Plant-derived proteins have been suggested to have less anabolic properties when compared with animal-derived proteins. Whether blends of plant- and animal-derived proteins can compensate for their lesser anabolic potential has not been assessed. This study compares post-prandial muscle protein synthesis rates following the ingestion of milk protein with wheat protein or a blend of wheat plus milk protein in healthy, young males. In a randomized, double blind, parallel-group design, 36 males (23±3 y) received a primed continuous L-[ring-13C6]-phenylalanine infusion after which they ingested 30 g milk protein (MILK), 30 g wheat protein (WHEAT), or a 30 g blend combining 15 g wheat plus 15 g milk protein (WHEAT+MILK). Blood and muscle biopsies were collected frequently for 5 hours to assess post-prandial plasma amino acid profiles and subsequent myofibrillar protein synthesis rates. Ingestion of protein increased myofibrillar protein synthesis rates in all treatments (P<0.001). Post-prandial myofibrillar protein synthesis rates did not differ between MILK vs WHEAT (0.053±0.013 vs 0.056±0.012 %∙h-1, respectively; t-test P=0.56) or between MILK vs WHEAT+MILK (0.053±0.013 vs 0.059±0.025 %∙h-1, respectively; t-test P=0.46). In conclusion, ingestion of 30 g milk protein, 30 g wheat protein, or a blend of 15 g wheat plus 15 g milk protein increases muscle protein synthesis rates in young males. Furthermore, muscle protein synthesis rates following the ingestion of 30 g milk protein do not differ from rates observed after ingesting 30 g wheat protein or a blend with 15 g milk plus 15 g wheat protein in healthy, young males.

Background Poor nutritional status is frequently observed in end-stage renal disease patients and associated with adverse clinical outcomes and increased mortality. Loss of amino acids (AAs) during hemodialysis (HD) may contribute to protein malnutrition in these patients. Objective We aimed to assess the extent of AA loss during HD in end-stage renal disease patients consuming their habitual diet. Methods Ten anuric chronic HD patients (mean ± SD age: 67.9 ± 19.3 y, BMI: 23.2 ± 3.5 kg/m2), undergoing HD 3 times per week, were selected to participate in this study. Spent dialysate was collected continuously and plasma samples were obtained directly before and after a single HD session in each participant. AA profiles in spent dialysate and in pre-HD and post-HD plasma were measured through ultra-performance liquid chromatography to determine AA concentrations and, as such, net loss of AAs. In addition, dietary intake before and throughout HD was assessed using a 24-h food recall questionnaire during HD. Paired-sample t tests were conducted to compare pre-HD and post-HD plasma AA concentrations. Results During an HD session, 11.95 ± 0.69 g AAs were lost via the dialysate, of which 8.26 ± 0.46 g were nonessential AAs, 3.69 ± 0.31 g were essential AAs, and 1.64 ± 0.17 g were branched-chain AAs. As a consequence, plasma total and essential AA concentrations declined significantly from 2.88 ± 0.15 and 0.80 ± 0.05 mmol/L to 2.27 ± 0.11 and 0.66 ± 0.05 mmol/L, respectively (P &lt; 0.05). AA profiles of pre-HD plasma and spent dialysate were similar. Moreover, AA concentrations in pre-HD plasma and spent dialysate were strongly correlated (Spearman's ρ = 0.92, P &lt; 0.001). Conclusions During a single HD session, ∼12 g AAs are lost into the dialysate, causing a significant decline in plasma AA concentrations. AA loss during HD can contribute substantially to protein malnutrition in end-stage renal disease patients. This study was registered at the Netherlands Trial Registry (NTR7101).

End-stage renal disease patients have insufficient renal clearance capacity left to adequately excrete metabolic waste products. Hemodialysis (HD) is often employed to partially replace renal clearance in these patients. However, skeletal muscle mass and strength start to decline at an accelerated rate after initiation of chronic HD therapy. An essential anabolic stimulus to allow muscle maintenance is dietary protein ingestion. Chronic HD patients generally fail to achieve recommended protein intake levels, in particular on dialysis days. Besides a low protein intake on dialysis days, the protein equivalent of a meal is extracted from the circulation during HD. Apart from protein ingestion, physical activity is essential to allow muscle maintenance. Unfortunately, most chronic HD patients have a sedentary lifestyle. Yet, physical activity and nutritional interventions to support muscle maintenance are generally not implemented in routine patient care. To support muscle maintenance in chronic HD patients, quantity and timing of protein intake should be optimized, in particular throughout dialysis days. Furthermore, implementing physical activity either during or between HD sessions may improve the muscle protein synthetic response to protein ingestion. A well-orchestrated combination of physical activity and nutritional interventions will be instrumental to preserve muscle mass in chronic HD patients.

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Skeletal muscle loss is the most important hallmark of protein energy wasting syndrome as it contributes to declines in physical independence, poor quality of life, and higher mortality risk in individuals with ESRD on maintenance hemodialysis (HD). As such, exercise and nutritional interventions have been investigated with the goal to preserve skeletal muscle mass and overall quality of life. Unfortunately, current efforts are unable to confirm the capacity of exercise to mitigate ESRD‐associated muscle wasting. However, the inconclusive data are often accompanied by suboptimal exercise prescriptions. Exercise sessions are often implemented in‐clinic during the catabolic and proinflammatory period of dialysis treatment and without concurrent nutritional support. Additionally, indirect considerations like exercise intolerance and exercise program compliance/adherence also inhibit exercise training potential. These shortcomings all stem from the current lack of understanding in skeletal muscle mass regulation within the context of ESRD and intermittent HD. As such, this review summarizes the current understanding of exercise regulation on skeletal muscle mass and ESRD‐related obstacles of anabolism to contextualize the ineffectiveness of current exercise interventions for HD patients.

Background Protein ingestion increases muscle protein synthesis rates. The food matrix in which protein is provided can strongly modulate the postprandial muscle protein synthetic response. So far, the muscle protein synthetic response to the ingestion of whole foods remains largely unexplored. Objectives To compare the impact of ingesting 30g protein provided as milk protein or cheese on postprandial plasma amino acid concentrations and muscle protein synthesis rates at rest and during recovery from exercise in vivo in young males. Methods In this randomized, parallel-group intervention trial, twenty healthy, 18–35y old males ingested 30g protein provided as cheese or milk protein concentrate following a single-legged resistance-type exercise session consisting of 12 sets of leg press and leg extension exercise. Primed, continuous intravenous L-[ring-13C6]-phenylalanine infusions were combined with the collection of blood and muscle tissue samples to assess postabsorptive and 4h postprandial muscle protein synthesis rates at rest and during recovery from exercise. Data were analyzed using repeated measures Time × Group (× Leg) ANOVA. Results Plasma total amino acid concentrations increased after protein ingestion (Time: P &lt; 0.001), with 38% higher peak concentrations following milk protein than cheese ingestion (Time x Group: P &lt; 0.001). Muscle protein synthesis rates increased following both cheese and milk protein ingestion from 0.037 ± 0.014 to 0.055 ± 0.018%·h–1 and 0.034 ± 0.008 to 0.056 ± 0.010%·h–1 at rest and even more following exercise from 0.031 ± 0.010 to 0.067 ± 0.013%·h–1 and 0.030 ± 0.008 to 0.063 ± 0.010%·h–1, respectively (Time: all P &lt; 0.05; Time × Leg: P = 0.002), with no differences between cheese and milk protein ingestion (Time x Group: both P &gt; 0.05). Conclusion Cheese ingestion increases muscle protein synthesis rates both at rest and during recovery from exercise. The postprandial muscle protein synthetic response to the ingestion of cheese or milk protein does not differ when 30g protein are ingested at rest or during recovery from exercise in healthy, young males. This trial was registered at www.trialregister.nl as NL7941 (https://www.trialregister.nl/trial/7941).

Introduction: Plant-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. Methods: In a randomized, double-blind, parallel-group design, 24 healthy young males (24 ± 4 yr) received primed continuous L-[ring-13 C 6 ]-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. Results: Ingestion 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). Conclusions: Ingestion 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.

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