Evaluation of 11beta-HSD activities in vivo following oral administration of cortisol-13C4,2H1 to a human subject

Using a biokinetic model to quantify and optimize cortisol measurements for acute and chronic environmental stress exposure during pregnancy

To fully understand the potentially harmful effects of prenatal stress exposure impacts, it is necessary to quantify long-term and episodic stress exposure during pregnancy. There is a strong body of research relating psychological stress to elevated cortisol levels in biomarkers. Recently, maternal hair has been used to measure cortisol levels, and provides the unique opportunity to assess stress exposure throughout gestation. Understanding how cortisol in the hair is related to more common biomarkers, such as, blood, saliva and urine is currently lacking. Therefore, we developed a biokinetic model to quantify the relationships between hair, blood, saliva and urine cortisol concentrations using published literature values. Hair concentrations were used to retrospectively predict peaks in blood and saliva concentrations over days and months. Simulations showed realistic values in all compartments when results were compared with published literature. We also showed that the significant variability of cortisol in blood leads to a weak relationship between long-term and episodic measurements of stress. To our knowledge, this is the first integrative biokinetic cortisol model for blood, urine, hair and saliva. As such, it makes an important contribution to our understanding of cortisol as a biomarker and will be useful for future epidemiological studies.

Pharmacokinetic-pharmacodynamic studies of the 11β-hydroxysteroid dehydrogenase type 1 inhibitor MK-0916 in healthy subjects

AIMS

To characterize pharmacokinetic parameters of MK-0916 and its safety and tolerability in lean, healthy male subjects following single and multiple oral doses. To assess (by stable-isotope labelling) the in vivo inhibition of cortisone-to-cortisol conversion following oral MK-0916.

METHODS

Data are presented from two randomized, controlled, double-blind, rising-dose phase I studies. In the first study, subjects received single oral doses of 0.4-100 mg MK-0916 (n = 16). In the second study, subjects received 0.2-225 mg MK-0916 followed by daily doses of 0.2-100 mg for 13 days beginning on day 2 or day 15 (n = 80). Plasma and urine drug concentrations were measured for pharmacokinetic analysis. For pharmacodynamic analysis, concentrations of plasma [(13)C4]cortisol were measured by high-pressure liquid chromatography and tandem mass spectrometry following a single oral dose of 5 mg [(13)C4]cortisone.

RESULTS

Doses ≥3 mg were rapidly absorbed (time at which maximal concentration was achieved in plasma, 1.1-1.8 h). Exposure (measured as the area under the concentration-time curve from 0 to 168 h) increased approximately in proportion to dose. Values for the maximal plasma concentration and the plasma concentration at 24 h increased in excess of dose proportionality at doses <6 mg and roughly in proportion to dose at doses >6 mg. In subjects dosed with 6 mg MK-0916 once daily for 14 days, the mean trough plasma concentration was 240 nm and in vivo cortisone-to-cortisol conversion was inhibited by 84%. The relationship between plasma MK-0916 and hepatic 11β-hydroxysteroid dehydrogenase type 1 inhibition was well represented by a simple Emax model with an IC50 of 70.4 nm. Exposure to MK-0916 was generally well tolerated.

CONCLUSIONS

These findings indicate that 11β-hydroxysteroid dehydrogenase type 1 is effectively inhibited in human subjects by doses of MK-0916 that are well tolerated.

Sex-specific difference in the interconversion of cortisol and cortisone in men and women

OBJECTIVE

Our objective was to demonstrate that the smaller oxoreductase activity of 11beta-HSD1 in women would shift the interconversion of cortisol and cortisone toward cortisone, resulting in a larger amount of generated labeled cortisone in healthy women than in healthy men.

RESEARCH METHODS AND PROCEDURES

Using mass spectrometry, the amount of cortisone generated from a continuous infusion (8 am to 6 pm) of stable-labeled cortisol (1alpha,2alpha-d-cortisol) was determined in non-obese and in obese (BMI>35 kg/m2) men and women during steady-state conditions (from 2 pm to 6 pm). In this setting, the amount of generated labeled cortisone (expressed as % of the achieved steady-state concentrations of labeled cortisol) reflects the sum of the bi-directional conversion of cortisol into cortisone (and vice versa) by 11beta-hydroxysteroid dehydrogenase.

RESULTS

The amount of generated labeled cortisone was higher in men than in women (p<0.0001). This sex difference was higher in obese than in non-obese patients (p=0.0062).

CONCLUSIONS

The interconversion of cortisol and cortisone during steady-state conditions is shifted toward cortisol in men as compared with women. This suggests a higher overall oxoreductase activity of 11beta-hydroxysteroid dehydrogenase type 1 in men than in women. This sex-specific difference is maintained in obesity.

Validation of the plasma half-life of 11alpha-deuterium cortisol as a sensitive index for the analysis of human 11beta-HSD2 activity in vivo

This study is concerned with validating the measurement of the plasma half-life of 11alpha-(2)H cortisol in an attempt to accurately assess the in vivo activity of 11beta-HSD2 in man. Oral administration of 5mg of cortisol-(13)C(4),(2)H(1) to a human subject after repeated ingestions of 130mg/day of glycyrrhetinic acid for 5 days resulted in a decrease in the rate constant of the cortisol-(13)C(4),(2)H(1) to cortisone-(13)C(4) conversion, a direct index reflecting 11beta-HSD2 activity. The reduced 11beta-HSD2 activity led to an increase in the elimination half-life of cortisol-(13)C(4),(2)H(1), indicating that the loss of 11alpha-(2)H is a sensitive in vivo means of assessing 11beta-HSD2 activity. A simultaneous oral administration of 3mg each of [1,2,4,19-(13)C(4),11alpha-(2)H]cortisol (cortisol-(13)C(4),(2)H(1)) and 11alpha-(2)H cortisol to another human subject confirmed the bioequivalency of the two labeled cortisols. The information obtained from the kinetic analysis of the 11beta-HSD2-catalyzed conversion of cortisol-(13)C(4),(2)H(1) to cortisone-(13)C(4) indicated that the elimination half-life of 11alpha-(2)H cortisol was a sensitive index of renal 11beta-HSD2 activity. The use of 11alpha-(2)H cortisol as a tracer appears to offer a significant advance in evaluating human 11beta-HSD2 activity in vivo.

Simultaneous determination of endogenous and stable isotope-labelled 6beta-hydroxycortisols in human urine by stable isotope dilution mass spectrometry

This study describes a capillary GC-MS method for the simultaneous determination of endogenous 6beta-hydroxycortisol (6beta-OHF) and its stable isotope-labelled analogue, 6beta-hydroxy-[1,1,19,19,19-2H(5)]cortisol (6beta-OHF-2H(5)), in human urine. 6beta-Hydroxy-[1,2,4,19-13C(4),1,1,19,19,19-2H(5)]cortisol (cortisol-13C(4),(2)H(5)) was used as an analytical internal standard. The methoxime trimethylsilyl ether (MO-TMS) derivatization was employed for the GC-MS analysis of 6beta-OHF. Quantitation was carried out by selected-ion monitoring (SIM) of the characteristic fragment ion ([M-31](+.)) of the MO-TMS derivative of 6beta-OHF. The sensitivity limit of the present GC-MS-SIM method was found to be 25 pg per injection for 6beta-OHF (S/N ratio=5.6). The within-day reproducibility in the amounts of unlabelled and labelled 6beta-OHFs determined were in good agreement with the actual amounts added, the relative errors being less than 5.30%. The inter-assay RSDs were less than 4.95% for unlabelled and labelled 6beta-OHFs.