Disbalance of the natural ratio of cations in water as a factor affecting synthesis of lipids and fatty acids in fish eggs

The effects on the lipid status of developing embryos of a disturbed natural ratio of cations in water as a result of the pollution of water bodies by waste with a high potassium content (130–140 mg/l) were studied in the laboratory. The results obtained confirm the indication of reduced lipid synthesis and altered formation of phospholipids in embryos developing in a medium with a disturbed natural ratio of cations. In addition, the lysophospholipid fraction increased in these embryos, which indicates activation of phospholipid hydrolysis. It was also found that changes in the salt regime lead to a decreased content of cholesterol, the main membrane thickener. It was proposed that the changes discovered lead to disturbed stability and permeability of the membranes of fish eggs, with the subsequent death of embryos.     

Bone lipids and fatty acids of Peru fish

The neurocranium of the vieja, Pimelometopon darwini, and the cojinoba, Seriolella violacea, contained 29.5 and 26% lipid (as percent dry weight), mostly as triacylglycerol. The anchoveta, Engraulis ringens; sardina, Sardinops sagax sagax; doncella, Halichoeres dispilis; and mackerel, Scomber japonicus, contained less lipid in the neurocranium (3.3–18.4%). Polyunsaturated fatty acids, dominated by 20:5 and 22:6, were highest for S. violacea (10.6–56.1%) and P. darwini (12.2–28.9%). Lower levels of polyunsaturated fatty acids were found in E. ringens. The major monosaturated fatty acids in all Peruvian fish included 16:1n7, 18:1n9 + 11, and 18:n7, whereas the major saturated fatty acids were 14:0 and 16:0 with lesser amounts of 18:0.     

Volatile fatty acids as indicators of process imbalance in anaerobic digestors

In continuously stirred tank reactor experiments, with manure as substrate at thermophilic temperatures, the use of volatile fatty acids (VFA) as process indicators was investigated. Changes in VFA level were shown to be a good parameter for indicating process instability. The VFA were evaluated according to their relative changes caused by changes in hydraulic loading, organic loading or temperature. Butyrate and isobutyrate together were found to be particularly good indicators. Butyrate and isobutyrate concentrations increased significantly 1 or 2 days after the imposed perturbation, which makes these acids suitable for process monitoring and important for process control of the anaerobic biological system. In addition it was shown in a batch experiment that VFA at concentrations up to 50 mM did not reduce the overall methane production rate. This showed that VFA accumulation in anaerobic reactors was the result of process imbalance, not the cause of inhibition, thus justifying the use of VFA as process indicators.     

Multiscale structures of lipids in foods as parameters affecting fatty acid bioavailability and lipid metabolism

On a nutritional standpoint, lipids are now being studied beyond their energy content and fatty acid (FA) profiles. Dietary FA are building blocks of a huge diversity of more complex molecules such as triacylglycerols (TAG) and phospholipids (PL), themselves organised in supramolecular structures presenting different thermal behaviours. They are generally embedded in complex food matrixes. Recent reports have revealed that molecular and supramolecular structures of lipids and their liquid or solid state at the body temperature influence both the digestibility and metabolism of dietary FA. The aim of the present review is to highlight recent knowledge on the impact on FA digestion, absorption and metabolism of: (i) the intramolecular structure of TAG; (ii) the nature of the lipid molecules carrying FA; (iii) the supramolecular organization and physical state of lipids in native and formulated food products and (iv) the food matrix. Further work should be accomplished now to obtain a more reliable body of evidence and integrate these data in future dietary recommendations. Additionally, innovative lipid formulations in which the health beneficial effects of either native or recomposed structures of lipids will be taken into account can be foreseen.     

Isolation and characterization of unsaturated fatty acids as natural ligands for the retinoid-X receptor

The retinoid-X receptor (RXR) is a ligand activated nuclear receptor that is the heterodimer partner for many class II nuclear receptors. Previously identified natural ligands for this receptor include 9-cis retinoic acid (9cRA), docosahexaenoic acid, and phytanic acid. Our studies were performed to determine if there are any unidentified, physiologically important RXR ligands. Agonists for RXR were purified from rat heart and testes lipid extracts with the use of a cell-based reporter assay to monitor RXR activation. Purified active fractions contained a variety of unsaturated fatty acids and components were quantified by gas-liquid chromatography of derivatized samples. The corresponding fatty acid standards elicited a similar response in the reporter cell assay. Competition binding analysis revealed that the active fatty acids compete with [3H]9cRA for binding to RXR. Non-esterified fatty acids were analyzed from lipid extracts of isolated heart and testes nuclei and endogenous concentrations were found to be within the range of their determined binding affinities. Our studies reveal tissue dependent profiles of RXR agonists and support the idea of unsaturated fatty acids as physiological ligands of RXR.     

Composition of lipids, fatty acids and sterols in Okinawan corals

A survey of lipid composition was made for 15 cnidarians from Okinawa, Japan. Eleven zooxanthellate scleractinian corals, an azooxanthellate scleractinian coral Tubastrea sp., a soft coral Lobophytum crassum, a hydroid coral Millepora murrayi and a sea anemone Boloceroides sp. were examined to elucidate the total lipid content, fatty acid composition for each lipid class and sterol composition. All specimens contained monoalkyldiacylglycerol which migrated between the triacylglycerols and esters on thin layer chromatography (TLC). Analysis by high performance thin layer chromatography (HPTLC) and Gas chromatography-mass spectrometry (GC-MS) revealed that these cnidarians were rich in wax ester and triacylglycerol, and that palmitic acid (16:0) was the most abundant fatty acid component of these lipid classes, followed by stearic (18:0) and oleic (18:1, n-9) acid in order of concentration. Of 11 sterols separated, four sterols were identified. It is suggested that sterol composition may be more useful for the biochemical classification of these cnidarians than fatty acid composition.     

Biochemical characterization of polyunsaturated fatty acid synthesis in Schizochytrium: Release of the products as free fatty acids

In marine bacteria and some thraustochytrids (marine stramenopiles) long-chain polyunsaturated fatty acids (LC-PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are produced de novo by PUFA synthases. These large, multi-domain enzymes carry out the multitude of individual reactions required for conversion of malonyl-CoA to the final LC-PUFA products. Here we report on the release of fatty acids from the PUFA synthase found in Schizochytrium, a thraustochytrid that has been developed as a commercial source for DHA-enriched biomass and oil. Data from in vitro activity assays indicate that the PUFAs are released from the enzyme as free fatty acids (FFAs). Addition of ATP and Mg²⁺ to in vitro assays facilitates appearance of radiolabel from ¹⁴C-malonyl-CoA in a triacylglycerol fraction, suggesting the involvement of acyl-CoA synthetases (ACS). Furthermore, addition of triascin C, an inhibitor of ACSs, to the assays blocks this conversion. When the Schizochytrium PUFA synthase is expressed in Escherichia coli, the products of the enzyme accumulate as FFAs, suggesting that the thioesterase activity required for fatty acid release is an integral part of the PUFA synthase.     

The role of triacylglycerol as a reservoir of polyunsaturated fatty acids for the rapid production of chloroplastic lipids in certain microalgae

Many microalgae are known to accumulate triacylglycerols (TAGs), especially under nitrate starvation. Generally, these TAGs are predominantly constructed of saturated and monounsaturated fatty acids. In contrast, the TAGs of the red microalga Porphyridium cruentum are rich in arachidonic acid (AA, 20:4 omega6) and eicosapentaenoic acid (EPA, 20:5 omega3). A mutant of this alga, impaired of growth at suboptimal temperatures, was shown to have reduced levels of EPA and of the eukaryotic molecular species of monogalactosyldiacylglycerol (MGDG) and an elevated level of TAG. Labelling experiments have shown that labelling of wild-type TAGs decreased, whereas that of the mutant remained high. Contemporarily, eukaryotic MGDG of the mutant was less labelled. Similarly, TAGs of the green alga Tl2, which can grow at a low temperature, are extremely rich in AA. We have labelled exponentially growing cultures of T12 kept at 25 degrees C with radioactive AA and cultivated the cultures for a further 12 h at 25 degrees C, 12 degrees C or 4 degrees C. At low temperatures, labelled AA was transferred from TAGs to polar lipids. These findings may indicate that polyunsaturated fatty acids that can be incorporated into the membranes, enabling the organism to quickly respond to low-temperature-induced stress.     

Role of lipids and fatty acids in macrosomic offspring of diabetic pregnancy

Diabetic pregnancy frequently results in macrosomia or fetal obesity. It seems that the anomalies in carbohydrate and lipid metabolism in macrosomic infants of diabetic mothers are due to maternal hyperglycemia, which leads to fetal hyperinsulinemia. We have developed a rat model of macrosomic offspring and assessed the onset of obesity in these animals. The macrosomic offspring born to diabetic mothers are prone to the development of glucose intolerance and obesity as a function of age. It seems that in utero programing during diabetic pregnancy creates a “metabolic memory” which is responsible for the development of obesity in macrosomic offspring. We have demonstrated that the metabolism of lipids, and altered anti-oxidant status and immune system are implicated in the etiopathology of obesity in these animals. We have reported beneficial effects of n-3 polyunsaturated fatty acids (PUFAs) in obese animals, born to diabetic dams.     

Carotenoid-to-chlorophyll ratio as a proxy for assay of total fatty acids and arachidonic acid content in the green microalga Parietochloris incisa

The relationships between pigment (carotenoid and chlorophyll) content with accumulation of total fatty acids (TFA) and arachidonic acid (AA) were studied in the green microalga Parietochloris incisa (Trebouxiophyceae, Chlorophyta) grown under different PFDs (35, 200, and 400 μmol photons m⁻² s⁻¹) and nitrogen availabilities. The growth of P. incisa under higher light and nitrogen deficiency was accompanied by accumulation of FA, an increase in carotenoid and a decline in chlorophyll content. It was found that the carotenoid-to-chlorophyll ratio (but not the individual pigment content) correlates closely with the volumetric content of both TFA and AA. Analysis of scattering-compensated absorption spectra of P. incisa suspensions revealed their tight relationship in the blue-green range of the spectrum with the carotenoid-to-chlorophyll ratio, TFA, and AA content. These findings allowed the development of algorithms for the non-destructive assay of TFA and AA in cell suspensions in the ranges of 0.09–3.04 and 0.04–1.7 μg mL⁻¹, with accuracy of 0.06 and 0.01 μg mL⁻¹, respectively, via analytically measured carotenoid-to-chlorophyll ratio and using the ratio of absorption coefficients at 510 and 678 nm, with accuracy of 0.07 and 0.02 μg mL⁻¹, respectively. The feasibility of obtaining essential spectral information concerning the physiological condition of P. incisa using a standard spectrophotometer is also shown.     

Unusual fatty acids in the lipids from organs and cell cultures ofPetroselinum crispum

The lipids of seeds, leaves, and roots of parsley,Petroselinum crispum, and of heterotrophic as well as photomixotrophic cell cultures of this plant were characterized with the aim of finding a system for studying the biosynthesis of unusual fatty acids. It was found that (Z)-6-octadecenoic acid, petroselinic acid, which is the typical constituent fatty acid of triacylglycerols in seeds, occurs only in small proportions, if at all, in leaves, roots, and cell cultures of parsley. In all lipid classes studied petroselinic acid is accompanied by its (Z)-9- and (Z)-11-isomers, oleic and vaccenic acid, respectively. The phosphatidylcholines, phosphatidylethanolamines, and triacylglycerols of both heterotrophic and photomixotrophic callus cultures contain no petroselinic acid but rather oleic and vaccenic acids in equal ratios. Thus, cell cultures of parsley appear to be suitable for studying the biosynthesis of vaccenic acid. The constituent octadecadienoic acids in the lipids of various tissues and cell cultures of parsley consist almost exclusively of the (Z),(Z)-9,12-isomer, linoleic acid, which is derived from oleic acid. (Z),(Z)-6,9- and (Z),(Z)-11,14-Octadecadienoic acids, which could be expected as products of desaturation of petroselinic and vaccenic acids, were not found in any of the lipids of organs and cell cultures investigated.Abbreviations TLC thin-layer chromatography - GLC gas-liquid chromatography     

Manipulation of dietary lipids, fatty acids and vitamins in zooplankton cultures

1. A wide range of species that are cultivated in commercial mariculture are planktonic during at least part of their life cycle; for example, the larval stages of shellfish (shrimp and molluscs) and the live feeds (rotifers, brine shrimp, copepods) used in the larviculture of marine fish and shellfish. Over the last decades various techniques have been developed to deliver nutrients to these zooplanktonic organisms either through artificial diets or by manipulating the composition of the live prey fed to the carnivorous stages. This paper reviews the methodology that has allowed aquaculturists to gain knowledge of nutritional requirements and may offer interesting opportunities for ecologists to verify the importance of key nutrients in the natural food chain of marine as well as freshwater ecosystems.
2. Live micro-algae can be replaced partially or completely in the diet of filter-feeders such as rotifers, Artemia , shrimp larvae and bivalves, by various types of preserved algae, micro-encapsulated diets and yeast-based diets, whereas lipid emulsions and liposomes may be utilized to supplement specific lipid-and water-soluble nutrients, respectively. Microbound and micro-encapsulated diets have been designed to supplement live feed in the culture of micro-predators such as fish and shrimp larvae.
3. Live prey organisms, in particular rotifers and Artemia , can be 'bio-encapsulated' with a variety of enrichment diets to manipulate their content in certain nutrients, including ω3 highly unsaturated fatty acids (FA) and the vitamins C, A and E. Nevertheless, the enrichment techniques are not applicable for all nutrients and prey organisms. Phospholipid composition is difficult to manipulate through the diet of live feed and the enrichment of the essential FA docosahexaenoic acid (DHA) is hampered in most Artemia species due to the catabolism of this FA following enrichment.     

Combination and positional distribution of fatty acids in lipids from blue-green algae

The main glycerolipids (monogalactosyl-, digalactosyl-, sulphoquinovosyl diacylglycerol, phosphatidylglycerol) from five blue-green algae (Microcystis, Anabaena, Nostoc, Oscillatoria, Tolypothrix) were analyzed for fatty acid composition, occurrence of diglyceride species and positional distribution of fatty acids between thesn-1- andsn-2-position of glycerol. In contrast to eucaryotic plants biosynthetically closely related lipids (monogalactosyl-, digalactosyl-, trigalactosyl diacylglycerol) show nearly identical diglyceride moieties, whereas sulphoquinovosyl diacylglycerol and phosphatidylglycerol are separated from galactolipids by composition as well as occurrence of fatty acids. On the other hand the positional distribution of fatty acids in all lipids is controlled exclusively by chain length and not by degree of unsaturation with C₁₈-fatty acids at thesn-1- and C₁₆-fatty acids at thesn-2-position. These results show that in procaryotic organisms the diversity in diglyceride portions of lipids is reduced as compared to eucaryotic organisms, but nevertheless does exist.Abbreviations MGD, DGD, TGD, SQD monogalactosyl-, digalactosyl-, trigalactosyl-, sulphoquinovosyl diacylglycerol - PG phosphatidyl glycerol