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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.
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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Tadalafil | Active Comparator | Subjects will be randomized to one of two arms. 50 obese adult subjects will be randomized to the Tadalafil arm following the screening visit. Beginning at their baseline visit, they will receive an oral daily dose of Tadalafil (20mg) that they will take for 12 weeks (through their completion of the study). After randomization has occurred, the active comparator subjects will undergo the following visit protocol: screening visit, baseline visit, an interim visit (10 weeks post-baseline), and a 12-week visit. |
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| Placebo | Placebo Comparator | Subjects will be randomized to one of two arms. 50 obese adult subjects will be randomized to the placebo arm following the screening visit. Beginning at their baseline visit, they will receive an oral daily dose of a placebo pill (20mg) that they will take for 12 weeks (through their completion of the study). After randomization has occurred, the placebo comparator subjects will undergo the following visit protocol: screening visit, baseline, an interim visit (10 weeks post-baseline), and a 12-week visit. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| 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. |
| Measure | Description | Time Frame |
|---|---|---|
| Thermoneutral FSF of WAT at the level of the umbilicus at 12 Weeks. | MRI measurement of lipid content | 12 weeks |
| Subcutaneous adipose tissue expression of UCP1 (normalized expression units) | Measurement of gene expression in adipose sample | 12 weeks |
| Measure | Description | Time Frame |
|---|---|---|
| Thermoneutral fat signal fraction of brown adipose tissue | MRI measurement of lipid content | Baseline to 12 weeks |
| Cold-exposed fat signal fraction of white adipose tissue and grown adipose tissue |
| Measure | Description | Time Frame |
|---|---|---|
| BAT perfusion under thermoneutral and cold conditions | MRI measurement of blood flow | Baseline to 12 weeks |
| Change in BNP concentration during cold exposure | Blood measurement of hormone |
Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Evan Brittain, MD, MSci | VUMC | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Vanderbilt University Medical Center | Nashville | Tennessee | 37203 | United States |
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| Type | Includes Protocol | Includes SAP | Includes ICF | Document Label | Document Date | Document Uploaded Date | Document File Name |
|---|---|---|---|---|---|---|---|
| ICF | No | No | Yes | Informed Consent Form | Nov 14, 2024 | Aug 21, 2025 | ICF_000.pdf |
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| Release Date | Unrelease Date | Unrelease Date Unknown | Reset Date | MCP Release Number |
|---|---|---|---|---|
| Jul 2, 2026 |
| ID | Term |
|---|---|
| D009765 | Obesity |
| ID | Term |
|---|---|
| D050177 | Overweight |
| D044343 | Overnutrition |
| D009748 | Nutrition Disorders |
| D009750 | Nutritional and Metabolic Diseases |
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| ID | Term |
|---|---|
| D000068581 | Tadalafil |
| ID | Term |
|---|---|
| D002243 | Carbolines |
| D011725 | Pyridines |
| D006573 | Heterocyclic Compounds, 1-Ring |
| D006571 | Heterocyclic Compounds |
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Half of participants to get tadalafil and half to get placebo.
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Double blinded
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| Placebo | Drug | Subjects in this arm will be provided with 20mg Placebo to take every day for 12 weeks, beginning at their baseline visit. |
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MRI measurement of lipid content
| Baseline to 12 weeks |
| Subcutaneous adipose tissue gene expression of mitochondrial genes (normalized expression units) | Measurement of gene expression in adipose sample | Baseline to 12 weeks |
| Subcutaneous adipose tissue natriuretic peptide receptor expression | Measurement of gene expression in adipose sample | Baseline to 12 weeks |
| Baseline to 12 weeks |
| Change in free fatty acid level during cold exposure | Blood measurement of fat | Baseline to 12 weeks |
| Change in whole body subcutaneous and visceral fat mass | Measurement of fat mass will be examined using dual x-ray absorptiometry to assess for changes in fat mass. | Baseline to 12 weeks |
| Resting energy expenditure | Measurement of energy expended | Baseline to 12 Weeks |
| Homeostatic Index of Insulin Resistance | Blood measurement of insulin resistance | Baseline to 12 Weeks |
| D001835 |
| Body Weight |
| D012816 | Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |
| D026121 |
| Indole Alkaloids |
| D007211 | Indoles |
| D006574 | Heterocyclic Compounds, 2-Ring |
| D000072471 | Heterocyclic Compounds, Fused-Ring |
| D006575 | Heterocyclic Compounds, 3-Ring |