Steroid Response Elements Research Articles

Quantitative Evaluation of the Transcriptional Activity of Steroid Hormone Receptor Mutants and Variants Using a Single Vector With Two Reporters and a Receptor Expression Cassette.

Although the rapid development of high-throughput sequencing has led to the identification of a large number of truncated or mutated steroid hormone receptor (SHR) variants, their clinical relevance remains to be defined. A platform for functional analysis of these SHR variants in cells would be instrumental for better assessing their impact on normal physiology and SHR-associated diseases. Here we have developed a new reporter system that allows rapid and accurate assessment of the transcriptional activity of SHR variants in cells. The reporter is a single construct containing a firefly luciferase reporter gene, whose expression is under the control of a promoter with multiple steroid hormone responsive elements, and a Renilla luciferase reporter gene, that is constitutively expressed under the control of an internal ribosome entry site (IRES) and is not regulated by steroid hormones. The corresponding SHR (wildtype or mutant/variant) is also expressed from the same construct. Using this improved reporter system, we revealed a large spectrum of transactivation activities within a set of previously identified mutations and variations of the androgen receptor (AR), the estrogen receptor α (ERα) and the glucocorticoid receptor (GR). This novel reporter system enables functional analysis of SHR mutants and variants in physiological and pathological settings, offering valuable preclinical, or diagnostic information for the understanding and treatment of associated diseases.

Procyanidin B2 protects against diet-induced obesity and non-alcoholic fatty liver disease via the modulation of the gut microbiota in rabbits.

BACKGROUNDProcyanidins have beneficial effects on metabolic syndrome and antimicrobial activity, but the mechanisms underlying these effects are unclear.AIMTo investigate the effects of procyanidin B2 (PB2) on non-alcoholic fatty liver disease and to explore the possible mechanism.METHODSThirty male New Zealand white rabbits were randomized into three groups. All of them were fed either a high-fat-cholesterol diet (HCD) or chow diet. HCD-fed rabbits were treated with vehicle or PB2 daily for 12 wk. Body weight and food intake were evaluated once a week. Serum biomarkers, such as total cholesterols, triglycerides, and aspartate transaminase, were detected. All rabbits were sacrificed and histological parameters of liver were assessed by hematoxylin and eosin-stained sections. Moreover, several lipogenic genes and gut microbiota (by 16S rRNA sequencing) were investigated to explore the possible mechanism.RESULTSThe HCD group had higher body weight, liver index, serum lipid profile, insulin resistance, serum glucose, and hepatic steatosis compared to the CHOW group. PB2 treatment prevented HCD-induced increases in body weight and hypertriglyceridemia in association with triglyceride accumulation in the liver. PB2 also ameliorated low-grade inflammation, which was reflected by serum lipopolysaccharides and improved insulin resistance. In rabbit liver, PB2 prevented the upregulation of steroid response element binding protein 1c and fatty acid synthase and the downregulation of carnitine palmitoyltransferase, compared to the HCD group. Moreover, HCD led to a decrease of Bacteroidetes in gut microbiota. PB2 significantly improved the proportions of Bacteroidetes at the phylum level and Akkermansia at the genus level.CONCLUSIONOur results indicate the possible mechanism of PB2 to improve HCD-induced features of metabolic syndrome and provide a new dietary supplement.

Theca Cell INSL3 and Steroids Together Orchestrate the Growing Bovine Antral Follicle.

Insulin-like peptide 3 (INSL3) and its specific receptor RXFP2 are both expressed by theca interna cells of the growing antral follicle where they form an essential regulatory element in the production of the steroid precursor androstenedione. Using primary cultures of bovine theca cells from the mid follicular phase together with steroid agonists and antagonists we have examined how ovarian steroids modulate INSL3 expression. Transcript analysis shows that these cells express estrogen receptors α and β, androgen and progesterone receptors, besides the orphan nuclear receptors SF1 and nur77. Whereas, exogenous androgens have little or no effect, the androgen antagonist bicalutamide stimulates INSL3 production. In contrast, estrogen receptor agonists, as also progesterone, are stimulatory. Importantly, estrogen receptor signaling is convergent with the protein kinase A signaling pathway activated by LH, such that the estrogen receptor antagonist can inhibit the mild stimulatory effect of LH, and vice versa the PKA antagonist H89 blocks stimulation by estradiol. A significant finding is that the major steroid metabolite androstenedione appears to act predominantly as an estrogen and not an androgen in this system. Transfection of INSL3 gene promoter-reporter constructs together with various steroid receptor expression plasmids supports these findings and shows that steroid action uses non-classical pathways not requiring canonical steroid-responsive elements in the proximal promoter region. Together, the results indicate that increasing estrogens in the follicular phase stimulate a feedforward loop driving INSL3 signaling and thereby promoting steroidogenesis in the growing antral follicle until the LH surge which effectively switches off INSL3 expression.

Dietary flavones counteract 5'-adenosine monophosphate-activated protein kinase-independent steroid response element binding protein-2 processing in cultured hepatocytes

Consumption of fruits and vegetables is generally regarded as beneficial to plasma lipid profile. The mechanism by which the plant foods induce desirable lipid changes remains unclear. Steroid response element binding protein-2 (SREBP-2) is a crucial in cholesterol metabolism, and it is a major regulator of the cholesterol biosynthesis enzyme HMG CoA reductase (HMGCR). Our lab has previously illustrated that apigenin[1] and luteolin[2] could attenuate the nuclear translocation of SREBP-2 through an adenosine monophosphate-activated protein kinase (AMPK)-dependent pathway. In the present study, these two flavones were studied for their ability to deter the same in an AMPK-independent signaling route. The processing of SREBP-2 protein was promoted by phorbol 12-myristate 13-acetate (PMA) in the hepatic cells WRL and HepG2, and the increased processing was reversed by apigenin or luteolin co-administration. Electromobility shift assay results demonstrated that the PMA-induced DNA-binding activity was weakened by the flavones. The increased amount of nuclear SREBP-2 in cells was attenuated by the flavonoid as shown by immunocytochemical imaging. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay demonstrated that the transcription of HMGCR under both flavone treatments was reduced. However, apigenin appeared to be stronger than luteolin in restraining PMA-induced HMGCR mRNA expression. Because PMA is a diacylglycerol (DAG) analogue, these findings might have significant implications on conditions like overeating and obesity, leading to hepatic accumulation of DAG.

Phorbol 12-myristate 13-acetate promotes nuclear translocation of hepatic steroid response element binding protein-2

Sterol regulatory element-binding protein (SREBP)-2 is a pivotal transcriptional factor in cholesterol metabolism. Factors interfering with the proper functioning of SREBP-2 potentially alter plasma lipid profiles. Phorbol 12-myristate 13-acetate (PMA), which is a common protein kinase C (PKC) activator, was shown to promote the post-translational processing and nuclear translocation of SREBP-2 in hepatic cells in the current study. Following SREBP-2 translocation, the transcripts of its target genes HMGCR and LDLR were upregulated as demonstrated by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay. Electrophoretic mobility shift assays (EMSA) also demonstrated an induced DNA-binding activity on the sterol response element (SRE) domain under PMA treatment. The increase of activated Srebp-2 without the concurrent induced mRNA expression was also observed in an animal model. As the expression of SREBP-2 was not increased by PMA, the activation of PKC was the focus of investigation. Specific PKC isozyme inhibition and overexpression supported that PKCβ was responsible for the promoting effect. Further studies showed that the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinases (ERK) and c-Jun N-terminal kinases (JNK), but not 5′ adenosine monophosphate-activated protein kinase (AMPK), were the possible downstream signaling proteins of PKCβ. In conclusion, this study illustrated that PKCβ increased SREBP-2 nuclear translocation in a pathway mediated by MEK/ERK and JNK, rather than the one dictated by AMPK. These results revealed a novel signaling target of PKCβ in the liver cells.

Minireview: neural signaling of estradiol in the hypothalamus.

Many of the actions of estradiol in the central nervous system (CNS) are mediated via intracellular estrogen receptors (ERs)/transcription factors that interact with steroid response elements on target genes. In addition, there is compelling evidence for membrane-associated ERs in hypothalamic and other CNS neuron; but it is not well understood how estradiol signals via membrane-associated receptors and how these signals impact neuronal excitability and physiological functions. It has been known for some time that estradiol can rapidly alter neuronal activity within seconds, indicating that some cellular effects can occur via membrane initiated events. Thus, estradiol can affect second messenger systems, including calcium mobilization and a plethora of kinases to alter cell excitability and even gene transcription in hypothalamic neurons. Therefore, this minireview will summarize our current knowledge of rapid membrane-initiated and intracellular signaling by estradiol in the hypothalamus, the nature of receptors involved, and how they contribute not only to control of reproduction but other vital homeostatic functions.

Evolution of DNA Specificity in a Transcription Factor Family Produced a New Gene Regulatory Module

Complex gene regulatory networks require transcription factors (TFs) to bind distinct DNA sequences. To understand how novel TF specificity evolves, we combined phylogenetic, biochemical, and biophysical approaches to interrogate how DNA recognition diversified in the steroid hormone receptor (SR) family. After duplication of the ancestral SR, three mutations in one copy radically weakened binding to the ancestral estrogen response element (ERE) and improved binding to a new set of DNA sequences (steroid response elements, SREs). They did so by establishing unfavorable interactions with ERE and abolishing unfavorable interactions with SRE; also required were numerous permissive substitutions, which nonspecifically improved cooperativity and affinity of DNA binding. Our findings indicate that negative determinants of binding play key roles in TFs' DNA selectivity and-with our prior work on the evolution of SR ligand specificity during the same interval-show how a specific new gene regulatory module evolved without interfering with the integrity of the ancestral module.

Design and characterization of a dual-mode promoter with activation and repression capability for tuning gene expression in yeast.

Modularity in controlling gene expression artificially is becoming an essential aspect of synthetic biology. Artificial transcriptional control of gene expression is one of the most well-developed methods for the design of novel synthetic regulatory networks. Such networks are intended to help understand natural cellular phenomena and to enable new biotechnological applications. Promoter sequence manipulation with cis-regulatory elements is a key approach to control gene expression transcriptionally. Here, we have designed a promoter that can be both activated and repressed, as a contribution to the library of synthetic biological ‘parts’. Starting with the minimal cytochrome C (minCYC) promoter in yeast, we incorporated five steroid hormone responsive elements (SHREs) and one lac operator site, respectively, upstream and downstream of the TATA box. This allows activation through the testosterone-responsive androgen receptor, and repression through the LacI repressor. Exposure to varying concentrations of testosterone (to vary activation) and IPTG (to vary repression) demonstrated the ability to tune the promoter's output curve over a wide range. By integrating activating and repressing signals, the promoter permits a useful form of signal integration, and we are optimistic that it will serve as a component in future regulatory networks, including feedback controllers.

Characterization of sea bass FSHβ 5′ flanking region: transcriptional control by 17β-estradiol

The sea bass follicle-stimulating hormone 5' flanking region (sbFSHβ 5' FR) was cloned and characterized in order to study the molecular mechanisms underlying transcriptional regulation of the sbFSHβ gene. Analysis of the ~3.5kb of this region revealed the presence of several putative cis-acting elements, including steroid hormone response elements, cAMP response elements, pituitary-specific transcription factor response elements, activator protein-1 response elements and TATA sequence. Deleted constructs containing ~3.5kb of the sbFSHβ 5' FR fused to a luciferase reporter gene were transiently transfected into human embryonic kidney (HEK 293) and mouse mature gonadotrope (LβT2) cell lines. The sbFSHβ 5' FR was efficiently expressed under basal conditions in LβT2 but not in HEK 293, pointing to both positive and negative regulatory elements. In order to elucidate the estrogen-mediated sbFSHβ transcriptional activity, in vitro treatments with 17β-estradiol were carried out on primary cultures of pituitary cells and LβT2 cells transiently expressing luciferase under the control of sbFSHβ 5' FR. Overall, these results demonstrate that 17β-estradiol inhibits sbFSHβ gene expression directly at the level of the pituitary. However, it was also shown that estrogen did not induce changes of the sbFSH promoter-directed luciferase activity, suggesting that sbFSHβ 5'FR (~3.5kb) activity is cell type dependent and its estrogen regulation could require cis-acting elements located upstream of the promoter region, which is characterized in this article.

C/EBP maintains chromatin accessibility in liver and facilitates glucocorticoid receptor recruitment to steroid response elements

Mechanisms regulating transcription factor interaction with chromatin in intact mammalian tissues are poorly understood. Exploiting an adrenalectomized mouse model with depleted endogenous glucocorticoids, we monitor changes of the chromatin landscape in intact liver tissue following glucocorticoid injection. Upon activation of the glucocorticoid receptor (GR), proximal regions of activated and repressed genes are remodelled, and these remodelling events correlate with RNA polymerase II occupancy of regulated genes. GR is exclusively associated with accessible chromatin and 62% percent of GR-binding sites are occupied by C/EBPβ. At the majority of these sites, chromatin is preaccessible suggesting a priming function of C/EBPβ for GR recruitment. Disruption of C/EBPβ binding to chromatin results in attenuation of pre-programmed chromatin accessibility, GR recruitment and GR-induced chromatin remodelling specifically at sites co-occupied by GR and C/EBPβ. Collectively, we demonstrate a highly cooperative mechanism by which C/EBPβ regulates selective GR binding to the genome in liver tissue. We suggest that selective targeting of GR in other tissues is likely mediated by the combined action of cell-specific priming proteins and chromatin remodellers.

A selective membrane estrogen receptor agonist maintains autonomic functions in hypoestrogenic states

It is well known that many of the actions of estrogens in the central nervous system are mediated via intracellular receptor/transcription factors that interact with steroid response elements on target genes. But there is also a compelling evidence for the involvement of membrane estrogen receptors in hypothalamic and other CNS functions. However, it is not well understood how estrogens signal via membrane receptors, and how these signals impact not only membrane excitability but also gene transcription in neurons. Indeed, it has been known for sometime that estrogens can rapidly alter neuronal activity within seconds, indicating that some cellular effects can occur via membrane delimited events. In addition, estrogens can affect second messenger systems including calcium mobilization and a plethora of kinases within neurons to alter cellular functions. Therefore, this brief review will summarize our current understanding of rapid membrane-initiated and intracellular signaling by estrogens in the hypothalamus, the nature of receptors involved and how these receptors contribute to maintenance of homeostatic functions, many of which go awry in menopausal states.This article is part of a Special Issue entitled Hormone Therapy.

Membrane-initiated actions of estradiol that regulate reproduction, energy balance and body temperature

It is well known that many of the actions of estrogens in the central nervous system are mediated via intracellular receptor/transcription factors that interact with steroid response elements on target genes. However, there now exists compelling evidence for membrane estrogen receptors in hypothalamic and other brain neurons. But, it is not well understood how estrogens signal via membrane receptors, and how these signals impact not only membrane excitability but also gene transcription in neurons. Indeed, it has been known for sometime that estrogens can rapidly alter neuronal activity within seconds, indicating that some cellular effects can occur via membrane delimited events. In addition, estrogens can affect second messenger systems including calcium mobilization and a plethora of kinases to alter cell signaling. Therefore, this review will consider our current knowledge of rapid membrane-initiated and intracellular signaling by estrogens in the hypothalamus, the nature of receptors involved and how they contribute to homeostatic functions.

20β-hydroxysteroid dehydrogenase gene promoter: Potential role for cyclic AMP and xenobiotic responsive elements

Teleostean 20β-hydroxysteroid dehydrogenase (20β-HSD) is involved in final oocyte maturation and steroid hormone metabolism. It has structural and functional similarities to mammalian carbonyl reductases that are involved in the metabolism of endogenous carbonyl and xenobiotic compounds. To understand the transcriptional regulation of 20β-HSD, here we report the cloning of 20β-HSD promoter from two fish species, rainbow trout and air-breathing catfish. Analysis of the promoter motifs, in silico identified the presence of several sites for transcription factor binding including cAMP, xenobiotic and steroid hormone responsive elements. Luciferase reporter assays with progressive deletion constructs demonstrated that 20β-HSD type B of trout has no promoter activity while 20β-HSD type A of trout and catfish 20β-HSD promoters showed basal promoter activity. A TATA box flanked by a CAAT box is important for basal transcription. Deletion of cAMP responsive element in the promoter decreased basal promoter activity significantly. Reporter assays with forskolin and IBMX, drugs that increase intracellular cAMP induced the promoter activity over the basal level. Intriguingly, β-nafthoflavone, an arylhydrocarbon receptor ligand, induced the 20β-HSD promoter activity and is further evidenced by the induction of 20β-HSD expression in the livers of catfish, in vivo. These results demonstrate for the first time that 20β-HSD expression is not only modulated by cAMP but also by xenobiotics and further studies may provide significance to the ubiquitous distribution and broad substrate specificity of this enzyme.

Reply to Scott, Sale, Greeves, and Fraser

to the editor: We thank Scott et al.([1][1]) for their interest in our recent study ([2][2]) that examined the acute response of bone turnover markers to a single bout of resistance training (RT) or plyometrics (PLY). We appreciate the acknowledgement of the strengths of our study design: we

Selective changes of retroelement expression in human prostate cancer

Retroelements constitute a large part of the human genome. These sequences are mostly silenced in normal cells, but genome-wide DNA hypomethylation in cancers might lead to their re-expression. Whether this re-expression really occurs in human cancers is largely unkown. We therefore investigated expression and DNA methylation of several classes of retroelements in human prostate cancer tissues and cell lines by quantitative reverse transcription-polymerase chain reaction and pyrosequencing, respectively. The most striking finding was strong and generalized increased expression of the HERV-K_22q11.23 provirus in cancers, including de novo expression of a spliced accessory Np9 transcript in some tumors. In parallel, DNA methylation in the long terminal repeat (LTR) decreased. Conversely, HERVK17 expression was significantly diminished in cancer tissues, but this decrease was unrelated to LTR methylation. Expression of both proviruses was restricted to androgen-responsive prostate cancer cell lines and LTRs sequences containing steroid hormone-responsive elements bound the androgen receptor and conferred androgen responsiveness to reporter constructs. Expression of LINE-1 5'-untranslated region (UTR) and 3'-UTR sequences in prostate cancers rather decreased, despite significant hypomethylation of the internal LINE-1 promoter. Increased expression of the young AluYa5 and AluYb8 families was restricted to individual tumors. Our findings demonstrate a surprising specificity of changes in expression and DNA methylation of retroelements in prostate cancer. In particular, LINE-1 hypomethylation does not lead to generalized overexpression, but specific human endogenous retrovirus-K proviruses display conspicuous changes in their expression hinting at significant functions during prostate carcinogenesis.

Two Panels of Steroid Receptor Luciferase Reporter Cell Lines for Compound Profiling

Steroid hormone receptors represent a major target in drug discovery. As ligand inducible transcription factors, their activity can be modulated by small lipophilic molecules. Here we describe two panels of potent and selective luciferase reporter cell lines based on cells with low endogenous steroid receptor activity (U2OS). The panels contain reporter cell lines for estrogen receptors α and β, androgen, glucocorticoid, mineralocorticoid, and progesterone receptors. In the first panel, the activation of either synthetic, steroid response elements containing promoter or viral promoter is mediated by full-length steroid receptors. The second panel is based on the expression of the chimeric receptor, which was created by the replacement of the N-terminal part of the molecule by Gal4 DBD and that binds to multiple UAS sites in the reporter promoter. Both panels were extensively characterized by profiling 28 ligands in dose response manner in agonist and antagonist mode. We have analyzed and compared the responses to tested ligands from both panels and concluded that in general both systems generated similar qualitative response in terms of potency, efficacy, partial agonism/antagonism, mixed agonistic/antagonistic profiles and the rank of potencies was well conserved between both panels. However, we have also identified some artifacts introduced by the Gal4/LBD reporter assays in contrast to their full-length receptor reporter counterparts. Keeping in mind the advantages and drawbacks of each reporter format, these cell lines represent powerful and selective tools for profiling large compound libraries (HTS) and for detailed study of mechanisms by which compounds exert their biological effects.

Functional Single-Nucleotide Polymorphism in Acetyl-CoA Carboxylase ACACB Gene Promoter

The acetyl-CoA carboxylase isoform ACC2 expressed in the liver generates malonyl-CoA, which primarily regulates fatty acid oxidation through inhibition of the mitochondrial carrier carnitine palmitoyl-CoA transferase-I. Activity is initiated by sterol regulatory element-binding protein-1 (SREBP-1) binding to steroid response elements SRE in ACACB gene promoter P-II. We proposed that sequence variation in the promoter might affect expression. We investigated the effect of a single-nucleotide polymorphism -368 C/T (rs16939972) in ACACB P-II on activity in transfected HepG2 hepatoma cells. The T-allele construct showed significantly lower activity than the C-allele (p = 0.016) but only in the presence of SREBP-1a overexpression. Electrophoretic mobility shift assays showed that HepG2 nuclear proteins bound specifically to both allele probes, but with higher affinity to the T-allele. We tested competition for nuclear protein binding between the T-allele probe and unlabeled probes containing consensus sequences for six candidate transcription factors plus SREBP-1a. The SREBP-1a competitor probe had no effect on the shifted complex. GATA, c-Myb, and GR competitor probes abolished the complex; however, these proteins were undetectable in mass spectrometry of gel extracts from shifted bands. In conclusion, the -368 C/T single-nucleotide polymorphism in ACACB P-II binds HepG2 nuclear proteins that affect promoter activity in an allele-specific fashion.

Histone H1 phosphorylation is associated with transcription by RNA polymerases I and II

Histone H1 phosphorylation affects chromatin condensation and function, but little is known about how specific phosphorylations impact the function of H1 variants in higher eukaryotes. In this study, we show that specific sites in H1.2 and H1.4 of human cells are phosphorylated only during mitosis or during both mitosis and interphase. Antisera generated to individual H1.2/H1.4 interphase phosphorylations reveal that they are distributed throughout nuclei and enriched in nucleoli. Moreover, interphase phosphorylated H1.4 is enriched at active 45S preribosomal RNA gene promoters and is rapidly induced at steroid hormone response elements by hormone treatment. Our results imply that site-specific interphase H1 phosphorylation facilitates transcription by RNA polymerases I and II and has an unanticipated function in ribosome biogenesis and control of cell growth. Differences in the numbers, structure, and locations of interphase phosphorylation sites may contribute to the functional diversity of H1 variants.

Do GnRH analogues directly affect human endometrial epithelial cell gene expression?

We examined whether Gonadotrophin-releasing hormone (GnRH) analogues [leuprolide acetate (LA) and ganirelix acetate (GA)] modulate gene expression in Ishikawa cells used as surrogate for human endometrial epithelial cells in vitro. The specific aims were: (i) to study the modulatory effect of GnRH analogues by RT-PCR [in the absence and presence of E(2) and P4, and cyclic adenosine monophosphate (cAMP)] on mRNA expression of genes modulated during the window of implantation in GnRH analogues/rFSH-treated assisted reproductive technology cycles including OPTINEURIN (OPTN), CHROMATIN MODIFYING PROTEIN (CHMP1A), PROSAPOSIN (PSAP), IGFBP-5 and SORTING NEXIN 7 (SNX7), and (ii) to analyze the 5'-flanking regions of such genes for the presence of putative steroid-response elements [estrogen-response elements (EREs) and P4-response element (PREs)]. Ishikawa cells were cytokeratin+/vimentin- and expressed ERalpha, ERbeta, PR and GnRH-R proteins. At 6 and 24 h, neither LA nor GA alone had an effect on gene expression. GnRH analogues alone or following E(2) and/or P4 co-incubation for 24 h also had no effect on gene expression, but P4 significantly increased expression of CHMP1A. E(2) + P4 treatment for 4 days, alone or followed by GA, had no effect, but E(2) + P4 treatment followed by LA significantly decreased IGFBP-5 expression. The addition of 8-Br cAMP did not modify gene expression, with the exception of IGFBP-5 that was significantly increased. The GnRH analogues did not modify intracellular cAMP levels. We identified conserved EREs for OPN, CHMP1A, SNX7 and PSAP and PREs for SNX7. We conclude that GnRH analogues appear not to have major direct effects on gene expression of human endometrial epithelial cells in vitro.

Dietary procyanidins enhance transcriptional activity of bile acid‐activated FXR in vitro and reduce triglyceridemia in vivo in a FXR‐dependent manner

Consumption of dietary flavonoids has been associated with reduced mortality and risk of cardiovascular disease, partially by reducing triglyceridemia. We have previously reported that a grape seed procyanidin extract (GSPE) reduces postprandial triglyceridemia in normolipidemic animals signaling through the orphan nuclear receptor small heterodimer partner (SHP) a target of the bile acid receptor farnesoid X receptor (FXR). Our aim was to elucidate whether FXR mediates the hypotriglyceridemic effect of procyanidins. In FXR-driven luciferase expression assays GSPE dose-dependently enhanced FXR activity in the presence of chenodeoxycholic acid. GSPE gavage reduced triglyceridemia in wild type mice but not in FXR-null mice, revealing FXR as an essential mediator of the hypotriglyceridemic actions of procyanidins in vivo. In the liver, GSPE downregulated, in an FXR-dependent manner, the expression of the transcription factor steroid response element binding protein 1 (SREBP1) and several SREBP1 target genes involved in lipogenesis, and upregulated ApoA5 expression. Altogether, our results indicate that procyanidins lower triglyceridemia following the same pathway as bile acids: activation of FXR, transient upregulation of SHP expression and subsequent downregulation of SREBP1 expression. This study adds dietary procyanidins to the arsenal of FXR ligands with potential therapeutic use to combat hypertriglyceridemia, type 2 diabetes and metabolic syndrome.