Submitted to: Polyphenols and Health
Publication Type: Abstract Only
Publication Acceptance Date: 8/15/2005
Publication Date: 10/4/2005
Citation: Anderson, R.A., Dawson, H.D., Kelly, M.A., Hiniger, I., Coves, S., and Roussel, A.M. 2005. PCR analyses demonstrate that tea increases insulin sensitivity and insulin signaling in rats with metabolic syndrome[abstract]. Polyphenols and Health. 2:14. Interpretive Summary:
Technical Abstract: Metabolic syndrome is characterized by insulin resistance, impaired glucose tolerance, elevated blood lipids and related risk factors of diabetes and cardiovascular diseases. The objective of this study was to determine the beneficial effects of green tea on insulin sensitivity using an animal model of the metabolic syndrome. Wistar rats, 10 per group, received a high fructose diet for six weeks to induce the metabolic syndrome or the same high fructose diet plus either 1 or 2 g of green tea solid extract/kg diet. Tea caused significant decreases in insulin from 412 ± 100 pmol/L to 113 ± 28 and 197 ± 43 after consuming 1 and 2 g of green tea solids/kg diet, respectively, for six weeks. There were also associated decreases in glucose and triglycerides due to tea consumption. Real time PCR measurements demonstrated that increases in insulin sensitivity were associated with an up regulation of GLUT4, insulin receptor, IRS-2, glycogen synthetase kinase, p-110 phosphoinositol kinase (PI3-K), and protein kinase B with no significant changes in IRS1, GLUT1, GLUT2, GLUT3, SOS1, p85 PI3K and GYS1 in the liver. Changes in gene expression in the muscle were not significant. These data demonstrate that tea has significant beneficial effects on insulin sensitivity, glucose and triglycerides of rats fed a diet to induce the metabolic syndrome. Tea consumption caused a significant up regulation in the insulin signaling cascade in the liver but not in the muscle. In summary, these data suggest that tea may be beneficial in the control of insulin resistance, impaired glucose tolerance and elevated triglycerides associated with the metabolic syndrome.