Characterization of D-amino acids in colostral, transitional, and mature preterm human milk.

D-Amino acids are regulatory molecules that affect biological processes. Therefore, being able to accurately detect and quantify these compounds is important for understanding their impact on nutrition and health. There is a paucity of information regarding D-amino acids in human milk. We developed a fast method for simultaneous analysis of amino acid enantiomers in human milk using liquid chromatography with tandem mass spectrometry. The method enables the separation of 41 amino acids without chemical derivatization. Our results revealed that human milk from mothers of preterm infants contains concentrations of D-amino acids that range from 0.5 to 45% that of their L-counterparts and that levels of most D-amino acids decrease as the milk production matures. Moreover, we found that Holder pasteurization of milk does not cause racemization of L-amino acids. To our knowledge, this is the first study to describe percentages of D-amino acid levels in human milk; changes in D-amino acid concentration as the milk matures; and the effect of Holder pasteurization on D- and L-amino acid concentrations in human milk.

Plasma lipidome of healthy and Rhodococcus equi-infected foals over time.

BACKGROUND: Many foals that develop thoracic ultrasonographic lesions as a result of Rhodococcus equi infection heal on their own. However, most of these foals receive antimicrobials because foals at risk of developing clinical pneumonia cannot be identified. Untargeted lipidomics is useful to identify candidate biomarkers. OBJECTIVES: (a) To describe the changes that occur in foal lipidomics as a result of ageing (birth to 8 weeks) and (b) To compare these results with those observed in foals after experimental infection with R. equi. STUDY DESIGN: Experimental study. METHODS: Healthy newborn foals (n = 9) were challenged with R. equi intratracheally the first week of life. Foals were treated with antimicrobials if they developed clinical pneumonia (n = 4, "clinical group") or were closely monitored if they showed no signs of disease (n = 5 "subclinical group"). An unchallenged group (n = 4) was also included. All foals were free of disease (transtracheal wash fluid evaluation and culture as well as thoracic ultrasonography) by 8 weeks of life. Plasma lipidomics was determined by LC-MS weekly for the study duration (8 weeks). RESULTS: Both ageing and experimental infection altered the foal's plasma lipidome as demonstrated by multivariate statistical analysis. The intensities of 31 lipids were altered by ageing and 12 by infection (P < .05). Furthermore, nine lipids changed by more than twofold between clinical and subclinical groups. MAIN LIMITATIONS: The number of foals is limited. Foals were experimentally challenged with R. equi. CONCLUSIONS: Ageing and R. equi infection induced changes in the plasma lipidome of foals. These experimental results provide the background for future work in the discovery of earlier biomarkers of R. equi pneumonia. Early identification of foals at risk of developing clinical pneumonia is key in order to decrease antimicrobial use and development of antimicrobial resistance.

Feline urine metabolomic signature: characterization of low-molecular-weight substances in urine from domestic cats.

Objectives This aim of this study was to characterize the composition and content of the feline urine metabolome. Methods Eight healthy domestic cats were acclimated at least 10 days before starting the study. Urine samples (~2 ml) were collected by ultrasound-guided cystocentesis. Samples were centrifuged at 1000 × g for 8 mins, and the supernatant was analyzed by gas chromatography/time-of-flight mass spectrometery. The urine metabolome was characterized using an untargeted metabolomics approach. Results Three hundred and eighteen metabolites were detected in the urine of the eight cats. These molecules are key components of at least 100 metabolic pathways. Feline urine appears to be dominated by carbohydrates, carbohydrate conjugates, organic acid and derivatives, and amino acids and analogs. The five most abundant molecules were phenaceturic acid, hippuric acid, pseudouridine phosphate and 3-(4-hydroxyphenyl) propionic acid. Conclusions and relevance This study is the first to characterize the feline urine metabolome. The results of this study revealed the presence of multiple low-molecular-weight substances that were not known to be present in feline urine. As expected, the origin of the metabolites detected in urine was diverse, including endogenous compounds and molecules biosynthesized by microbes. Also, the diet seemed to have had a relevant role on the urine metabolome. Further exploration of the urine metabolic phenotype will open a window for discovering unknown, or poorly understood, metabolic pathways. In turn, this will advance our understanding of feline biology and lead to new insights in feline physiology, nutrition and medicine.

Development and validation of an ultrafast chromatographic method for quantification of the immunosuppressant mycophenolic acid in canine, feline and human plasma.

Mycophenolic acid (MPA) is the active metabolite of the prodrug mycophenolate mofetil. In this study, we developed and validated a novel ultra-high performance liquid chromatography (UHPLC) method for the rapid quantification of MPA in plasma from dogs, cats and humans. Following the protein precipitation, calibration standards and quality controls were separated by UHPLC reversed-phase on a 1.5µm 2.1×100mmC18 column and quantified using UV detection at 215nm. The procedure produced a linear curve (r2>0.997) over the concentration range 0.4-50µg/mL and exhibited a high degree of repeatability (CV% <11%). The limit of detection (LOD) and lower limit of quantitation (LLOQ) were 0.1 and ≤0.4µg/mL, respectively and the overall recovery was ≥87%. By combining isocratic conditions with a UHPLC column containing solid core particles, we were able to elute MPA and the internal standard (mycophenolic acid carboxybutoxy ether) within 3.0min. The short total run time makes this method ideal to study the disposition of MPA in large batches of plasma samples and/or monitor plasma drug concentrations, as recommended for patients that require optimized immunosuppression.

Guide for Carotenoid Identification in Biological Samples.

In recent years there has been considerable interest in carotenoids with respect to their biological roles in animals, microorganisms, and plants, in addition to their use in the chemical, cosmetics, food, pharmaceutical, poultry, and other industries. However, the structural diversity, the different range of concentration, and the presence of cis/trans-isomers complicate the identification of carotenoids. This review provides updated information on their physical and chemical properties as well as spectroscopic and chromatographic data for the unambiguous determination of carotenoids in biological samples.