Changes In Fatty Acid Metabolism Research Articles

Impaired mitochondrial beta-oxidation in a patient with an abnormality of the respiratory chain. Studies in skeletal muscle mitochondria.

Defects of complex I of the mitochondrial respiratory chain are important causes of neurological disease. We report studies that demonstrate a severe deficiency of complex I activity with less severe abnormalities of complexes III and IV (less than 5, 63, and 30% of control values, respectively) in a skeletal muscle mitochondrial fraction from a 22-yr-old female with weakness, lactic acidemia, and the deposition of intramuscular neutral lipid. The observation that lipid accumulates in this and other patients with complex I deficiency suggests impaired mitochondrial fatty acid oxidation. To investigate this mechanism we have shown impaired flux through beta-oxidation [( U-14C]hexadecanoate oxidation was 66% of control rate) and accumulation of specific acyl-CoA ester intermediates. The changes in fatty acid metabolism in complex I deficiency are secondary to the reduced state within the mitochondrial matrix with low NAD+/NADH ratios.

Characteristics of changes in fatty acid metabolism by suppression of the activities of peroxisomal .BETA.-oxidation system and glyoxylic acid cycle in Tetrahymena pyriformis.

The effects of inhibitors on peroxisomal enzymes were examined in order to clarify the role of peroxisomes in the grouwth of Tetrahymena pyriformis. With the supplementation of chlorpromazine, known as an inhibitor of the peroxisomal β-oxidation system, to the culture medium, the growth of T. pyriformis was suppressed and the activity of the glyoxylate cycle which is linked to β-oxidation, was reduced. Supplementation of itaconic acid to the medium, a competitive inhibitor of isocitrate lyase of the glyoxylic acid cycle, also inhibited the growth. In these cases, no change in the activity of mitochondrial β-oxidation was observed. On the other hand, in an experiment concerning the fatty acid metabolism using [U-14C]palmitic acid conversions to glycogen and proteins were significantly inhibited by these inhibitors. Thus, a decrease in the supply of carbon atoms, which are necessary for energy production and the biosynthesis of materials used in cell construction, was suggested. The acyl-coenzyme A not subjected to β-oxidation might be used for lipid synthesis, resulting in an accumulation of triglyceride and phospholipids.From these results, it was concluded that in Tetrahymena peroxisome is not merely an assistant in the mitochondrial metabolic system, but has an important role in the production of energy essential for cell movement and cell growth, and in the conversion of fatty acids to carbohydrates and proteins.

Increased levels of vaccenic acid in bronchogenic carcinoma tissue.

Employing capillary gas liquid chromatography the levels of palmitic, palmitoleic, stearic, oleic, cis-vaccenic, linoleic, arachidonic and docosahexaenoic acids were measured in lung tissue and lung tumours from 28 patients undergoing surgery for bronchogenic carcinoma. There were significant increases in the majority of fatty acids in tumour tissue compared to normal tissue when the results were expressed in absolute units. However, when the relative changes in fatty acid concentration were studied, the most consistent findings were a significant rise in vaccenic acid and a fall in palmitic acid in tumour tissue compared to normal tissue. This change in the vaccenic:palmitic acid ratio may reflect specific changes in fatty acid metabolism in bronchogenic carcinoma tissue involving a delta-9 desaturase.

Inhibition of mitochondrial functions by margosa oil: possible implications in the pathogenesis of Reye's syndrome.

Margosa oil (MO), a fatty acid-rich extract of the seeds of the neem tree and a reported cause of Reye's syndrome, has been used in the induction of an experimental model of Reye's syndrome in rats. It has been reported that MO causes a decrease in in vivo mitochondrial enzyme activity similar to that seen in Reye's syndrome. We have attempted to uncover some of the biochemical mechanisms of MO's toxicity by examining its effect in vitro on isolated rat liver mitochondria. Male rat liver mitochondria were isolated by centrifugation; oxygen uptake, reduced forms of cytochrome b, c + c1, a + a3, and flavoprotein, intramitochondrial concentrations of acetyl coA, acid-soluble coA, acid-insoluble coA, and ATP content were measured after incubation with and without MO. Our results reveal that MO is a mitochondrial uncoupler. State 4 respiration was increased while the respiratory control ratio was decreased. The intramitochondrial content of ATP was also decreased. There were substantial changes in the reduction of the respiratory chain components after incubation of mitochondria with MO. This decelerative effect on mitochondrial electron transport was alleviated by the addition of coenzyme Q and/or carnitine. These effects of MO on mitochondrial respiration may be due to changes in fatty acid metabolism caused by MO as MO caused a shift in the proportion of acid-soluble or acid-insoluble coA esters. Supplementary therapy with L-carnitine and coenzyme Q may be useful in the management of MO-induced Reye's syndrome.

Blood carnitine concentrations are increased after surgical stress

Elevated plasma carnitine concentrations are demonstrated in surgically stressed and partially hepatectomized rats. The response to surgical stress was observed only when the rats were fed, suggesting that exogenous sources of carnitine may be required for maintaining tissue carnitine concentrations during stress. The results are discussed with respect to the changes in fatty acid metabolism which are assciated with these conditions.

Uptake of fatty acids and their mobilization from phospholipids in cultured monocyte-macrophages from rheumatoid arthritis patients

Prostaglandins (PG) and related eicosanoids which derive from essential fatty acids are important mediators and modulators of inflammation. Macrophages (Mϕ), which derive from peripheral blood monocytes (PBM), are prominent cells in the synovium of patients with rheumatoid arthritis (RA), and are a major source of synovial PGE 2. In addition, fresh and cultured PBM from RA patients produce more PG than normal control cells. When allowed to mature in culture PBM exhibit many characteristics of macrophages (M-Mϕ). We examined uptake by M-Mϕ of eicosanoid precursor fatty acids (FA), their incorporation into cellular phospholipid (PL), and mobilization of FA after cell stimulation. Cultured M-Mϕ from treated and untreated RA patients (RA M-Mϕ) took up significantly more linoleic acid (LA), dihomogammalinolenic acid (DHLA) and arachidonic acid (AA) than M-Mϕ from normal volunteers (N M-Mϕ). The enhanced uptake of FA observed in 12-day cultures of RA M-Mϕ was similar to uptake seen in normal human peritoneal macrophages (PMϕ). After uptake FA were incorporated mainly into phosphatidylcholine (PC). M-Mϕ from untreated RA patients incorporated a smaller proportion of [ 14C]LA into PC (37.0 ± 12.7% of total PL label) than normal cells (86.0 ± 4.2%), and a greater proportion of [ 3H]AA into PC (57.1 ± 7.1%) than normals (23.9 ± 6.9%). Stimulation of M-Mϕ with calcium ionophore A23187 resulted in significantly greater hydrolysis of LA and AA from PC in RA M-Mϕ from both treated and untreated patients than from PC in N M-Mϕ. The data indicate that M-Mϕ from RA patients mature more rapidly in vitro than M-Mϕ from controls as uptake of FA by RA M-Mϕ increases with duration of culture and by 12 days in culture equals uptake by normal human peritoneal Mϕ. Also, RA M-Mϕ exhibit differences from N M-Mϕ in uptake, PL distribution, and hydrolysis of eicosanoid precursor FA. Such changes in FA metabolism might influence cell function and inflammatory responses.

Adipose tissue fatty acid metabolism during pregnancy in swine.

In vitro adipose tissue fatty acid pool size (POOL), fatty acid release (FAR) and esterification (EST) were measured in peritoneal (PFP) and subcutaneous mammary (MFP) fat pads of swine at d 15, 30, 45, 60, 75, 90, 105 and 112 of pregnancy. Plasma free fatty acids (FFA) and triglycerides (TG) were not altered by stage of pregnancy. Basal EST in PFP was generally constant across pregnancy with a peak at d 75. Basal EST in MFP was elevated at d 30, 75 and 112. Esterification in response to norepinephrine stimulus (NE) was lower than basal rates in both fat depots. Basal FAR was constant throughout pregnancy in PFP, but elevated at d 75 and 90 in MFP. Fatty acid release in response to NE was biphasic with peaks at d 30 and in late pregnancy (in MFP, micromolar FAR in response to NE was 69.3% greater on d 75 to 112 than on d 45 to 60). Basal POOL was constant throughout pregnancy in both depots and lower than NE-stimulated POOL. All responses to NE were greater in MFP than in PFP, indicating that adipose tissue surrounding the developing mammary gland had higher metabolic activity and a greater response to NE than peritoneal adipose. Changes in fatty acid metabolism during pregnancy in swine are temporally related to published values for plasma steroids, fetal growth and mammary development. Metabolic adaptations in adipose and mannary epithelial tissue occur in synchrony with changing plasma estrogen concentrations, redirecting energy flow from maternal adipose tissue toward developing mammary and fetal tissue.

246 GROWTH AND FATTY ACID METABOLISM IN EXPERIMENTAL INTRAUTERINE GROWTH RETARDATION: EFFECTS OF POSTNATAL NUTRITION

Growth rate and fatty acid (FA) metabolism were evaluated in the first 3½ days of life in rats as a function of degree of intrauterine growth retardation (IUGR) and of postnatal nutrition. IUGR (mild, BW≤1 SD and severe, BW≤2 SD) was produced by uterine artery ligation on 18th day of gestation, and controls were sham operated. Food intake was manipulated by varying the litter size per dam; n=16 for underfeeding, n=10 for normal feeding and n=4 for overfeeding. The growth rate in the control pups was reduced by underfeeding while overfeeding and normal feeding resulted in the same rate. The mild IUGR responded the same way as in control. In severe IUGR group, the growth rate was similar regardless of the feeding protocol. The fatty acid content in carcass was reduced as a result of either prenatal or postnatal undernutrition in spite of a higher fatty acid synthesis rate (FASR) (tritiated water technique). In liver and lung, there was no difference in FASR between controls and IUGR and feeding did not influence the rate; the fat content was lower in under fed control and in IUGR rats. In the brain, FASR of normal fed IUGR was markedly higher and the rate almost doubled in underfed IUGR. This was accompanied by significantly less FA contents in both normal fed and under fed IUGR group. We conclude that postnatal undernutrition retards postnatal growth of normal and mildly affected IUGR rats, but no additional growth retardation was observed in the severely affected IUGR pups. The changes in fatty acid metabolism in various organs studied were consistent with the alterations in growth.

Progressive changes in fatty acid metabolism in rat liver and muscle during exercise

This study was undertaken to determine the effects of increasing exercise time until exhaustion on the capacity of liver to synthesize and oxidize fatty acids, as well as the capacity of muscle to oxidize fatty acids. Additionally, the same parameters were examined during various periods of recovery after exhaustion. These studies were prompted by the scarcity of information relating the effects of exercise on the metabolism of fatty acids in liver, and by our findings and those of others where exhaustive exercise was reported to cause a decrease in the capacity of muscle to oxidize fatty acids. The latter led to the hypothesis that the reported decrease in fatty acid oxidation may be a factor in fatigue. Thus the purpose of the present studies was threefold. The first was to determine changes in fatty acid metabolism in liver during exercise and recovery; the second was to test the above hypothesis by following time-course changes of fatty acid oxidation by muscle; and the third was to determine whether or not the effects of exhaustion are reversible. The results obtained showed that fatty acid synthesis in liver decreased with increasing time but returned to normal levels by approximately 12 hr of rest after exhaustion. Oxidation of fatty acids by liver remained unchanged during the first hour of exercise but steadily increased afterwards until it reached a maximum at exhaustion. Oxidation returned to control level after 12 hr of rest and remained so during the subsequent recovery period. Fatty acid oxidation by muscle was maximally depressed after 1 hr of exercise, yet the animals continued to run, thus ruling out the possibility that the decreased oxidation of fatty acids with exhaustion is a factor in fatigue. Finally, recovery studies showed that the biochemical processes that were examined returned to control levels within 12–24 hr after exercise demonstrating that these effects are not permanent.

Selective changes in fatty acid composition of phosphatidylserine in rat erythrocyte membrane induced by nitrate

The relationship between nitrate which is formed from inhaled nitrogen dioxide, a common air pollutant, and changes in fatty acid metabolism of phosphatidylserine in rat erythrocytes has been examined. When erythrocytes were incubated at 37°C for 60 min with fatty acid, the incorporation rate of [1- 14C]arachidonic acid and [9,10- 3H]palmitic acid into phosphatidylserine was 15% (80 pmol/h per μmol lipid phosphorus) and 20% (12 pmol/h per μmol lipid phosphorus) of those into phosphatidylethanolamine, respectively. By the addition of 1.0 mM sodium nitrate or 0.5 μM ionophore A23187 to the incubation mixture, the rate of incorporation of both arachidonic acid and palmitic acid into phosphatidylethanolamine was stimulated 1.45-fold. On the other hand, the incorporation of palmitic acid into phosphatidylserine was little affected, while that of arachidonic acid was stimulated 1.35-fold. An increase in arachidonic acid of phosphatidylserine was also found by the addition of nitrate or ionophore A23187. This increase was dependent on the concentration of extracellular calcium and observed by the addition of other chaotropic anions in the order SCN >CIO 4 − > NO 3 −. It seems likely, therefore, that nitrate causes changes in erythrocyte membranes to facilitate calcium uptake. Increasing the concentration of intracellular calcium may cause stimulation of acyl-CoA:lysophospholipid acyltransferase and/or endogenous phospholipase A 2.

Effects of exogenous fatty acid concentration on glucagon-induced changes in hepatic fatty acid metabolism.

Studies were conducted to clarify the relationship between the external fatty acid concentration and glucagon in the regulation of hepatic fatty acid metabolism. Hepatocytes from fed rats were incubated with increasing concentrations of oleate (up to 1 mM) in the presence and absence of glucagon and the time sequence of changes in cellular malonyl-CoA levels, fatty acid synthesis, fatty acid oxidation, and ketogenesis were measured. At low concentrations of fatty acid the effect of glucagon was to abolish malonyl-CoA synthesis and lipogenesis and to produce a marked stimulation of fatty acid oxidation and ketogenesis. Similar effects were obtained with high concentrations of fatty acid in the absence of glucagon and, under these conditions, the additional presence of the hormone produced little further response. The results are consistent with the concept that the rate of fatty acid oxidation in liver is dictated largely by the relative concentrations of long-chain acyl-CoA (substrate for carnitine acyltransferase I) and malonyl-CoA (inhibitor of the transferase). They also indicate that the preemptive effect of fatty acids on glucagon-induced changes in fatty acid metabolism stems from their ability to reduce the tissue malonyl-CoA content, probably through long-chain acyl-CoA suppression of acetyl-CoA carboxylase.

Fatty-acid metabolism in senescing and regreening soybean cotyledons

Changes in fatty-acid metabolism were studied in soybean (Glycine max Merr.) cotyledons during senescence as well as in cotyledons which had been caused to regreen by removal of the epicotyl from the seedling. The activities of the enzymes acetyl-CoA synthetase (EC 6.2.1.1) and fatty-acid synthetase in plastids isolated from the cotyledons decreased during senescence but increased in response to regreening. These changes in enzyme activities followed the same pattern as changes in the quantities of chlorophyll and polyunsaturated fatty acids in this tissue. The in-vivo incorporation of [(14)C]acetate into total fatty acids in the senescing and regreening cotyledons did not vary markedly with age. In addition, the quantity of label in fatty acids did not decrease for as much as 60 h after the removal of the substrate. During this 60-h period however, there was substantial redistribution of the label among the individual fatty acids. While the labelling pattern of the individual fatty acids did not vary significantly with respect to age in the senescing cotyledons, there was a substantial increase in the synthesis of labelled polyunsaturated fatty acids in the regreening tissue. Thus, the incorporation of [(14)C]acetate into fatty acids did not reflect the changes in the quantities of the individual fatty acids in senescing tissue as well as they did in regreening tissue.

Changes in fatty acid metabolism after erythrocyte peroxidation: stimulation of a membrane repair process.

To study certain membrane repair processes in human erythrocytes, vitamin E-deficient cells were incubated with hydrogen peroxide. The incorporation of exogenous fatty acid and the transfer of fatty acid from phosphatidylcholine and neutral lipid into phosphatidylethanolamine were examined using radioactive fatty acids. Hydrogen peroxide stimulated the incorporation of fatty acid into all membrane phospholipids. The specific activity of phosphatidylethanolamine was increased disproportionately. The lipids of the membranes of erythrocytes were labeled with saturated and unsaturated fatty acid. When these erythrocytes were subsequently incubated with hydrogen peroxide, both types of fatty acid were transferred from superficial erythrocyte neutral lipids into phosphatidylethanolamine. However, the unsaturated fatty acids of phosphatidylethanolamine were subsequently altered by hydrogen peroxide, whereas the saturated fatty acids were not. The cumulative effect of these processes was a relative decrease in unsaturated fatty acid and an increase in saturated fatty acid in the phosphatidylethanolamine of the erythrocyte membrane. The net effect of these events represents the operation of repair processes which distort the usual fatty acid composition of erythrocyte membranes in the presence of H(2)O(2). This distortion may contribute to membrane permeability changes which occur during peroxide exposure and which precede the eventual hemolysis of these cells.