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.

Profiled tea extracts exemplifying the importance of characterizing food bioactives: opinion piece

“…Therefore, catechins from green tea are responsible for the reduction of insulin resistance, while theaflavins in black tea play a critical role in stimulating β-cell insulin secretion (Tang et al, 2013), indicating different hypoglyceamic mechanisms by catechins and theaflavins. Further anti-diabetic effects of TF-BTE was confirmed in an obese ZDF rat model with findings of anti-inflammatory activity of theaflavins (Gosslau et al, 2018).…”

“…Obesity and T2D are closely correlated with each other and also with chronic inflammation. Tea polyphenols exert hypoglycemic activity (Tang et al, 2013;Miao et al, 2015;Huang et al, 2015;Gosslau et al, 2018). Tea extracts in the market vary dramatically in their content and type of bioactive chemical entities, particularly polyphenols, which can be very much misleading when referring to anti-diabetic activity of tea extracts in the absence of characterization of compounds involved.…”

Do Flavonoids from Durum Wheat Contribute to Its Bioactive Properties? A Prospective Study

“…Accordingly, several sources of phenolic compounds have been tested for their inhibitory activity toward alpha-glucosidase [ 66 , 67 ]. The antidiabetic effect of natural compounds has been in the spotlight of various researchers [ 68 , 69 ]. Alpha-glucosidase, an enzyme found in the brush border of the small intestine, inhibits the absorption of carbohydrates and may suppress the postprandial blood glucose and insulin levels, while pancreatic lipase is a key enzyme regulating the absorption of triacylglycerols [ 19 ].…”

Yellow Tea Stimulates Thermogenesis in Mice through Heterogeneous Browning of Adipose Tissues

“…[ 17,43 ] Catechin polymers, formed under the high temperature conditions, may also contribute to the activities of YTE; several reports showed that catechin dimers theaflavins lowered body lipid in obese rat, [ 44 ] and theaflavin‐enriched black tea extract protected against obesity‐related inflammation in the obese ZDF rat model. [ 45 ] Careful studies on the active compounds in YTE for the induction of thermogenesis are essential for elucidating the detailed mechanisms involved.…”