Effects of dietary genistein on mouse reproduction, postnatal development and weight-regulation

From Gut to Hormones: Unraveling the Role of Gut Microbiota in (Phyto)Estrogen Modulation in Health and Disease

The human gut microbiota regulates estrogen metabolism through the "estrobolome," the collection of bacterial genes that encode enzymes like β-glucuronidases and β-glucosidases. These enzymes deconjugate and reactivate estrogen, influencing circulating levels. The estrobolome mediates the enterohepatic circulation and bioavailability of estrogen. Alterations in gut microbiota composition and estrobolome function have been associated with estrogen-related diseases like breast cancer, enometrial cancer, and polycystic ovarian syndrome (PCOS). This is likely due to dysregulated estrogen signaling partly contributed by the microbial impacts on estrogen metabolism. Dietary phytoestrogens also undergo bacterial metabolism into active metabolites like equol, which binds estrogen receptors and exhibits higher estrogenic potency than its precursor daidzein. However, the ability to produce equol varies across populations, depending on the presence of specific gut microbes. Characterizing the estrobolome and equol-producing genes across populations can provide microbiome-based biomarkers. Further research is needed to investigate specific components of the estrobolome, phytoestrogen-microbiota interactions, and mechanisms linking dysbiosis to estrogen-related pathology. However, current evidence suggests that the gut microbiota is an integral regulator of estrogen status with clinical relevance to women's health and hormonal disorders.

Genistein lowers fertility with pronounced effect in males: Meta-analyses on pre-clinical studies

Genistein, an isoflavonoid, is found in a plethora of plant-based foods, and has been approved for use in various therapies. A couple of studies in adult men observed a negative correlation between genistein exposure and reproductive parameters. To assess the effects of genistein exposure on reproduction and fertility in males and females, we performed quantitative meta-analyses by pooling data from published studies on animals that assessed various reproductive parameters. Pooled analysis showed significant decreases in sperm count in males exposed to genistein during adulthood (Hedges's g = -2.51, p = 0.013) and in utero (Hedges's g = -0.861, p = 0.016) compared with controls. In males exposed to genistein in utero, serum testosterone levels decreased (Hedges's g = -6.301, p = 0.000) and luteinizing hormone (LH) (Hedges's g = 7.127, p = 0.000) and FSH (Hedges's g = 6.19, p = 0.000) levels increased in comparison with controls. In females, the number of corpora lutea (Hedges's g = -2.103, p = 0.019) and the litter size (Hedges's g = -1.773, p-value = 0.000) decreased; however, female reproductive hormones remained unaffected. These meta-analyses show that genistein has detrimental effects on male reproductive system and on the progression and sustenance of pregnancy, with more pronounced adverse impact in males, particularly when exposed in utero.

Food composition can influence how much alcohol your animal model drinks: A mini-review about the role of isoflavones

Standard laboratory diets used have similar concentrations of proteins, carbohydrates and fat, but the concentration of some micronutrients can vary considerably. For example, the concentration of isoflavones can vary between 20 mg and 600 mg per gram of diet. Exposure to different concentrations of isoflavones interacts with alcohol (EtOH) intake, thereby influencing the results of alcohol research. In this mini-review, we describe correlations between isoflavone concentrations and alcohol intake based on data from previously published work. Although the administration of low doses of isoflavones can decrease alcohol intake in rats, there is a positive correlation between the isoflavone content in diets and alcohol intake in mice. This interaction seems to depend on the dose, route of administration, and time of exposure to isoflavones and may be related to specific neurobiological mechanisms. The literature also indicates that isoflavones can interact with some of alcohol's molecular targets and with neural pathways crucial to the alcohol reward process. Given these findings, more attention should be given to the different types of laboratory diets used in alcohol studies to allow better comparison and replication of animal research.

Early Postnatal Genistein Administration Affects Mice Metabolism and Reproduction in a Sexually Dimorphic Way

The phytoestrogen genistein (GEN) may interfere with permanent morphological changes in the brain circuits sensitive to estrogen. Due to the frequent use of soy milk in the neonatal diet, we aimed to study the effects of early GEN exposure on some physiological and reproductive parameters. Mice of both sexes from PND1 to PND8 were treated with GEN (50 mg/kg body weight, comparable to the exposure level in babies fed with soy-based formulas). When adult, we observed, in GEN-treated females, an advanced pubertal onset and an altered estrous cycle, and, in males, a decrease of testicle weight and fecal testosterone concentration. Furthermore, we observed an increase in body weight and altered plasma concentrations of metabolic hormones (leptin, ghrelin, triiodothyronine) limited to adult females. Exposure to GEN significantly altered kisspeptin and POMC immunoreactivity only in females and orexin immunoreactivity in both sexes. In conclusion, early postnatal exposure of mice to GEN determines long-term sex-specific organizational effects. It impairs the reproductive system and has an obesogenic effect only in females, which is probably due to the alterations of neuroendocrine circuits controlling metabolism; thus GEN, should be classified as a metabolism disrupting chemical.

A BRIEF COMMUNICATION

Nutritional supplements containing soybean phytoestrogens, the isoflavones genistein (G) and daidzein (D), are increasingly used as alternative therapy for osteoporosis, cancer, and cardiovascular and other diseases with a frequency that increases with advancing age. In this study we examined the effects of subcutaneous administration of either G or D on serum lipid levels in orchidectomized (Orx) and intact (IA) middle-aged male rats, which are experimental models of andropause. Sixteen-month-old Wistar rats were treated with 10 mg/kg and 30mg/kg of either G or D. The control groups received testosterone, estradiol, or vehicle for 3 weeks, after which the total serum cholesterol (TC), low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), and total triglycerides (TT) were measured. Compared with the matching vehicle-treated controls, the higher doses of G and D and testosterone treatment significantly ( P < 0.05) lowered the TC and lipoprotein cholesterol levels. The greatest effect was observed regarding LDL-C in both Orx and IA males after G and D treatments, in which LDL-C decreased by more than 30%. The lower isoflavone doses induced a significant cholesterol-lowering effect ( P < 0.05) only in the Orx group. Like the estradiol treatment, the higher doses of G and D increased the TT levels in both rat models by more than 50% ( P < 0.05). The lower doses of isoflavones increased TT only in the Orx group. In male middle-aged rats, injections of higher doses of G and D decreased the serum cholesterol levels, as did testosterone injection, and brought about an increase in serum triglycerides similar to that observed after estradiol treatment.

Genistein exposure inhibits growth and alters steroidogenesis in adult mouse antral follicles

Genistein is a naturally occurring isoflavone phytoestrogen commonly found in plant products such as soybeans, lentils, and chickpeas. Genistein, like other phytoestrogens, has the potential to mimic, enhance, or impair the estradiol biosynthesis pathway, thereby potentially altering ovarian follicle growth. Previous studies have inconsistently indicated that genistein exposure may alter granulosa cell proliferation and hormone production, but no studies have examined the effects of genistein on intact antral follicles. Thus, this study was designed to test the hypothesis that genistein exposure inhibits follicle growth and steroidogenesis in intact antral follicles. To test this hypothesis, antral follicles isolated from CD-1 mice were cultured with vehicle (dimethyl sulfoxide; DMSO) or genistein (6.0 and 36μM) for 18-96h. Every 24h, follicle diameters were measured to assess growth. At the end of each culture period, the media were pooled to measure hormone levels, and the cultured follicles were collected to measure expression of cell cycle regulators and steroidogenic enzymes. The results indicate that genistein (36μM) inhibits growth of mouse antral follicles. Additionally, genistein (6.0 and 36μM) increases progesterone, testosterone, and dehydroepiandrosterone (DHEA) levels, but decreases estrone and estradiol levels. The results also indicate that genistein alters the expression of steroidogenic enzymes at 24, 72 and 96h, and the expression of cell cycle regulators at 18h. These data indicate that genistein exposure inhibits antral follicle growth by inhibiting the cell cycle, alters sex steroid hormone levels, and dysregulates steroidogenic enzymes in cultured mouse antral follicles.

Inhibitory effect of melatonin on testosterone synthesis is mediated via GATA-4/SF-1 transcription factors

The aim of the present study was to elucidate whether the GATA-4/SF-1 signalling pathway is involved in the inhibitory effects of melatonin on testosterone production in both the TM3 Leydig cell line and in C57BL/6J mice. In-vitro experiments demonstrated that melatonin treatment significantly reduced testosterone levels in cell culture medium (P < 0.05 or P < 0.01); and decreased intracellular cyclic adenosine monophospha accumulation (P < 0.05 or P < 0.01) and mRNA/protein expression of GATA-4, SF-1 (NR5A1), StAR, P450SCC (CYP11A1) and 3β-HSD (P < 0.05 or P < 0.01). These effects were blocked by N-acetyl-2-benzyltryptamin, a melatonin receptor antagonist. Similar effects of melatonin on testosterone production (P < 0.05 or P < 0.01) and down-regulation of transcription factors GATA-4 and SF-1 (P < 0.01) were also observed in mice treated with intratesticular injections of melatonin. Overall, the data suggest that the inhibitory effects of melatonin on testosterone production are mediated via down-regulation of GATA-4 and SF-1 expression.

Assessment of the Effects of 6 Standard Rodent Diets on Binge-Like and Voluntary Ethanol Consumption in Male C57BL/6J Mice

BACKGROUND

In recent years, much attention has been given to the lack of reproducibility in biomedical research, particularly in preclinical animal studies. This is a problem that also plagues the alcohol research field, particularly in consistent consumption in animal models of alcohol use disorders. One often overlooked factor that could affect reproducibility is the maintenance diet used in preclinical studies.

METHODS

Herein, 2 well-established models of alcohol consumption, the "drinking in the dark" (DID) procedure and the continuous 2-bottle choice (C2BC) paradigm, were employed to determine the effects of diet on ethanol (EtOH) consumption. Male C57BL/6J mice were given 1 of 6 standard rodent chow diets obtained from Purina LabDiet(®) , Inc. (Prolab(®) RMH 3000) or Harlan(®) Laboratories, Inc. (Teklad Diets T.2916, T.2918, T.2920X, T.7912, or T.8940). A separate group of animals were used to test dietary effects on EtOH pharmacokinetics and behavioral measures following intraperitoneal (IP) injections of various doses of EtOH.

RESULTS

Mice eating Harlan diets T.2916 (H2916) and T.2920X (H2920) consumed significantly less EtOH and exhibited lower blood EtOH concentrations (BECs) during DID; however, during C2BC, animals maintained on Harlan T.7912 (H7912) consumed more EtOH and had a higher EtOH preference than the other diet groups. EtOH consumption levels did not stem from changes in alcohol pharmacokinetics, as a separate group of animals administered EtOH IP showed no difference in BECs. However, animals on Harlan diet T.2920X (H2920) were more sensitive to alcohol-induced locomotor activity in an open-field task. No diet-dependent differences were seen in alcohol-induced sedation as measured with loss of righting reflex.

CONCLUSIONS

Although these data do not identify a specific mechanism, together, they clearly show that the maintenance diet impacts EtOH consumption. It is incumbent upon the research community to consider the importance of describing nutritional information in methods, which may help decrease interlaboratory reproducibility issues.

Reproductive impairment and endocrine disruption in goldfish by feeding diets containing soybean meal

A long-term feeding experiment was conducted to investigate the inclusion of soybean meal in diets for goldfish (Carassius auratus) on fish reproduction. In the present study, 20 weeks after hatching, goldfish with an initial average weight of 2±0.03g (mean±SD) were divided into 12 groups (three tanks per dietary treatment) and fed 400gkg(-1) crude protein diets. The four experimental diets were as follows: diet 1, fish meal (FM); diet 2, 35% soybean meal (SBM35%); diet 3, 65% soybean meal (SBM65%); diet 4, 100% soybean meal (SBM100%). After feeding with experimental diets, the impact on reproduction was investigated. In both males and females, the plasma testosterone (T) was significantly decreased, while 17β-estradiol (E2) levels were significantly increased. Levels of 17α, hydroxyprogesterone. (17-OH-P) did not differ as a result of soybean meal feeding in either males or females. The average number of eggs spawned and sperm quality were reduced on feeding with soybean inclusion. Histological examination showed impact on oocyte maturation progress and spermatogenesis process in female and male fish, respectively. In addition, feeding goldfish with soybean meal until maturation caused reduction in fertilization and hatching rates in parallel to increasing soybean meal inclusion. The results demonstrated that inclusion of soybean meal might cause sex hormone biosynthesis disruption and reproductive impairments in fish, ultimately decreased fertilization as well as hatching rates in the offspring.

Improvement of high-fat diet-induced obesity by a mixture of red grape extract, soy isoflavone and L-carnitine: implications in cardiovascular and non-alcoholic fatty liver diseases

In the present study, we examined the effect of a mixture of dietary components, including red grape extract, soy isoflavone and L-carnitine (RISC), on obesity. RISC substantially inhibited high-fat diet (HFD)-induced increase in body weight in a dose-dependent manner in C57BL/6 mice. The amount of subcutaneous and mesenteric fat was also significantly decreased by RISC treatment in HFD-fed C57BL/6 mice, whereas epididymal fat was not affected. Moreover, HFD-induced plasma leptin levels were down-regulated by RISC treatment. In these mice, RISC treatment significantly increased the plasma level of high density lipoprotein cholesterol without affecting the level of low density lipoprotein cholesterol and triglycerides. In addition, HFD-induced increase in liver weight and lipid accumulation in liver was significantly suppressed by RISC treatment in C57BL/6mice. Plasma level of glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase was also inhibited by RISC treatment. These results demonstrate that RISC suppresses HFD-induced obesity and suggest that RISC supplementation might be a promising adjuvant therapy for the treatment of obesity and its complications, such as cardiovascular and non-alcoholic fatty liver diseases.

Soy, phyto-oestrogens and male reproductive function: a review

There is growing interest in the possible health threat posed by the effects of endocrine disruptors on reproduction. Soy and soy-derived products contain isoflavones that mimic the actions of oestrogens and may exert adverse effects on male fertility. The purpose of this review was to examine the evidence regarding the potential detrimental effects of soy and phyto-oestrogens on male reproductive function and fertility in humans and animals. Overall, there are some indications that phyto-oestrogens, alone or in combination with other endocrine disruptors, may alter reproductive hormones, spermatogenesis, sperm capacitation and fertility. However, these results must be interpreted with care, as a result of the paucity of human studies and as numerous reports did not reveal any adverse effects on male reproductive physiology. Further investigation is needed before a firm conclusion can be drawn. In the meantime, caution would suggest that perinatal phyto-oestrogen exposure, such as that found in infants feeding on soy-based formula, should be avoided.

The potential role of soyfoods in weight and adiposity reduction: an evidence-based review

Evidence concerning the relationship between soyfoods and weight loss was reviewed. Detailed searches of PubMed and Web of Science were performed to identify and evaluate evidence for or against four propositions related to soyfoods and weight loss (Data from in vitro, animal, epidemiologic, and clinical studies were evaluated and summarized). (1) Certain soyfoods will improve weight and/or fat loss when fed at isolcaloric levels (similar calories given across experimental conditions, but not necessarily at a level to maintain current body weight); generally supportive evidence in animal studies, but there is no compelling support in human studies. (2) Certain soyfoods will improve weight and fat loss when included as part of a diet by affecting caloric intake; limited supportive evidence in animal and human studies. (3) Certain soyfoods will prevent/improve risk factors related to glucoregulatory function and cardiovascular health during weight loss; some evidence supporting this proposition, but additional evidence is needed before conclusions can be made. (4) Certain soyfoods will minimize the loss of bone mass during weight loss; no data available pertinent to this proposition. Limitations in existing data make it difficult to reach conclusions regarding these four propositions. Overall, the current data suggest that soyfoods are as good as other protein sources for promoting weight loss and there is a suggestive body of evidence that soyfoods may confer additional benefits, but results must be carefully interpreted and additional evidence is needed before making firm conclusions concerning soyfoods and weight loss.

Genistein--a dietary compound inducing hormonal and metabolic changes

Genistein is a plant-derived compound possessing well-known preventive activity in breast and prostate cancer, cardiovascular diseases and post-menopausal problems. Lately, the interests in genistein have widened. The studies concerning effects of genistein performed on animals and humans revealed other aspects of its action -- the metabolic alterations at the cellular level and in the whole organism. It was shown that genistein decreased body and fat tissue weight gains accompanied by reduced food intake. After ingestion of dietary genistein, the alterations in concentrations of hormones such as: insulin, leptin, thyroid hormones, adrenocorticotropic hormone, cortisol and corticosterone were observed. The changes in lipid parameters -- triglycerides and cholesterol were also noticed as a consequence of genistein administration. Moreover, the altered expression of genes engaged in lipid metabolism, disturbed glucose transport into cells, affected lipolysis and lipogenesis and changed ATP synthesis were found as a result of genistein action.

The impact of dietary oestrogens on male and female fertility

PURPOSE OF REVIEW

Modern consumer needs have stimulated a vast expansion in the dietary supplement market, in an attempt to improve general well being and prevent, rather than cure, disease. Isoflavones form a large part of this market. Their oestrogenic properties are still largely unknown and must be thoroughly researched to ensure they cause no adverse effects, particularly on hormone-dependent reproductive physiology.

RECENT FINDINGS

As a result of the increasing availability of phytoestrogens, research into their actions now covers a very wide field, many of which impact on reproductive potential. Time of exposure is crucial, as is interaction with other dietary components. Their putative role as chemoprotective agents has been expanded in recent years which may have an indirect impact on fertility by decreasing mortality rates in both men and women.

SUMMARY

Phytoestrogens are still a current research topic in reproduction and fertility. Genistein is a putative therapeutic tool in cancer treatment although this must be considered along with evidence that it may cause DNA damage in sperm, depending on the concentration. The effects of phytoestrogen in the body are not limited to oestrogenic action. Much more epidemiological data are required to interpret current molecular studies, and those of previous years.

Dietary soya protein during pregnancy and lactation in rats with hereditary kidney disease attenuates disease progression in offspring

Dietary soya protein substitution for casein initiated at weaning slows disease progression in animal models of chronic renal disease. As there is increasing evidence that fetal programming can have a significant impact on kidney physiology and function in offspring, the objective of the current study was to determine whether exposure to soya protein in the diet earlier than weaning would have further benefits. Han:SPRD-cy (cy/+) breeder rats were fed a casein-based or soya protein-based diet 2 weeks prior to mating, throughout pregnancy and during lactation. Following this maternal period, 3-week-old pups were given either the same or the alternate diet for a 7-week weaning period. Dietary soya protein compared with casein in the maternal or weaning period both independently resulted in less renal inflammation (macrophage infiltration lower by 24% (P=0.0003) and 32% (P<0.001), respectively). When soya protein was given in both feeding periods, the effect was additive. Soya protein substitution for casein resulted in less oxidative damages as indicated by 28% lower oxidized-LDL staining (P=0.013) when present in the maternal period, or in the weaning period (by 56%, P<0.0001). Renal cell proliferation was reduced by 29-33% (P<0.05) in rats given soya protein whether the exposure was during the maternal or weaning period. Soya protein compared with casein in the maternal period also resulted in 33% (P=0.0013) less proteinuria, indicating superior renal function. Dietary soya protein during pregnancy and lactation represents a potential preventative approach in treating for those with congenital kidney diseases.

Effects of Genistein, an Isoflavone, on Pregnancy Outcome and Organ Weights of Pregnant and Lactating Rats and Development of Their Suckling Pups

There is a general agreement that isoflavones can be beneficial to health in adults. However, isoflavones are well known as endocrine-disrupting chemicals. It should be considered that soy foods might adversely affect the reproductive system and infants. The aim of this study was to evaluate the effects of genistein, an isoflavone, on dams and their offspring. Maternal rats were fed diets containing genistein at levels of 0 and 0.5 g/kg diet from pregnancy day 5 to postnatal day 13. No effects of genistein on the delivery, anogenital distance, reproductive organ weight, and body weight of the infants at birth were observed. There were no consistent effects on suckling pups after continuous genistein exposure during their fetal and suckling stages through their mothers, and there was no difference in effects according to the periods of exposure during pregnancy and lactation. We also observed no significant effect on the growth of offspring after weaning. Moreover, while we observed that the serum concentration of triiodothyronine (T3) in dams decreased, the result was a tendency, not a significant decrease. Our study suggested that maternal ingestion of genistein might have not induced serious adverse effects on dams, fetuses, infants or offspring during growth. However, the results indicated in many papers suggest the necessity of further study on the safety of genistein.