Mixed Muscle Protein Synthesis Research Articles

Muscle Protein Synthesis in Response to Plant-Based Protein Isolates With and Without Added Leucine Versus Whey Protein in Young Men and Women

BackgroundPlant-based protein supplements often contain lower amounts of leucine and other essential amino acids (EAAs), potentially making them less effective in stimulating muscle protein synthesis (MPS) than animal-based proteins. Combining plant proteins could improve the EAA profile and more effectively support MPS. ObjectivesThe aim of this study was to determine the effect of a novel plant-based blend protein (PBP), PBP with added leucine (PBP + Leu) to levels equivalent to whey protein isolate (WHEY) on aminoacidemia and MPS responses in young men and women. We hypothesized that PBP + Leu would stimulate MPS equivalent to WHEY, and both would be greater than PBP. MethodsWe employed a randomized, double-blind, crossover study consisting of 3 separate study visits to compare PBP, PBP + Leu, and WHEY. To measure MPS response to ingestion of the supplements, a primed continuous infusion of L-[ring13C6] phenylalanine was administered for 8 h at each study visit. Skeletal muscle tissue and blood samples were collected to measure aminoacidemia and MPS. ResultsAll protein supplements increased mixed MPS above postabsorptive levels (P < 0.001). However, MPS increase following ingestion of PBP was less than that following ingestion of PBP + Leu (P = 0.002) and WHEY (P = 0.046). There were no differences in MPS between PBP + Leu and WHEY (P = 0.052). ConclusionsConsumption of PBP isolate with added leucine stimulated MPS to a similar extent as whey protein in young men and women. PBPs containing higher leucine content promote anabolism to a similar extent as animal-based proteins.This study was registered at clinicaltrials.gov as NCT05139160.

Postabsorptive muscle protein synthesis is higher in outpatients as compared to inpatients.

Several factors affect muscle protein synthesis (MPS) in the postabsorptive state. Extreme physical inactivity (e.g., bedrest) may reduce basal MPS, whereas walking may augment basal MPS. We hypothesized that outpatients would have a higher postabsorptive MPS than inpatients. To test this hypothesis, we conducted a retrospective analysis. We compared 152 outpatient participants who arrived at the research site the morning of the MPS assessment with 350 Inpatient participants who had an overnight stay in the hospital unit before the MPS assessment the following morning. We used stable isotopic methods and collected vastus lateralis biopsies ∼2 to 3 h apart to assess mixed MPS. MPS was ∼12% higher (P < 0.05) for outpatients than inpatients. Within a subset of participants, we discovered that after instruction to limit activity, outpatients (n = 13) took 800 to 900 steps in the morning to arrive at the unit, seven times more steps than inpatients (n = 12). We concluded that an overnight stay in the hospital as an inpatient is characterized by reduced morning activity and causes a slight but significant reduction in MPS compared with participants studied as outpatients. Researchers should be aware of physical activity status when designing and interpreting MPS results.NEW & NOTEWORTHY The postabsorptive muscle protein synthesis rate is lower in the morning after an overnight inpatient hospital stay compared with an outpatient visit. Although only a minimal amount of steps was conducted by outpatients (∼900), this was enough to increase postabsorptive muscle protein synthesis rate.

Combined effects of heavy ion exposure and simulated Lunar gravity on skeletal muscle

BackgroundThe limitations to prolonged spaceflight include unloading-induced atrophy of the musculoskeletal system which may be enhanced by exposure to the space radiation environment. Previous results have concluded that partial gravity, comparable to the Lunar surface, may have detrimental effects on skeletal muscle. However, little is known if these outcomes are exacerbated by exposure to low-dose rate, high-energy radiation common to the space environment. Therefore, the present study sought to determine the impact of highly charge, high-energy (HZE) radiation on skeletal muscle when combined with partial weightbearing to simulate Lunar gravity. We hypothesized that partial unloading would compromise skeletal muscle and these effects would be exacerbated by radiation exposure. MethodsFor month old female BALB/cByJ mice were -assigned to one of 2 groups; either full weight bearing (Cage Controls, CC) or partial weight bearing equal to 1/6th bodyweight (G/6). Both groups were then divided to receive either a single whole body absorbed dose of 0.5 Gy of 300 MeV 28Si ions (RAD) or a sham treatment (SHAM). Radiation exposure experiments were performed at the NASA Space Radiation Laboratory (NSRL) located at Brookhaven National Laboratory on Day 0, followed by 21 d of CC or G/6 loading. Muscles of the hind limb were used to measure protein synthesis and other histological measures. ResultsTwenty-one days of Lunar gravity (G/6) resulted in lower soleus, plantaris, and gastrocnemius muscle mass. Radiation exposure did not further impact muscle mass. 28Si exposure in normal ambulatory animals (RAD+CC) did not impact gastrocnemius muscle mass when compared to SHAM+CC (p>0.05), but did affect the soleus, where mass was higher following radiation compared to SHAM (p<0.05). Mixed gastrocnemius muscle protein synthesis was lower in both unloading groups. Fiber type composition transitioned towards a faster isoform with partial unloading and was not further impacted by radiation. The combined effects of partial loading and radiation partially mitigated fiber cross-sectional area when compared to partial loading alone. Radiation and G/6 reduced the total number of myonuclei per fiber while leading to elevated BrdU content of skeletal muscle. Similarly, unloading and radiation resulted in higher collagen content of muscle when compared to controls, but the effects of combined exposure were not additive. ConclusionsThe results of this study confirm that partial weightbearing causes muscle atrophy, in part due to reductions of muscle protein synthesis in the soleus and gastrocnemius as well as reduced peripheral nuclei per fiber. Additionally, we present novel data illustrating 28Si exposure reduced nuclei in muscle fibers despite higher satellite cell fusion, but did not exacerbate muscle atrophy, CSA changes, or collagen content. In conclusion, both partial loading and HZE radiation can negatively impact muscle morphology.

Acute responsiveness to single leg cycling in adults with obesity.

Obesity is associated with several skeletal muscle impairments which can be improved through an aerobic exercise prescription. The possibility that exercise responsiveness is diminished in people with obesity has been suggested but not well-studied. The purpose of this study was to investigate how obesity influences acute exercise responsiveness in skeletal muscle and circulating amino metabolites. Non-obese (NO; n= 19; 10F/9M; BMI=25.1± 2.8kg/m2 ) and Obese (O; n= 21; 14F/7M; BMI=37.3± 4.6kg/m2 ) adults performed 30 min of single-leg cycling at 70% of VO2 peak. 13 C6 -Phenylalanine was administered intravenously for muscle protein synthesis measurements. Serial muscle biopsies (vastus lateralis) were collected before exercise and 3.5- and 6.5-h post-exercise to measure protein synthesis and gene expression. Targeted plasma metabolomics was used to quantitate amino metabolites before and 30 and 90 min after exercise. The exercise-induced fold change in mixed muscle protein synthesis trended (p= 0.058) higher in NO (1.28 ± 0.54-fold) compared to O (0.95 ± 0.42-fold) and was inversely related to BMI (R2 = 0.140, p= 0.027). RNA sequencing revealed 331 and 280 genes that were differentially expressed after exercise in NO and O, respectively. Gene set enrichment analysis showed O had six blunted pathways related to metabolism, cell to cell communication, and protein turnover after exercise. The circulating amine response further highlighted dysregulations related to protein synthesis and metabolism in adults with obesity at the basal state and in response to the exercise bout. Collectively, these data highlight several unique pathways in individuals with obesity that resulted in a modestly blunted exercise response.

Effects of Testosterone on Mixed-Muscle Protein Synthesis and Proteome Dynamics During Energy Deficit.

Effects of testosterone on integrated muscle protein metabolism and muscle mass during energy deficit are undetermined. The objective was to determine the effects of testosterone on mixed-muscle protein synthesis (MPS), proteome-wide fractional synthesis rates (FSR), and skeletal muscle mass during energy deficit. This was a randomized, double-blind, placebo-controlled trial. The study was conducted at Pennington Biomedical Research Center. Fifty healthy men. The study consisted of 14 days of weight maintenance, followed by a 28-day 55% energy deficit with 200 mg testosterone enanthate (TEST, n = 24) or placebo (PLA, n = 26) weekly, and up to 42 days of ad libitum recovery feeding. Mixed-MPS and proteome-wide FSR before (Pre), during (Mid), and after (Post) the energy deficit were determined using heavy water (days 1-42) and muscle biopsies. Muscle mass was determined using the D3-creatine dilution method. Mixed-MPS was lower than Pre at Mid and Post (P < 0.0005), with no difference between TEST and PLA. The proportion of individual proteins with numerically higher FSR in TEST than PLA was significant by 2-tailed binomial test at Post (52/67; P < 0.05), but not Mid (32/67; P > 0.05). Muscle mass was unchanged during energy deficit but was greater in TEST than PLA during recovery (P < 0.05). The high proportion of individual proteins with greater FSR in TEST than PLA at Post suggests exogenous testosterone exerted a delayed but broad stimulatory effect on synthesis rates across the muscle proteome during energy deficit, resulting in muscle mass accretion during subsequent recovery.

Exercise Responsiveness in Obese Adults

Obesity is associated with several skeletal muscle impairments which can be improved through an aerobic exercise prescription. The possibility that exercise responsiveness is diminished in people with obesity has been suggested but not well‐studied.PURPOSEThe purpose of this study was to investigate how obesity influences acute exercise responsiveness within skeletal muscle.METHODSNon‐obese (NO; n=19; 10F/9M; BMI=25.1 ± 2.8 kg/m2) and Obese (O; n=21; 14F/7M; BMI=37.3 ± 4.6 kg/m2) adults performed 30 minutes of single‐leg cycling at 70% of VO2peak. Serial muscle biopsies (vastus lateralis) were collected before exercise and 3 and 6 hours post‐exercise to measure protein synthesis and gene expression.RESULTSThe exercise‐induced fold change in mixed muscle protein synthesis trended (p=0.058) higher in NO (1.28 ± 0.54‐fold) compared to O (0.95 ± 0.42‐fold) and was inversely related to BMI (r=‐.374, p=0.027). RNA sequencing revealed 331 and 280 genes that were up or downregulated after exercise in NO and O, respectively. Gene set enrichment analysis showed O had blunted post‐exercise pathways related to MAPK signaling, chemokine‐mediated signaling, FC receptor mediated stimulation signaling, cell proliferation, apoptosis, and RNA polymerase II promotion. Quantitative polymerase chain reaction of select metabolic (PGC1a, PGC1b, TFAM, PDK4, IRS, MAPK, and PRKAA1) and muscle growth (SLC, TBC, MSTN, MyoD, TRIM32, FOX03, and FBXO3) genes were similar between groups 3 and 6 hours after exercise.ConclusionThese data highlight several unique pathways in individuals with obesity that result in a blunted exercise response.

Potato Protein Ingestion Increases Muscle Protein Synthesis Rates at Rest and during Recovery from Exercise in Humans.

ABSTRACTIntroductionPlant-derived proteins have received considerable attention as an alternative to animal-based proteins and are now frequently used in both plant-based diets and sports nutrition products. However, little information is available on the anabolic properties of potato-derived protein. This study compares muscle protein synthesis rates after the ingestion of 30 g potato protein versus 30 g milk protein at rest and during recovery from a single bout of resistance exercise in healthy, young males.MethodsIn a randomized, double-blind, parallel-group design, 24 healthy young males (24 ± 4 yr) received primed continuous l-[ring-13C6]-phenylalanine infusions while ingesting 30 g potato-derived protein or 30 g milk protein after a single bout of unilateral resistance exercise. Blood and muscle biopsies were collected for 5 h after protein ingestion to assess postprandial plasma amino acid profiles and mixed muscle protein synthesis rates at rest and during recovery from exercise.ResultsIngestion of both potato and milk protein increased mixed muscle protein synthesis rates when compared with basal postabsorptive values (from 0.020% ± 0.011% to 0.053% ± 0.017%·h−1 and from 0.021% ± 0.014% to 0.050% ± 0.012%·h−1, respectively; P < 0.001), with no differences between treatments (P = 0.54). In the exercised leg, mixed muscle protein synthesis rates increased to 0.069% ± 0.019% and 0.064% ± 0.015%·h−1 after ingesting potato and milk protein, respectively (P < 0.001), with no differences between treatments (P = 0.52). The muscle protein synthetic response was greater in the exercised compared with the resting leg (P < 0.05).ConclusionsIngestion of 30 g potato protein concentrate increases muscle protein synthesis rates at rest and during recovery from exercise in healthy, young males. Muscle protein synthesis rates after the ingestion of 30 g potato protein do not differ from rates observed after ingesting an equivalent amount of milk protein.

Ingestion of Free Amino Acids Compared with an Equivalent Amount of Intact Protein Results in More Rapid Amino Acid Absorption and Greater Postprandial Plasma Amino Acid Availability Without Affecting Muscle Protein Synthesis Rates in Young Adults in a Double-Blind Randomized Trial

BackgroundThe rate of protein digestion and amino acid absorption determines the postprandial rise in circulating amino acids and modulates postprandial muscle protein synthesis rates. ObjectiveWe sought to compare protein digestion, amino acid absorption kinetics, and the postprandial muscle protein synthetic response following ingestion of intact milk protein or an equivalent amount of free amino acids. MethodsTwenty-four healthy, young participants (mean ± SD age: 22 ± 3 y and BMI 23 ± 2 kg/m2; sex: 12 male and 12 female participants) received a primed continuous infusion of l-[ring-2H5]-phenylalanine and l-[ring-3,5–2H2]-tyrosine, after which they ingested either 30 g intrinsically l-[1–13C]-phenylalanine–labeled milk protein or an equivalent amount of free amino acids labeled with l-[1–13C]-phenylalanine. Blood samples and muscle biopsies were obtained to assess protein digestion and amino acid absorption kinetics (secondary outcome), whole-body protein net balance (secondary outcome), and mixed muscle protein synthesis rates (primary outcome) throughout the 6-h postprandial period. ResultsPostprandial plasma amino acid concentrations increased after ingestion of intact milk protein and free amino acids (both P < 0.001), with a greater increase following ingestion of the free amino acids than following ingestion of intact milk protein (P-time × treatment < 0.001). Exogenous phenylalanine release into plasma, assessed over the 6-h postprandial period, was greater with free amino acid ingestion (76 ± 9%) than with milk protein treatment (59 ± 10%; P < 0.001). Ingestion of free amino acids and intact milk protein increased mixed muscle protein synthesis rates (P-time < 0.001), with no differences between treatments (from 0.037 ± 0.015%/h to 0.053 ± 0.014%/h and 0.039 ± 0.016%/h to 0.051 ± 0.010%/h, respectively; P-time × treatment = 0.629). ConclusionsIngestion of a bolus of free amino acids leads to more rapid amino acid absorption and greater postprandial plasma amino acid availability than ingestion of an equivalent amount of intact milk protein. Ingestion of free amino acids may be preferred over ingestion of intact protein in conditions where protein digestion and amino acid absorption are compromised.

Unravelling protein turnover in Duchenne muscular dystrophy: one protein at a time.

Unravelling protein turnover in Duchenne muscular dystrophy: one protein at a time.

Lack of Increase in Muscle Mitochondrial Protein Synthesis During the Course of Aerobic Exercise and Its Recovery in the Fasting State Irrespective of Obesity.

Acute aerobic exercise induces skeletal muscle mitochondrial gene expression, which in turn can increase muscle mitochondrial protein synthesis. In this regard, the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), is a master regulator of mitochondrial biogenesis, and thus mitochondrial protein synthesis. However, PGC-1α expression is impaired in muscle of humans with obesity in response to acute aerobic exercise. Therefore, we sought to determine whether muscle mitochondrial protein synthesis is also impaired under the same conditions in humans with obesity. To this end, we measured mitochondrial and mixed-muscle protein synthesis in skeletal muscle of untrained subjects with (body fat: 34.7 ± 2.3%) and without (body fat: 25.3 ± 3.3%) obesity in a basal period and during a continuous period that included a 45 min cycling exercise (performed at an intensity corresponding to 65% of heart rate reserve) and a 3-h post-exercise recovery. Exercise increased PGC-1α mRNA expression in muscle of subjects without obesity, but not in subjects with obesity. However, muscle mitochondrial protein synthesis did not increase in either subject group. Similarly, mixed-muscle protein synthesis did not increase in either group. Concentrations of plasma amino acids decreased post-exercise in the subjects without obesity, but not in the subjects with obesity. We conclude that neither mitochondrial nor mixed-muscle protein synthesis increase in muscle of humans during the course of a session of aerobic exercise and its recovery period in the fasting state irrespective of obesity.Trial Registration: The study has been registered within ClinicalTrials.gov (NCT01824173).

Basal protein synthesis rates differ between vastus lateralis and rectus abdominis muscle.

Background In vivo muscle protein synthesis rates are typically assessed by measuring the incorporation rate of stable isotope labelled amino acids in skeletal muscle tissue collected from vastus lateralis muscle. It remains to be established whether muscle protein synthesis rates in the vastus lateralis are representative of muscle protein synthesis rates of other muscle groups. We hypothesized that post‐absorptive muscle protein synthesis rates differ between vastus lateralis and rectus abdominis, pectoralis major, or temporalis muscle in vivo in humans.MethodsTwenty‐four patients (62 ± 3 years, 42% female), scheduled to undergo surgery, participated in this study and underwent primed continuous intravenous infusions with l‐[ring‐13C6]‐phenylalanine. During the surgical procedures, serum samples were collected, and muscle tissue was obtained from the vastus lateralis as well as from the rectus abdominis, pectoralis major, or temporalis muscle. Fractional mixed muscle protein synthesis rates (%/h) were assessed by measuring the incorporation of l‐[ring‐13C6]‐phenylalanine into muscle tissue protein.ResultsSerum l‐[ring‐13C6]‐phenylalanine enrichments did not change throughout the infusion period. Post‐absorptive muscle protein synthesis rates calculated based upon serum l‐[ring‐13C6]‐phenylalanine enrichments did not differ between vastus lateralis and rectus abdominis (0.032 ± 0.004 vs. 0.038 ± 0.003%/h), vastus lateralis and pectoralis major, (0.025 ± 0.003 vs. 0.022 ± 0.005%/h) or vastus lateralis and temporalis (0.047 ± 0.005 vs. 0.043 ± 0.005%/h) muscle, respectively (P > 0.05). When fractional muscle protein synthesis rates were calculated based upon tissue‐free l‐[ring‐13C6]‐phenylalanine enrichments as the preferred precursor pool, muscle protein synthesis rates were significantly higher in rectus abdominis (0.089 ± 0.008%/h) compared with vastus lateralis (0.054 ± 0.005%/h) muscle (P < 0.01). No differences were observed between fractional muscle protein synthesis rates in vastus lateralis and pectoralis major (0.046 ± 0.003 vs. 0.041 ± 0.008%/h) or vastus lateralis and temporalis (0.073 ± 0.008 vs. 0.083 ± 0.011%/h) muscle, respectively.ConclusionsPost‐absorptive muscle protein synthesis rates are higher in rectus abdominis when compared with vastus lateralis muscle. Post‐absorptive muscle protein synthesis rates do not differ between vastus lateralis and pectoralis major or temporalis muscle. Protein synthesis rates in muscle tissue samples obtained during surgery do not necessarily represent a good proxy for appendicular skeletal muscle protein synthesis rates.

Understanding the effects of nutrition and post-exercise nutrition on skeletal muscle protein turnover: Insights from stable isotope studies

Understanding the effects of nutrition and post-exercise nutrition on skeletal muscle protein turnover: Insights from stable isotope studies

Essential amino acid-enriched whey enhances post-exercise whole-body protein balance during energy deficit more than iso-nitrogenous whey or a mixed-macronutrient meal: a randomized, crossover study

BackgroundThe effects of ingesting varying essential amino acid (EAA)/protein-containing food formats on protein kinetics during energy deficit are undetermined. Therefore, recommendations for EAA/protein food formats necessary to optimize both whole-body protein balance and muscle protein synthesis (MPS) during energy deficit are unknown. We measured protein kinetics after consuming iso-nitrogenous amounts of free-form essential amino acid-enriched whey (EAA + W; 34.7 g protein, 24 g EAA sourced from whey and free-form EAA), whey (WHEY; 34.7 g protein, 18.7 g EAA), or a mixed-macronutrient meal (MEAL; 34.7 g protein, 11.4 g EAA) after exercise during short-term energy deficit.MethodsTen adults (mean ± SD; 21 ± 4 y; 25.7 ± 1.7 kg/m2) completed a randomized, double-blind crossover study consisting of three, 5 d energy-deficit periods (− 30 ± 3% of total energy requirements), separated by 14 d. Whole-body protein synthesis (PS), breakdown (PB), and net balance (NET) were determined at rest and in response to combination exercise consisting of load carriage treadmill walking, deadlifts, and box step-ups at the end of each energy deficit using L-[2H5]-phenylalanine and L-[2H2]-tyrosine infusions. Treatments were ingested immediately post-exercise. Mixed-muscle protein synthesis (mixed-MPS) was measured during exercise through recovery.ResultsChange (Δ postabsorptive + exercise to postprandial + recovery [mean treatment difference (95%CI)]) in whole-body (g/180 min) PS was 15.8 (9.8, 21.9; P = 0.001) and 19.4 (14.8, 24.0; P = 0.001) greater for EAA + W than WHEY and MEAL, respectively, with no difference between WHEY and MEAL. ΔPB was − 6.3 (− 11.5, − 1.18; P = 0.02) greater for EAA + W than WHEY and − 7.7 (− 11.9, − 3.6; P = 0.002) greater for MEAL than WHEY, with no difference between EAA + W and MEAL. ΔNET was 22.1 (20.5, 23.8; P = 0.001) and 18.0 (16.5, 19.5; P = 0.00) greater for EAA + W than WHEY and MEAL, respectively, while ΔNET was 4.2 (2.7, 5.6; P = 0.001) greater for MEAL than WHEY. Mixed-MPS did not differ between treatments.ConclusionsWhile mixed-MPS was similar across treatments, combining free-form EAA with whey promotes greater whole-body net protein balance during energy deficit compared to iso-nitrogenous amounts of whey or a mixed-macronutrient meal.Trial registrationClinicalTrials.gov, Identifier no. NCT04004715. Retrospectively registered 28 June 2019, first enrollment 6 June 2019

Effects of high versus standard essential amino acid intakes on whole-body protein turnover and mixed muscle protein synthesis during energy deficit: A randomized, crossover study

Consuming 0.10-0.14g essential amino acids (EAA)/kg/dose (0.25-0.30g protein/kg/dose) maximally stimulates muscle protein synthesis (MPS) during energy balance. Whether consuming EAA beyond that amount enhances MPS and whole-body anabolism following energy deficit is unknown. The aims of this study were to determine the effects of standard and high EAA ingestion on mixed MPS and whole-body protein turnover following energy deficit. Nineteen males (mean±SD; 23±5y; 25.4±2.7kg/m2) completed a randomized, double-blind crossover study consisting of two, 5-d energy deficits (-30±4% of total energy requirements), separated by 14-d. Following each energy deficit, mixed MPS and whole-body protein synthesis (PS), breakdown (PB), and net balance (NET) were determined at rest and post-resistance exercise (RE) using primed, constant L-[2H5]-phenylalanine and L-[2H2]-tyrosine infusions. Beverages providing standard (0.1g/kg, 7.87±0.87g) or high (0.3g/kg, 23.5±2.54g) EAA were consumed post-RE. Circulating EAA were measured. Postabsorptive mixed MPS (%/h) at rest was not different (P=0.67) between treatments. Independent of EAA, postprandial mixed MPS at rest (standard EAA, 0.055±0.01; high EAA, 0.061±0.02) and post-RE (standard EAA, 0.055±0.01; high EAA, 0.065±0.02) were greater than postabsorptive mixed MPS at rest (P=0.02 and P=0.01, respectively). Change in (Δ postabsorptive) whole-body (g/180min) PS and PB was greater for high than standard EAA [mean treatment difference (95% CI), 3.4 (2.3, 4.4); P=0.001 and-15.6 (-17.8, -13.5); P=0.001, respectively]. NET was more positive for high than standard EAA [19.0 (17.3, 20.7); P=0.001]. EAA concentrations were greater in high than standard EAA (P=0.001). These data demonstrate that high compared to standard EAA ingestion enhances whole-body protein status during underfeeding. However, the effects of consuming high and standard EAA on mixed MPS are the same during energy deficit. NCT03372928, https://clinicaltrials.gov.

Effects of Testosterone on Mixed Muscle Protein Synthesis and Proteome Dynamics During Energy Deficit

Abstract Objectives Short-term energy deficit reduces acute measures of mixed muscle protein synthesis (MPS) and suppresses the hypothalamic-pituitary axis and endogenous testosterone synthesis. We hypothesized that testosterone supplementation could mitigate the effects of energy deficit on MPS. We conducted a randomized, double-blind, placebo-controlled trial to determine the effects of 28 days of tightly-controlled severe energy deficit (deficit 55% of total energy requirements) on measures of mixed-MPS and proteome-wide protein dynamics in non-obese men either given 200 mg testosterone enanthate (Testosterone, n = 24) or placebo (Placebo, n = 26) injections per week. Methods Participants received daily aliquots of deuterated water (2H2O) for 42 consecutive days (14-d weight maintenance period followed by 28-d energy deficit). Muscle biopsies were collected at rest in a fasted state at the end of the weight maintenance phase (PRE) and at the middle (MID) and end (POST) of the 28-d energy deficit. Mixed-MPS and proteome-wide protein fractional synthesis rates (FSR) were quantified. Changes over time and differences between Testosterone and Placebo were determined for mixed-MPS, and cross-sectional comparisons between Testosterone and Placebo were performed at MID and POST for proteome dynamics. Results In both Testosterone and Placebo, mixed-MPS were 40% and 33% lower (P &amp;lt; 0.0005) at MID and POST energy deficit, respectively, compared to PRE, with no differences between groups or between MID and POST. Proteome-wide FSR of individual muscle proteins did not differ between Testosterone and Placebo at any time point. However, at POST, the number of individual proteins with higher FSR in Testosterone than Placebo was significant by 2-tailed binomial test (P &amp;lt; 0.05), with values ranging from 20–32% higher FSR for myofibrillar, mitochondrial and cytosolic proteins. Conclusions Findings confirm the pronounced effect of short-term severe energy deficit on mixed-MPS and suggest the anabolic suppression occurs largely independent of testosterone. However, proteome-wide protein dynamics may reveal a novel time sensitive signal by which supplemental testosterone triggers a delayed increase in MPS, providing a synthetic mechanism for muscle mass preservation or accrual. Funding Sources Supported by DHP JPC-5/MOMRP; authors’ views not official U.S. Army or DoD policy.

Endurance-Type Exercise Increases Bulk and Individual Mitochondrial Protein Synthesis Rates in Rats.

Physical activity increases muscle protein synthesis rates. However, the impact of exercise on the coordinated up- and/or downregulation of individual protein synthesis rates in skeletal muscle tissue remains unclear. The authors assessed the impact of exercise on mixed muscle, myofibrillar, and mitochondrial protein synthesis rates as well as individual protein synthesis rates in vivo in rats. Adult Lewis rats either remained sedentary (n = 3) or had access to a running wheel (n = 3) for the last 2 weeks of a 3-week experimental period. Deuterated water was injected and subsequently administered in drinking water over the experimental period. Blood and soleus muscle were collected and used to assess bulk mixed muscle, myofibrillar, and mitochondrial protein synthesis rates using gas chromatography-mass spectrometry and individual muscle protein synthesis rates using liquid chromatography-mass spectrometry (i.e.,dynamic proteomic profiling). Wheel running resulted in greater myofibrillar (3.94 ± 0.26 vs. 3.03 ± 0.15%/day; p < .01) and mitochondrial (4.64 ± 0.24 vs. 3.97 ± 0.26%/day; p < .05), but not mixed muscle (2.64 ± 0.96 vs. 2.38 ± 0.62%/day; p = .71) protein synthesis rates, when compared with the sedentary condition. Exercise impacted the synthesis rates of 80 proteins, with the difference from the sedentary condition ranging between -64% and +420%. Significantly greater synthesis rates were detected for F1-ATP synthase, ATP synthase subunit alpha, hemoglobin, myosin light chain-6, and synaptopodin-2 (p < .05). The skeletal muscle protein adaptive response to endurance-type exercise involves upregulation of mitochondrial protein synthesis rates, but it is highly coordinated as reflected by the up- and downregulation of various individual proteins across different bulk subcellular protein fractions.

Supplement with whey protein hydrolysate in contrast to carbohydrate supports mitochondrial adaptations in trained runners

BackgroundProtein supplementation has been suggested to augment endurance training adaptations by increasing mixed muscle and myofibrillar protein synthesis and lean body mass. However, a potential beneficial effect on mitochondrial adaptations is yet to be clarified.The aim of the present study was to investigate the effect of consuming whey protein hydrolysate before and whey protein hydrolysate plus carbohydrate (PRO-CHO) after each exercise session during a six-week training period compared to similarly timed intake of isocaloric CHO supplements on biomarkers of mitochondrial biogenesis, VO2max and performance in trained runners.MethodsTwenty-four trained runners (VO2max 60.7 ± 3.7 ml O2 kg− 1 min1) completed a six-week block randomized controlled intervention period, consisting of progressive running training. Subjects were randomly assigned to either PRO-CHO or CHO and matched in pairs for gender, age, VO2max, training and performance status. The PRO-CHO group ingested a protein beverage (0.3 g kg− 1) before and protein-carbohydrate beverage (0.3 g protein kg− 1 and 1 g carbohydrate kg− 1) after each exercise session. The CHO group ingested an energy matched carbohydrate beverage. Resting muscle biopsies obtained pre and post intervention were analyzed for mitochondrial specific enzyme activity and mitochondrial protein content. Subjects completed a 6 K time trial (6 K TT) and a VO2max test pre, midway (only 6 K TT) and post intervention.ResultsFollowing six weeks of endurance training Cytochrome C (Cyt C) protein content was significantly higher in the PRO-CHO group compared to the CHO group (p < 0.05), with several other mitochondrial proteins (Succinate dehydrogenase (SDHA), Cytochrome C oxidase (COX-IV), Voltage-dependent anion channel (VDAC), Heat shock protein 60 (HSP60), and Prohibitin (PHB1)) following a similar, but non-significant pattern (p = 0.07–0.14). β-hydroxyacyl-CoA dehydrogenase (HAD) activity was significantly lower after training in the CHO group (p < 0.01), but not in the PRO-CHO group (p = 0.24). VO2max and 6 K TT was significantly improved after training with no significant difference between groups.ConclusionIntake of whey PRO hydrolysate before and whey PRO hydrolysate plus CHO after each exercise session during a six-week endurance training period may augment training effects on specific mitochondrial proteins compared to intake of iso-caloric CHO but does not alter VO2max or 6 K TT performance.Trial registrationclinicaltrials.gov, NCT03561337. Registered 6 June 2018 – Retrospectively registered.

Whey Protein Hydrolysate Increases Amino Acid Uptake, mTORC1 Signaling, and Protein Synthesis in Skeletal Muscle of Healthy Young Men in a Randomized Crossover Trial

Muscle protein synthesis (MPS) can be stimulated by ingestion of protein sources, such as whey, casein, or soy. Protein supplementation can enhance muscle protein synthesis after exercise and may preserve skeletal muscle mass and function in aging adults. Therefore, identifying protein sources with higher anabolic potency is of high significance. The aim of this study was to determine the anabolic potency and efficacy of a novel whey protein hydrolysate mixture (WPH) on mechanistic target of rapamycin complex 1 (mTORC1) signaling and skeletal MPS in healthy young subjects. Ten young men (aged 28.7 ± 3.6 y, 25.2 ± 2.9 kg/m2 body mass index [BMI]) were recruited into a double-blind two-way crossover trial. Subjects were randomized to receive either 0.08 g/kg of body weight (BW) of WPH or an intact whey protein (WHEY) mixture during stable isotope infusion experiments. Fractional synthetic rate, leucine and phenylalanine kinetics, and markers of amino acid sensing were assessed as primary outcomes before and 1-3 h after protein ingestion using a repeated measures mixed model. Blood leucine concentration, delivery of leucine to muscle, transport of leucine from blood into muscle and intracellular muscle leucine concentration significantly increased to a similar extent 1 h after ingestion of both mixtures (P<0.05). Phosphorylation of S6K1 (i.e. a marker of mTORC1 activation) increased equally by ∼20% 1-h postingestion (P<0.05). Ingestion of WPH and WHEY increased mixed MPS similarly in both groups by ∼43% (P<0.05); however, phenylalanine utilization for synthesis increased in both treatments 1-h postingestion but remained elevated 3-h postingestion only in the WPH group (P<0.05). We conclude that a small dose of WPH effectively increases leucine transport into muscle, activating mTORC1 and stimulating MPS in young men. WPH anabolic potency and efficacy for promoting overall muscle protein anabolism is similar to WHEY, an intact protein source. This trial was registered at clinicaltrials.gov as NCT03313830.

Resistance exercise stimulates mixed muscle protein synthesis in lean and obese young adults.

Obese individuals exhibit a diminished muscle protein synthesis response to nutrient stimulation when compared with their lean counterparts. However, the effect of obesity on exercise‐stimulated muscle protein synthesis remains unknown. Nine lean (23.5 ± 0.6 kg/m2) and 8 obese (33.6 ± 1.2 kg/m2) physically active young adults participated in a study that determined muscle protein synthesis and intracellular signaling at rest and following an acute bout of resistance exercise. Mixed muscle protein synthesis was determined by combining stable isotope tracer ([13C6]phenylalanine) infusion with serial biopsies of the vastus lateralis. A unilateral leg resistance exercise model was adopted so that resting and postexercise measurements of muscle protein synthesis could be obtained simultaneously. Obesity was associated with higher basal levels of serum insulin (P < 0.05), plasma triacylglycerol (P < 0.01), plasma cholesterol (P < 0.01), and plasma CRP (P < 0.01), as well as increased insulin resistance determined by HOMA‐IR (P < 0.05). However, resting and postexercise rates of muscle protein synthesis were not significantly different between lean and obese participants (P = 0.644). Furthermore, resistance exercise stimulated muscle protein synthesis (~50% increase) in both groups (P < 0.001), with no difference between lean and obese (P = 0.809). Temporal increases in the phosphorylation of intracellular signaling proteins (AKT/4EBP1/p70S6K) were observed within the exercised leg (P < 0.05), with no differences between lean and obese. These findings suggest a normal anabolic response to muscle loading in obese young adults.

Influence of omega-3 fatty acids on skeletal muscle protein metabolism and mitochondrial bioenergetics in older adults.

Omega-3 polyunsaturated fatty acids (n3-PUFA) are recognized for their anti-inflammatory effects and may be beneficial in the context of sarcopenia. We determined the influence of n3-PUFA on muscle mitochondrial physiology and protein metabolism in older adults. Twelve young (18-35 years) and older (65-85 years) men and women were studied at baseline. Older adults were studied again following n3-PUFA supplementation (3.9g/day, 16 weeks). Muscle biopsies were used to evaluate respiratory capacity (high resolution respirometry) and oxidant emissions (spectrofluorometry) in isolated mitochondria. Maximal respiration was significantly lower in older compared to young. n3-PUFA did not change respiration, but significantly reduced oxidant emissions. Participants performed a single bout of resistance exercise, followed by biopsies at 15 and 18 hours post exercise. Several genes involved in muscle protein turnover were significantly altered in older adults at baseline and following exercise, yet muscle protein synthesis was similar between age groups under both conditions. Following n3-PUFA supplementation, mixed muscle, mitochondrial, and sarcoplasmic protein synthesis rates were increased in older adults before exercise. n3-PUFA increased post-exercise mitochondrial and myofibrillar protein synthesis in older adults. These results demonstrate that n3-PUFA reduce mitochondrial oxidant emissions, increase postabsorptive muscle protein synthesis, and enhance anabolic responses to exercise in older adults.