Metabolomics in human SGBS cells as new approach method for studying adipogenic effects: Analysis of the effects of DINCH and MINCH on central carbon metabolism

Growing evidence suggests that exposure to certain metabolism-disrupting chemicals (MDCs), such as the phthalate plasticizer DEHP, might promote obesity in humans, contributing to the spread of this global health problem. Due to the restriction on the use of phthalates, there has been a shift to safer declared substitutes, including the plasticizer diisononyl-cyclohexane-1,2-dicarboxylate (DINCH). Notwithstanding, recent studies suggest that the primary metabolite monoisononyl-cyclohexane-1,2-dicarboxylic acid ester (MINCH), induces differentiation of human adipocytes and affects enzyme levels of key metabolic pathways. Given the lack of methods for assessing metabolism-disrupting effects of chemicals on adipose tissue, we used metabolomics to analyze human SGSB cells exposed to DINCH or MINCH. Concentration analysis of DINCH and MINCH revealed that uptake of MINCH in preadipocytes was associated with increased lipid accumulation during adipogenesis. Although we also observed intracellular uptake for DINCH, the solubility of DINCH in cell culture medium was limited, hampering the analysis of possible effects in the μM concentration range. Metabolomics revealed that MINCH induces lipid accumulation similar to peroxisome proliferator-activated receptor gamma (PPARG)-agonist rosiglitazone through upregulation of the pyruvate cycle, which was recently identified as a key driver of de novo lipogenesis. Analysis of the metabolome in the presence of the PPARG-inhibitor GW9662 indicated that the effect of MINCH on metabolism was mediated at least partly by a PPARG-independent mechanism. However, all effects of MINCH were only observed at high concentrations of 10 μM, which are three orders of magnitudes higher than the current concentrations of plasticizers in human serum. Overall, the assessment of the effects of DINCH and MINCH on SGBS cells by metabolomics revealed no adipogenic potential at physiologically relevant concentrations. This finding aligns with previous in vivo studies and supports the potential of our method as a New Approach Method (NAM) for the assessment of adipogenic effects of environmental chemicals.

Pharmacological activation of constitutive androstane receptor induces female-specific modulation of hepatic metabolism

Background & Aims

The constitutive androstane receptor (CAR) is a nuclear receptor that binds diverse xenobiotics and whose activation leads to the modulation of the expression of target genes involved in xenobiotic detoxification and energy metabolism. Although CAR hepatic activity is considered to be higher in women than in men, its sex-dependent response to an acute pharmacological activation has seldom been investigated.

Methods

The hepatic transcriptome, plasma markers, and hepatic metabolome, were analysed in Car+/+ and Car-/- male and female mice treated either with the CAR-specific agonist 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) or with vehicle.

Results

Although 90% of TCPOBOP-sensitive genes were modulated in a sex-independent manner, the remaining 10% showed almost exclusive female liver specificity. These female-specific CAR-sensitive genes were mainly involved in xenobiotic metabolism, inflammation, and extracellular matrix organisation. CAR activation also induced higher hepatic oxidative stress and hepatocyte cytolysis in females than in males. Hepatic expression of flavin monooxygenase 3 (Fmo3) was almost abolished and was associated with a decrease in hepatic trimethylamine-N-oxide (TMAO) concentration in TCPOBOP-treated females. In line with a potential role in the control of TMAO homeostasis, CAR activation decreased platelet hyper-responsiveness in female mice supplemented with dietary choline.

Conclusions

More than 10% of CAR-sensitive genes are sex-specific and influence hepatic and systemic responses such as platelet aggregation. CAR activation may be an important mechanism of sexually-dimorphic drug-induced liver injury.

Impact and implications

CAR is activated by many drugs and pollutants. Its pharmacological activation had a stronger impact on hepatic gene expression and metabolism in females than in males, and had a specific impact on liver toxicity and trimethylamine metabolism. Sexual dimorphism should be considered when testing and/or prescribing xenobiotics known to activate CAR.

DSS treatment does not affect murine colonic microbiota in absence of the host

The prevalence of inflammatory bowel disease (IBD) is rising globally; however, its etiology is still not fully understood. Patient genetics, immune system, and intestinal microbiota are considered critical factors contributing to IBD. Preclinical animal models are crucial to better understand the importance of individual contributing factors. Among these, the dextran sodium sulfate (DSS) colitis model is the most widely used. DSS treatment induces gut inflammation and dysbiosis. However, its exact mode of action remains unclear. To determine whether DSS treatment induces pathogenic changes in the microbiota, we investigated the microbiota-modulating effects of DSS on murine microbiota in vitro. For this purpose, we cultured murine microbiota from the colon in six replicate continuous bioreactors. Three bioreactors were supplemented with 1% DSS and compared with the remaining PBS-treated control bioreactors by means of microbiota taxonomy and functionality. Using metaproteomics, we did not identify significant changes in microbial taxonomy, either at the phylum or genus levels. No differences in the metabolic pathways were observed. Furthermore, the global metabolome and targeted short-chain fatty acid (SCFA) quantification did not reveal any DSS-related changes. DSS had negligible effects on microbial functionality and taxonomy in vitro in the absence of the host environment. Our results underline that the DSS colitis mouse model is a suitable model to study host-microbiota interactions, which may help to understand how intestinal inflammation modulates the microbiota at the taxonomic and functional levels.

Human gut microbiome and metabolite dynamics under simulated microgravity

The Artificial Gravity Bed Rest - European Space Agency (AGBRESA) study was the first joint bed rest study by ESA, DLR, and NASA that examined the effect of simulated weightlessness on the human body and assessed the potential benefits of artificial gravity as a countermeasure in an analog of long-duration spaceflight. In this study, we investigated the impact of simulated microgravity on the gut microbiome of 12 participants during a 60-day head-down tilt bed rest at the :envihab facilities. Over 60 days of simulated microgravity resulted in a mild change in the gut microbiome, with distinct microbial patterns and pathway expression in the feces of the countermeasure group compared to the microgravity simulation-only group. Additionally, we found that the countermeasure protocols selectively increased the abundance of beneficial short-chain fatty acids in the gut, such as acetate, butyrate, and propionate. Some physiological signatures also included the modulation of taxa reported to be either beneficial or opportunistic, indicating a mild adaptation in the microbiome network balance. Our results suggest that monitoring the gut microbial catalog along with pathway clustering and metabolite profiling is an informative synergistic strategy to determine health disturbances and the outcome of countermeasure protocols for future space missions.

The effect of polyphenols on DNA methylation-assessed biological age attenuation: the DIRECT PLUS randomized controlled trial

BACKGROUND

Epigenetic age is an estimator of biological age based on DNA methylation; its discrepancy from chronologic age warrants further investigation. We recently reported that greater polyphenol intake benefitted ectopic fats, brain function, and gut microbiota profile, corresponding with elevated urine polyphenols. The effect of polyphenol-rich dietary interventions on biological aging is yet to be determined.

METHODS

We calculated different biological aging epigenetic clocks of different generations (Horvath2013, Hannum2013, Li2018, Horvath skin and blood2018, PhenoAge2018, PCGrimAge2022), their corresponding age and intrinsic age accelerations, and DunedinPACE, all based on DNA methylation (Illumina EPIC array; pre-specified secondary outcome) for 256 participants with abdominal obesity or dyslipidemia, before and after the 18-month DIRECT PLUS randomized controlled trial. Three interventions were assigned: healthy dietary guidelines, a Mediterranean (MED) diet, and a polyphenol-rich, low-red/processed meat Green-MED diet. Both MED groups consumed 28 g walnuts/day (+ 440 mg/day polyphenols). The Green-MED group consumed green tea (3-4 cups/day) and Mankai (Wolffia globosa strain) 500-ml green shake (+ 800 mg/day polyphenols). Adherence to the Green-MED diet was assessed by questionnaire and urine polyphenols metabolomics (high-performance liquid chromatography quadrupole time of flight).

RESULTS

Baseline chronological age (51.3 ± 10.6 years) was significantly correlated with all methylation age (mAge) clocks with correlations ranging from 0.83 to 0.95; p < 2.2e - 16 for all. While all interventions did not differ in terms of changes between mAge clocks, greater Green-Med diet adherence was associated with a lower 18-month relative change (i.e., greater mAge attenuation) in Li and Hannum mAge (beta =  - 0.41, p = 0.004 and beta =  - 0.38, p = 0.03, respectively; multivariate models). Greater Li mAge attenuation (multivariate models adjusted for age, sex, baseline mAge, and weight loss) was mostly affected by higher intake of Mankai (beta =  - 1.8; p = 0.061) and green tea (beta =  - 1.57; p = 0.0016) and corresponded with elevated urine polyphenols: hydroxytyrosol, tyrosol, and urolithin C (p < 0.05 for all) and urolithin A (p = 0.08), highly common in green plants. Overall, participants undergoing either MED-style diet had ~ 8.9 months favorable difference between the observed and expected Li mAge at the end of the intervention (p = 0.02).

CONCLUSIONS

This study showed that MED and green-MED diets with increased polyphenols intake, such as green tea and Mankai, are inversely associated with biological aging. To the best of our knowledge, this is the first clinical trial to indicate a potential link between polyphenol intake, urine polyphenols, and biological aging.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03020186.

The impact of amine and carboxyl functionalised microplastics on the physiology of daphnids

Plastic waste is considered a major threat for terrestrial, marine and freshwater ecosystems. Ingestion of primary or secondary microparticles resulting from plastic degradation can lead to their trophic transfer raising serious health concerns. In this study, the effect of amine and carboxy functionalized polystyrene microparticles on the physiology of daphnids was investigated with a combination of phenotypic and metabolic endpoints. Carboxy functionalized microparticles showed higher toxicity in acute exposures compared to their amine counterparts. Accumulation of both microparticles in animal gut was confirmed by stereo-microscopy as well as fluorescent microscopy which showed no presence of particles in the rest of the animal. Fluorescence based quantification of microparticles extracted from animal lysates validated their concentration-dependent uptake. Additionally, exposure of daphnids to amine and carboxy functionalized microparticles resulted in increased activities of key enzymes related to metabolism and detoxification. Finally, significant metabolic perturbations were discovered following exposure to microplastics. These findings suggest that polystyrene microparticles can hinder organism performance of the freshwater species and highlight the importance of seeking for holistic and physiological endpoints for pollution assessment.

A polyphenol-rich green Mediterranean diet enhances epigenetic regulatory potential: the DIRECT PLUS randomized controlled trial

BACKGROUND

The capacity of a polyphenol-enriched diet to modulate the epigenome in vivo is partly unknown. Given the beneficial metabolic effects of a Mediterranean (MED) diet enriched in polyphenols and reduced in red/processed meat (green-MED), as previously been proven by the 18-month DIRECT PLUS randomized controlled trial, we analyzed the effects of the green-MED diet on methylome and transcriptome levels to highlight molecular mechanisms underlying the observed metabolic improvements.

METHODS

Our study included 260 participants (baseline BMI = 31.2 kg/m², age = 5 years) of the DIRECT PLUS trial, initially randomized to one of the intervention arms: A. healthy dietary guidelines (HDG), B. MED (440 mg polyphenols additionally provided by walnuts), C. green-MED (1240 mg polyphenols additionally provided by walnuts, green tea, and Mankai: green duckweed shake). Blood methylome and transcriptome of all study subjects were analyzed at baseline and after completing the 18-month intervention using Illumina EPIC and RNA sequencing technologies.

RESULTS

A total of 1573 differentially methylated regions (DMRs; false discovery rate (FDR) < 5 %) were found in the green-MED compared to the MED (177) and HDG (377) diet participants. This corresponded to 1753 differentially expressed genes (DEGs; FDR < 5 %) in the green-MED intervention compared to MED (7) and HDG (738). Consistently, the highest number (6 %) of epigenetic modulating genes was transcriptionally changed in subjects participating in the green-MED intervention. Weighted cluster network analysis relating transcriptional and phenotype changes among participants subjected to the green-MED intervention identified candidate genes associated with serum-folic acid change (all P < 1 × 10^-3) and highlighted one module including the KIR3DS1 locus, being negatively associated with the polyphenol changes (e.g. P < 1 × 10^-4), but positively associated with the MRI-assessed superficial subcutaneous adipose area-, weight- and waist circumference- 18-month change (all P < 0.05). Among others, this module included the DMR gene Cystathionine Beta-Synthase, playing a major role in homocysteine reduction.

CONCLUSIONS

The green-MED high polyphenol diet, rich in green tea and Mankai, renders a high capacity to regulate an individual's epigenome. Our findings suggest epigenetic key drivers such as folate and green diet marker to mediate this capacity and indicate a direct effect of dietary polyphenols on the one‑carbon metabolism.

The effect of high-polyphenol Mediterranean diet on visceral adiposity: the DIRECT PLUS randomized controlled trial

BACKGROUND

Mediterranean (MED) diet is a rich source of polyphenols, which benefit adiposity by several mechanisms. We explored the effect of the green-MED diet, twice fortified in dietary polyphenols and lower in red/processed meat, on visceral adipose tissue (VAT).

METHODS

In the 18-month Dietary Intervention Randomized Controlled Trial PoLyphenols UnproceSsed (DIRECT-PLUS) weight-loss trial, 294 participants were randomized to (A) healthy dietary guidelines (HDG), (B) MED, or (C) green-MED diets, all combined with physical activity. Both isocaloric MED groups consumed 28 g/day of walnuts (+ 440 mg/day polyphenols). The green-MED group further consumed green tea (3-4 cups/day) and Wolffia globosa (duckweed strain) plant green shake (100 g frozen cubes/day) (+ 800mg/day polyphenols) and reduced red meat intake. We used magnetic resonance imaging (MRI) to quantify the abdominal adipose tissues.

RESULTS

Participants (age = 51 years; 88% men; body mass index = 31.2 kg/m²; 29% VAT) had an 89.8% retention rate and 79.3% completed eligible MRIs. While both MED diets reached similar moderate weight (MED: - 2.7%, green-MED: - 3.9%) and waist circumference (MED: - 4.7%, green-MED: - 5.7%) loss, the green-MED dieters doubled the VAT loss (HDG: - 4.2%, MED: - 6.0%, green-MED: - 14.1%; p < 0.05, independent of age, sex, waist circumference, or weight loss). Higher dietary consumption of green tea, walnuts, and Wolffia globosa; lower red meat intake; higher total plasma polyphenols (mainly hippuric acid), and elevated urine urolithin A polyphenol were significantly related to greater VAT loss (p < 0.05, multivariate models).

CONCLUSIONS

A green-MED diet, enriched with plant-based polyphenols and lower in red/processed meat, may be a potent intervention to promote visceral adiposity regression.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT03020186.

Effects of Different Formulations of Glyphosate on Rumen Microbial Metabolism and Bacterial Community Composition in the Rumen Simulation Technique System

The use of the herbicide glyphosate and its formulations on protein-rich feedstuff for cattle leads to a considerable intake of glyphosate into the rumen of the animals, where glyphosate may potentially impair the 5-enolpyruvylshikimate-3-phosphate pathway of the commensal microbiota, which could cause dysbiosis or proliferation of pathogenic microorganisms. Here, we evaluated the effects of pure glyphosate and the formulations Durano TF and Roundup® LB plus in different concentrations on the fermentation pattern, community composition and metabolic activity of the rumen microbiota using the Rumen Simulation Technique (RUSITEC). Application of the compounds in three concentrations (0.1 mg/l, 1.0 mg/l or 10 mg/l, n = 4 each) for 9 days did not affect fermentation parameters such as pH, redox potential, NH3-N concentration and production of short-chain fatty acids compared to a control group. Microbial protein synthesis and the degradation of different feed fractions did not vary among the treatments. None of the used compounds or concentrations did affect the microbial diversity or abundance of microbial taxa. Metaproteomics revealed that the present metabolic pathways including the shikimate pathway were not affected by addition of glyphosate, Durano TF or Roundup® LB plus. In conclusion, neither pure glyphosate, nor its formulations Durano TF and Roundup® LB plus did affect the bacterial communities of the rumen.

MAIT cell activation is reduced by direct and microbiota-mediated exposure to bisphenols

Oral uptake is the primary route of human bisphenol exposure, resulting in an exposure of the intestinal microbiota and intestine-associated immune cells. Therefore, we compared the impact of bisphenol A (BPA), bisphenol F (BPF) and bisphenol S (BPS) on (i) intestinal microbiota, (ii) microbiota-mediated immunomodulatory effects and (iii) direct effects on mucosal-associated invariant T (MAIT) cells in vitro. We acutely exposed human fecal microbiota, Bacteroides thetaiotaomicron and Escherichia coli to BPA and its analogues BPF and BPS referring to the European tolerable daily intake (TDI), i.e. 2.3 µg/mL, 28.3 µg/mL and 354.0 µg/mL. Growth and viability of E. coli was most susceptible to BPF, whereas B.thetaiotaomicron and fecal microbiota were affected by BPA > BPF > BPS. At 354.0 µg/mL bisphenols altered microbial diversity in compound-specific manner and modulated microbial metabolism, with BPA already acting on metabolism at 28.3 µg/mL. Microbiota-mediated effects on MAIT cells were observed for the individual bacteria at 354.0 µg/mL only. However, BPA and BPF directly modulated MAIT cell responses at low concentrations, whereby bisphenols at concentrations equivalent for the current TDI had no modulatory effects for microbiota or for MAIT cells. Our findings indicate that acute bisphenol exposure may alter microbial metabolism and impact directly on immune cells.

A dual-function RNA balances carbon uptake and central metabolism in Vibrio cholerae

Bacterial small RNAs (sRNAs) are well known to modulate gene expression by base pairing with trans‐encoded transcripts and are typically non‐coding. However, several sRNAs have been reported to also contain an open reading frame and thus are considered dual‐function RNAs. In this study, we discovered a dual‐function RNA from Vibrio cholerae, called VcdRP, harboring a 29 amino acid small protein (VcdP), as well as a base‐pairing sequence. Using a forward genetic screen, we identified VcdRP as a repressor of cholera toxin production and link this phenotype to the inhibition of carbon transport by the base‐pairing segment of the regulator. By contrast, we demonstrate that the VcdP small protein acts downstream of carbon transport by binding to citrate synthase (GltA), the first enzyme of the citric acid cycle. Interaction of VcdP with GltA results in increased enzyme activity and together VcdR and VcdP reroute carbon metabolism. We further show that transcription of vcdRP is repressed by CRP allowing us to provide a model in which VcdRP employs two different molecular mechanisms to synchronize central metabolism in V. cholerae.

The Metabolomic-Gut-Clinical Axis of Mankai Plant-Derived Dietary Polyphenols

BACKGROUND

Polyphenols are secondary metabolites produced by plants to defend themselves from environmental stressors. We explored the effect of Wolffia globosa 'Mankai', a novel cultivated strain of a polyphenol-rich aquatic plant, on the metabolomic-gut clinical axis in vitro, in-vivo and in a clinical trial.

METHODS

We used mass-spectrometry-based metabolomics methods from three laboratories to detect Mankai phenolic metabolites and examined predicted functional pathways in a Mankai artificial-gut bioreactor. Plasma and urine polyphenols were assessed among the 294 DIRECT-PLUS 18-month trial participants, comparing the effect of a polyphenol-rich green-Mediterranean diet (+1240 mg/polyphenols/day, provided by Mankai, green tea and walnuts) to a walnuts-enriched (+440 mg/polyphenols/day) Mediterranean diet and a healthy controlled diet.

RESULTS

Approximately 200 different phenolic compounds were specifically detected in the Mankai plant. The Mankai-supplemented bioreactor artificial gut displayed a significantly higher relative-abundance of 16S-rRNA bacterial gene sequences encoding for enzymes involved in phenolic compound degradation. In humans, several Mankai-related plasma and urine polyphenols were differentially elevated in the green Mediterranean group compared with the other groups (p < 0.05) after six and 18 months of intervention (e.g., urine hydroxy-phenyl-acetic-acid and urolithin-A; plasma Naringenin and 2,5-diOH-benzoic-acid). Specific polyphenols, such as urolithin-A and 4-ethylphenol, were directly involved with clinical weight-related changes.

CONCLUSIONS

The Mankai new plant is rich in various unique potent polyphenols, potentially affecting the metabolomic-gut-clinical axis.

A Multi-Omics Analysis of Mucosal-Associated-Invariant T Cells Reveals Key Drivers of Distinct Modes of Activation

The function of mucosal-associated invariant T (MAIT) cells highly depends on the mode of activation, either by recognition of bacterial metabolites via their T cell receptor (TCR) or in a TCR-independent manner via cytokines. The underlying molecular mechanisms are not entirely understood. To define the activation of MAIT cells on the molecular level, we applied a multi-omics approach with untargeted transcriptomics, proteomics and metabolomics. Transcriptomic analysis of E. coli- and TCR-activated MAIT cells showed a distinct transcriptional reprogramming, including altered pathways, transcription factors and effector molecules. We validated the consequences of this reprogramming on the phenotype by proteomics and metabolomics. Thus, and to distinguish between TCR-dependent and -independent activation, MAIT cells were stimulated with IL12/IL18, anti-CD3/CD28 or both. Only a combination of both led to full activation of MAIT cells, comparable to activation by E. coli. Using an integrated network-based approach, we identified key drivers of the distinct modes of activation, including cytokines and transcription factors, as well as negative feedback regulators like TWIST1 or LAG3. Taken together, we present novel insights into the biological function of MAIT cells, which may represent a basis for therapeutic approaches to target MAIT cells in pathological conditions.

The glyphosate formulation Roundup® LB plus influences the global metabolome of pig gut microbiota in vitro

Glyphosate is the world's most widely used herbicide, and its potential side effects on the intestinal microbiota of various animals, from honeybees to livestock and humans, are currently under discussion. Pigs are among the most abundant livestock animals worldwide and an impact of glyphosate on their intestinal microbiota function can have serious consequences on their health, not to mention the economic effects. Recent studies that addressed microbiota-disrupting effects focused on microbial taxonomy but lacked functional information. Therefore, we chose an experimental design with a short incubation time in which effects on the community structure are not expected, but functional effects can be detected. We cultivated intestinal microbiota derived from pig colon in chemostats and investigated the acute effect of 228 mg/d glyphosate acid equivalents from Roundup® LB plus, a frequently applied glyphosate formulation. The applied glyphosate concentration resembles a worst-case scenario for an 8-9 week-old pig and relates to the maximum residue levels of glyphosate on animal fodder. The effects were determined on the functional level by metaproteomics, targeted and untargeted meta-metabolomics, while variations in community structure were analyzed by 16S rRNA gene profiling and on the single cell level by microbiota flow cytometry. Roundup® LB plus did not affect the community taxonomy or the enzymatic repertoire of the cultivated microbiota in general or on the expression of the glyphosate target enzyme 5-enolpyruvylshikimate-3-phosphate synthase in detail. On the functional level, targeted metabolite analysis of short chain fatty acids (SCFAs), free amino acids and bile acids did not reveal significant changes, whereas untargeted meta-metabolomics did identify some effects on the functional level. This multi-omics approach provides evidence for subtle metabolic effects of Roundup® LB plus under the conditions applied.

Following the community development of SIHUMIx - a new intestinal in vitro model for bioreactor use

Diverse intestinal microbiota is frequently used in in vitro bioreactor models to study the effects of diet, chemical contaminations, or medication. However, the reproducible cultivation of fecal microbiota is challenging and the resultant communities behave highly dynamic. To approach the issue of reproducibility in in vitro models, we established an intestinal microbiota model community of reduced complexity, SIHUMIx, as a valuable model for in vitro use. The development of the SIHUMIx community was monitored over time with methods covering the cellular and the molecular level. We used microbial flow cytometry, intact protein profiling and terminal restriction fragment length polymorphism analysis to assess community structure. In parallel, we analyzed the functional level by targeted analysis of short-chain fatty acids and untargeted metabolomics. The stability properties constancy, resistance, and resilience were approached both on the structural and functional level of the community. We show that the SIHUMIx community is highly reproducible and constant since day 5 of cultivation. Furthermore, SIHUMIx has the ability to resist and recover from a pulsed perturbation, with changes in community structure recovered earlier than functional changes. Since community structure and function changed divergently, both levels need to be monitored at the same time to gain a full overview of the community development. All five methods are highly suitable to follow the community dynamics of SIHUMIx and indicated stability on day five. This makes SIHUMIx a suitable in vitro model to investigate the effects of e.g. medical, chemical, or dietary interventions.

Screening for New Markers to Assess Thyroid Hormone Action by OMICs Analysis of Human Samples

Determination of the levels of thyroid-stimulating hormone (TSH) and free thyroid hormones (fTHs) is crucial for assessing thyroid function. However, as a result of inter-individual genetic variability and different environmental factors individual set points exist for TSH and fTHs and display considerable variation. Furthermore, under specific pathophysiological conditions like central hypothyroidism, TSH secreting pituitary tumors, or thyroid hormone resistance the established markers TSH and fTH fail to reliably predict thyroid function and adequate supply of TH to peripheral organs. Even in case of overt hyper- and hypothyroidism circulating fTH concentrations do not correlate with clinical symptoms. Therefore, there is a clear need for novel, more specific biomarkers to diagnose and monitor thyroid function. OMICs screening approaches allow parallel profiling of hundreds to thousands of molecules and thus comprehensive monitoring of molecular alterations in tissues and body fluids that might be associated with changes in thyroid function. These techniques thus constitute promising tools for the identification of urgently needed novel biomarkers. This mini review summarizes the findings of OMICs studies in thyroid research with a particular focus on population-based and patient studies as well as interventional approaches investigating the effects of thyroid hormone administration.

CD5L Constitutes a Novel Biomarker for Integrated Hepatic Thyroid Hormone Action

Background: Pathological conditions of the thyroid hormone (TH) system are routinely diagnosed by using serum concentrations of thyrotropin (TSH), which is sufficient in most cases. However, in certain conditions, such as resistance to TH due to mutations in THRB (RTHb) or TSH-releasing pituitary adenoma (TSHoma), TSH may be insufficient for a correct diagnosis, even in combination with serum TH concentrations. Likewise, under TH replacement therapy, these parameters can be misleading and do not always allow optimal treatment. Hence, additional biomarkers to assess challenging clinical conditions would be highly beneficial. Methods: Data from untargeted multi-omics analyses of plasma samples from experimental thyrotoxicosis in human and mouse were exploited to identify proteins that might represent possible biomarkers of TH function. Subsequent mouse studies were used to identify the tissue of origin and the involvement of the two different TH receptors (TR). For in-depth characterization of the underlying cellular mechanisms, primary mouse cells were used. Results: The analysis of the plasma proteome data sets revealed 16 plasma proteins that were concordantly differentially abundant under thyroxine treatment compared with euthyroid controls across the two species. These originated predominantly from liver, spleen, and bone. Independent studies in a clinical cohort and different mouse models identified CD5L as the most robust putative biomarker under different serum TH states and treatment periods. In vitro studies revealed that CD5L originates from proinflammatory M1 macrophages, which are similar to liver-residing Kupffer cells, and is regulated by an indirect mechanism requiring the secretion of a yet unknown factor from hepatocytes. In agreement with the role of TRα1 in immune cells and the TRβ-dependent hepatocyte-derived signaling, the in vivo regulation of Cd5l expression depended on both TR isoforms. Conclusion: Our results identify several novel targets of TH action in serum, with CD5L as the most robust marker. Although further studies will be needed to validate the specificity of these targets, CD5L seems to be a promising candidate to assess TH action in hepatocyte-macrophage crosstalk.

Quantification of glyphosate and aminomethylphosphonic acid from microbiome reactor fluids

RATIONALE

Glyphosate is one of the most widely used herbicides and it is suspected to affect the intestinal microbiota through inhibition of aromatic amino acid synthesis via the shikimate pathway. In vitro microbiome bioreactors are increasingly used as model systems to investigate effects on intestinal microbiota and consequently methods for the quantitation of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) in microbiome model systems are required.

METHODS

An optimized protocol enables the analysis of both glyphosate and AMPA by simple extraction with methanol:acetonitrile:water (2:3:1) without further enrichment steps. Glyphosate and AMPA are separated by liquid chromatography on an amide column and identified and quantified with a targeted tandem mass spectrometry method using a QTRAP 5500 system (AB Sciex).

RESULTS

Our method has a limit of detection (LOD) in extracted water samples of <2 ng/mL for both glyphosate and AMPA. In complex intestinal medium, the LOD is 2 and 5 ng/mL for glyphosate and AMPA, respectively. These LODs allow for measurement at exposure-relevant concentrations. Glyphosate levels in a bioreactor model of porcine colon were determined and consequently it was verified whether AMPA was produced by porcine gut microbiota.

CONCLUSIONS

The method presented here allows quantitation of glyphosate and AMPA in complex bioreactor fluids and thus enables studies of the impact of glyphosate and its metabolism on intestinal microbiota. In addition, the extraction protocol is compatible with an untargeted metabolomics analysis, thus allowing one to look for other perturbations caused by glyphosate in the same sample.

The Simplified Human Intestinal Microbiota (SIHUMIx) Shows High Structural and Functional Resistance against Changing Transit Times in In Vitro Bioreactors

Many functions in host-microbiota interactions are potentially influenced by intestinal transit times, but little is known about the effects of altered transition times on the composition and functionality of gut microbiota. To analyze these effects, we cultivated the model community SIHUMIx in bioreactors in order to determine the effects of varying transit times (TT) on the community structure and function. After five days of continuous cultivation, we investigated the influence of different medium TT of 12 h, 24 h, and 48 h. For profiling the microbial community, we applied flow cytometric fingerprinting and revealed changes in the community structure of SIHUMIx during the change of TT, which were not associated with changes in species abundances. For pinpointing metabolic alterations, we applied metaproteomics and metabolomics and found, along with shortening the TT, a slight decrease in glycan biosynthesis, carbohydrate, and amino acid metabolism and, furthermore, a reduction in butyrate, methyl butyrate, isobutyrate, valerate, and isovalerate concentrations. Specifically, B. thetaiotaomicron was identified to be affected in terms of butyrate metabolism. However, communities could recover to the original state afterward. This study shows that SIHUMIx showed high structural stability when TT changed-even four-fold. Resistance values remained high, which suggests that TTs did not interfere with the structure of the community to a certain degree.

Circulating proteomic patterns in AF related left atrial remodeling indicate involvement of coagulation and complement cascade

BACKGROUND

Left atrial (LA) electro-anatomical remodeling and diameter increase in atrial fibrillation (AF) indicates disease progression and is associated with poor therapeutic success. Furthermore, AF leads to a hypercoagulable state, which in turn promotes the development of a substrate for AF and disease progression in the experimental setting. The aim of this study was to identify pathways associated with LA remodeling in AF patients using untargeted proteomics approach.

METHODS

Peripheral blood samples of 48 patients (62±10 years, 63% males, 59% persistent AF) undergoing AF catheter ablation were collected before ablation. 23 patients with left atrial low voltage areas (LVA), defined as <0.5 mV, and 25 patients without LVA were matched for age, gender and CHA2DS2-VASc score. Untargeted proteome analysis was performed using LC-ESI-Tandem mass spectrometry in a label free intensity based workflow. Significantly different abundant proteins were identified and used for pathway analysis and protein-protein interaction analysis.

RESULTS

Analysis covered 280 non-redundant circulating plasma proteins. The presence of LVA correlated with 30 differentially abundant proteins of coagulation and complement cascade (q<0.05).

CONCLUSIONS

This pilot proteomic study identified plasma protein candidates associated with electro-anatomical remodeling in AF and pointed towards an imbalance in coagulation and complement pathway, tissue remodeling and inflammation.

Plasma proteome and metabolome characterization of an experimental human thyrotoxicosis model

BACKGROUND

Determinations of thyrotropin (TSH) and free thyroxine (FT4) represent the gold standard in evaluation of thyroid function. To screen for novel peripheral biomarkers of thyroid function and to characterize FT4-associated physiological signatures in human plasma we used an untargeted OMICS approach in a thyrotoxicosis model.

METHODS

A sample of 16 healthy young men were treated with levothyroxine for 8 weeks and plasma was sampled before the intake was started as well as at two points during treatment and after its completion, respectively. Mass spectrometry-derived metabolite and protein levels were related to FT4 serum concentrations using mixed-effect linear regression models in a robust setting. To compile a molecular signature discriminating between thyrotoxicosis and euthyroidism, a random forest was trained and validated in a two-stage cross-validation procedure.

RESULTS

Despite the absence of obvious clinical symptoms, mass spectrometry analyses detected 65 metabolites and 63 proteins exhibiting significant associations with serum FT4. A subset of 15 molecules allowed a robust and good prediction of thyroid hormone function (AUC = 0.86) without prior information on TSH or FT4. Main FT4-associated signatures indicated increased resting energy expenditure, augmented defense against systemic oxidative stress, decreased lipoprotein particle levels, and increased levels of complement system proteins and coagulation factors. Further association findings question the reliability of kidney function assessment under hyperthyroid conditions and suggest a link between hyperthyroidism and cardiovascular diseases via increased dimethylarginine levels.

CONCLUSION

Our results emphasize the power of untargeted OMICs approaches to detect novel pathways of thyroid hormone action. Furthermore, beyond TSH and FT4, we demonstrated the potential of such analyses to identify new molecular signatures for diagnosis and treatment of thyroid disorders. This study was registered at the German Clinical Trials Register (DRKS) [DRKS00011275] on the 16th of November 2016.

Effect of Experimental Thyrotoxicosis onto Blood Coagulation: A Proteomics Study

BACKGROUND

Hyperthyroidism is known to induce a hypercoagulable state. It stimulates plasma levels of procoagulative factors and reduces fibrinolytic activity. So far most of the data have been derived from patients with endogenous hyperthyroidism with a wide variability in the underlying pathogenesis and severity of the disease.

OBJECTIVES

In this study we experimentally induced thyrotoxicosis in healthy volunteers to explore the effects of thyroxine excess on the plasma proteome. Using a shotgun proteomics approach, the abundance of plasma proteins was monitored before, during and after thyrotoxicosis.

METHODS

Sixteen healthy male subjects were sampled at baseline, 4 and 8 weeks under 250 µg/day thyroxine p.o., as well as 4 and 8 weeks after stopping the application. Plasma proteins were analyzed after depletion of 6 high-abundance proteins (MARS6) by LC-ESI-MS/MS mass spectrometry. Mass spectrometric raw data were processed using a label-free, intensity-based workflow. Subsequently, the linear dependence between protein abundances and fT4 levels were calculated using a Pearson correlation.

RESULTS

All subjects developed biochemical thyrotoxicosis, and this effect was reversed within the first 4 weeks of follow-up. None of the volunteers noticed any subjective symptoms. Levels of 10 proteins involved in the coagulation cascade specifically correlated with fT4, supporting an influence of thyroid hormone levels on blood coagulation even at nonpathological levels.

CONCLUSIONS

The results suggest that experimental thyrotoxicosis exerts selective and specific thyroxine-induced effects on coagulation markers. Our study design allows assessment of thyroid hormone effects on plasma protein levels without secondary effects of other diseases or therapies.

Crossroads of coagulation and innate immunity: the case of deep vein thrombosis

Deep vein thrombosis (DVT) is a common condition characterized by the formation of an occlusive blood clot in the venous vascular system, potentially complicated by detachment and embolization of thrombi into the lung. Recent evidence from mouse models has shed light on the sequence of events and on the cellular (innate immune cells, platelets) and molecular (hematopoietic tissue factor, nucleic acids) components involved. In response to decreased blood flow, circulating neutrophils and monocytes adhere to the activated endothelium within hours. They initiate and propagate DVT by interacting with platelets and by the exposure and activation of circulating tissue factor and FXII. Intravascular blood coagulation is also induced by extracellular nucleosomes released mainly from activated neutrophils. Interestingly, these mechanisms are closely linked to an evolutionary conserved immune defense mechanism activated in response to infections. In this review, we will give an overview of DVT and the role of innate immune pathways supporting this process. While the latter are aimed at preserving tissue integrity and function, uncontrolled blood coagulation and activation of immune cells may result in pathological thrombus formation and vascular occlusion. Understanding the molecular and cellular players triggering occlusion of large veins, and their distinction from physiological hemostasis, is important for the development of strategies to prevent and treat DVT.

Plasmalogens: targets for oxidants and major lipophilic antioxidants

Cellular membranes and plasma lipoproteins are less efficiently protected against oxidative stress than the various aqueous compartments of mammalian organisms. Here, previous results on the role of plasmalogens in lipid oxidation are evaluated on the basis of criteria required for an antioxidant. The plasmalogen-specific enol ether double bond is targeted by a vast variety of oxidants, including peroxyl radicals, metal ions, singlet oxygen and halogenating species. Oxidation of the vinyl ether markedly prevents the oxidation of highly polyunsaturated fatty acids, and products of plasmalogen degradation do not propagate lipid oxidation. This protection is also demonstrated intramolecularly, thus ascertaining the function of plasmalogens as a major storage pool for polyunsaturated fatty acids. Although cells rapidly incorporate and synthesize plasmalogens de novo, their plasmalogen contents can be deliberately increased by supplementation with precursors. Thus plasmalogens terminate lipid-oxidation processes, are present in adequate locations at sufficient concentrations, and are rapidly regenerated, classifying them as efficient antioxidants in vitro. Future work should address the in vivo role of plasmalogens in lipid oxidation and the biological function of plasmalogen interactions with oxidants.

Phosphatidylethanolamine participates in the stimulation of the contact system of coagulation by very-low-density lipoproteins

We have analyzed the influence of plasma lipoproteins on the activation of the contact pathway of blood coagulation in platelet-rich plasma (PRP). The formation of thrombin in PRP incubated in vitro was abolished by the factor XIIa antagonist corn trypsin inhibitor and by severe factor XII deficiency, indicating mediation by the contact system. Addition of VLDL to the PRP shortened the lag period and increased the generation of thrombin. There was no effect of HDL and LDL. In whole blood, VLDL accelerated the rate of fibrin formation, the procoagulant effect being prevented by factor XII deficiency and by corn trypsin inhibitor. The thrombin formation in the PRP was strongly increased by microemulsions of the VLDL lipids while it was reduced by the aqueous phase of the particles. Separation of the VLDL lipids indicated the phospholipid component as the major activating principle. Vesicles supplemented with all VLDL phospholipids but lacking specifically the fraction containing phosphatidylethanolamine (PE) prolonged the lag time. The PE containing fraction alone as well as vesicles enriched with egg PE shortened the lag period. In summary, VLDL stimulates the contact pathway of blood coagulation, ethanolamine phospholipids being the most active components of the particles.

Modified phosphatidylethanolamine as the active component of oxidized low density lipoprotein promoting platelet prothrombinase activity

We analyzed the influence of the atherogenic oxidized low density lipoproteins (LDL) on the activity of the platelet prothrombinase complex, a major contributor to overall thrombin formation in vivo. Platelet dependent thrombin generation was found to be strongly stimulated by in vitro oxidized LDL. The enhancement was additive to that observed with the platelet agonist thrombin. Oxidized LDL increased the platelet binding of annexin-V, suggesting that the augmented surface exposure of aminophospholipids promoted the prothrombinase activity. All of the stimulatory activity of the oxidized LDL could be recovered in the microemulsions prepared from the lipid portion of the modified particles. Phospholipid vesicles were prepared containing the total lipids of the oxidized LDL but lacking specifically in one lipid component. Following the selective removal of the ethanolamine phospholipids (PE) from the LDL lipids, the platelet-dependent thrombin formation was markedly reduced. Vesicles enriched with the isolated PE fraction alone enhanced the thrombin generation. Analyses with autoxidized phospholipids indicated that oxidation products of unsaturated diacyl-PE were mainly responsible for the increased prothrombinase activity. Oxidized LDL and its PE fraction lost their stimulatory activity after treatment with NaCNBH(3), a chemical reductant of Schiff base adducts. Phospholipid vesicles supplemented with synthetic aldehyde-PE adducts largely reproduced the stimulation of the thrombin generation. We conclude that the oxidized LDL particles elicit a pronounced prothrombotic response by increasing the activity of the platelet prothrombinase complex. Specific oxidative modifications of the LDL-associated ethanolamine phospholipids are mainly responsible for this stimulation.

Platelet-associated tissue factor contributes to the collagen-triggered activation of blood coagulation

The extravascular localization of tissue factor (TF), the central initiator of coagulation, is thought to ensure that thrombus formation is prevented in the intact vessel. We observed that during a 5-min stimulation of human blood with collagen (type I), TF antigen appeared on the surface of platelets adhering to leukocytes. The rapidly presented intravascular TF was competent to start the coagulation cascade. The isolated platelets from healthy donors contained appreciable amounts of the TF protein, while no TF antigen was detected in the neutrophils and rapidly isolated monocytes. Direct interactions with the neutrophils and monocytes were apparently necessary to activate the platelet-associated TF. This was most likely mediated by inactivation of tissue factor pathway inhibitor through leukocyte elastase. In summary, the leukocyte-elicited activation of the platelet TF participates in the rapid initiation of coagulation by collagen.

Differential antiplatelet effects of various glycoprotein IIb-IIIa antagonists

The blockade of platelet glycoprotein IIb-IIIa (GPIIb-IIIa) was recently introduced as a new antiplatelet strategy. At present, various GPIIb-IIIa inhibitors are available to treat patients with acute coronary syndrome or when undergoing percutaneous coronary interventions. The current study systematically evaluates the antiplatelet effects of GPIIb-IIIa inhibitors in clinical use. Using conformation-dependent monoclonal antibodies [ligand-induced binding sites (LIBS-1), PMI-1] and flow cytometry, we showed that the GPIIb-IIIa antagonists abciximab, integrelin, lamifiban, and tirofiban, but not EMD 122347 or YM 337, induced LIBS activity of platelet GPIIb-IIIa. The LIBS activity of GPIIb-IIIa antagonists correlates with a proaggregatory response of fixed platelets pretreated with GPIIb-IIIa antagonists (intrinsic activity). All tested GPIIb-IIIa antagonists completely inhibit concentration-dependent ADP (20 micromol/l)-induced aggregation. In contrast, substantial TRAP (25 micromol/l)-induced platelet aggregation still occurs even at high inhibitor concentrations of the tested GPIIb-IIIa antagonists. In addition, we show that GPIIb-IIIa antagonists are poor inhibitors of platelet release reaction (ATP and P-selectin secretion) especially when strong agonists such as TRAP are used to activate platelets. Inhibition of platelet procoagulant activity (thrombin generation) by GPIIb-IIIa antagonists is dependent on the type and concentration of antagonists and on the strength of stimulus (thrombin, tissue factor) used to induce platelet-dependent thrombin generation. The present data show that significant pharmacological differences exist between GPIIb-IIIa antagonists that may have consequences for antithrombotic strategies and for future drug development.

Stimulation of cellular sphingomyelin import by the chemokine connective tissue-activating peptide III

The selective import of phospholipids into cells could be mediated by proteins secreted from the cells into the extracellular compartment. We observed that the supernatants obtained from suspensions of thrombin-activated platelets stimulated the exchange of pyrene (py)-labeled sphingomyelin between lipid vesicles in vitro. The proteins with sphingomyelin transfer activity were purified and identified as the chemokine connective tissue-activating peptide III (CTAP-III) and platelet basic protein. Isolated CTAP-III stimulated the exchange of py-sphingomyelin between lipid vesicles but did not affect the translocations of py-labeled phosphatidylcholine and phosphatidylethanolamine. CTAP-III rapidly increased the transfer of py-sphingomyelin from low density lipoproteins into peripheral blood lymphocytes, other immune cells, and fibroblasts. In the presence of heparin, CTAP-III was unable to insert sphingomyelin into the peripheral blood lymphocytes. The activation energy of the py-sphingomyelin transfer suggested that the translocation proceeded entirely in a hydrophobic environment. [(3)H]Sphingomyelin transferred to the cells by CTAP-III was hydrolyzed to [(3)H]ceramide and [(3)H]sphingosine after activation with tumor necrosis factor alpha. The generation of the [(3)H]sphingolipid messengers was catalyzed by acid sphingomyelinase. Our results identify CTAP-III as the first mediator of the selective (endocytosis-independent) cellular import of sphingomyelin allowing the paracrine modulation of the sphingolipid signaling.

Scavenger receptor BI transfers major lipoprotein-associated phospholipids into the cells

The phospholipids of lipoproteins can be transferred to cells by an endocytosis-independent uptake pathway. We analyzed the role of scavenger receptor BI (SR-BI) for the selective cellular phospholipid import. Human monocytes rapidly acquired the pyrene (py)-labeled phospholipids sphingomyelin (SM), phosphatidylcholine, and phosphatidylethanolamine from different donors (low and high density lipoproteins (LDL, HDL), lipid vesicles). The anti-SR-BI antibody directed against the extracellular loop of the membrane protein lowered the cellular import of the phospholipids by 40-80%. The phospholipid transfer from the lipid vesicles into the monocytes was suppressed by LDL, HDL, and apoprotein AI. Transfection of BHK cells with the cDNA for human SR-BI enhanced the cellular import of the vesicle-derived py-phospholipids by 5-6-fold. In the case of the LDL donors, transfer of py-SM to the transfected cells was stimulated to a greater extent than the uptake of the other py-phospholipids. Similar differences were not observed when the vesicles and HDL were used as phospholipid donors. The concentration of LDL required for the half-maximal phospholipid import was close to the previously reported apparent dissociation constant for LDL binding to SR-BI. The low activation energy of the SR-BI-mediated py-phospholipid import indicated that the transfer occurs entirely in a hydrophobic environment. Disruption of cell membrane caveolae by cyclodextrin treatment reduced the SR-BI-catalyzed incorporation of py-SM, suggesting that intact caveolae are necessary for the phospholipid uptake. In conclusion, SR-BI mediates the selective import of the major lipoprotein-associated phospholipids into the cells, the transfer efficiency being dependent on the structure of the donor lipoprotein.

Inhibition of peroxyl radical-mediated lipid oxidation by plasmalogen phospholipids and alpha-tocopherol

The recently discovered peroxyl radical scavenging properties of plasmalogen phospholipids led us to evaluate their potential interactions with alpha-tocopherol. The oxidative decay of plasmalogen phospholipids and of polyunsaturated fatty acids as induced by peroxyl radicals (generated from 2,2'-azobis-2-amidinopropane hydrochloride; AAPH) was studied in micelles using 1H-NMR and chemical analyses. In comparison with alpha-tocopherol, a 20- to 25-fold higher concentration of plasmalogen phospholipids was needed to induce a similar inhibition of peroxyl radical-mediated oxidation of polyunsaturated fatty acids. Plasmalogen phospholipids and alpha-tocopherol protected each other from oxidative degradation. In low-density lipoproteins (LDL) and micelles supplemented with plasmalogen phospholipids plus alpha-tocopherol, the peroxyl radical-promoted oxidation was additively diminished. The differences in the capacities to inhibit oxidation processes induced by peroxyl radicals between the plasmalogen phospholipids and alpha-tocopherol were less pronounced in the LDL particles than in the micelles. In conclusion, plasmalogen phospholipids and alpha-tocopherol apparently compete for the interaction with the peroxyl radicals. Oxidation processes induced by peroxyl radicals are inhibited in an additive manner in the presence of the two radical scavengers. The contribution of the plasmalogen phospholipids to the protection against peroxyl radical promoted oxidation in vivo is expected to be at least as important as that of alpha-tocopherol.

Role of plasmalogens in the enhanced resistance of LDL to copper-induced oxidation after LDL apheresis

Extracorporeal reduction of plasma low density lipoproteins (LDLs) by LDL apheresis was shown to attenuate the proatherogenic influences of LDL, such as impairment of vasodilation and increased monocyte adhesion to the endothelium. In 16 patients with familial hypercholesterolemia, we analyzed whether LDL apheresis by the heparin precipitation procedure affected the oxidative resistance of LDL. Plasma LDL cholesterol concentrations were reduced by 65% after the apheresis. The lag time of copper-mediated LDL oxidation was increased from 103 to 117 minutes (P<0.0005). The LDL contents of alpha-tocopherol and beta-carotene, as well as the ratio of monounsaturated to polyunsaturated fatty acids in LDL, were not altered. However, the LDL apheresis induced a 15% increase in the LDL contents of plasmalogen phospholipids (P<0.0005), a class of ether phospholipids that were recently shown to prevent lipid oxidation. The phosphatidylcholine (PC) to lysoPC ratio was elevated by 16% after the apheresis (P<0.0005). The percent increase in LDL plasmalogen phospholipids showed a close association with the increased lag time after apheresis (P<0.0005). The LDL plasmalogen contents of the blood samples from patients and from normolipidemic donors were also positively related to the lag time (P<0.005). In vitro loading of LDL with plasmalogen phospholipids resulted in a prolongation of the lag time and an increase in the PC/lysoPC ratio. In conclusion, the rapid rise in LDL contents of plasmalogen phospholipids most probably causes the increase in lag time after LDL apheresis. Plasmalogens appear to play an important role in the oxidation resistance of LDL in vivo.

Contribution of copper binding to the inhibition of lipid oxidation by plasmalogen phospholipids

The role of plasmalogen phospholipids for copper-induced lipid oxidation was evaluated. Using 1H-NMR we observed that the copper (CuSO4)-promoted oxidative degradation of polyunsaturated fatty acids in micellar solution was dose-dependently attenuated by the plasmalogen lysoplasmenylethanolamine from bovine brain (lysoBP-PtdEtn). This was due to a direct interaction of copper ions with the plasmalogen-specific enol ether double bond. The enol ether methine 1H signal decreased on the addition of copper, saturation being reached at a molar ratio of lysoBP-PtdEtn to copper of 1:1. The original 1H signal was recovered almost completely after the addition of EDTA. Enrichment of micelles and low-density lipoproteins (LDLs) with plasmalogen phospholipids led to a decrease in the Cu(II) concentration in the aqueous media. After loading of LDLs in vitro with BP-PtdEtn, the LDL-dependent formation of Cu(I) was decreased, in particular in particles experimentally supplemented with alpha-tocopherol. The suppression of copper-promoted lipid oxidation that was observed in the presence of plasmalogen phospholipids plus alpha-tocopherol was greater than the sum of the protective effects elicited by the two substances alone. In conclusion, the formation of a complex between copper ions and the plasmalogens accounts partly for their inhibition of copper-induced lipid oxidation.

Platelet high affinity low density lipoprotein binding and import of lipoprotein derived phospholipids

The binding of low density lipoprotein (LDL) to the platelet cell membrane could facilitate the transfer of phospholipids from LDL to the platelets. A polyclonal antibody against the platelet glycoproteins IIb/IIIa inhibited the high affinity binding of 125I-LDL by up to 80%. The transfer of pyrene (py)-labeled sphingomyelin (SM), phosphatidylcholine and phosphatidylethanolamine from LDL to the platelets was unaffected by the antibody. The lectin wheat germ agglutinin (WGA) reduced the binding of 125I-LDL to the platelets by approximately 80%. In contrast, the lectin stimulated the transfer of SM from LDL into the platelets by about three-fold. WGA also specifically augmented the transfer of py-SM between lipid vesicles and the platelets, the stimulation being abolished in the presence of N-acetylglucosamine. Dextran sulfate (DS) increased the specific binding of 125I-LDL to the platelets by up to 2.8-fold. On the other hand, the import of LDL-derived py-phospholipids was unaffected by DS. Together, the results indicate that the phospholipid transfer from LDL to the platelets is independent of the high affinity LDL binding to the platelets and is specifically stimulated by WGA. Thus, the interactions of platelets with LDL phospholipids differ markedly from those with the apoprotein components of the lipoproteins.

Tissue factor expression of human monocytes is suppressed by lysophosphatidylcholine

The expression of tissue factor (TF), the principal initiator of coagulation, is increased during inflammation and atherosclerosis. Both conditions are promoted by lysophosphatidylcholine (lysoPC). We observed in the present study that lysoPC (1 to 10 micromol/L) dose-dependently reduced TF activity in human monocytes, as elicited by lipopolysaccharide (LPS). Lysophosphatidylethanolamine (lysoPE) and other lysophospholipids did not affect LPS-induced TF activity of human monocytes. TF antigen expression as elicited by LPS was also lowered by lysoPC. Phospholipid analyses indicated a selective increase in the lysoPC content of the monocytes after preincubation with the lysophospholipid. LysoPC inhibited the TF activity of Mono Mac-6 cells to a similar extent as in the monocytes. LPS binding to plasma membrane receptors and internalization of LPS into monocytes were not affected by lysoPC. In contrast, LPS-mediated nuclear binding of nuclear factor-kappaB/Rel to a TF-specific kappaB site was inhibited by lysoPC. Induction of TF mRNA expression by LPS tended to be partially reduced by the lysophospholipid. Preincubation with lysoPC increased monocytic cAMP levels. Inhibition of adenylyl cyclase by pretreatment with 2'-deoxy-3'-adenosine monophosphate partially reversed the inhibition of TF activity promoted by lysoPC. In conclusion, lysoPC markedly decreases LPS-mediated TF expression of human monocytes, the effect probably being mediated by both transcriptional and posttranscriptional mechanisms. LysoPC may thus attenuate activation of coagulation during inflammation and atherosclerosis.

Low-density lipoproteins supply phospholipid-bound arachidonic acid for platelet eicosanoid production

After the rapid extracorporal reduction of plasma low-density lipoprotein (LDL) by LDL apheresis, the percentages of arachidonic acid (AA)-containing species of phosphatidylcholine (PC) were lowered in the plasma of patients with hypercholesterolemia. The same PC species with AA were also decreased in the patient's platelets. Thus the supply of phospholipid-bound AA from LDL to the platelets was probably diminished after the apheresis. We therefore analyzed the concentration dependence of the transfer of phospholipid-bound AA from LDL to the platelets under in vitro conditions. The amount of [14C]AA-PC transferred to platelets strongly increased upon elevation of LDL from 0.1 to 1 mg protein/ml, with a less marked elevation being noted at higher LDL concentrations. After stimulation with thrombin (0.5 U/ml), 7.1% ([14C]AA-PC) and 10.6% ([14C]AA-phosphatidylethanolamine) of the 14C transferred from LDL to the platelets were recovered in the eicosanoids [14C]thromboxane B2 (TxB2) plus 12-[14C]hydroxyeicosatetraenoic acid. Experimental increases and reductions of the [14C]AA-PC import were associated with comparable modifications in the [14C]TxB2 production of the platelets. Accordingly, the import of phospholipid-bound [14C]AA is a necessary prerequisite for the formation of 14C-labeled eicosanoids. In summary, the transfer of phospholipids from LDL to the platelets markedly varies within the physiological range of lipoprotein concentrations. LDL contributes to platelet eicosanoid formation by supplying platelets with phospholipid-bound AA.

Platelet agonists enhance the import of phosphatidylethanolamine into human platelets

It is unknown whether the endocytosis-independent transfer of phospholipids from lipoproteins to platelets is regulated by platelet agonists such as thrombin. The movements of the choline phospholipids phosphatidylcholine and sphingomyelin (labeled with either 14C or the fluorescent pyrenedecanoic acid) between low density lipoproteins and platelets were unaffected by thrombin (0.5 unit/ml). In contrast, thrombin accelerated the import of diacyl phosphatidylethanolamine (PE) and alkenylacyl phosphatidylethanolamine into platelets by about 4-fold. Similarly, thrombin receptor-activating peptide (15 microM), collagen (10 microgram/ml), and ADP (10 microM) enhanced PE uptake. High density lipoprotein particles and egg phosphatidylcholine vesicles were also donors for stimulation of platelet PE import. Part of the [14C]arachidonic acid-labeled PE transferred from low density lipoprotein to platelets activated by thrombin and collagen was metabolized to 14C-eicosanoids. Inhibitors of protein kinase C partially prevented thrombin-induced [14C]PE uptake, while direct activators of protein kinase C increased incorporation of [14C]PE into platelets. Proteinaceous factor(s) recovered in the extracellular medium from ADP- and thrombin-activated platelet suspensions were found to accelerate the transfer of pyrenedecanoic acid-labeled PE between donor and acceptor lipid vesicles. The stimulation of import of ethanolamine phospholipids led to a 2-fold enhancement of the prothrombinase activity of thrombin-activated platelets. Our study demonstrates that physiological platelet stimuli increase specifically the transfer of ethanolamine phospholipids from lipoproteins to platelets through a secretion-dependent mechanism. This might contribute to the increase of procoagulant activity of stimulated platelets.

Phospholipid source and molecular species composition of 1,2-diacylglycerol in agonist-stimulated rat cardiomyocytes

OBJECTIVE

The aim was to investigate the consequences of simultaneous stimulation of phospholipase C and D by agonists for the molecular species composition of 1,2-diacylglycerol and phospholipids in cardiomyocytes.

METHODS

Serum-free cultured neonatal rat cardiomyocytes were stimulated by endothelin-1, phenylephrine or phorbolester. The molecular species of 1,2-diacylglycerol (in mol%) and those derived from phosphatidylcholine and phosphatidylinositol were analyzed by high-performance liquid chromatography and their absolute total concentration (nmol per dish) by gas-liquid chromatography. Phospholipids were labelled with [14C]glycerol or double-labelled with [14C]16:0 and [3H]20:4n6 for measurements of respectively, the amount of or relative rate of label incorporation into 1,2-diacylglycerol.

RESULTS

The major molecular species of 1,2-diacylglycerol in unstimulated cells was found to be 18:0/20:4 (57 mol%). The same species was observed predominantly in phosphatidylinositol (73 mol% compared to 11 mol% in phosphatidylcholine). A significant decrease (about 10 mol%) was found for the 18:0/20:4 species of 1,2-diacylglycerol during stimulation (10-40 min) with endothelin-1 or phorbolester, but not phenylephrine. The results of the double-labelling experiments were consistent with the latter finding: the ratio [3H]20:4 over [14C]16:0 in 1,2-diacylglycerol decreased from 1.70 in the control to 1.40 during 10-min endothelin-1 or phorbolester stimulation, but not during phenylephrine stimulation. The [14C]glycerol incorporation into 1,2-diacylglycerol remained relatively constant under agonist-stimulated conditions as did the total concentration of 1,2-diacylglycerol.

CONCLUSIONS

1,2-Diacylglycerol present in unstimulated cardiomyocytes is likely derived from phosphatidylinositol. During stimulation with endothelin-1 and phorbolester, but not phenylephrine, phosphatidylcholine becomes an increasingly important source for 1,2-diacylglycerol due to sustained activation of phospholipase D. The 1,2-diacylglycerol level remains relatively constant during agonist stimulation which strongly indicates that particular molecular species of 1,2-diacylglycerol more than its total concentration determine the activation of protein kinase C isoenzymes.

Arachidonic acid of platelet phospholipids is decreased after extracorporeal removal of plasma low density lipoproteins in patients with familial hypercholesterolemia

Platelet phospholipid composition was analyzed before and after extracorporeal removal of low density lipoproteins (LDL) by LDL apheresis in six patients with familial hypercholesterolemia. Elevated levels of total plasma cholesterol and the portion of plasma cholesterol carried by LDL were reduced by 56 and 66% after LDL apheresis. Platelet cholesterol contents remained unaffected. While the phosphatidylcholine (PC):sphingomyelin (SM) ratio in plasma lipoproteins was increased by 22% following apheresis, the same parameter was lowered by 14% in platelets. LDL apheresis induced decreases in the percentages of distinct molecular species containing arachidonic acid in platelet diacyl subgroups of PC, phosphatidylinositol (PI) and phosphatidylserine (PS) as well as in alkenylacyl (plasmalogen) phosphatidylethanolamine (PE). Directly after apheresis, the percentages of molecular species with arachidonic acid of diacyl PC, diacyl PI and alkenylacyl PE were reduced by 20, 23 and 8%, respectively. Two days after the procedure, total arachidonic acid of diacyl PC, diacyl PS and alkenylacyl PE was lowered by 11, 20 and 8%. Overall, the amount of phospholipid bound arachidonic acid was reduced by 16% after apheresis (from 79.1 to 66.4 nmol/10(8) platelets). The results are thus in agreement with previous data indicating decreased phospholipid bound arachidonic acid in red blood cells after apheresis (Engelman B. Bräutigam C, Kulschar R et al. Biochim Biophys Acta 1994:1196:154). Urinary 2,3-dinor thromboxane B2, an estimate of platelet thromboxane A2 (TXA2) production, tended to be decreased following the procedure. The percentage change in the TXA2 metabolite was positively related to the magnitude of change induced by apheresis in phospholipid bound arachidonic acid. In summary, the results suggest that in patients with hypercholesterolemia, the level of plasma LDL is an important determinant of the arachidonic acid content of several platelet phospholipids.

Delayed oxidative degradation of polyunsaturated diacyl phospholipids in the presence of plasmalogen phospholipids in vitro

The oxidative degradation of plasmalogen (alkenylacyl) phospholipids was analysed in the absence and the presence of polyunsaturated ester phospholipids by 1H-NMR and by chemical determination. Brain lysoplasmenylethanolamine (lyso-P-PE), brain P-PE and erythrocyte P-PE, containing an increasing number of intrachain double bonds at sn2, were oxidized with 2,2'-azobis-(2-amidinopropane hydrochloride) (AAPH; 2 or 10 mM) in Triton X-100 micelles (detergent/phospholipid 1:5, mol/mol). The formation of two peroxyl radicals was accompanied by the degradation of approx. one molecule of brain lyso-P-PE. On oxidation of brain P-PE or erythrocyte P-PE (320 nmol) with 2 mM AAPH, the (alpha-vinyl) methine 1H signal of the enol ether decreased more rapidly than the methine proton peak of intrachain double bonds. The rate of enol ether degradation increased in the order: erythrocyte P-PE>brain P-PE>brain lyso-P-PE. The disappearance of the polyunsaturated ester phospholipids 1-palmitoyl-2-arachidonoyl phosphatidylcholine (16:0/20:4-PC) and 1-palmitoyl-2-linoleoyl phosphatidylcholine (16:0/18:2-PC) (100 nmol), as induced by 10 mM AAPH, was nearly completely inhibited by the plasmalogens (25 nmol) in the first 30 and 60 min of incubation respectively, and was delayed at later time points. Plasmalogens and vitamin E (4-25 nmol) mitigated the decreases in 16:0/[3H]20:4-PC (100 nmol) induced by 2 mM AAPH in a similar manner. The initial rate of degradation of intrachain double bonds of 16:0/20:4-PC and 16:0/18:2-PC (320 nmol; 2 mM AAPH) was decreased by 59% and 81% respectively in the presence of 80 nmol of brain lyso-P-PE. In conclusion, plasmalogens markedly delay the oxidative degradation of intrachain double bonds under in vitro conditions. Interactions of enol ether double bonds with initiating peroxyl radicals as well as with products generated by prior oxidation of polyunsaturated fatty acids are proposed to be responsible for this capacity of plasmalogens. Furthermore, the products of enol ether oxidation apparently do not propagate the oxidation of polyunsaturated fatty acids.

Transfer of phosphatidylcholine, phosphatidylethanolamine and sphingomyelin from low- and high-density lipoprotein to human platelets

Following a 1 h incubation of human platelets with low-density lipoprotein (LDL) labelled in the apoprotein fraction (125I-apoB) or in phospholipid fractions [14C-labelled phosphatidylcholine (PC), phosphatidylethanolamine (PE) or sphingomyelin (SM)], the percentage of total 14C associated with the cells was about 3-fold higher than the percentage of 125I. Differences in temperature sensitivity also indicated differential interactions of phospholipids and apoprotein with platelets. In order to assess the amount of [14C]phospholipid transferred from LDL or high-density lipoprotein (HDL) to the cells, the quantity of bound lipoproteins was estimated by adding an excess of unlabelled lipoprotein, or by selectively degrading LDL- and HDL-associated [14C]PC and [14C]PE with phospholipase C. Incubation of platelets with LDL or HDL containing pyrenedecanoic acid-labelled PC or SM (py-PC, py-SM) increased pyrene monomer fluorescence, indicating incorporation of the phospholipids into platelets. With HDl as donor, incorporation of py-SM was greater than uptake of py-PC. Pretreating platelets with elastase dose-dependently inhibited uptake of py-SM and py-PC. Treatment of cells with phospholipase C indicated that the uptake of [14C]PC by platelets, and not the binding of lipoproteins to the cells, was partially inhibited by elastase. In conclusion, LDL and HDL rapidly deliver SM, PC and PE to platelets. Incorporation of LDL-derived phospholipids into platelets is unlikely to be mediated by endocytosis of lipoprotein particles. The uptake of the two choline-containing phospholipids appears to require the presence of specialized platelet membrane protein(s).

Diradylglycerol formation in cholecystokinin-stimulated rabbit pancreatic acini. Assessment of precursor phospholipids by means of molecular species analysis

The aim of the present study was to assess the origin of the 1,2-diradylglycerols produced during prolonged hormonal stimulation of rabbit pancreatic acini by comparison of their relative molecular species composition with that of the major acinar phospholipids. Both phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn) consisted of 1,2-diacyl as well as 1-alk-1-2-acyl species. In contrast, phosphatidylinositol (PtdIns), phosphatidylserine and phosphatidic acid existed only in the 1,2-diacyl form. Acinar cells did not contain detectable amounts of 1-alkyl-2-acyl phospholipids. Similarly, the acinar 1,2-diradylglycerol fraction consisted of 1,2-diacylglycerols and 1-alk-1-enyl-2-acylglycerols. Mass 1,2-diradylglycerol measurements revealed that prolonged stimulation with cholecystokinin resulted in a marked and sustained increase in acinar 1,2-diradylglycerol content. Based on the relative amounts of the 1,2-diacyl species present in both the 1,2-diradylglycerol fraction and the individual phospholipids, it is calculated that under control conditions 60% of the 1,2-diacylglycerols originate from PtdCho and 40% from PtdIns, whereas under stimulatory conditions 53% is calculated to be derived from PtdCho, 46% from PtdIns and 1% from PtdEtn. Likewise, it is calculated that in control as well as stimulated acini 100% of the 1-alk-l-enyl-2-acylglycerols originate from plasmenylcholine. Further evidence in favour of the idea that at least a considerable part of the 1,2-diacylglycerols produced during prolonged hormonal stimulation originate from inositolphospholipids is provided by the observation that labeling of phosphatidylinositol 4,5-bisphosphate with inorganic phosphate reached isotopic equilibrium markedly faster under stimulatory conditions as compared to the control situation, which is in agreement with an elevated turnover rate. The data presented support the idea that PtdCho and inositolphospholipids are the major precursors in basal and stimulated 1,2-diradylglycerol production in rabbit pancreatic acini.

Plasmalogen phospholipids in plasma lipoproteins of normolipidemic donors and patients with hypercholesterolemia treated by LDL apheresis

Recent evidence indicates that plasmalogen phospholipids are particularly sensitive to oxidation and may possess antioxidative properties. Approximately 4.4%-5.5% of phosphatidylcholine (PC), and 53%-60% of phosphatidylethanolamine (PE) consisted of the plasmalogen phospholipids, plasmenylcholine and plasmenylethanolamine, respectively, in whole plasma, low density lipoprotein (LDL) and high density lipoprotein (HDL) of 11 normolipidemic donors. Of total plasmalogen phospholipids in plasma, slightly more was associated with LDL particles (about 42%) than with HDL (36%). Plasmalogen phospholipid levels were analyzed in 12 patients with familial hypercholesterolemia (FH) regularly treated by LDL apheresis, of whom 6 were supplemented with vitamin E (alpha tocopherol, 400 IU/day), the remaining 6 not receiving the antioxidant. Before apheresis (pre), total plasmalogen phospholipid levels in plasma and LDL (expressed as mumol/mmol cholesterol of compartment) decreased as follows: patients receiving vitamin E > normolipidemia > patients not receiving vitamin E. In both hypercholesterolemic groups, the contents of plasmalogen phospholipids in whole plasma and LDL were 3-5-fold higher than those of vitamin E. Directly after apheresis (post), plasmalogen phospholipid levels in plasma were raised by about 50% in the two hypercholesterolemic groups, mostly due to increases in plasmenylethanolamine levels. Two days after apheresis (48 h post), plasmalogen contents were still elevated in plasma and red blood cell membranes of patients receiving vitamin E, while they had already reached pre-apheresis values in those not supplemented with alpha tocopherol. Molecular species of plasma diacyl phospholipids containing polyunsaturated fatty acids were elevated at pre in patients receiving vitamin E as compared to patients without supplementation. At 48 h post, LDL apheresis induced an increase in these molecular species only in patients receiving vitamin E. In conclusion, the contents of plasmalogen phospholipids in plasma lipoproteins are at least three times higher than those of vitamin E. LDL apheresis raises the level of plasmalogen phospholipids in plasma, the increase persisting longer in patients supplemented with vitamin E. Supplementation with vitamin E appears to protect plasmalogen phospholipids in plasma lipoproteins against oxidative degradation.

Fast transmission of alterations in plasma phosphatidylcholine/sphingomyelin ratio and lyso phosphatidylcholine levels into changes of red blood cell membrane phospholipid composition after low density lipoprotein apheresis

In order to evaluate whether changes in plasma phospholipid composition are rapidly transmitted to the red blood cell membrane (RBCM) under in vivo conditions, the levels of major phospholipids in plasma, low density and high density lipoproteins (LDL and HDL) as well as in RBCM were determined before (pre), directly after (post) and 2 days after (48 h post) LDL apheresis in six patients with severe hypercholesterolaemia. LDL apheresis induced a 30-70% decrease in plasma and LDL cholesterol and total phospholipid levels within 2-3 h. Concomitantly, the percentages of plasma phosphatidylcholine (PC) and the PC/sphingomyelin (SM) ratio were increased compared to initial values. The percentage of plasma lyso PC (LPC) determined before apheresis in the patients was 30% lower with respect to the mean level of LPC in a normolipidaemic control. For LPC of LDL no differences were observed between normolipidaemia and hypercholesterolaemia. LDL apheresis induced a rise by about one third in the percentage of plasma LPC. At 48 h post, plasma LPC levels reapproached pre-apheresis levels, while the percentages of PC and the PC/SM ratio remained elevated. The pattern of changes induced by apheresis in plasma PC, SM and LPC levels was mimicked by changes in RBCM phospholipids. Strong positive relationships were noted for PC, SM and PC/SM as determined at pre, post and 48 h post between plasma and RBCM. In summary, changes in plasma PC, LPC, and PC/SM ratios as induced by LDL apheresis are rapidly transmitted to the RBCM under in vivo conditions, most probably as a result of phospholipid transfer between both compartments.(ABSTRACT TRUNCATED AT 250 WORDS)