Alpha lipoamide inhibits diabetic kidney fibrosis via improving mitochondrial function and regulating RXRα expression and activation.

Previous studies have shown mitochondrial dysfunction in various acute kidney injuries and chronic kidney diseases. Lipoic acid exerts potent effects on oxidant stress and modulation of mitochondrial function in damaged organ. In this study we investigated whether alpha lipoamide (ALM), a derivative of lipoic acid, exerted a renal protective effect in a type 2 diabetes mellitus mouse model. 9-week-old db/db mice were treated with ALM (50 mg·kg-1·d-1, i.g) for 8 weeks. We showed that ALM administration did not affect blood glucose levels in db/db mice, but restored renal function and significantly improved fibrosis of kidneys. We demonstrated that ALM administration significantly ameliorated mitochondrial dysfunction and tubulointerstitial fibrotic lesions, along with increased expression of CDX2 and CFTR and decreased expression of ß-catenin and Snail in kidneys of db/db mice. Similar protective effects were observed in rat renal tubular epithelial cell line NRK-52E cultured in high-glucose medium following treatment with ALM (200 µM). The protective mechanisms of ALM in diabetic kidney disease (DKD) were further explored: Autodock Vina software predicted that ALM could activate RXRα protein by forming stable hydrogen bonds. PROMO Database predicted that RXRα could bind the promoter sequences of CDX2 gene. Knockdown of RXRα expression in NRK-52E cells under normal glucose condition suppressed CDX2 expression and promoted phenotypic changes in renal tubular epithelial cells. However, RXRα overexpression increased CDX2 expression which in turn inhibited high glucose-mediated renal tubular epithelial cell injury. Therefore, we reveal the protective effect of ALM on DKD and its possible potential targets: ALM ameliorates mitochondrial dysfunction and regulates the CDX2/CFTR/ß-catenin signaling axis through upregulation and activation of RXRα. Schematic figure illustrating that ALM alleviates diabetic kidney disease by improving mitochondrial function and upregulation and activation of RXRα, which in turn upregulated CDX2 to exert an inhibitory effect on ß-catenin activation and nuclear translocation. RTEC renal tubular epithelial cell. ROS Reactive oxygen species. RXRα Retinoid X receptor-α. Mfn1 Mitofusin 1. Drp1 dynamic-related protein 1. MDA malondialdehyde. 4-HNE 4-hydroxynonenal. T-SOD Total-superoxide dismutase. CDX2 Caudal-type homeobox transcription factor 2. CFTR Cystic fibrosis transmembrane conductance regulator. EMT epithelial mesenchymal transition. α-SMA Alpha-smooth muscle actin. ECM extracellular matrix. DKD diabetic kidney disease. Schematic figure was drawn by Figdraw ( www.figdraw.com ).

[Effects of hexabromocyclododecanes on retinoid X receptor α, pregnane X receptor and peroxisome proliferator-activated receptor γ].

OBJECTIVE: To investigate the effect of hexabromocyclododecanes( HBCDs) on cell proliferation and the expression of the three important cell nuclear receptor of retinoic X receptor α( RXRα), peroxisome proliferator-activated receptor-γ( PPARγ), pregnane X receptor( PXR) and their interaction in Neuro-2a(N2a). METHODS: Neuro-2a cells were treated with different concentrations of diastereoisomers, of HBCDs which were α-HBCD, ß-HBCD, γ-HBCD, respectively, and cell toxicity was analyzed using the cell counting kit-8( CCK-8) assay. The impact of HBCDs on cell cycles of Neuro-2a were analyzed by flow cytometry analysis, and the expression levels in mRNA and protein for the three nuclearreceptors( RXRα, PPARγ, PXR andits target genes CYP3A11) were determined by RT-PCR and Western blot, respectively. The interaction between the receptors of RXRα, PXR, PPARγ was explored by immunoprecipitation. RESULTS: Cytotoxicity of ß-HBCD was the greatest among the three diastereoisomers, it was significantly greater than α-HBCD, however cytotoxicity of γ-HBCD for the Neuro-2a cells couldn 't be determined. Moreover α-HBCD, ß-HBCD induced significant cytotoxicity in a time-dose-response relationship to Neuro-2a cells( P < 0. 05), IC_(50) of α-HBCD, ß-HBCD to Neuro-2a cells were 60. 07 and 10. 52 µmol/L, respectively. α-, ß-HBCD blocked the cell cycle at G2/M phase. The expression levels in mRNA and protein of RXRα, PPARγ, PXR, CYP3A11 were significantly increased after cells exposure to α-HBCD and ß-HBCD 24 h. An interaction between RXRα, PPARγ and PXR in Neuro-2a cells existed no matter before and after exposure to HBCD. CONCLUSION: α-HBCD, ß-HBCD inhibit proliferation of Neuro-2a cells, cell cycle mainly was arrested at G2/M phase. α-HBCD, ß-HBCD could up-regulated the expression levels of RXRα, PPARγ, PXR. Meanwhile, the expression of CYP3A11 which is downstream gene of PXR also significantly increased( P < 0. 05). Interaction between RXRα, PPARγ and PXR exist whether or not exposure to α-, ß-HBCD. The molecular mechanisms of interaction between the receptors need further study.

TRC4, an improved triptolide derivative, specifically targets to truncated form of retinoid X receptor-alpha in cancer cells.

The nuclear retinoid X receptor-α (RXRα) plays critical roles in cell homeostasis and in many physiological processes mainly through its transcriptional function. However, an N-terminal truncated form of RXRα, tRXRα, was frequently described in various cancer cells and tumor tissues, thus representing a new promising drug target. We recently demonstrated that triptolide (TR01) could target to the oncogenic activity of tRXRα. To improve its tumor selectivity, we developed several TR01 derivatives by introducing different amine ester groups on C-14-hydroxyl site. Interestingly, C-14 modification could differently affect the expression of tRXRα without interfering the level of its full length RXRα. Among the derivatives, TRC4 could strongly reduce tRXRα expression, while TRC5-7 increased it. The capability of inhibiting tRXRα expression was shown to be closely associated with its inactivation of AKT and induction of apoptosis in various cancer cells. Conversely, treatment of cancer cells with the tRXRα-stabilizing compounds TRC5-7 resulted in enhanced AKT activity and apoptosis-resistance. However, although TR01 could strongly reduce tRXRα expression and AKT activity, it also strongly inhibited the expression and transcriptional activity of RXRα in normal cells. Importantly, the tRXRα-selective TRC4 that did not significantly inhibit RXRα transcriptional function retained the most potency of the anticancer effect of TR01 and had no significant effect on the viability of normal cells. In conclusion, our results demonstrated that tRXRα-selective TRC4 will have potential clinical application in terms of drug target and side effects. Our findings will offer new strategies to develop improved triptolide analogs for cancer therapy.

Effect of diosgenin on metabolic dysfunction: Role of ERß in the regulation of PPARγ.

The present study was designed to investigate the effect of diosgenin (DSG) on metabolic dysfunction and to elucidate the possible molecular mechanisms. High fat (HF) diet-fed mice and 3T3-L1 preadipocytes was used to evaluate the effect of DSG. We showed that DSG attenuated metabolic dysfunction in HF diet-fed mice, as evidenced by reduction of blood glucose level and improvement of glucose and insulin intolerance. DSG ameliorated oxidative stress, reduced body weight, fat pads, and systematic lipid profiles and attenuated lipid accumulation. DSG inhibited 3T3-L1 adipocyte differentiation and reduced adipocyte size through regulating key factors. DSG inhibited PPARγ and its target gene expression both in differentiated 3T3-L1 adipocytes and fat tissues in HF diet-fed mice. Overexpression of PPARγ suppressed DSG-inhibited adipocyte differentiation. DSG significantly increased nuclear expression of ERß. Inhibition of ERß significantly suppressed DSG-exerted suppression of adipocyte differentiation and PPARγ expression. In response to DSG stimulation, ERß bound with RXRα and dissociated RXRα from PPARγ, leading to the reduction of transcriptional activity of PPARγ. These data provide new insight into the mechanisms underlying the inhibitory effect of DSG on adipocyte differentiation and demonstrate that ERß-exerted regulation of PPARγ expression and activity is critical for DSG-inhibited adipocyte differentiation.

Bioactive prenylated xanthones from the stems of Cratoxylum cochinchinense.

Cochinchinones M-U (1-9), together with 12 known compounds (10-21), were isolated from the stems of Cratoxylum cochinchinense (Lour.) Blume. Their structures were determined on the basis of extensive spectroscopic data analyses. In addition, their retinoid X receptor-α transcriptional activities were evaluated using an in vitro assay.

Oroxylin A has therapeutic potential in acute myelogenous leukemia by dual effects targeting PPARγ and RXRα.

Oroxylin A (OA) is a flavonoid derived from a Chinese herb that has previously been reported to inhibit the proliferation of several cancer cell lines. It is found that OA significantly inhibited the growth of myeloid leukemia cell lines and as xenografts in immunodeficient mice and primary blasts from acute myelogenous leukemia (AML) patients. Furthermore, OA-induced cell cycle arrest and differentiation were observed in OA-treated AML cell lines. OA-induced increase of CD11b/CD14 expression was reversed by GW9662, a specific PPARγ inhibitor, or transient transfection with PPARγ siRNA. Docking study showed OA bound to ligand-binding domain of PPARγ via forming hydrogen bonds with Arg288 and Leu340 sites. Results of fluorescence polarization-based ligand assay verified PPARγ-binding activity of OA, and in OA-treated cells, intranuclear accumulation and increased binding activity of PPARγ to PPRE were detected. We also found that GW9662 attenuated OA-induced upregulation of C/EBPß, an important regulator of leukemic differentiation, and p21, which is a potent inhibitor of CDKs that can inhibit phosphorylation of Rb by cyclin D1-CDK4 complexes. Moreover, our results showed that OA displayed synergistic effects with all-trans retinoic acid and VD3 in part related to reduction of intranuclear phosphorylated RXRα that has been reported to block nuclear receptor/RXRα heterodimer transcriptional activity. This reduction of phosphorylated RXRα was associated with inhibition of the specific upstream MAP kinase ERK1/2. We suggest that OA may provide a novel complement to AML treatment by its dual effects of augmenting PPARγ activity and sensitizing nuclear receptors to specific ligands.

Adapalene suppresses sebum accumulation via the inhibition of triacylglycerol biosynthesis and perilipin expression in differentiated hamster sebocytes in vitro.

BACKGROUND: Acne is a chronic inflammatory disease in sebaceous glands and pilosebaceous units where excess sebum production and follicular hyperkeratinization are observed. Adapalene, which exerts comedolytic and anti-inflammatory effects, is used for the topical treatment of mild to moderate acne. OBJECTIVE: We examined the effect of adapalene on sebum production and accumulation in sebaceous gland cells (sebocytes). METHODS: The regulation of sebum production was examined by oil red O and nile red staining and the measurement of triacylglycerols (TGs) in differentiated hamster sebocytes. The gene expression and production of diacylglycerol acyltransferase-1 (DGAT-1) and perilipin 1 (PLIN1) were analyzed using real-time PCR and Western blotting, respectively. RESULTS: Adapalene suppressed sebum accumulation as lipid droplets in spontaneously and insulin-differentiated hamster sebocytes. The TG production, and the gene expression and production of DGAT-1, a rate-limiting enzyme of TG biosynthesis, were dose-dependently inhibited by adapalene in insulin-, 5α-dihydrotestosterone- or a peroxisome proliferator activating receptor γ agonist, troglitazone-differentiated hamster sebocytes. In addition, the inhibition of TG production by adapalene interfered with antagonists against nuclear retinoic acid and retinoid X receptors (CD2665 and UVI3006, respectively) in the differentiated sebocytes. Furthermore, the production of PLIN1, a lipid storage droplet protein, was transcriptionally inhibited by adapalene in the differentiated sebocytes. CONCLUSIONS: These results suggest that adapalene exerts an inhibitory action for sebum accumulation due to the suppression of TG and PLIN1 production in differentiated hamster sebocytes. Furthermore, these findings may contribute to a novel understanding of the molecular mechanisms of adapalene for acne treatment and prevention.

Gene-specific alterations of hepatic gene expression by ligand activation or hepatocyte-selective inhibition of retinoid X receptor-α signalling during inflammation.

BACKGROUND: Inflammation leads to transcriptional downregulation of many hepatic genes, particularly those activated by retinoid X receptor-α (RXRα) heterodimers. Inflammation-mediated reduction of nuclear RXRα levels is a main factor in reduced nuclear receptor (NR)-regulated hepatic gene expression, eventually leading to cholestasis and liver damage. AIM: To investigate roles for RXRα in hepatic gene expression during inflammation, using two complementary mouse models: ligand activation of RXRα, and in mice expressing hepatocyte-specific expression of RXRα missing its DNA-binding domain (DBD; hs-RxrαΔex4(-/-) ). METHODS: To activate RXRα, mice were gavage-fed with LG268 or vehicle for 5 days. To inhibit RXRα function, hs-RxrαΔex4(-/-) mice were used. All mice were injected intraperitoneally with lipopolysaccharides (LPS) or saline for 16 h prior to analysis of hepatic RNA, protein and NR-DNA binding. RESULTS: LG268 treatment attenuated the LPS-mediated reductions of several RXRα-regulated genes, coinciding with maintained RXRα occupancy in both Bsep and Ostß promoters. Lacking full hepatocyte RXRα function (hs-RxrαΔex4(-/-) mice) led to enhancement of LPS-mediated changes in gene expression, but surprisingly, maintenance of RNA levels of some RXRα-regulated genes. Investigations revealed that hs-RxrαΔex4(-/-) hepatocytes expressed an internally truncated, approximately 44 kDa, RXRα-form. DNA-binding capacity of NR heterodimers was equivalent in wild-type and hs-RxrαΔex4(-/-) livers, but reduced by LPS in both. Chromatin immunoprecipitation quantitative PCR revealed that RXRα occupancy to the Bsep RXRα:Farnesoid X Receptor site was reduced, but not absent, in hs-RxrαΔex4(-/-) livers. CONCLUSIONS: There are differential regulatory roles for hepatic RXRα, both in basal and inflammatory states, suggesting new and complex multidomain roles for RXRα in regulating hepatic gene expression. Moreover, there is an unexpected non-obligate role for the DBD of RXRα.

Bioactive xanthones from the stems of Cratoxylum formosum ssp. pruniflorum.

Six new compounds, pruniflorones M-R (1-6), together with 19 known compounds (7-25) were isolated from the stems of Cratoxylum formosum ssp. pruniflorum. The structures of the new compounds were established on the basis of extensive spectroscopic data interpretation. In addition, their RXRalpha transcriptional activities were evaluated using an in vitro assay.

Inhibition of liver x receptor/retinoid X receptor-mediated transcription contributes to the proatherogenic effects of arsenic in macrophages in vitro.

OBJECTIVE: To determine whether arsenic inhibits transcriptional activation of the liver X receptor (LXR)/retinoid X receptor (RXR) heterodimers, thereby impairing cholesterol efflux from macrophages and potentially contributing to a proatherogenic phenotype. METHODS AND RESULTS: Arsenic is an important environmental contaminant and has been linked to an increased incidence of atherosclerosis. Previous findings showed that arsenic inhibits transcriptional activation of type 2 nuclear receptors, known to heterodimerize with RXR. Environmentally relevant arsenic doses decrease the LXR/RXR ligand-induced expression of the LXR target genes (ABCA1 and SREBP-1c). Arsenic failed to decrease cAMP-induced ABCA1 expression, suggesting a selective LXR/RXR effect. This selectivity correlated with the ability of arsenic to decrease LXR/RXR ligand-induced, but not cAMP-induced, cholesterol efflux. By using chromatin immunoprecipitation assays, we found that arsenic inhibits the ability of LXR/RXR ligands to induce activation markers on the ABCA1 and SREBP-1c promoters and blocks ligand-induced release of the nuclear receptor coexpressor (NCoR) from the promoter. Arsenic did not alter the ability of LXR to transrepress inflammatory gene transcription, further supporting our hypothesis that RXR is the target for arsenic inhibition. CONCLUSIONS: Exposure to arsenic enhances the risk of atherosclerosis. We present data that arsenic inhibits the transcriptional activity of the liver X receptor, resulting in decreased cholesterol-induced gene expression and efflux from macrophages. Therefore, arsenic may promote an athersclerotic environment by decreasing the ability of macrophages to efflux excess cholesterol, thereby favoring increased plaque formation.

Detection of agonistic activities against five human nuclear receptors in river environments of Japan using a yeast two-hybrid assay.

A total of 16 water samples from four rivers in Japan were examined for their agonistic activities against five human nuclear receptors (estrogen receptor [ER] alpha, thyroid hormone receptor alpha, retinoic acid receptor [RAR] alpha, retinoid X receptor alpha, and vitamin D receptor) by using a yeast two-hybrid assay. The results suggest that the river environment is contaminated with endocrine disrupting chemicals (EDCs) that can interact with a variety of nuclear receptors and that contamination with those that have RAR agonistic activity may be more serious than contamination with well-known EDCs that act as ER agonists.

Strategy and mechanism for the prevention of hepatocellular carcinoma: phosphorylated retinoid X receptor alpha is a critical target for hepatocellular carcinoma chemoprevention.

Hepatocellular carcinoma (HCC) is a major health care problem worldwide. The prognosis of patients with HCC is poor because even in the early stages when surgical treatment might be expected to be curative, the incidence of recurrence in patients with underlying cirrhosis is very high due to multicentric carcinogenesis. Therefore, strategies to prevent recurrence and second primary HCC are required to improve the prognosis. One of the most practical approaches to prevent the multicentric development of HCC is 'clonal deletion' therapy, which is defined as the removal of latent (i.e. invisible) (pre)malignant clones from the liver in a hypercarcinogenic state. Retinoids, a group of structural and functional analogs of vitamin A, exert their biological function primarily through two distinct nuclear receptors, retinoic acid receptors and retinoid X receptors (RXR), and abnormalities in the expression and function of these receptors are highly associated with the development of various cancers, including HCC. In particular, a malfunction of RXRalpha due to phosphorylation by the Ras-mitogen-activated protein kinase signaling pathway is profoundly associated with the development of HCC and thus may be a critical target for HCC chemoprevention. Acyclic retinoid, which has been clinically shown to reduce the incidence of a post-therapeutic recurrence of HCC, can inhibit Ras activity and phosphorylation of the extracellular signal-regulated kinase and RXRalpha proteins. In conclusion, the inhibition of RXRalpha phosphorylation and the restoration of its physiological function as a master regulator for nuclear receptors may be a potentially effective strategy for HCC chemoprevention and clonal deletion. Acyclic retinoid, which targets phosphorylated RXRalpha, may thus play a critical role in preventing the development of multicentric HCC.

Retinoids induce cytochrome P450 3A4 through RXR/VDR-mediated pathway.

A panel of retinoids and carotenoids was screened as potential inducers of CYP3A4 through the RXR/VDR-mediated signaling pathway. Transient transfection assays revealed that 3 out of 12 retinoids screened transactivated RXRalpha/VDR and induced CYP3A4 reporter activity. These three retinoids are the active metabolites of retinoids, 9-cis-retinal, 9-cis-retinoic acid (9-cis-RA), and all-trans-retinoic acid (all-trans-RA). 9-cis-RA and all-trans-RA preferentially transactivated the RXR/VDR heterodimers and RXR homodimers. Retinoids and VDR agonist 1alpha, 25-dihydroxyvitamin D(3), but not PXR or CAR activator, could induce Cyp3a11 mRNA level in hepatocytes derived from PXR/CAR-double null mouse. Moreover, retinoids induced CYP3A4 enzyme activity in HepG2 human hepatoma and Caco-2 human colorectal adenocarcinoma cells. A direct role of retinoid-mediated CYP3A4 induction through RXRalpha/VDR was proved by the results that 9-cis-retinal, 9-cis-RA, and all-trans-RA recruited RXRalpha and VDR to CYP3A4 regulatory region pER6 (proximal everted repeat with a 6-nucleotide spacer) and dXREM (distal xenobiotic-responsive enhancer module). Thus, using various approaches, we have unequivocally demonstrated that retinoids transactivate RXR/VDR heterodimers and RXR homodimers and induce CYP3A expression at mRNA as well as enzyme activity levels in both liver and intestinal cells. It is possible that retinoids might alter endobiotic metabolism through CYP3A4 induction in vivo.

S 26948: a new specific peroxisome proliferator activated receptor gamma modulator with potent antidiabetes and antiatherogenic effects.

OBJECTIVE: Rosiglitazone displays powerful antidiabetes benefits but is associated with increased body weight and adipogenesis. Keeping in mind the concept of selective peroxisome proliferator-activated receptor (PPAR)gamma modulator, the aim of this study was to characterize the properties of a new PPARgamma ligand, S 26948, with special attention in body-weight gain. RESEARCH DESIGN AND METHODS: We used transient transfection and binding assays to characterized the binding characteristics of S 26948 and GST pull-down experiments to investigate its pattern of coactivator recruitment compared with rosiglitazone. We also assessed its adipogenic capacity in vitro using the 3T3-F442A cell line and its in vivo effects in ob/ob mice (for antidiabetes and antiobesity properties), as well as the homozygous human apolipoprotein E2 knocking mice (E2-KI) (for antiatherogenic capacity). RESULTS: S 26948 displayed pharmacological features of a high selective ligand for PPARgamma with low potency in promoting adipocyte differentiation. It also displayed a different coactivator recruitment profile compared with rosiglitazone, being unable to recruit DRIP205 or PPARgamma coactivator-1 alpha. In vivo experiments showed that S 26948 was as efficient in ameliorating glucose and lipid homeostasis as rosiglitazone, but it did not increase body and white adipose tissue weights and improved lipid oxidation in liver. In addition, S 26948 represented one of the few molecules of the PPARgamma ligand class able to decrease atherosclerotic lesions. CONCLUSIONS: These findings establish S 26948 as a selective PPARgamma ligand with distinctive coactivator recruitment and gene expression profile, reduced adipogenic effect, and improved biological responses in vivo.

Valproic acid induces CYP3A4 and MDR1 gene expression by activation of constitutive androstane receptor and pregnane X receptor pathways.

In our study, we tested the hypothesis whether valproic acid (VPA) in therapeutic concentrations has potential to affect expression of CYP3A4 and MDR1 via constitutive androstane receptor (CAR) and pregnane X receptor (PXR) pathways. Interaction of VPA with CAR and PXR nuclear receptors was studied using luciferase reporter assays, real-time reverse transcriptase polymerase chain reaction (RT-PCR), electrophoretic mobility shift assay (EMSA), and analysis of CYP3A4 catalytic activity. Using transient transfection reporter assays in HepG2 cells, VPA was recognized to activate CYP3A4 promoter via CAR and PXR pathways. By contrast, a significant effect of VPA on MDR1 promoter activation was observed only in CAR-cotransfected HepG2 cells. These data well correlated with up-regulation of CYP3A4 and MDR1 mRNAs analyzed by real-time RT-PCR in cells transfected with expression vectors encoding CAR or PXR and treated with VPA. In addition, VPA significantly up-regulated CYP3A4 mRNA in primary hepatocytes and augmented the effect of rifampicin. EMSA experiments showed VPA-mediated augmentation of CAR/retinoid X receptor alpha heterodimer binding to direct repeat 3 (DR3) and DR4 responsive elements of CYP3A4 and MDR1 genes, respectively. Finally, analysis of specific CYP3A4 catalytic activity revealed its significant increase in VPA-treated LS174T cells transfected with PXR. In conclusion, we provide novel insight into the mechanism by which VPA affects gene expression of CYP3A4 and MDR1 genes. Our results demonstrate that VPA has potential to up-regulate CYP3A4 and MDR1 through direct activation of CAR and/or PXR pathways. Furthermore, we suggest that VPA synergistically augments the effect of rifampicin in transactivation of CYP3A4 in primary human hepatocytes.

Dietary levels of all-trans retinol affect retinoid nuclear receptor expression and skeletal development in European sea bass larvae.

European sea bass larvae were fed different dietary vitamin A levels. Growth, skeletal development and the expression of genes involved in larval morphogenesis were evaluated. From 7 to 42 d post-hatching, larvae were fed five isoproteic and isolipidic compound diets with graded levels of retinyl acetate (RA; RA0, RA10, RA50, RA250 and RA1000, containing 0, 10, 50, 250 and 1000 mg RA/kg DM, respectively), resulting in an incorporation of 12, 13, 31, 62 and 196 mg all-trans retinol/kg DM. Larvae fed extreme levels of RA had weights 19 % and 27 % lower than those of the RA50 group. The RA1000 diet induced a fall in growth with an increase of circulating and storage retinol forms in larvae, revealing hypervitaminosis. High levels of RA affected maturation of the pancreas and intestine. These data indicated that the optimal RA level was close to 31 mg/kg DM. Inappropriate levels of dietary RA resulted in an alteration of head organisation characterised by the abnormal development of the splanchnocranium and neurocranium, and scoliotic fish. Of the larvae fed RA1000, 78.8 % exhibited skeletal abnormalities, whereas the RA50 group presented with 25 % malformations. A linear correlation between vitamin A level and malformation percentage was observed and mainly associated with an upregulation of retinoic acid receptor-gamma expression in the RA1000 group during the 2 first weeks after hatching. The expression of retinoid X receptor-alpha decreased during normal larval development when that of the retinoic acid receptors increased. This work highlights the involvement of retinoid pathways in the appearance of dietary-induced skeletal malformations during post-hatching development in sea bass.