Showing papers on "Fatty acid published in 1994"

Arabidopsis FAD2 Gene Encodes the Enzyme That Is Essential for Polyunsaturated Lipid Synthesis

Abstract: The polyunsaturated fatty acids linoleate and alpha-linolenate are important membrane components and are the essential fatty acids of human nutrition. The major enzyme responsible for the synthesis of these compounds is the plant oleate desaturase of the endoplasmic reticulum, and its activity is controlled in Arabidopsis by the fatty acid desaturation 2 (fad2) locus. A fad2 allele was identified in a population of Arabidopsis in which mutations had been created by T-DNA insertions. Genomic DNA flanking the T-DNA was cloned by plasmid rescue and used to isolate cDNA and genomic clones of FAD2. A cDNA containing the entire FAD2 coding sequence was expressed in fad2 mutant plants and shown to complement the mutant fatty acid phenotype. The deduced amino acid sequence from the cDNA showed homology to other plant desaturases, and this confirmed that FAD2 is the structural gene for the desaturase. Gel blot analyses of FAD2 mRNA levels showed that the gene is expressed throughout the plant and suggest that transcript levels are in excess of the amount needed to account for oleate desaturation. Sequence analysis identified histidine-rich motifs that could contribute to an iron binding site in the cytoplasmic domain of the protein. Such a position would facilitate interaction between the desaturase and cytochrome b5, which is the direct source of electrons for the desaturation reaction, but would limit interaction of the active site with the fatty acyl substrate.

Long-term exposure of rat pancreatic islets to fatty acids inhibits glucose-induced insulin secretion and biosynthesis through a glucose fatty acid cycle.

Abstract: We tested effects of long-term exposure of pancreatic islets to free fatty acids (FFA) in vitro on B cell function. Islets isolated from male Sprague-Dawley rats were exposed to palmitate (0.125 or 0.25 mM), oleate (0.125 mM), or octanoate (2.0 mM) during culture. Insulin responses were subsequently tested in the absence of FFA. After a 48-h exposure to FFA, insulin secretion during basal glucose (3.3 mM) was severalfold increased. However, during stimulation with 27 mM glucose, secretion was inhibited by 30-50% and proinsulin biosynthesis by 3040%. Total protein synthesis was similarly affected. Conversely, previous palmitate did not impair a-ketoisocaproic acid (5 mM)-induced insulin release. Induction and reversibility ofthe inhibitory effect on glucose-induced insulin secretion required between 6 and 24 h. Addition of the carnitine palmitoyltransferase I inhibitor etomoxir (1 ,uM) partially reversed (by > 50%) FFA-associated decrease in secretory as well as proinsulin biosynthetic responses to 27 mM glucose. The inhibitory effect of previous palmitate was similar when co-culture was performed with 5.5, 11, or 27mM glucose. Exposure to palmitate or oleate reduced the production of 14CO2 from D-[U-14C1 glucose, and of "4CO2 from D-13,4-"CIglucose, both effects being reversed by etomoxir. Conclusions: long-term exposure to FFA inhibits glucose-induced insulin secretion and biosynthesis probably through a glucose fatty acid

Fatty acid synthesis: a potential selective target for antineoplastic therapy

Abstract: OA-519 is a prognostic molecule found in tumor cells from breast cancer patients with markedly worsened prognosis. We purified OA-519 from human breast carcinoma cells, obtained its peptide sequence, and unambiguously identified it as fatty acid synthase through sequence homology and enzymology. Tumor fatty acid synthase is an approximately 270-kDa polypeptide which specifically abolished immunostaining of human breast cancers by anti-OA-519 antibodies. Tumor fatty acid synthase oxidized NADPH in a malonyl-CoA-dependent fashion and synthesized fatty acids composed of 80% palmitate, 10% myristate, and 10% stearate from acetyl-CoA, malonyl-CoA, and NADPH with a specific activity of 624 nmol of NADPH oxidized per min per mg. Tumor cell lines with elevated fatty acid synthase showed commensurate increases in incorporation of [U-14C]acetate into acylglycerols demonstrating that fatty acid synthase increases occur in the context of overall increases in endogenous fatty acid synthesis. Cerulenin inhibited acylglycerol synthesis in tumor cells and fibroblast controls in a dose-dependent fashion and also caused a growth inhibition which generally paralleled the level of endogenous fatty acid synthesis. Supraphysiologic levels of palmitate, 14 microM in dimethyl sulfoxide, significantly reversed the growth inhibition caused by cerulenin at concentrations of up to 5 micrograms/ml, indicating that cerulenin-mediated growth inhibition was due to fatty acid synthase inhibition.

The animal fatty acid synthase: one gene, one polypeptide, seven enzymes.

Abstract: The animal fatty acid synthase comprises two multifunctional polypeptide chains, each containing seven discrete functional domains, juxtaposed head-to-tail such that two separate centers for fatty acid assembly are formed at the subunit interface. The kinetics and specificities of the component enzymes are well adapted to ensure that, at each of the two centers, the iterative condensation of an acetyl moiety with successive malonyl moieties and complete reduction of the beta-keto intermediates normally results in the formation of palmitic acid as the major product. Nevertheless, utilization of alternative substrates and alternative chain-terminating mechanisms can extend the range of products to include branched-chain, odd carbon-numbered, and shorter chain-length fatty acids. The potential of this multifunctional form of molecular architecture for the elaboration of more complex natural products has been further exploited in microorganisms that, by the use of different fatty acid synthase "modules" that ...

Effect of nutrient limitation on fatty acid and lipid content of marine microalgae1

Abstract: Phaeodactylum tricornutum and Chaetoceros sp. (Badllariophyceae), Isochrysis galbana (clone T-Iso) and Pavlova lutheri (Prymnesiophyceae), Nannochloris atomus (Chlorophyceae), Tetraselmis sp. (Prasinophyceae), and Gymnodinum sp. (Dinophyceae) were cultured at different extents of nutrient-limited growth: 50 and 5% of μmax. The lipid content of the algae was in the range 8.3–29.5% of dry matter and was generally higher in the Prymnesiophyceae than in the Prasinophyceae and the Chlorophyceae. Increasing extent of phosphorus limitation resulted in increased lipid content in the Bacillariophyceae and Prymnesiophyceae and decreased lipid content in the green flagellates N. atomus and Tetraselmis sp. The fatty acid composition of the algae showed taxonomic conformity, especially for the Bacillariophyceae, where the major fatty adds were 14:0, 16:0, 16:1, and 20:5n-3. These fatty acids were dominant also in the Prymnesiophyceae together with 22:6n-3. An exception was I. galbana, in which 18:1 was the major monounsaturated fatty add and 20:5n-3 was absent. The fatty acids of N. atomus and Tetraselmis sp. varied somewhat, but 16:0, 16:1, 18:1, 18:3n-3, and 20:5n-3 were most abundant. Gymnodinum sp. contained mainly 16:0, 18:4n-3, 20: 5n-3, and 22:6n-3. An increased level of nutrient limitation (probably phosphorus) resulted in a higher relative content of 16:0 and 18:1 and a lower relative content of 18:4n-3, 20:5n-3, and 22:6n-3. The nutrient limitation probably reduced the synthesis of n-3 polyunsaturated fatty acids.

In situ preparation of fatty acid methyl esters for analysis of fatty acid composition in foods

Abstract: Lipid extraction preceding fatty acid methyl esters (FAME) preparation for gas chromatography is time-consuming and cumbersome. We omitted the lipid extraction and performed in situ transesterification (ISTE) by heating lipid-containing foods at 90°for 10 min after adding 0.5N NaOH in methanol for methanolysis and continued heating another 10 min for further methylation after adding 14% BF3 in methanol. FAME prepared by ISTE showed fatty acid composition virtually identical to FAME prepared after lipid extraction from powder, liquid, phospholipid-rich, and tissue products. Due to its simplicity, speed, and reduced organic solvent usage, ISTE should be useful to determine overall fatty acid composition of foods.

Preparation of fatty acid methyl esters for gas-chromatographic analysis of lipids in biological materials

Abstract: Theoretically, preparation of fatty acid methyl esters (FAMEs) deals with reversible chemical reactions in a complex system. Methodologically, there are numerous ways, generally characterized by the type of catalysts used and steps involved. Although there are more than a half dozen common catalysts, the majority fall into either acidic (HCl, H2SO4 and BF3) or alkaline types (NaOCH3, KOH and NaOH), with each having its own catalytic capability and application limitations. In terms of steps, many conventional methods, including those officially recognized, consist of drying, digestion, extraction, purification, alkaline hydrolysis, transmethylation/methylation and postreaction work-up. Although these methods are capable of providing reliable estimates if some precautions are taken, they are cumbersome, time-consuming and cost-inefficient. A new approach has been to transmethylate lipidsin situ. Due to its simplicity, high sensitivity, comparable reliability and capability to determine total fatty acids, the method of direct transmethylation is finding a unique place in lipid determination. Regardless of which method is used, quantitative methylation requires chemists to take precautions at every step involved, particularly during FAME formation and subsequent recovery steps. Evidently, there is an urgent need for more systematic studies, guided by the chemical principle of reactions involved and physicochemical properties of regents and end products, into factors affecting these steps. Hopefully, this will lead to an improved method, which measures lipid composition in biological materials not only with high accuracy but also with high efficiency and minimum costs.

Prospective Study of Plasma Fatty Acids and Risk of Prostate Cancer

Abstract: BACKGROUND: Although some evidence suggests that dietary fat intake is related to prostate cancer, epidemiologic studies have been inconsistent. PURPOSE: Our purpose was to assess the association between plasma lipid levels, particularly linoleic and alpha-linolenic acids, and the development of prostate cancer. METHODS: In 1982, at the start of the Physicians' Health Study, 14916 U.S. male physicians provided plasma samples, which were frozen at -82 degrees C. Data accumulated from a series of questionnaires were used to assess the intake of various foods. We used a nested case-control design to compare the fatty acid compositions in plasma from 120 men who later developed prostate cancer with 120 matched controls who did not. Individual fatty acids were measured in plasma as a percentage of total fatty acids, using capillary gas chromatography. Conditional logistic regression models were used to obtain odds ratio estimates while adjusting simultaneously for the effects of one or more potential confounders. RESULTS: The relative risks (RRs) of prostate cancer for men in successively higher quartiles of plasma alpha-linolenic acid level were 3.0 (95% confidence interval [CI] = 1.2-7.3), 3.4 (95% CI = 1.6-7.5), and 2.1 (95% CI = 0.9-4.9), compared with those with levels below the detection threshold (P trend =.03). For linoleic acid, RRs in successively higher quartiles were 0.7 (95% CI = 0.4-1.5), 0.8 (95% CI = 0.4-1.6), and 0.6 (95% CI = 0.3-1.3), with the lowest quartile as referent (P trend =.24). The effect estimates were not notably altered by adjustment for exercise, body mass, meat and dairy consumption, or other fatty acid levels in the plasma. The RR for eating red meat at least five times per week compared with less than once a week was 2.5 (95% CI = 0.9-6.7) and was little changed by adjustment for alpha-linolenic acid, although alpha-linolenic acid levels were correlated with intake of red meat and butter. The association of alpha-linolenic acid levels with prostate cancer was greater among men with low linoleic acid and reduced meat intake. CONCLUSIONS: These results suggest that low plasma levels of alpha-linolenic acid might be associated with reduced risk of prostate cancer, independently of high meat intake. High linoleic acid and low marine fatty oils were not associated with increased risk, as previously hypothesized. IMPLICATIONS: The effects of dietary alpha-linolenic acid, particularly from vegetable sources, warrant further study. The effects of dietary linoleic acid and marine fatty acids seen in animal bioassays might not apply to human prostate cancer.

Heterotrophic production of long chain omega-3 fatty acids utilizing algae and algae-like microorganisms

Abstract: Although some interest in growing microalgae heterotrophically for the production of pigments was generated in the 1960s, only minimal commercial research was focused on this type of production technology until the 1980s. Recent developments indicating the nutritional and pharmaceutical importance of long chain omega-3 polyunsaturated fatty acids in the human diet have stimulated interest in microalgae as a source of these vital compounds, for they are the primary producers of these fatty acids in marine food webs. Food and pharmaceutical quality production can be enhanced both by the degree of process control and by the sterility achieved through a fermentation process, when compared to outdoor solar pond production. The data presented illustrate that microalgal-based heterotrophic production systems can exhibit omega-3 fatty acid productivities 2–3 orders of magnitude greater than those of outdoor pond systems. Additionally, long chain omega-3 fatty acid productivities reported for the microalgal fermentation systems are 1–2 orders of magnitude greater than productivities reported for fungal or bacterial systems.

Accuracy, reproducibility, and interpretation of Fatty Acid methyl ester profiles of model bacterial communities.

Abstract: We determined the accuracy and reproducibility of whole-community fatty acid methyl ester (FAME) analysis with two model bacterial communities differing in composition by using the Microbial ID, Inc. (MIDI), system. The biomass, taxonomic structure, and expected MIDI-FAME profiles under a variety of environmental conditions were known for these model communities a priori. Not all members of each community could be detected in the composite profile because of lack of fatty acid “signatures” in some isolates or because of variations (approximately fivefold) in fatty acid yield across taxa. MIDI-FAME profiles of replicate subsamples of a given community were similar in terms of fatty acid yield per unit of community dry weight and relative proportions of specific fatty acids. Principal-components analysis (PCA) of MIDI-FAME profiles resulted in a clear separation of the two different communities and a clustering of replicates of each community from two separate experiments on the first PCA axis. The first PCA axis accounted for 57.1% of the variance in the data and was correlated with fatty acids that varied significantly between communities and reflected the underlying community taxonomic structure. On the basis of our data, community fatty acid profiles can be used to assess the relative similarities and differences of microbial communities that differ in taxonomic composition. However, detailed interpretation of community fatty acid profiles in terms of biomass or community taxonomic composition must be viewed with caution until our knowledge of the quantitative and qualitative distribution of fatty acids over a wide variety of taxa and the effects of growth conditions on fatty acid profiles is more extensive.

Changes in Ester-Linked Phospholipid Fatty Acid Profiles of Subsurface Bacteria during Starvation and Desiccation in a Porous Medium

Abstract: Ester-linked phospholipid fatty acid (PLFA) profiles of a Pseudomonas aureofaciens strain and an Arthrobacter protophormiae strain, each isolated from a subsurface sediment, were quantified in a starvation experiment in a silica sand porous medium under moist and dry conditions. Washed cells were added to sand microcosms and maintained under saturated conditions or subjected to desiccation by slow drying over a period of 16 days to final water potentials of approximately - 7.5 MPa for the P. aureofaciens and - 15 MPa for the A. protophormiae. In a third treatment, cells were added to saturated microcosms along with organic nutrients and maintained under saturated conditions. The numbers of culturable cells of both bacterial strains declined to below detection level within 16 days in both the moist and dried nutrient-deprived conditions, while direct counts and total PLFAs remained relatively constant. Both strains of bacteria maintained culturability in the nutrient-amended microcosms. The dried P. aureofaciens cells showed changes in PLFA profiles that are typically associated with stressed gram-negative cells, i.e., increased ratios of saturated to unsaturated fatty acids, increased ratios of trans- to cis-monoenoic fatty acids, and increased ratios of cyclopropyl fatty acids to their monoenoic precursors. P. aureofaciens starved under moist conditions showed few changes in PLFA profiles during the 16-day incubation, whereas cells incubated in the presence of nutrients showed decreases in the ratios of both saturated fatty acids to unsaturated fatty acids and cyclopropyl fatty acids to their monoenoic precursors. The PLFA profiles of A. protophormiae changed very little in response to either nutrient deprivation or desiccation. Diglyceride fatty acids, which have been proposed to be indicators of dead or lysed cells, remained relatively constant throughout the experiment. Only the A. protophormiae desiccated for 16 days showed an increase in the ratio of diglyceride fatty acids to PLFAs. The results of this laboratory experiment can be useful for interpreting PLFA profiles of subsurface communities of microorganisms for the purpose of determining their physiological status.

Alteration of the specificity and regulation of fatty acid synthesis of Escherichia coli by expression of a plant medium-chain acyl-acyl carrier protein thioesterase.

Abstract: The expression of a plant (Umbellularia californica) medium-chain acyl-acyl carrier protein (ACP) thioesterase (BTE) cDNA in Escherichia coli results in a very high level of extractable medium-chain-specific hydrolytic activity but causes only a minor accumulation of medium-chain fatty acids. BTE9s full impact on the bacterial fatty acid synthase is apparent only after expression in a strain deficient in fatty acid degradation, in which BTE increases the total fatty acid output of the bacterial cultures fourfold. Laurate (12:0), normally a minor fatty acid component of E. coli, becomes predominant, is secreted into the medium, and can accumulate to a level comparable to the total dry weight of the bacteria. Also, large quantities of 12:1, 14:0, and 14:1 are made. At the end of exponential growth, the pathway of saturated fatty acids is almost 100% diverted by BTE to the production of free medium-chain fatty acids, starving the cells for saturated acyl-ACP substrates for lipid biosynthesis. This results in drastic changes in membrane lipid composition from predominantly 16:0 to 18:1. The continued hydrolysis of medium-chain ACPs by the BTE causes the bacterial fatty acid synthase to produce fatty acids even when membrane production has ceased in stationary phase, which shows that the fatty acid synthesis rate can be uncoupled from phospholipid biosynthesis and suggests that acyl-ACP intermediates might normally act as feedback inhibitors for fatty acid synthase. As the fatty acid synthesis is increasingly diverted to medium chains with the onset of stationary phase, the rate of C12 production increases relative to C14 production. This observation is consistent with activity of the BTE on free acyl-ACP pools, as opposed to its interaction with fatty acid synthase-bound substrates. Images

Dietary polyunsaturated fatty acid regulation of gene transcription.

Abstract: We have known for nearly 30 years that dietary polyenoic (n-6) and (n-3) fatty acids potentially inhibit hepatic fatty acid biosynthesis. The teleological explanation for this unique action of PUFAs resides in their ability to suppress the synthesis of (n-9) fatty acids. By inhibiting fatty acid biosynthesis, dietary PUFAs reduce the availability of substrate for delta 9 desaturase (7, 22, 34, 36) and in turn reduce the availability of (n-9) fatty acids for incorporation into plasma membranes. In this way, essential biological processes dependent on essential fatty acids (e.g. reproduction and trans-dermal water loss) continue to operate normally. Therefore, if essential fatty acid intake did not regulate (n-9) fatty acid synthesis, the survival of the organism would be threatened. During the past 20 years, we have gradually elucidated the cellular and molecular mechanisms by which dietary PUFAs modulate fatty acid biosynthesis and (n-9) fatty acid availability. Central to this mechanism has been our ability to determine that dietary PUFAs regulate the transcription of genes coding for lipogenic enzymes (12, 40). The potential mechanisms by which PUFAs govern gene transcription are numerous, and it is unlikely that any one mechanism can fully elucidate the nuclear actions of PUFA. The difficulty in providing a unifying hypothesis at this time stems from: (a) the many metabolic routes taken by PUFAs upon entering the hepatocyte (Figure 1); and (b) the lack of identity of a specific PUFA-regulated trans-acting factor. However, the studies described above indicate that macronutrients, like PUFA, are not only utilized as fuel and structural components of cells, but also serve as important mediators of gene expression (12, 14, 40). As regulators of gene expression, PUFAs (or metabolites) are thought to affect the activity of transcription factors, which in turn target key cis-linked elements associated with specific genes. Whether this targeting involves DNA-protein interaction or the interaction of PUFA-regulated factors is unclear. A better understanding of the nuclear actions of PUFA will clarify the role of these compounds in lipid metabolism and lead to a better understanding of the role of PUFAs in disease processes such as insulin-resistant diabetes and certain forms of cancer.

Effects of Sieving, Storage, and Incubation Temperature on the Phospholipid Fatty Acid Profile of a Soil Microbial Community

Abstract: Disturbances typically associated with the study of soil microbial communities, i.e., sieving, storage, and subsequent incubation at elevated temperatures, were investigated with phospholipid fatty acid (PLFA) analyses. Treatment effects were quantified by statistical analyses of the mole percentage distribution of the individual fatty acids. Changes in the concentrations of individual fatty acids over a 7-week storage period at 4.5°C were generally not statistically significant. Sieving effects (mesh size, 4 or 2 mm) on CO2 evolution and the PLFA profile were monitored over 3 weeks; the physical disturbance had only minor effects, although some damage to fungal hyphae by the first sieving (

Prevention of ischemia-induced ventricular fibrillation by omega 3 fatty acids

Abstract: A specially prepared dog model of myocardial infarction was used to test the efficacy of the long-chain polyunsaturated fish oil omega 3 fatty acids eicosapentaenoic (20:5 n-3) and docosahexaenoic (22:6 n-3) acids to prevent ischemia-induced malignant cardiac arrhythmias. The dogs had sustained a prior experimental myocardial infarction from ligation of the left anterior descending coronary artery, and a hydraulic cuff was implanted around the left circumflex artery at that operation. After recovery from that procedure the animals were tested during a treadmill exercise test. With compression of the left circumflex artery sensitive animals will predictably develop ventricular fibrillation (VF). In such prepared dogs an emulsion of fish oil fatty acids was infused i.v. over a 50- to 60-min period just before the exercise-plus-ischemia test, and the effect on development of VF was recorded. The infusion was 100 ml of a 10% (vol/vol) emulsion of a fish oil concentrate containing 70% omega 3 fatty acids with free eicosapentaenoic acid and docosahexaenoic acid composing 33.9% and 25.0% of that total, respectively. Alternatively, some animals similarly received an emulsion containing 5 ml of the free fatty acid concentrate plus 5 ml of a triacylglyerol concentrate containing 65% omega 3 fatty acids with eicosapentaenoic acid and docosahexaenoic acid composing 34.0% and 23.6% of that total, respectively. In seven of eight animals the infusion of the fish oil emulsion completely prevented the acute occurrence of VF in the susceptible animals (P < 0.005). In five of five of these animals the subsequent exercise-plus-ischemia test after a similar infusion of an emulsion in which soy bean oil replaced the fish oil fatty acid concentrates resulted in prompt development of VF. Possible mechanisms for this protective effect of omega 3 fatty acids against exercise and ischemia-induced malignant arrhythmias are considered.

Incorporation of fatty acids by concanavalin A-stimulated lymphocytes and the effect on fatty acid composition and membrane fluidity

Abstract: The fatty acid compositions of the neutral lipid and phospholipid fractions of rat lymph node lymphocytes were characterized. Stimulation of rat lymphocytes with the T-cell mitogen concanavalin A resulted in significant changes in the fatty acid composition of both neutral lipids and phospholipids (a decrease in the proportions of stearic, linoleic and arachidonic acids and an increase in the proportion of oleic acid). Membrane fluidity was measured using nitroxide spin-label e.s.r., and increased during culture with concanavalin A. Culturing the lymphocytes in the absence of mitogen did not affect fatty acid composition or membrane fluidity. The uptake and fate of palmitic, oleic, linoleic and arachidonic acids were studied in detail; there was a time-dependent incorporation of each fatty acid into all lipid classes but each fatty acid had a characteristic fate. Palmitic and arachidonic acids were incorporated principally into phospholipids whereas oleic and linoleic acids were incorporated in similar proportions into phospholipids and triacylglycerols. Oleic acid was incorporated mainly into phosphatidylcholine, palmitic and linoleic acids were incorporated equally into phosphatidylcholine and phosphatidylethanolamine, and arachidonic acid was incorporated mainly into phosphatidylethanolamine. Supplementation of the culture medium with particular fatty acids (myristic, palmitic, stearic, oleic, linoleic, alpha-linolenic, arachidonic, eicosapentaenoic or docosahexaenoic acid) led to enrichment of that fatty acid in both neutral lipids and phospholipids. This generated lymphocytes with phospholipids differing in saturated/unsaturated fatty acid ratio, degree of polyunsaturation, index of unsaturation and n - 6/n - 3 ratio. This method allowed the introduction into lymphocyte phospholipids of fatty acids not normally present (e.g. alpha-linolenic) or usually present in low proportions (eicosapentaenoic and docosahexaenoic). These three n - 3 polyunsaturated fatty acids replaced arachidonic acid in lymphocyte phospholipids. Fatty acid incorporation led to an alteration in lymphocyte membrane fluidity: palmitic and stearic acids decreased fluidity whereas the unsaturated fatty acids increased fluidity. It is proposed that the changes in lymphocyte phospholipid fatty acid composition and membrane fluidity brought about by culture in the presence of polyunsaturated fatty acids are responsible for the inhibition of lymphocyte functions caused by these fatty acids.

Mechanisms of the stimulation of insulin release by saturated fatty acids. A study of palmitate effects in mouse beta-cells

Abstract: The mechanisms by which fatty acids increase insulin release are not known. In this study, mouse islets were used as a model and palmitate as a reference compound to study in vitro how saturated fatty acids influence pancreatic beta-cells. Palmitate (625 microM) was bound to albumin. It did not affect basal insulin release (3 mM glucose) but increased the release induced by 10-15 mM glucose. This effect was dependent on the concentration of free rather than total palmitate. It was reversible and abolished by epinephrine, diazoxide, nimodipine, or omission of extracellular Ca. Bromopalmitate and methyl palmoxirate, two inhibitors of fatty acid oxidation, were ineffective alone, and only bromopalmitate partially inhibited the effects of palmitate on insulin release. The increase in insulin release produced by palmitate could not be ascribed to a blockade of ATP-sensitive K(+)-channels because the fatty acid only barely decreased 86Rb efflux and did not depolarize beta-cells in 3 mM glucose. The small effect on 86Rb efflux might be attributed to a slight rise in the ATP/ADP ratio. No such rise occurred when palmitate was tested in 15 mM glucose, and the fatty acid consistently accelerated 86Rb efflux under these conditions. Measurements of beta-cell membrane potential (intracellular microelectrodes) and of free cytoplasmic calcium (Cai2+) in beta-cells (Fura 2 technique) showed that palmitate increases Ca2+ influx; it also caused a very small mobilization of intracellular Ca. The persistence of this stimulation of Ca2+ influx in the presence of diazoxide and high K+ suggests that palmitate might act on Ca2+ channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum lipoprotein lipid profile in women with the polycystic ovary syndrome : relation to anthropometric, endocrine and metabolic variables

Abstract: Summary OBJECTIVE Although often associated with insulin resistance and glucose intolerance, various lipoprotein abnormalities have been found in polycystic ovary syndrome (PCOS) but not Invariably so when the degree of obesity is taken into account. We have therefore Investigated the serum lipid profile in a group of women with polycystic ovary syndrome with and without obesity. DESIGN Cross-sectional study of serum lipoprotein lipids and plasma free fatty acids in relation to anthropometric, metabolic and hormonal variables in women with PCOS and weight-matched controls. PATIENTS Twenty-four obese (Pob, mean BMI ± SD 30·6±3·3kg/m2) and 25 non-obese (Pnob, 22·2 ±2·3kg/m2) women with PCOS. Twenty obese (Cob, 30·2 ± 3·5 kg/m2) and 20 non-obese (Cnob, 21·4 ± 1·5 kg/m2) controls. MEASUREMENTS Fasting concentrations of plasma free fatty acids, serum cholesterol and triglycerides in high density lipoproteins (HDL), low density lipoproteins (LDL) and very low density lipoproteins (VLDL) In relation to insulin sensitivity index (M/I; assessed with the euglycaemic insulin clamp), glucose tolerance (k-value; intravenous glucose tolerance test), basal serum hormone concentrations, and body fat distribution (skinfolds and waist hip ratio). RESULTS Plasma concentrations of free fatty acids were markedly higher in Pob than in the other groups (all P < 0 001). The lipoprotein lipids did not differ between Pob and Cob, or between the non-obese groups, whereas both obese groups had higher serum concentrations of triglycerides, totally and in VLDL, and lower HDL-cholesterol than their non-obese counterparts. Pob also had higher serum levels of total and LDL-cholesterol than Pnob. Pob had a more pronounced subcutaneous truncal-abdominal adiposity, higher fasting insulin levels and lower M/I than the other groups, and a lower k-value than Cob. Cob had higher levels of fasting insulin than Cnob. Free fatty acid levels correlated with the k-value (inversely) in both women with PCOS and controls, and with M/I (inversely), age and testosterone levels in PCOS. Step-wise regression analysis for the total population, comparing endocrine, anthropometric and metabolic explanatory variables, showed that the serum levels of HDL-cholesterol and triglycerides were mainly correlated with body fat distribution (both) and fasting insulin levels (triglycerides), and levels of total and LDL-cholesterol with BMI and age. CONCLUSIONS Plasma free fatty acid correlations were markedly increased In obese women with PCOS, closely associated with the lower insulin sensitivity and lower glucose tolerance in these women. In spite of these profound metabolic aberrations, the lipoprotein lipid profile was not significantly more abnormal in obese women with PCOS than in their weight-matched controls.

Microbial biomass, metabolic activity and nutritional status determined from fatty acid patterns and poly-hydroxybutyrate in agriculturally-managed soils

Abstract: Soil microbial biomass, fatty acid pattern, poly-β-hydroxybutyrate content and selected physiological variables were studied in agriculturally-managed soils with different cropping histories: crop rotation, hops and grassland. Significant correlation was observed between substrate-induced respiration, the amounts of adenine nucleotides and the total amounts of phospholipid fatty acids. The highest microbial biomass was found in a grassland soil, the lowest in soils which were formerly cultivated with hops. Additionally, the highest ratio of poly-β-hydroxybutyrate: total phospholipid fatty acids, the largest specific respiration rate and the lowest amounts of the adenylate energy charge were obtained in one of the former hop yards. Due to the frequent treatment of hop plants with fungicides a large amount of copper had accumulated in this former hop yard. The condition of the soil had resulted in the creation of a microbial community with markedly different biochemical characteristics compared to communities associated with grassland soil or crop rotation soil. The principal component analysis was able to discriminate the different soils when applied to hydroxy fatty acids. The profile of fatty acids in the copper-contaminated soil indicated an increase in numbers of Gram-negative bacteria. A lower concentration of branched chain fatty acids revealed a decreased proportion of Gram-positive bacteria in both former hop yard soils.