Uric Acid Metabolism, Endothelial Function and Oxidative Stress in Vegans and Omnivores.
Condition: Healthy; Diet Modification
Study type: Observational

Summary: 
      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.
    

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.
    

Intervention name(s): Endothelial function and inflammation
Intervention type(s): Other
Intervention description(s): Analysis of endothelial function, oxidative stress
Observational model: Case-Control
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Participants will be recruited upon invitation on social network mainly.
      
Biospecimen description: 
      Blood and urine
    
Keywords: uric acid; hemodynamic parameters; endothelial function; oxidative stress and inflammation; vegan; omnivore