Inactivity in most mammals lead to atrophy of skeletal muscle. In humans, prolonged periods of immobilization, as in the cases of bed rest or space flights, result in muscle weakening and atrophy. This muscle atrophy in space can not only affect the performance of astronauts during missions, but it can also lead to severe muscle injuries upon return on Earth, reduce their aerobic capacity and slow down their immune and cardiovascular systems. Without regular exercise, astronauts can lose up to 20% of their muscle mass in just 5 to 11 days and up to 50% for long duration missions. In addition, posture-related slow twitch endurance fibers are replaced by fast twitch rapidly contracting fibers that are insufficient for any heavy labor.
To reduce muscle atrophy, the international space station has on board devices allowing astronauts to perform at least 2.5 h/day of muscle training. In addition, space programs are also focusing on food and nutriment regimens to sustain astronaut musculoskeletal health. Nevertheless, current countermeasures are hardly effective at mitigating muscular atrophy and do not succeed at maintaining neither protein homeostasis, nor muscle mass, function nor strength. This is exactly the problem. CITRAGE, a French biotechnology SME founded in 2009 and specialized in the development of solutions for degenerative diseases, proposes to tackle in the AstroCIT project by developing an efficient nutraceutical. By combining the L-Citrulline, an amino acid the SME and its academic partner has proven to improve muscle protein synthesis, muscle mass, strength and function on earth (resulting in the commercialization of a product for age-related muscular dystrophy since 2012) and its hitherto unseen polyamine, a precursor affecting red muscle fibers, CITRAGE aims at providing astronauts and the general population with a mean to care for muscle loss.
It has been estimated that each shuttle flight costs 1.4 Bi$ or 7.5 M$ per person-day on the international space station. The economic benefit then appears clearly by calculating spending linked to time taken by each astronaut to exercise in order to fight against muscle atrophy (781.3 k$ per day). If AstroCIT consumption leads to 10 % time saving (15 min per day), this would allow an economic benefit of 78 k$ per day per astronaut, along with the clear medical advantages. Although it costs from 11,538 to 50,847 $ to send a kg of equipment into geostationary transfer orbit and taking into account the weight of a typical treadmill (about 100kg), financial equilibrium would be reached after sending the daily dose of the proposed nutraceuticals for 18 astronauts during 3 years.
In healthcare applications (age-related muscular dystrophy or disuse muscle atrophy after injury, immobilization or surgery), direct and indirect expenditures cost more than 800 € per person per year. Because a portion of the proposed nutraceuticals could be charged up to 1,2 € a day, a 3 months cure would be equivalent to less than 13,5% of the cost induced by caring for the disease and still yield a positive impact due to a decrease in falls, invalidity or time required to care for patients. Taking into account that muscular degeneration will affect 500 million people by 2050, key prescribers will be public and private insurers, along with nursing homes, clinics and hospitals.
The overall objectives of AstroCIT are answering two key EU challenges: (a) fighting more efficiently muscle atrophy during human space flights by developing and validating a breakthrough nutritional solution and (b) preventing muscle degeneration on earth by applying this new knowledge into a second generation product.
