Docosahexaenoic Acid (DHA) but not Eicosapentaenoic Acid (EPA) induces the trans‐differentiation of C2C12 into white‐like adipocytes phenotype

Abstract

Muscle derived stem cells (MDSCs) and myoblasts play an important role in the regeneration of myotubes when muscle tissue is injured. However, these cells can be induced to differentiate to other lineages during embryonic development such as adipocytes, osteocytes, and chondrocytes in response to external stimuli like maternal diet enriched with EPA and DHA that are highly suggested during pregnancy because of their neuronal development benefits and positive role in improving retinal and immune functions. The objective of this study is to explore the effect of isolated EPA and DHA on myoblasts undergoing differentiation into brown and white adipocytes. C2C12 myoblasts were cultured to confluency and then treated with white and brown adipogenic differentiation medium with and without 50μM EPA and 50μM DHA separately. DHA treated group but not EPA reprogrammed C2C12 into white like adipocyte phenotype by down‐regulation the expression (P<0.05) of genes involved in regulation the terminal differentiation of myoblasts into myotubes such as MyoD, MyoG, and Mrf4 and up‐regulation the expression of white adipogenesis specific markers including PPARγ, C/EBPα, C/EBPβ, aP2, BMP4, FAT, ZFP423, and Il‐6 (P<0.05). Furthermore, DHA reduced the thermogenic capacity of brown adipocytes derived from C2C12 independent of UCP1 by significantly suppressing (P<0.05) the expression of PGC1α and DIO2 genes and mitochondrial biogenesis by down‐regulation the expression of PGC1α and TFAM followed by decreasing mDNA copy number (P<0.05). Accordingly, DHA treated group showed an increased accumulation of large monocular lipid droplets, suppressed respiration and spare capacity. EPA, on the other hand, reduced the myogenesis process at the terminal stage by inhibiting the expression of MyoD, MyoG, and Mrf4 (P<0.05), but no significant differences were observed in adipogenesis regulating genes such as PPARγ, C/EBPα, C/EBPβ, and aP2 (P>0.05). Likewise, EPA treatment suppressed the expression of WAT signature genes BMP4, FAT, and ZFP423 (P<0.05) indicating its antagonist effect to DHA. Although PGC1α and TFAM expression were reduced in the EPA treated group, no significant changes in mDNA copy number and mitochondrial function were observed. Unlike DHA treatment, EPA supplementation has no effect on the differential route of C2C12 into brown adipocytes. It is to be included that EPA and DHA may similarly affect the integrity of muscle tissue, but DHA is a potent adipogenic and lipogenic factor that can change the metabolic profile of the body by increasing intramuscular fat.