CAV3 mediates IMGU and NIMGU in skeletal muscle and cardiac myocytes

Objective:To observe whether CAV3 is involved in the physiological process of IMGU and NIMGU.Down-regulation of caveolin-3(CAV3)protein expression by small interference RNAs(iRNA)has been studied.Insulin-mediated glucose uptake(IMGU)is critical in skeletal muscle and cardiac myocytes,but non-insulin-mediated glucose uptake(NIMGU)should not be neglected.Methods:CAV3 siRNAs were designed and transfected in C2C12 cells and H9c2 cells in skeletal muscle and cardiac muscle,respectively,and C2C12 and H9c2 cells were cultured in DMEM medium with and without insulin,respectively.Glucose transporter 4(GLUT4)protein expression was detected by Western blot,and the glucose uptake rate of cells was measured by biochemical kit.Results:Transfection with CAV3 siRNA successfully down-regulated CAV3 protein expression in C2C12 and H9c2 cells.In the absence of insulin stimulation,GLUT4 expression was decreased(P<0.01)and glucose uptake was reduced(P<0.05)after 48 h of transfection in C2C12 cells,and GLUT4 expression was decreased(P<0.05)and glucose uptake was reduced(P<0.01)after 48 h of transfection in H9c2 cells.In the presence of insulin stimulation,GLUT4 expression was decreased(P<0.01)and glucose uptake was reduced(P<0.01)after 48 h of transfection in C2C12 cells,and the downregulation of GLUT4 was not statistically significant and glucose uptake was reduced(P<0.01)after 48 hours of transfection in H9c2 cells.Conclusion:Two different states,IMGU and NIMGU,exist in C2C12 cells and H9c2 cells.Both in the quiet state stimulated by insulin as well as in the absence of insulin stimulation,the cellular uptake of glucose is affected by GLUT4 changes regulated by CAV3.

BTG1 as a New Candidate Gene for Muscle Growth in Pigs: Cloning,Expression and Association Analysis

BTG1 （B-cell Translocation Gene 1） , a member of the BTG / TOB （Transducer of ErbB-2） family of anti-proliferation factors,has been proven to have an unfavorable effect on muscle fiber growth in several species. The porcine BTG1 gene was cloned and its 5＇ flanking promoter region sequence, and characterized the expression patterns in different tissues of adult pigs and in fetal skeletal muscle at different developmental stages in two breeds. The tissue distribution pattern analyses revealed that the mRNA of porcine BTG1 was ubiquitously expressed in the six tissues of both Landrace and Tongcheng pigs. Real-time quantitative reverse transcriptase-PCR results showed that BTG1 mRNA expression levels were significantly different among the three fetal ages in Tongcheng pigs,while no significant differences were found among the three ages in Landrace pigs. Furthermore,the expression of BTG1 in Landrace pigs was significantly lower than in Tongcheng pigs at all three ages. The temporal expression profiles of the BTG1 gene in mouse myoblast C 2 C 12 cells were shown to be consistent with those of the myogenin gene. A single nucleotide polymorphism （SNP） ,g. 281C 〉 T,was identified in the 3＇UTR and allele frequencies were detected in seven pig breed populations. Significant associations were found between the g. 281C 〉 T polymorphism and growth and meat quality traits. Our results indicate that the porcine BTG1 gene could play a potential role in markerassisted selection and as such may be a gene of economic importance.