Presence and differential expression of SGLT1, GLUT1, GLUT2, GLUT3 and GLUT5 hexose-transporter mRNAs in Caco-2 cell clones in relation to cell growth and glucose consumption

Abstract

Seven clones from the Caco-2 cell line, three isolated from passage 29 (PD7, PD10, PF11) and four from passage 198 (TB10, TC7, TF3, TG6), all of them selected on the basis of differences in the levels of expression of sucrase-isomaltase and rates of glucose consumption, were analysed for the expression of hexose-transporter mRNAs (SGLT1, GLUT1-GLUT5) in relation to the phases of cell growth and the associated variations of the rates of glucose consumption. All clones showed a similar pattern of evolution of the rates of glucose consumption, which decreased from the exponential to the late-stationary phase, but differed, in a 1-40-fold range, in the values observed at late postconfluency. According to these values, clones could be divided into high- (PD10, PF11) and low-glucose-consuming cells (PD7, TB10, TC7, TF3 and TG6). GLUT1 and GLUT3 mRNAs were expressed in all clones and showed a similar pattern of evolution: their level decreased, from the exponential to the stationary phase, in close correlation with the decrease in rates of glucose consumption, with only high-glucose-consuming clones maintaining high levels in the stationary phase. In contrast, SGLT1, GLUT2 and GLUT5 mRNAs were only expressed, like sucrase-isomaltase mRNA, in the low-glucose-consuming clones, and their level increased from the exponential to the stationary phase, in parallel with the differentiation of the cells. GLUT4 was undetectable in all the clones. Glucose deprivation generally resulted in a discrete decrease in the levels of all transporter mRNAs in all clones, one exception being GLUT2, which in the high-glucose-consuming clones is only detectable when the cells are grown in low glucose. These clones should be ideal tools with which to study in vitro, at the single-cell level, how these transporters concur to the utilization and transport of hexoses and how their exclusive or co-ordinated expression is regulated.

Regulation of the fructose transporter GLUT5 in health and disease

“…Interestingly, by use if glucokinase activity as an indicator of the rate of glucose metabolism, the intestine can be categorized more like a low-glucose-metabolizing tissue compared with the liver, brain, or adipose tissue in rats fed a carbohydrate diet (1). Although glucose under in vivo conditions does not alter GLUT5 mRNA and protein levels in enterocytes, both glucose and fructose are potent activators of GLUT5 in Caco2 cells (93,94,102,105). Hence, under most conditions, GLUT5 regulation in Caco2 cells does not distinguish between glucose and fructose.…”

“…Since cAMP is involved in GLUT5 regulation in Caco2 cells (93,94,105), increased mRNA stability may result from an inhibitory effect of cAMP on the formation of a complex between the GLUT5 3Ј UTR area and PABP (polyadenylatebinding protein)-interacting protein (Paip2). PABP proteins are found in all eukaryotes and are implicated primarily in mRNA maturation, export, and turnover (141).…”

Insulin Internalizes GLUT2 in the Enterocytes of Healthy but Not Insulin-Resistant Mice

“…The effects of insulin on enterocytes were studied in Caco-2/TC7 cells (15,24), which enabled a separation between the effects of insulin and glucose in vitro. Differentiated Caco-2/TC7 cells segregate sucrase-isomaltase in BBM and NaKATPase in BLM (Supplemental Fig.…”

“…The aim of this study was therefore to analyze the impact of insulin on intestinal sugar absorption, focusing on the localization of GLUT2 in enterocyte membranes in colon carcinoma TC7 subclone (Caco-2/TC7) cells (15) and in vivo in mice. In addition, we aimed to establish whether enterocytes would respond to elevated blood glucose or to plasma insulin under hyperinsulinemic-euglycemic clamp conditions or during the course of a test meal in mice.…”

Differential regulation of the fructose transporters GLUT2 and GLUT5 in the intestinal cell line Caco-2

“…The membrane localization of these transporters is identical with that observed in normal intestinal absorbing cells. However, Caco-2 cells also express GLUTl and GLUT3, which are associated with the fetal and/or transformed phenotype (Mahraoui et al 1992(Mahraoui et al , 1994a. GLUTl was found to be present in the basolateral domain of the cells (Mahraoui eta/.…”