Liquid chromatography-mass spectrometry untargeted metabolomics reveals increased levels of tryptophan indole metabolites in urine of metabolic syndrome patients.

Metabolic syndrome (MetS) is a multifactor condition predisposing for diabetes, cardiovascular diseases and other degenerative disorders. Although several diagnostic criteria have been established, none of them is specific and there is a call for better pathophysiological explanation of MetS and for the discovery of molecular biomarkers. Phenotype characterization at metabolome level might be useful for both purposes. To this end, our aim was to perform comparative untargeted metabolomics of urines from MetS patients and from the control group. The study participants included 52 diagnosticated and 50 healthy individuals from Leon city in central Mexico; 23 anthropometric and clinical parameters were measured and submitted to Principal Component Analysis (PCA). The obtained PCA model allowed us for selection of 11 MetS patients and 13 control subjects, correspondingly representative for each of the two groups (clearly separated in PCA). The first morning urines from these subjects were ambulatory collected and, after methanol extraction and acidification, were submitted to capillary liquid chromatography-high resolution mass spectrometry (LC-HRMS). The obtained data were analyzed on MetaboScape® platform (Bruker Daltonics). Specifically, t-test applied to LC-HRMS data revealed several ions presenting at least 3-fold higher intensities in MetS with respect to the control samples (p < 0.05). Data analysis and complementary experiments yielded the identification of the following metabolites: indole-3-acetic acid, indole-3-acetic acid-O-glucuronide, N-(indol-3-ylacetyl) glutamine, indole-3-carbaldehyde and hydroxyhexanoycarnitine. Additionally, indole-3-carboxylic acid was annotated with 2.13-fold higher abundance in MetS patients. To assess the contribution of individual metabolites in the difference between two groups of subjects, partial least square discriminant analysis was performed for LC-HRMS data and the obtained values of variable importance in projection (VIP), confirmed the association of six above mentioned compounds with MetS. Overall, this study provides direct evidence on the disturbed catabolism of tryptophan in metabolic syndrome.

Determination of copper and lead in tequila by conventional matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and partial least squares regression.

RATIONALE: Quantification of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is challenging yet attractive, due to micro-scale procedural simplicity, high throughput and lack of memory effects. Since these features are important while analyzing trace elements in quality control schemes, MALDI-TOFMS was used for the determination of copper (Cu) and lead (Pb) in tequila with quantification carried out by partial least squares regression (PLS2) and by univariate calibration (UC). METHODS: In the proposed procedure, Bi(III) was added as internal standard (IS), diethyldithiocarbamate complexes were formed (pH 7.4) and extracted into chloroform; after solvent evaporation and re-constitution in acetonitrile, the sample was co-crystallized with α-cyano-4-hydroxycinnamic acid on a steel target. From the acquired mass spectra, UC was performed using IS-normalized signals of the monoisotopic ions of analytes, and the m/z range 350-513 was used for PLS2. Accuracy was tested by recovery experiments and by inductively coupled plasma (ICP)-MS analysis. RESULTS: When compared with direct analyte signal measurements, application of IS yielded enhanced analytical performance using either UC or PLS2; the method quantification limits were: 11.1 µg L-1 , 23.4 µg L-1 for Cu and 89.8 µg L-1 , 97.1 µg L-1 for Pb, respectively. In tequila, MALDI-TOFMS and ICP-MS provided consistent results for Cu (165-2599 µg L-1 ); Pb was not detected in any sample by MALDI-TOFMS, yet recoveries obtained after standard addition were indicative of acceptable accuracy (400 µg L-1 Pb added; recoveries: 91.2-108% for UC and 98.8-120% for PLS2). CONCLUSIONS: New experimental evidence has been provided supporting the inclusion of trace metals quantification within a range of MALDI-TOFMS applications. Slightly better results were obtained for UC as compared with PLS2 yet both methods can be recommended for testing the compliance of Cu and Pb levels with Official Mexican Norm. Of note, while using PLS2, there is no need for signal integration nor for IS normalization.

Determination of putrescine, cadaverine, spermidine and spermine in different chemical matrices by high performance liquid chromatography-electrospray ionization-ion trap tandem mass spectrometry (HPLC-ESI-ITMS/MS).

The goal of this work was to establish a simple HPLC-ESI-ITMS/MS procedure, suitable for the determination of four common aliphatic polyamines in two different types of biological matrices. To this end, 1,6-diaminohexane was used as the internal standard (IS) and 4-fluoro-3-nitrobenzenotrifluoride (FNBT) as the derivatizing agent. Formation of fully derivatized compounds was confirmed by high resolution ESI-QTOFMS and MS/MS analysis. Reversed phase chromatographic separation was carried out by gradient elution with 0.1% (v/v) formic acid and methanol. In a positive ESI mode, the following pairs of precursor/quantifier ions were used for multiple reaction monitoring: 467.4/261.0 for PUT, 481.2/461.1 for CAD, 713.7/261.0 for SPD, 959.8/507.2 for SPM and 495.3/475.2 for IS. On-column instrumental detection limits of four polyamines were in the range 0.62-2.14fmol (0.039-0.215ng/ml). Versatility was demonstrated by analyzing plant extracts and human urine; prior to derivatization, all samples were cleaned-up by dichloromethane extraction. The evaluated signal suppression/enhancement was in the range 82.3-115.4% and the percentage recoveries obtained in the method of standard addition were in the range 83.7-114.4%. Statistically significant differences in polyamines concentrations were found in garden cress exposed to Cd(II) versus control seedlings (t-test, p<0.05); results obtained for urine from healthy volunteers and diabetic patients at different clinical conditions suggested possible utility of free polyamines as biomarkers of progressive diabetes.

Molybdenum and copper in four varieties of common bean (Phaseolus vulgaris): new data of potential utility in designing healthy diet for diabetic patients.

Experimental evidence indicates that diabetic patients and individuals with impaired copper homeostasis could be at risk of molybdenum toxicity. A self-administered food frequency questionnaire revealed that in central Mexico, diabetic patients with severe complications tend to consume beans more often than individuals with less advanced disease. Four varieties of Phaseolus vulgaris were comparatively evaluated as the dietary sources of two elements; the results showed molybdenum concentration decreasing in the order peruvian > pinto > mayflower > black, whereas for copper, the order was peruvian > pinto ∼ black > mayflower. The two elements were determined in pre-soaking water, cooked legumes, and broth obtained in cooking procedure; an in vitro gut model was also applied to assess potentially bioavailable fraction of both elements in cooked beans. The results indicated that the black variety would be the healthiest bean choice for diabetic patients and individuals susceptible to Mo toxicity. Relatively low total molybdenum was found in this variety (2.9 ± 1.4 versus 4.3-10.9 µg g(-1) in other types), element availability was also low (15 % in supernatant from enzymolysis, 24.9 % in combined broth + supernatant fractions), and the molar ratio of Cu/Mo was the highest among four types (41, versus Cu/Mo <10 in peruvian, pinto, or mayflower). Considering peruvian and pinto beans, broth elimination would help to lower molybdenum intake with marginal effect on Cu/Mo molar ratio. This recommendation would be especially important for peruvian variety, which provided 1090, 803, and 197 µg day(-1) of molybdenum in raw grains, broth + supernatant, and supernatant, respectively (based on 100-g portion), exceeding the recommended daily allowance of 45 µg day(-1).

High-performance liquid chromatography determination of glyoxal, methylglyoxal, and diacetyl in urine using 4-methoxy-o-phenylenediamine as derivatizing reagent.

Bioanalytical relevance of glyoxal (Go) and methylglyoxal (MGo) arises from their role as biomarkers of glycation processes and oxidative stress. The third compound of interest in this work is diacetyl (DMGo), a component of different food products and alcoholic beverages and one of the small α-ketoaldehydes previously reported in urine. The original idea for the determination of the above compounds by reversed phase high-performance liquid chromatography (HPLC) with fluorimetric detection was to use 4-methoxy-o-phenylenediamine (4MPD) as a derivatizing reagent and diethylglyoxal (DEGo) as internal standard. Acetonitrile was added to urine for matrix precipitation, and derivatization reaction was carried out in the diluted supernatant at neutral pH (40 °C, 4 h); after acidification, salt-induced phase separation enabled recovery of the obtained quinoxalines in the acetonitrile layer. The separation was achieved within 12 min using a C18 Kinetex column and gradient elution. The calibration detection limits for Go, MGo, and DMGo were 0.46, 0.39, and 0.28 µg/L, respectively. Within-day precision for real-world samples did not exceed 6%. Several urine samples from healthy volunteers, diabetic subjects, and juvenile swimmers were analyzed. The sensitivity of the procedure proposed here enabled detection of differences between analyte concentrations in urine from patients at different clinical or exposure-related conditions.