Saturated fatty acid palmitate-induced insulin resistance is accompanied with myotube loss and the impaired expression of health benefit myokine genes in C2C12 myotubes

Abstract

BackgroundExcessive circular fatty acid, particlarly saturated fatty acid, can result in insulin resistance in skeletal muscle, but other adverse effects of fatty acid accumulation in myocytes remain unclear.MethodsDifferentiated C2C12 myotubes were used. The effects of palmitate on cell viability, glucose uptake, gene expression and myotube loss were evaluated by MTT assay, 2NBDG uptake, qRT-PCR, Western Blot and crystal staining-based myotube counting, respectively. In some expreiments, oleate was administrated, or the inhibitors of signaling pathways were applied.ResultsPalmitate-induced cellular insulin resistance was clarified by the reduced Akt phosphorylation, glucose uptake and Glut4 expression. Palmitate-caused myotube loss was clearly observed under microscope and proved by myotube counting and expression analysis of myotube marker genes. Moreover, palmitate-induced transcriptional suppression of three health benefit myokine genes (FNDC5, CTRP15 and FGF21) was found, and the different involvement of p38 and PI3K in the transcription of these genes was noticed.ConclusionsPalmitate-induced insulin resistance accompanys myotube loss and the impaired expression of FNDC5, CTRP15 and FGF21genes in C2C12 myotubes. These results provide novel evidence indicating the negative role of high concentration of palmitate in myotubes.

Aspalathin improves glucose and lipid metabolism in 3T3‐L1 adipocytes exposed to palmitate

“…In this study, the addition 0.75 mM palmitate significantly reduced insulin‐stimulated glucose uptake in 3T3‐L1 adipocytes confirming reduced insulin sensitivity without affecting the cell density. A similar reduction in glucose uptake by palmitate in C2C12 myotubules and in C3A liver cells have previously been reported at a concentration range of 0.1 to 0.6 mM and at a concentration of 0.5 mM, respectively. Adding GRE and ASP to the media of palmitate‐induced insulin resistant 3T3‐L1 adipocytes fully restored glucose uptake and insulin responsiveness.…”

Palmitate exerts opposite effects on proliferation and differentiation of skeletal myoblasts

“…The onset of myocyte fusion and myotube number were similar in control and fatty acid-treated cultures (Figure 6), indicating proper dynamics of early myogenesis, similar to that described previously (Ferri et al, 2009). Interestingly, Yang et al (2013) recently found negative effects of high palmitate (0.2-0.6 mmol/l) on C2C12 myotubes, manifested by drop in expression of late myogenic markers (myosin heavy chain 2b and muscle creatine kinase), health benefit myokines (FGF21, FnDC5, CTRP15) and an increase in proteolytic system expression. Fatty acid-induced stimulation of protein degradation through the ubiquitin-proteasome pathway, as well as an inhibition of protein synthesis through the increased phosphorylation of eukaryotic initiation factor 2 (eIF2) in skeletal muscle cells have already been described (Zhou et al, 2007).…”

Ameliorative effect of Ruellia tuberosa L. on hyperglycemia in type 2 diabetes mellitus and glucose uptake in mouse C2C12 myoblasts

“…This phenomenon may be because C2C12 cells uptake of glucose has been saturated, leading to cellular uptake of fluorescent glucose 2‐NBDG has been metabolically utilized by cells to reduce the amount of fluorescence. Finally, in accordance with previous studies (Arora & Dey, 2014; Yang et al., 2013), follow‐up experiments were performed with 100 μM of 2‐NBDG for 30 min.…”