The Sleep-Mitochondria Connection: A Look at Fission and Fusion

The connection between sleep and mitochondria is deeper than just energy production. New
research shows that sleep loss causes physical changes to mitochondria in key sleep-regulating
neurons. After a night of sleep deprivation, mitochondria in dFBNs (dorsal fan-shaped body
neurons) became fragmented, meaning they broke down into smaller, less elongated pieces. This
change was accompanied by an increase in mitophagy, the process of clearing out damaged
mitochondria, and more frequent contact between mitochondria and the endoplasmic reticulum.
These physical changes are a direct response to the stress of prolonged wakefulness.
Interestingly, these physical changes were reversible with recovery sleep. The mitochondria
returned to their normal, elongated shape after the flies were allowed to sleep. The study also
found a way to prevent this fragmentation. By giving the flies a protein that creates an "electron
overflow," the mitochondria were protected from the sleep loss-induced fragmentation. This
reinforces the idea that the electron leak, which happens during waking, is the initial trigger for
these physical changes.
The researchers also manipulated the mitochondria's shape to see how it aected sleep. When
they induced mitochondrial fragmentation in dFBNs, the flies slept less. This also eliminated the
normal increase in sleep that happens after sleep deprivation, a process known as homeostatic
rebound. Conversely, when they tipped the balance toward mitochondrial fusion (making them
more elongated), the flies slept more and were harder to wake up. This shows a direct link
between the physical state of the mitochondria and the regulation of sleep.
This study suggests that the sleep-wake cycle and the process of mitochondrial fission and fusion
are part of a feedback loop. When there's a mismatch between energy supply and demand, it
leads to mitochondrial changes that trigger the need for sleep. This insight could change how we
think about sleep and its fundamental purpose.