Effect of Nitric Oxide on the Interaction Between Mitochondrial Malate Dehydrogenase and Citrate Synthase

Mitochondrial malate dehydrogenase （mMDH） and citrate synthase （CS） are sequential enzymes in Krebs cycle. mMDH, CS and the complex between mMDH and CS （mMDH＋CS） were treated with nitric oxide solution. The roles of notric oxide （NO） on the secondary structures and the interactions between mMDH and CS were studied using circular diehroism （CD） and Fourier transform surface plasmon resonance （FT-SPR）, respectivley. The effects of NO on the activities of mMDH, CS and mMDH＋CS were also studied. And the regulations by NO on mMDH and CS were simulated by PyMOL software. The results of SPR conifrmed that strong interaction between mMDH and CS existed and NO could signiifcantly regulate the interaction between the two enzymes. NO reduced the mass percents ofα-helix and increased that of random in mMDH, CS and mMDH＋CS. NO increased the activities of CS and mMDH＋CS, and inhibited the activity of mMDH. Graphic simulation indicated that covalent bond was formed between NO and Asn242 in active site of CS. However, there was no direct bond between NO and mMDH. The increase in activity of mMDH＋CS complex depended mostly on the interaction between NO and CS. All the results suggested that the regulations by NO on the activity and interaction between mMDH and CS were accord with the changes in mMDH, CS and mMDH＋CS caused by NO.

Inhibition of metabolic disorders in vivo and in vitro by main constituent of Coreopsis tinctoria

Objective：To investigate the effects of the ethyl acetate extract of Coreopsis tinctoria（EAEC）on insulin resistance（IR）in rats fed a high-fat diet.Methods：Male Sprague-Dawley（SD）rats were fed a HFD（60%fat）supplemented with EAEC for 8 weeks.The administration of EAEC to the rats with HFD-induced insulin resistance reduced hyperglycemia,plasma levels of insulin,and steatosis in the liver.Metabolomic study was used to analyze the metabolic levels of the high glucose-treated cells,control cells and marein-treated cells.Results：High glucose and high fat conditions caused a significant increase in blood glucose,insulin,serum TC,TG and LDL-C levels,leading to abnormal IR in rats.However,treatment with EAEC protects against HFD-induced IR by improving the fasting serum glucose homeostasis and lipid homeostasis.The high glucose conditions significantly decreased glycogen synthesis and increased PEPCK,G6Pase and Krebs cycle-related enzyme protein levels,leading to an abnormal metabolic state in Hep G2 cells.However,treatment with marein improved IR by increasing glucose uptake and glycogen synthesis and by downregulating PEPCK and G6Pase protein levels.The statistical analysis of the HPLC/MS data demonstrated that marein could restore the normal metabolic state.Conclusion：The results revealed that EAEC ameliorates IR in rats,and marein has the potential to improve IR by ameliorating glucose metabolism disorders.