Anti‐obesity actions of green tea: Possible involvements in modulation of the glucose uptake system and suppression of the adipogenesis‐related transcription factors

Abstract

To investigate mechanisms of the anti-obesity actions of green tea in vivo, rats were given green tea instead of drinking water for 3 weeks. It was confirmed that green tea reduced adipose tissue weight without any change in body weight, other tissue weights, and food and water intakes. Green tea also significantly reduced the plasma levels of cholesterols and free fatty acids. Certain catechins existed in the plasma at 0.24 microM under our experimental conditions, though most of them existed as conjugated forms. For mechanisms of the anti-obesity actions, green tea significantly reduced glucose uptake accompanied by a decrease in translocation of glucose transporter 4 (GLUT4) in adipose tissue, while it significantly stimulated the glucose uptake with GLUT4 translocation in skeletal muscle. Moreover, green tea suppressed the expression of peroxisome proliferator-activated receptor gamma and the activation of sterol regulatory element binding protein-1 in adipose tissue. In conclusion, green tea modulates the glucose uptake system in adipose tissue and skeletal muscle and suppresses the expression and/or activation of adipogenesis-related transcription factors, as the possible mechanisms of its anti-obesity actions.

Green tea catechins prevent obesity through modulation of peroxisome proliferator-activated receptors

“…Food intake by rats has been shown to be reduced by the treatment of EGCG and is proposed to contribute to the weight-loss effect of EGCG [22]. In contrast, there are also reports claiming that supplementation with green tea or GTCs does not significantly affect food consumption [4,23]. These discrepancies may be caused by different supplementation methods and concentrations of GTCs.…”

“…Epidemiological studies and experimental data show that drinking green tea or administration of its components, green tea catechins (GTCs), is associated with a lower risk of obesity [3][4][5][6][7][8][9][10]. Moreover, GTCs are involved in modulating fat metabolism [3,5,6,8,[11][12][13], but the mechanisms are not clear.…”

“…Tea catechins were also found to suppress adipocyte differentiation accompanied by down-regulation of PPAR and CCAAT-enhancer-binding protein (C/EBP) [5]. Moreover, Ashida et al [4] reported that green tea suppressed the expression of PPAR, decreased the translocation of glucose transporter 4 (GLUT4), and decreased the activation of sterol regulatory element binding protein-1 in adipose tissue. Therefore, PPARs may be involved in the anti-obesity effects of green tea but no clear mechanisms have been proposed.…”

The Hypoglycaemic Potential of Antioxidant-Rich Food Extracts

“…It has been proposed that certain phenolic compounds present in antioxidant-rich extracts may improve the status of at-risk individuals by ameliorating oxidative stress [18,42], improving insulin sensitivity [22], enhancing the capacity of adipocytes and skeletal muscle for glucose uptake [43,44] and by directly regulating the expression of genes related to the glycemic control [23,44,45]. It has been reported that propolis may enhance the activity of key antioxidant enzymes [46] such as superoxide dismutase, catalase and glutathione peroxidase.…”

Relationship between Common Dietary Polyphenols and Obesity-Induced Inflammation

“…Its anti-obesity effects are displayed through suppression of adipocyte differentiation and proliferation, inhibition of fat absorption from the gut and suppression of catechol-o-methyl transferase (COMT) [27]. Catechins intake decreases the risk of type 2 diabetes by increased glucose uptake into the skeletal muscles through up-regulating glucose transporter 4 (Glut 4) and by reducing translocation of Glut 4 and insulin levels in adipose tissues [57,58]. In a cell model, gamma-tocopherol treatment increases the glucose uptake by skeletal muscles under induced oxidative stress as well [59].…”