Hepatotoxicity induced by neonatal exposure to diethylstilbestrol is maintained throughout adulthood via the nuclear receptor SHP

Farnesoid X receptor alpha (FXRα) is a critical actor of the development and pathologies of the male reproductive system

The farnesoid-X-receptorα (FXRα; NR1H4) is one of the main bile acid (BA) receptors. During the last decades, through the use of pharmalogical approaches and transgenic mouse models, it has been demonstrated that the nuclear receptor FXRα controls numerous physiological functions such as glucose or energy metabolisms. It is also involved in the etiology or the development of several pathologies. Here, we will review the unexpected roles of FXRα on the male reproductive tract. FXRα has been demonstrated to play functions in the regulation of testicular and prostate homeostasis. Even though additional studies are needed to confirm these findings in humans, the reviewed reports open new field of research to better define the effects of bile acid-FXRα signaling pathways on fertility disorders and cancers.

Multigenerational impacts of bile exposure are mediated by TGR5 signaling pathways

Besides their well-known roles in digestion and fat solubilization, bile acids (BAs) have been described as signaling molecules activating the nuclear receptor Farnesoid-X-receptor (FXRα) or the G-protein-coupled bile acid receptor-1 (GPBAR-1 or TGR5). In previous reports, we showed that BAs decrease male fertility due to abnormalities of the germ cell lineage dependent on Tgr5 signaling pathways. In the presentstudy, we tested whether BA exposure could impact germ cell DNA integrity leading to potential implications for progeny. For that purpose, adult F0 male mice were fed a diet supplemented with cholic acid (CA) or the corresponding control diet during 3.5 months prior mating. F1 progeny from CA exposed founders showed higher perinatal lethality, impaired BA homeostasis and reduced postnatal growth, as well as altered glucose metabolism in later life. The majority of these phenotypic traits were maintained up to the F2 generation. In F0 sperm cells, differential DNA methylation associated with CA exposure may contribute to the initial programming of developmental and metabolic defects observed in F1 and F2 offspring. Tgr5 knock-out mice combined with in vitro strategies defined the critical role of paternal Tgr5 dependent pathways in the multigenerational impacts of ancestral CA exposure.

Crosstalk between BPA and FXRα Signaling Pathways Lead to Alterations of Undifferentiated Germ Cell Homeostasis and Male Fertility Disorders

Several studies have reported an association between the farnesoid X receptor alpha (FXRα) and estrogenic signaling pathways. Fxrα could thus be involved in the reprotoxic effects of endocrine disruptors such as bisphenol-A (BPA). To test this hypothesis, mice were exposed to BPA and/or stigmasterol (S), an FXRα antagonist. Following the exposure to both molecules, wild-type animals showed impaired fertility and lower sperm cell production associated with the alteration of the establishment and maintenance of the undifferentiated germ cell pool. The crosstalk between BPA and FXRα is further supported by the lower impact of BPA in mice genetically ablated for Fxrα and the fact that BPA counteracted the effects of FXRα agonists. These effects might result from the downregulation of Fxrα expression following BPA exposure. BPA and S act additively in human testis. Our data demonstrate that FXRα activity modulates the impact of BPA on male gonads and on undifferentiated germ cell population.

•

BPA and S exposures synergistically induce male fertility disorders

•

BPA regulates Fxr expression

•

BPA and S act additively in human testis

Bile acid homeostasis controls CAR signaling pathways in mouse testis through FXRalpha

Bile acids (BAs) are molecules with endocrine activities controlling several physiological functions such as immunity, glucose homeostasis, testicular physiology and male fertility. The role of the nuclear BA receptor FXRα in the control of BA homeostasis has been well characterized. The present study shows that testis synthetize BAs. We demonstrate that mice invalidated for the gene encoding FXRα have altered BA homeostasis in both liver and testis. In the absence of FXRα, BA exposure differently alters hepatic and testicular expression of genes involved in BA synthesis. Interestingly, Fxrα-/- males fed a diet supplemented with BAs show alterations of testicular physiology and sperm production. This phenotype was correlated with the altered testicular BA homeostasis and the production of intermediate metabolites of BAs which led to the modulation of CAR signaling pathways within the testis. The role of the CAR signaling pathways within testis was validated using specific CAR agonist (TCPOBOP) and inverse agonist (androstanol) that respectively inhibited or reproduced the phenotype observed in Fxrα-/- males fed BA-diet. These data open interesting perspectives to better define how BA homeostasis contributes to physiological or pathophysiological conditions via the modulation of CAR activity.

Impact of Drug Treatment at Neonatal Ages on Variability of Drug Metabolism and Drug-drug Interactions in Adult Life

PURPOSE OF REVIEW

As the number of patients taking more than one medication concurrently continues to increase, predicting and preventing drug-drug interactions (DDIs) is now more important than ever. Administration of one drug can cause changes in the expression and activity of drug metabolizing enzymes (DMEs) and alter the efficacy or toxicity of other medications that are substrates for these enzymes, resulting in a DDI. In today's medical practice, potential DDIs are evaluated based on the current medications a patient is taking with little regard to drugs the patient has been exposed to in the past. The purpose of this review is to discuss potential impacts of drug treatment at neonatal ages on the variability of drug metabolism and DDIs in adult life.

RECENT FINDINGS

Existing evidence from the last thirty years has shown that exposure to certain xenobiotics during neonatal life has the potential to persistently alter DME expression through adult life. With recent advancements in the understanding of epigenetic regulation on gene expression, this phenomenon is resurfacing in the scientific community in hopes of defining possible mechanisms. Exposure to compounds that have the ability to bind nuclear receptors and trigger epigenetic modifications at neonatal and pediatric ages may have long-term, if not permanent, consequences on gene expression and DME activity.

SUMMARY

The information summarized in this review should challenge the way current healthcare providers assess DDI potential and may offer an explanation to the significant interindividual variability in drug metabolism that is observed among patients.

Bile Acid Alters Male Mouse Fertility in Metabolic Syndrome Context

Bile acids have recently been demonstrated as molecules with endocrine activities controlling several physiological functions such as immunity and glucose homeostases. They act mainly through two receptors, the nuclear receptor Farnesol-X-Receptor alpha (FXRα) and the G-protein coupled receptor (TGR5). These recent studies have led to the idea that molecules derived from bile acids (BAs) and targeting their receptors must be good targets for treatment of metabolic diseases such as obesity or diabetes. Thus it might be important to decipher the potential long term impact of such treatment on different physiological functions. Indeed, BAs have recently been demonstrated to alter male fertility. Here we demonstrate that in mice with overweight induced by high fat diet, BA exposure leads to increased rate of male infertility. This is associated with the altered germ cell proliferation, default of testicular endocrine function and abnormalities in cell-cell interaction within the seminiferous epithelium. Even if the identification of the exact molecular mechanisms will need more studies, the present results suggest that both FXRα and TGR5 might be involved. We believed that this work is of particular interest regarding the potential consequences on future approaches for the treatment of metabolic diseases.