Saturable and nonsaturable process of sugar uptake: effect of oncogenic transformation in transport and uptake of nutrients

Catabolic control of hybridoma cells by glucose and glutamine limited fed batch cultures

Substrate limited fed batch cultures were used to study growth and overflow metabolism in hybridoma cells. A glucose limited fed batch, a glutamine limited fed batch, and a combined glucose and glutamine limited red batch culture were compared with batch cultures. In all cultures mu reaches its maximum early during growth and decreases thereafter so that no exponential growth and decreases thereafter so that no exponential growth rate limiting, although the glutamine concentration (>0.085mM) was lower than reported K(s) vales and glucose was below 0.9mM; but some other nutrients (s) was the cause as verified by simulations. Slightly more cells and antibodies were produced in the combined fed batch compared with the batch culture. The specific rates for consumption of glucose and glutamine were dramatically influenced in fed batch cultures resulting in major metabolic changes. Glucose limitation decreased lactate formation, but increased glutamine consumption and ammonium formation. Glutamine limitation decreased ammonium and alanine formation of lactate, alanine, and ammonium was negligible in the dual-substrate limited fed batch culture. The efficiency of the energy metabolism increased, as judged by the increase in the cellular yield coefficient for glucose by 100% and for glutamine by 150% and by the change in the metabolic ratios lac/glc, ala/ln, and NH(x)/ln, in the combined fed culture. The data indicate that a larger proportion of consumed glutamine enters the TCA cycle through the glutamate dehydrogenase pathway, which releases more energy from glutamine than the transamination pathway. We suggest that the main reasons for these changes are decreased uptake rates of glucose and glutamine, which in turn lead to a reduction of the pyruvate pool and a restriction of the flux through glutaminase and lactate dehydrogenase. There appears to be potential for further cell growth in the dual-substrate-limited fed batch culture as judged by a comparison of mu in the different cultures. (c) 1994 John Wiley & Sons, Inc.

Possible effects of hepatocyte growth factor for the prevention of peritoneal fibrosis

OBJECTIVE

Some patients who had carried out long-term continuous ambulatory peritoneal dialysis discontinued the treatment because of progressive peritoneal fibrosis. It has been previously reported that transforming growth factor-beta1 (TGF-beta1) is one of the factors that induces peritoneal fibrosis. Also, hepatocyte growth factor (HGF) plays a role in the prevention of fibrosis and in inhibiting TGF-beta1 production. In this study, we examined the effects of HGF on peritoneal fibrosis by TGF-beta1 induced by high concentrations of D-glucose.

DESIGN

We transfected a full-length human HGF cDNA in an expression vector into human peritoneal mesothelial cells (HPMCs) using the calcium phosphate method. Transfected HPMCs were cultured with high concentrations of D-glucose solution and co-cultured with fibroblasts using a transwell system. Cell proliferation was determined using the Tetra Color One method. TGF-beta1 and HGF protein were measured by enzyme-linked immunosorbent assay.

RESULTS

In addition to recombinant HGF, the growth inhibition of HPMCs by high concentration D-glucose or TGF-beta1 was significant. By transfecting HGF cDNA into HPMCs, growth inhibition by high concentration D-glucose was completely restored. Furthermore, the production of TGF-beta1 was also significantly decreased.

CONCLUSION

These results suggested that exogenous HGF could possibly prevent peritoneal fibrosis.

Synthesis and purification of 2-deoxy-2-[18F]fluoro-D-glucose and 2-deoxy-2-[18F]fluoro-D-mannose: characterization of products by 1H- and 19F-NMR spectroscopy

A procedure has been developed that allows the separation of 2-deoxy-2-[18F]fluoro-D-glucose from 2-deoxy-2-[18F]fluoro-D-mannose employing selectively optimized ion-moderated partition chromatography. Both compounds can be obtained with a greater than 98% chemical and radiochemical purity in about one half-life of 18F. Both the alpha- and beta-anomers of both sugars were completely characterized by high-resolution 1H- and 19F-NMR spectroscopy. Various convenient preparation methods for 2-deoxy-2-[18F]fluoro-D-glucose were compared.

The effect of insulin on glucose transport in rabbit erythrocytes and reticulocytes

Insulin binding and 3-0-Methylglucose transport have been studied in erythrocyte- and reticulocyte-enriched fractions of blood cells in order to determine if the increased number of insulin binding sites in reticulocytes is associated with a glucose transport response to insulin. In these experiments rabbit reticulocytes demonstrate an eightfold increase in total insulin receptors when compared to erythrocytes. Glucose transport activity in the erythrocyte has Km of 3.2 mM. Reticulocytes demonstrate a saturable glucose transport activity of lower affinity, Km 18.9 mM. Neither the erythrocyte, nor the the reticulocyte glucose transport activity, was capable of an increased response to insulin. the low affinity glucose transport activity in reticulocytes could allow a fourfold increase in facilitated glucose transport at supraphysiological glucose concentrations that might occur in poorly controlled diabetes mellitus.

Transport of D-glucose by membrane vesicles from normal and avian sarcoma virus-transformed chicken embryo fibroblasts

Transport of D-glucose was examined in membrane vesicles from normal and avian sarcoma virus (ASV)-transformed chicken embryo fibroblasts. The initial rates of D-glucose transport were found to be 3- to 5-fold higher for vesicles from glucose-starved normal cells and ASV-transformed cells when compared with transport rates for vesicles from normal cells and serum-starved normal cells. Cytochalasin B, phloretin, and diethylstilbestrol inhibited the initial rate of transport in all types of vesicles, and 2-deoxyglucose, 3-O-methylglucose, and galactose were competitive inhibitors. At D-glucose concentrations between 0.25 and 5 mM, vesicles from normal and ASV-transformed cells displayed saturation kinetics with a Km value of 5 mM for both types of vesicles, with transformed cell vesicles showing a 3-fold increase in Vmax compared with normal cell vesicles. At D-glucose concentrations between 5 and 25 mM the initial rate of D-glucose transport was proportional to D-glucose concentration. The vesicles also showed an inhibitor-sensitive efflux at rates similar to those observed for influx.

Insulin and growth factors stimulate rapid posttranslational changes in glucose transport in ovarian granulosa cells

The glucose analogues, 3-O-methyl-D-glucose and 2-deoxy-D-glucose, have been used to characterize glucose transport and its regulation by serum and growth factors in monolayer cultures of granulosa cells obtained from bovine ovaries. Uptake of 3-O-methylglucose was shown to be independent of the Na+-gradient, independent of energy, did not show accelerated exchange, and was stereospecific. Serum withdrawal resulted in a biphasic decrease in initial rates of glucose uptake with half-times for the two phases of 50 minutes and 3 hours. Insulin could prevent the decrease in uptake rates with a half-maximum concentration of 10.0 1/8 3 nM. Insulin was shown to stimulate DNA synthesis with a concentration of half-maximum response of 28 nM. Insulin or serum stimulation of 3-O-methylglucose uptakes in serum-starved cells resulted in a two threefold increase in initial rates, with a time for half-maximum stimulation of 3 minutes. The insulin-stimulated increase was insensitive to cycloheximide and cyanide during the first 30 minutes, and this early, rapid stimulation was also produced by brain FGF (fibroblast growth factor), pituitary FGF, epidermal growth factor, calf serum, and some but not all samples of follicular fluid. Insulin also stimulated 2-deoxyglucose and a-aminoisobutyric acid uptake during the first 5 minutes of addition and these early stimulations were shown to be posttranslational changes.

Regulation of ether lipids and their precursors in relation to glycolysis in cultured neoplastic cells

Tumors typically show high rates of glycolysis and elevated levels of ether lipids, particularly the alkyldiacylglycerols; thus, we investigated the relationship between ether lipid accumulation and glucose metabolism in a neoplastic cell line (B2-1). The B2-1 cells grown in 5.5 mM galactose in the absence of glucose produced very low levels of alkyldiacylglycerols, triacylglycerols, lactic acid, and dihydroxyacetone-P. Increasing concentrations of glucose caused a progressive increase in lactic acid, dihydroxyacetone-P, and up to a ten-fold increase in alkyldiacylglycerols and triacylglycerols. Glucose supplements also caused an increased incorporation of [9,10-3H]palmitic acid into alkyldiacylglycerols and triacylglycerols. These metabolic changes appeared to be independent of altered growth rates of the cells. The addition of hexadecanol along with glucose to the cultures resulted in a shorter lag and a more rapid rate of accumulation of alkyldiacylglycerols; hexadecanol supplements alone had no effect. The extent of uptake and oxidation of hexadecanol was similar in both the glucose and galactose-grown cells. These results indicate that the levels of alkyldiacylglycerols in neoplastic cells can be regulated by the extent their precursors are formed from glucose.

Transport and phosphorylation of hexoses in normal and Rous sarcoma virus-transformed chick embryo fibroblasts

Effects of transformation by Rous sarcoma virus on sugar uptake and activity and the subcellular distribution of hexokinase isozymes in chick embryo fibroblasts were examined. Transformation caused a several-fold increase in the maximum velocity for uptake of 2-deoxyglucose without a significant change in Km. Cytochalasin B (CB), was used to differentiate between the effects of transformation on facilitated diffusion and the nonsaturable (CB-insensitive) mode. Transformation was found to stimulate 2-deoxyglucose transport by both mechanisms, but the increase in transport by the CB-insensitive mode was greater. Transformation enhances the activity of hexokinase, the enhancement being confined to the particulate fraction of the enzyme. Heat-inactivation and electrophoretic mobility studies showed that although hexokinase Type I is the major form in both normal and transformed fibroblasts, there is a significant increase in the proportion of the Type II isozyme in the transformed cells.