Physical Activity and Insulin Sensitivity Dynamics

Summary

The study investigates the role of one single bout of exercise in mediating enhancement of muscle insulin sensitivity following a single bout of exercise. Furthermore, the study is aiming to elucidate the temporal development in insulin signaling, at the early timepoints of insulin stimulation that may be responsible for the enhanced muscle insulin sensitivity.

This will be investigated in young healthy males subjected to a one-legged knee-extensor exercise followed by a hyperinsulinemic-euglycemic clamp, a setup known to enhance muscle insulin sensitivity.

Conditions

• Insulin Sensitivity

Interventions

OTHER

One-legged-knee extensor exercise

1 hour of one-legged-knee-extensor exercise followed by 4 hours of rest

PROCEDURE

Insulin infusion

The hyperinsulinemic-euglycemic clamp is a well-established and recognized method for determining glucose uptake at a specific insulin infusion rate. It is a technique with which we have 25 years of uncomplicated experience. During the clamp, insulin (human recombinant insulin) is infused (1.42 mU/kg/min) into an arm vein (antecubital vein), while glucose (20% solution) is administered in an amount adjusted to maintain blood glucose (plasma glucose concentration) at basal levels. The amount of insulin administered raises the participant's plasma insulin concentration (blood concentration) to approximately 100 μU/mL, which is considered within the physiological range. Blood samples are collected and analyzed continuously for glucose content, allowing for the determination of glucose uptake at the whole-body level and across the legs. Later, these blood samples will also be analyzed for relevant metabolites and proteins, including insulin, to assess the metabolism of these substances.

PROCEDURE

Muscle Biopsy Medication: Lidocaine

During supine rest, the skin on the outer thigh, approximately 15 cm above the knee, is disinfected with chlorhexidine alcohol. Subsequently, 3-4 mL of local anesthetic (lidocaine 20 mg/mL) is administered into the skin, subcutaneous tissue, and the upper portion of the muscle using a very thin needle. A pinprick test is performed after a few minutes to ensure the anesthetic is effective. A small incision is then made in the skin and subcutaneous tissue to allow the biopsy needle to pass through to the muscle. Using the biopsy needle, a small sample of muscle tissue (approximately 150 mg) is collected. This may cause some discomfort but is very brief (\~1-2 seconds). The needle is removed, a sterile dressing is applied, and the participant can leave the facility after completing the study. The biopsy may result in mild muscle soreness for 2-3 days, similar to a minor muscle bruise. Regular physical activities can be resumed after the biopsy. However, it is advised to avoid swimming.

OTHER

Exercise

The participants' maximal oxygen uptake is determined through a test on a cycle ergometer before the start of the experiment. The test begins with a 20-minute warm-up at two different low workloads, after which the workload is gradually increased until the predetermined cadence can no longer be maintained, or the participant indicates exhaustion. During the test, the participant's exhaled air is collected. After completing the warm-up, it typically takes between 4 and 7 minutes to complete the test.

Sponsors & Collaborators

• University of Copenhagen

  lead OTHER

Principal Investigators

• Jørgen FP Wojtaszewski, Prodessor · Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Denmark

Study Design

Allocation

NA

Purpose

BASIC_SCIENCE

Masking

NONE

Model

SINGLE_GROUP

Eligibility

Min Age

22 Years

Max Age

35 Years

Sex

MALE

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-05-05

Primary Completion

2025-08-26

Completion

2027-01-31

Countries

• Denmark

Study Locations