Author(s): KOSTOV, T., CHEN, S., ESATBEYOGLU, T., HABERSATTER, E., DIEL, P., Institution: GERMAN SPORT UNIVERSITY COLOGNE, Country: GERMANY, Abstract-ID: 1691

INTRODUCTION:
Black chokeberry extract (BCE) is rich in polyphenols such as anthocyanins, which are known for a variety of bioactive properties. However, potential anabolic effects of BCE on skeletal muscle cells and the underlying molecular mechanisms have not yet been systematically investigated. Therefore, the aim of the present study was to examine the anabolic effects of BCE and its bioactive fractions in an in vitro model using differentiated C2C12 myotubes.
METHODS:
BCE as well as its anthocyanin (ANTH) and copigment (COPIG) fractions were prepared at the University of Hannover. Dose-dependent effects on myotube hypertrophy and cell viability were investigated in differentiated C2C12 myotubes. Cell viability was assessed using an MTT assay. Myotube diameter was quantified by microscopic image analysis. The mRNA expression levels of insulin-like growth factor 1 (IGF-1) and mechanistic target of rapamycin (mTOR) were determined by quantitative RT-qPCR, while protein expression of myosin heavy chain was analyzed by Western blotting. Binding affinities to androgen and estrogen receptors were analyzed using a yeast-based transactivation assay.
RESULTS:
Treatment with BCE did not affect C2C12 cell viability across the investigated concentration range. BCE induced a significant dose-dependent increase in myotube diameter at concentrations between 10 ng/mL and 1 µg/mL. The mRNA expression of IGF-1 and mTOR was significantly stimulated by BCE treatment in C2C12 myotubes. In parallel, BCE treatment resulted in a significant increase of myosin heavy chain protein expression. Co-treatment with dexamethasone was associated with reduced catabolic responses in BCE-treated myotubes. Only at very high concentrations were antiandrogenic (100 µg/mL) and antiestrogenic (10 µg/mL) activities observed. Fractionation experiments indicated that anabolic activity was mediated by the ANTH fraction, whereas the COPIG fraction was associated with catabolic changes in C2C12 myotube diameter.
CONCLUSION:
BCE induced significant anabolic and anticatabolic effects in differentiated C2C12 myotubes. These effects were associated with enhanced myosin heavy chain protein synthesis and activation of molecular signalling pathways, particularly the IGF-1/mTOR signalling. The results further indicate that the ANTH fraction represents the primary bioactive component responsible for the observed anabolic effects. Future studies should investigate the anabolic and anticatabolic potential of BCE and its ANTH fraction in additional in vitro models and human intervention studies.