Euonymus alatus prevents the hyperglycemia and hyperlipidemia induced by high-fat diet in ICR mice

Antihyperglycemic effect of a caffeamide derivative, KS370G, in normal and diabetic mice

The antihyperglycemic actions of caffeamide derivatives, especially KS370G, in normal ICR, streptozotocin-induced diabetic (T1DM) and diet-induced diabetic (T2DM) mice were investigated in this study. Oral administration of the compound decreased the plasma glucose levels in both normal and diabetic mice, and appeared to be in a dose-dependent manner in normal and diet-induced type 2 diabetic mice. It was found that KS370G could stimulate the release of insulin in both normal and T2DM mice, and a dose of 1 mg per kg KS370G could significantly attenuate the increase of plasma glucose induced by an intraperitoneal glucose challenge test in normal and diabetic mice. Similar treatment with KS370G significantly increased glycogen content in both liver and skeletal muscle. Hence, the hypoglycemic effect of KS370G in normal and diabetic mice could be attributed to the stimulation of insulin release and the increase of glucose utilization.

Eugenosedin-A prevents hyperglycaemia, hyperlipidaemia and lipid peroxidation in C57BL/6J mice fed a high-fat diet

Objectives

Eugenosedin-A is a serotonin (5-hydroxytryptamine; 5-HT) 5-HT1b/2a and α1/α2/β1-adrenoceptor blocker with anti-oxidative, anti-inflammatory and free-radical scavenging activities. Previous reports demonstrated that 5-HT2a blockers could diminish hyperlipidaemia. This study therefore aimed to investigate the possible uses and mechanisms of eugenosedin-A and other agents in treating hyperlipidaemia.

Methods

C57BL/6J mice were randomly divided into seven groups, fed a regular diet or a high-fat diet alone or supplemented with one of five agents: eugenosedin-A, ketanserin, prazosin, propranolol or atorvastatin (5 mg/kg p.o.) for 8 weeks.

Key findings

Compared with the regular diet, the mice fed the high-fat diet had significantly higher body weight and glucose, insulin and lipid levels. Brain malondialdehyde concentration was increased and liver glutathione peroxidase activity decreased. Addition of eugenosedin-A to the high-fat diet resulted in less weight gain and reduced hyperglycaemia, hyperinsulinaemia and hyperlipidaemia. Lipid and glucose homeostasis were related to decreased hepatic lipogenesis mRNAs and proteins (sterol regulatory element binding protein 1a, fatty acid synthase, sterol-CoA desaturase) and restored adipose peroxisome proliferator-activated receptor γ expression. Eugenosedin-A also enhanced low-density lipoprotein receptor mRNA expression.

Conclusions

Eugenosedin-A may improve plasma lipid metabolism by increasing low-density lipoprotein receptor and peroxisome proliferator-activated receptor γ expression and diminishing sterol regulatory element binding protein 1a, fatty acid synthase and sterol-CoA desaturase. Reduction of plasma glucose and lipid levels may, in turn, reduce insulin concentration, which would explain the marked improvement in obesity-related hyperglycaemia and hyperlipidaemia. Furthermore, eugenosedin-A affected malondialdehyde concentration and glutathione peroxidase activity, suggesting it may have anti-peroxidation effects in mice fed a high-fat diet.

Effects on lipid peroxidation and antioxidative enzymes of Euonymus alatus in cultured rat hepatocytes

The Euonymus alatus (Thunb.) Sieb. has long been used as a crude drug. In this paper, we investigate the effects of E. alatus on cultured hepatocyte cell system and lipid peroxidation in hydrogen peroxide (H(2)O(2)) treatment conditions. The study covers the physiological activity (the antioxidative activity and the nitrite-scavenging effect) of E. alatus. H(2)O(2) that can produce intracellular free radical was used for inducer of the peroxidation of cellular lipids. Treatment of E. alatus attenuated in cell killing enhanced by increasing concentrations of H(2)O(2). The increased malondialdehyde level induced by H(2)O(2) treatment was reduced by pre-treatment of E. alatus. Furthermore, addition of E. alatus in cell culture medium significantly reduced cell killing and content of intracellular antioxidants. Changes in nitrite-scavenging effect of E. alatus at various concentrations (5-25 mg/ml) and various pH levels (pH 1.2, 4.2 and 6.0) were also observed. The present study was also done to investigate the effects of E. alatus on cultured hepatocyte cell system, H(2)O(2)-induced cytotoxicity and antioxidative enzyme activities, including catalase, superoxide dismutase, glutathione peroxidase and glutathione S-transferase in H(2)O(2 )treatment conditions. E. alatus treatment had significant protective or elevating activities on these antioxidative enzyme activities compared to a normal group. The results indicate that E. alatus provides a strong antioxidant protection of cells against H(2)O(2)-induced oxidative stress.

Alleviating effects of active fraction of Euonymus alatus abundant in flavonoids on diabetic mice

Euonymus alatus (E. alatus) has been used as a folk medicine for diabetes in China for more than one thousand years. In order to identify major active components, effects of different fractions of E. alatus on the plasma glucose levels were investigated in normal mice and alloxan-induced diabetic mice. Our results show that ethyl acetate fraction (EtOAc Fr.) displayed significant effects on reducing plasma glucose. In oral glucose tolerance, EtOAc Fr. at 17.2 mg/kg could significantly decrease the blood glucose of both normal mice and diabetic mice. After 4 weeks administration of the EtOAc Fr, when compared with the diabetic control, there were significant difference in biochemical parameters, such as glycosylated serum protein, superoxide dismutase and malondial dehyde, triglyceride, and total cholesterol, between alloxan-induced diabetic mice and the control group. Additional histopathological studies of pancreatic islets also showed EtOAc Fr. has beneficial effects on diabetic mice. Chemical analysis with three-dimensional HPLC demonstrated that the major components from EtOAc Fr were flavonoids and phenolic acids, which had anti-oxidative effects on scavenging DPPH-radical in vitro. All these experimental results suggest that EtOAc Fr. is an active fraction of E. alatus and can prevent the progress of diabetes. The mechanism of E. alatus for glucose control may be by stimulating insulin release, improving glucose uptake and improving oxidative-stress.

Inhibitory activity of Euonymus alatus against alpha-glucosidase in vitro and in vivo

The major goal in the treatment of diabetes mellitus is to achieve near-normal glycemic control. To optimize both fasting blood glucose and postprandial glucose levels is important in keeping blood glucose levels as close to normal as possible. α-Glucosidase is the enzyme that digests dietary carbohydrate, and inhibition of this enzyme could suppress postprandial hyperglycemia. The purpose of this study was to test the inhibitory activity of methanol extract of Euonymus alatus on α-glucosidase in vitro and in vivo to evaluate its possible use as an anti-diabetic agent. Yeast α-glucosidase inhibitory activities of methanol extract of E. alatus were measured at concentrations of 0.50, 0.25, 0.10, and 0.05 mg/ml. The ability of E. alatus to lower postprandial glucose was studied in streptozotocin-induced diabetic rats. A starch solution (1 g/kg) with and without E. alatus extract (500 mg/kg) was administered to diabetic rats by gastric intubation after an overnight fast. Plasma glucose levels were measured at 30, 60, 90, 120, 180, and 240 min. Plasma glucose levels were expressed in increments from baseline, and incremental areas under the response curve were calculated. Extract of E. alatus,which had an IC₅₀ value of 0.272 mg/ml, inhibited yeast α-glucosidase activity in a concentration-dependent manner. A single oral dose of E. alatus extract significantly inhibited increases in blood glucose levels at 60 and 90 min (p<0.05) and significantly decreased incremental response areas under the glycemic response curve (p<0.05). These results suggest that E. alatus has an antihyperglycemic effect by inhibiting α-glucosidase activity in this animal model of diabetes mellitus.