Overactivation of NF-κB impairs insulin sensitivity and mediates palmitate-induced insulin resistance in C2C12 skeletal muscle cells

Abstract

Lipid-induced insulin resistance is associated with inflammatory state in epidemiological studies. However, it is still unclear whether the activation of NF-κB, a pivotal transcription factor of inflammation, plays a crucial role in mediating skeletal muscle insulin resistance. This study addressed what was the role of NF-κB in lipid-induced insulin resistance and whether NF-κB activation was sufficient to cause insulin resistance in C2C12 myotubes. A 16 h exposure of myotubes to palmitate reduced net insulin-stimulated glucose uptake by 48%, GLUT4 translocation by 52%, Akt phosphorylation by 54%, induced a 1.8-fold increase in insulin-stimulated insulin receptor substrate (IRS) phosphorylation, and doubled NF-κB activation. Myotubes transfected with NF-κB p65 siRNA for 24 h and followed by a treatment with palmitate for 16 h efficiently blocked NF-κB activation, and prevented the detrimental effects of palmitate on the metabolic actions of insulin. Transfection of myotubes with I-κBα siRNA for 24 h also led to a twofold induction of NF-κB activation, and reduced net insulin-stimulated glucose uptake by 30%, GLUT4 translocation by 35%, Akt phosphorylation by 31%, induced a 0.7-fold increase in insulin-stimulated IRS phosphorylation. These findings suggest that NF-κB overexpression per se is sufficient to impair insulin sensitivity and palmitate-induced insulin resistance is mediated by NF-κB in skeletal muscle cells.

GPR119 regulates genetic markers of fatty acid oxidation in cultured skeletal muscle myotubes

“…Pre-treatment with palmitate, a saturated fatty acid, was used to induce a state of relative insulin resistance in C 2 C 12 myotubes as previously described (Rodriguez et al, 2010;Zhang et al, 2010). Consistent with reports of others (Rodriguez et al, 2010) we show that exposure to a high fat environment lead to aberrant expression of genes that regulate skeletal muscle oxidative capacity in this cell line.…”

Palmitate exerts opposite effects on proliferation and differentiation of skeletal myoblasts

“…In fact, several disturbances in hormone signaling, i.e. enhanced phosphorylation of protein kinase C-theta (Wang et al, 2010), increased protein tyrosine phosphatase-1B (Bakhtiyari et al, 2010), decreased phosphorylation of Akt (Feng et al, 2012) or activation of NF-kB (Barma et al, 2009;Zhang et al, 2010;Salvad o et al, 2013), usually attributed to palmitate-induced insulin resistance, could also affect myoblast differentiation. Clarification of this issue requires further investigation, involving transcriptional profiling or proteomic studies.…”

18-Carbon polyunsaturated fatty acids ameliorate palmitate-induced inflammation and insulin resistance in mouse C2C12 myotubes

“…Lipid overload, especially with PA, activates NF-κB transcriptional activity, which results in subclinical inflammation and has been linked to the pathogenesis of IR in skeletal muscle [4,5]. Inhibition of NF-κB activity by pharmacological means or by use of small interfering RNA technology can ameliorate PA-induced proinflammatory cytokine expression and IR [4,5,8]. Previous data showed that oleic acid can prevent PA-induced IL-6 expression and NF-κB activation and can ameliorate PA-induced inhibition of AKT phosphorylation and glucose uptake by insulin stimulation [33].…”

“…Of note, activation of upstream stress kinases such as the mitogenactivated protein kinases (MAPKs) and protein kinase C-θ (PKC-θ) is involved in PA-induced NF-κB activation and proinflammatory cytokine expression in myotubes [4,5]. Moreover, inhibitors of MAPK, PKC-θ, and NF-κB can reverse PA-induced IR in skeletal myotubes [4,8].…”