Sterol Biomarkers Research Articles

Tracking pollution from fur farms using forensic paleolimnology

Eutrophication, which remains one of the greatest threats to water quality worldwide, is particularly acute in agricultural areas. Here we assessed long-term drivers of potential pollution inputs to lakes in southwest Nova Scotia (Canada), a region marked by fur farming (mainly mink) and other agricultural activities. We used a BACI (before-after-control-impact) study design with sediment cores collected from 14 lakes selected based on their proximity to mink farms. We combined economic data, mink faecal samples, and a series of geochemical markers in dated sediment cores, including sterols, δ15N, visible reflectance spectroscopy (VRS)-inferred chlorophyll-a, and heavy metals, to relate changes in sediment geochemistry to the growth of mink farms in the region. Sterol biomarkers (cholesterol and β-sitosterol) measured in a range of samples (i.e. mink faeces and feed, aquaculture feed), were elevated where mink farms were located close to each study lake. Mink-related sterols (cholesterol, β-sitoserol), δ15N measurements, VRS chlorophyll-a, and heavy metals As, Cu, Sr increased in the 1980s coeval with a ∼400% increase of mink farms in the region, especially near Nowlans Lake. Agricultural impacts were subtler in other lakes. Our study expands on prior applications of geochemical fingerprinting in forensic paleolimnology when direct monitoring data are incomplete. This multi-proxy approach has promising applications for environmental pollution assessments in other lake ecosystems experiencing water quality issues.

Archaeological soil from Roman occupational layers can be differentiated by microbial and chemical signatures

IntroductionSoil at the Roman site of Vindolanda (Northumberland, UK) provides excellent preservation of wooden artefacts including Roman writing tablets.MethodsIn this study we examined chemical and microbial signature changes within varied occupation contexts of archaeological soil. Analysis included investigating elemental composition, sterol biomarkers, bacterial diversity and community structures from excavation trenches at Vindolanda using pXRF, GC-MS and 16S rRNA gene amplicon sequencing. Samples were taken from varying depths starting at topsoil and working down through layers of Roman occupation including one cavalry stable floor, two infantry barracks and a cook house, and layers which contained Roman writing tablets.Results and DiscussionThe chemical results indicate that areas where wooden artefacts were found had increased soil moisture which was also correlated with specific chemical conditions including shifts in iron, sulphur and phosphorous concentration. Steroid biomarkers indicate the presence of faecal matter in layers, supporting occupation descriptions. Overall microbial diversity did not change across the depth profile but was correlated with soil moisture. Anaerobic soils associated with more optimal preservation differed to other soils with increases in Firmicutes, Proteobacteria, Campilobacterota and Bacteroidota observed. Microbial community structure and putative function as revealed by PICRUSt2 is linked to occupation usage rather than depth of samples with laminated floor layers differing from turf structures. Understanding the complex processes within archaeological soil can help us to understand dynamics of decomposition and preservation. In addition, the apparent preservation of the environmental microbial community as well as the artefacts themselves allows us to understand the microbial environments of the past, how they relate to the present and what this means for our changing environments in the future.

Microbial utilization of recently fixed, plant-derived organic carbon in shallow Holocene and Pleistocene aquifers in Bangladesh

The presence of dissolved arsenic in shallow aquifers of Bangladesh is widely accepted to require microbial dissimilatory iron-reduction in anoxic aquifers utilizing organic carbon as an electron donor. However, the various potential sources of this carbon, and whether organic carbon sources vary with sediment age (i.e. < 12 kyr-old Holocene vs older Pleistocene sediments) are still poorly understood. To shed light on these questions, natural abundance radiocarbon signatures of in situ microbial phospholipids fatty acids (PLFA), concentrations of sterol biomarkers, and aqueous [Cl-] and [Br-] were compared in two Bangladesh aquifers; a shallow (11–15 m) aquifer low in dissolved arsenic containing oxidized (orange) Pleistocene sands, Dopar Tek (DT), and a shallow (6–21 m) aquifer high in dissolved arsenic containing reduced (grey) Holocene sands, Desert Island (DI). Radiocarbon signatures of PLFA (Δ14CPLFA = −30 to −63 ‰ and +9 to +25 ‰, respectively) indicate microbial utilization of carbon fixed from the atmosphere within the last several decades, the drawdown of which into the shallow portions of both the Pleistocene Dopar Tek and Holocene Desert Island aquifers was likely enhanced by regional pumping activities. Similar results were previously obtained for two other Holocene aquifers in the same region, but to our knowledge this is the first time modern PLFA has been extracted from Pleistocene sediments. At both sites, high proportions of phytosterols, low sewage contamination indices (SCI < 0.7), and generally low Cl/Br ratios (averaging 434 and 544 at Desert Island and Dopar Tek respectively), are consistent with predominantly plant-derived organic carbon inputs. This contrasts with sewage-derived input inferred from higher sewage contamination index values (>0.7) previously observed at the two other shallow Holocene aquifers in the same region. Overall, our observations show that microbial communities within shallow aquifers, including those of Pleistocene age, utilize very recently fixed organic carbon associated with both plant and/or sewage origin. The microbial utilization of organic carbon fixed within the past several decades, likely derived from plants, in the anaerobic Pleistocene, has not, as of yet, led to iron reduction that would be sufficient to increase arsenic concentrations in groundwater. However, the observed microbial utilization of recently fixed carbon within all Bangladesh aquifers studied to date, indicates that pumping enhanced drawdown represents a potential risk to any systems where it might occur.

Sterols of Amphidinium species in the Operculatum Clade: Predominance of cholesterol instead of Δ8 (14) sterols previously considered Amphidinium-specific biomarkers.

The dinoflagellates Amphidinium carterae and Amphidinium corpulentum have been previously characterized as having Δ8(14) -nuclear unsaturated 4α-methyl-5α-cholest-8(14)-en-3β-ol (C28:1 ) and 4α-methyl-5α-ergosta-8(14),24(28)-dien-3β-ol (amphisterol; C29:2 ) as predominant sterols, where they comprise approximately 80% of the total sterol composition. These two sterols have hence been considered as possible major sterol biomarkers for the genus. Here, we have examined the sterols of four recently identified species of Amphidinium (Amphidinium fijiense, Amphidinium magnum, Amphidinium theodori, and Amphidinium tomasii) that are closely related to Amphidinium operculatum as part of what is termed the Operculatum Clade to show that each species has its sterol composition dominated by the common dinoflagellate sterol cholesterol (cholest-5-en-3β-ol; C27:1 ), which is found in many other dinoflagellate genera, rather than Δ8(14) sterols. While the Δ8(14) sterols 4α-methyl-5α-cholest-8(14)-en-3β-ol and 4α,23,24-trimethyl-5α-cholest-8(14),22E-dien-3β-ol (C30:2 ) were present as minor sterols along with another common dinoflagellate sterol, 4α,23,24-trimethyl-5α-cholest-22E-en-3β-ol (dinosterol; C30:1 ), in some of these four species, amphisterol was not conclusively observed. From a chemotaxonomic perspective, while this does reinforce the genus Amphidinium's ability to produce Δ8(14) sterols, albeit here as minor sterols, these results demonstrate that caution should be used when considering Δ8(14) sterols, especially amphisterol, as Amphidinium-specific biomarkers within these species where cholesterol is the predominant sterol.

EVALUATION OF SEDIMENT CONTAMINATION BY URBAN SEWAGE IN A STRETCH OF CAPIBARIBE RIVER, PERNAMBUCO, BRAZIL

Anthropic activities are responsible for the increase in environmental contamination, especially in aquatic systems, demanding studies to assess and monitor contamination levels in different water bodies. We have done a chemical characterization of eleven sediments in order to evaluate the level of contamination by domestic sewage from the Capibaribe River, between the cities of Santa Cruz do Capibaribe and Toritama in the state of Pernambuco, Brazil. The classical analyses were performed, as well as the determination of sterol biomarkers using liquid chromatography coupled to tandem mass spectrometry. Sterol ratios corroborated the presence of fecal-derived organic matter, mainly in the sediments collected in regions of higher population occupation. The multivariate statistical analysis clearly showed the regions from the most contaminated to the least contaminated, indicating the severe contamination by domestic sewage in the region. To the best of our knowledge, this is the first study to assess anthropic contamination of the Capibaribe River by using sterol biomarkers and classical analyses in an integrative data interpretation. This can be helpful when making decisions about preventive and corrective actions for human health concerns.

Exploring the application of TEX86 and the sources of organic matter in the Antarctic coastal region

Isoprenoidal glycerol dialkyl glycerol tetraethers (isoGDGTs) are archaeal biomarkers. In many settings, the degree of cyclization of isoGDGTs is correlated with temperature, forming the basis of the TEX86 paleothermometer that is widely used to reconstruct sea surface temperature (SST) across a range of time scales. However, the application of TEX86 to the polar regions is relatively limited and there is currently no consensus on which calibration is best suited for polar environments. In addition, application of TEX86 to the polar regions is complicated by uncertainty regarding the source of organic matter input in coastal polar environments. We tested five different calibrations for TEX86 in marine sediments from the Antarctic coastal region of Admiralty Bay near King George Island, using four short cores that span the second half of the 20th century. We also explored the possible sources of organic matter in these cores using sterol biomarkers. Best results for TEX86 were obtained using a quadratic calibration. The TEX86 signal presented a strong seasonal signal and best matched reanalysis temperatures of the austral spring season (Oct-Nov-Dec). The most abundant compounds observed in the sediments were the sterols cholest-5-en-3β-ol and 24-ethylcholest-5-en-3β-ol, the fatty alcohols C16 and phytol, and isoGDGT-0, indicating a dominant marine origin of the organic matter. Differences in their vertical distributions suggests that some compounds (such as cholest-5-en-3β-ol and phytol) may have had different sources over the evaluated period. Together our results indicate that TEX86 can be used to reconstruct SSTs in the Antarctic coastal region.

Seasonal shifts in fatty acids and sterols in sponges, corals, and bivalves, in a southern Gulf of Mexico coral reef under river influence

Tropical coral reefs influenced by rivers are exposed to changes in turbidity, sedimentation, and wastewater discharges that might affect the growth and survival of the corals and their associated community. However, riverine nutrients and fine particulate organic matter can constitute food resources for suspension-feeding animals within reef ecosystems. Organic biomarkers from sessile suspension feeders represent their surrounding environment more reliably and can assist in monitoring the health of ecosystems. Here we evaluated the seasonal (dry and rainy) effect of natural and anthropogenic sources of organic matter on fatty acid and sterol biomarkers of sessile suspension and filter-feeding animals such as the sponge Aplysina sp., the great star coral Montastraea cavernosa, and the amber pen shell Pinna carnea in a coral reef under river influence. Sponges did not show significant differences in their fatty acid profiles between dry and rainy seasons, except for increases in fatty acids associated with the consumption of bacteria in the rainy season. However, they shifted from higher proportions of episterol, brassicasterol, and poriferasterol, which are abundant in phytoplankton, red, and brown algae, respectively, in the dry season, to higher proportions of β-sitosterol abundant in higher plants such as seagrass and mangrove, in the rainy season. In contrast, the fatty acid profile of the whole coral M. cavernosa had an 80% multivariate similarity with that of its symbiont Symbiodiniaceae, a fraction which was separated only in the rainy season. The whole coral M. cavernosa also had a higher proportion of gorgosterol, in the dry season. However, during the rainy season, the whole coral shifted from higher proportions of gorgosterol and campesterol to higher proportions of cholesterol, brassicasterol from red algae and episterol, a distinctive sterol of phytoplankton. Bivalves reflected a significant shift in their fatty acids following seasonal phytoplankton changes, but did not show seasonal changes in their sterols. Sterol profiles in sponges, corals, and bivalves were significantly different from the sterol profile in sewage. However, in the rainy season, their similarity increased compared to the dry season. Still, coprostanol, a human feces biomarker indicative of sewage input, was detected in the suspended particulate matter at the surface, but not in any of the suspension-feeding animals studied. This suggests that marine currents dispersed urban sewage before reaching benthic organisms. Alternatively, coprostanol could have been metabolized before reaching the filter feeders or by the filter feeders themselves.

Plant wax evidence for precipitation and vegetation change from a coastal sinkhole lake in the Bahamas spanning the last 3000 years

Plant wax hydrogen isotopic composition is commonly used to reconstruct the hydrogen isotopic composition of precipitation used by terrestrial vegetation. However, mangroves growing in coastal environments take up a mixture of freshwater and seawater. Biosynthetic fractionation (between source water and plant wax) differs between plant types and as a function of salinity, potentially complicating interpretations of past precipitation in coastal environments. In order to reconstruct Holocene hydrologic and ecologic changes archived within sediments from Blackwood Sinkhole on Abaco Island in The Bahamas, we adopt a multi-proxy approach using plant wax hydrogen isotopic composition (δ2H) to reconstruct paleohydrology, together with plant wax carbon isotopic composition (δ13Cwax), sterol biomarkers and pollen abundances to identify vegetation change. When pollen indicates a stable terrestrial plant community (2950–850 cal yrs BP), variations of δ2H values measured on the plant wax C28n-alkanoic acid are interpreted in terms of precipitation isotope (δ2Hprecip) changes, with 2H-depletion from 2950 to ∼2100 cal yrs BP and ∼1700 to 1000 cal yrs BP. However, interpretation is complicated at 850 cal yrs BP, when δ2H values decrease (−50‰) concurrent with increased Laguncularia racemosa (white mangrove) and Conocarpus erectus (buttonwood mangrove), and the mangrove-derived biomarker, taraxerol. We develop a pollen-based correction for mangrove inputs, yielding reconstructed precipitation isotope estimates (δ2Hprecip-corr). Low δ2Hprecip-corr values are synchronous with increased abundance of pine pollen, both of which may indicate wetter conditions from 850 cal yrs BP to present. This study provides additional evidence that mangroves can complicate hydrologic reconstructions from n-alkyl terrestrial plant wax biomarkers, and that such complication can be removed by pollen-based correction. After correcting for mangrove inputs, we obtain estimates of δ2Hprecip-corr from −33 to +25‰ throughout the last 2950 years, with uncertainties on the order of 10–20‰.

Holocene organic geochemical record from the Western Indus continental shelf (northern Arabian Sea)

Primary production on the Western Indus continental shelf has been linked to the large quantities of nutrients delivered to the shelf by the Indus River. Multiple geochemical tracers and biomarker records, including stable isotopes (δ13C and δ15N), total organic carbon (TOC), total nitrogen (TN), molar carbon/nitrogen (C/N) ratio, the branched and isoprenoid tetraether (BIT) index, and glycerol dialkyl glycerol tetraether (GDGT), have been analyzed from the Indus-23AP sediment core recovered from the northern Arabian Sea. Our records show evidence of a mixture of marine and terrestrially derived organic matter (OM) during the last 14,000 years, as indicated by the C/N ratio, δ13C, δ15N, and the BIT index. The three sterol biomarkers (brassicasterol, dinosterol, and cholesterol) show concurrent enrichments during the last 3 millennia reflecting increased phytoplankton abundance because of increased Indus river discharge of nutrients during the summer monsoon. GDGT crenarchaeol enrichment is related to the BIT index. The TEX86-derived sea surface temperature (SST) record is shifted toward the summer season because Crenarchaeota are more abundant and active during periods of high primary production. SSTs indicate a long-term warming trend during the Holocene related to increasing winter insolation in the low latitudes northern Hemisphere.

Alterations in the sterol signature of detritivorous fish along pollution gradients in the Río de la Plata basin (Argentina): From plant to sewage-based diet

In order to assess the impact of sewage pollution on the diet of the strict detritivorous and migratory South American fish, Prochilodus lineatus, 16 sterol biomarkers were analyzed by gas chromatography-mass spectrometry from fish muscle (n: 144) collected along 1200 km in the Rio de la Plata basin. Sterol concentrations were fairly homogeneous (2.4 ± 1.3 mg g−1 dry weight), but their proportion in lipids was highly variable and inversely related to both body mass and lipid contents, reflecting the more conservative character of sterols compared to the rapid accumulation of fat as fish grows. As expected, the muscle sterol signature was widely dominated by cholesterol (92 ± 4.5% of total sterols), but it exhibited a remarkable diversity with variable proportions of fecal coprostanol (4.0 ± 4.4%) and plant sterols (3.1 ± 1.9%, e.g. sitosterol and campesterol). Muscle sterols exhibited contrasting geographical differences associated with dietary shifts from plant-derived detritus in the northern reaches of the basin (N: Paraná and Uruguay Rivers), to sewage dominated inputs at Buenos Aires (BA). Fish from BA are fattier (lipids: 35 ± 18 vs. 15 ± 9.0% at N), with higher total sterol contents (2.6 ± 1.3 vs. 1.9 ± 1.0 mg g−1), abundant coprostanol (5.3 ± 4.4 vs. 0.46 ± 1.1%) and lower plant sterols (2.6 ± 1.6 vs 4.6 ± 2.0%), reflecting a diet shifted to anthropogenic organic matter as opposed to vegetal detritus in the north. Accordingly, BA fish presented lower phyto/fecal sterol ratios (0.37 ± 0.21 vs. 0.91 ± 0.12 at N) and higher copro/epicoprostanol ratios (0.95 ± 0.082 vs 0.51 ± 0.25 at N), indicating fresh fecal inputs which provide a valuable supply of easily absorbed organic matter at this site. In addition, the sterol signature allowed to distinguish migratory fish from BA collected 900 km north (previously identified by their pollutant fingerprint and biochemical composition). In fact, coprostanol concentrations show a direct relationship with human populations along the basin, highlighting the usefulness of fecal sterol biomarkers as tracers of polluted fish stocks.

Sterol biomarkers and fecal coliforms in a tropical estuary: Seasonal distribution and sources

The Sergipe River estuary has been subjected to a range of anthropogenic activities including food, plastic, textile, ceramic and metallurgical production plants along with domestic sewage inputs, all of which are of environmental concern. In this study, the levels of fecal coliforms (FC) in surface water samples and sterols in superficial sediment samples collected from the Sergipe River estuary were determined. Based on the FC concentrations, 58% of the water samples were considered Water Potentially Unusable (WPU) according to the United States Environmental Protection Agency (USEPA). Concentrations of coprostanol ranged from 13 to 1072 ng g−1, indicating a significant input of sewage at some points in the estuary. Principal Component Analysis (PCA) showed that there is no clear correlation between the coprostanol and coliform data, which may be due to the high resistance to degradation of coprostanol in sediments and to recent inputs of sewage at the water sample collection points.

Sewage contamination of Amazon streams crossing Manaus (Brazil) by sterol biomarkers

Sewage pollution is a principal factor of decreasing water quality, although it has not been considered a real impact in Amazonia that is still considered a pristine environment around the world. Thus, this study aimed to assess the levels of sewage contamination in sediments from three streams crossing Manaus − a Brazilian city of 2,403,796 inhabitants in the heart of the Amazon rain forest. Cholesterol, cholestanol, brassicasterol, ergosterol, stigmasterol, β-sitosterol, campesterol, stigmastanol, coprostanol, and epicoprostanol levels were determined by liquid chromatography tandem mass spectrometry (LC−MS/MS). The fecal indicator, coprostanol, was found in high concentrations (509−12 830 ng g−1) and high relative proportions (21–54%) in all samples collected in the Mindu stream that crosses many heavily populated districts of the city, and in the Quarenta stream that crosses the Industrial District of Manaus. The sediments of the Tarumã-Açu stream also presented coprostanol; however, concentrations (<LOQ−142 ng g−1) and relative proportions (0–7%) were much lower in this stream. Sterol ratios indicate a severe contamination of the urban streams (Mindu and Quarenta) and a low to moderate contamination of the partially urban stream (Tarumã-Açu). This is the first study evaluating the levels of sewage contamination of Amazon streams using sterol biomarkers and the results obtained herein indicate the need of an immediate implementation of effective sewage treatment strategies. Additionally, these findings may be considered as baseline concentrations for future monitoring programs of that globally important environment.

Paradox of hypercholesterolaemia in highly trained, keto-adapted athletes

ObjectiveA growing number of ultra-endurance athletes have switched to a very low-carbohydrate/high-fat eating pattern. We compared markers of cholesterol and the lipoprotein profile in a group of elite ultra-runners consuming...

Using fecal sterols to assess dynamics of sewage input in sediments along a human-impacted river-estuary system in eastern China

Sedimentary fecal sterols and other sterol biomarkers, combined with bulk total organic carbon (TOC) and its stable carbon isotope were applied to characterize the sewage contamination across a ca. 280 km transect from the Xiaoqing River to the Laizhou Bay, a typical river-estuary system subjected to extensive anthropogenic stress due to rapid regional urbanization and industrialization in eastern China. Two sampling events were performed in both spring and summer seasons in the Laizhou Bay adjacent to the Xiaoqing River in order to assess the potential seasonal variation. Fecal sterols such as coprostanol and epicoprostanol, which are typical indicators of anthropogenic sewage input, displayed high concentrations of up to 63.2 μg g−1 dry weight (dw) and 13.1 μg g−1 dw, respectively. Results suggested that most of the stations along the Xiaoqing River were severely contaminated by fecal inputs with a decreasing trend from the river to the estuary that was mainly explained by the increasing distance from the diffuse sewage sources and the gradual dilution by sea water. Although there was no significant difference in fecal sterol concentrations between spring and summer in the Laizhou Bay, suggestive of no significant difference in sewage abundance, significantly higher average epicoprostanol/coprostanol and lower coprostanol/epicoprostanol ratios were observed in spring than summer, indicative of different sewage sources (e.g., human vs. non-human). Seasonal discharge and land-runoff, air temperature related to microbial activity differences and different extend of animal manure irrigation during agricultural planting could be additional reasons and need further investigation. Nevertheless, fecal sterol concentrations, distributions and diagnostic ratios should all be taken into consideration to better understand sewage inputs and source dynamics in river-estuary ecosystems.

Early diagenetic alterations of sterol biomarkers during particle settling and burial in polluted and pristine areas of the Rio de la Plata Basin

Sources and diagenetic alterations of sterol markers were studied in settling material and sediments near the Buenos Aires main sewer (BA), and at a relatively non-polluted northern site at the Uruguay River (N). Vertical particle fluxes were 7-times higher at BA relative to N (34 ± 24 vs 4.6 ± 3.6 mg/cm2/day; mean ± standard deviation), increasing during rainy months. Total sterol contents were consistently higher at BA, both in settling material (7140 ± 7905 vs 41 ± 47 μg/g at N) and sediments (708 ± 454 vs 1.9 ± 0.18 μg/g). This difference was further amplified in the vertical flux of sterols (116 ± 168 vs 0.070 ± 0.13 mg/cm2/year). At BA, sterol composition of settling material and sediments was dominated by fecal sterols (75–77%), with extreme coprostanol concentrations (3.6 ± 4.8 vs 0.35 ± 0.28 mg/g at N) which are similar to sewage sludge. In contrast, at N the sterol profile was dominated by plant sterols (57–64%), mainly sitosterol, stigmasterol and campesterol. At BA the discharge of fresh sewage was confirmed by the high coprostanol/(coprostanol + epicoprostanol) ratio. At N, the overwhelming dominance of plant sterols over herbivore fecal sterols was reflected by the high sitosterol/(sitosterol + 24-ethylcoprostanol) ratio and the low coprostanol/(coprostanol + 24-ethylcoprostanol) ratio. The coprostanol/(coprostanol + epicoprostanol) and cholesterol/(cholesterol + cholestanol) ratios were lower in sediments than in settling material, reflecting the sterol degradation at the sediment surface. The accumulation efficiencies, calculated as the difference between trap fluxes and sediment inventories, were 2–7 times higher at BA reflecting strong vertical fluxes and enhanced preservation under anoxic conditions. During diagenetic processes, epicoprostanol (partially produced in situ), cholestanol and plant sterols were the best-preserved sterols, while cholesterol was the most labile during burial.

Distribution and sources of sterol biomarkers in sediments collected from a tropical estuary in Northeast Brazil.

The Piauí-Real estuary is located along the southern coast of Sergipe state, Northeast Brazil. This estuary has great economic importance due to its physical, biological, and socioeconomic diversity, but it is subject to anthropogenic stress since the resident population in the town bordered by the estuarine system has grown in recent years. Thus, the possibility of sewage contamination originating from the approximately 450,000 inhabitants living within its drainage basin was investigated in this study. Sediment samples were collected from 15 sampling stations along the estuarine system and extracted, followed by gas chromatography-mass spectrometry (GC-MS) analysis. Six sterols were quantified, indicating natural and anthropogenic sources. Coprostanol concentrations higher than 100ngg-1 were observed in 47% of the stations analyzed, indicating sewage contamination, which was confirmed by the diagnostic ratios calculated. Based on the Pearson correlation test, a significant correlation between coprostanol concentrations and total organic carbon content (TOC) was observed, indicating that sterols record the history of sewage inputs in this area. These results indicate that control of the organic inputs into the estuarine system is required. Graphical abstract Sterol markers were determined and sources assessed in surface sediments from Piauí-Real estuarine system.

Fecal Contamination in Laolongdong Underground River as Measured by the Sterol Biomarkers

To investigate whether the underground river was polluted or not, and trace the source of fecal sterols, the particulate water samples were collected from typical karst underground river named Laolongdong in Nan'an District, Chongqing Municipality in October, 2014, January, March and May, 2015. Ten prior steroids in the underground river were quantitatively analyzed by the gas chromatography-mass spectrometer (GC-MS). The results showed ten steroids including 9 sterols and 1 ketone were detected. During the sampling period, the mass concentrations of particulate steroids (ranging between 1573 and 5007 ng·L-1) in March and May were higher than those in October and January. The 3 principal steroids-cholesterol, β-sitosterol and coprosterol-in the river accounted for 50.8%-80.4% of the total steroids. The ratios of (epicoprostanol+coprostanol) to (coprostanol+epicoprostanol+cholestanol) of three samples were greater than 0.7, which indicated the river was contaminated in sampling months. The ratio of epicoprostanol to coprostanol was less than 0.2 in October, which indicated the wastewater came from the upstream sewage treatment plant. The ratios of coprostanol to ΣSteroids and coprostanol to 24-ethylcoprostanol in January, March and May were respectively 0.109-0.254 and 6.3-10.3, which indicated that Laolongdong underground river was mainly polluted by human feces. The ratio of 24-ethylcoprostanol to 24-ethylcholestanol in March (0.86) was less than those in January (5.4) and May (2.3), which showed the river was polluted more severely in March than in January and May by poultry dung.

Sterol ratios as a tool for sewage pollution assessment of river sediments in Serbia

In this work, source pollution tracing of the sediments of the Danube River and its tributaries in Serbia was performed using sterol ratios. Improved liquid chromatography-tandem mass spectrometry method, which enabled complete chromatographic separation of four analytes with identical fragmentation reactions (epicoprostanol, coprostanol, epicholestanol and cholestanol), was applied for the determination of steroid compounds (hormones, human/animal and plant sterols). A widespread occurrence of sterols was identified in all analyzed samples, whereas the only detected hormones were mestranol and 17α-estradiol. A human-sourced sewage marker coprostanol was detected at the highest concentration (up to 1939 ng g−1). The ratios between the key sterol biomarkers, as well as the percentage of coprostanol relative to the total sterol amount, were applied with the aim of selecting the most reliable for distinction between human-sourced pollution and the sterols originated from the natural sources in river sediments. The coprostanol/(cholesterol + cholestanol) and coprostanol/epicoprostanol ratios do not distinguish between human and natural sources of sterols in the river sediments in Serbia. The most reliable sterol ratios for the sewage pollution assessment of river sediments in the studied area were found to be coprostanol/(coprostanol + cholestanol), coprostanol/cholesterol and epicoprostanol/coprostanol. For the majority of sediments, human-derived pollution was determined. Two sediment samples were identified as influenced by a combination of human and natural biogenic sources.

Cholesterol metabolism in cholestatic liver disease and liver transplantation: From molecular mechanisms to clinical implications

The aim of this review is to enlighten the critical roles that the liver plays in cholesterol metabolism. Liver transplantation can serve as gene therapy or a source of gene transmission in certain conditions that affect cholesterol metabolism, such as low-density-lipoprotein (LDL) receptor gene mutations that are associated with familial hypercholesterolemia. On the other hand, cholestatic liver disease often alters cholesterol metabolism. Cholestasis can lead to formation of lipoprotein X (Lp-X), which is frequently mistaken for LDL on routine clinical tests. In contrast to LDL, Lp-X is non-atherogenic, and failure to differentiate between the two can interfere with cardiovascular risk assessment, potentially leading to prescription of futile lipid-lowering therapy. Statins do not effectively lower Lp-X levels, and cholestasis may lead to accumulation of toxic levels of statins. Moreover, severe cholestasis results in poor micellar formation, which reduces cholesterol absorption, potentially impairing the cholesterol-lowering effect of ezetimibe. Apolipoprotein B-100 measurement can help distinguish between atherogenic and non-atherogenic hypercholesterolemia. Furthermore, routine serum cholesterol measurements alone cannot reflect cholesterol absorption and synthesis. Measurements of serum non-cholesterol sterol biomarkers - such as cholesterol precursor sterols, plant sterols, and cholestanol - may help with the comprehensive assessment of cholesterol metabolism. An adequate cholesterol supply is essential for liver-regenerative capacity. Low preoperative and perioperative serum cholesterol levels seem to predict mortality in liver cirrhosis and after liver transplantation. Thus, accurate lipid profile evaluation is highly important in liver disease and after liver transplantation.

Lipid markers of diet history and their retention during experimental starvation in the Bering Sea euphausiid Thysanoessa raschii

Two extended pulsed feeding experiments, following the spring bloom period, investigated lipid retention in the prominent Bering Sea euphausiid (krill) Thysanoessa raschii. These experiments occurred during late spring and early summer of 2010. Concurrent taxonomic analysis of the natural algal community allowed prey type to be linked to lipid composition of the natural communities. In late spring, experimental periods of feeding followed by starvation showed an overall decrease in total lipid for T. raschii. In early summer, no consistent trend was observed for total lipid with the visible presence of storage lipid in some animals. Polar lipids, as phospholipids, were the dominant krill lipid class in both experiments constituting ≥88% of total lipid, and triacylglycerols reached a maximum of 5% of total lipid. The sterols cholesterol and brassicasterol+desmosterol comprised 98–99% of total sterol abundances in T. raschii throughout both experiments, even after feeding periods when alternative sterols (i.e. the algal sterol 24-methylenecholesterol) accounted for up to 39% of sterols in potential food particles. Cholesterol abundance and concentration increased during both incubations, likely due to the metabolism of dietary sterols. Major fatty acids observed in krill included C14:0n, C16:0n, C16:1(n-7), C18:1(n-7), C18:1(n-9), C20:5(n-3), and C22:6(n-3) with the diatom-attributed C16:1(n-7) decreasing in abundance and concentration during starvation. Low concentrations of the dinoflagellate-derived sterol and a novel C28:8 PUFA, typically found in dinoflagellates and prymnesiophytes, indicated predation on protozooplankton in early summer when diatom abundances were low. The stability of lipid distributions over periods of starvation and intermittent feeding suggest that fatty acid and sterol biomarkers present in this polar euphausiid principally reflect long-term diet history rather than short-term feeding episodes.