[Ameliorative effects and the mechanism of lyceum barbarum polysaccharide on insulin resistance of HepG2 cell].

OBJECTIVE: To observe the effects of lyceum barbarum polysaccharide (LBP) on insulin resistance of HepG2 cells and investigate its possible mechanism. METHODS: IR-HepG2 cell model was induced with high glucose and high insulin in combination for 24 hours,with 104/vaccination in the 96-well plates, hole density after adherent cells (30 µg/ml、100 µg/ml、300 µg/ml) LBP cultivate 48 h, 200 µl/hole, each all had four holes. The effects of LBP at different concentrations on HepG2 cell activity and insulin resistance were tested. Intracellular malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were detected. The expressions of related proteins in insulin signal transduction pathways such as insulin receptor substrate-2(IRS-2), phosphatidylinositol-3-kinase(PI3-K), protein kinase B(Akt) and glucose transport-2(GLUT2) were determined. RESULTS: Compared with normal control group, the content of MDA was increased significantly and the activity of SOD and the expression levels of IRS-2,PI-3K,Akt and GLUT2 were decreased significantly in the IR model group. Compared with IR model group, medium and high concentrations of LBP decreased the content of MDA and increased the activity of SOD and the expression levels of IRS-2, PI-3K, Akt and GLUT2 in insulin-resistant HepG2 cells. MTT showed that at the same time, the OD value gradually decreased with the increase of LBP's concentration; under the same concentration of LBP, the OD value also gradually decreased with the extension of time, which indicated that LBP inhibited the proliferation of HepG2 cells with time and concentration-dependent manner. Glucose consumption experiment indicated that medium and high concentration of LBP could increase the glucose consumption of insulin-resistant HepG2 cells significantly, but low concentration of LBP had no significant impacted on glucose consumption of insulin-resistant HepG2 cells. CONCLUSIONS: Medium and high concentration of LBP can improve insulin resistance of HepG2 cell, its mechanisns may be associated with decreasing the level of oxidative stress and increasing the protein expressions of insulin signaling pathway.

Arecoline improves vascular endothelial function in high fructose-fed rats via increasing cystathionine-γ-lyase expression and activating K(ATP) channels.

AIM: To investigate the effect of arecoline, a major component of betel nut, on vascular endothelial function in high fructose-fed rats and the potential mechanisms underlying the effect. METHODS: Male Wistar rats were fed a high-fructose or control diet for 16 weeks. At the beginning of week 13, the rats were injected ip with low (0.5 mg·kg(-1)·d(-1)), medium (1.0 mg·kg(-1)·d(-1)) or high (5.0 mg·kg(-1)·d(-1)) doses of arecoline for 4 weeks. At the termination of the treatments, blood was collected, fasting blood glucose (FBG) and serum insulin (FSI) levels were measured, and insulin sensitivity index (ISI) was calculated. The thoracic aortas were isolated and aortic rings were prepared for studying ACh-induced endothelium-dependent vasorelaxation (EDVR). The mRNA and protein expression of cystathionine-γ-lyase (CSE) in the thoracic aortas was analyzed using RT-PCR and Western blot analysis, respectively. RESULTS: In high fructose-fed rats, the levels of FBG and FSI were remarkably increased, whereas the ISI and the mRNA and protein expression of CSE were significantly decreased. ACh-induced EDVR in the aortic rings from high fructose-fed rats was remarkably reduced. These changes were reversed by treatment with high dose arecoline. Pretreatment of the aortic rings rings from high fructose-fed rats with the CSE inhibitor propargylglycine (10 mmol/L) or the ATP-sensitive potassium (K(ATP)) channel blocker glibenclamide (10 mmol/L) abolished the restoration of ACh-induced EDVR by high dose arecoline. On the contrary, treatment with high dose arecoline significantly impaired ACh-induced EDVR in the aortic rings from control rats, and pretreatment with propargylglycine or glibenclamide did not cause further changes. CONCLUSION: Arecoline treatment improves ACh-induced EDVR in high fructose-fed rats, and the potential mechanism of action might be associated with increase of CSE expression and activation of K(ATP) channels by arecoline.