Heat, Microvascular Function and Aging

July 8, 2026 updated by: William Hughes
Vascular dysfunction is a common factor in many chronic debilitating diseases, contributing to morbidity and mortality. With the onset of chronic disease or exposure to stress, the vasculature displays an inability to adequately respond to increased blood flow demands, manifesting in a reduced ability or altered mechanism of vasodilation. Aging is an independent risk factor in the development of cardiovascular disease, and reduces vasodilator capacity, or alters the mechanism by which vasodilation occurs in multiple vascular beds. Chronic exercise/physical activity is one of the most potent ways to enhance vascular function, resulting in favorable outcomes such as reductions in blood pressure, and improved ability to perform activities of daily living. Barriers to exercise or failure of long-term adherence preclude many populations from the cardiovascular benefits of exercise, thus further enhancing cardiovascular risk. Avenues to mimic blood flow patterns observed with exercise may exert beneficial effects without the need for the ability to exercise. Recent evidence has demonstrated that passive heat therapy, or chronic heat exposure (~ +1°C in core temperature) results in reductions in major adverse cardiovascular events, blood pressure and improved large artery endothelial function, primarily through preservation of large artery function in response to vascular stress. It is unclear whether microvascular function is augmented in response to acute heat exposure, or whether this can protect against vascular insults particularly in older adults. Some preliminary evidence in humans suggest that autophagy, a cell recycling process is involved in the beneficial cardiovascular effects, as short-term heat exposure upregulates markers of autophagy. Previous evidence from our lab indicates that autophagy governs the mechanism by which microvascular vasodilation occurs. The role of autophagy in mediating the beneficial effects of passive heating is unknown.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Active, not recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
20

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Early Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.
  • Name: William E Hughes, Ph.D.
  • Phone Number: 414-955-7519
  • Email: whughes@mcw.edu

Study Locations

  • United States
    • Wisconsin
      • Milwaukee, Wisconsin, United States, 53226
        • Medical College of Wisconsin

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Participants must be between 18-80 yrs. of age
  • No more than 1 cardiovascular risk factor (see list in exclusion criteria)

Exclusion Criteria:

  • Cardiovascular Risk Factors
  • Uncontrolled/unmanaged hypertension and/or use of current anti-hypertensive therapy
  • Current Tobacco product use or within last 6 months
  • BMI greater than 30
  • Hyperlipidemia - diagnosed and/or taking medications to manage
  • Hypercholesterolemia - diagnosed and/or taking medications to manage (e.g. statins)
  • Type 1 or Type 2 Diabetes
  • Use of anti-coagulant or anti-platelet drugs
  • Use of beta blockers
  • Symptomatic coronary artery disease
  • Diagnosed Heart Failure (Any classification above Class I as defined by NY Heart Association)
  • Diagnosed renal impairment Renal impairment defined, according to National Kidney Foundation as abnormalities of kidney structure or function, present for greater than 3 months, including:
  • Albuminuria (ACR ≥ 30 mg/g)
  • Urine sediment abnormalities
  • Electrolyte and other abnormalities due to tubular disorders
  • Structural abnormalities detected by imaging
  • History of kidney transplantation
  • Decreased glomerular filtration rate (GFP < 60 mL/min/1.73 m2)
  • Current Hormone Replacement Therapy Use
  • History of retinopathy
  • Documented neuromuscular disorders
  • Porphyria Cutanea Tarda (blistering of skin to sun; photosensitivity)
  • Pregnancy (Young Female subjects)
  • Allergies to povidone iodine
  • Tattoos on lower arm (forearm)
  • Use of erectile dysfunction medication in the past 6 months
  • Use of topical/non-topical steroids in last 6 months (e.g. cortisone cream)
  • Active anti-cancer treatment or treatment within last 12 months
  • Active COVID-19 or within the past 3 months
  • Gender Reassignment Therapy

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Passive Heating of lower limbs
The lower limbs will be immersed in warm circulating water for 60 minutes.
Procedure: Passive Heating
The lower limbs will be immersed in warm (42C) circulating water for 60 minutes.
Drug: L-NAME
L-NAME will be used during measurement of cutaneous microvascular function to test the dependency upon NO to elicit vasodilation.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Change in cutaneous microvascular function
Time Frame: Baseline, 60 minutes post I/R, and 60 minutes post hot water immersion + I/R injury
Change in cutaneous microvascular function assessed via microdialysis infusion of acetylcholine (dose response) in the presence and absence of L-NAME to test the dependency upon NO to elicit vasodilation.
Baseline, 60 minutes post I/R, and 60 minutes post hot water immersion + I/R injury

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Spontaneous baroreflex sensitivity
Time Frame: Baseline, 60 minutes post I/R, 60 minutes post hot water immersion + I/R injury
Change in spontaneous BRS
Baseline, 60 minutes post I/R, 60 minutes post hot water immersion + I/R injury
24-hour (Ambulatory) Blood Pressure
Time Frame: Baseline
Ambulatory blood pressure (systolic, diastolic) for both peripheral and aortic blood pressure
Baseline
Change in plasma concentration of heat shock proteins
Time Frame: Baseline and 60 minutes post hot water immersion
Change in the plasma concentrations of various heat shock proteins (HSP 70, 90)
Baseline and 60 minutes post hot water immersion

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
William Hughes

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
May 1, 2025

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 31, 2028

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 31, 2028

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
October 4, 2024

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 7, 2024

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
October 9, 2024

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
July 9, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 8, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • PRO00052867

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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