The effect of bilberry consumption on antioxidant status and biomarkers of oxidative stress in patients with type 2 diabetes

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The effect of bilberry consumption on antioxidant status and biomarkers of oxidative stress in patients with type 2 diabetes


Author: Chu, Wing-kwan
Title: The effect of bilberry consumption on antioxidant status and biomarkers of oxidative stress in patients with type 2 diabetes
Degree: M.Sc.
Year: 2009
Subject: Hong Kong Polytechnic University -- Dissertations.
Bilberry -- Therapeutic use.
Diabetes -- Treatment.
Oxidative stress.
Biochemical markers.
Department: Dept. of Health Technology and Informatics
Pages: xiii, 158 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record:
Abstract: Introduction: Bilberry (Vaccinium myrtillus L.), a European native small fruit with dark blue color, is often consumed as fresh or frozen forms, and as processed products such as jam and juice. In addition, bilberry extracts are put into capsules and sold as a food supplement in Hong Kong and elsewhere. Bilberry is the major dietary source of anthocyanin, a plant polyphenol, which has been shown to have high antioxidant power and is suggested to have anti-hyperglycaemic effect. Diabetes is a progressive disease characterized by chronic hyperglycaemia and is a huge problem in Hong Kong, where prevalence is high (~11%) and because of its associated heavy burden of vascular disease that is believed to be caused, at least in part, by increased oxidative stress. Therefore, it was of interest to study whether ingestion of bilberry extract could improve antioxidant status, lower oxidative stress and help ameliorate grycaemic control, and hence improve the condition of diabetic patients and lower the risk of diabetic complications. Therefore, the aim of this study was to determine changes in biomarkers of glycaemic control, antioxidant status and oxidative stress of diabetic patients after 4 weeks' supplementation with bilberry, and to investigate inter-relationships between glycaemic control, antioxidant status and oxidative stress biomarkers in diabetic patients. A secondary aim was to compare biomarker results in the type 2 diabetic patients studied with those of healthy age-and sex -matched controls in order to confirm if the type 2 diabetic subject studied were indeed under increased oxidative stress. Methods: Eleven type 2 diabetic patients were recruited in this double-blinded placebo controlled cross-over intervention study. Patients took two capsules twice a day of either bilberry extract or placebo for 4 weeks. Five subjects started with one of the treatments, and six started with the other treatment. After a 6 weeks washout the subjects crossed-over onto the other treatment. The effects of bilberry on biomarkers of antioxidant defence, oxidative stress and glycaemic control in fasting plasma, red blood cell (rbc) and urine were measured in samples collected pre- and post- supplementation. For each diabetic patient, data from two sex- and age-matched healthy subjects were selected from our research team database, to compare the difference in baseline levels of the biomarkers of interest. Results: Consumption of bilberry extract for 4 weeks did not change any of the selected biomarkers of antioxidant defence, oxidative stress or glycaemic control in diabetic patients. A significant inverse correlation was seen between rbc GPx activity (an antioxidant enzyme) and both fasting glucose (r = -0.85; P=0.001) and HbAlc (r=-0.63;P<0.05) of diabetic subjects. Diabetic patients had significantly higher oxidative stress, as evidenced by plasma allantoin (16.8 vs 10.0 umol/L; P<0.05) and urinary F2isoprostanes (905 vs. 575nmol/mol creatinine; P<0.05), and lower antioxidant defence, as evidenced by plasma ascorbic acid (50 vs. 67 umol/L;P<0.05) when compared with normal subjects. Conclusion: Our results show that the diabetic subjects studied did have increased oxidative stress and lower antioxidant defence compared to age- and sex- matched normal subjects of the same ethnicity (Hong Kong Chinese). However, our data indicate that 4 week's supplementation with bilberry extract in a pattern of normal usage (2 capsules twice a day) did not make significant changes in biomarkers of antioxidant defence and oxidative stress, or in biomarkers of glycaemic control.

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