Correlation between medium C-chain fatty acids and polyunsaturated fatty acids

The medium C-chain fatty acids increased in the muscle, lungs, pancreas and adipose tissue (and not in the liver) of the rats injected with CCl4 or nourished with "balanced" diet for the lipids. When CCl4 and balanced diet are furnished together, these acids decrease strongly: the discussion of the results is difficult.     

Pathogenesis of carbon tetrachloride-induced hepatocyte injury bioactivation of CCI4 by cytochrome P450 and effects on lipid homeostasis

The CCl4-induced development of liver damage was studied in monolayer cultures of primary rat hepatocytes: (1) CCl4 caused accumulation of triglycerides in hepatocytes following cytochrome P450 induction with beta-naphthoflavone or metyrapone. Ethanol or a high dose of insulin plus triiodothyronine had the same effect. (2) CCl4 increased the synthesis of fatty acids and triglycerides and the rate of lipid esterification. Cholesterol and phospholipid synthesis from acetate was also increased. (3) CCl4 reduced beta-oxidation of fatty acids as assessed by CO2-release and ketone body formation. Hydrolysis of triglycerides was also reduced. (4) The content of unsaturated fatty acids in microsomal lipids was decreased by almost 50% after incubation with CCl4, while saturated fatty acids increased slightly. (5) CCl4 exerted a pronounced inhibitory effect on the exocytosis of macromolecules (albumin), but did not affect secretion of bile acids from hepatocytes.     

Lipid peroxidation and molecular damage to polyunsaturated fatty acids in rat liver. Recognition of two classes of hydroperoxides formed under conditions in vivo

The diene conjugates formed during the autoxidation of microsomal lipid extracts, and in endoplasmic reticulum in vivo after exposing rats to CCl4 have been examined by second derivative absorption spectrophotometry. Within a few minutes after administering CCl4 to a rat there is a pronounced signal in microsomal lipid extracts that is ascribed to the cis-trans diene conjugates of microsomal polyunsaturated fatty acids. Somewhat later a second signal becomes evident that is ascribed to trans-trans isomers. The appearance of the trans-trans isomer is very strongly suppressed by prior administration of vitamin E to the rat. It is concluded that the relative contents of cis-trans and trans-trans dienes in lipid extracts of tissue reflect the tissue contents of hydrogen donors as already established for model experiments with polyunsaturated fatty acids in vitro.     

Fatty acids in the development and stabilization of the rat brain

The development of the rat's brain demonstrates the increase of the short, medium and long C-chain saturated fatty acids and of the docosahexaenoic acids and the decrease of the mono-unsaturated fatty acids, of the linoleic-arachidonic acids, of the alpha-linolenic-eicosapentaenoic acids. The stabilization of the brain in the adult rat increases all the saturated and mono-unsaturated fatty acids and triene, while it decreases all the poly-unsaturated (omega-6; omega-3) fatty acids. The CCl4 poisoning cuts down the linoleic-arachidonic acids and the alpha-linolenic acid throughout the development of the rat's brain; after the growth, CCl4 increases triene, ac. eicosapentaenoic and reduces the linoleic-arachidonic and alpha-linolenic-ac. docosahexaenoic acids.     

Effect of "marine" phospholipids omega-3 fatty acids on the composition of fatty acids of rat liver microsomal membrane under oxidative stress

As a result of experiments conducted the marine phospholipids preparation enriched by omega-3 fatty acids was defined to modify fatty acids content due to changes of fatty acids level change in the neutral lipids and phospholipids fractions. As well it was identified, that at the oxidative stress induced by administration of CCl4 the growth of arachidonic and docozahexaenoic acids in the neutral lipids fractions was observed if compare with the norm. At the same time, the presented fatty acids in the phospholipids fractions remained unchanged. At oxidative stress the phospholipids fraction reacts to levels of arachidonic and docozahexaenoic acids just only as a result of administrating phospholipids with omega-3 fatty acids. The most attractive is the change of correlation C20:4/C22:6--increasing at administration of CCl4 and decreasing both at phospolipids and vitamin E injection. Thus, at the oxidative stress the first reacting ones are the fatty acids of neutral lipids microsomal membranes.     

Fatty acids in striated muscle of the rat treated with toxic radicals

In the striated muscle of the growing and adult rat CCl4 poisoning increases all the saturated fatty acids and decreases the mono-unsaturated and arachidonic fatty acids. The supplementation with poly-unsaturated fatty acids increases, in rat's striated muscle, mono-unsaturated acids and decreases saturated, arachidonic, docosaexahenoic acids.     

Relationship between lysosomal damage, fatty infiltration and hepatocellular necrosis in the course of acute liver injury induced by carbon tetrachloride in the rat.

In the course of liver injury induced by CCl4 in rats the change of the endoplasmic reticulum takes 5 hours and that of the lysosomal membrane, 18 hours to develop. The latter change precedes hepatocellular necrosis. Elevation of plasma free fatty acids and fatty infiltration of the liver can be observed at 3 hours after CCl4 administration. The maximum of fatty infiltration, hepatocellular necrosis and the highest degree of lysosomal damage develop at the same time. Since CCl4 is eliminated in a few hours, it must initiate a cellular process which then leads to lysosomal membrane damage and hepatocellular necrosis.     

Modulation of carbon tetrachloride-induced oxidative stress by dietary fat in rats(open star)

Oxidative stress is believed to be involved in the pathophysiology of a number of chronic diseases including atherosclerosis, diabetes, and cataracts and to accelerate the aging process. The aim of this study was to elucidate the role of various dietary fats in the in vivo modulation of CCl(4) induced oxidative stress using rat as a model. Rats were raised on diets enriched with saturated (Beef Tallow), n-9 (Sunola oil), n-6 (Safflower oil) or n-3 (Flaxseed oil) fatty acids and exposed to elevated oxidative stress by administration of CCl(4.) Plasma concentration of 8-iso-PGF(2alpha), antioxidant micronutrients and antioxidant enzymes were measured to examine changes to oxidative stress subsequent to the administration of CCl(4). The fatty acid profiles of plasma and RBC membranes reflected the fats fed in the different diets. CCl(4) administration had no significant effect on fatty acid composition of plasma or RBC lipids. Plasma 8-iso-PGF(2alpha) concentrations were elevated by CCl(4) administration regardless of the dietary fat fed. Within the induced oxidative groups the 8-iso-PGF(2alpha) concentrations were highest in Safflower oil followed by Sunola oil, Tallow and finally Flaxseed oil. Induction of oxidative stress by CCl(4) administration was associated with a significant reduction in Vitamin A content reaching a significantly lower concentration (P <0.05) in the Tallow and Flaxseed oil groups. Vitamin E concentrations were significantly lower (p = 0.01) in the Safflower oil and the Flaxseed oil than in the Tallow diet group following CCl(4) administration. Superoxide Dismutase (SOD) and Glutathione Peroxidase (GSHPx) activities were not affected by dietary fat manipulation. The results of this study indicate that dietary fat can modulate lipid peroxidation and antioxidant defenses when exposed to a pro-oxidant challenge.     

Effect of radical stress and ageing on the occurrence of trans fatty acids in rats fed a trans-free diet

In a previous paper, we demonstrated that tissue trans fatty acids can not only derive from the diet but also be endogenously formed. The central focus of this study was to prove that the in vivo isomerization occurs via a radical process. Two different models of radical insult were used: CCl(4) and AAPH injection to rats fed a diet completely free of trans isomers. Following this acute radical stress, a significant increase in unnatural trans fatty acid content of erythrocyte, kidney, and heart, but not liver, was observed. These results can be mainly explained by the high content, particularly in the liver, of antioxidant vitamins A and E that exhibit also an "anti-isomerizing" effect. Since during ageing cellular components are exposed to increasing radical insults, the observation of a significant trans fatty acid accumulation in 30-month-old rats could confirm that the in vivo formation of unnatural isomers is due to a radical process. Trans fatty acids can influence the physical characteristics of bilayer microdomains, affecting membrane properties and functions; thus, knowledge of biological radical species responsible for cis/trans isomerization and their possible sources can provide protective systems for preserving lipid geometry.     

Mass spectrometric detection of cross-linked fatty acids formed during radical-induced lesion of lipid membranes.

A mass spectrometric method is described for the quantitative determination of dimers of polyunsaturated fatty acids (PUFA) formed in the hepatic endoplasmic reticulum of rats upon inhalation of tetrachloromethane. The results show that dimers account for a considerable fraction of microsomal PUFA which disappear during CCl4 metabolism. Cross-linking of the membrane lipids of the endoplasmic reticulum seems to be a significant process with respect to cell toxicity.     

Carbon tetrachloride toxicity as a model for studying free-radical mediated liver injury

A single dose of CCl4 when administered to a rat produces centrilobular necrosis and fatty degeneration of the liver. These hepatotoxic effects of CCl4 are dependent upon its metabolic activation in the liver endoplasmic reticulum to reactive intermediates, including the trichloromethyl free radical. Positive identification of the formation of this free radical in vivo, in isolated liver cells and in microsomal suspensions in vitro has been achieved by e.s.r. spin-trapping techniques. The trichloromethyl radical has been found to be relatively unreactive in comparison with the secondarily derived peroxy radical CCl3O2., although each free radical species contributes significantly to the biological disturbances that occur. Major early perturbations produced to liver endoplasmic reticulum by exposure in vivo or in vitro to CCl4 include covalent binding and lipid peroxidation; studies of these processes occurring during CCl4 intoxication have uncovered a number of concepts of general relevance to free-radical mediated tissue injury. Lipid peroxidation produces a variety of substances that have high biological activities, including effects on cell division; many liver tumours have a much reduced rate of lipid peroxidation compared with normal liver. A discussion of this rather general feature of liver tumours is given in relation to the liver cell division that follows partial hepatectomy.     

Beta-hexosaminidase activity in alcoholic fatty liver and in CCl4-induced liver fibrosis of the rat

beta-Hexosaminidase (Hex) activity was previously found to be increased in the sera of patients with liver cirrhosis, cholestasis and acute alcohol intoxication, as well as in rats with CCl4-induced liver cirrhosis. We studied this enzymatic activity in the sera and liver tissue of rats with alcoholic fatty liver due to prolonged alcohol intake and CCl4-induced liver fibrosis in association with moderate alterations in liver function tests. Serum and liver Hex activity did not show any significant change in both experimental models. These data suggest that Hex is not an alcohol-induced enzyme, and that severe, but not moderate, liver damage can determine the increase in this lysosomal enzymatic activity.     

Taurocholate feeding prevents CCl4-induced damage of large cholangiocytes through PI3-kinase-dependent mechanism

Bile acids are cytoprotective in hepatocytes by activating phosphatidylinositol-3-kinase (PI3-K) and its downstream signal AKT. Our aim was to determine whether feeding taurocholate to CCl(4)-treated rats reduces cholangiocyte apoptosis and whether this cytoprotective effect is dependent on PI3-K. Cholangiocyte proliferation, secretion, and apoptosis were determined in cholangiocytes from bile duct ligation (BDL), CCl(4)-treated BDL rats, and CCl(4)-treated taurocholate-fed rats. In vitro, we tested whether CCl(4) induces apoptosis and whether loss of cholangiocyte proliferation and secretion is dependent on PI3-K. The CCl(4)-induced cholangiocyte apoptosis and loss of cholangiocyte proliferation and secretion were reduced in CCl(4)-treated rats fed taurocholate. CCl(4)-induced cholangiocyte apoptosis, loss of cholangiocytes secretion, and proliferation were prevented by preincubation with taurocholate. Taurocholate cytoprotective effects were ablated by wortmannin. Taurocholate prevented, in vitro, CCl(4)-induced decrease of phosphorylated AKT protein expression in cholangiocytes. The cytoprotective effects of taurocholate on CCl(4) effects on cholangiocyte proliferation and secretion were abolished by wortmannin. Taurocholate protects cholangiocytes from CCl(4)-induced apoptosis by a PI3-K-dependent mechanism. Bile acids are important in the prevention of drug-induced ductopenia in cholangiopathies.     

The pattern of fatty acid synthesis in lactating rabbit mammary gland studied in vivo

The biosynthesis of fatty acids has been studied in lactating rabbits at 6h after intravenous injection of sodium [1-(14)C]acetate. The specific radioactivities of the individual fatty acids (C(6:0) to C(14:0)) and the proportions of these fatty acids synthesized were similar in mammary tissue and milk. Hexanoic acid had the highest specific radioactivity, and the C(8:0)-C(14:0) fatty acids had similar specific radioactivities, which were about five times those of C(16) and C(18) acids. No radioactivity was detected in fatty acids of chain length C(14) in these tissues were similar to those of the long-chain fatty acids in the milk and mammary gland. The results show that the C(4:0)-C(14:0) fatty acids are synthesized within the mammary gland rather than by fatty acid uptake from circulating blood or by oxidation of long-chain fatty acids within the gland. We conclude that de novo synthesis of esterified fatty acids in vivo by this tissue has a high degree of chain-length specificity.     

Movement of lipolytic products to mitochondria in brown adipose tissue of young rats: an electron microscope study

Lipolysis occurred and lamellar structures with a periodicity of 40 A developed in glutaraldehyde-fixed brown adipose tissue of suckling rats when the tissue was incubated at 25 degrees C. The lamellar structures were found in capillaries, associated with chylomicrons, in intracellular channels of capillary endothelium, in extracellular space, and in channels near lipid droplets in adipocytes in tissue of fed rats injected intravenously with chylomicrons. They were also found in channels near mitochondria and inside mitochondria in adipocytes in incubated-fixed tissue of rats exposed to 4 degrees C for 2 hr or unsuckled overnight. In addition, aqueous spaces developed adjacent to lipid droplets in incubated tissue of cold-exposed and unsuckled rats. Development of lamellar structures under conditions causing lipolysis and accumulation of fatty acids in fixed tissue indicated the lamellae were composed primarily of fatty acids. We conclude that fatty acids formed by lipolysis of chylomicrons in tissue from fed rats accumulated in a continuum of the outer leaflets of cell membranes extending from capillary lumen to lipid droplets of adipocytes, and fatty acids formed by lipolysis of intracellular lipid in tissue from cold-exposed or unsuckled rats accumulated mostly in a continuum extending from lipid droplets to the interior of mitochondria. When fatty acids overcrowded the continuum in fixed tissue, they formed lamellar extensions of the continuum at different sites along its course through the tissue.     

Lipogenesis in liver and adipose tissue of the domestic cat (Felis domestica)

1. Production of fatty acids, CO2 and glycerol from glucose and acetate was determined in slices of liver and adipose tissue taken from mature cats. 2. Acetate was the predominant carbon source for de novo fatty acid synthesis in both liver and adipose tissue. 3. Fatty acid synthesis occurred at much greater rates in adipose tissue than in liver. 4. Relative lipogenic capacity (ratio of production of long-chain fatty acids and glycerol to oxidation of substrates) was 20 times greater in adipose tissue than in liver with both substrates.     

Effect of dietary fatty acids on lipoprotein lipase gene expression in the liver and visceral adipose tissue of fed and starved red sea bream Pagrus major

Juvenile red sea bream Pagrus major were fed either a commercial diet (diet 1) or diets supplemented with 10% oleate (diet 2), 5% oleate+5% linoleate (diet 3) or 5% oleate+5% n-3 polyunsaturated fatty acid mixture (diet 4) for 4 weeks. Following the conditioning period, the effects of dietary fatty acids on lipoprotein lipase (LPL) gene expression in the liver and visceral adipose tissue of fed (5 h post-feeding) and starved (48 h post-feeding) fish were investigated by competitive polymerase chain reaction. Fish liver showed substantial LPL mRNA expression that is not found in adult rat liver. When compared with diet 1, diets 2-4 tended to increase the LPL mRNA level in the liver, but tended to decrease it in the visceral adipose tissue under the fed condition. The reciprocal regulation of the liver and visceral adipose LPL mRNA abundance by dietary fatty acids was comparable to that of rat brown and white adipose tissue, respectively. The change in the LPL mRNA level by fatty acids was not completely consistent with the degree of fatty acid unsaturation. Our results indicate that the regulatory effect of dietary fatty acids on LPL gene expression was tissue-specific and related to feeding conditions, but was not solely dependent on the degree of unsaturation of fatty acids.     

Extracts of Phellinus linteus grown on germinated brown rice suppress liver damage induced by carbon tetrachloride in rats

Extracts of Phellinus linteus (EPB), grown on germinated brown rice, protected rats from liver injury induced by carbon tetrachloride (CCl4). Peroxidation products in the liver were decreased to 10% by EPB. Catalase and superoxide dismutase activities were significantly decreased to 55% and 39% by CCl4 administration, but EPB blocked this effect, resulting in enzyme activities at control levels. Expression of cytochromeP450 2E1 (CYP2E1) protein was significantly decreased to 88% in CCl4-treated rats but remained at control levels when EPB was also administered. EPB did not affect the altered fatty acid composition induced by CCl4. The hepatoprotective effect of EPB may be mediated by EPB's prevention of CCl4-induced CYP2E1 degradation.     

Lipid peroxidation in purified plasma membrane fractions of rat liver in relation to the hepatoxicity of carbon tetrachloride

Preparations of rat liver sinusoidal plasma membrane have been tested for their ability to metabolize the hepatotoxin carbon tetrachloride (CCl4) to reactive free radicals in vitro and compared in this respect with standard preparations of rat liver microsomes. The sinusoidal plasma membranes were relatively free of endoplasmic reticulum-associated activities such as the enzymes of the cytochrome P450 system and glucose-6-phosphatase. CCl4 metabolism was measured as (i) covalent binding of [14C]-CCl4 to membrane protein, (ii) electron spin resonance spin-trapping of CCl3. radicals and (iii) CCl4-induced lipid peroxidation. By all of these tests, purified sinusoidal plasma membranes were found unable to metabolize CCl4. The fatty acid composition of the plasma membranes was almost identical to that of the microsomal preparation and both membrane fractions exhibited similar rates of the lipid peroxidation that was stimulated non-enzymically by gamma-radiation or incubation with ascorbate and iron. The absence of CCl4-induced lipid peroxidation in the plasma membranes seems to be due, therefore, to an absence of CCl4 activation rather than an inherent resistance to lipid peroxidation. We conclude that damage to the hepatocyte plasma membrane during CCl4 intoxication is not due to a significant local activation of CCl4 to CCl3. within that membrane.     

Symbiotic zooxanthellae provide the host-coral Montipora digitata with polyunsaturated fatty acids

We compared the fatty acid composition of the host-coral Montipora digitata with the fatty acid composition in the coral's endosymbiotic dinoflagellates (zooxanthellae). Fatty acids as methyl esters were determined using gas chromatography (GC) and verified by GC-mass spectrometry. We found the main difference between the fatty acids in the host and their symbionts were that zooxanthellae supported higher proportions of polyunsaturated fatty acids. The presence of fatty acids specific to dinoflagellates (i.e. 18:4omega3, 22:5omega3 and 22:6omega3) in the host tissue suggests that zooxanthellae provide the coral host not only with saturated fatty acids, but also with diverse polyunsaturated fatty acids.