Effect and possible mechanisms of dioscin on ameliorating metabolic glycolipid metabolic disorder in type-2-diabetes.

BACKGROUND: Our previous study revealed that microRNA-125a-5p plays a crucial role in regulating hepatic glycolipid metabolism by targeting STAT3 in type 2 diabetes mellitus (T2DM). Dioscin, a major active ingredient in Dioscoreae nipponicae rhizomes, displays various pharmacological activities, but its role in T2DM has not been reported. PURPOSE: The aim of this study was to investigate the effect of dioscin on T2DM and elucidate its potential mechanism. METHODS: The effect of dioscin on glycolipid metabolic disorder in insulin-induced HepG2 cells, palmitic acid-induced AML12 cells, high-fat diet- and streptozotocin- induced T2DM rats, and spontaneous T2DM KK-Ay mice were evaluated. Then, the possible mechanisms of dioscin were comprehensively evaluated. RESULTS: Dioscin markedly alleviated the dysregulation of glycolipid metabolism in T2DM by reducing hyperglycemia and hyperlipidemia, improving insulin resistance, increasing hepatic glycogen content, and attenuating lipid accumulation. When the mechanism was investigated, dioscin was found to markedly elevate miR-125a-5p level and decrease STAT3 expression. Consequently, dioscin increased phosphorylation levels of STAT3, PI3K, AKT, GSK-3ß, and FoxO1 and decreased gene levels of PEPCK, G6Pase, SREBP-1c, FAS, ACC, and SCD1, leading to an increase in glycogen synthesis and a decrease in gluconeogenesis and lipogenesis. The effects of dioscin on regulating miR-125a-5p/STAT3 pathway were verified by miR-125a-5p overexpression and STAT3 overexpression. CONCLUSIONS: Dioscin showed potent anti-T2DM activity by improving the inhibitory effect of miR-125a-5p on STAT3 signaling to alleviate glycolipid metabolic disorder of T2DM.

Enhancement of apoptosis of human hepatocellular carcinoma SMMC-7721 cells through synergy of berberine and evodiamine.

Berberine and evodiamine, two kinds of alkaloids, have been reported to show many activities. In the present paper, inhibitory activities of the two compounds and their mixtures on human hepatocellular carcinoma SMMC-7721 cells were investigated, and the inhibitory rates, apoptosis, cell cycle distribution and tumor necrosis factor-alpha (TNF-alpha) were all tested and described. The results indicate that the mixtures of the two compounds showed the highest inhibition effect (50.00%) as compared with berberine and evodiamine used individually (20.24% and 16.33%, respectively) over 48 h. Through fluorescence microscope and flow cytometry (FCM) analysis, the cell apoptosis and cell cycle distribution of SMMC-7721 induced by the synergy of the two compounds was made evident. Furthermore, the TNF-alpha value in the mixture treated group was much higher (p<0.05) than in the other two groups. Thus, the combined use of berberine and evodiamine could significantly enhance the apoptosis of SMMC-7721 cells, which will be useful to further anti-cancer therapy and research.

Mechanism of phosphoryl transfer by nucleoside diphosphate kinase pH dependence and role of the active site Lys16 and Tyr56 residues.

Nucleoside diphosphate (NDP) kinase phosphorylates nucleoside diphosphates with little specificity for the base and the sugar. Although nucleotide analogues used in antiviral therapies are also metabolized to their triphosphate form by NDP kinase, their lack of the 3'-hydroxyl of the ribose, which allows them to be DNA chain terminators, severely impairs the catalytic efficiency of NDP kinase. We have analyzed the kinetics parameters of several mutant NDP kinases modified on residues (Lys16, Tyr56, Asn119) interacting with the gamma-phosphate and/or the 3'-OH of the Mg2+-ATP substrate. We compared the relative contributions of the active-site residues and the substrate 3'-OH for point mutations on Lys16, Tyr56 and Asn119. Analysis of additional data from pH profiles identify the ionization state of these residues in the enzyme active form. X-ray structure of K16A mutant NDP kinase shows no detectable rearrangement of the residues of the active site.