Combined in vivo muscle mass, muscle protein synthesis and muscle protein breakdown measurement: a ‘Combined Oral Stable Isotope Assessment of Muscle (COSIAM)’ approach

Optimising approaches for measuring skeletal muscle mass and turnover that are widely applicable, minimally invasive and cost effective is crucial in furthering research into sarcopenia and cachexia. Traditional approaches for measurement of muscle protein turnover require infusion of expensive, sterile, isotopically labelled tracers which limits the applicability of these approaches in certain populations (e.g. clinical, frail elderly). To concurrently quantify skeletal muscle mass and muscle protein turnover i.e. muscle protein synthesis (MPS) and muscle protein breakdown (MPB), in elderly human volunteers using stable-isotope labelled tracers i.e. Methyl-[D3]-creatine (D3-Cr), deuterium oxide (D2O), and Methyl-[D3]-3-methylhistidine (D3-3MH), to measure muscle mass, MPS and MPB, respectively. We recruited 10 older males (71 ± 4 y, BMI: 25 ± 4 kg.m2, mean ± SD) into a 4-day study, with DXA and consumption of D2O and D3-Cr tracers on day 1. D3-3MH was consumed on day 3, 24 h prior to returning to the lab. From urine, saliva and blood samples, and a single muscle biopsy (vastus lateralis), we determined muscle mass, MPS and MPB. D3-Cr derived muscle mass was positively correlated to appendicular fat-free mass (AFFM) estimated by DXA (r = 0.69, P = 0.027). Rates of cumulative myofibrillar MPS over 3 days were 0.072%/h (95% CI, 0.064 to 0.081%/h). Whole-body MPB over 6 h was 0.052 (95% CI, 0.038 to 0.067). These rates were similar to previous literature. We demonstrate the potential for D3-Cr to be used alongside D2O and D3-3MH for concurrent measurement of muscle mass, MPS, and MPB using a minimally invasive design, applicable for clinical and frail populations.

Acute Effect of the Timing of Resistance Exercise and Nutrient Intake on Muscle Protein Breakdown

Background: Combining resistance exercise (RE) with nutrient intake stimulates muscle protein net balance. However, it is still unclear whether the optimal timing of nutrient intake is before or after RE, especially on muscle protein breakdown (MPB) for an augmented muscle anabolic response. The aim of this study was to investigate the effect of a substantial mixed meal (i.e., nutrient- and protein-dense whole foods) before or after RE, compared with RE without a meal on the acute response of MPB in a crossover-design study. Methods: Eight healthy young men performed three trials: (1) meal intake before RE (Pre), (2) meal intake after RE (Post), and (3) RE without meal intake (No). Plasma insulin and 3-methylhistidine (3-MH), an MPB marker, were measured. Results: Time course change in plasma insulin level after RE was significantly higher in the Post condition than in the Pre and No conditions. The area under the curve of 3-MH concentration was significantly lower in the Post condition than in the Pre and No conditions. Conclusions: These results suggest that a substantial mixed meal immediately after RE may effectively suppress MPB in the morning.

Muscle Protease Activities in Salmo Trutta L. Inhabiting the Krivoi Ruchey River

The effects of size, age, and smoltification on muscle protein breakdown systems were studied in wild brown trout Salmo trutta L. inhabiting the Krivoi Ruchey River of the White Sea basin, Kola Peninsula. Activities of autophagy-related proteases including cathepsin B and D, calpains, and proteasome were assayed in the skeletal muscle of brown trout parr and smolt of different age group. Youngest fish group consisted of the most actively growing individuals possessed the higher rate of protein breakdown compared to older groups. Different patterns of muscle protein breakdown inherent to brown trout parr and smolts were shown to be associated with calpain system and cathepsin D activities. Thus, increased activity of these proteases in smoltifying individuals obviously results in amino acid accumulation that could be a mechanism of seawater tolerance required for seaward migration. This study is the first to show the age- and stage-related dynamics in protease activities in skeletal muscle of brown trout inhabiting the Krivoi Ruchey River. Growth- and smoltification-related patterns of protease activities were quite similar in brown trout from the Krivoi Ruchey River and previously studied rivers of the White Sea basin, however, some habitat-related differences were observed.

GLUTATHIONE, MITOCHONDRIAL DEFECTS, AND A UNIQUE METABOLIC CYCLE IN OLDER HUMANS: IMPLICATIONS FOR SARCOPENIA

Sarcopenia in aging leads to decreased muscle mass and physical-function (muscle strength and exercise capacity), but underlying mechanisms are not well understood and effective interventions are limited. We hypothesized that deficiency of the intracellular antioxidant protein Glutathione initiates a unique self-perpetuating metabolic cycle linking impaired fasted mitochondrial fuel-oxidation (fMFO) to protein catabolism and contributes to sarcopenia. We also hypothesized that supplementing the Glutathione precursor amino-acids glycine and N-acetylcysteine (GlyNAC) to correct Glutathione deficiency in older humans could reverse these defects. We tested our hypothesis in a 24-week open-label clinical-trial in 8 older-humans (74y) studied before and 24-weeks after GlyNAC supplementation, compared to 8 gender-matched unsupplemented young-controls (25y), and measured intracellular Glutathione concentrations, fMFO, physical-function, muscle-protein breakdown-rate (MPBR), gluconeogenesis, and urine nitrogen-excretion (UNE). GlyNAC supplementation in older humans corrected Glutathione deficiency and restored impaired fMFO (to levels in young controls), lowered MPBR and UNE, and increased physical-function, but did not affect gluconeogenesis or increase lean-mass, and suggest that muscle amino-acids are utilized for energy needs rather than glucose production. The absence of an increase in lean-mass suggests that GlyNAC should be combined with anabolic agents for potential benefits in combating sarcopenia. Overall, these results indicate the presence of a unique reversible metabolic cycle in older humans initiated by Glutathione deficiency which results in impaired mitochondrial fatty-acid and glucose oxidation, muscle-protein breakdown, UNE, and leads to deficiency of glycine and cysteine which re-initiate the cycle. These data have implications for improving physical-function and muscle mass in age-associated sarcopenia, and warrants further investigation.

Pengaruh Pemberian Whey Protein Terhadap Pengurangan Gejala Kerusakan Otot Setelah Aktivitas Eksentrik

Aktivitas eksentrik adalah salah satu jenis aktivitas resistance yang sering menimbulkan kerusakan otot, yang dimulai dari 24 jam setelah aktivitas dan mencapai puncaknya pada 48 jam setelah aktivitas. Kerusakan otot menyebabkan hilangnya kekuatan otot, menurunkan range of motion sendi, meningkatkan inflamasi dan konsentrasi protein miofibril dalam darah. Rangsangan sintesis protein dan meminimalisasi muscle protein breakdown (proteolisis) adalah dua proses seluler yang penting untuk pemulihan setelah kerusakan otot. Tujuan dari penelitian ini adalah untuk membuktikan pengaruh suplementasi whey protein terhadap pengurangan gejala kerusakan otot setelah aktivitas eksentrik. Subjek penelitian ini adalah mahasiswa PJKR IKIP Budi Utomo yang dibagi secara acak ke dalam dua kelompok, 22 orang coba kelompok kontrol dan 22 orang coba kelompok perlakuan. Desain penelitian ini adalah randomized group pretest and posttest design. Aktivitas eksentrik yang dilakukan adalah aktivitas Drop Jumps pada bangku dengan ketinggian 0.5 meter. Whey protein diberikan setelah aktivitas eksentrik sebanyak 20 gram/subjek. Dalam penelitian ini whey protein diberikan dalam bentuk serbuk yang dilarutkan dengan 240 ml air mineral. Waktu pemberian whey protein dilakukan segera setelah aktivitas eksentrik, 24 dan 48 jam setelah aktivitas eksentrik (selama 3 hari pemulihan). Pengukuran kekuatan otot tungkai menggunakan back and leg dynamometer sedangkan pengukuran ROM sendi menggunakan alat goniometer. Dari hasil penelitian diketahui bahwa pemberian asupan whey protein pada kelompok perlakuan setelah aktivitas eksentrik dapat meningkatkan kekuatan otot tungkai pada 48 jam (72,3±16,1kg) dengan nilai p=0,003 (p<0,05) dan pada 72 jam (80,3±17,2) dengan nilai p=0,00 (p<0,05). Pemberian asupan whey protein pada kelompok perlakuan setelah aktivitas eksentrik juga dapat meningkatkan ROM sendi lutut pada 72 jam (130,8±3,1) whey protein sebesar 20 gram /hari setelah aktivitas eksentrik dapat meningkatkan kekuatan otot tungkai lutut pada jam ke 48 dan 72 serta ROM sendi pada jam ke 72