Hypoglycemic and lipid lowering effects of theaflavins in high-fat diet-induced obese mice.

Theaflavins (TFs) are the characteristic components of black tea and have been widely acknowledged for their health benefits. The current study aimed to investigate the effects and mechanism of TFs, TF1, TF2a and TF3 on glycolipid metabolism in obese mice induced by a high-fat diet (HFD). Mice were randomly divided into seven groups (n = 8 per group) as follows: low-fat diet (LFD), HFD, HFD + metformin (Met, 100 mg kg-1 d-1), HFD + TFs (TFs, 200 mg kg-1 d-1), HFD + TF1 (TF1, 100 mg kg-1 d-1), HFD + TF2a (TF2a, 100 mg kg-1 d-1), and HFD + TF3 (TF3, 100 mg kg-1 d-1). All groups were studied for 9 weeks continuously. The levels of serum glucose, insulin, TC, TG, LDL and HLD in the plasma, lipid accumulation in the liver, and injury of the liver were investigated. In addition, the effects of TFs and their monomers on the SIRT6/AMPK/SREBP-1/FASN pathway were also evaluated. The results showed that oral administration of TFs, TF1, TF2a and TF3 not only dramatically suppressed weight gain, reduced blood glucose level, and ameliorated insulin resistance but also obviously lowered the levels of serum TC, TG and LDL, suppressed the activities of ALT and AST, and ameliorated hepatic damage in mice fed a HFD when compared to the HFD group. Western blot analysis showed that TFs, TF1, TF2a and TF3 treatments increased the expression of SIRT6 and suppressed the expression levels of SREBP-1 and FASN significantly in mice fed a HFD as compared to the HFD group. The phosphorylation of AMPK in mice fed a HFD was obviously elevated by TF2a and TF3 when compared to the HFD group. These results proved for the first time that TF1, TF2a and TF3 improved the glucolipid metabolism of mice fed a HFD, and activated the SIRT6/AMPK/SREBP-1/FASN signaling pathway to inhibit the synthesis and accumulation of lipids in the liver to ameliorate obesity in mice fed a HFD. These findings indicate that TFs, TF1, TF2a and TF3 as the main functional components of black tea might potentially be used as a food additive for improving glycolipid metabolism and ameliorating obesity, and TF3 may be the best choice.

Effects of epigallocatechin-3-gallate combined with ascorbic acid and glycerol on the stability and uric acid-lowering activity of epigallocatechin-3-gallate.

CONTEXT: Epigallocatechin-3-gallate (EGCG) is unstable and easily oxidized, which limits its applications. Ascorbic acid (Vc) is a natural antioxidant. OBJECTIVE: The effects of EGCG combined with Vc and glycerol on stability and uric acid-lowering activity of EGCG were examined. MATERIALS AND METHODS: EGCG (aqueous solution), EGCG + Vc (aqueous solution), EGCG (glycerol solution) and EGCG + Vc (glycerol solution) were prepared and incubated under different conditions in vitro. The recovery rate of EGCG was calculated by HPLC. Kunming mice were randomly divided into normal control group, model group, allopurinol (5 mg/kg), EGCG (10 mg/kg), EGCG + Vc (both 10 mg/kg), EGCG (10 mg/kg) + glycerol (60%), and EGCG (10 mg/kg) + Vc (10 mg/kg) + glycerol (60%) (n = 6). Allopurinol was injected intraperitoneally to mice, others were administered intragastrically to (2 cases) mice. All mice were continuously administrated for 7 days, once a day. RESULTS: EGCG recovery rates of EGCG group and EGCG + Vc + glycerol group respectively reached to 32.34 ± 1.86% and 98.90 ± 0.64% when they were incubated for 4 h at 80 °C. EGCG recovery rates reached to 91.82 ± 5.13% (incubated for 6 h at pH 8) and 88.85 ± 2.63% (incubated for 4 h in simulated intestinal fluid) when EGCG incubated with Vc and glycerol. Compared with the model group, UA values of EGCG + Vc + glycerol group reduced by 43.49% while EGCG group reduced by 25.63%. The activities of xanthine oxidase (XOD, 31.41 U/gprot) and adenosine deaminase (ADA, 10.05 U/mgprot), and the mRNA expression levels of glucose transporter 9 (GLUT9, 1.03) and urate transporter 1 (URAT1, 0.44) in EGCG + Vc + glycerol group were notably lower than those of EGCG group (38.12 U/gprot, 13.16 U/mgprot, 1.54, and 0.55). The mRNA expression levels of ATP-binding cassette superfamily G member 2 (ABCG2, 1.39) and organic anion transport 1/2 (OAT1/2, 2.34, 2.53) in EGCG + Vc + glycerol group were notably higher than those of EGCG group (0.57, 1.13, and 1.16). DISCUSSION AND CONCLUSIONS: Our findings suggest that when EGCG used in combination with Vc and glycerol could effectively increase its biology activities and can be generalized to the broader pharmacological studies. This sheds light on the development and application of EGCG in the fields of food and medicine.

Preparation and characterization of epigallocatechin gallate, ascorbic acid, gelatin, chitosan nanoparticles and their beneficial effect on wound healing of diabetic mice.

The wounds of diabetic patients are difficult to heal, which could lead to a limb amputation or even death. The experiment aims to develop a new type of nanoparticles that could accelerate wound healing. Epigallocatechin gallate, ascorbic acid, gelatin and chitosan nanoparticles (EV NPS) were prepared by ion cross-linking method, and their properties were studied. The optimal formula ratio of EV NPS is Vc:EGCG:Gel:CS = 0.2:3:1:1. Transmission electron microscope (TEM) images show that it is a roughly uniform spherical nanoparticle with a diameter of 200 nm. ICR mice were intraperitoneally injected with streptozocin (STZ) to establish diabetic mice. Full-thickness excisional wounds were established on the back of mice. The results showed that EV NPS can promote wound healing in diabetic mice, and the mechanism may be through increasing collagen accumulation, promoting angiogenesis and reducing the infiltration of inflammatory cells. EV NPS may have potential application values for wound healing in diabetic mice.