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Microgravity

Author(s): Joanne R. Lupton, PhD
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Portfolio of the NSBRI Muscle Team

This diagram presents some of the key skeletal muscle projects currently being conducted by the NSBRI research program. One project, by Dr. Ken Baldwin at UC Irvine, is designed to ascertain specific molecular markers in the muscle cell that can be used to predict whether the muscle cell is in a net anabolic (building up muscle) or a net catabolic (wasting) state. This research uses resistance exercise involving animals (the same type of exercise used with humans) that are undergoing hind limb suspension (a well accepted ground-based analogue that mimics the muscle wasting of rodents seen during space flight). Baldwin’s findings have identified several markers in conjunction with a resistance exercise prescription that are effective in preventing muscle atrophy. The current goal is to extend this research to studies involving humans.

Another project focusing on animal subjects is that of Dr. Fred Goldberg at Harvard University. Goldberg’s project seeks to identify a safe and effective pharmacological agent that successfully inhibits the primary pathway in which skeletal muscle proteins (especially actin and myosin) are normally degraded. If this could be accomplished, it would provide a way to preserve skeletal muscle and thus reduce the amount of time astronauts have to spend carrying out specific exercise regimens.

A third NSBRI project is being directed by Dr. Vince Caiozzo, also at UC Irvine. Dr. Caiozzo and his colleagues have designed and built a unique type of bicycle device that, when pedaled at different speeds, creates a “merry-go-round” type of spinning that produces an acceleration field that translates into gravity equivalents actually much greater than normal gravity (i.e., 2x, 3x Earth gravity). The idea is to create hyper G stimuli for different durations in order to impose brief episodes of gravity, in the hope that intermittent stimuli will provide sufficient stress on the body to maintain muscle mass and strength as occurs in the normal state of gravity stress on Earth. Under the conditions of hyper-gravity, one goal is to have subjects perform exercises that would be equivalent to those seen in heavy resistance exercise paradigms on Earth.

The fourth project involves a unique approach to administering high levels of antioxidant substances (common in the normal diet) to see if they can prevent the fatigue common in the hands and forearm muscles when performing long duration activities linked to the building of the ISS. These endurance exercise experiments specifically target the forearm muscles using hand grip dynamometers.

All of these projects are critical to improving the health and performance of astronauts. Can you think of any other experiments that the NSBRI should be doing to benefit the functional properties of the skeletal muscle system?

Suggested Reading:
Garma, T., Kobayashi, C., Haddad, F., Adams, G. R., Bodell, P. W., & Baldwin, K. M. (2007).  Similar acute molecular responses to equivalent volumes of isometric, lengthening or shortening modes of resistance exercise. J. Appl. Physiol. 102: 135-143.
Goldberg, A. L. (2007). Functions of the proteasome: from protein degradation and immune surveillance to cancer therapy. Biochem Soc Trans.;35(Pt 1): 12-7.
Reid, M. (2007). Highlighted Topic: Oxidant Activity in Skeletal Muscle. J Appl Physiol. [Epub ahead of print] PMID: 17204571 [PubMed - as supplied by publisher]
Yang, Y., Kaplan, A., Pierre, M., Adams, G., Cavanagh, P., Takahashi, C., Kreitenberg, A., Hicks, J., Keyak, J., & Caiozzo, V. (2007). Space Cycle: A Human Powered Centrifuge That Can Be Used for Hypergravity Resistance training. Aviation Space Environmental Medicine.

ADDITIONAL NOTES FROM SPEAKER’S TRANSCRIPT (http://www.bioedonline.org/presentations/)
At the University of California, Dr. Vince Caiozzo has designed a space cycle, a very unique device. An individual, or two individuals, will sit on the space cycle. One of them will ride just like you would pedal a bike, and this will sort of make it like a gondola, or a merry-go-round. Another individual can be standing on this platform and doing resistance exercises, because you can spin this at a sufficient speed for the individual actually to be spun at one G, two Gs, and three Gs. And so these individuals, when they are riding on the platform and doing these squat exercises, actually get to a point where they have to lift three times their bodyweight. This is a tremendous stress on the muscle, and it illustrates one of the strategies being considered for counteracting the loss of muscle mass. My project involves both animal and human subjects. We can design a heavy resistance training program, that will put stress on the muscles. This would be complementary to the artificial gravity program. In the lower right hand corner of the slide is a project being conducted by Dr. Michael Reed at the University of Kentucky. You see here is an individual gripping a hand ergometer, which allows one to improve the strength of the forearm and fingers. These muscles are used extensively when an individual performs EVA, extra vehicle activity, mentioned a number of slides ago. Dr. Reed is trying to provide anti-oxidants that are normal in the diet, along with resistance exercise, to induce a stronger and more fatigue-resistant forearm muscle, so that the astronauts are more effective in performing their duties outside the spacecraft. Finally, this slide tries to illustrate the unique protein degradation pathways that get activated when an individual’s muscles become unloaded. It breaks the proteins down into individual amino acids. If one could design a pharmacological drug or agent that blocks this pathway, or slows it down, it would play a significant role in trying to reduce the atrophy process.

Can you think of something that one could do that might play a role in reducing this atrophy process?