Direct determination of human urinary cortisol metabolites by HPLC/CRIMS

Rapid comparison of metabolites in humans and rats of different sexes using untargeted UPLC-TOFMS and an in-house software platform

Metabolite differences between sexes have rarely been observed in a global manner, but it has recently been made possible by the advancement in metabolomics techniques. In this study, untargeted ultraperformance liquid chromatography coupled to time-of-flight mass spectrometry and an in-house software platform were used for a rapid comparison of sex differences in urinary metabolites in humans and in urinary and serum metabolites in Sprague Dawley (SD) rats. In addition, the species differences of urinary metabolites between humans and SD rats were also observed. Principle component analysis showed that all the observed metabolite sex differences were more distinct in SD rats than in humans, indicating that the sex differences of human urinary metabolites is small compared with that of SD rats. In SD rats, the observed metabolite sex differences were more distinct in urine than in serum, indicating the importance of urine analysis for metabolomics studies. The species differences in the urinary metabolites of humans and SD rats were much more distinct than any of the observed sex differences. Many sex- and species-related markers were discovered and putatively identified. In both humans and SD rats, steroid metabolites appeared to constitute a major sex difference in urinary metabolites. This provides new proof of the special importance of steroid metabolites in sex differences from an untargeted metabolomics investigation, which is rare for sex differences. Contrary patterns involving adrenocortical activity appeared to exist between rodents and humans, which agrees with previous reports. In the serum metabolites of SD rats, sex differences in ascorbic acid or its isomer and pantothenic acid or its isomer, but not in steroid metabolites, were prominent. Human-specific α-N- phenylacetyl-l-glutamine and androsterone glucuronide were among the putative identities of the markers discriminating humans and SD rats. This study demonstrated the feasibility of an in-house software platform and provides metabolite-related information on sex and species differences.

Study of natural and artificial corticosteroid phase II metabolites in bovine urine using HPLC-MS/MS

Corticosteroid compounds are widely used therapeutically for their anti-inflammatory properties and sometimes as growth promoters in food producing animals. In the field of drug residue analysis, knowledge of the main metabolic pathways of target analytes improves the efficiency of the corresponding control. Thus, phase II metabolism of corticosteroids, for which very little literature is available, was investigated in cattle. An LC-MS/MS detection method was developed for five commercially available conjugated corticosteroids, permitting direct monitoring during the development of their separation on anion exchange SPE. This separation method is further applicable to other potential urinary conjugated corticosteroids. Because our purpose was not to identify all the existing corticosteroid phase II metabolites, but to obtain their total relative proportions, enzymatic hydrolysis was optimized and performed on each separated fraction (glucuronides and sulfates). Finally, the phase II metabolic profiles of natural and artificial corticosteroids in bovine urine were studied and compared. LC-MS/MS detection with negative electrospray ionization appeared efficient for both glucuronide and sulfate conjugated corticosteroids, and quaternary ammonium stationary phase permitted their effective separation. The experimental design used for optimization of the enzymatic hydrolysis with a purified Helix pomatia preparation demonstrated optimal values for pH 5.2, temperature of 50 degrees C and incubation duration of 4h. Results on bovine urine samples collected on two animals before and after dexamethasone administration showed important differences regarding the proportion of total conjugated forms between endogenous cortisol, endogenous tetrahydrocortisol, and exogenous dexamethasone. This proportion appeared significantly higher for tetrahydrocortisol (40-65%) than cortisol (2-8%) or dexamethasone (4-27%). This innovative methodology demonstrates the suitability of anion exchange SPE and LC-MS/MS for the study of steroid hormones phase II metabolism, and appears promising to investigate metabolic profile differences linked to the hormone administration mode or origin, with direct application in the field of doping controls.

Gas chromatography and high-performance liquid chromatography of natural steroids

This review article underlines the importance of gas chromatography (GC), high-performance liquid chromatography (HPLC) and their hyphenated techniques using mass spectrometry (MS) for the determination of natural steroids, especially in human biological fluids. Steroids are divided into eight categories based on their structures and functions, and recent references using the above methodologies for the analysis of these steroids are cited. GC and GC-MS are commonly used for the determination of volatile steroids. Although HPLC is a widely used analytical method for the determination of steroids including the conjugated type in biological fluids, LC-MS is considered to be the most promising one for this purpose because of its sensitivity, specificity and versatility.

Improved determination of urinary cortisol and cortisone, or corticosterone and 11-dehydrocorticosterone by high-performance liquid chromatography with ultraviolet absorbance detection

A sensitive assay was developed for the determination of low levels of free (unconjugated) glucocorticoids in human, swine (cortisol and cortisone) and rat urine (corticosterone and 11-dehydrocorticosterone), using solid-phase extraction and HPLC with UV absorbance detection (254 nm). Precise quantitation is allowed by the use of internal standards (dexamethasone for swine urine and Reichstein's substance S for rat urine). This simple method allows the use of small urine samples (less than 2 ml), and is suitable for a wide range of applications in human and animal clinical and physiological studies.

Element- and isotope-specific detection for high-performance liquid chromatography using chemical reaction interface mass spectrometry

We have developed a combination of high-performance liquid chromatography (HPLC) and the chemical reaction interface mass spectrometry (CRIMS) method by using a Vestec Universal Interface (UI). This interface provides the extremely high degree of solvent removal that the CRIMS process requires. In doing so, we have produced an HPLC detector with the ability to carry out the element- and isotope-selective analyses with detection that is inherently: linear, structure-independent, sensitive, selective, comprehensive and flexible. The characteristics of the instrumentation and its performance are described.