scholarly journals Reduction pathway of cis-5 unsaturated fatty acids in intact rat-liver and rat-heart mitochondria: assessment with stable-isotype-labelled substrates

1996 ◽  
Vol 313 (2) ◽  
pp. 581-588 ◽  
Author(s):  
Kou-Yi TSERNG ◽  
Shiow-Jen JIN ◽  
Lin-Su CHEN
Keyword(s):  
Fatty Acids ◽  
Rat Liver ◽  
Rat Heart ◽  
Unsaturated Fatty Acids ◽  
Direct Reduction ◽  
Saturated Fatty Acids ◽  
Liver Mitochondria ◽  
Hydroxy Fatty Acids ◽  
Heart Mitochondria ◽  
Rat Heart Mitochondria

Besides the conventional isomerase-mediated pathway, unsaturated fatty acids with odd-numbered double bonds are also metabolized by reduction pathways with NADPH as cofactor. The relative contributions of these pathways were measured in intact rat-liver and rat-heart mitochondria with a novel stable isotope tracer technique. A mixture of equal amounts of unlabelled cis-5-enoyl-CoA and 13C4-labelled acyl-CoA of equal chain lengths was incubated with mitochondria. The isotope distribution of 3-hydroxy fatty acids produced from the first cycle of β-oxidation was analysed with selected ion monitoring by gas chromatograph-mass spectrometer. 3-Hydroxy fatty acids produced from the reduction pathway of unsaturated fatty acids were unlabelled (m+0) whereas those produced from saturated fatty acids were labelled (m+4). The m+0 content serves to indicate the extent of reduction pathway. Rotenone treatment was used to switch the pathway completely to reduction. The extent of m+0 enrichment in untreated mitochondria normalized to the m+0 enrichment of rotenone-treated mitochondria was the percentage of reduction pathway. With this technique, cis-4-decenoate was found to be metabolized completely by the reduction pathway in both liver and heart mitochondria. cis-5-Dodecenoate was metabolized essentially by the reduction pathway in liver mitochondria, but only to 75% in heart mitochondria. When the chain length was extended to cis-5-tetradecenoate, the reduction pathway in liver mitochondria decreased to 86% and that in heart mitochondria to 65%. The effects of carnitine, clofibrate and other conditions on the reduction pathway were also studied. Enrichments of the label on saturated fatty acids and 3-hydroxy fatty acids indicated that the major pathway of reduction was not by the direct reduction of the cis-5 double bond. Instead, it is most probably by a pathway that does not involve forming a reduced saturated fatty acid first.

scholarly journals Oxidation of cis-5-unsaturated fatty acids in intact rat liver mitochondria: the operation of reduction pathways

1995 ◽  
Vol 308 (1) ◽  
pp. 39-44 ◽  
Author(s):  
K Y Tserng ◽  
S J Jin
Keyword(s):  
Fatty Acids ◽  
Rat Liver ◽  
Capillary Column ◽  
Unsaturated Fatty Acids ◽  
Direct Reduction ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Capillary Column Gas Chromatography ◽  
Coa Reductase ◽  
Direct Quantification

The metabolism of cis-5 unsaturated fatty acids was studied in intact rat liver mitochondria to assess the operation of a reduction pathway. By using direct quantification of metabolites with a capillary-column gas chromatography, 3-hydroxydodecanoate was identified among other metabolites when cis-5-dodecenoate was metabolized in intact rat liver mitochondria. The formation of 3-hydroxydodecanoate supports the existence of a reduction pathway in the metabolism of cis-5-unsaturated fatty acids. This metabolite cannot be produced from the conventional isomerase-mediated pathway. However, the data also indicated the possible operation of the conventional isomerase-mediated pathway in intact rat liver mitochondria. The reduction pathway appears to account for at least 61% of the pathway for cis-5-dodecenoate. This reduction pathway was likely to proceed from the dehydrogenation to trans-2,cis-5-dodecadienoyl-CoA, which was isomerized to delta 3, delta 5-dodecadienoyl-CoA, then to trans-2,trans-4-dodecadienoate. The reduction was mediated by 2,4-dienoyl-CoA reductase by the conversion of trans-2,trans-4-dodecadienoyl-CoA into trans-3-dodecenoyl-CoA. However, direct reduction of the cis-5 double bond was also shown to be operating, although to a lesser extent.

Structure of paracrystalline arrays on outer membranes of rat-liver and rat-heart mitochondria

1992 ◽  
Vol 108 (3) ◽  
pp. 227-237 ◽  
Author(s):  
C.A. Mannella ◽  
A. Ribeiro ◽  
B. Cognon ◽  
D. D'Arcangelis
Keyword(s):  
Rat Liver ◽  
Rat Heart ◽  
Heart Mitochondria ◽  
Outer Membranes ◽  
Rat Heart Mitochondria

scholarly journals Fatty acid metabolism in the perfused rat liver

1970 ◽  
Vol 119 (3) ◽  
pp. 525-533 ◽  
Author(s):  
H. A. Krebs ◽  
R. Hems
Keyword(s):  
Fatty Acids ◽  
Rat Liver ◽  
Ketone Body ◽  
Unsaturated Fatty Acids ◽  
Ketone Bodies ◽  
Saturated Fatty Acids ◽  
Perfused Rat Liver ◽  
Body Formation ◽  
Body Production ◽  
Chain Fatty Acids

1. The formation of acetoacetate, β-hydroxybutyrate and glucose was measured in the isolated perfused rat liver after addition of fatty acids. 2. The rates of ketone-body formation from ten fatty acids were approximately equal and independent of chain length (90–132μmol/h per g), with the exception of pentanoate, which reacted at one-third of this rate. The [β-hydroxybutyrate]/[acetoacetate] ratio in the perfusion medium was increased by long-chain fatty acids. 3. Glucose was formed from all odd-numbered fatty acids tested. 4. The rate of ketone-body formation in the livers of rats kept on a high-fat diet was up to 50% higher than in the livers of rats starved for 48h. In the livers of fat-fed rats almost all the O2 consumed was accounted for by the formation of ketone bodies. 5. The ketone-body concentration in the blood of fat-fed rats rose to 4–5mm and the [β-hydroxybutyrate]/[acetoacetate] ratio rose to 11.5. 6. When the activity of the microsomal mixed-function oxidase system, which can bring about ω-oxidation of fatty acids, was induced by treatment of the rat with phenobarbitone, there was no change in the ketone-body production from fatty acids, nor was there a production of glucose from even-numbered fatty acids. The latter would be expected if ω-oxidation occurred. Thus ω-oxidation did not play a significant role in the metabolism of fatty acids. 7. Arachidonate was almost quantitatively converted into ketone bodies and yielded no glucose, demonstrating that gluconeogenesis from poly-unsaturated fatty acids with an even number of carbon atoms does not occur. 8. The rates of ketogenesis from unsaturated fatty acids (sorbate, undecylenate, crotonate, vinylacetate) were similar to those from the corresponding saturated fatty acids. 9. Addition of oleate together with shorter-chain fatty acids gave only a slightly higher rate of ketone-body formation than oleate alone. 10. Glucose, lactate, fructose, glycerol and other known antiketogenic substances strongly inhibited endogenous ketogenesis but had no effects on the rate of ketone-body formation in the presence of 2mm-oleate. Thus the concentrations of free fatty acids and of other oxidizable substances in the liver are key factors determining the rate of ketogenesis.

scholarly journals The regulation of the oxidation of fatty acids and other substrates in rat heart mitochondria by changes in the matrix volume induced by osmotic strength, valinomycin and Ca2+

1987 ◽  
Vol 244 (1) ◽  
pp. 159-164 ◽  
Author(s):  
A P Halestrap
Keyword(s):  
Rat Heart ◽  
Electron Flow ◽  
Liver Mitochondria ◽  
Heart Mitochondria ◽  
Acid Oxidation ◽  
Maximal Effect ◽  
Physiological Conditions ◽  
Matrix Volume ◽  
The Matrix ◽  
Rat Heart Mitochondria

1. The rate of ADP-stimulated respiration with various substrates and the matrix volume of rat heart mitochondria were measured over a range of osmolarities of the medium. 2. The rate of oxidation of palmitoylcarnitine (in the presence of malate) was stimulated 7-fold by increasing the matrix volume from 0.6 to 1.0 microliter/mg of protein. Oxidation of octanoate showed a similar sensitivity to the matrix volume, whereas oxidation of other substrates showed little sensitivity until the volume fell below 0.7 microliter/mg of protein. 3. The matrix volume of heart mitochondria incubated under physiological conditions was about 0.8 microliter/mg of protein. 4. Low concentrations of valinomycin added to mitochondria incubated under such physiological conditions could activate the rate of ADP-stimulated palmitoylcarnitine oxidation by at least 100%. 5. Decreasing the matrix volume increased the reduction of the electron-transferring flavoprotein (ETF), suggesting an effect on electron flow between ETF and ubiquinone, as has been observed for liver mitochondria [Halestrap & Dunlop (1986) Biochem. J. 239, 559-565]. 6. A rapid decrease in light-scattering by heart mitochondria incubated in State 4 was induced by addition of Ca2+, reaching 50% of the maximal effect after about 30 s at 30 degrees C and with K0.5 for Ca2+ of 0.3 microM. This was not associated with a change in matrix volume, and is discussed in terms of a conformational change whose identity remains to be determined. 7. However, incubation of heart mitochondria at 37 degrees C in the presence of 0.65 microM-Ca2+ for 4 min did increase the matrix volume significantly, by 0.181 +/- 0.029 microliter/mg of protein (n = 7, P less than 0.001), similar to the Ca2+-induced changes observed with liver mitochondria [Halestrap, Quinlan, Whipps & Armston (1986) Biochem. J. 236, 779-787]. 8. The possible significance of these results in the co-ordinate regulation of fatty acid oxidation and the citric acid cycle in the heart responding to increased work load or hormonal stimulation is discussed.

scholarly journals β-oxidation of polyunsaturated fatty acids with conjugated double bonds. Mitochondrial metabolism of octa-2,4,6-trienoic acid

1989 ◽  
Vol 264 (1) ◽  
pp. 47-52 ◽  
Author(s):  
H Y Wang ◽  
H Schulz
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Unsaturated Fatty Acids ◽  
Liver Mitochondria ◽  
Trienoic Acid ◽  
Rat Liver Mitochondria ◽  
Double Bonds ◽  
Beta Oxidation ◽  
Rat Heart Mitochondria ◽  
Coa Reductase

The mitochondrial beta-oxidation of octa-2,4,6-trienoic acid was studied with the aim of elucidating the degradation of unsaturated fatty acids with conjugated double bonds. Octa-2,4,6-trienoic acid was found to be a respiratory substrate of coupled rat liver mitochondria, but not of rat heart mitochondria. Octa-2,4,6-trienoyl-CoA, the product of the inner-mitochondrial activation of the acid, was chemically synthesized and its degradation by purified enzymes of beta-oxidation was studied spectrophotometrically and by use of h.p.l.c. This compound is a substrate of NADPH-dependent 2,4-dienoyl-CoA reductase or 4-enoyl-CoA reductase (EC 1.3.1.34), which facilitates its further beta-oxidation. The product obtained after the NADPH-dependent reduction of octa-2,4,6-trienoyl-CoA and one round of beta-oxidation was hex-4-enoyl-CoA, which can be completely degraded via beta-oxidation. It is concluded that polyunsaturated fatty acids with two conjugated double bonds extending from even-numbered carbon atoms can be completely degraded via beta-oxidation because their presumed 2,4,6-trienoyl-CoA intermediates are substrates of 2,4-dienoyl-CoA reductase.

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