Showing papers on "Fatty acid synthesis published in 1976"

The antibiotic cerulenin, a novel tool for biochemistry as an inhibitor of fatty acid synthesis.

Abstract: One ofthe most versatile uses of antibiotics is as potent drugs for clinical application. In recent years, attention has also been paid to agricultural uses of antibiotics, such as for feed additives for protecting plants and livestock against infectious diseases and for accelerating their growth. They are also used as food additives to retain freshness for an extended period. The usefulness of antibiotics is not limited only to our daily needs, but also encompasses our research interests: they offer us remarkable experimental devices for biochemistry novel biochemical tools, which have made a significant contribution to progress in this field (18). Cerulenin, an antibiotic discovered by Hata et al. in 1960, was originally found as an antifungal antibiotic (30). Studies of its mode of action have revealed that it specifically inhibits the biosynthesis of fatty acids and sterols involving yeasts (55, 56). It should be particularly noted that such specificity of cerulenin has been used by investigators in various fields of biochemistry. In this connection, the present review deals with studies, which have hitherto been reported, on the production, isolation, structure, and mode of action of cerulenin and its application as a biochemical tool. Unfortunately, the instability of the antibiotic in the animal body prevents its use in therapy as an antimicrobial agent or as an antilipogenic agent.

Acute effects in vivo of anti-insulin serum on rates of fatty acid synthesis and activities of acetyl-coenzyme A carboxylase and pyruvate dehydrogenase in liver and epididymal adipose tissue of fed rats.

Abstract: Plasma insulin concentrations in fed rats were altered acutely by administration of glucose or anti-insulin serum. Rates of fatty acid synthesis in adipose tissue and liver were estimated from the incorporation of 3H from 3H2O. In the adipose tissue dehydrogenase and acetyl-CoA carboxylase were evident. In liver, although changes in rates of fatty acid synthesis were found, the initial activity of pyruvate dehydrogenase did not alter, but small parallel changes in acetyl-CoA carboxylase activity were observed.

Purification and some properties of a medium-chain acyl-thioester hydrolase from lactating-rabbit mammary gland which terminates chain elongation in fatty acid synthesis.

Abstract: 1. An acyl-thioester hydrolase was isolated from the cytosol of lactating-rabbit mammary gland. The purified enzyme terminates fatty acid synthesis at medium-chain (C8:0-C12:0) acids when it is incubated with fatty acid synthetase and rate-limiting concentrations of malonyl-CoA. These acids are characteristic products of the lactating gland. 2. The mol.wt. of the enzyme is 29000±500 (mean±S.D. of three independent preparations), as estimated by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. 3. The enzyme also hydrolyses acyl-CoA esters of chain lengths C10:0-C16:0 when these are used as model substrates. The greatest activity was towards dodecanoyl-CoA, and the three preparations had specific activities of 305, 1130 and 2010 nmol of dodecanoyl-CoA hydrolysed/min per mg of protein when 56muM substrate was used. 4. The way in which this enzyme controls the synthesis of medium-chain fatty acids by fatty acid synthetase is briefly discussed.

Intermediary metabolism of adipose tissue.

Abstract: Metabolism of ruminant adipocytes involves the synthesis and mobilization of lipids. Rates of lipid synthesis from the uptake of preformed fatty acids (via lipoprotein lipase) and de novo synthesis of fatty acids are related to the energy balance. Acetate is the major carbon source for fatty acid synthesis with NADPH originating from the pentose cycle and the isocitrate cycle. Ruminant adipose tissue lacks the ability to utilize for lipogenesis those substrates that generate mitochondrial acetyl CoA because of an absence of ATP citrate-lyase and NADP-malate dehydrogenase. Lipid mobilization in ruminant adipocytes is apparently regulated via cAMP levels and a summary of the compounds investigated for lipolytic responses is presented. The control of lipid synthesis and mobilization is interrelated in ruminant adipose tissue. The coordinated manner in which these two functions are regulated is examined with regard to adipocyte responses to insulin and epinephrine. In both lipid synthesis and lipid mobilization, ruminant adipocytes are uniquely different from nonruminant adipose tissue. The physiological significance and possible basis for these species differences in adipose metabolism are discussed.

Galactolipid Synthesis in Vicia faba Leaves: II. Formation and Desaturation of Long Chain Fatty Acids in Phosphatidylcholine, Phosphatidylglycerol, and the Galactolipids.

Abstract: The labeling kinetics of the fatty acids of phosphatidylcholine (PC), phosphatidylglycerol (PG), monogalactosyldiglyceride (MGDG), and digalactosyldiglyceride (DGDG) were examined after 14CO2 feeding and incubation of leaf discs of Vicia faba over 72 hours in continuous light. The results indicate a rapid accumulation and turnover of radioactivity into PC and PG fatty acids (oleic acid in PC and oleic and palmitic acids in PG). Radioactivity accumulates in MGDG and DGDG fatty acids much more slowly and continuously over 72 hours. Most of this activity is found in linoleic and linolenic acids; very little activity is found in the more saturated fatty acids. Little or no desaturation occurs in situ in conjunction with the galactolipids. The results suggest that PC and PG may act as “carriers” for MGDG and DGDG fatty acid synthesis. Analyses of the labeling patterns of the molecular species of MGDG after 14CO2 and 14C-acetate feeding confirm that MGDG is formed by galactosylation of a preformed diglyceride containing predominantly unsaturated fatty acids.

Effect of Glycerol on Lipogenic Enzyme Activities and on Fatty Acid Synthesis in the Rat and Chicken

Abstract: The influence of glycerol on the rates of fatty acid snythesis in liver slices from rats and chickens in pieces of adipose tissue from rats was first studied. Then the effect of dietary glycerol on lipid metabolism in rats and cheickens was examined. Media containing 3 or 10 mM glycerol depressed the rate of glucose conversion to fatty acids in rat liver slices. However, media containing up to 25 mM glycerol did not influence the rate of fatty acid synthesis in chick liver slices. The inhibitory action of glycerol in rat liver slices might occur at the level of glucose (or glycogen) conversion to pyruvate because glycerol did not inhibit pyruvate or acetate conversion to fatty acids. Rats and chickens were fed glycerol containing diets for either 3 days or 3 weeks. Feeding diets containing 20.5 parts glycerol (22% of dietary energy) to rats or chickens did not influence the growth rate of the animals. However, substitution of 42.2 parts glycerol (43% of dietary energy) for glucose in the diet significantly depressed food intake and growth rate in both rats and chickens. The activities of citrate cleavage enzyme, fatty acid synthetase and malic enzyme in livers of rats fed the glycerol-containing diets were dramatically increased. However, this stimulation of enzyme activity occurred without a concomitant increase in the in vivo rate of fatty acid synthesis in the rat liver. In the chicken, unlike the rat, dietary glycerol did not stimulate but instead decreased hepatic malic enzyme and fatty acid synthetase activities. No significant differences in adipose tissue lipogenic enzyme activities or in the rates of fatty acid synthesis were observed in rats fed glycerol-containing diets. The lipogenic response to glycerol feeding depends on the species as well as the organ.

A comparison of the enzyme levels and the in vitro utilization of various substrates for lipogenesis in pair-fed lean and obese pigs.

Abstract: In this study of spontaneous obesity of pigs, specific metabolic shifts were observed, which explain an increase in fat deposition. Liver tissue utilization of pyruvate and glucose for oxidation and lipogenesis showed no significant difference between lean and obese pigs. Adipose tissue utilization of glucose, acetate and glycerol for triglyceride and fatty acid synthesis was greater in obese pigs than lean pigs (P less than 0.01). No significant difference in leucine incorporation into lipid fractions was found. Of the substrates utilized, glucose supplied 86 and 94% of the glyceride-glycerol synthesized in lean and obese pigs, respectively. Glycerol was not a major contributor to glyceride-glycerol synthesis (3.5 to 5.5%), in spite of the presence of adipose tissue glycerokinase. An increase (P less than 0.05) in alanine incorporation into glucose was observed in liver tissue from obese pigs. In general, the levels of enzymes activities associated with gluconeogenesis, glycolysis, and lipogenesis supported the findings of in vitro utilization of these substrates.

Specific inhibition of hepatic fatty acid synthesis exerted by dietary linoleate and linolenate in essential fatty acid adequate rats.

Abstract: Dietary linoleate and linolenate were investigated for their ability to specifically inhibit liver and adipose tissue lipogenesis in meal-fed (access to food 900-1,200 hr), essential fatty acid (EFA) adequate rats. Supplementing a high carbohydrate diet containing 2.5% safflower oil with 3% palmitate 16∶0, oleate 18∶1, or linoleate 18∶2 did not affect in vivo liver or adipose tissue fatty acid synthesis. However, 18∶2 addition to the basal diet did result in a significant (P<0.05) decline of liver fatty acid synthetase (FAS) and glucose-6-phosphate dehydrogenase (G6PD) activities. When the safflower oil content of the basal diet was reduced to 1%, the addition of 3% 18∶2 or linolenate 18∶3 significantly (P<0.05) depressed hepatic FAS, G6PD, and in vivo fatty acid synthesis by 50%. Addition of 18∶1 caused no depression in hepatic FAS activity but did result in a significant (P<0.05) decline in liver G6PD activity and fatty acid synthesis which was intermediate between basal and basal +18∶2-or+18∶3-fed animals. Adipose tissue rates of lipogenesis were completely unaffected by dietary fatty acid supplementation. Similarly, the addition of 3 or 5% 18∶3 to a basal diet for only one meal resulted in no change in lipogenesis relative to that in animals fed the basal diet. The data indicate that, like rats fed EFA-deficient diets, dietary 18∶2 and 18∶3 exert a specific capacity to depress rat liver FAS and G6PD activities and rate of fatty acid synthesis.

High rates of [1-14C]acetate incorporation into the lipid of isolated spinach chloroplasts.

Abstract: Spinach chloroplasts, isolated by techniques yielding preparations with high O2- evolving activity, showed rates of light-dependent acetate incorporation into lipids 3-4 fold higher than any previously reported. Incorporation rates as high as 500 nmol of acetate/h per mg of chlorophyll were measured in buffered sorbitol solutions containing only NaHCO3 and [1-14C]acetate, and as high as 800 nmol/h per mg of chlorophyll when 0.13 mM-Triton X-100 was also included in the reaction media. The fatty acids synthesized were predominantly oleic (70-80% of the total fatty acid radioactivity) and palmitic (20-25%) with only minor amounts (1-5%) of linoleic acid. Linolenic acid synthesis was not detected in the system in vitro. Free fatty acids accounted for 70-90% of the radioactivity incorporated and the remainder was shared fairly evenly between 1,2-diacylglycerols and polar lipids. Oleic acid constituted 80-90% of the free fatty acids synthesized, but the diacylglycerols and polar lipids contained slightly more palmitic acid than oleic acid. Triton X-100 stimulated the synthesis of diacylglycerols 3-6 fold, but stimulated free fatty acid synthesis only 1-1.5-fold. Added glycerol 1-phosphate stimulated both the synthesis of diacylglycerols and palmitic acid relative to oleic acid, but did not increase acetate incorporation into total chloroplast lipids. CoA and ATP, when added separately, stimulated acetate incorporation into chloroplast lipids to variable extents and had no effect on the types of lipid synthesized, but when added together resulted in 34% of the incorporated acetate appearing in long-chain acyl-CoA. Pyruvate was a much less effective precursor of chloroplast fatty acids than was acetate.

On the mechanism of malonyl-CoA-independent fatty-acid synthesis. Different properties of the mitochondrial chain elongation and enoylCoA reductase in various tissues.

Abstract: 1. NADPH-specific mitochondrial enoyl-CoA reductase can be assayed by a sensitive radioactive test, employing tritium-labelled NADPH, synthesized in a prefixed reaction from D-[1-3H]-glucose via the hexokinase and glucose-6-phosphate dehydrogenase reactions. 2. Liver, kidney cortex, heart muscle, skeletal muscle, brown adipose tissue, brain cortex, and aortic intimal tissue are investigated concerning chain lengths specificity of the chain elongation and the enoyl-CoA reductase. Medium-chain acyl-CoA compounds prove to be the best primers for the chain elongation. Enoyl-CoA reductases still show large incorporation rates with hexadecenoyl-CoA. 3. The differences in the chain lengths specificity of the chain elongation and enoyl-CoA reductase can be explained by the inhibitory effect of long-chain acyl-CoA derivatives on the 3-hydroxyacyl-CoA dehydrogenase. 4. The nucleotide specificity in the different tissues reveals two types of chain elongation: In addition to liver and kidney cortex, mitochondria of brown adipose tissue need NADH + NADPH for optimal chain elongation, whereas heart muscle, skeletal muscle and aortic intimal mitochondria only need NADH. 5. Different physiological roles are proposed for the two types. The "heart type" may be of importance in the conservation of reducing equivalents or acetate units in the anaerobic state, the "liver type" may play a role in the transfer of hydrogen from NADPH to the respiratory chain. In addition, the mitochondrial chain elongation may serve as bypass of the first part of the respiratory chain.

Fatty acid synthesis in the perfused liver of adrenalectomized rats

Abstract: 1. Fatty acid synthesis, measured in the perfused liver of fed adrenalectomized rats with 3H2O and 14C-labelled precursors, was less than in control sham-operated rats. 2. This defect was more extensive for synthesis of fatty acids incorporated into triacylglycerols than into phospholipids. 3. There was impairment in desaturation and export of newly synthesized fatty acid. 4. Fatty acid synthesis and desaturation were restored to normal rates 5h after treatment with cortisol in vivo. 5. Fatty acid synthesis was seasonally variable, being highest in the winter; the impairment after adrenalectomy was observed in all seasons. 6. In perfusions with oleate (0.7 mM), no further impairment in fatty acid synthesis was discerned in livers from adrenalectomized rats, in which the rate resembled that in control livers. 7. No defect in the incorporation of oleate into glycerides was discerned in livers from adrenalectomized rats. 8. Cortisol exerted no stimulatory effect on fatty acid synthesis when added to perfusion media. 9. The impairment in hepatic lipogenesis, demonstrable after adrenalectomy, shows that adrenal glucocorticoids promote hepatic capacity for fatty acid synthesis de novo, at least in intact non-diabetic rats. It is suggested that this effect is mediated by insulin, perhaps through direct action on the liver.

In vivo estimation of fatty acid synthesis in the chicken (Gallus domesticus) utilizing 3H2O.

Abstract: 1. 1. Tritiated water was found to rapidly equilibrate with the body water of chicks after injection. 2. 2. The 3H also rapidly appeared in both liver and carcass fatty acids, with the greatest rates of incorporation occurring in the initial time periods of measurement. 3. 3. Incorporation of 3H into fatty acids in the liver appeared to proceed primarily via de novo synthesis whereas incorporation of 3H into fatty acids in the carcass occurred primarily via chain elongation.

Cholesterol and fatty acid synthesis in swine.

Abstract: In incubation studies with swine tissue slices, acetate-1-14C or glucose-U-14C as substrates were incorporated more readily into fatty acids and cholesterol in adipose tissue than other tissues tested. Cholesterol and fatty acid synthesizing activity was substantial in the small intestine. When acetate was available, liver, small intestine, and adipose tissue were important sites for cholesterol synthesis. Heart and aortic tissue had marginal levels of cholesterol synthesizing ability. Lipogenesis in adult swine liver, heart, and aortic tissue was extremely low. As in tissue slices, incorporation of acetyl-1-14C CoA into fatty acids by adipose homogenates indicated high lipogenic activity. Subcellular fractionations of heart and aortic tissue indicated that the heart microsomal fraction had the highest lipogenic activity as measured by the incorporation of acetyl-1-14C CoA into fatty acids. In adult swine adipose tissue, the incorporation of glucose-U-14C into fatty acid was higher than its incorporation into glyceride-glycerol. The synthesis of glyceride-glycerol from glucose-U-14C or acetate-1-14C in liver was higher than for fatty acid synthesis. The activity of acetyl CoA carboxylase, fatty acid synthetase, citrate cleavage enzyme, nicotinamide adenine dinucleotide phosphate-malate dehydrogenase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase was considerably higher in adipose tissue than in other tissues tested, paralleling its high lipogenic capacity.

EPTC Altered Beet Disc Betacyanin Efflux and Fatty Acid Synthesis

Abstract: Betacyanin efflux from “aged” red beet (Beta vulgaris L.) root tissue, measured spectrophotometrically, was increased as temperature and EPTC (S-ethyl dipropylthiocarbamate) concentration increased. Acetate-2-14C (∗Ac) incorporation into the total fatty acid content was inhibited by EPTC. EPTC inhibited the incorporation of ∗Ac into the dienoic fatty acids and NA (1,8-naphthalic anhydride) reversed the EPTC induced inhibition of the incorporation of ∗Ac into dienoic fatty acids.

Resistance to hepatic action of vasopressin in genetically obese (ob/ob) mice.

Abstract: 1. Fatty acid synthesis, measured in the perfused liver of genetically obese (ob/ob) mice with 3H2O or [14C]actate, did not show the inhibition by [8-arginine]vasopressin (antidiuretic hormone) that is observed in livers from normal mice. 2. Hepatic glycogen breakdown in obese mice was stimuulated by vasopressin, but not as extensively as in lean mice. 3. If obese mice received a restricted amount of food, then fatty acid synthesis still did not respond to vasopressin, but glycogen breakdown was fully stimulated. 4. Cholesterol synthesis was not inhibited by vasopressin in livers from obese mice. 5. Vasopressin inhibited fatty acid synthesis in intact lean mice, but not in obese animals. 6. These results suggest that genetic obesity could be due to an inborn error within the mechanisms (other than adenylate cyclase) which mediate responses to extracellular effectors.

Effect of cerulenin on the growth and differentiation of Dictyostelium discoideum.

Abstract: The growth of Dictyostelium discoideum Ax-2 was inhibited completely by cerulenin at a concentration of 5 mug/ml. This inhibition of growth was found to be due to the inhibition of fatty acid synthesis. Acetate incorporation into a long-chain fatty acid was inhibited completely by cerulenin, and the growth inhibition could be reversed by inclusion of certain saturated fatty acids in the medium. Unsaturated fatty acids and sterols failed to reverse the inhibitory effect. The fatty acid and sterol compositions of cerulenin-treated cells were determined to establish whether the drug could be used to manipulate the organism's lipid composition. Only relatively small manipulations were obtained under the conditions employed in this study. Cerulenin inhibited differentiation but only at high concentrations (150 mug/ml). This inhibition could be reversed by palmitic acid, suggesting that the prime cause of the inhibition was an inhibition of fatty acid synthesis. Thus, it appears that continued fatty acid synthesis is required for the cellular process of differentiation in D. discoideum.

Cycloalkanones. 9. Comparison of analogues which inhibit cholesterol and fatty acid synthesis.

Abstract: A number of 2,8-dibenzylcyclooctanone analogues inhibited the HMG-CoA reductases activity of Holtzman male rat liver, whereas only 2-octanone, 2-hexadecanone, 2,8-dibenzylcyclooctanone derivatives, and 2-bis(4-chlorophenyl)-3,5-dimethyltetrahydro-4-pyrone inhibited fatty acid synthetase activity. 2-Octanone significantly lowered serum cholesterol, triglycerides, and glycerol levels in Holtzman male rats and serlm cholesterol in male CF1 mice. Serum lipase activity was significantly elevated in rats administered 20 mg/kg/day of 2-octanone for 16 days. The activity of liver HMG-CoA reductase was inhibited in mice administered 10 mg/kg/day of 2-octanone for 10 days and in mouse and rat liver in vitro by 10 mg of 2-octanone. In mice, fecal excretion of [14C]cholesterol and tripalmitin was accelerated whereas palmitic acid and cholesteryl oleate were not affected by 10 mg/kg/day of 2-octanone. The LD50 in male mice for 2-octanone was 1.6g/kg.