CE34 - Contaminants, écosystèmes et santé

MetAbolisM impact on Bisphenol S effects in the Ovary – MAMBO

Variability in sensitivity to the effects of endocrine disruptors according to individual metabolic status

The challenge of the project is to study whether an individual's metabolic status could affect the sensitivity to the effects of the endocrine disruptor bisphenol S

Effects and mechanism of action of bisphenol S on the ovary

Bisphenol A (BPA) has been used to produce plastics in the food industry. BPA has deleterious effects on the reproductive function of males and females. Because of its harmful effects, BPA has been banned in the food industry and structural analogues such as bisphenol S (BPS) have been widely used as a substitute for BPA. Initial data obtained on BPS suggest similar effects of the two molecules.<br /> This proposal aims to assess whether BPS can affect human reproduction and its potential interactions with metabolic status in women. We will therefore study the acute and chronic effects of BPS on metabolism and ovarian physiology at several stages of development in a human and ovarian model.<br /> So far, the effects of BPS are mainly described in zebrafish or rodent models, with little study of the metabolic components. We therefore plan to study the effects of BPS on ovarian function and adult and fetal metabolism using human ovaries and experimental sheep models. In humans, the effects of BPS on the initiation of meiosis in human germ cells and the formation of follicles will be studied after xenotransplantation of human fetal ovaries in immunodeficient mice. In adults, we will evaluate the relationship between the effects of BPS, clinical metabolic data in women (BMI, blood glucose, free fatty acids in plasma) and folliculogenesis. We will collect human granulosa cells and follicular fluid from women undergoing an in vitro fertilization (IVF) procedure and study both the level and effects of BPS in these compartments.

One of the objectives of this project is the in vivo study in sheep of the dose-effects of BPS. Using the sheep model, whose metabolic status has been controlled (induced by high or low energy diets), the impact of a 3-month chronic exposure to BPS will be studied on the follicular population and oocyte quality in adults. Fetal metabolism, placental function, ovarian and hypothalamic physiology will also be studied after a 3-month chronic fetal exposure to BPS in sheep. The specific steps of folliculogenesis will be investigated following BPS exposure, allowing the study of primordial follicular activation, pre-antral to antral follicular growth, oocyte quality and granulosa steroidogenesis.
It is difficult to evaluate the in vivo effects of BPS at multiple doses. Therefore, a dose of BPS, corresponding to the TDI of BPA of 50 µg/kg/day, will be used by all three partners. In the sheep model, an even lower dose of BPS will be used (4 µg/kg/day) to evaluate different parameters. Additional concentrations of BPS will be evaluated in vitro. The dose effect of acute exposure of BPS will be studied in vitro on ovine and human granulosa cells and ovine oocytes.
The sheep used by the partners will be raised in the same experimental unit, which will ensure that both partners work on the same breed and metabolic status model.

The first milestones of the project indicate that acute in vitro exposure of BPS is sufficient to induce effects on sheep and human granulosa cells and sheep oocyte. The oocyte appears to be much more sensitive to the effects of BPS, as environmental concentrations are sufficient to alter its quality. In granulosa cells, alterations in steroidogenesis are only observed at relatively high concentrations.
With regard to chronic exposure of animals to BPS for 3 months, it would appear that the doses tested do not impair oocyte quality in adults and do not alter the metabolism in the fetus. On the other hand, the metabolic status of the mothers (lean or fat) affects the weight and energy metabolism of the fetus.
The culture media tested all showed non-negligible levels of BPS, suggesting that embryo production procedures in either humans (medically assisted reproduction) or animals (embryo production companies, especially livestock) are additional exposure risks that may alter the quality of the embryos produced or the success rates of these procedures.

The project has several socio-economic perspectives in terms of human health and raises the question of the human population's exposure to endocrine disruptors and the variability of individual sensitivity to these environmental pollutants. Indeed, our metabolic approach to the potential effects of BPS could lead to individual recommendations to target populations (pregnant women of a BMI category identified as sensitive to bisphenols) who follow an IVF protocol, in order to improve the success rate. It would thus be possible to reduce the cost of assisted reproductive technologies for couples exposed to this compound, by avoiding trials in unfavorable times. The project has other economic benefits. If the results show deleterious effects of BPS on oocyte quality and fetal development, the prospects of the project could help raise awareness among government agencies and support the removal of BPS from the list of BPA substitutes. By providing evidence of the negative effects of BPS, this project could help limit its use, thereby avoiding the cost of banning a widely distributed environmentally harmful substance.

The prospects of the project could also lead to replacements of reagents used in ART services to limit exposure to bisphenols. Finally, the data generated feed the reflection on the fact of analyzing the different pollutants individually, or on the possibility of having regulations by family of compounds, especially in the case of families such as bisphenols, whose different members seem to share at least partly the same effects, leading to potential additive effects between the different bisphenols.

The results generated in this project have so far led to the publication of 3 scientific articles. The 1st article shows that at environmental concentrations, BPS is capable of altering oocyte capacity. The 2nd shows that BPS alters the steroidogenesis of ovine granulosa cells in a similar way to BPA. The 3rd shows that these alterations in steroidogenesis are also found in human granulosa cells and presents a first estimate of the exposure of the human population via the determination of follicular fluids in women following an ART protocol.
• Amar S, Binet A, Téteau O, Desmarchais A, Papillier P, Lacroix MZ, Maillard V, Guérif F, Elis S. (2020). Bisphenol S Impaired Human Granulosa Cell Steroidogenesis in Vitro. Int J Mol Sci. 2020 Mar 6;21(5):1821. doi: 10.3390/ijms21051821.
• Desmarchais A, Téteau O, Papillier P, Jaubert M, Druart X, Binet A, Maillard V, Elis S. (2020). Bisphenol S Impaired In Vitro Ovine Early Developmental Oocyte Competence. Int J Mol Sci. 2020 Feb 12;21(4). pii: E1238. doi: 10.3390/ijms21041238.
• Téteau O, Jaubert M, Desmarchais A, Papillier P, Binet A, Maillard V, Elis S. (2020). Bisphenol A and S impaired ovine granulosa cell steroidogenesis. Reproduction. 2020 May;159(5):571-583. doi: 10.1530/REP-19-0575.

Bisphenol A (BPA) has been used to produce plastic as tin can coating, polycarbonate and epoxy resins in the food industry. BPA was shown to exhibit deleterious effects on the reproductive function (hypothalamus and gonads) in both males and females. Because of all its side effects, BPA has been prohibited from food industry (French law n°2012-1442) and new formulations containing bisphenol S (BPS) as substitute have been proposed. It is, therefore, of importance to investigate BPS effects in human (before environmental exposure rises), as first data obtained in rodents and zebrafish suggest similar effects of both molecules. On the other hand, BPA has also been described as a risk factor for metabolic disorders such as diabetes and obesity. Lipid metabolism is crucial for ovarian functions and oocyte developmental competence and there is an increasing proportion of obese women with reproductive complications.
This proposal aimed to assess whether BPS can affect female reproduction in human, and to decipher the potential interactions with metabolic status. BPA showed estrogenic effects affecting folliculogenesis (follicle activation, growth and steroidogenesis). We will thus study acute and chronic effects of BPS on metabolism and ovarian physiology, at several stages of development in both human and ovine model. We chose the ovine model as it is physiologically closer to the human species in terms of metabolism and reproduction, compared to rodent models. The kinetics of folliculogenesis, embryo development and fetal development are comparable between the ovine and human species. Moreover, during ovine and human fetal development, endocrine disruptors have been shown to impact the ovary, pancreas and brain (hypothalamus) in similar temporal windows of sensitivity.
So far, BPS effects are mostly described in zebrafish or rodent models, and the metabolic components have not yet been investigated. We therefore plan to study the BPS effects on both the ovarian function and metabolism using human ovaries and ovine experimental models. Several physiological stages will be investigated. The ovary (and especially the fetal ovary) is a sensitive tissue affected even by low dose of BPA and thus a relevant tissue to investigate BPS effects. In human, ovarian studies will be developed in relation with metabolic clinical data from women (BMI, glycemia) and will concern 2 stages, fetal ovaries and granulosa cells in adults. The effects of BPS on meiosis initiation in human germ cells and follicle formation will be studied after xenografting human fetal ovaries in immunodeficient mice. We will also collect human granulosa cells and follicular fluid from women undergoing in vitro fertilization (IVF) procedure, and study both the level and the effects of BPS in these compartments. Using the ovine model, we will compare and complete the physiological stages studied in human. The ovine model enables to study 2 groups of ewes with metabolic differences (induced by high or low energy diets). Fetal metabolism, placental functions, ovarian and hypothalamic physiology will be studied after acute or chronic fetal exposure to bisphenol in sheep (maternal perfusion). Precise steps of folliculogenesis will be studied after BPS exposure, enabling to study primordial follicle activation, pre-antral to antral follicle growth, oocyte quality and granulosa steroidogenesis.
The originality of MAMBO proposal is therefore to investigate the effects of BPS at various sensitive stages: follicle and oocyte development in adults, early embryo development, and the development of fetus and young females following in utero exposure.

Project coordination

Sébastien ELIS (Physiologie de la reproduction et des comportements)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

TOXALIM Toxicologie Alimentaire
PRC Physiologie de la reproduction et des comportements
SCSR Stabilité génétique, Cellules Souches et Radiations

Help of the ANR 492,828 euros
Beginning and duration of the scientific project: January 2019 - 48 Months

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