Publications by authors named "Lex B Verdijk"

117 Publications

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.

J Nutr 2021 Oct 12. Epub 2021 Oct 12.

Department of Human Biology, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Centre+, Maastricht, The Netherlands.

Background: The rate of protein digestion and amino acid absorption determines the postprandial rise in circulating amino acids and modulates postprandial muscle protein synthesis rates.

Objective: We 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.

Methods: Twenty-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.

Results: Postprandial 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).

Conclusions: Ingestion 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.
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http://dx.doi.org/10.1093/jn/nxab305DOI Listing
October 2021

Nutritional supplementation to enhance the efficacy of exercise training in older adults: what is the evidence from the latest randomized controlled trials?

Authors:
Lex B Verdijk

Curr Opin Clin Nutr Metab Care 2021 Nov;24(6):504-510

Department Human Biology, Faculty of Health, Medicine, and Life Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, the Netherlands.

Purpose Of Review: This review summarizes recent studies that assessed whether nutritional supplementation enhances the efficacy of exercise training in older adults, focusing on the benefits for physical/functional performance of protein, vitamin D, or multi-ingredient supplementation.

Recent Findings: Studies applying long-term exercise training strongly support the benefits of different exercise regimens for muscle strength and function but most studies do not provide direct evidence for protein, vitamin D, or multi-ingredient supplementation to further augment such improvements in older adults. Several methodological limitations are addressed that likely limited the reliability to convincingly establish or refute any additive effects of supplementation. Only when specifically tailored to the population under study, ensuring proper intensity, duration, and adherence to exercise, and aiming for a daily intake of ∼1.5 g protein per kg body mass, and ∼800 IU of vitamin D supplementation, there appears to be some potential to augment the efficacy of long-term exercise training in older adults, with potentially greater benefits in compromised older subpopulations.

Summary: There is some support for the efficacy of nutritional supplementation to further augment the beneficial effects of prolonged exercise training in older adults but any intervention needs tailoring of both the exercise and the nutritional intervention towards the intended (sub)population.
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http://dx.doi.org/10.1097/MCO.0000000000000792DOI Listing
November 2021

Amino acid removal during hemodialysis can be compensated for by protein ingestion and is not compromised by intradialytic exercise: a randomized controlled crossover trial.

Am J Clin Nutr 2021 Sep 12. Epub 2021 Sep 12.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands.

Background: Patients with end-stage renal disease (ESRD) undergoing hemodialysis experience a rapid decline in skeletal muscle mass and strength. Hemodialysis removes amino acids (AAs) from the circulation, thereby lowering plasma AA concentrations and stimulating proteolysis.

Objectives: In the present study, we evaluate the impact of intradialytic protein ingestion at rest and following exercise on AA removal and plasma AA availability in patients with ESRD.

Methods: Ten patients (age: 65 ± 16 y, male/female: 8/2, BMI: 24.2 ± 4.8 kg/m2, serum albumin: 3.4 ± 0.3 g/dL) with ESRD undergoing hemodialysis participated in this randomized controlled crossover trial. During 4 hemodialysis sessions, patients were assigned to ingest 40 g protein or a placebo 60 min after initiation, both at rest (PRO and PLA, respectively) and following exercise (PRO + EX and PLA + EX, respectively). Spent dialysate and blood samples were collected every 30 min throughout hemodialysis to assess AA removal and plasma AA availability.

Results: Plasma AA concentrations declined by 26.1 ± 4.5% within 30 min after hemodialysis initiation during all interventions (P < 0.001, η2p > 0.79). Protein ingestion, but not intradialytic exercise, increased AA removal throughout hemodialysis (9.8 ± 2.0, 10.2 ± 1.6, 16.7 ± 2.2, and 17.3 ± 2.3 g during PLA, PLA + EX, PRO, and PRO + EX interventions, respectively; protein effect P < 0.001, η2p = 0.97; exercise effect P = 0.32, η2p = 0.11). Protein ingestion increased plasma AA concentrations until the end of hemodialysis, whereas placebo ingestion resulted in decreased plasma AA concentrations (time effect P < 0.001, η2p > 0.84). Plasma AA availability (incremental AUC) was greater during PRO and PRO + EX interventions (49 ± 87 and 70 ± 34 mmol/L/240 min, respectively) compared with PLA and PLA + EX interventions (-227 ± 54 and -208 ± 68 mmol/L/240 min, respectively; protein effect P < 0.001, η2p = 0.98; exercise effect P = 0.21, η2p = 0.16).

Conclusions: Protein ingestion during hemodialysis compensates for AA removal and increases plasma AA availability both at rest and during recovery from intradialytic exercise. Intradialytic exercise does not compromise AA removal or reduce plasma AA availability during hemodialysis in a postabsorptive or postprandial state.
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http://dx.doi.org/10.1093/ajcn/nqab274DOI Listing
September 2021

Acute Effects of Dietary Nitrate on Exercise Tolerance, Muscle Oxygenation, and Cardiovascular Function in Patients With Peripheral Arterial Disease.

Int J Sport Nutr Exerc Metab 2021 Jul 20:1-12. Epub 2021 Jul 20.

Radboud University Medical Center.

Previous studies have used supplements to increase dietary nitrate intake in clinical populations. Little is known about whether effects can also be induced through vegetable consumption. Therefore, the aim of this study was to assess the impact of dietary nitrate, through nitrate-rich vegetables (NRV) and beetroot juice (BRJ) supplementation, on plasma nitrate and nitrite concentrations, exercise tolerance, muscle oxygenation, and cardiovascular function in patients with peripheral arterial disease. In a randomized crossover design, 18 patients with peripheral arterial disease (age: 73 ± 8 years) followed a nitrate intake protocol (∼6.5 mmol) through the consumption of NRV, BRJ, and nitrate-depleted BRJ (placebo). Blood samples were taken, blood pressure and arterial stiffness were measured in fasted state and 150 min after intervention. Each intervention was followed by a maximal walking exercise test to determine claudication onset time and peak walking time. Gastrocnemius oxygenation was measured by near-infrared spectroscopy. Blood samples were taken and blood pressure was measured 10 min after exercise. Mean plasma nitrate and nitrite concentrations increased (nitrate; Time × Intervention interaction; p < .001), with the highest concentrations after BRJ (494 ± 110 μmol/L) compared with NRV (202 ± 89 μmol/L) and placebo (80 ± 19 μmol/L; p < .001). Mean claudication onset time and peak walking time did not differ between NRV (413 ± 187 s and 745 ± 220 s, respectively), BRJ (392 ± 154 s and 746 ± 176 s), and placebo (403 ± 176 s and 696 ± 222 s) (p = .762 and p = .165, respectively). Gastrocnemius oxygenation, blood pressure, and arterial stiffness were not affected by the intervention. NRV and BRJ intake markedly increase plasma nitrate and nitrite, but this does not translate to improved exercise tolerance, muscle oxygenation, and/or cardiovascular function.
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http://dx.doi.org/10.1123/ijsnem.2021-0054DOI Listing
July 2021

Increasing Nitrate-Rich Vegetable Intake Lowers Ambulatory Blood Pressure in (pre)Hypertensive Middle-Aged and Older Adults: A 12-Wk Randomized Controlled Trial.

J Nutr 2021 Sep;151(9):2667-2679

Institute for Health Sciences, Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands.

Background: Emerging evidence suggests that increasing dietary nitrate intake may be an effective approach to improve cardiovascular health. However, the effects of a prolonged elevation of nitrate intake through an increase in vegetable consumption are understudied.

Objective: Our primary aim was to determine the impact of 12 wk of increased daily consumption of nitrate-rich vegetables or nitrate supplementation on blood pressure (BP) in (pre)hypertensive middle-aged and older adults.

Methods: In a 12-wk randomized, controlled study (Nijmegen, The Netherlands), 77 (pre)hypertensive participants (BP: 144 ± 13/87 ± 7 mmHg, age: 65 ± 10 y) either received an intervention with personalized monitoring and feedback aiming to consume ∼250-300 g nitrate-rich vegetables/d (∼350-400 mg nitrate/d; n = 25), beetroot juice supplementation (400 mg nitrate/d; n = 26), or no intervention (control; n = 26). Before and after intervention, 24-h ambulatory BP was measured. Data were analyzed using repeated measures ANOVA (time × treatment), followed by within-group (paired t-test) and between-group analyses (1-factor ANOVA) where appropriate.

Results: The 24-h systolic BP (SBP) (primary outcome) changed significantly (P-interaction time × treatment = 0.017) with an increase in the control group (131 ± 8 compared with 135 ± 10 mmHg; P = 0.036); a strong tendency for a decline in the nitrate-rich vegetable group (129 ± 10 compared with 126 ± 9 mmHg; P = 0.051) which was different from control (P = 0.020); but no change in the beetroot juice group (133 ± 11 compared with 132 ± 12 mmHg; P = 0.56). A significant time × treatment interaction was also found for daytime SBP (secondary outcome, P = 0.011), with a significant decline in the nitrate-rich vegetable group (134 ± 10 compared with 129 ± 9 mmHg; P = 0.006) which was different from control (P = 0.010); but no changes in the beetroot juice (138 ± 12 compared with 137 ± 14 mmHg; P = 0.41) and control group (136 ± 10 compared with 137 ± 11 mmHg; P = 0.08). Diastolic BP (secondary outcome) did not change in any of the groups.

Conclusions: A prolonged dietary intervention focusing on high-nitrate vegetable intake is an effective strategy to lower SBP in (pre)hypertensive middle-aged and older adults. This trial was registered at www.trialregister.nl as NL7814.
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http://dx.doi.org/10.1093/jn/nxab157DOI Listing
September 2021

Insects are a viable protein source for human consumption: from insect protein digestion to postprandial muscle protein synthesis in vivo in humans: a double-blind randomized trial.

Am J Clin Nutr 2021 09;114(3):934-944

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands.

Background: Insects have recently been identified as a more sustainable protein-dense food source and may represent a viable alternative to conventional animal-derived proteins.

Objectives: We aimed to compare the impacts of ingesting lesser mealworm- and milk-derived protein on protein digestion and amino acid absorption kinetics, postprandial skeletal muscle protein synthesis rates, and the incorporation of dietary protein-derived amino acids into de novo muscle protein at rest and during recovery from exercise in vivo in humans.

Methods: In this double-blind randomized controlled trial, 24 healthy, young men ingested 30 g specifically produced, intrinsically l-[1-13C]-phenylalanine and l-[1-13C]-leucine labeled lesser mealworm- or milk-derived protein after a unilateral bout of resistance-type exercise. Primed continuous l-[ring-2H5]-phenylalanine, l-[ring-3,5-2H2]-tyrosine, and l-[1-13C]-leucine infusions were applied, with frequent collection of blood and muscle tissue samples.

Results: A total of 73% ± 7% and 77% ± 7% of the lesser mealworm and milk protein-derived phenylalanine was released into the circulation during the 5 h postprandial period, respectively, with no significant differences between groups (P < 0.05). Muscle protein synthesis rates increased after both lesser mealworm and milk protein concentrate ingestion from 0.025 ± 0.008%/h to 0.045 ± 0.017%/h and 0.028 ± 0.010%/h to 0.056 ± 0.012%/h at rest and from 0.025 ± 0.012%/h to 0.059 ± 0.015%/h and 0.026 ± 0.009%/h to 0.073 ± 0.020%/h after exercise, respectively (all P < 0.05), with no differences between groups (both P > 0.05). Incorporation of mealworm and milk protein-derived l-[1-13C]-phenylalanine into de novo muscle protein was greater after exercise than at rest (P < 0.05), with no differences between groups (P > 0.05).

Conclusions: Ingestion of a meal-like amount of lesser mealworm-derived protein is followed by rapid protein digestion and amino acid absorption and increases muscle protein synthesis rates both at rest and during recovery from exercise. The postprandial protein handling of lesser mealworm does not differ from ingesting an equivalent amount of milk protein concentrate in vivo in humans.This trial was registered at www.trialregister.nl as NL6897.
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http://dx.doi.org/10.1093/ajcn/nqab115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8408844PMC
September 2021

No differences in muscle protein synthesis rates following ingestion of wheat protein, milk protein, and their protein blend in healthy, young males.

Br J Nutr 2021 Feb 18:1-11. Epub 2021 Feb 18.

TiFN, Wageningen, The Netherlands.

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. The present 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 randomised, double-blind, parallel-group design, 36 males (23 (sd 3) years) 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 h 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 v. WHEAT (0·053 (sd 0·013) v. 0·056 (sd 0·012) %·h-1, respectively; t test P = 0·56) or between MILK v. WHEAT+MILK (0·053 (sd 0·013) v. 0·059 (sd 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.
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http://dx.doi.org/10.1017/S0007114521000635DOI Listing
February 2021

Exercise Plus Presleep Protein Ingestion Increases Overnight Muscle Connective Tissue Protein Synthesis Rates in Healthy Older Men.

Int J Sport Nutr Exerc Metab 2021 Feb 14;31(3):217-226. Epub 2021 Feb 14.

Maastricht University Medical Centre.

Protein ingestion and exercise stimulate myofibrillar protein synthesis rates. When combined, exercise further increases the postprandial rise in myofibrillar protein synthesis rates. It remains unclear whether protein ingestion with or without exercise also stimulates muscle connective tissue protein synthesis rates. The authors assessed the impact of presleep protein ingestion on overnight muscle connective tissue protein synthesis rates at rest and during recovery from resistance-type exercise in older men. Thirty-six healthy, older men were randomly assigned to ingest 40 g intrinsically L-[1-13C]-phenylalanine and L-[1-13C]-leucine-labeled casein protein (PRO, n = 12) or a nonprotein placebo (PLA, n = 12) before going to sleep. A third group performed a single bout of resistance-type exercise in the evening before ingesting 40 g intrinsically-labeled casein protein prior to sleep (EX+PRO, n = 12). Continuous intravenous infusions of L-[ring-2H5]-phenylalanine and L-[1-13C]-leucine were applied with blood and muscle tissue samples collected throughout overnight sleep. Presleep protein ingestion did not increase muscle connective tissue protein synthesis rates (0.049 ± 0.013 vs. 0.060 ± 0.024%/hr in PLA and PRO, respectively; p = .73). Exercise plus protein ingestion resulted in greater overnight muscle connective tissue protein synthesis rates (0.095 ± 0.022%/hr) when compared with PLA and PRO (p < .01). Exercise increased the incorporation of dietary protein-derived amino acids into muscle connective tissue protein (0.036 ± 0.013 vs. 0.054 ± 0.009 mole percent excess in PRO vs. EX+PRO, respectively; p < .01). In conclusion, resistance-type exercise plus presleep protein ingestion increases overnight muscle connective tissue protein synthesis rates in older men. Exercise enhances the utilization of dietary protein-derived amino acids as precursors for de novo muscle connective tissue protein synthesis during overnight sleep.
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http://dx.doi.org/10.1123/ijsnem.2020-0222DOI Listing
February 2021

Myonuclear content and domain size in small versus larger muscle fibres in response to 12 weeks of resistance exercise training in older adults.

Acta Physiol (Oxf) 2021 04 20;231(4):e13599. Epub 2020 Dec 20.

Human Biology, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University, Maastricht, The Netherlands.

Aim: To assess the relation between muscle fibre hypertrophy and myonuclear accretion in relatively small and large muscle fibre size clusters following prolonged resistance exercise training in older adults.

Methods: Muscle biopsies were collected before and after 12 weeks of resistance exercise training in 40 healthy, older men (70 ± 3 years). All muscle fibres were ordered by size and categorized in four muscle fibre size clusters: 'Small': 2000-3999 µm , 'Moderate': 4000-5999 µm , 'Large': 6000-7999 µm and 'Largest': 8000-9999 µm . Changes in muscle fibre size cluster distribution were related to changes in muscle fibre size, myonuclear content and myonuclear domain size.

Results: With training, the percentage of muscle fibres decreased in the Small (from 23 ± 12 to 17 ± 14%, P < .01) and increased in the Largest (from 11 ± 8 to 15 ± 10%, P < .01) muscle fibre size clusters. The decline in the percentage of Small muscle fibres was accompanied by an increase in overall myonuclear domain size (r = -.466, P = .002) and myonuclear content (r = -.390, P = .013). In contrast, the increase in the percentage of the Largest muscle fibres was accompanied by an overall increase in myonuclear content (r = .616, P < .001), but not in domain size.

Conclusion: Prolonged resistance-type exercise training induces a decline in the percentage of small as well as an increase in the percentage of the largest muscle fibres in older adults. Whereas the change in the percentage of small fibres is best predicted by an increase in overall myonuclear domain size, the change in the percentage of the largest fibres is associated with an overall increase in myonuclear content.
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http://dx.doi.org/10.1111/apha.13599DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8047909PMC
April 2021

Casein Protein Processing Strongly Modulates Post-Prandial Plasma Amino Acid Responses In Vivo in Humans.

Nutrients 2020 Jul 31;12(8). Epub 2020 Jul 31.

NUTRIM School of Nutrition and Translation Research in Metabolism, Maastricht University Medical Centre, P.O. Box 616, 6200 MD Maastricht, The Netherlands.

Micellar casein is characterized as a slowly digestible protein source, and its structure can be modulated by various food processing techniques to modify its functional properties. However, little is known about the impact of such modifications on casein protein digestion and amino acid absorption kinetics and the subsequent post-prandial plasma amino acid responses. In the present study, we determined post-prandial aminoacidemia following ingestion of isonitrogenous amounts of casein protein (40 g) provided as micellar casein (Mi-CAS), calcium caseinate (Ca-CAS), or cross-linked sodium caseinate (XL-CAS). Fifteen healthy, young men (age: 26 ± 4 years, BMI: 23 ± 1 kg·m) participated in this randomized cross-over study and ingested 40 g Mi-Cas, Ca-CAS, and XL-CAS protein, with a ~1 week washout between treatments. On each trial day, arterialized blood samples were collected at regular intervals during a 6 h post-prandial period to assess plasma amino acid concentrations using ultra-performance liquid chromatography. Plasma amino acid concentrations were higher following the ingestion of XL-CAS when compared to Mi-CAS and Ca-CAS from t = 15 to 90 min (all < 0.05). Plasma amino acid concentrations were higher following ingestion of Mi-CAS compared to Ca-CAS from t = 30 to 45 min (both < 0.05). Plasma total amino acids iAUC were higher following the ingestion of XL-CAS when compared to Ca-CAS (294 ± 63 vs. 260 ± 75 mmol·L, = 0.006), with intermediate values following Mi-CAS ingestion (270 ± 63 mmol·L, > 0.05). In conclusion, cross-linked sodium caseinate is more rapidly digested when compared to micellar casein and calcium caseinate. Protein processing can strongly modulate the post-prandial rise in plasma amino acid bioavailability in vivo in humans.
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http://dx.doi.org/10.3390/nu12082299DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7468913PMC
July 2020

The impact of beetroot juice supplementation on muscular endurance, maximal strength and countermovement jump performance.

Eur J Sport Sci 2021 Jun 21;21(6):871-878. Epub 2020 Jul 21.

School of Sport and Exercise, HAN University of Applied Sciences, Nijmegen, Netherlands.

: Dietary nitrate has been shown to enhance muscle contractile function and has, therefore, been linked to increased muscle power and sprint exercise performance. However, the impact of dietary nitrate supplementation on maximal strength, performance and muscular endurance remains to be established. : Fifteen recreationally active males (25 ± 4 y, BMI 24 ± 3 kg/m) participated in a randomized double-blinded cross-over study comprising two 6-d supplementation periods; 140 mL/d nitrate-rich (BR; 985 mg/d) and nitrate-depleted (PLA; 0.37 mg/d) beetroot juice. Three hours following the last supplement, we assessed countermovement jump (CMJ) performance, maximal strength and power of the upper leg by voluntary isometric (30° and 60° angle) and isokinetic contractions (60, 120, 180 and 300°·s), and muscular endurance (total workload) by 30 reciprocal isokinetic voluntary contractions at 180°·s. : Despite differences in plasma nitrate (BR: 879 ± 239 vs. PLA: 33 ± 13 μmol/L,  < 0.001) and nitrite (BR: 463 ± 217 vs. PLA: 176 ± 50 nmol/L,  < 0.001) concentrations prior to exercise testing, CMJ height (BR: 39.3 ± 6.3 vs. PLA: 39.6 ± 6.3 cm;  = 0.39) and muscular endurance (BR: 3.93 ± 0.69 vs. PLA: 3.90 ± 0.66 kJ;  = 0.74) were not different between treatments. In line, isometric strength ( > 0.50 for both angles) and isokinetic knee extension power ( > 0.33 for all velocities) did not differ between treatments. Isokinetic knee flexion power was significantly higher following BR compared with PLA ingestion at 60°·s ( = 0.001), but not at 120°·s ( = 0.24), 180°·s ( = 0.066), and 300°·s ( = 0.36). : Nitrate supplementation does not improve maximal strength, countermovement jump performance and muscular endurance in healthy, active males.
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http://dx.doi.org/10.1080/17461391.2020.1788649DOI Listing
June 2021

During Hospitalization, Older Patients at Risk for Malnutrition Consume <0.65 Grams of Protein per Kilogram Body Weight per Day.

Nutr Clin Pract 2020 Aug 24;35(4):655-663. Epub 2020 Jun 24.

Department of Human Biology, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Centre+, Maastricht, the Netherlands.

Background: Malnutrition is prevalent in hospitalized patients. To support muscle maintenance in older and chronically ill patients, a protein intake of 1.2-1.5 g/kg/d has been recommended during hospitalization. We assessed daily protein intake levels and distribution in older patients at risk for malnutrition during hospitalization.

Methods: In this prospective, observational study, we measured actual food and food supplement consumption in patients (n = 102; age, 68 ± 14 years; hospital stay, 14 [8-28] days) at risk of malnutrition during hospitalization. Food provided by hospital meals, ONS, and snacks and the actual amount of food (not) consumed were weighed and recorded for all patients.

Results: Hospital meals provided 1.03 [0.77-1.26] protein, whereas actual protein consumption was only 0.65 [0.37-0.93] g/kg/d. Protein intake at breakfast, lunch, and dinner was 10 [6-15], 9 [5-14], and 13 [9-18] g, respectively. The use of ONS (n = 62) resulted in greater energy (1.26 [0.40-1.79] MJ/d, 300 [100-430] kcal/d) and protein intake levels (11 [4-16] g/d), without changing the macronutrient composition of the diet.

Conclusion: Despite protein provision of ∼1.0 g/kg/d, protein intake remains well below these values (∼0.65 g/kg/d), as 30%-40% of the provided food and supplements is not consumed. Provision of ONS may increase energy and protein intake but does not change the macronutrient composition of the diet. Current nutrition strategies to achieve the recommended daily protein intake in older patients during their hospitalization are not as effective as generally assumed.
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http://dx.doi.org/10.1002/ncp.10542DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7384011PMC
August 2020

A Nitrate-Rich Vegetable Intervention Elevates Plasma Nitrate and Nitrite Concentrations and Reduces Blood Pressure in Healthy Young Adults.

J Acad Nutr Diet 2020 08 5;120(8):1305-1317. Epub 2020 May 5.

Background: Emerging evidence suggests that increasing dietary nitrate intake may be an effective approach to reduce blood pressure. Beetroot juice is often used to supplement dietary nitrate, whereas nitrate intake levels from habitual diet are low. An increase in the habitual intake of nitrate-rich vegetables may represent an alternative to nitrate supplementation. However, the effectiveness and acceptability of a nitrate-rich-vegetables diet remain to be established.

Objective: The aim was to investigate the effect and feasibility of two different intervention strategies to increase dietary nitrate intake, on plasma nitrate/nitrite concentrations and blood pressure.

Design: A randomized, crossover trial was used.

Participants: Participants were healthy men and women (both n=15; age: 24±6 years) from the Netherlands.

Intervention: Participants were instructed to consume ∼400 mg nitrate at lunch, provided through nitrate-rich vegetables and dietary counseling, or beetroot juice supplementation. Both interventions lasted 1 week, with 1-week washout (January to April 2017).

Main Outcome: Plasma nitrate and nitrite concentrations and resting systolic and diastolic blood pressure were measured in an overnight fasted state (before and after intervention) and ∼2.5 hours after lunch (before and throughout intervention on day 1, 4, and 7).

Statistical Analysis: Two-factor (time × treatment) repeated-measures analyses of variance were performed.

Results: Mean plasma nitrate concentrations increased with both interventions, with a larger increase in beetroot juice vs nitrate-rich vegetables, both in a fasted state and ∼2.5 hours after lunch (day 1, beetroot juice: 2.31±0.56 mg/dL [373±90 μmol/L] vs nitrate-rich vegetables: 1.71±0.83 mg/dL [277±134 μmol/L]; P<0.001). Likewise, mean plasma nitrite concentrations increased with both interventions, but were higher after lunch in beetroot juice than in nitrate-rich vegetables (day 1: 2.58±1.52 μg/dL [560±331 nmol/L] vs 2.15±1.21 μg/dL [468±263 nmol/L]; P=0.020). Fasting mean systolic and diastolic blood pressure did not change, but mean systolic and diastolic blood pressure assessed ∼2.5 hours after lunch were significantly reduced throughout both intervention periods (P<0.05), with no differences between beetroot juice and nitrate-rich vegetables (day 1, systolic blood pressure: -5.1±9.5 mm Hg and diastolic blood pressure: -5.3±8.9 mm Hg).

Conclusion: Short-term consumption of dietary nitrate in the form of nitrate-rich vegetables represents an effective means to increase plasma nitrate and nitrite concentrations, and reduces blood pressure to the same extent as beetroot juice supplementation.
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http://dx.doi.org/10.1016/j.jand.2020.02.014DOI Listing
August 2020

Dose-response effects of dietary protein on muscle protein synthesis during recovery from endurance exercise in young men: a double-blind randomized trial.

Am J Clin Nutr 2020 08;112(2):303-317

NUTRIM School of Nutrition and Translational Research in Metabolism, Department of Human Biology, Maastricht University Medical Center+, Maastricht, Netherlands.

Background: Protein ingestion increases skeletal muscle protein synthesis rates during recovery from endurance exercise.

Objectives: We aimed to determine the effect of graded doses of dietary protein co-ingested with carbohydrate on whole-body protein metabolism, and skeletal muscle myofibrillar (MyoPS) and mitochondrial (MitoPS) protein synthesis rates during recovery from endurance exercise.

Methods: In a randomized, double-blind, parallel-group design, 48 healthy, young, endurance-trained men (mean ± SEM age: 27 ± 1 y) received a primed continuous infusion of l-[ring-2H5]-phenylalanine, l-[ring-3,5-2H2]-tyrosine, and l-[1-13C]-leucine and ingested 45 g carbohydrate with either 0 (0 g PRO), 15 (15 g PRO), 30 (30 g PRO), or 45 (45 g PRO) g intrinsically l-[1-13C]-phenylalanine and l-[1-13C]-leucine labeled milk protein after endurance exercise. Blood and muscle biopsy samples were collected over 360 min of postexercise recovery to assess whole-body protein metabolism and both MyoPS and MitoPS rates.

Results: Protein intake resulted in ∼70%-74% of the ingested protein-derived phenylalanine appearing in the circulation. Whole-body net protein balance increased dose-dependently after ingestion of 0, 15, 30, or 45 g protein (mean ± SEM: -0.31± 0.16, 5.08 ± 0.21, 10.04 ± 0.30, and 13.49 ± 0.55 μmol phenylalanine · kg-1 · h-1, respectively; P < 0.001). 30 g PRO stimulated a ∼46% increase in MyoPS rates (%/h) compared with 0 g PRO and was sufficient to maximize MyoPS rates after endurance exercise. MitoPS rates were not increased after protein ingestion; however, incorporation of dietary protein-derived l-[1-13C]-phenylalanine into de novo mitochondrial protein increased dose-dependently after ingestion of 15, 30, and 45 g protein at 360 min postexercise (0.018 ± 0.002, 0.034 ± 0.002, and 0.046 ± 0.003 mole percentage excess, respectively; P < 0.001).

Conclusions: Protein ingested after endurance exercise is efficiently digested and absorbed into the circulation. Whole-body net protein balance and dietary protein-derived amino acid incorporation into mitochondrial protein respond to increasing protein intake in a dose-dependent manner. Ingestion of 30 g protein is sufficient to maximize MyoPS rates during recovery from a single bout of endurance exercise.This trial was registered at trialregister.nl as NTR5111.
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http://dx.doi.org/10.1093/ajcn/nqaa073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7398777PMC
August 2020

Multifrequency bioelectrical impedance analysis may represent a reproducible and practical tool to assess skeletal muscle mass in euvolemic acutely ill hospitalized geriatric patients.

Eur Geriatr Med 2020 02 2;11(1):155-162. Epub 2019 Nov 2.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands.

Purpose: Geriatric patients with low skeletal muscle mass (SMM) and strength have a poor clinical outcome following acute illness. Consequently, it is recommended to assess SMM and strength in patients admitted to the acute care geriatric ward. Bio-impedance analysis (BIA) is a practical tool to assess SMM in hospitalized patients. However, the reproducibility of this assessment may be compromised due to changing clinical conditions. The objective was to study the reproducibility of SMM assessment using multifrequency BIA (mf-BIA) in acutely ill geriatric patients.

Methods: A total of 47 geriatric patients (age: 83 ± 7 years; n = 31 female) admitted to the acute geriatric ward participated in this pilot study. SMM was assessed on three occasions within the first week of hospital admission using the Maltron Bioscan-920-II.

Results: Total skeletal SMM averaged 21.4 ± 5.7, 20.7 ± 5.4, and 20.8 ± 5.1 kg assessed at 2 ± 1, 3 ± 1 and 5 ± 2 days after hospital admission, respectively. Coefficient of variation (COV) of the three SMM measurements was 4.9 ± 4.5% with an intraclass correlation coefficient (ICC) of 0.976 (CI 95%: 0.961-0.986; P < 0.001). Hydration status affected the reproducibility of the measurement, with non-euvolemic patients (n = 16) showing a significantly higher COV (7.6 ± 5.9% vs 3.5 ± 2.9%; P < 0.01) and a lower ICC (0.983 vs 0.913; P < 0.001) when compared to the euvolemic patients (n = 31).

Conclusion: Mf-BIA seems a highly reproducible and reliable method to assess SMM throughout the first week of hospitalization in geriatric patients. However, since abnormal hydration status may compromise reliability of the measurement, assessment of SMM using mf-BIA may better be performed when euvolemic status has been established.
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http://dx.doi.org/10.1007/s41999-019-00253-6DOI Listing
February 2020

Could intramuscular storage of dietary nitrate contribute to its ergogenic effect? A mini-review.

Free Radic Biol Med 2020 05 26;152:295-300. Epub 2020 Mar 26.

NUTRIM, School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, the Netherlands. Electronic address:

Extensive research performed over the past 10 years has resulted in dietary nitrate being considered a nutritional supplement that can improve exercise performance. However, there is still limited insight in the metabolic fate of dietary nitrate following the appearance of nitrate and nitrite in the circulation. Recent observations in humans suggest the storage of nitrate in skeletal muscle tissue. This short review discusses the possibility of nitrate being stored and utilized in human skeletal muscle tissue, and why confirming this may increase our understanding of how the nitrate-nitrite-NO pathway improves exercise performance. Further insight in skeletal muscle nitrate storage and metabolism may provide answers to current gaps in knowledge, such as the ergogenic benefit of acute vs multiday dietary nitrate supplementation, as well as the suggested muscle fiber-type specific effects on exercise performance. In this mini-review, specific questions that need further exploration are also discussed.
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http://dx.doi.org/10.1016/j.freeradbiomed.2020.03.025DOI Listing
May 2020

Casein Ingestion Does Not Increase Muscle Connective Tissue Protein Synthesis Rates.

Med Sci Sports Exerc 2020 09;52(9):1983-1991

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, THE NETHERLANDS.

Purpose: This study aimed to assess the effect of dietary protein ingestion on intramuscular connective tissue protein synthesis rates during overnight recovery from a single bout of resistance exercise.

Methods: Thirty-six healthy, young males were randomly assigned to one of three treatments. One group ingested 30 g intrinsically L-[1-C]-phenylalanine-labeled casein protein before sleep (PRO, n = 12). The other two groups performed a bout of resistance exercise in the evening and ingested either placebo (EX, n = 12) or 30 g intrinsically L-[1-C]-phenylalanine-labeled casein protein before sleep (EX + PRO, n = 12). Continuous intravenous infusions of L-[ring-H5]-phenylalanine and L-[1-C]-leucine were applied, and blood and muscle tissue samples were collected to assess connective tissue protein synthesis rates and dietary protein-derived amino acid incorporation in the connective tissue protein fraction.

Results: Resistance exercise resulted in higher connective tissue protein synthesis rates when compared with rest (0.086 ± 0.017%·h [EX] and 0.080 ± 0.019%·h [EX + PRO] vs 0.059 ± 0.016%·h [PRO]; P < 0.05). Postexercise casein protein ingestion did not result in higher connective tissue protein synthesis rates when compared with postexercise placebo ingestion (P = 1.00). Dietary protein-derived amino acids were incorporated into the connective tissue protein fraction at rest, and to a greater extent during recovery from exercise (P = 0.002).

Conclusion: Resistance exercise increases intramuscular connective tissue protein synthesis rates during overnight sleep, with no further effect of postexercise protein ingestion. However, dietary protein-derived amino acids are being used as precursors to support de novo connective tissue protein synthesis.
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http://dx.doi.org/10.1249/MSS.0000000000002337DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7431152PMC
September 2020

Hot-water immersion does not increase postprandial muscle protein synthesis rates during recovery from resistance-type exercise in healthy, young males.

J Appl Physiol (1985) 2020 04 19;128(4):1012-1022. Epub 2020 Mar 19.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.

The purpose of this study was to assess the impact of postexercise hot-water immersion on postprandial myofibrillar protein synthesis rates during recovery from a single bout of resistance-type exercise in healthy, young men. Twelve healthy, adult men (age: 23 ± 1 y) performed a single bout of resistance-type exercise followed by 20 min of water immersion of both legs. One leg was immersed in hot water [46°C: hot-water immersion (HWI)], while the other leg was immersed in thermoneutral water (30°C: CON). After water immersion, a beverage was ingested containing 20 g intrinsically L-[1-C]-phenylalanine and L-[1-C]-leucine labeled milk protein with 45 g of carbohydrates. In addition, primed continuous L-[-H]-phenylalanine and L-[1-C]-leucine infusions were applied, with frequent collection of blood and muscle samples to assess myofibrillar protein synthesis rates in vivo over a 5-h recovery period. Muscle temperature immediately after water immersion was higher in the HWI compared with the CON leg (37.5 ± 0.1 vs. 35.2 ± 0.2°C; < 0.001). Incorporation of dietary protein-derived L-[1-C]-phenylalanine into myofibrillar protein did not differ between the HWI and CON leg during the 5-h recovery period (0.025 ± 0.003 vs. 0.024 ± 0.002 MPE; = 0.953). Postexercise myofibrillar protein synthesis rates did not differ between the HWI and CON leg based upon L-[1-C]-leucine (0.050 ± 0.005 vs. 0.049 ± 0.002%/h; = 0.815) and L-[-H]-phenylalanine (0.048 ± 0.002 vs. 0.047 ± 0.003%/h; = 0.877), respectively. Hot-water immersion during recovery from resistance-type exercise does not increase the postprandial rise in myofibrillar protein synthesis rates. In addition, postexercise hot-water immersion does not increase the capacity of the muscle to incorporate dietary protein-derived amino acids in muscle tissue protein during subsequent recovery. This is the first study to assess the effect of postexercise hot-water immersion on postprandial myofibrillar protein synthesis rates and the incorporation of dietary protein-derived amino acids into muscle protein. We observed that hot-water immersion during recovery from a single bout of resistance-type exercise does not further increase myofibrillar protein synthesis rates or augment the postprandial incorporation of dietary protein-derived amino acids in muscle throughout 5 h of postexercise recovery.
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http://dx.doi.org/10.1152/japplphysiol.00836.2019DOI Listing
April 2020

The concept of skeletal muscle memory: Evidence from animal and human studies.

Acta Physiol (Oxf) 2020 07 3;229(3):e13465. Epub 2020 Apr 3.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, the Netherlands.

Within the current paradigm of the myonuclear domain theory, it is postulated that a linear relationship exists between muscle fibre size and myonuclear content. The myonuclear domain is kept (relatively) constant by adding additional nuclei (supplied by muscle satellite cells) during muscle fibre hypertrophy and nuclear loss (by apoptosis) during muscle fibre atrophy. However, data from recent animal studies suggest that myonuclei that are added to support muscle fibre hypertrophy are not lost within various muscle atrophy models. Such myonuclear permanence has been suggested to constitute a mechanism allowing the muscle fibre to (re)grow more efficiently during retraining, a phenomenon referred to as "muscle memory." The concept of "muscle memory by myonuclear permanence" has mainly been based on data attained from rodent experimental models. Whether the postulated mechanism also holds true in humans remains largely ambiguous. Nevertheless, there are several studies in humans that provide evidence to potentially support or contradict (parts of) the muscle memory hypothesis. The goal of the present review was to discuss the evidence for the existence of "muscle memory" in both animal and human models of muscle fibre hypertrophy as well as atrophy. Furthermore, to provide additional insight in the potential presence of muscle memory by myonuclear permanence in humans, we present new data on previously performed exercise training studies. Finally, suggestions for future research are provided to establish whether muscle memory really exists in humans.
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http://dx.doi.org/10.1111/apha.13465DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317456PMC
July 2020

Protein Type, Protein Dose, and Age Modulate Dietary Protein Digestion and Phenylalanine Absorption Kinetics and Plasma Phenylalanine Availability in Humans.

J Nutr 2020 08;150(8):2041-2050

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+), Maastricht, Netherlands.

Background: Dietary protein ingestion stimulates muscle protein synthesis by providing amino acids to the muscle. The magnitude and duration of the postprandial increase in muscle protein synthesis rates are largely determined by dietary protein digestion and amino acid absorption kinetics.

Objective: We assessed the impact of protein type, protein dose, and age on dietary protein digestion and amino acid absorption kinetics in vivo in humans.

Methods: We included data from 18 randomized controlled trials with a total of 602 participants [age: 53 ± 23 y; BMI (kg/m2): 24.8 ± 3.3] who consumed various quantities of intrinsically l-[1-13C]-phenylalanine-labeled whey (n = 137), casein (n = 393), or milk (n = 72) protein and received intravenous infusions of l-[ring-2H5]-phenylalanine, which allowed us to assess protein digestion and phenylalanine absorption kinetics and the postprandial release of dietary protein-derived phenylalanine into the circulation. The effect of aging on these processes was assessed in a subset of 82 young (aged 22 ± 3 y) and 83 older (aged 71 ± 5 y) individuals.

Results: A total of 50% ± 14% of dietary protein-derived phenylalanine appeared in the circulation over a 5-h postprandial period. Casein ingestion resulted in a smaller (45% ± 11%), whey protein ingestion in an intermediate (57% ± 10%), and milk protein ingestion in a greater (65% ± 13%) fraction of dietary protein-derived phenylalanine appearing in the circulation (P < 0.001). The postprandial availability of dietary protein-derived phenylalanine in the circulation increased with the ingestion of greater protein doses (P < 0.05). Protein digestion and phenylalanine absorption kinetics were attenuated in older when compared with young individuals, with 45% ± 10% vs. 51% ± 14% of dietary protein-derived phenylalanine appearing in the circulation, respectively (P = 0.001).

Conclusions: Protein type, protein dose, and age modulate dietary protein digestion and amino acid absorption kinetics and subsequent postprandial plasma amino acid availability in vivo in humans. These trials were registered at clinicaltrials.gov as NCT00557388, NCT00936039, NCT00991523, NCT01317511, NCT01473576, NCT01576848, NCT01578590, NCT01615276, NCT01680146, NCT01820975, NCT01986842, and NCT02596542, and at http://www.trialregister.nl as NTR3638, NTR3885, NTR4060, NTR4429, and NTR4492.
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http://dx.doi.org/10.1093/jn/nxaa024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7398787PMC
August 2020

Postexercise cooling impairs muscle protein synthesis rates in recreational athletes.

J Physiol 2020 02 29;598(4):755-772. Epub 2019 Dec 29.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands.

Key Points: Protein ingestion and cooling are strategies employed by athletes to improve postexercise recovery and, as such, to facilitate muscle conditioning. However, whether cooling affects postprandial protein handling and subsequent muscle protein synthesis rates during recovery from exercise has not been assessed. We investigated the effect of postexercise cooling on the incorporation of dietary protein-derived amino acids into muscle protein and acute postprandial (hourly) as well as prolonged (daily) myofibrillar protein synthesis rates during recovery from resistance-type exercise over 2 weeks. Cold-water immersion during recovery from resistance-type exercise lowers the capacity of the muscle to take up and/or direct dietary protein-derived amino acids towards de novo myofibrillar protein accretion. In addition, cold-water immersion during recovery from resistance-type exercise lowers myofibrillar protein synthesis rates during prolonged resistance-type exercise training. Individuals aiming to improve skeletal muscle conditioning should reconsider applying cooling as a part of their postexercise recovery strategy.

Abstract: We measured the impact of postexercise cooling on acute postprandial (hourly) as well as prolonged (daily) myofibrillar protein synthesis rates during adaptation to resistance-type exercise over 2 weeks. Twelve healthy males (aged 21 ± 2 years) performed a single resistance-type exercise session followed by water immersion of both legs for 20 min. One leg was immersed in cold water (8°C: CWI), whereas the other leg was immersed in thermoneutral water (30°C: CON). After water immersion, a beverage was ingested containing 20 g of intrinsically (l-[1- C]-phenylalanine and l-[1- C]-leucine) labelled milk protein with 45 g of carbohydrates. In addition, primed continuous l-[ring- H ]-phenylalanine and l-[1- C]-leucine infusions were applied, with frequent collection of blood and muscle samples to assess myofibrillar protein synthesis rates in vivo over a 5 h recovery period. In addition, deuterated water ( H O) was applied with the collection of saliva, blood and muscle biopsies over 2 weeks to assess the effects of postexercise cooling with protein intake on myofibrillar protein synthesis rates during more prolonged resistance-type exercise training (thereby reflecting short-term training adaptation). Incorporation of dietary protein-derived l-[1- C]-phenylalanine into myofibrillar protein was significantly lower in CWI compared to CON (0.016 ± 0.006 vs. 0.021 ± 0.007 MPE; P = 0.016). Postexercise myofibrillar protein synthesis rates were lower in CWI compared to CON based upon l-[1- C]-leucine (0.058 ± 0.011 vs. 0.072 ± 0.017% h , respectively; P = 0.024) and l-[ring- H ]-phenylalanine (0.042 ± 0.009 vs. 0.053 ± 0.013% h , respectively; P = 0.025). Daily myofibrillar protein synthesis rates assessed over 2 weeks were significantly lower in CWI compared to CON (1.48 ± 0.17 vs. 1.67 ± 0.36% day , respectively; P = 0.042). Cold-water immersion during recovery from resistance-type exercise reduces myofibrillar protein synthesis rates and, as such, probably impairs muscle conditioning.
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http://dx.doi.org/10.1113/JP278996DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7028023PMC
February 2020

The glycation level of milk protein strongly modulates post-prandial lysine availability in humans.

Br J Nutr 2020 03 15;123(5):545-552. Epub 2019 Nov 15.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6229 ERMaastricht, the Netherlands.

Industrial heat treatment of milk results in protein glycation. A high protein glycation level has been suggested to compromise the post-prandial rise in plasma amino acid availability following protein ingestion. In the present study, we assessed the impact of glycation level of milk protein on post-prandial plasma amino acid responses in humans. Fifteen healthy, young men (age 26 (SEM 1) years, BMI 24 (SEM 1) kg/m2) participated in this randomised cross-over study and ingested milk protein powder with protein glycation levels of 3, 20 and 50 % blocked lysine. On each trial day, arterialised blood samples were collected at regular intervals during a 6-h post-prandial period to assess plasma amino acid concentrations using ultra-performance liquid chromatography. Plasma essential amino acid (EAA) concentrations increased following milk protein ingestion, with the 20 and 50 % glycated milk proteins showing lower overall EAA responses compared with the 3 % glycated milk protein (161 (SEM 7) and 142 (SEM 7) v. 178 (SEM 9) mmol/l × 6 h, respectively; P ≤ 0·011). The lower post-prandial plasma amino acid responses were fully attributed to an attenuated post-prandial rise in circulating plasma lysine concentrations. Plasma lysine responses (incremental AUC) following ingestion of the 20 and 50 % glycated milk proteins were 35 (SEM 4) and 92 (SEM 2) % lower compared with the 3 % glycated milk protein (21·3 (SEM 1·4) and 2·8 (SEM 0·7) v. 33·3 (SEM 1·7) mmol/l × 6 h, respectively; P < 0·001). Milk protein glycation lowers post-prandial plasma lysine availability in humans. The lower post-prandial availability of lysine following ingestion of proteins with a high glycation level may compromise the anabolic properties of a protein source.
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http://dx.doi.org/10.1017/S0007114519002927DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7015880PMC
March 2020

Mitochondrial DNA copy number associates with insulin sensitivity and aerobic capacity, and differs between sedentary, overweight middle-aged males with and without type 2 diabetes.

Int J Obes (Lond) 2020 04 22;44(4):929-936. Epub 2019 Oct 22.

MRC/ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, School of Life Sciences, Nottingham University Medical School, Nottingham, NG7 2UH, UK.

Background/objectives: Increased risk of type 2 diabetes mellitus (T2DM) is linked to impaired muscle mitochondrial function and reduced mitochondrial DNA copy number (mtDNA). However, studies have failed to control for habitual physical activity levels, which directly influences both mtDNA copy number and insulin sensitivity. We, therefore, examined whether physical conditioning status (maximal oxygen uptake, V̇O) was associated with skeletal muscle mitochondrial volume and mtDNA, and was predictive of T2DM in overweight, middle-aged men.

Methods: Whole-body physiological (ISI-insulin sensitivity index, HOMA-IR, V̇O) and muscle biochemical/molecular (vastus lateralis; mtDNA, mitochondrial and glycolytic enzymes activity, lipid content and markers of lipid peroxidation) measurements were performed in three groups of overweight, middle-aged male volunteers (n = 10 per group): sedentary T2DM (ST2DM); sedentary control (SC) and non-sedentary control (NSC), who differed in aerobic capacity (ST2DM < SC < NSC).

Results: mtDNA was greater in NSC versus SC and ST2DM (P < 0.001; P < 0.001), and less in ST2DM versus SC (P < 0.01). Across all groups, mtDNA positively correlated with ISI (P < 0.001; r = 0.688) and V̇O (normalised to free fat mass; r = 0.684, P < 0.001), and negatively correlated to HOMA-IR (r = -0.544, P < 0.01). The activity of mitochondrial enzymes (GluDH, CS and β-HAD) was greater in NSC than ST2DM (P < 0.01, P < 0.001 and P < 0.05) and SC (P < 0.05, P < 0.01 and P < 0.05), but similar between ST2DM and SC. Intramuscular-free fatty acids, triglycerides and malondialdehyde contents were similar between ST2DM and SC.

Conclusions: Body composition and indices of muscle mitochondrial volume/function were similar between SC and ST2DM. However, mtDNA differed and was positively associated with ISI, HOMA-IR and V̇O across all groups. Collectively, the findings support the contention that habitual physical activity is a key component of T2DM development, possibly by influencing mtDNA.
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http://dx.doi.org/10.1038/s41366-019-0473-2DOI Listing
April 2020

Skeletal muscle unloading results in increased mitophagy and decreased mitochondrial biogenesis regulation.

Muscle Nerve 2019 12 23;60(6):769-778. Epub 2019 Oct 23.

Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands.

Introduction: Physical inactivity significantly contributes to loss of muscle mass and performance in bed-bound patients. Loss of skeletal muscle mitochondrial content has been well-established in muscle unloading models, but the underlying molecular mechanism remains unclear. We hypothesized that apparent unloading-induced loss of muscle mitochondrial content is preceded by increased mitophagy- and decreased mitochondrial biogenesis-signaling during the early stages of unloading.

Methods: We analyzed a comprehensive set of molecular markers involved in mitochondrial-autophagy, -biogenesis, -dynamics, and -content, in the gastrocnemius muscle of C57BL/6J mice subjected to 0- and 3-days hind limb suspension, and in biopsies from human vastus lateralis muscle obtained before and after 7 days of one-leg immobilization.

Results: In both mice and men, short-term skeletal muscle unloading results in molecular marker patterns indicative of increased receptor-mediated mitophagy and decreased mitochondrial biogenesis regulation, before apparent loss of mitochondrial content.

Discussion: These results emphasize the early-onset of skeletal muscle disuse-induced mitochondrial remodeling.
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http://dx.doi.org/10.1002/mus.26702DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6900132PMC
December 2019

Branched-chain amino acid and branched-chain ketoacid ingestion increases muscle protein synthesis rates in vivo in older adults: a double-blind, randomized trial.

Am J Clin Nutr 2019 10;110(4):862-872

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, Netherlands.

Background: Protein ingestion increases muscle protein synthesis rates. However, limited data are currently available on the effects of branched-chain amino acid (BCAA) and branched-chain ketoacid (BCKA) ingestion on postprandial muscle protein synthesis rates.

Objective: The aim of this study was to compare the impact of ingesting 6 g BCAA, 6 g BCKA, and 30 g milk protein (MILK) on the postprandial rise in circulating amino acid concentrations and subsequent myofibrillar protein synthesis rates in older males.

Methods: In a parallel design, 45 older males (age: 71 ± 1 y; BMI: 25.4 ± 0.8 kg/m2) were randomly assigned to ingest a drink containing 6 g BCAA, 6 g BCKA, or 30 g MILK. Basal and postprandial myofibrillar protein synthesis rates were assessed by primed continuous l-[ring-13C6]phenylalanine infusions with the collection of blood samples and muscle biopsies.

Results: Plasma BCAA concentrations increased following test drink ingestion in all groups, with greater increases in the BCAA and MILK groups compared with the BCKA group (P < 0.05). Plasma BCKA concentrations increased following test drink ingestion in all groups, with greater increases in the BCKA group compared with the BCAA and MILK groups (P < 0.05). Ingestion of MILK, BCAA, and BCKA significantly increased early myofibrillar protein synthesis rates (0-2 h) above basal rates (from 0.020 ± 0.002%/h to 0.042 ± 0.004%/h, 0.022 ± 0.002%/h to 0.044 ± 0.004%/h, and 0.023 ± 0.003%/h to 0.044 ± 0.004%/h, respectively; P < 0.001), with no differences between groups (P > 0.05). Myofibrillar protein synthesis rates during the late postprandial phase (2-5 h) remained elevated in the MILK group (0.039 ± 0.004%/h; P < 0.001), but returned to baseline values following BCAA and BCKA ingestion (0.024 ± 0.005%/h and 0.024 ± 0.005%/h, respectively; P > 0.05).

Conclusions: Ingestion of 6 g BCAA, 6 g BCKA, and 30 g MILK increases myofibrillar protein synthesis rates during the early postprandial phase (0-2 h) in vivo in healthy older males. The postprandial increase following the ingestion of 6 g BCAA and BCKA is short-lived, with higher myofibrillar protein synthesis rates only being maintained following the ingestion of an equivalent amount of intact milk protein. This trial was registered at Nederlands Trial Register (www.trialregister.nl) as NTR6047.
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http://dx.doi.org/10.1093/ajcn/nqz120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6766442PMC
October 2019

Basal and Postprandial Myofibrillar Protein Synthesis Rates Do Not Differ between Lean and Obese Middle-Aged Men.

J Nutr 2019 09;149(9):1533-1542

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, Netherlands.

Background: Excess lipid availability has been associated with the development of anabolic resistance. As such, obesity may be accompanied by impairments in muscle protein metabolism.

Objective: We hypothesized that basal and postprandial muscle protein synthesis rates are lower in obese than in lean men.

Methods: Twelve obese men [mean ± SEM age: 48 ± 2 y; BMI (in kg/m2): 37.0 ± 1.5; body fat: 32 ± 2%] and 12 age-matched lean controls (age: 43 ± 3 y; BMI: 23.4 ± 0.4; body fat: 21 ± 1%) received primed continuous L-[ring-2H5]-phenylalanine and L-[ring-3,5-2H2]-tyrosine infusions and ingested 25 g intrinsically L-[1-13C]-phenylalanine labeled whey protein. Repeated blood and muscle samples were obtained to assess protein digestion and amino acid absorption kinetics, and basal and postprandial myofibrillar protein synthesis rates.

Results: Exogenous phenylalanine appearance rates increased after protein ingestion in both groups (P < 0.001), with a total of 53 ± 1% and 53 ± 2% of dietary protein-derived phenylalanine appearing in the circulation over the 5-h postprandial period in lean and obese men, respectively (P = 0.82). After protein ingestion, whole-body protein synthesis and oxidation rates increased to a greater extent in lean men than in the obese (P-interaction < 0.05), resulting in a higher whole-body protein net balance in the lean than in the obese (7.1 ± 0.2 and 4.6 ± 0.4 µmol phenylalanine · h-1 · kg-1, respectively; P-interaction < 0.001). Myofibrillar protein synthesis rates increased from 0.030 ± 0.002 and 0.028 ± 0.003%/h in the postabsorptive period to 0.034 ± 0.002 and 0.035 ± 0.003%.h-1 in the 5-h postprandial period (P = 0.03) in lean and obese men, respectively, with no differences between groups (P-interaction = 0.58).

Conclusions: Basal, postabsorptive myofibrillar protein synthesis rates do not differ between lean and obese middle-aged men. Postprandial protein handling, including protein digestion and amino acid absorption, and the postprandial muscle protein synthetic response after the ingestion of 25 g whey protein are not impaired in obese men. This trial was registered at www.trialregister.nl as NTR4060.
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http://dx.doi.org/10.1093/jn/nxz104DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6736155PMC
September 2019

No effect of 25-hydroxyvitamin D supplementation on the skeletal muscle transcriptome in vitamin D deficient frail older adults.

BMC Geriatr 2019 05 28;19(1):151. Epub 2019 May 28.

Top Institute Food and Nutrition, P.O. Box 557, 6700, AN, Wageningen, The Netherlands.

Objective: Vitamin D deficiency is common among older adults and has been linked to muscle weakness. Vitamin D supplementation has been proposed as a strategy to improve muscle function in older adults. The aim of this study was to investigate the effect of calcifediol (25-hydroxycholecalciferol) on whole genome gene expression in skeletal muscle of vitamin D deficient frail older adults.

Methods: A double-blind placebo-controlled trial was conducted in vitamin D deficient frail older adults (aged above 65), characterized by blood 25-hydroxycholecalciferol concentrations between 20 and 50 nmol/L. Subjects were randomized across the placebo group and the calcifediol group (10 μg per day). Muscle biopsies were obtained before and after 6 months of calcifediol (n = 10) or placebo (n = 12) supplementation and subjected to whole genome gene expression profiling using Affymetrix HuGene 2.1ST arrays.

Results: Expression of the vitamin D receptor gene was virtually undetectable in human skeletal muscle biopsies, with Ct values exceeding 30. Blood 25-hydroxycholecalciferol levels were significantly higher after calcifediol supplementation (87.3 ± 20.6 nmol/L) than after placebo (43.8 ± 14.1 nmol/L). No significant difference between treatment groups was observed on strength outcomes. The whole transcriptome effects of calcifediol and placebo were very weak, as indicated by the fact that correcting for multiple testing using false discovery rate did not yield any differentially expressed genes using any reasonable cut-offs (all q-values ~ 1). P-values were uniformly distributed across all genes, suggesting that low p-values are likely to be false positives. Partial least squares-discriminant analysis and principle component analysis was unable to separate treatment groups.

Conclusion: Calcifediol supplementation did not significantly affect the skeletal muscle transcriptome in frail older adults. Our findings indicate that vitamin D supplementation has no effects on skeletal muscle gene expression, suggesting that skeletal muscle may not be a direct target of vitamin D in older adults.

Trial Registration: This study was registered at clinicaltrials.gov as NCT02349282 on January 28, 2015.
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http://dx.doi.org/10.1186/s12877-019-1156-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6540468PMC
May 2019

Leucine coingestion augments the muscle protein synthetic response to the ingestion of 15 g of protein following resistance exercise in older men.

Am J Physiol Endocrinol Metab 2019 09 21;317(3):E473-E482. Epub 2019 May 21.

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.

Older adults have shown an attenuated postexercise increase in muscle protein synthesis rates following ingestion of smaller amounts of protein compared with younger adults. Consequently, it has been suggested that older adults require the ingestion of more protein to increase postexercise muscle protein synthesis rates compared with younger adults. We investigated whether coingestion of 1.5 g of free leucine with a single 15-g bolus of protein further augments the postprandial muscle protein synthetic response during recovery from resistance-type exercise in older men. Twenty-four healthy older men (67 ± 1 yr) were randomly assigned to ingest 15 g of milk protein concentrate (MPC80) with (15G+LEU; = 12) or without (15G; = 12) 1.5 g of free leucine after performing a single bout of resistance-type exercise. Postprandial protein digestion and amino acid absorption kinetics, whole body protein metabolism, and postprandial myofibrillar protein synthesis rates were assessed using primed, continuous infusions with l-[-H]phenylalanine, l-[-H]tyrosine, and l-[1-C]leucine combined with ingestion of intrinsically l-[1-C]phenylalanine-labeled milk protein. A total of 70 ± 1% (10.5 ±0.2 g) and 75 ± 2% (11.2 ± 0.3 g) of the protein-derived amino acids were released in the circulation during the 6-h postexercise recovery phase in 15G+LEU and 15G, respectively ( < 0.05). Postexercise myofibrillar protein synthesis rates were 16% (0.058 ± 0.003 vs. 0.049 ± 0.002%/h, < 0.05; based on l-[-H]phenylalanine) and 19% (0.071 ± 0.003 vs. 0.060 ± 0.003%/h, < 0.05; based on l-[1-C]leucine) greater in 15G+LEU compared with 15G. Leucine coingestion further augments the postexercise muscle protein synthetic response to the ingestion of a single 15-g bolus of protein in older men.
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http://dx.doi.org/10.1152/ajpendo.00073.2019DOI Listing
September 2019

The Impact of Pre-sleep Protein Ingestion on the Skeletal Muscle Adaptive Response to Exercise in Humans: An Update.

Front Nutr 2019 6;6:17. Epub 2019 Mar 6.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre (MUMC+), Maastricht, Netherlands.

This review provides an update on recent research assessing the effect of pre-sleep protein ingestion on muscle protein synthesis rates during overnight sleep and the skeletal muscle adaptive response to exercise training. Protein ingested prior to sleep is effectively digested and absorbed during overnight sleep, thereby increasing overnight muscle protein synthesis rates. Protein consumption prior to sleep does not appear to reduce appetite during breakfast the following day and does not change resting energy expenditure. When applied over a prolonged period of resistance-type exercise training, pre-sleep protein supplementation has a beneficial effect on the increase in muscle mass and strength. Protein ingestion before sleep is hypothesized to represent an effective nutritional strategy to preserve muscle mass in the elderly, especially when combined with physical activity or muscle contraction by means of neuromuscular electrical stimulation. In conclusion, protein ingestion prior to sleep is an effective interventional strategy to increase muscle protein synthesis rates during overnight sleep and can be applied to support the skeletal muscle adaptive response to resistance-type exercise training.
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http://dx.doi.org/10.3389/fnut.2019.00017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6415027PMC
March 2019

Dose-Dependent Increases in Whole-Body Net Protein Balance and Dietary Protein-Derived Amino Acid Incorporation into Myofibrillar Protein During Recovery from Resistance Exercise in Older Men.

J Nutr 2019 02;149(2):221-230

NUTRIM School of Nutrition and Translational Research in Metabolism.

Background: Age-related decline in skeletal muscle mass is at least partly attributed to anabolic resistance to food intake. Resistance exercise sensitizes skeletal muscle tissue to the anabolic properties of amino acids.

Objective: The present study assessed protein digestion and amino acid absorption kinetics, whole-body protein balance, and the myofibrillar protein synthetic response to ingestion of different amounts of protein during recovery from resistance exercise in older men.

Methods: Forty-eight healthy older men [mean ± SEM age: 66 ± 1 y; body mass index (kg/m2): 25.4 ± 0.3] were randomly assigned to ingest 0, 15, 30, or 45 g milk protein concentrate after a single bout of resistance exercise consisting of 4 sets of 10 repetitions of leg press and leg extension and 2 sets of 10 repetitions of lateral pulldown and chest press performed at 75-80% 1-repetition maximum. Postprandial protein digestion and amino acid absorption kinetics, whole-body protein metabolism, and myofibrillar protein synthesis rates were assessed using primed, continuous infusions of l-[ring-2H5]-phenylalanine, l-[ring-2H2]-tyrosine, and l-[1-13C]-leucine combined with ingestion of intrinsically l-[1-13C]-phenylalanine and l-[1-13C]-leucine labeled protein.

Results: Whole-body net protein balance showed a dose-dependent increase after ingestion of 0, 15, 30, or 45 g of protein (0.015 ± 0.002, 0.108 ± 0.004, 0.162 ± 0.008, and 0.215 ± 0.009 μmol Phe · kg-1 · min-1, respectively; P < 0.001). Myofibrillar protein synthesis rates were higher after ingesting 30 (0.0951% ± 0.0062%/h, P = 0.07) or 45 g of protein (0.0970% ± 0.0062%/h, P < 0.05) than after 0 g (0.0746% ± 0.0051%/h). Incorporation of dietary protein-derived amino acids (l-[1-13C]-phenylalanine) into de novo myofibrillar protein showed a dose-dependent increase after ingestion of 15, 30, or 45 g protein (0.0171 ± 0.0017, 0.0296 ± 0.0030, and 0.0397 ± 0.0026 mole percentage excess, respectively; P < 0.05).

Conclusions: Dietary protein ingested during recovery from resistance exercise is rapidly digested and absorbed. Whole-body net protein balance and dietary protein-derived amino acid incorporation into myofibrillar protein show dose-dependent increases. Ingestion of ≥30 g protein increases postexercise myofibrillar protein synthesis rates in older men. This trial was registered at Nederlands Trial Register as NTR4492.
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http://dx.doi.org/10.1093/jn/nxy263DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6374151PMC
February 2019
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