Anti-diabetic effects of a theaflavin-enriched black tea extract in the obese ZDF rat model

Abstract

Effects of a theaflavin-enriched black tea extract (BTE) against type 2 diabetes (T2D) were analyzed using the obese ZDF model. ZDF rats were hyperglycemic, dyslipidemic and express pro-inflammatory markers. BTE was well tolerated and caused an elevation of fasted and fed glucose as well as lower glucose tolerance in contrast to hypoglycemic effects by metformin. However, the BTE group showed decreased levels of LDL and triacylglycerols which corresponded to an increase in free fatty acids. Positive effects against dyslipidemia of BTE corresponded to a significant decrease in weight gain. The impact on inflammatory pathways was analyzed by expression analysis of inflammatory mediators in whole blood and epididymal adipose tissue using TaqMan PCR and ELISA. Whole blood analysis revealed a significant down-regulation of ICAM-1 and TNF-α, whereas IL-4, IL-6, IL-10, IL-13 and IFN-γ were elevated to higher levels as compared to ibuprofen. In adipose tissue, BTE treatment induced an upregulation of COX-2 and IL-6. Thus, BTE treatment showed strong effects against systemic inflammation and caused a reduction of weight gain with positive effects against dyslipidemia. The complexity of signaling pathways leading to complications in diabetes suggest a treatment of BTE in combination with antidiabetic therapeutics as promising strategy against T2D.