Varietal difference in lipid content and fatty acid composition of highbush blueberries

Lipids from five cultivars of highbush blueberries (Vaccinium corymbosum L.) were extracted and fractionated into neutral lipids (60–66%), glycolipids (20–22%) and phospholipids (14–18%). The major fatty acids in all fractions were palmitic (16∶0), oleic (18∶1), linoleic (18∶2), and linolenic (18∶3) acids. All lipid classes had a large concentration of C₁₈ polyunsaturated acids (84–92%), indicating that blueberries are a rich source of linoleic and linolenic acids. Changes in the fatty acid composition of neutral lipids and phospholipids were not significantly different among the five cultivars, but significant differences were noted in the ratios of linoleic and linolenic acids in the glycolipids fraction.     

The Treatment of Dyslipidemia—What's Left in the Pipeline?

Dyslipidemia is a pathological alteration of serum lipid levels. The most common forms are either elevations of triglycerides or low density lipoprotein cholesterol associated with a reduction of high density lipoprotein cholesterol. Most frequently both forms of lipid disorders are combined. Elevations of free fatty acid blood levels are commonly not subsumed under the term dyslipidemia. However, free fatty acids should also be considered, as they are frequently associated with dyslipidemia and represent a risk factor for cardiovascular diseases. Dyslipidemias are among the major etiologic factors for arterial occlusive diseases. Resulting in fatal implications such as stroke and coronary heart disease, dyslipidemias contribute to the most prevalent causes of death. Lowering of low density lipoprotein and raising of high density lipoprotein cholesterol levels have been shown in both epidemiologic and intervention studies to decrease mortality. Established treatments of dyslipidemias are statins and fibrates. However, recent research has established some new potential therapeutic targets which are currently investigated in clinical trials. New therapeutic approaches include subtype selective, dual, and pan-agonists of the peroxisome proliferator activated receptor, inhibitors of the cholesterol ester transfer protein, Acyl-CoA-cholesterol-acyltransferase, squalene synthase, microsomal triglycerid-transfer-protein, and cholesterol absorption. Clinical implications of new drugs under investigation are discussed in this review.     

Separation and quantitation of hydroxy and epoxy fatty acid by high-performance liquid chromatography with an evaporative light-scattering detector

A new high-performance liquid chromatography technique with an evaporative light-scattering detector (ELSD) has been developed for the separation and quantitative analysis of hydroxy and epoxy fatty acids. This method employs a gradual binary gradient (hexane/isopropanol) and ELSD detection. The minimum limit of detection is about 1 μg and ratio of mass to signal is essentially linear in the range of 10 to 200 μg. This high-performance liquid chromatography (HPLC) technique is able to separate various positional isomers of mono-hydroxy and dihydroxy fatty acids and can also discriminate between monohydroxy, epoxy, epoxyhydroxy, dihydroxy and trihydroxy fatty acids.     

Geometrical trans lipid isomers: a new target for lipidomics

Evidence that lipids play different roles in the biological environment, particularly in dealing with metabolic regulation and cell signaling, has led to a growing interest in these molecules, and nowadays the research field of lipid structures and functions is called lipidomics. The term describes diverse research areas, from mapping the entire spectrum of lipids in organisms to describing the function and metabolism of individual lipids. Recent investigations on geometrical trans isomers of fatty acid derivatives, which have the double bonds in the same position as the natural compounds but with the trans instead of the naturally occurring cis geometry, highlighted these compounds as a new target for lipidomics. In addition to the identification of their structures and functions, research in a multidisciplinary context aims at understanding the biochemical significance of cis and trans lipid geometry, and a chemical biology approach can be envisaged to explore the role of the geometry change as either an alteration or a signal that can perturb a biological system and induce a cellular response.     

θ3 fatty acids in freshwater fish from south brazil

Lipid and fatty acid levels in the edible flesh of 17 freshwater fish from Brazil’s southern region were determined. Analyses of fatty acid methyl esters were performed by gas chromatography. Palmitic acid (C_16:0) was the predominant saturated fatty acid, accounting for 50–70% of total saturated acids. Oleic acid (C_18:1θ9) was the most abundant monounsaturated fatty acid. Linoleic acid (C_18:2θ6), linolenic acid (C_18:3θ3), and docosahexaenoic acid (C_22:6θ3) were the predominant polyunsaturated fatty acids (PUFA). The data revealed that species such as truta, barbado, and corvina were good sources of eicosapentaenoic acid (C_20:5θ3) and docosahexaenoic acid (C_22:6θ3), and that most freshwater fish examined were good sources of PUFA θ3.     

Important Differences Exist in the Dose–Response Relationship between Diet and Immune Cell Fatty Acids in Humans and Rodents

Omega-3 polyunsaturated fatty acids (n-3 PUFA) are noted for their ability to diminish inflammatory and immune responses in vitro and in a variety of animal-based models of autoimmunity and inflammation. Yet, recent systematic reviews suggest that the evidence for these fatty acids having beneficial effects on inflammation or autoimmunity in humans is equivocal. A possible explanation for these disappointing and somewhat paradoxical findings emerged from the analyses described in this review. The available data on the changes in immune cell fatty acid profiles in mice, rats and humans, fed various forms and amounts of n-3 PUFA are summarized and displayed graphically. The dose–response curves generated provide new insights into the relationship between dietary n-3 PUFA and immune cell fatty acid profiles. The author suggests that the poor predictive value of most in vitro as well as many animal trials may, in part, be a consequence of the frequent adoption of experimental conditions that create differences in immune cell fatty acid profiles that far exceed what is possible in free-living humans through dietary intervention. Recommendations for improving the preclinical value of future in vitro and animal-based studies with n-3 PUFA are provided.     

Effects of some leaf-emitted volatile compounds on aphid population increase

A role of some volatile compounds produced by plant tissues may be as defensive molecules against various pests, including arthropods. Volatile six-carbon compounds derived in plant tissue from polyunsaturated fatty acids via lipoxygenase/hydroperoxide lyase reduced tobacco aphid fecundity at certain concentrations when added to headspace vapor to which aphids were exposed. Both C₆ aldehydes and alcohols were effective, with the alcohols having greater activity. (Z)-3-Hexenyl acetate at levels in the headspace similar to those of the alcohols and aldehydes did not reduce aphid fecundity. A 6-hr exposure period to the C₆ aldehydes and alcohols was needed for maximum effect on the aphids feeding on tobacco leaves. Analysis of the direct versus indirect effects of these compounds indicates that the volatile aldehydes had both direct effects on aphid fecundity and indirect effects due to induced changes in the leaves upon which the aphids were feeding, while only indirect effects were observed for the alcohols. Tomato leaves have the capacity to produce volatile compounds at levels that impact aphid population increase, with the volatiles produced from crushed leaves having a much larger effect. The C₆ aldehydes and alcohols may be components of the fecundity reduction seen with tomato volatiles; however, volatile terpenes showed no effect. These results can be of significance for the genetic alteration of plants for improved aphid resistance.The investigation reported in this paper (No. 93-3-1) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director.     

Production of C6–C14 Medium-Chain Fatty Acids in Seeds and Leaves via Overexpression of Single Hotdog-Fold Acyl-Lipid Thioesterases

ACYL-LIPID THIOESTERASES (ALT) are a type of plant acyl–acyl carrier protein thioesterase that generate a wide range of medium-chain fatty acids and methylketone (MK) precursors when expressed heterologously in Escherichia coli. While this makes ALT-type thioesterases attractive as metabolic engineering targets to increase production of high-value medium-chain fatty acids and MKs in plant systems, the behavior of ALT enzymes in planta was not well understood before this study. To profile the substrate specificities of ALT-type thioesterases in different plant tissue types, AtALT1-4 from Arabidopsis thaliana, which have widely varied chain length and oxidation state preferences in E. coli, were overexpressed in Arabidopsis seeds, Camelina sativa seeds, and Nicotiana benthamiana leaves. Seed-specific overexpression of ALT enzymes led to medium-chain fatty acid accumulation in Arabidopsis and Camelina seed triacylglycerols, and transient overexpression in N. benthamiana demonstrated that the substrate preferences of ALT-type thioesterases in planta generally agree with those previously determined in E. coli. AtALT1 and AtALT4 overexpression in leaves and seeds resulted in the accumulation of 12–14 carbon-length fatty acids and 6–8 carbon-length fatty acids, respectively. While it was difficult to completely profile the products of ALT-type thioesterases that generate MK precursors (i.e. β-keto fatty acids), our results nonetheless demonstrate that ALT enzymes are catalytically diverse in planta. The knowledge gained from this study is a significant step towards being able to use ALT-type thioesterases as metabolic engineering tools to modify the fatty acid profiles of oilseed crops, other plants, and microorganisms.     

Lipid and fatty acid composition of diatoms revisited: rapid wound-activated change of food quality parameters influences herbivorous copepod reproductive success

Lipid and fatty acid composition are considered to be key parameters that determine the nutritive quality of phytoplankton diets for zooplanktonic herbivores. The fitness, reproduction and physiology of the grazers are influenced by these factors. The trophic transfer of lipids and fatty acids from algal cells has been typically studied by using simple extraction and quantification approaches, which, as we argue here, do not reflect the actual situation in the plankton. We show that cell disruption, as it occurs during a predator's grazing on diatoms can drastically change the lipid and fatty acid content of the food. In some algae, a rapid depletion of polyunsaturated fatty acids (PUFAs) is observed within the first minutes after cell disruption. This fatty acid depletion is directly linked to the production of PUFA-derived polyunsaturated aldehydes (PUA); these are molecules that are thought to be involved in the chemical defence of the algae. PUA-releasing diatoms are even capable of transforming lipids from other sources if these are available in the vicinity of the wounded cells. Fluorescent staining reveals that the enzymes involved in lipid transformation are active in the foregut of copepods, and therefore link the depletion processes directly to food uptake. Incubation experiments with the calanoid copepod Temora longicornis showed that PUFA depletion in PUA-producing diatoms is correlated to reduced hatching success, and can be compensated for by externally added single fatty acids.