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Metabolic SyndromeNCT06025357

Effects of L-citrulline Supplementation on Vascular Function in Metabolic Syndrome

A study testing L-Citrulline supplementation in people with Metabolic Syndrome and Menopause, run by Texas Tech University at 1 site in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

The objective of this project is to provide evidence that L-Citrulline (CIT) supplementation can improve vascular function in the fasted and acute hyperglycemia conditions in middle-aged and older women with metabolic syndrome. Read more about this study

Who is it for?
Ages 45 to 79 years, women onlyHealthy volunteers can take part
Conditions the study is for
Metabolic Syndrome, Menopause
What is being tested?
L-Citrulline supplementation
Could I receive a placebo?
Yes, some participants may receive a placebo
How many people
24 participants
Where
1 siteUnited States
Study dates
1 Jan 2023to 1 Aug 2024
Phase
Interventional
Are there results?
None posted in the registry

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 45 to 79 years
  • Women only
  • Healthy volunteers accepted
  • Adult, Older adult

Who may be able to join

  • Must present at least 3 of the following 5 cardiometabolic risk factors
  • Waist circumference ≥88 cm
  • Fasting glucose between 100-125 mg/dL or HbA1c between 5.7-6.4%.
  • Blood pressure ≥130 mm Hg
  • Triglyceride ≥ 150 mg/dL
  • HDL <50 mg/dL
Show all 11Show fewer
  • The following are also inclusion criteria's:
  • Women aged 45-79 years old
  • Body mass index ≤ 39.9 kg/m2
  • Sedentary (defined as < 120 min/week of exercise)
  • Abstain from any dietary supplements with vascular effects for one month prior to the beginning of the study and until participation in study has terminated.

Who cannot join

  • < 45 and > 79 years of age
  • Use of medications and/or any supplements that may affect outcome variables (such as arginine-containing supplements, nitroglycerin, statin drugs, biguanides, insulin, beta blockers, statins, verapamil)
  • Systolic blood pressure ≥ 160 mmHg
  • BMI > 40 kg/m2
  • Recent changes in medication (3 months)
  • Current smoking any tobacco use
  • Cardiovascular disease, diabetes (Type 1 or 2), and other metabolic or chronic diseases
  • More than 7 alcoholic drinks/week of consumption

Trial locations and contacts

1 site in 1 country.

United States1 site
  • TTU Kinesiology and Sport Management Building

    Lubbock, Texas, 79409

Other trials in United States

About this study

Official title: Effects of L-Citrulline Supplementation on Vascular Function During Fasted and Acute Hyperglycemia in Middle-aged and Older Women With Metabolic Syndrome

The objective of this project is to provide evidence that L-Citrulline (CIT) supplementation can improve vascular function in the fasted and acute hyperglycemia conditions in middle-aged and older women with metabolic syndrome.

Read the detailed description

Using a double-blind, randomized, placebo-controlled, and parallel design, middle-aged and older women with metabolic syndrome will be randomized into receiving either CIT supplementation (10g/day) or placebo (Microcrystalline Cellulose) for 4 weeks.

The first visit will be approximately 1hr and 30 minutes. The 2nd and 3rd visits will each be approximately 2hrs and 30 minutes, separated by 4 weeks in between each visit. During visits 2 and 3, vascular measurements will be assessed in the fasted state and 30, 60, and 90 minutes after acute glucose ingestion (75g).

Being tested
L-Citrulline supplementation, Placebo
Keywords
Endothelial function, Aortic Hemodynamics, Blood pressure, Obesity, Hypertension
Medical subject headings
Metabolic Syndrome, Obesity, Hypertension

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • L-Citrulline supplementationDietary supplement

    4 weeks of L-Citrulline supplementation (10 grams/day).

  • PlaceboDietary supplement

    4 weeks of microcrystalline Cellulose supplementation.

Study groups in NCT06025357
Study groupRoleWhat they receive
L-citrullineExperimentalL-citrulline: 10 grams/day
Receives: Dietary Supplement: L-Citrulline supplementation
PlaceboExperimentalMicrocrystalline Cellulose
Receives: Dietary Supplement: Placebo

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Macrovascular Endothelial function in the fasted condition

    Endothelial function will be measured via brachial artery flow mediated dilation (ultrasonography) during reactive hyperemia at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  2. Microvascular endothelial function in the fasted condition

    Endothelial function will be measured using forearm muscle oxygenation (near-infrared spectroscopy) will assessed during reactive hyperemia at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  3. Microvascular digital endothelial function in the fasted condition

    Endothelial function will be measured using peripheral (finger) arterial tonometry (EndoPAT device) during reactive hyperemia at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  4. Macrovascular Endothelial function during acute hyperglycemia

    Endothelial function will be measured via brachial artery flow mediated dilation (ultrasonography) during reactive hyperemia at 30, 60, and 90 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  5. Microvascular forearm endothelial function during acute hyperglycemia

    Endothelial function will be measured using forearm muscle oxygenation (near-infrared spectroscopy) during reactive hyperemia at 30, 60, and 90 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  6. Central and peripheral arterial stiffness in the fasted condition

    Arterial stiffness will be measured using central (carotid-femoral) and peripheral (femoral-ankle) PWV at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  7. Central arterial stiffness during acute hyperglycemia

    Arterial stiffness will be measured using central (carotid-femoral) PWV at 30, 60, and 90 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  8. Blood pressure in the fasted condition

    Brachial and aortic blood pressures will be assessed using an automated sphygmomanometry arm cuff (SphygmoCor XCEL). Beat-to-beat blood pressure will be measured using an automated photoplethysmography finger cuff (Fineometer). Blood pressure will be measured at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  9. Blood pressure during acute hyperglycemia

    Brachial and aortic blood pressures (systolic and diastolic) will be assessed using an automated sphygmomanometry arm cuff (SphygmoCor XCEL). Beat-to-beat blood pressure will be measured using an automated photoplethysmography finger cuff (Fineometer). Blood pressure will be measured after an oral glucose ingestion at 30, 60, and 90 minutes at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  10. Total peripheral resistance in the fasted condition.

    Total peripheral resistance will be measured using an automated photoplethysmography finger cuff (Finometer) at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  11. Total peripheral resistance during acute hyperglycemia

    Total peripheral resistance will be measured using an automated photoplethysmography finger cuff (Finometer) at 30, 60, and 90 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  12. Stroke volume in the fasted condition

    Stroke volume will be measured using an automated photoplethysmography finger cuff (Finometer) at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  13. Stroke volume during acute hyperglycemia

    Stroke volume will be measured using an automated photoplethysmography finger cuff (Finometer) at 30, 60, and 90 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  14. 24-hour ambulatory blood pressure monitoring

    An ambulatory blood pressure cuff, measuring blood pressure for 24-hours will be obtained on two separate days at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

Secondary outcomes (5)
  1. Serum glucose and insulin levels.

    Serum glucose and insulin levels will be tested at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  2. Serum arginine levels

    Serum L-Arginine levels will be tested at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  3. Serum arginase levels

    Serum arginase levels will be tested at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  4. Serum Nitric Oxide levels

    Serum nitric oxide levels will be tested at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

  5. Serum Endothelin-1 levels

    Serum endothelin-1 levels will be tested at baseline and after 4 weeks of supplementation.

    Measured: 4 weeks

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted6 Sep 2023
  2. Study start1 Jan 2023
  3. Primary completion1 May 2024
  4. Study completion1 Aug 2024

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase N/A
Primary purpose
Basic science
Allocation
Randomised
Intervention model
Parallel groups
Model description
Parallel Assignment Double (Participant, Investigator) Randomized, double-blind, placebo-controlled, parallel study design
Masking
Double blind
Who is masked
Participant, Investigator
Enrolment
24 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06025357
Sponsor's protocol ID
IRB2022-362
Status last verified
Aug 2023
First submitted
27 Jul 2023
Last updated
15 May 2025
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No

Publications

  • Figueroa A, Maharaj A, Kang Y, Dillon KN, Martinez MA, Morita M, Nogimura D, Fischer SM. Combined Citrulline and Glutathione Supplementation Improves Endothelial Function and Blood Pressure Reactivity in Postmenopausal Women. Nutrients. 2023 Mar 23;15(7):1557. doi: 10.3390/nu15071557.

    PubMed 37049398
  • Maharaj A, Fischer SM, Dillon KN, Kang Y, Martinez MA, Figueroa A. Acute Citrulline Blunts Aortic Systolic Pressure during Exercise and Sympathoactivation in Hypertensive Postmenopausal Women. Med Sci Sports Exerc. 2022 May 1;54(5):761-768. doi: 10.1249/MSS.0000000000002848. Epub 2022 Jan 3.

    PubMed 34974502
  • McDonald JD, Mah E, Chitchumroonchokchai C, Dey P, Labyk AN, Villamena FA, Volek JS, Bruno RS. Dairy milk proteins attenuate hyperglycemia-induced impairments in vascular endothelial function in adults with prediabetes by limiting increases in glycemia and oxidative stress that reduce nitric oxide bioavailability. J Nutr Biochem. 2019 Jan;63:165-176. doi: 10.1016/j.jnutbio.2018.09.018. Epub 2018 Sep 25.

    PubMed 30412905
  • Figueroa A, Alvarez-Alvarado S, Ormsbee MJ, Madzima TA, Campbell JC, Wong A. Impact of L-citrulline supplementation and whole-body vibration training on arterial stiffness and leg muscle function in obese postmenopausal women with high blood pressure. Exp Gerontol. 2015 Mar;63:35-40. doi: 10.1016/j.exger.2015.01.046. Epub 2015 Jan 28.

    PubMed 25636814
  • Maharaj A, Fischer SM, Dillon KN, Kang Y, Martinez MA, Figueroa A. Effects of L-Citrulline Supplementation on Endothelial Function and Blood Pressure in Hypertensive Postmenopausal Women. Nutrients. 2022 Oct 20;14(20):4396. doi: 10.3390/nu14204396.

    PubMed 36297080

Questions about this trial

What is this clinical trial studying?

A study testing L-Citrulline supplementation in people with Metabolic Syndrome and Menopause, run by Texas Tech University at 1 site in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 11 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 15 May 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Macrovascular Endothelial function in the fasted condition (time frame: 4 weeks). The study lists 14 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06025357, which also lists 5 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 15 May 2025.

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