Effects of Obesity on Autophagy and mTORC1 Signalling in Skeletal Muscle

Understanding the Effects of Obesity on Autophagic and mTORC1 Signalling Following Resistance Exercise and Protein Ingestion in Skeletal Muscle.

It is well known that individuals living with overweight or obesity are not able to activate skeletal muscle growth processes to the same extent as lean individuals following activities such as weightlifting (resistance exercise) or protein ingestion. However, the underlying cell signalling pathways which may be regulating these impairments are not fully understood. This study aims to understand if skeletal muscle signalling responses to resistance exercise and protein intake differ between lean individuals and those living with overweight or obesity. The investigators will recruit a cohort of lean individuals and a cohort of individuals living with overweight/obesity who will undertake a bout of single-leg resistance exercise and consume a protein-rich drink. Before and after this, muscle samples will be obtained from each leg of participants at different timepoints to understand the effects of exercise and feeding combined (exercised leg) and feeding alone (rested leg) on different cellular processes which regulate muscle growth. This will allow the investigators to understand if their are specific pathways within skeletal muscle which could be targeted in future interventions to overcome impaired protein metabolism in those living with overweight/obesity.

Study Overview

• Status: Recruiting
• Conditions: Overweight and Obese Adults
• Intervention / Treatment: Procedure: Skeletal muscle biopsy; Procedure: venous blood sampling; Dietary supplement: Protein-Rich Beverage; Other: Single-leg resistance exercise; Radiation: Dual-Energy X-ray Absorptiometry (DEXA) Scan; Other: Maximal Strength Testing

Detailed Description

As skeletal muscle is a major contributor to basal metabolic rate and glucose control, increasing the quality of skeletal muscle in those living with obesity could improve the long-term success of subsequent weight loss programs. There are two main activities which are often recommended to improve skeletal muscle quality, resistance exercise (i.e. weightlifting) and adequate protein intake, however, recent research has suggested that individuals living with obesity do not respond as well to these activities as a non-obese person. This research project aims to investigate if certain processes within muscle cells, which regulate muscle size and quality, are reduced in people living with obesity following a single session of resistance exercise and a protein-rich drink. This will hopefully identify processes we can target specifically to improve skeletal muscle quality. The project involves participants attending the lab and completing a session of single-leg resistance exercise and ingesting a protein drink. Before and after this the investigators will take a number of blood samples and small pieces of muscle from each thigh to understand how muscle reacts to exercise/feeding and whether this differs between individuals with and without obesity. Following the visit investigators will the conduct a variety of laboratory analysis on these samples to understand the responses. Overall, this project has the potential to help design future programmes which can improve skeletal muscle quality in those living with obesity, improving general health and increasing success of weight loss interventions.

To date, the acute effects anabolic stimulation by resistance exercise and protein ingestion in individuals with obesity have been shown to be blunted. However, the mechanisms responsible for this have scarcely been investigated. We intend to build on current evidence by identifying what causes this blunted response to anabolic stimulation in individuals with obesity.

This project aims to determine whether individuals with obesity exhibit differential mTORC1-lysosomal translocation in response to anabolic signaling following a single bout of resistance exercise combined with protein ingestion.

• Study Type: Observational
• Enrollment (Estimated): 24

Contacts and Locations

• Study Contact: Name: Jennifer Barrett, PhD; Phone Number: +447875713844; Email: j.s.barrett@bham.ac.uk

Study Locations

• United Kingdom
  • Birmingham, United Kingdom, B152TT
    • Recruiting
    • School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham
    • Contact: Jennifer Barrett, PhD; Phone Number: +447875713844; Email: j.s.barrett@bham.ac.uk
    • Contact: Email: n.w.hodson@bham.ac.uk
    • Principal Investigator: Nathan Hodson, PhD
    • Sub-Investigator: Jennifer Barrett, PhD
    • Sub-Investigator: Jordan Acheson, MSc

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

Participants will be recruited from around the West Midlands area via recruitment media.

Description

Inclusion Criteria:

• Age - 18-45yrs
• BMI - 18.5-24.9kg/m2 OR >28kg/m2 (self-declaration, or calculated by research team based on height and weight)
• Weight Stable i.e. no change in weight of more than 5% in previous 6 months
• Meeting UK Physical activity guidelines (150 mins moderate or 75 mins vigorous activity/wk)
• Not involved in structured exercise training in previous 6 months
• No other diagnosed metabolic or neuromuscular conditions (self-declaration)

Exclusion Criteria:

• Currently using anti-diabetes medication (insulin, metformin, sulphonylureas, meglitinides, thiazolidinediones, DPP- 4 inhibitors, GLP-1 inhibitors).
• Currently taking cholesterol lowering medications (statins)
• Currently engaged in active weight loss programmes or using weight loss medication
• Chronic kidney disease (moderate to severe reduction in kidney function), defined as eGFR <30 ml/min/1.73m2 identified by self declaration.
• Pregnant or breast feeding
• Currently using anti-coagulation medication
• Hypothyroidism
• Type 1 diabetes
• Current or recent weakness/injury to either leg that may affect muscle function or ability to exercise
• Current gastrointestinal issue/condition that may affect digestion and absorption of protein drink
• Individuals who follow a vegan diet or have intolerance/allergies to Whey protein.
• Previous adverse reaction to local anaethetic (lidocaine or marcaine).

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Lean Individuals; This cohort will be aged between 18-45yrs and have a Body Mass index (BMI) of 18.5-25.9kg/m2. They will also have been weight-stable (<5% bodyweight change in previous 6 months).	Procedure: Skeletal muscle biopsy; On five occasions throughout the experimental visit, skeletal muscle biopsies will be obtained from the vastus lateralis of participants (3 in rested leg, 2 in exercised leg). These will be completed under local anaesthetic using the Bergstrom needle technique, modified for suction.; Procedure: venous blood sampling; Upon arrival at the experimental visit, participant will have a cannula inserted into their antecubital vein for repeated blood sampling. 12 blood samples will then be taken throughout the course of the experimental trial from which both plasma and serum will be isolated.; Dietary supplement: Protein-Rich Beverage; Following completion of the acute, single-leg resistance exercise bout, participants will consumed a protein-rich beverage containing 0.25g/kg bodyweight whey protein (dissolved in 300ml water).; Other: Single-leg resistance exercise; During the experimental visit, participants will complete an acute bout of single-leg knee extensions on a randomised leg. This will be comprised of 6 sets of knee extensions at 80% of participants pre-determined 1 repetition maximum (1RM), with each set completed to volitional failure separated by a 2 minute rest interval.; Radiation: Dual-Energy X-ray Absorptiometry (DEXA) Scan; During Visit 1 of the study, participants will undergo a whole-body DEXA scan to assess body composition (body fat and fate-free mass). This short, painless scan exposes participants to a small amount of radiation which is equivalent to the amount exposed to during a transatlantic flight.; Other: Maximal Strength Testing; During Visit 1 of the study, participants will undergo maximal knee extension strength testing using a randomised leg (which will complete exercise during experimental trial). This will involve increasing the weight on the knee extension machine until the participant can no longer complete a single repetition. This weight will then be used to calculate the workload at which the participant will complete the exercise bout during the experimental trial.; Other Names: 1RM testing
Individuals with Overweight or Obesity; This cohort will be aged between 18-45yrs and have a Body Mass index (BMI) of >28kg/m2. They will also have been weight-stable (<5% bodyweight change in previous 6 months).	Procedure: Skeletal muscle biopsy; On five occasions throughout the experimental visit, skeletal muscle biopsies will be obtained from the vastus lateralis of participants (3 in rested leg, 2 in exercised leg). These will be completed under local anaesthetic using the Bergstrom needle technique, modified for suction.; Procedure: venous blood sampling; Upon arrival at the experimental visit, participant will have a cannula inserted into their antecubital vein for repeated blood sampling. 12 blood samples will then be taken throughout the course of the experimental trial from which both plasma and serum will be isolated.; Dietary supplement: Protein-Rich Beverage; Following completion of the acute, single-leg resistance exercise bout, participants will consumed a protein-rich beverage containing 0.25g/kg bodyweight whey protein (dissolved in 300ml water).; Other: Single-leg resistance exercise; During the experimental visit, participants will complete an acute bout of single-leg knee extensions on a randomised leg. This will be comprised of 6 sets of knee extensions at 80% of participants pre-determined 1 repetition maximum (1RM), with each set completed to volitional failure separated by a 2 minute rest interval.; Radiation: Dual-Energy X-ray Absorptiometry (DEXA) Scan; During Visit 1 of the study, participants will undergo a whole-body DEXA scan to assess body composition (body fat and fate-free mass). This short, painless scan exposes participants to a small amount of radiation which is equivalent to the amount exposed to during a transatlantic flight.; Other: Maximal Strength Testing; During Visit 1 of the study, participants will undergo maximal knee extension strength testing using a randomised leg (which will complete exercise during experimental trial). This will involve increasing the weight on the knee extension machine until the participant can no longer complete a single repetition. This weight will then be used to calculate the workload at which the participant will complete the exercise bout during the experimental trial.; Other Names: 1RM testing

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
mTORC1-lysosomal translocation	The translocation of the mTORC1-lysosomal complex toward the cell periphery following resistance exercise and/or protein ingestion will be assessed in skeletal muscle cross sections via immunofluorescence microscopy.	From completion of experimental testing/biosample collection until end of study, an average of 1 year.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
mTORC1 activation	Markers of mTORC1 activation (phosphorylation of downstream signalling targets) will be assessed via immunoblotting on homogenised skeletal muscle samples.	From completion of experimental testing/biosample collection until end of study, an average of 1 year.
Autophagic Flux	Skeletal muscle autophagic flux will be assessed on skeletal muscle samples using a novel ex vivo assay followed by immunoblotting.	From completion of experimental testing/biosample collection until end of study, an average of 1 year.
Lysosomal Content	Skeletal muscle lysosomal content will be assessed via immunoblotting for markers of the lysosome on homogenised skeletal muscle samples	From completion of experimental testing/biosample collection until end of study, an average of 1 year.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Circulating Amino Acids Concentrations	Amino acid concentrations will be assessed via high performance liquid chromatography to determine how much of the protein ingested arrives in circulation	From completion of experimental testing/biosample collection until end of study, an average of 1 year.
Circulating Hormone Concentrations	Hormones associated with glycaemic control (glucose & insulin) will be assessed in plasma/serum samples via colorometric assay or ELISA	From completion of experimental testing/biosample collection until end of study, an average of 1 year.

Collaborators and Investigators

• Sponsor: University of Birmingham
• Investigators: Principal Investigator: Nathan Hodson, University of Birmingham

Study record dates

Study Major Dates

• Study Start (Actual): April 15, 2026
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): December 1, 2027

Study Registration Dates

• First Submitted: August 12, 2026
• First Submitted That Met QC Criteria: August 17, 2026
• First Posted (Actual): August 19, 2026

Study Record Updates

• Last Update Posted (Actual): August 19, 2026
• Last Update Submitted That Met QC Criteria: August 17, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: Obesity; Overweight; Autophagy; Skeletal muscle; Protein metabolism; mTORC1 signalling
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Overweight; Obesity; Investigative Techniques; Specimen Handling; Clinical Laboratory Techniques; Diagnostic Techniques and Procedures; Diagnosis; Punctures; Surgical Procedures, Operative; Diagnostic Imaging; Chemistry Techniques, Analytical; Radiography; Densitometry; Photometry; Absorptiometry, Photon; Blood Specimen Collection
• Other Study ID Numbers: RG_25-084

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: IPD used in publications arising from the project will be shared upon request
• IPD Sharing Time Frame: IPD will be available upon request following publication of the IPD with no end date
• IPD Sharing Access Criteria: Qualified researchers with an approved scientifically sound research proposal from recognized academic, clinical, or commercial institutions can request IPD from the principal investigator. In such cases, the de-identified data long with the study protocol will be provided via a secure cloud-based research environment.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL

Drug and device information, study documents

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