| Objective To evaluate the expression level of NR2E1 (nuclear receptor subfamily 2, group E, member 1) and its correlation with type 2 diabetes (T2DM). To investigate the role of NR2E1 in cultured β-cells using the mouse pancreatic (3-cell line MIN6 under the condition of glucotoxicity.Methods Plasma and peripheral blood mononuclear cells (PBMCs) were collected from 54 T2DM and 88 healthy individuals. The levels of free fatty acids (FFAs), total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL-c), low density lipoprotein (LDL-c), fasting insulin (FIN), and fasting blood glucose (FBG) were measured. The insulin resistance index was calculated using the homeostasis model assessment (HOMA). NR2E1 in PBMCs were analyzed using real-time RT-PCR and Western blots. Tumor necrosis factor a (TNF-a) and interleukin-6 (IL-6) in the plasma were measured by enzyme-linked immunosorbent assay (ELISA). PBMCs isolated from healthy volunteers were treated with glucose or palmitate for 24h, followed by analysis for the expression level of NR2E1.The amount of TNF-aand IL-6 secreted into the supernatant were measured by ELISA. To further investigate the role of NR2E1, cell viability, cell cycle, apoptosis, and were analyzed by using flow cytometry, the MTT assay, western-blot and reverse transcriptase (RT)-PCR between overexpressing NR2E1 cell line O-NR2E1-MIN6 cells and control Ctrl-MIN6 cells. Upregulating or downregulating NR2E1 expression before exposure to 25 mmol/L glucose, then cells viability and cells apoptosis were measured. mRNA abundance of PDX-1 and PCNA were detected. The phosphorylation of JNK and ERK, and Bcl-2 protein levels were evaluated by Western-blot.Results FIN, FBG, HOMA and TNF-a, IL-6 were significantly higher in diabetic patients, compared to the control group. Levels of NR2E1 were significantly higher in the PBMCs isolated from the diabetic group, compared to the control group. NR2E1 expression was positively correlated with FBG, FIN, HOMA, FFAs, TNF-a and IL-6. Glucose and palmitate treatment significantly increased NR2E1 gene expression and inflammatory cytokines production in PBMCs in vitro. In MIN6 cells, overexpression of NR2E1 promoted cell viability by enhancing the number of cells in S phase and increasing PCNA expression. We also found that overexpression of NR2E1 could increase Bcl-2 expression and decrese the levels of phosphorylated ERK. However, apoptosis rate and levels of PDX-1 expression were not significantly altered in MIN6 cells. Upregulating NR2E1 increased cells viability, declined cell apoptosis in hyperglycemia-treated MN6 cells, whereas downregulating NR2E1 promoted β cells apoptosis under the conditon of hyperglycemia. NR2E1 overproduction increased PDX-1, PCNA mRNA levels in 30mmol/L glucose-treated MIN6 cells, whereas NR2E1 inhibition had the contrary results. Furthermore, NR2E1 decreased phosphorylated JNK and ERK1/2 levels and enhanced Bcl-2 level in the presence of 25 mmol/L glucose.Conclusions Increased NR2E1 level may be closely associated with inflammation and disorder of lipid and glucose metabolism in diabetic patients. NR2E1 is involved in the proliferation and apoptosis of pancreatic beta cells.. Upregulation of NR2E1 expression may reverse the damage of pancreatic beta cells from glucotoxicity... |
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