Early life exposure to isoflavones adversely affects reproductive health in first but not second generation female CD-1 mice

Associations of maternal soy product consumption and urinary isoflavone concentrations with neonatal anthropometry: A prospective cohort study

Isoflavones (ISOs) are naturally occurring endocrine-disrupting compounds. Few human studies have evaluated the effects of ISO exposure on neonatal anthropometry. This study aimed to examine the associations of maternal soy product consumption and urinary ISO concentrations, including genistein, daidzein, glycitein, and equol, with neonatal anthropometry, based on a Chinese cohort study. In Shanghai-Minhang Birth Cohort Study, pregnant women at 12-16 weeks of gestation were recruited, and they completed a structured questionnaire to assess soy product consumption during pregnancy. They also provided a single spot urine sample for the ISO assay. Neonatal anthropometric indices (birth weight; arm, waist, and head circumference; and triceps, back, and abdominal skinfold thickness) were measured at birth. Multivariable linear regression analysis was performed among the 1188 mother-infant pairs to examine the associations between maternal soy product consumption and neonatal anthropometry. The same statistical model was applied to examine the associations between maternal ISO exposure and neonatal anthropometry among 480 mother-infant pairs. Neonate girls born to mothers who "sometimes" and "frequent" consumed soy products had 169.1 g (95% confidence interval [CI], -68.9-407.1) and 256.5 g (95% CI, 17.1-495.8) higher birth weight, respectively, than those born to mothers who "never" consumed soy products during pregnancy. We observed consistent associations between higher maternal urine ISO concentrations and increased anthropometric indices (birth weight, arm and waist circumference, and triceps and abdominal skinfold thickness) in neonate girls, while no association was observed among boys. The findings suggested that maternal dietary ISO intake during pregnancy is associated with fetal development in a sex-specific pattern. In addition, follow-up studies are required to evaluate whether the observed changes in anthropometric indices at birth are associated with health conditions later in life.

Association between parental self-reported knowledge on soy and phytoestrogen and their children's intake of soy-based infant formulae-a cross-sectional study of Israeli parents

OBJECTIVES

Though natural phytoestrogen (PE) is a major factor in health authorities' considerations regarding soy-based infant formula (SBIF), missing their concentrations may interfere with parents' informed decision.

METHODS

We performed an Internet survey investigating soy-related knowledge of parents. We built multiple logistic regression models adjusted for personal covariates for the association between parental knowledge on PE and children intake of SBIF and checked the effect of having children ≤ 2 years old on this association.

RESULTS

We enrolled 304 parents, 48.3% men, mean age 33.8 (standard deviation, SD 4.9), mostly with higher education. Of them, 76% had children under two years of age. Mean parental knowledge on PE was 9.83 (SD 3.28) from 20 possible points. Parental knowledge on PE reduced children's intake of SBIF (odds ratio, OR = 0.85 [95% confidence interval 0.70; 1.02]). Stronger inverse association was found for parents with children ≤ 2 comparing with those with older children (OR = 0.85 [0.67; 1.09] and OR = 0.68 [0.39; 1.18], respectively), although these differences were not statistically significant.

CONCLUSIONS

Adding PE content to information on SBIF may support informed decision.

Fetal and neonatal genistein exposure aggravates to interfere with ovarian follicle development of obese female mice induced by high-fat diet

With epidemic of obesity, it affects aspects of female reproduction. Genistein could ameliorate obesity in people and animals, but might exert adverse effects on the female reproductive system. To evaluate the effects of fetal and neonatal genistein exposure on the ovarian health of F1 obese female mice with obesity induced by high-fat diet after weaning, we simulated a diet-induced obesity model to observe and determine biological effects of genistein exposure on the ovarian follicle of overfed female mice. Results showed that F1 female mice with obesity induced by high-fat diet significantly prolonged the estrus cycle, disrupted sex hormonal balance and ovarian follicle development after they were exposed to 25 mg/kg b.w./day of genistein during the fetal and neonatal stages. Genistein significantly up-regulated the ovarian mRNA expression of estrogen receptor beta in F1 obese female mice, and high-fat diet influenced the ovarian mRNA expression of estrogen receptor alpha, luteinizing hormone receptor and follicle-stimulating hormone receptor. Hence, genistein exposure from the fetal stage might increase the risk of reproductive diseases in obese females in later life. Thus, the long-term risks of genistein to obese females should be thoroughly assessed.

Isoflavones

Phytoestrogens are naturally occurring nonsteroidal phenolic plant compounds that, due to their molecular structure and size, resemble vertebrate steroids estrogens. This review is focused on plant flavonoids isoflavones, which are ranked among the most estrogenic compounds. The main dietary sources of isoflavones for humans are soybean and soybean products, which contain mainly daidzein and genistein. When they are consumed, they exert estrogenic and/or antiestrogenic effects. Isoflavones are considered chemoprotective and can be used as an alternative therapy for a wide range of hormonal disorders, including several cancer types, namely breast cancer and prostate cancer, cardiovascular diseases, osteoporosis, or menopausal symptoms. On the other hand, isoflavones may also be considered endocrine disruptors with possible negative influences on the state of health in a certain part of the population or on the environment. This review deals with isoflavone classification, structure, and occurrence, with their metabolism, biological, and health effects in humans and animals, and with their utilization and potential risks.

Neonatal isoflavone exposure interferes with the reproductive system of female Wistar rats

There is increasing concern about possible adverse effects of soy based infant formulas (SBIF) due to their high amount of isoflavones (ISO). The aim of the present study was to investigate effects of neonatal exposure to ISO on reproductive system of female Wistar rats. Animals were exposed to an ISO depleted diet or a diet enriched with an ISO extract (IRD; 508mg ISO/kg) during embryogenesis and adolescence. Pups of each group were fed daily by pipette with ISO-suspension (ISO+; 32mg ISO/kg bw) or placebo from postnatal day (PND) 1 until PND23 resulting in plasma concentrations similar to levels reported in infants fed SBIF. The visceral fat mass was reduced by long-term IRD. Vaginal epithelial height was increased at PND23 and vaginal opening was precocious in ISO+ groups. Later in life, more often irregular estrus cycles were observed in rats of ISO+ groups. In addition, FSH levels and uterine epithelial heights were increased at PND80 in ISO+ groups. In summary, the results indicate that neonatal ISO intake, resulting in plasma concentrations achievable through SBIF, has an estrogenic effect on prepubertal rats and influences female reproductive tract later in life.

A Mouse Model for Studying Nutritional Programming: Effects of Early Life Exposure to Soy Isoflavones on Bone and Reproductive Health

Over the past decade, our research group has characterized and used a mouse model to demonstrate that "nutritional programming" of bone development occurs when mice receive soy isoflavones (ISO) during the first days of life. Nutritional programming of bone development can be defined as the ability for diet during early life to set a trajectory for better or compromised bone health at adulthood. We have shown that CD-1 mice exposed to soy ISO during early neonatal life have higher bone mineral density (BMD) and greater trabecular inter-connectivity in long bones and lumbar spine at young adulthood. These skeletal sites also withstand greater forces before fracture. Because the chemical structure of ISO resembles that of 17-β-estradiol and can bind to estrogen receptors in reproductive tissues, it was prudent to expand analyses to include measures of reproductive health. This review highlights aspects of our studies in CD-1 mice to understand the early life programming effects of soy ISO on bone and reproductive health. Preclinical mouse models can provide useful data to help develop and guide the design of studies in human cohorts, which may, depending on findings and considerations of safety, lead to dietary interventions that optimize bone health.

Transgenerational developmental programming

BACKGROUND

The concept of developmental programming suggests that the early life environment influences offspring characteristics in later life, including the propensity to develop diseases such as the metabolic syndrome. There is now growing evidence that the effects of developmental programming may also manifest in further generations without further suboptimal exposure. This review considers the evidence, primarily from rodent models, for effects persisting to subsequent generations, and evaluates the mechanisms by which developmental programming may be transmitted to further generations. In particular, we focus on the potential role of the intrauterine environment in contributing to a developmentally programmed phenotype in subsequent generations.

METHODS

The literature was systematically searched at http://pubmed.org and http://scholar.google.com to identify published findings regarding transgenerational (F2 and beyond) developmental programming effects in human populations and animal models.

RESULTS

Transmission of programming effects is often viewed as a form of epigenetic inheritance, either via the maternal or paternal line. Evidence exists for both germline and somatic inheritance of epigenetic modifications which may be responsible for phenotypic changes in further generations. However, there is increasing evidence for the role of both extra-genomic components of the zygote and the interaction of the developing conceptus with the intrauterine environment in propagating programming effects.

CONCLUSIONS

The contribution of a suboptimal reproductive tract environment or maternal adaptations to pregnancy may be critical to inheritance of programming effects via the maternal line. As the effects of age exacerbate the programmed metabolic phenotype, advancing maternal age may increase the likelihood of developmental programming effects being transmitted to further generations. We suggest that developmental programming effects could be propagated through the maternal line de novo in generations beyond F2 as a consequence of development in a suboptimally developed intrauterine tract and not necessarily though directly transmitted epigenetic mechanisms.

Diverse effects of phytoestrogens on the reproductive performance: cow as a model

Phytoestrogens, polyphenolic compounds derived from plants, are more and more common constituents of human and animal diets. In most of the cases, these chemicals are much less potent than endogenous estrogens but exert their biological effects via similar mechanisms of action. The most common source of phytoestrogen exposure to humans as well as ruminants is soybean-derived foods that are rich in the isoflavones genistein and daidzein being metabolized in the digestive tract to even more potent metabolites-para-ethyl-phenol and equol. Phytoestrogens have recently come into considerable interest due to the increasing information on their adverse effects in human and animal reproduction, increasing the number of people substituting animal proteins with plant-derived proteins. Finally, the soybean becomes the main source of protein in animal fodder because of an absolute prohibition of bone meal use for animal feeding in 1995 in Europe. The review describes how exposure of soybean-derived phytoestrogens can have adverse effects on reproductive performance in female adults.