Uric Acid Metabolism, Endothelial Function and Oxidative Stress in Vegans and Omnivores.

Differential Analysis of Uric Acid Metabolism, Endothelial Function, Oxidative Stress and Cardiovascular Parameters in Vegans and Omnivores.

50 vegans and 50 omnivores will be recruited at the Erasme Hospital, Brussels.

Hypothesis

• Relative induced-hyperuricemia by the vegan diet is not associated with impaired endothelial function if vitamin B12 and folic acid levels are normal.
• Quantification of xanthine oxidoreductase (XOR) isoforms varies according to the diet. Omnivores present more xanthine oxidase (XO) than vegans in which the xanthine dehydrogenase (XD) isoform is more prevalent.
• The vegan group has more favorable oxidant, metabolic and inflammatory profiles than the omnivore group.

Study Overview

• Status: Completed
• Conditions: Healthy; Diet Modification
• Intervention / Treatment: Other: Endothelial function and inflammation

Detailed Description

Non-meat eaters rise widely worldwide. This choice answers ideological, ecological or health concerns. Several vegetarian diets exist and the vegan diet is the most restricted one as it excludes all animal products, eggs and dairy.

Beside benefits on health and particularly on the cardiovascular system (blood pressure, weight, lipid profile), some authors described less favorable lipid and oxidative profiles and others described an impairment in endothelial function markers in 'vegans'. These effects were attributed to low vitamin B12 and folate levels and high homocystein levels. However, vitamin B12 supplementation improved these parameters. Epidemiological studies also showed that 'vegans' disclose higher uric acid levels than other vegetarians or omnivores. Uric acid acts as an antioxidant in the plasma but can be deleterious for vascular cells leading to endothelial dysfunction. The main enzyme involved in uric acid metabolism is xanthine oxidoreductase which exists under two interconvertible isoforms. Xanthine dehydrogenase is the main form and uses nicotinamide adenine dinucleotide (NAD+) as electron acceptor and does not produce reactive oxygen species (ROS). In contrast, the other isoform xanthine oxidase uses oxygen as an electron acceptor and produces reactive oxygen species (ROS). The investigators wish to test the hypothesis that it is not uric acid per se, but which isoform of xanthine oxidoreductase which alters endothelial function. This is why the investigators wish to determine if regular 'vegans' (with normal vitamin B12 and folate levels) disclose increased uric acid levels in the presence of a reduced inflammation, oxidative stress and improved endothelial function, as compared to matched 'omnivores'.

50 vegans and 50 omnivores will be recruited at the Erasme Hospital, Brussels.

Hypothesis

• Relative induced-hyperuricemia by the vegan diet is not associated with impaired endothelial function if vitamin B12 and folic acid levels are normal.
• Quantification of oxidoreductase (XOR) isoforms varies according to the diet. Omnivores present more xanthine oxidase (XO) than vegans in which the xanthine dehydrogenase (XD) isoform is more prevalent.
• The vegan group has more favorable oxidant, metabolic and inflammatory profiles than the omnivore group.

• Study Type: Observational
• Enrollment (Actual): 103

Contacts and Locations

Study Locations

• Belgium
  • Belgique
    • Brussels, Belgique, Belgium, 1070
      • Erasme hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 48 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

Participants will be recruited upon invitation on social network mainly.

Description

Inclusion Criteria:

• Vegan or omnivore diet for at least one year (matched for age, gender, BMI, socio-economic status and weight)
• Healthy

Exclusion Criteria:

• Smoking
• Chronic treatment
• No allowed drugs taking
• Excessive alcohol consumption

Study Plan

How is the study designed?

Design Details

• Observational Models: Case-Control
• Time Perspectives: Cross-Sectional

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Omnivore	Other: Endothelial function and inflammation; Analysis of endothelial function, oxidative stress
Vegan	Other: Endothelial function and inflammation; Analysis of endothelial function, oxidative stress

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Measure of the perfusion of the microcirculation of the skin	Endothelial function assessment will be performed through analyse of the perfusion of the microcirculation of the skin in the forearm will be assessed by means of a laser Doppler imager and iontophoresis of acetylcholine and sodium nipride. Heating-induced hyperemia will be assessed after iontophoresis of inhibitor of NO synthase and saline. Units are perfusion unit. Iontophoresis is a non-invasive tool which permits to infuse molecules in the first micrometers of the skin. The used molecules are vasodilative, saline or NO synthase inhibitor.	2 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Concentration of Uric acid	Uric acid (mg/dL or SI)	2 hours
Concentration of xanthine oxidase and xanthine dehydrogenase in blood	western blot	2 hours
Measure of hemoglobin	g/l	2 hours
Measure of white blood cells, red blood cells and platelets	cells/µl of blood	2 hours
Measure of urea, creatinine, bilirubin, albumine, prealbumin, LDL, HDL, lp(a), total cholesterol, triglyceride, apolipoprotein A and B	mg/dl	2 hours
Measure of glycemia, vitamine and iron status (B3, B6, B12, C, D, E, B9, Zn, Cu, Selenium, iron, ferritin), c-reactive protein, homocystein	mg/dl	2 hours
Measure of sodium, potassium, chlore, phosphor, calcium, magnesium, HbA1c, omega 3 et 6	mmol/l	2 hours
Measure of glomerular filtration rate	ml/min	2 hours
Measure of gamma-glutamyltransferase, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatin phosphokinase, insulin, TSH	u/l	2 hours
Measure of allantoin, homocitrulline/lysine, chloro-tyrosine/tyrosine, Il-8, myeloperoxidase	Mass spectrometry and Elisa Kits	2 hours
Measure of renin, aldosterone, angiotensin 2, angiotensin converting enzyme		2 hours
Measure of main proteomes and metabolomes in cells incubated with sera from participants	Sera will be used for cell cultures. Theses cells will be lysed and used to analyse and compare the different proteomes / metabolomes according to the groups. We will be able to understand which protein groups are reduced or enhanced according to the diet.	2 hours
Measure of blood pressure	Systolic and diastolic blood pressure	2 hours
Measure of baroreflex sensitivity	finometer	2 hours
Measure of heart rate	finometer	2 hours
Measure of augmentation index	Assessment of the arterial stiffness	2 hours
Measure of pulse wave velocity	Assessment of the arterial stiffness	2 hours
Diet questionary	Diet History Questionnaire third version provides estimation of one year consumption of proteins, carbohydrates, lipids, micronutrient and vitamines	2 hours

Collaborators and Investigators

• Sponsor: Erasme University Hospital
• Collaborators: Fonds National de la Recherche Scientifique; Fonds Erasme; Fonds pour la chirurgie cardiaque

Study record dates

Study Major Dates

• Study Start (Actual): March 10, 2019
• Primary Completion (Actual): March 30, 2020
• Study Completion (Actual): June 20, 2020

Study Registration Dates

• First Submitted: February 6, 2019
• First Submitted That Met QC Criteria: February 19, 2019
• First Posted (Actual): February 21, 2019

Study Record Updates

• Last Update Posted (Actual): July 1, 2020
• Last Update Submitted That Met QC Criteria: June 29, 2020
• Last Verified: June 1, 2020

More Information

Terms related to this study

• Keywords: uric acid; endothelial function; vegan; omnivore; hemodynamic parameters; oxidative stress and inflammation
• Other Study ID Numbers: 34735921

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No