Abstract
Objective. Liquorice‐induced increase in blood pressure (BP) is more profound in subjects with essential hypertension (HT) than in healthy individuals. Liquorice induces pseudohyperaldosteronism by inhibiting the 11β‐hydroxysteroid dehydrogenase type 2 and is also known to inhibit the renin–angiotensin–aldosterone system (RAAS). We explored the difference in response in BP, considering the RAAS and the genders. Design. Patients with HT (eight men and three women, mean age 40.7 years) and healthy controls (13 men and 12 women, mean age 31.2 years) consumed 100 g of liquorice (150 mg glycyrrhetinic acid) daily for 4 weeks. Methods. Blood, urine samples and BP were evaluated before and after 4 weeks of liquorice consumption and 4 weeks after cessation of liquorice consumption. Results. The relative change in serum aldosterone levels differed between the genders (p<0.02), men being more responsive than women, but not between patients with HT and healthy subjects. Conclusion. The liquorice‐induced inhibition of aldosterone secretion differs between the genders and is not influenced by the BP levels. This difference between the genders has not been exposed before.
Introduction
Liquorice is a popular candy and frequently an ingredient in herbal tea and alcoholic beverages, a foaming agent in beer, a masking agent in cosmetics and drugs as well as a substance for colouring and flavouring tobacco Citation[1]. It is well known that the active substance in liquorice, glycyrrhetinic acid (GA), inhibits the 11β‐hydroxysteroid dehydrogenase type 2 (11βHSD2), leading to a decreased conversion of cortisol to cortisone Citation[2,3]. Cortisol, which has the same affinity to the mineralocorticoid receptors as aldosterone, will be more abundant in the vicinity of the mineralocorticoid receptor, and thereby increases the mineralocorticoid effect Citation[4]. This leads to the syndrome of pseudohyperaldosteronism with sodium and fluid retention, increased blood pressure (BP), decreased serum potassium and aldosterone levels Citation[2]. GA is also known to inhibit the renin–angiotensin–aldosterone system (RAAS) as GA has been found to decrease the renin secretion Citation[3],Citation[5,6].
We have previously shown that subjects with essential hypertension (HT) are more sensitive to the inhibition of 11βHSD2 than healthy normotensive (NT) subjects and that the increase in BP is independent of the change in plasma renin activity and age. We also found a difference in response to liquorice between the genders Citation[7]. Moreover, data from epidemiological surveys and clinical investigations suggest that the RAAS is affected by gender Citation[8]. We have also noticed that many clinicians consider women more sensitive to the liquorice effect than men. This motivated us to explore further the liquorice effect on the RAAS considering potential difference between HT and NT subjects as well as between the genders. We were interested in studying liquorice, as it is commonly consumed (sweets). Therefore, the study could not be performed as a placebo‐controlled, blinded, crossover study. We used sweet liquorice and not salted, which would have increased the fluid retention and influenced the results. The GA content in liquorice products can be measured by an HPLC method Citation[9–12]. To assess compliance, a measurement of the 11βHSD2 activity was performed by calculating the quotient of urinary free cortisol/free cortisone (Q) Citation[13].
Materials and methods
Study design
Twenty‐five NT individuals (13 men and 12 women, mean age 31.2 years) and 11 patients with treated HT (eight men and three women, mean age 40.7 years), consumed 100 g liquorice (150 mg GA, information from the supplier) daily for 4 weeks. Systolic BP (SBP) below 140 mmHg, diastolic BP (DBP) below 90 mmHg, with no change in BP for the last 3 months, was a prerequisite. To compare the genders, all women constituted one group (12 NT and three HT, mean age 35.0 years), and all men (13 NT and eight HT, mean age 33.5 years) another. All women began the liquorice consumption at days 1–4 in the menstrual cycle. To minimize the effect on the RAAS, we excluded patients receiving anti‐hypertensive drugs other than β‐receptor inhibitors and/or Ca2+‐antagonists. Subjects using tobacco in any form and hormone treatment except for l‐thyroxin, as well as women in early menopause and pregnant women were also excluded.
During the run‐in period, 24‐h ambulatory BP (Space labs model 90207) was measured, and blood and urine samples collected. After 4 weeks consumption, the BP measurements, blood and 24‐h urine samples were repeated, the women always being at days 1–4 in the menstrual cycle.
The study was approved by the ethical committee of the Göteborg University and a written informed consent was obtained from all subjects before participation.
Analytical methods
The serum level of angiotensin‐converting enzyme (ACE) was measured with a radioenzymatic method (Bühlmann Laboratories AG, Allschwil, Switzerland), and angiotensin II (AII) by using radio‐immunoassay (RIA) mainly according to Kappelgaard et al. but using SEP‐PAK as described by Morton & Webb. RIA was used to measure serum levels of aldosterone (BioChem ImmunoSystems, Diagnostic division, Roma, Italy). Levels of urinary free cortisol and cortisone were determined by HPLC with UV‐detection (254 nm) following extraction and purification on a small octylsilane‐bonded silica column and the quotient Q calculated, to estimate the 11βHSD2 activity.
Statistical analysis
Fisher's permutation test was used for paired comparisons, and in correlation calculations, the Pearson's coefficient was calculated for the whole group and the regression tested with t‐test. For between‐group comparisons, the relative changes were calculated and the Mann–Whitney test used for statistical analyses. The Fishers exact test was used for group comparison of gender with respect to hypertension. A p‐value of less then 0.05 was considered significant.
Results
Data on changes in BP, body weight, serum electrolytes, plasma renin activity (PRA), serum cortisol and urinary free cortisol and cortisone, have previously been reported Citation[7]. Briefly, the liquorice‐induced inhibition of 11βHSD2 and reduction in PRA did not differ between the groups. All groups increased in BP, the HT group most markedly. Results on PRA and office BP are presented in Tables and respectively, in more detail than in the earlier publication.
Table I. Serum levels of aldosterone, angiotensin II (AII), angiotensin‐converting enzyme (ACE) and plasma renin activity (PRA) at baseline, after 4 weeks of liquorice consumption and 4 weeks after cessation of liquorice consumption.
Table II. Results on office systolic and diastolic blood pressure (SBP and DBP respectively) at baseline, after 4 weeks of liquorice consumption and 4 weeks after cessation of the liquorice consumption.
The RAAS
Plasma AII and ACE did not change significantly after liquorice consumption (). Serum aldosterone concentrations, however, decreased (), and the relative change in serum aldosterone was more marked in men then women (p<0.02). The change in serum aldosterone levels did not differ between the NT and HT groups. No difference was found between the genders or between the NT and the HT groups in serum aldosterone levels at baseline. The decrease in serum aldosterone correlated inversely to the increase in SBP (r = −0.6, p<0.001) and DBP (r = −0.6, p<0.001) in the whole group. In men, the correlation to SBP was significant (r = −0.6; p<0.004), but not in women (r = −0.5; p<0.07).
No difference was found between the genders with respect to hypertension, in spite of the difference in number of HT women and men.
Discussion
The gender difference in the liquorice effect on the RAAS is independent of the BP levels as there was no difference between the NT subjects and the patients with HT. The decrease in aldosterone secretion was more marked in men than in women, although the women received a larger dose per kilogram body weight Citation[7]. Thus, a different mechanism for the liquorice‐induced inhibition of the RAAS may be between the genders, the men being more sensitive than the women, which is contradictory to common opinion as far as we know. That the liquorice‐induced increase in BP, secondary to the inhibition of the 11βHSD2, is more pronounced in patients with HT compared to NT subjects Citation[7] whilst the effect on the RAAS does not differ between these groups, further supports that the liquorice‐induced inhibition on the 11βHSD2 and the RAAS can be through different mechanisms. We find the results of broad interest as drugs affecting the RAAS nowadays are of great importance in the treatment of hypertension, women and men being treated in the same way, without respect to the gender. Pharmaceutical studies on hypertension should compare the genders, in fertile ages. Thus, gender just as genetics may in the future be important factors when choosing the right treatment for hypertension.
We conclude that liquorice‐induced effect on the RAAS differs between the genders independent of the BP levels and that the liquorice‐induced effect on the 11βHSD2 and the RAAS may be by different mechanisms.
Acknowledgements
The study was supported by The Göteborg Medical Society and The Swedish Hypertension society. We thank Malaco‐leaf sweet factory in Sweden for kindly supplying the liquorice used in the presented study and Anders Odén for professional statistical analysis.
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