11β-hydroxysteroid dehydrogenase type-II activity is affected by grapefruit juice and intense muscular work

OBJECTIVE

The enzymatic activity of 11β-hydroxysteroid dehydrogenase-2 (11β-HSD2) is key to protecting mineral corticoid receptors from cortisol and has been implicated in blood pressure regulation. Grapefruit juice (GFJ) and acidity are thought to inhibit this enzyme in vitro. This study examines the effect of GFJ and intense exercise on 11β-HSD2 enzyme activity in vivo.

SUBJECTS AND METHODS

Eighteen subjects ingested GFJ or apple juice (CON) on separate days prior to reporting to the laboratory in a randomized order. Saliva (Sal) samples were obtained at baseline, 15 and 45 minutes post-treadmill stress test; Sal cortisone (E) and cortisol (F) levels were determined, and the Sal cortisone:cortisol (E:F) ratio was used as an index of 11β-HSD2 enzyme activity at rest and after intense muscular work.

RESULTS

GFJ treatment decreased baseline 11β-HSD2 enzyme activity (44%) and Sal-E (28%) compared to CON (both, p < 0.05). Sal-E (r = 0.61, p < 0.05) and Sal-F (r = 0.66, p < 0.05) were correlated with diastolic blood pressure (DBP) in GFJ-treated individuals. Treadmill stress significantly increased Sal-E and Sal-F but did not alter 11β-HSD2 enzyme activity regardless of treatment. When treatments were examined separately, CON 11β-HSD2 enzyme activity decreased by 36% (p < 0.05) from baseline to 15 post-treadmill exercise.

CONCLUSION

Our findings suggest that GFJ and intense muscular work decrease 11β-HSD-2 activity independently, and no additive effect was noted. The association between DBP and the levels of Sal-F and Sal-E during the GFJ trial should be interpreted cautiously and warrants further investigation.

Salivary but not plasma cortisone tracks the plasma cortisol response to exercise: effect of time of day

INTRODUCTION

The cortisol, cortisone, corticosterone, and CBG responses to exercise in the AM and PM have not been described. This study examined the response of these glucocorticoids and CBG to intense exercise in 12 endurance-trained men in plasma (Pl) and saliva (Sa).

METHODS

Each subject completed treadmill exercise in the morning and evening. Paired blood and Sa samples were obtained at rest before and after exercise.

RESULTS

Significant time effect existed for Pl-cortisol and Sa-cortisol from baseline in the AM and PM (p < 0.01). Pl-cortisone and CBG significantly increased in the PM (p < 0.01). Pl-corticosterone increased in the AM and PM (p < 0.01). Unlike Pl-cortisone, Sa-cortisone was significantly higher in the AM compared to the PM, increasing in the AM and PM (All p < 0.01). Strong associations were found between Pl-cortisol and Sa-cortisol (r = 0.81, p < 0.0001), Pl-cortisol and Sa-cortisone (r = 0.81, p < 0.0001).

CONCLUSIONS

(1) Intense EX induces a similar increase in Pl-cortisone (~90 %) and corticosterone (~200 %) in the AM and PM, whereas exercise increases CBG in the PM, but not in the AM; (2) vigorous exercise increases Sa-cortisone; (3) Sa-cortisone and cortisol are equally strongly correlated to Pl-cortisol, suggesting a significant role for Sa-cortisone as a novel marker of free cortisol during exercise.