Clinical trial NCT04770155: Vascular Dysfunction in Black Individuals: Roles of Nitric Oxide and Endothelin-1
Official title: Vascular Dysfunction in Black Individuals: Roles of Nitric Oxide and Endothelin-1
Study type: INTERVENTIONAL
Overall status: TERMINATED
Phase: EARLY_PHASE1
Conditions: Vascular Function
Racial Disparity
Keywords: Black
African American
White
Caucasian American
Hyperemia
Blood Flow
Conductance
Lead sponsor: University of Mississippi Medical Center
Sponsor class: OTHER
First posted: 2021-02-25
Enrollment: 8
Sex: ALL
Minimum age (years): 18
Maximum age (years): 40
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: BASIC_SCIENCE

Brief summary: The research aims of this proposal are:

* Specific Aim 1: To test whether an increase in nitric oxide signaling can increase vasodilator responses in young Black individuals.
* Specific Aim 2: To test whether a decrease in endothelin-1 signaling can increase vasodilator responses in young Black individuals.

Detailed description: Studies will be conducted in the Clinical Research and Trials Unit at the University of Mississippi Medical Center. All study visits will follow the same procedures, except for the drug or supplement being administered.

For Aim 1, double-blind, randomized, placebo-controlled crossover designs will examine the effects of increasing nitric oxide and cyclic guanosine monophosphate bioavailability on vascular function of young Black and White individuals. Three sets of two visits will be performed:

* Aim 1a: At the beginning of each visit, participants will ingest either a nitrate-rich beetroot juice or a nitrate-depleted beetroot juice (serving as placebo) in their liquid commercial form, which has a distinct color and flavor. The nitrates will be absorbed and reduced in the plasma to nitrite and nitric oxide, increasing endothelium-independent nitric oxide bioavailability.
* Aim 1b: Participants will receive a 7-day supplement of L-citrulline or placebo before each study visit, with a washout period of 7 days between visits. The activity of the endothelial nitric oxide synthase converts L-arginine into nitric oxide and L-citrulline, which is normally recycled back into L-arginine. Unlike L-arginine, oral ingestion of L-citrulline is not catabolized in the gut, nor is it extracted from systemic circulation through hepatic first-pass metabolism. Thus, ingested L-citrulline becomes available in large quantities in the plasma for enzymatic conversion into L-arginine, increasing endothelium-dependent nitric oxide bioavailability.
* Aim 1c: At the beginning of each visit, participants will ingest a liquid mixture prepared by Investigational Drug Services at the University of Mississippi Medical Center containing Sildenafil or placebo. Sildenafil inhibits phosphodiesterase 5, an enzyme that degrades cyclic guanosine monophosphate in the vascular smooth muscle cells inactivating the nitric oxide-mediated signal; thus, Sildenafil will prolong the availability of cyclic guanosine monophosphate, enhancing the nitric oxide-mediated intracellular cascade.

For Aim 2, a double-blind, randomized, placebo-controlled crossover design will examine the role of endothelin-1 on the vascular function of young Black and White individuals. Two visits will be performed, with a minimum of 7 days between them.

• Aim 2: At the beginning of each visit, participants will ingest a liquid mixture prepared by Investigational Drug Services at the University of Mississippi Medical Center containing Bosentan or placebo. Bosentan blocks ETA and ETB receptors, leading to a reduction in vasoconstrictor tone and a greater magnitude of vasodilator responses.

Eligibility criteria: Inclusion Criteria:

* Self-identification of their race and the race of their biological parents as being only Black (i.e., African American) or only White (i.e., Caucasian American)
* Born and raised in the United States

Exclusion Criteria:

* Mixed races
* Any chronic or ongoing disease
* Prescribed pharmacological treatment
* Smoking or tobacco use
* Obesity (body mass index \> 30 kg / m2)

Primary outcomes:
measure: Flow-mediated Dilation
timeFrame: Within 4 hours of drug/supplement administration.
measure: Reactive Hyperemia (Cuff Release)
timeFrame: Within 4 hours of drug/supplement administration.
measure: Muscle Hyperemia (Passive Leg Movement)
timeFrame: Within 4 hours of drug/supplement administration.
measure: Muscle Hyperemia (Rhythmic Handgrip Exercise)
timeFrame: Baseline measurements with no drug/supplement administration before or after.
measure: Muscle Hyperemia (Rhythmic Knee Extension Exercise)
timeFrame: Within 4 hours of drug/supplement administration.
Secondary outcomes:
Other outcomes:
Locations:
city: Jackson
country: United States
facility: University of Mississippi Medical Center
state: Mississippi
Study officials:
affiliation: University of Mississippi Medical Center
name: Thales C Barbosa, Ph.D.
role: PRINCIPAL_INVESTIGATOR
References:
citation: Barbosa TC, Young BE, Stephens BY, Nandadeva D, Kaur J, Keller DM, Fadel PJ. Functional sympatholysis is preserved in healthy young Black men during rhythmic handgrip exercise. Am J Physiol Regul Integr Comp Physiol. 2020 Sep 1;319(3):R323-R328. doi: 10.1152/ajpregu.00105.2020. Epub 2020 Aug 12.
citation: Barbosa TC, Kaur J, Stephens BY, Akins JD, Keller DM, Brothers RM, Fadel PJ. Attenuated forearm vascular conductance responses to rhythmic handgrip in young African-American compared with Caucasian-American men. Am J Physiol Heart Circ Physiol. 2018 Nov 1;315(5):H1316-H1321. doi: 10.1152/ajpheart.00387.2018. Epub 2018 Aug 17.
citation: Kaur J, Barbosa TC, Nandadeva D, Young BE, Stephens BY, Brothers RM, Fadel PJ. Attenuated Rapid-Onset Vasodilation to Forearm Muscle Contraction in Black Men. Med Sci Sports Exerc. 2021 Mar 1;53(3):590-596. doi: 10.1249/MSS.0000000000002511.
citation: Young BE, Kaur J, Vranish JR, Stephens BY, Barbosa TC, Cloud JN, Wang J, Keller DM, Fadel PJ. Augmented resting beat-to-beat blood pressure variability in young, healthy, non-Hispanic black men. Exp Physiol. 2020 Jul;105(7):1102-1110. doi: 10.1113/EP088535. Epub 2020 May 27.
citation: Vranish JR, Holwerda SW, Young BE, Credeur DP, Patik JC, Barbosa TC, Keller DM, Fadel PJ. Exaggerated Vasoconstriction to Spontaneous Bursts of Muscle Sympathetic Nerve Activity in Healthy Young Black Men. Hypertension. 2018 Jan;71(1):192-198. doi: 10.1161/HYPERTENSIONAHA.117.10229. Epub 2017 Dec 4.