scholarly journals Coupled Glucose Transport and Metabolism in Cultured Neuronal Cells: Determination of the Rate-Limiting Step

1995 ◽  
Vol 15 (5) ◽  
pp. 814-826 ◽  
Author(s):  
Richard R. Whitesell ◽  
Michael Ward ◽  
Anthony L. McCall ◽  
Daryl K. Granner ◽  
James M. May
Keyword(s):  
Glucose Transport ◽  
Glucose Utilization ◽  
Neuroblastoma Cell ◽  
Neuronal Cells ◽  
Neuronal Cell ◽  
Cell Types ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Intracellular Glucose

In brain and nerves the phosphorylation of glucose, rather than its transport, is generally considered the major rate-limiting step in metabolism. Since little is known regarding the kinetic coupling between these processes in neuronal tissues, we investigated the transport and phosphorylation of [2-3H]glucose in two neuronal cell models: a stable neuroblastoma cell line (NCB20), and a primary culture of isolated rat dorsal root ganglia cells. When transport and phosphorylation were measured in series, phosphorylation was the limiting step, because intracellular glucose concentrations were the same as those outside of cells, and because the apparent Km for glucose utilization was lower than expected for the transport step. However, the apparent Km was still severalfold higher than the Km of hexokinase I. When [2-3H]glucose efflux and phosphorylation were measured from the same intracellular glucose pool in a parallel assay, rates of glucose efflux were three- to-fivefold greater than rates of phosphorylation. With the parallel assay, we observed that activation of glucose utilization by the sodium channel blocker veratridine caused a selective increase in glucose phosphorylation and was without effect on glucose transport. In contrast to results with glucose, both cell types accumulated 2-deoxy-d-[14C]glucose to concentrations severalfold greater than extracellular concentrations. We conclude from these studies that glucose utilization in neuronal cells is phosphorylation-limited, and that the coupling between transport and phosphorylation depends on the type of hexose used.

In vivo location of the rate-limiting step of hexose uptake in muscle and brain tissue of rats

1991 ◽  
Vol 261 (3) ◽  
pp. E337-E347 ◽  
Author(s):  
S. M. Furler ◽  
A. B. Jenkins ◽  
L. H. Storlien ◽  
E. W. Kraegen
Keyword(s):  
Glucose Utilization ◽  
Quadriceps Muscle ◽  
Relative Contribution ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Red Muscle ◽  
Hexose Uptake ◽  
Rate Limiting ◽  
Intracellular Glucose

The uptake of glucose proceeds via facilitated transport from the plasma followed by phosphorylation of intracellular glucose. We have quantified the relative contribution of transport and phosphorylation to the overall rate of hexose utilization into the quadriceps muscle (red and white) and cerebellum of rats anesthetized with pentobarbital sodium. The method employed simultaneous infusions of radiolabeled 3-O-methyl-D-glucose and 2-deoxy-D-glucose. Results were expressed in terms of a parameter ft*, which has theoretical limits of 0 and 1 corresponding to phosphorylation and transport limitation, respectively. In cerebellum, basal rates of transport and phosphorylation were comparable (ft* = 0.32 +/- 0.02). Under conditions of hyperglycemia plus maximum insulin stimulation, phosphorylation limited glucose utilization to a greater extent (ft* = 0.12 +/- 0.02). No effect of hyperinsulinemia alone was observed. In red muscle, transport determined overall glucose utilization in the basal (ft* = 0.96 +/- 0.05) and euglycemic insulin-stimulated states (ft* = 0.90 +/- 0.02). A shift of the rate-limiting step from transport toward phosphorylation was observed in insulin-stimulated red muscle when blood glucose (ft* = 0.64 +/- 0.05) or epinephrine levels (ft* = 0.66 +/- 0.07) were elevated. Neither effect was seen in white muscle. We conclude that the transport step dominates but is not the only determinant of muscle hexose utilization under all conditions.

scholarly journals Mechanistic insights into the protective roles of polyphosphate against amyloid cytotoxicity

2019 ◽  
Vol 2 (5) ◽  
pp. e201900486 ◽  
Author(s):  
Justine Lempart ◽  
Eric Tse ◽  
James A Lauer ◽  
Magdalena I Ivanova ◽  
Alexandra Sutter ◽  
...  
Keyword(s):  
Extracellular Space ◽  
Therapeutic Strategy ◽  
Neuronal Cells ◽  
Lewy Bodies ◽  
Fibril Formation ◽  
Amyloid Protein ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Fibril Morphology ◽  
Rate Limiting

The universally abundant polyphosphate (polyP) accelerates fibril formation of disease-related amyloids and protects against amyloid cytotoxicity. To gain insights into the mechanism(s) by which polyP exerts these effects, we focused on α-synuclein, a well-studied amyloid protein, which constitutes the major component of Lewy bodies found in Parkinson’s disease. Here, we demonstrate that polyP is unable to accelerate the rate-limiting step of α-synuclein fibril formation but effectively nucleates fibril assembly once α-synuclein oligomers are formed. Binding of polyP to α-synuclein either during fibril formation or upon fibril maturation substantially alters fibril morphology and effectively reduces the ability of α-synuclein fibrils to interact with cell membranes. The effect of polyP appears to be α-synuclein fibril specific and successfully prevents the uptake of fibrils into neuronal cells. These results suggest that altering the polyP levels in the extracellular space might be a potential therapeutic strategy to prevent the spreading of the disease.

scholarly journals Glucose transport as rate-limiting step in the growth of Escherichia coli on glucose

1976 ◽  
Vol 156 (2) ◽  
pp. 477-480 ◽  
Author(s):  
D Herbert ◽  
H L Kornberg
Keyword(s):  
Escherichia Coli ◽  
Continuous Culture ◽  
Glucose Transport ◽  
Growth Rates ◽  
Glucose Limitation ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Wide Range ◽  
Rate Limiting

Over a wide range of growth rates, two strains of Escherichia coli growing aerobically in continuous culture under glucose limitation utilized glucose at rates identical with those at which cells harvested from the chemostats transported [14C]glucose.

THE EFFECT OF INSULIN ON HUMAN ADIPOSE TISSUE

1964 ◽  
Vol 42 (11) ◽  
pp. 1623-1635 ◽  
Author(s):  
A. Kahlenberg ◽  
N. Kalant
Keyword(s):  
Serum Albumin ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Glucose Utilization ◽  
Fatty Acid Content ◽  
Diabetic Patients ◽  
Fat Pad ◽  
Glucose Content ◽  
Rate Limiting ◽  
Intracellular Glucose

The effects of insulin on glucose transport and dissimilation have been studied in the rat fat pad and in human omentum. Intracellular glucose could not be demonstrated in the non-diabetic rat fat pad, with or without insulin. Slices of omentum, obtained during surgery from diabetic and non-diabetic patients, were incubated in a bicarbonate medium with a glucose concentration of 5.6 mM. Omentum from non-diabetic patients had intracellular glucose while diabetic tissue had none. Diabetic tissue had a significantly lower glucose uptake. In both, insulin stimulated glucose uptake in inverse relation to the basal uptake; but for comparable basal uptakes, the response to insulin was decreased in diabetic tissue. Glucose phosphorylation in omental tissue from non-diabetic humans had an apparent Km of 1.10 m M and a Vmax of 1.44 mg/g hour.Insulin (0.1 units/ml), bovine or human serum albumin, or a combination of insulin and bovine albumin, each increased glucose utilization by slices of non-diabetic omentum without affecting the intracellular glucose content or the free fatty acid content. In omental homogenates (cell-free), insulin and bovine serum albumin each increased the glucose utilization. In the presence of albumin, insulin increased the utilization only after the addition of glucose-6-phosphate dehydrogenase and phosphohexose isomerase in amounts sufficient to establish that hexokinase was rate-limiting for glucose utilization.It is concluded that (A) in diabetic human omentum and in normal rat fat pad, transport is rate-limiting in glucose utilization; (B) insulin and albumin each stimulate both transport and phosphorylation in human omentum; (C) in human diabetes, the glucose transport process of omentum has a decreased basal rate and a decreased responsiveness to insulin.

Rate-limiting steps for insulin-mediated glucose uptake into perfused rat hindlimb

1986 ◽  
Vol 250 (1) ◽  
pp. E100-E102 ◽  
Author(s):  
K. Kubo ◽  
J. E. Foley
Keyword(s):  
Glucose Uptake ◽  
Glucose Transport ◽  
Transport System ◽  
Glucose Concentration ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Glucose Transport System ◽  
Glucose Clearance ◽  
Rate Limiting ◽  
Uptake And Metabolism

To determine the glucose and insulin concentrations at which glucose transport is rate limiting for insulin-mediated glucose uptake and metabolism in muscle, glucose clearance was determined in the presence of glucose concentrations ranging from trace to 20 mM and in the absence or presence of insulin in the perfused rat hindlimb. In the absence of insulin and at submaximally stimulating insulin concentrations glucose clearance was constant up to 7 mM glucose and then decreased as the glucose concentration was raised. At maximally stimulating insulin concentrations glucose clearance was constant up to 2 mM glucose and then decreased. The decrease in glucose clearance between 2 and 7 mM glucose in the presence of maximally stimulating insulin concentrations could not be accounted for by competition among glucose molecules for the glucose transport system. The results suggest that at physiological glucose concentrations in the presence of maximally stimulating insulin concentrations the rate-limiting step for insulin-mediated glucose uptake and metabolism in muscle shifts from glucose transport to some step beyond transport.

THE UPTAKE OF GLUCOSE INTO CELLS AND THE ROLE OF INSULIN IN GLUCOSE TRANSPORT

1964 ◽  
Vol 42 (6) ◽  
pp. 933-944 ◽  
Author(s):  
Margaret J. Henderson
Keyword(s):  
Cell Membrane ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Glucose Levels ◽  
Insulin Transport ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Extracellular Glucose ◽  
Rate Limiting

This presentation has been restricted to the role of insulin in glucose transport in muscle cells and deals mainly with experiments using the perfused rat heart. The several possible means for glucose transfer into cells, diffusion, pores, pinocytosis, carriers, and dimerization, have been discussed; and arguments in favor of the carrier theory, namely, specificity, kinetics, inhibition, competition, and counterflow, have been elaborated. Glucose uptake has been considered to consist of three sequential steps: (1) passage of glucose from within the capillary to the cell surface, (2) transport across the cell membrane, and (3) metabolism of glucose within the cell. The first is considered to take place by diffusion and not to be significantly limiting under normal conditions, nor to be influenced by insulin. Transport across the cell membrane is thought to be mainly under the control of insulin and is the major rate-limiting step in glucose uptake when the extracellular glucose levels are in the normal range. Metabolism of glucose within the cell is the major rate-limiting step in glucose uptake when intracellular glucose concentration is so high that its phosphorylation is near saturation.

Defect in glucose metabolism in aortic tissue from alloxan diabetic rabbits

1963 ◽  
Vol 205 (6) ◽  
pp. 1253-1259 ◽  
Author(s):  
Saliha Yalcin ◽  
Albert I. Winegrad
Keyword(s):  
Glucose Utilization ◽  
Aortic Tissue ◽  
Hexokinase Activity ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Glucose Phosphorylation ◽  
Tubular Sections ◽  
Diabetic Rabbits ◽  
Rate Limiting

The glucose, raffinose, and inulin spaces in tubular sections of rabbit thoracic aorta were compared. The glucose space exceeded the raffinose and inulin spaces in tissue from normal rabbits. Insulin in vitro did not alter the relative sizes of the glucose and raffinose spaces in tissue from normal animals. In aortic tissue from alloxan diabetic rabbits, the glucose space exceeded the raffinose space, and the ratio of these spaces was unaltered by insulin in vitro. Hexokinase activity was significantly reduced in tissue from diabetic rabbits. Aortic hexokinase activity was inhibited by glucose 6-phosphate, and no activity resembling hepatic glucokinase was detected. Phosphohexose isomerase and phosphohexokinase activities were not significantly different in normal and diabetic tissues. Transport into cells does not appear to be a rate-limiting step in glucose utilization by aortic tissue from normal or diabetic rabbits incubated in vitro. The impaired glucose utilization previously observed in tissue from diabetic rabbits appears to be related to decreased glucose phosphorylation which may be localized at the hexokinase reaction.

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