Correlation between the serum FABP4, ANGPTL3, and ANGPTL4 levels and coronary artery disease.

BACKGROUND: Lipid metabolism related factors, such as angiopoietin-like protein 3 (ANGPTL3), angiopoietin-like 4 (ANGPTL4), fatty acid-binding protein 4 (FABP4) are newly discovered factors that can affect coronary artery disease (CAD). In this study, we aimed to investigate the relationship between CAD and these lipid metabolism factors. HYPOTHESIS: ANGPTL3, ANGPTL4, and FABP4 may provide a new method for the control of CAD risk factors and the prevention and treatment of CAD. METHODS: We enrolled 284 consecutive inpatients with suspected CAD and divided them into CAD and non-CAD groups based on the coronary angiography results. Serum ANGPTL3, ANGPTL4, FABP4, and tumor necrosis factor-α (TNF-α) levels were estimated using the enzyme-linked immunosorbent assay. Multivariate logistic regression was used to assess the risk factors for CAD. The receiver operating characteristic curve was used to determine the cutoff and diagnostic values. RESULTS: The serum TNF-α, FABP4, ANGPTL3, and ANGPTL4 values showed a significant difference between the CAD and non-CAD groups (p < .05). After adjusting for confounding factors, the FABP4, ANGPTL3, and ANGPTL4 levels were independently associated with CAD (p < .05). The ANGPTL3 expression level was an independent risk factor for CAD in patients with hypertension, but not in those without hypertension. The ANGPTL3 > 67.53 ng/mL, ANGPTL4 > 29.95 ng/mL, and FABP4 > 1421.25 ng/L combination had the highest diagnostic value for CAD. CONCLUSION: ANGPTL3, ANGPTL4, and FABP4 were identified as independent risk factors for CAD and have valuable clinical implications for the diagnosis and treatment of CAD.

Angiopoietin-Related Protein 4-Transcript 3 Increases the Proliferation, Invasion, and Migration of Hepatocellular Carcinoma Cells and Inhibits Apoptosis.

To investigate the functional differences of angiopoietin-related protein 4 (ANGPTL4) transcripts in hepatocellular carcinoma (HCC) cells. By transfecting ANGPTL4-Transcript 1 and ANGPTL4-Transcript 3 overexpression vectors into HepG2 and Huh7 cell lines with ANGPTL4 knockdown, the effects of overexpression of two transcripts on cell viability, invasion, migration, and apoptosis were analyzed. The expression of two transcripts was compared in human liver cancer tissue, and their effects on tumor development were validated in vivo experiments in mice. Compared with control, the overexpression of ANGPTL4-Transcript 1 had no significant effect on viability, invasion, healing, and apoptosis of HepG2 and Huh7 cells. However, these two cell lines overexpressing ANGPTL4-Transcript 3 showed remarkably enhanced cell viability, invasive and healing ability, and decreased apoptosis ability. Furthermore, the mRNA level of ANGPTL4-Transcript 3 was significantly increased in human HCC tissues and promoted tumor growth compared with Transcript 1. Different transcripts of gene ANGPTL4 have distinct effects on HCC. The abnormally elevated Transcript 3 with the specific ability of promoting HCC proliferation, infiltration, and migration is expected to become a new biological marker and more precise intervention target for HCC.

Characterization of sexual dimorphism in ANGPTL4 levels and function.

ANGPTL4 is an attractive pharmacological target for lowering plasma triglycerides and cardiovascular risk. Since most preclinical studies on ANGPTL4 were performed in male mice, little is known about sexual dimorphism in ANGPTL4 regulation and function. Here, we aimed to study potential sexual dimorphism in ANGPTL4 mRNA and protein levels and ANGPTL4 function. Additionally, we performed exploratory studies on the function of ANGPTL4 in the liver during fasting using Angptl4-transgenic and Angptl4-/- mice. Compared to female mice, male mice showed higher hepatic and adipose ANGPTL4 mRNA and protein levels, as well as a more pronounced effect of genetic ANGPTL4 modulation on plasma lipids. By contrast, very limited sexual dimorphism in ANGPTL4 levels was observed in human liver and adipose tissue. In human and mouse adipose tissue, ANGPTL8 mRNA and/or protein levels were significantly higher in females than males. Adipose LPL protein levels were higher in female than male Angptl4-/- mice, which was abolished by ANGPTL4 (over) expression. At the human genetic level, the ANGPTL4 E40K loss-of-function variant was associated with similar plasma triglyceride reductions in women and men. Finally, ANGPTL4 ablation in fasted mice was associated with changes in hepatic gene expression consistent with PPARα activation. In conclusion, the levels of ANGPTL4 and the magnitude of the effect of ANGPTL4 on plasma lipids exhibit sexual dimorphism. Nonetheless, inactivation of ANGPTL4 should confer a similar metabolic benefit in women and men. Expression levels of ANGPTL8 in human and mouse adipose tissue are highly sexually dimorphic, showing higher levels in females than males.

Construction of an Anoikis-Related Gene Prognostic Signature and Identification of ANGPTL4 as a Key Oncogene in Lung Adenocarcinoma.

Anoikis plays an important role in cancer invasion and metastasis. However, the role of anoikis-related genes, AnRGs, in lung adenocarcinoma (LUAD) is not clear. First, anoikis-related genes (AnRGs) were obtained from the Genecard database. Second, the prognostic risk model of AnRGs was established by univariate Cox analysis, the Least Absolute Shrinkage and Selection Operator (LASSO) analysis, and multivariate Cox analysis. Finally, in vitro cell experiments were carried out to determine the expression and function of the key gene AnRGs. Three AnRGs (angiopoietin-like 4, ANGPTL4; Cyclin-Dependent Kinase Inhibitor 3, CDKN3; Solute Carrier Organic Anion Transporter Family Member 1B3, SLCO1B3) were screened for the construction of risk prediction model. Additionally, ANGPTL4 was significantly highly expressed in tumor cells, and the knockdown of ANGPTL4 expression on tumor cells could inhibit tumor cell migration and apoptosis. Constructing a risk model based on anoikis-related genes can effectively differentiate the prognosis of LUAD. ANGPTL4 can be used as a potential new target for LUAD treatment.

Effect of Deletion of ANGPTL4 Gene on Viability, Migration and Invasion Ability and Apoptosis of Hepatocellular Carcinoma Cells.

BACKGROUND: Hepatocellular carcinoma (HCC) is a malignant tumor that impacts individuals worldwide and is particularly prevalent in Asia. Angiopoietin-like protein 4 (ANGPTL4) plays an important role in regulating glucose and lipid metabolism in mouse liver. We sought to explore the effects of the ANGPTL4 gene on cell viability, migration, invasive capacity, and apoptosis of HCC cells. METHODS: The expression of ANGPTL4 in HCC and paracancerous tissues was determined by immunohistochemistry and immunofluorescence assays. The ANGPTL4 knockdown cells were established by shRNA transfection. The effect of ANGPTL4 knockdown on HepG2 and Huh7 cells was determined by Cell Count Kit-8 (CCK-8), wound healing and transwell assays. Cell apoptosis was determined by flow cytometry. RESULTS: The ANGPTL4 expression was dramatically enhanced in HCC tissues than in paracancerous tissues (p < 0.001). HCC cell lines HepG2 and Huh7 with knockdown of ANGPTL4 gene showed lower cell viability, migration, and invasion ability while inducing higher apoptosis levels than the control group (p < 0.001). CONCLUSIONS: High expression of ANGPTL4 is closely related to HCC. Knockdown of ANGPTL4 significantly inhibits the proliferation of HCC cells. This study provides a rationale for the ANGPTL4 gene, a molecular marker of HCC.

Suppression of angiopoietin-like 4 reprograms endothelial cell metabolism and inhibits angiogenesis.

Angiopoietin-like 4 (ANGPTL4) is known to regulate various cellular and systemic functions. However, its cell-specific role in endothelial cells (ECs) function and metabolic homeostasis remains to be elucidated. Here, using endothelial-specific Angptl4 knock-out mice (Angptl4iΔEC), and transcriptomics and metabolic flux analysis, we demonstrate that ANGPTL4 is required for maintaining EC metabolic function vital for vascular permeability and angiogenesis. Knockdown of ANGPTL4 in ECs promotes lipase-mediated lipoprotein lipolysis, which results in increased fatty acid (FA) uptake and oxidation. This is also paralleled by a decrease in proper glucose utilization for angiogenic activation of ECs. Mice with endothelial-specific deletion of Angptl4 showed decreased pathological neovascularization with stable vessel structures characterized by increased pericyte coverage and reduced permeability. Together, our study denotes the role of endothelial-ANGPTL4 in regulating cellular metabolism and angiogenic functions of EC.

ANGPTL4, a direct target of hsa-miR-133a-3p, accelerates lung adenocarcinoma lipid metabolism, proliferation and invasion.

BACKGROUND: Globally, lung adenocarcinoma (LUAD) is the most common type of lung cancer. The secreted protein angiopoietin-like 4 (ANGPTL4) has been implicated in a number of physiological and pathological processes, including angiogenesis and lipid metabolism. But the role of ANGPTL4 in LUAD remains unknown. METHODS: The expression of ANGPTL4 and miR-133a-3p was confirmed by public database analysis. Xenograft model, MTT, Clone formation and EdU analysis were used to confirm the effects of miR-133a-3p/ANGPTL4 on LUAD cell proliferation and growth. Wound healing and Transwell analysis were used to elucidate the role of miR-133a-3p/ANGPTL4 in LUAD cell migration and invasion. Oil red O staining was used to confirm ANGPTL4 in LUAD lipids production. Dual-luciferase reporter gene analysis was used to demonstrate miR-133a-3p could directly bind ANGPTL4 3'-UTR. WB and PCR were used to confirm the protein expression of ANGPTL4. RESULTS: ANGPTL4 was significantly increased in LUAD samples, which could promote LUAD cell proliferation, migration, invasion, growth and lipid production. miR-133a-3p could directly bind to ANGPTL4 mRNA, and repress the expression ANGPTL4, resulting in suppressing LUAD proliferation and metastasis. CONCLUSION: In conclusion, miR-133a-3p/ANGPTL4 axis might be a potential biomarker and therapeutic target for LUAD patients.

Dual role of ANGPTL4 in inflammation.

BACKGROUND: Angiopoietin-like 4 (ANGPTL4) belongs to the angiopoietin-like protein family and mediates the inhibition of lipoprotein lipase activity. Emerging evidence suggests that ANGPTL4 has pleiotropic functions with anti- and pro-inflammatory properties. METHODS: A thorough search on PubMed related to ANGPTL4 and inflammation was performed. RESULTS: Genetic inactivation of ANGPTL4 can significantly reduce the risk of developing coronary artery disease and diabetes. However, antibodies against ANGPTL4 result in several undesirable effects in mice or monkeys, such as lymphadenopathy and ascites. Based on the research progress on ANGPTL4, we systematically discussed the dual role of ANGPTL4 in inflammation and inflammatory diseases (lung injury, pancreatitis, heart diseases, gastrointestinal diseases, skin diseases, metabolism, periodontitis, and osteolytic diseases). This may be attributed to several factors, including post-translational modification, cleavage and oligomerization, and subcellular localization. CONCLUSION: Understanding the potential underlying mechanisms of ANGPTL4 in inflammation in different tissues and diseases will aid in drug discovery and treatment development.

HIF-1α regulates osteoclastogenesis and alveolar bone resorption in periodontitis via ANGPTL4.

OBJECTIVE: The mechanism of alveolar bone resorption caused by periodontitis is not fully understood. We sought to investigate whether microenvironmental changes of local hypoxia are involved in these processes. METHODS: In this study, periodontitis models of control mice and knockout of Hypoxia Induced Factor 1α (HIF-1α) harboring Cathepsin K (CTSK) Cre mice were constructed to study the effect of osteoclasts affected by hypoxic environment on alveolar bone resorption. RAW264.7 cells were subsequently induced by CoCl2 to observe the effects of HIF-1α and Angiopoietin-like Protein 4 (ANGPTL4) on osteoblast differentiation and fusion. RESULTS: The degree of alveolar bone resorption in the periodontitis tissues was lesser in mice with conditional knockout of HIF-1α in osteoclasts than in wild-type mice. We also observed that HIF-1α conditional knockout mice had fewer osteoclasts on the alveolar bone surface than control mice. HIF-1α increases the expression of ANGPTL4 and promotes the differentiation of RAW264.7 cells into osteoblasts and cell fusion under chemically simulated hypoxic conditions. CONCLUSION: HIF-1α regulates osteoclastogenesis and participates in bone resorption in periodontitis through ANGPTL4.

Transcriptomic and functional analysis of ANGPTL4 overexpression in pancreatic cancer nominates targets that reverse chemoresistance.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers based on five-year survival rates. Genes contributing to chemoresistance represent novel therapeutic targets that can improve treatment response. Increased expression of ANGPTL4 in tumors correlates with poor outcomes in pancreatic cancer. METHODS: We used statistical analysis of publicly available gene expression data (TCGA-PAAD) to test whether expression of ANGPTL4 and its downstream targets, ITGB4 and APOL1, were correlated with patient survival. We measured the impact of ANGPTL4 overexpression in a common pancreatic cancer cell line, MIA PaCa-2 cells, using CRISPRa for overexpression and DsiRNA for knockdown. We characterized global gene expression changes associated with high levels of ANGPTL4 and response to gemcitabine treatment using RNA-sequencing. Gemcitabine dose response curves were calculated on modified cell lines by measuring cell viability with CellTiter-Glo (Promega). Impacts on cell migration were measured using a time course scratch assay. RESULTS: We show that ANGPTL4 overexpression leads to in vitro resistance to gemcitabine and reduced survival times in patients. Overexpression of ANGPTL4 induces transcriptional signatures of tumor invasion and metastasis, proliferation and differentiation, and inhibition of apoptosis. Analyses revealed an overlapping signature of genes associated with both ANGPTL4 activation and gemcitabine response. Increased expression of the genes in this signature in patient PDAC tissues was significantly associated with shorter patient survival. We identified 42 genes that were both co-regulated with ANGPTL4 and were responsive to gemcitabine treatment. ITGB4 and APOL1 were among these genes. Knockdown of either of these genes in cell lines overexpressing ANGPTL4 reversed the observed gemcitabine resistance and inhibited cellular migration associated with epithelial to mesenchymal transition (EMT) and ANGPTL4 overexpression. CONCLUSIONS: These data suggest that ANGPTL4 promotes EMT and regulates the genes APOL1 and ITGB4. Importantly, we show that inhibition of both targets reverses chemoresistance and decreases migratory potential. Our findings have revealed a novel pathway regulating tumor response to treatment and suggest relevant therapeutic targets in pancreatic cancer.

Inverse effects of APOC2 and ANGPTL4 on the conformational dynamics of lid-anchoring structures in lipoprotein lipase.

The lipolytic processing of triglyceride-rich lipoproteins (TRLs) by lipoprotein lipase (LPL) is crucial for the delivery of dietary lipids to the heart, skeletal muscle, and adipose tissue. The processing of TRLs by LPL is regulated in a tissue-specific manner by a complex interplay between activators and inhibitors. Angiopoietin-like protein 4 (ANGPTL4) inhibits LPL by reducing its thermal stability and catalyzing the irreversible unfolding of LPL's α/ß-hydrolase domain. We previously mapped the ANGPTL4 binding site on LPL and defined the downstream unfolding events resulting in LPL inactivation. The binding of LPL to glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 protects against LPL unfolding. The binding site on LPL for an activating cofactor, apolipoprotein C2 (APOC2), and the mechanisms by which APOC2 activates LPL have been unclear and controversial. Using hydrogen-deuterium exchange/mass spectrometry, we now show that APOC2's C-terminal α-helix binds to regions of LPL surrounding the catalytic pocket. Remarkably, APOC2's binding site on LPL overlaps with that for ANGPTL4, but their effects on LPL conformation are distinct. In contrast to ANGPTL4, APOC2 increases the thermal stability of LPL and protects it from unfolding. Also, the regions of LPL that anchor the lid are stabilized by APOC2 but destabilized by ANGPTL4, providing a plausible explanation for why APOC2 is an activator of LPL, while ANGPTL4 is an inhibitor. Our studies provide fresh insights into the molecular mechanisms by which APOC2 binds and stabilizes LPL-and properties that we suspect are relevant to the conformational gating of LPL's active site.

Application of systemic inflammation indices and lipid metabolism-related factors in coronary artery disease.

OBJECTIVE: We aimed to investigate the relationship between coronary artery disease (CAD) and systemic inflammation indices and lipid metabolism-related factors and subsequently, discuss the clinical application of these factors in CAD. METHODS: We enrolled 284 consecutive inpatients with suspected CAD and divided them into a CAD group and a non-CAD group according to coronary angiography results. Serum levels of angiopoietin-like protein 3 (ANGPTL3), angiopoietin-like protein 4 (ANGPTL4), fatty acid-binding protein 4 (FABP4), and tumor necrosis factor-α (TNF-α) levels were assessed using the ELISA and the systemic inflammation indices were calculated. Multivariate logistic regression was used to assess the risk factors of CAD. The receiver operating characteristic curve was used to determine the cutoff and diagnostic values. RESULTS: The neutrophil-to-high density lipoprotein cholesterol ratio (5.04 vs. 3.47), neutrophil-to-lymphocyte ratio (3.25 vs. 2.45), monocyte-to-high density lipoprotein cholesterol ratio (MHR) (0.46 vs. 0.36), monocyte-to-lymphocyte ratio (0.31 vs. 0.26), systemic immune-inflammation index (SII) (696.00 vs. 544.82), serum TNF-α (398.15 ng/l vs. 350.65 ng/l), FABP4 (1644.00 ng/l vs. 1553.00 ng/l), ANGPTL3 (57.60 ng/ml vs. 52.85 ng/ml), and ANGPTL4 (37.35 ng/ml vs. 35.20 ng/ml) values showed a significant difference between the CAD and non-CAD groups ( P  < 0.05). After adjusting for confounding factors, the following values were obtained: ANGPTL3 > 67.53 ng/ml [odds ratio (OR) = 8.108, 95% confidence interval (CI) (1.022-65.620)]; ANGPTL4 > 29.95 ng/ml [OR = 5.599, 95% CI (1.809-17.334)]; MHR > 0.47 [OR = 4.872, 95% CI (1.715-13.835)]; SII > 589.12 [OR = 5.131, 95% CI (1.995-13.200)]. These factors were found to be independently associated with CAD ( P  < 0.05). Diabetes combined with MHR > 0.47, SII > 589.12, TNF-α >285.60 ng/l, ANGPTL3 > 67.53 ng/ml, and ANGPTL4 > 29.95 ng/l had the highest diagnostic value for CAD [area under the curve: 0.921, 95% CI, (0.881-0.960), Sensitivity: 88.9%, Specificity: 82.2%, P  < 0.001]. CONCLUSION: MHR > 0.47, SII > 589.12, TNF-α >285.60 ng/l, ANGPTL3 > 67.53 ng/ml, and ANGPTL4 > 29.95 ng/l were identified as independent CAD risk factors and have valuable clinical implications in the diagnosis and treatment of CAD.

STAT2-induced linc02231 promotes tumorigenesis and angiogenesis through modulation of hnRNPA1/ANGPTL4 in colorectal cancer.

BACKGROUND: Long non-coding RNAs (lncRNAs) play a critical role in regulating various human diseases including cancer. In colorectal cancer (CRC), there are still some undervalued lncRNAs with potential functions and mechanisms that need to be clarified. The present study aimed to investigate the role of linc02231 in the progression of CRC. METHODS: The proliferation of CRC cells was evaluated using Cell Counting Kit-8, colony formation, and 5-ethynyl-2'-deoxyuridine (EdU) assays. Cell migration was examined through wound healing and Transwell analyses. The impact of linc02231 on angiogenesis was determined through a tube formation assay. Western blotting was used to detect the expression of specific proteins. A mouse xenograft model is established to observe the effect of linc02231 on the in vivo growth of CRC cells. Target genes of linc02231 are screened using high-throughput sequencing. The transcriptional activity of STAT2 on linc02231 and the binding activity between linc02231/miR-939-5p/hnRNPA1 were analyzed by a luciferase assay. RESULTS: Based on public databases and comprehensive bioinformatics analysis, we found that lncRNA linc02231 was upregulated in CRC tumor tissues, which is consistent with our clinical results. linc02231 promoted the proliferation and migration of CRC cells in vitro and their tumorigenicity in vivo. Furthermore, linc02231 promotes the angiogenic ability of human umbilical vein endothelial cells. Mechanistically, the transcription factor STAT2 binds to the promoter region of linc02231 and activates its transcription. linc02231 also competes with miR-939-5p for binding to the pro-oncogenic target gene hnRNPA1, preventing its degradation. hnRNPA1 prevents the maturation of angiopoietin-like protein 4 (ANGPTL4) messenger RNA, leading to impaired tumor angiogenesis and increased metastasis of CRC. CONCLUSIONS: The expression of linc02231, which is induced by STAT2, has been found to enhance the proliferation, metastasis, and angiogenesis of CRC by binding to miR-939-5p and increasing the expression of hnNRPA1 at the same time as suppressing ANGPTL4. These findings suggest that linc02231 could serve as a potential biomarker and therapeutic target for CRC.

Linoleic acid-induced ANGPTL4 inhibits C2C12 skeletal muscle differentiation by suppressing Wnt/ß-catenin.

Skeletal muscle differentiation is an essential process in embryonic development as well as regeneration and repair throughout the lifespan. It is well-known that dietary fat intake impacts biological and physiological function in skeletal muscle, however, understanding of the contribution of nutritional factors in skeletal muscle differentiation is limited. Therefore, the objective of the current study was to evaluate the effects of free fatty acids (FFAs) on skeletal muscle differentiation in vitro. We used C2C12 murine myoblasts and treated them with various FFAs, which revealed a unique response of angiopoietin-like protein-4 (ANGPTL4) with linoleic acid (LA) treatment that was associated with reduced differentiation. LA significantly inhibited myotube formation and lowered the protein expression of myogenic regulatory factors, including MyoD and MyoG and increased Pax7 during cell differentiation. Next, recombinant ANGPTL4 protein or siRNA knockdown of ANGPTL4 was employed to examine its role in skeletal muscle differentiation, and we confirmed that ANGPTL4 knockdown at day two and six of differentiation restored myotube formation in the presence of LA. RNA-sequencing analysis revealed that ANGPTL4-mediated inhibition of skeletal muscle differentiation at day two as well as LA at day two or -6 led to a reduction in Wnt/ß-catenin signaling pathways. We confirmed that LA reduced Wnt11 and Axin2 while increasing expression of the Wnt inhibitor, Dkk2. ANGPTL4 knockdown increased ß-catenin protein in the nucleus in response to LA and increased Axin2 and Wnt11 expression. Taken together, these results demonstrate that LA induced ANGPTL4 inhibits C2C12 differentiation by suppressing Wnt/ß-catenin signaling.

ANGPTL4 inhibits granulosa cell proliferation in polycystic ovary syndrome by EGFR/JAK1/STAT3-mediated induction of p21.

Polycystic ovary syndrome (PCOS) is one of the most common, heterogenous endocrine disorders and is the leading cause of ovulatory obstacle associated with abnormal folliculogenesis. Dysfunction of ovarian granulosa cells (GCs) is recognized as a major factor that underlies abnormal follicle maturation. Angiopoietin-like 4 (ANGPTL4) expression in GCs differs between patients with and without PCOS. However, the role and mechanism of ANGPTL4 in impaired follicular development are still poorly understood. Here, the case-control study was designed to investigate the predictive value of ANGPTL4 in PCOS while cell experiments in vitro were set for mechanism research. Results found that ANGPTL4 levels in serum and in follicular fluid, and its expression in GCs, were upregulated in patients with PCOS. In KGN and SVOG cells, upregulation of ANGPTL4 inhibited the proliferation of GCs by blocking G1/S cell cycle progression, as well as the molecular activation of the EGFR/JAK1/STAT3 cascade. Moreover, the STAT3-dependent CDKN1A(p21) promoter increased CDKN1A transcription, resulting in remarkable suppression effect on GCs. Together, our results demonstrated that overexpression of ANGPTL4 inhibited the proliferation of GCs through EGFR/JAK1/STAT3-mediated induction of p21, thus providing a novel epigenetic mechanism for the pathogenesis of PCOS.

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

BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: Periodontitis increases ANGPTL4 expression in the gingiva, further suggesting that increased ANGPTL4 may be a factor involved in enhancing MMP13 expression.

ANGPTL4 promotes nephrotic syndrome by downregulating podocyte expression of ACTN4 and podocin.

BACKGROUND: lipopolysaccharide (LPS) can induce nephrotic syndrome-like features such as massive proteinuria, hyperlipidemia, and fusion of glomerular podocytes with foot processes (FPs) in mice. Angiopoietin-like protein 4 (ANGPTL4) neutralized the negative charge of glomerular basement membrane charge and aggravated renal injury. The mechanism of ANGPTL4 aggravating podocyte injury has not been well clarified. In this study, we aimed to investigate the potential role of ANGPTL4 on podocyte FPs fusion and podocyte signal molecules. METHODS: We built angptl4 gene knocked out in C57BL6 mice using CRISPR/Cas9 technique. Nephrotic model was built by LPS in wild type and angptl4-/- mice. Expression of ACTN4, podocin and TRPC6 in the glomerulus were determined by immunohistochemistry. RESULTS: In physical condition, the wild type and angptl4-/- mice showed no significant differences in biochemical indicators and kidney pathology. But in nephrotic condition, compared with wild type mice hyperlipidemia and proteinuria with the angptl4-/- mice was significantly relieved. Moreover, the degree of FPs fusion was notably improved in the nephrotic mice knocked out angptl4 gene. Expression of ACTN4 and podocin decreased drastically in the glomerulus of wild-type nephrotic mice. Different from wild-type, the ACTN4 and podocin expression showed slight weakening in angptl4-/- nephrotic mice. As transient receptor potential cation channel subfamily member, TRPC6 expression had no visible change in glomerulus of each group. CONCLUSIONS: ANGPTL4 induces hyperlipidemia and podocyte injury in nephrotic mice, thereby promoting the formation of proteinuria. Its molecular mechanism may be related to ANGPTL4 down-regulating actin cytoskeletal regulatory signals ACTN4 and podocin.

ANGPTL4 functions as an oncogene through regulation of the ETV5/CDH5/AKT/MMP9 axis to promote angiogenesis in ovarian cancer.

BACKGROUND: Angiopoietin-like 4 (ANGPTL4) is highly expressed in a variety of neoplasms and promotes cancer progression. Nevertheless, the mechanism of ANGPTL4 in ovarian cancer (OC) metastasis remains unclear. This study aimeds to explore whether ANGPTL4 regulates OC progression and elucidate the underlying mechanism. METHODS: ANGPTL4 expression in clinical patient tumor samples was determined by immunohistochemistry (IHC) and high-throughput sequencing. ANGPTL4 knockdown (KD) and the addition of exogeneous cANGPTL4 protein were used to investigate its function. An in vivo xenograft tumor experiment was performed by intraperitoneal injection of SKOV3 cells transfected with short hairpin RNAs (shRNAs) targeting ANGPTL4 in nude mice. Western blotting and qRT-PCR were used to detect the levels of ANGPTL4, CDH5, p-AKT, AKT, ETV5, MMP2 and MMP9 in SKOV3 and HO8910 cells transfected with sh-ANGPTL4 or shRNAs targeting ETV5. RESULTS: Increased levels of ANGPTL4 were associated with poor prognosis and metastasis in OC and induced the angiogenesis and metastasis of OC cells both in vivo and in vitro. This tumorigenic effect was dependent on CDH5, and the expression levels of ANGPTL4 and CDH5 in human OC werepositively correlated. In addition, CDH5 activated p-AKT, and upregulated the expression of MMP2 and MMP9. We also found that the expression of ETV5 was upregulated by ANGPTL4, which could bind the promoter region of CDH5, leading to increased CDH5 expression. CONCLUSION: Our data indicated that an increase in the ANGPTL4 level results in increased ETV5 expression in OC, leading to metastasis via activation of the CDH5/AKT/MMP9 signaling pathway.

Exosomal protein angiopoietin-like 4 mediated radioresistance of lung cancer by inhibiting ferroptosis under hypoxic microenvironment.

BACKGROUND: Hypoxia-mediated radioresistance is a major reason for the adverse radiotherapy outcome of non-small cell lung cancer (NSCLC) in clinical, but the underlying molecular mechanisms are still obscure. METHODS: Cellular and exosomal ANGPTL4 proteins under different oxygen status were examined. Colony survival, lipid peroxidation and hallmark proteins were employed to determine the correlation between ferroptosis and radioresistance. Gene regulations, western blot and xenograft models were used to explore the underlying mechanisms of the role of ANGPTL4 in radioresistance. RESULTS: ANGPTL4 had a much higher level in hypoxic NSCLC cells compared to normoxic cells. Up- or down- regulation of ANGPTL4 positively interrelated to the radioresistance of NSCLC cells and xenograft tumours. GPX4-elicited ferroptosis suppression and lipid peroxidation decrease were authenticated to be involved in the hypoxia-induced radioresistance. ANGPTL4 encapsulated in the exosomes from hypoxic cells was absorbed by neighbouring normoxic cells, resulting in radioresistance of these bystander cells in a GPX4-dependent manner, which was diminished when ANGPTL4 was downregulated in the donor exosomes. CONCLUSION: Hypoxia-induced ANGPTL4 rendered radioresistance of NSCLC through at least two parallel pathways of intracellular ANGPTL4 and exosomal ANGPTL4, suggesting that ANGPTL4 might applicable as a therapeutic target to improve the therapeutic efficacy of NSCLC.

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

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.