VDR DEPENDENT EFFECTS ON MYOGENESIS INDUCED BY 1α,25(OH)2D3-GLYCOSIDES FROM SOLANUM GLAUCOPHYLLUM LEAVES EXTRACT (SOLBONE A; HERBONIS AG) AND SYNTHETIC 1α,25(OH)2D3

VERONICA GONZALEZ PARDO; PAULA IRAZOQUI; PABLO DE GENERARO; CLAUDIA BUITRAGO; HEINI BACHMANN; ANA RUSSO DE BOLAND

Congreso; 19TH WORKSHOP ON VITAMIN D; 2016

The presence of glycoside derivatives of 1,25(OH)2D3 endows plants to gradual release of the free bioactive form of 1,25(OH)2D3 from its glycoconjugates by endogenous animal tissue glycosidases. This results in increased half-life of the hormone in blood when purified plant fractions are administered for therapeutic purposes. In this work, we compared the effects of 1,25(OH)2D3-glycosides enriched natural product (Solbone A) from Solanum glaucophyllum leaf extract with synthetic 1,25(OH)2D3 in muscle cells C2C12 undergoing differentiation and the role of vitamin D receptor (VDR) on this process. For these, differentiation markers and myogenic parameters were studied. Results showed that Solbone A and synthetic 1,25(OH)2D3 increased VDR protein expression at 10 nM (50 and 30 %, respectively). Both compounds induced the expression of tropomyosin (20%), a protein involved in skeletal muscle contraction. In addition, the protein expression of myosin heavy chain (MHC), a marker of fiber production in muscle cells, was increased 50 % at day 4 of differentiation. Moreover, Solbone A, as well as synthetic 1,25(OH)2D3, augmented the index fusion of cultured muscle fibers. In order to explore the dependence of VDR on C2C12 differentiation, cells were stable transfected with a shRNA against VDR. Cells undergoing differentiation were treated with Solbone A and synthetic 1,25(OH)2D3 (10 nM, 48 h). Micrographs, of control and treated cells, showed that VDR expression is essential for C2C12 differentiation. Furthermore, Western blot and qRT-PCR analysis indicated that VDR expression was greatly decreased in VDR knockdown cells. Also, myogenin, another differentiation marker protein which we have previously shown to increase with both compounds, was absent in VDR knockdown C2C12 cells. In conclusion, these results demonstrated that VDR expression is crucial for C2C12 differentiation. More important, Solbone A exhibit at least equal or greater effects on early myoblast differentiation as the synthetic hormone suggesting that plant glycosides could be an effective substitute to promote muscle growth.