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Marine-derived proteins, such as blue whiting-derived protein hydrolysates (BWPH), represent high-quality sources of dietary protein, but their ability to support postexercise anabolism is not established. The impact of BWPH on whole-body anabolism was compared with an isonitrogenous whey protein isolate (WPI) and nonessential amino acid (NEAA) control in 10 trained young males (31 ± 4 years) who, on three separate visits, performed a session of whole-body resistance exercise and then consumed, in randomized crossover fashion, BWPH, WPI, or NEAA (0.33 g/kg; 19, 33, and 0 mg/kg leucine, respectively) with L-[1-13C]leucine. Breath, blood, and urine samples were collected for 6-hr postprandial to assess dietary leucine oxidation, amino acid (AA) concentrations, and 3-methylhistidine: creatinine ratio. Peak and area under the curve concentrations for leucine, branched-chain amino acids, and essential amino acids were greater in WPI compared with BWPH (all p <.05) but with no differences in time to peak concentration. Total oxidation reflected leucine intake (WPI > BWPH > NEAA; p <.01), whereas relative oxidation was greater (p <.01) in WPI (28.6 ± 3.6%) compared with NEAA (21.3 ± 4.2%), but not BWPH (28.6 ± 8.8%). Leucine retention, a proxy for whole-body protein synthesis, was greater in WPI (185.6 ± 9.5 μmol/kg) compared with BWPH (109.3 ± 14.1 μmol/kg) and NEAA (5.74 ± 0.30 μmol/kg; both p <.01), with BWPH being greater than NEAA (p <.01). Urinary 3-methylhistidine: creatinine ratio did not differ between conditions. Both WPI and BWPH produced essential aminoacidemia and supported whole-body anabolism after resistance exercise, but a higher intake of BWPH to better approximate the leucine and EAA content of WPI may be needed to produce an equivalent anabolic response. Consuming protein after exercise is generally considered to be important for recovery from a single session of exercise, and over time can support muscle growth in response to long-term strength training. This study aimed to understand how different types of protein might affect these so-called "anabolic" processes by studying a marker of the body's ability to recovery and grow muscle after exercise. Specifically, this study compared how well three different protein sources—a dairy-based protein in the form of whey protein isolate, a novel fish protein powder derived from blue whiting, and a blend of what are known as nonessential amino acids—help the body retain another amino acid named leucine, which is a key indicator of muscle-building potential, during the 6 hr of recovery after exercise. There are 20 amino acids that are used in the body, some come from our food and some can be made in the body, but regardless of source, these amino acids serve as building blocks for all of the proteins in the body. Ten healthy young men who had been regularly doing strength training participated in the study. On three different occasions, each participant completed a full-body workout and then drank one of the three protein drinks. The amount of protein they consumed was based on their body weight. The drink provided 20–30 g of protein depending, on body size. After each workout, how much leucine the body retained over a 6-hr period was assessed by collecting samples of blood, breath, and urine which effectively measures how well the proteins were absorbed and used by the body for processes supporting muscle recovery, repair, and growth. One of the key questions was whether this fish-derived protein could be a good alternative to whey protein for supporting muscle recovery after exercise. Whey protein is well-known for its ability to support these processes and help build muscle, but there is much interest in whether other protein sources, particularly those from fish, could offer similar benefits. Fish proteins may also have the added advantage of being more sustainable, which is increasingly important in today's world. The nonessential amino acid blend served as a control, as it was not expected to contribute to processes that support muscle recovery and growth due to its lack of essential amino acids. The results showed that whey protein was the most effective by leading to the highest concentrations of essential amino acids in the blood, and the greatest amount of leucine retained in the body, meaning that the body was potentially able to use more of it for muscle recovery and growth. The fish protein performed better than the nonessential amino acids, supporting the idea that it could help with muscle recovery, but it was not as effective as whey protein. This finding is likely because the fish protein contained less essential amino acids, which are critical for muscle recovery and growth processes. Consuming a larger amount of the fish protein could potentially provide benefits similar to whey protein, but more studies would be needed to confirm this. The nonessential amino acid blend was the least effective, as expected, because it lacked the necessary components to stimulate these anabolic processes in muscle. The interpretation of these results is that while whey protein would be the most effective of the three protein sources for promoting muscle recovery after exercise, fish-derived proteins, like the one tested in this study, could be a good alternative, especially for those who are looking for nondairy sources of protein. While the fish protein didn't perform as well as whey protein in this study, it did still support muscle recovery, suggesting it could be a viable option to match the effects of whey if provided at the right dosage. Overall, this research adds to our understanding of how different protein sources can help the body recover after exercise, and suggests that future research could focus on how adjusting the amount of fish protein consumed could improve its potential to support recovery and growth in response to exercise. Consuming protein after exercise is generally considered to be important for recovery from a single session of exercise, and over time can support muscle growth in response to long term strength training. This study aimed to understand how different types of protein might affect these so-called "anabolic" processes by studying a marker of the body's ability to recovery and grow muscle after exercise. Specifically, this study compared how well three different protein sources—a dairy-based protein in the form of whey protein isolate, a novel fish protein powder derived from blue whiting, and a blend of what are known as nonessential amino acids—help the body retain another amino acid named leucine, which is a key indicator of muscle-building potential, during the 6 hr of recovery after exercise. There are 20 amino acids that are used in the body, some come from our food and some can be made in the body, but regardless of source, these amino acids serve as building blocks for all of the proteins in the body. Ten healthy young men who had been regularly doing strength training participated in the study. On three different occasions, each participant completed a full-body workout and then drank one of the three protein drinks. The amount of protein they consumed was based on their body weight, and so the drink provided 20–30 g of protein depending on body size. After each workout, how much leucine the body retained over a 6-hr period was assessed by collecting samples of blood, breath, and urine, and this is effectively a measure of how well the proteins were absorbed and used by the body for processes supporting muscle recovery, repair, and growth. One of the key research questions was whether this fish-derived protein could be a good alternative to whey protein for supporting muscle recovery after exercise. Whey protein is well-known for its ability to support these processes and help build muscle, but there is much interest in whether other protein sources, particularly those from fish, could offer similar benefits. Fish proteins may also have the added advantage of being more sustainable, which is increasingly important in today's world. The nonessential amino acid blend served as a control, as it was not expected to contribute to processes that support muscle recovery and growth due to its lack of essential amino acids. The results showed that whey protein was the most effective by leading to the highest concentrations of essential amino acids in the blood, and the greatest amount of leucine retained in the body, meaning that the body was potentially able to use more of it for muscle recovery and growth. The fish protein performed better than the nonessential amino acids, supporting the idea that it could help with muscle recovery, but it was not as effective as whey protein. This finding is likely because the fish protein contained less essential amino acids, which are critical for muscle recovery and growth processes. Consuming a larger amount of the fish protein could potentially provide similar benefits to whey protein, but more studies would be needed to confirm this. The nonessential amino acid blend was the least effective, as expected, because it lacked the necessary components to stimulate these anabolic processes in muscle. The interpretation of these results is that while whey protein would be the most effective of the three protein sources for promoting muscle recovery after exercise, fish-derived proteins like the one tested in this study could still be a good alternative, especially for those who are looking for nondairy sources of protein. While the fish protein didn't perform as well as whey protein in this study, it did still support muscle recovery, suggesting it could be a viable option to match the effects of whey if provided at the right dosage. Overall, this research adds to our understanding of how different protein sources can help the body recover after exercise, and suggests that future research could focus on how adjusting the amount of fish protein consumed could improve its potential to support recovery and growth in response to exercise. [ABSTRACT FROM AUTHOR]

BackgroundGiven limited experience in applying the creatine-(methyl-D3) (D3Cr) dilution method to measure skeletal muscle mass (SMM) in young children, the feasibility of deployment in a fielding setting and performance of the method was assessed in a cohort of 4-year-old children in Dhaka, Bangladesh.MethodsFollowing D3Cr oral dose (10 mg) administration, single fasting urine samples were collected at 2-4 days (n = 100). Twenty-four-hour post-dose collections and serial spot urine samples on days 2, 3 and 4 were obtained in a subset of participants (n = 10). Urinary creatine, creatinine, D3Cr and D3-creatinine enrichment were analyzed by liquid chromatography-tandem mass spectrometry. Appendicular lean mass (ALM) was measured by dual-energy x-ray absorptiometry and grip strength was measured by a hand-held dynamometer.ResultsSMM was measured successfully in 91% of participants, and there were no adverse events. Mean ± SD SMM was greater than ALM (4.5 ± 0.4 and 3.2 ± 0.6 kg, respectively). Precision of SMM was low (intraclass correlation = 0.20; 95% CI: 0.02, 0.75; n = 10). Grip strength was not associated with SMM in multivariable analysis (0.004 kg per 100 g of SMM; 95% CI: -0.031, 0.038; n = 91).ConclusionsThe D3Cr dilution method was feasible in a community setting. However, high within-child variability in SMM estimates suggests the need for further optimization of this approach.ImpactThe D3-creatine (D3Cr) stable isotope dilution method was considered a feasible method for the estimation of skeletal muscle mass (SMM) in young children in a community setting and was well accepted among participants. SMM was weakly associated with both dual-energy x-ray absorptiometry-derived values of appendicular lean mass and grip strength. High within-child variability in estimated values of SMM suggests that further optimization of the D3Cr stable isotope dilution method is required prior to implementation in community research settings.

The branch chain amino acid leucine is a potent stimulator of protein synthesis in skeletal muscle. Leucine rapidly enters the cell via the L-Type Amino Acid Transporter 1 (LAT1); however, little is known regarding the localisation and distribution of this transporter in human skeletal muscle. Therefore, we applied immunofluorescence staining approaches to visualise LAT1 in wild type (WT) and LAT1 muscle-specific knockout (mKO) mice, in addition to basal human skeletal muscle samples. LAT1 positive staining was visually greater in WT muscles compared to mKO muscle. In human skeletal muscle, positive LAT1 staining was noted close to the sarcolemmal membrane (dystrophin positive staining), with a greater staining intensity for LAT1 observed in the sarcoplasmic regions of type II fibres (those not stained positively for myosin heavy-chain 1, Type II-25.07 ± 5.93, Type I-13.71 ± 1.98, p < 0.01), suggesting a greater abundance of this protein in these fibres. Finally, we observed association with LAT1 and endothelial nitric oxide synthase (eNOS), suggesting LAT1 association close to the microvasculature. This is the first study to visualise the distribution and localisation of LAT1 in human skeletal muscle. As such, this approach provides a validated experimental platform to study the role and regulation of LAT1 in human skeletal muscle in response to various physiological and pathophysiological models.

The branch chain amino acid leucine is a potent stimulator of protein synthesis in skeletal muscle. Leucine rapidly enters the cell via the L-Type Amino Acid Transporter 1 (LAT1); however, little is known regarding the localisation and distribution of this transporter in human skeletal muscle. Therefore, we applied immunofluorescence staining approaches to visualise LAT1 in wild type (WT) and LAT1 muscle-specific knockout (mKO) mice, in addition to basal human skeletal muscle samples. LAT1 positive staining was visually greater in WT muscles compared to mKO muscle. In human skeletal muscle, positive LAT1 staining was noted close to the sarcolemmal membrane (dystrophin positive staining), with a greater staining intensity for LAT1 observed in the sarcoplasmic regions of type II fibres (those not stained positively for myosin heavy-chain 1, Type II-25.07 ± 5.93, Type I-13.71 ± 1.98, p < 0.01), suggesting a greater abundance of this protein in these fibres. Finally, we observed association with LAT1 and endothelial nitric oxide synthase (eNOS), suggesting LAT1 association close to the microvasculature. This is the first study to visualise the distribution and localisation of LAT1 in human skeletal muscle. As such, this approach provides a validated experimental platform to study the role and regulation of LAT1 in human skeletal muscle in response to various physiological and pathophysiological models.