Les anomalies caracteristiques des sterols circulants et tissulaires associes au syndrome de Smit... more Les anomalies caracteristiques des sterols circulants et tissulaires associes au syndrome de Smith-Lemli-Opitz ont ete decrites en 1994 [1]. Le syndrome hereditaire recessif de Smith-Lemli-Opitz decrit 30 ans auparavant par ces trois pediatres s'est ainsi trouve rattache a un deficit de la voie de biosynthese du cholesterol. Independamment, les modeles animaux de teratogenese crees il y a tres longtemps grâce a des inhibiteurs des etapes terminales de la cholesterologenese [2] ont permis d'emblee de mieux interpreter les mecanismes des malformations chez l'embryon. La demonstration recente que l'activite du gene Sonic hedgehog (SHH) est dependante du cholesterol [3] a confirme le role de celui-ci dans le developpement du systeme nerveux central, des membres et du cœur.
Low cholesterol and high 7-dehydrocholesterol (7DHC) levels are associated with a blockade of ⌬ 7... more Low cholesterol and high 7-dehydrocholesterol (7DHC) levels are associated with a blockade of ⌬ 7-reductase in the Smith-Lemli-Opitz syndrome (SLOS) and in the animals treated with the inhibitor AY9944. The impact of the cholesterol deficit and of the accumulation of 7DHC on the embryo were investigated in AY9944-treated pregnant rats receiving an enriched cholesterol or 7DHC diet. Sterol profiling was performed under the various nutritional conditions. AY9944 caused a severe decrease in the maternal and embryo cholesterol. The deficit in the embryo was sustained by the embryonic uptake of the inhibitor. A cholesterol-rich diet was efficient in restoring the maternal and embryonic cholesterol and phenotype but a 7DHC-rich diet did not modify the sterol status compared with dams treated with only AY9944. The offspring phenotype remained deleterious whether or not the dams received 7DHC-rich diet. Over 80% of the 7DHC was absorbed, as was cholesterol, which was not quantitatively influenced by AY9944. When cholesterol and 7DHC were simultaneously administered, a competition for intestinal absorption enhanced the lowering cholesterol effect of AY9944. Whether or not the dams received a 7DHC dietary supplement, the offspring's phenotype became normal when the diet was supplemented with cholesterol. Under conditions in which the ratio of cholesterol/7DHC is substantially varied, the normal development of embryos can be achieved as long as the cholesterol is sufficient. The phenotype is reversed in vivo by cholesterol which contrasts with the irreversible effects manifested in vitro by oxidized 7DHC by-products.-Gaoua, W., C. Wolf, F. Chevy, F. Ilien, and C. Roux. Cholesterol deficit but not accumulation of aberrant sterols is the major cause of the teratogenic activity in the Smith-Lemli-Opiz syndrome animal model.
Advances in Experimental Medicine and Biology, 1978
In the present investigation we have shown that cytoplasmic membranes of adipocytes contain A1 an... more In the present investigation we have shown that cytoplasmic membranes of adipocytes contain A1 and A2 phospholipase activities which are optimal in a buffer with 5 mM Ca2+ (pH 8.5). Insulin enhances these activities within phosphatidylethanolamine. Insulin increases also the amount of free fatty acids in membranes. Rodbell and Blecher have already shown an insulin-like action of phospholipases towards the uptake of glucose and amino-acids by adipocytes. Shier and Asakawa have recently described that lysolecithin and unsaturated fatty acids can change nucleotide-cyclase activities of cytoplasmic membranes towards GTP and ATP; lysolecithins and Triton X 100 seem to react in an identical way. Results from these studies give new suggestions on insulin action; phospholipase activation changes membrane physiochemical properties inducing an increase of glucose carrier mobility and leading the membrane cyclase enzyme (s) towards GMP cyclic synthesis.
The lipid matrix of biological membranes is composed of a complex mixture of polar lipids. It has... more The lipid matrix of biological membranes is composed of a complex mixture of polar lipids. It has been estimated that more than 600 distinct molecular species oflipid are constituents of biological membranes. This rather remarkable feature raises the questions of why such complexity is required when barrier properties and many protein functions can be reconstituted with relatively simple lipid systems. Secondly, the molecular species composition of morphologically distinct membranes appears to be preserved within fairly narrow limits. The biochemical mechanism(s) responsible for this homeostasis are not fully understood. This review examines the origin of membrane lipid complexity, the methods that are currently employed to measure and detect lipid molecular species and the biochemical reactions associated with the turnover of membrane lipids in resting and stimulated cells.
Prostaglandins, Leukotrienes and Essential Fatty Acids, 2015
Long-chain n À3 (or omega 3) fatty acids, namely docosahexaenoic acid (DHA, 22:6n À 3) and eicosa... more Long-chain n À3 (or omega 3) fatty acids, namely docosahexaenoic acid (DHA, 22:6n À 3) and eicosapentaenoic acid (EPA, 20:5n À 3) have been attributed cardioprotective properties. In this study, we evaluated the incorporation of DHA into cardiomyocytes and the shift in the omega 3/omega 6 ratio after supplementation of primary cardiomyocyte culture. Results are compared with atrial tissue concentrations attained after prolonged feeding of rats. The major difference between in vitro vs. in vivo supplementation is the paradoxical accumulation of arachidonic acid in cultured cardiomyocyte. However, this increase does not give rise to a higher PGE 2 production after cellular stimulation, as compared with controls, possibly because of the associated inhibition of sPLA 2 by DHA. Notably, in vitro supplementations with DHA 10 to 25 μM approximate in vivo pharmacological treatments.
Cells grown in culture are frequently employed to model lipid metabolism in vivo. There are reaso... more Cells grown in culture are frequently employed to model lipid metabolism in vivo. There are reasons of convenience for this but examination of the lipidome of cultured cells and their metabolic responses to lipid supplementation give cause to indicate disparity with their counterparts in living animals. The reason is mainly that homeostatic regulation is exercised in animals supplied with an adequate diet in which the adipose tissue and liver represent plentiful sources of lipid integrated via inter-organ collaboration and able to buffer transient fluctuations in dietary lipid and essential fatty acids (EFAs). Moreover, conventional culture media are generally deficient in total lipids as well as essential EFAs. Cultured cells exposed to high glucose concentrations and lipid deficit typically manifest accelerated rates of lipogenesis evidenced by high rates of de novo FA biosynthesis. A more realistic model may be obtained by increasing supplements of lipid especially enriched in essential EFAs in the growth medium. Increasing concentrations of 3 FAs, in particular, attenuate the rate of de novo lipogenesis. The improvement of cell culture models for pharmacological screening of drug-candidates targeting lipid or glucose metabolism is highlighted.
S29 significantly lower in HBeAg-negative patients (I. I x I O5 vs. 2. 6~ lo7; p = 0.000 I). Inte... more S29 significantly lower in HBeAg-negative patients (I. I x I O5 vs. 2. 6~ lo7; p = 0.000 I). Interestingly, the ratios between serum HBsAg levels and intrahepatic cccDNA were comparable (p i 0.09) between HBeAg positive and negative patients (26 vs. 70, respectively), suggesting that the transcriptional activity of the cccDNA was similar in the two groups. Conclusions: We observed substantial differences in term of viral production between HBeAg positive and negative patients, which appeared to be due not only to the lower cccDNA copy number, but also to an impaired replicative activity of the cccDNA in HBeAg-negative patients.
m The influence of PAF-acether on natural ovolecithin oriented multibilayers is detected by ESR o... more m The influence of PAF-acether on natural ovolecithin oriented multibilayers is detected by ESR of intercalated 5 doxyl stearic acid. Simulation of lineshapes demonstrates an enlarged orientational distribution of the local director of the phospholipid phase and a small increase of the order parameter. The amount of PAF-acether required to destabilize the ovolecithin lamellar phase depends on the degree of hydration. By contrast, cholesterol displays an organizing effect on the PAF-acether phase. Simulation establishes a sharp orientational distribution of the local director when cholesterol reaches stoichiometric ratio relative to PAF-acether. At the same time, cholesterol increases the order narameter
Biochemical and Biophysical Research Communications, 1983
Plasma membrane phospholipids were modified by incubation in the presence of linoleyl-CoA with or... more Plasma membrane phospholipids were modified by incubation in the presence of linoleyl-CoA with or without added lysolecithin (LPC) for various length of time. In the absence of LPC, a maximum of 10 nmoles linoleyl-phosphatidylcholine (PC) were synthesized and the ATPase specific activities were not affected whereas in the presence of LPC, when linoleyl-PC synthesis rose from 10 to 80 nmoles, the ATPase activities were decreased. The decrease was similar in the Na,K- or in the Mg-dependent-ATPase and reached maximally 30-40%. LPC by itself did not modify the ATPases. A concomitant decrease in DPH polarization was observed when linoleate was incorporated into phospholipids. We concluded that the decreased ATPase specific activities may be due to an increased fluidity of membranes produced by linoleyl- PC synthesis. We compare this modulation of ATPases by the membrane fluidity with the specific effect of linoleyl- PC species on adenylate cyclase.
This study supports the possibility for multiple subcellular forms of lipoprotein lipase. 1. The ... more This study supports the possibility for multiple subcellular forms of lipoprotein lipase. 1. The total activity of lipoprotein lipase per g of intact epididymal adipose tissue from fed rats is much higher than that from starved rats. 2. The isolated fat-cells of fed and of starved rats have lipoprotein lipase of almost the same activity per g of fat-pads. The isolated fat-cells of starved rats have a much higher proportion of total activity per g of the intact tissue than do those of fed rats. 3. Under the conditions of homogenization used, only a small proportion of the total activity per g of intact tissue from fed rats was associated with the fat layer which floated to the top of the homogenate during low-speed centrifugation. The different proportions of the specific enzyme activity found in each subcellular fraction are described. 4. Lipoprotein lipase from plasma membranes and microsomal fractions from starved and fed rats was purified by affinity chromatography. 5. The total ...
The binding to human intact erythrocytes of two different spin-labelled derivatives of chlorproma... more The binding to human intact erythrocytes of two different spin-labelled derivatives of chlorpromazine has been studied. The influence of the positively charged side chain of the drug has been the focus of our attention. The positively charged amphiphilic compound (spin derivative I) is water-soluble up to 80 microM at pH values below 5.9. The apolar analogue (spin derivative II) aggregates in aqueous buffer from the lowest concentration tested. Both spin derivatives undergo a slow reduction inside the erythrocyte. The reduced nitroxides are readily reoxidized by adding a low, non-quenching, concentration of potassium ferricyanide to the intact erythrocytes. The fractions of spin label I and II bound to the erythrocyte membrane or to the erythrocyte-extracted lipids remain constant as a function of the temperature (3-42 degrees C) and as a function of the concentration of the spin label up to 150 microM. E.s.r. spectra of both spin labels show a two-component lineshape when they are ...
Les anomalies caracteristiques des sterols circulants et tissulaires associes au syndrome de Smit... more Les anomalies caracteristiques des sterols circulants et tissulaires associes au syndrome de Smith-Lemli-Opitz ont ete decrites en 1994 [1]. Le syndrome hereditaire recessif de Smith-Lemli-Opitz decrit 30 ans auparavant par ces trois pediatres s'est ainsi trouve rattache a un deficit de la voie de biosynthese du cholesterol. Independamment, les modeles animaux de teratogenese crees il y a tres longtemps grâce a des inhibiteurs des etapes terminales de la cholesterologenese [2] ont permis d'emblee de mieux interpreter les mecanismes des malformations chez l'embryon. La demonstration recente que l'activite du gene Sonic hedgehog (SHH) est dependante du cholesterol [3] a confirme le role de celui-ci dans le developpement du systeme nerveux central, des membres et du cœur.
Low cholesterol and high 7-dehydrocholesterol (7DHC) levels are associated with a blockade of ⌬ 7... more Low cholesterol and high 7-dehydrocholesterol (7DHC) levels are associated with a blockade of ⌬ 7-reductase in the Smith-Lemli-Opitz syndrome (SLOS) and in the animals treated with the inhibitor AY9944. The impact of the cholesterol deficit and of the accumulation of 7DHC on the embryo were investigated in AY9944-treated pregnant rats receiving an enriched cholesterol or 7DHC diet. Sterol profiling was performed under the various nutritional conditions. AY9944 caused a severe decrease in the maternal and embryo cholesterol. The deficit in the embryo was sustained by the embryonic uptake of the inhibitor. A cholesterol-rich diet was efficient in restoring the maternal and embryonic cholesterol and phenotype but a 7DHC-rich diet did not modify the sterol status compared with dams treated with only AY9944. The offspring phenotype remained deleterious whether or not the dams received 7DHC-rich diet. Over 80% of the 7DHC was absorbed, as was cholesterol, which was not quantitatively influenced by AY9944. When cholesterol and 7DHC were simultaneously administered, a competition for intestinal absorption enhanced the lowering cholesterol effect of AY9944. Whether or not the dams received a 7DHC dietary supplement, the offspring's phenotype became normal when the diet was supplemented with cholesterol. Under conditions in which the ratio of cholesterol/7DHC is substantially varied, the normal development of embryos can be achieved as long as the cholesterol is sufficient. The phenotype is reversed in vivo by cholesterol which contrasts with the irreversible effects manifested in vitro by oxidized 7DHC by-products.-Gaoua, W., C. Wolf, F. Chevy, F. Ilien, and C. Roux. Cholesterol deficit but not accumulation of aberrant sterols is the major cause of the teratogenic activity in the Smith-Lemli-Opiz syndrome animal model.
Advances in Experimental Medicine and Biology, 1978
In the present investigation we have shown that cytoplasmic membranes of adipocytes contain A1 an... more In the present investigation we have shown that cytoplasmic membranes of adipocytes contain A1 and A2 phospholipase activities which are optimal in a buffer with 5 mM Ca2+ (pH 8.5). Insulin enhances these activities within phosphatidylethanolamine. Insulin increases also the amount of free fatty acids in membranes. Rodbell and Blecher have already shown an insulin-like action of phospholipases towards the uptake of glucose and amino-acids by adipocytes. Shier and Asakawa have recently described that lysolecithin and unsaturated fatty acids can change nucleotide-cyclase activities of cytoplasmic membranes towards GTP and ATP; lysolecithins and Triton X 100 seem to react in an identical way. Results from these studies give new suggestions on insulin action; phospholipase activation changes membrane physiochemical properties inducing an increase of glucose carrier mobility and leading the membrane cyclase enzyme (s) towards GMP cyclic synthesis.
The lipid matrix of biological membranes is composed of a complex mixture of polar lipids. It has... more The lipid matrix of biological membranes is composed of a complex mixture of polar lipids. It has been estimated that more than 600 distinct molecular species oflipid are constituents of biological membranes. This rather remarkable feature raises the questions of why such complexity is required when barrier properties and many protein functions can be reconstituted with relatively simple lipid systems. Secondly, the molecular species composition of morphologically distinct membranes appears to be preserved within fairly narrow limits. The biochemical mechanism(s) responsible for this homeostasis are not fully understood. This review examines the origin of membrane lipid complexity, the methods that are currently employed to measure and detect lipid molecular species and the biochemical reactions associated with the turnover of membrane lipids in resting and stimulated cells.
Prostaglandins, Leukotrienes and Essential Fatty Acids, 2015
Long-chain n À3 (or omega 3) fatty acids, namely docosahexaenoic acid (DHA, 22:6n À 3) and eicosa... more Long-chain n À3 (or omega 3) fatty acids, namely docosahexaenoic acid (DHA, 22:6n À 3) and eicosapentaenoic acid (EPA, 20:5n À 3) have been attributed cardioprotective properties. In this study, we evaluated the incorporation of DHA into cardiomyocytes and the shift in the omega 3/omega 6 ratio after supplementation of primary cardiomyocyte culture. Results are compared with atrial tissue concentrations attained after prolonged feeding of rats. The major difference between in vitro vs. in vivo supplementation is the paradoxical accumulation of arachidonic acid in cultured cardiomyocyte. However, this increase does not give rise to a higher PGE 2 production after cellular stimulation, as compared with controls, possibly because of the associated inhibition of sPLA 2 by DHA. Notably, in vitro supplementations with DHA 10 to 25 μM approximate in vivo pharmacological treatments.
Cells grown in culture are frequently employed to model lipid metabolism in vivo. There are reaso... more Cells grown in culture are frequently employed to model lipid metabolism in vivo. There are reasons of convenience for this but examination of the lipidome of cultured cells and their metabolic responses to lipid supplementation give cause to indicate disparity with their counterparts in living animals. The reason is mainly that homeostatic regulation is exercised in animals supplied with an adequate diet in which the adipose tissue and liver represent plentiful sources of lipid integrated via inter-organ collaboration and able to buffer transient fluctuations in dietary lipid and essential fatty acids (EFAs). Moreover, conventional culture media are generally deficient in total lipids as well as essential EFAs. Cultured cells exposed to high glucose concentrations and lipid deficit typically manifest accelerated rates of lipogenesis evidenced by high rates of de novo FA biosynthesis. A more realistic model may be obtained by increasing supplements of lipid especially enriched in essential EFAs in the growth medium. Increasing concentrations of 3 FAs, in particular, attenuate the rate of de novo lipogenesis. The improvement of cell culture models for pharmacological screening of drug-candidates targeting lipid or glucose metabolism is highlighted.
S29 significantly lower in HBeAg-negative patients (I. I x I O5 vs. 2. 6~ lo7; p = 0.000 I). Inte... more S29 significantly lower in HBeAg-negative patients (I. I x I O5 vs. 2. 6~ lo7; p = 0.000 I). Interestingly, the ratios between serum HBsAg levels and intrahepatic cccDNA were comparable (p i 0.09) between HBeAg positive and negative patients (26 vs. 70, respectively), suggesting that the transcriptional activity of the cccDNA was similar in the two groups. Conclusions: We observed substantial differences in term of viral production between HBeAg positive and negative patients, which appeared to be due not only to the lower cccDNA copy number, but also to an impaired replicative activity of the cccDNA in HBeAg-negative patients.
m The influence of PAF-acether on natural ovolecithin oriented multibilayers is detected by ESR o... more m The influence of PAF-acether on natural ovolecithin oriented multibilayers is detected by ESR of intercalated 5 doxyl stearic acid. Simulation of lineshapes demonstrates an enlarged orientational distribution of the local director of the phospholipid phase and a small increase of the order parameter. The amount of PAF-acether required to destabilize the ovolecithin lamellar phase depends on the degree of hydration. By contrast, cholesterol displays an organizing effect on the PAF-acether phase. Simulation establishes a sharp orientational distribution of the local director when cholesterol reaches stoichiometric ratio relative to PAF-acether. At the same time, cholesterol increases the order narameter
Biochemical and Biophysical Research Communications, 1983
Plasma membrane phospholipids were modified by incubation in the presence of linoleyl-CoA with or... more Plasma membrane phospholipids were modified by incubation in the presence of linoleyl-CoA with or without added lysolecithin (LPC) for various length of time. In the absence of LPC, a maximum of 10 nmoles linoleyl-phosphatidylcholine (PC) were synthesized and the ATPase specific activities were not affected whereas in the presence of LPC, when linoleyl-PC synthesis rose from 10 to 80 nmoles, the ATPase activities were decreased. The decrease was similar in the Na,K- or in the Mg-dependent-ATPase and reached maximally 30-40%. LPC by itself did not modify the ATPases. A concomitant decrease in DPH polarization was observed when linoleate was incorporated into phospholipids. We concluded that the decreased ATPase specific activities may be due to an increased fluidity of membranes produced by linoleyl- PC synthesis. We compare this modulation of ATPases by the membrane fluidity with the specific effect of linoleyl- PC species on adenylate cyclase.
This study supports the possibility for multiple subcellular forms of lipoprotein lipase. 1. The ... more This study supports the possibility for multiple subcellular forms of lipoprotein lipase. 1. The total activity of lipoprotein lipase per g of intact epididymal adipose tissue from fed rats is much higher than that from starved rats. 2. The isolated fat-cells of fed and of starved rats have lipoprotein lipase of almost the same activity per g of fat-pads. The isolated fat-cells of starved rats have a much higher proportion of total activity per g of the intact tissue than do those of fed rats. 3. Under the conditions of homogenization used, only a small proportion of the total activity per g of intact tissue from fed rats was associated with the fat layer which floated to the top of the homogenate during low-speed centrifugation. The different proportions of the specific enzyme activity found in each subcellular fraction are described. 4. Lipoprotein lipase from plasma membranes and microsomal fractions from starved and fed rats was purified by affinity chromatography. 5. The total ...
The binding to human intact erythrocytes of two different spin-labelled derivatives of chlorproma... more The binding to human intact erythrocytes of two different spin-labelled derivatives of chlorpromazine has been studied. The influence of the positively charged side chain of the drug has been the focus of our attention. The positively charged amphiphilic compound (spin derivative I) is water-soluble up to 80 microM at pH values below 5.9. The apolar analogue (spin derivative II) aggregates in aqueous buffer from the lowest concentration tested. Both spin derivatives undergo a slow reduction inside the erythrocyte. The reduced nitroxides are readily reoxidized by adding a low, non-quenching, concentration of potassium ferricyanide to the intact erythrocytes. The fractions of spin label I and II bound to the erythrocyte membrane or to the erythrocyte-extracted lipids remain constant as a function of the temperature (3-42 degrees C) and as a function of the concentration of the spin label up to 150 microM. E.s.r. spectra of both spin labels show a two-component lineshape when they are ...
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