ObjectiveTo optimize the extraction method for polysaccharides from turnip（Brassica rapa）， and analyze and evaluate the primary structure of the isolated and purified turnip polysaccharide fraction（BP-1） and its hypoglycemic effects in diabetic zebrafish. MethodsTaking polysaccharide yield as the evaluation index， a semi-bionic extraction method was employed. Single-factor experiments and Box-Behnken response surface methodology were used to investigate three factors of solid-to-liquid ratio， extraction time and extraction temperature， in order to optimize the extraction process. BP-1 was isolated and purified using the Sevage method and DEAE-52 cellulose column chromatography. Structural characterization of the turnip polysaccharides was performed using ultraviolet-visible spectrophotometry（UV）， gas chromatography-mass spectrometry（GC-MS）， Congo red assay， and Fourier-transform infrared spectroscopy（FT-IR） to determine purity， monosaccharide composition， triple-helix structure， and functional groups. The microstructure of the polysaccharides was observed using scanning electron microscopy（SEM） and atomic force microscopy（AFM）. Zebrafish were divided into the blank group（adding E3 medium）， and BP-1-1， BP-1-10， BP-1-50， BP-1-200， BP-1-1 000 groups（adding BP-1 solutions at concentrations of 1， 10， 50， 200， 1 000 mg·L^-1， respectively）， and zebrafish embryos were subjected to a 96-hour exposure experiment. The maximum tolerated concentration of BP-1 in zebrafish was determined by evaluating its effects on phenotype， survival rate， malformation rate， and heart rate. Experimental animals were randomly divided into the blank group， model group， BP-1-10 group（10 mg·L^-1）， BP-1-50 group（50 mg·L^-1）， and BP-1-200 group（200 mg·L^-1）. The blank group was cultured in E3 medium， the model and treatment groups were induced to establish a diabetic model in 4 day-post-fertilization（dpf） zebrafish embryos using 10 g·L^-1 of glucose combined with 500 µmol·L^-1 of alloxan. The treatment groups received corresponding doses of BP-1 solution， while the blank and model groups received an equal volume of saline. Glucose and insulin（INS） levels were measured using enzyme-linked immunosorbent assay（ELISA） kits， the effects on the liver were observed by hematoxylin-eosin（HE） histopathological sections. The mRNA expression levels of glucagon（Glucagon）， insulin（Insa）， and phosphoenolpyruvate carboxykinase 1（PCK1） were detected with real-time fluorescence quantitative polymerase chain reaction（Real-time PCR）. ResultsThe optimized extraction conditions were determined as follows：solid-to-liquid ratio of 1∶40（g·mL^-1）， extraction time of 66 min， and extraction temperature of 79 ℃. Under these conditions， the yield of turnip polysaccharides was （10.34±0.96）%. UV analysis indicated that BP-1 contained no proteins or nucleic acids， GC-MS analysis revealed that BP-1 consisted of six monosaccharides（arabinose， rhamnose， ribose， mannose， galactose and glucose）. Congo red assay indicated that the molecular conformation did not exhibit a triple-helix structure， FT-IR analysis showed the presence of α-glycosidic bonds and uronic acids， SEM analysis revealed an irregular flaky structure with a flat and smooth surface， AFM analysis suggested that the aggregated structure might be formed by the entanglement of molecular chains and intramolecular hydrogen bonding. The maximum tolerated concentration of BP-1 in zebrafish over 96 h was determined to be 200 mg·L^-1. Pharmacodynamic results showed that， compared with the blank group， the model group exhibited significantly increased glucose levels and significantly decreased INS levels（P<0.01）. Compared with the model group， the BP-1-50 group significantly reduced glucose levels and increased INS levels（P<0.05）. Histopathological examination of liver tissue revealed that various doses of BP-1 had a certain reparative effect on damaged liver tissue. The liver tissue structure in the BP-1-200 group was nearly normal， with hepatocytes appearing plump. Real-time PCR results showed that， compared with the blank group， the model group exhibited significantly upregulated mRNA expressions of Glucagon and PCK1， and significantly downregulated mRNA expression of Insa（P<0.01）. Compared with the model group， the BP-1-50 and BP-1-200 groups showed significantly downregulated mRNA expressions of Glucagon and PCK1， and significantly upregulated mRNA expression of Insa（P<0.01）. ConclusionThe semi-bionic extraction method for turnip polysaccharides yields a high extraction rate， is simple to operate， has low costs， making it suitable for large-scale industrial production. BP-1 consists of six monosaccharides， contains α-glycosidic bonds and uronic acids， exhibits hypoglycemic activity， and provides a certain protective effect on the liver of alloxan-induced diabetic model zebrafish.

ObjectiveTo optimize the extraction method for polysaccharides from turnip（Brassica rapa）， and analyze and evaluate the primary structure of the isolated and purified turnip polysaccharide fraction（BP-1） and its hypoglycemic effects in diabetic zebrafish. MethodsTaking polysaccharide yield as the evaluation index， a semi-bionic extraction method was employed. Single-factor experiments and Box-Behnken response surface methodology were used to investigate three factors of solid-to-liquid ratio， extraction time and extraction temperature， in order to optimize the extraction process. BP-1 was isolated and purified using the Sevage method and DEAE-52 cellulose column chromatography. Structural characterization of the turnip polysaccharides was performed using ultraviolet-visible spectrophotometry（UV）， gas chromatography-mass spectrometry（GC-MS）， Congo red assay， and Fourier-transform infrared spectroscopy（FT-IR） to determine purity， monosaccharide composition， triple-helix structure， and functional groups. The microstructure of the polysaccharides was observed using scanning electron microscopy（SEM） and atomic force microscopy（AFM）. Zebrafish were divided into the blank group（adding E3 medium）， and BP-1-1， BP-1-10， BP-1-50， BP-1-200， BP-1-1 000 groups（adding BP-1 solutions at concentrations of 1， 10， 50， 200， 1 000 mg·L^-1， respectively）， and zebrafish embryos were subjected to a 96-hour exposure experiment. The maximum tolerated concentration of BP-1 in zebrafish was determined by evaluating its effects on phenotype， survival rate， malformation rate， and heart rate. Experimental animals were randomly divided into the blank group， model group， BP-1-10 group（10 mg·L^-1）， BP-1-50 group（50 mg·L^-1）， and BP-1-200 group（200 mg·L^-1）. The blank group was cultured in E3 medium， the model and treatment groups were induced to establish a diabetic model in 4 day-post-fertilization（dpf） zebrafish embryos using 10 g·L^-1 of glucose combined with 500 µmol·L^-1 of alloxan. The treatment groups received corresponding doses of BP-1 solution， while the blank and model groups received an equal volume of saline. Glucose and insulin（INS） levels were measured using enzyme-linked immunosorbent assay（ELISA） kits， the effects on the liver were observed by hematoxylin-eosin（HE） histopathological sections. The mRNA expression levels of glucagon（Glucagon）， insulin（Insa）， and phosphoenolpyruvate carboxykinase 1（PCK1） were detected with real-time fluorescence quantitative polymerase chain reaction（Real-time PCR）. ResultsThe optimized extraction conditions were determined as follows：solid-to-liquid ratio of 1∶40（g·mL^-1）， extraction time of 66 min， and extraction temperature of 79 ℃. Under these conditions， the yield of turnip polysaccharides was （10.34±0.96）%. UV analysis indicated that BP-1 contained no proteins or nucleic acids， GC-MS analysis revealed that BP-1 consisted of six monosaccharides（arabinose， rhamnose， ribose， mannose， galactose and glucose）. Congo red assay indicated that the molecular conformation did not exhibit a triple-helix structure， FT-IR analysis showed the presence of α-glycosidic bonds and uronic acids， SEM analysis revealed an irregular flaky structure with a flat and smooth surface， AFM analysis suggested that the aggregated structure might be formed by the entanglement of molecular chains and intramolecular hydrogen bonding. The maximum tolerated concentration of BP-1 in zebrafish over 96 h was determined to be 200 mg·L^-1. Pharmacodynamic results showed that， compared with the blank group， the model group exhibited significantly increased glucose levels and significantly decreased INS levels（P<0.01）. Compared with the model group， the BP-1-50 group significantly reduced glucose levels and increased INS levels（P<0.05）. Histopathological examination of liver tissue revealed that various doses of BP-1 had a certain reparative effect on damaged liver tissue. The liver tissue structure in the BP-1-200 group was nearly normal， with hepatocytes appearing plump. Real-time PCR results showed that， compared with the blank group， the model group exhibited significantly upregulated mRNA expressions of Glucagon and PCK1， and significantly downregulated mRNA expression of Insa（P<0.01）. Compared with the model group， the BP-1-50 and BP-1-200 groups showed significantly downregulated mRNA expressions of Glucagon and PCK1， and significantly upregulated mRNA expression of Insa（P<0.01）. ConclusionThe semi-bionic extraction method for turnip polysaccharides yields a high extraction rate， is simple to operate， has low costs， making it suitable for large-scale industrial production. BP-1 consists of six monosaccharides， contains α-glycosidic bonds and uronic acids， exhibits hypoglycemic activity， and provides a certain protective effect on the liver of alloxan-induced diabetic model zebrafish.

ObjectiveTo analyze the pharmacodynamic activity of Bupleuri Radix processed with Trionyx sinensis blood in the treatment of Yin deficiency and study the spectrum-effect relationship of this medicine. MethodsHigh performance liquid chromatography was employed to establish the fingerprints of 15 batches of Bupleuri Radix processed with Trionyx sinensis blood， and the similarity was evaluated according to the SOP of Similarity Evaluation System of Chromatographic Fingerprint of TCM （version 2012）. A mouse model of Yin deficiency induced by thyroxine was established. The relationship between the active components and the effect on Yin deficiency was explored by grey correlation analysis and partial least squares method based on the changes in the serum levels of triiodothyronine （T3）， thyroxine （T4）， cyclic adenosine phosphate （cAMP）， and cyclic guanosine phosphate （cGMP）. The components screened out based on the spectrum-effect relationship were used for retrieval of the targets from the Traditional Chinese Medicine Systems Pharmacology and Analysis Database （TCMSP）， The Encyclopedia of Traditional Chinese Medicine （ETCM）， and Integrative Pharmacology-based Research Platform of Traditional Chinese Medicine （TCMIP）. Furthermore， the Online Mendelian Inheritance in Man （OMIM）， GeneCards， TTD， DisGeNET， and Drugbank were employed to establish the active component-target against Yin deficiency network of Bupleuri Radix processed with Trionyx sinensis blood. Gene Ontology （GO） and Kyoto Encyclopedia of Genes and Genomes （KEGG） pathway enrichment analyses were carried out for the core targets. Real-time PCR was conducted to verify the predicted key pathways and mechanisms. ResultsThe fingerprints of the 15 batches of Bupleuri Radix processed with Trionyx sinensis blood showed the similarities of 0.976-0.999 with the control fingerprint. Compared with the model group， the drug administration group showed elevated levels of T3 and T4 and lowered levels of cAMP， cGMP and cAMP/cGMP. The results of grey correlation analysis showed that active components in terms of the correlations followed the trend of saikosaponin B₁ > saikosaponin B₂ > saikosaponin C > saikosaponin D > saikosaponin A. The partial least squares analysis showed that saikosaponins A， D， B₁， and B₂ had higher VIP values. Network pharmacology predicted a total of 30 common targets， which were enriched in 276 GO terns and 115 KEGG pathways. The results of Real-time PCR showed that the model group had lower mRNA levels of Caspase-9， kinase insert domain receptor （KDR）， and mammalian target of rapamycin （mTOR） and higher mRNA level of mouse double minute 2 homolog （MDM2） than the blank group and the drug administration group. ConclusionBupleuri Radix processed with Trionyx sinensis blood has therapeutic effect on Yin deficiency syndrome， which provides a new idea for studying Bupleuri Radix processed with Trionyx sinensis blood.

ObjectiveTo understand the development stages and use of policy tools of general practitioner policies in China since it was first proposed, to summarize the experience and explore the shortcomings, so as to provide references for the adjustment and optimization of China’s general practitioner policies. MethodsContent analysis and mathematical statistics analysis were used to conduct a quantitative research on 111 policy documents with 422 policy items involving general practitioners at the national level from 1997 to 2023, through a three-dimensional analysis framework integrating policy tools, human capital process and policy development stages. ResultsCapacity‑building policy tools were most frequently used in general practitioner policies, and the policy tools gradually shifted from mandate to inducement. The general practitioner policies paid less attention to the career selection link, but paid full attention to every segment of human capital links, with a comprehensive application of policy tools observed in the integrated development stage, despite the existence of unbalanced internal distribution. ConclusionIt is suggested to promote the use of incentive policy tools and to explore multiple approaches based on incentive theory; pay attention to the career selection link for guiding the employment of general practitioners; take the appropriateness between the policy tools and human capital process into comprehensive consideration, striking a dynamic balance of the internal structure of general practitioner policies.

Objective:To explore the clinical phenotype and genetic characteristics of a patient with Progressive pseudorheumatoid dysplasia (PPRD) due to compound heterozygous variants of CCN6 gene. Methods:A patient who was admitted to Qilu Hospital of Shandong University due to " bilateral finger joint deformity, bilateral hip and knee joint movement limitation for 19 years" was selected as the study subject. Clinical data of the patient were retrospectively collected. Peripheral blood samples were collected from the patient and her parents and subjected to whole exome sequencing (WES). Long-read sequencing (LRS) and Sanger sequencing were used to verify the candidate variants. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the pathogenicity of candidate variants was classified. This study was approved by the Medical Ethics Committee of Qilu Hospital of Shandong University (Ethics No.: KYLL-202502 061).Results:The patient, a 23-year-old female, presented with progressive polyarticular deformity, limited movement and abnormal growth and development since childhood. She was initially misdiagnosed as Ankylosing spondylitis and had poor response to sulphasalazine and etoricoxib treatment. WES revealed that she has harbored two heterozygous variants of the CCN6 gene (NM_198239.2), namely c. 348C>A and c. 676G>C. LRS confirmed that the two variants are located on two homologous chromosomes and constitute compound heterozygous variants. Based on the ACMG guidelines, both variants were rated as pathogenic (PVS1+ PM2_Supporting+ PM3; PM1+ PM2_Supporting+ PM3_Supporting+ PM5+ PP3_Strong). The c. 676G>C variant has not been recorded by the HGMD and ClinVar databases. Conclusion:The c. 348C>A and c. 676G>C compound heterozygous variants of the CCN6 gene probably underlay the pathogenesis of PPRD in this patient. Above finding has enriched the mutational spectrum of PPRD and provided a basis for the clinical diagnosis and genetic counseling.

Objective:To discuss the correlation between Helicobacter pylori(Hp) infection and serum 25-hydroxyvitamin D3(25(OH)D 3)level in the elderly physical examination population. Methods:It was a cross-sectional study. Selecting individuals who met the inclusion and exclusion criteria as the subjects of the study and underwent health check-ups between January 2018 and December 2019 in the Second Medical Center of Chinese PLA General Hospital.According to the Delta Over Baseline (DOB) value of 13C urea breath test, the subjects were divided into two groups: those with DOB value≥4 ( n=1 018) were diagnosed as Hp-positive and were included in the positive group, and the others were Hp-negative and were included in the negative group (DOB value<4, n=2 067). The age, gender, height, weight, disease history, family disease history and other basic medical records were recorded; and blood samples were drawn for analysis of blood test, blood biochemical test etc. Then the serum 25(OH)D 3 levels were compared between the two groups. The influencing factors of Hp infection were analyzed using a multifactor logistic regression model and the confounding factors were also adjusted. Results:A total of 3 085 elderly people (male 1 838, female 1 247) were selected in this study, the median age is 64 years, the detection rate of Hp was 33%. Single factor analysis showed that the serum 25(OH)D 3 level in the positive group was significantly lower than that in the negative group (20.59 ng/ml vs 21.07 ng/ml, P=0.012). Binary logistic regression analysis showed that the serum 25(OH)D 3 level was a negative influence factor on Hp infection( OR=0.984, P=0.008). High level of serum 25(OH)D 3 can reduce the risk of Hp infection ( OR=0.707, P=0.002). The three constructed Hp infection risk prediction models still showed statistically significant after controlling for confounding factors. Conclusion:The study shows a correlation between serum 25(OH)D 3 level and the Hp infection in the elderly people, and low level of serum 25(OH)D 3 is an independent risk factor for Hp infection in the elderly population.

OBJECTIVE: To explore the clinical phenotype and genetic characteristics of a patient with Progressive pseudorheumatoid dysplasia (PPRD) due to compound heterozygous variants of CCN6 gene. METHODS: A patient who was admitted to Qilu Hospital of Shandong University due to "bilateral finger joint deformity, bilateral hip and knee joint movement limitation for 19 years" was selected as the study subject. Clinical data of the patient were retrospectively collected. Peripheral blood samples were collected from the patient and her parents and subjected to whole exome sequencing (WES). Long-read sequencing (LRS) and Sanger sequencing were used to verify the candidate variants. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the pathogenicity of candidate variants was classified. This study was approved by the Medical Ethics Committee of Qilu Hospital of Shandong University (Ethics No.: KYLL-202502 061). RESULTS: The patient, a 23-year-old female, presented with progressive polyarticular deformity, limited movement and abnormal growth and development since childhood. She was initially misdiagnosed as Ankylosing spondylitis and had poor response to sulphasalazine and etoricoxib treatment. WES revealed that she has harbored two heterozygous variants of the CCN6 gene (NM_198239.2), namely c.348C>A and c.676G>C. LRS confirmed that the two variants are located on two homologous chromosomes and constitute compound heterozygous variants. Based on the ACMG guidelines, both variants were rated as pathogenic (PVS1+PM2_Supporting+PM3; PM1+PM2_Supporting+PM3_Supporting+PM5+PP3_Strong). The c.676G>C variant has not been recorded by the HGMD and ClinVar databases. CONCLUSION The c.348C>A and c.676G>C compound heterozygous variants of the CCN6 gene probably underlay the pathogenesis of PPRD in this patient. Above finding has enriched the mutational spectrum of PPRD and provided a basis for the clinical diagnosis and genetic counseling.
Humans ; Female ; CCN Intercellular Signaling Proteins/genetics* ; Phenotype ; Heterozygote ; Young Adult ; Mutation ; Exome Sequencing ; Joint Diseases/congenital*

This study explored whether Astragalus polysaccharide(APS)can regulate the VEGF/VEGFR signaling pathway to affect the proliferative activity of rat intestinal mucosal microvascu-lar endothelial cells(RIMMVECs).RIMMVECs were isolated from newborn rats,then purified and treated with APS at concentrations of 0.1,1.0,10.0,100.0,1 000.0,and 10 000.0 mg/L.MTT was used to determine the effect of APS on RIMMVECs proliferation and screen for the optimal concentration of APS.Subsequently,flow cytometry was used to detect the changes in cell cycle to evaluate the stage of action of APS on the cell cycle in RIMMVECs.Then,the ELISA was used to detect the changes of VEGFA in cell supernatant to evaluate the potential of cell proliferation and angiogenesis.The changes in fluorescence intensity of Fluo-8AM was observed using fluorescence microscopy to evaluate intracellular Ca2+levels.Finally,Western blot was used to detect the ex-pression of PERK in RIMMVECs to analyze the possible mechanism of APS.The results showed that 100 mg/L APS significantly enhanced the proliferative activity of RIMMVECs,increased the content of VEGFA in the cell supernatant,the intracellular Ca2+levels,and the expression of PERK protein,indicating that APS promotes the proliferation of RIMMVECs,which may be a-chieved by promoting the expression of VEGFA and activating the ERK pathway.

Objective To observe the effect of a heavy load exercise on the ultrastructure,function and fission of skeletal muscle mitochondria in rats,and to analyze the changes of the phosphorylation expression of mitochondrial fission protein and upstream kinase at different times postexercise,and to explore the effect of acute heavy load exercise on mitochondrial fission in skeletal muscle of rats and its possible mechanism.Methods Forty-eight adult male Sprague-Dawley rats were randomly divided in-to a quiet control group(C,n=8)and an exercise group(E,n=40).Rats in the E group exercised on a treadmill down a 16° decline at 16 m/min for 90 min and were further divided into 0 h,12 h,24 h,48 h,and 72 h postexercise subgroups.Soleus muscle was isolated and mitochondria were ex-tracted at the corresponding time points after exercise.The ultrastructure of mitochondria in the soleus muscle was observed using transmission electron microscopy,and mitochondrial quantity and morphomet-ric analysis were conducted.Moreover,the colocalization and quantity of dynamin-related protein 1(Drp1)and cytochrome C oxidease subunit Ⅳ(COXⅣ)in the soleus muscle were detected using im-munofluorescence double-labeling techniques.Meanwhile,protein levels of soleus musclep-Drp1Ser616,p-Drp1Ser637,p-extracellular regulatory protein kinaseThr202/Tyr204(p-ERKThr202/Tyr204),p-protein kinaseAThr197(p-PKAThr197),and mitochondrial NADH of ubiquinone oxidoreductase subunit B8(NDUFB8)and ubiqui-nol-cytochrome C reductase core protein 2(UQCRC2)were determined by using Western blotting.An-other twenty-four rats were randomly divided into a DMSO group(CD),a U0126 group(CU),an Ex-ercise+DMSO group(ED),and an Exercise+U0126 group(EU).Six mice in each group were giv-en a single intra-bitoneal injection of DMSO or ERK inhibitor U0126 20 min before acute downhill running.Then,their phosphorylated expressions of ERKThr202/Tyr204 and Drp1Ser616 in soleus muscle were de-tected by Western blotting.Results(1)From 0 h to 48 h after exercise,the soleus muscle mitochon-dria showed swelling,rounding,and uneven distribution of mitochondria,among which the degree of mitochondrial damage was the most serious at 12 h and 24 h after exercise.Moreover,the protein ex-pression of NDUFB8 and UQCRC2 in the mitochondria fractions from soleus muscle was significantly lower at 12 h post-exercise(P<0.05).(2)The co-localization of Drp1 and COXⅣ in the skeletal muscle increased significantly at 12 h to 24 h after a heavy load exercise compared with group C and group E0(P<0.01).Moreover,the mitochondrial area,circumference,aspect ratio and Ferret diameter in the skeletal muscle were significantly lower at 12 h to 24 h postexercise(P<0.05).Meanwhile,the number of mitochondria was significantly higher at 24 h after exercise(P<0.01).(3)The phosphoryla-tion of ERKThr202/Tyr204,PKAThr197 and Drp1Ser616 was significantly higher at 24 h after exercise(P<0.01),while that of Drp1Ser637 was significantly lower at 48 h and 72 h post-exercise(P<0.01).However,the phosphorylated expressions of ERKThr202/Tyr204 and Drp1Ser616 were significantly down-regulated by U0126 treatment before exercise.Conclusion A session of heavy load exercise caused mitochondrial structure and function damage and induced mitochondrial fission in the skeletal muscle,and then to maintain the homeostasis of skeletal muscle cells by cleaving damaged mitochondria.The mechanism of promot-ing skeletal muscle repair may be related to the positive and negative regulation of Drp1 activity by the phosphorylation of Drp1Ser616 and Drp1Ser637,respectively.Among them,the activation of ERKThr202/Tyr204 mediates the phosphorylation activation of Drp1Ser616,but PKAThr197 is not an upstream kinase that medi-ates the inactivation of Drp1Ser637 phosphorylation.

Objective To observe the effect of a heavy load exercise on the ultrastructure,function and fission of skeletal muscle mitochondria in rats,and to analyze the changes of the phosphorylation expression of mitochondrial fission protein and upstream kinase at different times postexercise,and to explore the effect of acute heavy load exercise on mitochondrial fission in skeletal muscle of rats and its possible mechanism.Methods Forty-eight adult male Sprague-Dawley rats were randomly divided in-to a quiet control group(C,n=8)and an exercise group(E,n=40).Rats in the E group exercised on a treadmill down a 16° decline at 16 m/min for 90 min and were further divided into 0 h,12 h,24 h,48 h,and 72 h postexercise subgroups.Soleus muscle was isolated and mitochondria were ex-tracted at the corresponding time points after exercise.The ultrastructure of mitochondria in the soleus muscle was observed using transmission electron microscopy,and mitochondrial quantity and morphomet-ric analysis were conducted.Moreover,the colocalization and quantity of dynamin-related protein 1(Drp1)and cytochrome C oxidease subunit Ⅳ(COXⅣ)in the soleus muscle were detected using im-munofluorescence double-labeling techniques.Meanwhile,protein levels of soleus musclep-Drp1Ser616,p-Drp1Ser637,p-extracellular regulatory protein kinaseThr202/Tyr204(p-ERKThr202/Tyr204),p-protein kinaseAThr197(p-PKAThr197),and mitochondrial NADH of ubiquinone oxidoreductase subunit B8(NDUFB8)and ubiqui-nol-cytochrome C reductase core protein 2(UQCRC2)were determined by using Western blotting.An-other twenty-four rats were randomly divided into a DMSO group(CD),a U0126 group(CU),an Ex-ercise+DMSO group(ED),and an Exercise+U0126 group(EU).Six mice in each group were giv-en a single intra-bitoneal injection of DMSO or ERK inhibitor U0126 20 min before acute downhill running.Then,their phosphorylated expressions of ERKThr202/Tyr204 and Drp1Ser616 in soleus muscle were de-tected by Western blotting.Results(1)From 0 h to 48 h after exercise,the soleus muscle mitochon-dria showed swelling,rounding,and uneven distribution of mitochondria,among which the degree of mitochondrial damage was the most serious at 12 h and 24 h after exercise.Moreover,the protein ex-pression of NDUFB8 and UQCRC2 in the mitochondria fractions from soleus muscle was significantly lower at 12 h post-exercise(P<0.05).(2)The co-localization of Drp1 and COXⅣ in the skeletal muscle increased significantly at 12 h to 24 h after a heavy load exercise compared with group C and group E0(P<0.01).Moreover,the mitochondrial area,circumference,aspect ratio and Ferret diameter in the skeletal muscle were significantly lower at 12 h to 24 h postexercise(P<0.05).Meanwhile,the number of mitochondria was significantly higher at 24 h after exercise(P<0.01).(3)The phosphoryla-tion of ERKThr202/Tyr204,PKAThr197 and Drp1Ser616 was significantly higher at 24 h after exercise(P<0.01),while that of Drp1Ser637 was significantly lower at 48 h and 72 h post-exercise(P<0.01).However,the phosphorylated expressions of ERKThr202/Tyr204 and Drp1Ser616 were significantly down-regulated by U0126 treatment before exercise.Conclusion A session of heavy load exercise caused mitochondrial structure and function damage and induced mitochondrial fission in the skeletal muscle,and then to maintain the homeostasis of skeletal muscle cells by cleaving damaged mitochondria.The mechanism of promot-ing skeletal muscle repair may be related to the positive and negative regulation of Drp1 activity by the phosphorylation of Drp1Ser616 and Drp1Ser637,respectively.Among them,the activation of ERKThr202/Tyr204 mediates the phosphorylation activation of Drp1Ser616,but PKAThr197 is not an upstream kinase that medi-ates the inactivation of Drp1Ser637 phosphorylation.