scholarly journals Quantitative analysis of intermediary metabolism in rat hepatocytes incubated in the presence and absence of ethanol with a substrate mixture including ketoleucine

1989 ◽  
Vol 258 (1) ◽  
pp. 121-140 ◽  
Author(s):  
J M Baranyai ◽  
J J Blum
Keyword(s):  
Ketone Bodies ◽  
Rat Hepatocytes ◽  
Metabolic Model ◽  
Oxygen Utilization ◽  
Acetyl Coa ◽  
Atp Production ◽  
Considerable Excess ◽  
Metabolic Conditions ◽  
Label Incorporation

Hepatocytes isolated from livers of fed rats were incubated with a mixture of glucose (10 mM), ribose (1.0 mM), acetate (1.25 mM), alanine (3.5 mM), glutamate (2.0 mM), aspartate (2.0 mM), 4-methyl-2-oxovaleric acid (ketoleucine) (3.0 mM), and, in paired flasks, 10 mM-ethanol. One substrate was 14C-radiolabelled in any given incubation. Incorporation of 14C into glucose, glycogen, CO2, lactate, alanine, aspartate, glutamate, acetate, urea, lipid glycerol, fatty acids and the 1- and 2,3,4-positions of ketone bodies was measured after 20 and 40 min of incubation under quasi-steady-state conditions. Data were analysed with the aid of a realistic structural metabolic model. In each of the four conditions examined, there were approx. 77 label incorporation measurements and several measurements of changes in metabolite concentrations. The considerable excess of measurements over the 37 independent flux parameters allowed for a stringent test of the model. A satisfactory fit to these data was obtained for each condition. There were large bidirectional fluxes along the gluconeogenic/glycolytic pathways, with net gluconeogenesis. Rates of ureagenesis, oxygen consumption and ketogenesis were high under all four conditions studied. Oxygen utilization was accurately predicted by three of the four models. There was complete equilibration between mitochondrial and cytosolic pools of acetate and of CO2, but for several of the metabolic conditions, two incompletely equilibrated pools of mitochondrial acetyl-CoA and oxaloacetate were required. Ketoleucine was utilized at a rate comparable to that reported by others in perfused liver and entered the mitochondrial pool of acetyl-CoA directly associated with ketone body formation. Ethanol, which was metabolized at rates comparable to those in vivo, caused relatively few changes in overall flux patterns. Several effects related to the increased NADH/NAD+ ratio were observed. Pyruvate dehydrogenase was completely inhibited and the ratio of acetoacetate to 3-hydroxybutyrate was decreased; flux through glutamate dehydrogenase, the citric acid cycle, and ketoleucine dehydrogenase were, however, only slightly inhibited. Net production of ATP occurred in all conditions studied and was increased by ethanol. Futile cycling was quantified at the glucose/glucose 6-phosphate, glycogen/glucose 6-phosphate, fructose 6-phosphate/fructose 1,6-bis-phosphate, and phosphoenolpyruvate/pyruvate/oxaloacetate substrate cycles. Cycling at these four loci consumed about 22% of cellular ATP production in control hepatocytes and 14% in ethanol-treated cells.

scholarly journals Cortical Substrate Oxidation during Hyperketonemia in the Fasted Anesthetized Rat in Vivo

2011 ◽  
Vol 31 (12) ◽  
pp. 2313-2323 ◽  
Author(s):  
Lihong Jiang ◽  
Graeme F Mason ◽  
Douglas L Rothman ◽  
Robin A de Graaf ◽  
Kevin L Behar
Keyword(s):  
Time Course ◽  
Ketone Bodies ◽  
Tricarboxylic Acid Cycle ◽  
Metabolic Model ◽  
Substrate Oxidation ◽  
Resonance Spectroscopy ◽  
Neural Function ◽  
Anesthetized Rats ◽  
Time Courses

Ketone bodies are important alternate brain fuels, but their capacity to replace glucose and support neural function is unclear. In this study, the contributions of ketone bodies and glucose to cerebral cortical metabolism were measured in vivo in halothane-anesthetized rats fasted for 36 hours ( n=6) and receiving intravenous [2,4-13C2]-d- β-hydroxybutyrate (BHB). Time courses of 13C-enriched brain amino acids (glutamate-C4, glutamine-C4, and glutamate and glutamine-C3) were measured at 9.4 Tesla using spatially localized 1H-[13C]-nuclear magnetic resonance spectroscopy. Metabolic rates were estimated by fitting a constrained, two-compartment (neuron–astrocyte) metabolic model to the 13C time-course data. We found that ketone body oxidation was substantial, accounting for 40% of total substrate oxidation (glucose plus ketone bodies) by neurons and astrocytes. d- β-Hydroxybutyrate was oxidized to a greater extent in neurons than in astrocytes (∼70:30), and followed a pattern closely similar to the metabolism of [1-13C]glucose reported in previous studies. Total neuronal tricarboxylic acid cycle (TCA) flux in hyperketonemic rats was similar to values reported for normal (nonketotic) anesthetized rats infused with [1-13C]glucose, but neuronal glucose oxidation was 40% to 50% lower, indicating that ketone bodies had compensated for the reduction in glucose use.

scholarly journals Protection of Hypoglycemia-Induced Neuronal Death by β-Hydroxybutyrate Involves the Preservation of Energy Levels and Decreased Production of Reactive Oxygen Species

2015 ◽  
Vol 35 (5) ◽  
pp. 851-860 ◽  
Author(s):  
Alberto Julio-Amilpas ◽  
Teresa Montiel ◽  
Eva Soto-Tinoco ◽  
Cristian Gerónimo-Olvera ◽  
Lourdes Massieu
Keyword(s):  
Reactive Oxygen Species ◽  
Protective Effect ◽  
Neuronal Death ◽  
Ketone Bodies ◽  
Reactive Oxygen ◽  
Glucose Deprivation ◽  
Oxygen Species ◽  
Atp Production

Glucose is the main energy substrate in brain but in certain circumstances such as prolonged fasting and the suckling period alternative substrates can be used such as the ketone bodies (KB), beta-hydroxybutyrate (BHB), and acetoacetate. It has been shown that KB prevent neuronal death induced during energy limiting conditions and excitotoxicity. The protective effect of KB has been mainly attributed to the improvement of mitochondrial function. In the present study, we have investigated the protective effect of D-BHB against neuronal death induced by severe noncoma hypoglycemia in the rat in vivo and by glucose deprivation (GD) in cortical cultures. Results show that systemic administration of D-BHB reduces reactive oxygen species (ROS) production in distinct cortical areas and subregions of the hippocampus and efficiently prevents neuronal death in the cortex of hypoglycemic animals. In vitro results show that D-BHB stimulates ATP production and reduces ROS levels, while the nonphysiologic isomer of BHB, L-BHB, has no effect on energy production but reduces ROS levels. Data suggest that protection by BHB, not only results from its metabolic action but is also related to its capability to reduce ROS, rendering this KB as a suitable candidate for the treatment of ischemic and traumatic injury.

scholarly journals The estimation of rates of utilization of glucose and ketone bodies in the brain of the suckling rat using compartmental analysis of isotopic data

1974 ◽  
Vol 142 (3) ◽  
pp. 527-544 ◽  
Author(s):  
Jill E. Cremer ◽  
Dennis F. Heath
Keyword(s):  
Ketone Bodies ◽  
Lipid Synthesis ◽  
Compartmental Analysis ◽  
British Library ◽  
Acetyl Coa ◽  
Intermediary Metabolites ◽  
Lending Library ◽  
Old Rats ◽  
The Brain

The brains of 18-day-old rats utilize glucose and ketone bodies. The rates of acetyl-CoA formation from these substrates and of glycolysis were determined in vivo from the labelling of intermediary metabolites after intraperitoneal injection of d-[2-14C]glucose, l(+)-[3-14C]- and l(+)-[U-14C]-lactate and d(−)-3-hydroxy[14C]butyrate. Compartmental analysis was used in calculating rates to allow for the rapid exchange of blood and brain lactate, the presence in brain of at least two pools each of glucose and lactate, and the incomplete equilibration of oxaloacetate with aspartate and of 2-oxoglutarate with glutamate. Results were as follows. 1. Glucose and ketone bodies labelled identical pools of tricarboxylate-cycle metabolites, and were in every way alternative substrates. 2. The combined rate of oxidation of acetyl-CoA derived from pyruvate (and hence glucose) and ketone bodies was 1.05μmol/min per g. 3. Ketone bodies contributed 0.11–0.53μmol/min per g in proportion to their concentration in blood, with a mean rate of 0.30μmol/min per g at 1.24mm. 4. Pyruvate and ketone bodies were converted into lipid at 0.018 and 0.008μmol/min per g respectively. 5. Glycolysis, at 0.48μmol/min per g, was more rapid in most rats than pyruvate utilization by oxidation and lipid synthesis, resulting in a net output of lactate from brain to blood. 6. Rates of formation of brain glutamate, glutamine and aspartate were also measured. Further information on the derivation of the models has been deposited as Supplementary Publication SUP 50034 (18 pages) at the British Library, Lending Division (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7QB, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1973) 131, 5.

scholarly journals Quantitative analysis of intermediary metabolism in hepatocytes incubated in the presence and absence of glucagon with a substrate mixture containing glucose, ribose, fructose, alanine and acetate

1985 ◽  
Vol 225 (3) ◽  
pp. 761-786 ◽  
Author(s):  
M Rabkin ◽  
J J Blum
Keyword(s):  
Pyruvate Kinase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Krebs Cycle ◽  
Metabolic Model ◽  
Pentose Phosphate ◽  
Atp Production ◽  
Considerable Excess ◽  
Net Flux ◽  
Presence And Absence ◽  
Pentose Phosphate Pathways

Hepatocytes were isolated from the livers of fed rats and incubated, in the presence and absence of 100 nM-glucagon, with a substrate mixture containing glucose (10 mM), fructose (4 mM), alanine (3.5 mM), acetate (1.25 mM), and ribose (1 mM). In any given incubation one substrate was labelled with 14C. Incorporation of 14C into glucose, glycogen, CO2, lactate, alanine, glutamate, lipid glycerol and fatty acids was measured after 20 and 40 min of incubation under quasi-steady-state conditions [Borowitz, Stein & Blum (1977) J. Biol. Chem. 252, 1589-1605]. These data and the measured O2 consumption were analysed with the aid of a structural metabolic model incorporating all reactions of the glycolytic, gluconeogenic, and pentose phosphate pathways, and associated mitochondrial and cytosolic reactions. A considerable excess of experimental measurements over independent flux parameters and a number of independent measurements of changes in metabolite concentrations allowed for a stringent test of the model. A satisfactory fit to the data was obtained for each condition. Significant findings included: control cells were glycogenic and glucagon-treated cells glycogenolytic during the second interval; an ordered (last in, first out) model of glycogen degradation [Devos & Hers (1979) Eur. J. Biochem. 99, 161-167] was required in order to fit the experimental data; the pentose shunt contributed approx. 15% of the carbon for gluconeogenesis in both control and glucagon-treated cells; net flux through the lower Embden-Meyerhof pathway was in the glycolytic direction except during the 20-40 min interval in glucagon-treated cells; the increased gluconeogenesis in response to glucagon was correlated with a decreased pyruvate kinase flux and lactate output; fluxes through pyruvate kinase, pyruvate carboxylase, and phosphoenolpyruvate carboxykinase were not coordinately controlled; Krebs cycle activity did not change with glucagon treatment; flux through the malic enzyme was towards pyruvate formation except for control cells during interval II; and ‘futile’ cycling at each of the five substrate cycles examined (including a previously undescribed cycle at acetate/acetyl-CoA) consumed about 26% of cellular ATP production in control hepatocytes and 21% in glucagon-treated cells.

Interrelationships between acetylation and the disposal of acetyl groups in the livers of dairy cows

1978 ◽  
Vol 45 (3) ◽  
pp. 331-338 ◽  
Author(s):  
Alan M. Snoswell ◽  
Nicholas D. Costa ◽  
Jock G. Mclean ◽  
G.david Baird ◽  
Michael A. Lomax ◽  
...  
Keyword(s):  
Dairy Cows ◽  
Ketone Bodies ◽  
Significant Rise ◽  
Total Acid ◽  
Acetyl Coa ◽  
Lactating Cows ◽  
Degree Of Acetylation ◽  
Liver Homogenates

SummaryPossible mechanisms by which the degree of acetylation of hepatic CoA might be regulated were examined in lactating and in non-lactating dairy cows. This involved the measurement of the hepatic steady-state concentrations of free CoA, acetyl-CoA, free carnitine, acetylcarnitine and total acid-soluble carnitine in freezeclamped biopsy samples, the measurement of the hepatic release of acetate from acetylcarnitine in vitro, and the measurement of the rate of hepatic output of acetate and ketone bodies in vivo.The hepatic ratio of [free CoA]/[acetyl-CoA] was 0·11 in lactating cows and 0·59 in non-lactating cows. There was a significant rise in the hepatic concentration of acetyl-CoA and a significant fall in that of total acid-soluble carnitine in the lactating cows as compared with the non-lactating cows.There was a net in vivo output of acetate and of ketone bodies from the livers of both lactating and non-lactating cows. The rates of output amounted to 7·77 and 2·00 mmole/min for acetate and ketone bodies respectively in the lactating cows, and 4·95 and 2·14 mmole/min in the non-lactating cows.The rate of enzymic release of acetate from acetylcarnitine in vitro amounted to 0·93 and 0·34 μmole min−1 (g wet wt)−1 at 37 °C for liver homogenates derived from lactating and non-lactating cows respectively. The activity observed in the case of the lactating cows was sufficient to account for the rate of hepatic acetate output observed in vivo.

scholarly journals Lipid Droplets Degradation by Autophagy Connects Mitochondria Metabolism to PROX1-driven Expression of Lymphatic Genes and Lymphangiogenesis

2021 ◽  
Author(s):  
Odeta Mece ◽  
Diede Houbaert ◽  
Tania Durré ◽  
Hannelore Maes ◽  
Marco Schaaf ◽  
...  
Keyword(s):  
Gene Expression ◽  
Lipid Droplets ◽  
Target Genes ◽  
Mitochondrial Dynamics ◽  
Lymphatic Vessels ◽  
Acid Oxidation ◽  
Acetyl Coa ◽  
Atp Production ◽  
Corneal Lymphangiogenesis

Abstract Autophagy has an emerging vasculoprotective role but whether and how it regulates lymphatic endothelial cells (LEC) and lymphangiogenesis is unknown. Here, we show that genetic deficiency of autophagy in LEC impairs the responses to VEGF-C and injury-driven corneal lymphangiogenesis. Loss of autophagy compromises expression of lymphatic markers, affects mitochondrial dynamics and causes an accumulation of lipid droplets (LDs) in LEC and lymphatic vessels in vivo. When LDs accumulate because lipophagy is impaired, mitochondrial ATP production, fatty acid oxidation (FAO), acetyl-CoA/CoA ratio and expression of lymphangiogenic PROX1 target genes are dwindled. Enforcing mitochondria fusion by silencing dynamin-related-protein 1 (DRP1) in autophagy-deficient LEC fails to affect LDs turnover and lymphatic gene expression, whereas supplementing the acetyl-CoA precursor acetate rescues LEC identity and lymphangiogenesis in LEC-Atg5-/- mice. Our findings reveal that lipophagy in LEC by supporting FAO, preserves a mitochondrial-PROX1 gene expression circuit that ensures LEC identity, responsiveness to lymphangiogenic mediators and lymphangiogenesis.

Synthesis and Biological Evaluation of Scutellarein Alkyl Derivatives as Preventing Neurodegenerative Agents with Improved Lipid Soluble Properties

2019 ◽  
Vol 15 (7) ◽  
pp. 771-780
Author(s):  
He-Min Li ◽  
Ting Gu ◽  
Wen-Yu Wu ◽  
Shao-Peng Yu ◽  
Tian-Yuan Fan ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Neuronal Damage ◽  
Thiobarbituric Acid ◽  
Rat Hepatocytes ◽  
Biological Evaluation ◽  
Thiobarbituric Acid Reactive Substance ◽  
Alkyl Derivatives ◽  
Promising Therapeutic Approach ◽  
Microsomal Membranes

Background: Exogenous antioxidants are considered as a promising therapeutic approach to treat neurodegenerative diseases since they could prevent and/or minimize the neuronal damage by oxidation. Objective: Three series of lipophilic compounds structurally based on scutellarein (2), which is one metabolite of scutellarin (1) in vivo, have been designed and synthesized. Methods: Their antioxidant activity was evaluated by detecting the 2-thiobarbituric acid reactive substance (TBARS) produced in the ferrous salt/ascorbate-induced autoxidation of lipids, which were present in microsomal membranes of rat hepatocytes. The lipophilicity of these compounds indicated as partition coefficient between n-octanol and buffer was investigated by ultraviolet (UV) spectrophotometer. Results: This study indicated that compound 5e which had a benzyl group substituted at the C4'- OH position showed a potent antioxidant activity and good lipophilicity. Conclusion: 5e could be an effective candidate for preventing or reducing the oxidative status associated with the neurodegenerative processes.

scholarly journals Polymer-protomer transition of acetyl-CoA carboxylase occurs in vivo and varies with nutritional conditions.

1980 ◽  
Vol 255 (21) ◽  
pp. 10033-10035
Author(s):  
B.A. Ashcraft ◽  
W.S. Fillers ◽  
S.L. Augustine ◽  
S.D. Clarke
Keyword(s):  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Nutritional Conditions
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