An improved molecular test system for the screening of human PPAR transactivation by conjugated linoleic acid isomers and their precursor fatty acids

To investigate the potentials of cis‐9,trans‐11 and trans‐10,cis‐12 conjugated linoleic acid (9‐CLA and 10‐CLA, respectively) isomers and their precursors trans‐11 vaccenic (VA), linoleic (LA) and oleic (OA) acids for interactions with genes, we determined their binding affinities to the ligand binding domains of the human peroxisome proliferator‐activated receptor (PPAR) α, β and γ subtypes by a fluorescent binding assay. Then, we elaborated a transactivation‐chemiluminescent assay using HepG2 cells transfected with full‐length cDNAs encoding human PPARs and retinoic acid (RA) receptors (RXRs) and with the ideal PPAR response element (iPPRE)‐luciferase reporter. Binding affinity of 9‐CLA was two times higher (but weaker than of precursor VA and OA) than that of 10‐CLA for PPARβ, the opposite was observed with PPARβ; binding affinities of CLAs and precursor fatty acids with PPARγ were comparable. Unlike in binding studies, transactivation potentials of 9‐ and 10‐CLAs were comparable in the human system. Comparing the transactivation potentials of CLAs and their precursors in toto, those obtained for PPARα (two‐ to fourfold) in both human and murine systems (the latter was used in this study as reference) were comparable, but for PPARβ and γ, fold inductions obtained in the human system were unique. Inclusion of the coactivator RXR and its natural ligand RA in the system was found unnecessary and would lead to false positive values. Taken together, the human transactivation‐based test system – which was found to be superior to the murine system – comprises only iPPRE and human PPARs for rapid screening of potential CLA and other PPAR agonists.     

Marine phospholipids as dietary carriers of long‐chain polyunsaturated fatty acids

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are polyunsaturated fatty acids (PUFA) of the n‐3 series. Fish oil is a classical source of n‐3 PUFA, where they occur in the form of triacylglycerols (TAG). However, new sources of n‐3 PUFA esterified in phospholipids (PL) are emerging. We prepared liposomes from a natural marine lipid extract and examined their behaviour under conditions mimicking that of the gastrointestinal tract. This physicochemical approach proved that liposomes could be used as an effective oral PUFA delivery system. In vivo studies in rats were performed to examine the metabolic fate of EPA (20:5 n‐3) and DHA (22:6 n‐3) delivered either in PL from liposomes or in TAG from oil. Liposome ingestion increased PUFA bioavailability in lymph compared with fish oil. The proportion of n‐3 PUFA esterified in the sn‐2 position of chylomicron TAG depended on the dietary lipid source. Complex time‐course profiles were observed for plasma lipids with liposome supplementation over a 2‐week period, suggesting time‐dependent regulations. Taken together, the type of PUFA, EPA or DHA, as well as its intramolecular distribution in chylomicron TAG seemed to influence the metabolic fate of the fatty acids and their physiological activities.     

Issues surrounding fish as a source of omega‐3 long‐chain polyunsaturated fatty acids

Fish are a virtually unique, rich source of omega‐3 long‐chain polyunsaturated fatty acids (ω3 LC‐PUFA) in the human diet. This article describes the origins of ω3 LC‐PUFA in fish and the increasingly important role of aquaculture in the provision of fish for human consumption. It also highlights the major issues currently facing aquaculture, focusing on sustainability, driven by the urgent need to replace traditional fish oil and meal in formulated diets, and safety, driven by the requirement to reduce feed‐derived contaminants.     

Microalgae as an alternative source of omega‐3 long chain polyunsaturated fatty acids

The health benefits of omega‐3 long chain polyunsaturated fatty acids (omega‐3 LC‐PUFA) are recognized worldwide. The traditional source of omega‐3 LC‐PUFA is fish. However, global consumer needs cannot be supplied by the current global fish harvest. Therefore, new sources of omega‐3 LC‐PUFA have to be found. Microalgae are producers of omega‐3 LC‐PUFA and a potential alternative for seafood. Other sources of omega‐3 LC‐PUFA include krill oil, calamari oil and genetically engineered land plant crops.     

Short‐chain fatty acids as marker for the degradation of frying fats and oils

The determination of fatty acid composition by gas chromatography as a routine task is established in most laboratories dealing with oils and fats. The scope of this method can be enlarged for a preliminary quality control of used frying fats and oils, which is commonly characterized by the determination of polar compounds and polymerized triacylglycerols. However, for screening purposes the determination of the short‐chain fatty acids C7:0 and C8:0 can give an early indication about the quality of used frying fats and oils.     

Synthesis and Reactions of Branched‐chain Anhydrouloses with Push Pull Functionality

The α‐oxoketene dithioacetal 1 was demethylthiolated with sodium borohydride to give the branched chain anhydroulose 2 which yielded with amines the corresponding aminomethylene enuloses 3 , 4 and 5 . The heterocyclic anellated pyranose derivatives 6 , 7 and 8 were prepared by reaction of 2 with hydrazine hydrate, methylhydrazine and hydroxylamine, respectively. By treatment of methylthiomethylene enulose 18 with guanidine, acetamidine and benzamidine the pyrimidoanellated pyranose derivatives 12—14 have been obtained.     

The production of n‐3 long‐chain polyunsaturated fatty acids in transgenic plants

Long‐chain polyunsaturated fatty acids (LC‐PUFA) now have a proven role in human health and nutrition, including the n‐3 forms normally found in fish oils. Unfortunately, global fish stocks are now more than ever subject to over‐fishing and environmental pollution, indicating the need for an alternative source of fish oils. Recent efforts have focussed on the production of LC‐PUFA in transgenic plants to provide a sustainable and clean source of fish oils. The current progress in this area is considered, as well as the bottlenecks that remain to be overcome.     

Synthesis of regioisomerically pure triacylglycerols containing n‐3 very long‐chain polyunsaturated fatty acids

There is growing scientific evidence that consumption of n‐3 very long‐chain polyunsaturated fatty acids (n‐3 VLC‐PUFA) helps in brain and eye development, and protects against a range of common degenerative diseases. This has provided the impetus to the scientists to develop new and renewable sources for these important fatty acids so that the food industry is able to produce and market products fortified with n‐3 VLC‐PUFA. The bioactive efficacy and stability of food products containing n‐3 VLC‐PUFA may be determined not only by the amount of n‐3 VLC‐PUFA present but also by the positional distribution of these acids within the triacylglycerol (TAG) molecules (regiopurity). Studies of the effects of positional distribution on the functionality of n‐3 VLC‐PUFA containing oils have been hampered by a general lack of pure TAG regioisomers for experimentation. This paper reviews methods that have been used for the synthesis of TAG regioisomers containing n‐3 VLC‐PUFA, with special reference to those in which one n‐3 VLC‐PUFA occurs in combination with two long‐chain saturated acids.     

Biomarkers of long‐chain PUFA omega‐3 fatty acids and the human nutritional status

The association of dietary fats with disease risk or outcome can be determined from epidemiological studies and/or from food frequency questionnaires; a better assessment of the dietary intake of the long‐chain polyunsaturated fatty acids omega‐3 is obtained by the fatty acid composition of the platelets or of erythrocyte membranes yet these procedures are lengthy. Other investigators have used adipose tissue obtained by percutaneous biopsy, but it must be pointed out that this procedure is not only invasive but time‐consuming as well. Also, it has to be noted that the turnover time for fatty acids has been estimated to be 1–3 years.     

Thermal degradation of long‐chain polyunsaturated fatty acids during deodorization of fish oil

Long‐chain polyunsaturated fatty acids (LC‐PUFA) of the n‐3 series, particularly eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid, have specific activities especially in the functionality of the central nervous system. Due to the occurrence of numerous methylene‐interrupted ethylenic double bonds, these fatty acids are very sensitive to air (oxygen) and temperature. Non‐volatile degradation products, which include polymers, cyclic fatty acid monomers (CFAM) and geometrical isomers of EPA and DHA, were evaluated in fish oil samples obtained by deodorization under vacuum of semi‐refined fish oil at 180, 220 and 250 °C. Polymers are the major degradation products generated at high deodorization temperatures, with 19.5% oligomers being formed in oil deodorized at 250 °C. A significant amount of CFAM was produced during deodorization at temperatures above or equal to 220 °C. In fact, 23.9 and 66.3 mg/g of C20 and C22 CFAM were found in samples deodorized at 220 and 250 °C, respectively. Only minor changes were observed in the EPA and DHA trans isomer content and composition after deodorization at 180 °C. At this temperature, the formation of polar compounds and CFAM was also low. However, the oil deodorized at 220 and 250 °C contained 4.2% and 7.6% geometrical isomers, respectively. Even after a deodorization at 250 °C, the majority of geometrical isomers were mono‐ and di‐trans. These results indicate that deodorization of fish oils should be conducted at a maximal temperature of 180 °C. This temperature seems to be lower than the activation energy required for polymerization (intra and inter) and geometrical isomerization.     

Efficient stabilization of bulk fish oil rich in long‐chain polyunsaturated fatty acids

The aim of the present study was to systematically investigate the possibilities of stabilizing a bulk oil rich in long‐chain polyunsaturated fatty acids under ambient conditions. Combinations of different antioxidants (α‐, γ‐ and/or δ‐tocopherol, rosmarinic acid and rosemary extract rich in carnosic acid) as well as lecithin and citric acid were systematically investigated. Efficient stabilization was achieved by choosing a combination of tocopherols rich in γ‐ or δ‐tocopherol and low in α‐tocopherol, by including tocopherol‐sparing synergists like ascorbyl palmitate and carnosic acid from rosemary extract and metal‐chelating agents. For carnosic acid, a concentration of 400 mg/kg oil provides sufficient protection; the concentration of the metal chelator should be adapted to the concentration of metal ions present in the oil. As an alternative ingredient with metal‐chelating and tocopherol‐sparing activity, lecithin may be included in the formulation, but its poor solubility in bulk oils limits its use.     

Synthesis of alkyl‐branched fatty acids

Alkyl‐branched fatty compounds are of interest for industrial products in the cosmetics and lubricant areas. In this review, clay‐ and zeolite‐catalyzed isomerizations of unsaturated fatty compounds, especially of oleic acid, are discussed. While clay‐catalyzed reactions give most complex mixtures of dimeric fatty acids and of monomeric so‐called “isostearic acid”, the zeolite‐catalyzed process yields preferentially an isomeric mixture of isostearic acids having the methyl branch on the 8–14 positions of the alkyl chain. Synthetically useful additions of alkyl radicals can only be performed on ω‐unsaturated fatty compounds, whereas perfluoroalkyl iodides were added to fatty compounds with terminal as well as internal double bonds using electron transfer‐initiated radical addition reactions. Electrophilic additions of alkyl carbenium ions generated by decomposition of alkyl chloroformates by ethylaluminum sesquichloride give well‐defined alkyl‐branched oleochemicals with good yields.     

Biotechnological synthesis of long‐chain dicarboxylic acids as building blocks for polymers

An important field in sustainable industrial chemistry is the development of new applications for fats and oils. One of the promising applications is the use of fatty acid derivatives, e.g. dicarboxylic acid (DCA), as polymer building blocks. In contrast to conventional plastics, bioplastics are polymers derived from renewable biomass sources. In addition to their contribution to the conservation of fossil resources and reduction in CO₂ emissions by waste incineration, many bioplastics are biodegradable. The majority of industrial DCA production for polyamide (PA) and polyester (PE) synthesis is still done via chemical synthesis. While short‐chain DCA can be synthesized in high yields, costs of long‐chain DCA production rise significantly due to the generation of various by‐products and are connected mostly to a costly purification. Thus biotechnology provides novel biochemical approaches for long‐chain DCA synthesis that can provide an eco‐efficient process alternative. In the present article, strategies for the development of high‐level production strains for long‐chain DCA are illustrated. Basic strategies for strain development, in order to achieve an effective enrichment of DCA, require the knowledge of the respective biochemical pathways. These are discussed in detail. Furthermore an overview of fermentation strategies and characteristics of corresponding polymers is given.