Racial Differences in Serum Sodium and Blood Pressure Regulation

Blood Pressure Clinical Trial

Official title:

Racial Differences in Serum Sodium and Blood Pressure Regulation

Clinical Trial Details — Status: Recruiting

Administrative data

• NCT number: NCT04244604
• Other study ID #: AU IRB#19-390
• Status: Recruiting
• Phase: N/A
• Start date: May 3, 2021
• Est. completion date: May 31, 2025

Study information

• Verified date: August 2023
• Source: Auburn University
• Contact: Rodney Greer, PhD
• Phone: (334) 844-3597
• Email: rjg0008[@]auburn.edu
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

Nearly nine-in-ten Americans overconsume salt. Black individuals are more prone to salt-sensitive hypertension. The central goal of the study is to determine if dietary sodium influences blood vessel function and nervous system regulation of blood pressure differentially in black, compared to white individuals. These findings may help to explain why high dietary salt causes increases in blood pressure more frequently in black, compared to white individuals. A secondary goal of this project is to also determine the role of lifestyle factors (i.e., sleep, physical activity, and nutrition) on potential baseline racial differences in cardiovascular function.

Description:

The investigators aim to study racial differences in cardiovascular responses to high dietary sodium. An overwhelming majority of Americans consume more dietary sodium than what is recommended by the American Heart Association and the Dietary Guidelines for Americans. The investigators recently published data demonstrating that compared to white individuals, 1) black individuals have augmented increases in serum sodium concentration to a hypertonic saline infusion; and 2) exhibit higher blood pressure for a given serum sodium. In this proposal, the investigators will translate these findings by comprehensively assessing neurovascular responses to acute (single meal) high dietary sodium. The central hypothesis is that high dietary sodium influences sympathetic nerve activity similarly in black and white individuals; however, diminished vasodilator capacity and augmented sympathetic transduction (vasoconstrictor responses to sympathetic nerve bursts) contribute to exaggerated blood pressure dysregulation in black individuals. The investigators will also determine the role of lifestyle factors (i.e., sleep, physical activity, and nutrition) on potential baseline racial differences in cardiovascular function.

Recruitment information / eligibility

• Status: Recruiting
• Enrollment: 100
• Est. completion date: May 31, 2025
• Est. primary completion date: August 31, 2024
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 19 Years to 75 Years

Eligibility

Inclusion Criteria:

1. Are between the ages of 19-75.

2. Have blood pressure no higher than 150/90 mmHg.

3. Have a BMI below 35 Kg/m2 (otherwise healthy)

4. Free from metabolic disease (diabetes or renal disease), pulmonary disorders (e.g., COPD & cystic fibrosis), and cardiovascular disease (peripheral vascular, cardiac, or cerebrovascular).

5. Do not have any precluding medical issues that prevent participants from exercising (i.e., cardiovascular issues, or muscle/joint issues including painful arthritis) or giving blood (e.g., blood thinners).

6. Are not currently smoking, using smokeless tobacco, nor smoked within the past 12 months.

Exclusion Criteria:

1. High blood pressure - greater the 150/90 mmHg

2. Low blood pressure - less than 90/50 mmHg

3. History of cardiovascular disease

4. History of cancer

5. History of diabetes

6. History of kidney disease

7. Obesity (BMI > 30 kg/m2)

8. Smoking or tobacco use

9. Current pregnancy

10. Nursing mothers

11. Communication barriers

Related Conditions & MeSH terms

• Blood Pressure
• Cardiovascular Risk Factor
• Hypernatremia
• Racial Disparities
• Sodium Excess

Intervention

Other:
• Acute Salt (sodium chloride)
Varied amounts of salt (sodium chloride) will be added to a very low sodium soup to determine the effects of a single high sodium meal on measures of vascular function and autonomic regulation of blood pressure

Locations

Country	Name	City	State
United States	Auburn University	Auburn	Alabama
United States	Kinesiology Building	Auburn	Alabama

Sponsors (2)

Lead Sponsor	Collaborator
Auburn University	University of Delaware

Country where clinical trial is conducted

United States, 

References & Publications (4)

Babcock MC, Robinson AT, Migdal KU, Watso JC, Wenner MM, Stocker SD, Farquhar WB. Reducing Dietary Sodium to 1000 mg per Day Reduces Neurovascular Transduction Without Stimulating Sympathetic Outflow. Hypertension. 2019 Mar;73(3):587-593. doi: 10.1161/HYPERTENSIONAHA.118.12074. — View Citation

Dickinson KM, Clifton PM, Burrell LM, Barrett PH, Keogh JB. Postprandial effects of a high salt meal on serum sodium, arterial stiffness, markers of nitric oxide production and markers of endothelial function. Atherosclerosis. 2014 Jan;232(1):211-6. doi: 10.1016/j.atherosclerosis.2013.10.032. Epub 2013 Nov 20. — View Citation

Migdal KU, Robinson AT, Watso JC, Babcock MC, Serrador JM, Farquhar WB. A high-salt meal does not augment blood pressure responses during maximal exercise. Appl Physiol Nutr Metab. 2020 Feb;45(2):123-128. doi: 10.1139/apnm-2019-0217. Epub 2019 Jun 25. — View Citation

Wenner MM, Paul EP, Robinson AT, Rose WC, Farquhar WB. Acute NaCl Loading Reveals a Higher Blood Pressure for a Given Serum Sodium Level in African American Compared to Caucasian Adults. Front Physiol. 2018 Oct 1;9:1354. doi: 10.3389/fphys.2018.01354. eCollection 2018. — View Citation

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Changes in muscle sympathetic nerve activity (MSNA) and sympathetic transduction	The investigators will directly record MSNA using an active tungsten microelectrode inserted into a nerve near the fibular head or popliteal fossa using standard microneurography techniques. The raw signal will be amplified, band-pass filtered, rectified, and integrated using a nerve traffic analyzer. The presence of MSNA will be confirmed by a pulse-synchronous signal that responds to an end-expiratory breath-hold and stimulation of muscle (tendon tapping), but not skin afferents (gentle skin stroke and/or startle stimulus). MSNA will be expressed as bursts per minute and per 100 cardiac cycles. Further, the investigators will measure common femoral artery blood flow using ultrasound and mean arterial pressure using photoplethysmography. This will allow determination of sympathetic transduction (the vasoconstrictor and pressor effects of MSNA) expressed as changes in blood pressure (mmHg) or changes in vascular conductance (ml blood flow/mmHg).	Before and one hour after soup, both conditions (high- and low-salt)
Primary	Changes in flow-mediated dilation (FMD)	Flow-mediated vasodilation will be assessed using continuous measures of brachial artery diameter and velocity via duplex Doppler ultrasound (Hitachi Arietta 70). The brachial artery will be imaged in the longitudinal plane proximal to the medial epicondyle using a high-frequency (6-12 MHz) linear-array probe. The ultrasound probe will be stabilized using a custom-built clamp. Shear rate (sec-1) will be calculated as [(blood flow velocity (cm*s-1) *4)/blood vessel diameter (mm)] The image will be recorded throughout a 60-s baseline, a 300-s ischemic stimulus (250 mmHg), and 180 seconds post deflation. FMD will be expressed as % dilation (final diameter-baseline diameter/baseline diameter x 100) and also normalized to the shear stimulus. Allometric scaling will be used if appropriate, including if there are baseline differences in artery diameter by race or condition.	Before, 30 minutes, and one hour after soup, both conditions (high- and low- salt)
Primary	Changes in indices of arterial stiffness	The investigators will use the SphygmoCor XCEL system to assess pulse wave analysis (PWA) and pulse wave velocity (PWV). A high-fidelity strain-gauge transducer is used to obtain the pressure waveform at the carotid and radial pulse. Distances from the carotid artery sampling site to the femoral artery (upper leg instrumented with a thigh cuff for oscillometric sphygmomanometry), and from the carotid artery to the suprasternal notch will be recorded. The investigators will also assess forward and reflective wave magnitudes. PWV will be expressed as cm/s and PWA will be expressed as % (calculated as augmentation pressure divided by the pulse pressure).	Before 30 minutes, and one hour after soup, both conditions (high- and low- salt)
Primary	Changes in blood pressure reactivity	The investigators will measure systolic and diastolic pressure using photoplethysmography at the finger. Systolic and diastolic blood pressure will be assessed at rest and during handgrip exercise. Blood pressure reactivity will be expressed as a change in pressure (mmHg) from baseline to a predetermined time during the stressor (e.g., minute one average and minute two average).	Before and one hour after soup, both conditions (high- and low- salt)
Primary	Changes in blood biomarkers of nitric oxide bioavailability	The investigators will measure nitric oxide metabolites (nitrate and nitrite nanomolar concentration).	Before, 30 minutes, and one hour after soup, both conditions (high- and low- salt)
Primary	Changes in circulating reactive oxygen species	We will use electron paramagnetic resonance to measure reactive oxygen species (spectra units) in whole blood samples treated with a spin probe.	Before, 30 minutes, and one hour after soup, both conditions (high- and low- salt)
Primary	Changes in circulating inflammatory cytokines	We will measure inflammatory markers (nano- or picograms per deciliter) via enzym linked immunoabsorbent assays.	Before, 30 minutes, and one hour after soup, both conditions (high- and low- salt)
Secondary	Objective sleep duration and quality	Philips actiwatch spectrum will be used to quantify sleep duration. Participants will wear the watch units for 7 days. We will assess qualitative sleep scores and cross-check actigraphy wear times with a sleep diary.	Baseline (pre-intervention)
Secondary	Subjective Sleep duration and quality	We will use the Pittsburgh Sleep Quality Index to asses sleep duration and perceived sleep quality reflective of the one month period leading into the study.	Baseline (pre-intervention)
Secondary	Physical activity	Participants will wear an ActiGraph GT3X accelerometer for seven days to objectively quantify steps per day and metabolic equivalents per day.	Baseline (pre-intervention)
Secondary	Cardio-respiratory fitness	We will use indirect calorimetry to measure the participant's maximal oxygen consumption (VO2max) during incremental exercise on a treadmill. We will use a Parvo TrueOne metabolic cart and Woodway treadmill.	Baseline (pre-intervention)
Secondary	Mental health - social anxiety	We will administer the Liebowitz Social Anxiety Scale. The scale starts at 0 (none) and ends at 3 (severe) for 24 questions related to anxiety and avoidance, and a cumulative score is calculated.	Baseline (pre-intervention)
Secondary	Mental health - depression	We will administer the Beck's Depression Inventory. The scale starts at 0 and ends at 3 for 21 questions related to depression.	Baseline (pre-intervention)
Secondary	Habitual dietary intake	We will instruct participants to complete a diet log for 6 days which will be operationalized with Nutrition Data System for Research (NDSR).	Baseline (pre-intervention)

External Links

•   PI's laboratory