Glucagon like peptide-1 down-regulates dipeptidyl peptidase-4/nuclear factor-κB signaling pathway to inhibit mouse embryonic fibroblasts inflammation induced by oxidative stress
Objective We investigated the mechanisms of how glucagon-like peptide-1(GLP-1)affects adipose inflammation through the regulation of NADPH oxidase-4(Nox-4)and dipeptidyl peptidase-4(DPP-4)/nuclear factor-κB(NF-κB)signaling pathways.Methods Mouse embryonic fibroblasts(3T3-L1 cells,Procell,CL-0006)were cultured and further divided into a control group,TM group(added 5 μg/ml of the endoplasmic reticulum stress inducer tunicamycin,TM),and GLP-1 group(cells pre-trea-ted with 10 nmol/L GLP-1 for 24 h,then added TM),these three group cultured for 24 h.The expression of DPP-4 was silenced by small interfering RNA(siRNA)in 3T3-L1 adipocytes.All groups total RNA and protein samples were extracted,and their concentrations were determined.Nox-4,GLP-1 receptor(GLP-1 R),NF-κB subunit(p-50,p-65)proteins as well as mRNA and protein expression levels of in-flammatory factors such as monocyte chemotactic protein-1(MCP-1),interleukin-6(IL-6),and tumor nec-rosis factor-α(TNF-α)analyzed by real-time reverse transcription-polymerase chain reaction(RT-PCR)and Western blotting experiments respectively.The comparison of means between groups was performed by ANOVA.Results After the addition of GLP-1 to 3T3-L1 adipocytes,the mRNA expression level of GLP-1 R in the GLP-1 group was higher than that in the TM group(1.10±0.05 vs.0.47±0.07),had a significant difference(F=183.912,P＜0.01);and the mRNA expression levels of DPP-4 and Nox-4 were lower than those in the TM group(2.68±0.30 vs.1.31±0.0.15;2.04±0.0.21 vs.1.38± 0.11),had a significant difference(F=90.196,60.166,P＜0.01).p-50 and p-65 in the GLP-1 group were lower than those in the TM group(1.48±0.23 vs.1.22±0.03;1.66±0.13 vs.1.15±0.06),had a significant difference(F=13.049,73.488,P＜0.01);The mRNA relative expression levels of MCP-1,IL-6 and TNF-α in the GLP-1 group were lower than those in the TM group(1.62±0.18 vs.0.95±0.0.03;1.80±0.32 vs.1.23±0.02;2.05±0.02;1.80±0.32 vs.0.02;2.05±0.31 vs.1.30±0.03),had a significant difference(F=45.140,19.524,35.933,P＜0.01).siDPP-4 knock-down group had lower protein expression levels of p-50 and p-65 than the TM group(1.42±0.07 vs.1.13±0.02;1.59±0.18vs.1.12±0.03),had a significant difference(F=93.111,30.849,P＜0.01);Nox-4 expression(2.13±0.10 vs.1.34±0.05,F=219.708,P＜0.01)and inflammatory factors MCP-1,IL-6,and TNF-α expressions in si-DPP-4 knockdown group were a lower than those in the TM group(1.46±0.06 vs.1.19±0.04,1.79±0.13 vs.1.23±0.05,and 2.26±0.14 vs.1.32± 0.07),had a significant difference(F=87.228,72.369,153.372,P＜0.01).Conclusion GLP-1 in-hibits oxidative stress-induced 3T3-L1 adipocyte inflammation through down regulating the DPP4/NF-κB signaling pathway,and its in-depth mechanism needs to be further investigated.
AdipocytesOxidative stressDipeptidylpeptidase-4/nuclear factor-KB signal pathwayCytokines
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