One striking effect is seen in the inhibitory capacity
of 18
b-glycyrrhetinic acid (Fig. 5). This substance
found in licorice does not influence the oxidative pathway
but inhibits reduction of androstenedione to testosterone.
Previously, it has been observed that the serum
testosterone level in men consuming about 7 g of a
commercial preparation of licorice (containing 0.5 g of
18b-glycyrrhetinic acid) a day is significantly reduced. It
has been demonstrated that licorice consumption inhibits
11b-HSD (Walker et al., 1995) 17b-HSD and
17,20 lyase activity (Armanini et al., 1999). Reduced
17b-HSD activity might be due to the inhibition of
17b-HSD type 3 or 5. Decreased testosterone levels
result in reduced libido or other sexual dysfunction but
might have beneficial effects in cases of abnormal
prostate growth.
In summary, our results show that 17b-HSD 5 is a
potential target for the inhibitory effect of a variety of
phytoestrogens. Inhibition of 17b-HSD 5 might contribute
to the cancer preventive action of a soy-based
diet.
Phytoestrogens inhibit human 17b-hydroxysteroid dehydrogenase
type 5
A. Krazeisen, R. Breitling, G. Mo¨ ller, J. Adamski *
GSF National Research Center for En6ironment and Health, Institute for Experimental Genetics, Genome Analysis Center,
Ingolsta¨dter Landstraße 1, 85764 Neuherberg, Germany