Movement and coordination problems observed in mice after weeks in microgravity-like conditions may be caused by buildup of the compound formaldehyde in the legs and brain, according to a study published in Communications Biology. The authors suggest that a similar process could contribute to the movement problems experienced by astronauts after months in space.
Some astronauts experience muscle weakness and problems with movement after returning to Earth and can spend weeks relearning how to walk. How microgravity conditions cause these movement issues has been unclear.
Zhiqian Tong and colleagues simulated microgravity conditions by elevating the hindlimbs of eight adult mice for two weeks. The researchers found that after elevation these mice were less coordinated on a balance beam and could not stay on a rotating rod for as long as control mice. Hindlimb-elevated mice also had higher levels of formaldehyde in their calf muscles and cerebellum, a brain region that helps control movement. The authors then tested the impact of increased formaldehyde levels in mice. They found that mice lacking the enzyme needed to break down formaldehyde had poorer balance and coordination than control mice on the balance beam and rotating rod and that injecting formaldehyde into the cerebellum of healthy mice was associated with reduced coordination. Together, these results indicate that increased formaldehyde levels in the calf muscles and cerebellum are associated with impaired balance and coordination in mice. Reducing formaldehyde levels, either through daily injection of the drug coenzyme Q10 or twice daily exposure to red light, was found to improve balance and coordination in hindlimb-elevated mice.
The authors hypothesise that excess formaldehyde levels may impair balance and coordination by damaging the cerebellum and muscles. Treatment strategies aiming to reduce formaldehyde levels could be investigated as a potential method of improving astronaut health after space travel, according to the authors.