Oral Green Tea Catechins Transiently Lower Plasma Glucose Concentrations in Female db/db Mice

Abstract

Polyphenols, including green tea catechins, are secondary plant compounds often discussed in the context of health-promoting potential. Evidence for such effects is mainly derived from epidemiological and cell culture studies. The aim of the present study was to investigate antidiabetic, antiadipogenic, and anti-inflammatory effects at nonpharmacological doses in an obese diabetic mouse model that exerts early relevant clinical signs of non-insulin-dependent diabetes mellitus. Female db/db mice received a flavonoid-poor diet either without additive, with rosiglitazone (RSG, 0.02 g/kg diet), or with green tea extract (low-dose green tea extract [LGTE] and high-dose green tea extract [HGTE], 0.1 and 1 g/kg diet). Food and water were freely available. The body weight was monitored weekly. Blood was sampled (12-h fasted) from the tail vein on day 28 and analyzed for glucose, cholesterol, triacylglycerol, nonesterified fatty acids, insulin, adiponectin, and soluble intercellular adhesion molecule-1 (sICAM-1). Blood glucose was also analyzed on day 14. Furthermore, sICAM-1 release was investigated in tumor necrosis factor alpha-stimulated EAhy926 cells. After 14 days, fasting glycemia was improved by RSG or HGTE supplementation compared to controls. However, at the end of the study (day 28), only RSG exhibited glucose-lowering effects and induced plasma adiponectin concentrations, paralleled by higher body weight gain and reduced periuterine fat pads compared to controls. However, only GTE treatment reduced sICAM-1 release in vitro and in vivo. Nonpharmacological HGTE supplementation in db/db mice caused (1) no adiponectin-inducing or antiadipogenic effects, (2) reduced sICAM-1 release, thereby potentially exerting anti-inflammatory effects in the progressive diabetic state, and (3) a transient improvement in glycemia.

Green Tea Polyphenols Modify the Gut Microbiome in db/db Mice as Co‐Abundance Groups Correlating with the Blood Glucose Lowering Effect

“…Using a high‐fat diet (HFD)‐induced obesity model, we found that supplementation with EGCG significantly reduced body weight gain, visceral fat weights, and fasting blood glucose level . In db/db mice, a diabetes model, dietary EGCG was found to prevent the progression of glucose intolerance . Many epidemiological studies and short‐term randomized controlled trials (RCT) also showed an association between tea or catechin consumption and lower incidence of metabolic syndrome and diabetes, even though the results are not conclusive .…”

Green Tea Polyphenol Epigallocatechin-3-Gallate Enhance Glycogen Synthesis and Inhibit Lipogenesis in Hepatocytes

“…One such example of the beneficial effects of green tea consumption is its role in promoting fat oxidation, which is a key preventative of obesity in healthy individuals [3]. Another example of the benefits of green tea consumption is its observed effect in reducing the occurrence of T2D in both laboratory animal studies [4, 5] and clinical studies involving subjects with metabolic syndrome or prediabetes [6, 7] by improving insulin sensitivity and glucose tolerance.…”

Quercetin in Cancer Treatment, Alone or in Combination with Conventional Therapeutics?

“…Currently, it has been demonstrated that flavonoids such as genistein and quercetin, inhibit ATP binding tyrosine kinases and also have the ability to competitively inhibit GLUT-1 through this mechanism [11]. In fact, the effects of flavonoids on glucose absorption and digestion has been the subject of several studies [15][16][17][18]. The inhibitory effect of flavonoids on glucose uptake appears to be already well established, so these compounds have even been suggested for the treatment of diabetes [19][20][21].…”