To allow astronauts to operate safely on long missions to Mars — whose gravitational pull is just 40 per cent of Earth's — mitigating strategies will be needed to prevent muscle deconditioning.
A compound found in red wine, called resveratrol, may help keep astronauts preserve their muscle mass during trips in space or future Mars missions, a study conducted by Harvard researchers in mice suggests.
The NASA-funded study, published in the journal Frontiers in Physiology, shows that resveratrol substantially preserves muscle mass and strength in rats exposed to the wasting effects of simulated Mars gravity.
“After just three weeks in space, the human soleus muscle shrinks by a third,” said Marie Mortreux, from Harvard Medical School in the US.
“This is accompanied by a loss of slow-twitch muscle fibres, which are needed for endurance,” said Mortreux, lead author of the study.
To allow astronauts to operate safely on long missions to Mars — whose gravitational pull is just 40 per cent of Earth’s — mitigating strategies will be needed to prevent muscle deconditioning.
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“Dietary strategies could be key, especially since astronauts travelling to Mars won’t have access to the type of exercise machines deployed on the ISS,” 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.
“Resveratrol has been shown to preserve bone and muscle mass in rats during complete unloading, analogous to microgravity during spaceflight. So, we hypothesised that a moderate daily dose would help mitigate muscle deconditioning in a Mars gravity analogue, too,” said Mortreux.
To mimic Mars gravity, the researchers used an approach first developed in mice, in which rats were fitted with a full-body harness and suspended by a chain from their cage ceiling.
As many as 24 male rats were exposed to normal loading (Earth) or 40 per cent loading (Mars) for 14 days. In each group, half received resveratrol (150 miligrammes per kilogramme per day) in water; the others got just the water.
Calf circumference and front and rear paw grip force were measured weekly, and at 14 days the calf muscles were analysed.
As expected, the ‘Mars’ condition weakened the rats’ grip and shrank their calf circumference, muscle weight and slow-twitch fibre content, researchers said.
Resveratrol supplementation almost entirely rescued front and rear paw grip in the Mars rats, to the level of the non-supplemented Earth rats.
Resveratrol completely protected muscle mass (soleus and gastrocnemius) in the Mars rats, and in particular reduced the loss of slow-twitch muscle fibres.
The protection was not complete, the supplement did not entirely rescue average soleus and gastrocnemius fibres cross-sectional area, or calf circumference.
“A likely factor here is insulin sensitivity. Resveratrol treatment promotes muscle growth in diabetic or unloaded animals, by increasing insulin sensitivity and glucose uptake in the muscle fibres.
“This is relevant for astronauts, who are known to develop reduced insulin sensitivity during spaceflight,” Mortreux said.
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, she said.
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