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P Clouet

Publications and source records attributed to P Clouet.

At least 37 records · Page 2Linked to original sources
PubMed1991

Distribution of tritium labeled 12(S) hydroxy-eicosatetraenoic acid (12-HETE) in the rat.

The in vivo metabolism of 12-(S)-Hydroxy-eicosatetraenoic acid (12-HETE), the end-lipoxygenase product of arachidonic acid in platelets, has been investigated in the rat. Fifty microcuries of 5,6-[3H]-12-HETE (50 Ci/mmol) were injected to anesthetized rats and the radioactivity was followed in plasma. At the end of the experiment, various organs of the animal were removed and the radioactivity attached to them was determined. The label of the plasma plateaued to approximately one third of the initial radioactivity ten minutes after the injection. Among the various organs tested (brain, heart, intestine, kidney, liver, lungs, spleen, testis/uterus) the kidney was far the most active to accumulate 12-HETE and/or its labeled metabolites, and no radioactivity could be detected in urine during the course of the experiment. The analysis of lipid extracts from the various tissues revealed that 12-HETE was not accumulating in its unesterified form but was likely bound to phospholipids. We conclude that, although the label providing from the initial 12-HETE did not completely disappear from plasma, circulating 12-HETE cannot be considered as a circulating marker of cell activation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1990

Short term treatment by fenofibrate enhances oxidative activities towards long-chain fatty acids in the liver of lean Zucker rats.

Lean Zucker rats were dosed orally for 1 week with fenofibrate (100 mg/kg/day). Liver weights of treated rats, expressed as per cent of body weight, were increased, while protein, DNA and triacylglycerol contents were not changed to any great extent per gram of liver, but increased when expressed per whole liver. Compared with the control animals, activities of fatty acid oxidase, of the peroxisomal fatty acid-oxidizing system and of catalase were markedly enhanced by fenofibrate, both per gram of liver and per total liver, while urate oxidase activity was slightly depressed when expressed per gram of liver. The activity of cytochrome c oxidase used as a mitochondrial marker was only higher when expressed per total liver. Besides, fenofibrate treatment induced a pronounced increase in the mitochondrial activities of carnitine palmitoyl- and acetyltransferases, of palmitoyl-CoA dehydrogenase and of carnitine-dependent oleate oxidation. Fenofibrate also enhanced significantly the carnitine content in liver and hepatic mitochondria. Malonyl-CoA content per gram of liver was found to be twice as high as in control rats, while the sensitivity of carnitine acyltransferase I to malonyl-CoA inhibition was hardly altered. The drug enhanced the percentage of palmitic acid in lipids of liver, but not in adipose tissues. The present data show that fenofibrate induced greater oxidative activities towards fatty acids, even in the lean animal. This stimulation could be related to the energy used for building new cells. In turn, at the same time of treatment, an enhanced fatty acid synthesis would provide specific fatty acids for the formation of new membranes. This latter effect will eventually disappear and the maintenance of a higher fatty acid oxidation may explain part of the overall hypolipaemic effect of fenofibrate.

Animals↗
PubMed1989

Pathway of alpha-linolenic acid through the mitochondrial outer membrane in the rat liver and influence on the rate of oxidation. Comparison with linoleic and oleic acids.

The movement of alpha-linolenic acid (C18:3, n-3) through the mitochondrial outer membrane to oxidation sites was studied in rat liver and compared with the movement of linoleic acid (C18:2, n-6) and oleic acid (C18:1, n-9). All differ in the degree of unsaturation, but have the same chain length and the same position of the first double bond when counted from the carboxyl end. The following results were obtained. (1) The overall beta-oxidation in total mitochondria was in the order C18:3, n-3 greater than C18:2, n-6 greater than C18:1, n-9, independent of the amount of albumin in the medium. (2) The rate of formation of acylcarnitine from acyl-CoA was higher with oleoyl-CoA than with linoleoyl-CoA, and remained very low with alpha-linolenoyl-CoA for all concentrations studied. (3) When the formation of acylcarnitines originated from fatty acids (as potassium salts) in a medium containing CoA and ATP, the conversion of alpha-linolenate was greater than that of linoleate, which in turn was greater than that of oleate. (4) Use of a more purified mitochondrial fraction, practically devoid of peroxisomes, did not modify the results obtained with alpha-linolenate. (5) alpha-Linolenoyl-CoA did not inhibit oxidation of labelled alpha-linolenate, whereas the other acyl-CoAs did. (6) Transfer to carnitine of all three fatty acids (as potassium salts) by carnitine palmitoyltransferase-I (CPT-I) was similarly inhibited by increasing concentrations of malonyl-CoA. (7) On using a fraction containing mitochondrial outer membranes, the formation of acylcarnitines from potassium salts of fatty acids was qualitatively and quantitatively similar to that found with whole mitochondria. (8) Our observations show that alpha-linolenoyl-CoA synthesized other than in the mitochondria cannot be used to any great extent by the mitochondria due to its configuration. However when added as the unactivated form, alpha-linolenate appears to be very quickly oxidized, but should first be activated by acyl-CoA synthetase in the mitochondrion itself. Then it is rapidly channelled to CPT-I. These enzymic sites are probably close together in the mitochondrial outer membrane. The different behaviour of the alpha-linolenic group compared with the other acyl groups in the studied pathway can be explained by a different spatial arrangement due to the number and position of the double bonds.

Acyl Coenzyme A↗
PubMed1989

Octanoate metabolism in isolated hepatocytes and mitochondria from fetal, newborn and adult rabbit. Evidence for a high capacity for octanoate esterification in term fetal liver.

Ketogenesis from endogenous fatty acids or from exogenous octanoate has been studied in isolated hepatocytes from fetal. 24-h-old newborn and adult rabbit. In fed adult rabbits, endogenous ketogenesis is low and increases sixfold in the presence of 2 mM octanoate. At birth, endogenous ketogenesis is low and markedly increases 24 h after birth but, in both cases, the addition of 2 mM octanoate does not increase the rates of ketone body production. Hepatocytes isolated from 24-h-old newborn or fed adult rabbits and incubated with [1-14C]octanoate show a preferential channeling of fatty acid into oxidation (84-92% of octanoate metabolized). In contrast, esterification represents 43% of the amount of octanoate metabolized at birth. Chromatographic analysis of labelled triacylglycerols shows that 76 +/- 2% of labelled fatty acids are identified as octanoate and all of the radioactivity in the octanoate peak is due to the carboxyl carbon. In hepatocytes from term fetus, the low capacity for octanoate oxidation is associated with a high capacity for esterification, whatever the octanoate concentration in the medium. Octanoate activated to octanoyl-CoA in the cytosol of fetal hepatocyte is not oxidized in the mitochondria since carnitine acyltransferase I has a low activity at birth in the rabbit. This suggests that only a part of the octanoate pool is activated outside the mitochondria. Factors involved in the direct esterification of octanoate into triacylglycerols in term fetal hepatocytes are discussed.

Animals↗
PubMed1987

Effects of fenofibrate treatment on fatty acid oxidation in liver mitochondria of obese Zucker rats.

Obese Zucker rats were dosed orally for one week with fenofibrate (100 mg/kg). Liver weights of treated rats as expressed as percent of body weight were slightly increased, while protein, DNA and lipid contents were unaffected per g of liver or increased when expressed in whole liver. Compared with the control animals, activities of fatty acid oxidase, of the peroxisomal fatty acid-oxidizing system and of catalase were markedly increased by fenofibrate both per g of liver and per total liver, while urate oxidase activity was unchanged when expressed per g of liver. The activity of monoamine oxidase and that of cytochrome c oxidase used as marker enzymes for mitochondria were increased only when expressed per total liver. However, fenofibrate treatment induced a pronounced increase in the activities of mitochondrial palmitoyl-CoA dehydrogenase and carnitine acyltransferases, particularly carnitine acetyltransferase. Fenofibrate also caused a significant increase of carnitine content in liver and hepatic mitochondria. The greatest observed increases were in free carnitine and in the rate of carnitine-dependent oleate oxidation, which might be favoured in vivo by a lesser sensitivity of CPT-I to a malonyl-CoA inhibitory effect. The present results suggest that fenofibrate treatment induces increased hepatic mitochondrial beta-oxidation in obese Zucker rats.

Animals↗
PubMed1986

Study of some factors controlling fatty acid oxidation in liver mitochondria of obese Zucker rats.

Livers of genetically obese Zucker rats showed, compared with lean controls, hypertrophy and enrichment in triacylglycerols, indicating that fatty acid metabolism was directed towards lipogenesis and esterification rather than towards fatty acid oxidation. Mitochondrial activities of cytochrome c oxidase and monoamine oxidase were significantly lower when expressed per g wet wt. of liver, whereas peroxisomal activities of urate oxidase and palmitoyl-CoA-dependent NAD+ reduction were unchanged. Liver mitochondria were able to oxidize oleic acid at the same rate in both obese and lean rats. For reactions occurring inside the mitochondria, e.g. octanoate oxidation and palmitoyl-CoA dehydrogenase, no difference was found between both phenotypes. Total carnitine palmitoyl-, octanoyl- and acetyl-transferase activities were slightly higher in mitochondria from obese rats, whereas the carnitine content of both liver tissue and mitochondria was significantly lower in obese rats compared with their lean littermates. The carnitine palmitoyltransferase I activity was slightly higher in liver mitochondria from obese rats, but this enzyme was more sensitive to malonyl-CoA inhibition in obese than in lean rats. The above results strongly suggest that the impaired fatty acid oxidation observed in the whole liver of obese rats is due to the diminished transport of fatty acids across the mitochondrial inner membrane via the carnitine palmitoyltransferase I. This effect could be reinforced by the decreased mitochondrial content per g wet wt. of liver. The depressed fatty acid oxidation may explain in part the lipid infiltration of liver observed in obese Zucker rats.

Animals↗
PubMed1982

[Modes of action of a shortening system for erucic acid at the mitochondrial level of rat liver].

In this work, were studied the conditions of erucic acid (cis-docosenoic, n-9) shortening by using Rat liver mitochondrial preparations which were incubated in vitro with [14-14C] erucic acid (22:1), with inhibitors of the respiratory chain (rotenone, cyanide) or not, with activators of either the shortening reaction (NAD+, NADP+), or beta-oxidation (malate, carnitine, cytochrome c) or not. The shortening activity was measured by the amount of 14C radioactivity recovered in the shorter fatty acids formed (20:1, 18:1, 16:1) when beta-oxidation was inhibited. The beta-oxidation activity was measured by the amount of 14C recovered in the acid-soluble products (P A S). The incubations were performed under conditions which were the least favourable to peroxysomal activity. Data showed that, with increasing amounts of albumin, which inhibits peroxysomal activity, increasing amounts of shorter fatty acids (20:1, 18:1, 16:1) were formed from erucic acid. This shortening reaction was strongly stimulated by NAD+, more than by NADP+; it was also stimulated by cytochrome c and much more when both NAD+ and cytochrome c were added. Similar data were observed in beta-oxidation, except that practically NADP+ did not exhibit any stimulating effect. Oxidation of NADH by mitochondria only occurred when cytochrome c was added to the medium and was not modified by the addition of ADP or rotenone. These data show that liver mitochondria are capable of shortening erucic acid, as are peroxysomes. This shortening reaction is highly NAD+-dependent and seems to be localized outside the matrix. This system could constitute a second route for utilization of fatty acids in mitochondria, besides the well-known path of beta-oxidation.

Animals↗
PubMed1980

[Conversion of erucic acid in subcellular fractions from liver, kidneys and heart of rat, 8 min after intravenous injection (author's transl)].

Rats were intravenously injected with albumin-bound [14 14C] erucic acid, and after 8 min the 14C radioactivity (RA) of the fatty acids were studied in mitochondria, microsomes and other fractions of liver, kidneys and heart cells. 1. In liver, which contained 15% of the injected RA, oleic acid (18 : 1) was the main fatty acid (FA) formed (26% of the 14C recovered) whereas in kidneys (0,53% of the injected RA) the proportion of nervonic acid (24 : 1) was higher (20%) than that of 18 : 1 (14%). No appreciable transformation was encountered in heart, which contained 0,53% of the injected RA. 2. In liver, the microsomes showed the higher converted 14C RA (45%), mainly as 18 : 1 (33%), much higher than in mitochondria (11%), whereas the amount of total 14C FA was a little higher in the latter fraction. 3. In kidneys, the mitochondrial and microsomal fractions contained the same percentage of 14C oleic acid (15%), whereas nervonic acid was recovered in higher proportion, 29 and 20%, in microsomes and in mitochondria respectively. 4. Results show that the same kind of metabolic activity, i.e., shortening or elongation, was observed in the whole cell as that previously shown with isolated fractions. However, mitochondrial oxidation and exchanges of transformed fatty acids between organelles can modify the extent of the phenomenon.

Animals↗
PubMed1979

[Comparative oxidation of erucic and oleic acids by mitochondria isolated from heart auricle of living man].

Mitochondria were isolated from fragments of heart auricles, that were cut off during surgical intracardiac operations. They were incubated with either [14 14C] erucic acid or [10 14C] oleic acid as a control. In the experimental conditions used, the radioactive products soluble in perchloric acid, that are issued from the beta-oxidation reactions in mitochondria, were formed in much lower amounts from erucic acid than from oleic acid. These results show the very low capacity of human heart mitochondria to use directly erucic acid as a substrate for energy requirements, as has been observed before with other animal species. Activation of fatty acids, the preliminary step of their beta-oxidation, was also observed to be very much lower with erucic acid.

Adult↗
PubMed1979

In vitro conversion of erucic acid by microsomes and mitochondria from liver, kidneys and heart of rats.

Microsomes and mitochondria of liver, kidneys, and heart were incubated with [14-(14)C] erucic acid in three assay media: one favorable for chain elongation (NADPH + KCN), another favorable for beta-oxidation and the last one for shortening (NADP + KCN). Elongating reactions occurred mainly in microsomes, those of kidneys being very active; the mitochondria also showed some activity, heart mitochondria being, however, more active than the microsomes, when considering the amount of erucic acid activated. In the medium for beta-oxidation, practically no shortened fatty acids were found. On the contrary, when beta-oxidation was inhibited, and in the presence of NADP, the formation of shorter monoenes, probably in the outer membrane of the mitochondria, was observed, namely eicosenoic acid in high amount, oleic acid and hexadecenoic acid. Mitochondria from liver were very active as were those of heart, when compared with the quantity of activated erucic acid. In heart, the mitochondria shortened erucic acid into oleic acid and hexadecenoic acid, which were then probably used as energy substrates. With carnitine and without NADP, shortened fatty acids were formed in the mitochondria of liver, probably by the first reactions of beta-oxidation. In this case, the proportions of oleic acid and hexadecenoic acid were higher than with NADP alone. In the presence of carnitine and NADP, the level of the chain-shortening reaction did not differ from that observed with NADP alone. It appears, therefore, that the activated erucic acid is mainly directed towards shortening reactions and not towards transfer reactions across the mitochondrial membranes.

Animals↗
PubMed1976

[Influence of rapeseed oil feeding on morphology and oxidative properties of mitochondria isolated from the rat heart].

Mitochondria from heart of rats fed a diet rich in rapeseed oil for two months from weaning, oxidized oleic acid a little better than those from animals fed a control diet containing peanut oil; but their activity decreased much more in presence of potassium cyanide which is an oxidation inhibitor. When observed by electronic microscopy, mitochondria from heart of rats fed rapeseed oil were more mumerous and more mitochondria of great size were encountered as compared with control rats. Biochemical data seemed to show a decrease of activity or quantity of certain enzymatic systems in mitochondria from heart of animals fed rapseed oil. Cyanide could more easily inhibit these enzymatic systems because of their deficiency. It can be thought that it is the mitochondria of great size which are implicated in this phenomenon since their growth is not accompanied by an increase of their content in certain enzymes which are just sensitive to cyanide. A mixture richer in mitochondria of big size, thus poorer in certain enzymes for an equal protein content in drastic conditions, such as partial anoxia since cyanide blocks the respiratory chain.

Administration, Oral↗
PubMed1975

[Oxidation of erucic acid and erucyl-CoA by isolated rat heart mitochondria: comparison to oleic acid].

The oxidation of [14 14-C] or [1 14-C] erucic acid by isolated mitochondria from Rat heart has been studied and compared with that of [10 14-C] oleic acid in varying conditions of incubation. Erucic acid is converted to CO2 and acid-soluble compounds much more slowly than oleic acid. The acid-soluble compounds which have been identified are acylcarnitines, ketone bodies and intermediates from the Krebs cycle; they are found in similar proportions for both substrates. Moreover, the oxidation rate of erucyl-CoA is comparable, if not equal, to that of oleyl-CoA in the same conditions. These results are discussed here. They lead to the conclusion that erucic acid is oxidized by isolated Rat heart mitochondria through the beta oxidation pathway, and that its oxidation is limited owing to its slow activation rate.

Animals↗