Continuous inhibition of 11ß-hydroxysteroid dehydrogenase type I in adipose tissue leads to tachyphylaxis in humans and rats but not in mice.

BACKGROUND AND PURPOSE: 11ß-hydroxysteroid dehydrogenase type I (11ß-HSD1), a target for Type 2 diabetes mellitus, converts inactive glucocorticoids into bioactive forms, increasing tissue concentrations. We have compared the pharmacokinetic-pharmacodynamic (PK/PD) relationship of target inhibition after acute and repeat administration of inhibitors of 11ß-HSD1 activity in human, rat and mouse adipose tissue (AT). EXPERIMENTAL APPROACH: Studies included abdominally obese human volunteers, rats and mice. Two specific 11ß-HSD1 inhibitors (AZD8329 and COMPOUND-20) were administered as single oral doses or repeat daily doses for 7-9 days. 11ß-HSD1 activity in AT was measured ex vivo by conversion of (3) H-cortisone to (3) H-cortisol. KEY RESULTS: In human and rat AT, inhibition of 11ß-HSD1 activity was lost after repeat dosing of AZD8329, compared with acute administration. Similarly, in rat AT, there was loss of inhibition of 11ß-HSD1 activity after repeat dosing with COMPOUND-20 with continuous drug cover, but effects were substantially reduced if a 'drug holiday' period was maintained daily. Inhibition of 11ß-HSD1 activity was not lost in mouse AT after continuous cover with COMPOUND-20 for 7 days. CONCLUSIONS AND IMPLICATIONS: Human and rat AT, but not mouse AT, exhibited tachyphylaxis for inhibition of 11ß-HSD1 activity after repeat dosing. Translation of observed efficacy in murine disease models to human for 11ß-HSD1 inhibitors may be misleading. Investigators of the effects of 11ß-HSD1 inhibitors should confirm that desired levels of enzyme inhibition in AT can be maintained over time after repeat dosing and not rely on results following a single dose.

Differences between men and women in the regulation of adipose 11ß-HSD1 and in its association with adiposity and insulin resistance.

This study explored sex differences in 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) activity and gene expression in isolated adipocytes and adipose tissue (AT), obtained via subcutaneous biopsies from non-diabetic subjects [58 M, 64 F; age 48.3 ± 15.3 years, body mass index (BMI) 27.2 ± 3.9 kg/m²]. Relationships with adiposity and insulin resistance (IR) were addressed. Males exhibited higher 11ß-HSD1 activity in adipocytes than females, but there was no such difference for AT. In both men and women, adipocyte 11ß-HSD1 activity correlated positively with BMI, waist circumference, % body fat, adipocyte size and with serum glucose, triglycerides and low-density lipoprotein:high-density lipoprotein (LDL:HDL) ratio. Positive correlations with insulin, HOMA-IR and haemoglobin A1c (HbA1c) and a negative correlation with HDL-cholesterol were significant only in males. Conversely, 11ß-HSD1 activity in AT correlated with several markers of IR and adiposity in females but not in males, but the opposite pattern was found with respect to 11ß-HSD1 mRNA expression. This study suggests that there are sex differences in 11ß-HSD1 regulation and in its associations with markers of obesity and IR.