When you don’t get enough sleep, you can feel drained, sluggish and lazy. So, we sip our coffee, attempting to make it through the day, until it’s time to slip back into bed. But besides the fact that we feel terrible if we don’t get enough, researchers have struggled to figure out why humans and animals sleep.
A new study by scientists at Bar-Ilan University in Israel, though, may help us find out. While studying brain activity in live zebrafish, they found that DNA repaired itself much more quickly at night than during the day. During waking hours, strands of DNA were slow to fix themselves. But at night, repair was ramped up and daytime DNA damage was cleared out. The findings, published today in the journal Nature Communications, suggest that our brains need sleep to keep chromosomes and DNA healthy.
The need to catch some Zs, seen in almost all animals with central nervous systems, has long been a scientific mystery. We know that without proper sleep, humans are prone to things like cardiovascular disease, obesity, diabetes and compromised mental function. But determining what drives our need to sleep, on a cellular level, hasn’t been so easy. It’s been suggested that sleep restores energy levels, replenishes neurotransmitters in the brain and scraps useless information. None of these theories, though, have been definitively proven.
Lior Appelbaum, a professor at Bar-Ilan University’s Gonda Multidisciplinary Brain Research Center, thought that neurons in the brain — which transmit information and house DNA and chromosomes — might be repairing themselves while we sleep.
DNA is damaged by things like radiation, air pollution and tobacco smoke, but luckily, they’re often able to repair themselves. Chromosomes, which carry DNA and pass on our genetic information, are able to use healthy DNA strands to mend those that are damaged. But Appelbaum wondered if DNA would repair itself more quickly at night, while the body was at rest, versus in the day while it’s active.
“It’s like potholes in the road,” said Appelbaum, who was the lead author of the paper, in a media release. “Roads accumulate wear and tear, especially during daytime rush hours, and it is most convenient and efficient to fix them at night, when there is light traffic.”
Dreaming of DNA
To test this hypothesis, he and a team of researchers set out to study neurons in zebrafish. These little swimmers have brains similar to our own and are practically transparent, allowing researchers to see into their tiny bodies.
Using a high-powered microscope, they observed how their DNA repaired itself while the fish were both awake and asleep. They found that chromosomes within the DNA were much more active at night and were repairing DNA more efficiently than they were during the day. This suggests that, during sleep, the brain speeds up DNA repair to compensate for slow healing during the day. Without this speedy nighttime restoration, humans and animals could be prone to life-threatening diseases and ailments caused by damaged DNA.
“Despite the risk of reduced awareness to the environment, animals — ranging from jellyfish to zebrafish to humans — have to sleep to allow their neurons to perform efficient DNA maintenance, and this is possibly the reason why sleep has evolved and is so conserved in the animal kingdom,” said Appelbaum.
Follow-up research is definitely needed to confirm this theory, and to see if sleeping humans repair DNA as efficiently as zebrafish. But for now, we at least have a clue that could help us solve the mystery of sleep.