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Can blocking a nerve signal help insulin work better?
NCT ID NCT03318094
First seen Jun 24, 2026 · Last updated Jun 27, 2026 · Updated 1 time
Summary
This early-phase study at Vanderbilt University Medical Center is looking at how certain nerve signals (called sympathetic vasoconstriction) might interfere with insulin's ability to widen blood vessels and take up sugar. The researchers will give a drug called phentolamine into the arm to temporarily block those signals, then measure changes in blood flow and insulin sensitivity. The study involves 36 adults aged 18-60 who are obese and have insulin resistance or well-controlled type 2 diabetes.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- Phentolamine (alpha-adrenergic blocker)
- What this could lead to
- If successful, this study could point toward new ways to improve insulin sensitivity in people with obesity and insulin resistance.
- What could go wrong
- This is a very early, small study (36 people) testing a short-term drug infusion in the arm. It is not designed to prove a treatment works, only to understand the body's response.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
-
Phase 1
The first testing in people. Mainly checks safety and dose, usually in a small group.
- Participants
-
About 36 people
The number the study aims to enrol. It can still change while the study runs.
- Started
-
Oct 2017
- Expected to finish
-
Nov 2027
An estimate. End dates often move.
- Lead sponsor
-
Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
-
18 to 60 years
- Sex
-
Anyone
- Healthy volunteers
-
Accepted
You do not need to have the condition being studied to take part.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: * Males and females of all races between 18 and 60 years of age. * Obesity defined as body mass index between 30-40 kg/m2 * Insulin resistance defined as homeostasis model assessment 2 insulin resistance (HOMA2-IR) score \>1.6 (never diagnosed or treated type 2 diabetic), or being a well-controlled type 2 diabetic on metformin only. * Able and willing to provide informed consent Exclusion Criteria: * Pregnancy or breastfeeding * Current smokers or history of heavy smoking (\>2 packs/day) * History of alcohol or drug abuse * Morbid obesity (BMI \> 40 kg/m2) * Previous allergic reaction to study medications * Evidence of type I diabetes. * Cardiovascular disease other than hypertension such as myocardial infarction within 6 months prior to enrollment, presence of angina pectoris, significant arrhythmia, congestive heart failure (LV hypertrophy acceptable), deep vein thrombosis, pulmonary embolism, second or third-degree heart block, mitral valve stenosis, aortic stenosis, or hypertrophic cardiomyopathy * History of serious cerebrovascular disease such as cerebral hemorrhage, stroke, or transient ischemic attack * History or presence of immunological or hematological disorders * Impaired hepatic function \[aspartate amino transaminase (AST) and/or alanine amino transaminase (ALT) \> 2.0 x upper limit of normal range\] * Impaired renal function (serum creatinine \>1.5 mg/dl) * Moderate to severe anemia (hemoglobin \<11 g/dl) * Treatment with serotonin-norepinephrine reuptake inhibitors (SNRIs) or norepinephrine transporter (NET) inhibitors * Treatment with phosphodiesterase 5 inhibitors * Treatment with anticoagulants * Treatment with chronic systemic glucocorticoid therapy (more than 7 consecutive days in 1 month) * Treatment with any investigational drug in the 1 month preceding the study * Inability to give, or withdraw, informed consent * Other factors which in the investigator's opinion would prevent the subject from completing the protocol (i.e., clinically significant abnormalities on clinical, mental examination or laboratory testing or inability to comply with protocol)
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
-
Autonomic Dysfunction Center
Nashville, Tennessee, 37232, United States
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