Department of Surgery and the Gastroenterology Research Unit, Mayo Clinic, Rochester, MN 55905, USA.
Surgery. 2012 Jan;151(1):13-25. doi: 10.1016/j.surg.2011.07.010. Epub 2011 Sep 22.
GLUT2 is translocated to the apical membrane of enterocytes exposed to glucose concentrations >∼50 mM. Mechanisms of GLUT2-mediated glucose uptake in cell culture models of enterocytes have not been studied.
To explore mechanism(s) of glucose uptake in 3 enterocyte-like cell lines.
Glucose uptake was measured in Caco-2, RIE-1, and IEC-6 cell lines using varying concentrations of glucose (0.5-50 mM). Effects of phlorizin (SGLT1 inhibitor), phloretin (GLUT2 inhibitor), nocodazole and cytochalasin B (disrupters of cytoskeleton), calphostin C and chelerythrine (PKC inhibitors), and phorbol 12-myristate 13-acetate (PKC activator) were evaluated.
Phlorizin inhibited glucose uptake in all 3 cell lines. Phloretin inhibited glucose uptake in Caco-2 and RIE-1 cells. Starving cells decreased glucose uptake in Caco-2 and RIE-1 cells. Glucose uptake was saturated at >10 mM glucose in all 3 cell lines when exposed briefly (<1 min) to glucose. After exposure for >5 min in Caco-2 and RIE-1 cells, glucose uptake did not saturate and K(m) and V(max) increased. This increase in glucose uptake was inhibited by phloretin, nocodazole, cytochalasin B, calphostin C, and chelerythrine. PMA enhanced glucose uptake by 20%. Inhibitors and PMA had little or no effect in the IEC-6 cells.
Constitutive expression of GLUT2 in the apical membrane along with additional translocation of cytoplasmic GLUT2 to the apical membrane via an intact cytoskeleton and activated PKC appears responsible for enhanced carrier-mediated glucose uptake at greater glucose concentrations (>20 mM) in Caco-2 and RIE-1 cells. IEC-6 cells do not appear to express functional GLUT2.
GLUT2 易位到暴露于葡萄糖浓度>∼50mM 的肠细胞的顶膜。尚未研究细胞培养模型中肠细胞中 GLUT2 介导的葡萄糖摄取的机制。
探索 3 种肠细胞样细胞系中葡萄糖摄取的机制。
使用不同浓度的葡萄糖（0.5-50mM）在 Caco-2、RIE-1 和 IEC-6 细胞系中测量葡萄糖摄取。评估了根皮苷（SGLT1 抑制剂）、根皮素（GLUT2 抑制剂）、诺考达唑和细胞松弛素 B（细胞骨架破坏剂）、钙泊三醇 C 和石蒜碱（PKC 抑制剂）以及佛波醇 12-肉豆蔻酸 13-乙酸酯（PKC 激活剂）的作用。
根皮苷抑制 3 种细胞系的葡萄糖摄取。根皮素抑制 Caco-2 和 RIE-1 细胞的葡萄糖摄取。饥饿细胞减少 Caco-2 和 RIE-1 细胞的葡萄糖摄取。所有 3 种细胞系在短暂（<1 分钟）暴露于葡萄糖后，>10mM 葡萄糖时葡萄糖摄取达到饱和。在 Caco-2 和 RIE-1 细胞中暴露>5 分钟后，葡萄糖摄取不再饱和，K(m)和 V(max)增加。这种葡萄糖摄取的增加被根皮素、诺考达唑、细胞松弛素 B、钙泊三醇 C 和石蒜碱抑制。PMA 增强葡萄糖摄取 20%。抑制剂和 PMA 在 IEC-6 细胞中几乎没有或没有影响。
在 Caco-2 和 RIE-1 细胞中，顶膜中 GLUT2 的组成型表达以及通过完整的细胞骨架和激活的 PKC 将细胞质 GLUT2 易位到顶膜，似乎负责在更高的葡萄糖浓度（>20mM）下增强载体介导的葡萄糖摄取。IEC-6 细胞似乎不表达功能性 GLUT2。
