Strategies for the analysis of chlorinated lipids in biological systems

Myeloperoxidase-derived HOCl reacts with the vinyl ether bond of plasmalogens yielding α-chlorofatty aldehydes. These chlorinated aldehydes can be purified using thin-layer chromatography, which is essential for subsequent analysis of extracts from some tissues such as myocardium. The α-chlorofatty aldehyde 2-chlorohexadecanal (2-ClHDA) is quantified after conversion to its pentafluorobenzyl oxime derivative using gas chromatography–mass spectrometry and negative-ion chemical ionization detection. 2-ClHDA accumulates in activated human neutrophils and monocytes, as well as in atherosclerotic lesions and infarcted myocardium. Metabolites of 2-ClHDA have also been identified, including the oxidation product, 2-chlorohexadecanoic acid (2-ClHA), and the reduction product, 2-chlorohexadecanol. 2-ClHA can be quantified using LC–MS with selected reaction monitoring (SRM) detection. 2-ClHA can be ω-oxidized by hepatocytes and subsequently β-oxidized from the ω-end, leading to the production of the dicarboxylic acid, 2-chloroadipic acid. This dicarboxylic acid is excreted in the urine and can also be quantified using LC–MS methods with SRM detection. Quantitative analyses of these novel chlorinated lipids are essential to identify the role of these lipids in leukocyte-mediated injury and disease.     

Metabolic origin of urinary 3-hydroxy dicarboxylic acids

3-Hydroxy dicarboxylic acids with chain lengths ranging from 6 to 14 carbons are excreted in human urine. The urinary excretion of these acids is increased in conditions of increased mobilization of fatty acids or inhibited fatty acid oxidation. Similar urinary profiles of 3-hydroxy dicarboxylic acids were also observed in fasting rats. The metabolic genesis of these urinary 3-hydroxy dicarboxylic acids was investigated in vitro with rat liver postmitochondrial and mitochondrial fractions. 3-Hydroxy monocarboxylic acids ranging from 3-hydroxyhexanoic acid to 3-hydroxyhexadecanoic acid were synthesized. In the rat liver postmitochondrial fraction fortified with NADPH, these 3-hydroxy fatty acids with carbon chains equal to or longer than 10 were oxidized to (omega - 1)- and omega-hydroxy metabolites as well as to the corresponding 3-hydroxy dicarboxylic acids. 3-Hydroxyhexanoic (3OHMC6) and 3-hydroxyoctanoic (3OHMC8) acids were not metabolized. Upon the addition of mitochondria together with ATP, CoA, carnitine, and MgCl2, the 3-hydroxy dicarboxylic acids were converted to 3-hydroxyoctanedioic, trans-2-hexenedioic, suberic, and adipic acids. In the urine of children with elevated 3-hydroxy dicarboxylic acid levels, 3OHMC6, 3OHMC8, 3-hydroxydecanoic, 3,10-dihydroxydecanoic, 3,9-dihydroxydecanoic, and 3,11-dihydroxydodecanoic acids were identified. On the basis of these data, we propose that the urinary 3-hydroxy dicarboxylic acids are derived from the omega-oxidation of 3-hydroxy fatty acids and the subsequent beta-oxidation of longer chain 3-hydroxy dicarboxylic acids. These urinary 3-hydroxy dicarboxylic acids are not derived from the beta-oxidation of unsubstituted dicarboxylic acids.     

Integrated engineering of β-oxidation reversal and ω-oxidation pathways for the synthesis of medium chain ω-functionalized carboxylic acids

An engineered reversal of the β-oxidation cycle was exploited to demonstrate its utility for the synthesis of medium chain (6–10-carbons) ω-hydroxyacids and dicarboxylic acids from glycerol as the only carbon source. A redesigned β-oxidation reversal facilitated the production of medium chain carboxylic acids, which were converted to ω-hydroxyacids and dicarboxylic acids by the action of an engineered ω-oxidation pathway. The selection of a key thiolase (bktB) and thioesterase (ydiI) in combination with previously established core β-oxidation reversal enzymes, as well as the development of chromosomal expression systems for the independent control of pathway enzymes, enabled the generation of C₆–C₁₀ carboxylic acids and provided a platform for vector based independent expression of ω-functionalization enzymes. Using this approach, the expression of the Pseudomonas putida alkane monooxygenase system, encoded by alkBGT, in combination with all β-oxidation reversal enzymes resulted in the production of 6-hydroxyhexanoic acid, 8-hydroxyoctanoic acid, and 10-hydroxydecanoic acid. Following identification and characterization of potential alcohol and aldehyde dehydrogenases, chnD and chnE from Acinetobacter sp. strain SE19 were expressed in conjunction with alkBGT to demonstrate the synthesis of the C₆–C₁₀ dicarboxylic acids, adipic acid, suberic acid, and sebacic acid. The potential of a β-oxidation cycle with ω-oxidation termination pathways was further demonstrated through the production of greater than 0.8 g/L C₆–C₁₀ ω-hydroxyacids or about 0.5 g/L dicarboxylic acids of the same chain lengths from glycerol (an unrelated carbon source) using minimal media.     

Constituent acids of Pinus radiata stem cutin

Stem cutin from P. radiata seedlings grown under winter and summer environmental conditions comprised n-alkanoic, (C₁₀–C₂₆), α, ω-alkanedioic (C₁₄–C₂₂), ω-hydroxyalkanoic (C₁₂–C₂₄), hydroxy-α, ω-alkanedioic and polyhydroxyalkanoic acids. 9-Hydroxyheptadecane-1, 17-dioic, 9-hydroxyoctadecene-1, 18-dioic, 9-hydroxynonadecane-1, 19-dioic, and 10, 17-dihydroxyheptadecanoic acids are newly-identified constituents of gymnosperm cutin. Cutin grown under winter temperatures and photoperiod contained twice the amount of 9, 16-dihydroxyhexadecanoic acid than that in summer-grown cutin, suggesting that the winter-grown cutin was formed from a highly cross-linked polymer, and that summer-grown cutin contained more linear polyester portions in the polymer.     

Identification and quantitation of urinary dicarboxylic acids as their dicyclohexyl esters in disease states by gas chromatography mass spectrometry

Clinical studies were conducted by gas chromatography mass spectrometry selected ion monitoring of urinary dicarboxylic acids as dicyclohexyl esters. The dicyclohexyl esters of the dicarboxylic acids give characteristic electron impact mass spectra suitable for selected ion monitoring. The mass spectra exhibit a prominent acid + 1H ion and an (acid + 1H)-H2O ion for use as quantitating and confirming ions. The cyclohexyl esters are stable for days at room temperature and have excellent chromatographic properties. Dicarboxylic acid quantitation is performed within one hour using only 50 microliter of unpurified urine. A rapid method specifically for methylmalonic acid quantitation is described which has assisted physicians in the diagnosis of pernicious anemia and methylmalonic aciduria. This procedure is applicable for screening urinary organic acids for detection of inborn errors of metabolism. The detection of a child with elevated medium length dicarboxylic acids in the terminal urine specimen is reported. This condition, previously described as an inborn error, is attributed to a terminal event. Finally, an increase in urinary succinic acid paralleling putrescine levels is described during a response to cancer chemotherapy.     

Ca<Superscript>2+</Superscript>-dependent aggregation and permeabilization of erythrocytes by ω-hydroxypalmitic and α, ω-hexadecandioic acids

This paper presents the data and describes the Ca²⁺-dependent effect of the products of ω-oxidation of palmitic acid, as well as ω-hydroxypalmitic and α, ω-hexadecandioic acids, on rat erythrocytes. It is shown that in the presence of Ca²⁺ these acids induce aggregation of erythrocytes, which is accompanied by a reduction in the number of single cells in suspension. As well, a release of K⁺ from the cells occurs, which indicates the permeabilization of the plasma membrane. However, ω-hydroxypalmitic and α, ω-hexadecandioic acids are inferior to palmitic acid in their ability to induce Ca²⁺-dependent erythrocyte permeabilization. Bovine serum albumin and blood serum inhibit the effects of palmitic acid. At the same time, the influence of these agents on the effects of ω-hydroxypalmitic and α, ω-hexadecandioic acids appears to be much weaker. It is shown that ω-hydroxypalmitic and α, ω-hexadecandioic acids in the presence of Ca²⁺ induce an increase in the hydrodynamic diameter of single-walled lecithin liposomes, which indicates their fusion and (or) aggregation. The mechanisms of ω-hydroxypalmitic acid/Ca²⁺- and α, ω-hexadecandioic acid/Ca²⁺-induced effects on rat erythrocytes are discussed.     

On the metabolism of prostaglandin F 2 in female subjects. Structures of two C 14 metabolites

[9 beta-3H] prostaglandin F2alpha was injected intravenously into female subjects and the metabolites appearing in the urine were isolated. The structures of 2 metabolites were determined. These were C14 compounds and were assigned the structures alpha dihydroxy-11-keto(tetranor, omega-dinor)-prosta-1,14-dioic acid and 5 alpha, Palphoc 11-trihydroxy-(tetranor omega-dinor)-prosta-1,14-dioic acid (identified as its gamma lactone). Both these metabolites also occurred in their corresponding delta-lactone forms.     

Peroxisomal L-bifunctional enzyme (Ehhadh) is essential for the production of medium-chain dicarboxylic acids

L-bifunctional enzyme (Ehhadh) is part of the classical peroxisomal fatty acid β-oxidation pathway. This pathway is highly inducible via peroxisome proliferator-activated receptor α (PPARα) activation. However, no specific substrates or functions for Ehhadh are known, and Ehhadh knockout (KO) mice display no appreciable changes in lipid metabolism. To investigate Ehhadh functions, we used a bioinformatics approach and found that Ehhadh expression covaries with genes involved in the tricarboxylic acid cycle and in mitochondrial and peroxisomal fatty acid oxidation. Based on these findings and the regulation of Ehhadh's expression by PPARα, we hypothesized that the phenotype of Ehhadh KO mice would become apparent after fasting. Ehhadh mice tolerated fasting well but displayed a marked deficiency in the fasting-induced production of the medium-chain dicarboxylic acids adipic and suberic acid and of the carnitine esters thereof. The decreased levels of adipic and suberic acid were not due to a deficient induction of ω-oxidation upon fasting, as Cyp4a10 protein levels increased in wild-type and Ehhadh KO mice.We conclude that Ehhadh is indispensable for the production of medium-chain dicarboxylic acids, providing an explanation for the coordinated induction of mitochondrial and peroxisomal oxidative pathways during fasting.     

Long-chain α,ω-dioic acids as inducers of cyclosporin A-insensitive nonspecific permeability of the inner membrane of liver mitochondria loaded with calcium or strontium ions

Long-chain saturated monocarboxylic fatty acids can induce nonspecific permeability of the inner membrane (open pores) of liver mitochondria loaded with Ca²⁺ or Sr²⁺ by the mechanism insensitive to cyclosporin A. In this work we investigated the effect of their metabolites — α,ω-dioic (dicarboxylic) acids — as potential inducers of pore opening by a similar mechanism. It was established that the addition of α,ω-hexadecanedioic acid (HDA) at a concentration of 10–30 μM to liver mitochondria loaded with Ca²⁺ or Sr²⁺ leads to swelling of the organelles and release of these ions from the matrix. The maximum effect of HDA is observed at 50 μM Ca²⁺ concentration. Cyclosporin A at a concentration of 1 μM, previously added to the mitochondria, did not inhibit the observed processes. The calcium uniporter inhibitor ruthenium red, which blocks influx of Ca²⁺ and Sr²⁺ to the matrix of mitochondria, prevented HDA-induced swelling. The effect of HDA as inducer of swelling of mitochondria was compared with similar effects of α,ω-tetradecanedioic and α,ω-dodecanedioic acids whose acyl chains are two and four carbon atoms shorter than HDA, respectively. It was found that the efficiency of these α,ω-dioic acids decreases with reducing number of carbon atoms in their acyl chains. It was concluded that in the presence of Ca²⁺ or Sr²⁺ long-chain saturated α,ω-dioic acids can induce a cyclosporin A-insensitive permeability of the inner membrane (open pores) of liver mitochondria as well as their monocarboxylic analogs.     

Quantitative studies on prostaglandin synthesis in man. 3. Excretion of the major urinary metabolite of prostaglandins F 1 alpha and F 2 alpha during pregnancy

The mean urinary excretion of 5α, 7α-dihydroxy-11-ketotetranor-prostane-1,16-dioic acid, the major urinary metabolite of prostaglandins F_1α and F_2α, in eight women in pregnancy weeks 37–40 was 32.5 ± 12.2 μg/24 hours, representing a 2–5 fold increase compared to non-pregnant women. Determination of the metabolite throughout pregnancy in three subjects showed that there was a gradual increase in the urinary excretion as pregnancy progressed with maximum excretion (4–5 times the individual pre-pregnant value) at the end of pregnancy. After pregnancy there was a rapid normalization back to the pre-pregnant excretion value.     

The identification of 5beta,7alpha-dihydroxy-11-oxotetranor-prostane-1,16-dioic acid as a urinary metabolite of prostaglandin F2alpha in the rat.

5beta,7alpha-Dihydroxy-11-oxotetranor-prostane-1,16-dioic acid has been identified by gas chromatography-mass spectrometry as a urinary metabolite of [9beta-3H]prostaglandin F2alpha in the rat. This tetranor prostaglandin F derivative, which is the 5beta epimer of the major urinary metabolite of prostaglandin F2alpha, accounted for at least 2% of the total dose. Absence from the metabolite of tritium label at the C-5 position indicated the existence of a minor, previously unknown metabolic pathway by which prostaglandin Falpha derivatives may be converted by oxido-reduction into prostaglandins of Fbeta stereochemistry.     

Formation and degradation of dicarboxylic acids in relation to alterations in fatty acid oxidation in rats.

Dicarboxylic acids are excreted in urine when fatty acid oxidation is increased (ketosis) or inhibited (defects in beta-oxidation) and in Reye's syndrome. omega-Hydroxylation and omega-oxidation of C6-C12 fatty acids were measured by mass spectrometry in rat liver microsomes and homogenates, and beta-oxidation of the dicarboxylic acids in liver homogenates and isolated mitochondria and peroxisomes. Medium-chain fatty acids formed large amounts of medium-chain dicarboxylic acids, which were easily beta-oxidized both in vitro and in vivo, in contrast to the long-chain C16-dicarboxylic acid, which was toxic to starved rats. Increment of fatty acid oxidation in rats by starvation or diabetes increased C6:C10 dicarboxylic acid ratio in rats fed medium-chain triacylglycerols, and increased short-chain dicarboxylic acid excretion in urine in rats fed medium-chain dicarboxylic acids. Valproate, which inhibits fatty acid oxidation and may induce Reye like syndromes, caused the pattern of C6-C10-dicarboxylic aciduria seen in beta-oxidation defects, but only in starved rats. It is suggested, that the origin of urinary short-chain dicarboxylic acids is omega-oxidized medium-chain fatty acids, which after peroxisomal beta-oxidation accumulate as C6-C8-dicarboxylic acids. C10-C12-dicarboxylic acids were also metabolized in the mitochondria, but did not accumulate as C6-C8-dicarboxylic acids, indicating that beta-oxidation was completed beyond the level of adipyl CoA.     

Quantitative studies on prostaglandin synthesis in man. II. Determination of the major urinary metabolite of prostaglandins F1 alpha and F2 alpha

A method was developed for quantitative determination of 5α,7α-dihydroxy-11-ketotetranor-prostane-1,16-dioic acid, the major urinary metabolite of prostaglandins F_1α and F_2α in man. The method was based on the use of the O-methyloxime derivative of [5β-³H; 10,10,12,12-²H₄]5α,7α-dihydroxy-11-ketotetranor-prostane-1,16-dioic acid as internal standard and determination of ratios between unlabeled and deuterium-labeled molecules by multiple-ion analysis. Excretion values found for healthy human subjects were: males, $\text{10.8–59.0 μ}\text{g}\text{24 hr}$ (n = 10, mean value, 24.0 ± 17.2 (SD) μg) and females, $\text{7.6–13.6 μ}\text{g}\text{24 hr}$ (n = 10, mean value, 10.5 ± 2.1 (SD) μg).     

Abnormal urinary excretion of unsaturated dicarboxylic acids in patients with medium-chain acyl-CoA dehydrogenase deficiency

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most frequently described metabolic disorder of fatty acid oxidation in humans. Acute episodes are usually characterized biochemically by the appearance of nonketotic dicarboxylic aciduria. In addition, other abnormal metabolites, such as suberylglycine, n-hexanoylglycine, 3-phenylpropionylglycine, and octanoylcarnitine, are excreted in the urine. Urinary organic acids were determined using dual capillary column gas-liquid chromatography and gas-liquid chromatography/mass spectrometry. In three cases of MCAD deficiency we observed a disproportionate increase in the excretion of unsaturated dicarboxylic acids compared to either fasting control children with expected ketotic dicarboxylic aciduria or patients with nonketotic dicarboxylic aciduria not associated with MCAD deficiency. The most significant increase was in the urinary excretion of cis-4-decendioic acid. Additionally, the urinary excretions of cis-3-octenedioic and cis-5-decenedioic acids were slightly decreased whereas the excretion of cis-5-dodecenedioic acid was increased. These data are consistent with the notion that as a result of MCAD deficiency the metabolic oxidation of unsaturated fatty acids such as linoleate and oleate is inhibited more than saturated fatty acids.     

Measurement of icosanoids. Report of the Group for Standardization of Methods in Icosanoid Research

This statement from laboratories highly qualified in icosanoid analysis identifies the urgent need for the availability of the following compounds in labeled (deuterium and tritium) and unlabeled form: PGE2 PGF2 alpha PGD2 6-keto-PGF1 alpha Thromboxane B2 9 alpha,20-dihydroxy-11,15-dioxo-2,3- dinorprost -5-enoic acid 9 alpha-hydroxy-11,15-dioxo-2,3,18,19- tetranorprost -5-ene-1,20-dioic acid 15-keto-13,14-dihydro-PGE2 15-keto-13,14-dihydro-PGF2 alpha 5 alpha-7 alpha-dihydroxy-11- ketotetranorprosta -1,16-dioic acid 7 alpha-hydroxy-5,11-diketo- tetranorprosta -1,16-dioic acid 2,3 dinor-thromboxane B2 2,3 dinor-6-keto-PGF1 alpha 2,3 dinor-6,15-diketo 13,14 dihydro-20-carboxyl-PGF1 alpha 2,3 dinor-13,14-dihydro-6,15-diketo-PGF1 alpha LTB4 LTC4 LTD4 LTE4 LTF4 20-OH-LTB4 20-COOH-LTB4 5-HETE 12-HETE 15-HETE omega-OH-12-HETE 5S, 12S-di HETE 5S, 15S-di HETE HHT other hydroxylated polyunsaturated fatty acids and their epoxides.     

Omega oxidation of fatty acids and the pathway of 3-hydroxybutyric acid formation

Pathways followed by the carbons of long chain fatty acids in their conversion to 3-hydroxybutyric acid were traced and the contribution of ω-oxidation to fatty acid oxidation was determined in the cellular environment where ketone body formation occurs. 1-¹⁴C-, 2-¹⁴C-, and ω-¹⁴C-labeled fatty acids were injected into alloxan-induced diabetic rats in ketosis. 3-Hydroxybutyric acid was isolated from their urines and degraded. About 1.2 to 1.4 times as much ¹⁴C was found in carbon 1 as carbon 3 of 3-hydroxybutyric acid when the 1-¹⁴C-labeled fatty acids were injected and in carbon 2 as carbon 4 when the 2-¹⁴C-labeled fatty acids were injected. There was about 4 times as much incorporation into carbon 4 as carbon 2 of 3-hydroxybutyric acid formed from the ω-¹⁴C-labeled fatty acids. This means that 50% or more of the fatty acids were oxidized, so that the terminal two carbons of the fatty acids were converted to acetoacetyl-CoA without acetyl-CoA as an intermediate. Incorporation of ¹⁴C into carbons 1 and 2 of the hydroxybutyric acid reflects the distribution of ¹⁴C in acetyl-CoA. Incorporation into carbon 1 was very small when the ω-¹⁴C-labeled fatty acids were substrate. This means that ω-oxidation of fatty acids makes, at most, a small contribution to the formation of the acetyl-CoA pool from which acetoacetate is derived.     

Fatty acid omega-oxidation as a rescue pathway for fatty acid oxidation disorders in humans

Fatty acids (FAs) can be degraded via different mechanisms including α-, β- and ω-oxidation. In humans, a range of different genetic diseases has been identified in which either mitochondrial FA β-oxidation, peroxisomal FA β-oxidation or FA α-oxidation is impaired. Treatment options for most of these disorders are limited. This has prompted us to study FA ω-oxidation as a rescue pathway for these disorders, based on the notion that if the ω-oxidation of specific FAs could be upregulated one could reduce the accumulation of these FAs and the subsequent detrimental effects in the different groups of disorders. In this minireview, we describe our current state of knowledge in this area with special emphasis on Refsum disease and X-linked adrenoleukodystrophy.     

Metabolic engineering for the production of dicarboxylic acids and diamines

Microbial production of chemicals and materials from renewable carbon sources is becoming increasingly important to help establish sustainable chemical industry. In this paper, we review current status of metabolic engineering for the bio-based production of linear and saturated dicarboxylic acids and diamines, important platform chemicals used in various industrial applications, especially as monomers for polymer synthesis. Strategies for the bio-based production of various dicarboxylic acids having different carbon numbers including malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9), sebacic acid (C10), undecanedioic acid (C11), dodecanedioic acid (C12), brassylic acid (C13), tetradecanedioic acid (C14), and pentadecanedioic acid (C15) are reviewed. Also, strategies for the bio-based production of diamines of different carbon numbers including 1,3-diaminopropane (C3), putrescine (1,4-diaminobutane; C4), cadaverine (1,5-diaminopentane; C5), 1,6-diaminohexane (C6), 1,8-diaminoctane (C8), 1,10-diaminodecane (C10), 1,12-diaminododecane (C12), and 1,14-diaminotetradecane (C14) are revisited. Finally, future challenges are discussed towards more efficient production and commercialization of bio-based dicarboxylic acids and diamines.     

Metabolism of straight saturated medium chain length (C9 to C12) dicarboxylic acids

A method utilizing thin-layer chromatography, high performance liquid chromatography, and mass spectrometry was developed for the quantification of C9, C10, C11, and C12 dicarboxylic acids in serum, urine, and feces of human volunteers and rats after oral administration of the acids. The method allowed good resolution and measurement of the dicarboxylic acids at nanogram levels. In humans, excretion was independent of the dosage; about 60% of C9, 17% of C10, 5% of C11, and 1% of C12 were excreted in the urine during the first 12 hours after administration. The concentration of the acids in serum peaked between 2 and 3 hours. Excretion was also independent of dosage in rats. About 2.5% of C, 2.1% of C10, 1.8% of C11, and 1.6% of C12 were excreted in the urine over a period of 5 days. The serum concentration and the urinary excretion of the diacids reached a maximum at the second day after the oral dose. In both humans and rats, the dicarboxylic acids found in serum and urine were 2, 4, or 6 carbon atoms shorter than the corresponding administered diacid. This indicates that there was beta-oxidation of the ingested diacids to some extent. The administration of [1,9-14C]azeliac acid and of [10,11-3H]dodecandioic acid confirmed the occurrence of beta-oxidation, and led to elucidation of the fate of the ingested diacids that were not excreted as such in the urine.     

Radioimmunoassay of main urinary metabolite of prostaglandin F2alpha in normal subjects

Radioimmunoassay of 5alpha, 7alpha-dihydroxy-11-keto-tetranor-prosta-1,16-dioic acid, main urinary metabolite of prostaglandin F2alpha (PGF2alpha-MUM), was performed in normal subjects. Twenty-four hours secretion of PGF2alpha-MUM were 29.04 +/- 9.73 microgram in males and 18.22 +/- 5.88 microgram in females on an average. And an oral administration of aspirin resulted in the remarkable decrease of PGF2alpha-MUM in both sexes.