Gas chromatographic-mass spectrometric analyses of cholesterol and its precursors in rat plasma as tert-butyldimethylsilyl derivatives

Quantitation of 20 Phytosterols in 34 Different Accessions of Quinoa (Chenopodium quinoa)

Phytosterols were analyzed in 34 different quinoa accessions, which were obtained from the same field trial. Twenty different sterols were detected, and 17 could be structurally assigned by means of gas chromatography with mass spectrometry. Sterols were quantitated in selected ion monitoring mode (GC/MS-SIM) with the novel internal standard 3-O-tert-butyldimethylsilyl-cholestanol (cholestanyl-TBDMS). GC/MS-SIM response factors of minor sterols were determined after enrichment by countercurrent chromatography. The total sterol contents varied from 120 to 180 mg/100 g of seeds, which is higher than has been described in quinoa before. This was due to the fact that Δ7-sterols (e.g., Δ7-sitosterol, spinasterol, and Δ7-avenasterol) were quantitated for the first time in quinoa and contributed ∼64% to the total sterol content. Clustering allowed distributing of the 34 different quinoa accessions into four distinct groups on the basis of the different sterol patterns.

Blocking Kallikrein 6 promotes developmental myelination

Kallikrein related peptidase 6 (Klk6) is a secreted serine protease highly expressed in oligodendrocytes and implicated in demyelinating conditions. To gain insights into the significance of Klk6 to oligodendrocyte biology, we investigated the impact of global Klk6 gene knockout on CNS developmental myelination using the spinal cord of male and female mice as a model. Results demonstrate that constitutive loss of Klk6 expression accelerates oligodendrocyte differentiation developmentally, including increases in the expression of myelin proteins such as MBP, PLP and CNPase, in the number of CC-1+ mature oligodendrocytes, and myelin thickness by the end of the first postnatal week. Co-ordinate elevations in the pro-myelinating signaling pathways ERK and AKT, expression of fatty acid 2-hydroxylase, and myelin regulatory transcription factor were also observed in the spinal cord of 7d Klk6 knockouts. LC/MS/MS quantification of spinal cord lipids showed sphingosine and sphingomyelins to be elevated in Klk6 knockouts at the peak of myelination. Oligodendrocyte progenitor cells (OPCs)-derived from Klk6 knockouts, or wild type OPCs-treated with a Klk6 inhibitor (DFKZ-251), also showed increased MBP and PLP. Moreover, inhibition of Klk6 in OPC cultures enhanced brain derived neurotrophic factor-driven differentiation. Altogether, these findings suggest that oligodendrocyte-derived Klk6 may operate as an autocrine or paracrine rheostat, or brake, on pro-myelinating signaling serving to regulate myelin homeostasis developmentally and in the adult. These findings document for the first time that inhibition of Klk6 globally, or specifically in oligodendrocyte progenitors, is a strategy to increase early stages of oligodendrocyte differentiation and myelin production in the CNS.

A reliable tool for detecting 7-dehydrocholesterol and cholesterol in human plasma and its use in diagnosis of Smith-Lemli-Opitz syndrome

BACKGROUND

Smith-Lemli-Opitz syndrome is a birth defect caused by the deficiency of 7-dehydrocholesterol reductase in cholesterol biosynthesis pathway, which leads to accumulation of 7-dehydrocholesterol and reduction of cholesterol in body fluids. To effectively diagnose Smith-Lemli-Opitz syndrome and monitor therapy, a reliable method for simultaneous detection of 7-dehydrocholesterol and cholesterol is needed.

METHODS

In the presence of antioxidants (2,6-ditert-butyl-4-methylphenol and triphenylphosphine), 50 μL of human plasma were hydrolyzed at 70℃ for 40 min with 1 M potassium hydroxide in 90% ethanol, and then 7-dehydrocholesterol and cholesterol were extracted by 600 μL of n-hexane for three times. After microwave-assisted derivatization with 70 μL of N,O-Bis(trimethylsilyl)trifluoroacetamide at 460 W for 3 min, the analytes were measured by gas chromatography-mass spectrometry (GC-MS).

RESULTS

The limits of detection were 100 ng/mL for 7-dehydrocholesterol and 300 ng/mL for cholesterol. Good linearity was obtained in the range of 1-600 μg/mL for 7-dehydrocholesterol and 10-600 μg/mL for cholesterol, which completely covered the biochemical levels of Smith-Lemli-Opitz syndrome patients that have been reported.

CONCLUSION

A time-saving and accurate GC-MS based method was developed for the determination of 7-dehydrocholesterol and cholesterol in human plasma, which also serves as a useful tool for Smith-Lemli-Opitz syndrome diagnosis, treatment and research. This article is protected by copyright. All rights reserved.

Synergistic Inhibition of Mycotoxigenic Fungi and Mycotoxin Production by Combination of Pomegranate Peel Extract and Azole Fungicide

Fungal plant pathogens cause considerable losses in yield and quality of field crops worldwide. In addition, under specific environmental conditions, many fungi, including such as some Fusarium and Aspergillus spp., are further able to produce mycotoxins while colonizing their host, which accumulate in human and animal tissues, posing a serious threat to consumer health. Extensive use of azole fungicides in crop protection stimulated the emergence of acquired azole resistance in some plant and human fungal pathogens. Combination treatments, which become popular in clinical practice, offer an alternative strategy for managing potentially resistant toxigenic fungi and reducing the required dosage of specific drugs. In the current study we tested the effect of pomegranate peel extract (PPE) on the growth and toxin production of the mycotoxigenic fungi Aspergillus flavus and Fusarium proliferatum, both alone and in combination with the azole fungicide prochloraz (PRZ). Using time-lapse microscopy and quantitative image analysis we demonstrate significant delay of conidial germination and hyphal elongation rate in both fungi following PPE treatment in combination with PRZ. Moreover, PPE treatment reduced aflatoxin production by A. flavus up to 97%, while a combined treatment with sub-inhibitory doses of PPE and PRZ resulted in complete inhibition of toxin production over a 72 h treatment. These findings were supported by qRT-PCR analysis, showing down-regulation of key genes involved in the aflatoxin biosynthetic pathway under combined PPE/PRZ treatment al low concentrations. Our results provide first evidence for synergistic effects between the commercial drug PRZ and natural compound PPE. Future application of these findings may allow to reduce the required dosage of PRZ, and possibly additional azole drugs, to inhibit mycotoxigenic fungi, ultimately reducing potential concerns over exposure to high doses of these potentially harmful fungicides.

Superior anti-neoplastic activities of triacontanol-PEG conjugate: synthesis, characterization and biological evaluations

Triacontanol (TA, C30H62O), abundantly present in plant cuticle waxes and bee waxes, has been found to display promising anti-neoplastic potentials. As a long chain fatty alcohol, TA possesses limited aqueous solubility, which hinders its medicinal application. To overcome its solubility barrier, a polymer prodrug was synthesized through attaching TA to poly ethylene glycol (PEG), using succinic acid as a linker with bifunctional amide and ester bonds. Anti-neoplastic effects of PEG-TA were assessed in LoVo and MCF7 cells, anti-proliferative and apoptosis-inducing activities were subsequently confirmed in mouse xenograft model. Encouragingly, PEG-TA possessed selective anti-cancer ability. It did not exhibit significant cytotoxicity on normal cells. Mechanistic examination revealed inhibition of NF-κB nuclear translocation, suppression on matrix degradation enzyme and down-regulation of angiogenic signaling might contribute to its anti-malignant effects. Pharmacokinetics clearly indicated PEGylated TA (named as mPEG2K-SA-TA) substantially enhanced TA delivery with increased plasma exposure (19,791 vs. 336.25 ng·mL-1·h-1, p < .001), mean residence time (8.46 vs. 2.95 h, p < .001) and elimination half-life (7.78 vs. 2.57 h, p < .001) compared to those of original TA. Moreover, mPEG2K-SA-TA appeared to be safe in preliminary toxicological assessment. PEGylated TA also emerged as a functional carrier to deliver hydrophobic chemotherapeutic agents, since it readily self-assembled to micelles in aqueous solution with a low critical micelle concentration (CMC, 19.1 µg·mL-1). Conclusively, PEG-TA conjugate displayed superior anti-neoplastic activities and low toxicity, as well as facilitated the delivery of other hydrophobic agents, which appeared to be an innovative strategy for cancer therapy.

Covalent Surface Functionalization of Semiconducting Polymer Dots with β-Cyclodextrin for Fluorescent Ratiometric Assay of Cholesterol through Host-Guest Inclusion and FRET

Special functionalization of semiconducting polymer dots (Pdots) is highly desired to expand their applications in chemo/biosening. Herein, carboxyl-functionalized poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadiazole)] dots covalently tagged with aminated β-cyclodextrin (NH₂-CD) have been designed to construct a ratiometric sensor for cholesterol (Cho). Using CD-Pdots as energy donors with rhodamine B (RB) as energy acceptors, a fluorescence resonance energy transfer (FRET) pair has been built because the host-guest interaction between RB and CD attached to Pdots brings donors and acceptors into close proximity. In the presence of Cho, the acceptors will depart from the donors because of the competitive inclusion interaction between Cho and RB with CD, resulting in the hindering of the FRET process between CD-Pdots and RB. On the basis of the turn-on fluorescence of CD-Pdots and turn-off fluorescence of RB, a sensitive ratiometric method for the determination of Cho in the concentration range from 25 to 350 nM with a detection limit of 4.9 nM was achieved. The proposed method was validated to determine free Cho in human serum samples with satisfactory results.

Nuclear Magnetic Resonance (NMR) Study for the Detection and Quantitation of Cholesterol in HSV529 Therapeutic Vaccine Candidate

This study describes the NMR-based method to determine the limit of quantitation (LOQ) and limit of detection (LOD) of cholesterol, a process-related impurity in the replication-deficient Herpes Simplex Virus (HSV) type 2 candidate vaccine HSV529. Three signature peaks from the 1D ¹H NMR of a cholesterol reference spectrum were selected for the identification of cholesterol. The LOQ for a cholesterol working standard was found to be 1 μg/mL, and the LOD was found to be 0.1 μg/mL. The identity of cholesterol, separated from the formulation of growth supplement by thin layer chromatography (TLC), was confirmed by 1D ¹H NMR and 2D ¹H-¹³C HSQC NMR. The three signature peaks of cholesterol were detected only in a six-times concentrated sample of HSV529 candidate vaccine sample and not in the single dose HSV529 vaccine sample under similar experimental conditions. Taken together, the results demonstrated that NMR is a direct method that can successfully identify and quantify cholesterol in viral vaccine samples, such as HSV529, and as well as in the growth supplement used during the upstream stages of HSV529 manufacturing.

Systemic availability and metabolism of colonic-derived short-chain fatty acids in healthy subjects: a stable isotope study

KEY POINTS

The short-chain fatty acids (SCFAs) are bacterial metabolites produced during the colonic fermentation of undigested carbohydrates, such as dietary fibre and prebiotics, and can mediate the interaction between the diet, the microbiota and the host. We quantified the fraction of colonic administered SCFAs that could be recovered in the systemic circulation, the fraction that was excreted via the breath and urine, and the fraction that was used as a precursor for glucose, cholesterol and fatty acids. This information is essential for understanding the molecular mechanisms by which SCFAs beneficially affect physiological functions such as glucose and lipid metabolism and immune function.

ABSTRACT

The short-chain fatty acids (SCFAs), acetate, propionate and butyrate, are bacterial metabolites that mediate the interaction between the diet, the microbiota and the host. In the present study, the systemic availability of SCFAs and their incorporation into biologically relevant molecules was quantified. Known amounts of ¹³ C-labelled acetate, propionate and butyrate were introduced in the colon of 12 healthy subjects using colon delivery capsules and plasma levels of ¹³ C-SCFAs ¹³ C-glucose, ¹³ C-cholesterol and ¹³ C-fatty acids were measured. The butyrate-producing capacity of the intestinal microbiota was also quantified. Systemic availability of colonic-administered acetate, propionate and butyrate was 36%, 9% and 2%, respectively. Conversion of acetate into butyrate (24%) was the most prevalent interconversion by the colonic microbiota and was not related to the butyrate-producing capacity in the faecal samples. Less than 1% of administered acetate was incorporated into cholesterol and <15% in fatty acids. On average, 6% of colonic propionate was incorporated into glucose. The SCFAs were mainly excreted via the lungs after oxidation to ¹³ CO₂ , whereas less than 0.05% of the SCFAs were excreted into urine. These results will allow future evaluation and quantification of SCFA production from ¹³ C-labelled fibres in the human colon by measurement of ¹³ C-labelled SCFA concentrations in blood.

Application of a Dual-Arm Robot in Complex Sample Preparation and Measurement Processes

Automation systems with applied robotics have already been established in industrial applications for many years. In the field of life sciences, a comparable high level of automation can be found in the areas of bioscreening and high-throughput screening. Strong deficits still exist in the development of flexible and universal fully automated systems in the field of analytical measurement. Reasons are the heterogeneous processes with complex structures, which include sample preparation and transport, analytical measurements using complex sensor systems, and suitable data analysis and evaluation. Furthermore, the use of nonstandard sample vessels with various shapes and volumes results in an increased complexity. The direct use of existing automation solutions from bioscreening applications is not possible. A flexible automation system for sample preparation, analysis, and data evaluation is presented in this article. It is applied for the determination of cholesterol in biliary endoprosthesis using gas chromatography-mass spectrometry (GC-MS). A dual-arm robot performs both transport and active manipulation tasks to ensure human-like operation. This general robotic concept also enables the use of manual laboratory devices and equipment and is thus suitable in areas with a high standardization grade.

N-Alkylpyridinium isotope quaternization for matrix-assisted laser desorption/ionization Fourier transform mass spectrometric analysis of cholesterol and fatty alcohols in human hair

Isotope-coded reagents have been developed for labeling of amino acids, phenols and fatty acids, but not for alcohols. In this work, a simple reaction based on direct N-alkylpyridinium isotope quaternization (NAPIQ) was developed for mild derivatization of cholesterol and fatty alcohols. Different from the conventional quaternary reagents with cations on themselves, two simple and charge-neutral reagents: pyridine and d(5)-pyridine directly attached N-cationic tag onto the target compounds in the presence of trifluoromethanesulfonic anhydride (Tf(2)O) without tedious sample preparation. The derivatization completed in 5 min and achieved charge labeling of the target compounds, which significantly improved the detection limits of analytes by 10(3)-folds in further analysis by matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS). The use of commercially available d(0)/d(5)-pyridine pairs facilitated isotope-coded chemical derivatization and avoided the use of isotope-labeled internal standards; the excess pyridine did not affect the signals of analytes. Utility of the NAPIQ method was examined in the identification of cholesterol and fatty alcohols in small amount of human hair sample (<0.5mg). The fluctuation of total cholesterol in human body was profiled during time by quantitatively comparing the different segments of a single strand of hair. This study combines the direct pyridinium quaternization with MALDI-FTMS, which offers a perspective and an alternative tool for the identification and quantification of substances in biological matrix by comparing d(0)/d(5) pairs, especially when isotope-labeled internal standards are unavailable.

A simple and sensitive enzymatic method for cholesterol quantification in macrophages and foam cells

A precise and sensitive method for measuring cellular free and esterified cholesterol is required in order to perform studies of macrophage cholesterol loading, metabolism, storage, and efflux. Until now, the use of an enzymatic cholesterol assay, commonly used for aqueous phase plasma cholesterol assays, has not been optimized for use with solid phase samples such as cells, due to inefficient solubilization of total cholesterol in enzyme compatible solvents. We present an efficient solubilization protocol compatible with an enzymatic cholesterol assay that does not require chemical saponification or chromatographic separation. Another issue with enzyme compatible solvents is the presence of endogenous peroxides that interfere with the enzymatic cholesterol assay. We overcame this obstacle by pretreatment of the reaction solution with the enzyme catalase, which consumed endogenous peroxides resulting in reduced background and increased sensitivity in our method. Finally, we demonstrated that this method for cholesterol quantification in macrophages yields results that are comparable to those measured by stable isotope dilution gas chromatography with mass spectrometry detection. In conclusion, we describe a sensitive, simple, and high-throughput enzymatic method to quantify cholesterol in complex matrices such as cells.

Trace quantification of 1-octacosanol and 1-triacontanol and their main metabolites in plasma by liquid-liquid extraction coupled with gas chromatography-mass spectrometry

A method for the simultaneous determination of 1-octacosanol and 1-triacontanol and their main metabolites in rat plasma was developed. The procedure involved ethanolic NaOH saponification of the sample, acidification, liquid-liquid extraction, and derivatization of the analytes to its trimethylsilylether/ester, followed analysis by gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode. Quantification was performed by the internal standard method using betulin. The method had a good linearity over the range 8.4-540ng/ml (r>or=0.998) and showed an excellent intra-day (R.S.D.=0.59-3.06%) and inter-day (R.S.D.=2.99-5.22%) precision according to the acceptance criteria. The detection limits ranged between 1.32 and 3.47ng/ml. The method was applied successfully to study the total plasmatic concentration of 1-octacosanol, octacosanoic acid, 1-triacontanol, and triacontanoic acid, after an oral dose of policosanols mixture, using plasma samples of 100microl.

Combined gas chromatographic/mass spectrometric analysis of cholesterol precursors and plant sterols in cultured cells

We developed a powerful gas chromatographic/mass spectrometric method allowing quantitative analysis of 11 structurally similar cholesterol precursors and plant sterols (squalene, desmosterol, 7-dehydrocholesterol, lathosterol, zymosterol, dihydro-lanosterol, lanosterol, FF-MAS, T-MAS, campesterol, sitosterol) from cultured human hepatocytes in a single chromatographic run. Deuterium labelled cholesterol, sitosterol and lathosterol were used as internal standards. Care was taken to select ions for the detection that gave the most appropriate discrimination in the assay. Replicate analyses gave a coefficient of variation less than 6%. Recovery experiments were satisfactory for 7-dehydrocholesterol, campesterol, desmosterol, lathosterol, zymosterol and cholesterol with less than 7% difference between expected and found levels. For other sterols, the difference between expected and found levels varied between 10 and 16%. It is concluded that this method is suitable for studies on the effect of different inhibitors and stimulators of cholesterol synthesis in cultured cells. Additionally, the method is relevant also for clinical applications since abnormally increased late cholesterol intermediates in patients are representations of the inherited disorders linked to different enzyme defects in the post-squalene cholesterol biosynthesis.