Sleep is not merely a rest for the mind but may serve as essential maintenance for the body's energy supply, according to a new study by researchers at the University of Oxford. The research, published in Nature, suggests that the need to sleep arises from electrical stress building up in mitochondria, which are tiny energy generators inside brain cells.
The study was led by Professor Gero Miesenböck from the Department of Physiology, Anatomy and Genetics and Dr. Raffaele Sarnataro at Oxford’s Centre for Neural Circuits and Behaviour. They discovered that sleep is triggered by an energy imbalance in the brain. Mitochondria use oxygen to convert food into energy, and when they become overcharged, they leak electrons. This leakage produces reactive oxygen species, which can be damaging.
Dr. Sarnataro explained, "You don’t want your mitochondria to leak too many electrons. When they do, they generate reactive molecules that damage cells." Specialized neurons act like circuit breakers by measuring this electron leak and triggering sleep when necessary.
The researchers manipulated electron flow in these cells to control how much fruit flies slept. They even used light energy to replace electrons with similar effects: more energy led to more leaks and more sleep.
Professor Miesenböck stated, "We set out to understand what sleep is for, and why we feel the need to sleep at all... Our findings show that the answer may lie in aerobic metabolism."
This discovery provides insight into links between metabolism, sleep, and lifespan. Smaller animals consume more oxygen per gram of body weight and tend to sleep more while living shorter lives. Humans with mitochondrial diseases often experience fatigue without exertion due to this mechanism.
Dr. Sarnataro remarked on the significance of their work: "This research answers one of biology’s big mysteries... The answer appears to be written into the very way our cells convert oxygen into energy."
The paper titled 'Mitochondrial origins of the pressure to sleep' has been published in Nature.