A method for the estimation of the pentose phosphate cycle of glucose metabolism in liver

1. Investigations of the mechanism of the non-oxidative segment of the pentose phosphate cycle in isolatd hepatocytes by prediction-labelling studies following the metabolism of [2-14C]-, [5-14C]- and [4,5,6-14C]glucose are reported. The 14C distribution patterns in glucose 6-phosphate show that the reactions of the L-type pentose pathway in hepatocytes. 2. Estimates of the quantitative contribution of the L-type pentose cycle are the exclusive form of the pentose cycle to glucose metabolism have been made. The contribution of the L-type pentose cycle to the metabolism of glucose lies between 22 and 30% in isolated hepatocytes. 3. The distribution of 14C in the carbon atoms of glucose 6-phosphate following the metabolism of [4,5,6-14C]- and [2-14C]glucose indicate that gluconeogenesis from triose phosphate and non-oxidative formation of pentose 5-phosphate do not contribute significantly to randomization of 14C in isolated hepatocytes. The transaldolase exchange reaction between fructose 6-phosphate and glyceraldehyde 3-phosphate is very active in these cells.

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Interrelationship and control of glucose metabolism and lipogenesis in isolated fat-cells. Effect of the amount of glucose uptake on the rates of the pentose phosphate cycle and of fatty acid synthesis

Biochemical Journal ◽

10.1042/bj1281089 ◽

1972 ◽

Vol 128 (5) ◽

pp. 1089-1096 ◽

Cited By ~ 34

Author(s):

H. Kather ◽

M. Rivera ◽

K. Brand

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Glucose Metabolism ◽

Glucose Uptake ◽

Fatty Acid Synthesis ◽

Acid Synthesis ◽

Pentose Phosphate ◽

Fat Cells ◽

Pentose Phosphate Cycle ◽

Wide Range

In order to study the quantitative relationship between fatty acid synthesis and pentose phosphate-cycle activity under different hormonal and dietary conditions affecting the extent of glucose uptake, cells isolated from rat epididymal adipose tissue were incubated in bicarbonate buffer containing [U-14C]-, [1-14C]- or [6-14C]-glucose. From the amount of glucose taken up, the production of lactate and pyruvate, and the incorporation of 14C from differently labelled [14C]glucose into CO2, fatty acids and glyceride glycerol, the rates of glucose metabolism via different pathways and the extent of lipogenesis under various experimental conditions were determined. The contribution of the pentose phosphate-cycle to glucose metabolism under normal conditions was calculated to be 8%. Starvation and re-feeding, and the presence of insulin, caused an enhancement of glucose uptake, pentose phosphate-cycle activity and fatty acid synthesis. Plots of both pentose phosphate-cycle activity and fatty acid synthesis versus glucose uptake revealed that the extent of glucose uptake, over a wide range, determines the rates of fatty acid synthesis and glucose metabolism via the pentose phosphate cycle. A balance of formation and production of nicotinamide nucleotides in the cytoplasm was established. The total amount of cytoplasmic NADH and NADPH formed was only in slight excess over the hydrogen equivalents required for the synthesis of fatty acids, glyceride glycerol and lactate. Except in cells from starved animals, the pentose phosphate cycle was found to provide only about 60% of the NADPH required for fatty acid synthesis. The results are discussed with respect to an overall control of the different metabolic and biosynthetic reactions in the fat-cells by the amount of glucose transported into the cell.

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Mechanism and contribution of the pentose phosphate cycle to glucose metabolism in epididymal fat tissue

International Journal of Biochemistry ◽

10.1016/0020-711x(82)90136-7 ◽

1982 ◽

Vol 14 (3) ◽

pp. 171-186 ◽

Cited By ~ 14

Author(s):

Peter F. Blackmore ◽

John F. Williams ◽

P.J. Schofield ◽

P.A. Power

Keyword(s):

Glucose Metabolism ◽

Pentose Phosphate ◽

Fat Tissue ◽

Pentose Phosphate Cycle ◽

Epididymal Fat

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Interrelationship and control of glucose metabolism and lipogenesis in isolated fat-cells. Control of pentose phosphate-cycle activity by cellular requirement for reduced nicotinamide adenine dinucleotide phosphate

Biochemical Journal ◽

10.1042/bj1281097 ◽

1972 ◽

Vol 128 (5) ◽

pp. 1097-1102 ◽

Cited By ~ 38

Author(s):

H. Kather ◽

M. Rivera ◽

K. Brand

Keyword(s):

Fatty Acid ◽

Glucose Metabolism ◽

Fatty Acid Synthesis ◽

Nicotinamide Adenine Dinucleotide Phosphate ◽

Acid Synthesis ◽

Pentose Phosphate ◽

Fat Cells ◽

Isolated Fat Cells ◽

Pentose Phosphate Cycle ◽

Phenazine Methosulphate

By using inhibitors and stimulators of different metabolic pathways the interdependence of the pentose phosphate cycle and lipogenesis in isolated fat-cells was studied. Rotenone, which is known to inhibit electron transport in the respiratory chain, blocked glucose breakdown at the site of pyruvate dehydrogenase. Consequently, because of the lack of acetyl-CoA, fatty acid synthesis was almost abolished. A concomitant decrease in pentose phosphate-cycle activity was observed. Phenazine methosulphate stimulated pentose phosphate-cycle activity about five- to ten-fold without a considerable effect on fatty acid synthesis. The influence of rotenone on both the pentose phosphate cycle and lipogenesis could be overcome by addition of phenazine methosulphate, indicating that rotenone has no direct effect on these pathways. The decreased rate of the pentose phosphate cycle in the presence of rotenone therefore has to be considered as a consequence of decreased fatty acid synthesis. The rate of glucose catabolism via the pentose phosphate cycle in adipocytes appears to be determined by the requirement of NADPH for lipogenesis. Treatment of cells with 6-aminonicotinamide caused an accumulation of 6-phosphogluconate, indicating an inhibition of 6-phosphogluconate dehydrogenase. The rate of glucose metabolism via the pentose phosphate cycle as well as the rate of fatty acid synthesis, however, was not affected by 6-aminonicotinamide treatment and could still be stimulated by addition of insulin. Since even in cells from starved animals, in which the pentose phosphate-cycle activity is extremely low, no accumulation of 6-phosphogluconate was observed, it is concluded that the control of this pathway is achieved by the rate of regeneration of NADP at the site of glucose 6-phosphate dehydrogenase.

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Glucose metabolism in Pycnoporus cinnabarinus

Canadian Journal of Microbiology ◽

10.1139/m78-101 ◽

1978 ◽

Vol 24 (5) ◽

pp. 620-622 ◽

Cited By ~ 1

Author(s):

Emiko Hirono ◽

Glaci T. Zancan ◽

Déa Amaral

Keyword(s):

Glucose Metabolism ◽

Enzyme Activities ◽

Pentose Phosphate ◽

Glycolytic Pathway ◽

Pycnoporus Cinnabarinus ◽

Pentose Phosphate Cycle

It was demonstrated by the measurement of enzyme activities and by radiorespirometric assays that the basidiomycete Pycnoporus cinnabarinus metabolizes glucose through the glycolytic pathway and the pentose phosphate cycle.

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Rhythmic glucose metabolism regulates the redox circadian clockwork in human red blood cells

Nature Communications ◽

10.1038/s41467-020-20479-4 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Ratnasekhar Ch ◽

Guillaume Rey ◽

Sandipan Ray ◽

Pawan K. Jha ◽

Paul C. Driscoll ◽

...

Keyword(s):

Glucose Metabolism ◽

Red Blood Cells ◽

Blood Cells ◽

Mammalian Cells ◽

Metabolic Flux ◽

Pentose Phosphate ◽

Human Red Blood Cells ◽

Integral Process ◽

Metabolic Oscillations ◽

Human Rbcs

AbstractCircadian clocks coordinate mammalian behavior and physiology enabling organisms to anticipate 24-hour cycles. Transcription-translation feedback loops are thought to drive these clocks in most of mammalian cells. However, red blood cells (RBCs), which do not contain a nucleus, and cannot perform transcription or translation, nonetheless exhibit circadian redox rhythms. Here we show human RBCs display circadian regulation of glucose metabolism, which is required to sustain daily redox oscillations. We found daily rhythms of metabolite levels and flux through glycolysis and the pentose phosphate pathway (PPP). We show that inhibition of critical enzymes in either pathway abolished 24-hour rhythms in metabolic flux and redox oscillations, and determined that metabolic oscillations are necessary for redox rhythmicity. Furthermore, metabolic flux rhythms also occur in nucleated cells, and persist when the core transcriptional circadian clockwork is absent in Bmal1 knockouts. Thus, we propose that rhythmic glucose metabolism is an integral process in circadian rhythms.

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ROS/PI3K/Akt and Wnt/β-catenin signalings activate HIF-1α-induced metabolic reprogramming to impart 5-fluorouracil resistance in colorectal cancer

Journal of Experimental & Clinical Cancer Research ◽

10.1186/s13046-021-02229-6 ◽

2022 ◽

Vol 41 (1) ◽

Author(s):

Shuohui Dong ◽

Shuo Liang ◽

Zhiqiang Cheng ◽

Xiang Zhang ◽

Li Luo ◽

...

Keyword(s):

Colorectal Cancer ◽

Glucose Metabolism ◽

Pentose Phosphate ◽

Metabolic Reprogramming ◽

Cell Models ◽

Primary Tumors ◽

Pharmacological Inhibition ◽

Potential Biomarker

Abstract Background Acquired resistance of 5-fluorouracil (5-FU) remains a clinical challenge in colorectal cancer (CRC), and efforts to develop targeted agents to reduce resistance have not yielded success. Metabolic reprogramming is a key cancer hallmark and confers several tumor phenotypes including chemoresistance. Glucose metabolic reprogramming events of 5-FU resistance in CRC has not been evaluated, and whether abnormal glucose metabolism could impart 5-FU resistance in CRC is also poorly defined. Methods Three separate acquired 5-FU resistance CRC cell line models were generated, and glucose metabolism was assessed by measuring glucose and lactate utilization, RNA and protein expressions of glucose metabolism-related enzymes and changes of intermediate metabolites of glucose metabolite pool. The protein levels of hypoxia inducible factor 1α (HIF-1α) in primary tumors and circulating tumor cells of CRC patients were detected by immunohistochemistry and immunofluorescence. Stable HIF1A knockdown in cell models was established with a lentiviral system. The influence of both HIF1A gene knockdown and pharmacological inhibition on 5-FU resistance in CRC was evaluated in cell models in vivo and in vitro. Results The abnormality of glucose metabolism in 5-FU-resistant CRC were described in detail. The enhanced glycolysis and pentose phosphate pathway in CRC were associated with increased HIF-1α expression. HIF-1α-induced glucose metabolic reprogramming imparted 5-FU resistance in CRC. HIF-1α showed enhanced expression in 5-FU-resistant CRC cell lines and clinical specimens, and increased HIF-1α levels were associated with failure of fluorouracil analog-based chemotherapy in CRC patients and poor survival. Upregulation of HIF-1α in 5-FU-resistant CRC occurred through non-oxygen-dependent mechanisms of reactive oxygen species-mediated activation of PI3K/Akt signaling and aberrant activation of β-catenin in the nucleus. Both HIF-1α gene knock-down and pharmacological inhibition restored the sensitivity of CRC to 5-FU. Conclusions HIF-1α is a potential biomarker for 5-FU-resistant CRC, and targeting HIF-1a in combination with 5-FU may represent an effective therapeutic strategy in 5-FU-resistant CRC.

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Estrogen Regulates Glucose Metabolism in Cattle Neutrophils Through Autophagy

Frontiers in Veterinary Science ◽

10.3389/fvets.2021.773514 ◽

2021 ◽

Vol 8 ◽

Author(s):

Xinbo Wang ◽

Yuming Zhang ◽

Yansong Li ◽

Mingyu Tang ◽

Qinghua Deng ◽

...

Keyword(s):

Glucose Metabolism ◽

Opposite Effect ◽

Glycogen Synthesis ◽

Perinatal Period ◽

Negative Energy ◽

Pentose Phosphate ◽

Polymorphonuclear Neutrophils ◽

Atp Content ◽

Gsk 3Β ◽

Immune Potential

Hypoglycemia resulting from a negative energy balance (NEB) in periparturient cattle is the major reason for a reduced glycogen content in polymorphonuclear neutrophils (PMNs). The lack of glycogen induces PMNs dysfunction and is responsible for the high incidence of perinatal diseases. The perinatal period is accompanied by dramatic changes in sex hormones levels of which estrogen (17β-estradiol, E2) has been shown to be closely associated with PMNs function. However, the precise regulatory mechanism of E2 on glucose metabolism in cattle PMNs has not been elucidated. Cattle PMNs were cultured in RPMI 1640 with 2.5 (LG), 5.5 (NG) and 25 (HG) mM glucose and E2 at 20 (EL), 200 (EM) and 450 (EH) pg/mL. We found that E2 maintained PMNs viability in different glucose conditions, and promoted glycogen synthesis by inhibiting PFK1, G6PDH and GSK-3β activity in LG while enhancing PFK1 and G6PDH activity and inhibiting GSK-3β activity in HG. E2 increased the ATP content in LG but decreased it in HG. This indicated that the E2-induced increase/decrease of ATP content may be independent of glycolysis and the pentose phosphate pathway (PPP). Further analysis showed that E2 promoted the activity of hexokinase (HK) and GLUT1, GLUT4 and SGLT1 expression in LG, while inhibiting GLUT1, GLUT4 and SGLT1 expression in HG. Finally, we found that E2 increased LC3, ATG5 and Beclin1 expression, inhibited p62 expression, promoting AMPK-dependent autophagy in LG, but with the opposite effect in HG. Moreover, E2 increased the Bcl-2/Bax ratio and decreased the apoptosis rate of PMNs in LG but had the opposite effect in HG. These results showed that E2 could promote AMPK-dependent autophagy and inhibit apoptosis in response to glucose-deficient environments. This study elucidated the detailed mechanism by which E2 promotes glycogen storage through enhancing glucose uptake and retarding glycolysis and the PPP in LG. Autophagy is essential for providing ATP to maintain the survival and immune potential of PMNs. These results provided significant evidence for further understanding the effects of E2 on PMNs immune potential during the hypoglycemia accompanying perinatal NEB in cattle.

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