Pentamethylquercetin Improves Liver Damage In MSG Mice And GK Rats

Pentamethylquercetin (PMQ), which is present in sea buckthorn (Hippophae rhamnoides) and the rhizome of Kaempferia parviflora, is a typical member of the polymethoxylated flavone family in the natural products. PMQ in our laboratory is a methylation product of quercetin. It has significant pharmacokinetic and pharmacodynamic advantages. It is confirmed that PMQ has a number of considerable effects, including anti-metabolic syndrome, anti-inflammation, antioxidation, anti-myocardial hypertrophy, anti-STZ-induced diabetes mellitus, etc. The study had demonstrated that quercetin could significantly improve hepatic dysfunction in a NAFLD mice model. However, the influence of PMQ on liver damage in metabolic diseases has not been studied up until now. Therefore, in this study, the monosodium glutamate-induced metabolic syndrome mice model was successfully established to investigate the hepatic effects of PMQ and the possible mechanism. Furthermore, the effects of PMQ on glucose metabolic and hepatic disorders in GK rats and its mechanism were prepared to further research. Pentamethylquercetin Part I Pentamethylquercetin Improves Liver Damage in MSG MiceObjective:To study the effects of pentamethylquercetin(PMQ) on liver damage in MSG mice, which was induced by intervention of monosodium glutamate (newborn) during lactation.Methods:At the age of2days, male neonate Kunming mice were subcutaneously treated with MSG(3mg/g/day,10ul/g/day) and control group with the vehicle for7consecutive days(d2-d8). After weaning (21d), the mice were feeding daptivly until18-week-old. At the age of5weeks, MSG-injected mice were divided into six groups randomly as follows (n=10):vehicle group, PMQ2.5,5,10,20mg/kg groups, rosiglitazone5mg/kg group (ROS5). The consumption of food were recorded every week from the age of5weeks. At the age of18weeks, each group mice were measured body weight, body length and waist circumference of each mouse wihtout anaesthesia. At the age of18weeks, fasting blood glucose, triglyceride (TG), total cholesterol(TC), fasting serum insulin level, serum ALT, AST level were tested respectively. After been sacrificed, livers of the mice were weighted, frozen and prepared for testing. Liver index was calculated. The hepatic lipid TG content was measured. Pathological changes were also observed.Results:1) Treating neonate mice with MSG could successfully establish a MSG metabolic syndrome mice model with hepatic steatosis. Compared with control group, the body weight, waist circumference, LEE index had significantly increased in the vehicle group. And body length had significantly decreased in the vehicle group. At the age of18weeks, increased level of fasting blood glucose, serum TG and TC, serum insulin were observed. Insulin resistance also had been emerged.2) At the age of18weeks, significant characteristics of hepatic dysfunction in MSG obesity mice had been shown. The parameters of hepatic function were significant changed in the vehicle group. Compared with the control group, levels of serum ALT (from43.13IU/L to52.70IU/L), serum AST (from115.41IU/L to152.71IU/L) and liver weight (from1.4865to1.8065g), hepatic TG content were significant increased in the vehicle group. And the pathological results showed that hepatic steatosis were obvious in the vehicle group.3) In the present study, PMQ5,10,20mg/kg groups had played a significant role in weight loss. Compared with the vehicle group, the body weight, waist circumference, LEE index of18-week-old mice have significantly decreased. PMQ2.5mg/kg and ROS5mg/kg showed no effect on body weight lose.4) PMQ improved glucose and lipid metabolism in this mice model, especially showed a significant hypoglycemic and decreased serum TG, TC, serum insulin and insulin resistance index. Therefore, it also could significantly improve hyperinsulinaemie and insulin resistance.5) PMQ10,20mg/kg treatment could significantly improve hepatic dysfunction. Serum ALT, AST levels significantly decreased in the PMQ groups compared with the vehicle group.6) PMQ could not attenuate hepatic TG level. The pathological results showed that hepatic steatosis could also not be improved by PMQ treatment.Conclusion:The results suggested that the intervention of monosodium glutamate during lactation could cause significant metabolic syndrome in mice, including: central obesity, hyperglycaemia, hyperlipidemia, hypercholesterolemia, hyper insulinemia and insulin resistance. Hepatic dysfunction and hepatic steatosis could also be observed. PMQ had a significant role in the glucose and lipid metabolic disorders and liver damage. The effects were as follows:weight loss, improving glucose and lipid metabolism, improving insulin resistance, improving hepaticdysfunction. However, the hepatic pathological changes and hepatic lipid contentcould not be attenuated by PMQ.Part Ⅱ PMQ Ameliorates Glucose Metabolic Disorders And Hepatic Dysfunction in GK rats and The Related MechanismsObjective:To observe the effects of pentamethylquercetin (PMQ) on glucose metabolism and hepatic function in non-obese two type diabetes mellitus GK rats.Methods:Wistar rats were taken as the normal control group. According to the fasting serum glucose level, GK rats were randomly divided into the5groups:GK group(diabetic model group); PMQ groups (PMQ2.5,5.0,10.0mg/kg); positive control Metformin group(MET300mg/kg). All rat groups were treated for16consecutive weeks. Body weight, consumption of food and water were recorded weekly. Fasting and fed serum glucose, insulin levels and serum ALT, AST level were measured respectively. Oral glucose tolerance test were performed at the16th week after treatment. After been sacrificed, livers of the mice were weighted, frozen and prepared for testing. Liver index was calculated. The hepatic glycogen content was measured. Then, we assessed the effects of PMQ on the expression of certain genes that are known to play a critical role in the hepatic gluconeogenesis in the rat livers by RT-PCR. We next performed western blot experiment to measure the phosphorylation levels of AMPK, AKT and GSK3β in the livers of GK and Wistar rats.Results:1) Compared with Wistar rats, GK rats showed some disorders including polyuria, polydipsia, polyphagia and emaciation; a little higher fasting blood glucose, greatly increased postprandial blood glucose, markedly impaired glucose tolerance; significantly elevated fasting insulin, lower postprandial insulin; higher serum ALT levels.2) Compared with GK group, PMQ improved polyuria, polydipsia, polyphagia and emaciation, significantly ameliorated glucose intolerance, reduced postprandial blood glucose, lowered fasting insulin levels, lowered fed insulin levels significantly.3) PMQ also ameliorated hepatic dysfunction in GK rats. Serum ALT level were decreased in PMQ groups compared with model group.4) Compared with Wistar rats, GK rats showed lower hepatic glycogen content. PMQ could improve the abnomal hepatic glycogen content.5) RT-PCR analysis suggested that compared with Wistar rats, GK rats showed hepatic gluconeogenesis key enzymes G6pase, PEPCK mRNA expression were upregulated. Western blot analysis suggested that GK rats showed pAKT,pGSK3β pAMPK levels were downregulated. PMQ treatment could improve these changes.Conclusion:PMQ could ameliorate glucose metabolism and hepatic dysfunction in GK rats, in part via stimulation of AMPK, AKT, GSK3β phosphorylation activity.