IKKβ suppression of TSC1 function links the mTOR pathway with insulin resistance

The proinflammatory cytokine TNF alpha is one of the factors that links obesity-derived chronic inflammation with insulin resistance. Activation of mTOR signaling pathway has been found to suppress insulin sensitivity through serine phosphorylation and the inhibition of IRS1 by mTOR and its downstream effector, S6K1. It remains elusive that whether the mTOR pathway has a role in TNF alpha-mediated insulin resistance. In the present study, we demonstrated that TNF alpha-IKK beta-mediated inactivation of TSC1 resulted in increasing phosphorylation of IRS1 serine 307 and serine 636/639, impaired insulin-induced glucose uptake, tyrosine phosphorylation of IRS1, and the association between IRS1 and PI3K p85. Furthermore, a higher expression of pIKKss (S 18 1), pTSC1 (S511), and pS6(S240/244) was found in livers obtained from both C57BL/6J mice on a high-fat diet and B6.V-Lep(ob/J) mice. Collectively, dysregulation of the TSC1/TSC2/mTOR signaling pathway by IKK beta is a common molecular switch for both cancer pathogenesis and diet- and obesity-induced insulin resistance.