Minimal dose of milk protein concentrate to enhance the anabolic signalling response to a single bout of resistance exercise; a randomised controlled trial

Mycoprotein ingestion stimulates protein synthesis rates to a greater extent than milk protein in rested and exercised skeletal muscle of healthy young men: a randomized controlled trial

BACKGROUND

Mycoprotein is a fungal-derived sustainable protein-rich food source, and its ingestion results in systemic amino acid and leucine concentrations similar to that following milk protein ingestion.

OBJECTIVE

We assessed the mixed skeletal muscle protein synthetic response to the ingestion of a single bolus of mycoprotein compared with a leucine-matched bolus of milk protein, in rested and exercised muscle of resistance-trained young men.

METHODS

Twenty resistance-trained healthy young males (age: 22 ± 1 y, body mass: 82 ± 2 kg, BMI: 25 ± 1 kg·m-2) took part in a randomized, double-blind, parallel-group study. Participants received primed, continuous infusions of L-[ring-2H5]phenylalanine and ingested either 31 g (26.2 g protein: 2.5 g leucine) milk protein (MILK) or 70 g (31.5 g protein: 2.5 g leucine) mycoprotein (MYCO) following a bout of unilateral resistance-type exercise (contralateral leg acting as resting control). Blood and m. vastus lateralis muscle samples were collected before exercise and protein ingestion, and following a 4-h postprandial period to assess mixed muscle fractional protein synthetic rates (FSRs) and myocellular signaling in response to the protein beverages in resting and exercised muscle.

RESULTS

Mixed muscle FSRs increased following MILK ingestion (from 0.036 ± 0.008 to 0.052 ± 0.006%·h-1 in rested, and 0.035 ± 0.008 to 0.056 ± 0.005%·h-1 in exercised muscle; P <0.01) but to a greater extent following MYCO ingestion (from 0.025 ± 0.006 to 0.057 ± 0.004%·h-1 in rested, and 0.024 ± 0.007 to 0.072 ± 0.005%·h-1 in exercised muscle; P <0.0001) (treatment × time interaction effect; P <0.05). Postprandial FSRs trended to be greater in MYCO compared with MILK (0.065 ± 0.004 compared with 0.054 ± 0.004%·h-1, respectively; P = 0.093) and the postprandial rise in FSRs was greater in MYCO compared with MILK (Delta 0.040 ± 0.006 compared with Delta 0.018 ± 0.005%·h-1, respectively; P <0.01).

CONCLUSIONS

The ingestion of a single bolus of mycoprotein stimulates resting and postexercise muscle protein synthesis rates, and to a greater extent than a leucine-matched bolus of milk protein, in resistance-trained young men. This trial was registered at clinicaltrials.gov as 660065600.

Association of milk consumption frequency on muscle mass and strength: an analysis of three representative Korean population studies

PURPOSE

Sarcopenia is an involuntary loss of muscle mass, strength, and physical performance associated with aging. Sarcopenia contributes to adverse health outcomes. Milk contains essential amino acids important for maintaining muscle. We investigated the relationships among milk consumption frequency (MCF), muscle mass, and strength in Korean adults.

METHODS

We analyzed the data from 16,173 adults in the 2008-2011 Korean National Health and Nutrition Examination Survey (KNHANES), 13,537 adults in the 2014-2016 KNHANES, and 8254 adults in the Korean Genome and Epidemiology Study (KoGES). MCF was divided into two groups: (1) MCF less than once per day (MCF < 1 group) and (2) MCF greater than or equal to once per day (MCF ≥ 1 group). Low skeletal muscle mass index (LSMI) was defined using the Foundation for the National Institutes of Health sarcopenia project criteria for low muscle mass. Muscle strength was measured using the hand-grip strength test.

RESULTS

The odds ratio (95% confidence interval) for LSMI in the MCF < 1 group was 1.250 (1.013-1.543) after adjusting for confounding factors, compared with the MCF ≥ 1 group (2008-2011 KNHANES). The adjusted mean for hand-grip strength was higher in the MCF ≥ 1 group (2014-2016 KNHANES). After a mean follow-up of 9 years, fat-free mass/body mass index was higher in the MCF ≥ 1 group than the MCF < 1 group (KoGES).

CONCLUSION

We found that MCF ≥ 1 was significantly associated with higher skeletal muscle index and muscle strength than lower MCF. Milk consumption could help prevent sarcopenia in adults.

Effects of fish protein hydrolysate ingestion on postexercise aminoacidemia compared with whey protein hydrolysate in young individuals

The aminoacidemia resulting from food protein digestion in response to exercise plays an underlying role in the rate of muscle protein synthesis. Whey protein hydrolysate (WPH) has been demonstrated to cause more pronounced postexercise aminoacidemia compared with casein and soy. Although fish protein has been demonstrated to be a great source of amino acids, there is no data available providing information about the postexercise aminoacidemia after fish protein hydrolysate (FPH) intake. The present study investigated the characteristic patterns of postexercise aminoacidemia after WPH and FPH intake in nine physically active subjects (six males and three females). In a crossover, double-blind, and randomized design, all participants received oral doses of either 0.25 g/kg of FPH or WPH or placebo (PLA) immediately after a resistance exercise bout. Blood samples were taken before and at 30, 60, 90, 120 and 180 min after supplementation. There was a significant increase in plasma total amino acids (TAA), essential amino acids (EAA), branched-chain amino acids (BCAA), and leucine concentrations at 30 and 60 min after FPH supplementation, and at 30, 60, 90, and 120 min after WPH as compared to PLA. No significant differences were observed in plasma TAA, EAA, BCAA, and leucine concentrations between FPH and WPH at any time point, and there were no significant difference observed in the area under the curve for TAA, EAA, BCAA, and leucine between FPH and WPH. In conclusion, both FPH and WPH showed a rapid and pronounced postexercise aminoacidemia. FPH presented itself to be an alternative food source of rapidly digested proteins to be used after resistance exercise. PRACTICAL APPLICATION: Fish protein hydrolysate (FPH) demonstrated a rapid and pronounced postexercise aminoacidemia. Whey protein hydrolysate showed similar effects. FPH is presented as an alternative food source of rapidly digested proteins to be consumed by the population, especially physically active individuals.

The Degree of Aminoacidemia after Dairy Protein Ingestion Does Not Modulate the Postexercise Anabolic Response in Young Men: A Randomized Controlled Trial

BACKGROUND

Resistance exercise and dietary protein stimulate muscle protein synthesis (MPS). The rate at which proteins are digested and absorbed into circulation alters peak plasma amino acid concentrations and may modulate postexercise MPS. A novel mineral modified milk protein concentrate (mMPC), with identical amino acid composition to standard milk protein concentrate (MPC), was formulated to induce rapid aminoacidemia.

OBJECTIVES

The aim of this study was to determine whether rapid aminoacidemia and greater peak essential amino acid (EAA) concentrations induced by mMPC would stimulate greater postresistance exercise MPS, anabolic signaling, and ribosome biogenesis compared to standard dairy proteins, which induce a small but sustained plasma essential aminoacidemia.

METHODS

Thirty healthy young men (22.5 ± 3.0 y; BMI 23.8 ± 2.7 kg/m2) received primed constant infusions of l-[ring-13C6]-phenylalanine and completed 3 sets of leg presses and leg extensions at 80% of 1 repetition. Afterwards, participants were randomly assigned in a double-blind fashion to consume 25 g mMPC, MPC, or calcium caseinate (CAS). Vastus lateralis biopsies were collected at rest, and 2 and 4 h post exercise.

RESULTS

Plasma EAA concentrations, including leucine, were 19.2-26.6% greater in the mMPC group 45-90 min post ingestion than in MPC and CAS groups (P < 0.001). Myofibrillar fractional synthetic rate from baseline to 4 h was increased by 82.6 ± 64.8%, 137.8 ± 72.1%, and 140.6 ± 52.4% in the MPC, mMPC, and CAS groups, respectively, with no difference between groups (P = 0.548). Phosphorylation of anabolic signaling targets (P70S6KThr389, P70S6KThr421/Ser424, RPS6Ser235/236, RPS6Ser240/244, P90RSKSer380, 4EBP1) were elevated by <3-fold at both 2 and 4 h post exercise in all groups (P < 0.05).

CONCLUSIONS

The amplitude of plasma leucine and EAA concentrations does not modulate the anabolic response to resistance exercise after ingestion of 25 g dairy protein in young men. This trial was registered at http://www.anzctr.org.au/ as ACTRN12617000393358.

The contribution of myostatin (MSTN) and additional modifying genetic loci to race distance aptitude in Thoroughbred horses racing in different geographic regions

BACKGROUND

Race distance aptitude in Thoroughbred horses is highly heritable and is influenced largely by variation at the myostatin gene (MSTN).

OBJECTIVES

In addition to MSTN, we hypothesised that other modifying loci contribute to best race distance.

STUDY DESIGN

Using 3006 Thoroughbreds, including 835 'elite' horses, which were >3 years old, had race records and were sampled from Europe/Middle-East, Australia/New Zealand, North America and South Africa, we performed genome-wide association (GWA) tests and separately developed a genomic prediction algorithm to comprehensively catalogue additive genetic variation contributing to best race distance.

METHODS

48,896 single-nucleotide polymorphism (SNP) genotypes were generated from high-density SNP genotyping arrays. Heritability estimates, tests of GWA and genomic prediction models were derived for the phenotypes: average race distance, best race distance for elite, nonelite and all winning horses.

RESULTS

Heritability estimates were high ( h m 2  = 0.51, best race distance - elite; h m 2  = 0.42, best race distance - nonelite; h m 2  = 0.40, best race distance - all) and most of the variation was attributed to the MSTN gene. MSTN locus SNPs were the most strongly associated with the trait and included BIEC2-438999 (ECA18:66913090; P = 4.51 × 10^-110 , average race distance; P = 2.33 × 10^-42 , best race distance - elite). The genomic prediction algorithm enabled the inclusion of variation from all SNPs in a model that partitioned horses into short and long cohorts following assignment of MSTN genotype. Additional genes with minor contributions to best race distance were identified.

MAIN LIMITATIONS

The nongenetic influence of owner/trainer decisions on placement of horses in suitable races could not be controlled.

CONCLUSIONS

MSTN is the single most important genetic contributor to best race distance in the Thoroughbred. Employment of genetic prediction models will lead to more accurate placing of horses in races that are best suited to their inherited genetic potential for distance aptitude.

Circulatory microRNAs are not effective biomarkers of muscle size and function in middle-aged men

Loss of muscle size and strength with aging is a major cause of morbidity. Although muscle size and strength are measured by imaging or fiber cross-sectional staining and exercise testing, respectively, the development of circulatory biomarkers for these phenotypes would greatly simplify identification of muscle function deficits. MicroRNAs (miRNAs) are short noncoding RNAs that regulate gene translation and, thereby, contribute to muscle phenotype. To assess circulatory miRNAs (c-miRNAs) applicability as potential biomarkers of muscular phenotypes, fasting plasma and muscle samples were obtained from 50 middle-aged healthy men [mean  (SD); age: 48.8 yr (SD 4.5); BMI: 26.6 kg/m² (SD 3.3)]. RT-PCR of 38 miRNAs with known regulatory function within skeletal muscle identified four c-miRNAs (miR-221, miR-451a, miR-361, and miR-146a) related to either total body lean mass, leg lean mass, and 50% thigh cross-sectional area (CSA), but not strength. There was no relationship with the expression of these miRNAs in muscle. Six miRNAs within muscle were correlated with whole body lean mass, leg lean mass, and isometric knee extension torque (miR-133a and miR-146a), and 50% thigh CSA (miR-486, miR-208b, miR-133b, and miR-208a). Only miR-23b demonstrated a relationship between tissue and circulatory expression; however, only 10% of the variance was explained. miR-146a in both plasma and muscle was related to phenotype; however, no relationship between plasma and muscle expression was evident. A different subset of miRNAs correlated to muscle phenotype in muscle compared with plasma samples, suggesting that c-miRNA biomarkers of muscle phenotype are likely unrelated to muscle expression in healthy individuals.

Regulation of Amino Acid Transporters and Sensors in Response to a High protein Diet: A Randomized Controlled Trial in Elderly Men

BACKGROUND

The mammalian target of rapamycin complex 1 (mTORC1) is fundamental for many cellular processes, yet it is often dysregulated with aging. Increased amino acid (AA) availability is correlated with the expression of AA transporters (AAT) and mTORC1 activity. Although many AA sensors and mediators have been proposed to relay the AA signal to mTORC1, it has not yet been determined if chronic dietary intervention affects the expression of AAT, sensors and mediators and their relationships with mTORC1 activity.

OBJECTIVE AND DESIGN

This study investigated whether the consumption of a diet containing either the current recommended daily allowance (RDA) of protein intake (0.8 g/kg/d) or twice the RDA (2RDA) for ten weeks affected the expression of targets associated with AA transport, sensing and mTORC1 regulation in 26 older men (70-81 years).

METHOD

Muscle biopsies were collected before and after the intervention under fasting conditions. Diets were controlled by providing fully prepared meals and snacks. Western blot and quantitative polymerase chain reaction were used to measure protein and gene expression respectively.

RESULTS

Consumption of 2RDA reduced the protein expression of L-type amino acid transporter 1 (LAT1). However, plasma leucine concentration and basal mTORC1 activity were unaltered. The downregulation of LAT1 did not affect the expression of AA sensors and mediators, including leucyl tRNA synthetase (LRS), cytosolic arginine sensor for mTORC1 (CASTOR1), Sestrin2 and Rag proteins. Instead, total ribosomal protein S6 (RPS6) was upregulated with 2RDA.

CONCLUSION

Ten weeks of 2RDA diet did not affect the fasting mTORC1 signaling, but increased total RPS6 might suggest improved muscular translational capacity to maintain muscular mass.

Identification of human skeletal muscle miRNA related to strength by high-throughput sequencing

The loss of muscle size, strength, and quality with aging is a major determinant of morbidity and mortality in the elderly. The regulatory pathways that impact the muscle phenotype include the translational regulation maintained by microRNAs (miRNA). Yet the miRNAs that are expressed in human skeletal muscle and relationship to muscle size, strength, and quality are unknown. Using next-generation sequencing, we selected the 50 most abundantly expressed miRNAs and then analyzed them in vastus lateralis muscle, obtained by biopsy from middle-aged males ( n = 48; 50.0 ± 4.3 yr). Isokinetic strength testing and midthigh computed tomography was undertaken for muscle phenotype analysis. Muscle attenuation was measured by computerized tomography and is inversely proportional to myofiber lipid content. miR-486-5p accounted for 21% of total miR sequence reads, with miR-10b-5p, miR-133a-3p, and miR-22-3p accounting for a further 15, 12, and 10%, respectively. Isokinetic knee extension strength and muscle cross-sectional area were positively correlated with miR-100-5p, miR-99b-5p, and miR-191-5p expression. Muscle attenuation was negatively correlated to let-7f-5p, miR-30d-5p, and miR-125b-5p expression. In silico analysis implicates miRNAs related to strength and muscle size in the regulation of mammalian target of rapamycin, while miRNAs related to muscle attenuation may have potential roles regulating the transforming growth factor-β/SMAD3 pathway.

The putative leucine sensor Sestrin2 is hyperphosphorylated by acute resistance exercise but not protein ingestion in human skeletal muscle

PURPOSE

Dietary protein and resistance exercise (RE) are both potent stimuli of the mammalian target of rapamycin complex 1 (mTORC1). Sestrins1, 2, 3 are multifunctional proteins that regulate mTORC1, stimulate autophagy and alleviate oxidative stress. Of this family, Sestrin2 is a putative leucine sensor implicated in mTORC1 and AMP-dependent protein kinase (AMPK) regulation. There is currently no data examining the responsiveness of Sestrin2 to dietary protein ingestion, with or without RE.

METHODS

In Study 1, 16 males ingested either 10 or 20 g of milk protein concentrate (MPC) with muscle biopsies collected pre, 90 and 210 min post-beverage consumption. In Study 2, 20 males performed a bout of RE immediately followed by the consumption of 9 g of MPC or carbohydrate placebo. Analysis of Sestrins, AMPK and antioxidant responses was examined.

RESULTS

Dietary protein ingestion did not result in Sestrin2 mobility shift. After RE, Sestrin2 phosphorylation state was significantly altered and was not further modified by post-exercise protein or carbohydrate ingestion. With RE, AMPK phosphorylation remained stable, while the mRNA expressions of several antioxidants were upregulated.

CONCLUSIONS

Dietary protein ingestion did not affect the signalling by the family of Sestrins. With RE, Sestrin2 was hyperphosphorylated, with no further evidence of a relationship to AMPK signalling.

Leucine supplementation after mechanical stimulation activates protein synthesis via L-type amino acid transporter 1 in vitro

Branched-chain amino acid supplements consumed following exercise are widely used to increase muscle mass. Although both exercise (ie, mechanical stimulation) and branched-chain amino acid leucine supplementation have been reported to stimulate muscle protein synthesis by activating the mammalian target of rapamycin (mTOR) signaling pathway independently, the mechanisms underlying their synergistic effects are largely unknown. Utilizing cultured differentiated C2C12 myotubes, we established a combination treatment model in which the cells were subjected to cyclic uniaxial mechanical stretching (4 h, 15%, 1 Hz) followed by stimulation with 2 mM leucine for 45 min. Phosphorylation of p70 S6 kinase (p70S6K), an mTOR-regulated marker of protein translation initiation, was significantly increased following mechanical stretching alone but returned to the baseline after 4 h. Leucine supplementation further increased p70S6K phosphorylation, with a greater increase observed in the stretched cells than in the non-stretched cells. Notably, the expression of L-type amino acid transporter 1 (LAT1), a stimulator of the mTOR pathway, was also increased by mechanical stretching, and siRNA-mediated knockdown partially attenuated leucine-induced p70S6K phosphorylation. These results suggest that mechanical stretching promotes LAT1 expression and, consequently, amino acid uptake, leading to enhanced leucine-induced activation of protein synthesis. LAT1 has been demonstrated to be a point of crosstalk between exercise- and nutrition-induced skeletal muscle growth.