The Effect of Antioxidants on Skin Blood Flow During Local Heating

Cardiovascular Diseases Clinical Trial

Official title:

The Effect of Antioxidants on Skin Blood Flow During Local Heating

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT03680638
• Other study ID #: 2016-0268
• Status: Completed
• Phase: Phase 1
• Start date: September 7, 2016
• Est. completion date: October 9, 2017

Study information

• Verified date: September 2018
• Source: The University of Texas at Arlington
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

The goal of this study is to examine possible mechanisms of impaired vasodilaton in obese and Black/African American men and women as possible links to the elevated prevalence of cardiovascular dysfunction and disease. The main targets in this study are sources of oxidative stress.

Description:

The integrative vascular laboratory has recently observed that the small blood vessels in the skin (the cutaneous microvasculature) in obese (BMI>30kg/m2), but otherwise healthy individuals, require a greater amount of nitric oxide (NO) to achieve the same degree of dilation when compared to age, gender, and race matched lean (BMI<25kg/m2) individuals (34). In addition, it is well documented that African Americans have impaired blood vessel function which likely contributes to the elevated risk for developing a variety of cardiovascular and metabolic diseases including coronary artery disease, metabolic syndrome, hypertension and stroke in this population. The cutaneous circulation is recognized as a surrogate vascular bed for assessment of mechanisms underlying systemic vascular disease (7, 20, 22). This is particularly important as microvascular dysfunction is emerging as a critical step in the atherosclerotic process and a variety of conditions including hypertension, exercise intolerance, and insulin resistance (25). Furthermore, impaired cutaneous microvascular function mirrors impaired responses in other vascular beds (7, 12, 20, 22). A primary advantage to utilizing the cutaneous circulation is that it provides an accessible vascular bed through which processes of endothelial function can be systematically and mechanistically investigated, with virtually no risk, through thermal stimuli and local intra-dermal drug infusions. Mechanisms of impaired NO bioavailability have been assessed in various at-risk and diseased populations including, healthy aging, hypertension, postural tachycardia syndrome, hypercholesteremia, and chronic kidney disease (8, 16, 19, 24, 36, 37). Using approaches and techniques similar to those proposed in this application (see below) the findings have implicated that a number of factors, including elevated oxidative stress, contribute to the reduced bioavailability and/or action of NO (8, 16, 19, 24, 36, 37)

The recent findings suggest an impairment in the action of NO on the microvascular smooth muscle of obese young adults (34) as well as in college-aged otherwise healthy African Americans. Local heating is a common method to test nitric oxide-mediated vasodilation (3, 6, 31). Therefore, the investigators propose to test the following hypotheses:

1. Obesity results in impaired blood flow response to local heating and this will also be the case for African Americans.

2. Inhibition of superoxide, a common form of oxidative stress, augments the local heating response in obese individuals as well as in African Americans.

3. Inhibition of sources of superoxide, NADPH-oxidase and/or Xanthine-oxidase, augments skin blood flow local heating response in obese to that of their lean counterparts. This will also be the case for African Americans relative to their Caucasian American counterparts.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 44
• Est. completion date: October 9, 2017
• Est. primary completion date: October 9, 2017
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 18 Years to 35 Years

Eligibility

Inclusion Criteria:

• Individuals (ages 18-35, both genders) will be recruited from the greater Arlington area to participate in the study.

• Must self-report both parents as either African American or Caucasian American.

Exclusion Criteria:

• Individuals who have donated more than 550 ml of blood within the past 8 weeks will not have blood drawn from them in this protocol. However, if they remain interested in the study, and otherwise meet the inclusion criteria, than we may still opt to proceed with data collection.

• Individuals with cardiovascular, neurological, and/or metabolic illnesses will be excluded from participating as well as individuals with a history of various diseases of the microvasculature including Reynaud's disease, cold-induced urticaria, cryoglobulinemia, etc.

• Subjects currently taking any prescription medications and individuals with a body mass index about 30 kg/m2) will be excluded.

• Pregnant subjects and children (i.e. younger than 18) will not be recruited for the study. Eligible females will be scheduled for days 2-7 of their menstrual cycle to account for hormonal effects on blood flow. A regular menstrual cycle is required to identify and schedule the study for the low hormone period, therefore females who lack a regular cycle will be excluded from the study. Females currently taking birth control are eligible, as long as they can be scheduled during a low-hormone "placebo" week. If their hormone do not contain a placebo week than these individuals will not be eligible for data collection. Females who are breast-feeding will also be eligible as there are no systemic or lasting effects of the proposed vasoactive agents.

• Given that smoking can affect the peripheral vasculature, current smokers and individuals who regularly smoked (>1 pack per two weeks) within the prior 2 years will be excluded

Related Conditions & MeSH terms

• Cardiovascular Diseases
• Cardiovascular Risk Factor
• Vasodilation

Intervention

Other:
• Control (Lactated Ringer's)
This intervention is meant to serve as a control by which the experimental sites are compared to, to assess effectiveness.

Drug:
• Tempol
This intervention is meant to assess the impact of superoxide on vasodilator responses by scavenging available superoxide.
• Apocynin
This intervention is meant to assess the impact of NADPH oxidase-derived superoxide on vasodilator responses by inhibiting the enzyme NADPH oxidase.
• Allopurinol
This intervention is meant to assess the impact of xanthine oxidase-derived superoxide on vasodilator responses by inhibiting the enzyme xanthine oxidase.

Locations

Country	Name	City	State
United States	Engineering Research Building	Arlington	Texas

Sponsors (1)

Lead Sponsor	Collaborator
The University of Texas at Arlington

Country where clinical trial is conducted

United States, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Vasodilator Responses to Local Heating with Antioxidant Supplementation	Assess the impact of oxidative stress on impaired vasodilation to local heating. This will be elicited using intradermal microdialysis infusions of apocynin, allopurinol, or tempol, all of which are vasoactive substances. The changes in skin blood flux will be quantified using laser Doppler fluxmetry. All changes in flux will be normalized and reported as a percentage of maximal flux.	Through study completion, an average of 1 year