Angiopoietin-like Protein 4 Expression Research Articles

Angiopoietin-like protein 4 induces growth hormone variant secretion and aggravates insulin resistance during pregnancy, linking obesity to gestational diabetes mellitus.

Angiopoietin-like protein 4 (ANGPTL4) is a secretory glycoprotein involved in regulating glucose homeostasis in non-pregnant subjects. However, its role in glucose metabolism during pregnancy and the pathophysiology of gestational diabetes mellitus (GDM) remains elusive. Thus, this study aimed to clarify the relationship between ANGPTL4 and GDM and investigate the pathophysiology of placental ANGPTL4 in glucose metabolism. We investigated this issue using blood and placenta samples in 957 pregnant women, the human 3A-sub-E trophoblast cell line, and the L6 skeletal muscle cell line. We found that ANGPTL4 expression in the placenta was higher in obese pregnant women than in lean controls. Palmitic acid significantly induced ANGPTL4 expression in trophoblast cells in a dose-response manner. ANGPTL4 overexpression in trophoblast cells resulted in endoplasmic reticulum (ER) stress, which stimulated the expression and secretion of growth hormone-variant (GH2) but not human placental lactogen. In L6 skeletal muscle cells, soluble ANGPTL4 suppressed insulin-mediated glucose uptake through the epidermal growth factor receptor (EGFR)/extracellular signal-regulated kinases 1/2 (ERK 1/2) pathways. In pregnant women, plasma ANGPTL4 concentrations in the first trimester predicted the incidence of GDM and were positively associated with BMI, plasma triglyceride, and plasma GH2 in the first trimester. However, they were negatively associated with insulin sensitivity index ISI0,120 in the second trimester. Overall, placental ANGPTL4 is induced by obesity and is involved in the pathophysiology of GDM via the induction of ER stress and GH2 secretion. Soluble ANGPTL4 can lead to insulin resistance in skeletal muscle cells and is an early biomarker for predicting GDM.

Knockdown of ANGPTL4 inhibits adipogenesis of preadipocyte via autophagy.

It has been demonstrated that angiopoietin-like protein 4 (ANGPTL4) plays an important regulatory role in lipid metabolism and backfat deposition appears to vary in different pig breeds. However, the correlation between ANGPTL4 and backfat deposition have not been well characterized and the role of ANGPTL4 in regulating adipogenesis remains unclear. Therefore, this study aimed to investigate correlation between ANGPTL4 and backfat deposition and to explore the effects of ANGPTL4 on preadipocyte differentiation and the underlying mechanism. Our results showed that the backfat thickness and the ANGPTL4 gene expression of Laiwu pigs were significantly higher than those in DLY pigs and the ANGPTL4 gene expression was positively correlated with backfat thickness both in DLY pigs and Laiwu pigs. Moreover, an increase in ANGPTL4 expression and activation of autophagy were observed during the differentiation of stromal vascular fraction cells. In addition, knockdown of ANGPTL4 inhibited the differentiation of 3T3-L1 cells with decreased expression of LC3-II and ATG5 and increased expression of SQSTM1, suggesting the involvement of autophagy in ANGPTL4-mediated adipogenesis. In conclusion, these results suggested that ANGPTL4 is positively correlated with backfat deposition in pigs and knockdown of ANGPTL4 inhibits adipogenesis of preadipocyte via autophagy, providing new insights into the regulation of fat deposition and to improve the carcass quality and meat quality of porcine.

1188-P: Plasma ANGPTL4 Is Higher in Women with Advanced Maternal Age and Is Associated with Metabolic Disorders during Pregnancy and the Risk of Adverse Pregnancy Outcomes

Background: Advanced maternal age (AMA) is correlated with a higher risk of metabolic disorders during pregnancy, including gestational diabetes (GDM), gestational hypertriglyceridemia (GHTG), pregnancy-induced hypertension (PIH), and preeclampsia while the pathophysiology remains unclear. Angiopoietin-like protein 4 (ANGPTL4) is a lipoprotein lipase inhibitor which participates in the pathophysiology of metabolic disorders in non-pregnant population. We explored the role of ANGPTL4 in the link between AMA and metabolic disorders during pregnancy. Method: We recruited 571 pregnant women from November 2013 to April 2018 in National Taiwan University Hospital, Taiwan. ANGPTL4 expression level in placenta and maternal plasma ANGPTL4 level were measured. The correlations among age, plasma ANGPTL4 level, metabolic disorders during pregnancy, and adverse pregnancy outcome were analyzed. Result: Compared with women aged <30 years, women aged ≥40 years had higher body mass index (BMI), fasting plasma glucose, hemoglobin A1c, insulin resistance index, plasma triglyceride, blood pressure, and plasma ANGPTL4 level in the first trimester. The expression level of ANGPTL4 were higher in the placenta of women with AMA than in the placenta of women aged <30 years. The pregnant women with the highest quartile of plasma ANGPTL4 level had more metabolic disorders during pregnancy. Besides, higher plasma ANGPTL4 was associated with a higher risk of delivering neonates with large for gestational age and the presence of adverse pregnancy outcomes. Conclusion: Plasma ANGPTL4 is higher in women with AMA and is associated with metabolic disorders during pregnancy and the risk of adverse pregnancy outcomes. Disclosure I.Yen: None. H.Li: None.

Effects of Peroxisome Proliferator-Activated Receptor γ on Modulating Angiopoietin-Like Protein 4 Synthesis in Caco-2 Cells Exposed to <i>Clostridium butyricum</i>

Angiopoietin-like protein 4 (ANGPTL4) is considered to be one of the important circulating mediators linking intestinal microorganisms and host lipid metabolism. The objective of this study was to assess the effects of peroxisome proliferator-activated receptor у (PPARγ) on modulating ANGPTL4 synthesis in Caco-2 cells exposed to Clostridium butyricum. The viability of Caco-2 cells and the expression of PPARγ and ANGPTL4 in Caco-2 cells were detected after the Caco-2 cells were co-cultured with C. butyricum at the concentration of 1 x 10^(6), 1 x 10^(7) and 1 x 10^(8) CFU/mL. The results showed that cell viability was enhanced by C. butyricum. Besides, PPARγ and ANGPTL4 expression and secretion in Caco-2 cells was significantly increased by 1 x 10^(7) and 1 x 10^(8) CFU/mL of C. butyricum. Furthermore, the effects of PPARγ on modulating ANGPTL4 synthesis in Caco-2 cells regulated by 1 x 10^(8) CFU/mL of C. butyricum was also be expounded in PPARγ activation/inhibition model based on Caco-2 cells and via ChIP technique. It was found that C. butyricum promoted the binding of PPARγ to the PPAR binding site (chr19: 8362157-8362357, located upstream of the transcriptional start site of angptl4) of the angptl4 gene in Caco-2 cells. However, the PPARγ was not the only way for C. butyricum to stimulate ANGPTL4 production. Taken together, PPARγ played a role in the regulation of ANGPTL4 synthesis by C. butyricum in Caco-2 cells.

Effects of Peroxisome Proliferator-Activated Receptor γ on Modulating Angiopoietin-Like Protein 4 Synthesis in Caco-2 Cells Exposed to Clostridium butyricum

Angiopoietin-like protein 4 (ANGPTL4) is considered to be one of the important circulating mediators linking intestinal microorganisms and host lipid metabolism. The objective of this study was to assess the effects of peroxisome proliferator-activated receptor у (PPARγ) on modulating ANGPTL4 synthesis in Caco-2 cells exposed to Clostridium butyricum. The viability of Caco-2 cells and the expression of PPARγ and ANGPTL4 in Caco-2 cells were detected after the Caco-2 cells were co-cultured with C. butyricum at the concentration of 1 x 10^(6), 1 x 10^(7) and 1 x 10^(8) CFU/mL. The results showed that cell viability was enhanced by C. butyricum. Besides, PPARγ and ANGPTL4 expression and secretion in Caco-2 cells was significantly increased by 1 x 10^(7) and 1 x 10^(8) CFU/mL of C. butyricum. Furthermore, the effects of PPARγ on modulating ANGPTL4 synthesis in Caco-2 cells regulated by 1 x 10^(8) CFU/mL of C. butyricum was also be expounded in PPARγ activation/inhibition model based on Caco-2 cells and via ChIP technique. It was found that C. butyricum promoted the binding of PPARγ to the PPAR binding site (chr19: 8362157-8362357, located upstream of the transcriptional start site of angptl4) of the angptl4 gene in Caco-2 cells. However, the PPARγ was not the only way for C. butyricum to stimulate ANGPTL4 production. Taken together, PPARγ played a role in the regulation of ANGPTL4 synthesis by C. butyricum in Caco-2 cells.

Increased expression of angiopoietin-like protein 4 regulates matrix metalloproteinase-13 expression in Porphyromonas gingivalis lipopolysaccharides-stimulated gingival fibroblasts and ligature-induced experimental periodontitis.

Angiopoietin-like protein 4 (ANGPTL4) is produced in chronic or acute inflammation. Although ANGPTL4 increases in the periodontal ligament fibroblasts during hypoxia, the involvement and role of ANGPTL4 in periodontitis have not been elucidated. In this study, we investigated whether ligature-induced experimental periodontitis and/or Porphyromonas gingivalis lipopolysaccharides (Pg-LPS) would upregulate ANGPTL4 expression and whether ANGPTL4 would somehow involve in the expression of matrix metalloproteinases (MMPs) which are key molecules in the process of periodontal tissue destruction. Experimental periodontitis was induced in 6-week-old male Sprague-Dawley rats by placing a nylon suture around the neck of the maxillary second molar. Two weeks after the induction of periodontitis, the periodontal tissue was excised and analyzed by histological/immunohistochemical staining and gene expression analyses. Human gingival fibroblasts (hGFs) were stimulated with Pg-LPS. The gene expression of ANGPTLs and receptors involved in ANGPTL4 recognition were observed. We also confirmed the changes in gene expression of MMPs upon stimulation with human ANGPTL4. Furthermore, we downregulated ANGPTL4 expression by short interfering RNA in hGFs and investigated the effect of Pg-LPS on MMP production. Induction of periodontitis significantly increased the expression of ANGPTL4 in the gingiva. Pg-LPS significantly increased the gene and protein expression of ANGPTL4 in hGFs but not the gene expression of other ANGPTLs or ANGPTL receptors. Recombinant human ANGPTL4 significantly increased MMP13 gene expression in hGFs. We also confirmed that MMP13 expression was increased in the gingiva during experimental periodontitis. Pg-LPS induced MMP13 gene expression in hGFs. These results suggest the pivotal role of ANGPTL4 in periodontitis. Periodontitis increases ANGPTL4 expression in the gingiva, further suggesting that increased ANGPTL4 may be a factor involved in enhancing MMP13 expression.

Molecular characterisation, temporal expression and involvement of ANGPTL4 in fat deposition in Muscovy ducks

ABSTRACT 1. Angiopoietin-like protein 4 (ANGPTL4) plays a key role in promoting fat metabolism and reducing blood lipid. This study characterised the ANGPTL4 gene in Muscovy ducks (Cairina moschata) and investigated its potential functions in fat metabolism in Muscovy ducks. 2. The Muscovy duck ANGPTL4 cDNA was successfully cloned for the first time, showing a length of 2591 bp. After phylogenetic analysis by RT-qPCR analysis, it was found that the ANGPTL4 gene of Anas platyrhynchos shared the highest sequence similarity with that of Muscovy ducks. 3. The ANGPTL4 gene was commonly expressed in 23 different tissues with the highest expression in the abdominal fat in Muscovy ducks. A significant association was observed between abdominal fat percentage (AFP) and the mRNA expression of the ANGPTL4 gene. Moreover, Muscovy ducks showed a peak of ANGPTL4 expression in the liver and abdominal fat at 1–2 weeks old. 4. These findings suggest that the ANGPTL4 gene is related to fat deposition and regulation in Muscovy ducks.

Dual roles of ANGPTL4 in multiple inflammatory responses in stomatitis mice.

Stomatitis is inflammation of the oral mucosa. Angiopoietin-like protein 4 (ANGPTL4) has pleiotropic functions both anti-inflammatory and pro-inflammatory properties. In the present study, we tested whether there is a correlation between increased ANGPTL4 expression and inflammation in stomatitis mice and the mechanisms involved. In this study, the oral mucosa of mice was burned with 90% phenol and intraperitoneal injection of 5-fluorouracil to establish the model of stomatitis mice. The pathological changes of stomatitis mice were observed by H&E staining of paraffin section. The expressions of cytokines and ANGPTL4 were detected by fluorescence quantitative PCR, and the protein levels of ANGPTL4 were detected by western blot. Compared with control group, the oral mucosal structure of model mice was damaged. The expression of ANGPTL4 were significantly increased concomitantly with elevated production of anti-inflammatory cytokine (peroxisome proliferator-activated receptoralpha) and pro-inflammatory cytokines [nuclear transcription factor-kappaB, interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α] in mice with stomatitis. This study suggests that ANGPTL4 may be a double-edged sword in multiple inflammatory responses in stomatitis mice.

Angiopoietin-Like Protein 4 Is Involved in Manganese Superoxide Dismutase-Mediated Suppression of Breast Cancer Cell Growth.

This study aims to understand the molecular basis of manganese superoxide dismutase (MnSOD) impacts on breast cancer cell growth. Modulation of the level of MnSOD by genetic engineering led significant changes in the expression of angiopoietin-like protein 4 (ANGPTL4) and activity of peroxisome proliferator-activated receptor α (PPARα) in MCF7 cells. PPARα agonist increased ANGPTL4 expression inhibited by MnSOD. Proliferation of MCF7 cells was inhibited by MnSOD, however, ANGPTL4 transduction into MCF7 cells with MnSOD overexpression significantly stimulated cell proliferation. MnSOD induced G0/G1 cell cycle arrest, nevertheless, ANGPTL4 transduction significantly reduced the percentage of cells in G0/G1 phase overexpressing MnSOD. In conclusion, MnSOD suppressed the expression of ANGPTL4 in breast cancer cells via the PPARα signaling pathway, and ANGPTL4 was involved in MnSOD-mediated proliferation inhibition and cell cycle arrest.

Angiopoietin-Like Protein 4 and Insulin-Like Growth Factor-1 Expression in Invasive Breast Carcinoma in Young Women.

Simple SummaryBreast cancers arising before the age of 45 years, also known as early-onset breast cancers, have a more aggressive behavior and worse prognosis than late-onset breast cancers. Therefore, there is an urgent need to identify potential therapeutic targets for this group of tumors. In the last decade, angiopoietin-like protein 4 and insulin-like growth factor-1 have attracted attention in clinical research as independent markers of the progression and prognosis of malignancies. In this study, we investigated the expression of both proteins in breast carcinoma tissue from young patients and examined whether their expression can be predicted by clinicopathological parameters.Biomarker identification is imperative for invasive breast carcinoma, which is more aggressive and associated with higher mortality and worse prognosis in younger patients (<45 years) than in older patients (>50 years). The current study aimed to investigate angiopoietin-like protein 4 (ANGPTL4) and insulin-like growth factor-1 (IGF-1) protein expression in breast tissue from young patients with breast carcinoma. Immunohistochemical staining was applied in formalin-fixed, paraffin-embedded samples of breast carcinoma tissue from young patients aged <45 years at the time of diagnosis. Both proteins were expressed in the majority of cases. The highest frequency of positive ANGPTL4 and IGF-1 expression was observed in the luminal A subtype, whereas the HER2-overexpression subtype exhibited the lowest expression frequency for both proteins. There was no significant association between ANGPTL4 (p = 0.897) and IGF-1 (p = 0.091) expression and molecular subtypes of breast carcinoma. The histological grade was a significant predictor of ANGPTL4 expression (grade 1 vs. grade 3, adjusted odds ratio = 12.39, p = 0.040). Therefore, ANGPTL-4 and IGF-1 expressions are common in young breast carcinoma tissue. There is a potential use of them as biomarkers in breast carcinoma.

The human symbiont Bacteroides thetaiotaomicron promotes diet-induced obesity by regulating host lipid metabolism.

The gut microbiome plays an important role in lipid metabolism. Consumption of a high-fat diet (HFD) alters the bacterial communities in the gut, leading to metabolic disorders. Several bacterial species have been associated with diet-induced obesity, nonalcoholic fatty liver disease, and metabolic syndrome. However, the mechanisms underlying the control of lipid metabolism by symbiotic bacteria remain elusive. Here, we show that the human symbiont Bacteroides thetaiotaomicron aggravates metabolic disorders by promoting lipid digestion and absorption. Administration of B. thetaiotaomicron to HFD-fed mice promoted weight gain, elevated fasting glucose levels, and impaired glucose tolerance. Furthermore, B. thetaiotaomicron treatment upregulated the gene expression of the fatty acid transporter and increased fatty acid accumulation in the liver. B. thetaiotaomicron inhibits expression of the gene encoding a lipoprotein lipase inhibitor, angiopoietin-like protein 4 (ANGPTL4), thereby increasing lipase activity in the small intestine. In particular, we found that B. thetaiotaomicron induced the expression of hepcidin, the master regulator of iron metabolism and an antimicrobial peptide, in the liver. Hepcidin treatment resulted in a decrease in ANGPTL4 expression in Caco-2 cells, whereas treatment with an iron chelator restored ANGPTL4 expression in hepcidin-treated cells. These results indicate that B. thetaiotaomicron-mediated regulation of iron storage in intestinal epithelial cells may contribute to increased fat deposition and impaired glucose tolerance in HFD-fed mice.

Expression of ANGPTL4 in Nucleus Pulposus Tissues Is Associated with Intervertebral Disc Degeneration.

Objective Angiopoietin-like protein 4 (ANGPTL4), encoding a glycosylated secreted protein, has been reported to be closely related to many kinds of diseases, including diabetes, tumor, and some musculoskeletal pathologies, such as rheumatoid arthritis, osteoarthritis, and osteoporosis. The aim of the current study is to investigate the role of ANGPTL4 in intervertebral disc degeneration and analyze the association of ANGPTL4 expression with Pfirrmann grades. Methods A total of 162 nucleus pulposus tissues were collected from lumbar intervertebral disc herniation patients undergoing interforaminal endoscopic surgery. Real-time quantitative PCR and western blot were performed to determine the mRNA and protein expression of ANGPTL4 in nucleus pulposus samples. Statistical analysis was performed to analyze the association of ANGPTL4 expression with Pfirrmann grades. Results Based on the clinical data of 162 patients, results showed that Pfirrmann grades were significantly associated with patients' age (r = 0.162, P = 0.047) and were not significantly associated with patients' gender (P > 0.05). RT-qPCR and western blot results showed that the mRNA (r = 0.287, P < 0.05) and protein (r = 0.356, P < 0.05) expressions of ANGPTL4 were both closely associated with Pfirrmann grades. The expression of ANGPTL4 was remarkably increased in the groups of high IVDD Pfirrmann grades. Conclusion The results demonstrated that ANGPTL4 expression was positively associated with the Pfirrmann grades and the severity of intervertebral disc degeneration. ANGPTL4 may be served as a candidate biomarker for intervertebral disc degeneration.

Nickel chloride regulates ANGPTL4 via the HIF-1α-mediated TET1 expression in lung cells

Angiopoietin-like protein 4 (ANGPTL4) is a hypoxia-induced gene, and its high expression is associated with poor prognosis and promotion of tumour progression in several cancers. Some studies reported that ANGPTL4 is affected by epigenetic regulation. Our previous results demonstrated that ANGPTL4 is highly expressed in most lung cancer cell lines than in normal cell lines and is upregulated by HIF-1α accumulation under NiCl2 exposure. The accurate role of ANGPTL4 and its methylation status caused by nickel in the lung carcinogenesis is not fully explored yet. In this study, we found that ANGPTL4 and HIF-1α in lung adenocarcinoma (LUAD) tissues were significantly upregulated compared with those in normal tissues in The Cancer Genome Atlas (TCGA) cohort (p < 0.001). The ANGPTL4 expression was statistically correlated to advanced stage (p = 0.019) and N value (p = 0.002). The Kaplan–Meier analysis revealed that ANGPTL4 and HIF-1α expression levels were independently associated with the 5-year survival of patients with LUAD in TCGA database and immunohistochemistry staining. In vitro experiments indicated that ANGPTL4 was upregulated by the demethylation agent. The methylation-specific PCR and bisulfite sequencing assessed the methylation status of the ANGPTL4 promoter, and results showed that NiCl2-treated cells had low ANGPTL4 methylation status. We further demonstrated that the DNA demethylase, TET1, was significantly increased under NiCl2 exposure. The knockdown of TET1 expression repressed the NiCl2-induced ANGPTL4. We also showed that nickel-induced TET1 was stimulated by HIF-1α. Our work established ANGPTL4 as a potential oncogene that contributes to lung cancer progression and nickel-elicited carcinogenesis.

Differential Expression of the Host Lipid Regulators ANGPTL-3 and ANGPTL-4 in HCV Infection and Treatment.

Host lipid metabolism reprogramming is essential for hepatitis C virus (HCV) infection and progression to severe liver disease. Direct-acting antivirals (DAAs) achieve a sustained virological response (SVR) in most patients, but virus eradication does not always protect against hepatocellular carcinoma (HCC). Angiopoietin-like protein-3 (ANGPTL-3) and angiopoietin-like protein-4 (ANGPTL-4) regulate the clearance of plasma lipids by inhibiting cellular lipase activity and possess emerging roles in tumourigenesis. We used ELISA and RT-qPCR to investigate ANGPTL-3 and ANGPTL-4 expression in HCV patients with characterised fibrosis throughout the natural history of hepatitis C and in long-term HCV infection in vitro, before and after DAA treatment. ANGPTL-3 was decreased in patients with advanced fibrosis compared to other disease stages, while ANGPTL-4 was progressively increased from acute infection to cirrhosis and HCC, peaking at the advanced fibrosis stage. Only ANGPTL-3 mRNA was down-regulated during early infection in vitro, although both ANGPTLs were increased later. DAA treatment did not alter ANGPTL-3 levels in advanced fibrosis/cirrhosis and in HCV infection in vitro, in contrast to ANGPTL-4. The association between ANGPTLs and fibrosis in HCV infection was underlined by an inverse correlation between the levels of ANGPTLs and serum transforming growth factor- β (TGF-β). Collectively, we demonstrate the pivotal role of advanced fibrosis in defining the expression fate of ANGPTLs in HCV infection and after treatment and propose a role for ANGPTL-3 as a contributor to post-treatment deregulation of lipid metabolism that could predispose certain individuals to HCC development.

Angiopoietin-Like Protein 4 Overexpression in Visceral Adipose Tissue from Obese Subjects with Impaired Glucose Metabolism and Relationship with Lipoprotein Lipase.

Angiopoietin-like protein 4 (ANGPTL4) regulates lipid partitioning by inhibiting circulating and tissue lipoprotein lipase (LPL); ANGPTL4 loss-of-function variants improve insulin sensitivity and reduce type 2 diabetes (T2D) risk with mechanisms partially unknown. This study was designed to explore metabolic implications of differential ANGPTL4 and LPL expression in human adipose tissue (AT). We recruited eighty-eight obese individuals, with and without abnormal glucose metabolism (AGM), undergoing bariatric surgery; visceral AT (VAT) fragments were obtained intra-operatively and analyzed by immunohistochemistry and mRNA by rt-PCR. Data on hepatic ANGPTL4 mRNA were available for 40 participants. VAT ANGPTL4 expression was higher in AGM individuals than in those with normal glucose tolerance (NGT) and associated with VAT inflammation, insulin resistance, and presence of adipocyte size heterogeneity. Increased ANGPTL4 was associated with AGM with OR = 5.1 (95% C.I.: 1.2–23; p = 0.02) and AUROC = 0.76 (95% C.I.: 1.2–23; p < 0.001). High LPL was associated with the detection of homogeneous adipocyte size, reduced microvessel density, and higher HIF-1α levels and inversely correlated to blood transaminases. In conclusion, in obese individuals, VAT ANGPTL4 levels are increased in the presence of local inflammation and AGM. Conversely, higher LPL expression describes a condition of increased lipid storage in adipocytes, which may serve as a protective mechanism against ectopic fat accumulation and related metabolic disease in obesity.

Skeletal Muscle Angiopoietin-Like Protein 4 and Glucose Metabolism in Older Adults after Exercise and Weight Loss.

Angiopoietin-like protein 4 (ANGPTL4) is an adipokine that plays an important role in energy homoeostasis and lipid and lipoprotein metabolism. This study was designed to determine the effect of an exercise plus weight loss intervention on ANGPTL4 expression and its relationship with metabolic health. Thirty-five obese sedentary men (n = 18) and postmenopausal women (n = 17), (X ± SEM, age: 61 ± 1 years, BMI: 31.3 ± 0.7 kg/m2, VO2max: 21.7 ± 0.9 L/kg/min) completed a 6 month program of 3×/week aerobic exercise and 1×/week dietary instruction to induce weight loss (AEX + WL). Participants underwent vastus lateralis muscle biopsies, a hyperinsulinemic–euglycemic clamp, oral glucose tolerance tests and body composition testing. Basal skeletal muscle ANGPTL4 mRNA was lower in men than women (p < 0.01). Peroxisome proliferator-activated receptor (PPAR) alpha (PPARα) mRNA expression was higher in men than women (p < 0.05). There were no significance changes in serum or skeletal muscle ANGPTL4 (basal or insulin-stimulated) or muscle PPARα mRNA expression after AEX + WL. Muscle mRNA ANGPTL4 is correlated with serum ANGPTL4 (r = 0.41, p < 0.05), body fat (r = 0.64, p < 0.0001), and glucose utilization (r = 0.38, p < 0.05). AEX + WL does not change basal or insulin-stimulated skeletal muscle ANGPTL4 mRNA expression, suggesting other factors contribute to improved insulin sensitivity after the loss of body fat and improved fitness.

Decreased ANGPTL4 impairs endometrial angiogenesis during peri-implantation period in patients with recurrent implantation failure.

Insufficient endometrial angiogenesis during peri‐implantation impairs endometrial receptivity (ER), which contributes to recurrent implantation failure (RIF) during in vitro fertilization and embryo transfer (IVF‐ET). Angiopoietin‐like protein 4 (ANGPTL4) acts as a multifunctional secretory protein and is involved in the regulation of lipid metabolism and angiogenesis in various tissues including the endometrium. Herein, we found decreased ANGPTL4 expression in endometrial tissue and serum during peri‐implantation period in 18 RIF‐affected women with elevated uterine arterial impedance (UAI) compared with the pregnancy controls. ANGPTL4 and peroxisome proliferator‐activated receptor gamma (PPARγ) expression were up‐regulated upon decidualization on human endometrial stromal cells (HESCs). Rosiglitazone promoted the expression of ANGPTL4 in HESCs and human umbilical vein endothelial cells (HUVECs) via PPARγ. ANGPTL4 promoted the proliferation, migration and angiogenesis of HUVECs in vitro. Our results suggest that decreased abundance of ANGPTL4 in endometrial tissues impairs the endometrial receptivity via restraining endometrial angiogenesis during decidualization; while rosiglitazone‐induced ANGPTL4 up‐regulation in hESCs and HUVECs through PPARγ. Therefore, ANGPTL4 could be a potential therapeutic approach for some RIF‐affected women with elevated UAI.

Knockdown of Angiopoietin-like protein 4 suppresses the development of colorectal cancer

Colorectal cancer, is the growth of cancer cells in the part of the colon. Angiopeptin is one of the growth factors in the human body that is particularly effective in the regulatory process. In this research, the regulatory role and its mechanism of Angiopoietin-like protein 4 (ANGPTL4) in colorectal cancer (CRC) metastasis, has been studied. Protein expression of ANGPLT4 was analyzed by immunohistochemistry in tumor samples and adjacent normal specimens of 40 patients with CRC cancer of various phases. A gene knockout test was conducted, two effective siRNA of ANGPTL4, named siRNA1 and siRNA2, were constructed and transfected into two CRC cell lines SW480 and HT-29 to block the expression of ANGPTL4. QRT-PCR and western blotting were used to validate the knockdown efficiency of the mRNA and proteins. Based on the results, the protein expression of ANGPTL4 was increased in human CRC tissues with the development of CRC. Knockdown of ANGPTL4 by siRNA in SW480 and HT-29 cells in vitro inhibited cell proliferation, promoted cell apoptosis, and suppressed the ability of cell migration and invasion. Besides, the sensitivity of CRC cells to Cisplatin was increased in the low ANGPTL4 expression group. ANGPTL4 might be a new potential therapeutic target for patients with CRC.

Induction of Free Fatty Acid‐mediated Angiopoietin‐Like Protein‐4 Gene Expression is Independent of PPARδ Activity in Skeletal Muscle Cells In Vitro

Angiopoietin‐like protein‐4 (ANGPTL4) inhibits lipoprotein lipase activity in skeletal muscle. Free fatty acids (FFAs) activate ANGPTL4 expression, yet the method by which FFAs induce ANGPTL4 in skeletal muscle is not well‐known. The purpose of this study was to examine the effect of FFAs on peroxisome proliferator‐activated receptor δ (PPARδ)‐mediated ANGPTL4 expression in C2C12 cells. Chronic exposure of mono‐ (MUFA) and poly‐unsaturated fatty acids (PUFA), but not saturated fatty acids (SFA), significantly induced ANGPTL4 mRNA expression in C2C12 cells (MUFA: 4.5±1.1, p=0.02; PUFA: 5.6±1.6, p=0.02; SFA: 0.4±0.1, p=0.4 respectively). To analyze the mechanism of FFA‐induced PPARδ activation of ANGPTL4, mRNA expression of PPARδ, which is believed to induce ANGPTL4 activity, was measured. However, there was no significant difference in PPARδ expression after FFA treatments. Next, we used the PPARδ agonist (GW0742) and antagonist (GSK0660) to modulate PPARδ activity independent of FFA treatment and examined ANGPTL4 expression. GW0742 significantly increased ANGPTL4 in undifferentiated and differentiated C2C12 cells (12.6±3.9, p=0.01 and 2.8±0.2, p&lt;0.001 respectively), while GSK0660 significantly suppressed basal ANGPTL4 expression (0.2±0.1, p=0.05 and 0.2±0.03, p&lt;0.001 respectively). Yet, in the presence of FFA and GSK0660, ANGPTL4 gene expression significantly increased despite the absence of PPARδ activity in both undifferentiated and differentiated C2C12 cells (7.1±2.5, p=0.03 and 3.8±0.4, p&lt;0.001). Taken together, these results indicate that FFAs may activate ANGPTL4 in a PPARδ independent manner, and a revised mechanism of FFA‐induced skeletal muscle ANGPTL4 expression may be warranted.

Alteration of Angiopoietin-Like Protein 4 Levels in Serum or Urine Correlate with Different Biochemical Markers in Hyperlipidemia-Related Proteinuria.

Angiopoietin-like protein 4 (ANGPTL4) is widely known as a key regulator of lipid metabolism. We investigated the relationship between ANGPTL4 expression in serum or urine and blood lipid or urine protein levels of patients with hyperlipidemia- (HL-) related proteinuria. Sixty-eight patients with HL-related proteinuria (HL-Pro group), 68 patients with HL without proteinuria (HL-NPro group), 46 patients with non-HL-related proteinuria (NHL-Pro group), and 50 healthy control (Con) subjects were selected. There were no significant differences in serum ANGPTL4 levels between the Con group (36.82 ± 17.03 ng/ml) and the HL-Pro group (27.94 (18.90, 53.72) ng/ml). Additionally, the serum ANGPTL4 levels in the HL-Pro group were significantly lower than those in the HL-NPro group (53.32 ± 24.01 ng/ml) (P < 0.001). The urine ANGPTL4/Cr levels in the HL-Pro group (52.01 (45.25, 79.79) μg/g) were significantly higher than those in the HL-NPro group (9.96 (8.35, 12.43) ng/ml) (P < 0.05). A significant alteration in urine ANGPTL4/Cr levels was observed in the NHL-Pro group (69.41 ± 55.36 μg/g) and the Con group (10.08 ± 2.38 μg/g) as well. There was no correlation between serum and urine ANGPTL4 levels of the four groups (P > 0.05). Serum ANGPTL4 levels (HL-Pro/HL-NPro group) were positively correlated with total cholesterol (TC) and triglyceride (TG) levels in hyperlipidemia patients. However, there was no correlation between urinary ANGPTL4 levels and TC or TG (P > 0.05). Urine ANGPTL4 levels were positively correlated with 24hUPro in patients with renal impairment (HL-Pro/NHL-Pro group). To summarize, ANGPTL4 may be considered an accurate predictor of proteinuria with HL. Notably, serum or urine ANGPTL4 levels indicated the degree of proteinuria or hyperlipidemia, respectively, in HL patients.