The Impact of Energy Intake and Short-term Disuse on Muscle Protein Synthesis Rates and Skeletal Muscle Mass in Middle-aged Adults. (PIE)

In healthy middle-aged men and women, what is the effect of dietary energy restriction and energy surplus on daily muscle protein synthesis rates and muscle morphology, compared to energy balance, during free-living and immobilisation?

Study Overview

• Status: Completed
• Conditions: Aging; Muscle Atrophy; Energy Malnutrition Protein
• Intervention / Treatment: Other: Energy status

Detailed Description

Background Age related muscle tissue loss, which is associated with a number of negative health outcomes is partially caused by blunted muscle protein synthesis rates (MPS) in response to food ingestion, which is exacerbated by muscle disuse. Concomitantly, consuming an energy balanced diet appears to become more challenging with advancing age, due to a reduction in appetite. Of concern is that the impact of energy intake on muscle protein metabolism during ageing is poorly characterised.

Objective To determine daily MPS and muscle morphology in response to differing energy intakes, in free-living conditions and during immobilisation.

Methods Healthy middle-aged volunteers will consume a hypocaloric, energy-balanced, or hypercaloric diet (providing 1.4 g.kg.day protein) over a three-day free-living period, and a three day period of single leg immobilisation. Deuterium oxide and MRI scans will be used to measure daily MPS and muscle size, respectively.

Value The study will determine the effect of energy intake per se on daily muscle protein synthesis rates and muscle size, in free-living and immobilised conditions. This will inform how energy provision modulates tissue loss with ageing, and how this interacts with the catabolic stress of muscle disuse.

• Study Type: Interventional
• Enrollment (Actual): 23
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United Kingdom
  • Devon
    • Exeter, Devon, United Kingdom, EX1 2LU
      • University of Exeter, Sports & Health Sciences, College of Life & Environmental Sciences
    • Exeter, Devon, United Kingdom, EX1 2LU
      • Sport & Health Sciences University of Exeter

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 35 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

Age 35-65 Healthy Non-smoker Recreationally active

Exclusion Criteria:

Any diagnosed metabolic impairment (e.g. type 1 or 2 Diabetes) Any diagnosed cardiovascular disease or hypertension Elevated blood pressure at the time of screening. (An average systolic blood pressure reading of ≥150mmHg over two or more measurements and an average diastolic blood pressure of ≥90mmHg over two or more measurements.) Chronic use of diabetic medication. A personal or family history of epilepsy, seizures or schizophrenia. Allergic to mycoprotein / Quorn, penicillin, or cow's milk. Any musculoskeletal injury that may impair their use of crutches. Any diagnosed severe digestive illness. Any diagnosed severe autoimmune disease. Any diagnosed cancer. Any metal fragments in the eyes, a pacemaker, or metal implants in the body that preclude MRI scanning.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Hypocaloric; Participants placed in energy restriction.	Other: Energy status; Varying conditions of energy intake, thereby manipulating whether participants are in a state of energy restriction, balance, or surplus.
Experimental: Energy Balance; Participants placed in energy balance.	Other: Energy status; Varying conditions of energy intake, thereby manipulating whether participants are in a state of energy restriction, balance, or surplus.
Experimental: Hypercaloric; Participants placed in energy surplus.	Other: Energy status; Varying conditions of energy intake, thereby manipulating whether participants are in a state of energy restriction, balance, or surplus.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Muscle protein synthesis (MPS)	Daily muscle protein synthesis rates, expressed as fractional synthetic rate (FSR) (%/day)	6 days (3 days free-living, 3 days immobilised)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Muscle morphology.	Changes in muscle size, measured via MRI scanning, during immobilisation.	3 day immobilisation phase.

Collaborators and Investigators

• Sponsor: University of Exeter

Study record dates

Study Major Dates

• Study Start (Actual): November 1, 2021
• Primary Completion (Actual): June 3, 2024
• Study Completion (Actual): June 3, 2024

Study Registration Dates

• First Submitted: May 20, 2021
• First Submitted That Met QC Criteria: May 20, 2021
• First Posted (Actual): May 25, 2021

Study Record Updates

• Last Update Posted (Actual): May 8, 2026
• Last Update Submitted That Met QC Criteria: May 5, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Ageing; Dietary protein; Muscle protein synthesis; Disuse
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Neuromuscular Manifestations; Nutrition Disorders; Pathological Conditions, Anatomical; Atrophy; Deficiency Diseases; Malnutrition; Protein Deficiency; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Muscular Atrophy; Protein-Energy Malnutrition
• Other Study ID Numbers: 201209-B-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No