A novel fatty acid mimetic with pan-PPAR partial agonist activity inhibits diet-induced obesity and metabolic dysfunction-associated steatotic liver disease.

OBJECTIVE: The prevalence of metabolic diseases is increasing globally at an alarming rate; thus, it is essential that effective, accessible, low-cost therapeutics are developed. Peroxisome proliferator-activated receptors (PPARs) are transcription factors that tightly regulate glucose homeostasis and lipid metabolism and are important drug targets for the treatment of type 2 diabetes and dyslipidemia. We previously identified LDT409, a fatty acid-like compound derived from cashew nut shell liquid, as a novel pan-active PPARα/γ/δ compound. Herein, we aimed to assess the efficacy of LDT409 in vivo and investigate the molecular mechanisms governing the actions of the fatty acid mimetic LDT409 in diet-induced obese mice. METHODS: C57Bl/6 mice (6-11-month-old) were fed a chow or high fat diet (HFD) for 4 weeks; mice thereafter received once daily intraperitoneal injections of vehicle, 10 mg/kg Rosiglitazone, 40 mg/kg WY14643, or 40 mg/kg LDT409 for 18 days while continuing the HFD. During treatments, body weight, food intake, glucose and insulin tolerance, energy expenditure, and intestinal lipid absorption were measured. On day 18 of treatment, tissues and plasma were collected for histological, molecular, and biochemical analysis. RESULTS: We found that treatment with LDT409 was effective at reversing HFD-induced obesity and associated metabolic abnormalities in mice. LDT409 lowered food intake and hyperlipidemia, while improving insulin tolerance. Despite being a substrate of both PPARα and PPARγ, LDT409 was crucial for promoting hepatic fatty acid oxidation and reducing hepatic steatosis in HFD-fed mice. We also highlighted a role for LDT409 in white and brown adipocytes in vitro and in vivo where it decreased fat accumulation, increased lipolysis, induced browning of WAT, and upregulated thermogenic gene Ucp1. Remarkably, LDT409 reversed HFD-induced weight gain back to chow-fed control levels. We determined that the LDT409-induced weight-loss was associated with a combination of increased energy expenditure (detectable before weight loss was apparent), decreased food intake, increased systemic fat utilization, and increased fecal lipid excretion in HFD-fed mice. CONCLUSIONS: Collectively, LDT409 represents a fatty acid mimetic that generates a uniquely favorable metabolic response for the treatment of multiple abnormalities including obesity, dyslipidemia, metabolic dysfunction-associated steatotic liver disease, and diabetes. LDT409 is derived from a highly abundant natural product-based starting material and its development could be pursued as a therapeutic solution to the global metabolic health crisis.

Regulation of Alternative Splicing by Steroid Hormones.

Steroid hormone signaling pathways are critical for organismal development and act through binding to nuclear receptors (NRs) driving transcriptional regulation. In this review, we summarize evidence for another-underrated-mechanism of action for steroid hormones: their ability to modulate the alternative splicing of pre-messenger RNA. Thirty years ago, pioneering studies used in vitro transfection of plasmids expressing alternative exons under the control of hormone-responsive promoters in cell lines. These studies demonstrated that steroid hormones binding to their NRs affected both gene transcription and alternative splicing outcomes. The advent of exon arrays and next-generation sequencing has allowed researchers to observe the effect of steroid hormones at the whole-transcriptome level. These studies demonstrate that steroid hormones regulate alternative splicing in a time-, gene-, and tissue-specific manner. We provide examples of the mechanisms by which steroid hormones regulate alternative splicing including 1) recruitment of dual-function proteins that behave as coregulators and splicing factors, 2) transcriptional regulation of splicing factor levels, 3) the alternative splicing of splicing factors or transcription factors that feed-forward regulate steroid hormone signaling, and 4) regulation of elongation rate. Experiments performed in vivo and in cancer cell lines highlight that steroid hormone-mediated alternative splicing occurs both in physiological and pathophysiologic states. Studying the effect of steroid hormones on alternative splicing is a fruitful avenue for research that should be exploited to discover new targets for therapeutic intervention.

Antagonistic effects of finerenone and spironolactone on the aldosterone-regulated transcriptome of human kidney cells.

Aldosterone, the main mineralocorticoid hormone in humans, plays a pivotal role in the control of water and salt reabsorption via activation of the mineralocorticoid receptor (MR). Alterations in MR signaling pathway lead to renal dysfunction, including chronic kidney disease and renal fibrosis, that can be prevented or treated with mineralocorticoid receptor antagonists (MRAs). Here, we used RNA-Sequencing to analyze effects of two MRAs, spironolactone and finerenone, on the aldosterone-induced transcriptome of a human renal cell line stably expressing the MR. Bioinformatics analysis of the data set reveals the identity of hundreds of genes induced or repressed by aldosterone. Their regulation is modulated in a time-dependent manner and, for the induced genes, depends on the aldosterone-driven direct binding of the MR onto its genomic targets that we have previously characterized. Although both MRAs block aldosterone-induced as well as aldosterone-repressed genes qualitatively similarly, finerenone has a quantitatively more efficient antagonism on some aldosterone-induced genes. Our data provide the first complete transcriptome for aldosterone on a human renal cell line and identifies pro-inflammatory markers (IL6, IL11, CCL7, and CXCL8) as aldosterone-repressed genes.

ARGLU1 is a transcriptional coactivator and splicing regulator important for stress hormone signaling and development.

Stress hormones bind and activate the glucocorticoid receptor (GR) in many tissues including the brain. We identified arginine and glutamate rich 1 (ARGLU1) in a screen for new modulators of glucocorticoid signaling in the CNS. Biochemical studies show that the glutamate rich C-terminus of ARGLU1 coactivates multiple nuclear receptors including the glucocorticoid receptor (GR) and the arginine rich N-terminus interacts with splicing factors and binds to RNA. RNA-seq of neural cells depleted of ARGLU1 revealed significant changes in the expression and alternative splicing of distinct genes involved in neurogenesis. Loss of ARGLU1 is embryonic lethal in mice, and knockdown in zebrafish causes neurodevelopmental and heart defects. Treatment with dexamethasone, a GR activator, also induces changes in the pattern of alternatively spliced genes, many of which were lost when ARGLU1 was absent. Importantly, the genes found to be alternatively spliced in response to glucocorticoid treatment were distinct from those under transcriptional control by GR, suggesting an additional mechanism of glucocorticoid action is present in neural cells. Our results thus show that ARGLU1 is a novel factor for embryonic development that modulates basal transcription and alternative splicing in neural cells with consequences for glucocorticoid signaling.

Glucocorticoids stimulate hypothalamic dynorphin expression accounting for stress-induced impairment of GnRH secretion during preovulatory period.

Stress-induced reproductive dysfunction is frequently associated with increased glucocorticoid (GC) levels responsible for suppressed GnRH/LH secretion and impaired ovulation. Besides the major role of the hypothalamic kisspeptin system, other key regulators may be involved in such regulatory mechanisms. Herein, we identify dynorphin as a novel transcriptional target of GC. We demonstrate that only priming with high estrogen (E2) concentrations prevailing during the late prooestrus phase enables stress-like GC concentrations to specifically stimulate Pdyn (prodynorphin) expression both in vitro (GT1-7 mouse hypothalamic cell line) and ex vivo (ovariectomized E2-supplemented mouse brains). Our results indicate that stress-induced GC levels up-regulate dynorphin expression within a specific kisspeptin neuron-containing hypothalamic region (antero-ventral periventricular nucleus), thus lowering kisspeptin secretion and preventing preovulatory GnRH/LH surge at the end of the prooestrus phase. To further characterize the molecular mechanisms of E2 and GC crosstalk, chromatin immunoprecipitation experiments and luciferase reporter gene assays driven by the proximal promoter of Pdyn show that glucocorticoid receptors bind specific response elements located within the Pdyn promoter, exclusively in presence of E2. Altogether, our work provides novel understanding on how stress affects hypothalamic-pituitary-gonadal axis and underscores the role of dynorphin in mediating GC inhibitory actions on the preovulatory GnRH/LH surge to block ovulation.

Corticosteroid receptors adopt distinct cyclical transcriptional signatures.

Mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) are two closely related hormone-activated transcription factors that regulate major pathophysiologic functions. High homology between these receptors accounts for the crossbinding of their corresponding ligands, MR being activated by both aldosterone and cortisol and GR essentially activated by cortisol. Their coexpression and ability to bind similar DNA motifs highlight the need to investigate their respective contributions to overall corticosteroid signaling. Here, we decipher the transcriptional regulatory mechanisms that underlie selective effects of MRs and GRs on shared genomic targets in a human renal cellular model. Kinetic, serial, and sequential chromatin immunoprecipitation approaches were performed on the period circadian protein 1 ( PER1) target gene, providing evidence that both receptors dynamically and cyclically interact at the same target promoter in a specific and distinct transcriptional signature. During this process, both receptors regulate PER1 gene by binding as homo- or heterodimers to the same promoter region. Our results suggest a novel level of MR-GR target gene regulation, which should be considered for a better and integrated understanding of corticosteroid-related pathophysiology.-Le Billan, F., Amazit, L., Bleakley, K., Xue, Q.-Y., Pussard, E., Lhadj, C., Kolkhof, P., Viengchareun, S., Fagart, J., Lombès, M. Corticosteroid receptors adopt distinct cyclical transcriptional signatures.

Three Novel Heterozygous Point Mutations of NR3C1 Causing Glucocorticoid Resistance.

Generalized glucocorticoid resistance is associated with glucocorticoid receptor (GR; NR3C1) mutations. Three novel heterozygous missense NR3C1 mutations (R477S, Y478C, and L672P) were identified in patients presenting with adrenal incidentalomas, glucocorticoid excess without Cushing syndrome. Dexamethasone (DXM) binding studies demonstrated that the affinity of GRR477S and GRY478C mutants, located in the DNA-binding domain (DBD) of GR, was similar to wild-type GR (Kd  = 2-3 nM). In contrast, GRL672P mutant, located in the ligand-binding domain (LBD) of GR, was unable to bind glucocorticoids and was more sensitive to protein degradation. GR subcellular distribution revealed a marked decrease in DXM-induced nuclear translocation of GRR477S and GRY478C mutants, whereas GRL672P remained exclusively cytoplasmic. Chromatin immunoprecipitation demonstrated impaired recruitment of DBD mutants onto the regulatory sequence of FKBP5. Transactivation assays disclosed the lack of transcriptional activity of GRR477S and GRL672P , whereas GRY478C had a reduced transactivation capacity. Three-dimensional modeling indicated that R477S lost two essential hydrogen bonds with DNA, Y478C resulted in altered interaction with surrounding amino-acids, destabilizing DBD, whereas L672P altered the H8 helix folding, leading to unstructured LBD. This study identifies novel NR3C1 mutations with their molecular consequences on altered GR signaling and suggests that genetic screening of NR3C1 should be conducted in patients with subclinical hypercorticism.

Ulipristal Acetate Inhibits Progesterone Receptor Isoform A-Mediated Human Breast Cancer Proliferation and BCl2-L1 Expression.

The progesterone receptor (PR) with its isoforms and ligands are involved in breast tumorigenesis and prognosis. We aimed at analyzing the respective contribution of PR isoforms, PRA and PRB, in breast cancer cell proliferation in a new estrogen-independent cell based-model, allowing independent PR isoforms analysis. We used the bi-inducible human breast cancer cell system MDA-iPRAB. We studied the effects and molecular mechanisms of action of progesterone (P4) and ulipristal acetate (UPA), a new selective progesterone receptor modulator, alone or in combination. P4 significantly stimulated MDA-iPRA expressing cells proliferation. This was associated with P4-stimulated expression of the anti-apoptotic factor BCL2-L1 and enhanced recruitment of PRA, SRC-1 and RNA Pol II onto the +58 kb PR binding motif of the BCL2-L1 gene. UPA decreased cell proliferation and repressed BCL2-L1 expression in the presence of PRA, correlating with PRA and SRC1 but not RNA Pol II recruitment. These results bring new information on the mechanism of action of PR ligands in controlling breast cancer cell proliferation through PRA in an estrogen independent model. Evaluation of PR isoforms ratio, as well as molecular signature studies based on PRA target genes could be proposed to facilitate personalized breast cancer therapy. In this context, UPA could be of interest in endocrine therapy. Further confirmation in the clinical setting is required.

Finerenone Impedes Aldosterone-dependent Nuclear Import of the Mineralocorticoid Receptor and Prevents Genomic Recruitment of Steroid Receptor Coactivator-1.

Aldosterone regulates sodium homeostasis by activating the mineralocorticoid receptor (MR), a member of the nuclear receptor superfamily. Hyperaldosteronism leads todeleterious effects on the kidney, blood vessels, and heart. Although steroidal antagonists such as spironolactone and eplerenone are clinically useful for the treatment of cardiovascular diseases, they are associated with several side effects. Finerenone, a novel nonsteroidal MR antagonist, is presently being evaluated in two clinical phase IIb trials. Here, we characterized the molecular mechanisms of action of finerenone and spironolactone at several key steps of the MR signaling pathway. Molecular modeling and mutagenesis approaches allowed identification of Ser-810 and Ala-773 as key residues for the high MR selectivity of finerenone. Moreover, we showed that, in contrast to spironolactone, which activates the S810L mutant MR responsible for a severe form of early onset hypertension, finerenone displays strict antagonistic properties. Aldosterone-dependent phosphorylation and degradation of MR are inhibited by both finerenone and spironolactone. However, automated quantification of MR subcellular distribution demonstrated that finerenone delays aldosterone-induced nuclear accumulation of MR more efficiently than spironolactone. Finally, chromatin immunoprecipitation assays revealed that, as opposed to spironolactone, finerenone inhibits MR, steroid receptor coactivator-1, and RNA polymerase II binding at the regulatory sequence of the SCNN1A gene and also remarkably reduces basal MR and steroid receptor coactivator-1 recruitment, unraveling a specific and unrecognized inactivating mechanism on MR signaling. Overall, our data demonstrate that the highly potent and selective MR antagonist finerenone specifically impairs several critical steps of the MR signaling pathway and therefore represents a promising new generation MR antagonist.

Cistrome of the aldosterone-activated mineralocorticoid receptor in human renal cells.

Aldosterone exerts its effects mainly by activating the mineralocorticoid receptor (MR), a transcription factor that regulates gene expression through complex and dynamic interactions with coregulators and transcriptional machinery, leading to fine-tuned control of vectorial ionic transport in the distal nephron. To identify genome-wide aldosterone-regulated MR targets in human renal cells, we set up a chromatin immunoprecipitation (ChIP) assay by using a specific anti-MR antibody in a differentiated human renal cell line expressing green fluorescent protein (GFP)-MR. This approach, coupled with high-throughput sequencing, allowed identification of 974 genomic MR targets. Computational analysis identified an MR response element (MRE) including single or multiple half-sites and palindromic motifs in which the AGtACAgxatGTtCt sequence was the most prevalent motif. Most genomic MR-binding sites (MBSs) are located >10 kb from the transcriptional start sites of target genes (84%). Specific aldosterone-induced recruitment of MR on the first most relevant genomic sequences was further validated by ChIP-quantitative (q)PCR and correlated with concomitant and positive aldosterone-activated transcriptional regulation of the corresponding gene, as assayed by RT-qPCR. It was notable that most MBSs lacked MREs but harbored DNA recognition motifs for other transcription factors (FOX, EGR1, AP1, PAX5) suggesting functional interaction. This work provides new insights into aldosterone MR-mediated renal signaling and opens relevant perspectives for mineralocorticoid-related pathophysiology.