Angiopoietin-like 4 Levels Research Articles

Angiopoietin-like 4 is a potential biomarker for diabetic kidney disease in type 2 diabetes patients.

The association between serum angiopoietin-like 4 (ANGPTL4) levels and the severity of diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus remains unclear. A total of 1,115 type 2 diabetes mellitus patients were analyzed in this cross-sectional study. DKD index included DKD stages defined by estimated glomerular filtration rate, the albuminuria grades and DKD risk management grades. Serum levels of ANGPTL4 and other biomarkers were detected. Multivariable-adjusted linear and logistic analyses were used to study the association between ANGPTL4 and DKD. The protein levels of ANGPTL4 were assessed in the kidney. Renal tubular cells were stimulated with glucose to study ANGPTL4 expression. Compared with the participants in the third or fourth quantile of ANGPTL4, those in the first or second quantile of ANGPTL4 were younger, with lower glycated hemoglobin, triglycerides and urinary albumin creatinine ratio (all P < 0.05). There was a negative nonlinear relationship between ANGPTL4 and estimated glomerular filtration rate in type 2 diabetes mellitus patients. One standard deviation increased serum ANGPTL4 levels, the odds ratio of having DKD was 1.40 (95% confidence interval 1.08-1.80). The mediation analysis showed that triglycerides did not mediate the association between ANGPTL4 and DKD. Furthermore, ANGPTL4 could be the strongest among multiple panels of biomarkers in its association of DKD. Compared with mice at 8 weeks-of-age, db/db mice at 18 weeks-of-age had increased ANGPTL4 expression in glomeruli and tubular segments. In vitro, glucose could stimulate ANGPTL4 expression in tubular cells in a dose-dependent manner. ANGPTL4 could be a potential marker and therapeutic target for DKD treatment.

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

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. ANGPTL3, ANGPTL4, and FABP4 may provide a new method for the control of CAD risk factors and the prevention and treatment of CAD. 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. 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. ANGPTL3, ANGPTL4, and FABP4 were identified as independent risk factors for CAD and have valuable clinical implications for the diagnosis and treatment of CAD.

Deficiency of angiopoietin-like 4 enhances CD8+ T cell bioactivity via metabolic reprogramming for impairing tumour progression.

Angiopoietin-like 4 (ANGPTL4) is a secreted metabolism-modulating glycoprotein involved in the progression of tumours, cardiovascular diseases, metabolic syndrome and infectious diseases. In this study, more CD8+ T cells were activated to be effector T cells in ANGPTL4-/- mice. Impaired growth of tumours implanted in 3LL, B16BL6 or MC38 cells and reduced metastasis by B16F10 cells were observed in ANGPTL4-/- mice. Bone marrow (BM) transplantation experiments displayed that deficiency of ANGPTL4 in either host or BM cells promoted CD8+ T cell activation. However, ANGPTL4 deficiency in CD8+ T cells themselves showed more efficient anti-tumour activities. Recombinant ANGPTL4 protein promoted tumour growth in vivo with the less CD8+ T cell infiltration and it directly downregulated CD8+ T cell activation ex vivo. Transcriptome sequencing and metabolism analysis identified that ANGPTL4-/- CD8+ T cells increased glycolysis and decreased oxidative phosphorylation, which was dependent on the PKCζ-LKB1-AMPK-mTOR signalling axis. Reverse correlation of elevated ANGPTL4 levels in sera and tumour tissues with activated CD8+ T cells in the peripheral blood was displayed in patients with colorectal cancer. These results demonstrated that ANGPTL4 decreased immune surveillance in tumour progression by playing an immune-modulatory role on CD8+ T cells via metabolic reprogramming. Efficient blockade of ANGPTL4 expression in tumour patients would generate an effective anti-tumour effect mediated by CD8+ T cells.

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.

Angiopoietin-like 4 knockdown attenuates cigarette smoke extract-induced oxidative stress and apoptosis in lung bronchial epithelial cells by inhibiting NADPH oxidase.

It has been found that angiopoietin-like 4 (ANGPTL4) expression is increased in the serum of patients with chronic obstructive pulmonary disease (COPD). Herein, cigarette smoke extract (CSE) was used to stimulate oxidative stress in bronchial epithelial cells BEAS-2B, and the role and potential mechanism of ANGPTL4 in smoking-induced lung dysfunction were explored. The roles of different concentrations of CSE (0, 1, 2.5, 5, or 10%) in cell viability and ANGPTL4 levels were evaluated. Following ANGPTL4 being knocked down, the effects of ANGPTL4 knockdown on oxidative stress and apoptosis were determined. Moreover, the level of NADPH oxidase 2 (NOX2) was upregulated to assess the mediated role of NOX in the regulation of ANGPTL4, along with JNK/p38 MAPK signaling. CSE treatment elevated the level of ANGPTL4, and ANGPTL4 knockdown reduced CSE-induced oxidative stress, apoptosis, and NOX level in BEAS-2B cells. The greatest degree of alteration was found in NOX2, and additional NOX2 overexpression broke the inhibitory influences of ANGPTL4 knockdown on oxidative stress and apoptosis. Otherwise, ANGPTL4 knockdown hindered the activation of JNK/p38 MAPK signaling, whereas NOX2 overexpression activated this signaling pathway. Together, ANGPTL4 knockdown attenuated CSE-induced oxidative stress, apoptosis, and activation of JNK/MAPK signaling by inhibiting NOX.

Abstract P3010: Angptl4 Reduces Atherosclerosis And Promotes Fibrous Cap Stability By Targeting Klf4 In Vascular Smooth Muscle Cells

Background: Atherosclerosis is vascular disease of chronic inflammation, and we recently showed that angiopoietin-like 4 (ANGPTL4) promote cardiac repair by suppressing pathological inflammation. Given the contribution of inflammation to atherosclerosis, we assessed the effect of ANGPTL4 on atherosclerosis development. Methods: We injected recombinant ANGPTL4 protein or PBS to atherosclerotic Apoe-/- mice twice a week fed a high-fat diet for 8 weeks, and analyzed atherosclerotic lesion size, inflammation, and plaque stability. The effect of ANGPTL4 on vascular smooth muscle cells (VSMCs) was studied, and plasma levels of ANGPTL4 in patients were measured. Results: ANGPTL4 treatment reduced the atherosclerotic plaque size and vascular inflammation. In the atherosclerotic lesions, the number of α-SMA(+)MYH11(+) cells was higher, while the number of CD68(+)cells was lower in the ANGPTL4 group than in the vehicle-treated group. Moreover, α-SMA-expressing fibrous cap was significantly thicker in the ANGPTL4 group than in the PBS group. Then, we isolated VSMCs from atherosclerotic aortas, and found that CD68 and Krüppel-like factor 4 (KLF4) were significantly upregulated in the PBS group. As KLF4 is a phenotypic modulator and an inducer of NADP oxidase 1 (Nox1) in VSMCs, the effect of ANGPTL4 on VSMCs was assessed. Cholesterol-induced upregulations of Nox1 and KLF4 were substantially inhibited by ANGPTL4 treatment. Then, we analyzed the circulating ANGPTL4 levels of the cardiovascular disease patients, and found the positive correlation between high ANGPTL4 and low incidence of vascular events. Conclusions: Our results showed that ANGPTL4 inhibited atherogenesis by increasing the fibrous cap thickness. KLF4 and Nox1 were suggested as targets of ANGPTL4 in VSMCs to confer plaque stability by attenuating phenotypic changes of VSMCs toward inflammatory macrophage-like cells. Taken together, circulating ANGPTL4 may be associated with regulation of vascular events.

ANGPTL4 silencing via antisense oligonucleotides reduces plasma triglycerides and glucose in mice without causing lymphadenopathy

Angiopoietin-like 4 (ANGPTL4) is an important regulator of plasma triglyceride (TG) levels and an attractive pharmacological target for lowering plasma lipids and reducing cardiovascular risk. Here, we aimed to study the efficacy and safety of silencing ANGPTL4 in the livers of mice using hepatocyte-targeting GalNAc-conjugated antisense oligonucleotides (ASOs). Compared with injections with negative control ASO, four injections of two different doses of ANGPTL4 ASO over 2 weeks markedly downregulated ANGPTL4 levels in liver and adipose tissue, which was associated with significantly higher adipose LPL activity and lower plasma TGs in fed and fasted mice, as well as lower plasma glucose levels in fed mice. In separate experiments, injection of two different doses of ANGPTL4 ASO over 20 weeks of high-fat feeding reduced hepatic and adipose ANGPTL4 levels but did not trigger mesenteric lymphadenopathy, an acute phase response, chylous ascites, or any other pathological phenotypes. Compared with mice injected with negative control ASO, mice injected with ANGPTL4 ASO showed reduced food intake, reduced weight gain, and improved glucose tolerance. In addition, they exhibited lower plasma TGs, total cholesterol, LDL-C, glucose, serum amyloid A, and liver TG levels. By contrast, no significant difference in plasma alanine aminotransferase activity was observed. Overall, these data suggest that ASOs targeting ANGPTL4 effectively reduce plasma TG levels in mice without raising major safety concerns.

Increased angiopoietin-like 4 expression ameliorates inflammatory bowel diseases via suppressing CD8+ T cell activities

Angiopoietin-like 4 (ANGPTL4) is involved in inflammation-associated diseases, such as rheumatoid arthritis, type 2 diabetes, atherosclerosis, and chronic obstructive pulmonary disease. The role of ANGPTL4 in the pathogenesis of inflammatory bowel disease (IBD) remains unknown. Here, the plasma ANGPTL4 levels peaked on days 3 and 5, and expression of ANGPTL4 of inflamed colons peaked on days 5 and 7 in mice with dextran sulfate sodium (DSS)-induced colitis. Simultaneously, CD8+T cells in the inflamed colons peaked at day 5 but declined at day 7. However, the ANGPTL4−/− mice treated with DSS exhibited exacerbated colitis with more CD8+T cells and macrophages infiltrating the colons. The exogenous ANGPTL4 protein protected the mice against DSS-induced colitis with less CD8+T cell and macrophage recruitment in the colons. In addition, recombinant ANGPTL4 directly downregulated the IFN-γ and NKG2D expression of CD8+T cells but had no effects on the CD86 expression and TNF-α secretion of macrophages ex vivo. Adding ANGPTL4 protein into ANGPTL4−/− mice almost blocked the onset of DSS-induced colitis. In parallel, the plasma ANGPTL4 levels were elevated in patients with Crohn's disease and ulcerative colitis at mild/moderate stage and restored to normal levels in IBD patients at a severe stage. The higher ANGPTL4 expression in the inflamed colons of patients with IBD was correlated with lower CD8+ cell infiltration, whereas no associations with macrophages. Our results demonstrated the compensatory protective effect of ANGPTL4 on IBD development at least via the downregulation of CD8+T cell activities. Adding the ANGPTL4 protein would have beneficial effects to retard the progression of IBD.

The Regulation of Circulating Hepatokines by Fructose Ingestion in Humans.

ContextFibroblast growth factor 21 (FGF21), follistatin, angiopoietin-like 4 (ANGPTL4), and growth differential factor 15 (GDF15) are regulated by energy metabolism. Recent findings in humans demonstrate that fructose ingestion increases circulating FGF21, with increased response in conditions of insulin resistance.ObjectiveThis study examines the acute effect of fructose and somatostatin on circulating FGF21, follistatin, ANGPTL4, and GDF15 in humans.MethodsPlasma FGF21, follistatin, ANGPTL4, and GDF15 concentrations were measured in response to oral ingestion of 75 g of fructose in 10 young healthy males with and without a 15-minute infusion of somatostatin to block insulin secretion. A control infusion of somatostatin was also performed in the same subjects.ResultsFollowing fructose ingestion, plasma FGF21 peaked at 3.7-fold higher than basal concentration (P < 0.05), and it increased 4.9-fold compared with basal concentration (P < 0.05) when somatostatin was infused. Plasma follistatin increased 1.8-fold after fructose ingestion (P < 0.05), but this increase was blunted by concomitant somatostatin infusion. For plasma ANGPTL4 and GDF15, no increases were obtained following fructose ingestion. Infusion of somatostatin alone slightly increased plasma FGF21 and follistatin.ConclusionHere we show that in humans (1) the fructose-induced increase in plasma FGF21 was enhanced when somatostatin was infused, suggesting an inhibitory role of insulin on the fructose-induced FGF21 increase; (2) fructose ingestion also increased plasma follistatin, but somatostatin infusion blunted the increase; and (3) fructose ingestion had no stimulating effect on ANGPTL4 and GDF15 levels, demonstrating differences in the hepatokine response to fructose ingestion.

Relationship between serum angiopoietin-like 4 levels and recurrence of atrial fibrillation.

ObjectiveTo investigate the association between serum angiopoietin-like 4 (ANGPTL4) levels and recurrence of atrial fibrillation (AF) after catheter ablation.MethodsThis retrospective study recruited patients with AF undergoing catheter ablation and they were divided into two groups (new-onset AF group and recurrent AF group). Demographic, clinical, and laboratory parameters were collected.ResultsA total of 192 patients with AF were included, including 69 patients with recurrence of AF. Serum ANGPTL4 levels were lower in patients with recurrent AF than in those with new-onset AF. Serum ANGPTL4 levels were positively correlated with superoxide dismutase and peroxisome proliferator-activated receptor γ, and negatively correlated with the CHA2DS2-VASC score, left atrial diameter, and levels of brain natriuretic peptide, malondialdehyde, high-sensitivity C-reactive protein, and interleukin-6. The receiver operating characteristic curve showed that the best cut-off for recurrent AF was serum ANGPTL4 levels < 19.735 ng/mL, with a sensitivity and specificity of 63.9% and 74.5%, respectively. Serum ANGPTL4 levels were significantly associated with recurrence and new onset of AF (odds ratio, 2.241; 95% confidence interval, 1.081–4.648).ConclusionsSerum ANGPTL4 levels are lower in patients with recurrent AF than in those with new-onset AF, and are associated with cardiac hypertrophy, oxidative stress, and inflammation.

Prognostic Value of Angiopoietin-like 4 in Patients with Acute Respiratory Distress Syndrome.

Angiopoietin-like 4 (ANGPTL4) is a secreted glycoprotein that plays an important role in endothelial injury and the inflammatory response. Experimental models have implicated ANGPTL4 in acute respiratory distress syndrome (ARDS), but its impact on the progression of ARDS is unclear. Paired bronchoalveolar lavage fluid (BALF) and serum samples were obtained from patients with ARDS (n = 56) within 24 h of diagnosis and from control subjects (n = 32). ANGPTL4, angiopoietin-2, interleukin (IL)-6, and TNF-α levels were measured by magnetic Luminex assay. BALF albumin (BA) and serum albumin (SA) were evaluated by enzyme-linked immunosorbent assay. BALF and serum ANGPTL4 concentrations were higher in patients with ARDS than in controls and were even higher in non-survivors than in survivors. The serum ANGPTL4 level was higher in indirect (extrapulmonary) ARDS than in direct (pulmonary) ARDS. Furthermore, BALF and serum ANGPTL4 levels correlated well with angiopoietin-2, IL-6, and TNF-α levels in BALF and serum. BALF ANGPTL4 was positively correlated with the BA/SA ratio (an indicator of pulmonary vascular permeability), and serum ANGPTL4 was associated with the severity of multiple organ dysfunction syndrome based on SOFA and APACHE II scores. Moreover, serum ANGPTL4 was better able to predict 28-day ARDS-related mortality (AUC 0.746, P < 0.01) than the APACHE II score or PaO2/FiO2 ratio. Serum ANGPTL4 was identified as an independent risk factor for mortality in a univariate Cox regression model (P < 0.001). ANGPTL4 levels were elevated in patients with ARDS and significantly correlated with disease severity and mortality. ANGPTL4 may be a novel prognostic biomarker in ARDS.

ANGPTL4 exacerbates pancreatitis by augmenting acinar cell injury through upregulation of C5a

Pancreatitis is the inflammation of the pancreas. However, little is known about the genes associated with pancreatitis severity. Our microarray analysis of pancreatic tissues from mild and severe acute pancreatitis mice models identified angiopoietin‐like 4 (ANGPTL4) as one of the most significantly upregulated genes. Clinically, ANGPTL4 expression was also increased in the serum and pancreatic tissues of pancreatitis patients. The deficiency in ANGPTL4 in mice, either by gene deletion or neutralizing antibody, mitigated pancreatitis‐associated pathological outcomes. Conversely, exogenous ANGPTL4 exacerbated pancreatic injury with elevated cytokine levels and apoptotic cell death. High ANGPTL4 enhanced macrophage activation and infiltration into the pancreas, which increased complement component 5a (C5a) level through PI3K/AKT signaling. The activation of the C5a receptor led to hypercytokinemia that accelerated acinar cell damage and furthered pancreatitis. Indeed, C5a neutralizing antibody decreased inflammatory response in LPS‐activated macrophages and alleviated pancreatitis severity. In agreement, there was a significant positive correlation between C5a and ANGPTL4 levels in pancreatitis patients. Taken together, our study suggests that targeting ANGPTL4 is a potential strategy for the treatment of pancreatitis.

Association between ANGPTL-4 and the proinflammatory process in cancer cachexia patients.

BackgroundContradictory results are reported for the role of angiopoietin-like 4 (ANGPTL-4) in the development of cancer-cachexia and inflammation, given its importance in angiogenesis and inflammatory signaling. Our aim was to analyze the levels of ANGPTL-4 in colorectal cancer patients with a stable weight and those with cachexia in order to establish a relationship between ANGPTL-4 and the inflammatory process.ResultsPlasma and tumor levels of ANGPTL-4 were higher in CC in comparison to other groups. A positive association was verified between plasmatic ANGPTL-4 and NFκB levels in tumor from CC. In WSC, we identified an association between the plasmatic ANGPTL-4, IL-15, and IL-10 in tumor and IL-15 in MES. Increased levels of NFκB and TNF-R1 in MES were detected in CC in comparison to WSC. Specifically in CC-group, a positive correlation was found between ANGPTL-4 levels and those of IL-1β, TNF-α, and NFκB in tumor, along with an association between ANGPTL-4 levels with IL-1β and MCP-1 levels in tumor; and ANGPTL-4 and IL-1β levels in MES.MethodsWe studied 102 patients, who were divided into three groups: control patients (C, n=37), cancer patients with a stable weight (WSC, n=23), and cancer-cachexia patients (CC, n=42). Samples of plasma, tumor, mesenteric (MES) and subcutaneous adipose tissue were removed for the determination of ANGPTL-4 levels and other proinflammatory factors.ConclusionsANGPTL-4 levels were higher in plasma and tumor of CC-group, and positively associated with pro-inflammatory and pro-tumorigenic factors. Our results suggest an opposite effect of ANGPTL-4 depending on the concentration and presence of cachexia.

High Expression of Angiopoietin-like Protein 4 in Advanced Colorectal Cancer and its Association with Regulatory T Cells and M2 Macrophages.

Colorectal cancer (CRC) is one of the most aggressive tumours in the human digestive system. Most CRC patients have poor prognosis due to metastasis and recurrence. Angiopoietin-like 4 (ANGPTL4) is involved in tumour development. Regulatory T (Treg) cells and M2 macrophages promote tumour growth and metastasis. Herein, we explored the changes of ANGPTL4 expression in CRC patients at different stages and observed whether in situ tumour-Treg and -M2 macrophages are correlated with ANGPTL4 expression. Serum ANGPTL4 (sANGPTL4) levels of 70 CRC patients and 10 healthy controls were detected by ELISA. ANGPTL4, Foxp3 and CD163 expression levels in CRC tissues were measured by immunohistochemistry. Recombinant ANGPTL4 (rANGPTL4) proteins were further added into cell-culture systems for induction of Treg cells and M2 macrophages. The results showed both sANGPTL4 and in situ tumour-ANGPTL4 expression levels increased in Dukes C-D stage CRC patients. Foxp3+ and CD163+ cells in tumour tissue sections were also more intensive in Dukes C-D stage patients than in Dukes A-B stage patients. Foxp3+ and CD163+ cells in tumour tissues were positively correlated with both tissue and sANGPTL4 expression (P < 0.01). Recombinant ANGPTL4 promoted the induction of murine Treg cells and M2 macrophages ex vivo. Therefore, elevated ANGPTL4 expression could be a marker for advanced CRC. Treg cell and M2 macrophage induction could be one of the mechanisms of tumour promotion mediated by ANGPTL4.

Angiopoietin like-4 as a novel vascular mediator in capillary cerebral amyloid angiopathy.

Increasing evidence suggests that vascular dysfunction in the brain is associated with early stages of Alzheimer's disease. Amyloid-β deposition in the microvasculature of the brain, a process referred to as capillary cerebral amyloid angiopathy (capillary CAA), propagates vascular remodelling, which results in impaired function of the blood-brain barrier, reduced cerebral perfusion and increased hypoxia. While improving vascular function may be an attractive new way to fight capillary CAA, the underlying factors that mediate vascular alterations in Alzheimer's disease and capillary CAA pathogenesis remain largely unknown. Here we provide first evidence that angiopoietin like-4 (ANGPTL4), a hypoxia-induced factor, is highly expressed by reactive astrocytes in well characterized post-mortem tissues of patients with capillary CAA. Our in vitro studies reveal that ANGPTL4 is upregulated and secreted by human cortical astrocytes under hypoxic conditions and in turn stimulates endothelial cell migration and sprouting in a 3D spheroid model of human brain endothelial cells. Interestingly, plasma levels of ANGPTL4 are significantly increased in patients with vascular dementia compared to patients with subjective memory complaints. Overall, our data suggest that ANGPTL4 contributes to pathological vascular remodelling in capillary CAA and that detection of ANGPTL4 levels may improve current diagnostics. Ways of counteracting the detrimental effects of ANGPTL4 and thus promoting cerebral vascular function may provide novel treatment regimens to halt the progression of Alzheimer's disease.

Regulation of angiopoietin-like 4 and lipoprotein lipase in human adipose tissue

Elevated plasma triglycerides are increasingly viewed as a causal risk factor for coronary artery disease. One protein that raises plasma triglyceride levels and that has emerged as a modulator of coronary artery disease risk is angiopoietin-like 4 (ANGPTL4). ANGPTL4 raises plasma triglyceride levels by inhibiting lipoprotein lipase (LPL), the enzyme that catalyzes the hydrolysis of circulating triglycerides on the capillary endothelium. The objective of the present study was to assess the association between ANGPTL4 and LPL in human adipose tissue, and to examine the influence of nutritional status on ANGPTL4 expression. We determined ANGPTL4 and LPL mRNA and protein levels in different adipose tissue depots in a large number of severely obese patients who underwent bariatric surgery. Furthermore, in 72 abdominally obese subjects, we measured ANGPTL4 and LPL mRNA levels in subcutaneous adipose tissue in the fasted and postprandial state. ANGPTL4 mRNA levels were highest in subcutaneous adipose tissue, whereas LPL mRNA levels were highest in mesenteric adipose tissue. ANGPTL4 and LPL mRNA levels were strongly positively correlated in the omental and subcutaneous adipose tissue depots. In contrast, ANGPTL4 and LPL protein levels were negatively correlated in subcutaneous adipose tissue, suggesting a suppressive effect of ANGPTL4 on LPL protein abundance in subcutaneous adipose tissue. ANGPTL4 mRNA levels were 38% higher in the fasted compared to the postprandial state. Our data provide valuable insights into the relationship between ANGPTL4 and LPL in human adipose tissue, as well as the physiological function and regulation of ANGPTL4 in humans.

Short-term cooling increases serum angiopoietin-like 4 levels in healthy lean men

Cold exposure enhances sympathetic outflow to peripheral tissues, thereby stimulating intracellular lipolysis in white adipose tissue and increasing the lipoprotein lipase-dependent uptake and combustion of triglyceride-derived fatty acids (FAs) by brown adipose tissue. Angiopoietin-like 4 (ANGPTL4) inhibits lipoprotein lipase and can be regulated by cold exposure, at least in mice. In the present study, we examined the effect of short-term mild cooling on serum ANGPTL4 levels in healthy lean men of White Caucasian and South Asian descent. Healthy, lean White Caucasian (n=12) and South Asian (n=12) men were exposed to an individualized cooling protocol for 2hours. Serum ANGPTL4 levels were measured before and after cooling, and its relation with previously measured parameters (ie, free fatty acid [FFA] levels, body fat percentage, and resting energy expenditure) was determined. Short-term cooling increased ANGPTL4 levels (+17%, P<.001). Thermoneutral ANGPTL4 levels positively correlated with FFA levels (R2=0.250, P<.05) and body fat percentage (R2=0.338, P<.05). Furthermore, ANGPTL4 negatively correlated with resting energy expenditure (R2=0.235, P<.05). The relative increase in ANGPTL4 levels was higher in White Caucasians compared with South Asians (25±4 vs 9±4%, P<.05). Short-term cooling increases ANGPTL4 levels in healthy lean men. We anticipate that FFA liberated from white adipose tissue during cooling increases ANGPTL4 to limit uptake of triglyceride-derived FA by this tissue.

Hypoxia-induced ANGPTL4 sustains tumour growth and anoikis resistance through different mechanisms in scirrhous gastric cancer cell lines

Patients with scirrhous gastric cancer (SGC) frequently develop peritoneal dissemination, which leads to poor prognosis. The secreted protein angiopoietin-like-4 (ANGPTL4), which is induced by hypoxia, exerts diverse effects on cancer progression. Here, we aimed to determine the biological function of ANGPTL4 in SGC cells under hypoxia. ANGPTL4 levels were higher in SGC cells under hypoxia than in other types of gastric cancer cells. Hypoxia-induced ANGPTL4 mRNA expression was regulated by hypoxia-inducible factor-1α (HIF-1α). Under hypoxic conditions, monolayer cultures of ANGPTL4 knockdown (KD) 58As9 SGC (58As9-KD) cells were arrested in the G1 phase of the cell cycle through downregulation of c-Myc and upregulation of p27, in contrast to control 58As9-SC cells. Moreover, the ability of 58As9-KD xenografts to form tumours in nude mice was strongly suppressed. When 58As9-KD cells were cultured in suspension, hypoxia strongly increased their susceptibility to anoikis through suppression of the FAK/Src/PI3K-Akt/ERK pro-survival pathway, followed by activation of the apoptotic factors caspases-3, -8 and -9. The development of peritoneal dissemination by 58As9-KD cells was completely inhibited compared with that by 58As9-SC cells. In conclusion, ANGPTL4 is uniquely induced by hypoxia in cultured SGC cells and is essential for tumour growth and resistance to anoikis through different mechanisms.

Serum level of ANGPTL4 as a potential biomarker in renal cell carcinoma

ObjectivesThis study aimed to determine the serum levels of angiopoietin-like 4 (ANGPTL4) in patients with renal cell carcinoma (RCC) and explore its potential as a biomarker. Materials and methodsBlood samples were taken from 110 patients with RCC, 66 healthy controls, and patients with other solid tumors. Serum ANGPTL4 levels were measured using the enzyme-linked immunosorbent assay, and their correlation with clinical characteristics was further analyzed. Received operating characteristic (ROC) curves, Kaplan-Meier curves, and log-rank analyses were used to evaluate diagnostic and prognostic significance. ResultsSerum ANGPTL4 levels were significantly higher in patients with RCC compared with healthy controls and patients with other types of cancers (P<0.0001) and associated with sex, Fuhrman grades, metastasis states, and tumor node metastasis stages (P<0.05), but not with age, tumor size, and histological types (P>0.05). The ROCs/area under the ROC curve analysis indicated an area under the ROC curve of 0.844 (sensitivity = 0.691; specificity = 0.939) and 0.725 (sensitivity = 0.909; specificity = 0.568), respectively, to distinguish patients with RCC from healthy controls and those with metastasis from those without metastasis. The survival analysis revealed that patients with low serum ANGPTL4 had longer progression-free survival compared with those with high serum ANGPTL4 (P = 0.033). ConclusionThe present study suggested that the elevated serum ANGPTL4 level might be a novel diagnostic and prognostic biomarker for patients with RCC.

Aqueous Angiopoietin-Like 4 Levels Correlate With Nonperfusion Area and Macular Edema in Branch Retinal Vein Occlusion.

To investigate whether macular edema (ME) due to branch retinal vein occlusion (BRVO) associates with retinal overexpression of angiopoietin-like 4 (ANGPTL4). The aqueous ANGPTL4 and vascular endothelial growth factor (VEGF) levels in patients with ME due to BRVO were measured, and the relationships between ANGPTL4 levels and the degree of retinal ischemia and edema were determined. The study and control groups consisted of all consecutive patients who were scheduled to undergo intravitreal bevacizumab injection for treatment-naïve BRVO with ME and senile cataract surgery, respectively. The study group was divided into the major BRVO and macular BRVO subgroups on the basis of the involved retinal area. The aqueous ANGPTL4 and VEGF levels were measured by enzyme-linked immunosorbent assay. In the patients with BRVO, capillary nonperfusion area by fluorescein angiography and central subfield macular thickness (CSMT) and total macular volume (TMV) by spectral-domain optical coherence tomography were determined. Patients with ME due to BRVO (50 eyes) had higher aqueous ANGPTL4 and VEGF levels than the controls (61 eyes) (both P < 0.001). The major BRVO had higher ANGPTL4 and VEGF levels than the macular BRVO (both P < 0.001). The aqueous ANGPTL4 levels of all BRVO patients correlated positively with nonperfusion area (r = 0.901, P < 0.001), CSMT (r = 0.574, P < 0.001), and TMV (r = 0.453, P = 0.001), even after adjustment for VEGF levels. The aqueous ANGPTL4 levels correlated significantly with phenotypes of BRVO with ME. This suggests that ANGPTL4 may be a candidate biomarker and treatment target in ischemia-induced retinopathies, including BRVO.