LC/ESI-tandem mass spectrometric determination of bile acid 3-sulfates in human urine

Targeted and untargeted metabolomic profiles in wild rabbit does (Oryctolagus cuniculus) of different breeding states (pregnant and lactating)

Ecological nutrition aims to unravel the extensive web of nutritional links that drives animals in their interactions with their ecological environments. Nutrition plays a key role in the success of European wild rabbit (Oryctolagus cuniculus) and could be affected by the breeding status of the animals and reflected in the metabolome of this species. As nutritional needs are considerably increased during pregnancy and lactation, the main objective of this work was to determine how the breeding status (pregnant and lactating) of European wild rabbit does affects nutritional requirements and their metabolome (using targeted and untargeted metabolomics), aiming to find a useful biomarker of breeding status and for monitoring nutritional requirements. To address this gap, 60 wild European rabbits were studied. Animals were divided according to their breeding status and only pregnant (n = 18) and lactating (n = 11) rabbit does were used (n = 29 in total). The body weight and length of each animal were analyzed. The relative and absolute chemical composition of the gastric content and whole blood sample were taken, and targeted and untargeted metabolomics were analyzed. As a main result, there were no differences in biometric measurements, gastric content, and targeted metabolomics, except for live weight and nonesterified fatty acids (NEFA), as pregnant animals showed higher live weight (+12%; p = 0.0234) and lower NEFA acid levels (-46%; p = 0.0262) than lactating females. Regarding untargeted metabolomics, a good differentiation of the metabolome of the two breeding groups was confirmed, and it was proven that pregnant animals showed higher plasmatic levels of succinic anhydride (3.48 more times; p = 0.0236), succinic acid (succinate) (3.1 more times; p = 0.0068) and propionic acid (3.98 more times; p = 0.0121) than lactating animals. However, lactating animals showed higher levels of N-[(3a,5b,7b)-7-hydroxy-24-oxo-3-(sulfoxide) cholan-24-yl]-Glycine (cholestadien) (2.4 more times; p < 0.0420), 4-maleyl-acetoacetate (MAA) (3.2 more times; p < 0.0364) and irilone (2.2 more times; p = 0.0451) than pregnant animals, any of these metabolites could be used as a potential biomarker. From these results, it can be concluded that the most notable changes were observed in the metabolome of individuals, with most of the changes observed being due to energy and protein mobilisation.

Analysis of Metabolic Changes in Endogenous Metabolites and Diagnostic Biomarkers for Various Diseases Using Liquid Chromatography and Mass Spectrometry

Analysis of endogenous metabolites in various diseases is useful for searching diagnostic biomarkers and elucidating the molecular mechanisms of pathophysiology. The author and collaborators have developed some LC/tandem mass spectrometry (LC/MS/MS) methods for metabolites and applied them to disease-related samples. First, we identified urinary conjugated cholesterol metabolites and serum N-palmitoyl-O-phosphocholine serine as useful biomarkers for Niemann-Pick disease type C (NPC). For the purpose of intraoperative diagnosis of glioma patients, we developed the LC/MS/MS analysis methods for 2-hydroxyglutaric acid or cystine and found that they could be good differential biomarkers. For renal cell carcinoma, we searched for various biomarkers for early diagnosis, malignancy evaluation and recurrence prediction by global metabolome analysis and targeted LC/MS/MS analysis. In pathological analysis, we developed a simultaneous LC/MS/MS analysis method for 13 steroid hormones and applied it to NPC cells, we found 6 types of reductions in NPC model cells. For non-alcoholic steatohepatitis (NASH), model mice were prepared with special diet and plasma bile acids were measured, and as a result, hydrophilic bile acids were significantly increased. In addition, we developed an LC/MS/MS method for 17 sterols and analyzed liver cholesterol metabolites and found a decrease in phytosterols and cholesterol synthetic markers and an increase in non-enzymatic oxidative sterols in the pre-onset stage of NASH. We will continue to challenge themselves to add value to clinical practice based on cutting-edge analytical chemistry methodology.

Multi metabolomics-based analysis of application of Astragalus membranaceus in the treatment of hyperuricemia

Hyperuricemia (HUA) is a common metabolic disease that is an independent risk factor for comorbidities such as hypertension, chronic kidney disease, and coronary artery disease. The prevalence of HUA has increased over the last several decades with improved living standards and increased lifespans. Metabolites are considered the most direct reflection of individual physiological and pathological conditions, and represent attractive candidates to provide deep insights into disease phenotypes. Metabolomics, a technique used to profile metabolites in biofluids and tissues, is a powerful tool for identification of novel biomarkers, and can be used to provide valuable insights into the etiopathogenesis of metabolic diseases and to evaluate the efficacy of drugs. In this study, multi metabolomics-based analysis of the blood, urine, and feces of rats with HUA showed that HUA significantly altered metabolite profiles. Astragalus membranaceus (AM) and benbromomalone significantly mitigated these changes in blood and feces, but not in urine. Some crucial metabolic pathways including lipid metabolism, lipid signaling, hormones synthesis, unsaturated fatty acid (UFAs) absorption, and tryptophan metabolism, were seriously disrupted in HUA rats. In addition, AM administration exerted better treatment effects on HUA than benbromomalone. Furthermore, additional supplementation with UFAs and tryptophan may also induce therapeutic effects against HUA.

Identification cholesterol metabolites altered before the onset of nonalcoholic steatohepatitis by targeted metabolomics

Nonalcoholic steatohepatitis (NASH) is a disease with symptoms similar to those of alcoholic liver inflammation without alcohol intake. As an effective treatment strategy has not been established for this disease, a detailed understanding of the pathological progression mechanism is required. We focused on cholesterol metabolites, which are suspected to regulate NASH pathology, and investigated their relationship with the pathological progression in the early stages of NASH. First, the LC/MS/MS methods for bile acids and sterols were optimized and validated. Next, NASH model mice were established by feeding a choline-deficient, methionine-reduced high-fat diet, and the levels of hepatic cholesterol metabolites were measured. As a result, before the onset of NASH, desmosterol, 4β-hydroxycholesterol, campesterol, sitosterol, secondary bile acids such as taurodeoxycholic acid significantly decreased by up to 1/38 of NASH model group. Autoxidation-generated sterols significantly increased 2- to 5-fold, and various primary bile acids such as conjugated β-muricholic acids and cholic acids significantly increased 2- to 7-fold. In this study, the levels of cholesterol metabolites changed in the before the onset of NASH. These metabolic alterations involved in inflammation induction and detoxification for NASH may help the discovery of early diagnostic biomarkers in the future.

Searching, Structural Determination, and Diagnostic Performance Evaluation of Biomarker Molecules for Niemann-Pick Disease Type C Using Liquid Chromatography/Tandem Mass Spectrometry

Niemann-Pick disease type C (NPC) is an autosomal recessive disorder that is characterized by progressive neuronal degeneration. Patients with NPC have a wide age of onset and various clinical symptoms. Therefore, the discovery and diagnosis of NPC are very difficult. Conventional laboratory tests are complicated and time consuming. In this context, biomarker searches have recently been performed. Our research group has previously also investigated NPC biomarkers based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) and related techniques. To identify biomarker candidates, nontargeted analysis with high-resolution MS and MS/MS scanning is commonly used. Structural speculation has been performed using LC/MS/MS fragmentation and chemical derivatization, while identification is performed by matching authentic standards and sample specimens. Diagnostic performance evaluation was performed using the validated LC/MS/MS method and analysis of samples from patients and control subjects. NPC biomarkers, which have been identified and evaluated in terms of performance, are various classes of lipid molecules. Oxysterols, cholenoic acids, and conjugates are cholesterol-derived molecules detected in the blood or urine. Plasma lyso-sphingolipids are biomarkers for both NPC and other lysosomal diseases. N-palmitoyl-O-phosphocholine-serine is a novel class of lipid biomarkers for NPC. This article reviews biomarkers for NPC and the analysis methods employed to that end.

Analysis of eight bile acids in urine of gastric cancer patients based on covalent organic framework enrichment coupled with liquid chromatography-tandem mass spectrometry

Gastric carcinoma is one of the most common and deadly forms of cancer. Early detection is critical for successful treatment of gastric cancer, and examination of BAs in urine may provide a critical diagnostic tool for identifying gastric cancer at stages when it can still be cured. Bile acids (BAs) are a crucial toxic factor correlated with the injury of gastric mucosa and as such, quantifying the amount of BA in patient's urine could provide a new means to quickly and non-invasively identify the presence of gastric cancer in the early stages. Here, a covalent organic framework (COF) material synthesized on the basis of 1,3,5-tris(4-nitrophenyl)benzene (TAPB) and pyromellitic dianhydride (PMDA) was used as stationary phase for SPE column that was coupled to LC-MS/MS for quantitative analysis of eight BAs in human urine, including cholic acid (CA), deoxycholic acid (DCA), glycochenodeoxycholic acid (GCDCA), glycocholic acid (GCA), taurochenodeoxycholic acid (TCDCA), lithocholic acid (LCA), hyodeoxycholic acid (HDCA), and chenodeoxycholic acid (CDCA). The enrichment effect of synthesized COF material was better than commercial SPE and HLB column. The sensitivity can increase 9.37- to 54.30- fold (calculated by the ratio of peak area between before and after enrichment). The probable mechanism is due to the great porosity and the similar polarity with BAs of the COF material. By compared with previous literatures, our method had the minimum limit of detection, which achieved 46.40, 25.75, 47.40, 47.37, 30.42, and 33.92 pg /mL, respectively, for GCA, GCDCA, CA, CDCA, HDCA and DCA after enrichment. These eight BAs also accomplished excellent linearity from 0.34 to 10,000 ng/mL. This material was successfully applied in the measurements of these six BAs in human urine from 76 gastric cancer patients and 32 healthy people. Compared to healthy people, levels of CA, CDCA, DCA, and HDCA were significantly elevated and levels of GCDCA were depressed, respectively, in gastric cancer patients. Our work suggests that these acids may act as potential biomarkers for gastric cancer and our framework provides a method for "non-invasive" diagnosis of gastric cancer.

Changes in conjugated urinary bile acids across age groups

Bile acid compositions are known to change dramatically after birth with aging. However, no reports have described the transition of conjugated urinary bile acids from the neonatal period to adulthood, and such findings would noninvasively offer insights into hepatic function. The aim of this study was to investigate differences in bile acid species, conjugation rates, and patterns, and to pool characteristics for age groups. We measured urinary bile acids in spot urine samples from 92 healthy individuals ranging from birth to 58 years old using liquid chromatography tandem mass spectrometry (LC/ESI-MS/MS). Sixty-six unconjugated and conjugated bile acids were systematically determined. After birth, urinary bile acids dramatically changed from fetal (i.e., Δ⁴-, Δ⁵-, and polyhydroxy-bile acids) to mature (i.e., CA and CDCA) bile acids. Peak bile acid excretion was 6-8 days after birth, steadily decreasing thereafter. A major change in bile acid conjugation pattern (taurine to glycine) also occurred at 2-4 months old. Our data provide important information regarding transitions of bile acid biosynthesis, including conjugation. The data also support the existence of physiologic cholestasis in the neonatal period and the establishment of the intestinal bacterial flora in infants.

Serum metabolomic profiles reveal the impact of BuZangTongLuo formula on metabolic pathways in diabetic mice with hindlimb ischemia

ETHNOPHARMACOLOGICAL RELEVANCE

BuZangTongLuo Formula (BZTLF) was the decoction of eight traditional Chinese medicines including Astragalus membranaceus, Dioscorea opposita, Salvia miltiorrhiza, Scrophularia ningpoensis, Ophiopogon japonicus, Panax ginseng, Fritillariae cirrhosae and Whitmania pigra. This formula has been used as an effective remedy for treatment of diabetic ischemia clinically.

AIM OF THE STUDY

In previous study, we have reported the therapeutic effect of BZTLF on diabetic vascular dysfunction. However, it remains obscure about the role of metabolic pathways in BZTLF-initiated improvement on hindlimb ischemia.

MATERIALS AND METHODS

Diabetic mice with hindlimb ischemia were orally administrated with BZTLF by gavage. The serum samples were prepared for untargeted metabolomic analysis by ultra-performance liquid chromatography-mass spectrometer. The metabolic network was built by integrating metabolite data with the Gene Expression Omnibus (GEO) dataset (GSE3313). Further, quantitative PCR was used to confirm the key target genes.

RESULTS

BZTLF treatment remarkably led to the reversal of changed metabolite levels in serum of diabetic mice with hindlimb ischemia, which mainly derived from bacteria, plant and signaling molecules. Also, BZTLF reshaped the metabolic pathways, especially those responsible for metabolism of lipid, gluthanine and tryptophan. In addition, BZTLF led to the reduction of lysophosphatidic acids (LPAs) and increment of triglycerides (TGs) conjugation with non-saturated fatty acids in serum. BZTLF significantly restored the down-regulation of vascular endothelial growth factor receptor 2 (VEGFR2) and endothelial nitric oxide synthase (eNOS) or the up-regulation of interleukin 4-induced 1 (IL4I1) and cytochrome P450 family 1 subfamily B member 1 (CYP1B1) at mRNA level, which were key regulatory genes located in metabolic pathways of glutamate and tryptophan.

CONCLUSIONS

BZTLF improved hindlimb ischemia in diabetic mice by the positive regulation of metabolome changes in serum.

Analysis of bile acids in human biological samples by microcolumn separation techniques: A review

Bile acids are a group of compounds essential for lipid digestion and absorption with a steroid skeleton and a carboxylate side chain usually conjugated to glycine or taurine. Bile acids are regulatory molecules for a number of metabolic processes and can be used as biomarkers of various disorders. Since the middle of the twentieth century, the detection of bile acids has evolved from simple qualitative analysis to accurate quantification in complicated mixtures. Advanced methods are required to characterize and quantify individual bile acids in these mixtures. This article overviews the literature from the last two decades (2000-2020) and focuses on bile acid analysis in various human biological samples. The methods for sample preparation, including the sample treatment of conventional (blood plasma, blood serum, and urine) and unconventional samples (bile, saliva, duodenal/gastric juice, feces, etc.) are shortly discussed. Eventually, the focus is on novel analytical approaches and methods for each particular biological sample, providing an overview of the microcolumn separation techniques, such as high-performance liquid chromatography, gas chromatography, and capillary electrophoresis, used in their analysis. This is followed by a discussion on selected clinical applications.

Compensate for or Minimize Matrix Effects? Strategies for Overcoming Matrix Effects in Liquid Chromatography-Mass Spectrometry Technique: A Tutorial Review

In recent decades, mass spectrometry techniques, particularly when combined with separation methods such as high-performance liquid chromatography, have become increasingly important in pharmaceutical, bio-analytical, environmental, and food science applications because they afford high selectivity and sensitivity. However, mass spectrometry has limitations due to the matrix effects (ME), which can be particularly marked in complex mixes, when the analyte co-elutes together with other molecules, altering analysis results quantitatively. This may be detrimental during method validation, negatively affecting reproducibility, linearity, selectivity, accuracy, and sensitivity. Starting from literature and own experience, this review intends to provide a simple guideline for selecting the best operative conditions to overcome matrix effects in LC-MS techniques, to obtain the best result in the shortest time. The proposed methodology can be of benefit in different sectors, such as pharmaceutical, bio-analytical, environmental, and food sciences. Depending on the required sensitivity, analysts may minimize or compensate for ME. When sensitivity is crucial, analysis must try to minimize ME by adjusting MS parameters, chromatographic conditions, or optimizing clean-up. On the contrary, to compensate for ME analysts should have recourse to calibration approaches depending on the availability of blank matrix. When blank matrices are available, calibration can occur through isotope labeled internal standards and matrix matched calibration standards; conversely, when blank matrices are not available, calibration can be performed through isotope labeled internal standards, background subtraction, or surrogate matrices. In any case, an adjusting of MS parameters, chromatographic conditions, or a clean-up are necessary.

Quantification of eicosanoids and their metabolites in biological matrices: a review

The quantification of eicosanoids and their metabolites in biological samples remain an analytical challenge, even though a number of methodologies/techniques have been developed. The major difficulties encountered are related to the oxidation of eicosanoids and their low quantities in biological matrices. Among the known methodologies, liquid chromatography-mass spectrometry (LC-MS/MS) is the standard method for eicosanoid quantification in biological samples. Recently advances have improved the ability to identify and simultaneous quantitate eicosanoids in biological matrices. The present article reviews the quantitative analysis of eicosanoids in different biological matrices by LC and ultra performance liquid chromatography (UPLC)-MS/MS and discusses important aspects to be considered during the collection, sample preparation and the generation of calibration curves required for eicosanoid analysis.

Cell metabolomics identify regulatory pathways and targets of magnoline against prostate cancer

Prostate cancer is known as a common malignant tumor in clinics and moreover, traditional chemotherapeutic drugs have great toxic side effects and drug resistance. Therefore, the searching the highly efficient and low toxicity antitumor drugs from natural drugs has become an important approach for the treatment of prostate cancer. Many studies showed that Cortex Phellodendri has important therapeutic significance for prostate cancer. Magnoline is the main component of Cortex Phellodendri Amurensis, and it is of great significance to evaluate the effect of magnoline on prostate cancer. By using metabolomics, we established a comprehensive analysis strategy based on cell metabolic analysis to study the inhibitory effect of magnoline on the proliferation of prostate cancer cell line 22RV1, and finally conducted an analysis on the cell metabolism footprint samples. Results showed that magnoline had a significant inhibitory effect on the proliferation of the prostate cancer cell line 22RV1. According to the established cell metabolomics methods, we found that 12 metabolic biomarkers of the cell metabolic footprint samples, respectively, could inhibit the proliferation of prostate cancer cells. Magnoline could significantly affect these metabolic biomarkers to disrupt the growth and proliferation of the prostate cancer cell line 22RV1. Additionally, through MetPA analysis indicated that these biomarkers were closely correlated with a variety of metabolic pathways in tumor cells, including the energy metabolism, amino acid metabolism and fatty acid metabolism, most of which were associated with nutrition and energy metabolism. Therefore, we speculated that because of the disturbance of nutrition metabolism and energy metabolism of the prostate cancer cell line 22RV1, cells could not provide the material basis for rapid proliferation, eventually resulting in the inhibition effect.

A novel electrochemical biosensor for ultrasensitive detection of serum total bile acids based on enzymatic reaction combined with the double oxidation circular amplification strategy

Serum total bile acids (TBA) level is used as a sensitive and reliable index for hepatobiliary diseases in clinics. Herein, a novel electrochemical biosensor was fabricated using enzymatic reaction coupling with the double oxidation circular amplification strategy for the detection of human serum TBA. With the catalysis of 3α-hydroxysteroid dehydrogenase (3α-HSD), 3α-bile acids reacted specifically with nicotinamide adenine dinucleotide (NAD⁺). And then, the reduced nicotinamide adenine dinucleotide (NADH) was produced. After that, the NADH reacted with the electron mediator of tris(2,2'-bipyridine) ruthenium(Ⅲ) (Ru(bpy)₃³⁺), which was then transformed to Ru(bpy)₃²⁺. Ultimately, Ru(bpy)₃²⁺ was further oxidized to Ru(bpy)₃³⁺ under a certain voltage, which was detected by the chronoamperometry assay. The detection was performed using a disposable unmodified screen-printed carbon electrode (SPCE) without sample preparation. The proposed biosensor showed high sensitivity and accuracy with the linear range from 5.0 to 150.0 pmol/L in 10⁶-fold dilution serum. The established method had a good correlation with the enzymatic cycling method (r = 0.9372, P < 0.001, n = 72) commonly used in clinic. The electrochemical biosensor is simple, ultrasensitive and without sample pretreatment, showing great potential for point-of-care testing (POCT) of serum TBA in clinical samples. In addition, the biosensor is cost-effective with a small volume of samples, especially suitable for those who have difficulties in blood collection, such as infants, children and some small animals.

Targeted metabolomics of sulfated bile acids in urine for the diagnosis and grading of intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is related to cholestatic disorder in pregnancy. Total urinary sulfated bile acids (SBAs) were found increased in ICP. We distinguished the metabolic profiling of urinary SBAs in ICP to find potential biomarkers for the diagnosis and grading of ICP. The targeted metabolomics based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used to analyze urinary SBAs profiling in mild and severe ICP cases, as well as healthy controls. 16 kinds of urinary SBAs were determined by HPLC-MS/MS. Sulfated dihydroxy glycine bile acid (di-GBA-S), glycine cholic acid 3-sulfate (GCA-3S), sulfated dihydroxy taurine bile acid (di-TBA-S) and taurine cholic acid 3-sulfate (TCA-3S) increased significantly in ICP group compared with the control group. Seven kinds of SBAs were significantly different (p < 0.05) between the ICP group and the control group, with the variable importance in the projection (VIP) value more than one by the orthogonal partial least squares discriminant analysis (OPLS-DA). GCA-3S was well-suited to be used as the biomarker for the diagnosis of ICP with the sensitivity of 100% and specificity of 95.5%. A multi-variable logistic regression containing GCA-3S and di-GBA-S-1 was constructed to distinguish severe ICP from mild ICP, with the sensitivity of 94.4% and specificity of 100%. The developed HPLC-MS/MS method is suitable for the measurement of urinary SBAs profiling. Moreover, the urinary SBAs in the metabolomic profiling have the potential to be used as non-intrusive biomarkers for the diagnosis and grading of ICP.

Quantification of Oxidized and Unsaturated Bile Alcohols in Sea Lamprey Tissues by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

A sensitive and reliable method was developed and validated for the determination of unsaturated bile alcohols in sea lamprey tissues using liquid-liquid extraction and ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The liver, kidney, and intestine samples were extracted with acetonitrile and defatted by n-hexane. Gradient UHPLC separation was performed using an Acquity BEH C18 column with a mobile phase of water and methanol containing 20 mM triethylamine. Multiple reaction monitoring modes of precursor-product ion transitions for each analyte was used. This method displayed good linearity, with correlation coefficients greater than 0.99, and was validated. Precision and accuracy (RSD %) were in the range of 0.31%-5.28%, while mean recoveries were between 84.3%-96.3%. With this technique, sea lamprey tissue samples were analyzed for unsaturated bile alcohol analytes. This method is practical and particularly suitable for widespread putative pheromone residue analysis.

Focused metabolomics using liquid chromatography/electrospray ionization tandem mass spectrometry for analysis of urinary conjugated cholesterol metabolites from patients with Niemann-Pick disease type C and 3β-hydroxysteroid dehydrogenase deficiency

BACKGROUND

Various conjugated cholesterol metabolites are excreted in urine of the patients with metabolic abnormalities and hepatobiliary diseases. We aimed to examine the usefulness of precursor ion scan and neutral loss scan for the characterization of conjugated cholesterol metabolites in urine.

METHODS

A mixture of authentic standards of conjugated cholesterol metabolites was used for investigating the performance of the present method. The urine of patients with Niemann-Pick diseases type C and 3β-hydroxysteroid dehydrogenase deficiency were analysed by precursor ion scan of m/z 97, 74, and 124.

RESULTS

A precursor ion scan of m/z 97 was effective for identifying conjugates with ester sulphates on hydroxyl groups whereas ester sulphates on phenolic alcohols were signalled by a neutral loss scan of 80 Da. Monosaccharide-conjugated cholesterol metabolites were signalled by a precursor ion scan of m/z 113. Although precursor ion scan of m/z 74 and 124 was effective for finding glycine- and taurine-conjugated metabolites, high intensity of product ions (m/z 74 and 124) disturbed measurement of other multiply conjugated metabolites. The urine samples contained many conjugated cholesterol metabolites, and there were several disease-specific intense peaks. We found several unknown intense peaks with three known peaks in urine of the Niemann-Pick type C patient. In the patient with 3β-hydroxysteroid dehydrogenase deficiency, intense peaks that were tentatively identified as 5-cholenoic acid sulphates and their glycine and taurine conjugates were present.

CONCLUSION

The method should lead to the discovery of new urinary biomarkers for these disturbances of cholesterol catabolism and transport.

Characterization of animal models for primary sclerosing cholangitis (PSC)

Primary sclerosing cholangitis (PSC) is a chronic cholangiopathy characterized by biliary fibrosis, development of cholestasis and end stage liver disease, high risk of malignancy, and frequent need for liver transplantation. The poor understanding of its pathogenesis is also reflected in the lack of effective medical treatment. Well-characterized animal models are utterly needed to develop novel pathogenetic concepts and study new treatment strategies. Currently there is no consensus on how to evaluate and characterize potential PSC models, which makes direct comparison of experimental results and effective exchange of study material between research groups difficult. The International Primary Sclerosing Cholangitis Study Group (IPSCSG) has therefore summarized these key issues in a position paper proposing standard requirements for the study of animal models of PSC.

Evaluation of metabolite biomarkers for hepatocellular carcinoma through stratified analysis by gender, race, and alcoholic cirrhosis

BACKGROUND

The effects of hepatocellular carcinoma on liver metabolism and circulating metabolites have been subjected to continuing investigation. This study compares the levels of selected metabolites in sera of hepatocellular carcinoma cases versus patients with liver cirrhosis and evaluates the influence of gender, race, and alcoholic cirrhosis on the performance of the metabolites as candidate biomarkers for hepatocellular carcinoma.

METHODS

Targeted quantitation of 15 metabolites is performed by selected research monitoring in sera from 89 Egyptian subjects (40 hepatocellular carcinoma cases and 49 cirrhotic controls) and 110 U.S. subjects (56 hepatocellular carcinoma cases and 54 cirrhotic controls). Logistic regression models are used to evaluate the ability of these metabolites in distinguishing hepatocellular carcinoma cases from cirrhotic controls. The influences of gender, race, and alcoholic cirrhosis on the performance of the metabolites are analyzed by stratified logistic regression.

RESULTS

Two metabolites are selected on the basis of their significance to both cohorts. Although both metabolites discriminate hepatocellular carcinoma cases from cirrhotic controls in males and Caucasians, they are insignificant in females and African Americans. One metabolite is significant in patients with alcoholic cirrhosis and the other in nonalcoholic cirrhosis.

CONCLUSIONS

The study demonstrates the potential of two metabolites as candidate biomarkers for hepatocellular carcinoma by combining them with α-fetoprotein (AFP) and gender. Stratified statistical analyses reveal that gender, race, and alcoholic cirrhosis affect the relative levels of small molecules in serum.

IMPACT

The findings of this study contribute to a better understanding of the influence of gender, race, and alcoholic cirrhosis in investigating small molecules as biomarkers for hepatocellular carcinoma.

The profile of bile acids and their sulfate metabolites in human urine and serum

The role of sulfation in ameliorating the hepatotoxicity of bile acids (BAs) in humans remains unknown due to the lack of proper analytical methods to quantify individual BAs and their sulfate metabolites in biological tissues and fluids. To this end, a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to characterize the detailed BA profile in human urine and serum. The limit of quantification was 1ng/mL and baseline separation of all analytes was achieved within in a run time of 32min. The method was validated over the dynamic range of 1-1000ng/mL. The LC-MS/MS method was more accurate, precise, and selective than the commercially available kits for the quantification of sulfated and unsulfated BAs, and the indirect quantification of individual sulfated BAs after solvolysis. The LC-MS/MS method was applied to characterize the BA profile in urine and serum of healthy subjects. Thirty three percent of serum BAs were sulfated, whereas 89% of urinary BAs existed in the sulfate form, indicating the role of sulfation in enhancing the urinary excretion of BAs. The percentage of sulfation of individual BAs increased with the decrease in the number of hydroxyl groups indicating the role of sulfation in the detoxification of the more hydrophobic and toxic BA species. Eighty percent of urinary BAs and 55% of serum BAs were present in the glycine-amidated form, whereas 8% of urinary BAs and 13% of serum BAs existed in the taurine-amidated form.

LC/ESI-MS/MS analysis of urinary 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid and its amides: new biomarkers for the detection of Niemann-Pick type C disease

We developed a sensitive, reliable, and accurate LC/ESI-MS/MS method for measurement of 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid and its glycine and taurine amides in urine. This atypical C24 bile acid has been reported previously to be present in the urine of patients with Niemann-Pick Type C (NPC) disease. In the method, targeted analytes are concentrated at the front edge of a trapping column, Shim-pack MAYI-C8, which permits elimination of contaminating molecules in the urinary matrix. The trapped analytes are then eluted, separated on a YMC-Pack Pro C18, and quantified with MS/MS using selected reaction monitoring. The method could detect (as amount injected) 2pg of nonamidated 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid, 2pg of its glycine-amide, and 0.6pg of its taurine-amide, and is linear up to 300pg. The method was then used to measure the three analytes in the urine of NPC patients (N=2), 3β-hydroxysteroid dehydrogenase deficiency patients (N=2), and healthy volunteers (N=8). Measurable concentrations of all three analytes were present in all subjects. The urinary concentration of the sum of all three analytes was four hundred times greater in the 3month NPC patient and 40times greater in the adult patient than that of healthy volunteers. The markedly elevated urinary concentration of 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid and its amides in NPC patients suggests that these compounds may be valuable biomarkers for detection of NPC disease.

Mass spectrometry techniques in the survey of steroid metabolites as potential disease biomarkers: a review

Mass spectrometric approaches have been fundamental to the identification of metabolites associated with steroid hormones, yet this topic has not been reviewed in depth in recent years. To this end, and given the increasing relevance of liquid chromatography-mass spectrometry (LC-MS) studies on steroid hormones and their metabolites, the present review addresses this subject. This review provides a timely summary of the use of various mass spectrometry-based analytical techniques during the evaluation of steroidal biomarkers in a range of human disease settings. The sensitivity and specificity of these technologies are clearly providing valuable new insights into breast cancer and cardiovascular disease. We aim to contribute to an enhanced understanding of steroid metabolism and how it can be profiled by LC-MS techniques.

LC-MS based serum metabolomics for identification of hepatocellular carcinoma biomarkers in Egyptian cohort

Although hepatocellular carcinoma (HCC) has been subjected to continuous investigation and its symptoms are well-known, early stage diagnosis of this disease remains difficult and the survival rate after diagnosis is typically very low (3-5%). Early and accurate detection of metabolic changes in the sera of patients with liver cirrhosis can help improve the prognosis of HCC and lead to a better understanding of its mechanism at the molecular level, thus providing patients with in-time treatment of the disease. In this study, we compared metabolite levels in sera of 40 HCC patients and 49 cirrhosis patients from Egypt by using ultraperformance liquid chromatography coupled with quadrupole time-of-flight mass spectrometer (UPLC-QTOF MS). Following data preprocessing, the most relevant ions in distinguishing HCC cases from cirrhotic controls are selected by statistical methods. Putative metabolite identifications for these ions are obtained through mass-based database search. The identities of some of the putative identifications are verified by comparing their MS/MS fragmentation patterns and retention times with those from authentic compounds. Finally, the serum samples are reanalyzed for quantitation of selected metabolites as candidate biomarkers of HCC. This quantitation was performed using isotope dilution by selected reaction monitoring (SRM) on a triple quadrupole linear ion trap (QqQLIT) coupled to UPLC. Statistical analysis of the UPLC-QTOF data identified 274 monoisotopic ion masses with statistically significant differences in ion intensities between HCC cases and cirrhotic controls. Putative identifications were obtained for 158 ions by mass based search against databases. We verified the identities of selected putative identifications including glycholic acid (GCA), glycodeoxycholic acid (GDCA), 3β, 6β-dihydroxy-5β-cholan-24-oic acid, oleoyl carnitine, and Phe-Phe. SRM-based quantitation confirmed significant differences between HCC and cirrhotic controls in metabolite levels of bile acid metabolites, long chain carnitines and small peptide. Our study provides useful insight into appropriate experimental design and computational methods for serum biomarker discovery using LC-MS/MS based metabolomics. This study has led to the identification of candidate biomarkers with significant changes in metabolite levels between HCC cases and cirrhotic controls. This is the first MS-based metabolic biomarker discovery study on Egyptian subjects that led to the identification of candidate metabolites that discriminate early stage HCC from patients with liver cirrhosis.

Utilization of metabolomics to identify serum biomarkers for hepatocellular carcinoma in patients with liver cirrhosis

Characterizing the metabolic changes pertaining to hepatocellular carcinoma (HCC) in patients with liver cirrhosis is believed to contribute towards early detection, treatment, and understanding of the molecular mechanisms of HCC. In this study, we compare metabolite levels in sera of 78 HCC cases with 184 cirrhotic controls by using ultra performance liquid chromatography coupled with a hybrid quadrupole time-of-flight mass spectrometry (UPLC-QTOF MS). Following data preprocessing, the most relevant ions in distinguishing HCC cases from patients with cirrhosis are selected by parametric and non-parametric statistical methods. Putative metabolite identifications for these ions are obtained through mass-based database search. Verification of the identities of selected metabolites is conducted by comparing their MS/MS fragmentation patterns and retention time with those from authentic compounds. Quantitation of these metabolites is performed in a subset of the serum samples (10 HCC and 10 cirrhosis) using isotope dilution by selected reaction monitoring (SRM) on triple quadrupole linear ion trap (QqQLIT) and triple quadrupole (QqQ) mass spectrometers. The results of this analysis confirm that metabolites involved in sphingolipid metabolism and phospholipid catabolism such as sphingosine-1-phosphate (S-1-P) and lysophosphatidylcholine (lysoPC 17:0) are up-regulated in sera of HCC vs. those with liver cirrhosis. Down-regulated metabolites include those involved in bile acid biosynthesis (specifically cholesterol metabolism) such as glycochenodeoxycholic acid 3-sulfate (3-sulfo-GCDCA), glycocholic acid (GCA), glycodeoxycholic acid (GDCA), taurocholic acid (TCA), and taurochenodeoxycholate (TCDCA). These results provide useful insights into HCC biomarker discovery utilizing metabolomics as an efficient and cost-effective platform. Our work shows that metabolomic profiling is a promising tool to identify candidate metabolic biomarkers for early detection of HCC cases in high risk population of cirrhotic patients.

Detection of Δ4-3-oxo-steroid 5β-reductase deficiency by LC-ESI-MS/MS measurement of urinary bile acids

The synthesis of bile salts from cholesterol is a complex biochemical pathway involving at least 16 enzymes. Most inborn errors of bile acid biosynthesis result in excessive formation of intermediates and/or their metabolites that accumulate in blood and are excreted in part in urine. Early detection is important as oral therapy with bile acids results in improvement. In the past, these intermediates in bile acid biosynthesis have been detected in neonatal blood or urine by screening with FAB-MS followed by detailed characterization using GC-MS. Both methods have proved difficult to automate, and currently most laboratories screen candidate samples using LC-MS/MS. Here, we describe a new, simple and sensitive analytical method for the identification and characterization of 39 conjugated and unconjugated bile acids, including Δ(4)-3-oxo- and Δ(4,6)-3-oxo-bile acids (markers for Δ(4)-3-oxo-steroid 5β-reductase deficiency), using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). In this procedure a concentrated, desalted urinary sample (diluted with ethanol) is injected directly into the LC-ESI-MS/MS, operated with ESI and in the negative ion mode; quantification is obtained by selected reaction monitoring (SRM). To evaluate the performance of our new method, we compared it to a validated method using GC-MS, in the analysis of urine from two patients with genetically confirmed Δ(4)-3-oxo-steroid 5β-reductase deficiency as well as a third patient with an elevated concentration of abnormal conjugated and unconjugated Δ(4)-3-oxo-bile acids. The Δ(4)-3-oxo-bile acids concentration recovered in three patients with 5β-reductase deficiency were 48.8, 58.9, and 49.4 μmol/mmol creatinine, respectively by LC-ESI-MS/MS.

Bile acid profiling in human biological samples: comparison of extraction procedures and application to normal and cholestatic patients

The role of bile acids in cell metabolism, membrane biology and cell signaling is increasingly recognized, thus making necessary a robust and versatile technique to extract, separate and quantify a large concentration range of these numerous molecular species. HPLC-MS/MS analysis provides the highest sensitivity to detect and identify bile acids. However, due to their large chemical diversity, extraction methods are critical and quite difficult to optimize, as shown by a survey of the literature. This paper compares the performances of four bile acid extraction protocols applied to either liquid (serum, urine, bile) or solid (stool) samples. Acetonitrile was found to be the best solvent for deproteinizing liquid samples and NaOH the best one for stool extraction. These optimized extraction procedures allowed us to quantitate as much as 27 distinct bile acids including sulfated species in a unique 30 min HPLC run, including both hydrophilic and hydrophobic species with a high efficiency. Tandem MS provided a non ambiguous identification of each metabolite with a good sensitivity (LOQ below 20 nmol/l except for THDCA and TLCA). After validation, these methods, successfully applied to a group of 39 control patients, detected 14 different species in serum in the range of 30-800 nmol/l, 11 species in urine in the range of 20-200 nmol/l and 25 species in stool in the range of 0.4-2000 nmol/g. The clinical interest of this method has been then validated on cholestatic patients. The proposed protocols seem suitable for profiling bile acids in routine analysis.

Simultaneous characterization of bile acids and their sulfate metabolites in mouse liver, plasma, bile, and urine using LC-MS/MS

Sulfation is a major metabolic pathway involved in the elimination and detoxification of bile acids (BAs). Several lines of evidence are available to support the role of sulfation as a defensive mechanism to attenuate the toxicity of accumulated BAs during hepatobiliary diseases. Individual BAs and their sulfate metabolites vary markedly in their physiological roles as well as their toxicities. Therefore, analytical techniques are required for the quantification of individual BAs and BA-sulfates in biological fluids and tissues. Here we report a simple, sensitive, and validated LC-MS/MS method for the simultaneous quantification of major BAs and BA-sulfates in mouse liver, plasma, bile, and urine. One-step sample preparation using solid-phase extraction (for bile and urine) or protein precipitation (for liver and plasma) was used to extract BAs and BA-sulfates. Base-line separation of all analytes (unsulfated- and sulfated BAs) was achieved in 25min with a limit of quantification of 1ng/ml. This LC-MS/MS method was applied to simultaneously quantify BAs and BA-sulfates in both male and female mouse tissues and fluids. Less than 3% of total BAs are present in the sulfate form in the mouse liver, plasma, and bile, which provides strong evidence that sulfation is a minor metabolic pathway of BA elimination and detoxification in mice. Furthermore, we report that the marked female-predominant expression of Sult2a1 is not reflected into a female-predominant pattern of BA-sulfation.

Synthesis of the 3-sulfates of N-acetylcysteine conjugated bile acids (BA-NACs) and their transient formation from BA-NACs and subsequent hydrolysis by a rat liver cytosolic fraction as shown by liquid chromatography/electrospray ionization-mass spectrometry

Previous work from this laboratory has reported the chemical synthesis of N-acetylcysteine (NAC) conjugates of natural bile acids (BAs) and shown that such novel conjugates can be formed in vivo in rats to which NAC has been administered. The subsequent fate of such novel conjugates is not known. One possible biotransformation is sulfation, a major pathway for BAs N-acylamidates in patients with cholestatic liver disease. Here, we report the chemical synthesis of the 3-sulfates of the S-acyl NAC conjugates of five natural BAs (cholic, chenodeoxycholic, deoxycholic, ursodeoxycholic, and lithocholic). We also measured the sulfation of N-acetylcysteine-natural bile acid (BA-NAC) conjugates when they were incubated with a rat liver cytosolic fraction. The chemical structures of the BA-NAC 3-sulfates were confirmed by proton nuclear magnetic resonance, as well as by means of electrospray ionization-linear ion trap mass spectrometry with negative-ion detection. Upon collision-induced dissociation of singly and doubly charged deprotonated molecules, structurally informative product ions were observed. Using a triple-stage quadrupole instrument, selected reaction monitoring analyses by monitoring characteristic transition ions allowed the achievement of a highly sensitive and specific assay. When BA-NACs were incubated with a rat liver cytosolic fraction to which 3'-phosphoadenosine 5'-phosphosulfate was added, sulfation occurred, but the dominant reaction was hydrolysis of the S-acyl linkage to form the unconjugated BAs. Subsequent sulfation occurred at C-3 on the unconjugated BAs that had been formed from the BA-NACs. Such sulfation was proportional to the hydrophobicity of the unconjugated bile acid. Thus, NAC conjugates of BAs as well as their C-3 sulfates if formed in vivo are rapidly hydrolyzed by cytosolic enzymes.

Measurement of transport activities of bile acids in human multidrug resistance-associated protein 3 using liquid chromatography-tandem mass spectrometry

A method has been developed for the measurement of transport activities in membrane vesicles obtained from human multidrug resistance-associated protein 3-expressing Sf9 cells for 1beta-hydroxy-, 6alpha-hydroxy- and unsaturated bile acids by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. Calibration curves for the bile acids were linear over the range of 10 to 2000 pmol/mL, and the detection limit was less than 2 pmol/mL for all bile acids using selected reaction monitoring analysis. The method was applied to measurements of adenosine triphosphate-dependent transport activities of the membrane vesicles for the above-mentioned hydroxylated and unsaturated bile acids. The present study demonstrated that the human multidrug resistance-associated protein 3 vesicles accepted 1beta-, 6alpha-hydroxylated and unsaturated bile acids along with common bile acids, such as glycocholic acid and taurolithocholic acid 3-sulfate. The developed method is useful for measurements of bile acid transport activities.

Bile acids: analysis in biological fluids and tissues

The formation of bile acids/bile alcohols is of major importance for the maintenance of cholesterol homeostasis. Besides their functions in lipid absorption, bile acids/bile alcohols are regulatory molecules for a number of metabolic processes. Their effects are structure-dependent, and numerous metabolic conversions result in a complex mixture of biologically active and inactive forms. Advanced methods are required to characterize and quantify individual bile acids in these mixtures. A combination of such analyses with analyses of the proteome will be required for a better understanding of mechanisms of action and nature of endogenous ligands. Mass spectrometry is the basic detection technique for effluents from chromatographic columns. Capillary liquid chromatography-mass spectrometry with electrospray ionization provides the highest sensitivity in metabolome analysis. Classical gas chromatography-mass spectrometry is less sensitive but offers extensive structure-dependent fragmentation increasing the specificity in analyses of isobaric isomers of unconjugated bile acids. Depending on the nature of the bile acid/bile alcohol mixture and the range of concentration of individuals, different sample preparation sequences, from simple extractions to group separations and derivatizations, are applicable. We review the methods currently available for the analysis of bile acids in biological fluids and tissues, with emphasis on the combination of liquid and gas phase chromatography with mass spectrometry.

Chemical synthesis of 3beta-sulfooxy-7beta-hydroxy-24-nor-5-cholenoic acid: an internal standard for mass spectrometric analysis of the abnormal delta5-bile acids occurring in Niemann-Pick disease

In Niemann-Pick disease, type C1, increased amounts of 3beta,7beta-dihydroxy-5-cholenoic acid are reported to be present in urinary bile acids. The compound occurs as a tri-conjugate, sulfated at C-3, N-acetylglucosamidated at C-7, and N-acylamidated with taurine or glycine at C-24. For sensitive LC-MS/MS analysis of this bile acid, a suitable internal standard is needed. We report here the synthesis of a satisfactory internal standard, 3beta-sulfooxy-7beta-hydroxy-24-nor-5-cholenoic acid (as the disodium salt). The key reactions involved were (1) the so-called "second order" Beckmann rearrangement (one-carbon degradation at C-24) of hyodeoxycholic acid (HDCA) 3,6-diformate with sodium nitrite in a mixture of trifluoroacetic anhydride and trifluoroacetic acid, (2) simultaneous inversion at C-3 and elimination at C-6 of the ditosylate derivatives of the resulting 3alpha,6alpha-dihydroxy-24-nor-5beta-cholanoic acid with potassium acetate in aqueous N,N-dimethylformamide, and (3) regioselective sulfation at C-3 of an intermediary 3beta,7beta-dihydroxy-24-nor-Delta(5) derivative using sulfur trioxide-trimethylamine complex. Overall yield of the desired compound was 1.8% in 12 steps from HDCA.

Quantitative profiling of polar cationic metabolites in human cerebrospinal fluid by reversed-phase nanoliquid chromatography/mass spectrometry

Reversed-phase (RP) nanoliquid chromatography (LC)/mass spectrometry (MS) is widely used for proteome analysis, but hydrophilic metabolites are poorly retained on RP columns. We describe here the development and application of an efficient, robust, and quantitative nano-LC/MS method for cationic metabolome analysis in the positive ionization mode without any derivatization of analytes. Various stationary phases for nano-LC, coating of the internal wall of the capillary column, and various mobile phases were evaluated in terms of separation and peak shapes for 33 hydrophilic metabolites, including nonderivatized amino acids. Polar cationic compounds were strongly bound to mixed-functional RP with cation exchange mode resin, and the best separation was obtained with hydrophilic internal wall coating and a two-step trifluoroacetic acid (TFA) gradient in methanol as the mobile phase. Simple, but optimized, sample processing and the use of a high content of methanol allowed robust nano-LC/MS analysis. Our developed method was applied for biomarker discovery in Alzheimer's disease (AD). Several hundred peaks were detected from 10 microL of cerebrospinal fluid (CSF). In a principal component analysis (PCA) plot using peak intensities without normalization, peak separation depended on the experimental date, not disease state. Therefore, constant amounts of two stable isotope-labeled amino acids, Val and Lys, were added as internal standards (ISs) to each sample before processing. These ISs were eluted in different gradient slopes in the two-step gradient, and the normalized peak ratios using the corresponding ISs gave a unique group of PCA scores which could distinguish AD CSF samples from age-matched control CSF samples.

Bile Acid sulfation: a pathway of bile acid elimination and detoxification

Sulfotransferase-2A1 catalyzes the formation of bile acid-sulfates (BA-sulfates). Sulfation of BAs increases their solubility, decreases their intestinal absorption, and enhances their fecal and urinary excretion. BA-sulfates are also less toxic than their unsulfated counterparts. Therefore, sulfation is an important detoxification pathway of BAs. Major species differences in BA sulfation exist. In humans, only a small proportion of BAs in bile and serum are sulfated, whereas more than 70% of BAs in urine are sulfated, indicating their efficient elimination in urine. The formation of BA-sulfates increases during cholestatic diseases. Therefore, sulfation may play an important role in maintaining BA homeostasis under pathologic conditions. Farnesoid X receptor, pregnane X receptor, constitutive androstane receptor, and vitamin D receptor are potential nuclear receptors that may be involved in the regulation of BA sulfation. This review highlights current knowledge about the enzymes and transporters involved in the formation and elimination of BA-sulfates, the effect of sulfation on the pharmacologic and toxicologic properties of BAs, the role of BA sulfation in cholestatic diseases, and the regulation of BA sulfation.

Human cecal bile acids: concentration and spectrum

To obtain information on the concentration and spectrum of bile acids in human cecal content, samples were obtained from 19 persons who had died an unnatural death from causes such as trauma, homicide, suicide, or drug overdose. Bile acid concentration was measured via an enzymatic assay for 3alpha-hydroxy bile acids; bile acid classes were determined by electrospray ionization mass spectrometry and individual bile acids by gas chromatography mass spectrometry and liquid chromatography mass spectrometry. The 3alpha-hydroxy bile acid concentration (mumol bile acid/ml cecal content) was 0.4 +/- 0.2 mM (mean +/- SD); the total 3-hydroxy bile acid concentration was 0.6 +/- 0.3 mM. The aqueous concentration of bile acids (supernatant after centrifugation) was identical, indicating that most bile acids were in solution. By liquid chromatography mass spectrometry, bile acids were mostly in unconjugated form (90 +/- 9%, mean +/- SD); sulfated, nonamidated bile acids were 7 +/- 5%, and nonsulfated amidated bile acids (glycine or taurine conjugates) were 3 +/- 7%. By gas chromatography mass spectrometry, 10 bile acids were identified: deoxycholic (34 +/- 16%), lithocholic (26 +/- 10%), and ursodeoxycholic (6 +/- 9), as well as their primary bile acid precursors cholic (6 +/- 9%) and chenodeoxycholic acid (7 +/- 8%). In addition, 3beta-hydroxy derivatives of some or all of these bile acids were present and averaged 27 +/- 18% of total bile acids, indicating that 3beta-hydroxy bile acids are normal constituents of cecal content. In the human cecum, deconjugation and dehydroxylation of bile acids are nearly complete, resulting in most bile acids being in unconjugated form at submicellar and subsecretory concentrations.