Background Skeletal muscle growth and maintenance are essential for human health.

Background Skeletal muscle growth and maintenance are essential for human health. were no apparent differences in myostatin protein distribution in the muscle fibers between the transgenic and wild-type mice. Main individual muscles increased by 76-152% in the transgenic mice over their wild-type littermate mice at 12 months of age. A large number of nuclei were localized in the central and basal lamina of the myofibers in the transgenic mice as the number of nuclei per fiber and 100 μm2 area was significantly higher in transgenic mice than T0901317 wild-type mice. By systemic comparisons of global mRNA expression patterns between transgenic mice and wild-type littermates using microarray and qRT-PCR techniques we have identified distinct gene expression patterns to support adult muscle build-up by myostatin propeptide which are comprised of enhanced expressions of myogenic regulatory factors and extracelullar matrix components and differentially down-regulated expressions of genes related to protein degradation and mitochondrial ATP synthesis. Conclusion The results present a coordinated pattern of gene expressions for reduced energy utilization during muscle build-up in adult stage. Enhanced muscle buildup by myostatin propeptide is sustained by reduced ATP synthesis as a result of a decreased activity of protein degradation. Myostatin propeptide may have a therapeutic application to the treatment of clinical muscle wasting problems by depressing myostatin activity. Background Skeletal muscle growth and maintenance are essential for human health. A basic understanding of muscle growth has many clinical applications as it can be used to DCHS2 treat serious muscle-related diseases such as muscular dystrophy and muscle wasting. Muscle fibers elongate and increase in size by fusion of myoblast cells. Myoblasts are rapidly dividing cells in culture but cease the proliferation and DNA synthesis once T0901317 they fuse into myotube [1]. In mammals myofiber numbers are determined before birth postnatal muscle growth primarily results from elongation or increase in muscle fiber size. In adults skeletal muscle regenerative properties decline with age. Myostatin one of the muscle regulatory genes is a member of the transforming growth factor-β superfamily. It regulates muscle formation during embryogenesis and postnatal muscle development as an endogenous inhibitor of muscle mass. Myostatin mRNA sequences were conserved across most mammalian species. In the absence T0901317 of myostatin function massive muscle growth has been observed in mice cattle and humans [2]. In particular mice with null mutations in myostatin gene have twice the muscle mass as wild-type mice resulting from muscle fiber hyperplasia and hypertrophy [3]. Whereas mice with over-expression of myostatin in skeletal muscle is associated with lower muscle mass and decreased fiber size and increased fat mass [4]. Like other TGF-β family members myostatin is synthesized as a precursor protein which undergoes two post-translational cleavage events. The first cleavage event removes the 24-amino acid signal peptide and the second cleavage at an RSRR site located at amino acid sequence 240-243 generates an N-terminal and a C-terminal peptide. The N-terminal T0901317 peptide is referred to as myostatin propeptide while the C-terminal peptide is the actual mature form of myostatin with ligand binding activity. The protenase furin is showed to cleave the RSRR site in CHO cells [5 6 The precursor protein is detected as a predominant form of myostatin in muscle extracellular matrix and can also be cleaved by furin proteases [7]. Transgenic over-expression of myostatin propeptide in skeletal muscle increases animal growth and muscle mass [5 8 Enhanced muscle mass phenotype in the propeptide transgenic mice is primarily achieved by myofiber hypertrophy rather than myofiber hyperplasia. The size of fast-twitch glycolytic muscle fiber at 9 weeks of age T0901317 was increased by 60% compared with wild-type littermates [8]. Our recent study with the propeptide transgenic mouse model revealed that sufficient muscle growth during adolescence can prevent high-fat diet induced obesity and type II diabetes during adulthood [9]. Myostatin is secreted to the intramuscular spaces in the form of the so-called latent complex. Upon dissociation of the latent complex myostatin binds to activin receptor type IIB and activates Smad2/3 signaling pathway to inhibit myoblast cell proliferation and differentiation. During cell cycles.