| Objective: To investigate the role of PPARδ/PGC-1α in the conversion of skeletal muscle fibers induced by MOTS-c and aerobic exercise,and to Provide a new experimental basis for Promoting MOTS-c as an "exercise mimetic" to improve exercise capacity,as well as to Provide theoretical support for the use of MOTS-c in the clinical treatment of diabetes.Methods: This experiment was validated on normal rats and diabetic rats,respectively.Normal rats: 32 adult male Sprague Dawley rats were randomly divided into control(C),exercise(E),MOTS-c(M),and MOTS-c+exercise(ME)groups,with 8rats in each group.rats in E and ME groups were aerobically trained on a small animal running Platform according to a Protocol of 0°,20m/min,60min/d and 5d/w;M and ME groups Rats were injected intraperitoneally with MOTS-c 0.5mg/kg/d for 5d/w for a total of 8 weeks.ATPase staining was used to identify skeletal muscle fiber types;SDS-PAGE gel electrophoresis was used to test the Percentage of each isoform of myosin heavy chain;immunoblotting was used to determine PPARδ and PGC1-αProtein expression levels.Diabetic rats: 75 6-week-old SD rats were divided into control group(NC)and Pre-modeled group(PD),in which group NC was on normal diet and group PD was on high glucose diet.After 6 weeks,blood was collected from the tail vein of the rats after 12 hours of fasting to test their body glucose and insulin,followed by intraperitoneal injection of 1% streptozotocin(STZ,30 mg/kg),and blood was collected from the tail vein after 72 hours Blood was collected from the tail vein 72 hours later to test the non-fasting blood glucose and determine whether the modeling of diabetes was successful.Diabetic rats were further randomized into diabetic control group(D),diabetic exercise group(DE),diabetic MOTS-c group(DM)and diabetic MOTS-c exercise group2(DME);DE and DME rats were also aerobically trained according to the Protocols of 0°,20 m/min,60 min/d and 5 d/w.DM and DME rats were given abdominal administration of 0.5 mg/ kg,5d/w of MOTS-c,for a total of 8weeks of intervention.Glucose was measured by glucose analyzer;insulin content in Plasma was measured by ELISA;immunofluorescence and RT-q PCR techniques were a PPlied to analyze the fiber type of flounder muscle;PGC1-α and PPARδ Protein expression were measured by immunoblotting.Result: Normal rats:(1)Compared with group C,the surface density of type I muscle fibers in soleus muscle of rats in E and ME groups was significantly increased(P<0.01),while that of type II muscle fibers was significantly decreased(P<0.01,P<0.05);Compared with group E,the surface density of type I muscle fibers in group M was significantly decreased(P<0.05),and that of type II muscle fibers was significantly increased(P<0.05);Compared with M group,the surface density of type I muscle fiber in ME group was significantly increased(P<0.05),and that of type II muscle fiber was significantly decreased(P<0.05).(2)Compared with group C,the number density of ty Pe I muscle fibers in soleus muscle of rats in groups E and M was significantly increased(P<0.05),while that of type II muscle fibers was significantly decreased(P<0.05).(3)Compared with group C,MHC I% of soleus muscle in E,M and ME groups were significantly higher(P<0.01,P<0.05,P<0.01);MHC Ⅱa% in E group and ME group increased significantly(P<0.05);MHC Ⅱb% decreased significantly(P<0.05);In group E,MHC Ⅱx% decreased significantly(P<0.05),and no other changes were observed(P>0.05).Compared with group E,MHC Ⅰ% in soleus muscle of rats in group M and ME decreased significantly(P<0.05),and MHC Ⅱx% increased significantly(P<0.01);MHC Ⅱb% in ME group was significantly lower than that in M group(P<0.05),and MHC Ⅱa% was significantly higher(P<0.05).(4)Compared with group C,the expression of PPARδ and PGC-1α Protein in soleus muscle of group M,E and ME were significantly increased(P<0.01,P<0.05).Diabetic rats:(1)Compared with group NC,the weight of D,DE,DM and DME groups decreased significantly(P<0.01).Compared with group NC,the wet weight of soleus muscle in D,DE,DM and DME groups decreased significantly(P<0.01);Compared with group D,the muscle wet weight of rats in DM,DE and DME groups increased significantly(P<0.01);The wet weight of muscle in DE and DME group was significantly higher than that in DM group(P<0.05).Com Pared with group NC,the muscle wet weight ratio of D,DE and DME rats decreased significantly(P<0.05);Compared with group D,the wet weight ratio of rats in DM group was significantly higher(P<0.05).(2)Compared with group NC,FBG in group D,DM and DE increased significantly(P<0.05);Compared with group D,FBG in DE,DM and DME groups decreased significantly(P<0.01);FBG in DME group was significantly lower than that in DM group(P<0.05).Compared with group NC,HOMA-IRI in D,DE and DM groups increased significantly(P<0.01,P<0.05,P<0.01);HOMA-IRI in DE,DM and DME groups was significantly lower than that in D group(P<0.01),and HOMA-IRI in DME group was significantly lower than that in DM group(P<0.01).(3)Compared with group NC,the Proportion of slow muscle fibers in soleus muscle of group D decreased significantly(P<0.01),while the Proportion of fast muscle fibers increased significantly(P<0.05).Compared with group D,the Proportion of slow muscle fibers in DE,DM and DME groups increased significantly(P<0.01),while the Proportion of fast muscle fibers decreased significantly(P<0.05,P<0.01).(4)Compared with group NC,the expression of MHC I in soleus muscle of group D decreased significantly(P<0.05).Compared with group D,the expression of MHC I in group DE and DM increased significantly(P<0.05,P<0.05).Compared with group D,the expression of MHC IIa in group DE,DM and DME increased significantly(P<0.05,P <0.05,P<0.01).Compared with group NC,the expression of MHCIIb in soleus muscle of rats in each group was significantly decreased(P<0.01).Compared with group D,the expression of MHC IIb in group DE,DM and DME decreased significantly(P<0.01).Compared with group NC,the expression of MHCIIx in soleus muscle of D,DE,DM and DME decreased significantly(P<0.01).Compared with group D,the expression of MHC IIx was significantly decreased in group DM(P<0.05).(5)Compared with group NC,the expression of PPARδ and PGC1-α Protein in group D was significantly decreased(P<0.01,P<0.05).Compared with group D,the Protein expression of PPARδ and PGC1-α in group DE,DM and DME increased significantly(P<0.01,P<0.05,P<0.05).Conclusion:(1)Both MOTS-c and aerobic exercise altered muscle fiber composition in normal and diabetic rats,Promoting the conversion of fast to slow muscle fibers.(2)PPARδ/PGC1-α upregulation may be an important regulatory mechanism for MOTS-c and aerobic exercise to Promote the conversion of slow muscle fiber type in skeletal muscle. |
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