Puerariae Lobatae Radix elevated expression levels of OB-R, IRS2, GLUT1 and GLUT2 to regulate glucose metabolism in insulin-resistance HepG2 cells / 中国中药杂志

To observe the anti-hyperglycemic effect of Puerariae Lobatae Radix in hepatocyte insulin resistance(IR) models, and investigate its preliminary molecular mechanism. IR-HepG2 cell model was stably established with 1×10-9 mol•L⁻¹ insulin plus 3.75×10-6 mol•L-1 dexamethasone treatment for 48 h according to optimized protocol in our research group. After IR-HepG2 cells were treated with different concentrations(5%,10% and 15%) of Puerariae Lobatae Radix-containing serum, cell viability was detected by CCK-8 assay; the glucose consumptions in IR-HepG2 cells were separately detected at different time points (12, 15, 18, 21, 24, 30, 36 h) by using glucose oxidase method; intracellular glycogen content was detected by anthrone method; and the protein expression levels of leptin receptor (Ob-R), insulin receptor substrate-2 (IRS2), glucose transporter 1(GLUT1) and GLUT2 were detected by Western blot assay. The results showed that Puerariae Lobatae Radix-containing serum (5%, 10% and 15%) had no significant effect on IR-HepG2 cell viability; 5% and 10% Puerariae Lobatae Radix-containing serum significantly increased glucose consumption of IR-HepG2 cells (P<0.01) at 18, 21 and 24 h; 15% Puerariae Lobatae Radix-containing serum elevated the glucose consumption of IR-HepG2 cells at 15 h (P<0.05), and significantly elevated the glucose consumption at 18, 21, 24 and 30 h (P<0.01) in a dose-dependent manner. The optimized time of anti-hyperglycemic effect was defined as 24 h, and further study showed that Puerariae Lobatae Radix-containing serum could increase intracellular glycogen content after 24 h treatment (P<0.01), and up-regulate IRS2, Ob-R, GLUT1 and GLUT2 protein expression levels. Our results indicated that Puerariae Lobatae Radix-containing serum could achieve the anti-hyperglycemic effect through important PI3K/PDK signaling pathway partially by up-regulating the expression levels of Ob-R and IRS2, GLUT1 and GLUT2 in IR-HepG2 cells, accelerating the glucose transport into hepatocytes and increasing hepatic glycogen synthesis to enhance the anti-hyperglycemic effect of IR-HepG2 cells.

Leptin receptor (Ob-R) mRNA expression and serum leptin concentration in patients with colorectal and metastatic colorectal cancer

The objective of the present study was to investigate the effect of leptin on the progression of colorectal carcinoma to metastatic disease by analyzing the serum leptin concentration and Ob-R gene expression in colon cancer tissues. Tissue samples were obtained from 31 patients who underwent surgical resection for colon (18 cases) and metastatic colon (13 cases) cancer. Serum leptin concentration was determined by an enzyme-linked immunosorbent assay (ELISA) and Ob-R mRNA expression by real-time polymerase chain reaction (RT-PCR) for both groups. ELISA data were analyzed by the Student t-test and RT-PCR data were analyzed by the Mann-Whitney U-test. RT-PCR results demonstrated that mRNA expression of Ob-R in human metastatic colorectal cancer was higher than in local colorectal cancer tissues. On the other hand, mean serum leptin concentration was significantly higher in local colorectal cancer patients compared to patients with metastatic colorectal cancer. The results of the present study suggest a role for leptin in the progression of colon cancer to metastatic disease without weight loss. In other words, significantly increased Ob-R mRNA expression and decreased serum leptin concentration in patients with metastatic colon cancer indicate that sensitization to leptin activity may be a major indicator of metastasis to the colon tissue and the determination of leptin concentration and leptin gene expression may be used to aid the diagnosis.

Expression of OB-R, Regulation of Mitogen Activated Protein Kinase Activity and Maturation by Leptin in Mouse Oocytes / 대한불임학회지

OBJECTIVE: To verify the expression of leptin receptor (OB-R) in oocytes and preimplantation embryos, the involvement of mitogen activated protein kinase (MAPK or Erk1/2) in the leptin signaling, and effect of leptin on the oocyte maturation in mice. METHOD: RT-PCR analysis of OB-R was conducted in germinal vesicle (GV)-intact and MII stage oocytes, and 1, 2, 8-cell embryos and blastocysts. Germinal vesicle breakdown (GVB), polar body extrusion, monitored in the presence or absence of leptin (1 microM). Following the leptin treatment, temporal changes in MAPK activity were verified by immunoprecipitation and in vitro kinase assay in MII oocytes. RESULTS: The expression of OB-R mRNA was found in GV and MII oocyte but not in the embryos. MAPK activity of the MII oocytes was significantly increased by brief incubation in the HTF supplemented with leptin (1 microM). Priming of PD098059, a MEK inhibitor to leptin treatment attenuated the activation of MAPK by leptin in MII oocytes. Following 24 hrs of culture of the GV oocytes, leptin significant increased the GVB and 1st polar body extrusion. CONCLUSION: This result suggested that functional interaction between leptin and OB-R resulted in potentiation of MAPK (Erk1/2) activity in MII oocytes through MEK activation and that leptin might be a local regulator of meiotic maturation of the mouse oocytes.