Insulin and LiCl Synergistically Rescue Myogenic Differentiation of FoxO1 Over-Expressed Myoblasts

Abstract

Most recent studies reported that FoxO1 transcription factor was a negative regulator of myogenesis under serum withdrawal condition, a situation not actually found in vivo. Therefore, the role of FoxO1 in myogenesis should be re-examined under more physiologically relevant conditions. Here we found that FoxO1 was preferentially localized to nucleus in proliferating (PMB) and confluent myoblasts (CMB) and its nuclear exclusion was a prerequisite for formation of multinucleated myotubes (MT). The nuclear shuttling of FoxO1 in PMB could be prevented by leptomycin B and we further found that cytoplasmic accumulation of FoxO1 in myotubes was caused by the blockade of its nuclear import. Although over-expression of wildtype FoxO1 in C2C12 myoblasts significantly blocked their myogenic differentiation under serum withdrawal condition, application of insulin and LiCl, an activator of Wnt signaling pathway, to these cells successfully rescued their myogenic differentiation and generated myotubes with larger diameters. Interestingly, insulin treatment significantly reduced FoxO1 level and also delayed nuclear re-accumulation of FoxO1 triggered by mitogen deprivation. We further found that FoxO1 directly repressed the promoter activity of myogenic genes and this repression can be relieved by insulin and LiCl treatment. These results suggest that FoxO1 inhibits myogenesis in serum withdrawal condition but turns into a hypertrophy potentiator when other myogenic signals, such as Wnt and insulin, are available.

Disruption of nuclear factor (erythroid‐derived‐2)‐like 2 antioxidant signaling: a mechanism for impaired activation of stem cells and delayed regeneration of skeletal muscle

“…The reason for decreased MyoD transcript and protein expression in Nrf2 2/2 mice during the early stage of differentiation could be attributed to the decreased Pax3/7 levels that coordinately recruit RNA pol-II and form a preinitiation complex at the MyoD promoter to induce its transcription (56). In addition, it has been shown that depletion of GSH and the resultant oxidative intracellular environment impairs the differentiation process of C2C12 myoblasts by reducing MyoD and myogenin expression (57)(58)(59)(60) .B ec auselo ssofNr f 2iskn o w nt odisturb the GSH-redox homeostasis, it could impact the MyoD and myogenin expression, thus delaying the differentiation process during CTX injury in TA muscles. Histologic analysisdemonstratedthattheimprovementofTAmuscle morphology was more rapid in WT with d 4 of recovery similar to d 8 in Nrf2 2/2 (Fig.…”

Chemerin inhibition of myogenesis and induction of adipogenesis in C2C12 myoblasts

“…The differentiation of skeletal muscle cells is largely controlled by the musclerestricted basic helix-loop-helix transcription factors MyoD, Myogenin, myf5, and MRF4, which further regulate the expression of muscle determination, or the differentiation required of genes (Rawls et al, 1995). Many peptidic factors are able to stimulate myoblast proliferation or differentiation through signal transduction pathways (Wu et al, 2014). In our results, Chemerin exposure in C2C12 myotubes reduced the muscle specific Adipose tissue infiltration into skeletal muscle is demonstrated in Myogenin, Myf5, MyoD knockout or Myf5/MyoD compound mutants that are characterized by the defective differentiation of satellite cells (Gayraud-Morel et al, 2007).…”

Bioengineered human skeletal muscle with a Pax7+ satellite cell niche capable of functional regeneration

“…The roles of these components are broad with protection from redox stress and provision of trace nutrients likely to promote cell survival and lead to increased cell numbers (Shaban et al, 2017). Growth factors and steroid hormones are more likely to have cell type specific effects, with insulin having been shown in myoblasts to increase fusion and the expression of myogenic genes, as well as driving proliferation (Saini et al, 2018;Wu et al, 2014). Thyroid hormones have well established roles in regulating skeletal muscle growth and differentiation, with hypothyroidism leading to reduced muscle mass (Bloise et al, 2018).…”