Endocrine Abstracts

Cross-talk between adipose tissue and skeletal muscle via endocrine and paracrine mechanisms may be important in determining nutrient partitioning and lean-to-fat ratio. Such interactions could be mediated in part by adipokines secreted from adipose tissue. Little is known, however, about the role of adipokines in influencing growth and development of skeletal muscle.

The aim of this study was to determine the direct effects of leptin and adiponectin on the growth of porcine skeletal muscle cells in vitro. Adiponectin receptors (ADIPOR1, ADIPOR2) were abundant at mRNA and protein level in proliferating and differentiating myoblast cultures derived from semimembranosus and semitendinosus muscles of newborn piglets, whereas the long-form leptin receptor (LEPR) expression was close to the detection limit. In serum-free medium (SFM) adiponectin (10, 20, 40 μg/ml) attenuated the proliferation of porcine myoblasts, measured as [³H]-thymidine incorporation and live cell monitoring in response to 24-h and 48-h exposure, in a dose-dependent manner. This effect resulted from suppressed basic fibroblast growth factor (bFGF)-mediated stimulation of DNA synthesis that remained unchanged by adiponectin in serum-free medium (SFM) without bFGF. No effects of leptin (5, 10, 20, 40, 80 ng/ml) on myoblast proliferation in SFM were detectable. Neither leptin nor adiponectin altered protein synthesis and degradation, recorded as incorporation or release, respectively, of [³H]-phenylalanine, in differentiating porcine myoblasts cultured in SFM. The results on receptor abundance suggest that porcine skeletal muscle cells may be sensitive to adiponectin and leptin. However, except via inhibitory interaction of adiponectin with bFGF, these adipokines appear not to affect in vitro proliferation and protein metabolism of porcine muscle cells directly under serum-free culture conditions.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.