Exposure of Juvenile Rats to the Phytoestrogen Daidzein Impairs Erectile Function in a Dose‐Related Manner in Adulthood

Abstract

Health benefits of isoflavones such as genistein and daidzein have led to an increasing interest in consuming soybeans or soy-containing food. However, possible adverse effects of such plant estrogens on the male reproductive system, particularly penile erection, have not been sufficiently evaluated. In previous research, we observed that exposure of adult rats to daidzein could attenuate apomorphine-induced erections. To identify the impact of daidzein exposure in early life on erectile function, we evaluated erectile capacity using an apomorphine-induced erectile test and determining intracavernous pressure after exposure of juvenile rats to daidzein at a dose of 2, 20, or 100 mg/kg for 90 days. Meanwhile, the levels of sex hormones, including testosterone, luteinizing hormone, and follicle-stimulating hormone, were determined. Both subtypes of the estrogen receptor (alpha and beta) in the corpora cavernosa were also detected immunohistochemically. When the rats were examined at adulthood, we observed that those animals treated with a medium (20 mg/kg) or high (100 mg/kg) dose of daidzein, but not with a low dose (2 mg/kg), showed lower plasma testosterone levels and attenuated erectile parameters, including apomorphine-induced erections and intracavernous pressure concomitant with markedly decreased expression of estrogen receptor beta in the corpora cavernosa. However, the penis still grew to its normal size, as in controls. Thus, these results suggested that exposure of juvenile rats to daidzein in a relatively large amount could adversely affect penile erection in adulthood.

Effects of daidzein on testosterone secretion in cultured immature mouse testis

“…The results showed that daidzein enhanced hCGstimulated steroidogenesis of 3-day-old mouse Leydig cells at concentration of up to 10 -4 M. This is contradictory to many in vivo experiments showing that isoflavones, including daidzein, decrease testosterone concentration [6,7,9]. It has been reported that isoflavone, including daidzein can exert inhibitory feedback on the hypothalamus-pituitarygonadal axis [21].…”

“…For example, exposure of juvenile rats to daidzein in relatively large amounts could impair erectile function and decrease plasma testosterone levels in adulthood [6]. Soy formula milk could decrease marmoset monkey blood testosterone levels [7].…”

Effects of Transgenic Soybean and Organic Soybean on Rat Penis Morphology during the Aging Process

“…The presence of the soy phytoestrogens, can lead structural and functional modifications in the reproductive tract during development and adulthood (Cardozo & Baó, 2007;Cederroth et al, 2010). In concurrence with a report by Pan et al (2008), consumption of large amounts of soy phytoestrogens can trigger erectile dysfunction, which involves erectile tissue. Huang et al (2008) observed the morphological action of daidzein in 90-day-old rat penis.…”

Organic Causes of Erectile Dysfunction in Men Under 40

“…Relatively large amounts cause histological changes in the penile structure of rats, including an increase in collagen and a reduction in smooth muscle and elastic fiber content [34]. When juvenile rats were exposed to daidzein, erectile function was impaired when the rats matured into adults in a dose-dependent manner [35]. Apart from animal models, there has been a case report of an 18-year-old who developed hypogonadal ED due to a high soy vegan diet that was reversible with diet cessation [36].…”