The provocative new theory that could explain aging and disease | Scientific American

Sleep is extraordinarily important to mitochondrial health. That may be a big part of what drives our need for it. Neuroscientists at the University of Oxford have recently found direct links between oxidative stress in the brain and the need to sleep. As neurons fire furiously over the course of the day, ROS can accumulate. Specialized neurons track that buildup, and when a certain threshold is reached, they send a sleep signal to the brain at large. During sleep, neurons go quiet, ROS are cleared, and damaged mitochondria are repaired or recycled.

Exercise also improves the capacity of mitochondria to process energy, in part by stress-testing the system. Any kind of workout is a temporary emergency for the cells involved. Energy demand might rise to 100 times resting levels, which pushes mitochondria and their support systems to the limit, producing a burst of ROS and other stress signals. During recovery, though, the body responds to this challenge so it will be better prepared for the next one, fixing damaged tissue and building more blood vessels and mitochondria. The payoff is a system that can handle more energy without straining the rest of the time. The leg muscles of a marathoner can have twice as many mitochondria per cell as those of a couch potato, spreading the energetic load across much more capacity.

The system also gets better at repair, which may turn out to be a more important part of healthy aging than we’ve realized. Exercise triggers a process known as autophagy, the cell’s salvage system for worn-out parts, including mitochondria. Damaged material gets dismantled; useful components go back into circulation.

Recycling also seems to help explain another old standby: calorie restriction. “Autophagy is an adaptive response to nutrient deprivation,” Kaeberlein says. “When you’re in nutrient shortage, you don’t have the energy to produce a bunch of new complex machinery, so you break down the damaged machinery, and then you can reuse those components. And the most important time to recycle is when you don’t have sufficient nutrients to build new machinery.”
— Read on www.scientificamerican.com/article/the-provocative-new-theory-that-could-explain-aging-and-disease/