Baby boom for mice requires the lights to be off

Tick, tock, tick, tock……

The clock most women are worried about is the biological clock. Mother Nature only keeps the baby factory open for a short window of time – it is tough to get an education, build a career and conceive a family all before the age of 35.

But, the ticking of the biological clock, is not the only time piece wanna-be Moms need to keep an eye on. Wall clocks are ticking in the fertility game too.

Night owls have bad body chemistry

Countless epidemiological studies show a work schedule, that includes working through the night, is hard on body chemistry.

Most attention focuses on disruptions to body chemistry that result in obesity and the dreaded diseases, but disruptions to the menstrual cycle are a common side effect of shift work. 

A research team from Northwestern have begun to shine the light on how circadian rhythms matter when it comes to reproductive physiology.

Mice mom’s take to the skies

The Northwestern team simulated the shift work typically encountered by flight attendants on the London to New York route and nurses, in a group of mice. Okay, the mice didn’t smile graciously while offering… “Chicken or beef” or administer injections, but the lab residents were never-the-less forced to stay up late, when the research team failed to turn the lights on and off, in sync with the rising and setting of the sun.

The experimental set up started with a little hangy panky for some ordinary lab mice. Once the female mice had been mated, they were allocated into one of three groups.

Group 1 followed the typical day-night cycle. 12 hours of light, followed by 12 hours of dark.

Group 2 and group 3 followed the 12 hour day-night cycle with a little bit of a twist.

• For group 2 : Every 5 days, the lights went on 6 hours earlier (phase advanced group)
• For group 3 : Every 5 days, the lights went off 6 hours later (phase delayed group)

The phase shift happened 4 times during the study which lasted for the 21 days the mice carried their babies. (It only takes 21 days to make a baby mouse).

Giving birth when the lights are out of sync

The researchers monitored the mice pregnancies carefully, counting the number of baby mice born to each group of mice moms.

The mice living in a normal light-dark cycle produced the most number of baby mice. Only one of the 12 mice failed to produce a litter, which translates to a 90 % success rate.

But the mice with the slightly disrupted light-dark cycle did not fair quite as well. Only 9 of 18 mice i.e. 50 % of the mice in the group 3, phase delayed group, managed to produce a litter. In group 2, phase advanced group, only 4 of the 18 mice i.e. 22 % delivered

For mice, the lighting clearly matters.

Reproduction is light sensitive

For mice at least, the baby making factory tends to break down, when the lights are left on, inappropriately.

The team did not establish exactly what malfunctioned, but apparently “minor” disruptions to the internal rhythm, had big consequences.

Is reproduction light sensitive in man ?

What applies to mice, does not automatically apply to man, but clock genes are a standard operating procedure in biology. Disruptions to the normal circadian rhythm are common events in our 24/7 world, as is infertility.

If you’re struggling to get pregnant, it might be time to take a look at the timing of your light-dark cycle. Minor disruptions to your circadian rhythm could be contributing to fertility problems.

You want the lights turned on in your baby making factory.

Environmental Perturbation of the Circadian Clock Disrupts Pregnancy in the Mouse. PLoS ONE, 2012; 7 (5): e37668 Keith C. Summa, Martha Hotz Vitaterna, Fred W. Turek

 

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Further reading

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