Can Supplemental Leucine Offset Disuse-induced Muscle Atrophy?
United Kingdom24 participantsStarted 2017-03-01
Plain-language summary
Ageing is associated with a gradual decline in muscle mass that is detrimental to both physical function and metabolic health, increasing the risk of morbidity and mortality. The loss of protein muscle mass with ageing is poorly understood, but it may partly relate to inactivity/disuse (i.e. during injury or hospitalization). Periods of inactivity/disuse blunt the ability of muscle to grow (termed anabolic blunting), leading to a loss of muscle mass and strength. An accumulation of these periods over a lifetime promotes the devastating loss of muscle protein mass and strength seen with ageing.
Disuse-induced muscle loss is underpinned by a blunted muscle anabolic response to protein nutrition. Supplementing the diet with the amino acid leucine may offer a potential solution to alleviate muscle mass and strength loss during disuse. In fact, leucine is suggested to promote muscle protein growth and reduce muscle protein loss during disuse in rats, but this is yet to be shown in humans. Accordingly, the proposed study will investigate whether leucine supplementation can offset muscle and strength loss during short-term disuse.
Twenty-four healthy (non-obese, non-diabetic, non-smokers) men aged 18-35 years will initially complete a lower-limb strength assessment and undergo a body composition scan three days later. The following morning, participants will be randomly assigned to ingest either 5g of leucine (n=12) or a caloric-matched placebo (n=12) with each meal over a 7 d period of a single-leg immobilisation. Immediately following immobilisation participants will undergo another body composition scan. Additionally, a stable isotope infusion will be combined with serial muscle biopsies from the thigh of each leg to determine the measure rates of muscle protein synthesis in the fasted state and in the 'early' and 'late' phase of feeding. A day later, the assessment of muscle strength will be repeated.
Who can participate
Age range18 Years – 35 Years
SexMALE
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Inclusion criteria
✓. Age: 18-35 years old
✓. Sex: male
✓. BMI: 18-25 kg/m2
✓. Diagnosis and general health: Good general health defined as (i) no known cardiovascular or metabolic disease, ii) non-smokers, iii) accustomed to normal levels of physical activity
✓. Compliance: understands and is willing, able and likely to comply with all study procedures and restrictions.
✓. Consent: demonstrates understanding of the study and willingness to participate as evidenced by voluntary written informed consent
Exclusion criteria
✕. Health problems such as: i) heart disease, ii) rheumatoid arthritis, iii) diabetes, iv) poor lung function, v) uncontrolled hypertension, vi) lactose intolerance or viI) any health conditions that might put the participant at risk for this study.
✕. Family history of thrombosis
✕. Involvement in regular structured exercise (resistance or endurance) training at the time of the study.
What they're measuring
1
The change in the lean mass of the leg muscles following the 7 day immobilisation period.
Timeframe: At baseline and then 7-days following the onset of immobilisation
✕. Regular consumption of any analgesic or anti-inflammatory drug(s), either prescription or non-prescription
✕. Taking any medications known to affect protein metabolism (e.g. b-blockers, corticosteroids, non-steroidal anti- inflammatories, or prescription strength acne medications). Additional medications and/or supplementation aids (e.g. whey protein) will be deemed inappropriate based on the PI's discretion.
✕. Daily protein intake; individuals with protein intake that equates to \<0.8 or \>1.2 g/kg/day will be excluded from the proposed study, as altering the daily protein intake of individuals drastically over the 7 day period is expected to significantly impact muscle protein metabolism independent of the supplementation and/or immobilisation protocol.
✕. Infused with a stable isotope within 3 years prior to study participation