Regulation of fatty acid oxidation in isolated hepatocytes and liver mitochondria from newborn rabbits

Herbin, Catherine; Pégorier, Jean‐Paul; Duée, Pierre‐Henri; Kohl, Claude; Girard, Jean

doi:10.1111/j.1432-1033.1987.tb11212.x

Cited by 31 publications

(29 citation statements)

References 47 publications

(26 reference statements)

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“…In the presence of malate, the rates of oxygen consumption due to the oxidation of oleoylCoA or palmitoyl-L-carnitine were markedly enhanced compared with those measured in the presence of malonate (Table 3). Similar observations have been reported in newborn-rat (Escriva et al, 1986) or -rabbit (Herbin et al, 1987) mitochondria. These results suggest that the formation of ketone body from acetylCoA might be limiting as compared with fatty acid oxidation, as previously reported (Bremer and Wojtczak, 1972).…”

Section: Cpt and 11supporting

confidence: 78%

“…Measurement of enzyme activities In Isolated mitochondria CPT CPT I activity was assayed at 30°C as the formation ofpalmitoyl-L-[methyl-3H]carnitine from L-[methyl-3H]carnitine and palmitoyl-CoA as described previously (Herbin et al, 1987). The sensitivity ofCPT I to malonyl-CoA inhibition has been estimated by measuring the concentration of malonyl-CoA required for 50 % inhibition of the enzyme activity (IC50).…”

Section: Isolation Of Liver Mitochondria and Measurements Of Respirationmentioning

confidence: 99%

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Hepatic ketogenesis in newborn pigs is limited by low mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity

Duée

Pégorier

Quant

et al. 1994

Biochemical Journal

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In newborn-pig hepatocytes, the rate of oleate oxidation is extremely low, despite a very low malonyl-CoA concentration. By contrast, the sensitivity of carnitine palmitoyltransferase (CPT) I to malonyl-CoA inhibition is high, as suggested by the very low concentration of malonyl-CoA required for 50% inhibition of CPT I (IC50). The rates of oleate oxidation and ketogenesis are respectively 70 and 80% lower in mitochondria isolated from newborn-pig liver than from starved-adult-rat liver mitochondria. Using polarographic measurements, we showed that the oxidation of oleoyl-CoA and palmitoyl-L-carnitine is very low when the acetyl-CoA produced is channelled into the hydroxymethylglutaryl-CoA (HMG-CoA) pathway by addition of malonate. In contrast, the oxidation of the same substrates is high when the acetyl-CoA produced is directed towards the citric acid cycle by addition of malate. We demonstrate that the limitation of ketogenesis in newborn-pig liver is due to a very low amount and activity of mitochondrial HMG-CoA synthase as compared with rat liver mitochondria, and suggest that this could promote the accumulation of acetyl-CoA and/or beta-oxidation products that in turn would decrease the overall rate of fatty acid oxidation in newborn- and adult-pig livers.

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Section: Cpt and 11supporting

confidence: 78%

Section: Isolation Of Liver Mitochondria and Measurements Of Respirationmentioning

confidence: 99%

Hepatic ketogenesis in newborn pigs is limited by low mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity

Duée

Pégorier

Quant

et al. 1994

Biochemical Journal

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“…The antisera used were against the yeast cytochrome b 2 (1:1000), the yeast mitochondrial HSP70 (1:5000), the yeast porin (1:1000), the rat L-CPT1 (1:3000) (21), and the rat CPT2 (1:1000) (28). CPT activity was assayed at 30°C as palmitoyl-L-[methyl- in the presence of 1% bovine serum albumine (w/v) as described previously (29). Malonyl-CoA concentration was 150 M. When the CPT assay was performed using detergent-solubilized mitochondria, mitochondria were solubilized by 5% Triton X-100 as described in Ref.…”

Section: Miscellaneous Methods and Chemicalsmentioning

confidence: 99%

The N-terminal Domain of Rat Liver Carnitine Palmitoyltransferase 1 Mediates Import into the Outer Mitochondrial Membrane and Is Essential for Activity and Malonyl-CoA Sensitivity

Cohen¹,

Kohl²,

McGarry³

et al. 1998

Journal of Biological Chemistry

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The rat liver carnitine palmitoyltransferase 1 (L-CPT1), an integral outer mitochondrial membrane (OMM) protein, is the key regulatory enzyme of fatty acid oxidation and is inhibited by malonyl-CoA. In vitro import of L-CPT1 into the OMM requires the presence of mitochondrial receptors and is stimulated by ATP but is membrane potential-independent. Its N-terminal domain (residues 1-150), which contains two transmembrane segments, possesses all of the information for mitochondrial targeting and OMM insertion. Deletion of this domain abrogates protein targeting, whereas its fusion to non-OMM-related proteins results in their mitochondrial targeting and OMM insertion in a manner similar to L-CPT1. Functional analysis of chimeric CPTs expressed in Saccharomyces cerevisiae shows that this domain also mediates in vivo protein insertion into the OMM. When the malonyl-CoA-insensitive CPT2 was anchored at the OMM either by a specific OMM signal anchor sequence (pOM29) or by the N-terminal domain of L-CPT1, its activity remains insensitive to malonylCoA inhibition. This indicates that malonyl-CoA sensitivity is an intrinsic property of L-CPT1 and that its N-terminal domain cannot confer malonyl-CoA sensitivity to CPT2. Replacement of the N-terminal domain by pOM29 results in a less folded and less active protein, which is also malonyl-CoA-insensitive. Thus, in addition to its role in mitochondrial targeting and OMM insertion, the N-terminal domain of L-CPT1 is essential to maintain an optimal conformation for both catalytic function and malonyl-CoA sensitivity.

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“…For each time point, cells were scraped from five 115-mm diameter Petri dishes and washed twice with cold phosphate-buffered saline. Mitochondria were isolated by differential centrifugation (36), followed by purification on a Percoll gradient (37), and used for the assay of CPT I activity (36).…”

Section: Methodsmentioning

confidence: 99%

Fatty Acids Rapidly Induce the Carnitine Palmitoyltransferase I Gene in the Pancreatic β-Cell Line INS-1

Assimacopoulos-Jeannet

Thumelin

Roche

et al. 1997

Journal of Biological Chemistry

123

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Fatty acids are important metabolic substrates for the pancreatic ␤-cell, and long term exposure of pancreatic islets to elevated concentrations of fatty acids results in an alteration of glucose-induced insulin secretion. Previous work suggested that exaggerated fatty acid oxidation may be implicated in this process by a mechanism requiring changes in metabolic enzyme expression. We have therefore studied the regulation of carnitine palmitoyltransferase I (CPT I) gene expression by fatty acids in the pancreatic ␤-cell line INS-1 since this enzyme catalyzes the limiting step of fatty acid oxidation in various tissues. Palmitate, oleate, and linoleate (0.35 mM) elicited a 4 -6-fold increase in CPT I mRNA. The effect was dose-dependent and was similar for saturated and unsaturated fatty acids. It was detectable after 1 h and reached a maximum after 3 h. The induction of CPT I mRNA by fatty acids did not require their oxidation, and 2-bromopalmitate, a nonoxidizable fatty acid, increased CPT I mRNA to the same extent as palmitate. The induction was not prevented by cycloheximide treatment of cells indicating that it was mediated by pre-existing transcription factors. Neither glucose nor pyruvate and various secretagogues had a significant effect except glutamine (7 mM) which slightly induced CPT I mRNA. The half-life of the CPT I transcript was unchanged by fatty acids, and nuclear run-on analysis showed a rapid (less than 45 min) and pronounced transcriptional activation of the CPT I gene by fatty acids. The increase in CPT I mRNA was followed by a 2-3-fold increase in CPT I enzymatic activity measured in isolated mitochondria. The increase in activity was timedependent, detectable after 4 h, and close to maximal after 24 h.

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Regulation of fatty acid oxidation in isolated hepatocytes and liver mitochondria from newborn rabbits

Cited by 31 publications

References 47 publications

Hepatic ketogenesis in newborn pigs is limited by low mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity

Hepatic ketogenesis in newborn pigs is limited by low mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity

The N-terminal Domain of Rat Liver Carnitine Palmitoyltransferase 1 Mediates Import into the Outer Mitochondrial Membrane and Is Essential for Activity and Malonyl-CoA Sensitivity

Fatty Acids Rapidly Induce the Carnitine Palmitoyltransferase I Gene in the Pancreatic β-Cell Line INS-1

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