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Does bisphenol A (BPA) participates in the pathogenesis of Polycystic Ovary Syndrome (PCOS)?

Abstract

PCOS is an endocrine disorder characterized by chronic anovulation, hyperandrogenism, and polycystic ovaries. Its etiology is uncertain. It is debated whether BPA would be a component of the environmental factor in the etiology of PCOS. Contamination by BPA can occur from food packaging (exposure during the diet) and through skin absorption and/or inhalation. It can be transferred to the fetus via the placenta or to the infant via breast milk, and it can be found in follicular fluid, fetal serum, and amniotic fluid. The phenolic structure of BPA allows it to interact with Estrogen Receptors (ERs) through genomic signaling, in which BPA binds to nuclear ERα or Erβ, or through nongenomic signaling by binding to membrane ERs, prompting a rapid and intense response. With daily and constant exposure, BPA's tendency to bioaccumulate and its ability to activate nongenomic signaling pathways can alter women's metabolic and reproductive function, leading to hyperandrogenism, insulin resistance, obesity, atherogenic dyslipidemia, chronic inflammatory state, and anovulation and favoring PCOS. The harmful changes caused by BPA can be passed on to future generations without the need for additional exposure because of epigenetic modifications. Not only high BPA levels can produce harmful effects, but at low levels, BPA may be harmful when exposure occurs during the most vulnerable periods, such as the fetal and neonatal periods, as well as during the prepubertal age causing an early accumulation of BPA in the body. Learning how BPA participates in the pathogenesis of PCOS poses a challenge and further studies should be conducted.

Keywords
Bisphenol A; Endocrine disruptors; Hyperandrogenism; Insulin resistance; Obesity; Polycystic Ovary Syndrome

Highlights

  • Bisphenola A (BPA) is an endocrine disruptor widely investigated as a possible environmental contributor to the pathogenesis of Polycystic Ovary Syndrome (PCOS).

  • Due to its structural similarity with the Estrogen molecule (E2), it acts as a xenoestrogen, binding to genomic and non-genomic estrogen receptors, causing metabolic and hormonal changes that lead to PCOS (hyperandrogenism, insulin resistance, hyperinsulinemia, obesity, atherogenic dyslipidemia, anovulation, and ovarian cysts).

  • The aim and of this review were to present the mechanisms of bisphenol A participation in the pathogenesis of Polycystic Ovary Syndrome.

Highlights

  • Bisphenola A (BPA) is an endocrine disruptor widely investigated as a possible environmental contributor to the pathogenesis of Polycystic Ovary Syndrome (PCOS).

  • Due to its structural similarity with the Estrogen molecule (E2), it acts as a xenoestrogen, binding to genomic and non-genomic estrogen receptors, causing metabolic and hormonal changes that lead to PCOS (hyperandrogenism, insulin resistance, hyperinsulinemia, obesity, atherogenic dyslipidemia, anovulation, and ovarian cysts).

  • The aim and of this review were to present the mechanisms of bisphenol A participation in the pathogenesis of Polycystic Ovary Syndrome.

Endocrine-disrupting chemicals

An endocrine disruptor was defined as: “an exogenous chemical, or a mixture of chemicals, that interferes with any aspect of hormone action”, consequently causing adverse health effects.11 Zoeller RT, Brown TR, Doan LL, Gore AC, Skakkebaek NE, Soto AM, et al. Endocrine-disrupting chemicals, and public health protection: a statement of principles from The Endocrine Society. Endocrinology. 2012;153(9):4097-110.

The Endocrine-Disrupting Chemicals (EDCs) can affect not only the exposed individuals but also their children and subsequent generations. In the United States, more than 6 million pounds of Bisphenol A (BPA) are produced every year and it is considered the third most important environmental contaminant according to the US Environmental Protection Agency (EPA).22 Thoene M, Rytel L, Dzika E, Włodarczyk A, Kruminis-Kaszkiel E, Konrad P, et al. Bisphenol A causes liver damage and selectively alters the neurochemical coding of intrahepatic parasympathetic nerves in juvenile porcine models under physiological conditions. Int J Mol Sci. 2017;18(12):2726.

BPA may be associated with Polycystic Ovary Syndrome (PCOS), infertility in women, altering the morphology and function of the oviduct, uterus, ovary, and hypothalamic-pituitary-ovarian axis in animal models. Additionally, BPA can disrupt embryo implantation.33 Ziv-Gal A, Flaws JA. Evidence for bisphenol A-induced female infertility - review (2007-2016). Fertil Steril. 2016;106(4):827-56.

Understanding how BPA, the most widespread endocrine disruptor in nature, participates in the pathogenesis of PCOS, is the aim of this review.

Polycystic Ovarian Syndrome (PCOS)

PCOS is an endocrine alteration of uncertain etiology. A few of the etiologic hypotheses for the development of PCOS are hormonal imbalance, epigenetic and genetic defects, and environmental factors. It is debated whether BPA would be a component of the environmental factor in the etiology of PCOS. Exposure during the prenatal period to elevated levels of Anti-Müllerian Hormone (AMH), androgens, and endocrine disruptors such as BPA may also participate in the etiopathogenesis of PCOS.44 Siddiqui S, Mateen S, Ahmad R, Moin S A brief insight into the etiology, genetics, and immunology of polycystic ovarian syndrome (PCOS). J Assist Reprod Genet. 2022;39(11):2439-73.

PCOS is clinically characterized by hormonal alterations (chronic anovulation, hyperandrogenism, and polycystic ovarian morphology) and metabolic alterations characteristically referred to as obesity, Insulin Resistance (IR), atherogenic dyslipidemia, and metabolic syndrome.55 Zeng X, Xie YJ, Liu YT, Long SL, Mo ZC Polycystic ovarian syndrome: correlation between hyperandrogenism, insulin resistance and obesity. Clin Chim Acta. 2020;502:214-21. PCOS occurs in 6% to 20% of reproductive-age women.44 Siddiqui S, Mateen S, Ahmad R, Moin S A brief insight into the etiology, genetics, and immunology of polycystic ovarian syndrome (PCOS). J Assist Reprod Genet. 2022;39(11):2439-73.

Women with PCOS are at an increased risk of pregnancy complications and adverse outcomes in the offspring that could be related to factors involved in the pathogenesis of the Syndrome and the related comorbidities.66 Abruzzese GA, Silva AF, Velazquez ME, Ferrer MJ, Motta AB Hyperandrogenism and Polycystic Ovary Syndrome: effects in pregnancy and offspring development. WIREs Mech Dis. 2022;14(5):e1558. The hyperandrogenism present in PCOS can affect reproductive functions, not only ovarian folliculogenesis but also endometrial receptivity and the establishment and maintenance of pregnancy.77 Simitsidellis I, Saunders PTK, Gibson DA Androgens and endometrium: new insights and new targets. Mol Cell Endocrinol. 2018;465:48-60.

The Rotterdam Consensus published by the American Society for Reproductive Medicine (ASRM), along with the European Society of Human Reproduction and Embryology (ESHRE), in 2004 defined that a diagnosis of PCOS requires at least two of the following three criteria: oligoovulation and/or anovulation, clinical and/or biochemical evidence of hyperandrogenism, and morphology of polycystic ovaries. To confirm the syndrome, other causes of chronic anovulation should be ruled out, and so should the disorders that mimic the clinical features of PCOS, such as thyroid disorders, hyperprolactinemia, nonclassical congenital adrenal hyperplasia, androgen-secreting tumors, and Cushing's syndrome.88 Fauser BC, Tarlatzis BC, Rebar RW, Legro RS, Balen AH, Lobo R, et al. Consensus on women's health aspects of Polycystic Ovary Syndrome (PCOS): the Amsterdam ESHRE/ASRM-Sponsored 3rd PCOS Consensus Workshop Group. Fertil Steril. 2012;97(1):28-38.e25.

Bisphenol A (BPA)

Bisphenol A is considered an estrogen-like endocrine-disrupting chemical. It was first developed as a synthetic estrogen in the 1890s. It was later used as a monomer in the production of polycarbonate plastics and as an intermediate in the synthesis of epoxy. Polycarbonate is used in the composition of various objects such as CDs, cups, plastic bottles, baby bottles, etc., while epoxy resins are mainly used to coat the inside of food cans and in dental fillings. BPA is also used as a developer in thermal papers.99 Beausoleil C, Emond C, Cravedi JP, Antignac JP, Applanat M, Appenzeller BR, et al. Regulatory identification of BPA as an endocrine disruptor: Context and methodology. Mol Cell Endocrinol. 2018;475:4-9.

Some studies have reported that BPA exposure is associated with reproductive disorders, including obstetric complications such as those seen in women with PCOS.1010 Pergialiotis V, Kotrogianni P, Christopoulos-Timogiannakis E, Koutaki D, Daskalakis G, Papantoniou N Bisphenol A and adverse pregnancy outcomes: a systematic review of the literature. J Matern Fetal Neonatal Med. 2018;31(24):3320-7. BPA would be an ovarian toxicant that decreases oocyte quality in animal models and women undergoing In Vitro Fertilization (IVF), as well as a uterine toxicant because it decreases uterine receptivity and increases implantation failure in animal models. Exposure to BPA may be associated with adverse birth outcomes, hyperandrogenism, sexual dysfunction, and impaired implantation in humans.1111 Peretz J, Vrooman L, Ricke WA, Hunt PA, Ehrlich S, Hauser R, et al. Bisphenol A and reproductive health: update of experimental and human evidence, 2007-2013. Environ Health Perspect. 2014;122(8):775-86.

Daily, high-level exposure to BPA occurs mainly through the diet when the chemical leaches into foods and beverages from their packaging. Exposure to BPA also occurs through skin absorption and inhalation and it may be found in follicular fluid, fetal serum, and amniotic fluid. Transmission of BPA from the pregnant woman to the fetus during pregnancy through the placenta and to the child through breast milk has been demonstrated.1212 Lee J, Choi K, Park J, Moon HB, Choi G, Lee JJ, et al. Bisphenol A distribution in serum, urine, placenta, breast milk, and umbilical cord serum in a birth panel of mother-neonate pairs. Sci Total Environ. 2018;626:1494-501 These findings suggest early BPA accumulation and significant exposure.

BPA has a short half-life of 6 hours and is inactivated through glucuronidation by uridine diphosphate glucuronosyl-transferases and sulfation, by phenol-sulfotransferases in hepatocytes microsomes and it is eliminated as BPA-glucuronide (inactive form), primarily in the urine. However, BPA levels do not drop as quickly as expected after fasting, which suggests that BPA enters the human body through non-dietary routes or is considered persistent due to widespread and continuous population exposure.1313 Encarnação T, Pais AA, Campos MG, Burrows HD Endocrine disrupting chemicals: Impact on human health, wildlife, and the environment. Sci Prog. 2019;102(1):3-42.

Periods of human development, including the prenatal period and infancy, are critical in terms of sensitivity to the effects of BPA. This is because fetuses and babies, unlike adults, do not have protective mechanisms such as DNA repair capacity, a fully functional blood-brain barrier, hepatic metabolism, and a competent immune system.1414 Kawa IA, Akbar Masood, Fatima Q, Mir SA, Jeelani H, Manzoor S, et al. Endocrine disrupting chemical Bisphenol A and its potential effects on female health. Diabetes Metab Syndr. 2021;15(3):803-11. The increased sensitivity to BPA during fetal and neonatal development can be explained by the liver's limited capacity to conjugate (deactivate) BPA.

In tissues such as the lungs, liver, kidneys, and placenta of animals and humans, the β-glucuronidase enzyme cleaves the glucuronide group and ensures the deconjugation of BPA returning to its active form that circulates again through the body. During pregnancy, the conjugated form of BPA crosses the placenta and undergoes deconjugation and the fetus is exposed to the active form of BPA.1515 Gauderat G, Picard-Hagen N, Toutain PL, Corbel T, Viguie C, Puel S, et al. Bisphenol A glucuronide deconjugation is a determining factor of fetal exposure to bisphenol A. Environ Int. 2016;86:52-9.

The tolerable BPA daily intake proposed by the US Environmental Protection Agency (50 µg/kg/day) and the European Food Safety Authority (4 µg/kg/day) were based on the Lowest Observable Adverse Effect Level (LOAEL). Nevertheless, plentiful scientific evidence has accumulated to show that BPA can interfere with the endocrine signaling pathways at doses lower than the calculated safe dose.1616 Farrugia F, Aquilina A, Vassallo J, Pace NP Bisphenol A and type 2 diabetes mellitus: a review of epidemiologic, functional, and early life factors. Int J Environ Res Public Health. 2021;18(2):716. The harmful effects caused by low-dose BPA in fetuses and newborns can be transmitted to third or fourth generations. The suggested mechanism of transgeneration is epigenetic changes.1717 Hong Y-P, Yang Y-J “Low-dose exposure to bisphenol a in early life.” Bisphenol A Exposure and Health Risks. IntechOpen. 2017;127-141.

Bisphenol A and its action on estrogen receptors

BPA is an exogenous chemical substance that mimics the activity of 17-β estradiol and it is considered a xenoestrogen. Consequently, BPA is able to disrupt E2 feedback at the hypothalamus-pituitary level and also at the ovarian level, thereby suppressing HPO axis functions.1818 Wang Y, Zhu Q, Dang X, He Y, Li X, Sun Y. Local effect of Bisphenol A on the estradiol synthesis of ovarian granulosa cells from PCOS. Gynecol Endocrinol. 2017;33(1):21-5. BPA can also cause inadequate hormone production, menstrual cycle abnormalities, infertility, and impairing the development and functioning of the reproductive system.1919 Rattan S, Zhou C, Chiang C, Mahalingam S, Brehm E, Flaws JA Exposure to endocrine disruptors during adulthood: consequences for female fertility. J Endocrinol. 2017;233(3):R109-29.

The affinity of BPA for nuclear Etrogen Receptors (ERs) appears to be lower than 17-beta Estradiol (E2), but its estrogen potency equals that of E2 in the nonnuclear ER-mediated responses which are intense and rapid even at very low concentrations.2020 Alonso-Magdalena P, Ropero AB, Soriano S, García-Arévalo M, Ripoll C, Fuentes E et al. Bisphenol-A acts as a potent estrogen via non-classical estrogen triggered pathways. Mol Cell Endocrinol. 2012;355(2):201-7. BPA may trigger estrogen-activated pathways by binding to membrane ERs (nonnuclear ERs), such as transmembrane ERs like GPR30 (G Protein-coupled Receptor 30).1818 Wang Y, Zhu Q, Dang X, He Y, Li X, Sun Y. Local effect of Bisphenol A on the estradiol synthesis of ovarian granulosa cells from PCOS. Gynecol Endocrinol. 2017;33(1):21-5.

Kawa et al.1414 Kawa IA, Akbar Masood, Fatima Q, Mir SA, Jeelani H, Manzoor S, et al. Endocrine disrupting chemical Bisphenol A and its potential effects on female health. Diabetes Metab Syndr. 2021;15(3):803-11. related that BPA also would have the ability to interact with Estrogen-Related Receptors gamma (ERRg) which are nuclear receptors expressed highly in the placenta, fetus, and neonate; with Aryl Hydrocarbon Receptor (AhR) that are able to mediate the toxicity of various EDCs; androgen receptors causing an anti-androgenic effects and thyroid receptors with agonistic and antagonistic effects). BPA may have an anti-estrogenic effect by inhibiting the activity of the aromatase.2121 Santangeli S, Maradonna F, Olivotto I, Piccinetti CC, Gioacchini G, Carnevali O Effects of BPA on female reproductive function: the involvement of epigenetic mechanism. Gen Comp Endocrinol. 2017;245:122e6.

Bisphenol A and changes in steroidogenesis/hyperandrogenism

BPA appears to alter the gene expression of some PCOS-related genes and downregulates the level of their m-RNA transcribed altering the Hypothalamic-Pituitary-Ovarian axis (HPO axis), steroidogenic and metabolic pathways.2222 Mukhopadhyay R, Prabhu NB, Kabekkodu SP, Rai PS Review on bisphenol A and the risk of polycystic ovarian syndrome: an insight from endocrine and gene expression. Environ Sci Pollut Res Int. 2022;29(22):32631-32650.

The dysregulation of gene expression caused by BPA exposure, at the hypothalamus and pituitary level impacts the functioning of the ovary.2222 Mukhopadhyay R, Prabhu NB, Kabekkodu SP, Rai PS Review on bisphenol A and the risk of polycystic ovarian syndrome: an insight from endocrine and gene expression. Environ Sci Pollut Res Int. 2022;29(22):32631-32650. The chemical's activation of the Gonadotropin-Releasing Hormone (GnRH) pulse generator is thus exaggerated, which induces a constant increase in LH and a decline in FSH secretion through the hypophysis, harming follicle development and increasing ovarian androgen production. BPA also could alter the expression of genes of ovarian steroidogenesis increasing RNAm expression of key enzymes such as 17α-hydroxylase, leading to hyperandrogenism and ovulatory dysfunction.2323 Rutkowska AZ, Diamanti-Kandarakis EPCOS and environmental toxins. Fertil Steril 2016;106(4):948-58.

The BPA can directly prompt androgen production in the ovarian theca cells, causing hyperandrogenism, and it can also interact with receptors in adipose tissue and stimulate pancreatic beta cells to produce insulin, leading to hyperinsulinemia, which results in the accumulation of lipids in adipose tissue. All these effects harm ovarian folliculogenesis, bringing about anovulation and favoring PCOS.2323 Rutkowska AZ, Diamanti-Kandarakis EPCOS and environmental toxins. Fertil Steril 2016;106(4):948-58.

It has also been shown that BPA can have antiestrogen action by inhibiting the activity of aromatase. Such an inhibition heightens testosterone levels and causes hyperandrogenism.2121 Santangeli S, Maradonna F, Olivotto I, Piccinetti CC, Gioacchini G, Carnevali O Effects of BPA on female reproductive function: the involvement of epigenetic mechanism. Gen Comp Endocrinol. 2017;245:122e6.

BPA may also interact with SHBG and is also capable of displacing sex steroids from SHBG thus increasing the quantity of free testosterone. Rutkowska et al.2424 Rutkowska A, Olsson A, Wilczewska K, Łukasz Łaczmański Ł, Kuliczkowska-Płaksej J, Jędrzejuk D, et al. Bisphenol A impacts hormonal profile in patients with Polycystic Ovary Syndrome but not in healthy women. Gynecolog Reproduct Endocrinol Metabol (GREM). 2020;1:43-47. believe that increased serum concentration of BPA in women with PCOS compared to healthy controls, reduced levels of SHBG in the PCOS group, it is already known that it would be the action of insulin and androgens.

BPA exposure was negatively associated with peak serum estradiol levels during gonadotropin stimulation, number of recovered oocytes, number of normally fertilized oocytes, and implantation.2525 Pivonello C, Muscogiuri G, Nardone A, Garifalos F, Provvisiero DP, Verde N, et al. Bisphenol A: an emerging threat to female fertility. Reprod Biol Endocrinol. 2020;18(1):22. BPA has been linked to a decreased antral follicle count in infertile women with PCOS suggesting a role for BPA in impairing the ovarian reserve.2626 Zhou W, Fang F, Zhu W, Chen ZJ, Du Y, Zhang J Bisphenol A and ovarian reserve among infertile women with polycystic ovarian syndrome. Int J Environ Res Public Health. 2016;14(1):18. When exposed to high doses of BPA, changes in follicular growth may occur, leading to enlarged and atretic follicles with a decrease in the number of antral follicles.2727 Zhu X, Tian GG, Yu B, Yang Y, Wu J. Effects of bisfenol A on ovarian follicular development and female germline stem cells. Arch Toxicol. 2018;92(4):1581-91.

Bisphenol A and chronic inflammatory state

Adipose tissue is a fat storage reservoir, but it is also an endocrine organ that secretes adipokines, cytokines, and chemokines. Bisphenol A likely acts through ERs on the adipocytes and macrophages that infiltrate the adipose tissue, promoting a chronic inflammatory state.2222 Mukhopadhyay R, Prabhu NB, Kabekkodu SP, Rai PS Review on bisphenol A and the risk of polycystic ovarian syndrome: an insight from endocrine and gene expression. Environ Sci Pollut Res Int. 2022;29(22):32631-32650.

It has been found that BPA is capable of inhibiting adiponectin secretion in adipose tissue as well as stimulating Interleukin 6 (IL-6) and Tumor Necrosis Factor α (TNF-α) secretion. Inflammation and oxidative stress may further aggravate carbohydrate metabolism disorder including disrupted insulin signaling in adipose tissue and glucose intolerance.2828 Stojanoska MM, Milosevic N, Milic N, Abenavoli L The influence of phthalates and bisphenol A on the obesity development and glucose metabolism disorders. Endocrine. 2017;55(3):666-81.

In the study by Ariemma et al.,2929 Ariemma F, D'Esposito V, Liguoro D, Oriente F, Cabaro S, Liotti A, et al. Low-Dose Bisphenol-A impairs adipogenesis and generates dysfunctional 3T3-L1 adipocytes. PLoS One. 2016;11(3):e0150762. 3T3-L1 preadipocytes were exposed to 1 nM of BPA for two weeks before adipogenesis induction and found an increase in fat accumulation following stimulation of adipogenesis and reduced insulin-stimulated glucose uptake with an increase in mRNA levels of inflammatory markers such as IL6, INFγ.

Bisphenol A can stimulate cytokine production and the proliferative response of spleen and thymus cells in vitro. Besides, it is involved in the production of autoantibodies by β1 cells and may cause a rise in the incidence of autoimmune diseases. Dong et al.3030 Dong Y, Gao L, Sun Q, Jia L, Liu D Increased levels of IL-17 and autoantibodies following Bisphenol A exposure were associated with activation of PI3K/AKT/mTOR pathway and abnormal autophagy in MRL/lpr mice. Ecotoxicol Environ Saf. 2023;255:114788. related that BPA exposure increased the concentration of serum anti-dsDNA antibody and IL-17, and the level of RORγt protein (the transcription factor of Th17 cells) in MRL/lpr mice (Lupus-prone mice) and it may induce the development of Systemic Lupus Erythematosus (SLE). In SLE, inflammation, autoantibodies, and estrogen are important pathological mechanisms.

BPA acting as a xenoestrogen could alter the subset of T-cells, B-cell function, and dendritic cell activity, inducing abnormal immune response with alteration of the transcription of the target gene and disruption of ER and PPAR signaling.3131 Edwards M, Dai R, Ahmed SA Our environment shapes us: the importance of environment and sex differences in regulation of autoantibody production. Front Immunol. 2018;9:478.

Tarantino et al.3232 Tarantino G, Valentino R, Di Somma C, D'Esposito V, Passaretti F, Pizza G, et al. Bisphenol A in Polycystic Ovary Syndrome and its association with liver-spleen axis. Clinic Endocrinology. 2013;78:447-53. found that, regardless of age and Body Mass Index (BMI), higher serum BPA levels were detected in a subgroup of women with PCOS who had more severe IR and hyperandrogenism, a higher prevalence of hepatic steatosis, and evidence of a chronic low-grade inflammatory state.

Bisphenol A and insulin resistance

Estrogen receptors ER-α and ER-β are present in the islet of Langerhans and E2 modulate insulin secretion. It appears that BPA can regulate insulin concentration in the pancreas by activating ER-α with a similar response to E2. ER-α would be the main ER involved in the regulation of insulin secretion by E2 and BPA. Increased insulin gene expression and insulin release in response to stimulatory glucose concentrations, appears to be one of the mechanisms responsible for this estrogenic effect of BPA.2020 Alonso-Magdalena P, Ropero AB, Soriano S, García-Arévalo M, Ripoll C, Fuentes E et al. Bisphenol-A acts as a potent estrogen via non-classical estrogen triggered pathways. Mol Cell Endocrinol. 2012;355(2):201-7.

The endocrine pancreas is the target of BPA exposure with possibly different mechanisms depending on whether exposure occurs during fetal life or adulthood. Indeed, fetal pancreas differentiation appears to be highly sensitive to BPA exposure based on researched results, e.g., β-cell proliferation and apoptosis.3333 Magueresse-Battistoni BL, Multigner L, Beausoleil C, Rousselle C Effects of bisphenol A on metabolism and evidence of a mode of action mediated through endocrine disruption. Mol Cell Endocrinol. 2018;475:74-91.

BPA appears to alter insulin synthesis and/or release by pancreatic β-cells and insulin signaling within insulin-sensitive organs (liver, muscle, adipose tissue). This resulted in variations in the expression of liver or adipose tissue-specific markers, which are indicative of an IR state. IR leads to an increase in lipolysis with a consequent increase in the plasma concentration of free fatty acids, an increase in hepatic glucose production, and a decrease in muscle glucose uptake with an increase in concentration. of blood glucose.3333 Magueresse-Battistoni BL, Multigner L, Beausoleil C, Rousselle C Effects of bisphenol A on metabolism and evidence of a mode of action mediated through endocrine disruption. Mol Cell Endocrinol. 2018;475:74-91.

Exposure to BPA appears to decrease the sensitivity of adipocytes to insulin due to a decrease in Glucose Transporter 1 (GLUT1) expression and insulin receptor phosphorylation, suggesting that BPA may alter glucose metabolism and favor the onset of DM2.3434 Valentino R, D'Esposito V, Passaretti F, Liotti A, Cabaro S, Longo M, et al. Bisphenol-A impairs insulin action and up-regulates inflammatory pathways in human subcutaneous adipocytes and 3T3-L1 cells. PLoS One. 2013;8(12):e82099.

In Skeletal muscle and in hepatocytes, the Insulin Receptor Substrate 1 (IRS1) is upregulated by exposure to BPA under basal conditions.3535 Eckstein SS, Weigert C, Lehmann R Divergent roles of IRS (insulin receptor substrate) 1 and 2 in liver and skeletal muscle. Curr Med Chem 2017;24:1827-52. BPA also reduces glucokinase activity while estrogen stimulates its activity under the same conditions.3636 Perreault L, McCurdy C, Kerege AA, Houck J, Færch K, Bergman BC Bisphenol A impairs hepatic glucose sensing in C57BL/6 male mice. PLoS ONE. 2013;8(7):e69991. In this way, exposure to BPA can alter insulin signaling pathways.

Martinez-Pinna et al.3737 Martinez-Pinna J, Marroqui L, Hmadcha A, Lopez-Beas J, Soriano S, Villar-Pazos S, et al. Oestrogen receptor β mediates the actions of bisphenol-A on ion channel expression in mouse pancreatic beta cells. Diabetologia. 2019;62(9):1667-80. showed that β-murine cells exposed to BPA presented an imbalance in their electrical activity with a decrease in Na+ and K+ currents due to the deregulation of several genes that codify components of the Na+ and K+ channels. This change in the electrical activity of β cells could impair insulin secretion with diabetogenic effects.

Inflammation and oxidative stress caused by BPA exposure may also favor disruptive effects on glucose metabolism leading to glucose intolerance by disruption of insulin signaling in adipose tissue.2828 Stojanoska MM, Milosevic N, Milic N, Abenavoli L The influence of phthalates and bisphenol A on the obesity development and glucose metabolism disorders. Endocrine. 2017;55(3):666-81.

Bisphenol A and obesity

An excessive intake of energy and a sedentary lifestyle are known to be risk factors for gaining weight; nevertheless, there has been a growing interest in the effects environmental chemicals may have on the development of obesity. Given that the adipose tissue is considered an endocrine organ, it may be targeted by EDCs. When EDCs stimulate adipogenesis and obesity are termed “obesogens”.3838 Darbre PD Endocrine disruptors and obesity. Curr Obes Rep. 2017;6(1):18-27. Some EDCs may exert obesogenic effects by altering energy homeostasis.3939 Yilmaz B, Terekeci H, Sandal S, Kelestimur F Endocrine disrupting chemicals: exposure, effects on human health, mechanism of action, models for testing and strategies for prevention. Rev Endocr Metab Disord. 2020;21:127-47.

A particularly sensitive period of exposure is the intrauterine or neonatal period; early exposure to BPA is associated with child obesity.4040 Vafeiadi M, Roumeliotaki T, Myridakis A, Chalkiadaki G, Fthenou E, Dermitzaki E, et al. Association of early life exposure to bisphenol A with obesity and cardiometabolic traits in childhood. Environ Res. 2016;146:379-87. Chronic intrauterine exposure to low BPA dose may not only trigger obesity but also contribute to IR and chronic low-grade inflammation in women who will develop PCOS. A correlation between BMI and BPA exposure has been reported.4141 Mustieles V, Casas M, Ferrando-Marco P, Ocon-Hernandez O, Reina-Perez I, Rodríguez-Carrillo A, et al. Bisphenol A and adiposity measures in peripubertal boys from the INMA-granada cohort. Environ Res 2019;173:443-51.

Obesogens favor adipogenesis through such mechanisms as follows: an increase in the number and size of adipocytes; altering basal metabolism and hormones that regulate appetite and satiety; favoring calorie storage and altering insulin sensitivity in the liver, skeletal muscle, brain, pancreas, and gastrointestinal system.3939 Yilmaz B, Terekeci H, Sandal S, Kelestimur F Endocrine disrupting chemicals: exposure, effects on human health, mechanism of action, models for testing and strategies for prevention. Rev Endocr Metab Disord. 2020;21:127-47.,4242 Muscogiuri G, Barrea L, Laudisio D, Savastano S, Colao A Obesogenic endocrine disruptors, and obesity: myths and truths. Arch Toxicol. 2017;91(11):3469-3475.

BPA can also bind to nuclear receptors like the Peroxisome Proliferator-Activated Receptors (PPARs), favoring obesity by altering gene expression. The PPARs regulate adipocyte proliferation and/or differentiation.3939 Yilmaz B, Terekeci H, Sandal S, Kelestimur F Endocrine disrupting chemicals: exposure, effects on human health, mechanism of action, models for testing and strategies for prevention. Rev Endocr Metab Disord. 2020;21:127-47.

Prenatal exposure to BPA in animals enhances serum leptin levels and decreases serum adiponectin levels contributing to adipocyte disfunction. These results may explain lipid accumulation and the increase in fat mass and obesity.4343 Legeay S, Faure S Is bisphenol A an environmental obesogen? Fundam Clin Pharmacol. 2017;31(6):594-609.

BPA suppressed adiponectin release as efficiently or even more than E2 at equimolar concentrations. Although transcriptional stimulation of the Glucocorticoid Receptor (GR) is considered essential for adipocyte differentiation, BPA was shown to induce the differentiation of human adipocytes through a nonclassical ER pathway in the absence of exogenous glucocorticoids.4444 Boucher JG, Boudreau A, Atlas E. Bisphenol A induces differentiation of human preadipocytes in the absence of glucocorticoid and is inhibited by an estrogen-receptor antagonista. Nutrition Diabetes. 2014;4(1):e102.

BPA as an obesogenic not only alters BMI, it also affects adipose tissue and glucose and lipid metabolism.4545 Pérez-Bermejo M, Mas-Pérez I, Murillo-Llorente MT The role of the bisphenol A in diabetes and obesity. Biomedicines. 2021;9(6):666.

Bisphenol A and dyslipidemia

Exposure to BPA in women with PCOS increases the metabolic risk causing obesity, mainly visceral, insulin resistance, hyperinsulinemia, dyslipidemia, and hyperandrogenism.4646 Milanović M, Milošević N, Sudji J, Stojanoski S, Atanacković Krstonošić M, Bjelica A, et al. Can environmental pollutant bisphenol A increase metabolic risk in Polycystic Ovary Syndrome? Clin Chim Acta. 2020;507:257-63.

Animal studies suggest that BPA has the potential to induce lipid disorders. For example, early exposure to BPA showed an increase in the circulating levels of Total Cholesterol (TC), Triglycerides (TG), and LDL-C and a reduction in the HDL-C levels, characterizing atherogenic dyslipidemia.4747 Gao L, Wang HN, Zhang L, Peng FY, Jia Y, Wei W, et al. Effect of perinatal bisphenol A exposure on serum lipids and lipid enzymes in offspring rats of different sex. Biomed. Environ. Sci. 2016;29(9):686-9.

In a 5-year prospective study, Li et al. (2020) measured the serum concentrations of BPA, TGs, LDL-C, and HDL-C and found that greater exposure to BPA is associated with a higher prevalence of low HDL cholesterol.4848 Li R, Yang S, Gao R, Deng Y, Liu J, Yuan C, et al. Relationship between the environmental endocrine disruptor bisphenol A and dyslipidemia: a five-year prospective study. Endocr Pract. 2020;26(4):399-406.

Bisphenol A and epigenetic changes

BPA may exert them through epigenetic mechanisms which include DNA methylation, histone modifications, and changes in micro RNA expression.1414 Kawa IA, Akbar Masood, Fatima Q, Mir SA, Jeelani H, Manzoor S, et al. Endocrine disrupting chemical Bisphenol A and its potential effects on female health. Diabetes Metab Syndr. 2021;15(3):803-11.

Epigenetic modification can only occur if exposure to BPA occurs during the early developmental stage (critical developmental window), predisposing the subsequent generations to transgenerational inheritance of the diseases.1414 Kawa IA, Akbar Masood, Fatima Q, Mir SA, Jeelani H, Manzoor S, et al. Endocrine disrupting chemical Bisphenol A and its potential effects on female health. Diabetes Metab Syndr. 2021;15(3):803-11. BPA's deleterious effects vary depending on doses, route of administration, exposure period and animal models.2525 Pivonello C, Muscogiuri G, Nardone A, Garifalos F, Provvisiero DP, Verde N, et al. Bisphenol A: an emerging threat to female fertility. Reprod Biol Endocrinol. 2020;18(1):22.

Puttabyatappa et al.4949 Puttabyatappa M, Saadat N, Elangovan VR, Dou J, Bakulski K, Padmanabhan V Developmental programming: Impact of prenatal bisphenol-A exposure on liver and muscle transcriptome of female sheep. Toxicol Appl Pharmacol. 2022;451:116161. observed in female sheep offspring, that prenatal treatment with BPA deregulated the expression of 194 genes in the liver and 112 genes in muscle as well as 155 mitochondria-related genetic pathways in both liver and muscle; 1415 genetic pathways that participate in oxidative stress and lipid biosynthetic process in the liver; 192 genetic pathways related to RNA biosynthetic processes in muscle. These findings may explain the development and/or maintenance of defects contributing to BPA-induced prenatal metabolic dysfunctions.4949 Puttabyatappa M, Saadat N, Elangovan VR, Dou J, Bakulski K, Padmanabhan V Developmental programming: Impact of prenatal bisphenol-A exposure on liver and muscle transcriptome of female sheep. Toxicol Appl Pharmacol. 2022;451:116161.

Conclusions

Bisphenol A is considered a xenoestrogen that can bind to nuclear ERs (genomic signaling) as well as to membrane ERs (nongenomic signaling), where it elicits a rapid and intense response.

As exposure to BPA is chronic (daily and constant) with a tendency toward bioaccumulation and given that BPA can activate nongenomic signaling pathways quickly and intensely, BPA levels from environmental exposure may provoke harmful effects, such as hyperandrogenism, IR, obesity, atherogenic dyslipidemia, chronic inflammatory state, and anovulation, contributing to PCOS. Changes induced by BPA may be passed on to future generations without the need for additional exposure because of it's transgenerational effects and epigenetic modifications. Not only high BPA levels can produce harmful effects, but at low levels, BPA may be harmful when exposure occurs during the most vulnerable periods, such as the fetal and neonatal periods, as well as during the prepubertal age, causing an early accumulation of BPA in the body. Understanding how BPA participates in PCOS pathogenesis poses a challenge and further studies should be conducted.

Acknowledgments

The present review was not sponsored

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Publication Dates

  • Publication in this collection
    08 Jan 2024
  • Date of issue
    2023

History

  • Received
    23 Sept 2023
  • Reviewed
    24 Oct 2023
  • Accepted
    01 Nov 2023
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