In a study done in rats, a moderate daily dose of resveratrol — a natural antioxidant found in more than 70 species of plants such as grapes, cranberries, blueberries, and peanuts — preserved muscle function and mitigated muscle atrophy in the animals exposed to a ground-based partial gravity analog that mimicked Martian environment (0.4 g). The findings, published in the journal Frontiers in Physiology, suggest that supplementing future astronauts’ diets with resveratrol could help maintain their musculoskeletal health even on a long-term mission to Mars.
Muscle atrophy is an almost immediate consequence and one of the most serious side effects of spaceflight. Studies of crews over the last 50 years of manned spaceflight reveal that astronauts can lose up to 20% of their muscle mass in less than two weeks in microgravity.
To prevent this muscle decomposition, astronauts living and working in aboard the International Space Station (ISS) for extended missions exercise several hours each day. Yet, most return to Earth in a weakened state, requiring months of post-flight rehabilitation.
“After just 3 weeks in space, the human soleus muscle shrinks by a third. This is accompanied by a loss of slow-twitch muscle fibers, which are needed for endurance,” said study lead author Dr. Marie Mortreux, a researcher in the Department of Neurology at Beth Israel Deaconess Medical Center, Harvard Medical School.
To allow astronauts to operate safely on long missions to Mars, whose gravitational pull is just 40% of Earth’s, mitigating strategies will be needed to prevent muscle deconditioning.
“Dietary strategies could be key, especially since astronauts traveling to Mars won’t have access to the type of exercise machines deployed on the ISS,” Dr. Mortreux said.
“A strong candidate is resveratrol, a compound commonly found in grape skin and blueberries that has been widely investigated for its anti-inflammatory, anti-oxidative, and anti-diabetic effects.”
To mimic Mars gravity, Dr. Mortreux and colleagues used an approach in which rats were fitted with a full-body harness and suspended by a chain from their cage ceiling.
The team exposed 24 male rats to normal loading (Earth) or 40% loading (Mars) for 14 days.
In each group, half received resveratrol (150 mg/kg/day) in water; the others got just the water. Otherwise, they fed freely from the same chow.
Calf circumference and front and rear paw grip force were measured weekly, and at 14 days the calf muscles were analyzed.
As expected, the Mars conditions weakened the rats’ grip and shrank their calf circumference, muscle weight and slow-twitch fiber content. But incredibly, resveratrol supplementation almost entirely rescued front and rear paw grip in the Mars rats, to the level of the non-supplemented Earth rats.
What’s more, resveratrol completely protected muscle mass (soleus and gastrocnemius) in the Mars rats, and in particular reduced the loss of slow-twitch muscle fibers. The protection was not complete, though: the supplement did not entirely rescue average soleus and gastrocnemius fibers cross-sectional area, or calf circumference.
“Previous resveratrol research can explain these findings. A likely factor here is insulin sensitivity,” Dr. Mortreux said.
“Resveratrol treatment promotes muscle growth in diabetic or unloaded animals, by increasing insulin sensitivity and glucose uptake in the muscle fibers. This is relevant for astronauts, who are known to develop reduced insulin sensitivity during spaceflight.”
“The anti-inflammatory effects of resveratrol could also help to conserve muscle and bone, and other anti-oxidant sources such as dried plums are being used to test this.”
Marie Mortreux et al. A Moderate Daily Dose of Resveratrol Mitigates Muscle Deconditioning in a Martian Gravity Analog. Front. Physiol, published online July 18, 2019; doi: 10.3389/fphys.2019.00899