explanation of why older people often feel drowsy after lunch or why they lose their sleep-wake rhythm,” Talamanca points out . With advancing age, the rhythms of cholesterol metabolism detectable in the tissue of the coronary artery are also lost and this could be correlated with the occurrence of heart attacks more prevalently in the elderly and in the morning. “Our contribution aims to raise an important issue: personalized medicine must take into consideration not only the specific genetic or molecular targets but also the circadian rhythms of the tissues on which it acts. A research that needs to be deepened also and above all with a view to gender differences, starting from animal models”, concludes Talamanca.
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