Effects of Green Tea Extract (GTE) on Systemic Oxidative and Antioxidative Status in Chinese Patients With Stable Asthma
Condition: Asthma
MeSH terms: Asthma
Study type: Interventional

Summary: 
      Asthma is a disease characterized by chronic inflammation in the airways. Recent research has
      demonstrated that one of the reasons for the chronic inflammatory state is an imbalance
      between oxidative stress and antioxidative defenses in patients with asthma.

      Green tea is a common beverage consumed by Chinese patients from all walks of life. Green tea
      contains chemical components that are thought to have immunomodulatory actions in chronic
      inflammation.

      The investigators propose to recruit 35 patients with stable asthma. Recruited subject will
      be given oral tablets containing Green tea extract (GTE) to be taken daily for three months.
      Clinical follow up and assessment will be done at baseline, on completion of GTE intake at
      three months, and at three months after GTE intake has been stopped. A questionnaire on their
      health status and the frequency of symptoms and use of bronchodilators and inhaled steroids
      will be completed, spirometry will be done and a venous blood sample will be taken during
      recruitment and during each reassessment at 3 and 6 months. Measurement of
      oxidants/antioxidants (GSH, GSSG, SOD, CAT and GPx) will be carried out on the blood samples.
      Oxidants/antioxidants will be compared and correlated with lung function results.

      This study would provide us with pilot data as to whether GTE, a strong antioxidant with
      immunomodulatory actions, has any effect on reducing the oxidative stress and improving the
      antioxidant status in patients with asthma and whether these changes are accompanied
      improvement in clinical status.

      Hypothesis Green tea extract (GTE) reduces oxidative stress and improves antioxidant defenses
      in Chinese patients with asthma
    

Detailed description: 
      1. Background

           Asthma constitutes a significant health problem both in Hong Kong and worldwide (1).
           Different risk factors for asthma have been identified. These include atopy (2), family
           history of asthma, exposure to indoor aeroallergens (3) air pollution (4) and exposure
           to environmental tobacco smoke (5).

           Asthma is associated with a chronic inflammatory state in the airway. The inflammatory
           component is thought to result from an imbalance between an increased free radical
           formation (oxidative stress) and a reduction of antioxidative defenses. Reactive oxygen
           species (ROS) such as superoxide radicals and hydrogen peroxide were found to be
           increased in patients with asthma indicating the presence of oxidative stress, and the
           increased level of ROS has also been found to correlate with asthma severity (6).

           The airway displays a wide range of enzymatic and non-enzymatic antioxidant defenses,
           including reduced glutathione (GSH), superoxide dismutase (SOD), catalase and
           glutathione peroxidase (GPx). There is evidence of reduced antioxidant defenses, namely
           GPx and SOD activity, in asthma patients (6). Furthermore, the measurement of the
           oxidized form of glutathione, (glutathione disulfide, GSSG) could be used as an index to
           reflect the degree of oxidative stress in asthma and the level of GSSG has been reported
           to be high in the bronchial washings of asthma patients (7). We have reported that
           patients with asthma showed significantly increased erythrocyte GSSG, SOD and catalase
           activities with concomitant reduction of erythrocyte GPx (8). These results indicate a
           state of increased oxidative stress accompanied by an altered state of systemic
           antioxidant status in asthma patients.

           Green tea represents one of the common beverages consumed by people from all walks of
           life. Epigallocatechin gallate (EGCG) is the major polyphenol (catechin) in green tea.
           Green tea extract (GTE) demonstrates anti-inflammatory and immunomodulatory activities.
           GTE has been shown to damp down neutrophil chemotaxis and attenuates
           interleukin-mediated inflammatory reaction cascades (9). It has also been shown to
           attenuate lung injury in experimental mouse model (10).

           This proposal is to investigate the effects of GTE on systemic oxidative and
           antioxidative status, and whether these changes are associated with changes in clinical
           status in local Chinese patients with stable asthma.

        2. Research plan and methodology

      Aims of the study

        1. To determine and compare erythrocyte levels of GSSG, SOD, CAT and GPx in patients with
           asthma after 3 months of treatment with GTE and after GTE has been stopped for an
           equivalent period.

        2. To determine and compare plasma levels of inflammatory marker C-reactive protein (CRP)
           and inflammatory mediators, interleukin-6 (IL-6) and IL-8 in these patients.

      Study design This is an intervention study with patients serving as their own control

      Material and Methods Patients

      The investigators propose to recruit out-patients with asthma in stable clinical condition
      and have no acute asthmatic attack in the recent 3 months prior to recruitment. After initial
      assessment, recruited patients will be given GTE to be taken three times a day for 3 months.
      They will be reassessed at 3 months when GTE will be stopped and again at the end of 6
      months. The clinical status and biochemical parameters when they are on GTE will be compared
      with similar parameters when they are not on GTE.
    

Intervention name(s): green tea extract
Intervention type(s): Dietary Supplement
Intervention description(s): Green tea extract capsule, equivalent to 450 ml 2% Green tea containing 540mg EGCG/day
Other intervention name(s): Lung Chen green tea
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Asthma, green tea, antioxidants