Individual Fatty Acid Ethyl Esters Research Articles

Linear Versus Non-Linear Dose-Response Relationship Between Prenatal Alcohol Exposure and Meconium Concentration of Nine Different Fatty Acid Ethyl Esters.

Presence of individual fatty acid ethyl esters (FAEEs) in meconium is considered to be a reliable biomarker of prenatal alcohol exposure, and their concentration has been found to be linearly associated with poor postnatal development, supporting the widely extended idea that ethanol is a non-threshold teratogen. However, a growing number of epidemiological studies have consistently found a lack of adverse short- and long-term fetal outcomes at low exposure levels. We therefore aimed to investigate the relationship between the concentration of individual FAEEs and prenatal alcohol exposure in meconium samples collected within the first 6 to 12?h after birth from 182 babies born to abstainer mothers and from 54 babies born to women who self-reported either light or moderate alcohol ingestion in the second or third trimester of pregnancy. In most cases, the individual FAEE concentrations were negligible and not significantly different (P >0.05) between exposed and control babies. The concentrations appeared to increase linearly with the dose only in the few babies born to mothers who reported >3 drinks/week. These results provide evidence that the correlation between prenatal alcohol exposure and individual FAEE concentrations in meconium is non-linear shape, with a threshold probably at 3 drinks/week.

Altered hepatic lipid metabolism in C57BL/6 mice fed alcohol: a targeted lipidomic and gene expression study

Chronic alcohol consumption is associated with fatty liver disease in mammals. The object of this study was to gain an understanding of dysregulated lipid metabolism in alcohol-fed C57BL/6 mice using a targeted lipidomic approach. Liquid chromatography tandem mass spectrometry was used to analyze several lipid classes, including free fatty acids, fatty acyl-CoAs, fatty acid ethyl esters, sphingolipids, ceramides, and endocannabinoids, in plasma and liver samples from control and alcohol-fed mice. The interpretation of lipidomic data was augmented by gene expression analyses for important metabolic enzymes in the lipid pathways studied. Alcohol feeding was associated with i) increased hepatic free fatty acid levels and decreased fatty acyl-CoA levels associated with decreased mitochondrial fatty acid oxidation and decreased fatty acyl-CoA synthesis, respectively; ii) increased hepatic ceramide levels associated with higher levels of the precursor molecules sphingosine and sphinganine; and iii) increased hepatic levels of the endocannabinoid anandamide associated with decreased expression of its catabolic enzyme fatty acid amide hydrolase. The unique combination of lipidomic and gene expression analyses allows for a better mechanistic understanding of dysregulated lipid metabolism in the development of alcoholic fatty liver disease.

An improved method for rapidly quantifying fatty acid ethyl esters in meconium suitable for prenatal alcohol screening

Fatty acid ethyl esters (FAEEs) are nonoxidative metabolites of ethanol, and elevated levels of FAEE in meconium are a useful biomarker for heavy prenatal alcohol exposure. FAEE in meconium has been recommended as useful and cost-effective for universal screening for prenatal alcohol exposure. To support an efficient universal screening program, an analytical method to detect and quantify FAEE in meconium needs to be accurate, inexpensive, and rapid. The purpose of this study was to develop an analytical method that would satisfy these criteria and to validate this method using established laboratory guidelines. A method was developed and validated to detect and quantify four FAEEs (ethyl palmitate, ethyl linoleate, ethyl oleate, and ethyl stearate) from 0.5 g of meconium using d 5 -ethyl esters as internal standards. The sample undergoes liquid–liquid extraction with heptane:acetone, the heptane layer is isolated and evaporated, and then, the resulting residue undergoes headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry. The detection limits of the four FAEEs ranged from 0.020 to 0.042 nmol/g and are 6- to 25-fold lower than the individual FAEE threshold concentrations (0.5 nmol/g). This method also has good precision with the coefficient of variation ranging from 2.6 to 19.4% for concentrations of individual FAEE between 0.5 and 2.62 nmol/g meconium ( n = 4). Calculated concentrations of FAEE that underwent extraction from meconium were 100–101% of the expected concentration, demonstrating the accuracy of the method. The peak shape and retention time of each FAEE were unaffected by the presence of the matrix, and there is no carryover at clinically relevant concentrations. This method was also able to produce clean chromatograms from meconium samples that could not be quantified using a previous method because of high chromatographic background. This method provides an optimal approach to detecting and quantifying FAEE in meconium that could be used in a universal screening program for prenatal alcohol exposure.

Alarming Prevalence of Fetal Alcohol Exposure in a Mediterranean City

The prevalence of gestational ethanol exposure and subsequent fetal exposure has been assessed in a cohort of mother-infant dyads in a Mediterranean city (Barcelona, Spain) by meconium analysis of fatty acid ethyl esters (FAEEs) after showing in this population a high prevalence of meconium opiates (8.7%), cocaine (4.4%), and cannabis (5.3%). Of the 353 meconium samples analyzed for FAEEs, 159 (45%) contained a total amount of seven FAEEs equal or above 2 nmol/g meconium, the cutoff internationally accepted to differentiate heavy maternal alcohol consumption during pregnancy from occasional use or no use at all. No parental sociodemographic differences or maternal features differentiated exposed from unexposed newborns. The prevalence of gestational consumption of ethanol was similar between women using and not using drugs of abuse during pregnancy (45.7% and 44.7% of samples with total FAEEs equal or higher than 2 nmol/g meconium, respectively). Meconium samples from newborns exposed in utero to ethanol, and positive for at least one illicit drug (cocaine, opiates, or cannabis), had total FAEEs and five of nine individual FAEEs statistically higher than the meconium samples that were negative for the most frequently used illicit drugs of abuse. Among the most prevalent FAEEs, oleic acid ethyl ester showed the best correlation to total FAEE concentration followed by palmitoleic acid ethyl ester . This study, which highlights a 45% ethanol consumption during pregnancy in a low socioeconomic status cohort, may serve as an eye opener for Europeans that gestational alcohol exposure is not endemic only in areas outside of Europe.

FATTY ACID ETHYL ESTERS (FAEE); COMPARATIVE ACCUMULATION IN HUMAN AND GUINEA PIG HAIR AS A BIOMARKER FOR PRENATAL ALCOHOL EXPOSURE

To compare the incorporation rate (ICR) of fatty acid ethyl esters (FAEE) in hair between guinea pigs and humans, and to assess the relationship between ethanol exposure and FAEE concentrations in hair. Published data from pregnant guinea pigs, including maximum blood ethanol concentration (BEC), dosage regimen, and total hair FAEE concentration, were compared with published data from alcoholic patients, where dose of ethanol consumed and total hair FAEE concentration were reported. Mean values of ethanol Vmax for pregnant guinea pigs and humans were obtained from published data (26.2 and 24 mg/dl/h, respectively). Total and individual FAEE ICRs, defined as the ratio of hair FAEE to the area under the BEC-time curve (total systemic ethanol exposure), were found to be on average an order of magnitude lower in the guinea pig than in the human. The profiles of ester incorporation also differed slightly between species, with ethyl stearate being highly incorporated in guinea pig hair and less so in human hair. The results may reflect in the human greater FAEE production, greater FAEE deposition in hair, slower FAEE catabolism, differential sebum production and composition, or a combination thereof. Also, ethyl oleate was found to correlate with total systemic ethanol exposure for both guinea pigs and humans, correlation coefficients equalling 0.67 (P < 0.05) and 0.49 (P < 0.05), respectively. No other ethyl esters, nor total FAEE, were found to correlate with systemic ethanol exposure. When extrapolating FAEE concentrations in hair from guinea pigs to humans, an order of magnitude difference should be considered, with humans incorporating more FAEE per unit of ethanol exposure. Also, the results suggest caution should be taken when interpreting values of single esters because of their differential incorporation among species. Lastly, our findings suggest ethyl oleate may be of keen interest in FAEE hair analysis, particularly across species.

Chronic Prenatal Ethanol Exposure and Increased Concentration of Fatty Acid Ethyl Esters in Meconium of Term Fetal Guinea Pig

In humans, the occurrence of prenatal exposure to ethanol is difficult to validate objectively. Increased concentration of fatty acid ethyl esters (FAEE) in the meconium of the newborn may be a biomarker of prenatal ethanol exposure. The validity of this proposed biomarker was tested in pregnant guinea pigs that received chronic oral administration of 4 g ethanol/kg maternal body weight/day (n=8), isocaloric-sucrose/pair-feeding (n=8) or water (n=2) throughout gestation. At gestational day 65 (term, gestational day 66 to 69), each dam and her offspring were euthanized, and meconium was collected from the term fetal large intestine. Eight individual FAEE (lauric, myristic, palmitic, palmitoleic, stearic, oleic, linolenic and arachidonic AEE) were measured by gas chromatography--flame ionization detection and confirmed by gas chromatography--mass spectrometry. The chronic maternal ethanol regimen decreased fetal body weight and brain weight. There was virtually no measurable FAEE in the meconium for the water group (n=3 fetuses). For meconium of the ethanol offspring (n=25 fetuses) compared with the sucrose offspring (n=23 fetuses), the total FAEE concentration was 8-fold higher; and lauric, palmitic, stearic and oleic AEE concentrations were at least 5-fold higher for the ethanol group. The data indicate that fetal meconium FAEE constitute a biomarker of prenatal ethanol exposure for a maternal ethanol regimen that restricts fetal development, with an inverse relationship between meconium total FAEE concentration and both body weight and brain weight.

Ethanol Administration to Cystic Fibrosis Knockout Mice Results in Increased Fatty Acid Ethyl Ester Production

Fatty acid ethyl esters (FAEE) are nonoxidative ethanol metabolites shown to produce toxic effects in the liver and pancreas in vivo and in vitro. Because alcohol-induced chronic pancreatitis is associated with mutations in the gene responsible for cystic fibrosis (CFTR), we hypothesized that CFTR dysfunction leads to increased levels of these toxic nonoxidative ethanol metabolites following alcohol administration. Cystic fibrosis (CF) and wild-type (WT) mice were injected intraperitoneally with 1, 2, or 3 g/kg of 50% ethanol. Mice were sacrificed and the liver and pancreas removed for FAEE analysis. The mean FAEE concentration (pmol/g) detected in the liver of cftr mice following injection with 2 g/kg of ethanol was significantly greater than the amount detected in WT (p < 0.005). A similar trend in FAEE concentration was seen in the pancreas, but the difference was not statistically different. In both the liver and pancreas, analysis of individual FAEE species demonstrated a selective increase in ethyl oleate. These data show an association between CFTR dysfunction and qualitative and quantitative changes in FAEE in liver and pancreas upon ethanol exposure.

Fetal exposure to alcohol as evidenced by fatty acid ethyl esters in meconium in the absence of maternal drinking history in pregnancy.

The detection of fatty acid ethyl esters (FAEE) in neonatal meconium has been proposed as a novel screening method for intrauterine exposure to alcohol. We investigated the potential use of meconium FAEE screening in a high-risk neonatal population in the absence of maternal drinking history. One hundred forty-two meconium samples of neonates suspected of intrauterine illicit substance exposure and referred to the Motherisk Laboratory were analyzed for the existence of drugs by enzyme-linked immunosorbent assay (ELISA) and FAEE by gas chromatography-flame ionization detection (GC-FID). A positive FAEE test was previously defined as a cumulative measurement of 7 individual FAEE > or = 2 nmol/g. Seventy-one percent of the samples tested positive for at least 1 illicit drug, with cannabis being the most prevalent (52.3%). Fourteen percent of all samples tested positive for prenatal alcohol exposure, as evidenced by cumulative meconium FAEE > or = 2 nmol/g. Ethyl oleate, linoleate, palmitate, and arachidonate were detected most often and at the highest levels. At least 3 individual FAEE were detected in 95% of all positive samples, and none could be identified by the use of 1 selected FAEE. Significantly elevated levels of FAEE above the baseline and the presence of multiple FAEE species in meconium are exclusive to neonates who have likely been exposed to excessive amounts of alcohol in utero. Babies born to mothers who are suspected to use illicit drugs in pregnancy are at elevated risk for exposure also to alcohol in utero. Meconium FAEE are emerging biologic markers that can potentially facilitate earlier diagnosis and intervention for less apparent forms of alcohol-related disabilities that cannot be confirmed in the absence of maternal drinking history.

Placental handling of fatty acid ethyl esters: perfusion and subcellular studies.

The measurement of fatty acid ethyl esters (FAEE) in neonatal meconium is a novel test to confirm prenatal ethanol exposure. The origin of FAEE in the maternal-placental-fetal unit is not known. The objectives of this study were to investigate whether FAEE are transferred and metabolized by the human placenta. Isolated placental cotyledons were perfused with a mixture of four FAEE (palmitic, stearic, oleic, and linoleic acid ethyl esters) commonly detected in the meconium of neonates exposed to ethanol in utero, and the transfer of FAEE to the fetal unit was investigated in the absence and presence of albumin. The metabolic degradation of FAEE by human placental microsomes was subsequently determined. FAEE disappeared from the maternal circulation but remained undetectable in the fetal unit following perfusions. The addition of albumin had no effect on FAEE transfer. The unrecoverable fraction of individual FAEE in the perfusion system accounted for >50% of the initial amount used, suggesting significant metabolic degradation. Subcellular studies documented the enzymatic degradation of FAEE by placental microsomes (mean Km, 35-95 microM; Vmax, 0.6-1.8 nmol/min/mg for individual FAEE). FAEE at levels found in alcoholics that are originated from the mother are not transferred to the fetus because they are taken up and degraded extensively by the human placenta. Hence, FAEE detected in neonatal matrices are likely produced by the fetus from ethanol that has been transferred to and metabolized by the fetus, rendering FAEE a powerful direct biomarker reflective of true fetal exposure to ethanol in utero.

Purification of fatty acid ethyl esters by solid-phase extraction and high-performance liquid chromatography

We have developed a two-step method to purify fatty acid ethyl esters (FAEE) using solid-phase extraction (SPE), with a recovery of 70±3% (mean±S.E.M.) as assessed using ethyl oleate as a recovery marker from a standard lipid mixture in hexane. The first step of the SPE procedure involves application of a lipid mixture to an aminopropyl-silica column with simultaneous elution of FAEE and cholesteryl esters from the column with hexane. Gas chromatographic analysis of FAEE without interference from cholesteryl esters may be performed using the eluate from the aminopropyl-silica column, thus eliminating the need for an octadecylsily (ODS) column in this case. The FAEE can then be separated from the cholesteryl esters, if necessary, by chromatography on an ODS column and elution with isopropanol-water (5:1, v/v). Both the aminopropyl-silica and ODS columns were found to be effective for up to four uses. To permit isolation of specific FAEE species following isolation of total FAEE by the two-step SPE method, we have also developed a purification scheme for individaal FAEE by high-performance liquid chromatography (HPLC). Thus, this simple method allows for reproducible isolation of total FAEE by SPE and isolation of individual FAEE species by HPLC.

Identification and quantitation of fatty acid ethyl esters in biological specimens

Fatty acid ethyl esters, recently described as enzymatic products of nonoxidative ethanol metabolism in the heart, may represent a mediator or marker of ethanol-induced organ pathology such as alcoholic cardiomyopathy. This study was designed to develop a method for the extraction, quantitation, and definitive identification of fatty acid ethyl esters formed both in biological specimens and during enzymatic incubations. First, several potential sources of error were identified and characterized. Tissue extraction with alcohols led to the time, temperature, and concentration-dependent nonenzymatic formation of fatty acid alcohol esters. Contamination of both substrates, [ 14C]ethanol and 14C-fatty acid, used to measure enzymatically mediated fatty acid ethyl ester synthesis, could be removed by purification. Accurate quantitation of fatty acid ethyl esters in tissue was achieved using acetone as an extraction solvent, after which isolated lipids were thinlayer chromatographed on silica gel developed with an apolar solvent system (petroleum ether:diethyl ether:acetic acid, 75:5:1). Gas chromatography and mass spectroscopy identified individual fatty acid ethyl esters. The reproducibility of this assay was high, as assessed by quintuplicate determinations of fatty acid ethyl esters formed in liver and heart homogenates, a method with standard deviations 4 to 11% of the mean.