Adipocyte enhancer-binding protein 1 modulates adiposity and energy homeostasis

Inactive metallopeptidase homologs: the secret lives of pseudopeptidases

Inactive enzyme homologs, or pseudoenzymes, are proteins, found within most enzyme families, that are incapable of performing catalysis. Rather than catalysis, they are involved in protein-protein interactions, sometimes regulating the activity of their active enzyme cousins, or scaffolding protein complexes. Pseudoenzymes found within metallopeptidase families likewise perform these functions. Pseudoenzymes within the M14 carboxypeptidase family interact with collagens within the extracellular space, while pseudopeptidase members of the M12 "a disintegrin and metalloprotease" (ADAM) family either discard their pseudopeptidase domains as unnecessary for their roles in sperm maturation or utilize surface loops to enable assembly of key complexes at neuronal synapses. Other metallopeptidase families contain pseudopeptidases involved in protein synthesis at the ribosome and protein import into organelles, sometimes using their pseudo-active sites for these interactions. Although the functions of these pseudopeptidases have been challenging to study, ongoing work is teasing out the secret lives of these proteins.

Fibroblast-specific adipocyte enhancer binding protein 1 is a potential pathological trigger and prognostic marker for liver fibrosis independent of etiology

OBJECTIVES

Aortic carboxypeptidase-like protein (ACLP) is an extracellular protein involved in adipogenesis, epithelial-mesenchymal transition, epithelial cell hyperplasia, and collagen fibrogenesis. This study mainly aimed to analyze the potential role of adipocyte enhancer binding protein 1 (AEBP1), the ACLP-encoding gene, as a pathological target or prognostic marker for liver fibrosis regardless of etiology.

METHODS

Dysregulation pattern, clinical relevance, and biological significance of AEBP1 gene in liver fibrosis were analyzed using publicly available transcriptomic profiles, different liver fibrosis mouse models, biological databases, and AEBP1 gene silencing followed by RNA sequencing in human hepatic stellate cells (HSCs).

RESULTS

AEBP1 gene expression was upregulated and positively correlated with liver fibrogenesis independent of etiology, the protein of which was further verified in liver fibrosis mouse models induced by different pathogenic factors. A higher expression of liver AEBP1 gene had the potential to predict poor prognosis in liver fibrosis. Systematic bioinformatic analyses revealed that AEBP1 expression was HSCs-specific and associated with extracellular matrix (ECM) remodeling and its downstream mechanical-chemical signaling transition. AEBP1 knockdown by specific small interfering RNAs (siRNAs) in HSCs inhibited ECM-receptor interaction and immune-related pathways as well as HSC proliferation or activation.

CONCLUSION

A high expression of AEBP1 was specifically associated with liver fibrosis and was related to a poor prognosis and predicted the role of AEBP1 in HSCs, providing a new insight for understanding AEBP1 in liver fibrosis.

Effects of Extracellular Vesicles from Osteogenic Differentiated Human BMSCs on Osteogenic and Adipogenic Differentiation Capacity of Naïve Human BMSCs

Osteoporosis, or steroid-induced osteonecrosis of the hip, is accompanied by increased bone marrow adipogenesis. Such a disorder of adipogenic/osteogenic differentiation, affecting bone-marrow-derived mesenchymal stem cells (BMSCs), contributes to bone loss during aging. Here, we investigated the effects of extracellular vesicles (EVs) isolated from human (h)BMSCs during different stages of osteogenic differentiation on the osteogenic and adipogenic differentiation capacity of naïve (undifferentiated) hBMSCs. We observed that all EV groups increased viability and proliferation capacity and suppressed the apoptosis of naïve hBMSCs. In particular, EVs derived from hBMSCs at late-stage osteogenic differentiation promoted the osteogenic potential of naïve hBMSCs more effectively than EVs derived from naïve hBMSCs (naïve EVs), as indicated by the increased gene expression of COL1A1 and OPN. In contrast, the adipogenic differentiation capacity of naïve hBMSCs was inhibited by treatment with EVs from osteogenic differentiated hBMSCs. Proteomic analysis revealed that osteogenic EVs and naïve EVs contained distinct protein profiles, with pro-osteogenic and anti-adipogenic proteins encapsulated in osteogenic EVs. We speculate that osteogenic EVs could serve as an intercellular communication system between bone- and bone-marrow adipose tissue, for transporting osteogenic factors and thus favoring pro-osteogenic processes. Our data may support the theory of an endocrine circuit with the skeleton functioning as a ductless gland.

Integrative analysis reveals a lineage-specific circular RNA landscape for adipo-osteogenesis of human mesenchymal stem cells

Background

The balance between osteogenesis and adipogenesis of mesenchymal stem cells (MSCs) is critical to skeletal development and diseases. As a research hotspot, circular RNAs (circRNAs) have expanded our understanding of a hidden layer of the transcriptome. Yet, their roles during adipo-osteogenesis remain poorly described.

Methods

The identity of human MSCs derived from bone marrow and adipose were first determined by flow cytometry, cellular staining, and quantitative polymerase chain reaction (qPCR). Multi-strategic RNA-sequencing was performed using Poly A, RiboMinus and RiboMinus/RNase R methods. Integrative analysis was performed to identify lineage-specific expressed circRNAs. The structural and expressional characteristics were identified by Sanger sequencing and qPCR, respectively. The regulatory effects of adipogenesis-specific circ-CRLF1 were confirmed using siRNA transcfection and qPCR.

Results

We generated a whole transcriptome map during adipo-osteogenesis based on 10 Poly A, 20 RiboMinus and 20 RiboMinus/ RNase R datasets. A total of 31,326 circRNAs were identified and quantified from ~ 3.4 billion paired-end reads. Furthermore, the integrative analysis revealed that 1166 circRNA genes exhibited strong lineage-specific expression patterns. Their host genes were enriched in distinct biological functions, such as cell adhesion, cytokine signaling, and cell division. We randomly selected and validated the back-spliced junction sites and expression patterns of 12 lineage-specific circRNAs. Functional analysis indicated that circ-CRLF1 negatively regulated adipogenesis.

Conclusions

Our integrative analysis reveals an accurate and generally applicable lineage-specific circRNA landscape for adipo-osteogenesis of MSCs and provides a potential therapeutic target, circ-CRLF1, for the treatment of skeleton-related disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02792-5.

Animal Models of Ehlers-Danlos Syndromes: Phenotype, Pathogenesis, and Translational Potential

The Ehlers–Danlos syndromes (EDS) are a group of heritable connective tissues disorders mainly characterized by skin hyperextensibility, joint hypermobility and generalized tissue fragility. Currently, 14 EDS subtypes each with particular phenotypic features are recognized and are caused by genetic defects in 20 different genes. All of these genes are involved in the biosynthesis and/or fibrillogenesis of collagens at some level. Although great progress has been made in elucidating the molecular basis of different EDS subtypes, the pathogenic mechanisms underlying the observed phenotypes remain poorly understood, and consequentially, adequate treatment and management options for these conditions remain scarce. To date, several animal models, mainly mice and zebrafish, have been described with defects in 14 of the 20 hitherto known EDS-associated genes. These models have been instrumental in discerning the functions and roles of the corresponding proteins during development, maturation and repair and in portraying their roles during collagen biosynthesis and/or fibrillogenesis, for some even before their contribution to an EDS phenotype was elucidated. Additionally, extensive phenotypical characterization of these models has shown that they largely phenocopy their human counterparts, with recapitulation of several clinical hallmarks of the corresponding EDS subtype, including dermatological, cardiovascular, musculoskeletal and ocular features, as well as biomechanical and ultrastructural similarities in tissues. In this narrative review, we provide a comprehensive overview of animal models manifesting phenotypes that mimic EDS with a focus on engineered mouse and zebrafish models, and their relevance in past and future EDS research. Additionally, we briefly discuss domestic animals with naturally occurring EDS phenotypes. Collectively, these animal models have only started to reveal glimpses into the pathophysiological aspects associated with EDS and will undoubtably continue to play critical roles in EDS research due to their tremendous potential for pinpointing (common) signaling pathways, unveiling possible therapeutic targets and providing opportunities for preclinical therapeutic interventions.

Cooperation of ATF4 and CTCF promotes adipogenesis through transcriptional regulation

Adipogenesis is a multi-step process orchestrated by activation of numerous TFs, whose cooperation and regulatory network remain elusive. Activating transcription factor 4 (ATF4) is critical for adipogenesis, yet its regulatory network is unclarified. Here, we mapped genome-wide ATF4 binding landscape and its regulatory network by Chip-seq and RNA-seq and found ATF4 directly modulated transcription of genes enriching in fat cell differentiation. Motifs of TFs especially CTCF were found from ATF4 binding sites, suggesting a direct role of ATF4 in regulating adipogenesis associated with CTCF and other TFs. Deletion of CTCF attenuated adipogenesis while overexpression enhanced adipocyte differentiation, indicating CTCF is indispensable for adipogenesis. Intriguingly, combined analysis of Chip-seq data of these two TFs showed that ATF4 co-localized with CTCF in the promoters of key adipogenic genes including Cebpd and PPARg and co-regulated their transactivation. Moreover, ATF4 directly regulated CTCF expression and interacted with CTCF in differentiated 3T3-L1 cells. In vivo, downregulation of ATF4 suppressed the expression of CTCF, Cebpd, and PPARg, leading to reduced adipose tissue expansion in refeeding mice. Consistently, mRNA expression of ATF4 and CTCF was positively correlated with each other in human subcutaneous adipose tissue and inversely associated with BMI, indicating a possible involvement of these two TFs in adipose development. Taken together, our data propose for the first time that ATF4 and CTCF work cooperatively to control adipogenesis and adipose development via orchestrating transcription of adipogenic genes. Our findings reveal novel therapeutic targets in obesity treatment.

AEBP1 is a Novel Oncogene: Mechanisms of Action and Signaling Pathways

Adipocyte enhancer-binding protein 1 (AEBP1) is a transcriptional repressor involved in the regulation of critical biological processes including adipogenesis, mammary gland development, inflammation, macrophage cholesterol homeostasis, and atherogenesis. Several years ago, we first reported the ability of AEBP1 to exert a positive control over the canonical NF-κB pathway. Indeed, AEBP1 positively regulates NF-κB activity via its direct interaction with IκBα, a key NF-κB inhibitor. AEBP1 overexpression results in uncontrollable activation of NF-κB, which may have severe pathogenic outcomes. Recently, the regulatory relationship between AEBP1 and NF-κB pathway has been of great interest to many researchers primarily due to the implication of NF-κB signaling in critical cellular processes such as inflammation and cancer. Since constitutive activation of NF-κB is widely implicated in carcinogenesis, AEBP1 overexpression is associated with tumor development and progression. Recent studies sought to explore the effects of the overexpression of AEBP1, as a potential oncogene, in different types of cancer. In this review, we analyze the effects of AEBP1 overexpression in a variety of malignancies (e.g., breast cancer, glioblastoma, bladder cancer, gastric cancer, colorectal cancer, ovarian cancer, and skin cancer), with a specific focus on the AEBP1-mediated control over the canonical NF-κB pathway. We also underscore the ability of AEBP1 to regulate crucial cancer-related events like cell proliferation and apoptosis in light of other key pathways (e.g., PI3K-Akt, sonic hedgehog (Shh), p53, parthanatos (PARP-1), and PTEN). Identifying AEBP1 as a potential biomarker for cancer prognosis may lead to a novel therapeutic target for the prevention and/or treatment of various types of cancer.

AEBP1 down regulation induced cell death pathway depends on PTEN status of glioma cells

Glioblastoma (GBM) is the most common aggressive form of brain cancer with overall dismal prognosis (10–12 months) despite all current multimodal treatments. Previously we identified adipocyte enhancer binding protein 1 (AEBP1) as a differentially regulated gene in GBM. On probing the role of AEBP1 over expression in glioblastoma, we found that both cellular proliferation and survival were affected upon AEBP1 silencing in glioma cells, resulting in cell death. In the present study we report that the classical caspase pathway components are not activated in cell death induced by AEBP1 down regulation in PTEN-deficient (U87MG and U138MG) cells. PARP-1 was not cleaved but over-activated under AEBP1 down regulation which leads to the synthesis of PAR in the nucleus triggering the release of AIF from the mitochondria. Subsequently, AIF translocates to the nucleus along with MIF causing chromatinolysis. AEBP1 positively regulates PI3KinaseCβ by the binding to AE-1 binding element in the PI3KinaseCβ promoter. Loss of PI3KinaseCβ expression under AEBP1 depleted condition leads to excessive DNA damage and activation of PARP-1. Furthermore, over expression of PIK3CB (in trans) in U138MG cells prevents DNA damage in these AEBP1 depleted cells. On the contrary, AEBP1 down regulation induces caspase-dependent cell death in PTEN-proficient (LN18 and LN229) cells. Ectopic expression of wild-type PTEN in PTEN-deficient U138MG cells results in the activation of canonical caspase and Akt dependent cell death. Collectively, our findings define AEBP1 as a potential oncogenic driver in glioma, with potential implications for therapeutic intervention.

Adipose PTEN regulates adult adipose tissue homeostasis and redistribution via a PTEN-leptin-sympathetic loop

OBJECTIVE

Despite the large body of work describing the tumor suppressor functions of Phosphatase and tensin homologue deleted on chromosome ten (PTEN), its roles in adipose homeostasis of adult animals are not yet fully understood. Here, we sought to determine the role of PTEN in whole-body adipose homeostasis.

METHODS

We genetically manipulated PTEN in specific fat depots through recombinant adeno-associated viral vector (rAAV)-based gene transfer of Cre recombinase to adult PTEN^flox mice. Additionally, we used a denervation agent, 6OHDA, to assess the role of sympathetic signaling in PTEN-related adipose remodeling. Furthermore, we chemically manipulated AKT signaling via a pan-AKT inhibitor, MK-2206, to assess the role of AKT in PTEN-related adipose remodeling. Finally, to understand the role of leptin and central signaling on peripheral tissues, we knocked down hypothalamic leptin receptor with a microRNA delivered by a rAAV vector.

RESULTS

Knockdown PTEN in individual fat depot resulted in massive expansion of the affected fat depot through activation of AKT signaling associated with suppression of lipolysis and induction of leptin. This hypertrophic expansion of the affected fat depot led to upregulation of PTEN level, higher lipolysis, and induction of white fat browning in other fat depots, and the compensatory reduced fat mass to maintain a set point of whole-body adiposity. Administration of AKT inhibitor MK-2206 prevented the adipose PTEN knockdown-associated effects. 6OHDA-mediated denervation demonstrated that sympathetic innervation was required for the PTEN knockdown-induced adipose redistribution. Knockdown hypothalamic leptin receptor attenuated the adipose redistribution induced by PTEN deficiency in individual fat depot.

CONCLUSIONS

Our results demonstrate the essential role of PTEN in adipose homeostasis, including mass and distribution in adulthood, and reveal an "adipose PTEN-leptin-sympathetic nervous system" feedback loop to maintain a set point of adipose PTEN and whole-body adiposity.

Short communication: Adipogenic, metabolic, and apoptotic marker mRNA in cellular fractions of adipose tissue from chickens predisposed to be anorexic or obese

The body weight-selected lines of chickens are a model for understanding factors that predispose an individual to anorexia or obesity. The high body weight-selected (HWS) individuals are compulsive eaters that become obese whereas the low body weight-selected (LWS) are relatively lean and hypophagic. The objective of this study was to measure gene expression of various preadipocyte, proliferation, metabolic, and apoptotic markers in the stromal-vascular fraction and adipocytes from LWS and HWS adipose tissue. Although preadipocyte and proliferation markers were more highly expressed in the stromal-vascular fraction of LWS than HWS chicks, greater expression of granzyme-A and the presence of more annexin V-positive cells suggests that apoptosis may limit the adipogenic potential of adipocyte precursor cells and represent a novel mechanism that regulates the expansion of adipose tissue. Results provide insights on cellular mechanisms associated with adipose tissue development in the lean and obese state.

AEBP1 expression increases with severity of fibrosis in NASH and is regulated by glucose, palmitate, and miR-372-3p

Factors governing the development of liver fibrosis in nonalcoholic steatohepatitis (NASH) are only partially understood. We recently identified adipocyte enhancer binding protein 1 (AEBP1) as a member of a core set of dysregulated fibrosis-specific genes in human NASH. Here we sought to investigate the relationship between AEBP1 and hepatic fibrosis. We confirmed that hepatic AEBP1 expression is elevated in fibrosis compared to lobular inflammation, steatosis, and normal liver, and increases with worsening fibrosis in NASH patients. AEBP1 expression was upregulated 5.8-fold in activated hepatic stellate cells and downregulated during chemical and contact induction of biological quiescence. In LX-2 and HepG2 cells treated with high glucose (25 mM), AEBP1 expression increased over 7-fold compared to normal glucose conditions. In response to treatment with either fructose or palmitate, AEBP1 expression in primary human hepatocytes increased 2.4-fold or 9.6-fold, but was upregulated 55.8-fold in the presence of fructose and palmitate together. AEBP1 knockdown resulted in decreased expression of nine genes previously identified to be part of a predicted AEBP1-associated NASH co-regulatory network and confirmed to be upregulated in fibrotic tissue. We identified binding sites for two miRNAs known to be downregulated in NASH fibrosis, miR-372-3p and miR-373-3p in the AEBP1 3' untranslated region. Both miRNAs functionally interacted with AEBP1 to regulate its expression. These findings indicate a novel AEBP1-mediated pathway in the pathogenesis of hepatic fibrosis in NASH.

Selection signatures in four German warmblood horse breeds: Tracing breeding history in the modern sport horse

The study of selection signatures helps to find genomic regions that have been under selective pressure and might host genes or variants that modulate important phenotypes. Such knowledge improves our understanding of how breeding programmes have shaped the genomes of livestock. In this study, 942 stallions were included from four, exemplarily chosen, German warmblood breeds with divergent historical and recent selection focus and different crossbreeding policies: Trakehner (N = 44), Holsteiner (N = 358), Hanoverian (N = 319) and Oldenburger (N = 221). Those breeds are nowadays bred for athletic performance and aptitude for show-jumping, dressage or eventing, with a particular focus of Holsteiner on the first discipline. Blood samples were collected during the health exams of the stallion preselections before licensing and were genotyped with the Illumina EquineSNP50 BeadChip. Autosomal markers were used for a multi-method search for signals of positive selection. Analyses within and across breeds were conducted by using the integrated Haplotype Score (iHS), cross-population Extended Haplotype Homozygosity (xpEHH) and Runs of Homozygosity (ROH). Oldenburger and Hanoverian showed very similar iHS signatures, but breed specificities were detected on multiple chromosomes with the xpEHH. The Trakehner clustered as a distinct group in a principal component analysis and also showed the highest number of ROHs, which reflects their historical bottleneck. Beside breed specific differences, we found shared selection signals in an across breed iHS analysis on chromosomes 1, 4 and 7. After investigation of these iHS signals and shared ROH for potential functional candidate genes and affected pathways including enrichment analyses, we suggest that genes affecting muscle functionality (TPM1, TMOD2-3, MYO5A, MYO5C), energy metabolism and growth (AEBP1, RALGAPA2, IGFBP1, IGFBP3-4), embryonic development (HOXB-complex) and fertility (THEGL, ZPBP1-2, TEX14, ZP1, SUN3 and CFAP61) have been targeted by selection in all breeds. Our findings also indicate selection pressure on KITLG, which is well-documented for influencing pigmentation.

Aortic carboxypeptidase-like protein enhances adipose tissue stromal progenitor differentiation into myofibroblasts and is upregulated in fibrotic white adipose tissue

White adipose tissue expands through both adipocyte hypertrophy and hyperplasia and it is hypothesized that fibrosis or excess accumulation of extracellular matrix within adipose tissue may limit tissue expansion contributing to metabolic dysfunction. The pathways that control adipose tissue remodeling are only partially understood, however it is likely that adipose tissue stromal and perivascular progenitors participate in fibrotic remodeling and also serve as adipocyte progenitors. The goal of this study was to investigate the role of the secreted extracellular matrix protein aortic carboxypeptidase-like protein (ACLP) on adipose progenitor differentiation in the context of adipose tissue fibrosis. Treatment of 10T1/2 mouse cells with recombinant ACLP suppressed adipogenesis and enhanced myofibroblast differentiation, which was dependent on transforming growth factor-β receptor kinase activity. Mice fed a chronic high fat diet exhibited white adipose tissue fibrosis with elevated ACLP expression and cellular fractionation of these depots revealed that ACLP was co-expressed with collagens primarily in the inflammatory cell depleted stromal-vascular fraction (SVF). SVF cells isolated from mice fed a high fat diet secreted increased amounts of ACLP compared to low fat diet control SVF. These cells also exhibited reduced adipogenic differentiation capacity in vitro. Importantly, differentiation studies in primary human adipose stromal cells revealed that mature adipocytes do not express ACLP and exogenous ACLP administration blunted their differentiation potential while upregulating myofibroblastic markers. Collectively, these studies identify ACLP as a stromal derived mediator of adipose progenitor differentiation that may limit adipocyte expansion during white adipose tissue fibrosis.

Association of adipocyte enhancer-binding protein 1 with Alzheimer's disease pathology in human hippocampi

Adipocyte enhancer binding protein 1 (AEBP1) activates inflammatory responses via the NF-κB pathway in macrophages and regulates adipogenesis in preadipocytes. Up-regulation of AEBP1 in the hippocampi of patients with Alzheimer's disease (AD) has been revealed by microarray analyses of autopsied brains from the Japanese general population (the Hisayama study). In this study, we compared the expression patterns of AEBP1 in normal and AD brains, including in the hippocampus, using immunohistochemistry. The subjects were 24 AD cases and 52 non-AD cases. Brain specimens were immunostained with antibodies against AEBP1, tau protein, amyloid β protein, NF-κB, GFAP and Iba-1. In normal brains, AEBP1 immunoreactivity mainly localized to the perikarya of hippocampal pyramidal neurons, and its expression was elevated in the pyramidal neurons and some astrocytes in AD hippocampi. Although AEBP1 immunoreactivity was almost absent in neurons containing neurofibrillary tangles, AEBP1 was highly expressed in neurons with pretangles and in the tau-immunopositive, dystrophic neurites of senile plaques. Nuclear localization of NF-κB was also observed in certain AEBP1-positive neurons in AD cases. Comparison of AD and non-AD cases suggested a positive correlation between the expression level of AEBP1 and the degree of amyloid β pathology. These findings imply that AEBP1 protein has a role in the progression of AD pathology.

Identification of carboxypeptidase X (CPX)-1 as a positive regulator of adipogenesis

Adipose tissue expansion occurs through a combination of hypertrophy of existing adipocytes and generation of new adipocytes via the process of hyperplasia, which involves the proliferation and subsequent differentiation of preadipocytes. Deficiencies in hyperplasia contribute to adipose tissue dysfunction and the association of obesity with chronic cardiometabolic diseases. Thus, increased understanding of hyperplastic pathways may be expected to afford novel therapeutic strategies. We have reported that fibroblast growth factor (FGF)-1 promotes proliferation and differentiation of human preadipocytes and recently demonstrated that bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) is a central, proximal effector. Herein, we describe the identification and characterization of carboxypeptidase X (CPX)-1, a secreted collagen-binding glycoprotein, as a novel downstream effector in human primary and Simpson-Golabi-Behmel syndrome preadipocytes. CPX-1 expression increased after treatment of preadipocytes with FGF-1, BAMBI knockdown, or induction of differentiation. CPX-1 knockdown compromised preadipocyte differentiation coincident with reduced collagen expression. Furthermore, preadipocytes differentiated on matrix derived from CPX-1 knockdown cells exhibited reduced Glut4 expression and insulin-stimulated glucose uptake. Finally, CPX-1 expression was increased in adipose tissue from obese mice and humans. Collectively, these findings establish CPX-1 as a positive regulator of adipogenesis situated downstream of FGF-1/BAMBI that may contribute to hyperplastic adipose tissue expansion via affecting extracellular matrix remodeling.-Kim, Y.-H., Barclay, J. L., He, J., Luo, X., O'Neill, H. M., Keshvari, S., Webster, J. A., Ng, C., Hutley, L. J., Prins, J. B., Whitehead, J. P. Identification of carboxypeptidase X (CPX)-1 as a positive regulator of adipogenesis.

Exercise training as treatment in cancer cachexia

Cachexia is a wasting syndrome that may accompany a plethora of diseases, including cancer, chronic obstructive pulmonary disease, aids, and rheumatoid arthritis. It is associated with central and systemic increases of pro-inflammatory factors, and with decreased quality of life, response to pharmacological treatment, and survival. At the moment, there is no single therapy able to reverse cachexia many symptoms, which include disruption of intermediary metabolism, endocrine dysfunction, compromised hypothalamic appetite control, and impaired immune function, among other. Growing evidence, nevertheless, shows that chronic exercise, employed as a tool to counteract systemic inflammation, may represent a low-cost, safe alternative for the prevention/attenuation of cancer cachexia. Despite the well-documented capacity of chronic exercise to counteract sustained disease-related inflammation, few studies address the effect of exercise training in cancer cachexia. The aim of the present review was hence to discuss the results of cachexia treatment with endurance training. As opposed to resistance exercise, endurance exercise may be performed devoid of equipment, is well tolerated by patients, and an anti-inflammatory effect may be observed even at low-intensity. The decrease in inflammatory status induced by endurance protocols is paralleled by recovery of various metabolic pathways. The mechanisms underlying the response to the treatment are considered.

Identification of genes regulating growth and fatness traits in pig through hypothalamic transcriptome analysis

Previous studies on Iberian × Landrace (IBMAP) pig intercrosses have enabled the identification of several quantitative trait locus (QTL) regions related to growth and fatness traits; however, the genetic variation underlying those QTLs are still unknown. These traits are not only relevant because of their impact on economically important production traits, but also because pig constitutes a widely studied animal model for human obesity and obesity-related diseases. The hypothalamus is the main gland regulating growth, food intake, and fat accumulation. Therefore, the aim of this work was to identify genes and/or gene transcripts involved in the determination of growth and fatness in pig by a comparison of the whole hypothalamic transcriptome (RNA-Seq) in two groups of phenotypically divergent IBMAP pigs. Around 16,000 of the ∼25.010 annotated genes were expressed in these hypothalamic samples, with most of them showing intermediate expression levels. Functional analyses supported the key role of the hypothalamus in the regulation of growth, fat accumulation, and energy expenditure. Moreover, 58,927 potentially new isoforms were detected. More than 250 differentially expressed genes and novel transcript isoforms were identified between the two groups of pigs. Twenty-one DE genes/transcripts that colocalized in previously identified QTL regions and/or whose biological functions are related to the traits of interest were explored in more detail. Additionally, the transcription factors potentially regulating these genes and the subjacent networks and pathways were also analyzed. This study allows us to propose strong candidate genes for growth and fatness based on expression patterns, genomic location, and network interactions.

AEBP1 upregulation confers acquired resistance to BRAF (V600E) inhibition in melanoma

An activating BRAF (V600E) kinase mutation occurs in approximately half of melanomas. Recent clinical studies have demonstrated that vemurafenib (PLX4032) and dabrafenib, potent and selective inhibitors of mutant v-raf murine sarcoma viral oncogene homolog B1 (BRAF), exhibit remarkable activities in patients with V600 BRAF mutant melanomas. However, acquired drug resistance invariably develops after the initial treatment. Identification of acquired resistance mechanisms may inform the development of new therapies that elicit long-term responses of melanomas to BRAF inhibitors. Here we report that increased expression of AEBP1 (adipocyte enhancer-binding protein 1) confers acquired resistance to BRAF inhibition in melanoma. AEBP1 is shown to be highly upregulated in PLX4032-resistant melanoma cells because of the hyperactivation of the PI3K/Akt-cAMP response element-binding protein (CREB) signaling pathway. This upregulates AEBP1 expression and thus leads to the activation of NF-κB via accelerating IκBa degradation. In addition, inhibition of the PI3K/Akt-CREB-AEBP1-NF-κB pathway greatly reverses the PLX4032-resistant phenotype of melanoma cells. Furthermore, increased expression of AEBP1 is validated in post-treatment tumors in patients with acquired resistance to BRAF inhibitor. Therefore, these results reveal a novel PI3K/Akt-CREB-AEBP1-NF-κB pathway whose activation contributes to acquired resistance to BRAF inhibition, and suggest that this pathway, particularly AEBP1, may represent a novel therapeutic target for treating BRAF inhibitor-resistant melanoma.

Skeletal myoblast transplantation on gene expression profiles of insulin signaling pathway and mitochondrial biogenesis and function in skeletal muscle

AIM

The study aims to investigate the gene expression profiling of insulin signaling pathway and mitochondrial biogenesis and function in the skeletal muscle of KK mice.

METHODS

KK mice were divided into the following groups: KK control group, basal medium (M199) only; KK fibroblast group, with human fibroblast transplantation; KK myoblast group, with human skeletal myoblast transplantation. C57BL mice received hSkM transplantation as a normal control. Cells were transplanted into mice hind limb skeletal muscle. All animals were treated with cyclosporine for 6 weeks only. The mice were sacrificed in a fasting state at 12 weeks after treatment. Hind limb skeletal muscle was harvested and used for study of gene expression profiling.

RESULTS

hSkMs survived extensively in mice skeletal muscle at 12 weeks after cell transplantation. Glucose tolerance test showed a significant decrease of blood glucose in the mice of KK myoblast group compared to the KK control and fibroblast groups. Transcriptional patterns of insulin signaling pathway showed alterations in KK myoblast as compared with KK control group (23 genes), KK fibroblast group (7 genes), and C57BL group (8 genes). Transcriptional patterns of mitochondrial biogenesis and function also had alterations in KK myoblast as compared with KK control group (27 genes), KK fibroblast group (9 genes), and C57BL group (6 genes).

CONCLUSIONS

These data demonstrated for the first time that hSKM transplantation resulted in a change of gene transcript in multiple genes involved in insulin signaling pathway and mitochondrial biogenesis and function.

The role of inflammatory pathways in cancer-associated cachexia and radiation resistance

Dysregulated inflammatory responses are key contributors to a multitude of chronic ailments, including cancer. Evidence indicates that disease progression in cancer is dependent on the complex interaction between the tumor and the host microenvironment. Most recently, the inflammatory response has been suggested to be critical, as both the tumor and microenvironment compartments produce cytokines that act on numerous target sites, where they foster a complex cascade of biologic outcomes. Patients with cancer-associated cachexia (CAC) suffer from a dramatic loss of skeletal muscle and adipose tissue, ultimately precluding them from many forms of therapeutic intervention, including radiotherapy. The cytokines that have been linked to the promotion of the cachectic response may also participate in radiation resistance. The major changes at the cytokine level are, in part, due to transcriptional regulatory alterations possibly due to epigenetic modifications. Herein we discuss the role of inflammatory pathways in CAC and examine the potential link between cachexia induction and radiation resistance.

Stromal adipocyte enhancer-binding protein (AEBP1) promotes mammary epithelial cell hyperplasia via proinflammatory and hedgehog signaling

Disruption of mammary stromal-epithelial communication leads to aberrant mammary gland development and induces mammary tumorigenesis. Macrophages have been implicated in carcinogenesis primarily by creating an inflammatory microenvironment, which promotes growth of the adjacent epithelial cells. Adipocyte enhancer-binding protein 1 (AEBP1), a novel proinflammatory mediator, promotes macrophage inflammatory responsiveness by inducing NF-κB activity, which has been implicated in tumor cell growth and survival by aberrant sonic hedgehog (Shh) expression. Here, we show that stromal macrophage AEBP1 overexpression results in precocious alveologenesis in the virgin AEBP1 transgenic (AEBP1(TG)) mice, and the onset of ductal hyperplasia was accelerated in AEBP1(TG) mice fed a high fat diet, which induces endogenous AEBP1 expression. Transplantation of AEBP1(TG) bone marrow cells into non-transgenic (AEBP1(NT)) mice resulted in alveolar hyperplasia with up-regulation of NF-κB activity and TNFα expression as displayed in the AEBP1(TG) mammary macrophages and epithelium. Shh expression was induced in AEBP1(TG) macrophages and RAW264.7 macrophages overexpressing AEBP1. The Shh target genes Gli1 and Bmi1 expression was induced in the AEBP1(TG) mammary epithelium and HC11 mammary epithelial cells co-cultured with AEBP1(TG) peritoneal macrophages. The conditioned AEBP1(TG) macrophage culture media promoted NF-κB activity and survival signal, Akt activation, in HC11 cells, whereas such effects were abolished by TNFα neutralizing antibody treatment. Furthermore, HC11 cells displayed enhanced proliferation in response to AEBP1(TG) macrophages and their conditioned media. Our findings highlight the role of AEBP1 in the signaling pathways regulating the cross-talk between mammary epithelium and stroma that could predispose the mammary tissue to tumorigenesis.

Adipose tissue inflammation and cancer cachexia: possible role of nuclear transcription factors

Cancer cachexia is a multifaceted syndrome whose aetiology is extremely complex and is directly related to poor patient prognosis and survival. Changes in lipid metabolism in cancer cachexia result in marked reduction of total fat mass, increased lipolysis, total oxidation of fatty acids, hyperlipidaemia, hypertriglyceridaemia, and hypercholesterolaemia. These changes are believed to be induced by inflammatory mediators, such as tumour necrosis factor-α (TNF-α) and other factors. Attention has recently been drawn to the current theory that cachexia is a chronic inflammatory state, mainly caused by the host's reaction to the tumour. Changes in expression of numerous inflammatory mediators, notably in white adipose tissue (WAT), may trigger several changes in WAT homeostasis. The inhibition of adipocyte differentiation by PPARγ is paralleled by the appearance of smaller adipocytes, which may partially account for the inhibitory effect of PPARγ on inflammatory gene expression. Furthermore, inflammatory modulation and/or inhibition seems to be dependent on the IKK/NF-κB pathway, suggesting that a possible interaction between NF-κB and PPARγ is required to modulate WAT inflammation induced by cancer cachexia. In this article, current literature on the possible mechanisms of NF-κB and PPARγ regulation of WAT cells during cancer cachexia are discussed. This review aims to assess the role of a possible interaction between NF-κB and PPARγ in the setting of cancer cachexia as well as its significant role as a potential modulator of chronic inflammation that could be explored therapeutically.

Lactation defect with impaired secretory activation in AEBP1-null mice

Adipocyte enhancer binding protein 1 (AEBP1) is a multifunctional protein that negatively regulates the tumor suppressor PTEN and IκBα, the inhibitor of NF-κB, through protein-protein interaction, thereby promoting cell survival and inflammation. Mice homozygous for a disrupted AEBP1 gene developed to term but showed defects in growth after birth. AEBP1^−/− females display lactation defect, which results in the death of 100% of the litters nursed by AEBP1^−/− dams. Mammary gland development during pregnancy appears normal in AEBP1^−/− dams; however these mice exhibit expansion of the luminal space and the appearance of large cytoplasmic lipid droplets (CLDs) in the mammary epithelial cells at late pregnancy and parturition, which is a clear sign of failed secretory activation, and accumulation of milk proteins in the mammary gland, presumably reflecting milk stasis following failed secretory activation. Eventually, AEBP1^−/− mammary gland rapidly undergoes involution at postpartum. Stromal restoration of AEBP1 expression by transplanting wild-type bone marrow (BM) cells is sufficient to rescue the mammary gland defect. Our studies suggest that AEBP1 is critical in the maintenance of normal tissue architecture and function of the mammary gland tissue and controls stromal-epithelial crosstalk in mammary gland development.

Adipocyte enhancer-binding protein 1 (AEBP1) (a novel macrophage proinflammatory mediator) overexpression promotes and ablation attenuates atherosclerosis in ApoE (-/-) and LDLR (-/-) mice

Atherogenesis is a long-term process that involves inflammatory response coupled with metabolic dysfunction. Foam cell formation and macrophage inflammatory response are two key events in atherogenesis. Adipocyte enhancer-binding protein 1 (AEBP1) has been shown to impede macrophage cholesterol efflux, promoting foam cell formation, via peroxisome proliferator-activated receptor (PPAR)-γ1 and liver X receptor α (LXRα) downregulation. Moreover, AEBP1 has been shown to promote macrophage inflammatory responsiveness by inducing nuclear factor (NF)-κB activity via IκBα downregulation. Lipopolysaccharide (LPS)-induced suppression of pivotal macrophage cholesterol efflux mediators, leading to foam cell formation, has been shown to be mediated by AEBP1. Herein, we showed that AEBP1-transgenic mice (AEBP1(TG)) with macrophage-specific AEBP1 overexpression exhibit hyperlipidemia and develop atherosclerotic lesions in their proximal aortas. Consistently, ablation of AEBP1 results in significant attenuation of atherosclerosis (males: 3.2-fold, P = 0.001 [en face]), 2.7-fold, P = 0.0004 [aortic roots]; females: 2.1-fold, P = 0.0026 [en face], 1.7-fold, P = 0.0126 [aortic roots]) in the AEBP1(-/-)/low-density lipoprotein receptor (LDLR )(-/-) double-knockout (KO) mice. Bone marrow (BM) transplantation experiments further revealed that LDLR (-/-) mice reconstituted with AEBP1(-/-)/LDLR (-/-) BM cells (LDLR (-/-)/KO-BM chimera) display significant reduction of atherosclerosis lesions (en face: 2.0-fold, P = 0.0268; aortic roots: 1.7-fold, P = 0.05) compared with control mice reconstituted with AEBP1(+/+)/LDLR (-/-) BM cells (LDLR (-/-)/WT-BM chimera). Furthermore, transplantation of AEBP1(TG) BM cells with the normal apolipoprotein E (ApoE) gene into ApoE (-/-) mice (ApoE (-/-)/TG-BM chimera) leads to significant development of atherosclerosis (males: 2.5-fold, P = 0.0001 [en face], 4.7-fold, P = 0.0001 [aortic roots]; females: 1.8-fold, P = 0.0001 [en face], 3.0-fold, P = 0.0001 [aortic roots]) despite the restoration of ApoE expression. Macrophages from ApoE (-/-)/TG-BM chimeric mice express reduced levels of PPARγ1, LXRα, ATP-binding cassette A1 (ABCA1) and ATP-binding cassette G1 (ABCG1) and increased levels of the inflammatory mediators interleukin (IL)-6 and tumor necrosis factor (TNF)-α compared with macrophages of control chimeric mice (ApoE (-/-)/NT-BM ) that received AEBP1 nontransgenic (AEBP1(NT) ) BM cells. Our in vivo experimental data strongly suggest that macrophage AEBP1 plays critical regulatory roles in atherogenesis, and it may serve as a potential therapeutic target for the prevention or treatment of atherosclerosis.

Intrinsic depot-specific differences in the secretome of adipose tissue, preadipocytes, and adipose tissue-derived microvascular endothelial cells

OBJECTIVE

Visceral adipose tissue (VAT) is more closely linked to insulin resistance than subcutaneous adipose tissue (SAT). We conducted a quantitative analysis of the secretomes of VAT and SAT to identify differences in adipokine secretion that account for the adverse metabolic consequences of VAT.

RESEARCH DESIGN AND METHODS

We used lectin affinity chromatography followed by comparison of isotope-labeled amino acid incorporation rates to quantitate relative differences in the secretomes of VAT and SAT explants. Because adipose tissue is composed of multiple cell types, which may contribute to depot-specific differences in secretion, we isolated preadipocytes and microvascular endothelial cells (MVECs) and compared their secretomes to those from whole adipose tissue.

RESULTS

Although there were no discrete depot-specific differences in the secretomes from whole adipose tissue, preadipocytes, or MVECS, VAT exhibited an overall higher level of protein secretion than SAT. More proteins were secreted in twofold greater abundance from VAT explants compared with SAT explants (59% versus 21%), preadipocytes (68% versus 0%), and MVECs (62% versus 15%). The number of proteins in the whole adipose tissue secretome was greater than the sum of its cellular constituents. Finally, almost 50% of the adipose tissue secretome was composed of factors with a role in angiogenesis.

CONCLUSIONS

VAT has a higher secretory capacity than SAT, and this difference is an intrinsic feature of its cellular components. In view of the number of angiogenic factors in the adipose tissue secretome, we propose that VAT represents a more readily expandable tissue depot.

Identification of novel PTEN-binding partners: PTEN interaction with fatty acid binding protein FABP4

PTEN is a tumor suppressor with dual protein and lipid-phosphatase activity, which is frequently deleted or mutated in many human advanced cancers. Recent studies have also demonstrated that PTEN is a promising target in type II diabetes and obesity treatment. Using C-terminal PTEN sequence in pEG202-NLS as bait, yeast two-hybrid screening on Mouse Embryo, Colon Cancer, and HeLa cDNA libraries was carried out. Isolated positive clones were validated by mating assay and identified through automated DNA sequencing and BLAST database searches. Sequence analysis revealed a number of PTEN-binding proteins linking this phosphatase to a number of different signaling cascades, suggesting that PTEN may perform other functions besides tumor-suppressing activity in different cell types. In particular, the interplay between PTEN function and adipocyte-specific fatty-acid-binding protein FABP4 is of notable interest. The demonstrable tautology of PTEN to FABP4 suggested a role for this phosphatase in the regulation of lipid metabolism and adipocyte differentiation. This interaction was further studied using coimmunoprecipitation and gel-filtration assays. Finally, based on Biacore assay, we have calculated the K(D) of PTEN-FABP4 complex, which is around 2.8 microM.

PPARgamma1 and LXRalpha face a new regulator of macrophage cholesterol homeostasis and inflammatory responsiveness, AEBP1

Peroxisome proliferator-activated receptor γ1 (PPARγ1) and liver X receptor α (LXRα) are nuclear receptors that play pivotal roles in macrophage cholesterol homeostasis and inflammation; key biological processes in atherogenesis. The activation of PPARγ1 and LXRα by natural or synthetic ligands results in the transactivation of ABCA1, ABCG1, and ApoE; integral players in cholesterol efflux and reverse cholesterol transport. In this review, we describe the structure, isoforms, expression pattern, and functional specificity of PPARs and LXRs. Control of PPARs and LXRs transcriptional activity by coactivators and corepressors is also highlighted. The specific roles that PPARγ1 and LXRα play in inducing macrophage cholesterol efflux mediators and antagonizing macrophage inflammatory responsiveness are summarized. Finally, this review focuses on the recently reported regulatory functions that adipocyte enhancer-binding protein 1 (AEBP1) exerts on PPARγ1 and LXRα transcriptional activity in the context of macrophage cholesterol homeostasis and inflammation.

Regulation of IkappaBalpha function and NF-kappaB signaling: AEBP1 is a novel proinflammatory mediator in macrophages

NF-κB comprises a family of transcription factors that are critically involved in various inflammatory processes. In this paper, the role of NF-κB in inflammation and atherosclerosis and the regulation of the NF-κB signaling pathway are summarized. The structure, function, and regulation of the NF-κB inhibitors, IκBα and IκBβ, are reviewed. The regulation of NF-κB activity by glucocorticoid receptor (GR) signaling and IκBα sumoylation is also discussed. This paper focuses on the recently reported regulatory function that adipocyte enhancer-binding protein 1 (AEBP1) exerts on NF-κB transcriptional activity in macrophages, in which AEBP1 manifests itself as a potent modulator of NF-κB via physical interaction with IκBα and a critical mediator of inflammation. Finally, we summarize the regulatory roles that recently identified IκBα-interacting proteins play in NF-κB signaling. Based on its proinflammatory roles in macrophages, AEBP1 is anticipated to serve as a therapeutic target towards the treatment of various inflammatory conditions and disorders.

LPS-induced suppression of macrophage cholesterol efflux is mediated by adipocyte enhancer-binding protein 1

Macrophages facilitate clearance of cholesterol from the body via reverse cholesterol transport (RCT). The first event in RCT is internalization of modified low density lipoprotein by macrophages, upon which PPARgamma1 and LXRalpha signaling pathways are turned on, leading to the transactivation of a cascade of genes (e.g. ABCA1 and ABCG1), whose products promote macrophage cholesterol efflux. Down-regulation of macrophage cholesterol efflux mediators leads to an imbalance in cholesterol homeostasis, promoting foam cell formation. Lipopolysaccharide (LPS) has been shown to suppress PPARgamma1 and its downstream target genes in macrophages, inducing foam cell formation; a key mechanism proposed to underlie bacterial infection-induced atherosclerosis. Herein, we show that adipocyte enhancer-binding protein 1 (AEBP1) is up-regulated during monocyte differentiation. Moreover, we provide experimental evidence suggesting that AEBP1 expression is induced by LPS, and that LPS-induced down-regulation of pivotal macrophage cholesterol efflux mediators, leading to foam cell formation, is largely mediated by AEBP1. Although AEBP1-independent pathways seem to contribute to these LPS effects, such pathways can only mediate lesser and delayed effects of LPS on macrophage cholesterol efflux and development of foam cells. We speculate that AEBP1 may serve as a potential therapeutic target for the prevention/treatment of bacterial infection-induced atherosclerosis.

The Kampo medicines Orengedokuto, Bofutsushosan and Boiogito have different activities to regulate gene expressions in differentiated rat white adipocytes: comprehensive analysis of genetic profiles

Three Kampo medicines, Boiogito (BOT), Bofutsushosan (BTS) and Orengedokuto (OGT), used for obese patients were investigated for their effects on adipogenesis in cultured rat white adipocytes. Administration of the three extracts suppressed adipogenesis in concentration-dependent manners (1-100 microg/ml) without any cytotoxicity. Changes in mRNA expression levels were analyzed using a Rat 230 2.0 Affymetrix GeneChip microarray system. DNA microarray analysis (total probe set: 31099) using cDNAs prepared from adipocytes revealed that BOT, BTS and OGT increased the expression of 133-150 genes and decreased the expression of 42-110 genes by > or =2-fold. We identified 329 downregulated genes and 189 upregulated genes among a total set of 514 probes (overlap: 4). Overall, genes related to cellular movement, cell death, cell growth/differentiation and immune responses were the most downregulated, while those related to lipid metabolism and cell signaling were the most upregulated. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assays were conducted to confirm the microarray results. Analysis of the clustering profiles of the microarray results revealed that BOT and BTS changed the expression levels of similar genes mainly involved in small molecule biochemistry and cell differentiation, while OGT altered 10 genes related to lipid metabolism, in contrast to the effects of BOT and BTS. We also measured mRNA expression levels of seven selected genes highly contributing to the lipid metabolism by using semiquantitative RT-PCR assay, that were acetyl-Coenzyme A carboxylase alpha (ACACA), AE binding protein 1 (AEBP1), patatin-like phospholipase domain containing 8 (PNPLA8), secretoglobin (SCGB1A1), adrenergic (ADRB3), adiponectin (ADIPOQ), monoglyceride lipase (MGLL). Beta-actin (ACTB) gene was used as an endogenous internal standard. The present findings indicate that these three herbal extracts have the potential to prevent adipogenesis in rat white adipocytes through different mechanisms via modulation of gene expression levels.

Novel glioblastoma markers with diagnostic and prognostic value identified through transcriptome analysis

PURPOSE

Current methods of classification of astrocytoma based on histopathologic methods are often subjective and less accurate. Although patients with glioblastoma have grave prognosis, significant variability in patient outcome is observed. Therefore, the aim of this study was to identify glioblastoma diagnostic and prognostic markers through microarray analysis.

EXPERIMENTAL DESIGN

We carried out transcriptome analysis of 25 diffusely infiltrating astrocytoma samples [WHO grade II--diffuse astrocytoma, grade III--anaplastic astrocytoma, and grade IV--glioblastoma (GBM)] using cDNA microarrays containing 18,981 genes. Several of the markers identified were also validated by real-time reverse transcription quantitative PCR and immunohistochemical analysis on an independent set of tumor samples (n = 100). Survival analysis was carried out for two markers on another independent set of retrospective cases (n = 51).

RESULTS

We identified several differentially regulated grade-specific genes. Independent validation by real-time reverse transcription quantitative PCR analysis found growth arrest and DNA-damage-inducible alpha (GADD45alpha) and follistatin-like 1 (FSTL1) to be up-regulated in most GBMs (both primary and secondary), whereas superoxide dismutase 2 and adipocyte enhancer binding protein 1 were up-regulated in the majority of primary GBM. Further, identification of the grade-specific expression of GADD45alpha and FSTL1 by immunohistochemical staining reinforced our findings. Analysis of retrospective GBM cases with known survival data revealed that cytoplasmic overexpression of GADD45alpha conferred better survival while the coexpression of FSTL1 with p53 was associated with poor survival.

CONCLUSIONS

Our study reveals that GADD45alpha and FSTLI are GBM-specific whereas superoxide dismutase 2 and adipocyte enhancer binding protein 1 are primary GBM-specific diagnostic markers. Whereas GADD45alpha overexpression confers a favorable prognosis, FSTL1 overexpression is a hallmark of poor prognosis in GBM patients.