A new five-year, $2.7M NIH grant will improve our understanding of how flipped sleeping and eating schedules impact behaviors and hormonal signaling critical to reproductive health.
According to a 2019 report published by the US Bureau of Labor Statistics, 16 percent of workers participated in shift work, with six percent working in the evening, four percent working at night, and the remaining working rotating or split shifts.
Shift work, by definition, disrupts normal sleeping hours, which can interfere with the body’s circadian rhythms and, thus, the regulation of the metabolism and hormones, including hormones related to reproductive health. Furthermore, the Centers for Disease Control and Prevention notes connections between working at night and menstrual disorders, miscarriages, and preterm birth. While the correlations between shift work and reproductive health are clear, scientists are still working to understand the mechanisms contributing to this public health problem.
Sleep cycle disruptions accompanying shift work can also alter eating behaviors. Shift work can lead some to eat meals late at night or early in the morning when metabolic physiology is sub-optimum.
So, what’s the effect, if any, of the combination of mistimed sleep and mistimed food intake on reproductive health?
At the Oregon Institute of Occupational Health Sciences, Associate Professor Matthew Butler recently received a five-year, $2.7M grant from the National Institutes of Health (NIH) to study this question.
In preclinical studies supported by the Institute, Butler and his team found that eating meals during hours typically reserved for sleep reduced fertility in mice by altering mating behaviors and ovulation rhythms. The research team’s data showed that when mice ate during their normal resting period, the timing of the production of hormones that trigger ovulation, which typically occurs at night, was disrupted and could occur at any time of the day. The funding provided by the NIH allows Butler to continue this work and probe deeper into the physiological mechanisms underlying these changes.
“This project focuses on improving our understanding of the integration of light cues and food cues by biological clocks in the brain that trigger mating, ovulation, and related behaviors,” Butler said.
According to Butler, the project has three primary aims. The first is to study the sensitivity of the reproductive functions of male and female mice to disrupted feeding schedules. This will help the team better understand how mistimed feeding affects the reproductive behavior of male and female subjects and the differentiations between the two sexes.
The second aim is to study the integration of food cues with hormone-signaling neuropathways regulated by internal clocks in the brain. In this portion of the study, the team will try to understand how the rhythms of the internal clocks that regulate the production of hormones related to reproduction respond to daytime and nighttime feeding.
The final objective will address the driving factors of reproductive behaviors observed in previous studies—i.e., do the altered behaviors result from a mismatch between eating and rest cycles or the converse, and which of the observed factors has the dominant effect? Butler notes that by understanding the dynamics at play, it may be possible to improve reproductive health.
“I think the primary contribution this study will provide is a better understanding of how the timing of light and food intake affects the circuitry regulating hormones associated with reproductive health and behavior,” Butler said. “Ultimately, the goal of this work is to get to a point where we can take what we’re learning about the timing of food intake and apply it in clinical studies conducted by fertility researchers.”
There is much we still need to learn about the impact of shift work on human health and well-being. Shift work and its effects on reproductive health is one arena where many questions remain unanswered. At the Oregon Institute of Occupational Health Sciences, researchers, including Butler and his team, work to improve our understanding of the physiological mechanisms, behaviors, and other factors that lay the foundation for future solutions to pressing health issues.
