Microalgal triacylglycerols as feedstocks for biofuel production: perspectives and advances

Microalgae represent an exceptionally diverse but highly specialized group of micro-organisms adapted to various ecological habitats. Many microalgae have the ability to produce substantial amounts (e.g. 20-50% dry cell weight) of triacylglycerols (TAG) as a storage lipid under photo-oxidative stress or other adverse environmental conditions. Fatty acids, the building blocks for TAGs and all other cellular lipids, are synthesized in the chloroplast using a single set of enzymes, of which acetyl CoA carboxylase (ACCase) is key in regulating fatty acid synthesis rates. However, the expression of genes involved in fatty acid synthesis is poorly understood in microalgae. Synthesis and sequestration of TAG into cytosolic lipid bodies appear to be a protective mechanism by which algal cells cope with stress conditions, but little is known about regulation of TAG formation at the molecular and cellular level. While the concept of using microalgae as an alternative and renewable source of lipid-rich biomass feedstock for biofuels has been explored over the past few decades, a scalable, commercially viable system has yet to emerge. Today, the production of algal oil is primarily confined to high-value specialty oils with nutritional value, rather than commodity oils for biofuel. This review provides a brief summary of the current knowledge on oleaginous algae and their fatty acid and TAG biosynthesis, algal model systems and genomic approaches to a better understanding of TAG production, and a historical perspective and path forward for microalgae-based biofuel research and commercialization.

Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials

BACKGROUND

The effects of dietary fats on the risk of coronary artery disease (CAD) have traditionally been estimated from their effects on LDL cholesterol. Fats, however, also affect HDL cholesterol, and the ratio of total to HDL cholesterol is a more specific marker of CAD than is LDL cholesterol.

OBJECTIVE

The objective was to evaluate the effects of individual fatty acids on the ratis of total to HDL cholesterol and on serum lipoproteins.

DESIGN

We performed a meta-analysis of 60 selected trials and calculated the effects of the amount and type of fat on total:HDL cholesterol and on other lipids.

RESULTS

The ratio did not change if carbohydrates replaced saturated fatty acids, but it decreased if cis unsaturated fatty acids replaced saturated fatty acids. The effect on total:HDL cholesterol of replacing trans fatty acids with a mix of carbohydrates and cis unsaturated fatty acids was almost twice as large as that of replacing saturated fatty acids. Lauric acid greatly increased total cholesterol, but much of its effect was on HDL cholesterol. Consequently, oils rich in lauric acid decreased the ratio of total to HDL cholesterol. Myristic and palmitic acids had little effect on the ratio, and stearic acid reduced the ratio slightly. Replacing fats with carbohydrates increased fasting triacylglycerol concentrations.

CONCLUSIONS

The effects of dietary fats on total:HDL cholesterol may differ markedly from their effects on LDL. The effects of fats on these risk markers should not in themselves be considered to reflect changes in risk but should be confirmed by prospective observational studies or clinical trials. By that standard, risk is reduced most effectively when trans fatty acids and saturated fatty acids are replaced with cis unsaturated fatty acids. The effects of carbohydrates and of lauric acid-rich fats on CAD risk remain uncertain.

Crystal structure of human serum albumin complexed with fatty acid reveals an asymmetric distribution of binding sites

Human serum albumin (HSA) is the most abundant protein in the circulatory system. Its principal function is to transport fatty acids, but it is also capable of binding a great variety of metabolites and drugs. Despite intensive efforts, the detailed structural basis of fatty acid binding to HSA has remained elusive. We have now determined the crystal structure of HSA complexed with five molecules of myristate at 2.5 A resolution. The fatty acid molecules bind in long, hydrophobic pockets capped by polar side chains, many of which are basic. These pockets are distributed asymmetrically throughout the HSA molecule, despite its symmetrical repeating domain structure.

Lipid A modification systems in gram-negative bacteria

The lipid A moiety of lipopolysaccharide forms the outer monolayer of the outer membrane of most gram-negative bacteria. Escherichia coli lipid A is synthesized on the cytoplasmic surface of the inner membrane by a conserved pathway of nine constitutive enzymes. Following attachment of the core oligosaccharide, nascent core-lipid A is flipped to the outer surface of the inner membrane by the ABC transporter MsbA, where the O-antigen polymer is attached. Diverse covalent modifications of the lipid A moiety may occur during its transit from the outer surface of the inner membrane to the outer membrane. Lipid A modification enzymes are reporters for lipopolysaccharide trafficking within the bacterial envelope. Modification systems are variable and often regulated by environmental conditions. Although not required for growth, the modification enzymes modulate virulence of some gram-negative pathogens. Heterologous expression of lipid A modification enzymes may enable the development of new vaccines.

Fatty acid composition of adipose tissue and blood in humans and its use as a biomarker of dietary intake

Accurate assessment of fat intake is essential to examine the relationships between diet and disease risk but the process of estimating individual intakes of fat quality by dietary assessment is difficult. Tissue and blood fatty acids, because they are mainly derived from the diet, have been used as biomarkers of dietary intake for a number of years. We review evidence from a wide variety of cross-sectional and intervention studies and summarise typical values for fatty acid composition in adipose tissue and blood lipids and changes that can be expected in response to varying dietary intake. Studies in which dietary intake was strictly controlled confirm that fatty acid biomarkers can complement dietary assessment methodologies and have the potential to be used more quantitatively. Factors affecting adipose tissue and blood lipid composition are discussed, such as the physical properties of triacylglycerol, total dietary fat intake and endogenous fatty acid synthesis. The relationship between plasma lipoprotein concentrations and total plasma fatty acid composition, and the use of fatty acid ratios as indices of enzyme activity are also addressed.

Time evolution of the nanoparticle protein corona

In this work, we explore the formation of the protein corona after exposure of metallic Au nanoparticles (NPs), with sizes ranging from 4 to 40 nm, to cell culture media containing 10% of fetal bovine serum. Under in vitro cell culture conditions, zeta potential measurements, UV-vis spectroscopy, dynamic light scattering and transmission electron microscope analysis were used to monitor the time evolution of the inorganic NP-protein corona formation and to characterize the stability of the NPs and their surface state at every stage of the experiment. As expected, the red-shift of the surface plasmon resonance peak, as well as the drop of surface charge and the increase of the hydrodynamic diameter indicated the conjugation of proteins to NPs. Remarkably, an evolution from a loosely attached toward an irreversible attached protein corona over time was observed. Mass spectrometry of the digested protein corona revealed albumin as the most abundant component which suggests an improved biocompatibility.

Molecular recognition of fatty acids by peroxisome proliferator-activated receptors

The peroxisome proliferator-activated receptors (PPARs) are nuclear receptors for fatty acids (FAs) that regulate glucose and lipid homeostasis. We report the crystal structure of the PPAR delta ligand-binding domain (LBD) bound to either the FA eicosapentaenoic acid (EPA) or the synthetic fibrate GW2433. The carboxylic acids of EPA and GW2433 interact directly with the activation function 2 (AF-2) helix. The hydrophobic tail of EPA adopts two distinct conformations within the large hydrophobic cavity. GW2433 occupies essentially the same space as EPA bound in both conformations. These structures provide molecular insight into the propensity for PPARs to interact with a variety of synthetic and natural compounds, including FAs that vary in both chain length and degree of saturation.

Crystallographic analysis reveals common modes of binding of medium and long-chain fatty acids to human serum albumin

Human serum albumin (HSA) is an abundant plasma protein that is responsible for the transport of fatty acids. HSA also binds and perturbs the pharmacokinetics of a wide range of drug compounds. Binding studies have revealed significant interactions between fatty acid and drug-binding sites on albumin but high-resolution structural information on ligand binding to the protein has been lacking. We report here a crystallographic study of five HSA-fatty acid complexes formed using saturated medium-chain and long-chain fatty acids (C10:0, C12:0, C14:0, C16:0 and C18:0). A total of seven binding sites that are occupied by all medium-chain and long-chain fatty acids have been identified, although medium-chain fatty acids are found to bind at additional sites on the protein, yielding a total of 11 distinct binding locations. Comparison of the different complexes reveals key similarities and significant differences in the modes of binding, and serves to rationalise much of the biochemical data on fatty acid interactions with albumin. The two principal drug-binding sites, in sub-domains IIA and IIIA, are observed to be occupied by fatty acids and one of them (in IIIA) appears to coincide with a high-affinity long-chain fatty acid binding site.

Metal-catalyzed nitrogen-atom transfer methods for the oxidation of aliphatic C-H bonds

For more than a century, chemists have endeavored to discover and develop reaction processes that enable the selective oxidation of hydrocarbons. In the 1970s, Abramovitch and Yamada described the synthesis and electrophilic reactivity of sulfonyliminoiodinanes (RSO(2)N═IPh), demonstrating the utility of this new class of reagents to function as nitrene equivalents. Subsequent investigations by Breslow, Mansuy, and Müller would show such oxidants to be competent for alkene and saturated hydrocarbon functionalization when combined with transition metal salts or metal complexes, namely those of Mn, Fe, and Rh. Here, we trace our own studies to develop N-atom transfer technologies for C-H and π-bond oxidation. This Account discusses advances in both intra- and intermolecular amination processes mediated by dirhodium and diruthenium complexes, as well as the mechanistic foundations of catalyst reactivity and arrest. Explicit reference is given to questions that remain unanswered and to problem areas that are rich for discovery. A fundamental advance in amination technology has been the recognition that iminoiodinane oxidants can be generated in situ in the presence of a metal catalyst that elicits subsequent N-atom transfer. Under these conditions, both dirhodium and diruthenium lantern complexes function as competent catalysts for C-H bond oxidation with a range of nitrogen sources (e.g., carbamates, sulfamates, sulfamides, etc.), many of which will not form isolable iminoiodinane equivalents. Practical synthetic methods and applications thereof have evolved in parallel with inquiries into the operative reaction mechanism(s). For the intramolecular dirhodium-catalyzed process, the body of experimental and computational data is consistent with a concerted asynchronous C-H insertion pathway, analogous to the consensus mechanism for Rh-carbene transfer. Other studies reveal that the bridging tetracarboxylate ligand groups, which shroud the dirhodium core, are labile to exchange under standard reaction conditions. This information has led to the generation of chelating dicarboxylate dinuclear rhodium complexes, exemplified by Rh(2)(esp)(2). The performance of this catalyst system is unmatched by other dirhodium complexes in both intra- and intermolecular C-H amination reactions. Tetra-bridged, mixed-valent diruthenium complexes function as effective promoters of sulfamate ester oxidative cyclization. These catalysts can be crafted with ligand sets other than carboxylates and are more resistant to oxidation than their dirhodium counterparts. A range of experimental and computational mechanistic data amassed with the tetra-2-oxypyridinate diruthenium chloride complex, [Ru(2)(hp)(4)Cl], has established the insertion event as a stepwise pathway involving a discrete radical intermediate. These data contrast dirhodium-catalyzed C-H amination and offer a cogent model for understanding the divergent chemoselectivity trends observed between the two catalyst types. This work constitutes an important step toward the ultimate goal of achieving predictable, reagent-level control over product selectivity.

Biochemistry of mammalian peroxisomes revisited

In this review, we describe the current state of knowledge about the biochemistry of mammalian peroxisomes, especially human peroxisomes. The identification and characterization of yeast mutants defective either in the biogenesis of peroxisomes or in one of its metabolic functions, notably fatty acid beta-oxidation, combined with the recognition of a group of genetic diseases in man, wherein these processes are also defective, have provided new insights in all aspects of peroxisomes. As a result of these and other studies, the indispensable role of peroxisomes in multiple metabolic pathways has been clarified, and many of the enzymes involved in these pathways have been characterized, purified, and cloned. One aspect of peroxisomes, which has remained ill defined, is the transport of metabolites across the peroxisomal membrane. Although it is clear that mammalian peroxisomes under in vivo conditions are closed structures, which require the active presence of metabolite transporter proteins, much remains to be learned about the permeability properties of mammalian peroxisomes and the role of the four half ATP-binding cassette (ABC) transporters therein.

PLGA nanoparticles prepared by nanoprecipitation: drug loading and release studies of a water soluble drug

The nanoprecipitation technique for preparation of nanoparticles suffers the drawback of poor incorporation of water soluble drugs. The aim of this study was therefore to assess various formulation parameters to enhance the incorporation of a water soluble drug (procaine hydrochloride) into poly(dl-lactide-co-glycolide) (PLGA) nanoparticles prepared by this technique. Approaches investigated for drug incorporation efficiency enhancement included the influence of aqueous phase pH, replacement of procaine hydrochloride with procaine dihydrate and the inclusion of excipients: poly(dl-lactide) (PLA) oligomers, poly(methyl methacrylate-co-methacrylic acid) (PMMA-MA) or fatty acids into the formulation. The nanoparticles produced were submicron size (<210 nm) and of low polydispersity. It was found that an aqueous phase pH of 9.3, replacement of procaine hydrochloride with procaine dihydrate and the incorporation of PMMA-MA, lauric and caprylic acid into the formulation could enhance drug incorporation efficiency without the size, morphology and nanoparticle recovery being adversely influenced. For instance changing the aqueous phase pH from 5.8 to 9.3 increased nanoparticle recovery from 65.1 to 93.4%, drug content from 0.3 to 1.3% w/w and drug entrapment from 11.0 to 58.2%. However, the presence of high ratios of lauric acid and procaine dihydrate in the formulation adversely affected the morphology and size of the nanoparticles. Also, PLA oligomers were not considered a feasible approach since it decreased drug entrapment from 11.0 to 8.4% and nanoparticle recovery from 65.1 to 19.6%. Drug release from nanoparticles appears to consist of two components with an initial rapid release followed by a slower exponential stage. This study has demonstrated that formulation variables can be exploited in order to enhance the incorporation of a water soluble drug into PLGA nanoparticles by the nanoprecipitation technique.

The composition of bovine milk lipids: January 1995 to December 2000

Data from recent publications on bovine milk lipids are presented and discussed. This includes extraction of lipids, triacylglycerols, phospholipids, other complex lipids, sterols, isoflavones, and fatty acids. Improved gas-liquid and high performance liquid chromatography were used. Data on the trans and cis isomers of fatty acid and of conjugated linoleic acids are given, and the analyses are described. Papers about the lipids in milks and dairy products from the United States are few; where with the exception of trans-fatty acid isomers and conjugated linoleic acids, almost no research has been reported.

Physiological functions of the mitochondrial uncoupling proteins UCP2 and UCP3

Evidence for the physiological functions of UCP2 and UCP3 is critically reviewed. They do not mediate adaptive thermogenesis, but they may be significantly thermogenic under specific pharmacological conditions. There is strong evidence that the mild regulated uncoupling they cause attenuates mitochondrial ROS production, protects against cellular damage, and diminishes insulin secretion. Evidence that they export fatty acids physiologically is weak. UCP2 and UCP3 are important potential targets for treatment of aging, degenerative diseases, diabetes, and perhaps obesity.

A direct method for fatty acid methyl ester synthesis: application to wet meat tissues, oils, and feedstuffs

A simplified protocol to obtain fatty acid methyl esters (FAME) directly from fresh tissue, oils, or feedstuffs, without prior organic solvent extraction, is presented. With this protocol, FAME synthesis is conducted in the presence of up to 33% water. Wet tissues, or other samples, are permeabilized and hydrolyzed for 1.5 h at 55 degrees C in 1 N KOH in MeOH containing C13:0 as the internal standard. The KOH is neutralized, and the FFA are methylated by H(2)SO(4) catalysis for 1.5 h at 55 degrees C. Hexane is then added to the reaction tube, which is vortex-mixed and centrifuged. The hexane is pipetted into a gas chromatography vial for subsequent gas chromatography. All reactions are conducted in a single screw-cap Pyrex tube for convenience. The method meets many criteria for fatty acid analysis, including not isomerizing CLA or introducing fatty acid artifacts. It is applicable to fresh, frozen, or lyophilized tissue samples, in addition to oils, waxes, and feedstuffs. The method saves time and effort and is economical when compared with other methods. Its unique performance, including easy sample preparation, is achieved because water is included rather than eliminated in the FAME reaction mixtures.

The structural biology of type II fatty acid biosynthesis

The type II fatty acid synthetic pathway is the principal route for the production of membrane phospholipid acyl chains in bacteria and plants. The reaction sequence is carried out by a series of individual soluble proteins that are each encoded by a discrete gene, and the pathway intermediates are shuttled between the enzymes as thioesters of an acyl carrier protein. The Escherichia coli system is the paradigm for the study of this system, and high-resolution X-ray and/or NMR structures of representative members of every enzyme in the type II pathway are now available. The structural biology of these proteins reveals the specific three-dimensional features of the enzymes that explain substrate recognition, chain length specificity, and the catalytic mechanisms that define their roles in producing the multitude of products generated by the type II system. These structures are also a valuable resource to guide antibacterial drug discovery.

Influence of fatty acid composition of raw materials on biodiesel properties

The aim of this work was the study of the influence of the raw material composition on biodiesel quality, using a transesterification reaction. Thus, ten refined vegetable oils were transesterificated using potassium methoxide as catalyst and standard reaction conditions (reaction time, 1h; weight of catalyst, 1 wt.% of initial oil weight; molar ratio methanol/oil, 6/1; reaction temperature, 60 degrees C). Biodiesel quality was tested according to the standard [UNE-EN 14214, 2003. Automotive fuels. Fatty acid methyl esters (FAME) for diesel engines. Requirements and test methods]. Some critical parameters like oxidation stability, cetane number, iodine value and cold filter plugging point were correlated with the methyl ester composition of each biodiesel, according to two parameters: degree of unsaturation and long chain saturated factor. Finally, a triangular graph based on the composition in monounsaturated, polyunsaturated and saturated methyl esters was built in order to predict the critical parameters of European standard for whatever biodiesel, known its composition.

The surface of lipid droplets is a phospholipid monolayer with a unique Fatty Acid composition

We found that caveolin-2 is targeted to the surface of lipid droplets (Fujimoto, T., Kogo, H., Ishiguro, K., Tauchi, K., and Nomura, R. (2001) J. Cell Biol. 152, 1079-1085) and hypothesized that the lipid droplet surface is a kind of membrane. To elucidate the characteristics of the lipid droplet surface, we isolated lipid droplets from HepG2 cells and analyzed them by cryoelectron microscopy and by mass spectrometry. By use of cryoelectron microscopy at the stage temperature of 4.2 K, the lipid droplet surface was observed as a single line without any fixation or staining, indicating the presence of a single layer of phospholipids. This result appeared consistent with the hypothesis that the lipid droplet surface is derived from the cytoplasmic leaflet of the endoplasmic reticulum membrane and may be continuous to it. However, mass spectrometry revealed that the fatty acid composition of phosphatidylcholine and lysophosphatidylcholine in lipid droplets is different from that of the rough endoplasmic reticulum. The ample presence of free cholesterol in lipid droplets also suggests that their surface is differentiated from the bulk endoplasmic reticulum membrane. On the other hand, although caveolin-2beta and adipose differentiation-related protein, both localizing in lipid droplets, were enriched in the low density floating fraction, the fatty acid composition of the fraction was distinct from lipid droplets. Collectively, the result indicates that the lipid droplet surface is a hemi-membrane or a phospholipid monolayer containing cholesterol but is compositionally different from the endoplasmic reticulum membrane or the sphingolipid/cholesterol-rich microdomain.

Experimental models of primitive cellular compartments: encapsulation, growth, and division

The clay montmorillonite is known to catalyze the polymerization of RNA from activated ribonucleotides. Here we report that montmorillonite accelerates the spontaneous conversion of fatty acid micelles into vesicles. Clay particles often become encapsulated in these vesicles, thus providing a pathway for the prebiotic encapsulation of catalytically active surfaces within membrane vesicles. In addition, RNA adsorbed to clay can be encapsulated within vesicles. Once formed, such vesicles can grow by incorporating fatty acid supplied as micelles and can divide without dilution of their contents by extrusion through small pores. These processes mediate vesicle replication through cycles of growth and division. The formation, growth, and division of the earliest cells may have occurred in response to similar interactions with mineral particles and inputs of material and energy.

Structure and function of fatty acid amide hydrolase

Fatty acid amide hydrolase (FAAH) is a mammalian integral membrane enzyme that degrades the fatty acid amide family of endogenous signaling lipids, which includes the endogenous cannabinoid anandamide and the sleep-inducing substance oleamide. FAAH belongs to a large and diverse class of enzymes referred to as the amidase signature (AS) family. Investigations into the structure and function of FAAH, in combination with complementary studies of other AS enzymes, have engendered provocative molecular models to explain how this enzyme integrates into cell membranes and terminates fatty acid amide signaling in vivo. These studies, as well as their biological and therapeutic implications, are the subject of this review.

Defining high-fat-diet rat models: metabolic and molecular effects of different fat types

High-fat (HF)-diet rodent models have contributed significantly to the analysis of the pathophysiology of the insulin resistance syndrome, but their phenotype varies distinctly between different studies. Here, we have systematically compared the metabolic and molecular effects of different HF with varying fatty acid compositions. Male Wistar rats were fed HF diets (42% energy; fat sources: HF-L - lard; HF-O - olive oil; HF-C - coconut fat; HF-F - fish oil). Weight, food intake, whole-body insulin tolerance and plasma parameters of glucose and lipid metabolism were measured during a 12-week diet course. Liver histologies and hepatic gene expression profiles, using Affymetrix GeneChips, were obtained. HF-L and HF-O fed rats showed the most pronounced obesity and insulin resistance; insulin sensitivity in HF-C and HF-F was close to normal. Plasma omega-3 polyunsaturated fatty acid (omega-3-PUFA) and saturated fatty acid (C(12)-C(14), SFA) levels were elevated in HF-F and HF-C animals respectively. The liver histologies showed hepatic steatosis in HF-L, HF-O and HF-C without major inflammation. Hepatic SREBP1c-dependent genes were upregulated in these diets, whereas PPARalpha-dependent genes were predominantly upregulated in HF-F fed rats. We detected classical HF effects only in diets based on lard and olive oil (mainly long-chain, saturated (LC-SFA) and monounsaturated fatty acids (MUFA)). PUFA- or MC-SFA-rich diets did not induce insulin resistance. Diets based on LC-SFA and MUFA induced hepatic steatosis with SREBP1c activation. This points to an intact transcriptional hepatic insulin effect despite resistance to insulin's metabolic actions.

Binding of perfluorinated fatty acids to serum proteins

Perfluorooctane sulfonic acid (PFOS) accumulates in the liver and blood of exposed organisms. The potential for these surfactant molecules to interfere with hormone/protein interactions in blood is of concern given the importance of these interactions. The PFOS binding to serum proteins was investigated by assessing its ability to displace a variety of steroid hormones from specific binding proteins in the serum of birds and fishes. Perfluorooctane sulfonic acid had only a weak ability to displace estrogen or testosterone from carp serum steroid binding proteins. Displacement of cortisone in avian sera occurred at relatively low PFOS concentrations. Corticosterone displacement potency increased with chain length, and sulfonic acids were more potent than carboxylic acids. The PFOS concentrations estimated to cause these effects were 320 microM or greater, equivalent to serum concentrations greater than 160 mg/L. Using mass spectrometry and direct in vitro binding assays, PFOS was demonstrated to bind strongly to bovine serum albumin (BSA) in a 1:1 stoichiometric ratio. It appears that PFOS in serum is in general bound to albumins. Concentrations of PFOS required to saturate albumin would be in excess of 50 to 100 mg/L. Based on current environmental concentrations, it is unlikely that PFOS would cause displacement of hormones from serum proteins in wildlife.

Mercury, fish oils, and the risk of myocardial infarction

BACKGROUND

It has been suggested that mercury, a highly reactive heavy metal with no known physiologic activity, increases the risk of cardiovascular disease. Because fish intake is a major source of exposure to mercury, the mercury content of fish may counteract the beneficial effects of its n-3 fatty acids.

METHODS

In a case-control study conducted in eight European countries and Israel, we evaluated the joint association of mercury levels in toenail clippings and docosahexaenoic acid (C22:6n-3, or DHA) levels in adipose tissue with the risk of a first myocardial infarction among men. The patients were 684 men with a first diagnosis of myocardial infarction. The controls were 724 men selected to be representative of the same populations.

RESULTS

The average toenail mercury level in controls was 0.25 microg per gram. After adjustment for the DHA level and coronary risk factors, the mercury levels in the patients were 15 percent higher than those in controls (95 percent confidence interval, 5 to 25 percent). The risk-factor-adjusted odds ratio for myocardial infarction associated with the highest as compared with the lowest quintile of mercury was 2.16 (95 percent confidence interval, 1.09 to 4.29; P for trend=0.006). After adjustment for the mercury level, the DHA level was inversely associated with the risk of myocardial infarction (odds ratio for the highest vs. the lowest quintile, 0.59; 95 percent confidence interval, 0.30 to 1.19; P for trend=0.02).

CONCLUSIONS

The toenail mercury level was directly associated with the risk of myocardial infarction, and the adipose-tissue DHA level was inversely associated with the risk. High mercury content may diminish the cardioprotective effect of fish intake.

Acridine and phenothiazine derivatives as pharmacotherapeutics for prion disease

Prion diseases in humans and animals are invariably fatal. Prions are composed of a disease-causing isoform (PrP(Sc)) of the normal host prion protein (PrP(C)) and replicate by stimulating the conversion of PrP(C) into nascent PrP(Sc). We report here that tricyclic derivatives of acridine and phenothiazine exhibit half-maximal inhibition of PrP(Sc) formation at effective concentrations (EC(50)) between 0.3 microM and 3 microM in cultured cells chronically infected with prions. The EC(50) for chlorpromazine was 3 microM, whereas quinacrine was 10 times more potent. A variety of 9-substituted, acridine-based analogues of quinacrine were synthesized, which demonstrated variable antiprion potencies similar to those of chlorpromazine and emphasized the importance of the side chain in mediating the inhibition of PrP(Sc) formation. Thus, our studies show that tricyclic compounds with an aliphatic side chain at the middle ring moiety constitute a new class of antiprion reagents. Because quinacrine and chlorpromazine have been used in humans for many years as antimalarial and antipsychotic drugs, respectively, and are known to pass the blood-brain barrier, we suggest that they are immediate candidates for the treatment of Creutzfeldt-Jakob disease and other prion diseases.