Introduction
Obesity and obesity-related disease including diabetes mellitus type 2 and metabolic syndrome are among the most common reasons of mortality in modern world. Moreover, obesity promotes development of the latent inflammation in adipose tissue. For efficient treating these disorders, anti-inflammatory signaling agonists can be used as an alternative for traditional anti-inflammatory drugs. To address this question, we studied the influence of anti-inflammatory cytokine IL-4 on insulin signaling in FFA-induced insulin resistance in 3T3-L1 adipocytes.
Methods and materials
Adipogenesis of 3T3-L1 cell was induced by insulin, dexamethasone, rosiglitazone and IBMX according to Zebisch et al, 2012. Insulin resistance in mature 3T3-L1 adipocytes was induced by 24h incubation of the cells with conjugate of palmitic acid with BSA (FFA). Recombinant IL-4 (rIL-4) at concentrations 25, 50 and 100 ng/ml was used as anti-inflammatory signaling agonist. After FFA treatment we stimulated insulin signaling by 20-min adipocyte incubation with 100 nM insulin, then cells were lysed and insulin signaling was measured by immunoblotting to reveal pIRS-Y612, pAkt-S473, pAkt-T308 and pAS160-S318. The influence of rIL-4 on 3T3-L1 adipogenesis was also studied and quantitated by OilRedO staining and real-time PCR of PPARgamma and GLUT4 genes.
Results
We have found that FFA-induced insulin resistance causes a decrease of insulin-induced phosphorylation of all insulin signaling participants tested, namely pIRS-Y612, pAkt-T308, pAkt-S473 and pAS160-S318. Application of rIL-4 doesn’t affect the decrease of insulin signaling in concentrations 25 and 50 ng/ml, but restores normal level of insulin signaling/phosphorylation in concentration 100 ng/ml. rIL-4 also significantly decrease adipogenic capacity of 3T3-L1 preadipocytes at concentration 100 ng/ml.
Conclusion
According to these data we can propose that activation of anti-inflammatory signaling by IL-4 improves insulin sensitivity in 3T3-L1 cells, beneficially affecting cellular homeostasis. This therapeutic approach may be perspective for usage in animal model and clinical applications for treatment of diabetes mellitus type 2.
This work was supported by RFBR grant #17-34-80026.