Effect of the sulfonylurea glyburide on glycogen synthesis in alloxan-induced diabetic rat hepatocytes

Mango (Mangifera indica L.) seed kernel extract suppresses hyperglycemia by modulating pancreatic β cell apoptosis and dysfunction and hepatic glucose metabolism in diabetic rats

This study investigated the anti-hyperglycemic action of mango seed kernel extract (MKE) and various mechanisms involved in its actions to improve pancreatic β cells and hepatic carbohydrate metabolism in diabetic rats. An intraperitoneal injection of 60 mg/kg of streptozotocin (STZ) followed by 30 consecutive days of treatment with MKE (250, 500, and 1000 mg/kg body weight) was used to establish a study group of diabetic rats. Using liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS/MS) for identification, 26 chemical compounds were found in MKE and the high-performance liquid chromatography (HPLC) analysis of the MKE also revealed the existence of mangiferin, gallic acid, and quercetin. The results confirmed that in each diabetes-affected rat, MKE mitigated the heightened levels of fasting blood glucose, diabetic symptoms, glucose intolerance, total cholesterol (TC), and low-density lipoprotein-cholesterol (LDL-C). As demonstrated by a remarkable increment in serum and pancreatic insulin, the diabetic pancreatic β cell function was potentiated by treating with MKE. The effect of MKE on diabetic pancreatic apoptosis clearly reduced the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells, which was related to diminished levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and Bax and an increase in Bcl-xL protein expression. Furthermore, diabetes-induced liver damage was clearly ameliorated along with a notable reduction in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and abnormal liver histology. By enhancing anti-oxidant superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities, MKE alleviated diabetes-induced pancreatic and liver oxidative damage, as demonstrated by diminished levels of malondialdehyde. In minimizing the expression levels of glucose 6-phosphatase and phosphoenolpyruvate carboxykinase-1 proteins in the diabetic liver, MKE also enhanced glycogen content and hexokinase activity. Collectively, these findings indicate that by suppressing oxidative and inflammatory processes, MKE exerts a potent anti-hyperglycemic activity in diabetic rats which serve to protect pancreatic β cell apoptosis, enhance their function, and improve hepatic glucose metabolism.

The effects of sulfonylurea glyburide on superoxide dismutase, catalase, and glutathione peroxidase activities in the brain tissue of streptozotocin-induced diabetic rat

OBJECTIVES

A member of the second-generation sulfonylureas, glyburide (GLY; glibenclamide) provides an effective therapy for patients with type 2 diabetes. It stimulates pancreatic insulin secretion, suggesting that it is effective in the treatment of type 2 diabetes primarily by elevating the circulating insulin levels. However, experimental evidences have indicated that sulfonylureas have also had an extrapancreatic effect, which may directly contribute toward maintaining blood glucose homeostasis during diabetes.

METHODS

In this study, we administrated GLY to streptozotocin-induced diabetic rats and determined the effects of such treatment on activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) from brain tissue.

RESULTS AND DISCUSSION

Brain CAT and GPx activities were not significantly different in the diabetic group compared to controls (P>.05), but the SOD activity was significantly reduced in the diabetic group compared to controls (P<.001). GLY treatment of 4 weeks had restored the SOD and CAT enzyme activities in diabetic rat brain (P<.05). In addition, high blood glucose levels of untreated diabetic rats were decreased following the GLY treatment (P<.01). Administration of GLY to diabetic rats restored the diabetes-induced changes, suggesting that GLY could restore the brain SOD and CAT activities.

The effect of the sulfonylurea glyburide on nitric oxide in streptozotocin-induced diabetic rat

1. The interaction between nitric oxide (NO) and superoxide anions has received a great deal of attention. Because NO is rapidly inactivated by superoxide anions, it has been suggested that an enhanced formation of this radical may be involved in the accelerated breakdown of NO. 2. In the present study, we administrated glyburide (glibenclamide) to Streptozotocin-induced diabetic rats and determined the effect of such treatment on serum nitrite+nitrate levels. Serum nitrite+nitrate levels were reduced in diabetic animals (P<0.001). Administration of glyburide to diabetic rats reversed the diabetes-induced changes, suggesting that glyburide may directly increase serum nitrite+nitrate levels.

Effect of the sulfonylurea glyburide on superoxide dismutase in streptozotocin-induced diabetic rat muscle

1. The effect of glyburide (glibenclamide) treatment on the muscle superoxide dismutase (SOD) activity of diabetic rats has been studied. 2. Four weeks of treatment with glyburide (5 mg/kg, orally) increased muscle SOD activity and decreased blood glucose levels. 3. The results of this study demonstrate that the sulfonylurea, glyburide, is capable of exerting direct insulin-like effects on muscle SOD activity in vivo.