Myostatin Inhibits Myogenesis and Promotes Adipogenesis in C3H 10T(1/2) Mesenchymal Multipotent Cells

Abstract

Inactivating mutations of the mammalian myostatin gene are associated with increased muscle mass and decreased fat mass; conversely, myostatin transgenic mice that overexpress myostatin in the skeletal muscle have decreased muscle mass and increased fat mass. We investigated the effects of recombinant myostatin protein and antimyostatin antibody on myogenic and adipogenic differentiation of mesenchymal multipotent cells. Accordingly, 10T(1/2) cells were incubated with 5'-azacytidine for 3 d to induce differentiation and then treated with a recombinant protein for myostatin (Mst) carboxy terminal 113 amino acids or a polyclonal anti-Mst antibody for 3, 7, and 14 d. Cells were also cotransfected with a Mst cDNA plasmid expressing the full-length 375-amino acid protein (pcDNA-Mst375) and the silencer RNAs for either Mst (pSil-Mst) or a random sequence (pSil-RS) for 3 or 7 d, and Mst expression was determined. Adipogenesis was evaluated by quantitative image analysis of fat cells before and after oil-red-O staining, immunocytochemistry of adiponectin, and Western blot for CCAAT/enhancer binding protein-alpha. Myogenesis was estimated by quantitative image analysis-immunocytochemistry for MyoD (Myo differentiation protein), myogenin, and myosin heavy chain type II, or by Western blot for myogenin. 5'-Azacytidine-mediated differentiation induced endogenous full-length Mst expression. Recombinant Mst carboxy terminal 113 amino acids inhibited both early and late markers of myogenesis and stimulated both early and late markers of adipogenesis, whereas the antibody against Mst exerted the reverse effects. Myogenin levels at 7 d after transfection of pcDNA-Mst375 were reduced as expected and elevated by pSil-Mst, which blocked efficiently Mst375 expression. In conclusion, myostatin promotes the differentiation of multipotent mesenchymal cells into the adipogenic lineage and inhibits myogenesis.

Resistance to body fat gain in ‘double-muscled’ mice fed a high-fat diet

“…Alternatively, myostatin has been observed to promote adipogenesis in multipotential mesenchymal cells, suggesting that loss of myostatin function may directly suppress adipocyte differentiation. 9 Our results are consistent with these in vitro findings; however, it is also known that other mouse models showing increased muscle mass, such as transgenic mice overexpressing IGF-1, 10,11 Akt, 12 and ski 13 show decreased fat mass. It is therefore possible that an indirect effect of double-muscling on fat metabolism may also be involved in the resistance to body fat accumulation in the myostatin-deficient animals; however, indirect calorimetry studies have found no significant differences in the respiratory exchange ratio between normal mice and myostatin-deficient rodents.…”

Key signalling factors and pathways in the molecular determination of skeletal muscle phenotype

“…The use of both micro-array and proteomic analyses showed a clear fibre phenotype switch in Mst-null muscles from slow to fast-twitch fibres (Bouley et al, 2006;Steelman et al, 2006) (see section IGF-1, b 2 -agonist and myostatin-null signal fast fibre phenotype). Mst has been recently found to promote adipogenesis in C3H 10T(1/2) cells which appears to be associated with adipocyte lineage commitment (Artaza et al, 2005). However, in committed bovine preadipocytes, Mst clearly suppresses differentiation of preadipocytes into adipocytes (Hirai et al, 2007).…”

Intramuscular fat content in meat-producing animals: development, genetic and nutritional control, and identification of putative markers

“…As an example, impairment of insulin signalling has been demonstrated in muscle cells by in vitro coculture with human adipocytes (Dietze et al, 2002). Then, the activity of adipocytes in secreting adipokines (such as leptin; Kokta et al, 2004) as well as that of muscle fibres secreting myokines (such as myostatin, Artaza et al, 2005;Hirai et al, 2007) are among the key putative mechanisms of this interaction. For instance, mutations in the myostatin gene or growth differentiation factor-8 in beef cattle increase the muscle mass in the double-muscled phenotype and leads to smaller adipocytes and fewer fat islands in muscle (Wegner et al, 1998;Cassar-Malek et al, 2007a).…”