Tea, obesity, and diabetes

Abstract

Tea has been found to possess widespread biological functions based on a variety of laboratory data. The effects of tea on obesity and diabetes have received increasing attention. This paper reviews the evidence for the connections among tea catechins, and obesity and diabetes. Tea catechins, especially (-)-epigallocatechin gallate (EGCG), appear to have antiobesity and antidiabetic effects. While few epidemiological and clinical studies show the health benefits of EGCG on obesity and diabetes, the mechanisms of its actions are emerging based on the various laboratory data. These mechanisms may be related to certain pathways, such as through the modulations of energy balance, endocrine systems, food intake, lipid and carbohydrate metabolism, the redox status, and activities of different types of cells (i. e., fat, liver, muscle, and beta-pancreatic cells). Because the EGCG receptor, the so-called 67-kDa laminin receptor (LR), has been discovered with colocalization of other types of LR and cytoskeleton in both cancer cells and normal cells, this may explain that EGCG possesses numerous actions. The mechanistic results of this review may possibly be utilized in the treatment of obesity, diabetes, and other related diseases using tea- and EGCG-based folk medicines.

Preventive Effects of (−)-Epigallocatechin Gallate on Diethylnitrosamine-Induced Liver Tumorigenesis in Obese and Diabetic C57BL/KsJ-db/db Mice

“…The results of the present study clearly indicated that EGCG, which has been shown to improve dysregulation of energy homeostasis (17,18), effectively prevents the development of liver tumorigenesis in obese and diabetic db/db mice by improving hyperinsulinemia and hepatic steatosis. A recent study showed that EGCG suppressed the development of colonic premalignant lesions induced by azoxymethane in db/db mice through improvement of hyperinsulinemia and inhibition of the IGF/IGF-1R axis on the colonic mucosa (16).…”

“…In summary, the prevention of HCC by targeting the IGF/IGF-1R axis, hepatic steatosis, and chronic inflammation, which are caused by dysregulation of energy homeostasis, might represent a promising strategy for obese individuals who are at an increased risk of developing HCC (3,8). GTCs, including EGCG, seem to be potentially effective and critical candidates for this purpose because, as shown in the results of the present study and those from previous reports, these agents can target metabolic abnormalities and may therefore restore metabolic homeostasis (16)(17)(18)(19)(20)(21)(22).…”

“…In addition to anticancer and cancer chemopreventive effects, GTCs, especially EGCG, seem to have antiobesity and antidiabetic effects (17,18). GTCs also possess antiinflammatory properties because they inhibit the expression of proinflammatory cytokines TNF-a and interleukin (IL)-6, which are also associated with cancer prevention by GTCs (19)(20)(21).…”

Functional Characterization of Proanthocyanidin Pathway Enzymes from Tea and Their Application for Metabolic Engineering

“…Increasing evidence suggests that tea flavan-3-ols are beneficial for human health as a result of their antioxidant capacity (Luximon-Ramma et al, 2006), chemopreventive activities against prostate and ovarian cancers (Bemis et al, 2006;Ravindranath et al, 2006), antiobesity and antidiabetic effects (Yang and Koo, 2000;Kao et al, 2006;Wolfram et al, 2006), and cardiovascular disease prevention properties (Yang and Koo, 2000). Tea flavanols, especially catechins, may also play roles in the defense of tea against infection/infestation .…”

Hepatotoxicity from green tea: a review of the literature and two unpublished cases

“…The potential health benefits associated with tea consumption have been partially attributed to the antioxidative properties of polyphenols, particularly to catechins, among which EGCG is the most effective. Green tea seems to also have antidiabetic and anti-obesity properties [5]. On the basis of its potential anti-obesity effect, green tea has been marketed during recent years as a herbal supplement for the control of body weight.…”