Lipids and sterols of Pinus sylvestris L. sapwood and heartwood

Summary The lipid and sterol content and composition of three lipid fractions (free fatty acids/ sterols, triacylglycerols and sterol/triterpenoid esters) extracted from three stem discs of Pinus sylvestris were assessed to investigate metabolic changes related to heartwood formation. The wood was separated into (1) cambial zone, (2) outer sapwood, (3) inner sapwood, (4) transition zone, (5) outer heartwood and 6) inner heart-wood. The fractions were separated by thin-layer chromatography (TLC) and analysed by gas-liquid chromatography (GLC). The amount of fatty acids of sapwood triacylglycerols was about 1.5% (dry wt.) but a large reduction occurred in the transition zone. In contrast, noticeable amounts of free fatty acids were present only in the heart-wood. The most important fatty acids in the sapwood fractions were 16:0, 18:0, 18:1, 18:2 (the dominant fatty acid in all fractions), 18:3 and 20:3. Together 18:1 and 18:2 formed about 70% of the total triacylglycerol fatty acids. Of the sterol/ triterpenoid esters, 18:2 and 18:3 were predominant. The fatty acid composition of all fractions changed in the transition zone. The sterols found were sitosterol, stigmastanol, campesterol and campestanol. The amount of sterol esters increased towards the heartwood, and the amount of free sterols was lowest in the inner sapwood. Sitosterol was the dominant sterol in both free sterols and sterol esters.     

Environmentally-induced changes in the neutral lipids and intracellular vesicles of Saccharomyces cerevisiae and Kluyveromyces fragilis

Saccharomyces cerevisiae, grown aerobically or anaerobically under conditions which induce a requirement for a sterol and an unsaturated fatty acid, synthesized approximately the same amounts of neutral lipid and intracellular low-density vesicles, although the neutral lipids in aerobically-grown cells contained more esterified sterol and less triacylglycerol than those in anaerobically-grown cells. Kluyveromyces fragilis synthesized much less neutral lipid and a smaller quantity of low-density vesicles than S. cerevisiae whether grown at 30°C (generation time 1.1 h) or 20°C (generation time 2.1 h). Both yeasts synthesized highly saturated triacylglycerols, relatively unsaturated phospholipids, and esterified sterols with an intermediate degree of unsaturation irrespective of the conditions under which they were grown. Free sterols in the yeasts were rich in ergosterol and 22(24)-dehydroergosterol, while the esterified sterol fractions were richer in zymosterol.     

Using simple 13C NMR linewidth and relaxation measurements to make detailed chemical shift assignments in triacylglycerols and related compounds

Two simple experiments measuring the ¹³C linewidths ν_1/2 and spin–lattice relaxation times T₁ of each of the signals in the spectrum of trilinolein indicate that the ν_1/2 and T₁ values are consistent with the different degrees of motional freedom expected for the various ¹³C nuclei. However, for each chain, the ν_1/2 and T₁ measurements indicate a small reversal in mobility at C-10 relative to C-9 before motional freedom again steadily increases on each chain starting at C-11. The T₁ experiment allows unambiguous assignments of the C-8 signal and C-14 signal, which differ by only 0.010 ppm. Measurements of ¹³C ν_1/2 and T₁ values on tripalmitin provide secure assignments for the C-5 and C-6 signals, for which conflicting assignments have been reported. The T₁ measurements also show that among the tightly clustered C-8 through C-12 signals, the C-11 signals are the most downfield, while the C-12 signals are the most upfield, again contrary to a previous report. Similar measurements of ¹³C ν_1/2 and T₁ values on other triacylglycerols or related compounds may prove equally useful in making chemical shift assignments and detecting any discontinuities in motional freedom along a chain. The benefits and possible limitations of ultrahigh field NMR for studying triacylglycerols and related compounds are discussed.     

Long chain polyunsaturated fatty acid production and partitioning to triacylglycerols in four microalgae

Gas chromatographic profiling of fatty acids was performed during the growth cycle of four marine microalgae in order to establish which, if any, of these could act as a reliable source of genes for the metabolic engineering of long chain polyunsaturated fatty acid (LC-PUFA) synthesis in alternative production systems. A high-throughput column based method for extraction of triacylglycerols (TAGs) was used to establish how much and at what stage in the growth phase LC-PUFAs partition to storage lipid in the different species. Differences in the time course of production and incorporation of docosahexaenoic acid (22:6n-3, DHA) and eicosapentaenoic acid (20:5n-3, EPA) into TAGs were found in the marine microalgae Nannochloropsis oculata (Eustigmatophyceae), Phaeodactylum tricornutum and Thalassiosira pseudonana (Bacillariophyceae), and the Haptophyte Pavlova lutheri. Differences were not only observed between species but also during the different phases of growth within a species. A much higher percentage of the total cellular EPA was partitioned to TAGs in stationary phase cells of N. oculata compared to P. tricornutum. Although P. tricornutum produces DHA it does not partition it to TAGs. Both T. pseudonana and P. lutheri produce EPA and DHA and partition these to TAGs during the stationary phase of growth. These two species are therefore good candidates for further biochemical and molecular analysis, in order to understand and manipulate the processes that are responsible for the incorporation of LC-PUFAs into storage oils.     

Major human plasma lipid classes determined by quantitative high-performance liquid chromatography, their variation and associations with phospholipid fatty acids

An HPLC method with evaporative light-scattering detection (ELSD) was optimized and validated for the simultaneous quantitation of cholesteryl esters (CEs), triacylglycerols (TGs), free cholesterol (FC) and phosphatidylcholine (PC) in human plasma. The separation of CEs from TGs, the most variable plasma lipid class, was improved by speeding up the gradient steps and by increasing the re-equilibration time between runs. The calibrations were made at levels of 0.14–14 μg lipid/injection. The intra- and inter-day precision values of the method ranged between 1.9 and 4.5 and 2.3–7.2% (RSD, n=6), respectively, including determinations at two concentration levels. In comparison to other lipid classes, quantitation of PC proved to be equally repeatable despite its lowest detector response. The relative recoveries varied from 97.0 to 110.3%, showing good accuracy of the method. The methodological variation of the lipid classes covered 0.6–3.1% of their total variation in the study population (n=48). The CE/FC ratio showed an even closer relationship with phospholipid linoleic acid (18:2n−6; r=0.65, P<0.001) than with serum cholesterol levels, while eicosapentaenoic acid (20:5n−3) was significantly associated with PC (r=0.41, P<0.01). The CE/FC ratio increased (P<0.01) during soyabean oil substitution and the level of PC increased (P<0.01) during cold-pressed rapeseed oil substitution.     

The twists and turns of sphingolipid pathway in glucose regulation

Palmitic acid is a saturated fat found in foods that lead to obesity, cardiovascular disease, and Type II diabetes. It is linked to the development of resistance to insulin stimulation in muscle, liver and other organs involved in glucose metabolism, which, in turn, underlines the onset of Type II diabetes. The cellular and molecular mechanisms of this insulin resistance are complex and not completely understood. This article is focused on the role of palmitic acid as a precursor in the synthesis of sphingolipids, a class of lipid molecules that participate in cellular stress response. Recent evidence had indicated that increased dietary supply of palmitate can stimulate the rate of sphingolipid synthesis in “lean” tissues and generate excessive amounts of sphingolipid metabolites that have a negative effect on the insulin signaling cascade. Many experimental results point to the existence of a causative link between sphingolipid synthesis, insulin response, and hyperglycemia. It is not yet clear, however whether ceramides or glycosphingolipids are involved as both have been implicated to be inhibitors of the insulin signaling cascade. Evidence for a coordinated regulation of sphingolipid and tri/diacylglycerol metabolism complicates further the delineation of a single mechanism of sphingolipid effect on glucose homeostasis.     

Lipid and fatty acid composition of canine lipoproteins

Lipid classes and their fatty acids were studied in the major lipoprotein fractions from canine, in comparison with human, plasma. In dogs, high-density-lipoprotein (HDL), the main carrier of plasma phospholipid (PL), cholesterol ester (CE) and free cholesterol, was the most abundant lipoprotein, followed by low and very-low density lipoproteins (LDL and VLDL). Notably, LDL and VLDL contributed similarly to the total dog plasma triacylglycerol (TG). The PL composition was similar in all three lipoproteins, dominated by phosphatidylcholine (PC). Even though the content and composition of lipids within and among lipoproteins differed markedly between dog and man, the total amount of circulating lipid was similar. All canine lipoproteins were relatively richer than those from humans in long-chain (C20-C22) n-6 and n-3 polyunsaturated fatty acids (PUFA) but had comparable proportions of total saturated and monoenoic fatty acids, with 18:2n-6 being the main PUFA in both mammals. The fatty acid profile of canine and human lipoproteins differed because they had distinct proportions of their major lipids. There were more n-3 and n-6 long-chain PUFA in canine than in human plasma, because dogs had more HDL, their HDL had more PC and CE, and both these lipids were richer in such PUFA.     

不同氮源及CO_2浓度下湖泊微拟球藻的生长及产油特性分析

<正>工业生产排放的各种废气与污水污染人类赖以生存的环境。化石燃料燃烧除排放出大量CO2外,还释放出含有粉尘、SO[x和NOx等直接危害人类健康的有毒成分1]。其中NO]x与水结合后最终会转化成硝酸盐或亚硝酸盐等[2,导致污水中的含氮化合物氨氮、亚硝酸盐氮、硝酸盐氮和有机氮的含量通常偏高。如何有效去除污水中的氮是防治水体污染最关键的步骤之一,而利用微藻培养去除水体中的氮源是目前研究的热点。尽管生物燃料生产的成本远     

Apoptosis and lipoapoptosis in the fission yeast Schizosaccharomyces pombe

Yeasts being simple eukaryotes are established genetic systems that are often employed to solve important biological questions. Recently, it has become evident that certain cell death programs exist in these unicellular organisms. For example, it has been shown recently that strains of the fission yeast Schizosaccharomyces pombe deficient in triacylglycerol synthesis undergo cell death with prominent apoptotic markers. This minireview is intended to discuss key developments that have rendered fission yeast useful both as a tool and as a model for apoptosis and lipoapoptosis research. It is attempted to delineate a putative signaling pathway leading to the execution of lipoapoptosis in the fission yeast. Although in its infancy, apoptosis research in the fission yeast promises exciting breakthroughs in the near future.     

Chlorogenic acid modifies plasma and liver concentrations of: cholesterol,triacylglycerol, and minerals in (fa/fa) Zucker rats

Chlorogenic acid, a phenolic compound found ubiquitously in plants, is an in vitro antioxidant and metal chelator. Some derivatives of chlorogenic acid are hypoglycemic agents and may affect lipid metabolism. Concentrations of cholesterol and triacylglycerols are of interest due to their association with diseases such as non-insulin-dependent-diabetes- mellitus and obese insulin resistance. As little is known about the effects of chlorogenic acid in vivo, studies using obese, hyperlipidemic, and insulin resistant (fa/fa) Zucker rats were conducted to test the effect of chlorogenic acid on fasting plasma glucose, plasma and liver triacylglycerols and cholesterol concentrations. Aditionally, the effects of chlorogenic acid on selected mineral concentrations in plasma, spleen, and liver were determined. Rats were implanted with jugular vein catheters. Chlorogenic acid was infused (5 mg/Kg body weight/day) for 3 weeks via intravenous infusion. Chlorogenic acid did not promote sustained hypoglycemia and significantly lowered the postprandial peak response to a glucose challenge when compared to the same group of rats before Chlorogenic acid treatment. In Chlorogenic acid-treated rats, fasting plasma cholesterol and triacylglycerols concentrations significantly decreased by 44% and 58% respectively, as did in liver triacylglycerols concentrations (24%). We did not find differences (p > 0.05) in adipose triacylglycerols concentration. Significant differences (p < 0.05) in the plasma, liver, and spleen concentration of selected minerals were found in chlorogenic acid-treated rats. In vivo, chlorogenic acid was found to improve glucose tolerance, decreased some plasma and liver lipids, and improve mineral pool distribution under the conditions of this study.