Biomedical subjects

M Laposata

Publications and source records attributed to M Laposata.

At least 73 records · Page 4Linked to original sources

PubMed1995

Fatty acid ethyl esters decrease human hepatoblastoma cell proliferation and protein synthesis.

BACKGROUND/AIMS: Fatty acid ethyl esters (FAEEs) are nonoxidative products of ethanol metabolism. They have been implicated as mediators of ethanol-induced organ damage because FAEE and FAEE synthase have been found specifically in the organs damaged by ethanol abuse. This study showed toxicity specifically related to FAEE or their metabolites for intact human hepatoblastoma-derived cells (HepG2). METHODS: The lipid core of human low-density lipoprotein (LDL) was extracted and the LDL particle reconstituted with either ethyl oleate or ethyl arachidonate. Cultured HepG2 cells were incubated with LDL containing FAEE. Cell proliferation was measured by [methyl-3H]thymidine incorporation. Protein synthesis was determined using L-[35S]methionine. RESULTS: Incubation of cells with 600 mumol/L ethyl oleate or 800 mumol/L ethyl arachidonate decreased [methyl-3H]thymidine incorporation into HepG2 cells by 31% and 37%, respectively. LDL reconstituted with 400 mumol/L ethyl oleate decreased protein synthesis in intact HepG2 cells by 41%. Electron microscopy revealed significant changes in cell morphology, particularly involving the cell nucleus. FAEE delivered in reconstituted LDL were rapidly hydrolyzed and the fatty acids re-esterified into phospholipids, triglycerides, and cholesterol esters, with preference for triglycerides. CONCLUSIONS: These findings provide evidence that FAEE are toxic for intact human hepatoblastoma cells and that they or their metabolites may be an important causative agent in ethanol-induced liver damage.

Cell Division↗

PubMed1995

Fatty acids. Biochemistry to clinical significance.

Fatty acids are a major source of lipids in the diet. Dietary fatty acids are able to significantly influence the concentration of serum cholesterol and thereby influence the risk of atherosclerosis. This brief review on fatty acids will present information on the structure and nomenclature of fatty acids, the metabolic pathways for fatty acids in cells, and the influence of dietary fatty acids on serum cholesterol levels.

Cholesterol↗

PubMed1995

Low-density lipoprotein reconstituted with fatty acid ethyl esters as a physiological vehicle for ethyl ester delivery to intact cells.

Fatty acid ethyl esters (FAEEs), esterification products of ethanol and fatty acids, have been found selectively in the organs damaged by ethanol abuse, and on that basis have been implicated as contributors to ethanol-induced organ damage. To directly assess the cytotoxic potential of FAEEs with intact cells in a physiological system, solubility must be achieved for these highly nonpolar lipids in aqueous medium. After ethanol ingestion, FAEEs can be found within low-density lipoproteins (LDLs). Therefore, to achieve solubility with FAEEs bound to a naturally occurring lipid carrier, we developed a method for FAEE solubilization and delivery to cells in culture. We synthesized radiolabeled FAEEs and incorporated them into human LDL particles that bind to LDL receptors and deliver FAEEs to intact cells. Ethyl palmitate and ethyl oleate were incorporated into LDLs yielding molar ratios of FAEEs to LDLs of 2,153 +/- 249 and 4,208 +/- 403, respectively. LDL reconstituted with FAEE had the same electrophoretic mobility on agarose gel electrophoresis as native LDL, indicating that the reconstituted LDL (rLDL) was not oxidatively modified. Quantitative analysis of the solubilization of FAEEs in aqueous medium was investigated by adding FAEEs to tissue culture medium either directly or reconstituted in LDL at a concentration of 27 microM. The percentage of FAEE quantitated was 40.0 +/- 2.5% and 89.3 +/- 0.6% for FAEEs added directly and in rLDLs, respectively. After sterile filtration of these two media, the percentage of FAEE that remained was 11.8 +/- 1.3% (direct addition) and 74.9 +/- 1.3% (addition within rLDL), further demonstrating that the LDL particle did solubilize the FAEE.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinoma, Hepatocellular↗

PubMed1995

Near patient blood glucose monitoring.

This report describes the quality control and quality assurance programs for bedside glucometry at our institution. From our 3-year experience, a regular schedule of inspections is necessary for maintenance of high-quality bedside glucose testing. The most common violation of quality control/quality assurance in bedside glucometry in our institution was the failure to perform regular proficiency testing, in which one random patient's bedside capillary blood glucose value during each inspection period was compared to his or her venous plasma or serum glucose value obtained from the central laboratory. Failure to perform instrument maintenance and document operator certification were the next most common violations of quality control/quality assurance in our bedside glucometry program. Regarding the cost analysis for bedside glucometry, we conclude that bedside glucose testing is not inherently more expensive than testing performed within the clinical laboratory. The increased cost of bedside glucometry over laboratory testing can be significantly minimized by involvement of a limited number of health care workers and performance of bedside glucometry only on clinical units where testing is required more than five times per day.

Blood Glucose↗

PubMed1995

Mode of transport of fatty acid to endothelial cells influences intracellular fatty acid metabolism.

Fatty acids are transported to cells from a variety of different moieties in the plasma. In this study, using oleate and human umbilical vein endothelial cells, we asked whether the vehicle that delivers fatty acid to cells has an influence on its metabolism upon its incorporation into the cell. For oleate vehicles, we compared free oleate bound to albumin with oleate in low density lipoprotein (LDL) which was delipidated and reconstituted with either radiolabeled triolein or cholesteryl oleate. Using approximately physiologic concentrations of LDL and free oleate, we demonstrated by three lines of evidence unique patterns of cellular oleate metabolism for oleate delivered as triolein within LDL, for oleate delivered as cholesteryl oleate within LDL, and for oleate delivered as free oleate bound to albumin. In fact, the difference was most marked between cholesteryl oleate and triolein, even though the oleate in cholesteryl oleate and triolein was delivered in identically reconstituted LDL particles, which were presumably incorporated into the cells and degraded in lysosomes in a similar fashion. First, we demonstrated that oleate delivered as free oleate or as triolein in reconstituted LDL was desaturated and elongated to fatty acid metabolites, but cholesteryl oleate in reconstituted LDL was not similarly metabolized. The elongated and desaturated metabolites of oleate were preferentially esterified in cellular triglyceride when oleate was delivered as free oleate, but they were preferentially esterified in phospholipids when oleate was delivered as triolein in LDL. Second, we observed that there was a difference in the distribution of oleate among phospholipids when oleate was delivered as cholesteryl oleate in reconstituted LDL versus triolein in reconstituted LDL. When the oleate was delivered as triolein in reconstituted LDL, there was greater esterification in diacyl phosphatidylethanolamine, in phosphatidylserine, and in phosphatidylinositol. When oleate was delivered as cholesteryl oleate in reconstituted LDL, there was greater esterification in diacyl phosphatidylcholine. Third, there was a marked preference for oleate delivered from triolein in LDL over cholesteryl oleate in LDL for esterification into the sn-1 position of plasmalogens as a vinyl ether-linked fatty acid. These data indicate that mode of transport of fatty acid to cells influences fatty acid metabolism upon its incorporation into the cell, even when the fatty acid is delivered from the core of the same lipoprotein.

Binding Sites↗

PubMed1994

Covalent binding of arachidonate to G protein alpha subunits of human platelets.

The alpha subunits of GTP-binding regulatory proteins (G proteins) are subject to lipid modifications required for anchorage to membrane and/or interactions with other proteins. With the knowledge that alpha subunits are palmitoylated, which we demonstrate here for human platelets, we sought to determine whether these subunits also bind arachidonate and myristate in a covalent, post-translational manner. All alpha subunits examined were found to incorporate radioactivity upon incubation of human platelets with [3H]palmitate, [3H]arachidonate, and [3H]myristate. The identity of [3H]palmitate and [3H]arachidonate as covalently bound fatty acids was confirmed by high pressure liquid chromatography following alkaline methanolysis. With [3H]myristate, however, the bound fatty acid proved to be [3H]palmitate, presumably generated by a 2-carbon chain elongation. Protein-bound [3H]palmitate and [3H]arachidonate were released by hydroxylamine at neutral pH, implying a thioester linkage between protein and fatty acid. Thus, post-translational modifications of G protein alpha subunits include palmitoylation and arachidonoylation, but not myristoylation. Given the different physical properties of saturated and unsaturated fatty acids and the large-scale release of arachidonate during platelet activation, changes in arachidonate incorporation may serve as an important regulator of alpha subunit function.

Alprostadil↗

PubMed1994

Utilization and cost analysis of bedside capillary glucose testing in a large teaching hospital: implications for managing point of care testing.

PURPOSE: To study the use and cost of bedside capillary glucose testing in a large teaching hospital. PATIENTS AND METHODS: In a prospective study of 40 inpatient units and 10 outpatient units at Massachusetts General Hospital, records were maintained by each unit of the date, time, operator, and results of patient and quality control tests. Cost analysis was performed using data from time studies, test tallies in logbooks, and hospital administration records. RESULTS: The number of glucose meters in the hospital increased from 10 to 54 over a 2-year period. In 1992, 67,596 tests were performed by the bedside method, representing 30.7% of all glucose measurements performed in the institution. The majority of tests (94.7%) were performed on inpatients, and 10.2% of all hospital admissions underwent bedside glucose testing. The impact on the number of glucose tests performed in the clinical laboratories was minimal, indicating that bedside glucose testing was added as an extra test rather than as a substitute for laboratory-based glucose measurements. The cost of bedside glucose testing was $4.19 per test compared with $3.84 in the clinical laboratory. The cost varied from one unit to another (median $5.52, range $3.08 to $48.16), an effect largely attributed to the difference in the volume of tests performed by different units. In seven high-volume units the cost per test was lower than the corresponding value in the laboratory. The cost of bedside glucose testing included labor (80.2%) and supplies (19.8%). The percent of costs attributed directly to patient testing was 57.7%, whereas the costs for all other related activities (training, quality control, and quality assurance) was 42.3%. CONCLUSIONS: Bedside capillary glucose testing is a rapidly expanding technology and is performed on a significant percentage of hospital admissions. Bedside glucose testing is not inherently more expensive than centralized laboratory measurements but implementation on inefficient care units with low utilization can add substantially to the cost. Much of the excess cost of the bedside method can be attributed to the high costs of quality control and quality assurance, training, and documentation.

Blood Glucose↗

PubMed1994

Fatty acid ethyl esters are present in human serum after ethanol ingestion.

The aim of the study was to determine whether fatty acid ethyl esters, nonoxidative products of ethanol metabolism selectively present in organs damaged by ethanol abuse, are detectable in the serum after ethanol ingestion. Serum samples of hospital emergency room patients with positive (n = 32) and negative (n = 5) blood ethanol levels were assayed for fatty acid ethyl esters. In a separate study, five healthy subjects received an ethanol dose based on body weight mixed with fruit juice in a 1:2 ratio and administered by measured ingestion. Fatty acid ethyl esters were found in the serum of hospital emergency room patients with positive blood ethanol levels. The concentration of fatty acid ethyl esters in these patients correlated with the concentration of blood ethanol (r = 0.57; 95% confidence interval 0.28 to 0.77; P = 0.0002). In the controlled ethanol ingestion study with five healthy subjects, it was also determined that the serum fatty acid ethyl ester concentration began to decrease within 2 h of the time ethanol ingestion had been stopped. The fatty acid ethyl esters in the serum were bound to lipoprotein and albumin, and there was a higher percentage of saturated fatty acids in the FAEE pool than in the serum free fatty acid and triglyceride pools. These studies indicate that fatty acid ethyl esters, which have been implicated as mediators of ethanol-induced organ toxicity, are present in serum after ethanol ingestion.

Esters↗

PubMed1993

Covalent modification of proteins by arachidonate and eicosapentaenoate in platelets.

The posttranslational modification of proteins by fatty acids has been shown to involve long chain-saturated fatty acids, predominantly palmitate. In the present study, we demonstrated by metabolic labeling of human platelets with [3H]arachidonate and [3H]eicosapentaenoate that these polyunsaturated fatty acids can also become covalently linked to proteins. The extent of binding of arachidonate to proteins was somewhat less than that of palmitate. Arachidonate binding to platelet proteins was not significantly influenced by the inhibition of cyclooxygenase and lipoxygenase. This finding and the high performance liquid chromatography analysis of radiolabeled products removed from proteins by selective cleavage techniques established that arachidonate, and not its metabolic products, was the protein-linked radiolabeled moiety in [3H]arachidonate-labeled platelets. A 7.5-fold higher concentration of unlabeled palmitate competed to a small extent with [3H] arachidonate for protein labeling. Both arachidonate and eicosapentaenoate were bound to proteins almost exclusively through ester linkages. It was further demonstrated that 61 and 66% of total protein-linked arachidonate and eicosapentaenoate, respectively, were bound via thioester bonds. In contrast, 91% of the binding of palmitate to proteins occurred via thioester linkages. As demonstrated by SDS-polyacrylamide gel electrophoresis and fluorography, the patterns of palmitoylated and arachidonoylated proteins were similar but not identical, with selected proteins only palmitoylated or only arachidonoylated. [3H]Eicosapentaenoate labeled the same set of proteins as [3H]arachidonate. The fluorographic pattern of 3H-arachidonoylated proteins was not changed by cyclooxygenase and lipoxygenase inhibitors. The binding of a polyunsaturated fatty acid to a protein in place of a saturated fatty acid could significantly influence the hydrophobic interactions of the protein and, thereby, have important functional implications.

Arachidonic Acid↗

PubMed1993

P-selectin is acylated with palmitic acid and stearic acid at cysteine 766 through a thioester linkage.

We report that the adhesion receptor P-selectin can be metabolically labeled with [3H]palmitic acid in human platelets. Analysis of alkaline methanolysis products from labeled protein demonstrated that the radioactivity associated with P-selectin was covalently bound palmitic acid. [3H]Palmitic acid was cleaved by hydroxylamine treatment at neutral pH and by reducing agents, indicating that acylation occurred through a thioester linkage. Both stearic acid and palmitic acid were detected by gas chromatography-mass spectrometry analysis of alkaline hydrolysates of purified P-selectin. Deletion or mutation of Cys766 eliminated [3H] palmitic acid labeling of P-selectin in transfected COS-7 cells. We conclude that the cytoplasmic domain of P-selectin is acylated at Cys766 through a thioester bond. Fatty acid acylation may regulate intracellular trafficking or other functions of P-selectin.

Acylation↗

PubMed1993

Myristoylation of proteins in platelets occurs predominantly through thioester linkages.

We have demonstrated by several lines of evidence that in platelets myristate is linked to proteins predominantly via thioester bonds as is palmitate, and the covalent binding of the two long chain saturated fatty acids to proteins involves the same mechanisms. The first piece of evidence to support the thioester linkage between myristate and proteins is that [3H]myristate could be removed from proteins via alkaline methanolysis, which disrupts ester bonds but not amide bonds. The second piece of evidence is that unlabeled palmitate, which can form only thioester bonds in physiologic concentrations, competitively inhibits the formation of alkaline methanolysis-sensitive covalent bonds between [3H]myristate and proteins. Third, by SDS-polyacrylamide gel electrophoresis and fluorography, the patterns of labeled proteins from [3H]myristate- and [3H]palmitate-labeled platelets are identical. Fourth, [3H]myristate-labeled proteins, like [3H]palmitate-labeled proteins, both release their fatty acid moieties when exposed to hydroxylamine at neutral pH, which disrupts thioester but not hydroxyester bonds. These findings indicate that although the covalent binding of palmitate to proteins was found to occur at a faster rate than that of myristate, protein S fatty acid acylation that occurs posttranslationally is not specific for palmitate.

Blood Platelets↗

PubMed1993

Use of acetyl chloride/methanol for assumed selective methylation of plasma nonesterified fatty acids results in significant methylation of esterified fatty acids.

The albumin-bound nonesterified fatty acid pool in plasma, which represents a very small percentage of total plasma fatty acids, has previously been quantitated by a variety of methods. In the present study we determined that the nonesterified fatty acid concentrations in the plasma, quantitated by a popular method using acetyl chloride and methanol which is reported to be specific for methylation of nonesterified fatty acids in the presence of esterified fatty acids (i.e., without prior isolation of the plasma nonesterified fatty acids), were significantly overestimated due to cleavage and methylation of esterified fatty acids. Quantitation of the contaminating fatty acid from the esterified pool demonstrated that the amount of fatty acid cleaved from the esterified pool was enough to exceed the entire mass of nonesterified fatty acids. As an established method for comparison, we isolated nonesterified fatty acids from the plasma by thin-layer chromatography prior to methylation, using a number of simple precautions to limit oxidation. By performing all thin-layer chromatography steps in an atmosphere of nitrogen and by including fatty acid standards in the plasma with 0, 1, 2 or 4 double bonds, we were able to accurately and reproducibly determine the concentration of nonesterified fatty acids in the plasma, including arachidonate. We demonstrated that no oxidation occurred in the thin-layer chromatographic isolation of nonesterified fatty acids and that the coefficients of variation for repeat measurements of the same sample were < 11% using our reference method. Our data indicate that the use of acetyl chloride and methanol for assumed selective methylation of plasma nonesterified fatty acids results in significant methylation of esterified fatty acids.

Acetates↗

PubMed1992

Effects of tumor necrosis factor-alpha on peroxidation of plasma lipoprotein lipids in experimental animals and patients.

Changes in the plasma lipid composition are observed in patients and animals with malignancy and certain other diseases that are consistent with peroxidation of plasma lipoprotein lipids. These changes can be observed with water-suppressed proton (H-1) and carbon-13 (C-13) nuclear magnetic resonance spectroscopy (NMR) and gas chromatography. Gas chromatography provides evidence of a decrease in polyunsaturated fatty acids relative to monounsaturated fatty acids. This evidence is consistent with that observed by C-13 NMR spectroscopy. Mediators for these effects were sought. Cytokines, known to be released in response to malignant tumor cells and to affect lipid metabolism, were injected into normal mice and their effects on the H-1 and C-13 NMR spectra of plasma lipids were observed. Mouse recombinant tumor necrosis factor-alpha (mr-TNF-alpha) significantly decreased the H-1 methyl and methylene lipid linewidths, and the C-13 spectra indicated a decrease in the relative concentration of polyunsaturated fatty acids. The same changes were directly confirmed by gas chromatographic analysis, showing decreases in the amount of linoleic and arachidonic acids and other polyunsaturated fatty acids relative to monounsaturated fatty acids and in the ratio of polyunsaturated to monounsaturated fatty acids. Serial plasma samples from volunteers receiving an infusion of endotoxin showed similar changes in their C-13 NMR spectroscopy at times when peak TNF-alpha values were measured. In addition, in these samples the C-13 NMR spectra showed direct evidence of lipid peroxidation products. These changes were similar to those observed commonly in the plasma of cancer patients. Other cytokines (human recombinant interleukin-1 alpha [hr-IL-1 alpha], hr-IL-2, mouse recombinant interferon-gamma) did not produce these effects. We conclude that TNF-alpha is a mediator (but not necessarily the only one) of changes in plasma lipoprotein lipid composition due to peroxidation and that this is a mechanism for the changes observed in the NMR spectra of plasma from cancer patients and from normal animals injected with TNF-alpha.

Animals↗

PubMed1992

Implementation of capillary blood glucose monitoring in a teaching hospital and determination of program requirements to maintain quality testing.

PURPOSE: To study the implementation of bedside capillary glucose monitoring using a hospital-wide quality control (QC) program. METHODS: A prospective study of QC performance in 7 outpatient and 39 inpatient treatment units was performed in a large teaching hospital over a 2-year period. Approximately 800 nurses were trained to perform bedside capillary glucose monitoring (Accu-Chek II, Boehringer-Mannheim, Indianapolis, IN). An eight-point QC program was instituted including proficiency testing, instrument maintenance, performance of daily controls, storage of reagent strips and supplies, instrument calibration, and documentation procedures. RESULTS: Comparison of laboratory and bedside test results (split-sample proficiency testing) revealed Y = 1.004X + 7.26, r = 0.95, with a mean percent difference of -4.2% (p < 0.001). Less than 7% of results fell outside +/- 20% of the laboratory results. QC scores (0 = worst to 4 = best), based on adherence to the QC program, improved from 0 on the first inspection to 3.7 +/- 0.17 by the 11th inspection. The most common QC deficiencies were failure to perform split-sample testing (41.4%) and failure to perform instrument maintenance (30.2%). Significant differences were noted in the QC performance of different types of medical services. During the 2-year study period, the total number of glucose assays performed in the clinical laboratories decreased by 22.2% concurrent with initiation of bedside testing. The number of instruments in the hospital increased from 10 to 46. CONCLUSIONS: Bedside capillary glucose assays can be widely implemented in large hospitals with an acceptable degree of accuracy. QC programs with frequent inspections are necessary to identify units that function inadequately, and a formal disciplinary policy is required to ensure compliance with the program.

Blood Glucose↗

PubMed1992

An in vitro model for essential fatty acid deficiency: HepG2 cells permanently maintained in lipid-free medium.

A stable essential fatty acid-deficient cell type, known as HepG2-EFD, was derived from the lipoprotein-producing human hepatoma cell line HepG2. These cells are particularly useful for quantitative studies involving essential fatty acids (n-6 and n-3 fatty acids) in secreted lipoproteins. Radiolabeled essential fatty acids can be delivered to these cells without altering the specific activity of the fatty acids, since the deficient cells contain no endogenous essential fatty acids. Using these cells, radioactivity data (dpm) from metabolic studies can be converted directly to mass, and masses as low as a few pmoles can be accurately measured. HepG2-EFD cell cultures were established by growing HepG2 cells in medium containing delipidated serum. After 10 days of growth in delipidated medium, HepG2 cells were completely depleted of all essential fatty acids. Compensatory increases in nonessential fatty acids (n-9 and n-7 fatty acids) including 20:3n-9 (the Mead acid), which is the hallmark fatty acid of essential fatty acid deficiency, were also observed in HepG2-EFD cells. Despite the lack of exogenous fatty acids in the medium and the lack of essential fatty acids in the cells, export of very low density lipoprotein (VLDL)-associated apolipoprotein B by HepG2-EFD was the same as observed for parent HepG2 cells. However, the activity of beta-oxidation of fatty acids in HepG2-EFD cells was much lower than in the parent cell line.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoproteins B↗

PubMed1992

Cellular interactions between n-6 and n-3 fatty acids: a mass analysis of fatty acid elongation/desaturation, distribution among complex lipids, and conversion to eicosanoids.

The biologic effect of eicosanoids depends in large measure upon the relative masses in tissues of eicosanoids derived from the n-6 fatty acids, dihomogammalinolenic acid and arachidonic acid, and the n-3 fatty acid, eicosapentaenoic acid. Generation of this tissue balance is related to the relative cellular masses of these precursor fatty acids, the competition between them for entry into and release from cellular phospholipids, and their competition for the enzymes that catalyze their conversion to eicosanoids. In order to better understand these processes, we studied the cellular interactions of n-6 and n-3 fatty acids using an essential fatty acid-deficient, PGE-producing, mouse fibrosarcoma cell line, EFD-1. Unlike studies using cells with endogenous pools of n-6 and n-3 fatty acids, the use of EFD-1 cells enabled us to examine the metabolic fate of each family of fatty acids both in the presence and in the absence of the second family of fatty acids. Thus, the specific effects of one fatty acid family on the other could be directly assessed. In addition, we were able to replete the cells with dihomogammalinolenic acid (DHLA), arachidonic acid (AA), and eicosapentaenoic acid (EPA) of known specific activities; thus the masses of cellular DHLA, AA, and EPA, and their metabolites, PGE1, PGE2, and PGE3, respectively, could be accurately quantitated. The major findings of this study were: 1) n-6 fatty acids markedly stimulated the elongation of EPA to 22:5 whereas n-3 fatty acids inhibited the delta 5 desaturation of DHLA to AA and the elongation of AA to 22:4; 2) n-6 fatty acids caused a specific redistribution of cellular EPA from phospholipid to triacylglycerol; 3) n-3 fatty acids reduced the mass of DHLA and AA only in phosphatidylinositol whereas n-6 fatty acids reduced the mass of EPA to a similar extent in all cellular phospholipids; and 4) n-3 fatty acids caused an identical (33%) reduction in the bradykinin-induced release of PGE1 and PGE2, whereas n-6 fatty acids stimulated PGE3 release 2.3-fold. Together, these highly quantitative metabolic data increase our understanding of the regulation of both the cellular levels of DHLA, AA, and EPA, and their availability for eicosanoid synthesis. In addition, these findings provide a context for the effective use of these fatty acids in dietary therapies directed at modulation of eicosanoid production.

8,11,14-Eicosatrienoic Acid↗

PubMed1991

Regulation of agonist-induced prostaglandin E1 versus prostaglandin E2 production. A mass analysis.

Prostaglandin E1 (PGE1) and prostaglandin E2 (PGE2), derived by enzymatic oxidation of cellular dihomogammalinolenic acid (DHLA) and arachidonic acid (AA), respectively, have diverse and, at times, distinct biological actions. It has been suggested that PGE1 specifically inhibits a variety of inflammatory processes, and, in light of the potential therapeutic benefit of PGE1 and its fatty acid precursor in inflammatory disorders, there is growing interest in the biochemical mechanisms which determine the balance between PGE1 and PGE2 synthesis. Metabolic studies in this area have been hampered by the difficulties in measuring the extremely small masses of these prostaglandins which are generated in cell culture systems. We studied the regulation of PGE1 versus PGE2 synthesis using an essential fatty acid-deficient, PGE-producing, mouse fibrosarcoma cell line, EFD-1. Because EFD-1 cells contain no endogenous AA or DHLA, we were able to replete the cells with AA and DHLA of known specific activities; thus, the mass of both cellular AA and DHLA, and synthesized PGE1 and PGE2, could be accurately determined. The major finding of this study is that production of PGE2 was highly favored over production of PGE1 due to preferential incorporation of AA versus DHLA into, and release from, the total cellular phospholipid pool. Further, we correlated the selective release of AA versus DHLA from total cellular phospholipids with the selective incorporation of AA versus DHLA into specific phospholipid pools. In addition, we showed that conversion of DHLA to AA by delta 5 desaturase was enhanced by increasing the cellular mass of n-6 fatty acids and by increasing the cell proliferative activity. Together, these results indicate that the relative abundance of PGE2 versus PGE1 in vivo is not merely a function of the relative abundance of AA versus DHLA in tissues, but also relates to markedly different cellular metabolism of these two fatty acids.

8,11,14-Eicosatrienoic Acid↗

PubMed1990

Alteration of the cellular fatty acid profile and the production of eicosanoids in human monocytes by gamma-linolenic acid.

We administered borage seed oil (9 capsules/day) for 12 weeks to 7 normal controls and to 7 patients with active rheumatoid arthritis. The therapy provided 1.1 gm/day of gamma-linolenic acid (GLA). GLA administration resulted in increased proportions of its first metabolite, dihomo-gamma-linolenic acid (DGLA), in circulating mononuclear cells. The ratios of DGLA to arachidonic acid and DGLA to stearic acid increased significantly in these cells. Significant reductions in prostaglandin E2, leukotriene B4, and leukotriene C4 produced by stimulated monocytes were seen after 12 weeks of GLA supplementation. The antiinflammatory effects of GLA administration observed in animal models, and the apparent clinical improvement experienced by 6 or 7 rheumatoid arthritis patients given borage seed oil in this open, uncontrolled study may be due in part to reduced generation of arachidonic acid oxygenation products.

Administration, Oral↗