The beta-oxidation of arachidonic acid and the synthesis of docosahexaenoic acid are selectively and consistently altered in skin fibroblasts from three Zellweger patients versus X-adrenoleukodystrophy, Alzheimer and control subjects

The beta-oxidation of [3H] arachidonic acid (AA; 20:4 n-6) and the conversion of [1-14C]eicosapentaenoic acid (EPA, 20:5 n-3) to docosahexaenoic acid (DHA, 22:6 n-3) have been studied in skin fibroblasts from patients with inherited peroxisomal diseases, such as Zellweger (ZW) and X-linked adrenoleukodystrophy (X-ALD), from patients with Alzheimer's disease (AD), a non-inherited neuropathology, and from controls. EPA is not converted to DHA, while there is enhanced formation of the intermediate product 22:5 n-3 in ZW, when compared to X-ALD, AD and controls. We also confirmed that AA is not beta-oxidized to 4,7,10-hexadecatrienoic acid (16:3), a metabolite produced by peroxisomes, while being more effectively converted to the elongation product 22:4, in ZW, in comparison to X-ALD, AD and controls. The data demonstrate a defect in DHA synthesis and in AA beta-oxidation, and the occurrence of associated adaptative modifications in the metabolism of these long chain PUFA, in three Italian ZW patients.

Free radical-scavenging properties of olive oil polyphenols

Plants in the Mediterranean basin, such as vine and olive trees, have developed an array of antioxidant defences to protect themselves from environmental stress. Accordingly, the incidence of coronary heart disease and certain cancers is lower in the Mediterranean area, where olive oil is the dietary fat of choice. As opposed to other vegetable oils, extra virgin olive oil, which is obtained by physical pressure from a whole fruit, is rich in phenolic components that are responsible for the particular stability of the oil. We have investigated the scavenging actions of some olive oil phenolics, namely hydroxytyrosol and oleuropein, with respect to superoxide anion generation, neutrophils respiratory burst, and hypochlorous acid. The low EC50S indicate that both compounds are potent scavengers of superoxide radicals and inhibitors of neutrophils respiratory burst: whenever demonstrated in vivo, these properties may partially explain the observed lower incidence of CHD and cancer associated with the Mediterranean diet.

Ethanol enhances cholesterol synthesis and secretion in human hepatomal cells

Excessive consumption of alcohol leads to severe alterations of lipid metabolism, including hyperlipemia and hypercholesterolemia. Following these epidemiological observations, we investigated the effects of ethanol at the cellular level by employing a human hepatomal cell line (HepG2) and by evaluating the biosyntheses of lipid classes from different labeled precursors. Incubation of cells with 2% ethanol resulted in a decreased labeling of phospholipids and in an increase in cholesterol synthesis and secretion. Triglyceride synthesis was increased by ethanol but their secretion in the medium was reduced, suggesting that these alterations may be related to their accumulation in the liver. The alcohol-induced alterations of lipid metabolism are not due to its metabolite acetaldehyde and data suggest that alcohol enhances cholesterol synthesis by affecting the initial steps without increasing HMGCoA expression. The observed modifications of lipid metabolism in HepG2 may partially explain the enhanced incidence of cardiovascular disorders that has been associated with alcoholism.

The effect of minor constituents of olive oil on cardiovascular disease: new findings

There has been much interest regarding the components that contribute to the beneficial health effects of the Mediterranean diet. Recent findings suggest that polyphenolic compounds found in olive oil are endowed with several biologic activities that may contribute to the lower incidence of coronary heart disease in the Mediterranean area.

Oxidation of individual fatty acids yields different profiles of oxidation markers

Free radicals attack lipid molecules and initiate a chain of reactions that may trigger several diseases such as atherosclerosis and cancer. Several markers of oxidative stress have been proposed, including measurements of lipid peroxides and short-chain aldehydes levels and evaluation of conjugated diene formation. Although it is generally assumed that fatty acid oxidizability is directly proportional to their degree of unsaturation, little is known about the contribution of individual fatty acids to each of these markers. We investigated such contributions in a model of AAPH-mediated peroxidation of individual fatty acid micelles by assessing several indices of oxidative stress. The results suggest that the generation of oxidation products by individual fatty acids is not directly related to their degree of unsaturation and indicate that the differential contribution of individual fatty acids should be taken into account and more than one marker of lipid peroxidation should be included in in vivo studies of oxidative stress.

Evaluation of the Abbott LCx Mycobacterium tuberculosis assay in comparison with culture methods in selected Italian patients

A ligase chain reaction (LCR) DNA amplification method for the molecular diagnosis of Mycobacterium tuberculosis (Abbott LCx MTB) was evaluated in comparison with solid and liquid phase culture on 622 selected samples collected in two large Italian hospitals, of which 310 obtained from HIV-1 positive patients and 312 from HIV-negative individuals. The overall prevalence of mycobacteria by culture was 22% (137/622), and the apparent sensitivity and specificity of LCx vs. culture were 87.6% and 98.2%. Of the 26 culture positive/LCx negative samples, 22 were positive for MOTT and 4 for M. tuberculosis. All 9 samples positive by LCx and negative by culture were classified as true positive by clinical criteria. The final values of sensitivity, specificity, positive predictive value and negative predictive value for LCx rose to 96.8%, 100%, 100% and 99.2%, respectively. The adjusted sensitivity of culture methods was 89.5% for solid phase and 92.7% for Bactec. In view of the high sensitivity on both smear-positive (100%) and smear-negative (92.4%) samples and of the high negative predictive value, the LCR-based amplification method appears suitable as a routine screening method for the rapid diagnosis of M. tuberculosis in high-risk patients.

Effects of supplementation with unsaturated fatty acids on plasma and membrane lipid composition and platelet function in patients with cirrhosis and defective aggregation

BACKGROUND/AIMS

Defective platelet aggregation and reduced platelet production of thromboxane A2, a metabolite of arachidonic acid, are common findings in patients with cirrhosis. We evaluated the effects of dietary supplementation with two combinations of unsaturated fatty acids on platelet function and plasma and membrane fatty acids in patients with liver cirrhosis.

METHODS

In a double-blind study, 15 patients with cirrhosis and defective aggregation were randomized to receive a 6-week supplementation with gamma-linolenic and linoleic acid (1 g/day of each fatty acid) or with oleic acid and linoleic acid (groups GLA and OA, respectively).

RESULTS

Under baseline conditions, patients showed elevated concentrations of monounsaturated fatty acids and a reduction in polyunsaturated fatty acids. The product/precursor ratios for delta6 and delta5 desaturases, two key enzymes in the pathway leading to arachidonic acid, were significantly reduced in the group of patients. In the GLA group, a significant increase in the levels of dihomo-gamma-linolenic acid (20:3omega6) was observed in plasma and membranes, together with a parallel decrease in the 20:4/20:3omega6 ratio after supplementation. No significant changes were observed in the OA group. The levels of arachidonic acid did not change significantly in either group of patients. Platelet aggregation to collagen was unchanged in the GLA group, but significantly improved in the OA group.

CONCLUSIONS

These results show that supplementation with precursors of arachidonic acid is ineffective in elevating plasma or membrane arachidonate levels and does not improve platelet aggregation, suggesting that synthesis of arachidonic acid through the delta5 desaturase cannot be correspondingly activated or that incorporation/retention of the produced fatty acid into lipids is impaired. The increased platelet aggregation in the OA group is likely to be explained by the effect of oleic acid contained in the diet, the effects of which may have been counteracted by the elevation in 20:3omega6, a source of anti-aggregatory prostanoids, in the GLA group.

S-adenosyl-L-methionine: role in phosphatidylcholine synthesis and in vitro effects on the ethanol-induced alterations of lipid metabolism

Hepatic lipid metabolism is extremely modified by excessive ethanol consumption, but the cellular mechanisms of such alterations are still largely unexplored. S-Adenosyl-L-methionine (SAMe) is known as an important methylating agent and as a precursor of glutathione and it has been shown to prevent some of the toxic effects of ethanol in the liver. We therefore studied the effects of ethanol on cholesterol synthesis in a human hepatomal cell line (HepG2), the kinetics of SAMe, and its putative protective effects on the alterations of lipid metabolism induced by toxic concentrations of alcohol. Incubation of HepG2 cells with [3H]SAMe resulted in a progressive increase in the labelling of phosphatidylcholine and of its two intermediates during synthesis starting from phosphatidylethanolamine. This process is enzymatic, since it does not take place in heat-inactivated cells. Also, ethanol induced an increase in cholesterol and triglycerides syntheses and a decrease in phospholipid labelling. These alterations were not prevented by SAMe 10(-4) M, indicating that the protective effects of the drug are related to other mechanisms of action such as reduced formation of collagen, restoration of glutathione levels, and normalization of membrane functions.

Oleuropein, the bitter principle of olives, enhances nitric oxide production by mouse macrophages

The Mediterranean diet, rich in fresh fruits and vegetables, has been associated with a lower incidence of cardiovascular disease and cancer, partly because of its high proportion of bioactive compounds such as vitamins, flavonoids and polyphenols. The major lipid component of such diet is the drupe-derived olive oil, that can be distinguished from other seed oils for the peculiar composition of its non-triglyceride fraction. In fact, several minor components, including polyphenols, grant the oil its particular taste and aroma. Oleuropein, the most abundant among these components, has been shown to be a potent antioxidant endowed with antiinflammatory properties. We investigated the effects of oleuropein on NO release in cell culture and its activity toward nitric oxide synthase (iNOS) expression. The results show that oleuropein dose-dependently enhance nitrite production in LPS-challenged mouse macrophages. This effect was blocked by the iNOS inhibitor L-NAME, indicating increased iNOS activity. Also, Western blot analysis of cell homogenates show that oleuropein increases iNOS expression in such cells. Taken together, our data suggest that, during endotoxin challenge, oleuropein potentiates the macrophage-mediated response, resulting in higher NO production, currently believed to be beneficial for cellular and organismal protection.

[Neuroradiologic study of partial temporal epilepsy]

MR imaging is considered the neuroradiological procedure of choice for the study of intractable partial epileptic patients. The role of CT-scan is limited to the demonstration of calcific components of the lesion and of bony abnormalities of the adjacent skull. In this chapter we describe an MR protocol for the evaluation of temporal lobe epilepsy patient; moreover, here there are described neuroradiological characteristics (MR and CT) of the more frequent temporal lobe lesions.

Increased amyloidogenic secretion in cerebellar granule cells undergoing apoptosis

Some clues suggest that neuronal damage induces a secondary change of amyloid beta protein (Abeta) metabolism. We investigated this possibility by analyzing the secretion of Abeta and processing of its precursor protein (amyloid precursor protein, APP) in an in vitro model of neuronal apoptosis. Primary cultures of rat cerebellar granule neurons were metabolically labeled with [35S]methionine. Apoptosis was induced by shifting extracellular KCl concentration from 25 mM to 5 mM for 6 h. Control and apoptotic neurons were then subjected to depolarization-stimulated secretion. Constitutive and stimulated secretion media and cell lysates were immunoprecipitated with antibodies recognizing regions of Abeta, full-length APP, alpha- and beta-APP secreted forms. Immunoprecipitated proteins were separated by SDS/PAGE and quantitated with a PhosphorImager densitometer. Although intracellular full-length APP was not significantly changed after apoptosis, the monomeric and oligomeric forms of 4-kDa Abeta were 3-fold higher in depolarization-stimulated secretion compared with control neurons. Such increments were paralleled by a corresponding increase of the beta-APPs/alpha-APPs ratio in apoptotic secretion. Immunofluorescence studies performed with an antibody recognizing an epitope located in the Abeta sequence showed that the Abeta signal observed in the cytoplasm and in the Golgi apparatus of control neurons is uniformly redistributed in the condensed cytoplasm of apoptotic cells. These studies indicate that neuronal apoptosis is associated with a significant increase of metabolic products derived from beta-secretase cleavage and suggest that an overproduction of Abeta may be the consequence of neuronal damage from various causes.

In vitro techniques for the assessment of neurotoxicity

Risk assessment is a process often divided into the following steps: a) hazard identification, b) dose-response assessment, c) exposure assessment, and d) risk characterization. Regulatory toxicity studies usually are aimed at providing data for the first two steps. Human case reports, environmental research, and in vitro studies may also be used to identify or to further characterize a toxic hazard. In this report the strengths and limitations of in vitro techniques are discussed in light of their usefulness to identify neurotoxic hazards, as well as for the subsequent dose-response assessment. Because of the complexity of the nervous system, multiple functions of individual cells, and our limited knowledge of biochemical processes involved in neurotoxicity, it is not known how well any in vitro system would recapitulate the in vivo system. Thus, it would be difficult to design an in vitro test battery to replace in vivo test systems. In vitro systems are well suited to the study of biological processes in a more isolated context and have been most successfully used to elucidate mechanisms of toxicity, identify target cells of neurotoxicity, and delineate the development and intricate cellular changes induced by neurotoxicants. Both biochemical and morphological end points can be used, but many of the end points used can be altered by pharmacological actions as well as toxicity. Therefore, for many of these end points it is difficult or impossible to set a criterion that allows one to differentiate between a pharmacological and a neurotoxic effect. For the process of risk assessment such a discrimination is central. Therefore, end points used to determine potential neurotoxicity of a compound have to be carefully selected and evaluated with respect to their potential to discriminate between an adverse neurotoxic effect and a pharmacologic effect. It is obvious that for in vitro neurotoxicity studies the primary end points that can be used are those affected through specific mechanisms of neurotoxicity. For example, in vitro systems may be useful for certain structurally defined compounds and mechanisms of toxicity, such as organophosphorus compounds and delayed neuropathy, for which target cells and the biochemical processes involved in the neurotoxicity are well known. For other compounds and the different types of neurotoxicity, a mechanism of toxicity needs to be identified first. Once identified, by either in vivo or in vitro methods, a system can be developed to detect and to evaluate predictive ability for the type of in vivo neurotoxicity produced. Therefore, in vitro tests have their greatest potential in providing information on basic mechanistic processes in order to refine specific experimental questions to be addressed in the whole animal.

Psychiatric comorbidity in chronic daily headache

Clinical evidence suggests that chronic daily headache (CDH) occurs in association with psychopathologies: previous studies have focused particularly on migraine. To evaluate this association, we studied, using the DSM-IIIR criteria, a population of 88 patients (18M, 70F) affected by CDH (mean duration 7.4 +/- 8.7 years). We documented the presence of a psychiatric disorder in 90% of this population. The most frequent diagnosis was a comorbidity of anxiety and mood disorders. The comorbidity of psychiatric disorders and headache has important implications as far as treatment is concerned.

Selective inhibition of Ii-dependent antigen presentation by Helicobacter pylori toxin VacA

A major virulence factor in the stomach chronic infection by Helicobacter pylori is a protein toxin (VacA), which alters cell membrane trafficking of late endosomal/prelysosomal compartments. Its role in the chronic infection established by H. pylori is unknown. To test the possibility that VacA alters antigen processing taking place in prelysosomal compartments, we have used the well-established model of antigen processing and presentation consisting of tetanus toxoid-specific human (CD4(+)) T cells stimulated by autologous antigen-pulsed Epstein-Barr virus-transformed B cells. We found that VacA interferes with proteolytic processing of tetanus toxin and toxoid and specifically inhibits the Ii-dependent pathway of antigen presentation mediated by newly synthesized major histocompatibility complex (MHC) class II, while leaving unaffected the presentation pathway dependent on recycling MHC class II. The results presented here suggest that VacA may contribute to the persistence of H. pylori by interfering with protective immunity and that this toxin is a new useful tool in the study of the different pathways of antigen presentation.

Plasma arachidonic acid and serum thromboxane B2 concentrations in phenylketonuric children are correlated with dietary compliance

Phenylketonurics display lower arachidonic acid levels in plasma lipids, reflecting the lower intake due to the dietary treatment poor in phenylalanine-rich animal foods. Plasma arachidonic acid levels and serum thromboxane B2 concentrations have been measured in 13 treated phenylketonuric children and compared with those of 12 healthy controls. A direct relationship between plasma arachidonic acid and thromboxane B2 concentrations has been observed only in phenylketonurics, whose plasma arachidonic acid status correlated negatively with their dietary compliance. These results suggest that the low consumption of animal fats may contribute to modulate the production of arachidonic acid-derived platelet eicosanoids.

Action site and cellular effects of cytotoxin VacA produced by Helicobacter pylori

Cells treated with the VacA toxin from Helicobacter pylori develop large membrane-bound vacuoles that originate from the late endocytotic pathway. Using different experimental approaches, we showed that VacA can induce vacuoles by acting within the cell cytosol. Moreover, separation of VacA-induced vacuoles at an early stage of formation, using a novel isopycnic density ultracentrifugation method, allowed us to show that they resemble a hybrid compartment, containing elements of both late endosomes and lysosomes. Functional defects of the endocytotic pathway were also studied before any macroscopic vacuolation is evident. VacA-intoxicated cells degrade extracellular ligands with reduced efficiency and, at the same time, they secrete acidic hydrolases into the extracellular medium, normally sorted to lysosomes. All these findings indicate that VacA translocates into the cell cytosol where it causes a lesion of the late endosomal/lysosomal compartments, such that protein trafficking across this crucial cross-point is altered with consequences that may be relevant to the pathogenesis of gastroduodenal ulcers.

Premenstrual dysphoric disorder and eating disorders

Premenstrual Dysphoric Disorder (PMDD) can be differentiated from Premenstrual Syndrome (PMS) by the use of the research criteria provided by the Diagnostic and Statistical Manual (DSM) IV. Indeed, PMS corresponds to mild clinical symptoms, such as breast tenderness, bloating, headache and concomitant minor mood changes, while premenstrual magnification occurs when physical and psychological symptoms of a concurrent axis I disorder get worse during the late luteal phase. Changes in appetite and eating behavior have been documented in women suffering from PMS, with an increased food intake occurring during the luteal phase. Moreover, in women with PMS, a major effect of the phase of the menstrual cycle on appetite has been documented and a high correlation with self-ratings of mood, particularly depression, has been described only in such disturbance. The aim of the present study was to analyse the clinical similarities between PMDD and Eating Disorders (in particular Bulimia Nervosa and Binge Eating Disorder). Thus, we compared the DSM III-R comorbidity, the personality dimensions and the eating attitudes in these patients, attempting to identify any relationship between groups. Twelve PMDD women (mean age 28 years), diagnosed using DSM IV criteria and premenstrual assessor form, were compared with 10 eating disorder (ED) women (6 Bulimia Nervosa, 4 Binge Eating Disorder) (mean age 25 years) and with 10 control women matched for age. The following instruments were used: (i) clinical interview with DSM III-R criteria (SCID); (ii) a psychometric study with TPQ for the evaluation of three personality dimensions (novelty seeking, harm avoidance and reward dependence); (iii) EAT/26 for the evaluation of eating attitudes. Results show that a high comorbidity for mood and anxiety disorders in PMDD and ED is well documented. Our PMDD patients share a 16.6% of comorbidity with ED, whereas such an association is present only in 2.3% of the general population. In addition, as a common clue, the personality dimension, harm avoidance, linked to a serotonin mediation is significantly more frequent in PMDD and ED than in normal controls.

IN CONCLUSION

from the present study it seems clear that a certain degree of similarity exists between the PMDD and ED. However, whether or not these two disorders really share common ground from a physiopathological point of view still has to be clarified by more extensive studies.

Recent advances in the biology of n-6 fatty acids

The intensive research carried out in the last 10 years on the unique biological functions of n-3 fatty acids (FA), has promoted comparative investigations on various aspects (metabolic, functional) of the biology of n-6 FA. The involvement of peroxisomes in fatty acid metabolism, initially described for the n-3 acids, has now been shown also for the n-6 FA (formation of 22 carbon delta 4 unsaturated FA, formation of newly identified products of beta-oxidation of arachidonic acid, AA). Additional pathways of AA conversion, beyond the classical eicosanoids, give rise to a series of biologically active products, such as the epoxides, involved in the modulation of vascular functions, through the cytochrome p450 system, and to the AA-ethanolamide, anandamide, an endogenous ligand of the cannabinoid receptors, through a phospholipase-mediated process. Finally, nonenzymatic oxidation products of AA, the isoprostanes, isomers of prostaglandins, also endowed of potent biological activities, are generated both in in vitro-induced lipid oxidation and in vivo, being considered as reliable markers of in vivo oxidative stress. As to the nutritional aspects of the n-6 FA, attention is now paid to the intake of preformed long-chain polyunsaturated FA (PUFA) in the n-6 series, mainly AA, through the diet, in analogy with the intake of the long-chain n-3 FA, in fish-eating populations. The importance of the dietary intake of preformed AA is now recognized in newborns, through maternal milk. The ranges of the intakes of AA in population groups, not currently adequately estimated, appear to be wider than generally assumed, and the elevated intakes in some population groups, in the order of several hundred milligrams per day, may be partly responsible of yet unexplored population-based differences in physiologic variables. Recent research on the functional effects of n-6 FA has confirmed their lipid-lowering effects, which can be observed also in neonates, and has shown that, in cooperation with the n-3, they directly and indirectly contribute to modulate functional parameters at the cellular level, such as receptor function, ion channels, and gene expression. From a nutritional point of view, it is clear that PUFA represent the biologically most active component of dietary fat, and the n-6 are quantitatively the most relevant fraction in our diet. In the light of the diversified activities of n-6 and n-3 PUFA, a correct balance between the various fatty acids is recommended.

Vacuoles induced by Helicobacter pylori toxin contain both late endosomal and lysosomal markers

Intoxication of mammalian cells with the vacuolating toxin (VacA) released by Helicobacter pylori causes the formation of large acidic vacuoles containing the vacuolar ATPase proton pump and Rab7, a late endosome marker. Here, we describe a novel subcellular fractionation procedure, and we show that nanomolar concentrations of VacA induce a clear redistribution of lysosomal membrane glycoproteins among endocytic compartments. This redistribution is an early event in the process of cellular intoxication by VacA and precedes the formation of macroscopic vacuoles. The absence of the cation independent mannose 6-P receptor and the presence of Rab7 and of lysosomal membrane proteins in the newly formed compartment suggest that the vacuolating toxin induces the accumulation of a post-endosomal hybrid compartment presenting both late endosomal and lysosomal features.

Changes in right ventricular filling dynamics during left anterior descending, left circumflex and right coronary artery balloon occlusion

AIM

Transient coronary artery occlusion during percutaneous transluminal coronary angioplasty may cause left ventricular diastolic dysfunction. The aim of this study was to evaluate the effect of left anterior descending, left circumflex and right coronary artery balloon occlusion on right ventricular diastolic function.

METHODS

Thirty-five patients with single-vessel coronary artery disease and no previous myocardial infarction were selected. Left and right ventricular filling pressures were monitored by Doppler echocardiography and haemodynamic monitoring. This was performed during and immediately after 60 s of coronary balloon occlusion of the left anterior descending artery in 21 cases (Group 1), the left circumflex artery in eight cases (Group 2) and the right coronary artery in six cases (Group 3). Doppler analysis of left and right ventricular filling included peak velocity of early (PFVE) and late ventricular filling (PFVA) and PFVE to PFVA ratio (PFVE/PFVA).

RESULTS

In all three groups, balloon inflation induced a significant increase in left and right filling pressures (P < 0.05). No qualitative difference in haemodynamic changes was found between groups during inflation. Significant impairment in the Doppler pattern of left and right ventricular filling occurred after 20 s of coronary occlusion: PFVE values in mitral and tricuspid valves decreased by 14% and 25% in Group 1, 13% and 25% in Group 2, and 10% and 21% in Group 3, respectively, as PFVA remained unchanged in all groups, the PFVE/PFVA ratio of mitral and tricuspid valve flows significantly decreased (Group 1: -12% and -20%, Group 2: -10% and -21%, Group 3: -14% and -21%, respectively). All parameters returned to baseline within 30 s after each balloon deflation.

CONCLUSION

Our data suggest that brief episodes of acute myocardial ischaemia, such as those induced by 60 s of coronary artery occlusion during percutaneous transluminal coronary angioplasty, elicit simultaneous diastolic dysfunction of both ventricles, independent of the coronary artery involved.

Inhibition of leukocyte leukotriene B4 production by an olive oil-derived phenol identified by mass-spectrometry

We have evaluated the effects of hydroxytyrosol (HT), a potent antioxidant present in olive oil, on the formation of arachidonic acid 5-lipoxygenase metabolites by leukocytes in vitro. HT, a simple phenolic compound, extracted from first-pressure oil, was isolated by HPLC and characterized by gas chromatography/mass spectrometry. HT inhibited in a dose-related manner the production of leukotriene B4 (LTB4) by calcium ionophore-stimulated leukocytes. As expected, similar inhibition was observed for omega-oxidized metabolites of LTB4, namely 20-hydroxy and 20-carboxy-LTB4. The results disclose a new biological activity of olive oil-derived phenols on leukocyte eicosanoid production.

Effects of simvastatin on the metabolism of polyunsaturated fatty acids and on glycerolipid, cholesterol, and de novo lipid synthesis in THP-1 cells

In the monocytic THP-1 cells, the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor simvastatin (5 microM) enhances the conversion of exogenous linoleic (18:2 n-6) and eicosapentaenoic (20:5 n-3) acids to their long-chain polyunsaturated fatty acid (LC-PUFA) derivatives, and this effect is associated with changes in the desaturation steps. In addition, formation of monounsaturated fatty acids from endogenously synthesized precursors is increased. These metabolic changes lead to elevated LC-PUFA and fatty acid (FA) unsaturation in cells. The effects of simvastatin on FA metabolism are associated with increased synthesis of triglycerides from glycerol. The dose-effect relationships for the activity of simvastatin on total linoleic acid (LA) conversion and cholesterol synthesis reveal that enhancement of PUFA metabolism is already maximal at 0.5 microM simvastatin, whereas cholesterol synthesis is further inhibited by concentrations of simvastatin up to 5 microM. The effects of 5 microM simvastatin on PUFA metabolism are partially prevented by mevalonate (1 mM) and geranylgeraniol (5 microM) but not by farnesol (10 microM). These data indicate that HMG-CoA inhibitors have profound effects on PUFA metabolism, and that the pathways for cholesterol and PUFA synthesis are mutually modulated.