Transient Post-Natal Exposure to Xenoestrogens Induces Long-Term Alterations in Cardiac Calcium Signaling.

Today, non-communicable disorders are widespread worldwide. Among them, cardiovascular diseases represent the main cause of death. At the origin of these diseases, exposure to challenges during developmental windows of vulnerability (peri-conception, in utero, and early infancy periods) have been incriminated. Among the challenges that have been described, endocrine disruptors are of high concern because of their omnipresence in the environment. Worrisomely, since birth, children are exposed to a significant number of endocrine disruptors. However, the role of such early exposure on long-term cardiac health is poorly described. In this context, based on a model of rats exposed postnatally and transiently to an estrogenic compound prototype (estradiol benzoate, EB), we aimed to delineate the effects on the adult heart of such transient early exposure to endocrine disruptors and identify the underlying mechanisms involved in the potential pathogenesis. We found that this transient post-natal exposure to EB induced cardiac hypertrophy in adulthood, with increased cardiomyocyte size. The evaluation of cardiac calcium signaling, through immunoblot approaches, highlighted decreased expression of the sarcoplasmic reticulum calcium ATPase 2 (SERCA2) and decreased Nuclear Factor of Activated T Cells (NFAT3) phosphorylation as a potential underlying mechanism of cardiac hypertrophy. Furthermore, the treatment of cardiomyocytes with EB in vitro induced a decrease in SERCA2 protein levels. Overall, our study demonstrates that early transient exposure to EB induces permanent cardiac alterations. Together, our data highlight SERCA2 down-regulation as a potential mechanism involved in the cardiac pathogenesis induced by EB. These results suggest programming of adult heart dysfunctions such as arrhythmia and heart failures by early exposure to endocrine disruptors and could open new perspectives for treatment and prevention.

Epigenetics provides a bridge between early nutrition and long-term health and a target for disease prevention.

Exposure to nutritional imbalance during early life can influence disease risk lifelong and across generations. In this long-term conditioning, epigenetics constitutes a key mechanism. They bridge environmental cues and the expression of genes involved in the setting of long-standing biological regulations in numerous organs and species. Epigenetic marks are proposed as innovative diagnostic biomarkers and potential targets in the prevention of diseases. However, a number of uncertainties make them difficult to use in clinical approaches in the context of early exposure to nutritional challenge. In conclusion, active investigations in this field are still needed before clinical applications are considered.

Renal Programming by Transient Postnatal Overfeeding: The Role of Senescence Pathways.

BACKGROUND: Early nutrition influences the risk of chronic kidney diseases (CKDs) development in adulthood. Mechanisms underlying the early programming of altered renal function remain incompletely understood. This study aims at characterizing the role of cell senescence pathways in early programming of CKD after transient postnatal overfeeding. MATERIALS AND METHODS: Reduced litters of 3 mice pups and standard litters of 9 mice pups were obtained to induce overfed animals during lactation and control animals, respectively. Animals were sacrificed at 24 days (weaning) or at 7 months of life (adulthood). Body weight, blood pressure, kidney weight, and glomerular count were assessed in both groups. Senescence pathways were investigated using ß-Galactosidase staining and Western blotting of P16, P21, P53, P-Rb/Rb, and Sirtuin 1 (Sirt1) proteins. RESULTS: Early overfed animals had a higher body weight, a higher blood pressure at adulthood, and a higher glomerular number endowment compared to the control group. A higher ß-Galactosidase activity, a significant increase in P53 protein expression (p = 0.0045) and a significant decrease in P-Rb/Rb ratio (p = 0.02), were observed at weaning in animals who underwent early postnatal overfeeding. Protein expression of Sirt1, a protective factor against accelerated stress-induced senescence, was significantly decreased (p = 0.03) at weaning in early overfed animals. CONCLUSION: Early postnatal overfeeding by litter size reduction is associated with increased expression of factors involved in cellular senescence pathways, and decreased expression of Sirt 1 in the mouse kidney at weaning. These alterations may contribute to CKD programming after early postnatal overfeeding.

Maternal Exposure to High-Fat Diet Induces Long-Term Derepressive Chromatin Marks in the Heart.

Heart diseases are a leading cause of death. While the link between early exposure to nutritional excess and heart disease risk is clear, the molecular mechanisms involved are poorly understood. In the developmental programming field, increasing evidence is pointing out the critical role of epigenetic mechanisms. Among them, polycomb repressive complex 2 (PRC2) and DNA methylation play a critical role in heart development and pathogenesis. In this context, we aimed at evaluating the role of these epigenetic marks in the long-term cardiac alterations induced by early dietary challenge. Using a model of rats exposed to maternal high-fat diet during gestation and lactation, we evaluated cardiac alterations at adulthood. Expression levels of PRC2 components, its histone marks di- and trimethylated histone H3 (H3K27me2/3), associated histone mark (ubiquitinated histone H2A, H2AK119ub1) and target genes were measured by Western blot. Global DNA methylation level and DNA methyl transferase 3B (DNMT3B) protein levels were measured. Maternal high-fat diet decreased H3K27me3, H2Ak119ub1 and DNA methylation levels, down-regulated the enhancer of zeste homolog 2 (EZH2), and DNMT3B expression. The levels of the target genes, isl lim homeobox 1 (Isl1), six homeobox 1 (Six1) and mads box transcription enhancer factor 2, polypeptide C (Mef2c), involved in cardiac pathogenesis were up regulated. Overall, our data suggest that the programming of cardiac alterations by maternal exposure to high-fat diet involves the derepression of pro-fibrotic and pro-hypertrophic genes through the induction of EZH2 and DNMT3B deficiency.

Calorie Restriction in Adulthood Reduces Hepatic Disorders Induced by Transient Postnatal Overfeeding in Mice.

Impaired early nutrition influences the risk of developing metabolic disorders in later life. We observed that transient postnatal overfeeding (OF) in mice induces long-term hepatic alterations, characterized by microsteatosis, fibrosis associated with oxidative stress (OS), and stress-induced premature senescence (SIPS). In this study, we investigated whether such changes can be reversed by moderate calorie restriction (CR). C57BL/6 male mice pups were maintained during lactation in litters adjusted to nine pups in the normal feeding (NF) group and three pups in the transient postnatal OF group. At six months of age, adult mice from the NF and OF groups were randomly assigned to an ad libitum diet or CR (daily energy supply reduced by 20%) for one month. In each group, at the age of seven months, analysis of liver structure, liver markers of OS (superoxide anion, antioxidant defenses), and SIPS (lipofuscin, p53, p21, p16, pRb/Rb, Acp53, sirtuin-1) were performed. CR in the OF group reduced microsteatosis, decreased levels of superoxide anion, and increased protein expression of catalase and superoxide dismutase. Moreover, CR decreased lipofuscin staining, p21, p53, Acp53, and p16 but increased pRb/Rb and sirtuin-1 protein expression. CR did not affect the NF group. These results suggest that CR reduces hepatic disorders induced by OF.

Long-term impact of maternal high-fat diet on offspring cardiac health: role of micro-RNA biogenesis.

Heart failure is a worldwide leading cause of death. Diet and obesity are particularly of high concern in heart disease etiology. Gravely, altered nutrition during developmental windows of vulnerability can have long-term impact on heart health; however, the underlying mechanisms are poorly understood. In the understanding of the initiation of chronic diseases related to developmental exposure to environmental challenges, deregulations in epigenetic mechanisms including micro-RNAs have been proposed as key events. In this context, we aimed at delineating the role of micro-RNAs in the programming of cardiac alterations induced by early developmental exposure to nutritional imbalance. To reach our aim, we developed a human relevant model of developmental exposure to nutritional imbalance by maternally exposing rat to high-fat diet during gestation and lactation. In this model, offspring exposed to maternal high-fat diet developed cardiac hypertrophy and increased extracellular matrix depot compared to those exposed to chow diet. Microarray approach performed on cardiac tissue allowed the identification of a micro-RNA subset which was down-regulated in high-fat diet-exposed animals and which were predicted to regulate transforming growth factor-beta (TGFß)-mediated remodeling. As indicated by in vitro approaches and gene expression measurement in the heart of our animals, decrease in DiGeorge critical region 8 (DGCR8) expression, involved in micro-RNA biogenesis, seems to be a critical point in the alterations of the micro-RNA profile and the TGFß-mediated remodeling induced by maternal exposure to high-fat diet. Finally, increasing DGCR8 activity and/or expression through hemin treatment in vitro revealed its potential in the rescue of the pro-fibrotic phenotype in cardiomyocytes driven by DGCR8 decrease. These findings suggest that cardiac alterations induced by maternal exposure to high-fat diet is related to abnormalities in TGFß pathway and associated with down-regulated micro-RNA processing. Our study highlighted DGCR8 as a potential therapeutic target for heart diseases related to early exposure to dietary challenge.

Sperm epigenome as a marker of environmental exposure and lifestyle, at the origin of diseases inheritance.

Paternal exposure to environmental challenges plays a critical role in the offspring's future health and the transmission of acquired traits through generations. This review summarizes our current knowledge in the new field of epigenomic paternal transmission of health and disease. Epidemiological studies identified that paternal ageing or challenges (imbalanced diets, stress, toxicants, cigarette smoke, alcohol) increased the risk of offspring to develop diseases such as cancer, metabolic, cardiovascular, and neurological diseases. These data were confirmed and deepened in animal models of exposure to challenges including low-protein, low-folate, high-fat diets, exposure to chemicals such as pesticides and herbicides. Even though some toxicants have mutagenic effect on sperm DNA, changes in sperm epigenome seem to be a common thread between different types of challenges. Indeed, epigenetic changes (DNA methylation, chromatin remodeling, small non-coding RNA) in sperm are described as new mechanisms of intergenerational transmission as demonstrated for dioxin, for example. Those epimutations induce dysregulation in genes expression involved in key cellular pathways such as reactive oxygen species and genome stability regulation, in brain-derived neurotrophic factor, calcium and glucocorticoid signaling, and in lipid and glucose metabolism, leading to diseases in offspring. Finally, since each type of environmental challenges has its own signature by inducing epimutations at specific genomic loci, the sperm epigenome might be used as a biomarker in toxicological and risk assessments.

Offspring of mothers with hyperglycaemia in pregnancy: The short term and long-term impact. What is new?

The continuing rise in the global prevalence of diabetes and overweight or obesity has become a major burden for global health, as the pandemic is affecting both high and low-middle income countries (LMIC). At the same time, a similar pattern has been observed for all forms of hyperglycemia in pregnancy (HIP), diabetes during pregnancy and gestational diabetes. The offspring of mothers with HIP and/or overweight-obesity is receiving increasing attention as advances in early detection and treatment of HIP did not completely prevent macrosomia and its associated short-term perinatal disorders, whilst long term consequences are observed in the mother and in offspring as it reaches adulthood. This review discusses the current developments in the consequences of HIP in the offspring, with a particular focus on its long-term health at adulthood, and on intergenerational and transgenerational effects. HIP is emerging as one of the factors that can contribute, during the window of sensitivity to environmental cues constituted by the preconception, pregnancy, and early childhood, and as an amplifying factor linked to reproduction, to the current global epidemic of diabetes and non-communicable diseases (NCDs).

Perinatal Origins of Adult Disease.

Epidemiological and experimental studies have shown that the peri-conception period, pregnancy, and infancy are windows of particular sensibility to environmental clues which influence lifelong trajectories across health and disease. Nutrition, stress, and toxins induce epigenetic marks that control long-term gene expression patterns and can be transmitted transgenerationally. Chronic diseases of adulthood such as hypertension, diabetes, and obesity thus have early, developmental origins in the perinatal period. The early epigenome, in interaction with other actors such as the microbiome, add powerful layers of diversity to the biological predisposition generated by the genome. Such "programming" is a normal, adaptive component of development, including in normal pregnancies and births. However, perinatal disease, either maternal (such as pre-eclampsia, ges-tational diabetes, or inflammatory disease) or fetal, and neonatal diseases (such as intrauterine growth restriction and preterm birth) are major conditions of altered programming, translated into an increased risk for chronic disease in these patients when they reach adulthood. Early prevention, optimal perinatal nutrition, and specific follow-up measures are key factors in the early preservation of long-term health.

Transient postnatal overfeeding causes liver stress-induced premature senescence in adult mice.

Unbalanced nutrition early in life is increasingly recognized as an important factor in the development of chronic, non-communicable diseases at adulthood, including metabolic diseases. We aimed to determine whether transient postnatal overfeeding (OF) leads to liver stress-induced premature senescence (SIPS) of hepatocytes in association with liver structure and hepatic function alterations. Litters sizes of male C57BL/6 mice were adjusted to 9 pups (normal feeding, NF) or reduced to 3 pups during the lactation period to induce transient postnatal OF. Compared to the NF group, seven-month-old adult mice transiently overfed during the postnatal period were overweight and developed glucose intolerance and insulin resistance. Their livers showed microsteatosis and fibrosis, while hepatic insulin signaling and glucose transporter protein expressions were altered. Increased hepatic oxidative stress (OS) was observed, with increased superoxide anion production, glucose-6-phosphate dehydrogenase protein expression, oxidative DNA damage and decreased levels of antioxidant defense markers, such as superoxide dismutase and catalase proteins. Hepatocyte senescence was characterized by increased p21WAF, p53, Acp53, p16INK4a and decreased pRb/Rb and Sirtuin-1 (SIRT-1) protein expression levels. Transient postnatal OF induces liver OS at adulthood, associated with hepatocyte SIPS and alterations in liver structure and hepatic functions, which could be mediated by a SIRT-1 deficiency.

Developmental epigenetic programming of adult germ cell death disease: Polycomb protein EZH2-miR-101 pathway.

AIM: The Developmental Origin of Health and Disease refers to the concept that early exposure to toxicants or nutritional imbalances during perinatal life induces changes that enhance the risk of developing noncommunicable diseases in adulthood. Patients/materials & methods: An experimental model with an adult chronic germ cell death phenotype resulting from exposure to a xenoestrogen was used. RESULTS: A reciprocal negative feedback loop involving decreased EZH2 protein level and increased miR-101 expression was identified. In vitro and in vivo knockdown of EZH2 induced an apoptotic process in germ cells through increased levels of apoptotic factors (BIM and BAD) and DNA repair alteration via topoisomerase 2B deregulation. The increased miR-101 levels were observed in the animal blood, meaning that miR-101 may be a part of a circulating mark of germ cell death. CONCLUSION: miR-101-EZH2 pathway deregulation could represent a novel pathophysiological epigenetic basis for adult germ cell disease with environmental and developmental origins.

[Developmental and environnemental origin of male infertility: role of endocrine disruptors]. / Origine développementale et environnementale de l'infertilité masculine--Rôle des perturbateurs hormonaux.

Human and wildlife exposure to chemicals is thought to be extensive and particularly to endocrine-disrupting chemicals (EDCs) suspected to alter male reproductive tract. When the exposure occurs during perinatal period (fetal, neonatal periods or puberty) the reproductive health alterations are irreversible suggesting a developmental origin to male infertility. This concept is supported by numerous epidemiologic and experimental studies. This review summarizes the data concerning the epigenetic mechanisms (DNA methylation, chromatin remodelling, small-non coding RNAs) involved in developmentally-induced male infertility. These data open potentially to new diagnosis tools and new trails to assessment of EDCs risks.

Epigenetics and neonatal nutrition.

Epigenetic changes have long-lasting effects on gene expression and are related to, and often induced by, the environment in which early development takes place. In particular, the period of development that extends from pre-conception to early infancy is the period of life during which epigenetic DNA imprinting activity is the most active. Epigenetic changes have been associated with modification of the risk for developing a wide range of adulthood, non-communicable diseases (including cardiovascular diseases, metabolic diseases, diseases of the reproductive system, etc.). This paper reviews the molecular basis of epigenetics, and addresses the issues related to the process of developmental programming of the various areas of human health.

MicroRNAs as potential biomarkers in diseases and toxicology.

MiRNAs (microRNAs) are single-stranded non-coding RNAs of approximately 21-23 nucleotides in length whose main function is to inhibit gene expression by interfering with mRNA processes. MicroRNAs suppress gene expression by affecting mRNA (messenger RNAs) stability, targeting the mRNA for degradation, or both. In this review, we have examined how microRNA expression could be altered following exposure to chemicals and how they could represent appropriate tissue and more interestingly circulating biomarkers. Among the key questions before using the microRNA for evaluation of risk toxicity, it remains still to clarify how they could be causally involved in the adverse effects and how stable their changes are.

Poly(ADP-ribose) binding to Chk1 at stalled replication forks is required for S-phase checkpoint activation.

Damaged replication forks activate poly(ADP-ribose) polymerase 1 (PARP1), which catalyses poly(ADP-ribose) (PAR) formation; however, how PARP1 or poly(ADP-ribosyl)ation is involved in the S-phase checkpoint is unknown. Here we show that PAR, supplied by PARP1, interacts with Chk1 via a novel PAR-binding regulatory (PbR) motif in Chk1, independent of ATR and its activity. iPOND studies reveal that Chk1 associates readily with the unperturbed replication fork and that PAR is required for efficient retention of Chk1 and phosphorylated Chk1 at the fork. A PbR mutation, which disrupts PAR binding, but not the interaction with its partners Claspin or BRCA1, impairs Chk1 and the S-phase checkpoint activation, and mirrors Chk1 knockdown-induced hypersensitivity to fork poisoning. We find that long chains, but not short chains, of PAR stimulate Chk1 kinase activity. Collectively, we disclose a previously unrecognized mechanism of the S-phase checkpoint by PAR metabolism that modulates Chk1 activity at the replication fork.

XIAP as a radioresistance factor and prognostic marker for radiotherapy in human rectal adenocarcinoma.

A differential responsiveness of patients to ionizing radiation is observed after preoperative radiotherapy for rectal adenocarcinoma that might be related, in part, to an apoptosis defect. To establish if proteins of the apoptotic cascades [pro-apoptotic: active caspase 3, 8, and 9 and DIABLO (direct inhibitor of apoptosis-binding protein with low pI); anti-apoptotic: XIAP (X-linked inhibitor of apoptosis)] are involved, we analyzed their profile in radioresistant (SW480) and radiosensitive (SW48) human colorectal cell lines. We demonstrated that, after irradiation, the SW48 cells increased the expression of the pro-apoptotic proteins, whereas the SW480 cells increased the expression of the anti-apoptotic protein XIAP. Moreover, XIAP knockdown in SW480 cells enhanced the basal and radiation-induced apoptotic index; the propensity of the SW480 cells to undergo apoptosis after radiation was higher compared with SW48 cells. In a translational study of 38 patients with rectal carcinoma, we analyzed the apoptotic profile for tumor and noncancerous tissue for each biopsy specimen using IHC. According to their response to preoperative radiotherapy, patients were classified into two groups: responsive and nonresponsive. Although no difference in expression of caspase 3, 8, or 9 was observed in the tumor/normal tissue ratio between responsive and nonresponsive patients, the ratio decreased for DIABLO and increased for XIAP. In conclusion, inhibition of XIAP rescues cellular radiosensitivity and both DIABLO and XIAP might be potential predictive markers of radiation responsiveness in rectal adenocarcinoma.

GPR30, the non-classical membrane G protein related estrogen receptor, is overexpressed in human seminoma and promotes seminoma cell proliferation.

BACKGROUND: Testicular germ cell tumours are the most frequent cancer of young men with an increasing incidence all over the world. Pathogenesis and reasons of this increase remain unknown but epidemiological and clinical data have suggested that fetal exposure to environmental endocrine disruptors (EEDs) with estrogenic effects, could participate to testicular germ cell carcinogenesis. However, these EEDs (like bisphenol A) are often weak ligands for classical nuclear estrogen receptors. Several research groups recently showed that the non classical membrane G-protein coupled estrogen receptor (GPER/GPR30) mediates the effects of estrogens and several xenoestrogens through rapid non genomic activation of signal transduction pathways in various human estrogen dependent cancer cells (breast, ovary, endometrium). The aim of this study was to demonstrate that GPER was overexpressed in testicular tumours and was able to trigger JKT-1 seminoma cell proliferation. RESULTS: We report here for the first time a complete morphological and functional characterization of GPER in normal and malignant human testicular germ cells. In normal adult human testes, GPER was expressed by somatic (Sertoli cells) and germ cells (spermatogonia and spermatocytes). GPER was exclusively overexpressed in seminomas, the most frequent testicular germ cell cancer, localized at the cell membrane and triggered a proliferative effect on JKT-1 cells in vitro, which was completely abolished by G15 (a GPER selective antagonist) and by siRNA invalidation. CONCLUSION: These results demonstrate that GPER is expressed by human normal adult testicular germ cells, specifically overexpressed in seminoma tumours and able to trigger seminoma cell proliferation in vitro. It should therefore be considered rather than classical ERs when xeno-estrogens or other endocrine disruptors are assessed in testicular germ cell cancers. It may also represent a prognosis marker and/or a therapeutic target for seminomas.

Perinatal programming of adult rat germ cell death after exposure to xenoestrogens: role of microRNA miR-29 family in the down-regulation of DNA methyltransferases and Mcl-1.

Different studies have pointed out that developmental exposure to environmental endocrine disruptors can induce long-term testicular germ cell death probably through epigenetic mechanisms. By using a model of early neonatal post-natal day (PND) 1 to 5 exposure of male rats to a xenoestrogen, estradiol benzoate (EB), we investigated the role of microRNA and DNA methyltransferases (DNMT) on the developmental effects of EB on the adult germ cell death process. Neonatal exposure to EB induced adult germ cell apoptosis together with a dose-dependent increase in miR-29a, miR-29b, and miR-29c expression. Increased miR-29 expression resulted in a decrease in DNMT1, DNMT3a, and DNMT3b and antiapoptotic myeloid cell leukemia sequence 1 (Mcl-1) protein levels as shown in 1) germ cells of adult rats exposed neonatally to EB and 2) in spermatogonial GC-1 transfected with miR-29. The DNMT decrease was associated with a concomitant increase in transcript levels of DNA methylation target genes, such as L1td1-1 ORF1 and ORF2, Cdkn2a, and Gstp1, in correlation with their pattern of methylation. Finally, GC-1 cell lines transfection with miR-29a, miR-29b, or miR-29c undergo apoptosis evidenced by Annexin-V expression. Together, the increased miR-29 with a subsequent reduction in DNMT and Mcl-1 protein levels may represent a basis of explanation for the adult expression of the germ cell apoptosis phenotype. These observations suggest that the increased expression of the "apoptomir" miR-29 family represents the upstream mechanism identified until now that is involved in adult germ cell apoptosis induced by a neonatal hormonal disruption.

Alterations of Sertoli cell activity in the long-term testicular germ cell death process induced by fetal androgen disruption.

Fetal androgen disruption, induced by the administration of anti-androgen flutamide (0.4, 2, and 10 mg/kg day) causes a long-term apoptosis in testicular germ cells in adult male rat offspring. One of the questions raised by this observation is the role of the Sertoli cells in the adult germ cell apoptotic process. It is shown here that Sertoli cells originating from 15-day-old rats treated in utero with the anti-androgen (10 mg/kg d) did no longer protect adult germ cells against apoptosis. Indeed, untreated spermatocytes or spermatids exhibited increased (P<0.0001) active caspase-3 levels when co-cultured with Sertoli cells isolated from rat testes exposed in utero to the anti-androgen. This alteration of Sertoli cell functions was not due to modifications in the androgen signal in the adult (90-day-old) animals, since plasma testosterone and estradiol, androgen receptor expression, and androgen-targeted cell number (e.g., Sertoli cells in the seminiferous tubules) were not affected by the fetal androgen disruption. In contrast, this inability of Sertoli cells to protect germ cells against apoptosis could be accounted for by the potential failure of Sertoli cell functions. Indeed, adult testes exposed in utero to anti-androgens displayed decreased levels of several genes mainly expressed in adult Sertoli cells (anti-Mullerian hormone receptor type II (AMHR2), Cox-1, cyclin D2, cathepsin L, and GSTalpha). In conclusion, fetal androgen disruption may induce alterations of Sertoli cell activity probably related to Sertoli cell maturation, which potentially leads to increased adult germ cell apoptosis.

Multiple roles of the nuclear receptors for oxysterols liver X receptor to maintain male fertility.

Oxysterol nuclear receptors liver X receptor (LXR)alpha and LXRbeta are known to regulate lipid homeostasis in cells exposed to high amounts of cholesterol and/or fatty acids. In order to elucidate the specific and redundant roles of the LXRs in the testis, we explored the reproductive phenotypes of mice deficient of LXRalpha, LXRbeta, and both, of which only the lxralpha;beta-/- mice are infertile by 5 months of age. We demonstrate that LXRalpha-deficient mice had lower levels of testicular testosterone that correlated with a higher apoptotic rate of the germ cells. LXRbeta-deficient mice showed increased lipid accumulation in the Sertoli cells and a lower proliferation rate of the germ cells. In lxralpha;beta-/- mice, fatty acid metabolism was affected through a decrease of srebp1c and increase in scd1 mRNA expression. The retinoid acid signaling pathway was also altered in lxralpha;beta-/- mice, with a higher accumulation of all-trans retinoid receptor alpha, all-trans retinoid receptor beta, and retinoic aldehyde dehydrogenase-2 mRNA. Combination of these alterations might explain the deleterious phenotype of infertility observed only in lxralpha;beta-/- mice, even though lipid homeostasis seemed to be first altered. Wild-type mice treated with a specific LXR agonist showed an increase of testosterone production involving both LXR isoforms. Altogether, these data identify new roles of each LXR, collaborating to maintain both integrity and functions of the testis.