Molecular Mechanisms Underlying Anabolic Resistance to Protein Intake During Muscle Disuse

Molecular Regulation of Skeletal Muscle Anabolic Resistance to Dietary Protein in Response to Injury-mediated Muscle Disuse

This study will characterize intramuscular molecular mechanisms underlying anabolic resistance to protein ingestion during muscle disuse. Adults (n=12) will be studied using a unilateral leg immobilization model in which one leg will be randomly assigned to immobilization and the contralateral, active leg used as a within-subjects control. Immobilization will be implemented for five days using a rigid knee brace, during which time participants will ambulate using crutches. Integrated ribonucleic acid (RNA) synthesis will be determined during immobilization in the immobilized and non-immobilized legs using ingested deuterium oxide, salivary and blood sampling, and muscle biopsies. Immediately after immobilization, muscle biopsies will be collected before and 90 mins after consuming 25 g of whey protein from the immobilized and non-immobilized legs to characterize the intramuscular molecular response to protein feeding. Serial blood samples will be collected during that time to characterize the circulating metabolic response to protein ingestion. Knowledge generated from this effort will inform the development of targeted interventions for mitigating anabolic resistance to protein ingestion that develops during periods of muscle disuse.

Study Overview

• Status: Recruiting
• Conditions: Muscular Disorders, Atrophic; Muscle Atrophy; Disuse Atrophy; Atrophy, Disuse; Disuse Atrophy Muscle of Thigh
• Intervention / Treatment: Other: Unilateral leg immobilization; Other: Contralateral active leg

Detailed Description

Warfighters that sustain musculoskeletal injuries often experience decreased muscle loading and activation post-injury (i.e., muscle disuse) that results in a rapid loss of muscle mass and function. Loss of muscle under these conditions is attributed to a persistent negative net muscle protein balance (muscle protein synthesis [MPS] < muscle protein breakdown [MPB]) that results, in part, from a blunting of MPS in the postprandial state. Nutritional interventions that optimize postprandial MPS have been suggested as countermeasures for this "anabolic resistance" that develops during disuse to preserve muscle mass and accelerate return to duty. However, a poor understanding of mechanisms underlying anabolic resistance during disuse has made it difficult to determine an optimal nutritional intervention. The current study will address this knowledge gap directly by characterizing intramuscular molecular mechanisms underlying anabolic resistance to protein ingestion during muscle disuse. Healthy, recreationally active men and women (n=12) will be studied using a within-subjects, unilateral design. After completing baseline measures of height, weight, and body composition, participants will begin a 3-day run-in phase where they will receive diet instructions (no food provided). Muscle disuse will then be implemented for 5 days using a unilateral leg immobilization model with one leg randomly assigned to immobilization and the contralateral, active leg used as a within-subjects control. Immobilization will be implemented using a rigid knee brace, and participants will ambulate using crutches. Diets will be standardized during the immobilization phase (1.0 g protein/kg/d, 30% of energy intake from fat, and the remaining calories from carbohydrate). Integrated ribonucleic acid (RNA) synthesis will be determined during immobilization in the immobilized and non-immobilized legs using ingested deuterium oxide, salivary and blood sampling, and muscle biopsies. Immediately after immobilization, muscle biopsies will be collected before and 90 mins after consuming 25 g of whey protein from the immobilized and non-immobilized legs to characterize the intramuscular molecular response to protein feeding. Serial blood samples will be collected during that time to characterize the circulating metabolic response to protein ingestion. Knowledge generated from this effort will inform the development of targeted interventions for mitigating anabolic resistance to protein ingestion that develops during periods of muscle disuse.

• Study Type: Interventional
• Enrollment (Estimated): 12
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Emily E Howard, PhD; Phone Number: 508-206-2309; Email: emily.e.howard14.civ@health.mil

Study Locations

• United States
  • Massachusetts
    • Natick, Massachusetts, United States, 01760
      • Recruiting
      • US Army Research Institute of Environmental Medicine
      • Contact: Emily E Howard, PhD; Phone Number: 508-206-2309; Email: emily.e.howard14.civ@health.mil

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Men and women aged 18-39 years.
• Body mass index (BMI) between 18.5-30 kg/m2
• Healthy without evidence of chronic illness (e.g., diabetes, cardiovascular disease, Crohn's disease) or musculoskeletal injury as determined by the USARIEM Office of Medical Oversight (OMSO) or home duty station medical support.
• Routinely participate in aerobic and/or resistance exercise at least 2 days per week.
• Willing to refrain from alcohol, smoking, smokeless nicotine products (includes e-cigarettes, vaping, chewing tobacco), caffeine, and dietary supplements (i.e., vitamin D, probiotics) during the run-in diet, immobilization phase, and final testing day of the study.
• Supervisor approval for federal civilian employees and non-human research volunteer (HRV) active-duty military personnel stationed at Natick Soldier System Center (NSSC).
• Biological females must have normal menstrual cycles between 26-32 days in duration; 5 menstrual cycles within the past 6 months; or on continuous hormonal contraception (i.e., intrauteraine device (IUD) or oral contraceptives without placebo).

Exclusion Criteria:

• Musculoskeletal injuries that may interfere with the safe use of crutches.
• Personal or family history of thrombosis, or prior diagnosis of deep vein thrombosis (DVT) or pulmonary embolism (PE).
• Metabolic or cardiovascular abnormalities, gastrointestinal disorders, neuromuscular disorders, lower-limb amputation, or muscle/bone wasting disorders (e.g., diabetes, cardiovascular disease, Crohn's disease, etc.).
• Significantly abnormal blood clotting as determined by OMSO or home duty station medical support.
• Allergy to lidocaine (or similar local anesthetic)
• Present condition of alcoholism, anabolic steroid use, or other substance abuse issues as determined by OMSO or home duty station medical support.
• Blood donation within 8-wk of beginning the study.
• Pregnant, trying to become pregnant, and/or breastfeeding (results of urine pregnancy test and self-report for breastfeeding will be obtained before body composition testing).
• Unwilling or unable to consume study diets or foods provided due to personal preference and/or food allergies.
• Unwilling or unable to adhere to study physical restrictions (i.e., no structured physical activity or recreational activity beyond activities of daily living) 24 hours before and during immobilization, and the final testing day.
• Unwilling or unable to keep the knee brace on and walk with crutches during the immobilization phase.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Immobilized Leg; One leg of a young, healthy adult will be randomly assigned to undergo 5 days of immobilization using a rigid knee brace.	Other: Unilateral leg immobilization; Participants will have one leg immobilized using a rigid knee brace. Participants will be expected to keep the knee brace on for 5 days and remain non-weight bearing on the immobilized leg. Participants will use crutches to remain non-weight bearing on the immobilized leg.; Other Names: DISUSE
Experimental: Non-immobilized leg; One leg of a young, healthy adult will remain active and not immobilized for 5 days.	Other: Contralateral active leg; One leg will remain non-immobilized and active during the study. Participants will use this leg to walk with crutches.; Other Names: ACTIVE

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Integrated ribonucleic acid (RNA) synthesis	deuterium oxide coupled with muscle biopsies	5 days
Intramuscular protein signaling response to protein ingestion	muscle biopsies to assess protein signaling response to consuming 25 g of whey protein	90 minutes

Collaborators and Investigators

• Sponsor: United States Army Research Institute of Environmental Medicine
• Investigators: Principal Investigator: Emily E Howard, PhD, US Army Research Institute of Environmental Medicine

Study record dates

Study Major Dates

• Study Start (Actual): February 20, 2024
• Primary Completion (Estimated): May 1, 2025
• Study Completion (Estimated): May 1, 2025

Study Registration Dates

• First Submitted: January 18, 2024
• First Submitted That Met QC Criteria: January 18, 2024
• First Posted (Actual): January 29, 2024

Study Record Updates

• Last Update Posted (Actual): April 8, 2024
• Last Update Submitted That Met QC Criteria: April 5, 2024
• Last Verified: April 1, 2024

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Nervous System Diseases; Neurologic Manifestations; Musculoskeletal Diseases; Neuromuscular Diseases; Neuromuscular Manifestations; Pathological Conditions, Anatomical; Muscular Atrophy; Atrophy; Muscular Diseases; Muscular Disorders, Atrophic
• Other Study ID Numbers: 24-02

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