A second look at leptin and adiponectin actions on the growth of primary porcine myoblasts under serum-free conditions
Cross-talk between adipose tissue and skeletal muscle may be mediated in part by adipokines. This study was conducted to elucidate further aspects of a possible role of recombinant adiponectin and leptin in the in vitro growth of primary porcine skeletal muscle cells cultured in energetically balanced, growth factor-supplemented, serum-free medium (GF-SFM). Therefore, the effects of these adipokines on cell number (DNA content), DNA synthesis rate, cell death and on key intracellular signalling molecules were investigated. Short-term adiponectin and leptin treatment decreased DNA synthesis, measured as [ 3H]-thymidine incorporation, as early as after 4-h exposure (P<0.01), without alterations in DNA content. Both adipokines attenuated the rate of cell death in terms of lactate dehydrogenase (LDH) activity in the culture medium after 48-h treatment (P<0.05). The specific activation of p44/42 MAP kinase (MAPK) was reduced (P<0.05) after 15-min incubation with either adipokine. In conclusion, the early decreases in DNA synthesis of primary porcine myoblasts cultured in GF-SFM in response to adiponectin or leptin are related to p44/42 MAPK signalling and adipokine treatment does not impair cell viability.