Clinical trial NCT03738943: Pyridoxine, P2 Receptor Antagonism, and ATP-mediated Vasodilation in Young Adults
Official title: Pyridoxine, P2 Receptor Antagonism, and ATP-mediated Vasodilation in Young Adults
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: EARLY_PHASE1
Conditions: Receptor Blockade
Keywords: Adenosine Triphosphate
Pyridoxine
Cardiovascular
PLP
P5P
Lead sponsor: Colorado State University
Sponsor class: OTHER
First posted: 2018-11-13
Enrollment: 9
Sex: ALL
Minimum age (years): 18
Maximum age (years): 30
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: PARALLEL
Intervention model description: Participants will be assigned to one of three arms of the study. The arms of the study are based on the vasodilators being tested in order to determine the effect of pyridoxine or PLP on vasodilation in response to intra-arterial administration of the vasodilators.
Primary purpose: BASIC_SCIENCE

Brief summary: Previous research has identified adenosine triphosphate (ATP) as an important vasodilator that is released from red blood cells during exercise and exposure to hypoxic environments in adult humans. Further, older adults appear to have lower blood flow during both of these stressors and also have lower amounts of ATP released from their red blood cells. However, the contribution of ATP to vasodilation in response to exercise and hypoxia is currently unknown due to the lack of an effective ATP receptor antagonist. We aim to determine whether Vitamin B6 or its metabolite, Pyridoxal-5-Phosphate (PLP) is an effective ATP receptor antagonist.

Detailed description: Adenosine triphosphate (ATP) is an established vasodilator that is released from red blood cells during a variety of stimuli including exercise and exposure to hypoxic environments. Many studies have shown that infusion of ATP can lead to vasodilation similar to that which is achieved during exercise, and that plasma ATP concentrations increase in a graded fashion during graded exercise. Further, older adults have lower levels of blood flow during exercise and hypoxia compared to their younger counterparts, and the reduced blood flow is coupled with impaired release of ATP from red blood cells during these stimuli. Thus, ATP is believed to be an important vasodilator. However, the role of ATP in the regulation of blood flow is not fully understood due to the lack of an effective ATP receptor (P2Y2) antagonist. Development of an effective P2Y2 antagonist will allow researchers to determine the role of ATP in vasodilation to stimuli such as exercise by comparing blood flow during exercise with and without the blocker. Preliminary data from our laboratory suggests that Vitamin B6 (pyridoxine hydrochloride) or its metabolite Pyridoxal-5-Phosphate (PLP) may be an effective blocker of ATP-mediated vasodilation. As a result, the purpose of this study is to determine whether Vitamin B6 or PLP can inhibit vasodilation in response to intra-arterial infusions of ATP. This study also aims to determine the specificity of Vitamin B6 or PLP by measuring its effect on vasodilation in response to infusion of several other vasodilators.

Participants will be asked to complete one screening visit and one study visit. Once study eligibility has been determined, participants will report to the Human Performance Clinical Research Laboratory at Colorado State University following an overnight fast. A physician will then place a catheter in the brachial artery of the non-dominant arm, and participants will be randomized into one of three study arms to determine which drugs will be infused into the artery. Each arm includes ATP and two other vasodilators. The study will begin by measuring vasodilation in response to four standard doses of each vasodilator. Vasodilation in response to the vasodilators will then be assessed again following infusion of Vitamin B6 or PLP. Reduced vasodilation to any of the drugs during the second trial will suggest that Vitamin B6 or PLP is an antagonist to the channel through which the drug signals. Each study visit will last approximately 4-5 hours.

Eligibility criteria: Inclusion Criteria:

* Sedentary-moderately active
* Free of chronic disease

Exclusion Criteria:

* Current smoker
* BMI \> 29.9 kg/m2
* Blood pressure equal to or greater than 140/90 mmHg
* Use of any medications including vitamin B6 supplements or antioxidants

Primary outcomes:
measure: Vascular Conductance
timeFrame: Continuous measurement of vascular conductance during the 12 minute dose response for each drug. Measures are repeated following administration of Vitamin B6 or PLP.
Secondary outcomes:
Other outcomes:
Locations:
city: Fort Collins
country: United States
facility: Human Performance and Clinical Research Laboratory
state: Colorado
Study officials:
affiliation: Colorado State University
name: Frank Dinenno, PhD
role: PRINCIPAL_INVESTIGATOR
References: