Travels with carnitine palmitoyltransferase I: from liver to germ cell with stops in between

2001 ◽  
Vol 29 (2) ◽  
pp. 241-244 ◽  
Author(s):  
J. D. McGarry
Keyword(s):  
Acid Metabolism ◽  
Inhibitory Effect ◽  
Carnitine Palmitoyltransferase ◽  
Central Component ◽  
Body Tissues ◽  
Malonyl Coa ◽  
Sperm Development ◽  
Carnitine Palmitoyltransferase I ◽  
Cpt I

Although malonyl-CoA was first recognized as a central component in the regulation of hepatic ketogenesis, its inhibitory effect on mitochondrial carnitine palmitoyltransferase I (CPT I) has come to be viewed as a key element in fuel sensing in a variety of body tissues. This broadening role of the malonyl-CoA/CPT I partnership in the control of glucose and fatty acid metabolism, as well as current understanding of structure-function relationships surrounding the CPT proteins, are outlined. The intriguing question of whether CPT I has an important function in sperm development is also addressed briefly.

Overexpression of carnitine palmitoyltransferase I in skeletal muscle in vivo increases fatty acid oxidation and reduces triacylglycerol esterification

2007 ◽  
Vol 292 (4) ◽  
pp. E1231-E1237 ◽  
Author(s):  
Clinton R. Bruce ◽  
Camilla Brolin ◽  
Nigel Turner ◽  
Mark E. Cleasby ◽  
Feike R. van der Leij ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Carnitine Palmitoyltransferase ◽  
Acid Oxidation ◽  
Malonyl Coa ◽  
Carnitine Palmitoyltransferase I ◽  
Edl Muscle ◽  
Cpt I ◽  
The Right

A key regulatory point in the control of fatty acid (FA) oxidation is thought to be transport of FAs across the mitochondrial membrane by carnitine palmitoyltransferase I (CPT I). To investigate the role of CPT I in FA metabolism, we used in vivo electrotransfer (IVE) to locally overexpress CPT I in muscle of rodents. A vector expressing the human muscle isoform of CPT I was electrotransferred into the right lateral muscles of the distal hindlimb [tibialis cranialis (TC) and extensor digitorum longus (EDL)] of rats, and a control vector expressing GFP was electrotransferred into the left muscles. Initial studies showed that CPT I protein expression peaked 7 days after IVE (+104%, P < 0.01). This was associated with an increase in maximal CPT I activity (+30%, P < 0.001) and a similar increase in palmitoyl-CoA oxidation (+24%; P < 0.001) in isolated mitochondria from the TC. Importantly, oxidation of the medium-chain FA octanoyl-CoA and CPT I sensitivity to inhibition by malonyl-CoA were not altered by CPT I overexpression. FA oxidation in isolated EDL muscle strips was increased with CPT I overexpression (+28%, P < 0.01), whereas FA incorporation into the muscle triacylglycerol (TAG) pool was reduced (−17%, P < 0.01). As a result, intramyocellular TAG content was decreased with CPT I overexpression in both the TC (−25%, P < 0.05) and the EDL (−45%, P < 0.05). These studies demonstrate that acute overexpression of CPT I in muscle leads to a repartitioning of FAs away from esterification and toward oxidation and highlight the importance of CPT I in regulating muscle FA metabolism.

Cold acclimation increases carnitine palmitoyltransferase I activity in oxidative muscle of striped bass

1994 ◽  
Vol 266 (2) ◽  
pp. R405-R412 ◽  
Author(s):  
K. J. Rodnick ◽  
B. D. Sidell
Keyword(s):  
Cold Acclimation ◽  
Striped Bass ◽  
Fatty Acyl ◽  
Thermal Acclimation ◽  
Carnitine Palmitoyltransferase ◽  
Malonyl Coa ◽  
Red Muscle ◽  
Carnitine Palmitoyltransferase I ◽  
Cpt I ◽  
Long Chain

The effect of thermal acclimation on the activity of carnitine palmitoyltransferase I (CPT I), the rate-limiting enzyme for beta-oxidation of long-chain fatty acids, was determined in oxidative red muscle of striped bass (Morone saxatilis) acclimated at 5 or 25 degrees C. As observed in mammalian tissues, malonyl-CoA potently inhibited CPT I activity of mitochondria. Inhibition by malonyl-CoA required inclusions of both bovine serum albumin (BSA) and palmitoyl-CoA in the reaction media. Because BSA binds long-chain fatty acyl-CoAs, this observation suggests that free fatty acyl-CoAs may disrupt mitochondrial membranes and affect the CPT I protein. Cold acclimation increased citrate synthase activity 1.6-fold and total CPT activity 2-fold in homogenates of red muscle; free carnitine increased 62%, and specific activity of CPT I in mitochondria increased 2-fold. No differences were observed between cold- and warm-acclimated fish in substrate-binding properties of CPT I at an assay temperature of 15 degrees C, as judged by the Michaelis constant (Km) for carnitine (0.11 +/- 0.02 vs. 0.13 +/- 0.02 mM) or inhibition of CPT I, as determined by the half-maximal inhibition concentration (IC50) for malonyl-CoA (0.14 +/- 0.05 vs. 0.09 +/- 0.03 microM). Thermal sensitivity of CPT I (Q10 = 2.91 +/- 0.12 vs. 3.02 +/- 0.20) and preference of CPT I for different long-chain fatty acyl-CoA substrates (16:1-CoA = 16:0-CoA > 18:1-CoA) were not altered by thermal acclimation.(ABSTRACT TRUNCATED AT 250 WORDS)

Carnitine palmitoyltransferase I control of acetogenesis, the major pathway of fatty acid β-oxidation in liver of neonatal swine

2010 ◽  
Vol 298 (5) ◽  
pp. R1435-R1443 ◽  
Author(s):  
Xi Lin ◽  
Kwanseob Shim ◽  
Jack Odle
Keyword(s):  
Fatty Acid ◽  
Ketone Bodies ◽  
Carnitine Palmitoyltransferase ◽  
Acid Oxidation ◽  
Major Pathway ◽  
Malonyl Coa ◽  
Suckling Piglets ◽  
Carnitine Palmitoyltransferase I ◽  
Newborn Pigs ◽  
Cpt I

To examine the regulation of hepatic acetogenesis in neonatal swine, carnitine palmitoyltransferase I (CPT I) activity was measured in the presence of varying palmitoyl-CoA (substrate) and malonyl-CoA (inhibitor) concentrations, and [1-14C]-palmitate oxidation was simultaneously measured. Accumulation rates of 14C-labeled acetate, ketone bodies, and citric acid cycle intermediates within the acid-soluble products were determined using radio-HPLC. Measurements were conducted in mitochondria isolated from newborn, 24-h (fed or fasted), and 5-mo-old pigs. Acetate rather than ketone bodies was the predominant radiolabeled product, and its production increased twofold with increasing fatty acid oxidation during the first 24-h suckling period. The rate of acetogenesis was directly proportional to CPT I activity. The high activity of CPT I in 24-h-suckling piglets was not attributable to an increase in CPT I gene expression, but rather to a large decrease in the sensitivity of CPT I to malonyl-CoA inhibition, which offset a developmental decrease in affinity of CPT I for palmitoyl-CoA. Specifically, the IC50 for malonyl-CoA inhibition and Km value for palmitoyl-CoA measured in 24-h-suckling pigs were 1.8- and 2.7-fold higher than measured in newborn pigs. The addition of anaplerotic carbon from malate (10 mM) significantly reduced 14C accumulation in acetate ( P < 0.003); moreover, the reduction was much greater in newborn (80%) than in 24-h-fed (72%) and 5-mo-old pigs (55%). The results demonstrate that acetate is the primary product of hepatic mitochondrial β-oxidation in Sus scrofa and that regulation during early development is mediated primarily via kinetic modulation of CPT I.

scholarly journals Evidence that the sensitivity of carnitine palmitoyltransferase I to inhibition by malonyl-CoA is an important site of regulation of hepatic fatty acid oxidation in the fetal and newborn rabbit. Perinatal development and effects of pancreatic hormones in cultured rabbit hepatocytes

1990 ◽  
Vol 269 (2) ◽  
pp. 409-415 ◽  
Author(s):  
C Prip-Buus ◽  
J P Pegorier ◽  
P H Duee ◽  
C Kohl ◽  
J Girard
Keyword(s):  
Fatty Acid ◽  
Cyclic Amp ◽  
Fatty Acid Oxidation ◽  
Carnitine Palmitoyltransferase ◽  
Acid Oxidation ◽  
Fetal Hepatocytes ◽  
Malonyl Coa ◽  
Carnitine Palmitoyltransferase I ◽  
Cpt I ◽  
Hepatic Fatty Acid Oxidation

The temporal changes in oleate oxidation, lipogenesis, malonyl-CoA concentration and sensitivity of carnitine palmitoyltransferase I (CPT 1) to malonyl-CoA inhibition were studied in isolated rabbit hepatocytes and mitochondria as a function of time after birth of the animal or time in culture after exposure to glucagon, cyclic AMP or insulin. (1) Oleate oxidation was very low during the first 6 h after birth, whereas lipogenesis rate and malonyl-CoA concentration decreased rapidly during this period to reach levels as low as those found in 24-h-old newborns that show active oleate oxidation. (2) The changes in the activity of CPT I and the IC50 (concn. causing 50% inhibition) for malonyl-CoA paralleled those of oleate oxidation. (3) In cultured fetal hepatocytes, the addition of glucagon or cyclic AMP reproduced the changes that occur spontaneously after birth. A 12 h exposure to glucagon or cyclic AMP was sufficient to inhibit lipogenesis totally and to cause a decrease in malonyl-CoA concentration, but a 24 h exposure was required to induce oleate oxidation. (4) The induction of oleate oxidation by glucagon or cyclic AMP is triggered by the fall in the malonyl-CoA sensitivity of CPT I. (5) In cultured hepatocytes from 24 h-old newborns, the addition of insulin inhibits no more than 30% of the high oleate oxidation, whereas it stimulates lipogenesis and increases malonyl-CoA concentration by 4-fold more than in fetal cells (no oleate oxidation). This poor effect of insulin on oleate oxidation seems to be due to the inability of the hormone to increase the sensitivity of CPT I sufficiently. Altogether, these results suggest that the malonyl-CoA sensitivity of CPT I is the major site of regulation during the induction of fatty acid oxidation in the fetal rabbit liver.

scholarly journals Restoration of the properties of carnitine palmitoyltransferase I in liver mitochondria during re-feeding of starved rats

1986 ◽  
Vol 239 (2) ◽  
pp. 485-488 ◽  
Author(s):  
B D Grantham ◽  
V A Zammit
Keyword(s):  
Liver Mitochondria ◽  
Carnitine Palmitoyltransferase ◽  
Kinetic Properties ◽  
Malonyl Coa ◽  
Carnitine Palmitoyltransferase I ◽  
Cpt I

The recovery of the parameters of the kinetic properties of carnitine palmitoyltransferase (CPT) I in liver mitochondria of starved rats was studied after re-feeding animals for various periods of time. There were no significant changes either in the activity of the enzyme at high palmitoyl-CoA concentrations or in the affinity of the enzyme for palmitoyl-CoA, or in the sensitivity of CPT I to malonyl-CoA inhibition after 3 h or 6 h re-feeding. After 24 h re-feeding, both the affinity of the enzyme for palmitoyl-CoA and the activity of the enzyme were still not significantly different from those for the enzyme in mitochondria from 24 h-starved animals. By contrast, the sensitivity of CPT I to malonyl-CoA inhibition was largely, but not fully, restored to that observed in mitochondria from fed rats.

scholarly journals Cholate extracts of mitochondrial outer membranes increase inhibition by malonyl-CoA of carnitine palmitoyltransferase-I by a mechanism involving phospholipids

1994 ◽  
Vol 299 (3) ◽  
pp. 761-767 ◽  
Author(s):  
R L Mynatt ◽  
J J Greenhaw ◽  
G A Cook
Keyword(s):  
Regulatory Protein ◽  
Sodium Cholate ◽  
Carnitine Palmitoyltransferase ◽  
Proteinase K ◽  
Membrane Composition ◽  
Outer Membranes ◽  
Malonyl Coa ◽  
Increased Sensitivity ◽  
Carnitine Palmitoyltransferase I ◽  
Cpt I

It has been reported that sodium cholate can separate the catalytic component of carnitine palmitoyltransferase-I (CPT-I) from a putative malonyl-CoA-binding regulatory protein capable of conferring sensitivity to malonyl-CoA on CPT-II. We found that cholate preferentially extracted a contaminating malonyl-CoA-sensitive CPT from mitochondrial inner membranes. When cholate extracts of outer membranes were incubated either with cholate extracts of inner membranes or with osmotically swollen mitochondria, inhibition of CPT by malonyl-CoA was increased. Treatment of intact mitochondria with subtilisin abolished the increased inhibition by malonyl-CoA, suggesting that the outer-membrane CPT-I was responsible for the increased inhibition. Incubation of cholate extracts with proteinase K did not prevent the increased inhibition. Fractionation of the cholate extract indicated the presence of phospholipids. Addition of cardiolipin or phosphatidylglycerol to osmotically swollen mitochondria increased sensitivity of CPT to malonyl-CoA, but several other phospholipids did not. When cardiolipin was added to intact mitochondria from either starved or fed rats, there were large increases in inhibition by malonyl-CoA; sensitivity in mitochondria from starved rats increased to that normally observed with mitochondria from fed rats. These results suggest that phospholipids are responsible for the increased inhibition of CPT by malonyl-CoA with added cholate extracts and that changes in membrane composition may be involved in the physiological regulation of CPT-I.

scholarly journals Expression and Possible Role of Muscle-Type Carnitine Palmitoyltransferase I during Sperm Development in the Rat1

1998 ◽  
Vol 59 (6) ◽  
pp. 1399-1405 ◽  
Author(s):  
Sean H. Adams ◽  
Victoria Esser ◽  
Nicholas F. Brown ◽  
Nancy H. Ing ◽  
Larry Johnson ◽  
...  
Keyword(s):  
Carnitine Palmitoyltransferase ◽  
Muscle Type ◽  
Sperm Development ◽  
Carnitine Palmitoyltransferase I

scholarly journals Topology of carnitine palmitoyltransferase I in the mitochondrial outer membrane

1997 ◽  
Vol 323 (3) ◽  
pp. 711-718 ◽  
Author(s):  
Fiona FRASER ◽  
Clark G. CORSTORPHINE ◽  
Victor A. ZAMMIT
Keyword(s):  
Outer Membrane ◽  
Carnitine Palmitoyltransferase ◽  
Transmembrane Domains ◽  
Proteinase K ◽  
Mitochondrial Outer Membrane ◽  
Malonyl Coa ◽  
Cytosolic Side ◽  
Carnitine Palmitoyltransferase I ◽  
Cpt I ◽  
Peptide Antibodies

The topology of carnitine palmitoyltransferase I (CPT I) in the outer membrane of rat liver mitochondria was studied using several approaches. 1. The accessibility of the active site and malonyl-CoA-binding site of the enzyme from the cytosolic aspect of the membrane was investigated using preparations of octanoyl-CoA and malonyl-CoA immobilized on to agarose beads to render them impermeant through the outer membrane. Both immobilized ligands were fully able to interact effectively with CPT I. 2. The effects of proteinase K and trypsin on the activity and malonyl-CoA sensitivity of CPT I were studied using preparations of mitochondria that were either intact or had their outer membranes ruptured by hypo-osmotic swelling (OMRM). Proteinase K had a marked but similar effect on CPT I activity irrespective of whether only the cytosolic or both sides of the membrane were exposed to it. However, it affected sensitivity more rapidly in OMRM. By contrast, trypsin only reduced CPT I activity when incubated with OMRM. The sensitivity of the residual CPT I activity was unaffected by trypsin. 3. The proteolytic fragments generated by these treatments were studied by Western blotting using three anti-peptide antibodies raised against linear epitopes of CPT I. These showed that a proteinase K-sensitive site close to the N-terminus was accessible from the cytosolic side of the membrane. No trypsin-sensitive sites were accessible in intact mitochondria. In OMRM, both proteinase K and trypsin acted from the inter-membrane space side of the membrane. 4. The ability of intact mitochondria and OMRM to bind to each of the three anti-peptide antibodies was used to study the accessibility of the respective epitopes on the cytosolic and inter-membrane space sides of the membrane. 5. The results of all these approaches indicate that CPT I adopts a bitopic topology within the mitochondrial outer membrane; it has two transmembrane domains, and both the N- and C-termini are exposed on the cytosolic side of the membrane, whereas the linker region between the transmembrane domains protrudes into the intermembrane space.

scholarly journals Human skeletal muscle carnitine palmitoyltransferase I activity determined in isolated intact mitochondria

1998 ◽  
Vol 85 (1) ◽  
pp. 148-153 ◽  
Author(s):  
Phanélie M. Berthon ◽  
Richard A. Howlett ◽  
George J. F. Heigenhauser ◽  
Lawrence L. Spriet
Keyword(s):  
Skeletal Muscle ◽  
Citrate Synthase ◽  
Vastus Lateralis ◽  
Maximal Oxygen Consumption ◽  
Carnitine Palmitoyltransferase ◽  
Vastus Lateralis Muscle ◽  
Malonyl Coa ◽  
Human Muscle Biopsy ◽  
Carnitine Palmitoyltransferase I ◽  
Cpt I

This study was designed to compare the activity of skeletal muscle carnitine palmitoyltransferase I (CPT I) in trained and inactive men ( n = 14) and women ( n = 12). CPT I activity was measured in intact mitochondria, isolated from needle biopsy vastus lateralis muscle samples (∼60 mg). The variability of CPT I activity determined on two biopsy samples from the same leg on the same day was 4.4, whereas it was 7.0% on two biopsy samples from the same leg on different days. The method was sensitive to the CPT I inhibitor malonyl-CoA (88% inhibition) and therefore specific for CPT I activity. The mean CPT I activity for all 26 subjects was 141.1 ± 10.6 μmol ⋅ min−1 ⋅ kg wet muscle (wm)−1 and was not different when all men vs. all women (140.5 ± 15.7 and 142.2 ± 14.5 μmol ⋅ min−1 ⋅ kg wm−1, respectively) were compared. However, CPT I activity was significantly higher in trained vs. inactive subjects for both men (176.2 ± 21.1 vs. 104.1 ± 13.6 μmol ⋅ min−1 ⋅ kg wm−1) and women (167.6 ± 14.1 vs. 91.2 ± 9.5 μmol ⋅ min−1 ⋅ kg wm−1). CPT I activity was also significantly correlated with citrate synthase activity (all subjects, r = 0.76) and maximal oxygen consumption expressed in milliliters per kilogram per minute (all subjects, r = 0.69). The results of this study suggest that CPT I activity can be accurately and reliably measured in intact mitochondria isolated from human muscle biopsy samples. CPT I activity was not affected by gender, and higher activities in aerobically trained subjects appeared to be the result of increased mitochondrial content in both men and women.

scholarly journals Roles of the N- and C-terminal domains of carnitine palmitoyltransferase I isoforms in malonyl-CoA sensitivity of the enzymes: insights from expression of chimaeric proteins and mutation of conserved histidine residues

1998 ◽  
Vol 335 (3) ◽  
pp. 513-519 ◽  
Author(s):  
S. Todd SWANSON ◽  
Daniel W. FOSTER ◽  
J. Denis McGARRY ◽  
Nicholas F. BROWN
Keyword(s):  
Carnitine Palmitoyltransferase ◽  
Mitochondrial Outer Membrane ◽  
Irreversible Inhibitor ◽  
Muscle Enzymes ◽  
Histidine Residues ◽  
Terminal Domain ◽  
Malonyl Coa ◽  
Carnitine Palmitoyltransferase I ◽  
Cpt I ◽  
Terminal Domains

The mitochondrial outer membrane enzyme carnitine palmitoyltransferase I (CPT I) plays a major role in the regulation of fatty acid entry into the mitochondrial matrix for β-oxidation by virtue of its inhibition by malonyl-CoA. Two isoforms of CPT I, the liver type (L) and muscle type (M), have been identified, the latter being 100 times more sensitive to malonyl-CoA and having a much higher Km for the substrate carnitine. Here we have examined the roles of different regions of the CPT I molecules in their response to malonyl-CoA, etomoxir (an irreversible inhibitor) and carnitine. To this end, we analysed the properties of engineered rat CPT I constructs in which (a) the N-terminal domain of L-CPT I was deleted, (b) the N-terminal domains of L- and M-CPT I were switched, or (c) each of three conserved histidine residues located towards the N-terminus in L-CPT I was mutated. Several novel points emerged: (1) whereas the N-terminal domain is critical for a normal malonyl-CoA response, it does not itself account for the widely disparate sensitivities of the liver and muscle enzymes to the inhibitor; (2) His-5 and/or His-140 probably play a direct role in the malonyl-CoA response, but His-133 does not; (3) the truncated, chimaeric and point- mutant variants of the enzyme all bound the covalent, active-site- directed ligand, etomoxir; and (4) only the most radical alteration of L-CPT I, i.e. deletion of the N-terminal 82 residues, affected the response to carnitine. We conclude that the N-terminal domain of CPT I plays an essential, but permissive, role in the inhibition of the enzyme by malonyl-CoA. By contrast, the larger C-terminal region dictates the degree of sensitivity to malonyl-CoA, as well as the response to carnitine; it is also sufficient for etomoxir binding. Additionally, further weight is added to the notion that one or more histidine residues may be involved in the CPT I–malonyl-CoA interaction.

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