A study of effects of 12 weeks of green tea supplementation on oxidative stress in type 2 diabetes patients

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A study of effects of 12 weeks of green tea supplementation on oxidative stress in type 2 diabetes patients


Author: Cheung, So Sum Rebecca
Title: A study of effects of 12 weeks of green tea supplementation on oxidative stress in type 2 diabetes patients
Degree: M.Sc.
Year: 2013
Subject: Green tea -- Therapeutic use.
Oxidative stress.
Diabetes -- Treatment.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: xiii, 121 leaves : col. ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2637098
URI: http://theses.lib.polyu.edu.hk/handle/200/7200
Abstract: The incidence of diabetes is increasing rapidly and patients with diabetes are often unaware of their condition. Diabetes may lead to serious complications such as cardiovascular disease. Good glycemic control remains the main target of diabetes management. Many studies are ongoing to investigate different aspects of diabetes and increasing evidence has shown that oxidative stress plays a critical role in the pathogenesis of diabetes and its complications. Moreover, previous studies have shown that green tea has effective antioxidant effect. It has been shown to be rich in polyphenolic antioxidants and is hypothesised to have genoprotective and other beneficial effects when taken regularly as part of the diet, such as lowering oxidative stress, which can be assessed by specific biomarkers, such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG/ 8-OHdG) in urine. Another biomarker, allantoin in plasma, is a potentially specific sensitive index of oxidative stress, but has been rarely used to date. In the present study, Type 2 diabetes patients who were being given a dietary supplement of green tea (or water as control treatment) were tested for its effects on oxidative stress, as assessed by two biomarkers, urine 8-oxodG and plasma allantoin, measured by high performance liquid chromatography with tandem mass spectrometry (LCMS/MS). In the analysis, the recruited diabetes patients were also sub-grouped by age and gender to investigate if there was any significant difference in different groups. Correlations of oxidative stress biomarkers with glycemic control biomarkers (HbA1c and fasting plasma glucose) were also investigated.
The outcome of the present study did not show difference for 8-oxodG at pre-treatment 1 (entry) level and post-washout pre-treatment 2. However, for plasma allantoin, there was a statistically difference in the pre- 1st and pre 2nd treatment of all volunteers and within the male{174}s group (p=0.041) and in the age under 59 group (p=0.042). Furthermore, at the pre-post treatment level, in which green tea or water were given as supplements in the Type 2 diabetes patients recruited, there was no significant change in urine 8-oxodG or plasma allantoin in the study. The p values for the respective groups in urine 8-oxodG are: Pre and post tea (p=0.8075); Pre and post water (p=0.5520); Delta change with tea vs. delta change with water (p=0.8121). Also, the p values for the respective groups in plasma allantoin are: Pre and post tea, p=0.1595; Pre and post water, p =0.2488; Delta change with tea vs. delta change with water, p=0.8943. There was no significant correlation for 8-oxodG and plasma allantoin at pre-treatment level (Spearman rho =-0.0373, p value=0.735). Also, using the HbA1c and fasting glucose values provided, their correlations among 8-oxodG and urine allantoin at pre-treatment level were also carried out by Spearman correlation test at 95% confidence interval and there were no significant correlations. In conclusion, the present study did not find any significant changes in the two oxidative stress biomarkers assessed, urine 8-oxodG and plasma allantoin. Moreover, no correlations were seen between urine 8-oxodG and plasma allantoin at pre-treatment level and no significant correlations among urine 8-oxodG or plasma allantoin along with HbA1c or fasting glucose. Improvement on study design should be taken into account to have a more consolidated study and further study is needed to prove the effects of regular intake of green tea on oxidative stress in Type 2 DM patients.

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