Prandial Metabolic Phenotype in Adults

Overview

Previous studies suggest that changes in metabolism due to the effects of aging might serve as a potential for therapeutic agents. The investigating lab developed a pulse method combining multiple stable isotopes to study multiple metabolic pathways in the same individual simultaneously. By measuring whole-body metabolism in a large group of older adults, the investigators may be able to unravel age-related deterioration in protein turnover (synthesis and breakdown) that contributes to impaired functional capacity. Metabolic profiles could explain differences in pathways in the aging process with special interest in metabolism of amino acids as they have been associated with aging-related disorders.

Detailed description

The study involves 1 screening visits of approximately 3 hours and 6 study days of approximately 8 hours.

Subjects will be asked to arrive in the fasted state on all study days. Fasting prior to screening is not required. On the screening day, body weight, height, and body composition by Dual-energy X-ray absorptiometry (DXA) will be measured. In addition, The Six-Minute Walk Test (6MWT) and skeletal muscle function tests will be assessed at the end of each screening visit.

Each study visit will begin with vital signs. Before administration of the feeding or the tracer solution, baseline blood will be collected for measurement of the natural enrichment of metabolites. After the baseline sample is collected, feeding will begin and will be followed by tracers of several compounds that may be administered by IV pulse.

Next, the subjects will be fed one of six liquid nutritional supplement every 20 minutes for 6 hours. The liquid nutrition supplement will target the amino acid formulation in the following meals (1) total amino acid, (2) Essential Amino Acids (EAA), (3) EAA + -hydroxy -methylbutyric acid (HMB), (4) EAA + leucine (LEU), (5) EAA high, and (6) Placebo.

Interventions

• Dietary supplement Total Amino Acids
  Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine, Alanine, Arginine, Aspartate, Cystine, Glutamine, Glutamate, Glycine, Proline, Serine, Tyrosine. All supplements are commercially available.
• Dietary supplement Essential Amino Acids
  Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine. All supplements are commercially available.
• Dietary supplement Essential Amino Acids + Hydroxy-methylbutyric acid (HMB)
  Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine, HMB. All supplements are commercially available.
• Dietary supplement Essential Amino Acids + Leucine
  Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine, Extra leucine. All supplements are commercially available.
• Dietary supplement Essential Amino Acids High
  Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine. All supplements are commercially available.
• Dietary supplement Placebo Water
  Water

Primary outcome measures

• Feeding related changes in whole-body protein and amino acid metabolism [Time frame: up to 6 hours]

Eligibility criteria

Inclusion criteria

• Age: 60-80, inclusive
• Stable body-weight (± 5%) for the past 3 months
• Subject is judged to be in satisfactory health based on medical history, physical examination, and laboratory screening evaluations.
• Ability to walk, sit down and stand up independently or with walking mobility aids
• Ability to lie in supine or elevated position for up to 7 hours
• Willingness and ability to comply with the protocol

Exclusion criteria

• Established diagnosis of current malignancy
• History of untreated metabolic diseases including hepatic or renal disorder
• Presence of acute illness or metabolically unstable chronic illness
• Presence of fever within the last 3 days
• Use of short course of oral corticosteroids within 4 weeks preceding study day
• (Possible) pregnancy
• Failure to give informed consent or Investigator's uncertainty about the willingness or ability of the subject to comply with the protocol requirements
• Already enrolled in another clinical trial and that clinical trial interferes with participating in this study
• Any other condition according to the PI or nurse that was found during the screening visit, that would interfere with the study or safety of the patient

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

Healthy volunteers: Yes

Study design

Allocation

Randomized

Model

Crossover

Masking

Double blind

Primary purpose

Other

Study locations

United States · 1 center

• Human Clinical Research Facility — College Station

Publications

• Knezek SB, Engelen MPKJ, Coyle KS, Perez CN, Deutz NEP. Adding free leucine to a balanced essential amino acid mixture suppresses intracellular transamination of isoleucine and valine in healthy older adults. Clin Nutr. 2026 Jun;61:106659. doi: 10.1016/j.clnu.2026.106659. Epub 2026 Apr 9. PMID 42013668
• Deutz NEP, Knezek SB, Engelen MPKJ. A novel pulse tracer method to estimate the relationship between amino acid meal composition and its intracellular disposal. Clin Nutr. 2025 Dec;55:196-207. doi: 10.1016/j.clnu.2025.10.002. Epub 2025 Oct 22. PMID 41260190

Identifiers

NCT: NCT05400733 · 83 - Pulse Feeding

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗