The periods of sleep and wakefulness are regulated by the circadian rhythm generated by the body’s internal clocks synchronized with a 24-hour period during which changes in light occur. These internal clocks are in charge of regulating various biological processes and functions, such as the secretion of hormones, the digestion of food or reproduction, and also the aforementioned sleep-wake cycles, that is, the moments destined to sleep or be awake performing various activities.
The problem is that clocks can be easily disturbed by exposure to light at night, and shift workers experience this when they have to work at night. Various works have analyzed how this influences health and now a new study carried out with female mice has shown that just four weeks of shift work patterns are enough to alter their biological clock and reduce their fertility.
The research has just been presented at the 25th European Congress of Endocrinology and its results provide scientists with new clues to better understand how circadian disturbances affect female fertility, and could help develop future strategies to prevent fertility problems in women. women who carry out their professional work at non-standard hours.
Disrupting the circadian rhythm reduces reproductive capacity
The ‘master biological clock’ is found in the suprachiasmatic nuclei, a small area of the brain called the hypothalamus, which is also the regulatory center for reproductive function by acting on the pituitary gland – attached to the lower part of the hypothalamus – which It regulates ovarian activity to promote ovulation. Numerous studies in mice and humans have shown that disrupting the circadian rhythm has a negative impact on female reproduction. However, the reasons why it occurred were not well known.
“Understanding the mechanisms by which circadian disruption disrupts reproductive function may pave the way for reducing some of the negative effects of shift work on women’s fertility”
Researchers from the Institute for Cellular and Integrative Neurosciences (INCI) and the University of Strasbourg, France, have previously shown that shift work patterns over several weeks result in a decreased pregnancy rate in female mice. In the new study, the researchers mimicked long-term shift work conditions in female mice by constantly changing the light-dark cycle, moving light exposure back and forth by 10 hours over four weeks, and found that the massive release of the pituitary hormone called luteinizing hormone, which triggers ovulation, was removed, subsequently reducing fertility in these animals.
“The decrease in fertility is due to a disturbance in the master circadian clock that signals to the hypothalamic reproductive circuitry,” said lead researcher Marine Simonneaux. “Specifically, our research shows that four weeks of chronic exposure per shift impairs the transmission of light information from the master biological clock to kisspeptin neurons, known to drive the pre-ovulation or luteinizing hormone surge.”
The researchers’ next goal is to see if additional internal clocks are disturbed after shift work-like patterns change. “The circadian rhythm requires not only the correct functioning of the biological clock pattern, but also the synchronized activity of numerous secondary clocks found in other areas of the brain and peripheral organs, including the reproductive organs,” explained Ms Simonneaux. “Understanding the precise mechanisms by which circadian disruption alters reproductive function is important, as it may pave the way for potential preventive and therapeutic interventions to reduce some of the negative effects of shift work on women’s fertility.”
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