Fatty Acid Synthetase Activity Research Articles

Effet de la surrénalectomie sur la capacité de thermogenèse du tissu adipeux brun et le développement de l'obésité chez le rat Zucker fa/fa

This study was undertaken to examine whether adrenalectomy performed during the weaning period could correct some of the first metabolic abnormalities to develop in obese fa/fa rats: impaired thermogenesis in brown adipose tissue and hyperlipogenesis in interscapular brown and white (inguinal) adipose tissues. Pups were adrenalectomized or sham-operated at 23 days of age and studied at 30 days of age. Body weight, interscapular brown adipose tissue and inguinal white adipose tissue weight were decreased after adrenalectomy in Fa/fa and fa/fa pups. Adrenalectomy had no effect on the thermogenic capacity of brown adipose tissue (as assessed by GDP binding to mitochondria) which remained significantly lower in fa/fa than in Fa/fa rats. In both Fa/fa and fa/fa rats the lipogenic capacity of brown and white adipose tissues (as assessed by fatty acid synthetase activity) was dramatically reduced by adrenalectomy. However, in adrenalectomized rats, the fatty acid synthetase activity of brown and white adipose tissue remained 2 and 5-fold higher, respectively, in fa/fa than in Fa/fa rats. These results show that adrenalectomy at postweaning, did not affect specifically the rats bearing the fatty genotype but induced large alterations in both groups of rats. Adrenalectomized fa/fa animals remained obese as compared to the appropriate controls.

Effects of γ-linolenic acid supplementation on lipogenesis regulation in pregnant zinc-deficient rat and fetus

1. 1. In the liver of zinc-deficient pregnant rats fatty acid synthetase and Δ 9-desaturase activities decreased and diet supplementation with γ-linolenic acid potentiated this effect. 2. 2. However, in liver microsomes from the foetuses of zinc-deficient mothers, HMG CoA reductase and Δ 9-desaturase activities declined but fatty acid activity rose. 3. 3. The same applied to foetuses from mothers whose diet was supplemented with γ-linolenic acid and here again, the effect of zinc deficiency was potentiated. 4. 4. The fact that Δ 9 activity dropped whereas fatty acid synthetase activity rose implied a defect in the mechanism regulating the functioning of these enzymes. 5. 5. In the non zinc-deficient group of pregnant females, γ-linolenic acid supplementation had no effect on fatty acid synthetase and Δ 9-desaturase activities but significantly increased HMG CoA reductase activity. 6. 6. In foetuses from the same group, the activities of MHG CoA reductase, D 9-desaturase and fatty acid synthetase all increased.

Évolution de la teneur en lipides de Leptosphaeria typhae en fonction de sa croissance et de sa reproduction sexuée : activité de synthèse et étude des lipides neutres et polaires

When perithecia appear (on the 7th day of growth), the mycelial lipid content falls and the degree of fat insaturation increases; fatty acid synthetase activity greatly increases. Lipid turnover is therefore accelerated. Among neutral lipids, triglycerides constitute the largest pool and their proportion increases when perithecia appear. Free fatty acids also increase, confirming the lipid turnover's acceleration. Polar lipids especially disappear; the phosphatidylcholine/phosphatidylethanolamine ratio increases when the fungus ascosporulates.

Effect of a high cholesterol diet on lipid metabolizing enzymes in spontaneously hypertensive rats

A high cholesterol diet induced a fatty liver and an increase in cholesterol oleate in spontaneously hypertensive rats. The activity of microsomal glycerophosphate acyltransferase in liver increased 2–3-fold to meet the increased supply of oleate, the synthesis of which was stimulated by a 10-fold increase in microsomal Δ 9-desaturase activity. Hepatic fatty acid synthetase and diacylglycerol acyltransferase activities were decreased somewhat. These results, together with the fact that the large increases in hepatic cholesterol ester and triacylglycerol were not correspondingly reflected in plasma, indicated that the fatty liver resulted from decreased secretion of lipoprotein rather than increased lipogenesis. Endogenous cholesterol in liver microsomes increased 2-fold and hepatic acyl-CoA:cholesterol acyltransferase activity increased 3-fold, whereas plasma lecithin:cholesterol acyltransferase activity was unchanged. Thus, the increase in cholesterol oleate seen in spontaneously hypertensive rats fed a high cholesterol diet is due mainly to increases in acyl-CoA:choIesterol acyltransferase and Δ 9-desaturase activities.

The effect of progesterone on prolactin stimulation of fatty acid synthesis, glycerolipid synthesis and lipogenic-enzyme activities in mammary glands of pseudopregnant rabbits, after explant culture or intraductal injection.

The activities of lipogenic enzymes, such as acetyl-CoA carboxylase, fatty acid synthetase and glucose-6-phosphate dehydrogenase, and glycerolipid synthesis increased significantly in mammary explants of 11-day-pseudopregnant rabbits in response to prolactin, in the presence of near-physiological concentrations of insulin and corticosterone in culture. Increasing the concentration of progesterone in culture resulted in suppression of glycerolipid synthesis and activities of acetyl-CoA carboxylase and fatty acid synthetase, but not the pentose phosphate dehydrogenases. However, at near-physiological concentration of progesterone, only acetyl-CoA carboxylase activity was decreased. Injection of prolactin intraductally into 11-day-pseudopregnant rabbits stimulated glycerolipid synthesis, fatty acid synthesis and enzymes involved in fatty acid synthesis, after 3 days. Intraductal injection of progesterone separately or together with prolactin had no significant effect on basal or stimulated lipogenesis in mammary glands. Intramuscular injection of progesterone at 10 mg/day did not suppress fatty acid synthesis stimulated when prolactin was injected intraductally, but a significant inhibition was observed at a higher dose (80 mg/day).

Modification of mammalian fatty acid synthetase activity by NADP

Experiments are described which show that the mammalian fatty acid synthetase, in the presence of NADP, synthesizes stoichiometric amounts of enzyme-bound acetoacetyl moieties. The acetoacetyl moieties can neither undergo the normal transfer reaction to a CoA acceptor, nor participate in the normal reaction sequence once NADPH is made available. Our results indicate that, since it is the product of the condensation reaction which accumulates on the inhibited enzyme, the previously held view that NADP inhibits the condensation step in fatty acid synthesis is probably incorrect.

Increased insulin sensitivity and responsiveness of glucose metabolism in adipocytes from female versus male rats.

This study was undertaken to examine whether there were sex-associated differences in the action of insulin on glucose metabolism in adipocytes. Insulin binding and the dose-response curves for glucose transport (assessed by measuring the cell-associated radioactivity after 15-s incubation with 50 microM [6-14C]glucose) and [U-14C]glucose (5 mM) metabolism into CO2 and lipids were compared in retroperitoneal adipocytes from age-matched (84 d) male and female rats. In addition, the activity of fatty acid synthetase, one of the key lipogenic enzymes, was determined. Fat cell size was not significantly larger in females than in males (0.238 vs. 0.209 microgram lipid per cell). At insulin concentrations less than or equal to 1.6 nM, adipocytes from females bound significantly more insulin than did adipocytes from males, due to an increased apparent affinity of the receptors for insulin. Accordingly, the sensitivity of glucose transport to insulin was greater in females than in males: insulin concentration eliciting half-maximal stimulation (ED50) = 0.19 nM vs. 0.41 nM. At maximal insulin stimulation the rates of glucose transport (12 times the basal values) were similar in the two sexes. In contrast, the maximal effect of insulin on glucose conversion to CO2 plus lipids was much greater in the adipocytes from females than males (increment over basal: 472 vs. 249 nmol/10(6) cells per 2 h). Fatty acid synthesis contributed approximately 40% of the incremental difference between the two types of adipocytes, while glyceride-glycerol synthesis contributed less than 10%. The insulin dose-response curves for adipocytes from females were shifted to the left for all the metabolic pathways investigated. The mean ED50 for total glucose metabolism in females was 50% of that in males (0.07 nM vs. 0.15 nM). Marked sex-associated differences in the action of insulin on glucose metabolism were also observed in subcutaneous inguinal adipocytes (increment over basal: 137 and 56 nmol/10(6) cells per 2 h, ED50 = 0.13 nM and 0.30 nM in females and males, respectively). The intracellular capacity to metabolize glucose through the fatty acid synthesis pathway, as assessed by FAS activity, was higher in adipocytes from females than in those from males and was greater in retroperitoneal than in inguinal adipocytes. Furthermore, by plotting the individual data, a highly significant correlation (r = 0.92, P less than 0.001) was found between the absolute effect of insulin on glucose metabolism at maximal stimulation and the fatty acid synthetase activity of the cells. These results indicate that the response of glucose metabolism to insulin in adipocytes from female as compared with male rats is characterized by two main features: (a) an increased sensitivity primarily due to an increase in insulin binding, and (b) an increased responsiveness closely associated with a postreceptor increase in the lipogenic capacity of the cell. These findings might be relevant to the differential disposition of male and female rats to develop fatness.

Diurnal variations of lipogenic enzymes, their substrate and effector levels and lipogenesis from tritiated water in rat liver

The activities of glucose-6-phosphate dehydrogenase, malic enzyme, fatty acid synthetase and acetyl-CoA carboxylase (extracted with or without phosphatase inhibitor) in rat liver did not vary significantly during 24 h. The hepatic levels of glucose 6-phosphate and malate increased coordinately 3–6 h after the beginning (1900 h) of food intake and were high until morning, whereas the levels of acetyl-CoA and citrate peaked at 1900 h and then decreased. However, it is remarkable that the in vivo incorporation of 3H from tritiated water into fatty acids in liver increased with the level of inalonyl-CoA after food intake. Comparing the substrate and effector levels with the K m and K a values for the enzymes, the levels of acetyl-CoA, malonyl-CoA and citrate appear to limit the enzyme activities. It is suggested that, after food intake, the physiological activity of acetyl-CoA carboxylase was increased with the substrate increase and/or with the catalytic activation with citrate and consequently, the fatty acid synthetase activity was also increased, whereas the enzyme activities measured under optimum conditions were not.

Effect of Dietary Fat and Environment on Lipogenesis by Large White Breeder Turkeys

An experiment was conducted to evaluate the effects of either a low-fat (8% of total calories) or high-fat (47% of total calories) diet on Large White breeder females maintained at a constant (21 C) or a cyclic temperature regimen (12 to 27 C). Each diet was fed to 32 hens individually caged in the cyclic condition and 46 in the constant condition. Energy consumption, reproductive performance, and in vitro lipogenesis were monitored for hens subjected to both temperature and dietary treatments. Hens consumed more (P<.05) dietary energy when maintained at a constant temperature or when fed the low-fat diet. Hens also produced more (P<.05) eggs when maintained under cyclic temperature conditions, although this observation was tempered by the fact that fewer hens were broody. More (P<.05) of the fertile eggs from hens held at the cyclic temperature resulted in live poults. The high-fat diet decreased (P<.05) in vitro lipogenesis in hens and may also decrease the maintenance energy requirement by providing a preformed fatty acid pool for egg lipids. The high-fat also decreased (P<.05) liver lipid and the activities of fatty acid synthetase and malic enzyme.

Recovery from energy deficit in golden hamsters.

Hamsters feeding at greater than 2-h intermeal intervals (IMI) lose weight but recover from weight losses without hyperphagia if they are allowed to feed at 2-h IMIs (Am. J. Physiol. 236 (Endocrinol. Metab. Gastrointest. Physiol. 5): E105-E112, 1979). To determine the relative importance of changes in energy expenditure and fat synthesis in their energy regulation, measurements were made of resting metabolic rate, respiration by brown adipose tissue (BAT), locomotion, fecal energy content, and insulin and hepatic lipogenic enzyme responses to feeding in underweight hamsters allowed to feed at 2- or 5-h IMIs. Energy deficit suppressed the resting metabolic rate and general locomotor activity and increased the activity of fatty acid synthetase (FAS). Heat production by BAT increased in underweight hamsters. Increase in IMIs blocked the postprandial insulin release, reduced plasma insulin concentration and FAS activity, and increased malic enzyme activity. Thus ad libitum feeding hamsters recover from energy deficit by reducing energy expenditure, whereas failure to add additional meals and impaired insulin and changed lipogenic responses to feeding produce energy deficits in infrequently feeding hamsters.

Fatty Acid Synthesis in Aquatic Animals and Its Metabolism in Carp, Cyprinus cardo

Lipid metabolism and its regulation in aquatic organisms seed to differ considerably from those in mammals. In our experiments, carp starved for 10 days or fed fat-free diet for 35 days had almost the same hepatopancreas acetyl CoA carboxylase (ACC) specific activity levels as the controls. On supplementing the fat-free diets with 5% fatty acid, there was no depression of the specific activity of carp hepatopancreas ACC. The administration of a fat-free diet for 35 days resulted in increased specific activity of hepatopancreas fatty acid synthetase (FAS) and supplementing it of with 5% fatty acid decreased the specific activity of carp hepatopancreas FAS. An injection insulin or alloxan had no effect on the specific activity of carp hepatophacreas ACC or FAS. The activation of ACC from aquatic organisms required citrate and Mg2+ and that of FAS required NADPH, as is also the case in mammals. In carp hepatopancreas, the specific activity of ACC was 45mol/min/mg protein and that of FAS, 421pmol/min/mg protein. Both these values are low compared to those in mammals. In another aquatic 7 species tested, the specific activity of lipogenic enzymes was about one tenth that in carp hepatopancreas though crude enzymes prepared from whole body were examined. The present data indicate that lipogenesis in fish, and other aquatic organisms is apparently in a reduced state.

Rôle du tissu adipeux brun dans le développement de l'obésité génétique du rat Zucker obèse (fa/fa)

The lipogenic capacity and thermogenic activity (assessed by GDP binding to mitochondrial) of brown adipose tissue was studied in lean (Fa/fa) and obese (fa/fa) suckling Zucker rat pups 2 and 10 days old. By 10 days of age, fat deposition, lipogenesis in vivo and fatty acid synthetase activity were 1.5 to 2-fold higher, whereas GDP binding to mitochondria was 40% lower in pre obese than in lean pups. Compared with lean pups, 2-day old fa/fa pups showed a 60% increase in triglyceride accumulation in interscapular brown adipose tissue and a 30% decrease in GDP binding to mitochondria, while no change occurred in fatty acid synthetase activity. These results strongly suggest that an impaired thermogenic activity in the brown adipose tissue of fa/fa pups could play a key role in the development of obesity. However, the concomitant increase in fat content in the brown adipose tissue of 2-day old pre-obese pups raises the question of the causal relationship between these two disorders.

Fatty acid synthesis in relation to gametogenesis in the mussel Mytilus edulis L.

1. 1. Seasonal fluctuations of the lipid level in Mytilus edulis are small compared to the changes in proteins and glycogen. 2. 2. In the later stages of gametogenesis (March–May) there is an increase of neutral lipids in the mantle, while there is no concomitant decrease elsewhere in the animal. 3. 3. Fatty acid analysis shows an increase of probably de novo synthesized fatty acids. 4. 4. Activity of acetyl-CoA carboxylase and fatty acid synthetase are virtually absent in mantle, muscle and digestive gland. 5. 5. These enzyme activities increase strongly in female mantle tissue in the period preceding the spawning, but only slightly in male mantles.

The short-term regulation of fatty acid synthesis in the rat epididymal adipocytes

1. 1. Lipogenesis and fatty acid synthetase (FAS) activity of isolated rat adipocytes that were treated with insulin or epinephrine were studied. 2. 2. Insulin stimulated incorporation of radioactivity from d-[U- 14C]glucose into CO 2, saponifiable and non-saponifiable fractions, whereas epinephrine promoted lipolysis and oxidation of glucose into CO 2. 3. 3. Whereas insulin stimulated fatty acid synthesis, epinephrine had no effect. 4. 4. Changes in FAS specific activity of insulin- or epinephrine-treated adipocytes were insignificant and could not account for insulin-stimulated lipogenesis. 5. 5. Rat adipocyte FAS, unlike hepatic FAS, was not subject to short-term regulation by insulin, although fatty acid synthesis showed such a response.

Development under the control of insulin of lipogenic enzymes, lipoprotein lipase, isoproterenol and glucagon sensitivity in differentiating rat preadipocytes in primary culture

In preadipose cellular fractions (I, II and III) isolated by density gradient centrifugation from the inguinal tissue of young rats, we followed the activity of fatty acid synthetase, ATP citrate lyase and lipoprotein lipase during differentiation in culture. 1.5 nM insulin when added at confluence markedly induced the activity of ATP citrate lyase and fatty acid synthetase in the cells derived from the lighter fractions (I and II). The magnitude of this response was 25–50-fold the initial value 15 days after plating. In the cells of the heaviest fraction (III) both enzymes exhibited low activity which was slightly stimulated by the presence of insulin, VLDL and heparin. In contrast, the activity of lipoprotein lipase appeared before confluence in cells from all three fractions and peaked at day 6 after plating. This early emergence was independent of the addition of insulin to the medium. However, insulin slightly enhanced the peak activity in post-confluent cells. The development of cAMP production in response to isoproterenol (100 μM) and to glucagon (0.3 μM) was determined in the cells of fraction II in the same culture conditions. The responsiveness to isoproterenol was present very early in these cells and rose rapidly during the exponential growth phase, reaching a peak value at day 8 after plating. In contrast, the development of glucagon sensitivity occurred only during late differentiation. The stimulatory effect of glucagon was enhanced when VLDL and heparin were added with insulin to the medium.

Fatty acid elongation activity in fibroblasts from patients with adrenoleukodystrophy (ALD).

The activities of microsomal fatty acid elongation and cytoplasmic de novo fatty acid synthesis were measured in human cultured skin fibroblasts. Both activities in fibroblasts from normal controls and patients with adrenoleukodystrophy (ALD) were compared and slight but a significant increase of elongation activities in ALD fibroblasts was demonstrated. On the other hand, there were no significant differences in the fatty acid synthetase activities. In this study, we measured microsomal fatty acid elongation activities in the presence of N-ethylmaleimide, which completely inhibited the activity of contaminating fatty acid synthetase and also the degradation of fatty acids, and made accurate determination of the elongation activities possible.

The presence of essential arginine residues at the NADPH-binding sites of β-ketoacyl reductase and enoyl reductase domains of the multifunctional fatty acid synthetase of chicken liver

Treatment of chicken liver fatty acid synthetase with the arginine-specific reagent phenylglyoxal resulted in the pseudo-first-order loss of synthetase β-ketoacyl reductase and enoyl reductase activities. The sum of the second-order rate constants for the two reductase reactions equalled that for the synthetase reaction, suggesting that inactivation of either reductase was responsible for the loss of fatty acid synthetase activity. Double-log plots of pseudo-first-order rate constant versus reagent concentration yielded straight lines with slopes of unity for all three activities tested, suggesting the reaction of one reagent molecule in the inactivation process. In parallel experiments, complete inactivation of synthetase activity was accompanied by the incorporation of 4.5 [ 14C]phenylglyoxal, and the loss of 2.3 arginine residues per subunit. Reaction of essential sulfhydryl groups was not involved, since inactivation by phenylglyoxal was unaffected by reversible protection of these groups with 5,5′-dithiobis(2-nitrobenzoic acid). Inactivation of all three activities by phenylglyoxal was prevented by saturating amounts of the coenzyme NADPH, or its analogs 2′,5′-ADP and 2′-AMP, but not by the corresponding nucleotides containing only 5′-phosphate. Conversely, the ability of this enzyme to bind NADPH was abolished upon inactivation. These results are consistent with the presence of an essential arginine residue at the binding site for the 2′-phosphate group of NADPH at each of the two reductase domains of the multifunctional fatty acid synthetase subunit.

Effect of oestrogen administration on fatty acid synthetase activity in male chick liver

Effect of oestrogen administration on fatty acid synthetase activity in male chick liver

Suppression of cholesterol biosynthesis by constituents of Barley Kernel

Hepatic β-hydroxy-β-methylglutaryl CoA (HMG-CoA) reductase, cholesterol 7α-hydroxylase (7α-hyd), and fatty acid synthetase (FAS) activities and cholesterol levels were determined in chicks fed isonitrogenous corn- and high-protein barley flour (HPBF) based diets. HMG-CoA reductase (−27%), 7α-hyd (−30%), and serum cholesterol (−13%) were reduced, whereas FAS increased (28%) in comparison to a corn-based (control) diet. Fractions obtained by serial extractions of HPBF with solvents of increasing polarity were fed at levels equivalent to 20% HPBF in a corn-based diet to female White Leghorn (WHL) chickens for 3 weeks. A petroleum ether-soluble fraction of HPBF produced 3 effects: an increase in body weight (18%), a strong suppression of HMG-CoA reductase (−36%) and FAS (−40%) accompanied by decreases in serum triglyceride (−9%) and cholesterol levels (−23%). The methanol-soluble fraction produced a significant suppression of HMG-CoA reductase (−49%) and serum cholesterol level (−29%), and an increase in FAS activity (95%). These effects were duplicated in 7-week-old broiler chickens which also showed a significant decrease in chol-LDL (low density lipoprotein) levels by these fractions. The factor(s) lowering serum cholesterol concentration was about equally divided between the polar and non-polar fractions, and each was significantly more effective than the 20% HPBF in the corn-based diet. The observed effects on lipogenesis and cholesterogenesis might be attibuted to a number of chemical constituents of HPBF, but cannot be attributed to the water-insoluble plant fibers.

Metabolic alterations after dehydroepiandrosterone treatment in Zucker rats.

Dehydroepiandrosterone (DHEA) is a known noncompetitive inhibitor of glucose-6-phosphate dehydrogenase (G6PD). In the present investigation, the effects of chronic DHEA treatment on G6PD and several other enzymes involved in lipid metabolism were examined in lean and obese Zucker rats. Significant decreases in body weight were found in DHEA-treated rats in comparison with nontreated rats. In lean rats, DHEA treatment did not decrease either liver or adipose tissue G6PD and fatty acid synthetase activity, but malic enzyme activity was increased. In obese rats, decreased liver and adipose tissue G6PD and fatty acid synthetase activities were found. Malic enzyme activity in liver of obese DHEA rats was increased but not in adipose tissue. Adipose tissue lipoprotein lipase activity was decreased in both lean and obese DHEA rats. Serum insulin in obese DHEA rats was also decreased compared with control obese rats. These results indicate that the inhibition of G6PD may not be the mechanism of action of the antiobesity effect of DHEA. However, the metabolic effects of DHEA seen in obese rats may contribute to its antiobesity action.