Endocrine Abstracts

Cross-talk between adipose tissue and skeletal muscle could be mediated in part by adipokines secreted from adipose tissue. Previously, we observed that adiponectin but not leptin decreased DNA synthesis rate in proliferating porcine myoblasts in growth factor-supplemented serum-free medium (GF-SFM) after 48-h exposure (Will et al. 2012). To further elucidate the effects of adiponectin and leptin on muscle cell growth and their mode of action, this study was conducted to investigate the effects of these adipokines on cell number (DNA), DNA synthesis rate, and cell death as well as on the activation of key signalling molecules in proliferating porcine myoblasts either grown in low-serum (1% FBS) medium (LSM) or GF-SFM.

Recombinant porcine adiponectin (40 μg/ml) and leptin (20 ng/ml) supplemented to LSM increased DNA synthesis rate measured as (³H)-thymidine incorporation (P<0.01), probably related to increased DNA repair, and reduced cell viability in terms of lactate dehydrogenase release (P<0.05) and/or lowered DNA content after 24-h (P<0.05) but not 48-h exposure. Both adiponectin (P=0.07) and leptin (P<0.05) treatment resulted in an activation of ERK1/2 (p44-42) after 15 min followed by decreased activation after 60 and 180 min (P<0.05). Adiponectin tended to increase c-fos activation (P=0.08) and to decrease p53 activation at 180 min (P<0.05). In GF-SFM, in contrast, adiponectin and leptin treatment decreased DNA synthesis as early as after 4-h exposure (P<0.01) and diminished the rate of cell death after 48 h (P<0.05). Under these conditions, ERK1/2 activation was reduced (P<0.01) after 15- and 30-min treatment with adiponectin or leptin.

In conclusion, the effects of adiponectin and leptin on the growth of porcine myoblasts are dependent on the surrounding cellular milieu and related to ERK1/2 signalling. The presence of growth factors in culture medium seems to attenuate adverse effects of the adipokines on the growth of myoblasts.

Keywords: Adiponectin, Leptin, Skeletal muscle, Pig, Satellite cell culture, ERK1/2.