Protein Inhibitor of Activated STAT 1 (PIAS1) Protects Against Obesity-Induced Insulin Resistance by Inhibiting Inflammation Cascade in Adipose Tissue

Protein inhibitor of activated STAT1 (PIAS1) alleviates cerebral infarction and inflammation after cerebral ischemia in rats

Background

Ischemic stroke is a severe disorder with high incidence, disability rate and mortality. Multiple pathogenesis mechanisms are involved in ischemic stroke, such as inflammation and neuronal cell apoptosis. Protein inhibitor of activated signal transducer and activators of transcription 1 (PIAS1) plays a crucial role in various biological processes, including inflammation. PIAS1 is also downregulated in ischemia-reperfusion injury and involved in the disease processes. However, the role of PIAS1 in cerebral ischemia is unclear.

Methods

Sprague-Dawley (SD) rats were induced with middle cerebral artery occlusion (MCAO). The role and mechanisms of PIAS1 in ischemic cerebral infarction were explored by Longa test, 2,3,5-triphenyltetrazolium chloride (TTC) staining, Morris water maze (MWM) test, hematoxylin-eosin (HE) staining, quantification of brain water content, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay (ELISA), terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL), Western blot and immunofluorescence assays.

Results

The expression of PIAS1 in MCAO-induced rat was declined compared to sham rats. Overexpression of PIAS1 reduced the Longa neurological scores, the percent of infarction area, the pathological abnormality, the escape latency of swimming and the percent of brain water content, and increased the number of platform crossings and time in the target quadrant in the MCAO-induced rats. Besides, overexpression of PIAS1 decreased the MCAO-induced the contents of IL-1β, IL-6 and TNF-α, but further elevated the concentrations of IL-10 in both sera and brain tissues. Moreover, overexpression of PIAS1 reversed the MCAO-induced apoptosis rate and the relative protein level of Bax, cleaved caspase3 and Bcl-2. Overexpression of PIAS1 also reversed the level of proteins involved in NF-κB pathway.

Conclusion

PIAS1 reduced inflammation and apoptosis, thereby alleviating ischemic cerebral infarction in MCAO-induced rats through regulation NF-κB pathway.

NR2F6 is essential for brown adipocyte differentiation and systemic metabolic homeostasis

OBJECTIVE

Brown adipose tissue (BAT) development and function are essential for maintaining energy balance. However, the key factors that specifically regulate brown adipogenesis require further identification. Here, we demonstrated that the nuclear receptor subfamily 2 group F member 6 (NR2F6) played a pivotal role in brown adipogenesis and energy homeostasis.

METHODS

We examined the differentiation of immortalized brown adipocytes and primary brown adipocytes when NR2F6 were deleted, and explored the mechanism through which NR2F6 regulated adipogenesis using ChIP-qPCR in vitro. Male wild type (WT) and Pdgfra-Cre-mediated deletion of Nr2f6 in preadipocytes (NR2F6-PKO) mice were fed with high fat diet (HFD) for 12 weeks, and adiposity, glucose intolerance, insulin resistance and inflammation were assessed.

RESULTS

NR2F6 exhibited abundant expression in BAT, while its expression was minimal in white adipose tissue (WAT). Within BAT, NR2F6 was highly expressed in preadipocytes, experienced a transient increase in the early stage of brown adipocyte differentiation, and significantly decreased in the mature adipocytes. Depletion of NR2F6 in preadipocytes inhibited brown adipogenesis, caused hypertrophy of brown adipocytes, and impaired thermogenic function of BAT, but without affecting WAT development. NR2F6 transcriptionally regulated PPARγ expression to promote adipogenic process in brown adipocytes. Loss of NR2F6 in preadipocytes led to increased susceptibility to diet-induced metabolic disorders.

CONCLUSIONS

Our findings unveiled NR2F6 as a novel key regulator of brown adipogenesis, potentially opening up new avenues for maintaining metabolic homeostasis by targeting NR2F6.

Reappraisal of Adipose Tissue Inflammation in Obesity

Chronic low-grade inflammation is a central component in the pathogenesis of obesity-related expansion of adipose tissue and complications in other metabolic tissues. Five different signaling pathways are defined as dominant determinants of adipose tissue inflammation: These are increased circulating endotoxin due to dysregulation in the microbiota-gut-brain axis, systemic oxidative stress, macrophage accumulation, and adipocyte death. Finally, the nucleotide-binding and oligomerization domain (NOD) leucine-rich repeat family pyrin domain-containing 3 (NLRP3) inflammasome pathway is noted to be a key regulator of metabolic inflammation. The NLRP3 inflammasome and associated metabolic inflammation play an important role in the relationships among fatty acids and obesity. Several highly active molecules, including primarily leptin, resistin, adiponectin, visfatin, and classical cytokines, are abundantly released from adipocytes. The most important cytokines that are released by inflammatory cells infiltrating obese adipose tissue are tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), monocyte chemoattractant protein 1 (MCP-1) (CCL-2), and IL-1. All these molecules mentioned above act on immune cells, causing local and then general inflammation. Three metabolic pathways are noteworthy in the development of adipose tissue inflammation: toll-like receptor 4 (TLR4)/phosphatidylinositol-3'-kinase (PI3K)/Protein kinase B (Akt) signaling pathway, endoplasmic reticulum (ER) stress-derived unfolded protein response (UPR), and inhibitor of nuclear factor kappa-B kinase beta (IKKβ)-nuclear factor kappa B (NF-κB) pathway. In fact, adipose tissue inflammation is an adaptive response that contributes to a visceral depot barrier that effectively filters gut-derived endotoxin. Excessive fatty acid release worsens adipose tissue inflammation and contributes to insulin resistance. However, suppression of adipose inflammation in obesity with anti-inflammatory drugs is not a rational solution and paradoxically promotes insulin resistance, despite beneficial effects on weight gain. Inflammatory pathways in adipocytes are indeed indispensable for maintaining systemic insulin sensitivity. Cannabinoid type 1 receptor (CB1R) is important in obesity-induced pro-inflammatory response; however, blockade of CB1R, contrary to anti-inflammatory drugs, breaks the links between insulin resistance and adipose tissue inflammation. Obesity, however, could be decreased by improving leptin signaling, white adipose tissue browning, gut microbiota interactions, and alleviating inflammation. Furthermore, capsaicin synthesized by chilies is thought to be a new and promising therapeutic option in obesity, as it prevents metabolic endotoxemia and systemic chronic low-grade inflammation caused by high-fat diet.

SUMOylation and coupling of eNOS mediated by PIAS1 contribute to maintenance of vascular homeostasis

Endothelial dysfunction (ED) is commonly considered a crucial initiating step in the pathogenesis of numerous cardiovascular diseases. The coupling of endothelial nitric oxide synthase (eNOS) is important in maintaining normal endothelial functions. However, it still remains elusive whether and how eNOS SUMOylation affects the eNOS coupling. In the study, we investigate the roles and possible action mechanisms of protein inhibitor of activated STAT 1 (PIAS1) in ED. Human umbilical vein endothelial cells (HUVECs) treated with palmitate acid (PA) in vitro and ApoE-/- mice fed with high-fat diet (HFD) in vivo were constructed as the ED models. Our in vivo data show that PIAS1 alleviates the dysfunction of vascular endothelium by increasing nitric oxide (NO) level, reducing malondialdehyde (MDA) level, and activating the phosphatidylinositol 3-kinase-protein kinase B-endothelial nitric oxide synthase (PI3K-AKT-eNOS) signaling in ApoE-/- mice. Our in vitro data also show that PIAS1 can SUMOylate eNOS under endogenous conditions; moreover, it antagonizes the eNOS uncoupling induced by PA. The findings demonstrate that PIAS1 alleviates the dysfunction of vascular endothelium by promoting the SUMOylation and inhibiting the uncoupling of eNOS, suggesting that PIAS1 would become an early predictor of atherosclerosis and a new potential target of the hyperlipidemia-related cardiovascular diseases.

Sox6 impairs the adipogenic commitment of mesenchymal stem cells by targeting lysyl oxidase and preadipocyte factor 1

The commitment of mesenchymal stem cells (MSCs) to preadipocytes and the termination of differentiation to adipocytes are critical for maintaining systemic energy homeostasis. However, our knowledge of the molecular mechanisms governing the commitment of MSCs to preadipocytes and the subsequent termination of their differentiation into adipocytes remain limited. Additionally, the role of Sox6 sex-determining region Y (SRY)-box6 (Sox6), a transcription factor that regulates gene transcription, is reportedly involved in various cellular processes, including adipogenesis; however, its function in regulating preadipocyte development and the factors involved in the termination of adipogenic differentiation remain unexplored. Therefore, we investigated the role of Sox6 in regulating the differentiation of adipocytes by monitoring the effects of its overexpression in C3H10T1/2 cells (in vitro) and C57BL/6J mouse (in vivo) models of adipogenesis. We observed lower Sox6 expression in the adipose tissue of obese mice than that in control mice. Sox6 overexpression inhibited the differentiation of MSC by directly binding to the lysyl oxidase (Lox) and preadipocyte factor 1 (Pref1) promoters, which was potentiated by histone deacetylase-1(HDAC1). Our findings suggest that Sox6 is a key regulator of MSC commitment to adipocytes; therefore, targeting the Sox6-mediated regulation of this process could offer potential therapeutic avenues for addressing obesity and related metabolic disorders.

PIAS1 impedes vascular endothelial injury and atherosclerotic plaque formation in diabetes by blocking the RUNX3/TSP-1 axis

The protein PIAS1 functions as a type of ubiquitin-protease, which is known to play an important regulatory role in various diseases, including cardiovascular diseases and cancers. Its mechanism of action primarily revolves around regulating the transcription, translation, and modification of target proteins. This study investigates role and mechanism of PIAS1 in the RUNX3/TSP-1 axis and confirms its therapeutic effects on diabetes-related complications in animal models. A diabetic vascular injury was induced in human umbilical vein endothelial cells (HUVECs) by stimulation with H2O2 and advanced glycation end product (AGE), and a streptozotocin (STZ)-induced mouse model of diabetes was constructed, followed by detection of endogenous PIAS1 expression and SUMOylation level of RUNX3. Effects of PIAS1 concerning RUNX3 and TSP-1 on the HUVEC apoptosis and inflammation were evaluated using the ectopic expression experiments. Down-regulated PIAS1 expression and SUMOylation level of RUNX3 were identified in the H2O2- and AGE-induced HUVEC model of diabetic vascular injury and STZ-induced mouse models of diabetes. PIAS1 promoted the SUMOylation of RUNX3 at the K148 site of RUNX3. PIAS1-mediated SUMOylation of RUNX3 reduced RUNX3 transactivation activity, weakened the binding of RUNX3 to the promoter region of TSP-1, and caused downregulation of TSP-1 expression. PIASI decreased the expression of TSP-1 by inhibiting H2O2- and AGE-induced RUNX3 de-SUMOylation, thereby arresting the inflammatory response and apoptosis of HUVECs. Besides, PIAS1 reduced vascular endothelial injury and atherosclerotic plaque formation in mouse models of diabetes by inhibiting the RUNX3/TSP-1 axis. Our study proved that PIAS1 suppressed vascular endothelial injury and atherosclerotic plaque formation in mouse models of diabetes via the RUNX3/TSP-1 axis.

HIGD1A links SIRT1 activity to adipose browning by inhibiting the ROS/DNA damage pathway

Energy-dissipating adipocytes have the potential to improve metabolic health. Here, we identify hypoxia-induced gene domain protein-1a (HIGD1A), a mitochondrial inner membrane protein, as a positive regulator of adipose browning. HIGD1A is induced in thermogenic fats by cold exposure. Peroxisome proliferator-activated receptor gamma (PPARγ) transactivates HIGD1A expression synergistically with peroxisome proliferators-activated receptor γ coactivator α (PGC1α). HIGD1A knockdown inhibits adipocyte browning, whereas HIGD1A upregulation promotes the browning process. Mechanistically, HIGD1A deficiency impairs mitochondrial respiration to increase reactive oxygen species (ROS) level. This increases NAD⁺ consumption for DNA damage repair and curtails the NAD⁺/NADH ratio, which inhibits sirtuin1 (SIRT1) activity, thereby compromising adipocyte browning. Conversely, overexpression of HIGD1A blunts the above process to promote adaptive thermogenesis. Furthermore, mice with HIGD1A knockdown in inguinal and brown fat have impaired thermogenesis and are prone to diet-induced obesity (DIO). Overexpression of HIGD1A favors adipose tissue browning, ultimately preventing DIO and metabolic disorders. Thus, the mitochondrial protein HIGD1A links SIRT1 activity to adipocyte browning by inhibiting ROS levels.

Comparative three-dimensional genome architectures of adipose tissues provide insight into human-specific regulation of metabolic homeostasis

Elucidating the regulatory mechanisms of human adipose tissues (ATs) evolution is essential for understanding human-specific metabolic regulation, but the functional importance and evolutionary dynamics of three-dimensional (3D) genome organizations of ATs are not well defined. Here, we compared the 3D genome architectures of anatomically distinct ATs from humans and six representative mammalian models. We recognized evolutionarily conserved and human-specific chromatin conformation in ATs at multiple scales, including compartmentalization, topologically associating domain (TAD), and promoter-enhancer interactions (PEI), which have not been described previously. We found PEI are much more evolutionarily dynamic with respect to compartmentalization and topologically associating domain. Compared to conserved PEIs, human-specific PEIs are enriched for human-specific sequence, and the binding motifs of their potential mediators (transcription factors) are less conserved. Our data also demonstrated that genes involved in the evolutionary dynamics of chromatin organization have weaker transcriptional conservation than those associated with conserved chromatin organization. Furthermore, the genes involved in energy metabolism and the maintenance of metabolic homeostasis are enriched in human-specific chromatin organization, while housekeeping genes, health-related genes, and genetic variations are enriched in evolutionarily conserved compared to human-specific chromatin organization. Finally, we showed extensively divergent human-specific 3D genome organizations among one subcutaneous and three visceral ATs. Together, these findings provide a global overview of 3D genome architecture dynamics between ATs from human and mammalian models and new insights into understanding the regulatory evolution of human ATs.

Adipose Tissue Macrophage-Mediated Inflammation in Obesity: A Link to Posttranslational Modification

Adipose tissue macrophages (ATM) are an essential type of immune cells in adipose tissue. Obesity induces the inflammation of adipose tissues, as expressed by ATM accumulation, that is more likely to become a source of systemic metabolic diseases, including insulin resistance. The process is characterized by the transcriptional regulation of inflammatory pathways by virtue of signaling molecules such as cytokines and free fatty acids. Notably, posttranslational modification (PTM) is a key link for these signaling molecules to trigger the proinflammatory or anti-inflammatory phenotype of ATMs. This review focuses on summarizing the functions and molecular mechanisms of ATMs regulating inflammation in obese adipose tissue. Furthermore, the role of PTM is elaborated, hoping to identify new horizons of treatment and prevention for obesity-mediated metabolic disease.

Placental mesenchymal stem cells restore glucose and energy homeostasis in obesogenic adipocytes

Obesity (Ob) depicts a state of energy imbalance(s) being characterized by the accumulation of excessive fat and which predisposes to several metabolic diseases. Mesenchymal stem cells (MSCs) represent a promising option for addressing obesity and its associated metabolic co-morbidities. The present study aims at assessing the beneficial effects of human placental MSCs (P-MSCs) in mitigating Ob-associated insulin resistance (IR) and mitochondrial dysfunction both in vivo and in vitro. Under obesogenic milieu, adipocytes showed a significant reduction in glucose uptake, and impaired insulin signaling with decreased expression of UCP1 and PGC1α, suggestive of dysregulated non-shivering thermogenesis vis-a-vis mitochondrial biogenesis respectively. Furthermore, obesogenic adipocytes demonstrated impaired mitochondrial respiration and energy homeostasis evidenced by reduced oxygen consumption rate (OCR) and blunted ATP/NAD⁺/NADP⁺ production respectively. Interestingly, co-culturing adipocytes with P-MSCs activated PI3K-Akt signaling, improved glucose uptake, diminished ROS production, enhanced mitochondrial OCR, improved ATP/NAD⁺/NADP⁺ production, and promoted beiging of adipocytes evidenced by upregulated expression of PRDM16, UCP1, and PGC1α expression. In vivo, P-MSCs administration increased the peripheral blood glucose uptake and clearance, and improved insulin sensitivity and lipid profile with a coordinated increase in the ratio of ATP/ADP and NAD⁺ and NADP⁺ in the white adipose tissue (WAT), exemplified in WNIN/GR-Ob obese mutant rats. In line with in vitro findings, there was a significant reduction in adipocyte hypertrophy, increased mitochondrial staining, and thermogenesis. Our findings advocate for a therapeutic application of P-MSCs for improving glucose and energy homeostasis, i.e., probably restoring non-shivering thermogenesis towards obesity management.

CHCHD10 Modulates Thermogenesis of Adipocytes by Regulating Lipolysis

Brown and beige adipocytes dissipate energy in a nonshivering thermogenesis manner, exerting beneficial effects on metabolic homeostasis. CHCHD10 is a nuclear-encoded mitochondrial protein involved in cristae organization; however, its role in thermogenic adipocytes remains unknown. We identify CHCHD10 as a novel regulator for adipocyte thermogenesis. CHCHD10 is dramatically upregulated during thermogenic adipocyte activation by PPARγ-PGC1α and positively correlated with UCP1 expression in adipose tissues from humans and mice. We generated adipocyte-specific Chchd10 knockout mice (Chchd10-AKO) and found that depleting CHCHD10 leads to impaired UCP1-dependent thermogenesis and energy expenditure in the fasting state, with no effect in the fed state. Lipolysis in adipocytes is disrupted by CHCHD10 deficiency, while augmented lipolysis through ATGL overexpression recovers adipocyte thermogenesis in Chchd10-AKO mice. Consistently, overexpression of Chchd10 activates thermogenic adipocytes. Mechanistically, CHCHD10 deficiency results in the disorganization of mitochondrial cristae, leading to impairment of oxidative phosphorylation complex assembly in mitochondria, which in turn inhibits ATP generation. Decreased ATP results in downregulation of lipolysis by reducing nascent protein synthesis of ATGL, thereby suppressing adipocyte thermogenesis. As a result, Chchd10-AKO mice are prone to develop high-fat diet-induced metabolic disorders. Together, our findings reveal an essential role of CHCHD10 in regulating lipolysis and the thermogenic program in adipocytes.

The protease SENP2 controls hepatic gluconeogenesis by regulating the SUMOylation of the fuel sensor AMPKα

Uncontrolled gluconeogenesis results in elevated hepatic glucose production in type 2 diabetes. The SUMO-specific protease 2 (SENP2) is known to catalyze deSUMOylation of target proteins, with broad effects on cell growth, signal transduction, and developmental processes. However, the role of SENP2 in hepatic gluconeogenesis and the occurrence of type 2 diabetes remains unknown. Herein, we established SENP2 hepatic knockout mice and found that SENP2 deficiency could protect against high fat diet-induced hyperglycemia. Pyruvate or glucagon-induced elevation in blood glucose was attenuated by disruption of SENP2 expression, whereas overexpression of SENP2 in the liver facilitated high fat diet-induced hyperglycemia. Using an in vitro assay, we showed that SENP2 regulated hepatic glucose production. Mechanistically, the effects of SENP2 on gluconeogenesis were found to be mediated by the cellular fuel sensor kinase AMPKα, which is a negative regulator of gluconeogenesis. SENP2 interacted with and deSUMOylated AMPKα, thereby promoting its ubiquitination and reducing its protein stability. Inhibition of AMPKα kinase activity dramatically reversed impaired hepatic gluconeogenesis and reduced blood glucose levels in SENP2-deficient mice. Our study highlights the novel role of hepatic SENP2 in regulating gluconeogenesis and furthers our understanding of the pathogenesis of type 2 diabetes.

PIAS1 alleviates diabetic peripheral neuropathy through SUMOlation of PPAR-γ and miR-124-induced downregulation of EZH2/STAT3

Diabetic peripheral neuropathy (DPN) is a frequently occurring chronic complication of diabetes. In this study, we aim to explore the regulatory mechanism of protein inhibitor of activated STAT1 (PIAS1) in DPN in terms of autophagy and apoptosis of Schwann cells. The SUMOlation of PPAR-γ by PIAS1 was examined, and ChIP was performed to verify the binding of PPAR-γ to miR-124 promoter region. Dual-luciferase gene reporter assay was used to validate the binding affinity between miR-124 and EZH2/STAT3. Following loss‐ and gain‐of-function experiments, in vitro assays in high glucose-treated Schwann cells (SC4) and in vivo assays in db/db and ob/ob mice were performed to detect the effects of PIAS1 on autophagy and apoptosis of Schwann cells as well as symptoms of DPN by regulating the PPAR-γ-miR-124-EZH2/STAT3. The expression of PIAS1, PPAR-γ, and miR-124 was downregulated in the sciatic nerve tissue of diabetic mice. PIAS1 enhanced the expression of PPAR-γ through direct binding and SUMOlation of PPAR-γ. PPAR-γ enhanced the expression of miR-124 by enhancing the promoter activity of miR-124. Furthermore, miR-124 targeted and inversely modulated EZH2 and STAT3, promoting the autophagy of Schwann cells and inhibiting their apoptosis. In vivo experiments further substantiated that PIAS1 could promote the autophagy and inhibit the apoptosis of Schwann cells through the PPAR-γ-miR-124-EZH2/STAT3 axis. In conclusion, PIAS1 promoted SUMOlation of PPAR-γ to stabilize PPAR-γ expression, which upregulated miR-124 to inactivate EZH2/STAT3, thereby inhibiting apoptosis and promoting autophagy of Schwann cells to suppress the development of DPN.

Sparcl1 promotes nonalcoholic steatohepatitis progression in mice through upregulation of CCL2

Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of chronic liver disease ranging from simple steatosis (NAFL) to nonalcoholic steatohepatitis (NASH). However, the molecular mechanisms of NASH progression remain incompletely understood. White adipose tissue (WAT) has emerged as an important endocrine organ and contributes not only to the initial stage of NAFLD, but also to its severity. In the current study, through transcriptomic analysis we identified increased expression of Sparcl1, a secreted glycoprotein, in the WAT from NASH mice. Plasma Sparcl1 levels were similarly elevated and positively correlated with hepatic pathological features in NASH patients. Functional studies showed that both chronic injection of recombinant Sparcl1 protein and overexpression of Sparcl1 exaggerated hepatic inflammation and liver injury in mice. In contrast, genetic ablation of Sparcl1, knockdown of Sparcl1 in WAT, and treatment with a Sparcl1-neutralizing antibody dramatically alleviated diet-induced NASH pathogenesis. Mechanistically, Sparcl1 promoted the expression of C-C motif chemokine ligand 2 (CCL2) in hepatocytes through binding to Toll-like receptor 4 (TLR4) and activation of the NF-κB/p65 signaling pathway. Genetically or pharmacologically blocking the CCL2/CCR2 pathway attenuated the hepatic inflammatory response evoked by Sparcl1. Thus, our results demonstrated an important role for Sparcl1 in NASH progression, suggesting a potential target for therapeutic intervention.

The promise(s) of mesenchymal stem cell therapy in averting preclinical diabetes: lessons from in vivo and in vitro model systems

Obesity (Ob) poses a significant risk factor for the onset of metabolic syndrome with associated complications, wherein the Mesenchymal Stem Cell (MSC) therapy shows pre-clinical success. Here, we explore the therapeutic applications of human Placental MSCs (P-MSCs) to address Ob-associated Insulin Resistance (IR) and its complications. In the present study, we show that intramuscular injection of P-MSCs homed more towards the visceral site, restored HOMA-IR and glucose homeostasis in the WNIN/GR-Ob (Ob-T2D) rats. P-MSC therapy was effective in re-establishing the dysregulated cytokines. We report that the P-MSCs activates PI3K-Akt signaling and regulates the Glut4-dependant glucose uptake and its utilization in WNIN/GR-Ob (Ob-T2D) rats compared to its control. Our data reinstates P-MSC treatment's potent application to alleviate IR and restores peripheral blood glucose clearance evidenced in stromal vascular fraction (SVF) derived from white adipose tissue (WAT) of the WNIN/GR-Ob rats. Gaining insights, we show the activation of the PI3K-Akt pathway by P-MSCs both in vivo and in vitro (palmitate primed 3T3-L1 cells) to restore the insulin sensitivity dysregulated adipocytes. Our findings suggest a potent application of P-MSCs in  pre-clinical/Ob-T2D management.

CDKN2A deregulation in fatty liver disease and its accelerative role in the process of lipogenesis

Previous literature has indicated that cyclin-dependent kinase inhibitor 2 A (CDKN2A) is upregulated, while the Protein Inhibitor of Activated STAT1 (PIAS1) is downregulated in the liver tissues of obese mice. The current study aimed to investigate the relationship between CDKN2A and PIAS1 in the lipogenesis of fatty liver disease. In the C57BL/6J db/db mouse model and hepatocyte model of fatty liver, the expression pattern of CDKN2A, PIAS1, Protein arginine methyltransferase 1 (PRMT1) and CASP8 and FADD-like apoptosis regulator (CFLAR) was characterized by RNA quantitative and Western blot analysis. The lipogenesis-related genes (Srebp1c and Fas) in the liver tissues and cells were employed in the assessment of lipogenesis in response to gain- or loss-of-function of CDKN2A, PIAS1, PRMT1, and CFLAR, while triglyceride and fat content were evaluated in relation to fat accumulation. Western blot analysis was conducted to determine c-Jun amino-terminal kinase (JNK) phosphorylation, while the ubiquitination of CFLAR and SUMOylation of PIAS1 was examined by immunoprecipitation. PIAS1 and CFLAR were downregulated, while CDKN2A, PRMT1, and phosphorylation of JNK was elevated in the tissues and cells of the fatty liver models. Our results suggested that CDKN2A enhanced the SUMOylation of PIAS1 to reduce the expression of PIAS1. PRMT1 downregulated CFLAR by triggering its ubiquitination, while CFLAR repressed phosphorylation of JNK. The in vitro and in vivo results indicated that CDKN2A silencing prevented lipogenesis and fat accumulation by impairing the PRMT1-dependent ubiquitination of CFLAR and blocking the phosphorylation of JNK. Taken together, the central observations of our study demonstrate that targeting CDKN2A contributes to the suppression of lipogenesis and fat accumulation in fatty liver disease. The findings of our study highlight the potential of CDKN2A as a promising target against fatty liver.

Adipocyte-Derived Versican and Macrophage-Derived Biglycan Control Adipose Tissue Inflammation in Obesity

Obesity is characterized by adipose tissue inflammation. Because proteoglycans regulate inflammation, here we investigate their role in adipose tissue inflammation in obesity. We find that adipose tissue versican and biglycan increase in obesity. Versican is produced mainly by adipocytes and biglycan by adipose tissue macrophages. Both proteoglycans are also present in adipose tissue from obese human subjects undergoing gastric bypass surgery. Deletion of adipocyte-specific versican or macrophage-specific biglycan in mice reduces macrophage accumulation and chemokine and cytokine expression, although only adipocyte-specific versican deletion leads to sustained improvement in glucose tolerance. Macrophage-derived biglycan activates inflammatory genes in adipocytes. Versican expression increases in cultured adipocytes exposed to excess glucose, and adipocyte-conditioned medium stimulates inflammation in resident peritoneal macrophages, in part because of a versican breakdown product, versikine. These findings provide insights into the role of adipocyte- and macrophage-derived proteoglycans in adipose tissue inflammation in obesity.

Functional genomics study of protein inhibitor of activated STAT1 in mouse hippocampal neuronal cells revealed by RNA sequencing

Protein inhibitor of activated STAT1 (PIAS1), a small ubiquitin-like modifier (SUMO) E3 ligase, was considered to be an inhibitor of STAT1 by inhibiting the DNA-binding activity of STAT1 and blocking STAT1-mediated gene transcription in response to cytokine stimulation. PIAS1 has been determined to be involved in modulating several biological processes such as cell proliferation, DNA damage responses, and inflammatory responses, both in vivo and in vitro. However, the role played by PIAS1 in regulating neurodegenerative diseases, including Alzheimer’s disease (AD), has not been determined. In our study, significantly different expression levels of PIAS1 between normal controls and AD patients were detected in four regions of the human brain. Based on a functional analysis of Pias1 in undifferentiated mouse hippocampal neuronal HT-22 cells, we observed that the expression levels of several AD marker genes could be inhibited by Pias1 overexpression. Moreover, the proliferation ability of HT-22 cells could be promoted by the overexpression of Pias1. Furthermore, we performed RNA sequencing (RNA-seq) to evaluate and quantify the gene expression profiles in response to Pias1 overexpression in HT-22 cells. As a result, 285 significantly dysregulated genes, including 79 upregulated genes and 206 downregulated genes, were identified by the comparison of Pias1/+ cells with WT cells. Among these genes, five overlapping genes, including early growth response 1 (Egr1), early growth response 2 (Egr2), early growth response 3 (Egr3), FBJ osteosarcoma oncogene (Fos) and fos-like antigen 1 (Fosl1), were identified by comparison of the transcription factor binding site (TFBS) prediction results for STAT1, whose expression was evaluated by qPCR. Three cell cycle inhibitors, p53, p18 and p21, were significantly downregulated with the overexpression of Pias1. Analysis of functional enrichment and expression levels showed that basic region leucine zipper domain-containing transcription factors including zinc finger C2H2 (zf-C2H2), homeobox and basic/helix-loop-helix (bHLH) in several signaling pathways were significantly involved in PIAS1 regulation in HT-22 cells. A reconstructed regulatory network under PIAS1 overexpression demonstrated that there were 43 related proteins, notably Nr3c2, that directly interacted with PIAS1.

High expression of miR-483-5p aggravates sepsis-induced acute lung injury

Sepsis-induced acute lung injury (ALI) has high morbidity and mortality rates, and there remains a need for therapeutic methods to improve the outcome of ALI patients. miR-483-5p is an important regulator for the development of various diseases such as sepsis. Nevertheless, it is not known whether miR-483-5p has an effect on sepsis-induced ALI. To explore this issue, this study used cecal ligation and puncture (CLP)-treated mice and lipopolysaccharide (LPS)-treated pulmonary microvascular endothelial cells (PMVECs) cells to simulate the models of sepsis-induced ALI in vivo and in vitro. Pathological and histological changes of lungs from sepsis-induced ALI mice were detected by Hematoxylin-eosin staining. The detection levels of caspase-3, interleukin (IL)-6 and IL-1β were used to reflect the effect of miR-483-5p on apoptosis and inflammation of sepsis-induced ALI. The detection level of lactate dehydrogenase (LDH) in PMVECs cells was used to reflect the severe extent of sepsis-induced injury. The expression of miR-483-5p in lung tissues of sepsis-induced ALI mice was determined by qRT-PCR. In addition, the interaction of miR-483-5p with PIAS1 was identified and validated by Targetscan website and luciferase reporter assay, respectively. The results showed that miR-483-5p was up-regulated in the lung tissues of sepsis-induced ALI mice. Knockdown of miR-483-5p effectively ameliorated lung injury in mice with sepsis-induced ALI and inhibited inflammation and apoptosis of LPS-treated PMVECs cells. Furthermore, in vitro experiment revealed that PIAS1 was a potential target of miR-483-5p. Moreover, miR-483-5p could suppress PIAS1 expression to aggravate inflammation and apoptosis of LPS-treated PMVECs cells. These findings suggest miR-483-5p is a potential therapeutic and diagnostic biomarker for sepsis-induced ALI and provide a new insight for understanding the molecular mechanism of sepsis-induced ALI.

Age-Dependent and -Independent Effects of Perivascular Adipose Tissue and Its Paracrine Activities during Neointima Formation

Cardiovascular risk factors may act by modulating the composition and function of the adventitia. Here we examine how age affects perivascular adipose tissue (PVAT) and its paracrine activities during neointima formation. Aortic tissue and PVAT or primary aortic smooth muscle cells from male C57BL/6JRj mice aged 52 weeks (“middle-aged”) were compared to tissue or cells from mice aged 16 weeks (“adult”). Vascular injury was induced at the carotid artery using 10% ferric chloride. Carotid arteries from the middle-aged mice exhibited smooth muscle de-differentiation and elevated senescence marker expression, and vascular injury further aggravated media and adventitia thickening. Perivascular transplantation of PVAT had no effect on these parameters, but age-independently reduced neointima formation and lumen stenosis. Quantitative PCR analysis revealed a blunted increase in senescence-associated proinflammatory changes in perivascular tissue compared to visceral adipose tissue and higher expression of mediators attenuating neointima formation. Elevated levels of protein inhibitor of activated STAT1 (PIAS1) and lower expression of STAT1- or NFκB-regulated genes involved in adipocyte differentiation, inflammation, and apoptosis/senescence were present in mouse PVAT, whereas PIAS1 was reduced in the PVAT of patients with atherosclerotic vessel disease. Our findings suggest that age affects adipose tissue and its paracrine vascular activities in a depot-specific manner. PIAS1 may mediate the age-independent vasculoprotective effects of perivascular fat.

JNK2 in myeloid cells impairs insulin's vasodilator effects in muscle during early obesity development through perivascular adipose tissue dysfunction

Reduced vasodilator properties of insulin in obesity are caused by changes in perivascular adipose tissue and contribute to microvascular dysfunction in skeletal muscle. The causes of this dysfunction are unknown. The effects of a short-term Western diet on JNK2-expressing cells in perivascular adipose tissue (PVAT) on insulin-induced vasodilation and perfusion of skeletal muscle were assessed. In vivo, 2 wk of Western diet (WD) reduced whole body insulin sensitivity and insulin-stimulated muscle perfusion, determined using contrast ultrasonography during the hyperinsulinemic clamp. Ex vivo, WD triggered accumulation of PVAT in skeletal muscle and blunted its ability to facilitate insulin-induced vasodilation. Labeling of myeloid cells with green fluorescent protein identified bone marrow as a source of PVAT in muscle. To study whether JNK2-expressing inflammatory cells from bone marrow were involved, we transplanted JNK2^-/- bone marrow to WT mice. Deletion of JNK2 in bone marrow rescued the vasodilator phenotype of PVAT during WD exposure. JNK2 deletion in myeloid cells prevented the WD-induced increase in F4/80 expression. Even though WD and JNK2 deletion resulted in specific changes in gene expression of PVAT; epididymal and subcutaneous adipose tissue; expression of tumor necrosis factor-α, interleukin-1β, interleukin-6, or protein inhibitor of STAT1 was not affected. In conclusion, short-term Western diet triggers infiltration of JNK2-positive myeloid cells into PVAT, resulting in PVAT dysfunction, nonclassical inflammation, and loss of insulin-induced vasodilatation in vivo and ex vivo.NEW & NOTEWORTHY We demonstrate that in the earliest phase of weight gain, changes in perivascular adipose tissue in muscle impair insulin-stimulated muscle perfusion. The hallmark of these changes is infiltration by inflammatory cells. Deletion of JNK2 from the bone marrow restores the function of perivascular adipose tissue to enhance insulin's vasodilator effects in muscle, showing that the bone marrow contributes to regulation of muscle perfusion.

The investigation of relevancy between PIAS1 and PIAS2 gene expression and disease severity of multiple sclerosis

Introduction: PIAS1 and PIAS2 (protein inhibitor of activated STAT 1,2) play key roles in the pathogenesis of autoimmune and inflammatory diseases. This study aims to evaluate the gene expression of these factors in multiple sclerosis (MS) patients compared to healthy individuals and correlate them with the severity of MS. Materials and methods: Sixty participants, including 30 patients with MS and 30 healthy controls were studied. The expression of PIAS1 and PIAS2 genes in peripheral blood samples of all participants was measured by real-time PCR. The severity of MS was evaluated using the Expanded Disability Status Scale (EDSS). Finally, we evaluated the correlation between the expression of PIAS1 and PIAS2 genes with disease severity. Results: The expression of PIAS1 gene was increased in patients with MS compared to healthy subjects (P value<.001). Also, there was a significant correlation between the expression of PIAS1 and PIAS2 genes with disease severity according to EDSS. Conclusion: Our study suggests the expression of PIAS1 and PIAS2 genes as a prognostic and diagnostic marker in MS disease.

PIAS1 protects against myocardial ischemia-reperfusion injury by stimulating PPARγ SUMOylation

Background

Myocardial ischemia-reperfusion injury (IRI) has become one of the most serious complications after reperfusion therapy in patients with acute myocardial infarction. Small ubiquitin-like modification (SUMOylation) is a reversible process, including SUMO E1-, E2-, and E3-mediated SUMOylation and SUMO-specific protease-mediated deSUMOylation, with the latter having been shown to play a vital role in myocardial IRI previously. However, little is known about the function and regulation of SUMO E3 ligases in myocardial IRI.

Results

In this study, we found dramatically decreased expression of PIAS1 after ischemia/reperfusion (I/R) in mouse myocardium and H9C2 cells. PIAS1 deficiency aggravated apoptosis and inflammation of cardiomyocytes via activating the NF-κB pathway after I/R. Mechanistically, we identified PIAS1 as a specific E3 ligase for PPARγ SUMOylation. Moreover, H9C2 cells treated with hypoxia/reoxygenation (H/R) displayed reduced PPARγ SUMOylation as a result of down-regulated PIAS1, and act an anti-apoptotic and anti-inflammatory function through repressing NF-κB activity. Finally, overexpression of PIAS1 in H9C2 cells could remarkably ameliorate I/R injury.

Conclusions

Collectively, our findings demonstrate the crucial role of PIAS1-mediated PPARγ SUMOylation in protecting against myocardial IRI.

Electronic supplementary material

The online version of this article (10.1186/s12860-018-0176-x) contains supplementary material, which is available to authorized users.

Fibroblast growth factor 21 increases insulin sensitivity through specific expansion of subcutaneous fat

Although the pharmacological effects of fibroblast growth factor 21 (FGF21) are well-documented, uncertainty about its role in regulating excessive energy intake remains. Here, we show that FGF21 improves systemic insulin sensitivity by promoting the healthy expansion of subcutaneous adipose tissue (SAT). Serum FGF21 levels positively correlate with the SAT area in insulin-sensitive obese individuals. FGF21 knockout mice (FGF21KO) show less SAT mass and are more insulin-resistant when fed a high-fat diet. Replenishment of recombinant FGF21 to a level equivalent to that in obesity restores SAT mass and reverses insulin resistance in FGF21KO, but not in adipose-specific βklotho knockout mice. Moreover, transplantation of SAT from wild-type to FGF21KO mice improves insulin sensitivity in the recipients. Mechanistically, circulating FGF21 upregulates adiponectin in SAT, accompanied by an increase of M2 macrophage polarization. We propose that elevated levels of endogenous FGF21 in obesity serve as a defense mechanism to protect against systemic insulin resistance.

FGF21 has a number of beneficial metabolic effects. Here, Li et al. show that FGF21 promotes the healthy expansion of subcutaneous white adipose tissue, promoting the healthy expansion of fat tissue as a regulatory mechanism to maintain systemic insulin sensitivity during nutrient excess.

Protein inhibitor of activated STAT 4 (PIAS4) regulates pro-inflammatory transcription in hepatocytes by repressing SIRT1

Excessive nutrition promotes the pathogenesis of non-alcoholic steatohepatitis (NASH), characterized by the accumulation of pro-inflammation mediators in the liver. In the present study we investigated the regulation of pro-inflammatory transcription in hepatocytes by protein inhibitor of activated STAT 4 (PIAS4) in this process and the underlying mechanisms. We report that expression of the class III deacetylase SIRT1 was down-regulated in the livers of NASH mice accompanied by a simultaneous increase in the expression and binding activity of PIAS4. Exposure to high glucose stimulated the expression PIAS4 in cultured hepatocytes paralleling SIRT1 repression. Estrogen, a known NASH-protective hormone, ameliorated SIRT1 trans-repression by targeting PIAS4. Over-expression of PIAS4 enhanced, while PIAS4 knockdown alleviated, repression of SIRT1 transcription by high glucose. Lentiviral delivery of short hairpin RNA (shRNA) targeting PIAS4 attenuated hepatic inflammation in NASH mice by restoring SIRT1 expression. Mechanistically, PIAS4 promoted NF-κB-mediated pro-inflammatory transcription in a SIRT1 dependent manner. In conclusion, our study indicates that PIAS4 mediated SIRT1 repression in response to nutrient surplus contributes to the pathogenesis of NASH. Therefore, targeting PIAS4 might provide novel therapeutic strategies in the intervention of NASH.

The BMP4-Smad signaling pathway regulates hyperandrogenism development in a female mouse model

Polycystic ovary syndrome is a common endocrine disorder and a major cause of anovulatory sterility in women at reproductive age. Most patients with polycystic ovary syndrome have hyperandrogenism, caused by excess androgen synthesis. Bone morphogenetic protein 4 (BMP4) is an essential regulator of embryonic development and organ formation, and recent studies have also shown that BMP4 may be involved in female steroidogenesis process. However, the effect of BMP4 on hyperandrogenism remains unknown. Here, using a female mouse model of hyperandrogenism, we found that ovarian BMP4 levels were significantly decreased in hyperandrogenism. Elevated androgens inhibited BMP4 expression via activation of androgen receptors. Moreover, BMP4 treatment suppressed androgen synthesis in theca cells and promoted estrogen production in granulosa cells by regulating the expression of steroidogenic enzymes, including CYP11A, HSD3B2, CYP17A1, and CYP19A1 Consistently, knockdown of BMP4 augmented androgen levels and inhibited estrogen levels. Mechanistically, Smad signaling rather than the p38 MAPK pathway regulated androgen and estrogen formation, thereby mediating the effect of BMP4. Of note, BMP4-transgenic mice were protected against hyperandrogenism. Our observations clarify a vital role of BMP4 in controlling sex hormone levels and offer new insights into intervention for managing hyperandrogenism by targeting the BMP4-Smad signaling pathway.

Current Advances in the Biochemical and Physiological Aspects of the Treatment of Type 2 Diabetes Mellitus with Thiazolidinediones

The present review summarizes the current advances in the biochemical and physiological aspects in the treatment of type 2 diabetes mellitus (DM2) with thiazolidinediones (TZDs). DM2 is a metabolic disorder characterized by hyperglycemia, triggering the abnormal activation of physiological pathways such as glucose autooxidation, polyol's pathway, formation of advance glycation end (AGE) products, and glycolysis, leading to the overproduction of reactive oxygen species (ROS) and proinflammatory cytokines, which are responsible for the micro- and macrovascular complications of the disease. The treatment of DM2 has been directed toward the reduction of hyperglycemia using different drugs such as insulin sensitizers, as the case of TZDs, which are able to lower blood glucose levels and circulating triglycerides by binding to the nuclear peroxisome proliferator-activated receptor gamma (PPARγ) as full agonists. When TZDs interact with PPARγ, the receptor regulates the transcription of different genes involved in glucose homeostasis, insulin resistance, and adipogenesis. However, TZDs exhibit some adverse effects such as fluid retention, weight gain, hepatotoxicity, plasma-volume expansion, hemodilution, edema, bone fractures, and congestive heart failure, which limits their use in DM2 patients.