NR4A1 retards adipocyte differentiation or maturation via enhancing GATA2 and p53 expression

Cancer-associated fibroblasts contributed to hepatocellular carcinoma recurrence and metastasis via CD36-mediated fatty-acid metabolic reprogramming

Cancer-associated fibroblasts (CAFs) are the main components in the tumor microenvironment. Tumors activate fibroblasts from quiescent state into activated state by secreting cytokines, and activated CAFs may in turn promote tumor progression and metastasis. Therefore, studies targeting CAFs could enrich the therapeutic options for tumor treatment. In this study, we demonstrate that the content of lipid droplets and the expression of autophagosomes were higher in CAFs than in peri-tumor fibroblasts (PTFs), which was inhibited by 5-(tetradecyloxy)-2-furoic acid(TOFA). The expression of CD36 in CAFs was higher than that in PTFs at both mRNA and protein levels. Inhibition of CD36 activity using either the CD36 inhibitor SSO or siRNA had a significant negative impact on the proliferation and migration abilities of CAFs, which was associated with reduced levels of relevant activated genes (α-SMA, FAP, Vimentin) and cytokines (IL-6, TGF-β and VEGF-α). SSO also inhibited HCC growth and tumorigenesis in nude mice orthotopically implanted with CAFs and HCC cells. Our data further show that CD36+CAFs affected the expression of PD-1 in CTLs leading to CTL exhaustion, and that patients with high CD36 expression in CAFs were correlated with shorter overall survival (OS). Together, our data demonstrate that CAFs were active in lipid metabolism with increased lipid content and lipophagy activity. CD36 may play a key role in the regulation of the biological behaviors of CAFs, which may influence the proliferation and migration of tumor cells by reprograming the lipid metabolism in tumor cells. Thus, CD36 could be an effective therapeutic target for the treatment of HCC.

Distinct human stem cell subpopulations drive adipogenesis and fibrosis in musculoskeletal injury

Fibroadipogenic progenitors (FAPs) maintain healthy skeletal muscle in homeostasis but drive muscle degeneration in chronic injuries by promoting adipogenesis and fibrosis. To uncover how these stem cells switch from a pro-regenerative to pro-degenerative role we perform single-cell mRNA sequencing of human FAPs from healthy and injured human muscles across a spectrum of injury, focusing on rotator cuff tears. We identify multiple subpopulations with progenitor, adipogenic, or fibrogenic gene signatures. We utilize full spectrum flow cytometry to identify distinct FAP subpopulations based on highly multiplexed protein expression. Injury severity increases adipogenic commitment of FAP subpopulations and is driven by the downregulation of DLK1. Treatment of FAPs both in vitro and in vivo with DLK1 reduces adipogenesis and fatty infiltration, suggesting that during injury, reduced DLK1 within a subpopulation of FAPs may drive degeneration. This work highlights how stem cells perform varied functions depending on tissue context, by dynamically regulating subpopulation fate commitment, which can be targeted improve patient outcomes after injury.

High-Fat Diet Promotes Adipogenesis in Offspring Female Rats Induced by Perinatal Exposure to 4-Nonylphenol

Background

Both high-fat diet (HFD) and 4-nonylphenol (4-NP) could affect fat formation in adipose tissue individually. We investigated whether HFD promote abnormal adipose tissue formation caused by early exposure to 4-NP in life and preliminarily explore the possible mechanisms involved.

Methods

The first-generation rats were treated with HFD on postnatal day after pregnant rats exposure to 5 ug/kg/day 4-NP. Then, the second generation rats started to only receive normal diet without 4-NP or HFD. We analyzed organ coefficient and histopathology of fat tissues, biochemical index, and gene level involved in lipid metabolism in female offspring rats.

Results

HFD and 4-NP interaction synergistically increased birth weight, body weight, and organ coefficients of adipose tissue in offspring female rats. HFD accelerately aggravated abnormal lipid metabolism and increased the adipocyte mean areas around the uterus of the offspring female rats induced by prenatal exposure to 4-NP. HFD also facilitate the regulation of gene expression involved lipid metabolism in offspring female rats induced by perinatal exposure to 4-NP, even passed on to the second generation of female rats. Moreover, HFD and 4-NP interaction synergistically declined the gene and protein expression of estrogen receptor (ER) in the adipose tissue of second-generation female rats.

Conclusion

HFD and 4-NP synergistically regulate the expression of lipid metabolism genes in adipose tissue of F2 female rats and promote adipose tissue generation, leading to obesity in offspring rats, which is closely related to low expression of ER. Therefore, ER genes and proteins may be involved in the synergistic effect of HFD and 4-NP.

The nuclear receptor subfamily 4 group A1 in human disease

Nuclear receptor 4A1 (NR4A1), a member of the NR4A subfamily, acts as a gene regulator in a wide range of signaling pathways and responses to human diseases. Here, we provide a brief overview of the current functions of NR4A1 in human diseases and the factors involved in its function. A deeper understanding of these mechanisms can potentially improve drug development and disease therapy.

The 532 nm Laser Treatment Promotes the Proliferation of Tendon-Derived Stem Cells and Upregulates Nr4a1 to Stimulate Tenogenic Differentiation

Objective: This study aimed to verify the effect of photobiomodulation therapy (PBMT) with a wavelength of 532 nm on the proliferation and differentiation of tendon-derived stem cells (TDSCs) of Sprague-Dawley (SD) rats. Background: The combination of PBMT and stem cell transplantation with TDSCs provides a new treatment strategy for tendon injury. Nevertheless, the effect of PBMT on the biological behavior of TDSCs and its internal mechanisms remain unclear. Methods: TDSCs were isolated from Achilles tendons of SD rats and identified by cell morphology and flow cytometric analysis. Energy density gradient experiment was performed to determine the ideal energy. Then, TDSCs were treated with PBMT using a wavelength of 532 nm at a fluence of 15 J/cm² in 532 nm laser group, and the TDSC in control group were not treated with 532 nm laser. Cell response after irradiation was observed to ascertain cell morphology and cell proliferation in the 532 nm laser group and the control group. The RNA expression levels of the key genes of TDSC differentiation, including scleraxis (Scx), tenomodulin (Tnmd), Mohawk homeobox (Mkx), Decorin (Dcn), peroxisome proliferator-activated receptor gamma (PPARγ), SRY-box transcription factor 9 (Sox9), and RUNX family transcription factor 2 (Runx2), were detected by reverse transcription-polymerase chain reaction. Then, gene chip microarray was used to detect the expression of differential genes after 532 nm laser intervention in TDSCs, and the target genes were screened out to verify the role in this process in vitro and in vivo. Results: When the 532 nm laser energy density was 15 J/cm², the proliferation capacity of TDSCs was improved (2.73 ± 0.24 vs. 1.81 ± 0.71, p < 0.05), and the expression of genes related to tenogenic differentiation of TDSCs was significantly increased (p < 0.01). After RNA sequencing and bioinformatics analyses, we speculated that nuclear receptor subfamily 4 group A member 1 (Nr4a1) was involved in the tenogenic differentiation process of TDSCs regulated by 532 nm laser treatment. Subsequent experiments confirmed that Nr4a1 regulated the expression of the tenogenic differentiation genes Scx and Tnmd in TDSCs. Conclusions: A 532 nm laser with 15 J/cm² regulated the process of TDSC proliferation and upregulated Nr4a1 to stimulate tenogenic differentiation.

Mesenchymal stem cells-derived extracellular vesicles containing miR-378a-3p inhibit the occurrence of inflammatory bowel disease by targeting GATA2

This study sought to determine whether mesenchymal stem cells‐derived extracellular vesicles (MSCs‐EVs) carrying microRNA‐378a‐3p (miR‐378a‐3p) could affect the pathogenesis of inflammatory bowel disease (IBD) by regulating the GATA‐binding protein 2 (GATA2)/aquaporin‐4 (AQP4)/peroxisome proliferator‐activated receptor α (PPAR‐α) axis. Initially, colon mucosa biopsy tissues were harvested from healthy controls and patients with IBD for qRT‐PCR and immunohistochemistry analysis. EVs harvested from MSCs and lipopolysaccharide (LPS) were used to stimulate the M064 cells to establish an in vitro inflammation cell model. Besides, 2,4,6‐trinitrobenzene sulfonic acid intracolon administration was performed to establish in vivo IBD mouse models. After loss‐ and gain‐of‐function assays, the regulatory role of MSCs‐derived EVs loaded with manipulated miR‐378a‐3p in IBD in relation to GATA2/AQP4/PPAR‐α were explored. Upregulation of GATA2 was identified in the colon tissue of IBD patients. GATA2, which was a target gene of miR‐378a‐3p, transcriptionally upregulated AQP4. After silencing of GATA2, LPS‐induced apoptosis of M064 cells was reduced by the downregulation of AQP4. Decreased AQP4 contributed to PPAR‐α pathway inactivation and weakened the LPS‐induced apoptosis of M064 cells. MSCs‐EVs delivering miR‐378a‐3p suppressed the GATA2/AQP4/PPAR‐α pathway, which reduced LPS‐induced apoptosis of M064 cells and the occurrence of IBD in mice. Altogether, the current study illustrated that MSCs‐EVs transfer miR‐378a‐3p to reduce the GATA2 expression, which downregulates AQP4 to block the PPAR‐α signalling pathway, thus suppressing the occurrence of IBD.

Knockout of Nur77 Leads to Amino Acid, Lipid, and Glucose Metabolism Disorders in Zebrafish

Orphan nuclear receptor Nur77 has been reported to be implicated in a diverse range of metabolic processes, including carbohydrate metabolism and lipid metabolism. However, the detailed mechanism of Nur77 in the regulation of metabolic pathway still needs to be further investigated. In this study, we created a global nur77 knockout zebrafish model by CRISPR/Cas9 technique, and then performed whole-organism RNA sequencing analysis in wildtype and nur77-deficient zebrafish to dissect the genetic changes in metabolic-related pathways. We found that many genes involved in amino acid, lipid, and carbohydrate metabolism changed by more than twofold. Furthermore, we revealed that nur77^-/- mutant displayed increased total cholesterol (TC) and triglyceride (TG), alteration in total amino acids, as well as elevated glucose. We also demonstrated that the elevated glucose was not due to the change of glucose uptake but was likely caused by the disorder of glycolysis/gluconeogenesis and the impaired β-cell function, including downregulated insb expression, reduced β-cell mass, and suppressed insulin secretion. Importantly, we also verified that targeted expression of Nur77 in the β cells is sufficient to rescue the β-cell defects in global nur77^-/- larvae zebrafish. These results provide new information about the global metabolic network that Nur77 signaling regulates, as well as the role of Nur77 in β-cell function.

Targeting Orphan Nuclear Receptors NR4As for Energy Homeostasis and Diabetes

Orphan nuclear receptors are important members of the nuclear receptor family and may regulate cell proliferation, metabolism, differentiation, and apoptosis. NR4As, a subfamily of orphan nuclear receptors, have been reported to play key roles in carbohydrate and lipid metabolism and energy homeostasis. Popularity of obesity has resulted in a series of metabolic diseases such as diabetes and its complications. While imbalance of energy intake and expenditure is the main cause of obesity, the concrete mechanism of obesity has not been fully understood. It has been reported that NR4As have significant regulatory effects on energy homeostasis and diabetes and are expected to become new targets for discovering drugs for metabolic syndrome. A number of studies have demonstrated that abnormalities in metabolism induced by altered levels of NR4As may contribute to numerous diseases, such as chronic inflammation, tumorigenesis, diabetes and its complications, atherosclerosis, and other cardiovascular diseases. However, systematic reviews focusing on the roles of NR4As in mediating energy homeostasis and diabetes remain limited. Therefore, this article reviews the structure and regulation of NR4As and their critical function in energy homeostasis and diabetes, as well as small molecules that may regulate NR4As. Our work is aimed at providing valuable support for the research and development of drugs targeting NR4As for the treatment of obesity and related metabolic diseases.

Adipose-derived mesenchymal stem cells differentiate into pancreatic cancer-associated fibroblasts in vitro

Cancer-associated fibroblasts (CAFs) are key components of the dense, proliferating stroma observed in pancreatic ductal adenocarcinoma (PDAC), and CAF subpopulations drive tumor heterogeneity and play a major role in PDAC progression and drug resistance. CAFs consist of heterogenous subpopulations such as myoblastic CAF (myCAF) and inflammatory CAF (iCAF), and each has distinct essential roles. However, it is not clear how CAF subpopulations are formed in PDAC. Adipose-derived MSCs (AD-MSCs), which possess a high multilineage potential and self-renewal capacity, are reported to be one of the in vivo CAF sources. Here, we aimed to investigate whether AD-MSCs can act as precursors for CAFs in vitro. We recorded morphological features and collected omics data from two in vitro co-culture models for recapitulating clinical PDAC. Additionally, we tested the advantages of the co-culture model in terms of accurately modeling morphology and CAF heterogeneity. We showed that AD-MSCs differentiate into two distinct CAF subpopulations: Direct contact co-culture with PDAC cell line Capan-1 induced differentiation into myCAFs and iCAFs, while indirect co-culture induced differentiation into only iCAFs. Using these co-culture systems, we also identified novel CAF markers that may be helpful for elucidating the mechanisms of CAFs in the tumor microenvironment (TME). In conclusion, AD-MSCs can differentiate into distinct CAF subtypes depending on the different co-culture conditions in vitro, and the identification of potential CAF markers may aid in future investigations of the mechanisms underlying the role of CAFs in the TME.

Glycerol kinase enhances hepatic lipid metabolism by repressing nuclear receptor subfamily 4 group A1 in the nucleus

Glycerol kinase (GYK) plays a critical role in hepatic metabolism by converting glycerol to glycerol 3-phosphate in an ATP-dependent reaction. GYK isoform b is the only glycerol kinase present in whole cells, and has a non-enzymatic moonlighting function in the nucleus. GYK isoform b acts as a co-regulator of nuclear receptor subfamily 4 group A1 (NR4A1) and participates in the regulation of hepatic glucose metabolism by protein–protein interaction with NR4A1. Herein, GYK expression was found to upregulate the expression of NR4A1-mediated lipid metabolism-related genes (SREBP1C, FASN, ACACA, and GPAM) in HEK293T and L02 cells, and in mouse in vivo studies. GYK expression increased blood levels of cholesterol, triglyceride, and high-density lipoprotein cholesterol, but not low-density lipoprotein cholesterol levels. It enhanced the transcriptional activity of Nr4a1 target genes by negatively cooperating with NR4A1 and its enzymatic activity or by other undefined moonlighting functions. This enhancement was observed in both normal and diabetic mice. We also found a feed-forward regulation loop between GYK and NR4A1, serving as part of a GYK-NR4A1 regulatory mechanism in hepatic metabolism. Thus, GYK regulates the effect of NR4A1 on hepatic lipid metabolism in normal and diabetic mice, partially through the cooperation of GYK and NR4A1.

Function of Nr4a Orphan Nuclear Receptors in Proliferation, Apoptosis and Fuel Utilization Across Tissues

The Nr4a family of nuclear hormone receptors is composed of three members-Nr4a1/Nur77, Nr4a2/Nurr1 and Nr4a3/Nor1. While currently defined as ligandless, these transcription factors have been shown to regulate varied processes across a host of tissues. Of particular interest, the Nr4a family impinge, in a tissue dependent fashion, on cellular proliferation, apoptosis and fuel utilization. The regulation of these processes occurs through both nuclear and non-genomic pathways. The purpose of this review is to provide a balanced perspective of the tissue specific and Nr4a family member specific, effects on cellular proliferation, apoptosis and fuel utilization.

NR4A1 retards adipocyte differentiation or maturation via enhancing GATA2 and p53 expression

Nuclear receptor subfamily 4 group A member 1 (NR4A1) is an orphan nuclear receptor with diverse functions. It has been reported that NR4A1, as a transcriptional activator, is implicated in glucose and lipid metabolism. The aim of this study was to investigate the regulatory role of NR4A1 in adipogenesis and explore the underlying mechanisms. Quantitative real‐time PCR and Western blotting were used to analyse the expression of genes involved in synthesis and mobilization of fats in vivo and in vitro. Dual‐luciferase reporter assay was conducted to study the regulatory mechanisms of NR4A1. Our data from in vivo study confirmed that NR4A1 knockout (KO) mice fed with high‐fat diet were more prone to obesity, and gene expression levels of PPARγ and FAS were increased in KO mice compared to controls; our data from in vitro study showed that NR4A1 overexpression in 3T3‐L1 pre‐adipocytes inhibited adipogenesis. Moreover, NR4A1 enhanced GATA binding protein 2 (GATA2) expression, which in turn inhibited peroxisome proliferator‐activated receptor γ (PPARγ); NR4A1 inhibited sterol regulatory element binding transcription factor 1 (SREBP1) and its downstream gene fatty acid synthase (FAS) by up‐regulating p53. NR4A1 inhibits the differentiation and lipid accumulation of adipocytes by enhancing the expression of GATA2 and p53.