NCT Number: NCT04244604
This IRB will cover a current clinical trial (NCT04244604) that was started at Auburn University (AU IRB#19-390), the Principal Investigator's prior institution, and is supported by his NIH Career Development Award (NHLBI K01HL147998).
About nine out of ten Americans overconsume dietary salt. Compared to other racial groups, Black individuals are more prone to salt-sensitive hypertension and negative cardiovascular conditions associated with high salt intake. However, there is a critical need to determine the reasons behind and mechanisms that contribute to these racial disparities. Both acute (single meal) and chronic high-dietary sodium cause small but important increases in blood sodium concentration that are associated with altered blood pressure regulation and blood vessel dysfunction. However, racial differences in these measures have not been examined. This is important because Black individuals generally exhibit lower circulating concentrations of hormones (e.g., renin, aldosterone, angiotensin 2) that buffer changes in body sodium to regulate blood pressure, and this could make them more vulnerable to the negative effects of a high-sodium meal.
Therefore, the purpose of this study is to determine whether there are racial differences in blood pressure regulation and blood flow after a high-sodium meal. The investigators will assess blood pressure regulation, blood vessel stiffness, and the blood vessel's ability to dilate before and after a high-salt meal and a low-salt control meal (both meals are low-salt tomato soup with varied added salt). The investigators will also collect blood and urine to measure sodium and determine biochemical changes that may be contributing to racial differences in cardiovascular function.
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Notify Me19 year–75 year
All sexes
Interventional
Not applicable
Auburn University, Auburn, Alabama, United States
The investigators have previously used a high-sodium saline infusion to increase blood sodium and consequently increase blood pressure in Black and White individuals. The investigators' prior data suggest that increased blood sodium concentrations result in larger blood pressure elevations for a given elevation in blood sodium levels in Black compared to White adults. In this proposal, the investigators are seeking to translate these previous findings using a single high-salt meal (up to 2500 mg of sodium; similar to a few slices of pizza or a sandwich/burger and side dish). Our primary aims are to determine if the high-sodium meal causes greater 1) blood pressure dysregulation 2) decreases in blood vessel function and 3) larger changes in blood sodium in Black compared to White individuals. Other potential questions that could be determined include aging differences or an influence of fitness. The investigators will not exclude other races/ethnicities as the project will also determine the response of other minority groups (e.g. Asian or Latine/Hispanic adults) to a high-salt meal.
Participants will report to the laboratory for four visits. At the first visit, consent for study participation will be obtained and participants will be screened for eligibility. Baseline assessments will be completed which may include fitness testing and body composition assessments. If necessary, these assessments may be completed at a second in-person visit. Participants will then report to the laboratory for two experimental visits. At each visit, participants will consume a randomly assigned meal (i.e., a soup containing either low- or high-salt) and undergo assessments prior to and 30- and 60-minutes after consumption. During the study, all participants will consume both meals, however, the order of exposure will be randomly assigned.
Healthy volunteers accepted: Yes
Only the study team can determine whether someone qualifies for participation.
Inclusion criteria
Exclusion criteria
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. The Low Sodium soup will serve as the control condition.
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. The Low Sodium soup will serve as the control condition.
Time frame: Before and one hour after soup, both conditions (high- and low- salt)
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).
Time frame: Before, 30 minutes, and one hour after soup, both conditions (high- and low- salt)
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.
Time frame: Before 30 minutes, and one hour after soup, both conditions (high- and low- salt)
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).
Time frame: Before, 30 minutes, and one hour after soup, both conditions (high- and low- salt)
The investigators will measure nitric oxide metabolites (nitrate and nitrite nanomolar concentration).
Time frame: Before, 30 minutes, and one hour after soup, both conditions (high- and low- salt)
The investigators will use electron paramagnetic resonance to measure reactive oxygen species (spectra units) in whole blood samples treated with a spin probe.
Time frame: Before, 30 minutes, and one hour after soup, both conditions (high- and low- salt)
The investigators will measure plasma sodium levels.
Indiana University
Other
The Effects of a High Salt Meal on Blood Flow Regulation
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