In utero circadian changes; facing light pollution
Introduction
During gestation, the fetus follows a strict program that allows development and a successful transition to the extrauterine life, to which maternal circadian signals play a key role not only in the precise daily delivery of oxygen, nutrients, hormones and biophysical signals but also allowing fine coordination of the fetus with the external photoperiod. However, when the circadian signals from the mother to the fetus are interrupted or altered, the synchrony between the fetus and its mother disappear and detrimental effects are observed in fetal growth/development and postnatal physiology.
The evidence available suggests that maternal chronodisruption unsettles the fetal circadian system. Moreover, maternal chronodisruption in murine models (pregnant rats exposed to chronic photoperiod shift -CPS-), induces disarray of the circadian system in the adult offspring. The outcome is alterations in metabolic and cardiovascular physiology and lack of melatonin circadian rhythm [1, 2, 3, 4,5•,6], as seen in Non-Communicable Diseases (NCD) that infringe our modern society.
Section snippets
Circadian clocks
Life in the earth evolved predictively to accommodate the individual’s physiology and behavior to daily day/night changes induced by our planet rotation. In the mammals, the result is a marvelous mechanism in which integrated systems of biological clocks oscillate with a period close to a day (circa dies, 24 hours). Such clocks drive circadian rhythms at the cellular and systemic level, generating an internal temporal order in physiological functions tuned to the external environment.
The maternal circadian system
During pregnancy, maternal physiology changes to fulfill the increasing metabolic demands of the fetus, provide input for timely parturition and finally providing food and care for the newborn. As a result, the cardiorespiratory system, immune system, renal, hepatic and gastrointestinal function, and endocrine system differ from that of non-pregnant women [8,15]. The circadian system is not an exception. Compelling evidence support that a functional reorganization of the circadian system occur
Fetal circadian system
There is ample evidence that the fetus has a circadian system, based on the expression of clock genes, in several fetal tissues in ex vivo and in vivo condition (Review in Refs. [8,26]), persistence of these oscillations in vitro experiments [27,29,30] and presence the circadian rhythms in utero such as fetal movements (human, sheep), fetal breathing (sheep), plasma hormones (prolactin sheep, adrenal steroids fetal rat, human and nom human primates) (Review in Refs. [8,26]). Importantly, these
Long-term effects of gestational chronodisruption on the offspring
Epidemiological and experimental research studies call attention to the effect on the offspring of maternal chronodisruption induced by shift work during pregnancy. Shift work may disrupt the maternal melatonin rhythm and impose abnormal maternal sleep and feeding patterns. Epidemiological studies in women show that shift work increases the risks of spontaneous abortion, premature delivery and low birth weight babies (reviewed in Refs. [19••,38, 39, 40]). Meanwhile, in the rat, simulated shift
Conflict of interest statement
Nothing declared.
References and recommended reading
Papers of particular interest, published within the period of review, have been highlighted as:
• of special interest
•• of outstanding interest
Acknowledgement
This work was supported by Grants 1191207 (CTF) and 11170245 (NM) from Fondo Nacional de Desarrollo Científico y Tecnológico, Chile (FONDECYT).
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