RESUMO
A sucrose-rich diet generates time-dependent metabolic disorders similar to those found in diabetes type 2. After 8 month (mo) this diet evoked in the rat an increase of blood glucose, free fatty acids (FFA) and triacylycerides (TG) without insulin modification, an interruption of liver stearoyl-CoA desaturase-1 (SCD-1) mRNA and activity increase found at 6 mo, and an enhacement of Delta6 and Delta5 desaturase mRNA and Delta6 activity. We found that the administration of troglitazone (TRO), a peroxisome-proliferator-activated receptors gamma (PPAR-gamma) agonist, for 2 mo normalized plasma FFA, TG, and glucose without altering the insulinemia. It depressed liver SCD-1 mRNA in both control and sucrose-fed rats, decreasing the 18:1n-9/18:0 ratio in serum and liver lipids, and eliminated the increasing effect on mRNA and activity of Delta6 and Delta5 desaturases. These findings evidence again that desaturases are not affected through an insulin resistant effect evoked by the sucrose-rich diet and TRO recovers the altered metabolic plasma parameters as it corresponds to a PPAR-gamma agonist, but its effect on hepatic desaturases can not be attributed to a direct action on liver by PPAR-gamma, insulin, and even by an insulin sensitizing mechanism, suggesting it would be evoked indirectly through hepatic PPAR-alpha deactivation induced by the FFA decrease.
Assuntos
Cromanos/farmacologia , Carboidratos da Dieta/farmacologia , Modelos Animais de Doenças , Ácidos Graxos Dessaturases/metabolismo , Resistência à Insulina , Sacarose/farmacologia , Tiazolidinedionas/farmacologia , Animais , Carboidratos da Dieta/administração & dosagem , Fígado/efeitos dos fármacos , Fígado/enzimologia , Fígado/metabolismo , Masculino , Microssomos Hepáticos/metabolismo , Plasma/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Sacarose/administração & dosagem , TroglitazonaRESUMO
Streptozotocin diabetes depresses delta 9, delta 6 and delta 5 fatty acid desaturases, decreasing arachidonic acid and increasing linoleic acid, but also unexpectedly increasing docosahexaenoic acid in the different phospholipids of liver microsomal lipids. 18:0/20:4n-6, 16:0/20:4n-6 and 16:0/18:2n-6 are the predominant phosphatidyl choline (PC) molecular species in control rats, determining mainly PC contribution to the dynamic and biochemical properties of this bilayer. Diabetes decreases 20:4n-6 containing species and increases 18:2n-6 and 22:6n-3 containing species, maintaining the bulk dynamic properties in the hydrophobic interior of the bilayer, but changing its biochemical properties. The different dynamic parameters were measured by fluorometry using the probes 1,6-diphenyl-1,3,5-hexatriene (DPH), (4-trimethylammonium phenyl) 6-phenyl-1,3,5 (TMA-DPH) and 6-lauroyl-2,4-dimethyl aminonaphtalene (Laurdan). In the surrounding of the hydrophobic/hydrophilic interphase lipid molecules were less ordered and tightly packed in the diabetic samples, allowing a higher mobility of incorporated water molecules. The fact that diabetes decreases highly polyunsaturated acid of n-6 family, but increases docosahexaenoic acid, indicates the necessity of re-evaluating its effect in human physiology.
Assuntos
2-Naftilamina/análogos & derivados , Diabetes Mellitus Experimental/metabolismo , Difenilexatrieno/análogos & derivados , Ácidos Graxos/metabolismo , Fosfatidilcolinas/metabolismo , 2-Naftilamina/farmacologia , Animais , Membrana Celular/química , Membrana Celular/metabolismo , Difenilexatrieno/farmacologia , Ácidos Graxos/química , Corantes Fluorescentes/farmacologia , Fluorometria , Lauratos/farmacologia , Bicamadas Lipídicas/metabolismo , Masculino , Microssomos/química , Microssomos/metabolismo , Fosfatidilcolinas/química , Ratos , Ratos WistarRESUMO
After 21 days on a diet containing 1 g% cholesterol and 0.5 g% cholic acid, rats had an increased content of cholesterol in liver microsomal lipids. In liver, both cholesterol content and delta9 desaturase activity increased, whereas delta6 and delta5 desaturase activities decreased. These changes correlated with increases in oleic, palmitoleic, and linoleic acids and decreases in arachidonic and docosahexenoic acids in total microsomal lipids. Similar fatty acid changes were found in phosphatidylcholine (PC), the principal lipid of the microsomal membrane. In PC the predominant molecular fatty acid species (67% of the total) in the control rats were 18:0/20:4, 16:0/20:4, and 16:0/18:2; and they mainly determined the contribution of PC to the biophysical and biochemical properties of the phospholipid bilayer. The cholesterol diet decreased specifically the 18:0/20:4 species, and to a lesser extent, 16:0/20:4 and 18:0/22:6. The 18:1-containing species, especially 18:1/18:2 and less so 16:0/18:1 and 18:1/20:4, were increased. A new 18:1/18:1 species appeared. The independent effects of the presence of cholesterol and change of the fatty acid composition of the phospholipid bilayer of liver microsomes on the packing were studied by fluorescence methods using 6-lauroyl-2,4-dimethylaminonaphthalene, 1,6-diphenyl-1,3,5-hexatriene and 1-(4-trimethylammonium phenyl)-6-phenyl-1,3,5-hexatriene, which test different parameters and depths of the bilayer. Data showed that the increase of cholesterol in the membrane, and not the change of the fatty acid composition of phospholipids, was the main determinant of the increased bulk packing of the bilayer. The increase of fluid oleic- and linoleic-containing species almost compensated for the drop in 20:4- and 22:6-containing molecules. But the most important effect was that the general drop in essential n-6 and n-3 polyunsaturated fatty acids meant that this endogenous source for the needs of the animal decreased.
Assuntos
Colesterol/farmacologia , Microssomos Hepáticos/química , Fosfatidilcolinas/metabolismo , Animais , Ácido Araquidônico/metabolismo , Ácido Cólico/farmacologia , Cromatografia Líquida de Alta Pressão , Dessaturase de Ácido Graxo Delta-5 , Difenilexatrieno/análogos & derivados , Difenilexatrieno/farmacologia , Ácidos Docosa-Hexaenoicos/metabolismo , Ácidos Graxos Dessaturases/metabolismo , Ácidos Graxos/metabolismo , Ácidos Graxos Monoinsaturados/metabolismo , Ácido Linoleico/metabolismo , Linoleoil-CoA Desaturase , Bicamadas Lipídicas/metabolismo , Metabolismo dos Lipídeos , Masculino , Microssomos Hepáticos/efeitos dos fármacos , Microssomos Hepáticos/metabolismo , Modelos Teóricos , Ácido Oleico/metabolismo , Fosfolipídeos/metabolismo , Ratos , Ratos Wistar , Espectrometria de Fluorescência , Estearoil-CoA Dessaturase/metabolismo , Fatores de TempoRESUMO
The influence of a fat-free diet on the molecular species composition of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI) of rat liver microsomes was studied by using reversed-phase high-pressure liquid chromatography. In the three phosphoglyceride classes analyzed, the fat-free diet produced a large decrease in the 18:0/20:4n-6 species but less important changes were found in the 16:0/20:4n-6 species. In PC, the most abundant phosphoglyceride class of rat liver microsomes, the fall in the 18:0/20:4n-6 species was counterbalanced mainly by an enhancement in the 16:0/18:1n-9 species although it was not evident in PE. In PI, the decrease in the 18:0/20:4n-6 species was counterbalanced by an increase in the 18:0/20:3n-9 species. Fluorescence polarization measurements of 1,7-diphenyl-1,3,5-hexatriene in liposomes of 16:0/18:1n-9, 18:0/18:1n-9-, 16:0/20:4n-6-, and 18:0/20:4n-6-PC indicated that the change in the saturated fatty acid in the sn-1 position accompanying the replacement of 20:4n-6 by 18:1n-9 could be very important for a homeoviscous compensation, maintaining the membrane physical properties without large alterations in spite of the essential fatty acid deficiency due to the fat-free diet.
Assuntos
Dieta com Restrição de Gorduras , Ácidos Graxos/análise , Microssomos Hepáticos/química , Fosfatidilcolinas/química , Fosfatidiletanolaminas/química , Fosfatidilinositóis/química , Animais , Cromatografia Líquida de Alta Pressão , Ácidos Graxos Insaturados/análise , Polarização de Fluorescência , Lipossomos , Masculino , Fosfatidilcolinas/análise , Fosfatidiletanolaminas/análise , Fosfatidilinositóis/análise , Ratos , Ratos WistarRESUMO
The influence of a fat-free diet on the lipid dynamics of rat liver microsomes and liposomes of microsomal lipids was studied by using different fluorescence methods. Lifetime distribution and rotational diffusion of probes with different localization in the lipid bilayer were measured using multifrequency fluorometry. Lateral mobility was studied by measuring excimer formation of pyrenedodecanoic acid. Dipolar relaxation in the interfacial region was studied using 2-dimethyl-amino-6-lauroylnaphthalene (Laurdan). In spite of large changes in the fatty acid composition of microsomal lipids, polyunsaturated fatty acid deficiency showed no effect on the lifetime distribution and rotational mobility of 1,6-diphenyl-1,3,5-hexatriene (DPH). l-(4-(trimethylamino)phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), 2- 7- and 12-(9-anthroiloxy)stearic acids. The treatment did not change the lateral diffusion of pyrenedodecanoic acid, either. However, generalized polarization of Laurdan fluorescence was higher in polyunsaturated fatty acid deficient microsomes as compared to the polyunsaturated fatty acid sufficient ones. This effect was also observed in liposomes of the total microsomal lipids, indicating that the changes in fatty acid composition resulting from polyunsaturated fatty acid deficiency produced a small but significant decrease in the rate of dipolar relaxation in the region of the lipid polar groups of the bilayer. The absence of lipid gel phase domains in rat liver microsomes was also indicated by Laurdan fluorescence features.
Assuntos
Ácidos Graxos Essenciais/deficiência , Lipídeos de Membrana/química , Microssomos Hepáticos/química , Animais , Fenômenos Biofísicos , Biofísica , Transferência de Energia , Polarização de Fluorescência , Corantes Fluorescentes , Bicamadas Lipídicas/química , Lipossomos/química , Masculino , Ratos , Ratos Wistar , Espectrometria de FluorescênciaRESUMO
The fatty acid composition of muscle lipids from eadible fish from Paraná river such as Dorado (Salminus maxillosus), Boga (Leporinus affinis), Patí (Luciopimelodus pati) and Surubí (Pseudoplatistoma coruscans) was studied in order to determine their food value in relation to essential fatty acid n-3 and n-6 supply. Flesh from these fishes is relatively lean and its lipids only contain 35% to 38% saturated fatty acids. Significant amounts of n-6 polyethylenic acids, mainly linoleic, arachidonic and the n-3 acids, docosahexaenoic, docosapentaenoic, eicosapentaenoic and alpha-linolenic are found in these fishes. Patí flesh is the most abundant in n-6 acids with a value of 306 mg/100 g muscle, followed by Boga, Dorado and Surubí. A large proportion of n-3 acids is supplied by muscles of Dorado, 183 mg/100g muscle, followed by Patí, Boga and Surubí. More than 90% of the lipids that supply these acids are present in triacylglycerols in Dorado, Boga and Patí. In Surubí, triacylglycerols constitute 60% and the remaining lipids are phospholipids. Cholesterol content in flesh of fresh water fish was analyzed, and it did not exceed 4.7 micrograms/g muscle for Patí, being lower for the other species studied. Fish considered in this work represent a good dietary source of polyunsaturated fatty acids either n-6 or n-3 series for the mediterranean population in our country.
Assuntos
Dieta , Ácidos Graxos Essenciais/análise , Óleos de Peixe/análise , Valor Nutritivo , Animais , Brasil , Água Doce , HumanosRESUMO
The effect of essential fatty acid deficiency on the structural and dynamic properties of the lipid matrix of rat liver microsomes and erythrocyte membranes was studied. The rate and range of the rotational mobility of 1,6-diphenyl-1,3,5-hexatriene and 2-, 7-, and 12-(9-anthroyloxy)stearate probes in the native membranes and in lipid vesicles prepared with the total lipid extracts of these membranes were evaluated by using differential polarized phase fluorometry. For the anthroyloxystearate probes, two modes of rotation (in and out of the plane of the aromatic anthracene ring) were partially resolved by measuring at different excitation wavelengths. The fat-free diet produces important changes in the fatty acid composition of the different glycerophospholipid classes without affecting the total double-bond number, the relative contents of cholesterol, phospholipid, and protein, and the glycerophospholipid class distribution. The principal changes, more pronounced in liver microsomes than in erythrocytes, are: an increase in nonessential monoene and triene (18:1n-9 and 20:3n-9) and a decrease in essential diene (18:2n-6) and tetraene (20:4n-6). These changes modify the double-bond distribution as a function of the distance from the interphase toward the bilayer interior, with a significant deficit (15% in erythrocytes and 30% in liver microsomes) in the double-bond density in the intermediate region of the membrane leaflet, corresponding to the carbon number 11-12 of an extended saturated acyl chain, and where the 12-anthroyloxystearate probe is located. In spite of the changes in fatty acid composition and double-bond distribution, with the only exception of a slight increase (about 15%) in the "out of the plane" rotation rate of the 7-(9-anthroyloxy)stearate probe in the erythrocyte lipid vesicles, no other significant change is observed. Thus, the changes in fatty acid composition would take place in such a way that at least the average structural and viscotropic properties of the lipid phase of the membrane, sensed by these probes, would be almost exactly compensated.
Assuntos
Membrana Eritrocítica/química , Ácidos Graxos Essenciais/deficiência , Microssomos Hepáticos/química , Animais , Dieta com Restrição de Gorduras , Membrana Eritrocítica/metabolismo , Corantes Fluorescentes , Bicamadas Lipídicas/química , Masculino , Fluidez de Membrana , Lipídeos de Membrana/análise , Microssomos Hepáticos/metabolismo , Ratos , Ratos WistarRESUMO
1. Gas-liquid chromatography and mass spectrometry were used to verify the presence of arachidonic acid (20:4 omega 6) in adult male and female organs of the blood-suckling bug Triatoma infestans. Fat body, gonad and head lipids were analyzed. 2. Male gonads contained the highest percentage of phospholipids and the highest percentage of arachidonic acid. 3. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and sphingomyelin were isolated from gonads and heads of sexed insects and the fatty acid composition analyzed. 4. All the phospholipids analyzed contained relevant percentages of linoleic acid and fair percentages of arachidonic acid, except for sphingomyelin where no 20:4 omega 6 acid was found. 5. However, arachidonic acid was specifically incorporated in phosphatidylinositol since this phospholipid contained very large percentages of the acid. 6. In male gonads, phosphatidylcholine also contained a similar high percentage of the acid. Arachidonic acid is apparently incorporated, selectively, into these lipids from the blood of the host.