Retinoid Synthesis Regulation by Retinal Cells in Health and Disease.

Vision starts in retinal photoreceptors when specialized proteins (opsins) sense photons via their covalently bonded vitamin A derivative 11cis retinaldehyde (11cis-RAL). The reaction of non-enzymatic aldehydes with amino groups lacks specificity, and the reaction products may trigger cell damage. However, the reduced synthesis of 11cis-RAL results in photoreceptor demise and suggests the need for careful control over 11cis-RAL handling by retinal cells. This perspective focuses on retinoid(s) synthesis, their control in the adult retina, and their role during retina development. It also explores the potential importance of 9cis vitamin A derivatives in regulating retinoid synthesis and their impact on photoreceptor development and survival. Additionally, recent advancements suggesting the pivotal nature of retinoid synthesis regulation for cone cell viability are discussed.

Vitamin A - discovery, metabolism, receptor signaling and effects on bone mass and fracture susceptibility.

The first evidence of the existence of vitamin A was the observation 1881 that a substance present in small amounts in milk was necessary for normal development and life. It was not until more than 100 years later that it was understood that vitamin A acts as a hormone through nuclear receptors. Unlike classical hormones, vitamin A cannot be synthesized by the body but needs to be supplied by the food as retinyl esters in animal products and ß-carotene in vegetables and fruits. Globally, vitamin A deficiency is a huge health problem, but in the industrialized world excess of vitamin A has been suggested to be a risk factor for secondary osteoporosis and enhanced susceptibility to fractures. Preclinical studies unequivocally have shown that increased amounts of vitamin A cause decreased cortical bone mass and weaker bones due to enhanced periosteal bone resorption. Initial clinical studies demonstrated a negative association between intake of vitamin A, as well as serum levels of vitamin A, and bone mass and fracture susceptibility. In some studies, these observations have been confirmed, but in other studies no such associations have been observed. One meta-analysis found that both low and high serum levels of vitamin A were associated with increased relative risk of hip fractures. Another meta-analysis also found that low levels of serum vitamin A increased the risk for hip fracture but could not find any association with high serum levels of vitamin A and hip fracture. It is apparent that more clinical studies, including large numbers of incident fractures, are needed to determine which levels of vitamin A that are harmful or beneficial for bone mass and fracture. It is the aim of the present review to describe how vitamin A was discovered and how vitamin A is absorbed, metabolized and is acting as a ligand for nuclear receptors. The effects by vitamin A in preclinical studies are summarized and the clinical investigations studying the effect by vitamin A on bone mass and fracture susceptibility are discussed in detail.

Modulatory effects of rutin and vitamin A on hyperglycemia induced glycation, oxidative stress and inflammation in high-fat-fructose diet animal model.

In the current study we investigated the impact of combination of rutin and vitamin A on glycated products, the glyoxalase system, oxidative markers, and inflammation in animals fed a high-fat high-fructose (HFFD) diet. Thirty rats were randomly divided into six groups (n = 5). The treatments, metformin (120 mg/kg), rutin (100 mg/kg), vitamin A (43 IU/kg), and a combination of rutin (100 mg/kg) and vitamin A (43 IU/kg) were given to relevant groups of rats along with high-fructose high-fat diet for 42 days. HbA1c, D-lactate, Glyoxylase-1, Hexokinase 2, malondialdehyde (MDA), glutathione peroxidase (GPx), catalase (CAT), nuclear transcription factor-B (NF-κB), interleukin-6 (IL-6), interleukin-8 (IL-8) and histological examinations were performed after 42 days. The docking simulations were conducted using Auto Dock package. The combined effects of rutin and vitamin A in treated rats significantly (p < 0.001) reduced HbA1c, hexokinase 2, and D-lactate levels while preventing cellular damage. The combination dramatically (p < 0.001) decreased MDA, CAT, and GPx in treated rats and decreased the expression of inflammatory cytokines such as IL-6 andIL-8, as well as the transcription factor NF-κB. The molecular docking investigations revealed that rutin had a strong affinity for several important biomolecules, including as NF-κB, Catalase, MDA, IL-6, hexokinase 2, and GPx. The results propose beneficial impact of rutin and vitamin A as a convincing treatment strategy to treat AGE-related disorders, such as diabetes, autism, alzheimer's, atherosclerosis.

Interfacial Interactions between Nanoplastics and Biological Systems: toward an Atomic and Molecular Understanding of Plastics-Driven Biological Dyshomeostasis.

Micro- and nano-plastics (NPs) are found in human milk, blood, tissues, and organs and associate with aberrant health outcomes including inflammation, genotoxicity, developmental disorders, onset of chronic diseases, and autoimmune disorders. Yet, interfacial interactions between plastics and biomolecular systems remain underexplored. Here, we have examined experimentally, in vitro, in vivo, and by computation, the impact of polystyrene (PS) NPs on a host of biomolecular systems and assemblies. Our results reveal that PS NPs essentially abolished the helix-content of the milk protein ß-lactoglobulin (BLG) in a dose-dependent manner. Helix loss is corelated with the near stoichiometric formation of ß-sheet elements in the protein. Structural alterations in BLG are also likely responsible for the nanoparticle-dependent attrition in binding affinity and weaker on-rate constant of retinol, its physiological ligand (compromising its nutritional role). PS NP-driven helix-to-sheet conversion was also observed in the amyloid-forming trajectory of hen egg-white lysozyme (accelerated fibril formation and reduced helical content in fibrils). Caenorhabditis elegans exposed to PS NPs exhibited a decrease in the fluorescence of green fluorescent protein-tagged dopaminergic neurons and locomotory deficits (akin to the neurotoxin paraquat exposure). Finally, in silico analyses revealed that the most favorable PS/BLG docking score and binding energies corresponded to a pose near the hydrophobic ligand binding pocket (calyx) of the protein where the NP fragment was found to make nonpolar contacts with side-chain residues via the hydrophobic effect and van der Waals forces, compromising side chain/retinol contacts. Binding energetics indicate that PS/BLG interactions destabilize the binding of retinol to the protein and can potentially displace retinol from the calyx region of BLG, thereby impairing its biological function. Collectively, the experimental and high-resolution in silico data provide new insights into the mechanism(s) by which PS NPs corrupt the bimolecular structure and function, induce amyloidosis and onset neuronal injury, and drive aberrant physiological and behavioral outcomes.

Airway hillocks are injury-resistant reservoirs of unique plastic stem cells.

Airway hillocks are stratified epithelial structures of unknown function1. Hillocks persist for months and have a unique population of basal stem cells that express genes associated with barrier function and cell adhesion. Hillock basal stem cells continually replenish overlying squamous barrier cells. They exhibit dramatically higher turnover than the abundant, largely quiescent classic pseudostratified airway epithelium. Hillocks resist a remarkably broad spectrum of injuries, including toxins, infection, acid and physical injury because hillock squamous cells shield underlying hillock basal stem cells from injury. Hillock basal stem cells are capable of massive clonal expansion that is sufficient to resurface denuded airway, and eventually regenerate normal airway epithelium with each of its six component cell types. Hillock basal stem cells preferentially stratify and keratinize in the setting of retinoic acid signalling inhibition, a known cause of squamous metaplasia2,3. Here we show that mouse hillock expansion is the cause of vitamin A deficiency-induced squamous metaplasia. Finally, we identify human hillocks whose basal stem cells generate functional squamous barrier structures in culture. The existence of hillocks reframes our understanding of airway epithelial regeneration. Furthermore, we show that hillocks are one origin of 'squamous metaplasia', which is long thought to be a precursor of lung cancer.

Gene expression profiles in COVID-19-associated tracheal stenosis indicate persistent anti-viral response and dysregulated retinol metabolism.

INTRODUCTION: Coronavirus disease 2019 (COVID-19)-associated tracheal stenosis (COATS) may occur as a result of prolonged intubation during COVID-19 infection. We aimed to investigate patterns of gene expression in the tracheal granulation tissue of patients with COATS, leverage gene expression data to identify dysregulated cellular pathways and processes, and discuss potential therapeutic options based on the identified gene expression profiles. METHODS: Adult patients (age ≥ 18 years) presenting to clinics for management of severe, recalcitrant COATS were included in this study. RNA sequencing and differential gene expression analysis was performed with transcriptomic data for normal tracheal tissue being used as a control. The top ten most highly upregulated and downregulated genes were identified. For each of these pathologically dysregulated genes, we identified key cellular pathways and processes they are involved in using Gene Ontology (GO) and KEGG (Kyoto Encyclopedia of Genes and Genomes) applied via Database for Annotation, Visualization, and Integrated Discovery (DAVID). RESULTS: Two women, aged 36 years and 37 years, were included. The profile of dysregulated genes indicated a cellular response consistent with viral infection (CXCL11, PI15, CCL8, DEFB103A, IFI6, ACOD1, and DEFB4A) and hyperproliferation/hypergranulation (MMP3, CASP14 and HAS1), while downregulated pathways included retinol metabolism (ALDH1A2, RBP1, RBP4, CRABP1 and CRABP2). CONCLUSION: Gene expression changes consistent with persistent viral infection and dysregulated retinol metabolism may promote tracheal hypergranulation and hyperproliferation leading to COATS. Given the presence of existing literature highlighting retinoic acid's ability to favorably regulate these genes, improve cell-cell adhesion, and decrease overall disease severity in COVID-19, future studies must evaluate its utility for adjunctive management of COATS in animal models and clinical settings.

Uncommon opsin's retinal isomer is involved in mammalian sperm thermotaxis.

In recent years it became apparent that, in mammals, rhodopsin and other opsins, known to act as photosensors in the visual system, are also present in spermatozoa, where they function as highly sensitive thermosensors for thermotaxis. The intriguing question how a well-conserved protein functions as a photosensor in one type of cells and as a thermosensor in another type of cells is unresolved. Since the moiety that confers photosensitivity on opsins is the chromophore retinal, we examined whether retinal is substituted in spermatozoa with a thermosensitive molecule. We found by both functional assays and mass spectrometry that retinal is present in spermatozoa and required for thermotaxis. Thus, starvation of mice for vitamin A (a precursor of retinal) resulted in loss of sperm thermotaxis, without affecting motility and the physiological state of the spermatozoa. Thermotaxis was restored after replenishment of vitamin A. Using reversed-phase ultra-performance liquid chromatography mass spectrometry, we detected the presence of retinal in extracts of mouse and human spermatozoa. By employing UltraPerformance convergence chromatography, we identified a unique retinal isomer in the sperm extracts-tri-cis retinal, different from the photosensitive 11-cis isomer in the visual system. The facts (a) that opsins are thermosensors for sperm thermotaxis, (b) that retinal is essential for thermotaxis, and (c) that tri-cis retinal isomer uniquely resides in spermatozoa and is relatively thermally unstable, suggest that tri-cis retinal is involved in the thermosensing activity of spermatozoa.

Spectral and mass characterization of kinetic conversion from retinoids to retinoic acid in an in vitro 3-D human skin equivalent model.

To investigate the effect of retinoids, such as retinol (ROL), retinal (RAL), and retinyl palmitate (RP), on epidermal integrity, skin deposition, and bioconversion to retinoic acid (RA). 3-D human skin equivalent model (EpiDermFT™) was used. Epidermal cellular integrity measured by TEER values was significantly higher for a topical treatment of ROL and RAL than RP (p < 0.05). The skin deposition (µM) of ROL and RAL was approximately 269.54 ± 73.94 and 211.35 ± 20.96, respectively, greater than that of RP (63.70 ± 37.97) over 2 h incubation. Spectral changes were revealed that the CO maximum absorbance occurred between 1600∼1800 cm-1 and was greater from ROL than that from RAL and RP, indicating conjugation of R-OH to R-CHO or R-COOH could strongly occur after ROL treatment. Subsequently, a metabolite from the bioconversion of ROL and RAL was identified as RA, which has a product ion of m/z 283.06, by using liquid a chromatography-mass spectrometry (LC-MS) - total ion chromatogram (TIC). The amount of bioconversion from ROL and RAL to RA in artificial skin was 0.68 ± 0.13 and 0.70 ± 0.10 µM at 2 h and 0.60 ± 0.04 and 0.57 ± 0.06 µM at 24 h, respectively. RA was not detected in the skin and the receiver compartment after RP treatment. ROL could be a useful dermatological ingredient to maintain epidermal integrity more effectively, more stably deposit on the skin, and more steadily metabolize to RA than other retinoids such as RAL and RP.

Enhancing plant-based cheese formulation through molecular docking and dynamic simulation of tocopherol and retinol complexes with zein, soy and almond proteins via SVM-machine learning integration.

The current study addresses the growing demand for sustainable plant-based cheese alternatives by employing molecular docking and deep learning algorithms to optimize protein-ligand interactions. Focusing on key proteins (zein, soy, and almond protein) along with tocopherol and retinol, the goal was to improve texture, nutritional value, and flavor characteristics via dynamic simulations. The findings demonstrated that the docking analysis presented high accuracy in predicting conformational changes. Flexible docking algorithms provided insights into dynamic interactions, while analysis of energetics revealed variations in binding strengths. Tocopherol exhibited stronger affinity (-5.8Kcal/mol) to zein compared to retinol (-4.1Kcal/mol). Molecular dynamics simulations offered comprehensive insights into stability and behavior over time. The integration of machine learning algorithms improved the classification and the prediction accuracy, achieving a rate of 71.59%. This study underscores the significance of molecular understanding in driving innovation in the plant-based cheese industry, facilitating the development of sustainable alternatives to traditional dairy products.

The Logistical Backbone of Photoreceptor Cell Function: Complementary Mechanisms of Dietary Vitamin A Receptors and Rhodopsin Transporters.

In this review, we outline our current understanding of the mechanisms involved in the absorption, storage, and transport of dietary vitamin A to the eye, and the trafficking of rhodopsin protein to the photoreceptor outer segments, which encompasses the logistical backbone required for photoreceptor cell function. Two key mechanisms of this process are emphasized in this manuscript: ocular and systemic vitamin A membrane transporters, and rhodopsin transporters. Understanding the complementary mechanisms responsible for the generation and proper transport of the retinylidene protein to the photoreceptor outer segment will eventually shed light on the importance of genes encoded by these proteins, and their relationship on normal visual function and in the pathophysiology of retinal degenerative diseases.

Vitamin A Status Modulates Epithelial Mesenchymal Transition in the Lung: The Role of Furin.

Vitamin A deficiency (VAD) induced TGF-ß hyperactivation and reduced expression of cell adhesion proteins in the lung, suggesting that the disruption of retinoic acid (RA) signaling leads to epithelial-mesenchymal transition (EMT). To elucidate the role of lung vitamin A status in EMT, several EMT markers and the expression of the proprotein convertase furin, which activates TGF-ß, were analyzed in two experimental models. Our in vivo model included control rats, VAD rats, and both control rats and VAD rats, treated with RA. For the in vitro studies, human bronchoalveolar epithelial cells treated with RA were used. Our data show that EMT and furin are induced in VAD rats. Furthermore, furin expression continues to increase much more markedly after treatment of VAD rats with RA. In control rats and cell lines, an acute RA treatment induced a significant increase in furin expression, concomitant with changes in EMT markers. A ChIP assay demonstrated that RA directly regulates furin transcription. These results emphasize the importance of maintaining vitamin A levels within the physiological range since both levels below and above this range can cause adverse effects that, paradoxically, could be similar. The role of furin in EMT is discussed.

Retinol and retinol binding protein 4 levels and COVID-19: a Mendelian randomization study.

BACKGROUND: The Corona Virus Disease 2019 (COVID-19) pandemic has struck globally. Whether the related proteins of retinoic acid (RA) signaling pathway are causally associated with the risk of COVID-19 remains unestablished. We conducted a two-sample Mendelian randomization (MR) study to assess the associations of retinol, retinol binding protein 4 (RBP4), retinol dehydrogenase 16 (RDH16) and cellular retinoic acid binding protein 1 (CRABP1) with COVID-19 in European population. METHODS: The outcome utilized the summary statistics of COVID-19 from the COVID-19 Host Genetics Initiative. The exposure data were obtained from public genome wide association study (GWAS) database. We extracted SNPs from exposure data and outcome data. The inverse variance weighted (IVW), MR-Egger and Wald ratio methods were employed to assess the causal relationship between exposure and outcome. Sensitivity analyses were performed to ensure the validity of the results. RESULTS: The MR estimates showed that retinol was associated with lower COVID-19 susceptibility using IVW (OR: 0.69, 95% CI: 0.53-0.90, P: 0.0065), whereas the associations between retinol and COVID-19 hospitalization or severity were not significant. RBP4 was associated with lower COVID-19 susceptibility using the Wald ratio (OR: 0.83, 95% CI: 0.72-0.95, P: 0.0072). IVW analysis showed RDH16 was associated with increased COVID-19 hospitalization (OR: 1.10, 95% CI: 1.01-1.18, P: 0.0199). CRABP1 was association with lower COVID-19 susceptibility (OR: 0.95, 95% CI: 0.91-0.99, P: 0.0290) using the IVW. CONCLUSIONS: We found evidence of possible causal association of retinol, RBP4, RDH16 and CRABP1 with the susceptibility, hospitalization and severity of COVID-19. Our study defines that retinol is significantly associated with lower COVID-19 susceptibility, which provides a reference for the prevention of COVID-19 with vitamin A supplementation.

Metabolic Pathway Coupled with Fermentation Process Optimization for High-Level Production of Retinol in Yarrowia lipolytica.

Retinol is a lipid-soluble form of vitamin A that is crucial for human visual and immune functions. The production of retinol through microbial fermentation has been the focus of recent exploration. However, the obtained titer remains limited and the product is often a mixture of retinal, retinol, and retinoic acid, necessitating purification. To achieve efficient biosynthesis of retinol in Yarrowia lipolytica, we improved the metabolic flux of ß-carotene to provide sufficient precursors for retinol in this study. Coupled with the optimization of the expression level of ß-carotene 15,15'-dioxygenase, de novo production of retinol was achieved. Furthermore, Tween 80 was used as an extractant and butylated hydroxytoluene as an antioxidant to extract intracellular retinol and prevent retinol oxidation, respectively. This strategy significantly increased the level of retinol production. By optimizing the enzymes converting retinal to retinol, the proportion of extracellular retinol in the produced retinoids reached 100%, totaling 1042.3 mg/L. Finally, total retinol production reached 5.4 g/L through fed-batch fermentation in a 5 L bioreactor, comprising 4.2 g/L extracellular retinol and 1.2 g/L intracellular retinol. This achievement represents the highest reported titer so far and advances the industrial production of retinol.

Reactive Oxygen Species-Responsive Nanoparticles Toward Extracellular Matrix Normalization for Pancreatic Fibrosis Regression.

Pancreatic fibrosis (PF) is primarily characterized by aberrant production and degradation modes of extracellular matrix (ECM) components, resulting from the activation of pancreatic stellate cells (PSCs) and the pathological cross-linking of ECM mediated by lysyl oxidase (LOX) family members. The excessively deposited ECM increases matrix stiffness, and the over-accumulated reactive oxygen species (ROS) induces oxidative stress, which further stimulates the continuous activation of PSCs and advancing PF; challenging the strategy toward normalizing ECM homeostasis for the regression of PF. Herein, ROS-responsive and Vitamin A (VA) decorated micelles (named LR-SSVA) to reverse the imbalanced ECM homeostasis for ameliorating PF are designed and synthesized. Specifically, LR-SSVA selectively targets PSCs via VA, thereby effectively delivering siLOXL1 and resveratrol (RES) into the pancreas. The ROS-responsive released RES inhibits the overproduction of ECM by eliminating ROS and inactivating PSCs, meanwhile, the decreased expression of LOXL1 ameliorates the cross-linked collagen for easier degradation by collagenase which jointly normalizes ECM homeostasis and alleviates PF. This research shows that LR-SSVA is a safe and efficient ROS-response and PSC-targeted drug-delivery system for ECM normalization, which will propose an innovative and ideal platform for the reversal of PF.

LX-2 Stellate Cells Are a Model System for Investigating the Regulation of Hepatic Vitamin A Metabolism and Respond to Tumor Necrosis Factor α and Interleukin 1ß.

Hepatic stellate cells (HSCs) are the major site of vitamin A (retinol) esterification and subsequent storage as retinyl esters within lipid droplets. However, retinyl esters become depleted in many pathophysiological states, including acute and chronic liver injuries. Recently, using a liver slice culture system as a model of acute liver injury and fibrogenesis, a time-dependent increase and decrease in the apparent formation of the bioactive retinoid all-trans-retinoic acid (atRA) and retinyl palmitate was measured, respectively. This coincided with temporal changes in the gene expression of retinoid-metabolizing enzymes and binding proteins, that preceded HSC activation. However, the underlying mechanisms that promote early changes in retinoid metabolism remain unresolved. We hypothesized that LX-2 cells could be applied to investigate differences in quiescent and activated HSC retinoid metabolism. We demonstrate that the hypermetabolic state of activated stellate cells relative to quiescent stellate cells may be attributed to induction of STRA6, RBP4, and CYP26A1, thereby reducing intracellular concentrations of atRA. We further hypothesized that paracrine and autocrine cytokine signaling regulates HSC vitamin A metabolism in both quiescent and activated cells. In quiescent cells, tumor necrosis factor α dose-dependently downregulated LRAT and CRBP1 mRNA, with EC50 values of 30-50 pg/mL. Likewise, interleukin-1ß decreased LRAT and CRBP1 gene expression but with less potency. In activated stellate cells, multiple enzymes were downregulated, suggesting that the full effects of altered hepatic vitamin A metabolism in chronic conditions require both paracrine and autocrine signaling events. Further, this study suggests the potential for cell type-specific autocrine effects in hepatic retinoid signaling. SIGNIFICANCE STATEMENT: HSCs are the major site of vitamin A storage and important determinants of retinol metabolism during liver fibrogenesis. Here, two LX-2 culture methods were applied as models of hepatic retinoid metabolism to demonstrate the effects of activation status and dose-dependent cytokine exposure on the expression of genes involved in retinoid metabolism. This study suggests that compared to quiescent cells, activated HSCs are hypermetabolic and have reduced apparent formation of retinoic acid, which may alter downstream retinoic acid signaling.

Neutrophil-Based Bionic Delivery System Breaks Through the Capillary Barrier of Liver Sinusoidal Endothelial Cells and Inhibits the Activation of Hepatic Stellate Cells.

The capillarization of hepatic sinusoids resulting from the activation of hepatic stellate cells poses a significant challenge, impeding the effective delivery of therapeutic agents to the Disse space for liver fibrosis treatment. Therefore, overcoming these barriers and achieving efficient drug delivery to activated hepatic stellate cells (aHSCs) are pressing challenge. In this study, we developed a synergistic sequential drug delivery approach utilizing neutrophil membrane hybrid liposome@atorvastatin/amlisentan (NCM@AtAm) and vitamin A-neutrophil membrane hybrid liposome @albumin (VNCM@Bai) nanoparticles (NPs) to breach the capillary barrier for targeted HSC cell delivery. Initially, NCM@AtAm NPs were successfully directed to the site of hepatic fibrosis through neutrophil-mediated inflammatory targeting, resulting in the normalization of liver sinusoidal endothelial cells (LSECs) and restoration of fenestrations under the combined influence of At and Am. Elevated tissue levels of the p-Akt protein and endothelial nitric oxide synthase (eNOS) indicated the normalization of LSECs following treatment with At and Am. Subsequently, VNCM@Bai NPs traversed the restored LSEC fenestrations to access the Disse space, facilitating the delivery of Bai into aHSCs under vitamin A guidance. Lastly, both in vitro and in vivo results demonstrated the efficacy of Bai in inhibiting HSC cell activation by modulating the PPAR γ/TGF-ß1 and STAT1/Smad7 signaling pathways, thereby effectively treating liver fibrosis. Overall, our designed synergistic sequential delivery system effectively overcomes the barrier imposed by LSECs, offering a promising therapeutic strategy for liver fibrosis treatment in clinical settings.

ß-Carotene accelerates the resolution of atherosclerosis in mice.

ß-Carotene oxygenase 1 (BCO1) catalyzes the cleavage of ß-carotene to form vitamin A. Besides its role in vision, vitamin A regulates the expression of genes involved in lipid metabolism and immune cell differentiation. BCO1 activity is associated with the reduction of plasma cholesterol in humans and mice, while dietary ß-carotene reduces hepatic lipid secretion and delays atherosclerosis progression in various experimental models. Here we show that ß-carotene also accelerates atherosclerosis resolution in two independent murine models, independently of changes in body weight gain or plasma lipid profile. Experiments in Bco1-/- mice implicate vitamin A production in the effects of ß-carotene on atherosclerosis resolution. To explore the direct implication of dietary ß-carotene on regulatory T cells (Tregs) differentiation, we utilized anti-CD25 monoclonal antibody infusions. Our data show that ß-carotene favors Treg expansion in the plaque, and that the partial inhibition of Tregs mitigates the effect of ß-carotene on atherosclerosis resolution. Our data highlight the potential of ß-carotene and BCO1 activity in the resolution of atherosclerotic cardiovascular disease.

Retinoic acid signaling pathway in pancreatic stellate cells: Insight into the anti-fibrotic effect and mechanism.

Pancreatic stellate cells (PSCs) are activated following loss of cytoplasmic vitamin A (retinol)-containing lipid droplets, which is a key event in the process of fibrogenesis of chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDCA). PSCs are the major source of cancer-associated fibroblasts (CAFs) that produce stroma to induce PDAC cancer cell growth, invasion, and metastasis. As an active metabolite of retinol, retinoic acid (RA) can regulate target gene expression in PSCs through its nuclear receptor complex (RAR/RXR or RXR/RXR) or transcriptional intermediary factor. Additionally, RA also has extranuclear and non-transcriptional effects. In vitro studies have shown that RA induces PSC deactivation which reduces extracellular matrix production through multiple modes of action, such as inhibiting TßRⅡ, PDGFRß, ß-catenin and Wnt production, downregulating ERK1/2 and JNK phosphorylation and suppressing active TGF-ß1 release. RA alone or in combination with other reagents have been demonstrated to have an effective anti-fibrotic effect on cerulein-induced mouse CP models in vivo studies. Clinical trial data have shown that repurposing all-trans retinoic acid (ATRA) as a stromal-targeting agent for human pancreatic cancer is safe and tolerable, suggesting the possibility of using RA for the treatment of CP and PDCA in humans. This review focuses on RA signaling pathways in PSCs and the effects and mechanisms of RA in PSC-mediated fibrogenesis as well as the anti-fibrotic and anti-tumor effects of RA targeting PSCs or CAFs in vitro and in vivo, highlighting the potential therapies of RA against CP and PDAC.

Fatty acid/monoglyceride type and amount modulate fat-soluble vitamin absorption from mixed assemblies in mice.

We investigated the effects of fatty acid/ monoglyceride type and amount on the absorption of fat-soluble vitamins. Micelles or vesicles made with either caprylic acid (CA) + monocaprylin (MC) or oleic acid (OA) + monoolein (MO) at low or high concentrations were infused in bile duct-ligated mice. Retinol + retinyl ester and γ-tocopherol intestinal mucosa contents were higher in mice infused with CA + MC than with OA + MO (up to + 350 % for vitamin A and up to + 62 %, for vitamin E; p < 0.05). Cholecalciferol intestinal mucosa content was the highest in mice infused with micelles with CA + MC at 5 mg/mL (up to + 105 %, p < 0.05). Retinyl ester plasma response was higher with mixed assemblies formed at low concentration of FA + MG compared to high concentration (up to + 1212 %, p < 0.05), while no difference in cholecalciferol and γ-tocopherol plasma responses were measured. No correlation between size or zeta potential and vitamin absorption was found. The impact of FA and MG on fat-soluble vitamin absorption thus differs from one vitamin to another and should be considered to formulate adequate vitamin oral or enteral supplements.

Bioactive Vitamins and Epigenetic Modifications in Diabetes: A Perspective.

Diabetes is a complex metabolic disease that has been associated with epigenetic changes. External factors such as dietary patterns can induce an imbalance in the pools of micronutrients and macronutrients in the body. Consequently, bioactive vitamins may influence epigenetic mechanisms via several pathways: involvement in the control of gene expression, and in protein synthesis, by acting as coenzymes and co-factors in the metabolism of methyl groups or methylation of DNA and histones. Herein, we present a perspective on the relevance of bioactive vitamins in the epigenetic modifications that occur in diabetes.