Animals ; Male ; Muscle, Skeletal ; metabolism ; Myogenic Regulatory Factors ; metabolism ; Physical Conditioning, Animal ; Rats ; Rats, Sprague-Dawley ; Running

Myostatin (Mstn) is a member of the transforming growth factor-beta superfamily that functions as a negative regulator of skeletal muscle growth and differentiation in mammals. The transcriptional regulation of Mstn is controlled by multiple genes including MEF2, which raise the importance of identifying the binding sites of MEF2 on myostatin promoter region and mechanisms underlying. In this study, we investigated the transcriptional regulation of MEF2 on porcine Mstn promoter activity in C2C12 cells. Sequence analysis of the 1 969 bp porcine Mstn promoter region revealed that it contained three potential MEF2 motifs. Using a serial deletion strategy, we tested the activity of several promoter fragments by luciferase assay. Overexpression of MEF2C, but not MEF2A increased Mstn promoter activity in all the promoter fragments with MEF2 motifs by two to six folds, in both C2C12 myoblasts and myotubes. When we transfected exogenous MEF2C, Mstn mRNA level was also upregulated in C2C12 cells, but the protein level was only significantly increased in myotubes. Thus, we propose that MEF2C could modulate and restrain myogenesis by Mstn activation and Mstn-dependent gene processing in porcine. Our research also provided potential targets and an effective molecule to regulate Mstn expression and gave a new way to explore the functional performance of Mstn.
Animals ; Cells, Cultured ; Gene Expression Regulation ; MEF2 Transcription Factors ; Mice ; Muscle, Skeletal ; metabolism ; Myoblasts ; cytology ; Myogenic Regulatory Factors ; genetics ; physiology ; Myostatin ; genetics ; physiology ; Promoter Regions, Genetic ; Swine

Animals ; Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism* ; MEF2 Transcription Factors/metabolism* ; Muscle Fibers, Skeletal/metabolism* ; Muscle, Skeletal/metabolism* ; Myogenic Regulatory Factors/metabolism* ; Physical Conditioning, Animal/methods* ; Rats ; Signal Transduction

OBJECTIVE: To explore the expression of MEF2D in NPC tissues, study the relationship between the expression and prognostic. METHOD: Specimens from 101 NPC patients who were follow-up visited 1 to 7 years were analyzed for MEF2D by using immunohistochemistry. RESULT: (1) The expression of MEF2D was higher in the higher clinical stage. (2) Density and Grey of MEF2D was negative correlated (|r| = 0.865, P < 0.01). (3) NPC patients' survival rate after therapies was 52.5%, the survival curve of 1th clinical stage was higher than 4th. (4) The survival curves of MEF2D stages were no statistical significance. CONCLUSION There's statistical significance of the MEF2D expression in clinical stages, but not in survival curve, which indicated that MEF2D concerned with invasion and metastatic of NPC.
Adult ; Carcinoma ; Carcinoma, Squamous Cell ; metabolism ; pathology ; Female ; Humans ; Lymphatic Metastasis ; MADS Domain Proteins ; metabolism ; MEF2 Transcription Factors ; Male ; Middle Aged ; Myogenic Regulatory Factors ; metabolism ; Nasopharyngeal Carcinoma ; Nasopharyngeal Neoplasms ; metabolism ; pathology ; Neoplasm Staging ; Prognosis

Mammals have two major isoforms of acetyl-CoA carboxyase (ACC). The 275 kDa beta-form (ACC beta) is predominantly in heart and skeletal muscle while the 265 kDa alpha-form (ACC alpha) is the major isoform in lipogenic tissues such as liver and adipose tissue. ACC alpha is thought to control fatty acid oxidation by means of the ability of malonyl-CoA to inhibit carnitine palmitoyl-CoA transferase-1 (CPT-1), which is a rate-limiting enzyme of fatty acid oxidation in mitochondria. Previously, it was reported that MyoD and other muscle regulating factors (MRFs) up-regulate the expression of ACC beta by interactions between these factors and several cis-elements of ACC beta promoter. We described here that ACC beta expression mediated by MRFs is regulated by retinoic acids. Endogenous expression of ACCb in differentiated H9C2 myotube was significantly increased by retinoic acid treatment. However, on transient transfection assay in H9C2 myoblast, ACC beta promoter activity was suppressed by RXRa and more severely by RAR alpha. These effects on ACCb expression in myoblasts and myotubes by RXR alpha and RAR alpha seem to be mediated by their interactions with MRFs because no consensus sequence for RXR alpha and RAR alpha has been found in ACC beta promoter and retinoic acid receptors did not affect this promoter activities by itself. In transient transfection in NIH3T3 fibroblast, the activation of ACC beta promoter by MyoD, main MRF in myoblast, was significantly suppressed by RAR alpha and to a less extent by RXR alpha while the RXR alpha drastically augmented the activation by MRF4, major MRF in myotube. These results explained that retinoic acids differentially affected the action of MRFs according to their types and RXR alpha specially elevates the expression of muscle specific genes by stimulating the action of MRF4.
3T3 Cells ; Acetyl-CoA Carboxylase/genetics/*metabolism ; Animals ; Cell Differentiation ; Cells, Cultured ; Gene Expression Regulation, Enzymologic/drug effects ; Mice ; MyoD Protein/*metabolism ; Myoblasts/drug effects/metabolism ; Myogenic Regulatory Factors/*metabolism ; Promoter Regions (Genetics)/drug effects ; Receptors, Retinoic Acid/genetics/*metabolism ; Trans-Activation (Genetics) ; Transcription Factors/genetics/*metabolism ; Tretinoin/pharmacology

BACKGROUNDSome single nucleotide polymorphisms (SNPs) in the peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1alpha gene have been reported to be associated with type 2 diabetes in different populations, and studies on Chinese patients yielded controversial results. The objective of this case-control study was to explore the relationship between SNPs of PGC-1alpha and type 2 diabetes in the southern Chinese population and to determine whether the common variants: Gly482Ser and Thr394Thr, in the PGC-1alpha gene have any impacts on interaction with myocyte enhancer factor (MEF) 2C.

METHODSThe SNPs in all exons of the PGC-1alpha gene was investigated in 50 type 2 diabetic patients using polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) and direct sequencing. Thereafter, 263 type 2 diabetic patients and 282 healthy controls were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). A bacterial two-hybrid system and site-directed mutagenesis were used to investigate whether Gly482Ser and Thr394Thr variants in the PGC-1alpha gene alter the interaction with MEF2C.

RESULTSThree frequent SNPs (Thr394Thr, Gly482Ser and Thr528Thr) were found in exons of the PGC-1alpha gene. Only the Gly482Ser variant had a different distribution between diabetic patients and healthy subjects, with the 482Ser allele more frequent in patients than in controls (40.1% vs 29.3%, P < 0.01). Even in controls, the 482Ser (A) carriers were more likely to have higher levels of total cholesterol and low-density lipoprotein cholesterol than the 482Gly (G) carriers. The 394A-482G-528A haplotype was associated with protection from diabetes, while the 394A-482A-528A was associated with the susceptibility to diabetes. The bacterial two-hybrid system and site-directed mutagenesis revealed that the 482Ser variant was less efficient than the 482Gly variant to interact with MEF2C, whereas the 394Thr (A) had a synergic effect on the interaction between 482Ser variant and MEF2C.

CONCLUSIONSThe results suggested that the 482Ser variant of PGC-1alpha conferred the susceptibility to type 2 diabetes in the southern Chinese population. The underlying mechanism may be attributable, at least in part, to the altered interaction between the different variants (Gly482Ser, Thr394Thr) in the PGC-1alpha gene and MEF2C.

Aged ; Asian Continental Ancestry Group ; genetics ; China ; Diabetes Mellitus, Type 2 ; ethnology ; genetics ; Female ; Genotype ; Heat-Shock Proteins ; genetics ; metabolism ; Humans ; MEF2 Transcription Factors ; Male ; Middle Aged ; Myogenic Regulatory Factors ; metabolism ; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha ; Polymerase Chain Reaction ; Polymorphism, Single Nucleotide ; Polymorphism, Single-Stranded Conformational ; Protein Binding ; Transcription Factors ; genetics ; metabolism

OBJECTIVETo investigate the association of the 482G/A polymorphism of the PGC-1alpha gene with type 2 diabetes by family-based study in the Han population in South China, and to analyze the quantitative and qualitative binding force changes between the PGC-1alpha domain mutant and MEF2C, as well as to evaluate the possibility of PGC-1alpha -MEF2C-GLUT4 pathway in the pathogenesis of type 2 diabetes.

METHODSBlood samples were collected from 350 patients with type 2 diabetes and their first-degree relatives. Genomic DNA was extracted and polymorphic PGC-1alpha genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism and direct DNA sequencing. The results were analyzed by family-based transmission disequilibrium test (TDT) and haplotype relative risk (HRR). The protein-protein interaction between PGC-1alpha and MEF2C was detected by means of the site-directed mutagenesis kit and bacteriomatch two-hybrid system kit.

RESULTSIn the family-based study, HRR analyses demonstrated that the 482A allele was more often transmitted to patients than predicted by chance (chi (2)= 7.2170, P= 0.0072, HRR= 1.4496). TDT-extended test(ETDT) analyses also revealed that PGC-1alpha 482A allele was significantly deviated from 0.5 from heterozygous parents to patients than expected (219 trios, P= 0.0310; 350 trios, P= 0.0292). BacterioMatch Two-Hybrid System showed that 482A variation could lead to decreased binding force between PGC-1alpha and MEF2C (62.1+/- 8.97, P< 0.05).

CONCLUSIONThe 482A polymorphism increases the risk of developing type 2 diabetic mellitus in the South China Han population, which might be mediated by the PGC-1alpha -MEF2C-GLUT4 pathway.

Asian Continental Ancestry Group ; genetics ; Diabetes Mellitus, Type 2 ; genetics ; metabolism ; Ethnic Groups ; genetics ; Female ; Gene Frequency ; Genetic Predisposition to Disease ; Glucose Transporter Type 4 ; metabolism ; Haplotypes ; Heat-Shock Proteins ; genetics ; metabolism ; Humans ; Logistic Models ; MADS Domain Proteins ; genetics ; metabolism ; MEF2 Transcription Factors ; Male ; Middle Aged ; Myogenic Regulatory Factors ; genetics ; metabolism ; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha ; Polymorphism, Single Nucleotide ; genetics ; Protein Structure, Tertiary ; genetics ; Signal Transduction ; Transcription Factors ; genetics ; metabolism ; Two-Hybrid System Techniques

Chronic and heavy alcohol consumption is one of the causes of heart diseases. However, the effects of ethanol on insulin sensitivity in myocardium has been unclear. To investigate the effects of ethanol on the expression of AMP-activated protein kinase (AMPK), myocyte enhancer factor 2 (MEF2) and glucose transporter 4 (GLUT4), all of which are involved in the regulation of insulin sensitivity, in the myocardium, we performed three parts of experiments in vivo and in vitro. I: Rats were injected with 5-amino-4-imidazolecarboxamide ribonucleotide (AICAR, 0.8 mg.kg(-1)) for 2 h. II: Rats received different dose (0.5, 2.5 or 5 g.kg(-1).d(-1)) of ethanol for 22-week. III: Primary neonatal rat cardiomyocytes were isolated and treated with or without 100 mM ethanol or 1 mM AICAR for 4 h. The cardiac protein and mRNA expression of AMPKalpha subunits, MEF2 and GLUT4 were observed by western-blotting and RT-PCR, respectively. Serum TNFalpha levels were assessed by ELISA. The results showed chronic ethanol exposure induced insulin resistance. Ethanol decreased the mRNA levels of AMPKalpha1 and alpha2, the protein levels of total- and phospho-AMPKalpha in cardiomyocytes. Similarly, ethanol showed inhibitory effects on both the mRNA and protein levels of MEF2A and 2D, and GLUT4 in a dose-response-like fashion. Correlation analysis implied an association between phospho-AMPKalpha and MEF2A or MEF2D, and between the levels of MEF2 protein and GLUT4 transcription. In addition, ethanol elevated serum TNFalpha level. Taken together, chronic ethanol exposure decreases the expression of AMPKalpha and MEF2, and is associated with GLUT4 decline in rat myocardium.
AMP-Activated Protein Kinases/genetics/*metabolism ; Aminoimidazole Carboxamide/analogs & derivatives/pharmacology ; Animals ; Enzyme Activation/drug effects ; Ethanol/*administration & dosage/*pharmacology ; Feeding Behavior/*drug effects ; Gene Expression Regulation/drug effects ; Glucose Transporter Type 4/genetics/*metabolism ; Insulin/pharmacology ; Insulin Resistance ; Male ; Myocardium/*enzymology ; Myogenic Regulatory Factors/antagonists & inhibitors/genetics/*metabolism ; Protein Isoforms/antagonists & inhibitors/genetics/metabolism ; RNA, Messenger/genetics/metabolism ; Rats ; Rats, Wistar ; Ribonucleotides/pharmacology ; Time Factors ; Tumor Necrosis Factor-alpha/blood