Analysis of glucose metabolism in diabetic rat retinas

2006 ◽  
Vol 290 (6) ◽  
pp. E1057-E1067 ◽  
Author(s):  
M. Shamsul Ola ◽  
Deborah A. Berkich ◽  
Yuping Xu ◽  
M. Todd King ◽  
Thomas W. Gardner ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Glucose Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Lactate Production ◽  
Tricarboxylic Acid ◽  
Diabetic Rats ◽  
Glycolytic Flux ◽  
Acid Cycle

This study was conceived in an effort to understand cause and effect relationships between hyperglycemia and diabetic retinopathy. Numerous studies show that hyperglycemia leads to oxidative stress in the diabetic retinas, but the mechanisms that generate oxidative stress have not been resolved. Increased electron pressure on the mitochondrial electron transfer chain, increased generation of cytosolic NADH, and decreases in cellular NADPH have all been cited as possible sources of reactive oxygen species and nitrous oxide. In the present study, excised retinas from control and diabetic rats were exposed to euglycemic and hyperglycemic conditions. Using a microwave irradiation quenching technique to study retinas of diabetic rats in vivo, glucose, glucose-derived metabolites, and NADH oxidation/reduction status were measured. Studying excised retinas in vitro, glycolytic flux, lactate production, and tricarboxylic acid cycle flux were evaluated. Enzymatically assayed glucose 6-phosphate and fructose 6-phosphate were only slightly elevated by hyperglycemia and/or diabetes, but polyols were increased dramatically. Cytosolic NADH-to-NAD ratios were not elevated by hyperglycemia nor by diabetes in vivo or in vitro. Tricarboxylic acid cycle flux was not increased by the diabetic state nor by hyperglycemia. On the other hand, small increases in glycolytic flux were observed with hyperglycemia, but glycolytic flux was always lower in diabetic compared with control animals. An observed decrease in activity of glyceraldehyde-3-phosphate dehydrogenase may be partially responsible for slow glycolytic flux for retinas of diabetic rats. Therefore, it is concluded that glucose metabolism, downstream of hexokinase, is not elevated by hyperglycemia or diabetes. Metabolites upstream of glucose such as the sorbitol pathway (which decreases NADPH) and polyol synthesis are increased.

scholarly journals Up-regulation of glucose metabolism in Kupffer cells following infusion of tumour necrosis factor

1991 ◽  
Vol 278 (2) ◽  
pp. 515-519 ◽  
Author(s):  
Z Spolarics ◽  
G J Bagby ◽  
C H Lang ◽  
J J Spitzer
Keyword(s):  
Endothelial Cells ◽  
Kupffer Cells ◽  
Tumour Necrosis ◽  
Glucose Oxidation ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Necrosis Factor

Alterations of glucose metabolism and the oxidation of glutamine and palmitate were studied, by using specifically labelled substrates, in freshly isolated Kupffer cells and hepatic endothelial cells after infusion in vivo of human recombinant tumour necrosis factor-alpha (TNF; 7.5 x 10(5) IU/30 min per kg body wt., intravenously). Cells were incubated in a medium containing 5 mM-glucose, 0.4 mM-palmitate, 1 mM-lactate and 0.5 mM-glutamine. Administration of TNF in vivo increased glucose use in Kupffer cells by 70%. Glucose oxidation in the tricarboxylic acid cycle and flux in the Embden-Meyerhof (EM) pathway were elevated by 40 and 80% respectively. Treatment in vitro with 1 microM-phorbol 12-myristate 13-acetate (PMA) resulted in a similar percentage increase in glucose use by Kupffer cells prepared from either saline- or TNF-treated rats. However, PMA increased the activity of the hexose monophosphate shunt (HMS) by 3- and 10-fold in cells isolated from saline- or TNF-infused animals respectively. A phagocyte stimulus in vitro, opsonized zymosan, increased glucose use by 30% and doubled the flux through the HMS in Kupffer cells from saline-infused animals. The activity of the HMS in response to zymosan was increased by 400% after TNF treatment. In endothelial cells, basal glucose utilization was not altered by TNF treatment. PMA increased HMS activity in endothelial cells to a similar degree after saline or TNF infusion. Zymosan, however, increased HMS activity only in endothelial cells from TNF-treated rats. Oxidation of palmitate or glutamine was not affected by TNF treatment either under basal conditions or after challenge in vitro. Our data indicate that, after phagocytosis in vitro or protein kinase C activation, glucose use and flux through the HMS increase in Kupffer cells. This is accompanied by increased glycolytic flux, with no changes in glucose oxidation in the tricarboxylic acid cycle. After TNF exposure, followed by a secondary stimulus, the enhanced glucose use by Kupffer cells is primarily channelled through the HMS pathway. These data suggest that the increased glucose use in vivo by Kupffer cells found after immune-stimulated conditions may subserve primarily the increased need for NADPH and HMS intermediates.

C14-labeled glucose metabolism by bone from normal and parathyroid-treated rats

1965 ◽  
Vol 208 (5) ◽  
pp. 1036-1041 ◽  
Author(s):  
Haripada Chattopadhyay ◽  
Smith Freeman
Keyword(s):  
Glucose Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Bone Matrix ◽  
Tricarboxylic Acid ◽  
Bicarbonate Buffer ◽  
Acid Cycle ◽  
Growing Rats ◽  
Parathyroid Extract ◽  
Tricarboxylic Acid Cycle Intermediates

Calvaria and the metaphyseal and epiphyseal sections of tibia and femora freed of bone marrow from young growing rats were incubated in vitro for 2 hr at 37 C in Krebs-Ringer bicarbonate buffer containing 2 mm glucose. The glucose was labeled either in the 1 position or in the 6 position or uniformly in all positions with C14. The incorporation of C14 into citrate, lactate, and various tricarboxylic acid cycle intermediates was studied. The release of C14O2 and the incorporation of C14 into bone matrix were also measured. Results obtained from bones of untreated control, parathyroid extract-treated, and parathyroidectomized animals were compared. It was found that treatment of animals with parathyroid extract increased the total accumulation of labeled citrate and malate as well as the incorporation of these acids into bone mineral. Bones from extract-treated animals also exhibited a significant decrease in the total accumulation of radioactive fumarate, succinate, and pyruvate. Lactate was the major end product of glucose metabolism, but its accumulation was only slightly influenced by parathyroid extract.

scholarly journals Putrescine catabolism in mammalian brain

1974 ◽  
Vol 144 (1) ◽  
pp. 29-35 ◽  
Author(s):  
N. Seiler ◽  
M. J. Al-Therib
Keyword(s):  
Monoamine Oxidase ◽  
Diamine Oxidase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Mammalian Brain ◽  
Oxidative Deamination ◽  
Acid Cycle ◽  
Degradative Pathway

In contrast with putrescine (1,4-diaminobutane), which is a substrate of diamine oxidase, monoacetylputrescine is oxidatively deaminated both in vitro and in vivo by monoamine oxidase. The product of this reaction is N-acetyl-γ-aminobutyrate. The existence of a degradative pathway in mammalian brain for putrescine is shown, which comprises acetylation of putrescine, oxidative deamination of monoacetylputrescine to N-acetyl-γ-aminobutyrate, transformation of N-acetyl-γ-aminobutyrate to γ-aminobutyrate and degradation of γ-aminobutyrate to CO2 via the tricarboxylic acid cycle.

Glucose utilization by sheep embryos derived in vivo and in vitro

1991 ◽  
Vol 3 (5) ◽  
pp. 571 ◽  
Author(s):  
JG Thompson ◽  
AC Simpson ◽  
PA Pugh ◽  
RW Wright ◽  
HR Tervit
Keyword(s):  
Glucose Oxidation ◽  
Glucose Utilization ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Cell Stage ◽  
Glycolytic Activity ◽  
Total Utilization ◽  
Oxidation Of Glucose

Embryos were collected from superovulated donors at various intervals from onset of oestrus, ranging from Day 1.5 to Day 6. In addition, blastocysts obtained from the culture of 1-cell embryos collected in vivo or of oocytes matured and fertilized in vitro were used to assess the effects of in vitro manipulation and culture on glucose utilization. Glycolytic activity was determined by the conversion of [5-3H]glucose to 3H2O, and oxidation of glucose was determined by the conversion of [U-14C]glucose to 14CO2. Glucose utilization increases significantly from the 8-cell stage and during compaction and blastulation. Glucose oxidation was at a relatively low level (5-12% of total utilization) compared with glycolysis. No difference was observed between the glycolytic activity of blastocysts derived from in vivo or in vitro sources. However, glucose oxidation was lower (P less than 0.05) in blastocysts derived from the culture of 1-cell embryos or from oocytes matured and fertilized in vitro. Exogenous tricarboxylic acid cycle substrates (i.e. pyruvate and lactate supplied in the medium) affected the level of glucose oxidation.

scholarly journals Metabolic phases during the development of granulation tissue

1967 ◽  
Vol 105 (1) ◽  
pp. 333-341 ◽  
Author(s):  
Kirsti Lampiaho ◽  
E. Kulonen
Keyword(s):  
Granulation Tissue ◽  
Collagen Synthesis ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Pentose Phosphate ◽  
Acid Cycle ◽  
Short Period ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Observation Period

1. The metabolism of incubated slices of sponge-induced granulation tissue, harvested 4–90 days after the implantation, was studied with special reference to the capacity of collagen synthesis and to the energy metabolism. Data are also given on the nucleic acid contents during the observation period. Three metabolic phases were evident. 2. The viability of the slices for the synthesis of collagen was studied in various conditions. Freezing and homogenization destroyed the capacity of the tissue to incorporate proline into collagen. 3. Consumption of oxygen reached the maximum at 30–40 days. There was evidence that the pentose phosphate cycle was important, especially during the phases of the proliferation and the involution. The formation of lactic acid was maximal at about 20 days. 4. The capacity to incorporate proline into collagen hydroxyproline in vitro was limited to a relatively short period at 10–30 days. 5. The synthesis of collagen was dependent on the supply of oxygen and glucose, which latter could be replaced in the incubation medium by other monosaccharides but not by the metabolites of glucose or tricarboxylic acid-cycle intermediates.

scholarly journals HISTOCHEMICAL INVESTIGATIONS ON THE IN VIVO EFFECTS OF FLUORIDE ON TRICARBOXYLIC ACID CYCLE DEHYDROGENASES FROM PELARGONIUM ZONALE: PART II

1967 ◽  
Vol 15 (4) ◽  
pp. 202-206
Author(s):  
C. JAMES LOVELACE ◽  
GENE W. MILLER
Keyword(s):  
Sodium Fluoride ◽  
Reductase Activity ◽  
Tricarboxylic Acid Cycle ◽  
Leaf Tissue ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Pelargonium Zonale ◽  
Acid Cycle ◽  
In Vivo Effects

In vivo effects of fluoride on tricarboxylic acid (TCA) cycle dehydrogenase enzymes of Pelargonium zonale were studied using p-nitro blue tetrazoleum chloride. Plants were exposed to 17 ppb HF, and enzyme activities in treated plants were compared to those in controls. Leaves of control plants were incubated in 5 x 10–3 M sodium fluoride. Injuries observed in fumigation and solution experiments were similar. Leaf tissue subjected to HF or sodium fluoride evidenced less succinic p-nitro blue tetrazoleum reductase activity than did control tissue. Other TCA cycle dehydrogenase enzymes were not observably affected by the fluoride concentrations used in these experiments. Excised leaves cultured in 5 x 10–3 M sodium fluoride exhibited less succinic p-nitro blue tetrazoleum reductase activity after 24 hr than did leaves cultured in 5 x 10–3 M sodium chloride.

scholarly journals Fast Isotopic Exchange between Mitochondria and Cytosol in Brain Revealed by Relayed 13C Magnetization Transfer Spectroscopy

2009 ◽  
Vol 29 (4) ◽  
pp. 661-669 ◽  
Author(s):  
Jehoon Yang ◽  
Su Xu ◽  
Jun Shen
Keyword(s):  
Isotopic Exchange ◽  
Tricarboxylic Acid Cycle ◽  
Magnetization Transfer ◽  
Tricarboxylic Acid ◽  
Transfer Effect ◽  
Resonance Spectroscopy ◽  
Exchange Reactions ◽  
Acid Cycle ◽  
Longitudinal Relaxation

In vivo13C magnetic resonance spectroscopy has been applied to studying brain metabolic processes by measuring 13C label incorporation into cytosolic pools such as glutamate and aspartate. However, the rate of exchange between mitochondrial α-ketoglutarate/oxaloacetate and cytosolic glutamate/aspartate ( Vx) extracted from metabolic modeling has been controversial. Because brain fumarase is exclusively located in the mitochondria, and mitochondrial fumarate is connected to cytosolic aspartate through a chain of fast exchange reactions, it is possible to directly measure Vx from the four-carbon side of the tricarboxylic acid cycle by magnetization transfer. In isoflurane-anesthetized adult rat brain, a relayed 13C magnetization transfer effect on cytosolic aspartate C2 at 53.2ppm was detected after extensive signal averaging with fumarate C2 at 136.1ppm irradiated using selective radiofrequency pulses. Quantitative analysis using Bloch–McConnell equations and a four-site exchange model found that VxE13–19 µmol per g per min (≫ VTCA, the tricarboxylic acid cycle rate) when the longitudinal relaxation time of malate C2 was assumed to be within ±33% of that of aspartate C2. If VxE VTCA, the isotopic exchange between mitochondria and cytosol would be too slow on the time scale of 13C longitudinal relaxation to cause a detectable magnetization transfer effect.

Tricarboxylic acid cycle activity in perfused rat lungs after O2 exposure

1992 ◽  
Vol 262 (4) ◽  
pp. L495-L501 ◽  
Author(s):  
D. J. Bassett ◽  
S. S. Reichenbaugh
Keyword(s):  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Enzyme Inactivation ◽  
Pyridine Nucleotides ◽  
Acid Cycle ◽  
Metabolic Conditions ◽  
Steady State Levels ◽  
14Co2 Production ◽  
Tricarboxylic Acid Cycle Intermediates

O2-induced impairment of mitochondrial energy generation was examined in intact lungs isolated from rats after 18-30 h exposure to either air or 100% O2 in vivo. Mitochondrial metabolic rates were determined by separate measurements of 14CO2 production from [1-14C]pyruvate and [U-14C]palmitate, perfused under normal and stimulated metabolic conditions brought about by perfusion with the uncoupler of oxidative phosphorylation, 2,4-dinitrophenol (DNP). In the absence of DNP, O2 exposure did not significantly alter 14CO2 productions from either substrate. DNP increased lung pyruvate and palmitate catabolism to CO2 twofold in air-exposed lungs but did not alter 14CO2 production in lungs isolated from O2-exposed rats. These data demonstrated an O2-induced impairment of maximal mitochondrial metabolism of both pyruvate and palmitate that could not be explained by alterations in tissue free coenzyme A or by loss of pyridine nucleotides. However, comparisons of the steady-state levels of tricarboxylic acid cycle intermediates between O2- and air-exposed lungs did identify isocitrate dehydrogenase as a possible site of O2-induced enzyme inactivation.

Tricarboxylic acid cycle dehydrogenases inhibition by naringenin: experimental and molecular modelling evidence

2020 ◽  
Vol 123 (10) ◽  
pp. 1117-1126
Author(s):  
Pauline Maciel August ◽  
Mateus Grings ◽  
Marcelo Sartori Grunwald ◽  
Geancarlo Zanatta ◽  
Vinícius Stone ◽  
...  
Keyword(s):  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Cell Metabolism ◽  
Tricarboxylic Acid ◽  
Metabolic Effects ◽  
Similar Reduction ◽  
Acid Cycle ◽  
Docking Simulations ◽  
Female Wistar Rats

AbstractThe study of polyphenols’ effects on health has been gaining attention lately. In addition to reacting with important enzymes, altering the cell metabolism, these substances can present either positive or negative metabolic alterations depending on their consumption levels. Naringenin, a citrus flavonoid, already presents diverse metabolic effects. The objective of this work was to evaluate the effect of maternal naringenin supplementation during pregnancy on the tricarboxylic acid cycle activity in offspring’s cerebellum. Adult female Wistar rats were divided into two groups: (1) vehicle (1 ml/kg by oral administration (p.o.)) or (2) naringenin (50 mg/kg p.o.). The offspring were euthanised at 7th day of life, and the cerebellum was dissected to analyse citrate synthase, isocitrate dehydrogenase (IDH), α-ketoglutarate dehydrogenase (α-KGDH) and malate dehydrogenase (MDH) activities. Molecular docking used SwissDock web server and FORECASTER Suite, and the proposed binding pose image was created on UCSF Chimera. Data were analysed by Student’s t test. Naringenin supplementation during pregnancy significantly inhibited IDH, α-KGDH and MDH activities in offspring’s cerebellum. A similar reduction was observed in vitro, using purified α-KGDH and MDH, subjected to pre-incubation with naringenin. Docking simulations demonstrated that naringenin possibly interacts with dehydrogenases in the substrate and cofactor binding sites, inhibiting their function. Naringenin administration during pregnancy may affect cerebellar development and must be evaluated with caution by pregnant women and their physicians.

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