The Effects of Watermelon Juice Supplementation on Postprandial Vascular Endothelial Function
Condition: Endothelial Dysfunction
Study type: Interventional

Summary: 
      The purpose of this study is to test if watermelon juice supplementation improves vascular
      dysfunction experience during hyperglycemia.
    

Detailed description: 
      The objective of this pilot study is to determine the potential for watermelon juice to
      attenuate the reduction postprandial endothelial function and skeletal muscle microvascular
      blood flow (MVBF) experienced during hyperglycemia.

      We will attempt to answer the following hypotheses:

      Hypothesis 1: Watermelon juice supplementation will attenuate the reduction in endothelial
      dysfunction and microvascular blood flow during an oral glucose challenge.

      Hypothesis 2: Watermelon juice will increase L-arginine bioavailability during hyperglycemia
      and correlate with improved vascular response.

      Exploratory Aim: The postprandial period is defined by increased sympathetic nervous system
      activity (vasoconstriction) and NO• mediated vasodilation. Heart rate variability (HRV) is a
      measurement of the balance of parasympathetic to sympathetic activity. We will measure HRV
      during the oral glucose challenge to interrogate the possibility that watermelon juice can
      modulate the balance of blood vessel constriction and relaxation during an oral glucose

      Procedures Involved

      There will be 1 screening visit, and 2 outpatient visits. Participants will consume
      watermelon juice or placebo for 2 weeks. The washout period will last 2 weeks prior to the
      cross-over to the opposite condition. Participants visits will be conducted at the Vascular
      and Resting Metabolism Lab located in the department of kinesiology at LSU.

      Screening Visit

      Participants will undergo consenting and fasting blood draws to measure glucose, lipids, and
      CBC. Vital signs (blood pressure, body weight, body composition (DXA), heart rate, etc) will
      be measured. For DXA procedure participants will undergo a whole body scan lasting
      approximately 10 minutes. Participants will remove all metal objects from their body and lie
      down on the table. The legs will be secured together using two Velcro straps. The participant
      will be instructed to remain completely still during the scan. Randomization will be
      performed to allocate the study participant for their initial group assignment to either the
      watermelon juice group or placebo. The initial six participants will be assigned treatment A
      for phase 1 and treatment B for phase 2, thereafter the following 6 will be assigned
      treatment B first then treatment A. The remaining participant will be randomly assigned
      either treatment A or B in a counterbalanced fashion.

      Daily Juice Drop-in visits

      Since the required supplementation duration is 14 days participants will be provided with 2
      days (Saturday and Sunday) worth of watermelon juice or placebo to account for days when the
      LSU AG Center will not be open. To allow for scheduling conflicts and unforeseen
      circumstances a 3 day period of supplementation less then or greater than the 14 periods will
      be permitted. Participants will also be provided with juice or placebo for anticipated
      instances where they cannot be on campus. In order to monitor compliance participants will be
      asked return the juice container for the days where juice was consumed off premises.

      Visit 2 and 3: Oral Glucose Challenge - Postprandial FMD and MVBF

      Participants will arrive in morning at 6:00am fasted for 10-hours. Body composition will be
      measured by DXA. Next, participants will rest for 30 minutes in the supine positing while
      wearing a heart rate monitor (Zephyr, Bioharness) to measure heart rate and heart rate
      variability. Resting metabolic rate will be measured via indirect calorimetry for 20 minutes.
      Then fasting measures of blood glucose, FMD (ultrasound) and MVBF (near-infrared
      spectroscopy) will be taken followed by ingestion of 75 g of glucose (glucola). An IV line
      will be placed in the participants arm vein for blood draw purposes and will remain there
      throughout the testing. A blood sample will be drawn, and then the participant will drink a
      sugar solution consisting of 75 grams of glucose. Blood will be drawn at specific times after
      you consume the drink. Each blood sample will be about 1 tablespoon. (6 tablespoons total for
      the test). During the IV procedure, a small amount of the participant's own blood (less than
      1 teaspoon) will immediately be returned into your vein through the IV after each specimen is
      collected. Blood will be drawn at minute 15, 30, 60, 90, 120 minutes. Postprandial
      measurements of FMD and MVBF will be taken at 30, 60, 90, and 120 minutes.
    

Intervention name(s): Watermelon Juice
Intervention type(s): Dietary Supplement
Intervention description(s): 100% Watermelon Juice
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Treatment