Nutritional supplements may combat muscle loss

Related tags Muscle Metabolism Protein Amino acid

Early indications show that nutritional supplements may lessen
muscle atrophy brought on by space travel, prolonged bed
confinement or immobility.

Early indications show that nutritional supplements may lessen muscle atrophy brought on by space travel, prolonged bed confinement or immobility.

In a study designed to test the effects of an amino acid and carbohydrate supplement on astronauts, researchers claim the results could have benefits for patients suffering muscle loss after prolonged bed-rest.

To study space travel's effect on muscles, Dr Robert Wolfe of the University of Texas Medical Branch at Galveston enlisted healthy subjects to stay in bed 28 days during a National Space Biomedical Research Institute study.

"One cause of muscle atrophy in space is lack of muscular activity. That's why bed-rest is a good model because it minimises activity, and like astronauts, you lose muscle mass primarily in the legs,"​ said co-investigator Dr Arny Ferrando, a professor of surgery at UTMB and Shriners Hospital for Children in Galveston. "When muscles are inactive, as they are in space, they don't make new proteins. If muscle breakdown rates are the same, that means you lose muscle."

Researchers aimed to increase protein synthesis rates with supplements of amino acids, the raw materials of protein. Participants received the supplements three times a day, and researchers compared the protein synthesis/breakdown rates and muscle mass before and after the bed-rest study. This data was compared to results from a control group that received a placebo drink instead of the supplements.

"Early results suggest that the amino acid supplement is able to maintain synthesis rates and body mass,"​ Ferrando said.

During the study, subjects were required to remain in bed, only getting up briefly to use a bedside commode. Midway through the study, researchers determined muscle mass and function by testing the subjects' strength and body composition.

The researchers gather the most vital data, the protein synthesis and breakdown rates, by using stable isotope analysis. With the stable isotope technique, they attach a harmless tracer to specific amino acids that travel through the bloodstream. Then, they take blood samples to determine the amount of amino acids that enter and exit the leg.

"If 80 amino acids are coming into the artery and 60 are going out of the vein, we know that 20 were probably made into proteins in the muscle,"​ said Dr Douglas Paddon-Jones, also of UTMB and a co-investigator performing these studies.

"We complete the muscle analysis by removing a small piece of muscle and determining how many amino acids have been incorporated into proteins. Over time, we can calculate the rate at which the synthesis and breakdown occurs."

Space conditions also elevate the body's level of the stress hormone cortisol, which increases the breakdown rate of proteins. "Under stress, the body breaks down proteins to make energy for survival,"​ said Ferrando, a member of NSBRI's nutrition and fitness research team. "However, this process also causes muscle atrophy."

To study the supplement's effects on muscle loss due to elevated levels of cortisol, researchers infused the stress hormone into the participants' blood during the stable isotope tests. The researchers mimic the cortisol concentrations found during space flight, then determine protein synthesis and breakdown rates of the subjects taking the supplement and compare this to the rates of the control group.

Ferrando and Wolfe are also collaborating with other NSBRI researchers who use the subjects' body fluids to study changes in bone, immune function and cell damage induced by bed rest.

Findings from this research on nutritional supplements could benefit patients on Earth.

"Muscle atrophy is common in many populations: the elderly, kids with burns, patients in intensive care or people who have had major operations. We're looking at this phenomenon in terms of space flight, but the study has many other implications,"​ Ferrando said.

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