Tumor necrosis factor-α increases angiopoietin-like protein 2 gene expression by activating Foxo1 in 3T3-L1 adipocytes

Role of the angiopoietin-like protein family in the progression of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most frequent cause of chronic liver disease, with a range of conditions including non-alcoholic fatty liver, non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma (HCC). Currently recognized as the liver component of the metabolic syndrome, NAFLD is intimately linked to metabolic diseases. Angiopoietin-like proteins (ANGPTLs) comprise a class of proteins that resemble angiopoietins structurally. It is closely related to obesity, insulin resistance and lipid metabolism, and may be the critical factor of metabolic syndrome. In recent years, many studies have found that there is a certain correlation between ANGPTLs and the occurrence and progression of NAFLD disease spectrum. This article reviews the possible mechanisms and roles of ANGPTL protein in the pathogenesis and progression of NAFLD.

Tumor necrosis factor-α reduces adiponectin production by decreasing transcriptional activity of peroxisome proliferator-activated receptor-γ in calf adipocytes

Adiponectin (encoded by ADIPOQ) is an adipokine that orchestrates energy homeostasis by modulating glucose and fatty acid metabolism in peripheral tissues. During the periparturient period, dairy cows often develop adipose tissue inflammation and decreased plasma adiponectin levels. Proinflammatory cytokine tumor necrosis factor-α (TNF-α) plays a pivotal role in regulating the endocrine functions of adipocytes, but whether it affects adiponectin production in calf adipocytes remains obscure. Thus, the present study aimed to determine whether TNF-α could affect adiponectin production in calf adipocytes and to identify the underlying mechanism. Adipocytes isolated from Holstein calves were differentiated and used for (1) BODIPY493/503 staining; (2) treatment with 0.1 ng/mL TNF-α for different times (0, 8, 16, 24, or 48 h); (3) transfection with peroxisome proliferator-activated receptor-γ (PPARG) small interfering RNA for 48 h followed by treatment with or without 0.1 ng/mL TNF-α for 24 h; and (4) overexpression of PPARG for 48 h followed by treatment with or without 0.1 ng/mL TNF-α for 24 h. After differentiation, obvious lipid droplets and secretion of adiponectin were observed in adipocytes. Treatment with TNF-α did not alter mRNA abundance of ADIPOQ but reduced the total and high molecular weight (HMW) adiponectin content in the supernatant of adipocytes. Quantification of mRNA abundance of endoplasmic reticulum (ER)/Golgi resident chaperones involved in adiponectin assembly revealed that ER protein 44 (ERP44), ER oxidoreductase 1α (ERO1A), and disulfide bond-forming oxidoreductase A-like protein (GSTK1) were downregulated in TNF-α-treated adipocytes, while 78-kDa glucose-regulated protein and Golgi-localizing γ-adaptin ear homology domain ARF binding protein-1 were unaltered. Moreover, TNF-α diminished nuclear translocation of PPARγ and downregulated mRNA abundance of PPARG and its downstream target gene fatty acid synthase, suggesting that TNF-α suppressed the transcriptional activity of PPARγ. In the absence of TNF-α, overexpression of PPARG enhanced the total and HMW adiponectin content in supernatant and upregulated the mRNA abundance of ADIPOQ, ERP44, ERO1A, and GSTK1 in adipocytes. However, knockdown of PPARG reduced the total and HMW adiponectin content in supernatant and downregulated the mRNA abundance of ADIPOQ, ERP44, ERO1A, and GSTK1 in adipocytes. In the presence of TNF-α, overexpression of PPARG decreased, while knockdown of PPARG further exacerbated TNF-α-induced reductions in total and HMW adiponectin secretion and gene expression of ERP44, ERO1A, and GSTK1. Overall, TNF-α reduces adiponectin assembly in the calf adipocyte, which may be partly mediated by attenuation of PPARγ transcriptional activity. Thus, locally elevated levels of TNF-α in adipose tissue may be one reason for the decrease in circulating adiponectin in periparturient dairy cows.

Angiopoietin-like 2 Protein and Hidradenitis Suppurativa: A New Biomarker for Disease Severity

Hidradenitis suppurativa (HS) is a chronic inflammatory disease whose pathogenesis is not fully understood at present. The role of proinflammatory cytokines, several adipokines, retinol-binding protein 4, angiopoietin-2 and other molecules has been previously reported. Angiopoietin-like 2 protein (ANGPTL2) is a glycoprotein belonging to the angiopoietin-like family that may play a pivotal role in the pathogenesis of several chronic inflammatory diseases. To our knowledge, the role of serum ANGPTL2 levels in HS has not been assessed to date. In the current case-control study, we aimed to investigate serum ANGPTL2 levels in HS patients and controls and to assess whether ANGPTL2 levels could be associated with the severity of HS. Ninety-four patients with HS and sixty controls of similar age and sex were included in the study. Demographic, anthropometric, and clinical data, as well as routine laboratory parameters and serum concentrations of ANGPTL2, were assessed in all participants. HS patients had significantly higher serum ANGPTL2 levels than controls after adjusting for confounders. Moreover, ANGPTL2 concentrations positively correlated with disease duration and severity. Our results indicate for the first time that serum ANGPTL2 concentrations are elevated in HS patients compared to controls and correlate with the duration of the disease. Besides, ANGPTL2 might serve as a biomarker of HS severity.

Angiopoietin-Like Proteins 2 and 3 in Children and Adolescents with Obesity and Their Relationship with Hypertension and Metabolic Syndrome

Background

Angiopoietin-like protein 2 (ANGPTL2) is one of the adipocyte-derived inflammatory factors which connects obesity to insulin resistance. ANGPTL3 has a direct role in regulation of lipid metabolism. The objective of this study was to evaluate ANGPTL2 and ANGPTL3 in childhood obesity and their relationship with metabolic syndrome.

Methods

70 children and adolescents, 35 obese and 35 normal-weight subjects, were enrolled in this research after complete clinical examination and anthropometric evaluations. Serum ANGPTL2 and ANGPTL3 and insulin were measured by enzyme-linked immunosorbent assay (ELISA). Homeostatic model assessment of insulin resistance (HOMA-IR) was calculated and used to estimate insulin resistance (IR). Colorimetric methods were used for the assessment of fasting plasma glucose (FPG), LDL-C, HDL-C, total cholesterol (TC), and triglyceride (TG).

Results

The levels of ANGPTL2 and ANGPTL3 were significantly higher in obese subjects than those in controls, but they did not differ significantly in subjects with or without IR. ANGPTL3 was found to be significantly elevated in obese children with metabolic syndrome (MetS) in comparison with those without MetS. Both of the studied ANGPTLs were positively correlated with BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), TC, and LDL-C. The correlation between ANGPTL3 and either TC or LDL-C remained significant after adjusting for BMI.

Conclusion

Serum ANGPTL2 and ANGPTL3 were elevated in obesity and associated with blood pressure and indices of metabolic syndrome, suggesting that they might be involved in the advancement of obesity-related hypertension and metabolic syndrome.

Anti-inflammatory activity of berberine in non-alcoholic fatty liver disease via the Angptl2 pathway

Background

Nonalcoholic fatty liver disease (NAFLD) has become the most common liver disease worldwide. Recent studies have shown that the Angptl2 pathway mediated hepatic inflammatory response plays an important role in the progression of nonalcoholic fatty liver disease. Our study investigated the possible molecular mechanisms of berberine (BBR) in the treatment of the liver inflammatory response in the livers of rats with high-fat diet-induced NAFLD via the Angptl2 pathway.

Results

At the end of 12 weeks, compared with the control group rats, the high-fat- diet group rats showed obvious pathological and biochemical changes. The levels of pro-infalmmatory cytokines (CCL2, TNF-α) were increased, the infiltration of inflammatory cells (CCR2) was elevated, and the hepatic mRNA and protein levels of Angptl2, NF-κB and Foxo1 were increased to different degrees. Nevertheless, following treatment with BBR, liver tissue pathology, biochemical data, and Angptl2 pathway-related genes expression were significantly ameliorated.

Conclusions

Our findings demonstrate that BBR might attenuate the liver inflammatory response in the livers of rats with high-fat diet-induced NAFLD through the regulation of the Angptl2 pathway.

Remodeling adipose tissue inflammasome for type 2 diabetes mellitus treatment: Current perspective and translational strategies

Obesity-associated type 2 diabetes mellitus (T2DM) is characterized by low-grade chronic systemic inflammation that arises primarily from the white adipose tissue. The interplay between various adipose tissue-derived chemokines drives insulin resistance in T2DM and has therefore become a subject of rigorous investigation. The adipocytokines strongly associated with glucose homeostasis include tumor necrosis factor-α, various interleukins, monocyte chemoattractant protein-1, adiponectin, and leptin, among others. Remodeling the adipose tissue inflammasome in obesity-associated T2DM is likely to treat the underlying cause of the disease and bring significant therapeutic benefit. Various strategies have been adopted or are being investigated to modulate the serum/tissue levels of pro- and anti-inflammatory adipocytokines to improve glucose homeostasis in T2DM. These include use of small molecule agonists/inhibitors, mimetics, antibodies, gene therapy, and other novel formulations. Here, we discuss adipocytokines that are strongly associated with insulin activity and therapies that are under investigation for modulation of their levels in the treatment of T2DM.

Tumor necrosis factor α reduces gonadotropin-releasing hormone release through increase of forkhead box protein O1 activity

It has been found that hypothalamus helps to control aging, and hypothalamus-driven programmatic aging is associated with nuclear factor-κB (NF-κB)-mediated decrease of gonadotropin-releasing hormone (GnRH). However, the molecular mechanism(s) underlying aging-associated hypothalamic GnRH decline are largely unknown. Forkhead box O (FOXO), a family of transcription factors, has been demonstrated to be associated with aging. GnRH neuronal cell line GT1-7 was used in this study to determine whether FOXO1 was involved in tumor necrosis factor α (TNF-α)-induced decrease of GnRH. Our data showed that FOXO1 activity was increased by TNF-α through inhibition of its phosphorylation. Increased FOXO1 activity inhibited gnrh1 gene and activated NF-κB, thereby impairing the secretion of GnRH from GT1-7 cells. The increase of FOXO1 activity contributes to TNF-α-induced decrease of GnRH release, which may underscore the significance of this event to the development of aging and therapeutic interventions against age-dependent pathologies.

Angiopoietin-like protein 2 in psoriasis: a new linkage with metabolic syndrome

Introduction

Psoriasis is a chronic disease of inflammatory nature which can be considered as a systemic disorder. Metabolic syndrome is prevalent in psoriatic patients, with a negative impact on disease severity. Angiopoietin-like protein 2 (ANGPTL2) role has been investigated in several chronic inflammatory conditions, but not in psoriasis.

Aim

To evaluate the serum level of ANGPTL2 and its possible role in the occurrence of metabolic syndrome in psoriatic patients.

Material and methods

This study enrolled 180 participants divided into two groups: psoriatic group (120 patients with chronic plaque psoriasis) and control group (60 normal subjects). Psoriasis severity was determined by the psoriasis area severity index. Anthropometric measurements, lipid profile, fasting blood sugar and ANGPTL2 have been evaluated in both groups.

Results

Psoriatic patients had a higher body mass index (p = 0.014), waist circumference (p < 0.001), and blood pressure than controls (p Ł 0.001). Fasting blood sugar and the serum level of ANGPTL2 were also higher in psoriatic patients than in controls (p < 0.001, 0.025, respectively). In addition, the serum level of ANGPTL2 was significantly correlated with both disease severity (p < 0.001) and occurrence of metabolic syndrome (p < 0.001).

Conclusions

Serum ANGPTL2 is elevated in psoriasis patients compared to normal subjects. Serum ANGPTL2 elevation may have a role in chronic inflammatory status in psoriasis and occurrence of metabolic syndrome.

Adipocytokines in Steatotic Liver Surgery/Transplantation

Because of the shortage of liver grafts available for transplantation, the restrictions on graft quality have been relaxed, and marginal grafts, such as steatotic livers, are now accepted. However, this policy change has not solved the problem, because steatotic liver grafts tolerate ischemia-reperfusion (I/R) injury poorly. Adipocytokines differentially modulate steatosis, inflammation, and fibrosis and are broadly present in hepatic resections and transplants. The potential use of adipocytokines as biomarkers of the severity of steatosis and liver damage to aid the identification of high-risk steatotic liver donors and to evaluate hepatic injury in the postoperative period are discussed. The hope of finding new therapeutic strategies aimed specifically at protecting steatotic livers undergoing surgery is a strong impetus for identifying the mechanisms responsible for hepatic failure after major surgical intervention. Hence, the most recently described roles of adipocytokines in steatotic livers subject to I/R injury are discussed, the conflicting results in the literature are summarized, and reasons are offered as to why strategic pharmacologic control of adipocytokines has yet to yield clinical benefits. After this, the next steps needed to transfer basic knowledge about adipocytokines into clinical practice to protect marginal livers subject to I/R injury are presented. Recent strategies based on adipocytokine regulation, which have shown efficacy in various pathologies, and hold promise for hepatic resection and transplantation are also outlined.

LITAF Enhances Radiosensitivity of Human Glioma Cells via the FoxO1 Pathway

Lipopolysaccharide-induced tumor necrosis factor alpha factor (LITAF), also called p53-induced gene 7 (PIG7), was identified as a transcription factor that activates transcription of proinflammatory cytokines in macrophages in response to lipopolysaccharide (LPS). Previous studies have identified LITAF as a potential tumor suppressor in several neoplasms, including prostate cancer, B-NHL, acute myeloid leukemia, and pancreatic cancer. However, the expression and function of LITAF in human glioma remain unexplained. The present study aimed to analyze the regulation of LITAF in gliomas. Data from The Cancer Genome Atlas (TCGA) database revealed that LITAF mRNA expression in glioma tissues was higher than that in normal brain tissues, and lower LITAF expression in gliomas showed a good prognosis in patients who received radiotherapy, by Kaplan-Meier analysis. In our collected specimens, however, LITAF showed low expression in glioma tissues compared to that in the normal brain tissue. Proliferation and apoptosis of glioma cells were not affected by knockdown or overexpression of LITAF in glioma U251, U373, and U87 cells, but LITAF was able to enhance the radiosensitivity of glioma cells. Furthermore, we found that LITAF enhanced radiosensitivity via FoxO1 and its specific downstream targets BIM, TRAIL, and FASLG. Taken together, our present results demonstrate that LITAF expression is decreased in glioma tissues and might enhance radiosensitivity of glioma cells via upregulation of the FoxO1 pathway.

Enhanced ANGPTL2 expression in adipose tissues and its association with insulin resistance in obese women

Angiopoietin-like protein 2 has been proposed to be a key mediator linking obesity and insulin resistance. However, no detailed study of ANGPTL2 expression in human adipose tissues has yet been reported. To investigate the pattern and regulation of ANGPTL2 expression in human adipose tissues in obesity and its related diseases, we recruited 32 non-diabetic and 13 type 2 diabetic obese women and 32 normal-weight women. ANGPTL2 mRNA was expressed at a similar level in visceral and subcutaneous adipose tissues. Adipose tissue ANGPTL2 mRNA was much higher in obese patients. Adipose tissue ANGPTL2 mRNA and serum ANGPTL2 levels showed strong associations with metabolic parameters associated with insulin resistance. In adipose tissue, ANGPTL2 mRNA was closely correlated with the expression of genes involved in inflammation and ER stress. ANGPTL2 mRNA was principally expressed in adipocytes, and its expression was markedly higher in the adipocyte but non-adipocyte fraction of obese adipose tissues. Culture of human adipocytes under conditions mimicking the microenvironment of obese adipose tissue (especially, increased ER stress) stimulated ANGPTL2 gene expression and secretion. In addition, co-culture of adipocytes and macrophages suggested that ANGPTL2 excessively produced by adipocytes, may contribute inflammation and remodeling in obese adipose tissues, thereby promoting insulin resistance.

Bariatric Surgery-Induced Lower Angiopoietin-Like 2 Protein Is Associated With Improved Cardiometabolic Profile

BACKGROUND

Plasma angiopoietin-like 2 (Angptl2), a proinflammatory protein, has been associated with obesity and diabetes. Whether weight loss induced by bariatric surgery and associated improvement of the cardiometabolic risk profile influence circulating Angptl2 levels is unknown. We tested whether biliopancreatic diversion with duodenal switch (BPD-DS) surgery alters plasma Angptl2 concentrations.

METHODS

Severely obese patients (n = 73; body mass index: 49.8 ± 7.1) underwent BPD-DS. Plasma levels of Angptl2 and metabolic biomarkers were obtained acutely (days 1 and 5) and at 6 and 12 months after surgery, and compared with results in an age- and sex-matched control group (n = 33) remaining on the waiting list.

RESULTS

Preoperative Angptl2 levels were high (median: 12.3 ng/mL) and correlated with metabolic and anthropometric parameters. A significant (P < 0.01) increase in Angptl2 levels, fasting glucose, insulin, and interleukin-6 levels was observed acutely postoperatively (day 1) followed by a progressive decline from day 5. Besides weight loss, Angptl2 levels were decreased at the 12-month follow-up (11.5 ± 4.7 vs 14.0 ± 4.0 ng/mL, P < 0.0001), but not at the 6-month time point. Long-term changes in plasma Angptl2 levels showed significant positive correlations with changes in fasting glucose, insulin resistance, and tumour necrosis factor-α levels, and negative correlation with changes in leptin concentration (P < 0.05). No significant correlation was observed between changes in anthropometric parameters and Angptl2.

CONCLUSIONS

Plasma Angptl2 levels decreased after BPD-DS in severely obese patients; no changes occurred in control participants. Lowered circulating levels of the inflammatory factor Angptl2 because of BPD-DS were closely related to favourable changes in glucose-insulin homeostasis and inflammatory profiles.

ANGPTL2 is associated with an increased risk of cardiovascular events and death in diabetic patients

AIMS/HYPOTHESIS

A high serum angiopoietin-like 2 (ANGPTL2) concentration is an independent risk factor for developing diabetes and is associated with insulin resistance and atherosclerosis. In this work, we have examined the impact of serum ANGPTL2 on improving cardiovascular (CV) risk stratification in patients with type 2 diabetes.

METHODS

A prospective, monocentric cohort of consecutive type 2 diabetes patients (the SURDIAGENE cohort; total of 1353 type 2 diabetes patients; 58% men, mean ± SD age 64 ± 11 years) was followed for a median of 6.0 years for death as primary endpoint and major adverse CV events (MACE; i.e. CV death, myocardial infarction or stroke) as a secondary endpoint. Patients with end-stage renal disease, defined as a requirement for dialysis or a history of kidney transplantation, were excluded. Patients were grouped into quartiles according to ANGPTL2 concentrations at inclusion: <11.2 (Q1), 11.2-14.7 (Q2), 14.8-19.5 (Q3) or >19.5 (Q4) ng/ml.

RESULTS

During follow up, 367 patients (representing 4.5% of the total person-years) died and 290 patients (representing 3.7% of the total person-years) presented with MACE. Both the survival and MACE-free survival rates were significantly different between ANGPTL2 quartiles (logrank 82.12, p < 0.0001 for death; and logrank 65.14, p < 0.0001 for MACE). Patients with ANGPTL2 concentrations higher than 19.5 ng/ml (Q4) had a significantly higher risk of death and MACE than those with ANGPTL2 levels of 19.5 ng/ml or less (Q1-3) (HR for death 2.44 [95% CI 1.98, 3.00], p < 0.0001; HR for MACE 2.43 [95% CI 1.92, 3.06], p < 0.0001) after adjustment for sex, age and established CV risk factors. Using ANGPTL2 concentrations, prediction of the risk of mortality, as assessed by integrated discrimination improvement (IDI), was significantly improved (IDI 0.006 ± 0.002, p = 0.0002).

CONCLUSIONS/INTERPRETATION

In patients with type 2 diabetes, serum ANGPTL2 concentrations were independently associated with death and MACE. Therefore, ANGPTL2 is a promising candidate biomarker for improving risk stratification in type 2 diabetes patients, and may prove to be a valuable therapeutic target.

TNF-insulin crosstalk at the transcription factor GATA6 is revealed by a model that links signaling and transcriptomic data tensors

Signal transduction networks coordinate transcriptional programs activated by diverse extracellular stimuli, such as growth factors and cytokines. Cells receive multiple stimuli simultaneously, and mapping how activation of the integrated signaling network affects gene expression is a challenge. We stimulated colon adenocarcinoma cells with various combinations of the cytokine tumor necrosis factor (TNF) and the growth factors insulin and epidermal growth factor (EGF) to investigate signal integration and transcriptional crosstalk. We quantitatively linked the proteomic and transcriptomic data sets by implementing a structured computational approach called tensor partial least squares regression. This statistical model accurately predicted transcriptional signatures from signaling arising from single and combined stimuli and also predicted time-dependent contributions of signaling events. Specifically, the model predicted that an early-phase, AKT-associated signal downstream of insulin repressed a set of transcripts induced by TNF. Through bioinformatics and cell-based experiments, we identified the AKT-repressed signal as glycogen synthase kinase 3 (GSK3)-catalyzed phosphorylation of Ser(37) on the long form of the transcription factor GATA6. Phosphorylation of GATA6 on Ser(37) promoted its degradation, thereby preventing GATA6 from repressing transcripts that are induced by TNF and attenuated by insulin. Our analysis showed that predictive tensor modeling of proteomic and transcriptomic data sets can uncover pathway crosstalk that produces specific patterns of gene expression in cells receiving multiple stimuli.

GDC-0152 attenuates the malignant progression of osteosarcoma promoted by ANGPTL2 via PI3K/AKT but not p38MAPK signaling pathway

Angiopoietin-like protein 2 (ANGPTL2) plays an important role in inflammatory carcinogenesis and tumor metastasis. The compound GDC-0152 is a peptidomimetic small molecule antagonist of inhibitor of apoptosis (IAP) proteins with antitumor activity. However, the interaction between ANGPTL2 and GDC-0152 has not been studied. It has been proven that ANGPTL2 promotes metastasis of osteosarcoma. Therefore, in the present study, the effect of GDC-0152 on the malignant progression of osteosarcoma promoted by ANGPTL2 was investigated. Human osteosarcoma cell line SaOS2 cells were pre-treated or non-treated with GDC-0152 and then exposed to recombinant human ANGPTL2. The viability of SaOS2 cells was determined by MTT assay, the migration of SaOS2 cells was analyzed by chamber migration assay kit, and the SaOS2 cell apoptosis was determined by fluorescence-activated cell sorting (FACS) and nuclear staining. Treatment with ANGPTL2 increased SaOS2 cell growth and migration and decreased cell apoptosis. The increased cell growth and decreased cell apoptosis were significantly attenuated in SaOS2 cells receiving GDC-0152. However, the ANGPTL2-increased SaOS2 cell migration was not inhibited by GDC-0152 treatment. Furthermore, western blot analysis showed that the activation of phosphatidyl inositol 3-kinase (PI3K) (p85), PI3K (p110), protein kinase B (Akt) (Ser473), Akt (Thr308) and p38 mitogen-activated protein kinase (p38MAPK) were upregulated by ANGPTL2. Quantitative real-time polymerase chain reaction (qTR-PCR) and gelatin zymography showed that the mRNA expression and activity of matrix metalloproteinase-9 (MMP-9) and matrix metalloproteinase-2 (MMP-2) were also increased by ANGPTL2. The upregulated activation of PI3K and Akt were significantly suppressed by the treatment of GDC-0152. In contrast, GDC-0152 did not suppress ANGPTL2-induced p38MAPK phosphorylation, MMP-9/MMP-2 mRNA expression or MMP-9/MMP-2 activity. Taken together, these data indicate that GDC-0152 attenuates the malignant progression of osteosarcoma promoted by ANGPTL2 via PI3K/AKT but not p38MAPK signaling pathway. The present study indicated a novel therapeutic strategy to inhibit tumor growth by indirectly preventing ANGPTL2 signaling.

ANGPTL2 promotes tumor metastasis in hepatocellular carcinoma

BACKGROUND AND AIM

Angiopoietin-like protein 2 (ANGPTL2) plays various roles in metabolism, vascular biology, inflammation, and tumor metastasis, but little is known about its function in human hepatocellular carcinoma (HCC) metastasis. This study aimed to further explore the function of ANGPTL2 on migration and invasion of liver cancer cells.

METHODS

Quantitative real-time polymerase chain reaction, Western blotting, immunohistochemistry, transwell migration, and invasion assays were performed to clarify the function of ANGPTL2 in the regulation of cell migration and invasion in human HCC.

RESULTS

In HCC patients, ANGPTL2 expression was higher in HCC tissues compared with matched noncancerous liver tissues. And the ANGPTL2 levels of HCC tissues positively correlated with intrahepatic metastasis in HCC patients. Overexpression of ANGPTL2 significantly increased migration and invasion of HCC cells in vitro, and promoted intrahepatic and distal pulmonary metastasis in vivo, while knockdown of endogenous ANGPTL2 resulted in a reduced migration and invasion in vitro. Colony formation assay and 3-(4,5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay showed ANGPTL2 did not affect cell proliferation in vitro, whereas overexpression of ANGPTL2 promoted tumor formation in xenograft animal model.

CONCLUSIONS

Our findings show that ANGPTL2 drives human HCC metastasis and provides a potential therapeutic target for HCC treatment.

Angiopoietin-like-2: a multifaceted protein with physiological and pathophysiological properties

Angptl2 is a multifaceted protein, displaying both physiological and pathological functions, in which scientific and clinical interest is growing exponentially within the past few years. Its physiological functions are not well understood, but angptl2 was first acknowledged for its pro-angiogenic and antiapoptotic capacities. In addition, angptl2 can be considered a growth factor, since it increases survival and expansion of hematopoietic stem cells and may promote vasculogenesis. Finally, angptl2 has an important, but largely unrecognised, physiological role: in the cytosol, angptl2 binds to type 1A angiotensin II receptors and induces their recycling, with recovery of the receptor signal functions. Despite these important physiological properties, angptl2 is better acknowledged for its deleterious pro-inflammatory properties and its contribution in multiple chronic diseases such as cancer, diabetes, atherosclerosis, metabolic disorders and many other chronic diseases. This review aims at presenting an updated description of both the beneficial and deleterious biological properties of angptl2, in addition to its molecular signalling pathways and transcriptional regulation. The multiplicity of diseases in which angptl2 contributes makes it a new highly relevant clinical therapeutic target.

Angiopoietin-like proteins: a comprehensive look

Angiopoietin-like proteins (ANGPTLs) are a family of proteins structurally similar to the angiopoietins. To date, eight ANGPTLs have been discovered, namely ANGPTL1 to ANGPTL8. Emerging evidence implies a key role for ANGPTLs in the regulation of a plethora of physiological and pathophysiological processes. Most of the ANGPTLs exhibit multibiological properties, including established functional roles in lipid and glucose metabolism, inflammation, hematopoiesis, and cancer. This report represents a systematic and updated appraisal of this class of proteins, focusing on the main features of each ANGPTL.

Adipokines mediate inflammation and insulin resistance

For many years, adipose tissue was considered as an inert energy storage organ that accumulates and stores triacylglycerols during energy excess and releases fatty acids in times of systemic energy need. However, over the last two decades adipose tissue depots have been established as highly active endocrine and metabolically important organs that modulate energy expenditure and glucose homeostasis. In rodents, brown adipose tissue plays an essential role in non-shivering thermogenesis and in energy dissipation that can serve to protect against diet-induced obesity. White adipose tissue collectively referred too as either subcutaneous or visceral adipose tissue is responsible for the secretion of an array of signaling molecules, termed adipokines. These adipokines function as classic circulating hormones to communicate with other organs including brain, liver, muscle, the immune system, and adipose tissue itself. The dysregulation of adipokines has been implicated in obesity, type 2 diabetes, and cardiovascular disease. Recently, inflammatory responses in adipose tissue have been shown as a major mechanism to induce peripheral tissue insulin resistance. Although leptin and adiponectin regulate feeding behavior and energy expenditure, these adipokines are also involved in the regulation of inflammatory responses. Adipose tissue secretes various pro- and anti-inflammatory adipokines to modulate inflammation and insulin resistance. In obese humans and rodent models, the expression of pro-inflammatory adipokines is enhanced to induce insulin resistance. Collectively, these findings have suggested that obesity-induced insulin resistance may result, at least in part, from an imbalance in the expression of pro- and anti-inflammatory adipokines. Thus we will review the recent progress regarding the physiological and molecular functions of adipokines in the obesity-induced inflammation and insulin resistance with perspectives on future directions.

Angiopoietin-like protein ANGPTL2 gene expression is correlated with lymph node metastasis in lung cancer

Inflammation plays key roles at various stages of tumor development, including invasion and metastasis. In mice, the angiopoietin-like protein (ANGPTL2) gene has been implicated in inflammatory carcinogenesis. ANGPTL2 mRNA expression was investigated by real-time polymerase chain reaction (RT-PCR) assay using LightCycler in surgically treated non-small cell lung cancer (NSCLC) cases. In total, 110 surgically resected NSCLC cases were used for mRNA level analyses. The ANGPTL2/β-actin mRNA levels were not significantly different between lung cancer (1598.481±6465.781) and adjacent normal lung tissues (2116.639±8337.331, P=0.5453). The tumor/normal (T/N) ratio of ANGPTL2/β-actin mRNA levels was not different between gender, age, smoking status and pathological stages. The T/N ratio of ANGPTL2/β-actin mRNA levels was significantly higher in lymph node metastasis-positive cases (2.173±3.151) compared with lymph node metastasis-negative cases (1.212±1.778, P=0.0464). However, ANGPTL2 mRNA status was not correlated with tumor invasion status. Thus, ANGPTL2 may drive metastasis and provide a candidate for blockade of its function as a strategy to antagonize the metastatic process in NSCLC.