Abstract
The objective of this work was to study the direct effects of daidzein on steroidogenesis in cultured mouse Leydig cells. Adult mouse Leydig cells were purified by Percoll gradient centrifugation, and the cell purity was determined using a 3β-hydroxysteroid dehydrogenase (3β-HSD) staining method. The purified Leydig cells were exposed to different concentrations (10 -7 M to 10 -4 M) of daidzein for 24 h under basal and human chorionic gonadotropin (hCG)-stimulated conditions. The cell viability and testosterone production were determined, and the related mechanisms of daidzein action were also evaluated using the estrogen receptor antagonist ICI 182,780 and measuring the mRNA levels of steroidogenic acute regulatory protein (StAR). cholesterol side-chain cleavage enzyme (P450scc), and 3β-HSD-1 involved in testosterone biosynthesis. The results revealed that daidzein did not influence cell viability. Daidzein increased both basal and hCG-stimulated testosterone production in a dose-dependent manner, and this effect was statistically significant at concentrations of 10 -5 M and 10 -4 M daidzein (p<0.05). ICI 182.780 had no influence on daidzein action. RT-PCR results revealed that 10 -5 M and 10 -4 M daidzein did not exert any obvious influence on the mRNA level of P450scc in Leydig cells. However, in the presence of hCG, these concentrations of daidzein significantly increased the StAR and 3β-HSD-1 mRNA levels (p<0.05), but in the absence of hCG, only 10 -5 M and 10 -4 M daidzein up-regulated the StAR and 3β-HSD-1 mRNA expression (p<0.05), respectively. These results suggest that daidzein has direct effect on Leydig cells. Daidzein-induced increase of testosterone production is probably not mediated by the estrogen receptor but correlates with the increased mRNA levels of StAR and 3β-HSD-1.
Highlights
Daidzein is one of the major isoflavones in soybeans, and it is the most common form of phytoestrogens
Daidzein does not influence Leydig cell viability In order to answer whether 10-7 M to 10-4 M daidzein used in this study have cytotoxicity, basal and hCGstimulated Leydig cell viability was determined
The results showed that 10-5 M and 10-4 M daidzein significantly increased testosterone concentrations in the medium with or without human chorionic gonadotropin (hCG) (p
Summary
Daidzein is one of the major isoflavones in soybeans, and it is the most common form of phytoestrogens. Adult male rats were fed diet containing about 600 μg/g isoflavones for 5 weeks, plasma testosterone and androstenedione levels were significantly lower compared with animals fed the phytoestrogen-free diet (Weber et al, 2001). Exposure of juvenile and adult rats to 20 or 100 mg/kg daidzein for 90 days impaired the apomorphineinduced penile erection and decreased the plasma testosterone concentration (Pan et al, 2007; Pan et al, 2008). Contrary to these inhibitory effects, male rats in the perinatal period exposure to 1,000 ppm isoflavones elevated serum and testicular testosterone levels at 90 days of age (Akingbemi et al, 2007). There are reports that short or long period of feeding with soybean products rich in daidzein and other isoflavonoids did not have obvious
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