Exposure to BPA during pregnancy may result in changes in circadian rhythms

Exposure to bisphenol A (widely used chemical) during pregnancy, even at levels below the level of "safe" exposure regulated in humans, may cause changes in circadian rhythm, according to a study on mice presented Monday at the ENDO 2019, Annual Meeting of the Endocrine Society in New Orleans, Louisiana. The researchers reported that these changes could be a contributing factor to the hyperactivity seen in mice exposed to BPA.

"The hypothalamus, which we have identified as a region of the brain particularly susceptible to being disrupted by BPA, contains the site of the clock cells that regulate daily rhythms throughout the body," he said. said researcher Deborah Kurrasch, Ph.D., badociate professor. at the University of Calgary in Calgary, Canada. "We have shown in previous research that exposure to BPA in utero could cause defects in the development of hypothalamic nuclei and hyperactivity, and here we have sought to find out if a change in circadian biology could explain why the animals were moving further. "

BPA is a chemical added to many commercial products, including water bottles, paper containers, can liners and food storage containers. It is a chemical that disrupts the endocrine system – a chemical that interferes with the body's hormones.

Numerous animal and human epidemiological studies have demonstrated a link between BPA exposure and adverse health effects, noted Kurrasch. "Despite this considerable scientific evidence, government agencies around the world, including the United States, Canada, and Europe, say that BPA is safe," she said. One of the reasons for this disparity is the lack of evidence that BPA can affect brain development. "We wanted to provide this proof," she said.

The study started with two groups of pregnant mice. One group ate regular food while the second group ate foods containing low doses of BPA. Babies from these mice were grown up to 12 weeks of age, then separated and housed separately in a specialized light-controlled environment. Their sleep / wake cycle and activity were closely monitored for four months.

The baby mice were kept in a 12-hour light and 12-hour night cycle for four weeks, and a 24-hour night cycle for another four weeks. During the 24-hour dark cycle, the puppies were subjected to light pulses in order to examine their ability to adjust their rhythms in response to unexpected stimuli.

The researchers found that pups of mice exposed to low doses of BPA during gestation were significantly more active during semi-light and semi-dark periods, especially during the last third of the dark period. Disturbances in circadian rhythms were exaggerated in the 24-hour dark cycle.

Puppies exposed to BPA seem to adapt more quickly to new conditions, both when switching from darkness to total darkness to total darkness, and in response to short-term light impulses during the full cycle of darkness.

Mice exposed to BPA showed changes in their daily habits and activity schedule, indicating a disturbance of circadian signaling. The researchers also observed that these effects were more pronounced when animals were placed in the dark by 24 hours.

"Overall, we conclude that exposure to low dose gestational BPA alters circadian rhythms under various conditions and that this may contribute to the hyperactivity seen in BPA-exposed mice." Kurrasch said.