The Activation of Peroxisome Proliferator-activated Receptor γ Enhances Insulin Signaling Pathways Via Up-regulating Chemerin Expression in High Glucose Treated HTR-8/SVneo Cells

Abstract

Abstract Objective: To investigate whether peroxisome proliferator-activated receptor γ (PPARγ) agonists, rosiglitazone and GW1929, activate the phosphatidylinositol 3-kinase (PI3K)-AKT/protein kinase B pathway and the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase1/2 (ERK1/2) pathway by upgrading the expression of chemerin. Methods: The HTR-8/SVneo trophoblastic cells were cultured in vitro in high glucose concentration (25 mmol/L) to mimic gestational diabetic phenotypes. We transfected small interfering RNA into HTR-8/SVneo cells to silence two receptors of chemerin, that are chemokine-like receptor 1 (CMKLR1) and G protein-coupled receptor1 (GPR1). And recombinant human chemerin, PPARγ agonists (rosiglitazone, 10 μmol/L and GW1929, 10 μmol/L) and PPARγ inhibitor (GW9662, 5 μmol/L) were additionally added to the medium, respectively. The existence of chemerin was verified by immunocytochemistry, and the expressions of PPARγ, chemerin, and its receptors as well as insulin signaling-related factors PI3K, AKT2, and MAPK (ERK1/2) were detected by real time quantitative-polymerase chain reaction and western blot. Results: Chemerin existed in the HTR-8/SVneo cells. Effects of chemerin on PI3K-AKT pathway and MAPK (ERK1/2) pathway were dependent on the density of chemerin. When rosiglitazone and GW1929 were added to the medium, the mRNA levels of PI3K, AKT2, and MAPK1 were upregulated (P < 0.05). Conversely, GW9662 downregulated the mRNA levels of AKT2 and MAPK1 (P < 0.05). Rosiglitazone and GW1929 increased the protein levels of PPARγ, chemerin, CMKLR1 and GPR1 (P < 0.05). Rosiglitazone and GW1929 had no effect on the expression of PI3K p110β and phospho-AKT2 without CMKLR1 (P > 0.05). Meanwhile, the expression of phospho-ERK2 remained unaffected in the absence of GPR1 (P > 0.05). Conclusion: Both rosiglitazone and GW1929 have the effect of improving insulin signaling pathways via upgrading the level of chemerin in high glucose treated HTR-8/SVneo cells.