Glucose transporter isoform-3 (GLUT3) is the trophoblastic facilitative glucose transporter. To investigate the role of this isoform in embryonic development, we created a novel GLUT3-null mouse and observed arrested early embryonic development and loss at neurulation stage when both alleles were mutated. This loss occurred despite the presence of other related isoforms, particularly GLUT1. In contrast, when a single allele was mutated, despite increased embryonic cell apoptosis, adaptive changes in the subcellular localization of GLUT3 and GLUT1 in the preimplantation embryo led to postimplantation survival. This survival was compromised by decreased GLUT3-mediated transplacental glucose transport, causing late-gestation fetal growth restriction. This yielded young male and female adults demonstrating catch-up growth, with normal basal glucose, insulin, insulin-like growth factor-I and IGF-binding protein-3 concentrations, fat and lean mass, and glucose and insulin tolerance. We conclude that GLUT3 mutations cause a gene dose-dependent early pregnancy loss or late-gestation fetal growth restriction despite the presence of embryonic and placental GLUT1 and a compensatory increase in system A amino acid placental transport. This critical life-sustaining functional role for GLUT3 in embryonic development provides the basis for investigating the existence of human GLUT3 mutations with similar consequences during early pregnancy.

Glucocorticoid (GC) resistance in children with acute lymphoblastic leukemia (ALL) usually resulted in the failure of treatment. Exploring new agents to overcome GC resistance is important. Here we reported for the first time that low-dose anisomycin has the potential to sensitize GC-resistant T-ALL CEM-C1 cells to dexamethasone (DEX). Compared with the use of DEX or low-dose anisomycin alone, co-treatment with them resulted in a significant increase of growth inhibition, apoptosis and cell cycle arrest in CEM-C1 cells through induction of activated caspase-3 and up-regulation of Bim, p21and p27, and down-regulation of Mcl-1, Bcl-2, c-myc, cyclin A and cyclin D1. Furthermore, co-treatment remarkably activated glucocorticoid receptor (GR), p38-MAPK and JNK, and all of them were canceled only by the GR inhibitor RU486, indicating GR might be an at the upstream of GR-p38-MAPK/JNK pathway. We conclude that low-dose anisomycin sensitizes GC-resistant CEM-C1 cells to DEX and this effect is mediated, at least in part, by activation of the GR-p38-MAPK/JNK signaling pathway.

Although glucocorticoids (GCs) have been used to treat acute lymphoblast leukemia (ALL) for decades, the mechanisms of GC sensitivity and resistance in ALL cells are poorly understood. This study investigated the role and mechanisms of pro-apoptotic protein BIM in apoptosis of GC-sensitive and- resistant ALL cells. The dramatic apoptosis was observed in GC-sensitive CEM-C7 cells after incubated with DEX for 48 h, while not in GC-resistant CEM-C1 cells. The significant up-regulation of BIM in CEM-C7 cells induced by DEX was also observed, but no up-regulation of BIM was detected in DEX-induced CEM-C1 cells. When treated with DEX plus RU486, a glucocorticoid receptor blocker, the apoptosis and BIM expression of CEM-C7 cells were canceled. P38MAPK-blocking pharmacon SB203580 also significantly inhibited the up-regulation of BIM in CEM-C7 cells. These suggested that the absence of BIM up-regulation is one of the important mechanisms of GC resistance, GC-GR conjugation is indispensible in both GC-induced apoptosis and up-regulation of BIM, and p38 MAPK signal pathway is also involved in this process.