Effect of Tea on Endothelial Function and Ischaemia-reperfusion Injury
Condition: Ischaemia Reperfusion Injury
MeSH terms: Reperfusion Injury; Ischemia; Wounds and Injuries
Study type: Observational

Summary: 
      Tea consumption may impact upon the decrease in endothelial function after IR-injury.
      However, no previous study directly examined the potential of tea to impact upon the change
      in endothelial function after IR-injury.

      The investigators hypothesize that tea consumption counteracts endothelial damage in response
      to ischaemia reperfusion injury in healthy humans.
    

Detailed description: 
      Rationale: Occlusion of an artery (causing ischemia) is a frequently reported condition, e.g.
      myocardial infarction, cerebral infarction or during organ transplantations. The period of
      ischemia will be followed by reperfusion (possibly after an operation). The ischaemic period
      as well as the reperfusion are both associated with damage to the tissue, including the
      endothelium. It is hypothesised that production of oxidative stress and reduced NO
      bioactivity (through increased reactive oxygen production) during ischaemia and reperfusion
      is involved in the development of tissue damage to the endothelium. Interventions that can
      prevent or attenuate endothelial dysfunction in response to ischemia-reperfusion (IR)-injury
      have a potential clinical relevance to prevent (complications of) cardiovascular disease.

      Several studies have examined the effect of tea consumption on the endothelial function.
      These studies demonstrated a dose-dependent improvement of tea to improve endothelial
      function in healthy and diseased humans, possibly through the vasoactive effects of
      flavonoids, which may involve increased nitric oxide bioactivity and inhibition of NADPH
      oxidase. Based on the ability of flavonoids to decrease (the impact of) oxidative stress, tea
      consumption may also impact upon the decrease in endothelial function after IR-injury.
      However, no previous study directly examined the potential of tea to impact upon the change
      in endothelial function after IR-injury.

      Objective: To examine whether tea consumption counteracts endothelial damage in response to
      ischaemia reperfusion injury in healthy humans.

      Main study parameters: Change in endothelial function (measured with flow mediated dilation)
      after ischaemia reperfusion injury (induced by 20 minutes ischemia and 20 min reperfusion)
      with and without precedence of tea consumption.

      Nature and extent of the burden and risks associated with participation, benefit and group
      relatedness: Non-invasive cuff occlusion is used to examine endothelial function (5-minute
      ischaemia) and produce the stimulus that induces ischaemia-reperfusion injury (20-minute
      ischaemia). This repeated cuff inflation is non-invasive and not associated with a health
      risk for the subject. Tea consumption is safe and, most likely, daily routine for most
      participants. The only difference is that this study will monitor and instruct participants
      regarding their tea consumption in the week preceding the tests. The volunteers will not
      benefit directly from participating in this study.
    

Observational model: Case-Crossover
Time perspective: Cross-Sectional
Sampling method: Probability Sample
Study population: 
        Twenty-one volunteers, aged between 30 and 70 years, were included in our study. All
        subjects were healthy and free of (a history of) cardiovascular disease or obesity (BMI >30
        kg/m2). Individuals were excluded if they reported a chronic or acute disease, including
        any kind of metabolic abnormality (such as diabetes mellitus) or cardiovascular disease.
        Habitual smokers (n=3) were instructed to withdraw from smoking on the day of testing. To
        further avoid confounding factors, the investigators also excluded individuals reporting
        daily intense sporting activities (>10 h/w), and/or were treated with a diet due to any
        reason.
      
Keywords: Camellia sinensis; flavonoids; cardiovascular risk; flow mediated dilation