Angiopoietin-like proteins 3, 4 and 8: regulating lipid metabolism and providing new hope for metabolic syndrome

Whole genome sequencing of mouse lines divergently selected for fatness (FLI) and leanness (FHI) revealed several genetic variants as candidates for novel obesity genes

BACKGROUND

Analysing genomes of animal model organisms is widely used for understanding the genetic basis of complex traits and diseases, such as obesity, for which only a few mouse models exist, however, without their lean counterparts.

OBJECTIVE

To analyse genetic differences in the unique mouse models of polygenic obesity (Fat line) and leanness (Lean line) originating from the same base population and established by divergent selection over more than 60 generations.

METHODS

Genetic variability was analysed using WGS. Variants were identified with GATK and annotated with Ensembl VEP. g.Profiler, WebGestalt, and KEGG were used for GO and pathway enrichment analysis. miRNA seed regions were obtained with miRPathDB 2.0, LncRRIsearch was used to predict targets of identified lncRNAs, and genes influencing adipose tissue amount were searched using the IMPC database.

RESULTS

WGS analysis revealed 6.3 million SNPs, 1.3 million were new. Thousands of potentially impactful SNPs were identified, including within 24 genes related to adipose tissue amount. SNP density was highest in pseudogenes and regulatory RNAs. The Lean line carries SNP rs248726381 in the seed region of mmu-miR-3086-3p, which may affect fatty acid metabolism. KEGG analysis showed deleterious missense variants in immune response and diabetes genes, with food perception pathways being most enriched. Gene prioritisation considering SNP GERP scores, variant consequences, and allele comparison with other mouse lines identified seven novel obesity candidate genes: 4930441H08Rik, Aff3, Fam237b, Gm36633, Pced1a, Tecrl, and Zfp536.

CONCLUSION

WGS revealed many genetic differences between the lines that accumulated over the selection period, including variants with potential negative impacts on gene function. Given the increasing availability of mouse strains and genetic polymorphism catalogues, the study is a valuable resource for researchers to study obesity.

Silencing ANGPTL8 reduces mouse preadipocyte differentiation and insulin signaling

ANGPTL8, expressed mainly in the liver and adipose tissue, regulates the activity of lipoprotein lipase (LPL) present in the extracellular space and triglyceride (TG) metabolism through its interaction with ANGPTL3 and ANGPTL4. Whether intracellular ANGPTL8 can also exert effects in tissues where it is expressed is uncertain. ANGPTL8 expression was low in preadipocytes and much increased during differentiation. To better understand the role of intracellular ANGPTL8 in adipocytes and assess whether it may play a role in adipocyte differentiation, we knocked down its expression in normal mouse subcutaneous preadipocytes. ANGPTL8 knockdown reduced adipocyte differentiation, cellular TG accumulation and also isoproterenol-stimulated lipolysis at day 7 of differentiation. RNA-Seq analysis of ANGPTL8 siRNA or control siRNA transfected SC preadipocytes on days 0, 2, 4 and 7 of differentiation showed that ANGPTL8 knockdown impeded the early (day 2) expression of adipogenic and insulin signaling genes, PPARγ, as well as genes related to extracellular matrix and NF-κB signaling. Insulin mediated Akt phosphorylation was reduced at an early stage during adipocyte differentiation. This study based on normal primary cells shows that ANGPTL8 has intracellular actions in addition to effects in the extracellular space, like modulating LPL activity. Preadipocyte ANGPTL8 expression modulates their differentiation possibly via changes in insulin signaling gene expression.

Elevated angiopoietin-like protein 3 serum levels in diabetic nephropathy patients and its association with renal function and lipid profile

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a highly prevalent disease that has life-threatening consequences like micro and macrovascular complication. Diabetic nephropathy (DN) is one of the common consequences of T2DM which is related to secretory factors like hepatokines. Angiopoietin-Like Protein 3 (ANGPTL3) is a hepatokine that is perturbated in cardiometabolic diseases and experimental studies showed its effect on renal functions and lipid metabolism. For the first time, ANGPTL3 was measured in patients with T2DM and DN in the present study.

METHODS

Serum levels of ANGPTL3, IL-6, and TNF-α were measured in 60 healthy control, 60 T2DM patients, and 61 DN patients.

RESULTS

Serum levels of ANGPTL3 increased in T2DM (252.39 ± 66.01) and DN (284.59 ± 69.27) patients compared to controls (160.22 ± 48.96), and DN patients compared with T2DM patients. Urinary albumin excretion (UAE) was higher in the DN group compared to T2DM and control groups. Moreover, serum levels of IL-6 and TNF-α were elevated in both patient groups compared to controls. Moreover, ANGPTL3 represented a positive correlation with triglycerides, creatinine, and UAE in patients with both T2DM and DN groups and showed an inverse correlation with eGFR in patients with DN. Moreover, this hepatokine had a good potential to differentiate patients from controls, especially, DN patients.

CONCLUSIONS

these findings provide invivo evidence for the relation of ANGPTL3 with renal dysfunction and hypertriglyceridemia in patients with DN which is in line with experimental findings and suggested a potential role for this hepatokine in DN pathogenesis.

Increased Levels of ANGPTL3 and CTRP9 in Patients With Obstructive Sleep Apnea and Their Relation to Insulin Resistance and Lipid Metabolism and Markers of Endothelial Dysfunction

OBJECTIVE

Obstructive sleep apnea (OSA) has a close relation with obesity and perturbation in adipokines and hepatokines, which are linked to OSA consequences such as insulin resistance, dyslipidemia, and endothelial dysfunction. This study aimed to assess the relation of C1q/TNF-related protein 9 (CTRP9) and angiopoietin-like protein 3 (ANGPTL3) with OSA and biochemical measurements.

METHODS

Serum levels of ANGPTL3, CTRP9, adiponectin, leptin, intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion protein 1 (VCAM-1) were determined in 74 OSA patients and 27 controls using enzyme-linked immunosorbent assay kits.

RESULTS

Levels of ANGPTL3, CTRP9, leptin, ICAM-1, and VCAM-1 were increased in the patients compared to the controls, whereas adiponectin levels decreased. ANGPTL3 had a positive correlation with total cholesterol, triglyceride, low-density lipoprotein cholesterol, ICAM-1, and VCAM-1 and was inversely correlated with leptin. CTRP9 showed a positive correlation with body mass index, insulin resistance, ICAM-1, and VCAM-1.

CONCLUSION

The results indicated the relation of ANGLTP3 and CTRP9 with OSA and its complications, which suggested a possible role for these factors in the consequences of OSA.

Angiopoietin-like 3-derivative LNA043 for cartilage regeneration in osteoarthritis: a randomized phase 1 trial

Osteoarthritis (OA) is a common, debilitating, chronic disease with no disease-modifying drug approved to date. We discovered LNA043-a derivative of angiopoietin-like 3 (ANGPTL3)-as a potent chondrogenesis inducer using a phenotypic screen with human mesenchymal stem cells. We show that LNA043 promotes chondrogenesis and cartilage matrix synthesis in vitro and regenerates hyaline articular cartilage in preclinical OA and cartilage injury models in vivo. LNA043 exerts at least part of these effects through binding to the fibronectin receptor, integrin α5β1 on mesenchymal stem cells and chondrocytes. In a first-in-human (phase 1), randomized, double-blinded, placebo-controlled, single ascending dose, single-center trial ( NCT02491281 ; sponsored by Novartis Pharmaceuticals), 28 patients with knee OA were injected intra-articularly with LNA043 or placebo (3:1 ratio) either 2 h, 7 d or 21 d before total knee replacement. LNA043 met its primary safety endpoint and showed short serum pharmacokinetics, cartilage penetration and a lack of immunogenicity (secondary endpoints). Post-hoc transcriptomics profiling of cartilage revealed that a single LNA043 injection reverses the OA transcriptome signature over at least 21 d, inducing the expression of hyaline cartilage matrix components and anabolic signaling pathways, while suppressing mediators of OA progression. LNA043 is a novel disease-modifying OA drug candidate that is currently in a phase 2b trial ( NCT04864392 ) in patients with knee OA.

Genetic Factors for Coronary Heart Disease and Their Mechanisms: A Meta-Analysis and Comprehensive Review of Common Variants from Genome-Wide Association Studies

Genome-wide association studies (GWAS) have discovered 163 loci related to coronary heart disease (CHD). Most GWAS have emphasized pathways related to single-nucleotide polymorphisms (SNPs) that reached genome-wide significance in their reports, while identification of CHD pathways based on the combination of all published GWAS involving various ethnicities has yet to be performed. We conducted a systematic search for articles with comprehensive GWAS data in the GWAS Catalog and PubMed, followed by a meta-analysis of the top recurring SNPs from ≥2 different articles using random or fixed-effect models according to Cochran Q and I² statistics, and pathway enrichment analysis. Meta-analyses showed significance for 265 of 309 recurring SNPs. Enrichment analysis returned 107 significant pathways, including lipoprotein and lipid metabolisms (rs7412, rs6511720, rs11591147, rs1412444, rs11172113, rs11057830, rs4299376), atherogenesis (rs7500448, rs6504218, rs3918226, rs7623687), shared cardiovascular pathways (rs72689147, rs1800449, rs7568458), diabetes-related pathways (rs200787930, rs12146487, rs6129767), hepatitis C virus infection/hepatocellular carcinoma (rs73045269/rs8108632, rs56062135, rs188378669, rs4845625, rs11838776), and miR-29b-3p pathways (rs116843064, rs11617955, rs146092501, rs11838776, rs73045269/rs8108632). In this meta-analysis, the identification of various genetic factors and their associated pathways associated with CHD denotes the complexity of the disease. This provides an opportunity for the future development of novel CHD genetic risk scores relevant to personalized and precision medicine.

Angiopoietin-like 3 (ANGPTL3) drives cell proliferation, migration and angiogenesis in cervical cancer via binding to integrin alpha v beta 3

Angiopoietin-like 3 (ANGPTL3) has been uncovered to play an oncogenic role in several kinds of human malignancies. Nevertheless, whether ANGPTL3 functions in cervical cancer (CC) has not yet been reported. This paper is intended to explore the impact of ANGPTL3 on CC cells and elucidate the potential mechanism. In this study, quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were performed to analyze the ANGPTL3 expression. Western blot was also performed to examine integrin αvβ3 protein level. Cell proliferation was evaluated by MTT assay, EdU staining and Western blot analysis. In addition, the migratory and invasive abilities of cells were, respectively, estimated by wound healing and transwell assays. Tube formation assay was performed to determine endothelial cell angiogenesis. Levels of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (VEGFR2) were measured by ELISA. As a result, ANGPTL3 expression was significantly higher in CC cells relative to that in normal cervical cells. Silencing of ANGPTL3 suppressed cell proliferation, migration and invasion. Besides, downregulation of ANGPTL3 inhibited human umbilical vein endothelial cell (HUVEC) angiogenesis and repressed protein level of integrin alpha v beta 3 (αvβ3). Upregulation of αvβ3 offsets the inhibitory effect of ANGPTL3 on proliferation, migration and invasion in CC cells. Upregulated expression of αvβ3 promoted blood vessel formation and secretions of VEGF and VEGFR2. In conclusion, ANGPTL3 silencing may serve as a tumor suppressor in CC through integrin αvβ3, which provides a potentially novel therapeutic target for patients with CC.

Positive correlation of serum angiopoietin-like protein 3 levels with metabolic syndrome in patients with coronary artery disease

Objectives:

Angiopoietin-like protein 3 (ANGPTL3) regulates triglyceride metabolism by reversibly inhibiting the lipoprotein lipase activity. Metabolic syndrome (MetS) is an independent risk factor for further cardiovascular disease. This study evaluated the relationship between the fasting serum ANGPTL3 levels and MetS in patients with coronary artery disease (CAD).

Materials and Methods:

Fasting blood samples were obtained from 90 patients with CAD. Serum ANGPTL3 levels were measured using a commercial enzyme-linked immunosorbent assay kit. MetS and its components were defined using the diagnostic criteria of the International Diabetes Federation.

Results:

Fifty-three patients (58.9%) had MetS. The hypertension (P = 0.001), diabetes (P < 0.001), body weight (P = 0.027), body mass index (P = 0.001), waist circumference (P < 0.001), systolic blood pressure (P = 0.001), fasting glucose (P < 0.001), triglycerides (P < 0.001), blood urea nitrogen (P = 0.044), C-reactive protein (P = 0.010), insulin (P = 0.040), homeostasis model assessment of insulin resistance (P = 0.002), and ANGPTL3 level (P = 0.001) of CAD patients who had MetS were higher, and the high-density lipoprotein cholesterol (P = 0.001) and estimated glomerular filtration rate (P = 0.016) were lower. A binary logistic regression analysis of the significant variables also revealed that the ANGPTL3 level (odds ratio: 1.023, 95% confidence interval: 1.008–1.038, P = 0.002) was an independent predictor of MetS in patients with CAD.

Conclusion:

The results of our study indicated that the fasting ANGPTL3 level was positively associated with MetS among patients with CAD.

Impact of oral lipid and glucose tolerance tests on the postprandial concentrations of angiopoietin-like proteins (Angptl) 3 and 4

Background

The postprandial regulation of angiopoietin-like proteins (Angptls) and their expression in adipocytes is poorly characterized.

Objective

Circulating Angptl3 and 4 were analyzed in healthy individuals undergoing either an oral lipid tolerance test (OLTT; n = 98) or an oral glucose tolerance test (OGTT; n = 99). Venous blood was drawn after 0, 2, 4, and 6 h during OLTT and after 0, 1, and 2 h during OGTT. Anthropometric and laboratory parameters were assessed and concentrations of Angptls were quantified by enzyme-linked immunosorbent assay. Angptl gene expression in 3T3-L1 adipocytes and in murine adipose tissues and cellular fractions was analyzed by quantitative real-time PCR.

Results

Angptl3 concentrations significantly decreased while Angptl4 levels continuously increased during OLTT. Both proteins remained unaffected during OGTT. Angptl3 and Angptl4 were expressed in murine subcutaneous and visceral AT with higher mRNA levels in mature adipocytes when compared to the stroma-vascular cell fraction. Both proteins were strongly induced during 3T3-L1 adipocyte differentiation and they were unresponsive to glucose in mature fat cells. Adipocyte Angptl3 (but not Angptl4) mRNA expression was inhibited by the polyunsaturated fatty acids arachidonic acid and docosahexaenoic acid, whereas nine types of dietary fatty acids remained without any effect.

Conclusions

There is evidence of short-time regulation of Angptl3/4 levels upon metabolic stress. Angptl4 expression is high and Angptl3 expression is low in AT and restricted mainly to mature adipocytes without any differences concerning fat compartments. Whereas dietary fatty acids and glucose are without any effect, omega-3/-6-polyunsaturated fatty acids inhibited Anptl3 expression in adipocytes.

Human Angiopoietin-like Protein 3/ANGPTL3 Antibodies: Adding to the Armamentarium in the Management of Dyslipidemia

ABSTRACT

Cardiovascular (CV) disease remains the leading cause of death in the United States. In addition to lifestyle modifications, current guidelines primarily focus on lowering low-density lipoprotein cholesterol (LDL-C) to reduce atherosclerotic CV disease risk. However, despite aggressive management, a degree of residual risk remains, suggesting that focusing on lowering LDL-C alone may be inadequate and that other lipid parameters may need to be targeted. In patients who remain at high risk despite current pharmacologic options either because of inadequate response, elevated levels of other lipoproteins, or those who have genetic variants predisposing them to atherosclerotic CV disease, additional treatment strategies continue to be sought. One such group is the homozygous familial hypercholesterolemia population, especially those patients carrying the null low-density lipoprotein receptor mutation as they often fail to derive the same benefit from traditional LDL-C lower strategies such as statins and proprotein convertase subtilisin/kexin type 9 inhibitors that work by upregulating the LDL receptor. Emerging data also suggest that patients with increased levels of triglyceride-rich lipoproteins are also at increased risk as elevated levels are proposed to have a role in various pathways promoting atherogenesis. Angiopoietin-life protein 3 (ANGLTPL3) has recently become a target of interest because of the discovery that inhibiting its action leads to reductions in lipid parameters. Although the mechanism of action of ANGLTPL3 inhibitors is independent of the LDL receptor, their ability to significantly lower triglycerides and LDL-C make them an attractive option particularly in patients with homozygous familial hypercholesterolemia and hypertriglyceridemia. The efficacy and safety of 2 ANGLTPL3 inhibitor agents have been evaluated in clinical trials. In this review, the lipid lowering, metabolic effects, and safety are reported. Ongoing trials assessing CV outcomes as well as long-term safety data are still needed to provide a more definitive role for these agents in the overall management in these populations.

ANGPTL8 in metabolic homeostasis: more friend than foe?

ANGPTL8 is an important cytokine, which is significantly increased in type 2 diabetes mellitus (T2DM), obesity and metabolic syndrome. Many studies have shown that ANGPTL8 can be used as a bio-marker of these metabolic disorders related diseases, and the baseline ANGPTL8 level has also been found to be positively correlated with retinopathy and all-cause mortality in patients with T2DM. This may be related to the inhibition of lipoprotein lipase activity and the reduction of circulating triglyceride (TG) clearance by ANGPTL8. Consistently, inhibition of ANGPTL8 seems to prevent or improve atherosclerosis. However, it is puzzling that ANGPTL8 seems to have a directing function for TG uptake in peripheral tissues; that is, ANGPTL8 specifically enhances the reserve and buffering function of white adipose tissue, which may alleviate the ectopic lipid accumulation to a certain extent. Furthermore, ANGPTL8 can improve insulin sensitivity and inhibit hepatic glucose production. These contradictory results lead to different opinions on the role of ANGPTL8 in metabolic disorders. In this paper, the correlation between ANGPTL8 and metabolic diseases, the regulation of ANGPTL8 and the physiological role of ANGPTL8 in the process of glucose and lipid metabolism were summarized, and the physiological/pathological significance of ANGPTL8 in the process of metabolic disorder was discussed.

ANGPTL3 and ANGPTL8 in Thai subjects with hyperalphalipoproteinemia and severe hypertriglyceridemia

BACKGROUND

The role of ANGPTL3 and ANGPTL8 in lipid regulation in patients with very high levels of HDL-cholesterol and triglyceride is unknown.

OBJECTIVE

We examined plasma levels of ANGPTL3 and ANGPTL8 in subjects with hyperalphalipoproteinemia (HALP) and in those with severe hypertriglyceridemia (HTG).

METHODS

Plasma ANGPTL3 and ANGPTL8 levels were measured by ELISA in 320 subjects, consisting of HALP subjects with HDL-cholesterol ≥100 mg/dl (n=90) and healthy controls (n=90) and subjects with triglyceride ≥886 mg/dl (n=89) and control subjects (n=51).

RESULTS

The mean plasma ANGPTL3 level was significantly higher in the HALP group compared to that of the controls (297 ± 112 ng/mL vs. 230 ± 100 ng/mL, p<0.001). Similarly, the mean plasma ANGPTL8 level was also higher in the HALP group (30 ± 11 ng/mL vs. 20 ± 8 ng/mL, p<0.001). Both ANGPTL3 and ANGPTL8 levels positively correlated with HDL-cholesterol levels. In the severe HTG group, plasma ANGPTL3 level was significantly higher than those in the control group (223 ± 105 ng/mL vs. 151 ± 60 ng/mL, p<0.001), but not ANGPTL8 (23 ± 20 ng/mL vs. 31 ± 23 ng/mL in controls, p=0.028). Only ANGPTL3, but not ANGPTL8, levels positively correlated with triglyceride levels.

CONCLUSION

Plasma level of ANGPTL3 was increased in both HALP and severe HTG whereas an increase in plasma level of ANGPTL8 was found only in HALP, and not in severe HTG, suggesting that both ANGPTL3 and ANGPTL8 might play distinct roles in lipid regulation on these two extremes of dyslipidemia.

An Immune-Gene-Based Classifier Predicts Prognosis in Patients With Cervical Squamous Cell Carcinoma

Objective: Immunity plays a vital role in the human papilloma virus (HPV) persistent infection, and closely associates with occurrence and development of cervical squamous cell carcinoma (CSCC). Herein, we performed an integrated bioinformatics analysis to establish an immune-gene signature and immune-associated nomogram for predicting prognosis of CSCC patients. Methods: The list of immunity-associated genes was retrieved from ImmPort database. The gene and clinical information of CSCC patients were obtained from The Cancer Genome Atlas (TCGA) website. The immune gene signature for predicting overall survival (OS) of CSCC patients was constructed using the univariate Cox-regression analysis, random survival forests, and multivariate Cox-regression analysis. This signature was externally validated in GSE44001 cohort from Gene Expression Omnibus (GEO). Then, based on the established signature and the TCGA cohort with the corresponding clinical information, a nomogram was constructed and evaluated via Cox regression analysis, concordance index (C-index), receiver operating characteristic (ROC) curves, calibration plots and decision curve analyses (DCAs). Results: A 5-immune-gene prognostic signature for CSCC was established. Low expression of ICOS, ISG20 and high expression of ANGPTL4, SBDS, LTBR were risk factors for CSCC prognosis indicating poor OS. Based on this signature, the OS was significantly worse in high-risk group than in low-risk group (p-value < 0.001), the area under curves (AUCs) for 1-, 3-, 5-years OS were, respectively, 0.784, 0.727, and 0.715. A nomogram incorporating the risk score of signature and the clinical stage was constructed. The C-index of this nomogram was 0.76. AUC values were 0.811, 0.717, and 0.712 for 1-, 3-, 5-years OS. The nomogram showed good calibration and gained more net benefits than the 5-immune-gene signature and the clinical stage. Conclusion: The 5-immune-gene signature may serve as a novel, independent predictor for prognosis in patients with CSCC. The nomogram incorporating the signature risk score and clinical stage improved the predictive performance than the signature and clinical stage alone for predicting 1-year OS.

Circulating ANGPTL8 levels and risk of kidney function decline: Results from the 4C Study

Background

ANGPTL8, an important regulator of lipid metabolism, was recently proven to have additional intracellular and receptor-mediated functions. This study aimed to investigate circulating levels of ANGPTL8 and its potential association with the risk of kidney function decline in a cohort study.

Methods

We analysed 2,311 participants aged 40 years old and older from the China Cardiometabolic Disease and Cancer Cohort (4C) Study. Kidney function decline was defined as an estimated glomerular filtration rate (eGFR) less than 60 mL per minute per 1.73 m² of body surface area, a decrease in eGFR of ≥ 30% from baseline, chronic kidney disease (CKD)-related hospitalization or death, or end-stage renal disease. The association between baseline ANGPTL8 levels and kidney function decline was assessed using multivariable-adjusted Cox proportional hazards models, and inverse possibility of treatment weight (IPTW) was utilized to prevent overfitting.

Results

There were 136 (5.9%) cases of kidney function decline over a median of 3.8 years of follow-up. We found that serum ANGPTL8 levels at baseline were elevated in individuals with kidney function decline compared to those without kidney function decline during follow-up (718.42 ± 378.17 vs. 522.04 ± 283.07 pg/mL, p < 0.001). Compared with the first quartile, multivariable-adjusted hazard ratio (95% confidence intervals [CIs]) for kidney function decline was 2.59 (95% CI, 1.41–4.77) for the fourth ANGPTL8 quartile. Furthermore, compared with patients in the first ANGPTL8 quartile, those in the fourth ANGPTL8 quartile were more likely to report a higher stage of CKD (relative risk: 1.33; 95% CI, 1.01–1.74). The conclusions of the regression analyses were not altered in the IPTW models. Multivariable-adjusted restricted cubic spline analyses suggested a linear relationship of ANGPTL8 with kidney function decline (p for nonlinear trend = 0.66, p for linear trend < 0.001).

Conclusions

Participants with higher circulating ANGPTL8 levels were at increased risk for kidney function decline, highlighting the importance of future studies addressing the pathophysiological role of ANGPTL8 in CKD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01317-3.

The Clinical Role of Angiopoietin-Like Protein 3 in Evaluating Coronary Artery Disease in Patients with Obstructive Sleep Apnea

Purpose

Hyperlipidemia is the most important early atherosclerosis and coronary artery disease (CAD) indicator. Angiopoietin-like proteins (ANGPTLs) 3, 4, and 8 are lipid dysfunction markers that may be linked to CAD. We investigated whether these circulating ANGPTLs are associated with CAD in patients with obstructive sleep apnea (OSA).

Methods

A total of 327 individuals participated in this study: 221 patients with OSA and CAD, 50 patients with OSA alone, and 56 controls. The Gensini Score was used to assess the severity of CAD. Serum ANGPTL3, ANGPTL4, and ANGPTL8 were measured in all subjects using Human Magnetic Luminex Screening Assay. The independent association between levels of ANGPTLs and CAD was evaluated by multivariate regression analysis.

Results

Serum ANGPTL3 levels were significantly higher in patients suffering from OSA and CAD compared with patients having OSA alone (46.97 ± 13.89 vs 38.25 ± 15.94 ng/ml, P < 0.001). Univariate analysis demonstrated that ANGPTL3 was a risk factor for CAD (OR = 1.72/10 ng ANGPTL3, 95% CI, 1.29–2.28, P < 0.001). In addition, multivariate analysis revealed that ANGPTL3 was independently associated with the presence of CAD (OR = 1.74/10 ng ANGPTL3, 95% CI, 1.29–2.35, P < 0.001) even after adjusting for cofounding factors. Furthermore, circulating ANGPTL3 levels were positively associated with triglyceride (r = 0.16, P = 0.01) and total cholesterol (r = 0.14, P = 0.02) levels, while ANGPTL3 levels had no significant correlation with the severity of CAD. No significant associations were found between the levels of ANGPTL4 and ANGPTL8 and CAD even after adjusting for established risk factors.

Conclusion

Elevated levels of ANGPTL3 were independently associated with a higher likelihood of CAD in patients with OSA. It may be a novel biomarker for OSA patients at high risk of developing cardiovascular diseases.

Angiopoietin-like protein 8, molecular cloning and regulating lipid accumulation in goat intramuscular preadipocytes

This study aimed to clone the full-length open reading frame (ORF) of goat ANGPTL8 gene sequence, reveal its molecular and expression characteristics, and explore its effect on the differentiation of goat intramuscular preadipocytes. The full-length ORF sequence of goat ANGPTL8 gene was cloned by RT-PCR technology, and bioinformatics analysis was performed by related biological software. RT-qPCR was used to detect the expression of ANGPTL8 mRNA in goat tissues. Further use of RNA interference to study the effect of ANGPTL8 on the differentiation of goat intramuscular preadipocytes. The total length of the ANGPTL8 gene nucleotide sequence is 717 bp, including 597 bp of ORF, encoding 198 amino acids. Goat ANGPTL8 has the closest relationship with sheep, it was widely expressed in different tissues, and relatively enriched in liver. The silence of ANGPTL8 inhibited the accumulation of lipid droplets by 5.76% in goat intramuscular preadipocytes (p > 0.05) and significantly suppressed the expression of the genes related to preadipocytes differentiation, fatty acid synthesis and transport (p＜0.05 or p＜0.01). These data illuminate the speculation that ANGPTL8 may involve in the lipid accumulation regulation via the control of PPARγ and C/EBPβ in goat adipocytes.

Hepatocrinology

Hepatocrinology is defined as a bidirectional, complex relationship between hepatic physiology and endocrine function, hepatic disease and endocrine dysfunction, hepatotropic drugs and endocrine function, and endocrine drugs and hepatic health. The scope of hepatocrinology includes conditions of varied etiology (metabolic, infectious, autoimmune, and invasive) that we term as hepato-endocrine syndromes. This perspective shares the definition, concept, and scope of hepatocrinology and shares insight related to this aspect of medicine. It is hoped that this communication will encourage further attention and research in this critical field.

Circulating angiopoietin-like proteins in metabolic-associated fatty liver disease: a systematic review and meta-analysis

Background

Angiopoietin-like proteins (ANGPTLs) are closely related to insulin resistance and lipid metabolism, and may be a key in metabolic syndrome. Non-alcoholic fatty liver disease (NAFLD) (newly named metabolic-associated fatty liver disease (MAFLD)) is based on metabolic dysfunction. There may be some correlation between ANGPTLs and MAFLD, but the specific correlation is unclear. This study aims to explore the predictive role of ANGPTLs in MAFLD and its progression.

Methods

Seven databases (PubMed, EMBASE, Cochrane Library, CNKI, WANFANG, CBM and Clinicaltrials.gov) were searched with free terms and MeSH terms. The random-effects model was used to pool the data, and Standardized Mean Difference (SMD) and 95% confidence intervals (CI) were taken as the overall outcome. No language restrictions existed in the article selection. RevMan 5.3, Stata 16 and MetaXL software were applied to analyse the data and the GRADE system was utilized to assess the certainty of evidence.

Results

After reviewing 823 related articles, 13 studies (854 cases and 610 controls) met the inclusion criteria, and contributed to this meta-analysis. The results showed that circulating ANGPTL8 level was significantly elevated in the MAFLD group than in the healthy control group (SMD = 0.97 pg/mL, 95%CI: 0.77, 1.18). Conversely, there was no significant difference in the ANGPTL4 (SMD = 0.11 ng/mL, 95%CI: − 0.32, 0.54) and ANGPTL3 (SMD = − 0.95 ng/mL, 95%CI: − 4.38, 2.48) between the two groups. Subgroup analysis showed that: 1) the MAFLD group had significantly higher ANGPTL8 levels than the healthy control group in Asian and other races; 2) the ANGPTL8 levels in Body Mass Index (BMI) > 25 kg/m² patients with MAFLD were higher than those in the healthy control group; 3) the higher ANGPTL8 levels were observed in moderate to severe MAFLD group than the healthy control group. Meta-regression demonstrated that BMI might effectively explain the high heterogeneity. No significant publication bias existed (P > 0.05). The certainty of evidence was assessed as very low by the GRADE system.

Conclusions

The ANGPTLs may be related to MAFLD. The increased ANGPTL8 level may be positively correlated with different situations of MAFLD, which may act as a potential indicator to monitor the development trends.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01481-1.

ANGPTL8 roles in proliferation, metabolic diseases, hypothyroidism, polycystic ovary syndrome, and signaling pathways

A new and atypical member of the ANGPTL family is angiopoietin-like protein 8 (ANGPTL8). This newly discovered hormone is a drug target that can be used to treat diabetes and dyslipidemia. The protein, as a hepatocyte-derived circulating factor, can control the triglyceride level of plasma. ANGPTL8 is significantly associated with inflammation and metabolic syndrome consequences such as obesity, diabetes, hypothyroidism, and PCOS. ANGPTL8 gene has four exons encoding a 22/5 kDa weight of 198 amino acid polypeptides. A highly preserved ANGPTL8 gene among mammals exhibits the essential hormone functions of ANGPTL8. Nevertheless, the physiological function of this hormone in the body is poorly understood. Studies published in PubMed (2008-2020), Google Scholar (2004-2020), and Scopus (2004-2020) databases of clinical trials were reviewed. This analysis is aimed at collecting information on ANGPTL8. The emphasis of this review was on gathering information about the role of ANGPTL8 in the metabolism of glucose and lipids and cell proliferation. It addition to the different roles of ANGPTL8 in diabetes and lipid metabolism, this review emphasized on the protein role in signaling pathways. The study also proposes the signaling pathways that may be considered as a new target for treatment.

Analysis of ANGPTL8 promoter activity and screening of related transcription factors in bovine

Analysing the molecular regulation mechanism of fat deposition in yellow cattle can provide a theoretical basis for the breeding of excellent beef cattle. ANGPTL8 (angiopoietin-like protein 8) promotes the formation of lipid droplets during adipocyte differentiation. To explore the promoter active region of ANGPTL8 and predict potential transcription factors, we further provide a theoretical basis for the functional analysis and regulatory mechanism of ANGPTL8 in adipogenesis. The promoter region of bovine ANGPTL8 was cloned by overlap extension PCR. Online software was used to predict potential transcription factor binding sites, and it identified PPARγ, SREBP1, C/EBPα, and Znf423 transcription factor binding sites in ANGPTL8 promoter region. A luciferase reporter gene vector which contained different deletion fragments of the ANGPTL8 promoter was constructed. Then, the vectors were cotransfected into 293 T cells with the internal control plasmid pRL-TK by cationic liposomes, and the relative fluorescence intensity was detected by a microplate reader. The results of the luciferase activity analysis showed that the core promoter area of ANGPTL8 was in the -885/-227 bp region of the 5' flanking sequence, while just two SREBP1 binding sites occurred in this area. When SREBP1 was knocked down by siRNA, the expression level of ANGPTL8 was reduced, and we speculated that SREBP1 may be an important transcription factor regulating ANGPTL8 transcription.

From Congenital Disorders of Fat Malabsorption to Understanding Intra-Enterocyte Mechanisms Behind Chylomicron Assembly and Secretion

During the last two decades, a large body of information on the events responsible for intestinal fat digestion and absorption has been accumulated. In particular, many groups have extensively focused on the absorptive phase in order to highlight the critical "players" and the main mechanisms orchestrating the assembly and secretion of chylomicrons (CM) as essential vehicles of alimentary lipids. The major aim of this article is to review understanding derived from basic science and clinical conditions associated with impaired packaging and export of CM. We have particularly insisted on inborn metabolic pathways in humans as well as on genetically modified animal models (recapitulating pathological features). The ultimate goal of this approach is that "experiments of nature" and in vivo model strategy collectively allow gaining novel mechanistic insight and filling the gap between the underlying genetic defect and the apparent clinical phenotype. Thus, uncovering the cause of disease contributes not only to understanding normal physiologic pathway, but also to capturing disorder onset, progression, treatment and prognosis.

The multi-faces of Angptl8 in health and disease: Novel functions beyond lipoprotein lipase modulation

Angiopoietin-like protein (ANGPTL) family members, mainly ANGPTL3, ANGPTL4 and ANGPTL8, are physiological inhibitors of lipoprotein lipase (LPL), and play a critical role in lipoprotein and triglyceride metabolism in response to nutritional cues. ANGPTL8 has been described by different names in various studies and has been ascribed various functions at the systemic and cellular levels. Circulating ANGPTL8 originates mainly from the liver and to a smaller extent from adipose tissues. In the blood, ANGPTL8 forms a complex with ANGPTL3 or ANGPTL4 to inhibit LPL in fed or fasted conditions, respectively. Evidence is emerging for additional intracellular and receptor-mediated functions of ANGPTL8, with implications in NFκB mediated inflammation, autophagy, adipogenesis, intra-cellular lipolysis and regulation of circadian clock. Elevated levels of plasma ANGPTL8 are associated with metabolic syndrome, type 2 diabetes, atherosclerosis, hypertension and NAFLD/NASH, even though the precise relationship is not known. Whether ANGPTL8 has direct pathogenic role in these diseases, remains to be explored. In this review, we develop a balanced view on the proposed association of this protein in the regulation of several pathophysiological processes. We also discuss the well-established functions of ANGPTL8 in lipoprotein metabolism in conjunction with the emerging novel extracellular and intracellular roles of ANGPTL8 and the implicated metabolic and signalling pathways. Understanding the diverse functions of ANGPTL8 in various tissues and metabolic states should unveil new opportunities of therapeutic intervention for cardiometabolic disorders.

Angiopoietin-like protein 8 accelerates atherosclerosis in ApoE-/- mice

BACKGROUND AND AIMS

Angiopoietin-like protein 8 (ANGPTL8) is a hormone involved in regulating lipid metabolism. Patients with coronary artery disease have markedly higher plasma levels of ANGPTL8 than controls; however, the role of ANGPTL8 in atherosclerosis has not been explored. Therefore, we explored the effects of ANGPTL8 on atherosclerosis development in a mouse model.

METHODS

We induced experimental atherosclerosis in ApoE^-/- mice ANGPTL8-knockdown. and ANGPTL8-overexpression ApoE^-/- mice. We also explored the mechanism using ANGPTL8-overexpression macrophages.

RESULTS

ANGPTL8 expression was increased in human and mouse atherosclerotic lesions. ANGPTL8 overexpression promoted the development of atherosclerosis whereas ANGPTL8 knockdown protected against atherosclerosis. Immunofluorescence co-staining results showed that ANGPTL8 was expressed in macrophages in atherosclerotic plaques. Compared with wild type cells, ANGPTL8-overexpressing macrophages, including bone marrow-derived macrophages and Raw 264.7 macrophages, showed enhanced foam cell formation and increased accumulation of cholesterol that was induced by increased uptake and decreased efflux of cholesterol. The results of this study also showed that ANGPTL8 induced the expression of CD36 and scavenger receptor (SR)-A, and inhibited the expression of SR-BI.

CONCLUSIONS

Our findings demonstrate an unanticipated role of ANGPTL8 in the development of atherosclerosis and regulation of foam cell formation. ANGPTL8 may be a promising new target for atherosclerosis.

Association of a genetic variant in the angiopoietin-like protein 4 gene with cervical cancer

BACKGROUND

Cervical cancer is among the most aggressive gynecological tumors and is a consequence of interactions between genetic and epigenetic factors. Several genetic polymorphisms related to cervical cancer have been reported in previous clinical studies. In this study, we aimed to explore the possible relationship between polymorphisms of the ANGPTL4 gene locus and susceptibility to cervical cancer.

METHODS

We investigated the relationship between a single nucleotide polymorphism (SNP) in the ANPGTL4 gene (rs116843064) and risk of cervical cancer in a total of 378 individuals with (n = 151), or without (n = 227) cancer. DNA was extracted, and genotyped using a Taq-Man based real time PCR.

RESULTS

The ANPGTL4 polymorphism was found to be associated with an increased risk of developing cervical neoplasia using dominant model (OR = 12.48, CI = 4.9-31.82, p < 0.0001) and additive model (OR = 30.54, CI = 7.35-126.89, p < 0.0001).

CONCLUSION

Our results indicate that there is a strong association between ANPGTL4 and the susceptibility for cervical cancer suggesting that it is a potential risk factor for cervical neoplasia.

High-Serum Angiopoietin-Like Protein 3 Levels Associated with Cardiovascular Outcome in Patients with Coronary Artery Disease

Background

Angiopoietin-like protein 3 (ANGPTL3) plays a pivotal role in lipid metabolism and angiogenesis, and there is growing interest regarding the association between ANGPTL3 and coronary artery disease (CAD). This study aims to investigate whether ANGPTL3 levels can be used to predict the future occurrence of major adverse cardiovascular events (MACEs) in patients with CAD.

Methods

Overall, 90 patients with CAD were enrolled between January and December 2012. The study's primary endpoint was incidence of MACEs. Patient follow-up was completed on June 30, 2017.

Results

Following a median follow-up period of 54 months, 33 MACEs had occurred. Patients reporting MACEs had lower statin use (P=0.022) and higher serum C-reactive protein (P < 0.001) and serum ANGPTL3 (P < 0.001) levels than those without MACEs. Kaplan–Meier analysis revealed higher cumulative incidence of CV events in the high ANGPTL3 group (median ANGPTL3 level ≥ 222.37 ng/mL) than in the low ANGPTL3 group (log-rank P=0.046). Multivariable Cox regression analysis demonstrated that ANGPTL3 levels were independently associated with MACEs in patients with CAD (hazard ratio: 1.003; 95% confidence interval: 1.000–1.005; P=0.026) after adjusted for age, gender, and body mass index, classical risk factors, and potential confounders.

Conclusions

Serum ANGPTL3 levels could serve as a biomarker for future occurrence of MACEs in patients with CAD.

Histology and molecular biology studies on the expression and localization of angiopoietin-like protein 8 in human tissues

Angiopoietin-like protein (ANGPTL) 8 regulates the partitioning of triglycerides by inhibiting lipoprotein lipase in muscle and adipose tissues. ANGPTL8 is expressed in the liver and adipose tissue and secreted into the blood. However, the precise localization of ANGPTL8-expressing cells in these tissues remains unknown. The aim of the present study was to investigate the localization of ANGPTL8-expressing cells in human tissues. Using formalin-fixed paraffin-embedded human tissue specimens, the expression of ANGPTL8 was investigated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), immunohistochemistry (IHC) and in situ hybridization (ISH). The expression level of ANGPTL8 mRNA was the highest in the liver, followed by lipoma, hibernoma and normal adipose tissue. In the liver, wild type (KF809856) and two splice variants of ANGPTL8 mRNA (KF809857 and KF809858) were found to be expressed. The expression level of the splice variant KF809858, which produces a short form of ANGPTL8, accounted for <1% of ANGPTL8 in the liver. IHC revealed that ANGPTL8 was expressed in hepatocytes in zone 1 of the hepatic acinus in the liver. In the adipose tissue, mature adipocytes weakly expressed ANGPTL8, while immature adipocytes strongly expressed it. ISH confirmed ANGPTL8 mRNA expression in portal hepatocytes and immature adipocytes. ANGPTL8 was expressed in the cells, which actively uptake and metabolize triglycerides. In hibernoma, the ANGPTL8 protein and mRNA were homogeneously expressed in tumor cells. The expression of ANGPTL8 was associated with the differentiation state and activity of lipid metabolism in a subpopulation of cells in the liver and adipose tissue. The association may be helpful for the understanding of local metabolic state in organs and diseases associated with the lipid metabolism.

Anti-proteinuria effect of antibody against ANGPTL3 coil-coiled domain on adriamycin-induced nephropathy in mice

Proteinuria is an important marker and is closely related to the progressive decline of renal function. Our previous research showed that angiopoietin-like-3 (ANGPTL3) plays a crucial role in proteinuria. In this study, we prepared an antibody against ANGPTL3 coil-coiled domain (ANGPTL3-CCD) and investigated the protective effect of anti-ANGPTL3-CCD antibody in mice with adriamycin-induced nephropathy. Nephropathy was established by adriamycin injection at a dose of 25 mg per kg in 8-12 week-old male mice in the ADR group. Blockade of ANGPTL3 by anti-ANGPTL3-CCD antibody (20 mg per kg) was performed every three days nine times after adriamycin injection in the ADR plus anti-angptl3-antibody group. The anti-ANGPTL3-CCD antibody can specifically recognize ANGPTL3. After anti-ANGPTL3-CCD antibody intervention, the urinary protein level in the ADR plus anti-angptl3-antibody group was significantly lower than that in the ADR group. Serum albumin was higher and triglyceride and total cholesterol were lower in the ADR plus anti-angptl3-antibody group than in the ADR group. The levels of serum creatinine did not significantly differ among the groups. Focal sclerotic glomeruli and podocyte foot processes extensive fusion were found in the renal tissue of the ADR group, whereas no sclerotic glomeruli and only partial fusion were found in the ADR plus anti-angptl3-antibody group. This study demonstrated that the anti-ANGPTL3-CCD antibody ameliorated proteinuria and podocyte dysfunction in adriamycin-induced nephropathy in mice.

Hypocholesterolemia and dysregulated production of angiopoietin-like proteins in sickle cell anemia patients

Angiopoietin-like proteins (ANGPTL) are responsible for inhibiting lipoprotein lipase activity, and ANGPTL3 and ANGPTL4 deficiencies have been shown to lower lipoprotein levels in animal models and in humans carrying loss-of-function mutations. Sickle cell anemia (SCA) is a hereditary hemolytic anemia characterized by vaso-occlusive crises and end-organ damage, which is curiously associated with hypocholesterolemia and a low incidence of atherosclerosis, whose underlying mechanisms are unclear. We hypothesized that ANGPTL3 and ANGPTL4 dysregulation is responsible for the hypolipidemic phenotype in SCA. We measured circulating concentrations of ANGPTL3 and ANGPTL4 and correlated them with hemolytic biomarkers and lipoproteins in 40 patients with SCA and 30 control individuals. The association between hemolysis and low cholesterol levels in SCA was confirmed along with surprisingly higher levels of ANGPTL3 and ANGPTL4 in SCA patients than in controls. ANGPTL3 correlated with hemolysis markers LDH and reticulocyte counts, while ANGPTL4 did not. Our data show a paradoxical increase in production of ANGPTL3 and ANGPTL4 in SCA, which would be expected to cause hyperlipidemia, due to increased inhibition of lipoprotein lipase. ANGPTL3, exclusively produced by the liver, correlated with hemolysis markers, suggesting a possible hepatic response to hemolysis. Further functional studies and replication in larger cohorts are warranted to investigate the dysregulation of lipid metabolism in SCA.

ANGPTL8 regulates adipocytes differentiation and adipogenesis in bovine

The formation of bovine adipose tissue involves complex developmental and physiological processes that play a vital role in determining the quality of beef; however, the regulatory mechanisms are largely unknown. Angiopoietin-like protein 8 (ANGPTL8) has been reported to be involved in the development of adipose tissue; however, the mechanism of adipogenesis which is regulated by ANGPTL8 has not been revealed in cattle. In this study, RT-qPCR and Oil Red O staining were performed to detect the expression of ANGPTL8 and adipocyte differentiation in bovine. We found that ANGPTL8 had a high expression level in adipose tissue and that the expression pattern was consistent with those of PPARγ, C/EBPα and LPL which are key regulators and transcription factors involved in preadipocyte differentiation and adipogenesis. The overexpression of ANGPTL8 by the adenovirus vector promoted lipid droplet formation in adipocytes. Thus, we speculated that ANGPTL8 could significantly enhance lipid deposition. Moreover, the expression of LPL and SREBP1, key genes inhibiting adipogenesis, was significantly decreased by ANGPTL8 overexpression. These results suggested that ANGPTL8 promotes adipocyte differentiation. In conclusion, we consider that ANGPTL8 regulates adipocyte differentiation and adipogenesis in bovine.

Up-regulated of Angiopoietin-Like Protein 4 Predicts Poor Prognosis in Cervical Cancer

Background: Angiopoietin-like protein 4 (ANGPTL4) has been demonstrated highly expressed in some cancers, but it also was downregulated in others through DNA methylation. However, the expression status of ANGPTL4 in cancer of cervix remains unclear. Thus, our present study attempts to investigate the role of ANGPTL4 in the prognosis of patients with cervical cancer. Methods: Immunohistochemistry, western blotting and qRT-PCR were performed to investigate the expressive level of ANPGTL4 in cervical cancer tissues and paired noncancer tissues. The relationship of ANGPTL4 expression and clinicopathological factors was measured by Chi-square test. Overall and disease-free survival (OS and DFS) rates were estimated and compared by using Kaplan-Meier method and log-rank test, respectively. To assess the prognostic significance of ANGPTL4 in cervical cancer patients, the Cox regression model was utilized to process univariate and multivariate analyses. Results: ANGPTL4 was upregulated in cervical cancer samples and advanced tumor stage, deep stromal invasion, lymph node metastasis, lymphovascular space invasion, as well as poor OS and DFS were shown to be tightly correlated with it. Results of Cox multivariate analysis demonstrated that ANGPTL4 expression was an independent prognostic factor for OS and DFS in cervical cancer. Conclusion: Upregulated ANGPTL4 seems to be a useful marker for poor prognosis in cervical cancer.

The association between genetic variants of angiopoietin-like 3 and risk of diabetes mellitus is modified by dietary factors in Koreans

The role of angiopoietin-like 3 (ANGPTL3) in blood lipid levels, cardiovascular disease risk, and glucose metabolism has received wide attention. This study aimed to examine whether rs11207997 in ANGPTL3 is associated with a 10-year risk of diabetes mellitus (DM) and if the association is modified by the consumption of certain food groups or nutrients. A prospective cohort study was designed using the Ansan-Ansung data of the Korean Genome and Epidemiology Study (n = 7,358; age ≥40 years at baseline). Participants with the T allele of rs11207997, particularly TT homozygotes, had lower triglyceride (TG) and total cholesterol levels than those with CC. There was no association with fasting blood glucose or other biochemical parameters. ANGPTL3 mRNA was positively associated with circulating TG levels and blood pressure (all p < 0.05). Cox proportional hazard models showed that the rs11207997 T allele is associated with a lower risk of DM after adjusting for covariates (hazard ratio: 0.90, 95% confidence interval: 0.812-0.998, p = 0.046). Furthermore, the association between rs11207997 and the risk of DM was modified by dietary factors. These associations were no longer statistically significant when additionally adjusted for baseline TG, a potential mediator. Our data suggest that genetic variation of rs11207997 in the ANGPTL3 gene is associated with risk of DM, possibly through contributing to a lifelong set point of TG.

A 7-day high-PUFA diet reduces angiopoietin-like protein 3 and 8 responses and postprandial triglyceride levels in healthy females but not males: a randomized control trial

BACKGROUND

Polyunsaturated fatty acids (PUFAs) have beneficial effects on hypertriglyceridemia although their effect on angiopoietin-like proteins (ANGPTLs), specifically ANGPTL3, ANGPTL4 and ANGPTL8 is unknown.

OBJECTIVE

To determine whether a high-PUFA diet improves postprandial triglyceride (TG) levels through reducing ANGPTL responses following high saturated fat (SFA) meals.

METHODS

Twenty-six adults were randomized into a PUFA diet (n = 16) or a control diet group (n = 10). Participants completed a pre-diet visit (v1) where they were given two SFA-rich, high-fat meals. Blood draws were taken at fasting and every 2 h postprandially for a total of 8 h. After v1, participants completed a 7d diet of the same macronutrient proportions (50% carbohydrate, 35% fat, 15% protein) but with different fatty acid (FA) compositions (PUFA = 21% of total energy from PUFAs vs. Control = 7% of total energy from PUFA). All participants then completed the post-diet visit (v2) identical to v1.

RESULTS

In the PUFA group, females, but not males, reduced TG concentrations (Area under the curve (AUC): 141.2 ± 18.7 vs. 80.7 ± 6.5 mg/dL/h, p = 0.01, for v1 vs. v2, respectively). Fasting and postprandial AUC levels of ANGPTL3 and 8, but not ANGPTL4, also decreased from v1 to v2 in PUFA females, but not males. No changes from v1 to v2 were seen in either sex in the control group.

CONCLUSIONS

A PUFA-rich diet improves TG levels in response to high-SFA meals with reductions in ANGPTL3 and ANGPTL8. PUFAs may be more protective against hypertriglyceridemia in females, compared to males since no diet effect was observed in males.

TRIAL REGISTRATION

NCT02246933.

Betatrophin association with serum triglyceride levels in obstructive sleep apnea patients

BACKGROUND

Obstructive sleep apnea (OSA) is a common sleep problem, in which patients are at increased risk for metabolic and cardiovascular problems, including metabolic syndrome, diabetes mellitus (DM), and dyslipidemia. Betatrophin is a novel protein that regulates fatty acid and triglyceride (TG) metabolism and is related to obesity and metabolic abnormalities, including metabolic syndrome, DM, and dyslipidemia. Although OSA and betatrophin share common abnormalities, their relationship has not been investigated.

AIM

The aim of this study is to investigate the relationships among betatrophin, OSA, and the serum lipid profile.

METHODS

Ninety consecutive patients with suspected OSA underwent polysomnography (PSG) to confirm OSA. Plasma betatrophin, leptin, adiponectin, and the full lipid profile were analyzed. The patients were categorized as OSA or control based on the apnea-hypopnea index (AHI).

RESULTS

About 61% of patients had OSA, and 39% had normal PSG. The levels of betatrophin, leptin, and adiponectin were higher in patients with OSA (256.59 ± 29.35, 374.20 ± 37.93, and 17.86 ± 2.63 μg/mL, respectively) compared to the controls (141.86 ± 26.20, 205.53 ± 14.75, and 7.52 ± 1.02 μg/mL, respectively). Betatrophin levels were correlated with the AHI, leptin (r = 0.413, P = 0.002, r = 0.782, P = 0.000). TG levels were significantly higher, and high-density lipoprotein cholesterol (HDL-C) levels were lower, in OSA patients compared to controls (244 ± 20.33 vs. 138 ± 14.89, and 37.21 ± 1.26 vs. 43.78 ± 1.62, respectively). The TG level was correlated with betatrophin (r = 0.353, P = 0.013). Multiple regression analysis showed that the AHI, leptin, and arousals were independent predictors of betatrophin level (B = 1.70 P = 0.046 95%, B = 0.56 P < 0.005, and B = 1, 2, P = 0.003, respectively).

CONCLUSIONS

Our results suggest a complex relationship between OSA, betatrophin, TG, and HDL, as well as other adipokines. Our results require further investigation to assess this complex association and re-evaluate previous related studies.

Mapping the sites of the lipoprotein lipase (LPL)-angiopoietin-like protein 4 (ANGPTL4) interaction provides mechanistic insight into LPL inhibition

Cardiovascular disease has been the leading cause of death throughout the world for nearly 2 decades. Hypertriglyceridemia affects more than one-third of the population in the United States and is an independent risk factor for cardiovascular disease. Despite the frequency of hypertriglyceridemia, treatment options are primarily limited to diet and exercise. Lipoprotein lipase (LPL) is an enzyme responsible for clearing triglycerides from circulation, and its activity alone can directly control plasma triglyceride concentrations. Therefore, LPL is a good target for triglyceride-lowering therapeutics. One approach for treating hypertriglyceridemia may be to increase the amount of enzymatically active LPL by preventing its inhibition by angiopoietin-like protein 4 (ANGPTL4). However, little is known about how these two proteins interact. Therefore, we used hydrogen-deuterium exchange MS to identify potential binding sites between LPL and ANGPTL4. We validated sites predicted to be located at the protein-protein interface by using chimeric variants of LPL and an LPL peptide mimetic. We found that ANGPTL4 binds LPL near the active site at the lid domain and a nearby α-helix. Lipase lid domains cover the active site to control both enzyme activation and substrate specificity. Our findings suggest that ANGPTL4 specifically inhibits LPL by binding the lid domain, which could prevent substrate catalysis at the active site. The structural details of the LPL-ANGPTL4 interaction uncovered here may inform the development of therapeutics targeted to disrupt this interaction for the management of hypertriglyceridemia.

Dyslipidemias in clinical practice

Most dyslipidemic conditions have been linked to an increased risk of cardiovascular disease. Over the past few years major advances have been made regarding the genetic and metabolic basis of dyslipidemias. Detailed characterization of the genetic basis of familial lipid disorders and knowledge concerning the effects of environmental factors on the expression of dyslipidemias have increased substantially, contributing to a better diagnosis in individual patients. In addition to these developments, therapeutic options to lower cholesterol levels in clinical practice have expanded even further in patients with familial hypercholesterolemia and in subjects with cardiovascular disease. Finally, promising upcoming therapeutic lipid lowering strategies will be reviewed. All these advances will be discussed in relation to current clinical practice with special focus on common lipid disorders including familial dyslipidemias.

Association between circulating full-length angiopoietin-like protein 8 and non-high-density lipoprotein cholesterol levels in Chinese non-diabetic individuals: a cross-sectional study

Background

Angiopoietin-like protein 8 (ANGPTL8) is a novel hormone involved in the regulation of lipid metabolism and glucose homeostasis. There are inconsistent results regarding the association between ANGPTL8 and lipids in humans. We aimed to investigate the associations between ANGPTL8 and lipids in people without diabetes.

Methods

This was a cross-sectional study of 107 patients with dyslipidemia and 141 patients without. Dyslipidemia diagnosis was based on Chinese guidelines for the prevention and treatment of dyslipidemia in adults. Total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol (HDL-C) were examined. Non-HDL-C was calculated by subtracting HDL-C from TC. Circulating full-length ANGPTL8 concentrations were measured using enzyme-linked immunosorbent assay. Associations between log-transformed circulating full-length ANGPTL8 and serum lipids were examined using multivariate linear regression analysis.

Results

Circulating ANGPTL8 concentrations were significantly elevated in patients with dyslipidemia compared with patients without dyslipidemia. Circulating full-length ANGPTL8 concentrations were positively associated with non-HDL-C, TG and TC levels after adjusting for age, gender, body mass index, high-sensitivity C-reactive protein, alanine aminotransferase, and creatinine.

Conclusion

In people without diabetes, circulating full-length ANGPTL8 concentrations in patients with dyslipidemia were significantly elevated compared with non-dyslipidemia, and ANGPTL8 was positively associated with serum non-HDL-C levels.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0802-9) contains supplementary material, which is available to authorized users.

Associations between circulating full-length angiopoietin-like protein 8 levels and severity of coronary artery disease in Chinese non-diabetic patients: a case-control study

Background

Angiopoietin-like protein 8 (ANGPTL8), which is a novel hormone produced in liver and adipose tissue, is involved in regulating lipid metabolism. Patients with diabetes and coronary artery disease (CAD) have remarkably higher levels of ANGPTL8 than those with only diabetes. However, no studies have investigated the involvement of ANGPTL8 in CAD in Chinese non-diabetic individuals. Therefore, we investigated full-length circulating ANGPTL8 levels in patients with CAD and the association between ANGPT8 levels and severity of CAD in Chinese individuals without diabetes.

Methods

We performed a case–control study in 149 Chinese non-diabetic subjects, including 80 patients with CAD and 69 controls. The Gensini stenosis scoring system was used to assess the severity of CAD. Circulating full-length ANGPTL8 levels were measured by an enzyme-linked immunosorbent assay kit. The associations between circulating full-length ANGPTL8 levels and CAD were determined by multivariate logistic regression analysis. The association between ANGPTL8 levels and Gensini scores was determined by multivariate linear regression analysis.

Results

Circulating full-length ANGPTL8 levels were significantly higher in Chinese non-diabetic patients with CAD compared with controls (665.90 ± 243.49 vs 462.27 ± 151.85 pg/ml, P < 0.001). After adjusting for confounding factors, we found that circulating full-length ANGPTL8 levels were an independent risk factor for CAD (odds ratio = 2.002/100 pg ANGPTL8, 95% CI 1.430–2.803, P < 0.001) and circulating ANGPTL8 levels were positively associated with the Gensini score (β = 5.701/100 pg ANGPTL8, 95% CI 1.306–10.096, P = 0.012).

Conclusions

This study shows that the circulating ANGPTL8 levels are significantly increased in patients with CAD compared with controls in Chinese non-diabetic individuals. Circulating full-length ANGPTL8 levels are an independent risk factor for CAD and they are positively associated with the severity of CAD.

Trial registration This study was registered in the Chinese Clinical Trial Registry (No. ChiCTR-COC-17010792)

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0736-6) contains supplementary material, which is available to authorized users.

Angiopoietin-like protein 8 in early pregnancy improves the prediction of gestational diabetes

AIMS/HYPOTHESIS

Screening high-risk individuals for gestational diabetes mellitus (GDM) in early pregnancy conventionally relies on established maternal risk factors; however, the sensitivity and specificity of these factors are not satisfactory. The present study aimed to determine whether the concentration of angiopoietin-like protein 8 (ANGPTL8), either alone or combined with other risk factors in early pregnancy, could be used to predict subsequent GDM.

METHODS

From August 2015 to January 2016, 474 women receiving prenatal care at around 12-16 weeks of gestation were recruited into the study. ANGPTL8 levels were measured at the first prenatal visit. All the participants received a 75 g OGTT during weeks 24-28 of gestation.

RESULTS

ANGPTL8 levels in early pregnancy were considerably higher in women who developed GDM than those who maintained normal glucose tolerance (2822 ± 938 vs 2120 ± 1118 pg/ml, respectively; p < 0.0001). Multivariable logistic regression revealed that ANGPTL8 levels were significantly associated with risk of GDM independent of conventional risk factors. In addition, women in the highest quartile of ANGPTL8 concentration had an 8.75-fold higher risk of developing GDM compared with women in the lowest quartile (OR8.75, 95%CI 2.43, 31.58). More importantly, incorporating ANGPTL8 into the conventional prediction model significantly increased the AUC for prediction of GDM (0.772vs 0.725; p = 0.019).

CONCLUSIONS

Our study suggests that ANGPTL8 levels in early pregnancy are significantly and independently associated with risk of GDM at 24-28 weeks of gestation. Combining ANGPTL8 levels with conventional risk factors could thus improve the prediction of GDM.

Positive correlation of the serum angiopoietin-like protein 3 levels with the aortic augmentation index in patients with coronary artery disease

Purpose

Angiopoietin-like protein 3 (ANGPTL3) plays an important role in lipid metabolism and angiogenesis and is elevated in familial hypercholesterolemia, metabolic syndrome, and insulin resistance. This study aims to evaluate the relationship between the fasting serum ANGPTL3 levels and the aortic augmentation index (AIx) in patients with coronary artery disease (CAD).

Materials and methods

Fasting blood samples were obtained from 100 patients with CAD. The AIx was measured using a validated tonometry system (SphygmoCor). The serum ANGPTL3 levels were assessed using a commercial enzyme-linked immunosorbent assay kit.

Results

The aortic AIx values were higher in female patients with CAD (P=0.003) than those in male patients with CAD. The univariate linear analysis of the aortic AIx values reveals that the height (r=−0.363; P<0.001) and body weight (r=−0.350; P<0.001) were negatively correlated, whereas the age (r=0.202; P=0.044) and logarithmically transformed ANGPTL3 (log-ANGPTL3, r=0.357; P<0.001) were positively correlated with the aortic AIx values in patients with CAD. The multivariate forward stepwise linear regression analysis of the factors significantly associated with the aortic AIx revealed that the height (β=−0.269; adjusted R² change=0.123; P=0.007) and serum log-ANGPTL3 level (β=0.259; adjusted R² change=0.051; P=0.010) were independent predictors of the aortic AIx values in patients with CAD.

Conclusion

The fasting serum ANGPTL3 level positively correlated with the aortic AIx values among patients with CAD.

Feeding Angptl4-/- mice trans fat promotes foam cell formation in mesenteric lymph nodes without leading to ascites

Angiopoietin-like 4 (ANGPTL4) regulates plasma triglyceride levels by inhibiting LPL. Inactivation of ANGPTL4 decreases plasma triglycerides and reduces the risk of coronary artery disease. Unfortunately, targeting ANGPTL4 for the therapeutic management of dyslipidemia and atherosclerosis is hampered by the observation that mice and monkeys in which ANGPTL4 is inactivated exhibit lipid accumulation in the mesenteric lymph nodes (MLNs). In mice these pathological events exclusively unfold upon feeding a high saturated FA diet and are followed by an ultimately lethal pro-inflammatory response and chylous ascites. Here, we show that Angptl4^-/- mice fed a diet rich in trans FAs develop numerous lipid-filled giant cells in their MLNs, yet do not have elevated serum amyloid and haptoglobin, do not exhibit ascites, and survive, unlike Angptl4^-/- mice fed a saturated FA-rich diet. In RAW264.7 macrophages, the saturated FA, palmitate, markedly increased markers of inflammation and the unfolded protein response, whereas the trans-unsaturated elaidate and the cis-unsaturated oleate had the opposite effect. In conclusion, trans and saturated FAs have very distinct biological effects in macrophages. Furthermore, lipid accumulation in MLNs is uncoupled from activation of an acute-phase response and chylous ascites, suggesting that ANGPTL4 should not be fully dismissed as target for dyslipidemia.

ANGPLT3: A novel modulator of lipid metabolism

Angiopoietin-like proteins (ANGPTLs) have emerged as an important regulator of lipid and glucose metabolism as well as insulin sensitivity. ANGPTL3 plays a key role in regulating circulating triglycerides (TG) and cholesterol levels through reversible inhibition of lipoprotein lipase (LPL) and endothelial lipase enzymes activity. Loss of function mutation of ANGPTL3 gene has been identified in many subjects with familial combined hypolipidemia. ANGPTL4 produces irreversible inhibition of LPL activity, while ANGPTL8 enhances the activity of ANGPTL3, which highlight the interplay between the different ANGPTLs in a coordinated manner to regulate lipid metabolism during different nutritional states. This new class of lipid modulators may serve as potential novel therapeutic target for reducing plasma lipoprotein and treatment of metabolic syndrome.

Plasma and adipose tissue level of angiopoietin-like 7 (ANGPTL7) are increased in obesity and reduced after physical exercise

Objective

ANGPTL7 is a member of the Angiopoietin-like (ANGPTL) protein family that is composed of eight proteins (1–8). Increasing evidence is associating ANGPTL proteins to obesity and insulin resistance. The biological role of ANGPTL7 is yet to be understood except for a recently proposed role in the pathophysiology of glaucoma. This study was designed to shed light on the function of ANGPTL7 in obesity and its modulation by physical exercise as well as its potential association with lipid profile.

Methods

A total of 144 subjects were enrolled in this study and finished three months of physical exercise. The participants were classified based on their BMI, 82 subjects were non-obese and 62 obese. ANGPTL7 levels in plasma and adipose tissue were measured by ELISA, RT-PCR and immunohistochemistry.

Results

In this study, we showed that ANGPTL7 level was increased in the plasma of obese subjects (1249.05± 130.39 pg/mL) as compared to non-obese (930.34 ± 87.27 pg/mL) (p-Value = 0.032). ANGPTL7 Gene and protein expression levels in adipose tissue also showed over two fold increase. Physical exercise reduced circulating level of ANGPTL7 in the obese subjects to 740.98± 127.18 pg/mL, (p-Value = 0.007). ANGPTL7 expression in adipose tissue was also reduced after exercise. Finally, ANGPTL7 circulating level showed significant association with TG level in the obese subjects (R² = 0.183, p-Value = 0.03).

Conclusion

In conclusion, our data shows for the first time that obesity increases the level of ANGPTL7 in both plasma and adipose tissue. Increased expression of ANGPTL7 might play a minor role in the regulation of TG level in obese subjects either directly or through interaction with other ANGPTL protein members. Physical exercise reduced the level of ANGPTL7 highlighting the potential for targeting this protein as a therapeutic target for regulating dyslipidemia.

Betatrophin expression is promoted in obese hyperinsulinemic type 2 but not type 1 diabetic mice

Regeneration of pancreatic β-cell mass benefits both type 1 and type 2 diabetic patients. A recent study identified betatrophin as a β-cell proliferation factor. However, the expressional regulation of betatrophin remains less defined. In this study, we aimed to clarify the regulation of betatrophin expression in obese type 2 vs. type 1 diabetes model animals. We experimented type 2 diabetes models, diet-induced-obesity (DIO) mice and db/db mice, and type 1 diabetes models, C57B6 mice receiving streptozotocin (STZ) or 70% pancreatectomy to destroy or remove β-cells. Serum betatrophin levels and betatrophin mRNA expressions in the liver, white adipose tissue (WAT) and brown adipose tissue (BAT) were measured. In DIO mice and db/db mice, serum betatrophin and betatrophin mRNA expressions in the liver, WAT and BAT were elevated in parallel with increases in body weight and plasma insulin. These elevated betatrophin mRNA expressions were not altered by treatment with SGLT2 inhibitor that ameliorated hyperglycemia. In pancreatectomized mice, betatrophin expression in WAT decreased in parallel with reductions in weight and insulin. In STZ-treated mice, betatrophin expressions in the liver, WAT and BAT were reduced. However, when the mouse liver slices were cultured with STZ, betatrophin expression was significantly reduced, indicating a direct action of STZ on the liver. These results indicate that the expression of betatrophin is upregulated in the liver, WAT and BAT in obese hyperinsulinemic type 2 diabetes but decreased in WAT in hypoinsulinemic type 1 diabetes, suggesting its positive correlation with body weight and plasma insulin but not blood glucose.

The Effects of Serum ANGPTL8/betatrophin on the Risk of Developing the Metabolic Syndrome - A Prospective Study

ANGPTL8/betatrophin is a recently discovered hormone, which mainly synthesized and secreted by liver and adipose tissue, playing a critical role in pancreatic beta cell proliferation. Previous studies have suggested that serum ANGPTL8/betatrophin levels are associated with obesity and diabetes mellitus. Here, we evaluated the prospective association between ANGPTL8/betatrophin and the metabolic syndrome from a community-based cohort of 153 adults without metabolic syndrome. After 3.5-year follow-up, we observed an inverse correlation between the baseline ANGPTL8/betatrophin levels and the incidence of metabolic syndrome, even after multivariate adjustments. In receiver operating characteristic analysis, the area underneath the curve for ANGPTL8/betatrophin was 0.70 in males and 0.86 in females, and the optimal cut-off values were 23.9 ng/mL and 31.1 ng/mL, respectively. This article suggests that ANGPTL8/betatrophin might be useful in predicting newly-onset metabolic syndrome and its progression in clinical setting.

Circulating angiopoietin-like protein 8 (betatrophin) association with HsCRP and metabolic syndrome

Background

ANGPTL8 also called betatrophin is a regulator of lipid metabolism through its interaction with ANGPTL3. It has also been suggested to play a role in insulin resistance and beta-cell proliferation. Based on its function, we hypothesized that ANGPTL8 will play a role in Metabolic Syndrome (MetS). To test this hypothesis we designed this study to measure ANGPTL8 level in subjects with MetS as well as its association with high sensitivity C-reactive protein (HsCRP) level in humans.

Methods

ANGPTL8 level was measured using ELISA in subjects with MetS as well as their controls, a total of 1735 subjects were enrolled. HsCRP was also measured and its association with ANGPTL8 was examined.

Results

ANGPTL8 level was higher in subjects with MetS 1140.6 (171.9–11736.1) pg/mL compared to 710.5 (59.5–11597.2) pg/mL in the controls. Higher levels of ANGPTL8 were also observed with the sequential increase in the number of MetS components (p value = <0.0001). ANGPTL8 showed strong positive correlation with HsCRP (r = 0.15, p value = <0.0001). Stratifying the population into tertiles according to the level of HsCRP showed increased ANGPTL8 level at higher tertiles of HsCRP in the overall population (p value = <0.0001).A similar trend was also observed in MetS and non-MetS subjects as well as in non-obese and obese subjects. Finally, multiple logistic regression models adjusted for age, gender, ethnicity and HsCRP level showed that subjects in the highest tertiles of ANGPTL8 had higher odds of having MetS (odd ratio [OR] = 2.3, 95 % confidence interval [CI] = (1.6–3.1), p value <0.0001.

Conclusion

In this study we showed that ANGPTL8 is increased in subjects with MetS and it was significantly associated with HsCRP levels in different subgroups highlighting its potential role in metabolic and inflammatory pathways.