British Journal of Nutrition

Full Papers

Metabolism and Metabolic Studies

Modulatory effects of black v. green tea aqueous extract on hyperglycaemia, hyperlipidaemia and liver dysfunction in diabetic and obese rat models

Gamal Ramadana1 c1, Nadia M. El-Beiha1 and Eman A. Abd El-Ghffara1

a1 Zoology Department, Faculty of Science, Ain Shams University, Abbasseya 11566, Cairo, Egypt

Abstract

Cardiovascular complications are a major cause of morbidity and mortality in patients with diabetes, obesity and the metabolic syndrome. Recently, there has been an increasing interest in tea as a protective agent against CVD. Here, we compared the modulatory effects of two different doses (50 and 100 mg/kg body weight given orally for 28 consecutive days) of black tea aqueous extract (BTE, rich in theaflavins and thearubigins) and green tea aqueous extract (GTE, rich in catechins) on experimentally induced hyperglycaemia, hyperlipidaemia and liver dysfunction by alloxan (which destroys pancreatic β-cells and induces type 1 diabetes) and a cholesterol-rich diet (which induces obesity and type 2 diabetes) in male Wistar albino rats. Both tea extracts significantly alleviated most signs of the metabolic syndrome including hyperglycaemia (resulting from type 1 and 2 diabetes), dyslipidaemia and impairment of liver functions induced by alloxan or the cholesterol-rich diet in the animals. Also, the tea extracts significantly modulated both the severe decrease and increase in body weight induced by alloxan and the high-cholesterol diet, respectively. The modulatory effects obtained here were partial or complete, but significant and dose dependent, and slightly more in GTE in most cases. No harmful effects were detected for tea consumption on all parameters measured, except that the high dose of both tea extracts significantly decreased the spleen weight:body weight ratio and induced lymphopenia. The present study supports the hypothesis that both black and green teas may have beneficial effects against the risks of the metabolic syndrome and CVD as shown in rat models of human obesity and diabetes.

(Received April 09 2009)

(Revised August 14 2009)

(Accepted August 17 2009)

(Online publication October 13 2009)

Correspondence:

c1 Corresponding author: Dr Gamal Ramadan, fax +20 2 26842123, email gamal_ramadan@hotmail.com

Footnotes

Abbreviations: A:G, albumin:globulin; ALP, alkaline phosphatase; AMPK, AMP-activated protein kinase; BTE, black tea aqueous extract; GTE, green tea aqueous extract

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