Showing papers on "Fatty acid published in 1995"

Regulation of organic nutrient metabolism during transition from late pregnancy to early lactation

Abstract: Conceptus energy and nitrogen de- mands in late pregnancy are mostly met by placental uptake of maternal glucose and amino acids. The resulting 30 to 50% increase in maternal requirements for these nutrients is met partly by increased volun- tary intake and partly by an array of maternal metabolic adaptations. The latter include increased hepatic gluconeogenesis from endogenous substrates, decreased peripheral tissue glucose utilization, in- creased fatty acid mobilization from adipose tissue, and, possibly, increased amino acid mobilization from muscle. Within 4 d of parturition, mammary demands for glucose, amino acids, and fatty acids are several- fold those of the pregnant uterus before term. Even unusual postparturient increases in voluntary intake cannot satisfy this increased nutrient demand. There- fore, rates of hepatic gluconeogenesis and adipose fat mobilization are greatly accelerated. Concomitant changes in amino acid metabolism include increased hepatic protein synthesis and, possibly, decreased amino acid catabolism, and increased peripheral mobilization of amino acids. Insulin resistance in adipose tissue and muscle, developed during late pregnancy, continues postpartum; adipose lipolytic responsiveness and sensitivity to adrenergic agents are increased postpartum beyond their levels during late pregnancy. Before parturition, these homeorhetic adjustments may be coordinated with lactogenesis by increased secretion of estradiol and prolactin. Their amplification and reinforcement at and soon after parturition may be regulated mostly by somatotropin.

The genus Lactobacillus

Abstract: Lactobacilli are Gram-positive, non-spore-forming, rods or coccobacilli with a G+C content of DNA usually below 50 mol%. They are strictly fermentative, aero-tolerant or anaerobic, aciduric or acidophilic and have complex nutritional requirements (e.g. for carbohydrates, amino acids, peptides, fatty acid esters, salts, nucleic acid derivatives, and vitamins). They do not synthesize porphyrinoids and thus, are devoid of heme-dependent activities. Strains of some species can use porphorinoids from the environment and exhibit activities of catalase, nitrite reduction or even cytochromes (Meisel, 1991). Pseudo-catalase is formed in strains of Lb. mali. With glucose as a carbon source lactobacilli may be either homofermentative, producing more than 85% lactic acid, or hetero-fermentative, producing lactic acid, CO2, ethanol (and/or acetic acid) in equimolar amounts. In the presence of oxygen or other oxidants increased amounts of acetate may be produced at the expense of lactate or ethanol, whereby one additional mole of ATP is gained via the acetate kinase reaction. Thus, variations in the metabolic end products may occur. Various compounds (e.g. citrate, malate, tartrate, quinolate, nitrate, nitrite, etc.) may be metabolized, and used as energy source (e.g. via building up a proton motive force) or electron acceptors.

Chemical characterization of a family of brain lipids that induce sleep.

Abstract: A molecule isolated from the cerebrospinal fluid of sleep-deprived cats has been chemically characterized and identified as cis-9,10-octadecenoamide. Other fatty acid primary amides in addition to cis-9,10-octadecenoamide were identified as natural constituents of the cerebrospinal fluid of cat, rat, and human, indicating that these compounds compose a distinct family of brain lipids. Synthetic cis-9,10-octadecenoamide induced physiological sleep when injected into rats. Together, these results suggest that fatty acid primary amides may represent a previously unrecognized class of biological signaling molecules.

Metabolic coupling factors in pancreatic beta-cell signal transduction.

Abstract: This chapter focuses on the biochemical mechanisms that mediate glucose-stimulated insulin secretion (GSIS) from beta-cells of the islets of Langerhans and the potentiating role played by fatty acids. We summarize evidence supporting the idea that glucose metabolism is required for GSIS and that the GLUT-2 facilitated glucose transporter and the glucose phosphorylating enzyme glucokinase play important roles in measuring changes in extracellular glucose concentration. The idea that glucose metabolism is linked to insulin secretion through a sequence of events involving changes in ATP:ADP ratio, inhibition of ATP-sensitive K+ channels, and activation of voltage-gated Ca2+ channels is critically reviewed, and the relative importance of ATP generated from glycolytic versus mitochondrial metabolism is evaluated. We also present the growing concept that an important signal for insulin secretion may reside at the linkage between glucose and lipid metabolism, specifically the generation of the regulatory molecule malonyl CoA that promotes fatty acid esterification and inhibits oxidation. Finally, we show that in contrast to its short term potentiating effect on GSIS, long-term exposure of islets to high levels of fatty acids results in beta-cell dysfunction, suggesting that hyperlipidemia associated with obesity may play a causal role in the diminished GSIS characteristic of non insulin-dependent diabetes mellitus (NIDDM).

Differential incorporation of fatty acids into and peroxidative loss of fatty acids from phospholipids of human spermatozoa

Abstract: Intact human sperm incorporated radiolabelled fatty acids into membrane phospholipids when incubated in medium containing bovine serum albumin as a fatty acid carrier. The polyunsaturated fatty acids were preferentially incorporated into the plasmalogen fraction of phospholipid. Uptake was linear with time over 2 hr; at this time sufficient label was available to determine the loss of fatty acids under conditions of spontaneous lipid peroxidation. Loss of the various phospholipid types, the loss of the various fatty acids from these phospholipids, and the overall loss of fatty acids were all first order. The loss of saturated fatty acids was slow with first order rate constant k1 = 0.003 hr-1; for the polyunsaturated fatty acids, arachidonic and docosahexaenoic acids, k1 = 0.145 and 0.162 hr-1, respectively. The rate of loss of fatty acids from the various phospholipid types was dependent on the type, with loss from phosphatidylethanolamine being the most rapid. Among the phospholipid types, phosphatidylethanolamine was lost at the greatest rate. Analysis of fatty acid loss through oxidation products was determined for radiolabelled arachidonic acid. Under conditions of spontaneous lipid peroxidation at 37 degrees C under air in the absence of albumin, free arachidonic acid was found in the medium, along with minor amounts of hydroxylated derivative. All the hydroperoxy fatty acid remained in the cells. In the presence of albumin, all the hydroperoxy fatty acid was found in the supernatant bound to albumin; none could be detected in the cells. Albumin is known as a very potent inhibitor of lipid peroxidation in sperm; its action may be explained, based on these results, as binding the damaging hydroperoxy fatty acids. These results also indicate that a phospholipase A2 may act in peroxidative defense by excising a hydroperoxy acyl group from phospholipid and providing the hydroperoxy fatty acid product as substrate to glutathione peroxidase. This formulation targets hydroperoxy fatty acid as a key intermediate in peroxidative degradation.

1H nuclear magnetic resonance determination of the yield of the transesterification of rapeseed oil with methanol

Abstract: The formation of fatty acid methyl esters by transesterification with methanol can be monitored by1H nuclear magnetic resonance spectroscopy; this accurate determination is simpler than chromatographic methods

Albumin binding of insulins acylated with fatty acids: characterization of the ligand-protein interaction and correlation between binding affinity and timing of the insulin effect in vivo

Abstract: Albumin is a multifunctional transport protein that binds a wide variety of endogenous substances and drugs. Insulins with affinity for albumin were engineered by acylation of the epsilon-amino group of LysB29 with saturated fatty acids containing 10-16 carbon atoms. The association constants for binding of the fatty acid acylated insulins to human albumin are in the order of 10(4)-10(5) M-1. The binding apparently involves both non-polar and ionic interactions with the protein. The acylated insulins bind at the long-chain fatty acid binding sites, but the binding affinity is lower than that of the free fatty acids and depends to a relatively small degree on the number of carbon atoms in the fatty acid chain. Differences in affinity of the acylated insulins for albumin are reflected in the relative timing of the blood-glucose-lowering effect after subcutaneous injection into rabbits. The acylated insulins provide a breakthrough in the search for soluble, prolonged-action insulin preparations for basal delivery of the hormone to the diabetic patient. We conclude that the biochemical concept of albumin binding can be applied to protract the effect of insulin, and suggest that derivatization with albumin-binding ligands could be generally applicable to prolong the action profile of peptide drugs.

Maternal essential fatty acid patterns during normal pregnancy and their relationship to the neonatal essential fatty acid status

Abstract: Although essential fatty acids (EFA) and their longer chain, more unsaturated derivatives play a major role during pregnancy, hardly any information is available with respect to the course of the maternal EFA status during an uncomplicated pregnancy and its relationship to the neonatal EFA status. Therefore, a longitudinal study was started in which 110 pregnant women gave repeated blood samples from the 10th week of gestation until delivery. After birth a blood sample from the umbilical vein and a maternal venous blood sample were collected as well, and 6 months after delivery a final blood sample from the mother was taken. The absolute (mg/l) and relative (% total fatty acids) amounts of the fatty acids in plasma phospholipids were determined. The total amounts of fatty acids increased significantly during pregnancy. This pattern was similar for the individual fatty acids and fatty acid families. The relative amount of linoleic acid (18:2n-6) did not change during pregnancy, whereas the relative amount of arachidonic acid (20:4n-6) decreased. Despite maternal mobilization of docosahexaenoic acid (22:6n-3, DHA), suggested by a temporary increase in the DHA status until 18 weeks gestation, the DHA status steadily declined thereafter. This pattern was associated with a progressive increase in the DHA deficiency index in maternal blood throughout pregnancy and resulted in a sub-optimal neonatal DHA status. The overall maternal EFA status also declined steadily during pregnancy. Therefore, the question arises whether the mother, under the prevailing dietary conditions, is able to meet the high fetal requirement for EFA.

Directed tagging of the Arabidopsis FATTY ACID ELONGATION1 (FAE1) gene with the maize transposon activator.

Abstract: The FATTY ACID ELONGATION1 (FAE1) gene of Arabidopsis is required for the synthesis of very long chain fatty acids in the seed. The product of the FAE1 gene is presumed to be a condensing enzyme that extends the chain length of fatty acids from C18 to C20 and C22. We report here the cloning of FAE1 by directed transposon tagging with the maize element Activator (Ac). An unstable fae1 mutant was isolated in a line carrying Ac linked to the FAE1 locus on chromosome 4. Cosegregation and reversion analyses established that the new mutant was tagged by Ac. A DNA fragment flanking Ac was cloned by inverse polymerase chain reaction and used to isolate FAE1 genomic clones and a cDNA clone from a library made from immature siliques. The predicted amino acid sequence of the FAE1 protein shares homology with those of other condensing enzymes (chalcone synthase, stilbene synthases, and beta-ketoacyl-acyl carrier protein synthase III), supporting the notion that FAE1 is the structural gene for a synthase or condensing enzyme. FAE1 is expressed in developing seed, but not in leaves, as expected from the effect of the fae1 mutation on the fatty acid compositions of those tissues.

Neurodevelopmental quotient of healthy term infants at 4 months and feeding practice: The role of long-chain polyunsaturated fatty acids

Abstract: A direct influence of dietary long-chain polyunsaturated fatty acids (LC-PUFA) on the developmental quotient (DQ) of the healthy term infant remains unexplored. To test this hypothesis, we designed a prospective study of three types of diet. Twenty-nine infants received a LC-PUFA-supplemented formula, 31 received a standard infant formula, and 30 infants were breast-fed exclusively. Neurodevelopmental response was measured by the Brunet-Lezine psychomotor development test at 4 mo. The fatty acid status was also assessed among three diet subgroups (59 subjects) at 4 mo. Formula-fed infants who received LC-PUFA supplementation scored significantly higher (p < 0.01) on the Brunet-Lezine scale than infants who received the standard formula. Breast-fed infants also performed better than those fed the standard formula. Arachidonic acid and docosahexaenoic acid levels in circulating lipids and erythrocyte phospholipids were higher among breast-fed infants and among the group fed the arachidonic- and docosahexaenoic acid-supplemented formula. These findings are suggestive that formula supplementation with one or both of these fatty acids can benefit term infants in neurodevelopmental performance.

Skeletal Muscle Membrane Lipid Composition Is Related to Adiposity and Insulin Action

Abstract: The cellular basis of insulin resistance is still unknown; however, relationships have been demonstrated between insulin action in muscle and the fatty acid profile of the major membrane structural lipid (phospholipid). The present study aimed to further investigate the hypothesis that insulin action and adiposity are associated with changes in the structural lipid composition of the cell. In 52 adult male Pima Indians, insulin action (euglycemic clamp), percentage body fat (pFAT; underwater weighing), and muscle phospholipid fatty acid composition (percutaneous biopsy of vastus lateralis) were determined. Insulin action (high-dose clamp; MZ) correlated with composite measures of membrane unsaturation (% C20-22 polyunsaturated fatty acids [r= 0.463, P < 0.001], unsaturation index [r= -0.369, P < 0.01]), a number of individual fatty acids and with delta5 desaturase activity (r= 0.451, P < 0.001). pFAT (range 14-53%) correlated with a number of individual fatty acids and delta5 desaturase activity (r= -0.610, P < 0.0001). Indices of elongase activity (r= -0.467, P < 0.001), and delta9 desaturase activity (r= 0.332, P < 0.05) were also related to pFAT but not insulin action. The results demonstrate that delta5 desaturase activity is independently related to both insulin resistance and obesity. While determining the mechanisms underlying this relationship is important for future investigations, strategies aimed at restoring "normal" enzyme activities, and membrane unsaturation, may have therapeutic importance in the "syndromes of insulin resistance."

Alteration of seed fatty acid composition by an ethyl methanesulfonate-induced mutation in Arabidopsis thaliana affecting diacylglycerol acyltransferase activity.

Abstract: In characterizing the enzymes involved in the formation of very long-chain fatty acids (VLCFAs) in the Brassicaceae, we have generated a series of mutants of Arabidopsis thaliana that have reduced VLCFA content. Here we report the characterization of a seed lipid mutant, AS11, which, in comparison to wild type (WT), has reduced levels of 20:1 and 18:1 and accumulates 18:3 as the major fatty acid in triacylglycerols. Proportions of 18:2 remain similar to WT. Genetic analyses indicate that the fatty acid phenotype is caused by a semidominant mutation in a single nuclear gene, designated TAG1, located on chromosome 2. Biochemical analyses have shown that the AS11 phenotype is not due to a deficiency in the capacity to elongate 18:1 or to an increase in the relative delta 15 or delta 12 desaturase activities. Indeed, the ratio of desaturase/elongase activities measured in vitro is virtually identical in developing WT and AS11 seed homogenates. Rather, the fatty acid phenotype of AS11 is the result of reduced diacylglycerol acyltransferase activity throughout development, such that triacylglycerol biosynthesis is reduced. This leads to a reduction in 20:1 biosynthesis during seed development, leaving more 18:1 available for desaturation. Thus, we have demonstrated that changes to triacylglycerol biosynthesis can result in dramatic changes in fatty acid composition and, in particular, in the accumulation of VLCFAs in seed storage lipids.

Effect of propionate on fatty acid and cholesterol synthesis and on acetate metabolism in isolated rat hepatocytes

Abstract: In the present study the actual role of propionic acid in the control of fatty acid and cholesterol synthesis was investigated in isolated liver cells from fed rats maintained in the presence of near-physiological concentrations of glucose, glutamine and acetate. Using 3H2O for lipid labelling, propionate appears as an effective inhibitor of fatty acid synthesis and to a lesser extent of cholesterol synthesis, even at the lowest concentration used (0.6 mmol/l). Butyrate is a potent activator of both synthetic pathways, and the activating effect was not counteracted by propionate. Using 1-[14C]acetate, it was observed that propionate at a moderate concentration, or 1 mmol oleate/l, are both very effective inhibitors of 14C incorporation into fatty acid and cholesterol. This incorporation was drastically inhibited when propionate and oleate were present together in the incubation medium. The net utilization of acetate by rat hepatocytes was impaired by propionate, in contrast to oleate. 1-[14C]butyrate was utilized at a high rate for fatty acid synthesis, but to a lesser extent for cholesterol synthesis; both processes were unaffected by propionate. Intracellular citrate concentration was not markedly depressed by propionate, whereas it was strongly elevated by butyrate. In conclusion, propionate may represent an effective inhibitor of lipid synthesis when acetate is a major source of acetyl-CoA, a situation which is encountered with diets rich in readily-fermentable fibres. The present findings also suggest that propionate may be effective at concentrations close to values measured in vivo in the portal vein.

Long term exposure to fatty acids and ketones inhibits B-cell functions in human pancreatic islets of Langerhans.

Abstract: We previously demonstrated in the rat that long term exposure to fatty acids inhibits B-cell function in vivo and in vitro. To further assess the clinical significance of these findings, we tested in human islets the effects of fatty acids on glucose-induced insulin release and biosynthesis and on pyruvate dehydrogenase (PDH) activity. Human islets were obtained from the beta-Cell Transplant Unit (Brussels, Belgium). Exposure to 0.125 mmol/L palmitate or oleate for 48 h during tissue culture (RPMI-1640 and 5.5 mmol/L glucose) inhibited the postculture insulin response to 27 mmol/L glucose by 40% and 42% (P < 0.01 for difference). Inhibition was partly prevented by coculture with 1 mumol/L etomoxir, a carnitine-palmitoyl-transferase-I inhibitor (P < 0.05 for effect of etomoxir). Inhibitory effects on glucose-induced insulin secretion by previous palmitate were additive to the inhibitory effects exerted by previous high glucose (11 and 27 mmol/L). Palmitate-induced inhibition of insulin secretion was evident after exposure to 25 mumol/L added fatty acid. The insulin content of islets exposed to fatty acids was significantly reduced, and glucose-induced proinsulin biosynthesis was inhibited by 59% after palmitate addition and by 51% after oleate exposure (P < 0.01). These effects were partly prevented by etomoxir (P < 0.05). The activity of PDH in mitochondrial extracts of islets preexposed for 48 h to palmitate was decreased by 35% (P < 0.05) vs. that in control islets, whereas the activity of PDH kinase (which inactivates PDH) was significantly increased in the same preparations (P < 0.05). The effects of ketones were tested by 48-h exposure to beta-hydroxybutyrate (beta-D-OHB). Ten millimoles of D-beta-OHB per L inhibited the subsequently tested insulin response to 27 mmol/L glucose by 56% (P < 0.001). Half-maximal inhibitory effects of D-beta-OHB on insulin secretion and insulin content were seen at concentrations between 0.5-2.5 mmol/L. Inhibition by D-beta-OHB was partially reversed by etomoxir, whereas exposure to D-beta-OHB failed to affect PDH and PDH kinase activities. We conclude that fatty acids as well as ketone bodies diminish B-cell responsiveness to glucose in human islets by way of a glucose-fatty acid cycle. Increased plasma concentrations of fatty acids and ketones are likely to be important factors behind the negative influences on B-cell function exerted by a diabetic state in both type 1 and type 2 diabetes.

Influence of Diets Containing Eicosapentaenoic or Docosahexaenoic Acid on Growth and Metastasis of Breast Cancer Cells in Nude Mice

Abstract: Background: Diets rich in omega-6 polyunsaturated fatty acids (e.g., corn oil and other fats containing linoleic acid) stimulate the growth and metastasis of human breast cancer cells in athymic nude mice. On the other hand, diets containing fish oil, which is rich in omega-3 fatty acids (e.g., eicosapentaenoic and docosahexaenoic acids), exert suppressive effects. Purpose: Our objective was twofold: 1) to compare the effects of diets containing linoleic acid with those of diets containing eicosapentaenoic acid and docosahexaenoic acid on the growth and metastasis of MDA-MB-435 human breast cancer cells in the nude mouse model and 2) to determine how such effects relate to observed changes in the chemical content of tumor fatty acids and eicosanoid production. Methods: Groups of 30 female athymic nude mice were fed 20% (wt/wt) fat diets containing either linoleic acid (8%) alone, linoleic acid (8%) plus eicosapentaenoic acid (4%) or docosahexaenoic acid (4%), or linoleic acid (4%) plus eicosapentaenoic acid (8%) or docosahexaenoic acid (8%) for 7 days before one million MDA-MB-435 cells were injected into a thoracic mammary fat pad. Diets were continued for 12 more weeks. Primary tumors were measured weekly. The mice were then killed and necropsied, and tumor tissues preserved. Cell membrane phospholipid fatty acid analyses and eicosanoid assays were performed. All P values represent two-tailed tests of statistical significance. Results: The growth of the primary tumors was retarded in mice fed the diets supplemented with eicosapentaenoic or docosahexaenoic acid compared with the growth of primary tumors in mice fed the 8% linoleic acid diet. Growth inhibition was statistically significant (P<.05) and most effective in association with the diets containing 8% of either omega-3 fatty acid, where tumors were smaller than those in the group fed the diet containing 8% linoleic acid alone at all time points after the 2nd week. The occurrence and severity of lung metastases were reduced in the groups fed omega-3 fatty acid (P<.05). In groups of mice fed eicosapentaenoic or docosahexaenoic acid, the representation of these acids in tumor phospholipids increased, with a statistically significant reduction in the concentrations of arachidonic acid (all groups), tumor 12- and 15-hydroxyeicosatetraenoic acid, and prostaglandin E. Levels of 5-hydroxyeicosatetraenoic acid and leukotriene B4 were unaffected by the omega-3 fatty acids. Conclusion: The inhibitory effects of dietary fish oil on human breast cancer cell growth and metastasis in this model system are ascribable to its high eicosapentaenoic acid and docosahexaenoic acid content; the mechanism very likely involves suppression of tumor eicosanoid biosynthesis. Implication: Future dietary intervention trials designed to reduce the risk of recurrence in the postsurgical breast cancer patient should include the evaluation of eicosapentaenoic acid and docosahexaenoic acid supplementation

Fatty acid flip-flop in phospholipid bilayers is extremely fast

Abstract: The rate of movement of fatty acids (FA) across phospholipid bilayers is an important consideration for their mechanism of transport across cell membranes but has not yet been measured. When FA move undirectionally across phospholipid bilayers, the rapid movement of un-ionized FA compared to ionized FA results in transport of protons. We have previously used this property to show that FA move spontaneously ("flip-flop") across the bilayer of small unilamellar vesicles within approximately 1 s (Kamp & Hamilton, 1992, 1993). This work extends the time resolution of this assay into the millisecond time range by use of stopped flow fluorometry. In small unilamellar vesicles (diameter, approximately 25 nm) at neutral pH, flip-flop of all fatty acids studied (lauric, myristic, palmitic, oleic, and stearic) was > or = 80% complete within 5-10 ms. In large unilamellar vesicles (diameter, approximately 100 nm), the same fatty acids exhibited fast flip-flop but with a measureable rate (t 1/2 = 23 +/- 12 ms). The calculated pseudounimolecular rate constant of the un-ionized FA (kFAH) approximately 15 s-1. There was no dependence of the flip-flop rate on the fatty acid chain length or structure. We also monitored the rate of desorption and transbilayer movement of (anthroyloxy)stearic acid in small unilamellar vesicles. Whereas previous studies suggested slow flip-flop of this FA analogue, the present studies suggest that (anthroyloxy)stearic acid flip-flops rapidly and that earlier studies did not truly measure the transbilayer movement step. These findings further support the view that proteins are not required for translocation of FA across cell membranes.

Inhibition of calcium-independent phospholipase A2 prevents arachidonic acid incorporation and phospholipid remodeling in P388D1 macrophages

Abstract: Cellular levels of free arachidonic acid (AA) are controlled by a deacylation/reacylation cycle whereby the fatty acid is liberated by phospholipases and reincorporated by acyltransferases. We have found that the esterification of AA into membrane phospholipids is a Ca(2+)-independent process and that it is blocked up to 60-70% by a bromoenollactone (BEL) that is a selective inhibitor of a newly discovered Ca(2+)-independent phospholipase A2 (PLA2) in macrophages. The observed inhibition correlates with a decreased steady-state level of lysophospholipids as well as with the inhibition of the Ca(2+)-independent PLA2 activity in these cells. This inhibition is specific for the Ca(2+)-independent PLA2 in that neither group IV PLA2, group II PLA2, arachidonoyl-CoA synthetase, lysophospholipid:arachidonoyl-CoA acyltransferase, nor CoA-independent transacylase is affected by treatment with BEL. Moreover, two BEL analogs that are not inhibitors of the Ca(2+)-independent PLA2--namely a bromomethyl ketone and methyl-BEL--do not inhibit AA incorporation into phospholipids. Esterification of palmitic acid is only slightly affected by BEL, indicating that de novo synthetic pathways are not inhibited by BEL. Collectively, the data suggest that the Ca(2+)-independent PLA2 in P388D1 macrophages plays a major role in regulating the incorporation of AA into membrane phospholipids by providing the lysophospholipid acceptor employed in the acylation reaction.