Muscle atrophy can occur as a result of physical inactivity or bed rest (BR), a common occurrence in those affected by illness or the aging process.
Its prevention is important due to the role of muscle for functional-motor structure, as well as in metabolic control maintenance and nutrient availability.
Nutrition has a key role in the maintenance of this muscle mass and it is well established that diets containing high protein and those supplemented with essential amino acids (EAAs) may prevent this muscle protein loss.
Branched-chain amino acids (BCAAs) have exhibited particularly beneficial effects, with leucine shown to prevent protein degradation and promote its synthesis in skeletal muscle, via initiating protein synthesis translation as well as being a fuel for the muscle cells.
With this knowledge in mind, researchers assessed the ability of a high-protein diet enriched with BCAAs to prevent muscle atrophy in 16 healthy women during long-term BR.
They found the high-protein diet with BCAAs did prevent muscle atrophy, although only in the short-term.
The authors conclude: “From the results of our study, we believe that if BR is absolutely recommended, as clinical intervention for a variety of health problems, a high-protein diet strategy could be helpful in mitigating short-term disuse muscle atrophy.”
Preventative protein power
Sixteen medically and psychologically healthy females, aged 25–40 years (32 ± 4 years), participated in the Women’s International Space Simulation for Exploration (WISE)—2005 BR study. The study was completed in two campaigns (February 2005–May 2005, September 2005–December 2005). The study was performed at the Institute for Space Medicine and Physiology in Toulouse, France. Briefly, it consisted a 20-day ambulatory control period followed by 60 days of strict BR.
Following a 20-day period of adjustment to a control diet, participants were randomly assigned to two eucaloric diet groups, one with standard protein levels (1.1 ± 0.03 g protein/kg, 4.9 ± 0.3 g leucine per day) and one with high protein contents enriched with BCAAs (1.6 ± 0.03 g protein-amino acid/kg, 11.4 ± 0.6 g leucine per day).
The participants’ body compositions were assessed every two-weeks following a baseline measurement for a 60-day period, utilising dual energy x-ray absorptiometry. It was found that within the initial 15-day period of BR, there was a significantly reduced amount of lean mass lost in the high protein-BCAA group when compared with the conventional diet group. Researchers reported a 4.1 ± 0.9 loss in the conventional diet group, compared with 2.4 ± 2.1% in the high protein group.
In addition, nitrogen balance was significantly greater in the high protein-BCAA diet during this same time period. Yet, both associations did not continue beyond this time point, suggesting that the increased availability of protein slowed associated LBM losses exclusively during the early stages of BR.
Action of amino acids
Previous studies have highlighted that the benefits on LBM in these early stages may be mostly attributed to the presence of leucine, whilst maintaining intakes of protein and the other BCAAs.
“On one hand, leucine increases muscle protein synthesis by modulating the activation of mTOR signaling pathway, on the other it reduces protein degradation by regulating autophagy through the acetyl-coenzyme on mTOR complex 1 and by diminishing oxidative stress”, the researchers explain.
Whilst these findings suggest potential for improving the negative outcomes associated with BR, the short-term effect of the response limits the applications for treatment. Researchers propose this is due to a leucine “desynchronization effect”, whereby excess leucine may trigger key enzymes involved in BCAA catabolism.
Further research is required utilising larger, more representative samples to improve the reliability of the findings, yet the research highlights the potential for short-term protein-BCAA diet interventions to reduce LBM losses associated with bed rest.
“Early lean mass sparing effect of high-protein diet with excess leucine during long-term bed rest in women”
Pierandrea Vinci, Filippo Giorgio Di Girolamo, Alessandro Mangogna, Filippo Mearelli, Alessio Nunnari, Nicola Fiotti, Mauro Giordano, Marie-Pierre Bareille and Gianni Biolo.