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Journal: Lipids

34

We recently demonstrated that daily whole egg consumption during moderate carbohydrate restriction leads to greater increases in plasma HDL-cholesterol (HDL-C) and improvements in HDL profiles in metabolic syndrome (MetS) when compared to intake of a yolk-free egg substitute. We further investigated the effects of this intervention on HDL composition and function, hypothesizing that the phospholipid species present in egg yolk modulate HDL lipid composition to increase the cholesterol-accepting capacity of subject serum. Men and women classified with MetS were randomly assigned to consume either three whole eggs (EGG, n = 20) per day or the equivalent amount of egg substitute (SUB, n = 17) throughout a 12-week moderate carbohydrate-restricted (25-30 % of energy) diet. Relative to other HDL lipids, HDL-cholesteryl ester content increased in all subjects, with greater increases in the SUB group. Further, HDL-triacylglycerol content was reduced in EGG group subjects with normal baseline plasma HDL-C, resulting in increases in HDL-CE/TAG ratios in both groups. Phospholipid analysis by mass spectrometry revealed that HDL became enriched in phosphatidylethanolamine in the EGG group, and that EGG group HDL better reflected sphingomyelin species present in the whole egg product at week 12 compared to baseline. Further, macrophage cholesterol efflux to EGG subject serum increased from baseline to week 12, whereas no changes were observed in the SUB group. Together, these findings suggest that daily egg consumption promotes favorable shifts in HDL lipid composition and function beyond increasing plasma HDL-C in MetS.

Concepts: Cholesterol, Metabolism, Nutrition, Egg, Lipid, Lipid bilayer, Egg yolk, Lecithin

27

Eggs are a source of cholesterol and choline and may impact plasma lipids and trimethylamine-N-oxide (TMAO) concentrations, which are biomarkers for cardiovascular disease (CVD) risk. Therefore, the effects of increasing egg intake (0, 1, 2, and 3 eggs/day) on these and other CVD risk biomarkers were evaluated in a young, healthy population. Thirty-eight subjects [19 men/19 women, 24.1 ± 2.2 years, body mass index (BMI) 24.3 ± 2.5 kg/m(2)] participated in this 14-week crossover intervention. Participants underwent a 2-week washout with no egg consumption, followed by intake of 1, 2, and 3 eggs/day for 4 weeks each. Anthropometric data, blood pressure (BP), dietary records, and plasma biomarkers (lipids, glucose, choline, and TMAO) were measured during each intervention phase. BMI, waist circumference, systolic BP, plasma glucose, and plasma triacylglycerol did not change throughout the intervention. Diastolic BP decreased with egg intake (P < 0.05). Compared to 0 eggs/day, intake of 1 egg/day increased HDL cholesterol (HDL-c) (P < 0.05), and decreased LDL cholesterol (LDL-c) (P < 0.05) and the LDL-c/HDL-c ratio (P < 0.01). With intake of 2-3 eggs/day, these changes were maintained. Plasma choline increased dose-dependently with egg intake (P < 0.0001) while fasting plasma TMAO was unchanged. These results indicate that in a healthy population, consuming up to 3 eggs/day results in an overall beneficial effect on biomarkers associated with CVD risk, as documented by increased HDL-c, a reduced LDL-c/HDL-c ratio, and increased plasma choline in combination with no change in plasma LDL-c or TMAO concentrations.

Concepts: Cholesterol, Nutrition, Atherosclerosis, Cardiovascular disease, Low-density lipoprotein, Blood pressure, High-density lipoprotein, Body mass index

27

Human meibomian gland secretions (meibum) are the major lipid component of the human preocular tear film. The predominant lipid classes found in meibum include waxes (WE), cholesteryl esters (CE), and varying amounts of cholesterol (Chl). The classical sulfo-phospho-vanillin assay (SPVA), adapted for a microplate reader, was used to quantitate lipids in meibum. To account for varying reactivities of different lipids in SPVA, a model meibomian lipid mixture (MMx) that approximated the WE/CE/Chl composition of meibum was developed and used to quantitate meibomian lipids. The overall SPV responses of MMx and meibum were found to be close, with similar intermediate and final reaction products for both. Saturated WE that had not been expected to be reactive were found to be SPV-positive. A reaction mechanism for these compounds in SPVA which involves the formation of alkenyl ethers is proposed and discussed. Tested proteins were non-reactive in SPVA. Thus, by comparing the results of gravimetric analyses of meibum samples with the results of a properly calibrated SPVA, it was estimated that the SPV-reactive lipid content of dry meibum in tested samples was about 78 % (w/w). The SPV method can also be adopted for analyzing other types of complex lipids secretions, such as sebum, as well as whole lipid extracts from other lipid-enriched organs and tissues, if proper standards are chosen.

Concepts: Protein, Fat, Lipid, Biochemistry, Wax, Lipids, Gland, Meibomian gland

24

Diacylglycerol acyltransferase (DGAT) catalyzes the acyl-CoA-dependent acylation of sn-1, 2-diacylglycerol to produce triacylglycerol, which is the main component of the seed oil of Brassica oilseed species. Phylogenetic analysis of the amino acid sequences encoded by four transcriptionally active DGAT1 genes from Brassica napus suggests that the gene forms diverged over time into two clades (I and II), with representative members in each genome (A and C). The majority of the amino acid sequence differences in these forms of DGAT1, however, reside outside of motifs suggested to be involved in catalysis. Despite this, the clade II enzymes displayed a significantly enhanced preference for linoleoyl-CoA when assessed using in-vitro enzyme assays with yeast microsomes containing recombinant enzyme forms. These findings contribute to our understanding of triacylglycerol biosynthesis in B. napus, and may advance our ability to engineer DGAT1s with desired substrate selectivity properties.

Concepts: DNA, Protein, Gene, Bacteria, Amino acid, Metabolism, Enzyme, Peptide sequence

24

A detailed structural diversity of dienoic fatty acids (FA), including non-methylene-interrupted dienoic FA, of triacylglycerols and polar lipids in ovaries of Cellana toreuma was clarified for the first time by using capillary gas chromatography-mass spectrometry of their 3-pyridylcarbinol esters and argentation thin-layer chromatography. Interestingly, in addition to 5,9-octadecadienoic (18:2Δ5,9), 5,9-eicosadienoic (20:2Δ5,9), 5,9-heneicosadienoic (21:2Δ5,9), 5,9-docosadienoic (22:2Δ5,9), 5,9-tricosadienoic (23:2Δ5,9), and 5,9-tetracosadienoic (24:2Δ5,9) acids, previously identified in ovaries of C. grata, rare FA 5,9-hexadecadienoic (16:2Δ5,9), 5,9-nonadecadienoic (19:2Δ5,9), and 21-methyl-5,9-docosadienoic (iso 23:2Δ5,9) were newly recognized in ovaries of C. toreuma. Detectable amounts of four Δ9,15-dienoic FA were present in the ovary lipids. The FA identified were one novel 9,15-heneicosadienoic (21:2Δ9,15) acid and known 9,15-docosadienoic (22:2Δ9,15), 9,15-tricosadienoic (23:2Δ9,15), and 9,15-tetracosadienoic (24:2Δ9,15) acids. The findings help to explain the broad evidence of the structural diversity in marine gastropods and suggest biomarkers to evaluate marine food web relations.

Concepts: Fatty acid, Triglyceride, Fat, Chromatography, Lipid, Carboxylic acid, Ester, Glycerol

23

Ethanolamine plasmalogen (PlsEtn), a major phospholipid in neuronal membranes [60-90 mol% of ethanolamine glycerophospholipid (EtnGpl)], is specifically decreased in brains from patients with Alzheimer’s disease (AD). The present study investigated how PlsEtn administration affects cognitive deficits and lipid composition in an animal model of AD. AD model rats were infused with amyloid-β (Aβ) into the cerebral ventricle and divided into three groups. Control, Egg, and Ascidian groups were then orally administered vehicle, egg yolk EtnGpl (260 μmol as EtnGpl/kg BW/day; 10 μmol as PlsEtn/kg BW/day), or ascidian viscera EtnGpl (260 μmol as EtnGpl/kg BW/day; 209 μmol as PlsEtn/kg BW/day), respectively. After 4 weeks of dosing, Aβ-infused rats were tested for learning ability in an 8-arm radial maze. The administration of ascidian viscera EtnGpl improved both reference and working memory-related learning abilities. In lipid analysis, the Ascidian group showed higher levels of PlsEtn species in the plasma, erythrocytes, and liver when compared to other groups. In addition, although there were no differences at levels of total plasmalogen including choline plasmalogen, the Ascidian group had significantly higher levels of 18:0ol/22:6-PlsEtn in the cerebral cortex. These levels of 18:0ol/22:6-PlsEtn in the cerebral cortex were correlated with working memory-related learning ability. Moreover, 18:0ol/22:6-PlsEtn levels in the cerebral cortex showed positive correlations with those in the erythrocytes and liver. In summary, dietary PlsEtn, especially that with 22:6n-3 (docosahexaenoic acid, DHA), may ameliorate learning deficiencies in AD by altering lipid composition in the brain.

Concepts: Cholesterol, Alzheimer's disease, Neuron, Brain, Human brain, Cerebral cortex, Ventricular system, Lecithin

23

Our previous study characterized highly diverse dienoic fatty acids (FA), in particular an uncommon non-methylene-interrupted (NMI) FA, in the ovaries of the Japanese limpet Cellana toreuma belonging to the archaeogastropods, but many minor chemically unidentified FA remain. In this study, among previously unidentified FA (less than 0.1% of total FA), four novel NMI FA with a terminal double bond [7,18-nonadecadienoic (19:2Δ7,18), 11,18-nonadecadienoic (19:2Δ11,18), 7,20-heneicosadienoic (21:2Δ7,20), and 11,20-heneicosadienoic (21:2Δ11,20) acids] were found, along with known 14-pentadecenoic (15:1Δ14), 16-heptadecenoic (17:1Δ16), and 9,18-nonadecadienoic (19:2Δ9,18) acids, based on capillary GC-MS of their methyl esters, 3-pyridylcarbinol derivatives, and argentation thin-layer chromatography. From our findings, possible biosynthetic pathways for the novel FA are discussed.

Concepts: Fatty acid, Fat, Chromatography, Carboxylic acid, Ester, Biochemistry, Novel, Thin layer chromatography

23

Many uncommon non-methylene-interrupted fatty acids (NMI FA) are present in limpet gonads, but their biological properties remain unknown. To investigate new biological effects of naturally occurring NMI FA in eukaryotic cells, the biological activities of structurally analogous (4Z,15Z)-octadecadienoic acid (1), (9Z,20Z)-tricosadienoic acid (2), and (12Z,23Z)-hexacosadienoic acid (3) were examined by using a yeast-based drug-screening system using the Ca(2+)-sensitive mutant strain, Saccharomyces cerevisiae (zds1Δ erg3Δ pdr1Δ pdr3Δ). Among 1-3, 1 showed restored growth activity at a dose of 80 µg/disc in the mutant yeast strain. This phenotype suggests that 1 suppresses Ca(2+)-signaling of the mutant yeast through inhibition of glycogen synthase kinase-3β (GSK-3β) or calcineurin pathways or both. From this result, the inhibitory activity of 1-3 against GSK-3β was further determined. 1-3 showed potent inhibitory activity against GSK-3β with IC50 values ranging from 8.7 to 21.9 µM. Inhibition of GSK-3β reduces gene expression of the gluconeogenic key enzymes in liver, so we analyzed glucose production in rat hepatoma H4IIE cells to assess GSK-3β inhibitory activity of 1-3. Acid 1 inhibited glucose production at 25 µM in H4IIE cells. Our results would open up new possibilities for an anti-diabetic effect of 1 and might provide important insights into understanding the biological properties of naturally occurring NMI FA.

Concepts: DNA, Gene, Bacteria, Enzyme, Organism, Glucose, Fungus, Saccharomyces cerevisiae

13

The brain is enriched in arachidonic acid (ARA) and docosahexaenoic acid (DHA), long-chain polyunsaturated fatty acids (LCPUFAs) of the n-6 and n-3 series, respectively. Both are essential for optimal brain development and function. Dietary enrichment with DHA and other long-chain n-3 PUFA, such as eicosapentaenoic acid (EPA), has shown beneficial effects on learning and memory, neuroinflammatory processes, and synaptic plasticity and neurogenesis. ARA, DHA and EPA are precursors to a diverse repertoire of bioactive lipid mediators, including endocannabinoids. The endocannabinoid system comprises cannabinoid receptors, their endogenous ligands, the endocannabinoids, and their biosynthetic and degradation enzymes. Anandamide (AEA) and 2-arachidonoylglycerol (2-AG) are the most widely studied endocannabinoids and are both derived from phospholipid-bound ARA. The endocannabinoid system also has well-established roles in neuroinflammation, synaptic plasticity and neurogenesis, suggesting an overlap in the neuroprotective effects observed with these different classes of lipids. Indeed, growing evidence suggests a complex interplay between n-3 and n-6 LCPUFA and the endocannabinoid system. For example, long-term DHA and EPA supplementation reduces AEA and 2-AG levels, with reciprocal increases in levels of the analogous endocannabinoid-like DHA and EPA-derived molecules. This review summarises current evidence of this interplay and discusses the therapeutic potential for brain protection and repair.

Concepts: Fatty acid, Fatty acids, Essential fatty acid, Eicosapentaenoic acid, Prostaglandin, Arachidonic acid, Polyunsaturated fatty acid, Anandamide

5

Fillets of 76 finfish species (293 composites of three fish) were obtained from commercial seafood vendors in six regions of the United States (i.e., Great Lakes, Mid-Atlantic, New England, Northwest, Southeast, and Southwest). Full fatty acid profiles were determined for each species and are presented here. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been associated with many health benefits. Thus, fillets of each species were compared for total EPA plus DHA content, which ranged from 17 mg/100 g (pangasius/swai) to 2430 mg/100 g (Chilean sea bass). Of the top ten most popularly consumed seafoods in the US, finfish, including salmon species (717-1533 mg/100 g), Alaskan pollock (236 mg/100 g), tilapia (76 mg/100 g), channel catfish (44 mg/100 g), Atlantic cod (253 mg/100 g), and pangasius/swai (17 mg/100 g), exhibited a wide concentration range of EPA plus DHA. Large variances were found within many of the farmed species analyzed, which likely stems from dietary differences in the farm-fed diet. The results of this study provide current information on a broad range of species and will help nutritionists and the public make informed decisions regarding seafood consumption.

Concepts: Fish, United States, Omega-3 fatty acid, Eicosapentaenoic acid, Docosahexaenoic acid, Cod, Seafood, Great Lakes