The Signaling Pathways Of Resistin Downregulating Mitochondrial Contnet

Resistin is an important type of adipokine, which can effect adipose tissue, liver and skeletal muscle. Besides, it is closely related with insulin signaling pathways and inflammatory reaction by influencing glucose and fat metabolism.Consequently, it is involved in the regulation of energy metabolism.Mitochondria are important places for tricarboxylic acid cycle and fat oxidative phosphorylation, which are closely related with energy metabolism. Recent studies have demonstrated that the function of mitochondria was damaged in obese, diabetic people and the ones who had been accompanied with insulin resistance, besides, the content of mitochondria were also diminished in some obeses people.Based on the preview results, we have proved that resistin downregulated the number of mitochondria by the time and dose-dependent and induced fat accumulation. However, the resistin's receptors and the signaling pathways of resistin's effects on mitochondria are still unclear. In our study, we investigated the resistin's possible receptors and the signaling pathways of resistin on mitochondria in detail by using Realtime PCR, Western Blot, dual-luciferase reporter assay system and cell transfection and so on. At last, we got the following results:1. After using TLR4 antibody to incubate hepG2 cells, we found the content of mitochondria were still downregulated by resistin treatment. Besides, We found the content of mitochondria were still downregulated by resistin after using the decorin inhibitor to deal with hepG2 cells. And, the ROR1 was not expressed after resistin administration through gene chip analysis.Thus, we excluded that resistin effected on mitochondria through these three possible receptors in hepG2 cells.2. Resistin increased the level of cAMP, but did not affect the level of cGMP in the hepG2 cells. By the inhibitor treatment and RT-PCR, we proved that resistin activated the protein kinase G (PKG) by activating the protein kinase C (PKC) independent of cGMP.3. By using the gene chip technique and RT-PCR, we proved that resistin played an important role in the NF-kappa B signaling pathway. Overexpressing p65 could diminish mitochondrial content, however, by using RNAi technology to interfere p65 expression, we could block the resistin's functions on mitochonria. In addition, we found that PKG may activate p65 through phosphorylating the Thr464 of p65.4. Overexpression of PGC1? could reverse the resistin's effect on mitochondria. Besides, we found that overexpressing p65 could decrease the pgc1? expression and inhibiting p65 could increase pgcla expression, inversely. Besides, we proved that p65 and PGC1? were combined and competed with each other and resistin enhanced the interaction by PLA experiments. Then, we found resistin could inhibit the activity of pgc1? promoter in dose-dependent manner. And, p65 inhibited the activity of pgc1? promoter by the interaction with PGC1?, as a result, PGC1? could not coactive itself.5. By using RNAi technology, RT-PCR, we explored the possible factor involved in the upstream pathway of PKC. After inhibiting p62 by RNA interfence, we found it could block resistin's effect on mitochondria. Besides, we found TNFR1 may participate in the sigaling pathway of resistin on mitochondria.