Figure 1.

The effects of salicylates on insulin resistance. There is significant overlap between the intracellular events induced by TGs (or FFAs) and TNF regarding the mechanisms of insulin resistance. Both stimuli activate IKK-β and decrease insulin-induced tyrosine phosphorylation of IRS-1; both increase intracellular ceramide concentrations, which leads to inhibition of Akt/protein kinase B activation and inhibition of GLUT-4 translocation. These effects induce a state of insulin resistance. The effects of salicylate compounds on these pathways may be divergent. That is, they may improve insulin resistance by blocking the activation of IKK-β (top), or they may worsen insulin resistance by inhibiting PG synthesis and thus potentiating TNF release (bottom). In addition, inhibition of PG will decrease synthesis of leptin, which is known to improve insulin sensitivity by stimulating IRS-1–associated PI 3-kinase activity. The beneficial effect of leptin on insulin action is thus decreased (bottom).