Abstract
Age related muscle wasting leads to overall reductions of lean body mass, reduced muscle strength, and muscle function resulting in compromised quality of life. Utilizing novel nutritional strategies to attenuate such losses is of great importance in elderly individuals. We aimed to test if a complete dietary supplement containing 25 g of milk proteins and ingested in the evening before bed would improve protein metabolism in terms of whole body protein balance over a 10 h overnight period following ingestion of the test drink in healthy middle-aged male subjects. In addition we also assessed the rates of muscle protein synthesis during the second half of the night in order to see if previously reported extended amino acidemia during sleep results in increased rates of muscle protein synthesis. Seventeen healthy middle-aged male subjects (59.4 ± 3.2 year) consumed a dietary supplement drink at 21:00 containing either 25 g milk protein concentrate, 25 g maltodextrin, 7.75 g canola oil (treatment group), or an isocaloric protein void drink (placebo group). Muscle protein synthesis was assessed from a muscle biopsy following the continuous intravenous infusion of 13C-phenylalanine for 5 h (from 03:00 to 08:00). Whole body protein balance was greater in the treatment group (−0.13 ± 11.30 g prot/10 h) compared to placebo (−12.22 ± 6.91 g prot/10 h) (P ≤ 0.01). In contrast, no changes were observed on rates of muscle protein synthesis during the second half of the night. Ingestion of a dietary supplement containing 25 g of milk proteins significantly reduced the negative protein balance observed during the night. Therefore, pre-bedtime protein ingestion may attenuate overnight losses of lean tissue in healthy elderly men. Despite increases in aminoacidemia during the second part of the night, no changes were observed in the rates of muscle protein synthesis during this time.Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT02041143.
Highlights
Skeletal muscle is the most abundant tissue in the human body and plays a key role in both locomotion and metabolic health and it is important to maintain healthy muscle mass and function as we age [1]
We report that providing a complete protein containing drink to healthy middle-aged individuals before sleep, prevented the negative whole body protein balance and that muscle protein synthesis is not augmented in the later part of the night despite elevated aminoacidemia
Res et al, previously reported that a total of 60 g of casein resulted in greater whole body protein balance and increased muscle protein synthesis in young exercising participants [18] while Groen et al showed that nasogastric feeding of 40 g casein commencing at 02:00 in elderly resulted in normal digestion and absorption kinetics, stimulating muscle protein synthesis and improved overnight whole body protein balance [29]
Summary
Skeletal muscle is the most abundant tissue in the human body and plays a key role in both locomotion and metabolic health and it is important to maintain healthy muscle mass and function as we age [1]. Two triggers known to stimulate adaptations in skeletal muscle include nutrition (macro- and micro-nutrients) [2,3,4,5] and contractile activity (weight loading and unloading) [1, 6,7,8,9]. Repeated exposure to such stimuli over time initiate changes at the molecular level allowing skeletal muscle to adapt and alter its profile to meet the demands of its new environment [10]. This accumulated loss of muscle mass over time may lead to mobility limitations in older individuals [13]
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