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NCT Number: NCT04684589

Effect of PDE5 Inhibition on Adipose Metabolism in Humans

This is a randomized, double-blinded, placebo-controlled study of the effects of PDE5 inhibition with tadalafil on adipose tissue in obese individuals. Adipose metabolism will be measured using magnetic resonance imaging (MRI) scans and by aspirating a small amount of adipose to measure gene expression.

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Key information

Conditions

Obesity Body Weight Nutrition Disorders Nutritional and Metabolic Diseases Overnutrition Overweight Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

19 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 2

Primary location

Vanderbilt University Medical Center

Nashville, Tennessee, 37203, United States

About this study

The purpose of this study is to test whether tadalafil causes subcutaneous adipose tissue to have a "beige" phenotype. Participants will be randomized to either placebo or tadalafil for 12 weeks. Investigators will study adipose metabolism using MRI scans and aspiration of subcutaneous adipose from the abdomen. In addition to MRI scans at room temperature, the investigators will use a cooling protocol to test the combined effects of tadalafil and on adipose metabolism. Investigators will also measure the effects of the drug on body composition. In addition to the study visits, participants will wear an activity tracker (Fitbit) and log their dietary intake several times using an online tool. There will be a small amount of radiation exposure. Participants will be compensated for participation in this study.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adults
  • Obesity (BMI ≥ 30 kg/m2)

Exclusion criteria

  • Age <19 or > 50
  • BMI < 30 kg/m2
  • Systolic blood pressure (SBP) < 100, > 150 mmHg
  • Current anti-hypertensive medication use, including diuretics
  • Current use of organic nitrates
  • Current use of PDE-5 inhibitors (sildenafil, tadalafil, vardenafil)
  • History of reaction to PDE-5 inhibitors
  • Known HIV infection
  • Use of medications that strongly alter CYP3A4 activity
  • History of myocardial infarction, angina, uncontrolled cardiac arrhythmia, stroke, transient ischemic attack, or seizure
  • Known non-arteritic ischemic optic retinopathy (NAIOR)
  • History of hearing loss
  • Estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m2 by the modified diet in renal disease (MDRD) equation
  • Hepatic transaminase (AST and ALT) levels greater than three times the upper limit of normal
  • Known pregnancy or breastfeeding or those unwilling to avoid pregnancy during the course of the study
  • History of priapism
  • Use in excess of four alcoholic drinks daily
  • History of diabetes mellitus or use of anti-diabetic medications
  • Known anemia (men, Hct < 38% and women, Hct <36%)
  • Menopause
  • Weight > 300 pounds
  • Individuals with circadian rhythm disorders, shift workers, or those who travel across time zones frequently

Treatment and study plan

Tadalafil 20 mg

Drug

Tadalafil is an FDA approved, clinically-available drug that inhibits the enzyme phosphodiesterase type 5A (PDE5). Subjects who are randomized to this arm will be provided with 20mg of Tadalafil to take every day for 12 weeks, beginning at their baseline visit.

Other names: CIALIS

Placebo

Drug

Subjects in this arm will be provided with 20mg Placebo to take every day for 12 weeks, beginning at their baseline visit.

Primary outcomes

  1. Thermoneutral FSF of WAT at the Level of the Umbilicus at 12 Weeks.

    Time frame: 12 weeks

    Measured by fat signal fraction (FSF) at Week 12. FSF is the percent of MRI signal derived from lipids within a voxel. Lower FSF values indicate greater lipid consumption and correspond to brown adipose tissue (BAT), whereas higher FSF values indicate lipid storage and correspond to white adipose tissue (WAT).

  2. Thermoneutral Subcutaneous Adipose Tissue Expression of UCP1 (Normalized Expression Units) at 12 Weeks.

    Time frame: 12 weeks

    Measured by mRNA expression of subcutaneous adipose tissue obtained via biopsy at 12 weeks. Higher expression of UCP1 indicates increased thermogenic (beige/brown) adipose activity; lower expression indicates a white adipose phenotype associated with reduced energy expenditure.

Sponsors and collaborators

Lead sponsor

Vanderbilt University Medical Center

Other

Registry information

Important dates

Study start
2021
Primary completion
2025
Study completion
2025
First posted
Dec 24, 2020
Registry last updated
Jul 30, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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