Impact of Plant Proteins and Exercise on Protein Metabolism in Older Adults

Objective : to examine splanchnic extraction (SE), peripheral amino acid (AA) bioavailability and utilization (protein retention) from innovative plant proteins products, and muscle signalling markers before and after a physical activity (PA) program in inactive older persons

A randomized, crossover study including 12 inactive older men (65+ yrs) will be performed in order to compare the selected plant protein product to whey protein when included into a complete meal. During a kinetic day, each participant will consume alternatively, on 2 separate occasions, a test meal containing a plant protein mixture or 30 g whey protein. The methodology of stable isotope tracers: [15N] Leucine added to test meal and [1-13C] leucine administered intravenously will be used throughout a kinetic day, to evaluate the splanchnic extraction, the dietary amino acid bioavailability, and the whole body protein metabolism (protein synthesis, protein breakdown, AA oxidation and net balance). Carbon dioxide production rates will be measured by open-circuit indirect calorimetry. All measurements will be performed before the meal and post-prandial in regular intervals for 420 min.

In addition, postprandial plasma insulin and glucose will be determined in all samples, and a muscle biopsy will be collected post-prandially following the plant protein meal for examination of signalling markers of muscle plasticity (atrogin1, MURF1, LC3, BNIP3, Akt-dependent mTOR and FxO), metabolic adaptations (AMPK and PGC1alpha) and denervation (AChR subunits expression, agrin/MuSK/Lrp4, NCAM, and Myog) by UNIPD

Inclusion criteria

• BMI 22-30 kg/m²
• Inactive (<150 minutes of moderate to vigorous physical activity per week and no regular resistance training),
• Covered by a social security system
• Agrees to undergo the study interventions (undirect calorimetry, functional tests, physical activity program)

Exclusion criteria

• Hamilton HAD scale with a score > 9
• Subject with a pathology or treatment (diabetic on insulin, corticosteroids > 8 days, neuroleptics, anticoagulant, antiplatelet) judged by the investigator as incompatible with the study
• Subject with unstabilized thyroid dysfunction for at least 3 months
• Subject with unstabilized hypertension for at least 3 months
• Subject with a medical and/or surgical history judged by the investigator as incompatible with the trial
• More than 21 alcoholic drinks per week
• Heavy smoker (>10 cigarettes/day)
• Currently participating in another intervention study
• Absence of informed consent
• Inability to participate in physical activity
• Allergy(ies) or refusal to consume one of the foods tested as part of the the study
• Allergy to local anesthetics
• Declared glaucoma
• Prostate hypertrophy
• Refusal to register in the national file of volunteers who participate in research involving human beings
• Subject in a period of exclusion from a previous study or having received a total amount of compensation greater than 6,000 euros over the 12 months preceding the start of the trial (after verification in the File of Volunteers for Research involving Human Beings)
• Patients under guardianship, curatorship, deprived of liberty or legal protection
• Subject with claustrophobia