Effect of Fatty Acids on Myogenesis and Mitochondrial Biosynthesis during Murine Skeletal Muscle Cell Differentiation

Polyunsaturated fatty acids are important nutrients for human health, especially omega-3 fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which have been found to play positive roles in the prevention of various diseases. However, previous studies have reported that DHA and EPA can inhibit myoblast proliferation. In this study, we investigated the effect of fatty acids (state which FA) on mitochondrial function and gene expression in C2C12 myoblast cells in presence during skeletal muscle differentiation.

C2C12 myoblasts were cultured to confluency and then treated with differentiation medium that contained fatty acids (50µM EPA and DHA). After 72 hours of myogenic differentiation, cell mRNA was collected and gene expression was analyzed by real-time PCR. Microscopy was used to examine cell morphology following treatment with fatty acids. In addition, the effect of DHA/EPA on cellular oxygen consumption was measured using a Seahorse XF24 Analyzer.

Cells treated with fatty acids had fewer myotubes formed compared to control cells. The expression of MRF4 (myogenic regulatory factor 4), MyoD (myogenic differentiation), MyoG (myogenin) and Pax7 (paired box 7), genes related to myogenesis, was significantly lower in cells treated with fatty acids . Genes associated with adipogenesis, aP2 (adipocyte protein 2), c/EBPa (CCAAT/enhancer-binding protein alpha), c/EBPb, PPARg (peroxisome proliferator-activated receptor gamma), CPT1 (carnitine palmitoyltransferase I), and FAT/CD36 (fatty acid translocase), had higher expression after treatment with fatty acids. In addition, the mitochondrial biogenesis decreased with lower Mfn2 (mitofusin 2), ERRa (estrogen related receptor alpha), TFAM (mitochondrial transcription factor A), and PGC1a (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) expression and lower mtDNA/nDNA ratio in cells treated with fatty acids compared with control cells . However, the expression of PMP70 (70-kDa peroxisomal membrane protein), Pex2 (peroxisomal biogenesis factor 2), and Pex19, genes related to peroxisome biosynthesis, was higher in cells treated with fatty acids. Moreover, fatty acid treatment reduced oxygen consumption rate under oligomycin-inhibited (reflecting proton leak), and uncoupled conditions.

Our preliminary data implies that fatty acids might reduce myogenesis and increase adipogenesis in myotube formation. Fatty acids may also decrease cell metabolism by reducing mitochondrial biogenesis as well as respiration rate. This data suggests that high-fat diet or supplement may affect myotube formation during myogenesis in fetal stage and regeneration of skeletal muscle in adults via impaired mitochondrial metabolism.