Endocrinology. 2020 Feb 26. pii: bqaa028. [Epub ahead of print]
In female mammals, cycles in reproductive function depend both on the biological clock synchronized to the light/dark cycle, and a balance between the negative and positive feedbacks of estradiol whose concentration varies during oocyte maturation. In women, studies report that chronodisruptive environments such as shiftwork, may impair fertility and gestational success. The objective of this study was to explore the effects of shifted light/dark cycles on both the robustness of the estrous cycles and the timing of the preovulatory luteinizing hormone (LH) surge in female mice. When mice were exposed to a single 10 h-phase advance or 10 h-phase delay, the occurrence and timing of the LH surge and estrous cyclicity were recovered at the third estrous cycle. By contrast, when mice were exposed to chronic shifts (successive rotations of 10 h-phase advances for 3 days followed by 10 h-phase delays for 4 days), they exhibited a severely impaired reproductive activity. Most mice had no preovulatory LH surge already at the beginning of the chronic shifts. Furthermore, the gestational success of mice exposed to chronic shifts was reduced since the number of pups was two times lower in shifted as compared to control mice. In conclusion, this study reports that exposure of female mice to a single-phase shift has minor reproductive effects, whereas exposure to chronically disrupted light/dark cycles markedly impairs the occurrence of the preovulatory LH surge, leading to reduced fertility.
Keywords: Circadian disruptionShiftwork; Estrous cycle; Luteinizing Hormone surge