Disrupted methionine cycle triggers muscle atrophy in cancer cachexia through epigenetic regulation of REDD1.

The essential amino acid methionine plays a pivotal role in one-carbon metabolism, facilitating the production of S-adenosylmethionine (SAM), a critical supplier for DNA methylation and thereby a modulator of gene expression. Here, we report that the methionine cycle is disrupted in skeletal muscle during cancer cachexia, leading to endoplasmic reticulum stress and DNA hypomethylation-induced expression of the DNA damage inducible transcript 4 (Ddit4) gene, encoding the regulated in development and DNA damage response 1 (REDD1) protein. Targeting DNA methylation by depletion or pharmacological inhibition of DNA methyltransferase 3A (DNMT3A) exacerbates cachexia, while restoring DNMT3A expression or REDD1 knockout alleviates cancer cachexia-induced skeletal muscle atrophy in mice.

Reprogramming of the LXRα Transcriptome Sustains Macrophage Secondary Inflammatory Responses.

Macrophages regulate essential aspects of innate immunity against pathogens. In response to microbial components, macrophages activate primary and secondary inflammatory gene programs crucial for host defense. The liver X receptors (LXRα, LXRβ) are ligand-dependent nuclear receptors that direct gene expression important for cholesterol metabolism and inflammation, but little is known about the individual roles of LXRα and LXRβ in antimicrobial responses.

Transcriptional determinants of lipid mobilization in human adipocytes.

Defects in adipocyte lipolysis drive multiple aspects of cardiometabolic disease, but the transcriptional framework controlling this process has not been established. To address this, we performed a targeted perturbation screen in primary human adipocytes. Our analyses identified 37 transcriptional regulators of lipid mobilization, which we classified as (i) transcription factors, (ii) histone chaperones, and (iii) mRNA processing proteins.

Antioxidants stimulate BACH1-dependent tumor angiogenesis.

Lung cancer progression relies on angiogenesis, which is a response to hypoxia typically coordinated by hypoxia-inducible transcription factors (HIFs), but growing evidence indicates that transcriptional programs beyond HIFs control tumor angiogenesis. Here, we show that the redox-sensitive transcription factor BTB and CNC homology 1 (BACH1) controls the transcription of a broad range of angiogenesis genes. BACH1 is stabilized by lowering ROS levels; consequently, angiogenesis gene expression in lung cancer cells, tumor organoids, and xenograft tumors increased substantially following administration of vitamins C and E and N-acetylcysteine in a BACH1-dependent fashion under normoxia.

γ-Linolenic acid in maternal milk drives cardiac metabolic maturation.

Birth presents a metabolic challenge to cardiomyocytes as they reshape fuel preference from glucose to fatty acids for postnatal energy production. This adaptation is triggered in part by post-partum environmental changes, but the molecules orchestrating cardiomyocyte maturation remain unknown. Here we show that this transition is coordinated by maternally supplied γ-linolenic acid (GLA), an 18:3 omega-6 fatty acid enriched in the maternal milk.

Antagonistic action of GPS2 and KDM1A at enhancers governs alternative macrophage activation by interleukin 4.

The Th2 cytokine interleukin 4 (IL4) promotes macrophage differentiation into alternative subtypes and plays important roles in physiology, in metabolic and inflammatory diseases, in cancer and in tissue regeneration. While the regulatory transcription factor networks governing IL4 signaling are already well-characterized, it is currently less understood which transcriptional coregulators are involved and how they operate mechanistically. In this study, we discover that G protein pathway suppressor 2 (GPS2), a core subunit of the HDAC3 corepressor complex assembled by SMRT and NCOR, represses IL4-dependent enhancer activation in mouse macrophages.

An optimized 4C-seq protocol based on cistrome and epigenome data in the mouse RAW264.7 macrophage cell line.

Chromosome conformation capture combined with high-throughput sequencing (4C-seq) is a powerful tool to map genomic DNA regions that communicate with a specific locus of interest such as functional single-nucleotide polymorphism (SNPs)-containing regions. This protocol describes detailed steps to perform 4C-seq in mouse macrophage RAW264.7 cells, starting from the primer design based on cistrome and epigenome data, sample processing, and to the bioinformatics analysis.

Plaque Evaluation by Ultrasound and Transcriptomics Reveals BCLAF1 as a Regulator of Smooth Muscle Cell Lipid Transdifferentiation in Atherosclerosis.

Background: Understanding the processes behind carotid plaque instability is necessary to develop methods for identification of patients and lesions with stroke risk. Here, we investigated molecular signatures in human plaques stratified by echogenicity as assessed by duplex ultrasound.

Methods: Lesion echogenicity was correlated to microarray gene expression profiles from carotid endarterectomies (n=96).

Transcriptional and epigenetic control of adipocyte remodeling during obesity.

The rising prevalence of obesity over the past decades coincides with the rising awareness that a detailed understanding of both adipose tissue biology and obesity-associated remodeling is crucial for developing therapeutic and preventive strategies. Substantial progress has been made in identifying the signaling pathways and transcriptional networks that orchestrate alterations of adipocyte gene expression linked to diverse phenotypes. Owing to recent advances in epigenomics, we also gained a better appreciation for the fact that different environmental cues can epigenetically reprogram adipocyte fate and function, mainly by altering DNA methylation and histone modification patterns.

The corepressors GPS2 and SMRT control enhancer and silencer remodeling via eRNA transcription during inflammatory activation of macrophages.

While the role of transcription factors and coactivators in controlling enhancer activity and chromatin structure linked to gene expression is well established, the involvement of corepressors is not. Using inflammatory macrophage activation as a model, we investigate here a corepressor complex containing GPS2 and SMRT both genome-wide and at the Ccl2 locus, encoding the chemokine CCL2 (MCP-1). We report that corepressors co-occupy candidate enhancers along with the coactivators CBP (H3K27 acetylase) and MED1 (mediator) but act antagonistically by repressing eRNA transcription-coupled H3K27 acetylation.

Adipocyte Reprogramming by the Transcriptional Coregulator GPS2 Impacts Beta Cell Insulin Secretion.

Glucose homeostasis is maintained through organ crosstalk that regulates secretion of insulin to keep blood glucose levels within a physiological range. In type 2 diabetes, this coordinated response is altered, leading to a deregulation of beta cell function and inadequate insulin secretion. Reprogramming of white adipose tissue has a central role in this deregulation, but the critical regulatory components remain unclear.

Loss of G protein pathway suppressor 2 in human adipocytes triggers lipid remodeling by upregulating ATP binding cassette subfamily G member 1.

Objective: Adipogenesis is critical for adipose tissue remodeling during the development of obesity. While the role of transcription factors in the orchestration of adipogenic pathways is already established, the involvement of coregulators that transduce regulatory signals into epigenome alterations and transcriptional responses remains poorly understood. The aim of our study was to investigate which pathways are controlled by G protein pathway suppressor 2 (GPS2) during the differentiation of human adipocytes.

The Nuclear Receptor-Co-repressor Complex in Control of Liver Metabolism and Disease.

Hepatocytes are the major cell-type in the liver responsible for the coordination of metabolism in response to multiple signaling inputs. Coordination occurs primarily at the level of gene expression via transcriptional networks composed of transcription factors, in particular nuclear receptors (NRs), and associated co-regulators, including chromatin-modifying complexes. Disturbance of these networks by genetic, environmental or nutritional factors can lead to metabolic dysregulation and has been linked to the progression of non-alcoholic fatty liver disease (NAFLD) toward steatohepatitis and even liver cancer.

Preparation of Frozen Liver Tissues for Integrated Omics Analysis.

Next-generation sequencing (NGS) allows in-depth analysis of tissue-specific transcriptomes, cistromes, and epigenomes for a better understanding of molecular events at different levels and has proved to be a valuable tool to encrypt the complex transcription networks in both physiological and pathological processes. The preparation of tissues such as the liver for the omics analysis remains to be challenging due to time-consuming and tedious steps. Here we describe a protocol to process frozen liver tissue samples for reduced representation bisulfite sequencing (RRBS), chromatin immunoprecipitation sequencing (ChIP-seq), and RNA sequencing (RNA-seq).

Impaired LXRα Phosphorylation Attenuates Progression of Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) is a very common indication for liver transplantation. How fat-rich diets promote progression from fatty liver to more damaging inflammatory and fibrotic stages is poorly understood. Here, we show that disrupting phosphorylation at Ser196 (S196A) in the liver X receptor alpha (LXRα, NR1H3) retards NAFLD progression in mice on a high-fat-high-cholesterol diet.

Correction: The atypical ubiquitin ligase RNF31 stabilizes estrogen receptor α and modulates estrogen-stimulated breast cancer cell proliferation.

Since the publication of the above article, the authors have noted that the input data in Fig. 6E is incorrect. The correct data are included in the below Fig.

GPS2 Deficiency Triggers Maladaptive White Adipose Tissue Expansion in Obesity via HIF1A Activation.

Hypertrophic white adipose tissue (WAT) represents a maladaptive mechanism linked to the risk for developing type 2 diabetes in humans. However, the molecular events that predispose WAT to hypertrophy are poorly defined. Here, we demonstrate that adipocyte hypertrophy is triggered by loss of the corepressor GPS2 during obesity.

G protein pathway suppressor 2 (GPS2) links inflammation and cholesterol efflux by controlling lipopolysaccharide-induced ATP-binding cassette transporter A1 expression in macrophages.

Macrophages play important roles in linking alterations of cholesterol metabolism and inflammation to the development of atherosclerosis. Previous studies have identified several positive and negative crosstalk mechanisms that connect cholesterol efflux and inflammation at the transcriptional level. Of particular relevance is that the expression of ATP-binding cassette transporter A1 ( Abca1), a main regulator of cholesterol efflux, can be induced by oxysterol receptor LXR agonists but also by bacterial endotoxins, such as LPS, that activate TLR4 signaling.

Transcriptional repression in macrophages-basic mechanisms and alterations in metabolic inflammatory diseases.

Macrophage differentiation and signal responses are coordinated by closely linked transcriptional and epigenomic mechanisms that trigger gene expression. In contrast to well-characterized transcriptional activation pathways in response to diverse metabolic and inflammatory signals, we just begin appreciating that transcriptional repression is equally important. Here, we will highlight macrophage pathways that are controlled by multifaceted repression events, along with a discussion of underlying regulatory mechanisms and components.

Loss of the co-repressor GPS2 sensitizes macrophage activation upon metabolic stress induced by obesity and type 2 diabetes.

Humans with obesity differ in their susceptibility to developing insulin resistance and type 2 diabetes (T2D). This variation may relate to the extent of adipose tissue (AT) inflammation that develops as their obesity progresses. The state of macrophage activation has a central role in determining the degree of AT inflammation and thus its dysfunction, and these states are driven by epigenomic alterations linked to gene expression.

Nuclear Receptor Coregulators in Metabolism and Disease.

Within the past two decades, coregulators have emerged as essential chromatin components of metabolic signaling by nuclear receptors and additional metabolite-sensing transcription factors. Intriguingly, coregulators themselves are efficient sensors and effectors of metabolic stimuli that modulate gene expression at different levels, often via post-translational modifications of histones or other factors. There is already evidence that alterations of expression or function of coregulators contributes to metabolic disease by propagating disease-specific epigenomes linked to the dysregulation of transcription and downstream pathways.

The oxysterol receptor LXRβ protects against DSS- and TNBS-induced colitis in mice.

We examined the function of the oxysterol receptors (LXRs) in inflammatory bowel disease (IBD) through studying dextran sodium sulfate (DSS)- and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice and by elucidating molecular mechanisms underlying their anti-inflammatory action. We observed that Lxr-deficient mice are more susceptible to colitis. Clinical indicators of colitis including weight loss, diarrhea and blood in feces appeared earlier and were more severe in Lxr-deficient mice and particularly LXRβ protected against symptoms of colitis.