| Objective:The purpose of this study is to clarify the effect and partial mechanism of Huidouba on glucose and lipid metabolism and skeletal muscle metabolic flexibility in prediabetic mice;at the same time.Methods:1.Grouping and administration:SPF,6-week-old C57BL/6J male mice,body weight 20±2g,were randomly divided into 2 groups,blank control group(Control,=10),modeling replication group(n=60),the control diet D12450J and the high-fat diet D12492 were administered respectively for 12 weeks,and the changes in body constitution and fasting blood glucose(FBG)were detected.After 12 weeks,mice with FBG≧6.1mmol/L accompanied by impaired glucose tolerance were considered successful in modeling.After modeling,the model mice were randomly divided into five groups:model group(Model),metformin group(Met,200mg/kg),low-dose Huidouba group(HDB50,50 mg/kg),middle-dose Huidouba group(HDB100,100 mg/kg),and high-dose Huidouba group(HDB200,200 mg/kg).The drugs were administered by gavage for 6 weeks.2.Detection of biochemical indicators and observation of muscle histopathology:detection of FFA,TC,TG,HDL-C,LDL-C,and LDH levels in mice serum,and investigation of changes in lipid metabolism in model mice and the intervention effect of each administration group.Through HE staining,skeleton muscle tissue’s changes in morphology and pathology were observed,and we detected the level of TC and TG in the skeleton muscle tissue of the mice and oil red O staining,and PAS staining in order to observe muscle glycogen’s distribution,the intervention effe cts of each administration group on the shape and function of the mouse muscle tissue was investigated.3.Metabolism-related signaling pathways:through q-PCR and Western blot,we analyzed the expressions of MG53/AMPK/PGC-1α/PPARa and GLUT4 in the skeletal muscle tissue of mice.Results:1.Effects of Huidouba on glucose and lipid metabolism in prediabetic C57BL/6J mice(1)Changes in body weight and fasting blood glucose of the mice:after 12 weeks of modelling,a dramatically increased body weight in mice from the model group has occurred compared to the control group(P<0.01),FBG increased significantly(P<0.01),and the glucose tolerance also significant impaired(P<0.01).After 6 weeks of dosing,compared with model group,the body weight treated with metformin declined significantly(P<0.05),while the body weight in the group administered with HDB did not change significantly,but each administration groups’FBG declined significantly(P<0.01).(2)Glucose tolerance and insulin tolerance:in the prediabetic model group,glucose tolerance and insulin tolerance were dramatically impaired compared to the control group(P<0.01),but the HDB groups had improved the glucose tolerance and insulin tolerance(P<0.01).(3)Changes in serum lipid levels:serum levels of TG、FFA、LDLC and LDH were obviously higher in the model group(P<0.05;P<0.01),and HDL-C content was obviously lower than in blank control group(P<0.01);after administration,the contents of TG,FFA,LDL-C,and LDH in dosing group obviously declined(P<0.01),and the content of HDL-C increased significantly(P<0.01).2.The effect and mechanism of HDB in improving the metabolism flexibility of skeletal muscle in prediabetic C56BL/6J mice(1)Lipid metabolism:TC and TG levels in skeletal muscle tissue elevated dramatically in the model group compared to the control group(P<0.01),after administration of metformin and HDB200,the contents of TC and TG decreased significantly(P<0.05),and TC and TG in HDB50 and HDB100 groups showed a downward trend,but there was no statistical significance.(2)The morphology and function of skeletal muscle tissue:compared to the control group,the model group’s skeletal muscle structure was abnormal,muscle cells arrangement disordered,sarcolemma spacing increased,and muscle fiber cross-sectional area decreased(P<0.05)and there was diffuse fat accumulation in the muscle tissue of the model mice(P<0.01).After 6 weeks of administration,the histopathological structure of the skeletal muscle in the metformin and HDB groups improved,myofibrils were gradually regularized,muscle cells were arranged well,and the cross-sectional area of muscle fibers was obviously improved(P<0.01).The degree of fat mass and each administration group’s lipid accumulation was significantly reduced(P<0.05).(3)Accumulation of muscle glycogen:compared to the control group,the model group’s muscle glycogen declined(P<0.01),while the HDB200 group dramatically increased the accumulation of muscle glycogen in the muscle tissue of the mice(P<0.01).Metformin group,HDB50 and HDB100 groups had an upward trend of muscle glycogen,but there was no statistical significance.(4)Metabolism-related signaling pathways:in the prediabetic model group,the mRNA content and protein expression of AMPK/PGC1α/PPAR-α signaling pathways and GLUT-4 in skeletal muscle tissue significantly reduced compared to the blank control group(P<0.01).MG53’s mRNA increases significantly(P<0.01)and the protein expression tended to increase.After the treatment with HDB,AMPK,PGC-1α,PPAR-α and GLUT-4’s mRNA level and protein expression improved significantly(P<0.05),while MG53’s mRNA content and protein expression decreased significantly(P<0.05).Conclusion:1.Prediabetic C57BL/6J model mice showed a significant decrease in glucose and lipid metabolism,and obvious changes in skeletal muscle lipid metabolism and muscle tissue pathology,and decreased muscle glycogen accumulation which were in line with the various characteristics of decreased metabolic flexibility in prediabetes.HDB can effectively improve the glucose and lipid metabolism in prediabetic model mice,and increase sensitivity to glucose and insulin.2.HDB can significantly improve the lipid metabolism of skeletal muscle and the morphological function of muscle tissue in prediabetic model mice,and through regulating MG53/AMPK/PGC-1α/PPAR-αsignaling pathway and up-regulating GLUT-4 protein,it improves the metabolic flexibility of skeletal muscle in model mice and promote the accumulation of muscle glycogen. |
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