Fatty aldehyde dehydrogenase is up-regulated by polyunsaturated fatty acid via peroxisome proliferator-activated receptor α and suppresses polyunsaturated fatty acid-induced endoplasmic reticulum stress

ALDH1A1 as a marker for metastasis initiating cells: A mechanistic insight

Since metastasis accounts for the majority of cancer morbidity and mortality, attempts are focused to block metastasis and metastasis initiating cellular programs. It is generally believed that hypoxia, reactive oxygen species (ROS) and the dysregulated redox pathways regulate metastasis. Although induction of epithelial to mesenchymal transition (EMT) can initiate cell motility to different sites other than the primary site, the initiation of a secondary tumor at a distant site depends on self-renewal property of cancer stem cell (CSC) property. That subset of metastatic cells possessing CSC property are referred to as metastasis initiating cells (MICs). Among the different cellular intermediates regulating metastasis in response to hypoxia by inducing EMT and self-renewal property, ALDH1A1 is a critical molecule, which can be used as a marker for MICs in a wide variety of malignancies. The cytosolic ALDHs can irreversibly convert retinal to retinoic acid (RA), which initiates RA signaling, important for self-renewal and EMT. The metastasis permissive tumor microenvironment increases the expression of ALDH1A1, primarily through HIF1α, and leads to metabolic reprograming through OXPHOS regulation. The ALDH1A1 expression and its high activity can reprogram the cancer cells with the transcriptional upregulation of several genes, involved in EMT through RA signaling to manifest hybrid EMT or Hybrid E/M phenotype, which is important for acquiring the characteristics of MICs. Thus, the review on this topic highlights the use of ALDH1A1 as a marker for MICs, and reporters for the marker can be effectively used to trace the population in mouse models, and to screen drugs that target MICs.

Myeloid Trem2 ameliorates the progression of metabolic dysfunction-associated steatotic liver disease by regulating macrophage pyroptosis and inflammation resolution

BACKGROUND

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing year by year and has become one of the leading causes of end-stage liver disease worldwide. Triggering Receptor Expressed on Myeloid Cells 2 (Trem2) has been confirmed to play an essential role in the progression of MASLD, but its specific mechanism still needs to be clarified. This study aims to explore the role and mechanism of Trem2 in MASLD.

METHODS

Human liver tissues were obtained from patients with MASLD and controls. Myeloid-specific knockout mice (Trem2mKO) and myeloid-specific overexpression mice (Trem2TdT) were fed a high-fat diet, either AMLN or CDAHFD, to establish the MASLD model. Relevant signaling molecules were assessed through lipidomics and RNA-seq analyses after that.

RESULTS

Trem2 is upregulated in human MASLD/MASH-associated macrophages and is associated with hepatic steatosis and inflammation progression. Hepatic steatosis and inflammatory responses are exacerbated with the knockout of myeloid Trem2 in MASLD mice, while mice overexpressing Trem2 exhibit the opposite phenomenon. Mechanistically, Trem2mKO can aggravate macrophage pyroptosis through the PI3K/AKT signaling pathway and amplify the resulting inflammatory response. At the same time, Trem2 promotes the inflammation resolution phenotype transformation of macrophages through TGFβ1, thereby promoting tissue repair.

CONCLUSIONS

Myeloid Trem2 ameliorates the progression of Metabolic dysfunction-associated steatotic liver disease by regulating macrophage pyroptosis and inflammation resolution. We believe targeting myeloid Trem2 could represent a potential avenue for treating MASLD.

Cellular and Molecular Mechanisms of Pathogenesis Underlying Inherited Retinal Dystrophies

Inherited retinal dystrophies (IRDs) are congenital retinal degenerative diseases that have various inheritance patterns, including dominant, recessive, X-linked, and mitochondrial. These diseases are most often the result of defects in rod and/or cone photoreceptor and retinal pigment epithelium function, development, or both. The genes associated with these diseases, when mutated, produce altered protein products that have downstream effects in pathways critical to vision, including phototransduction, the visual cycle, photoreceptor development, cellular respiration, and retinal homeostasis. The aim of this manuscript is to provide a comprehensive review of the underlying molecular mechanisms of pathogenesis of IRDs by delving into many of the genes associated with IRD development, their protein products, and the pathways interrupted by genetic mutation.

iTRAQ Quantitative Proteomic Analysis of Different Expressed Proteins and Signal Pathways in Bakuchiol-Induced Hepatotoxicity

Bakuchiol (BAK) is an abundant natural compound. BAK has been reported to have several biological activities such as anticancer, antiaging, anti-inflammatory, and prevention of bone loss. However, it causes hepatotoxicity, the mechanism of which is not known. In this study, we explored the mechanism of BAK hepatotoxicity by treating rats with 52.5 mg/kg and 262.5 mg/kg of BAK, administered continuously for 6 weeks. We examined the liver pathology and biochemical composition of bile to determine toxicity. Mechanisms of BAK hepatotoxicity were analyzed based on relative and absolute quantification (iTRAQ) protein equivalent signatures and validated in vitro using LO2 cells. iTRAQ analysis revealed 281 differentially expressed proteins (DEPs) in liver tissue of the BAK-treated group, of which 215 were upregulated, and 66 were downregulated. GO and KEGG enrichment analysis revealed that bile secretion, lipid metabolism, and cytochrome P450 signaling pathways were enriched in DEPs. Among them, peroxisome proliferator-activated receptor α (PPARα), farnesoid X receptor (FXR), and cholesterol 7α-hydroxylase (CYP7a1) were closely associated with the development and progression of BAK-induced hepatic metabolic dysfunction and abnormal bile metabolism. This study shows that BAK can induce hepatotoxicity through multiple signaling pathways.

The Key Molecular Mechanisms of Sini Decoction Plus Ginseng Soup to Rescue Acute Liver Failure: Regulating PPARα to Reduce Hepatocyte Necroptosis?

Purpose

This study aimed to investigate the improvement effect of Sini Decoction plus Ginseng Soup (SNRS) on the LPS/D-GalN-induced acute liver failure (ALF) mouse model and the molecular mechanism of the SNRS effect.

Methods

To study the protective effect of SNRS on ALF mice, the ICR mice were firstly divided into 4 groups: Control group (vehicle-treated), Model group (LPS/D-GalN), SNRS group (LPS/D-GalN+SNRS), and Silymarin group (LPS/D-GalN+Silymarin), the therapeutic drug was administered by gavage 48h, 24h before, and 10 min after LPS/D-GalN injection. On this basis, the peroxisome proliferator-activated receptor (PPAR) α agonist (WY14643) and inhibitor (GW6471) were added to verify whether the therapeutic mechanism of SNRS is related to its promoting effect on PPARα. The animals are grouped as follows: Control group (vehicle-treated), Model group (LPS/D-GalN+DMSO), SNRS group (LPS/D-GalN+SNRS+DMSO), Inhibitor group (LPS/D-GalN+GW6471), Agonist group (LPS/D-GalN+WY14643), and Inhibitor+SNRS group (LPS/D-GalN+GW6471+SNRS).

Results

The protective effect of SNRS on the ALF model is mainly reflected in the reduction of serum alanine aminotransaminase (ALT) and aspartate aminotransaminase (AST) as well as the ameliorated pathology of the liver tissue. The survival rate of ALF mice treated with SNRS was significantly increased. Further mechanism studies showed that SNRS significantly promoted the protein expression of PPARα and decreased the expression of necroptosis proteins (RIP3, MLKL, p-MLKL) in ALF mice. Reduced necroptosis resulted in decreased HMGB1 release, which in turn inhibited the activation of TLR4-JNK and NLRP3 inflammasome signaling pathways and the expression of NF-κB protein induced by LPS/D-GalN. The expression of CPT1A, a key enzyme involved in fatty acid β-oxidation, was found to be significantly up-regulated in the SNRS treated group, accompanied by an increased adenosine-triphosphate (ATP) level, which may be the relevant mechanism by which SNRS reduces necroptosis.

Conclusion

The potential therapeutic effect of SNRS on ALF may be through promoting the expression of PPARα and increasing the level of ATP in liver tissue, thereby inhibiting necroptosis of hepatocytes, reducing hepatocyte damage, and improving liver function.

Population Genomics of Megalobrama Provides Insights into Evolutionary History and Dietary Adaptation

Simple Summary

Megalobrama is the economically most important freshwater fish genus in China. In recent years, germplasm resources of Megalobrama have been depleting as a result of environmental degradation and artificial factors. In this study, we established the whole genome database of Megalobrama populations using the whole genome re-sequencing technology, explored population genetic structure, and inferred comprehensive evolutionary relationships using principal component analysis and population structure analysis. Furthermore, employing selective sweep analysis, we identified candidate genes related to variations in feeding habits, revealing the molecular mechanisms of environmental adaptability in Megalobrama populations. Taken together, this study describes the population history and genetic diversity of Megalobrama populations and also the molecular mechanisms likely involved their environmental adaptability. These findings will make a substantial contribution to conservation and utilization of Megalobrama germplasm resources.

Abstract

Megalobrama, a genus of cyprinid fish, is an economically important freshwater fish widely distributed in major waters of China. Here, we report the genome resequencing of 180 Megalobrama fish including M. amblycephala, M. skolkovii, M. hoffmanni, and M. pellegrini. Population structure indicated that geographically divergent Megalobrama populations were separated into six subgroups. A phylogenetic tree showed that M. skolkovii was more closely related to M. pellegrini than other species and M. hoffmanni was clustered apart from other Megalobrama species, showing a high nucleotide diversity in geographic groups. Treemix validated gene flow from M. amblycephala to M. skolkovii, suggesting that introgression may provide an important source of genetic variation in the M. skolkovii populations. According to the demographic history analysis, it is speculated that Megalobrama might have been originally distributed in the Pearl River with some spread to Hainan Island and northern China due to lower sea levels during the glacial period. Whole-genome selective sweeps analysis demonstrated that M. amblycephala likely developed an enhanced energy metabolism mostly through fatty acid degradation pathways whereas M. hoffmanni possibly regulate lipid absorption via the cholesterol metabolism pathway. Taken together, this study provides a valuable genomic resource for future genetic investigations aiming to improve genome-assisted breeding of Megalobrama species.

Mechanisms Mediating the Regulation of Peroxisomal Fatty Acid Beta-Oxidation by PPARα

In mammalian cells, two cellular organelles, mitochondria and peroxisomes, share the ability to degrade fatty acid chains. Although each organelle harbors its own fatty acid β-oxidation pathway, a distinct mitochondrial system feeds the oxidative phosphorylation pathway for ATP synthesis. At the same time, the peroxisomal β-oxidation pathway participates in cellular thermogenesis. A scientific milestone in 1965 helped discover the hepatomegaly effect in rat liver by clofibrate, subsequently identified as a peroxisome proliferator in rodents and an activator of the peroxisomal fatty acid β-oxidation pathway. These peroxisome proliferators were later identified as activating ligands of Peroxisome Proliferator-Activated Receptor α (PPARα), cloned in 1990. The ligand-activated heterodimer PPARα/RXRα recognizes a DNA sequence, called PPRE (Peroxisome Proliferator Response Element), corresponding to two half-consensus hexanucleotide motifs, AGGTCA, separated by one nucleotide. Accordingly, the assembled complex containing PPRE/PPARα/RXRα/ligands/Coregulators controls the expression of the genes involved in liver peroxisomal fatty acid β-oxidation. This review mobilizes a considerable number of findings that discuss miscellaneous axes, covering the detailed expression pattern of PPARα in species and tissues, the lessons from several PPARα KO mouse models and the modulation of PPARα function by dietary micronutrients.

Nuclear receptors NHR-49 and NHR-79 promote peroxisome proliferation to compensate for aldehyde dehydrogenase deficiency in C. elegans

The intracellular level of fatty aldehydes is tightly regulated by aldehyde dehydrogenases to minimize the formation of toxic lipid and protein adducts. Importantly, the dysregulation of aldehyde dehydrogenases has been implicated in neurologic disorder and cancer in humans. However, cellular responses to unresolved, elevated fatty aldehyde levels are poorly understood. Here, we report that ALH-4 is a C. elegans aldehyde dehydrogenase that specifically associates with the endoplasmic reticulum, mitochondria and peroxisomes. Based on lipidomic and imaging analysis, we show that the loss of ALH-4 increases fatty aldehyde levels and reduces fat storage. ALH-4 deficiency in the intestine, cell-nonautonomously induces NHR-49/NHR-79-dependent hypodermal peroxisome proliferation. This is accompanied by the upregulation of catalases and fatty acid catabolic enzymes, as indicated by RNA sequencing. Such a response is required to counteract ALH-4 deficiency since alh-4; nhr-49 double mutant animals are sterile. Our work reveals unexpected inter-tissue communication of fatty aldehyde levels and suggests pharmacological modulation of peroxisome proliferation as a therapeutic strategy to tackle pathology related to excess fatty aldehydes.

Fatty aldehydes are generated during the turnover of membrane lipids and when cells are under oxidative stress. Because excess fatty aldehydes form toxic adducts with proteins and lipids, their levels are tightly controlled by a family of aldehyde dehydrogenases whose dysfunction has been implicated in genetic disease and cancer in humans. Here, we characterize mutant C. elegans that lack a conserved, membrane-associated aldehyde dehydrogenase ALH-4. Despite elevated levels of fatty aldehydes, these mutant worms survive by increasing the abundance of peroxisomes, which are important organelles for lipid metabolism. Such peroxisome proliferative response depends on the activation of transcription factors NHR-49 and NHR-79, via putative endocrine signals. Accordingly, the fertility of alh-4 mutant worms relies on NHR-49. Our work suggests a latent mechanism that may be activated during aldehyde dehydrogenase deficiency.

Quantitative proteomics analysis of Fructus Psoraleae-induced hepatotoxicity in rats

Fructus Psoraleae, which is commonly consumed for the treatment of osteoporosis, bone fracture, and leucoderma, induces liver injury. This study investigated the pathogenesis of the ethanol extract of Fructus Psoraleae (EEFP)-induced liver injury in rats. EEFP (1.35, 1.80, and 2.25 g·kg^-1) was administrated to Sprague Dawley (SD) rats for 30 d. We measured liver chemistries, histopathology, and quantitative isobaric tags for relative and absolute quantitation (iTRAQ)-based protein profiling. EEFP demonstrated parameters suggestive of liver injury with changes in bile secretion, bile flow rate, and liver histopathology. iTRAQ analysis showed that a total of 4042 proteins were expressed in liver tissues of EEFP-treated and untreated rats. Among these proteins, 81 were upregulated and 32 were downregulated in the treatment group. KEGG pathway analysis showed that the drug metabolic pathways of cytochrome P450, glutathione metabolism, glycerolipid metabolism, and bile secretion were enriched with differentially expressed proteins. The expression of key proteins related to the farnesoid X receptor (FXR), i.e., the peroxisome proliferators-activated receptor alpha (PPAR-α), were downregulated, and multidrug resistance-associated protein 3 (MRP3) was upregulated in the EEFP-treated rats. Our results provide evidence that EEFP may induce hepatotoxicity through various pathways. Furthermore, our study demonstrates changes in protein regulation using iTRAQ quantitative proteomics analysis.

Sjogren-Larsson Syndrome: Mechanisms and Management

Sjogren Larsson syndrome (SLS) is a rare autosomal recessive inborn error of lipid metabolism due to mutations in the ALDH3A2 that result in a deficiency of fatty aldehyde dehydrogenase (FALDH). The syndrome has a high prevalence in Sweden where it was first described, but now known to occur worldwide. The classical triad of ichthyosis, mental retardation and spasticity characterizes clinical features. Preterm birth is common. “Glistening white dots” in the retina is a pathognomic clinical feature. Magnetic resonance imaging of the brain demonstrates leukoencephalopathy predominant in the periventricular region. Cerebral MR spectroscopy reveals a characteristic abnormal lipid peak at 1.3ppm and a small peak at 0.9ppm. The primary role of FALDH is oxidation of medium and long-chain aliphatic aldehydes derived from fatty alcohol, phytanic acid, ether glycerolipids and sphingolipids. The diagnosis is based on the typical phenotype, demonstration of the enzyme deficiency and presence of biallelic mutations in the ALDH3A2. The management of SLS largely remains symptomatic currently. However, several potential therapeutic options are being developed, keeping in view of the fundamental metabolic defects or correcting the genetic defect. This review aims to summarize the clinical, genetic and biochemical findings, pathogenetic mechanisms and the current therapeutic options, in SLS.

Sjogren-Larsson syndrome associated hypermelanosis

BACKGROUND/OBJECTIVES

Sjogren - Larsson syndrome (SLS) is a rare autosomal recessive disease of the mutation ALDH3A2 that identifies a part of fatty acids for fatty aldehyde dehydrogenase: NAD-oxidoreductase enzyme complex. This study aimed to access variant ALDH3A2 gene coded for FALDH and products regulating pathogenic melanogenesis owing to increased oxidative stress and reactive oxygen species resulting in DNA harm in SLS. By turning them into fatty acids, FALDH avoids the accumulation of toxic fatty aldehydes. The mutation results in the accumulation of aldehyde-modified lipids or fatty alcohols that may interfere with skin and brain function.

METHODS

In Nov 2018, we performed a literature search in PubMed for clinical studies, clinical trials, case reports, controlled trials, randomized controlled trials, and systemic reviews. The search terms we used were "SJOGREN-LARSSON SYNDROME" AND "HYPERMELANNOSIS" OR "FALDH" (from 1985). The search resulted in 1,289 articles, out of these 95 articles met our inclusion exclusion criteria. Our inclusion criteria included relevant original articles relevant, critical systemic reviews, and crucial referenced articles, ex-clusion criteria included duplicates and articles not published in English language.

RESULTS

Toxicity of long-chain aldehydes to FALDH-deficient cells owing to accumulation under the profound epidermis layer improves oxidative stress in the cell resulting in keratinocyte hyperproliferation.

CONCLUSION

While it continues to be determined whether accumulated fatty alcohol and fatty aldehydes obtained from ether glycerolipids and sphingolipids improve the susceptibility of melanocytes and their element accountable for skin hyperpigmentation to biological colour.

Transcriptomic analysis of Pseudostellariae Radix from different fields using RNA-seq

Pseudostellariae Radix is an important traditional Chinese medicine (TCM), which is consumed commonly for its positive health effects. However, a lack of transcriptomic and genomic information hinders research on Pseudostellariae Radix. Here, high-throughput RNA sequencing (RNA-seq) was employed for the de novo assembly to analyze the transcriptome in Pseudostellariae Radix, finding significantly differentially expressed genes in this TCM from different fields based on RNA-seq and bioinformatic analysis. A total of 146,408,539 paired-end reads were generated and assembled into 89,857 unigenes with an average length of 862bp. All of the assembly unigenes were annotated by running BLASTx and BLASTn similarity searches on the Non-redundant nucleotide database (NT), the Non-redundant protein database (NR), Swiss-Prot, Cluster of Orthologous Groups (COG), Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and Interpro. On the basis of bioinformatic analysis and the expression profiles for Pseudostellariae Radix, 29 significantly differentially expressed genes were identified, which provides the basic information for exploring the molecular mechanisms that determine the quality of Pseudostellariae Radix from different fields. The expression levels of 29 genes were validated by real-time quantitative PCR (RT-qPCR). This is the first study to sample Pseudostellariae Radix, which provides an invaluable resource for understanding the genome of this herb.

Genetics and prospective therapeutic targets for Sjögren-Larsson Syndrome

INTRODUCTION

Sjögren-Larsson syndrome (SLS) is a rare neurocutaneous disease characterized by ichthyosis, spasticity, intellectual disability and a distinctive retinopathy. It is caused by inactivating mutations in ALDH3A2, which codes for fatty aldehyde dehydrogenase (FALDH) and results in abnormal metabolism of long-chain aliphatic aldehydes and alcohols. The potential disease mechanisms leading to symptoms include 1) accumulation of toxic fatty aldehydes that form covalent adducts with lipids and membrane proteins; 2) physical disruption of multi-lamellar membranes in skin and brain; 3) abnormal activation of the JNK cell signaling pathway; and 4) defective farnesol metabolism resulting in abnormal PPAR-α dependent gene expression. Currently, no effective pathogenesis-based therapy is available.

AREAS COVERED

The clinical, pathologic and genetic features of SLS are summarized. The biochemical abnormalities caused by deficient activity of FALDH are reviewed in the context of proposed pathogenic mechanisms and potential therapeutic interventions.

EXPERT OPINION

The most promising pharmacologic approach to SLS involves blocking the formation of potentially harmful fatty aldehyde adducts using aldehyde scavenging drugs, currently in phase 2 clinical trials. Other approaches needing further investigation include: 1) ALDH-specific activator drugs and PPAR-α agonists to increase mutant FALDH activity; 2) inhibitors of the JNK phosphorylation cascade; 3) antioxidants to decrease aldehyde load; 4) dietary lipid modification; and 5) gene therapy.

Expression Levels of the Oxidative Stress Response Gene ALDH3A2 in Granulosa-Lutein Cells Are Related to Female Age and Infertility Diagnosis

Oxidative stress (OS) plays an important role in all physiological processes. The effect of OS on cellular processes is modulated by the ability of the cell to express genes implicated in the reversal of lipid, protein, and DNA injury. Aldehyde dehydrogenase 3, member A2 (ALDH3A2) is a ubiquitous enzyme involved in lipid detoxification. The objective of this study was to investigate the expression ofALDH3A2in human granulosa-lutein (GL) cells of women undergoing in vitro fertilization (IVF) and its relationship with age, infertility diagnosis, and IVF outcome variables. Relative expression levels ofALDH3A2were determined by quantitative reverse transcription-polymerase chain reaction. To investigate the effect of age onALDH3A2expression, 72 women between 18 and 44 years of age with no ovarian factor (NOF) were analyzed. To evaluate the effect of infertility diagnosis onALDH3A2expression, the following groups were analyzed: 22 oocyte donors (ODs), 24 women >40 years old (yo) with tubal or male factor and no ovarian pathology, 18 poor responders (PRs), 19 cases with endometriosis (EM), and 18 patients with polycystic ovarian syndrome (PCOS). In NOF,ALDH3A2expression correlated positively with age and with the doses of follicle-stimulating hormone and luteinizing hormone administered and negatively with the number of total and mature oocytes. When different groups were analyzed,ALDH3A2expression levels were higher in patients >40 yo and in PR compared to OD. On the contrary, EM and PCOS levels were lower than expected for age. These data suggest that GL cellALDH3A2expression levels correlate with age, cause of infertility, and ovarian response to stimulation.

[Lessons Learned after 25 Years of Studies on the Physiological Roles of the Peroxisome Proliferator-activated Receptor]

The peroxisome proliferator-activated receptor (PPAR) was discovered a quarter of a century ago. PPAR was soon recognized as a general transcriptional regulator of lipid homeostasis, and several hypolipidemic and antidiabetic agents were shown to be effective ligands for it. Since then, many attempts to develop more potent drugs have been made worldwide, but most were unsuccessful due to serious side effects. It appears that the PPAR boom has ended. This review summarizes the short history of PPAR studies, including our own results, and discusses the lessons learned from the rise and fall of studies in this field for next-generation basic studies and drug development research.

Ketone Body Therapy Protects From Lipotoxicity and Acute Liver Failure Upon Pparα Deficiency

Acute liver failure (ALF) is a severe and rapid liver injury, often occurring without any preexisting liver disease, which may precipitate multiorgan failure and death. ALF is often associated with impaired β-oxidation and increased oxidative stress (OS), characterized by elevated levels of hepatic reactive oxygen species (ROS) and lipid peroxidation (LPO) products. Peroxisome proliferator-activated receptor (PPAR)α has been shown to confer hepatoprotection in acute and chronic liver injury, at least in part, related to its ability to control peroxisomal and mitochondrial β-oxidation. To study the pathophysiological role of PPARα in hepatic response to high OS, we induced a pronounced LPO by treating wild-type and Pparα-deficient mice with high doses of fish oil (FO), containing n-3 polyunsaturated fatty acids. FO feeding of Pparα-deficient mice, in contrast to control sunflower oil, surprisingly induced coma and death due to ALF as indicated by elevated serum alanine aminotransferase, aspartate aminotransferase, ammonia, and a liver-specific increase of ROS and LPO-derived malondialdehyde. Reconstitution of PPARα specifically in the liver using adeno-associated serotype 8 virus-PPARα in Pparα-deficient mice restored β-oxidation and ketogenesis and protected mice from FO-induced lipotoxicity and death. Interestingly, administration of the ketone body β-hydroxybutyrate prevented FO-induced ALF in Pparα-deficient mice, and normalized liver ROS and malondialdehyde levels. Therefore, PPARα protects the liver from FO-induced OS through its regulatory actions on ketone body levels. β-Hydroxybutyrate treatment could thus be an option to prevent LPO-induced liver damage.

Chemoproteomic Evaluation of the Polyacetylene Callyspongynic Acid

Polyacetylenes are a class of alkyne-containing natural products. Although potent bioactivities and thus possible applications as chemical probes have already been reported for some polyacetylenes, insights into the biological activities or molecular mode of action are still rather limited in most cases. To overcome this limitation, we describe the application of the polyacetylene callyspongynic acid in the development of an experimental roadmap for characterizing potential protein targets of alkyne-containing natural products. To this end, we undertook the first chemical synthesis of callyspongynic acid. We then used in situ chemical proteomics methods to demonstrate extensive callyspongynic acid-mediated chemical tagging of endoplasmic reticulum-associated lipid-metabolizing and modifying enzymes. We anticipate that an elucidation of protein targets of natural products may serve as an effective guide to the development of subsequent biological assays that aim to identify chemical phenotypes and bioactivities.

Paternal obesity in a rodent model affects placental gene expression in a sex-specific manner

Fetal growth restriction (FGR) is a major obstetric complication stemming from poor placental development. We have previously demonstrated that paternal obesity in mice is associated with impaired embryo development and significantly reduced fetal and placental weights. We hypothesised that the FGR observed in our rodent model of paternal diet-induced obesity is associated with alterations in metabolic, cell signalling and stress pathways. Male C57BL/6 mice were fed either a normal or high-fat diet for 10 weeks before sperm collection for IVF and subsequent embryo transfer. On embryonic day 14, placentas were collected and RNA extracted from both male and female placentas to assess mRNA expression of 24 target genes using custom RT-qPCR arrays. Peroxisome proliferator-activated receptor alpha (Ppara) and caspase-12 (Casp12) expression were significantly altered in male placentas from obese fathers compared with normal (P<0.05), but not female placentas. PPARA and CASP12 proteins were localised within the placenta to trophoblast giant cells by immunohistochemistry, and relative protein abundance was determined by western blot analysis. DNA was also extracted from the same placentas to determine methylation status. Global DNA methylation was significantly increased in female placentas from obese fathers compared with normal (P<0.05), but not male placentas. In this study, we demonstrate for the first time that paternal obesity is associated with changes in gene expression and methylation status of extraembryonic tissue in a sex-specific manner. These findings reinforce the negative consequences of paternal obesity before conception, and emphasise the need for more lifestyle advice for prospective fathers.

Fatty aldehyde and fatty alcohol metabolism: review and importance for epidermal structure and function

Normal fatty aldehyde and alcohol metabolism is essential for epidermal differentiation and function. Long-chain aldehydes are produced by catabolism of several lipids including fatty alcohols, sphingolipids, ether glycerolipids, isoprenoid alcohols and certain aliphatic lipids that undergo α- or ω-oxidation. The fatty aldehyde generated by these pathways is chiefly metabolized to fatty acid by fatty aldehyde dehydrogenase (FALDH, alternately known as ALDH3A2), which also functions to oxidize fatty alcohols as a component of the fatty alcohol:NAD oxidoreductase (FAO) enzyme complex. Genetic deficiency of FALDH/FAO in patients with Sjögren-Larsson syndrome (SLS) results in accumulation of fatty aldehydes, fatty alcohols and related lipids (ether glycerolipids, wax esters) in cultured keratinocytes. These biochemical changes are associated with abnormalities in formation of lamellar bodies in the stratum granulosum and impaired delivery of their precursor membranes to the stratum corneum (SC). The defective extracellular SC membranes are responsible for a leaky epidermal water barrier and ichthyosis. Although lamellar bodies appear to be the pathogenic target for abnormal fatty aldehyde/alcohol metabolism in SLS, the precise biochemical mechanisms are yet to be elucidated. Nevertheless, studies in SLS highlight the critical importance of FALDH and normal fatty aldehyde/alcohol metabolism for epidermal function. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.

Function annotation of hepatic retinoid x receptor α based on genome-wide DNA binding and transcriptome profiling

Background

Retinoid x receptor α (RXRα) is abundantly expressed in the liver and is essential for the function of other nuclear receptors. Using chromatin immunoprecipitation sequencing and mRNA profiling data generated from wild type and RXRα-null mouse livers, the current study identifies the bona-fide hepatic RXRα targets and biological pathways. In addition, based on binding and motif analysis, the molecular mechanism by which RXRα regulates hepatic genes is elucidated in a high-throughput manner.

Principal Findings

Close to 80% of hepatic expressed genes were bound by RXRα, while 16% were expressed in an RXRα-dependent manner. Motif analysis predicted direct repeat with a spacer of one nucleotide as the most prevalent RXRα binding site. Many of the 500 strongest binding motifs overlapped with the binding motif of specific protein 1. Biological functional analysis of RXRα-dependent genes revealed that hepatic RXRα deficiency mainly resulted in up-regulation of steroid and cholesterol biosynthesis-related genes and down-regulation of translation- as well as anti-apoptosis-related genes. Furthermore, RXRα bound to many genes that encode nuclear receptors and their cofactors suggesting the central role of RXRα in regulating nuclear receptor-mediated pathways.

Conclusions

This study establishes the relationship between RXRα DNA binding and hepatic gene expression. RXRα binds extensively to the mouse genome. However, DNA binding does not necessarily affect the basal mRNA level. In addition to metabolism, RXRα dictates the expression of genes that regulate RNA processing, translation, and protein folding illustrating the novel roles of hepatic RXRα in post-transcriptional regulation.

PPARα as a Transcriptional Regulator for Detoxification of Plant Diet-Derived Unfavorable Compounds

Plants contain potentially toxic compounds for animals and animals have developed physiological strategies to detoxify the ingested toxins during evolution. Feeding mice with various plant seeds and grains showed unexpected result that only sesame killed PPARα-null mice but not wild-type mice at all. A detailed analysis of this observation revealed that PPARα is involved in the metabolism of toxic compounds from plants as well as endobiotic substrates by inducing phase I and phase II detoxification enzymes. PPARα plays a vital role in direct or indirect activation of the relevant genes via the complex network among other xenobiotic nuclear receptors. Thus, PPARα plays its wider and more extensive role in energy metabolism from natural food intake to fat storage than previously thought.

Hydrophobic statins induce autophagy and cell death in human rhabdomyosarcoma cells by depleting geranylgeranyl diphosphate

Statins are the most common type of medicine used to treat hypercholesterolemia; however, they are associated with a low incidence of myotoxicity such as myopathy and rhabdomyolysis. The mechanisms for the adverse effects remain to be fully elucidated for safer chronic use and drug development. The results of our earlier work suggested that hydrophobic statins induce autophagy in cultured human rhabdomyosarcoma A204 cells. In this study, we first confirmed the statin-induced autophagy by assessing other criteria, including induced expression of the autophagy-related genes, enhanced protein degradation of autophagy marker protein p62 and electron microscopic observation of induced formation of autophagosome. We next demonstrated that the extent of inhibition of HMG-CoA reductase in the cell is parallel with the ability of a statin to induce autophagy. Thus, the primary activity of statins causes autophagy in A204 cells. Considering the mechanism for the induction, we showed that statins induce autophagy by depleting cellular levels of geranylgeranyl diphosphate (GGPP) mostly through an unknown pathway that does not involve two major small G proteins, Rheb and Ras. Finally, we demonstrated that the ability of statins to induce autophagy parallels their toxicity to A204 cells and that both can be suppressed by GGPP.

Physiologic roles of hepatic lipid droplets and involvement of peroxisome proliferator-activated receptor alpha in their dynamism

The liver is not a storage site of excess energy as triacylglycerides but a major site of carbohydrate storage, playing a vital role in glucose homeostasis, and the hepatic lipid droplets (LDs) should have a distinct physiologic role from those in lipid-storing tissues. Most studies so far have been limited to characterization of the LDs in cultured cells or of the liver of animals maintained on a normal laboratory diet, and little is known about the properties of the LDs in the liver responding to dietary excess, irregular fats, and potentially toxic compounds contained in a natural food diet. We started to characterize the hepatic LDs in wild-type and peroxisome proliferator-activated receptor alpha (PPARalpha)-null mice fed various natural diets by identifying the liver-enriched LD-associated proteins and the changes in lipid compositions. Based on the currently available data, we propose the hypothesis that hepatic LDs play vital protective roles against diet-derived excess fatty acids and potentially toxic hydrophobic compounds by temporarily storing them as neutral lipids or compounds until completion of the remodeling of fatty acids and detoxification of the compounds in a PPARalpha-dependent manner.