Re-evaluation of the Muscle-full Effect During Continuously Elevated Amino Acid Availability in Healthy Young Males

Overview

Muscle tissue consists of proteins. These proteins are built up of a collection of smaller building blocks: amino acids. When protein is consumed, it gets digested and absorbed into the blood. The body can use these amino acids, by taking them up from thecirculation. By consuming sufficient protein through our diet, we ensure that the body is provided with enough amino acids to enable muscle protein building. Sufficient muscle protein synthesis is important for maintaining muscle function and strength. Previous research has shown that when 20 to 25g of protein is eaten, muscle protein synthesis is maximized. It is therefore recommended to eat 20g of protein per meal. However, it is currently unclear what happens to muscle protein synthesis rates if multiple meals are eaten. When multiple meals are consumed, amino acids appear in the circulation for prolonged period of time. Theoretically, when there are a high amino acid concentrations in the blood, muscle protein synthesis rates will increase. Contrary to this theory, a study more than 20 years ago showed otherwise. It was observed that muscle protein synthesis rates are only elevated for2 hours afterwhich they decrease again. This phenomenon was referred to as the "muscle-full" effect. Because this phenomenon is in contrast with more previous studies, the objective is to replicate that study. This is important so that nutritional advice for healthy, but also clinical populations in the future can be improved.

Interventions

• Other Continuous intravenous stable isotope amino acid tracer infusion
  During the single 12 h trial day, a primed continuous stable isotope infusion will run in order to assess muscle protein synthesis in the basal (4 h) and post-prandial (8 h) state.
• Other Amino acid infusion
  In order to assess muscle protein synthesis rates during continuous elevated plasma amino acid availability, the amino acid infusion solution Vamin®14 EF will be used. Vamin® 14EF contains 85g amino acids per liter and will be administered in the post-prandial period for 8 hours to ensure a constant rate of amino acid infusion over the full assessment period of the primary outcome measure.

Primary outcome measures

• Muscle protein synthesis during continuous elevated plasma amino acid avaialbility in healthy young males [Time frame: 8 hours]

Secondary outcome measures (3)

• Basal muscle protein synthesis rates [Time frame: 3 hours]
• Whole-body protein kinetics [Time frame: 8 hours]
• Whole-body protein metabolism [Time frame: 8 hours]

Eligibility criteria

Inclusion criteria

• Male sex
• Aged between 18 - 35 years
• Healthy (assessed based on routine medical questionnaire)
• BMI between 18.5 - 30 kg/m2

Exclusion criteria

A potential subject who meets any of the following criteria will be excluded from participation in this study:

• Smoking
• Involved in progressive exercise training
• A history of neuromuscular problems
• Use of anticoagulants
• Recent (<12 months) participation in amino acid tracer (L-\[ring-13C6\] phenylalanineand L-\[3,5-2H2\]-tyrosine) studies
• Use of medication known to affect (muscle) protein metabolism (e.g. corticosteroids, non-steroidal anti-inflammatory drugs, acne medication)
• Phenylketonuria
• Diagnosed with or history of liver damage
• Diagnosed with or history of severe kidney damage and/or malfunction
• Diagnosed with inability to break down amino acids

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

N/A

Model

Single group

Masking

Open label

Primary purpose

Basic science

Study locations

Netherlands · 1 center

• Maastricht University Medical Centre+ — Maastricht

Identifiers

NCT: NCT06721026 · METC24-028

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗