This study aimed to investigate the function of fructose-1, 6-bisphosphatase 1 (FBP1) in regulating cell growth and metabolism through hypoxia-inducible factor 1α (HIF-1α)-dependent hypoxic response in breast cancer cells. Two human breast carcinoma cell lines, including luminal-like cell line MCF-7 and basal-like cell line MDA-MB-468, were cultured under hypoxia condition, then the expressions of FBP1 and HIF-1α were detected by western blotting. In addition, up-regulated FPB1 in MDA-MB-468 cells were induced by lentivirus. Next, cell growth, migration and glucose metabolism were evaluated by MTT assay, Transwell and commercial kits, as well as the expressions of HIF-1α target genes, including pyruvate dehydrogenase kinase 1 (PDK1), lactate dehydrogenase A (LDHA), glucose transporter 1 (GLUT1) and vascular endothelial growth factor (VEGF) were detected by RT-qPCR. Furthermore, chromatin immunoprecipitation was used to estimate whether the hypoxia response elements (HREs) of PDK1, LDHA, GLUT1 and VEGF promoters were incorporated with FBP1. FBP1 was downregulated in MDA-MB-468 cells compared with MCF-7 cells. Overexpression of FBP1 in MDA-MB-468 cells reduced cell growth (p < 0.05) and migration (p < 0.05) as well as glycose consumption (p < 0.05) and lactate production (p < 0.05). In addition, overexpressed FBP1 inhibited HIF-1α protein expression and the mRNA levels of PDK1, LDHA, GLUT1 and VEGF (p < 0.05) under hypoxia condition. Also, FBP1 was revealed to have a concrete connection with PDK1. This study reveal that overexpressed FBP1 may repress tumor growth, migration and glycolysis via targeting HIF-1α in BLBC.
The pancreatic B-cell GLUT2 transporter and glucose metabolism were examined in isolated rat islets subjected to treatments affecting insulin secretion. Diazoxide was used to inhibit, while glipizide or depolarization of the plasma membrane with a high extracellular K + concentration were used to stimulate insulin release in short-term experiments. Islet GLUT2 and insulin were determined by quantitative immunohistochemistry and GLUT2 was also determined by Western blot analysis. Islet net glucose uptake and glucose oxidation were measured using radioactively labelled glucose. Exposure of the islets to diazoxide was associated with a marked increase in the B-cell plasma membrane staining for GLUT2 and increased net glucose uptake. Glucose oxidation was not changed, which may reflect a lowered energy requirement. Conversely, islets subjected to a stimulated insulin secretion with glipizide or a high extracellular K + concentration showed a reduced staining of the GLUT2 transporter. The net glucose uptake and glucose oxidation were also reduced. In islets exposed to the high K + concentration no change in the molecular weight or phosphorylation of GLUT2 was observed but a lesser amount of the transporter was found by Western blot analysis. Thus, GLUT2 and glucose uptake in the pancreatic B-cell are modified by the secretory process, which suggests that changes in the glucose transporter have a functional role in normal B-cell physiology.
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