Telmisartan increases hepatic glucose production via protein kinase C ζ-dependent insulin receptor substrate-1 phosphorylation in HepG2 cells and mouse liver / 영남의대학술지

BACKGROUND: Dysregulation of hepatic glucose production (HGP) contributes to the development of type 2 diabetes mellitus. Telmisartan, an angiotensin II type 1 receptor blocker (ARB), has various ancillary effects in addition to common blood pressure-lowering effects. The effects and mechanism of telmisartan on HGP have not been fully elucidated and, therefore, we investigated these phenomena in hyperglycemic HepG2 cells and high-fat diet (HFD)-fed mice.METHODS: Glucose production and glucose uptake were measured in HepG2 cells. Expression levels of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase α (G6Pase-α), and phosphorylation levels of insulin receptor substrate-1 (IRS-1) and protein kinase C ζ (PKCζ) were assessed by western blot analysis. Animal studies were performed using HFD-fed mice.RESULTS: Telmisartan dose-dependently increased HGP, and PEPCK expression was minimally increased at a 40 μM concentration without a change in G6Pase-α expression. In contrast, telmisartan increased phosphorylation of IRS-1 at Ser302 (p-IRS-1-Ser302) and decreased p-IRS-1-Tyr632 dose-dependently. Telmisartan dose-dependently increased p-PKCζ-Thr410 which is known to reduce insulin action by inducing IRS-1 serine phosphorylation. Ectopic expression of dominant-negative PKCζ significantly attenuated telmisartan-induced HGP and p-IRS-1-Ser302 and -inhibited p-IRS-1-Tyr632. Among ARBs, including losartan and fimasartan, only telmisartan changed IRS-1 phosphorylation and pretreatment with GW9662, a specific and irreversible peroxisome proliferator-activated receptor γ (PPARγ) antagonist, did not alter this effect. Finally, in the livers from HFD-fed mice, telmisartan increased p-IRS-1-Ser302 and decreased p-IRS-1-Tyr632, which was accompanied by an increase in p-PKCζ-Thr410.CONCLUSION: These results suggest that telmisartan increases HGP by inducing p-PKCζ-Thr410 that increases p-IRS-1-Ser302 and decreases p-IRS-1-Tyr632 in a PPARγ-independent manner.

Expression and correlation of PKCζ, MMP-2 and MMP-9 in breast cancer / 临床与实验病理学杂志

Purpose To investigate the expressions of PKCζ, MMP-2, and MMP-9 in breast cancer and the relationship with the inva-sion and metastasis of breast cancer. Methods The expression of PKCζ, MMP-2 and MMP-9 in 100 cases with breast cancer was as-sessed with immunohistochemistry PV 9000 method. PKCζ-siRNA was transfected into MDA-MB-231 cell lines, called siPKCζ/MDA-MB-231. While siRNA construct containing a scrambled sequence was transfected into MDA-MB-231 cells to generate control cells, which were designated as Scr/MDA231 cells. Western blotting was used to measure the expression of PKCζ in transfected cells, and the Transwell invasion assay was used to detect the invasion ability in vitro. The content of MMP-2, MMP-9 were measured by ELISA. Results The expression rates of PKCζ, MMP-2 and MMP-9 in breast cancer tissues were 62.5%, 37.5% and 32.5%, and there were significant differences among them (P0.05). The expres-sion of PKCζ, MMP-2 and MMP-9 were lower in siPKCζ/ MDA-MB-231 group than those in scr/ MDA-MB-231 group, and the in vitro invasion ability was significantly decreased (P<0.05). Conclusions PKCζ can promote the invasion and metastasis of breast canc-er, and correlated with the expression of MMP-2, MMP-9(P<0.05).