ANGPTL8/betatrophin alleviates insulin resistance via the Akt-GSK3β or Akt-FoxO1 pathway in HepG2 cells

Association Between rs2278426 Polymorphism of the ANGPTL8 Gene and Polycystic Ovary Syndrome

Purpose

To study the relationship between the single nucleotide polymorphism (SNP) rs2278426 in the angiopoietin-like protein 8 gene (ANGPTL8) and polycystic ovary syndrome (PCOS).

Patients and methods

A total of 122 patients with PCOS and 108 controls were recruited for comparison of glucose, lipid, insulin, sex hormone, and ANGPTL8 levels. Polymerase chain reaction (PCR) and gene sequencing were performed for comparison of the frequency of the CC, CT, and TT rs2278426 genotypes and the rs2278426 allele distributions between the PCOS and control groups and between the obese and non-obese subgroups of the PCOS and control groups.

Results

The frequency of the T allele was significantly higher in the PCOS group than that in the controls (P = 0.037). In the dominant genetic model, the proportion of the CT+TT genotype in the PCOS group was significantly higher than that in the controls (P = 0.047). Subgroup analysis demonstrated that the T allele proportion was significantly higher in obese PCOS group than obese control group (P = 0.027). PCOS with the CT+TT genotype had significantly higher body mass index (BMI; P = 0.001), triglyceride (TG; P = 0.005), homeostasis model assessment of insulin resistance (HOMA-IR; P = 0.035), testosterone (P = 0.041), and ANGPTL8 (P = 0.037) levels and significantly lower high-density lipoprotein (HDL) levels (P = 0.025) than PCOS with the CC genotype. Obese PCOS group with the CT+TT genotype had significantly higher TG (P = 0.015), luteinizing hormone (LH; P = 0.030), fasting insulin (FINS; P = 0.039), HOMA-IR (P = 0.018), and ANGPTL8 (P = 0.049) levels than obese PCOS group with the CC genotype.

Conclusion

Polymorphisms of rs2278426 may induce glycolipid metabolic disorders by affecting ANGPTL8 levels and functions in Han Chinese females with obesity from the Shandong region, increasing the risk of PCOS in this population.

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.

Positive correlation of ANGPTL8 expression in human visceral adipose tissue with body mass index

BACKGROUND

Angiopoietin-like protein 8 (ANGPTL8) is an important regulator of lipid metabolism. We aimed to investigate the difference of ANGPTL8 expression in different depots of adipose tissues between individuals with and without obesity, and its correlation with various metabolic parameters.

METHODS

Subcutaneous (SAT) and visceral adipose tissue (VAT) samples were collected from patients who underwent bariatric or intra-abdominal surgery. Expression levels of ANGPTL8, monoglyceride lipase (MGL), monocyte chemoattractant protein-1 (MCP-1), leptin and adiponectin (APM1) were determined using real-time quantitative polymerase chain reaction. The correlation of ANGPTL8 expression with various metabolic parameters and other gene expression levels was analyzed using Person's correlation analysis. Logistic regression was used to establish a prediction model of obesity.

RESULTS

Totally 330 subjects (obese: 281, non-obese: 49) were recruited. ANGPTL8 expression in VAT was significantly higher in the obesity group than in the non-obesity group (P = 0.0096). ANGPTL8 expression in VAT was positively correlated with body mass index (BMI) (r = 0.1169, P < 0.05) and was independently associated with obesity (O.R., 1.246; 95 % C.I. 1.013-21.533, P = 0.038). We also found the gene expression of ANGPTL8 in SAT and VAT was negatively correlated with APM1 expression in respective SAT and VAT.

CONCLUSIONS

ANGPTL8 expression levels in VAT were higher in subjects with obesity, and positively correlated with BMI. This suggests a role of ANGPTL8 in the pathophysiology of obesity and may pave the way for novel treatment target of obesity.

Investigation of the relationship between betatrophin and certain key enzymes involved in carbohydrate and lipid metabolism in insulin-resistant mice

OBJECTIVES

The present study sought to examine the relationship of betatrophin with certain key enzymes, namely lactate dehydrogenase-5 (LDH5), citrate synthase (CS), and acetyl-CoA carboxylase-1 (ACC1), in insulin-resistant mice.

METHODS

Eight-week-old male C57BL6/J mice were used in this study (experimental group n=10 and control group n=10). S961 was administered using an osmotic pump to induce insulin resistance in the mice. The betatrophin, LDH5, CS, and ACC1 expression levels were determined from the livers of the mice using the real-time polymerase chain reaction (RT-PCR) method. Moreover, biochemical parameters such as the serum betatrophin, fasting glucose, insulin, triglyceride, total cholesterol, and high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol levels were analyzed.

RESULTS

The betatrophin expression and serum betatrophin (p=0.000), fasting glucose, insulin, triglyceride (p≤0.001), and total cholesterol (p=0.013) levels were increased in the experimental group. In addition, the CS gene expression level was statistically significantly decreased in the experimental group (p=0.01). Although strong correlation was found between the expression and serum betatrophin and triglyceride levels, no correlation was found between the betatrophin gene expression and the LDH5, ACC1, and CS gene expression levels.

CONCLUSIONS

The betatrophin level appears to play an important role in the regulation of triglyceride metabolism, while insulin resistance increases both the betatrophin gene expression and serum levels and decreases the CS expression level. The findings suggest that betatrophin may not regulate carbohydrate metabolism through CS and LDH5 or lipid metabolism directly through the ACC1 enzyme.

Dual role of ANGPTL8 in promoting tumor cell proliferation and immune escape during hepatocarcinogenesis

The interplay between hepatocellular carcinoma (HCC) cells and the tumor microenvironment is essential for hepatocarcinogenesis, but their contributions to HCC development are incompletely understood. We assessed the role of ANGPTL8, a protein secreted by HCC cells, in hepatocarcinogenesis and the mechanisms through which ANGPTL8 mediates crosstalk between HCC cells and tumor-associated macrophages. Immunohistochemical, Western blotting, RNA-Seq, and flow cytometry analyses of ANGPTL8 were performed. A series of in vitro and in vivo experiments were conducted to reveal the role of ANGPTL8 in the progression of HCC. ANGPTL8 expression was positively correlated with tumor malignancy in HCC, and high ANGPTL8 expression was associated with poor overall survival (OS) and disease-free survival (DFS). ANGPTL8 promoted HCC cell proliferation in vitro and in vivo, and ANGPTL8 KO inhibited the development of HCC in both DEN-induced and DEN-plus-CCL4-induced mouse HCC tumors. Mechanistically, the ANGPTL8-LILRB2/PIRB interaction promoted polarization of macrophages to the immunosuppressive M2 phenotype in macrophages and recruited immunosuppressive T cells. In hepatocytes, ANGPTL8-mediated stimulation of LILRB2/PIRB regulated the ROS/ERK pathway and upregulated autophagy, leading to the proliferation of HCC cells. Our data support the notion that ANGPTL8 has a dual role in promoting tumor cell proliferation and immune escape during hepatocarcinogenesis.

Maternal and cord blood betatrophin (angiopoietin-like protein 8) in pregnant women with gestational diabetes and normoglycemic controls: A systematic review, meta-analysis, and meta-regression

AIMS

This systematic review and meta-analysis examined maternal and cord blood betatrophin levels in pregnant women with gestational diabetes mellitus (GDM) and normoglycemic controls.

MATERIAL AND METHODS

PubMed, Cochrane Library, Embase, LILACS, WangFang, and China National Knowledge Infrastructure were searched for literature from inception until May 2022. The primary outcomes were maternal and cord blood betatrophin levels. A random-effect meta-analysis was used to estimate the pooled results. The mean differences (MDs) or standardised MDs (SMD) and their 95% confidence intervals (CIs) were calculated. I² tests were used to evaluate the heterogeneity. The quality of studies was evaluated using the Newcastle-Ottawa Scale.

RESULTS

Betatrophin levels were reported in 22 studies with a total of 3034 pregnant women, and in seven studies including cord blood from 456 infants. Women with GDM display higher betatrophin levels than the normoglycemic controls (SMD = 0.85, 95% CI: 0.38-1.31) during the second half of the pregnancy. The sensitivity analysis indicated that no single study had significantly influenced the betatrophin overall outcomes. There was heterogeneity between the studies as evidenced by high I² values. Meta-regression analysis indicated a significant regression coefficient for maternal betatrophin and glycosilated haemoglobin. There was no significant difference in cord blood betatrophin in infants from women with and without GDM (SMD = 0.34, 95% CI: -0.15-0.83). Women with GDM also had significantly higher insulin, glucose, glycosylated haemoglobin, HOMA-IR, LDL-cholesterol, HDL-cholesterol, triglycerides, and body mass index compared with the normoglycemic controls.

CONCLUSIONS

Maternal betatrophin levels were higher in women with GDM than in the normoglycemic controls. There was no difference in cord blood betatrophin.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022311372.

Betatrophin and Insulin Resistance

Betatrophin (angiopoietin-like protein 8 (ANGPTL8)) is a hormone that was recently discovered in the human liver. Multiple homologous sequences have been detected in mammalian liver, white adipose, and brown adipose tissues. Betatrophin is crucial for the development of type 2 diabetes (T2D), insulin resistance, and lipid metabolism. Similar to the intake of insulin, thyroid hormones, irisin, and calories, betatrophin expression in the organism is usually attributed to energy consumption or heat generation. It can mediate the activity of lipoprotein lipase (LPL), which is the key enzyme of lipoprotein lipolysis. Due to its association with metabolic markers and the roles of glucose and lipid, the physiological function of betatrophin in glucose homeostasis and lipid metabolism can be more comprehensively understood. Betatrophin was also shown to facilitate pancreatic β-cell proliferation in a mouse model of insulin resistance. There are also reports that demonstrate that betatrophin regulates triglycerides (TGs) in the liver. Therefore, the process of regulating the physiological function by betatrophin is complicated, and its exact biological significance remains elusive. This study provides a comprehensive review of the current research, and it discusses the possible physiological functions of betatrophin, and specifically the mechanism of betatrophin in regulating blood glucose and blood lipids.

Angiopoietin-like protein 8 (betatrophin) inhibits hepatic gluconeogenesis through PI3K/Akt signaling pathway in diabetic mice

BACKGROUND & AIMS

Angiopoietin-like protein 8 (ANGPTL8) is a 198 amino-acid long, novel secreted protein that is mainly expressed in the liver and brown adipose tissues. At present, evidence supporting the involvement of ANGPTL8 in the regulation of glucose metabolism is inconclusive, along with its function in the liver. Previous studies mainly focused on the effect of ANGPTL8 on glucose metabolism in non-diabetic mice, and few relevant studies in diabetic mice exist. Therefore, this study aimed to investigate the role of ANGPTL8 on glucose homeostasis and elucidate the underlying mechanisms in diabetic mice.

METHODS

db/db diabetic and high-fat diet/streptozotocin-induced diabetic mice were injected with adenovirus expressing ANGPTL8 through the tail vein. Blood glucose levels were measured and glucose, insulin, and pyruvate tolerance tests were performed. To explore the molecular mechanism by which ANGPTL8 regulates hepatic glucose metabolism and manipulate mouse ANGPTL8 expression levels both in vivo and in vitro based on adenoviral transduction, gain- and loss-of-function strategies were adopted.

RESULTS

Adenovirus-mediated overexpression of ANGPTL8 decreased fasting blood glucose levels and improved glucose tolerance and insulin sensitivity in db/db and high-fat diet/streptozotocin-induced diabetic mice. ANGPTL8 knockdown yielded the opposite effects. ANGPTL8 was upregulated in the cAMP/Dex-induced hepatocyte gluconeogenesis model. Moreover, ANGPTL8 overexpression in primary hepatocytes and diabetic mouse livers inhibited the expression of gluconeogenesis-related genes, including PEPCK and G6PC, by activating the AKT signaling pathway and, thereby, reducing glucose production. Therefore, the results demonstrated that ANGPTL8 improved glucose metabolism via inhibition of hepatic gluconeogenesis in diabetic mice.

CONCLUSIONS

Current findings highlight a critical role of hepatic ANGPTL8 in glucose homeostasis, suggesting that increased ANGPTL8 expression could be an underlying factor for the inhibition of hepatic gluconeogenesis, which could be targeted for the prevention and treatment of type 2 diabetes.

Analysis of the Expression and Prognostic Potential of a Novel Metabolic Regulator ANGPTL8/Betatrophin in Human Cancers

The angiopoietin-like protein (ANGPTL) family members, except for the novel atypical member ANGPTL8/betatrophin, have been reported to participate in angiogenesis, inflammation and cancer. ANGPTL8/betatrophin is a metabolic regulator that is involved in lipid metabolism and glucose homeostasis. However, little is known about the expression and prognostic value of ANGPTL8/betatrophin in human cancers. In this study, we first conducted detailed analyses of ANGPTL8/betatrophin expression in cancer/normal samples via the Human Protein Atlas (HPA), Gene Expression Profiling Interactive Analysis (GEPIA), DriverDBv3, ENCORI and UALCAN databases. ANGPTL8/betatrophin showed high tissue specificity (enriched in the liver) and cell-type specificity (enriched in HepG2 and MCF7 cell lines). More than one databases demonstrated that the gene expression of ANGPTL8/betatrophin was significantly lower in cholangiocarcinoma (CHOL), breast invasive carcinoma (BRCA), lung adenocarcinoma (LUAD), lung squamous cell carcinoma (LUSC), uterine corpus endometrial carcinoma (UCEC), and significantly higher in kidney renal clear cell carcinoma (KIRC) compared with that in normal samples. However, the protein expression of ANGPTL8/betatrophin displayed opposite results in clear cell renal cell carcinoma (ccRCC)/KIRC. Based on the expression profiles, the prognostic value was evaluated with the GEPIA, DriverDBv3, Kaplan Meier plotter and ENCORI databases. Two or more databases demonstrated that ANGPTL8/betatrophin significantly affected the survival of KIRC, uterine corpus endometrial carcinoma (UCEC), pheochromocytoma and paraganglioma (PCPG) and sarcoma (SARC); patients with PCPG and SARC may benifit from high ANGPTL8/betatrophin expression while high ANGPTL8/betatrophin expression was associated with poor prognosis in KIRC and UCEC. Functional analyses with the GeneMANIA, Metascape and STRING databases suggested that ANGPTL8/betatrophin was mainly involved in lipid homeostasis, especially triglyceride and cholesterol metabolism; glucose homeostasis, especially insulin resistance; AMPK signaling pathway; PI3K/Akt signaling pathway; PPAR signaling pathway; mTOR signaling pathway; HIF-1 signaling pathway; autophagy; regulation of inflammatory response. ANGPTL8/betatrophin may be a promising prognostic biomarker and therapeutic target, thus providing evidence to support further exploration of its role in defined human cancers.

Association of ANGPTL8 and Resistin With Diabetic Nephropathy in Type 2 Diabetes Mellitus

Background

Previous studies showed altered angiopoietin-like protein-8 (ANGPTL-8) and resistin circulating levels in type 2 diabetes mellitus (T2DM). Whether or not the alteration in ANGPTL-8 and resistin level can be a predictive maker for increased diabetic nephropathy risk remains unclear.

Aim

To Investigate the possible association of ANGPTL-8 and resistin with DN, and whether this association is affected by NAFLD status.

Methods

A total of 278 T2DM patients were enrolled. Serum levels of ANGPTL8, resistin, BMI, blood pressure, duration of diabetes, glycosylated hemoglobin (HbA1c), fasting blood glucose (FPG), hypersensitive C-reactive protein (hs-CRP), lipid profile, liver, and kidney function tests were assessed. The relationship between DN with ANGPTL8 and resistin was analyzed in the unadjusted and multiple-adjusted regression models.

Results

Serum levels of ANGPTL8 and resistin were significantly higher in DN compared with T2DM subjects without DN (respectively; P <0.001), especially in non-NAFLD populations. ANGPTL8 and resistin showed positive correlation with hs-CRP (respectively; P<0.01), and negative correlation with estimated GFR (eGFR) (respectively; P=<0.001) but no significant correlation to HOMA-IR(respectively; P>0.05). Analysis showed ANGPTL8 levels were positively associated with resistin but only in T2DM patients with DN(r=0.1867; P<0.05), and this significant correlation disappeared in T2DM patients without DN. After adjusting for confounding factors, both ANGPTL8(OR=2.095, 95%CI 1.253-3.502 P=0.005) and resistin (OR=2.499, 95%CI 1.484-4.208 P=0.001) were risk factors for DN. Data in non-NAFLD population increased the relationship between ANGPTL8 (OR=2.713, 95% CI 1.494-4.926 P=0.001), resistin (OR=4.248, 95% CI 2.260-7.987 P<0.001)and DN. The area under the curve (AUC) on receiver operating characteristic (ROC) analysis of the combination of ANGPTL8 and resistin was 0.703, and the specificity was 70.4%. These data were also increased in non-NAFLD population, as the AUC (95%CI) was 0.756, and the specificity was 91.2%.

Conclusion

This study highlights a close association between ANGPTL8, resistin and DN, especially in non-NAFLD populations. These results suggest that ANGPTL-8 and resistin may be risk predictors of DN.

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.

Down-regulation of betatrophin enhances insulin sensitivity in type 2 diabetes mellitus through activation of the GSK-3β/PGC-1α signaling pathway

OBJECTIVE

The incidence of type 2 diabetes mellitus (T2DM) among children and adolescents has been rising. Accumulating evidences have noted the significant role of betatrophin in the regulation of lipid metabolism and glucose homeostasis. In our study, we tried to figure out the underlying mechanism of betatrophin in insulin resistance (IR) in type 2 diabetes mellitus (T2DM).

METHODS

First, fasting serum betatrophin, fasting blood glucose (FBG), insulin, total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) were detected in T2DM children. The homeostasis model assessment of insulin resistance (HOMA-IR), Gutt insulin sensitivity index (ISI_G) and Matsuda insulin sensitivity index (ISI_M) were calculated. A T2DM-IR mouse model was induced by high-fat diet, with the expression of GSK-3β and PGC-1α detected. Besides, HepG2 cells were induced by a high concentration of insulin to establish an IR cell model (HepG2-IR). The cell viability, glucose consumption, liver glycogen content, inflammation, and fluorescence level of GSK-3β and PGC-1α were analyzed.

RESULTS

Betatrophin was highly expressed in serum of T2DM children and was positively correlated with FBG, insulin, TC, TG, LDL-C and HOMA-IR, while negatively correlated with ISI_G and ISI_M. Betatrophin and GSK-3β in the liver tissues of T2DM-IR mice were increased, while the PGC-1α expression was decreased. Betatrophin expression was negatively correlated with PGC-1α and positively correlated with GSK-3β. Silencing of betatrophin enhanced insulin sensitivity through the activation of GSK-3β/PGC-1α signaling pathway. In vitro experiments also found that silencing of betatrophin promoted glucose consumption and glycogen synthesis while inhibited inflammation.

CONCLUSION

Our findings concluded that silencing of betatrophin could enhance insulin sensitivity and improve histopathological morphology through the activation of GSK-3β/PGC-1α signaling pathway.

Potential of Phage Display Antibody Technology for Cardiovascular Disease Immunotherapy

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. CVD includes coronary artery diseases such as angina, myocardial infarction, and stroke. "Lipid hypothesis" which is also known as the cholesterol hypothesis proposes the linkage of plasma cholesterol level with the risk of developing CVD. Conventional management involves the use of statins to reduce the serum cholesterol levels as means for CVD prevention or treatment. The regulation of serum cholesterol levels can potentially be regulated with biological interventions like monoclonal antibodies. Phage display is a powerful tool for the development of therapeutic antibodies with successes over the recent decade. Although mainly for oncology, the application of monoclonal antibodies as immunotherapeutic agents could potentially be expanded to CVD. This review focuses on the concept of phage display for antibody development and discusses the potential target antigens that could potentially be beneficial for serum cholesterol management.

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.

ANGPTL8/Betatrophin Improves Glucose Tolerance in Older Mice and Metabolomic Analysis Reveals Its Role in Insulin Resistance in HepG2 Cells

BACKGROUND

Insulin resistance is a determining factor in the pathophysiology of type 2 diabetes mellitus (T2DM). Angiopoietin-like protein 8 (ANGPTL8, also known as betatrophin), associated with glucose homeostasis and lipid metabolism, has attracted attention. But its mechanism in glucose metabolism remains unclear. This study aimed to explore the effect of ANGPTL8/betatrophin on glucose tolerance in Kunming (KM) mice of different ages and metabolic profiles in insulin-resistant HepG2 cells. Our study may provide a new perspective of ANGPTL8/betatrophin in insulin resistance from the metabolic changes.

METHODS

Oral glucose tolerance test was performed in KM mice of different ages. Insulin concentration was measured by using a quantitative enzyme-linked immunosorbent assay (ELISA). ANGPTL8/betatrophin knockouts in HepG2 cells were established with clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) protein 9 (CRISPR/Cas9) system. Cell counting kit-8 (CCK-8) assay was used to determine cell viability after gene knockout. The effect of ANGPTL8/betatrophin on the metabolomic changes was evaluated in high insulin-induced insulin-resistant HepG2 cells by an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method.

RESULTS

ANGPTL8/betatrophin improved glucose tolerance in older mice not by altering the concentration of insulin. Cell growth was affected in ANGPTL8/betatrophin knockout HepG2. Based on UPLC-MS/MS, compared with wild type insulin-resistant HepG2 cells, we identified 83 differential metabolites in ANGPTL8/betatrophin knockout HepG2 cells after high insulin induction. Among the 14 differential up-regulated metabolites, D-mannose had the highest fold change. In insulin-resistant HepG2 cells, ANGPTL8/betatrophin knockout exerted an effect on the amino acid metabolism, carbohydrate metabolism, metabolism of cofactors and vitamins, lipid metabolism, nucleotide metabolism, and genetic information processing pathway.

CONCLUSION

This study identified the effect of ANGPTL8/betatrophin on glucose tolerance in mice of different ages and metabolic profiles in insulin-resistant HepG2 cells. These findings may contribute to a new understanding of its role in glucose metabolism in the context of insulin resistance.

Apolipoprotein CIII and Angiopoietin-like Protein 8 are Elevated in Lipodystrophy and Decrease after Metreleptin

Context

Lipodystrophy syndromes cause hypertriglyceridemia that improves with leptin treatment using metreleptin. Mechanisms causing hypertriglyceridemia and improvements after metreleptin are incompletely understood.

Objective

Determine relationship of circulating lipoprotein lipase (LPL) modulators with hypertriglyceridemia in healthy controls and in patients with lipodystrophy before and after metreleptin.

Methods

Cross-sectional comparison of patients with lipodystrophy (generalized lipodystrophy n = 3; partial lipodystrophy n = 11) vs age/sex-matched healthy controls (n = 28), and longitudinal analyses in patients before and after 2 weeks and 6 months of metreleptin. The study was carried out at the National Institutes of Health, Bethesda, Maryland. Outcomes were LPL stimulators apolipoprotein (apo) C-II and apoA-V and inhibitors apoC-III and angiopoietin-like proteins (ANGPTLs) 3, 4, and 8; ex vivo activation of LPL by plasma.

Results

Patients with lipodystrophy were hypertriglyceridemic and had higher levels of all LPL stimulators and inhibitors vs controls except for ANGPTL4, with >300-fold higher ANGPTL8, 4-fold higher apoC-III, 3.5-fold higher apoC-II, 1.9-fold higher apoA-V, 1.6-fold higher ANGPTL3 (P < .05 for all). At baseline, all LPL modulators except ANGPLT4 positively correlated with triglycerides. Metreleptin decreased apoC-II and apoC-III after 2 weeks and 6 months, and decreased ANGPTL8 after 6 months (P < 0.05 for all). Plasma from patients with lipodystrophy caused higher ex vivo LPL activation vs hypertriglyceridemic control plasma (P < .0001), which did not change after metreleptin.

Conclusion

Elevations in LPL inhibitors apoC-III and ANGPTL8 may contribute to hypertriglyceridemia in lipodystrophy, and may mediate reductions in circulating and hepatic triglycerides after metreleptin. These therefore are strong candidates for therapies to lower triglycerides in these patients.

Angiopoietin-like protein 3, an emerging cardiometabolic therapy target with systemic and cell-autonomous functions

Angiopoietin like protein 3 (ANGPTL3) is best known for its function as an inhibitor of lipoprotein and endothelial lipases. Due to the capacity of genetic or pharmacologic ANGPTL3 suppression to markedly reduce circulating lipoproteins, and the documented cardioprotection upon such suppression, ANGPTL3 has become an emerging therapy target for which both antibody and antisense oligonucleotide (ASO) therapeutics are being clinically tested. While the antibody is relatively selective for circulating ANGPTL3, the ASO also depletes the intra-hepatocellular protein, and there is emerging evidence for cell-autonomous functions of ANGPTL3 in the liver. These include regulation of hepatocyte glucose and fatty acid uptake, insulin sensitivity, LDL/VLDL remnant uptake, VLDL assembly/secretion, polyunsaturated fatty acid (PUFA) and PUFA-derived lipid mediator content, and gene expression. In this review we elaborate on (i) why ANGPTL3 is considered one of the most promising new cardiometabolic therapy targets, and (ii) the present evidences for its intra-hepatocellular or cell-autonomous functions.

Betatrophin is downregulated in pregnant women with a history of RYGB operation and a high risk of postprandial hypoglycaemia

Betatrophin is a liver and adipose tissue-derived protein which has recently been linked to glucose metabolism. So far, no data exist about the role of betatrophin in pregnant women with a history of Roux-En-Y gastric bypass (RYGB) operation with a high risk of postprandial hypoglycaemia. In this prospective clinical study, an oral glucose tolerance test (OGTT) and an intravenous glucose tolerance test (IVGTT) were performed between the 24th and 28th week of pregnancy and 3–6 months post-partum in a cohort of obese and normal-weight pregnant women, as well as in women with a history of RYGB operation. In the cohort of pregnant women with RYGB and exaggerated risk of postprandial hypoglycaemic events, basal and dynamic betatrophin levels during the OGTT were lower than in the obese or normal-weight pregnant women (basal levels: 13.66 ± 5.88 vs. 19.03 ± 4.15 vs. 15.68 ± 6.48, p = 0.016; OGTT 60′: 13.33 ± 5.40 vs. 17.37 ± 3.16 vs. 15.84 ± 4.99, p = 0.030). During the OGTT, basal and dynamic betatrophin levels at 60′ were positively associated with glucose levels at 60 min (r = 0.55, p = 0.01 and r = 0.45, p = 0.039). This positive association was followed by significant hypoglycaemic events in the RYGB group. It was only in the RYGB group that betatrophin was negatively related to the disposition index (rho = -0.53, p = 0.014). After pregnancy there was a decrease in basal and stimulated betatrophin levels during the OGTT in all three patient groups. In comparison to normal-weight and obese pregnant women, women with a history of RYGB operation and a high risk of postprandial hypoglycaemic events have lower levels of betatrophin. This indicate a mechanistic role in order to decrease the risk of postprandial hypoglycaemia in this specific cohort.

Anti proliferative and apoptotic effects on pancreatic cancer cell lines indicate new roles for ANGPTL8 (Betatrophin)

Despite considerable advances, the treatment of pancreatic cancer (PC) still requires much effort. Unusual regulation of the Wnt and apoptotic signaling pathways is widespread in cancer incidence. For instance, the WIF1 (Wnt inhibitory factor 1) gene is down-regulated in many cancers. The purpose of this study was to determine the effects of recombinant Betatrophin, a recently discovered hormone, on MiaPaca-II and Panc-1 pancreatic cell lines. Various concentrations of Betatrophin were added to MiaPaca-II and Panc-1 pancreatic cell lines during periods of 24 , 48, and 72 h. The MTT assay was applied to investigate cell proliferation after treatment. The rate of apoptotic cells was assessed using double-staining flow cytometry, and the expression levels of the WIF1 gene and Bcl2 protein was observed by real-time PCR and western blotting, respectively. The findings of this study suggest that Betatrophin has an anti-proliferative effect on both MiaPaca-II and Panc-1 cell lines, in line with the up-regulation of WIF1 as a tumor suppressor gene. Moreover, the induction of apoptosis by ANGPTL8 occurred by the down-regulation of Bcl2. Thus, Betatrophin can be proposed as a potential therapeutic drug for treating pancreatic cancer.

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.

ANGPTL8 enhances insulin sensitivity by directly activating insulin-mediated AKT phosphorylation

ANGPTL8 is a 22-KDa protein in the angiopoietin-like family. It is a liver-derived hormone that dynamically regulates glucose metabolism after refeeding. The mechanism of its regulation of glucose metabolism is unclear. We analyzed the effect of ANGPTL8 overexpression on glucose tolerance in the mouse liver by tail vein hydrodynamic transfection. The mechanism of ANGPTL8 improving insulin sensitivity was analyzed by the overexpression or knockdown of ANGPTL8 in mouse primary hepatocytes through in vitro synthetic mRNA and siRNA technology. The key site of ANGPTL8 protein regulating this signal pathway was screened by DNA point mutation and fragment truncation. The results showed that ANGPTL8 may directly regulate AKT protein phosphorylation in the insulin-mediated PI3K/AKT signaling pathway to improve insulin sensitivity. Ser94 and Thr98 are the key sites of ANGPTL8 protein in activating AKT protein phosphorylation. Present results indicate that ANGPTL8 may be a potential new agent to reduce postprandial blood glucose.

Deciphering the expression dynamics of ANGPTL8 associated regulatory network in insulin resistance using formal modelling approaches

ANGPTL8 is a recently identified novel hormone which regulates both glucose and lipid metabolism. The increase in ANGPTL8 during compensatory insulin resistance has been recently reported to improve glucose tolerance and a part of cytoprotective metabolic circuit. However, the exact signalling entities and dynamics involved in this process have remained elusive. Therefore, the current study was conducted with a specific aim to model the regulation of ANGPTL8 with emphasis on its role in improving glucose tolerance during insulin resistance. The main contribution of this study is the construction of a discrete model (based on kinetic logic of René Thomas) and its equivalent Stochastic Petri Net model of ANGPTL8 associated Biological Regulatory Network (BRN) which can predict its dynamic behaviours. The predicted results of these models are in‐line with the previous experimental observations and provide comprehensive insights into the signalling dynamics of ANGPTL8 associated BRN. The authors’ results support the hypothesis that ANGPTL8 plays an important role in supplementing the insulin signalling pathway during insulin resistance and its loss can aggravate the pathogenic process by quickly leading towards Diabetes Mellitus. The results of this study have potential therapeutic implications for treatment of Diabetes Mellitus and are suggestive of its potential as a glucose‐lowering agent.

Evidences for Expression and Location of ANGPTL8 in Human Adipose Tissue

The metabolism of triglycerides (TGs) is regulated, among others, by the lipoprotein lipase (LPL) that hydrolyses the TGs on endothelial cells. In turn, LPL is inhibited by the ANGPTLs family of proteins, such as ANGPTL3, 4, and, 8; the latter is the least known. In this work, we have tried to establish the expression and localisation of the Angiopoietin-like 8 (ANGPTL8) protein in the visceral adipose tissue (VAT) of morbid-obese and non-obese patients. 109 subjects (66 women and 43 men) undergoing laparoscopic surgery participated in this study. A blood sample and a portion of the VAT were obtained, and the patients were classified according to their Body Mass Index (BMI) as non-obese (19.5–30 kg/m²) and morbid-obese (40–50 kg/m²). No significant changes in ANGPTL8 plasma levels were determined by EIA in obese patients. The immunocytochemistry and Western blotting showed the presence of increased ANGPTL8 in morbid-obese patients (p < 0.05). In-situ hybridisation and a real time polymerase chain reaction (RT-PCR) confirmed that the mRNA that encodes ANGPTL8 was present in adipocytes, without differences in their nutritional state (p = 0.89), and even in the endothelial cells. Our data suggests that ANGPT8 plasmatic levels do not change significantly in patients with morbid obesity, although there is a modest difference related to gender. Besides, we demonstrate that in visceral adipose tissue, ANGPTL8 is well defined in the cytoplasm of adipocytes coexisting with perilipin-1 and its mRNA, also is present in endothelial cells. These findings suggest the possibility that among other functions, ANGPTL8 could perform either a paracrine and/or an endocrine role in the adipose tissue.

Angiopoietin-like proteins as therapeutic targets for cardiovascular disease: focus on lipid disorders

Introduction: Angiopoietin-like (ANGPTL) proteins belong to a family of eight secreted factors that are structurally related to proteins that modulate angiogenesi, commonly known as angiopoietins. Specifically, ANGPTL3, ANGPTL4, and ANGPTL8 (the 'ANGPT L3-4-8 triad'), have surfaced as principal regulators of plasma lipid metabolism by functioning as potent inhibitors of lipoprotein lipase. The targeting of these proteins may open up future therapeutic avenues for metabolic and cardiovascular disease.Areas covered: This article systematically summarizes the compelling literature describing the mechanistic roles of ANGPTL3, 4, and 8 in lipid metabolism, emphasizing their importance in determining the risk of cardiovascular disease. We shed light on population-based studies linking loss-of-function variations in ANGPTL3, 4, and 8 with decreased risk of metabolic conditions and cardiovascular disorders. We also discuss how the strategies aiming at targeting the ANGPT L3-4-8 triad could offer therapeutic benefit in the clinical scenario.Expert opinion: Monoclonal antibodies and antisense oligonucleotides that target ANGPTL3, 4, and 8 are potentially an efficient therapeutic strategy for hypertriglyceridemia and cardiovascular risk reduction, especially in patients with limited treatment options. These innovative therapeutical approaches are at an embryonic stage in development and hence further investigations are necessary for eventual use in humans.

The Role of PPARδ Agosnist GW501516 in Rats with Gestational Diabetes Mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is a disorder of glucose metabolism that occurs or is found for the first time during pregnancy. GDM is very harmful and urgently needs drug treatment to improve pregnancy outcome. PPARδ is involved in a variety of biological processes related to glycolipid metabolism in the body, suggesting that it may be closely related to insulin resistance and impaired glucose tolerance. The role of PPARδ agonist GW501516 in gestational diabetes has not been studied.

METHODS

Firstly, the rat model of GDM was established. Then, fasting blood-glucose (FGB), fasting insulin (FINS), HOMA-islet resistance index (HOMA-IR) and insulin sensitivity index (ISI) of GDM rats treated with GW501516 were measured on day 3, day 10 and day 17. Glucose tolerance test was performed on the 20th day of gestation to measure glucose tolerance in rats. The expression of PPARδ and Angptl8 in islet tissues of rats was detected by Western blot and immunohistochemistry (IHC). Histopathological changes of islet were detected by HE stain; apoptosis rate of islet cells was detected by Tunel; and expression of apoptosis-related proteins in the cells was detected by Western blot. The biochemical kits were used to detect the expression of lipid metabolism-related factors in blood of GDM rats after the PPARδ agonist GW501516 treatment. Finally, the expression of SREBP-1c and GLUT2 in islet tissues was detected by RT-qPCR and IHC.

RESULTS

The PPARδ agonist GW501516 decreased the expression of FGB, FINS and HOMA-IR in GDM rats, and we found that GW501516 decreased ISI in GDM rats. GW501516 increased glucose tolerance in GDM rats too. In GDM rats, the expression of PPARδ in islet decreased and the expression of Angptl8 increased, which was reversed by GW501516. In addition, we also found that GW501516 can improve the damaged islet tissue of GDM rats, reduce the apoptosis rate of islet cells and inhibit the expression of lipid metabolism-related factors in the blood. Finally, we found that GW501516 inhibited the expression of SREBP-1c and promoted the expression of GLUT2 in the islet tissue.

CONCLUSION

The PPARδ agonist GW501516 could improve the blood glucose level, damaged islet tissue and increase the insulin content in the rats with GDM, possibly by regulating the SREBP-1c/GLUT2 pathway. Our study provided a new basis for clinical treatment of GDM in pregnant women with PPARδ agonist GW501516.

ANGPTL8 Gene Polymorphism rs2278426 Is Related to Carotid Intima-Media Thickness in T2DM

AIM

ANGPTL8 is a cytokine expressed and secreted by liver and adipose tissue, and is involved in glucose, lipid, and energy metabolism. Although studies have shown that ANGPTL8 is elevated in type 2 diabetes mellitus (T2DM) and cardiovascular disease, few have examined the association between ANGPTL8 single-nucleotide polymorphisms and the risk of macrovascular complications in T2DM patients. This study aimed to explore the relationship between rs2278426 and carotid intima-media thickening (cIMT) in T2DM.

METHODS

A total of 217 T2DM patients and 201 healthy control subjects with normal glucose tolerance were recruited in the study. T2DM patients were divided into two groups: T2DM patients without cIM thickening (cIMT <1 mm, 109 cases) and T2DM patients with cIM thickening (cIMT ≥1 mm, 108 cases). rs2278426 genotypes in all 418 subjects were determined and the risk of T2DM and T2DM with cIM thickening analyzed.

RESULTS

CT+TT-genotype frequency in T2DM was higher than in controls with normal glucose tolerance, and the proportion of the CT+TT genotype in the group with cIMT was higher than in the group (P<0.05). In addition, T alleles were associated with waist:hip ratio, triglycerides, high density-lipoprotein cholesterol, plasma glucose at 2 hours' oral glucose tolerance, and homeostatic model assessment of insulin resistance (P<0.05).

CONCLUSION

Generally, carriers of the T allele at rs2278426 are more likely to develop T2DM, and the risk of cIM thickening is significantly increased for T-allele carriers with T2DM, which indicates an increased risk of macroangiopathy.

The ANGPTL8 rs2278426 (C/T) Polymorphism Is Associated with Prediabetes and Type 2 Diabetes in a Han Chinese Population in Hebei Province

BACKGROUND

Our aim was to investigate the association between the genetics of the angiopoietin protein-like 8 (ANGPTL8) rs2278426 (C/T) polymorphism with prediabetes (pre-DM) and type 2 diabetes (T2DM) in a Han Chinese population in Hebei Province, China.

METHODS

We enrolled 1,460 participants into this case-control study: healthy controls, n = 524; pre-DM, n = 460; and T2DM: n = 460. Ligase assays on blood samples from all participants were used to identify polymorphisms. Differences in genotype and allele distributions were compared by the chi-square test and one-way analysis of variance, and a post hoc pairwise analysis was performed using the Bonferroni test. The logistic regression technique was adjusted for age, sex, and body mass index.

RESULTS

The frequency of the TT (10.9%) genotype was significantly higher in pre-DM patients than in controls (odds ratio [OR] = 1.696, 95% confidence interval [CI] = 1.026-2.802, P=0.039). In the T2DM group, the CT (48%) and TT (15%) genotypes were significantly higher compared with those in the control group (CT : OR = 1.384, 95% CI = 1.013-1.890, P=0.041; TT : OR = 2.530, 95% CI = 1.476-4.334, P=0.001). The frequency of the T allele was significantly higher in the pre-DM (32.8%) and T2DM (39%) groups compared with the control group (26.9%) and was significantly associated with an increased risk of pre-DM (OR = 1.253, 95% CI = 1.017-1.544, P=0.034) and T2DM (OR = 1.518, 95% CI = 1.214-1.897, P=0.001). Furthermore, insulin levels in the pre-DM and T2DM groups were significantly decreased in those with the TT genotype compared with the CC and CT genotypes.

CONCLUSION

ANGPTL8 rs2278426 may be involved in the mechanism of insulin secretion and could lead to an increased risk of pre-DM and T2DM.

Glucometabolic consequences of acute and prolonged inhibition of fatty acid oxidation

Excessive circulating FAs have been proposed to promote insulin resistance (IR) of glucose metabolism by increasing the oxidation of FAs over glucose. Therefore, inhibition of FA oxidation (FAOX) has been suggested to ameliorate IR. However, prolonged inhibition of FAOX would presumably cause lipid accumulation and thereby promote lipotoxicity. To understand the glycemic consequences of acute and prolonged FAOX inhibition, we treated mice with the carnitine palmitoyltransferase 1 (CPT-1) inhibitor, etomoxir (eto), in combination with short-term 45% high fat diet feeding to increase FA availability. Eto acutely increased glucose oxidation and peripheral glucose disposal, and lowered circulating glucose, but this was associated with increased circulating FAs and triacylglycerol accumulation in the liver and heart within hours. Several days of FAOX inhibition by daily eto administration induced hepatic steatosis and glucose intolerance, specific to CPT-1 inhibition by eto. Lower whole-body insulin sensitivity was accompanied by reduction in brown adipose tissue (BAT) uncoupling protein 1 (UCP1) protein content, diminished BAT glucose clearance, and increased hepatic glucose production. Collectively, these data suggest that pharmacological inhibition of FAOX is not a viable strategy to treat IR, and that sufficient rates of FAOX are required for maintaining liver and BAT metabolic function.

A Short Review on ANGPTL-8 as an Important Regulator in Diabetes

ANGPTL8, a new hormone, is regarded as a novel target for type-2 diabetes and associated metabolic disorder. Nutritional state and hormonal factors are involved in the regulation of ANGPTL-8 expression. This protein is associated with some myokines or adipokines. Several studies confirmed the function of ANGPTL-8 in glucose metabolism and diabetes complications; however, there are opposite results. The accurate function of ANGPTL-8 in T2D remains unclear. Further strictly controlled studies including measuring methods, nutritional state, diagnostic criteria of overweight/obesity, age, and ethnicity may help to resolve discrepancies. In addition, more studies are demanded to clarify the potential role of ANGPTL-8 in humans, a cause or an effect of this protein in association with insulin resistance, the regulatory mechanism of ANGPTL-8 expression, and the association of ANGPTL8 with other adipokines or myokines. In this mini review, we described various roles of ANGPTL-8 in diabetes.

Regulation of angiopoietin-like protein 8 expression under different nutritional and metabolic status

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease with increasing prevalence worldwide. Angiopoietin-like protein 8 (ANGPTL8), a member of the angiopoietin-like protein family, is involved in glucose metabolism, lipid metabolism, and energy homeostasis and believed to be associated with T2DM. Expression levels of ANGPTL8 are often significantly altered in metabolic diseases, such as non-alcoholic fatty liver disease (NAFLD) and diabetes mellitus. Studies have shown that ANGPTL8, together with other members of this protein family, such as angiopoietin-like protein 3 (ANGPTL3) and angiopoietin-like protein 4 (ANGPTL4), regulates the activity of lipoprotein lipase (LPL), thereby participating in the regulation of triglyceride related lipoproteins (TRLs). In addition, members of the angiopoietin-like protein family are varyingly expressed among different tissues and respond differently under diverse nutritional and metabolic status. These findings may provide new options for the diagnosis and treatment of diabetes, metabolic syndromes and other diseases. In this review, the interaction between ANGPTL8 and ANGPTL3 or ANGPTL4, and the differential expression of ANGPTL8 responding to different nutritional and metabolic status during the regulation of LPL activity were reviewed.

Egg oil from Portunus trituberculatus alleviates insulin resistance through activation of insulin signaling in mice

Marine bioactive lipids have been utilized to overcome insulin resistance. However, oil from swimming crab has never been studied. Here, we analyzed the constituents of egg oil from Portunus trituberculatus (Pt-egg oil) and investigated its protective effects against insulin resistance in mice on a high-fat diet. The results showed that Pt-egg oil contained 52.05% phospholipids, 8.61% free fatty acids (especially eicosapentaenoic acid and docosahexaenoic acid), 32.38% triglyceride, 4.79% total cholesterol, and ditissimus astaxanthin. Animal experiments showed that Pt-egg oil significantly mitigated insulin resistance and was associated with reductions in blood glucose, insulin, glucose tolerance, insulin tolerance, serum lipids, and hepatic glycogen. Pt-egg oil activated the phosphatidylinositol 3-hydroxy kinase (PI3K)/protein kinase B (Akt)/glucose transporter 4 pathway in skeletal muscle both at the transcriptional level and at the translational level. Pt-egg oil also promoted hepatic glycogen synthesis through activation of the PI3K/Akt/glycogen synthase kinase-3 beta pathway. These indicate that Pt-egg oil can be used as an alternative to marine bioactive lipids to improve insulin resistance.

Short-Term Cooling Increases Plasma ANGPTL3 and ANGPTL8 in Young Healthy Lean Men but Not in Middle-Aged Men with Overweight and Prediabetes

Angiopoietin-like proteins (ANGPTLs) regulate triglyceride (TG)-rich lipoprotein distribution via inhibiting TG hydrolysis by lipoprotein lipase in metabolic tissues. Brown adipose tissue combusts TG-derived fatty acids to enhance thermogenesis during cold exposure. It has been shown that cold exposure regulates ANGPTL4, but its effects on ANGPTL3 and ANGPTL8 in humans have not been elucidated. We therefore investigated the effect of short-term cooling on plasma ANGPTL3 and ANGPTL8, besides ANGPTL4. Twenty-four young, healthy, lean men and 20 middle-aged men with overweight and prediabetes were subjected to 2 h of mild cooling just above their individual shivering threshold. Before and after short-term cooling, plasma ANGPTL3, ANGPTL4, and ANGPTL8 were determined by ELISA. In young, healthy, lean men, short-term cooling increased plasma ANGPTL3 (+16%, p < 0.05), ANGPTL4 (+15%, p < 0.05), and ANGPTL8 levels (+28%, p < 0.001). In middle-aged men with overweight and prediabetes, short-term cooling only significantly increased plasma ANGPTL4 levels (+15%, p < 0.05), but not ANGPTL3 (230 ± 9 vs. 251 ± 13 ng/mL, p = 0.051) or ANGPTL8 (2.2 ± 0.5 vs. 2.3 ± 0.5 μg/mL, p = 0.46). We show that short-term cooling increases plasma ANGPTL4 levels in men, regardless of age and metabolic status, but only overtly increases ANGPTL3 and ANGPTL8 levels in young, healthy, lean men.

Angptl8 mediates food-driven resetting of hepatic circadian clock in mice

Diurnal light-dark cycle resets the master clock, while timed food intake is another potent synchronizer of peripheral clocks in mammals. As the largest metabolic organ, the liver sensitively responds to the food signals and secretes hepatokines, leading to the robust regulation of metabolic and clock processes. However, it remains unknown which hepatokine mediates the food-driven resetting of the liver clock independent of the master clock. Here, we identify Angptl8 as a hepatokine that resets diurnal rhythms of hepatic clock and metabolic genes in mice. Mechanistically, the resetting function of Angptl8 is dependent on the signal relay of the membrane receptor PirB, phosphorylation of kinases and transcriptional factors, and consequently transient activation of the central clock gene Per1. Importantly, inhibition of Angptl8 signaling partially blocks food-entrained resetting of liver clock in mice. We have thus identified Angptl8 as a key regulator of the liver clock in response to food.

Angiopoietin-like protein 8 expression and association with extracellular matrix metabolism and inflammation during intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is considered the primary culprit for low back pain. Although the underlying mechanisms remain unknown, hyperactive catabolism of the extracellular matrix (ECM) and inflammation are suggested to play critical roles in IDD progression. This study was designed to elucidate the role of angiopoietin‐like protein 8 (ANGPTL8) in the progression of IDD, especially the relationship of ANGPTL8 with ECM metabolism and inflammation. A positive association between ANGPTL8 expression and degenerative grades of IDD was detected in the analysis of human nucleus pulposus tissue samples. Silencing of ANGPTL8 attenuated the degradation of the anabolic protein type collagen II, and reduced the expression of the catabolic proteins MMP3 and MMP9, and the inflammatory cytokine IL‐6 through inhibition of NF‐κB signalling activation. In addition, the effect of ANGPTL8 was evaluated in a rat model of puncture‐induced IDD. Based on the imaging results and histological examination in animal study, knockdown of ANGPTL8 was demonstrated to ameliorate the IDD progression. These results demonstrate the detrimental role of ANGPTL8 expression in the pathogenesis of IDD and may provide a new therapeutic target for IDD treatment.

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.

A long noncoding RNA LOC103690121 promotes hippocampus neuronal apoptosis in streptozotocin-induced type 1 diabetes

Diabetes related cognitive impairment is a severe complication. The diabetes-induced cognitive impairment is associated with insulin resistance and glucose-induced neuron apoptosis in the brain. We intended to investigate the association of long non-coding RNAs with diabetes-induced cognitive impairment in rats. Here, Type 1diabetes (T1D) rat model was induced using streptozotocin (STZ). The diabetic rats showed significant cognitive dysfunction, with increased latency period to find the hidden platform during morris water maze test. The brain injury and reduced neuronsin STZ-induced diabetic rats was determined using hematoxylin and eosin staining and Nissl's staining. We performed the LncRNA microarray analysis and identified 101 differentially expressed lncRNAs in streptozotocin (STZ)-induced type 1 diabetes (T1D) comparing with control. Among these lncRNA, LOC103690121 was upregulated. in vitro glucose treatment in hippocampal neurons showed LOC103690121 and neuron apoptosis was increased by glucose treatment. Transfection experiments showed LOC103690121 overexpression promoted neuron apoptosis, and its inhibition suppressed glucose-induced apoptosis. Western blot analysis showed that the expression profiles of apoptosis related proteins (cleaved-caspase-3, -8, -9, and Bax) were in line with LOC103690121 expression, while the profiles of Bcl-2 and PI3K/Akt signaling pathway was contrast to LOC103690121 expression. In conclusion, the results of our study confirmed lncRNA LOC103690121 promoted STZ-induced cognitive impairment in diabetic rats by promoting neuron apoptosis through PI3K/Akt signaling pathway.

Biological Pathways Leading From ANGPTL8 to Diabetes Mellitus-A Co-expression Network Based Analysis

Angiopoietin like protein 8 (ANGPTL8) is a newly identified hormone with unique nature due to its ability to regulate both glucose and lipid metabolic pathways. It is characterized as an important molecular player of insulin induced nutrient storage and utilization pathway during fasting to re-feeding metabolic transition. Several studies have contributed to increase our knowledge regarding its function and mechanism of action. Moreover, its altered expression levels have been observed in Insulin Resistance, Diabetes Mellitus (Types I & II) and Non Alcohlic Fatty Liver Disease emphasizing its assessment as a drug target. However, there is still a great deal of information that remains to be investigated including its associated biological processes, partner proteins in these processes, its regulators and its association with metabolic pathogenesis. In the current study, the analysis of a transcriptomic data set was performed for functional assessment of ANGPTL8 in liver. Weighted Gene Co-expression Network Analysis coupled with pathway analysis tools was performed to identify genes that are significantly co-expressed with ANGPTL8 in liver and investigate their presence in biological pathways. Gene ontology term enrichment analysis was performed to select the gene ontology classes that over-represent the hepatic ANGPTL8-co-expressed genes. Moreover, the presence of diabetes linked SNPs within the genes set co-expressed with ANGPTL8 was investigated. The co-expressed genes of ANGPTL8 identified in this study (n = 460) provides narrowed down list of molecular targets which are either co-regulated with it and/or might be regulation partners at different levels of interaction. These results are coherent with previously demonstrated roles and regulators of ANGPTL8. Specifically, thirteen co-expressed genes (MAPK8, CYP3A4, PIK3R2, PIK3R4,PRKAB2, G6PC, MAP3K11, FLOT1, PIK3C2G, SHC1, SLC16A2, and RAPGEF1) are also present in the literature curated pathway of ANGPTL8 (WP3915¹). Moreover, the gene-SNP analysis of highly associated biological processes with ANGPTL8 revealed significant genetic signals associated to Diabetes Mellitus and similar phenotypic traits. It provides meaningful insights on the influencing genes involved and co-expressed in these pathways. Findings of this study have implications in functional characterization of ANGPTL8 with emphasis on the identified genes and pathways and their possible involvement in the pathogenesis of Diabetes Mellitus and Insulin Resistance.

GLP-1 receptor agonists stimulate ANGPTL8 production through the PI3K/Akt pathway in a GLP-1 receptor-dependent manner

The level of serum angiopoietin-like protein 8 (ANGPTL8), a novel hepatokine, is associated with obesity and type 2 diabetes mellitus (T2DM). The aims of this study were to investigate whether serum ANGPTL8 level in patients with T2DM was affected by treatment with exenatide, a glucagon-like peptide-1 receptor (GLP-1R) agonist, and to determine whether and how GLP-1R agonists regulated ANGPTL8 production in hepatocytes. A multiple-center trial was conducted in China. Among 240 patients with T2DM enrolled in this trial, 195 patients adhered to a 16-week exenatide treatment and follow-up. Human liver cell line HepG2 cells were incubated for 24 h with either exendin-4 (a native form of exenatide) or liraglutide in the presence or absence of GLP-1R antagonist exendin (9-39) and PI3K inhibitor LY294002. Change of serum ANGPTL8 level in patients with T2DM and regulation of ANGPTL8 production by the GLP-1R agonists in HepG2 cells were evaluated. Results showed that compared with baseline, exenatide treatment significantly increased serum ANGPTL8 level, and lowered body weight, fasting blood glucose (FBG) and glycated hemoglobin A1c (HbA1c) in patients with T2DM (all P <  0.05). The exenatide treatment-mediated upregulation of serum ANGPTL8 level was not associated with the levels of its lowering effects on body weight, FBG and HbA1c stratified by the median. Moreover, exendin-4 or liraglutide dose-dependently upregulated the level of ANGPTL8 expression and secretion in HepG2 cells, which was eliminated by adding exendin (9-39) and LY294002. In conclusion, GLP-1R agonists enhance ANGPTL8 production in vivo and in vitro, which is mediated via the PI3K/Akt pathway in a GLP-1R-dependent manner.

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.

SARM1 deletion restrains NAFLD induced by high fat diet (HFD) through reducing inflammation, oxidative stress and lipid accumulation

SARM1 (Sterile alpha and armadillo motif-containing protein 1) is the recently identified TIR domain-containing cytosolic protein, which is involved in toll-like receptors (TLRs) signaling transduction. In the present study, the role of SARM1 in high fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) progression was explored. We found that SARM1 was expressed highly in fatty liver. And SARM1-knockout (KO) reduced steatohepatitis and metabolic disorders induced by HFD. SARM1-deletion decreased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels in HFD-fed mice. Additionally, inflammatory response caused by HFD was alleviated by SARM1-deletion through inactivating TLR4/7/9 and nuclear factor kappa B (NF-κB) pathways. Of note, SARM1-deletion also reduced the expressions of inflammation-associated molecules in hypothalamus of HFD-fed mice. Furthermore, HFD administration led to oxidative stress in liver of mice, while being decreased in SARM1-KO mice. Moreover, SARM1-ablation improved lipid dyslipidemia by suppressing the mRNA levels of genes, linked to glycolysis, lipogenesis and transcriptional regulation. Insulin resistance was also attenuated by SARM1-deficiency through enhancing the activation of liver Akt/glycogen synthase kinase-3β (GSK3β) and insulin receptor substrate-1 (IRS1)/FOXO1 pathways in HFD-fed mice. Also, SARM1-knockout improved neuropeptide Y (NPY), Pro-Opiomelanocortins (POMC), Agouti-related Protein (AGRP) and Cocaine-and-Amphetamine Responsive Transcript 1 (CART1) expressions in hypothalamus of mice after HFD administration. In vitro, we found that the reduction of inflammatory response, oxidative stress and dyslipidemia induced by SARM1-knockout in primary hepatocytes after fructose stimulation was largely attributed to its suppression to TLR4/7/9. Together, the findings demonstrated that SARM1 might be an effective target for developing effective therapeutic strategies against NAFLD.

ANGPTL8: An Important Regulator in Metabolic Disorders

Long-term controversy regarding the role of angiopoietin-like protein 8 (ANGPTL8) in beta-cell proliferation and diabetes progression made it a research spotlight. Recently, the controversy was resolved. Although ANGPTL8 could not control beta-cell expansion and islet function, ANGPTL8 was still considered as a novel but atypical member in the ANGPTL family because of its unique structure and crucial effects on lipid metabolism. Besides, ANGPTL8 also participated in some other disorders such as non-alcoholic fatty liver disease and renal dysfunction. Understanding the features of ANGPTL8 may offer new diagnostic and therapeutic approaches to metabolic-related diseases. Therefore, we reviewed most recent findings about ANGPTL8 and aimed to provide an integrated picture of ANGPTL8.

Cloning, expression, and spectral analysis of mouse betatrophin

Background: Betatrophin, a novel secretory protein from liver and fatty tissues, is believed to be involved in lipid and glucose metabolism. However, its precise physiological role remains unclear. Here, we report the cloning, expression, and purification steps of mouse betatrophin in a prokaryotic system, followed by its structural analysis. Methods: Specific cloning primers were used to amplify the coding sequence of mouse liver betatrophin. The product was cloned into pET28 and expressed in E.coli BL21 (DE3) cells. The suitability of the refolding procedure was assessed by determining secondary structures of the initial and refolded proteins using circular dichroism spectroscopy. Results: The polymerase chain reaction resulted in a 549 bp nucleotide sequence, encoding a 183 amino acid polypeptide, with an apparent molecular weight of 21 kDa, which was expressed in an inclusion body. Following an optimization and refolding procedure, the recombinant protein was purified by anion exchange and metal affinity chromatography. CD spectra revealed that the refolded protein has suitable configuration. Conclusion: We believe that the produced betatrophin is suitable for further biochemical studies on glucose and lipid metabolism.

Angiopoietin-like protein 8: An attractive biomarker for the evaluation of subjects with insulin resistance and related disorders

Insulin resistance is prevalent worldwide and is associated with many metabolic diseases, in particular, type 2 diabetes mellitus (T2DM), obesity, nonalcoholic fatty liver disease (NAFLD), polycystic ovary syndrome (PCOS) and metabolic syndrome (MetS). Angiopoietin-like protein 8 (ANGPTL8), a newly-identified secreted protein composing of 198 amino acids, is enriched in the liver of human. Considering its promising potential for β-cell proliferation and therapeutic prospect for diabetes, ANGPTL8 has aroused extensive interests. However, a recent collaborative study confirmed that ANGPTL8 didn't stimulate dramatic β-cell regeneration. At present, a controversial scientific discussion on whether and how ANGPTL8 regulate insulin resistance has been ongoing. Interestingly, several in vitro and in vivo studies have suggested the complex roles of ANGPTL8 in insulin resistance. Data resulting from cross-sectional and longitudinal researches in human individuals involving the influence of ANGPTL8 on the development of insulin resistance were controversial. We therefore summarize currently clinical literature to exploit whether this exciting hormone could be applied for clinical application asa potential clinical biomarker to predict insulin resistance and related disorders.

Insulin upregulates betatrophin expression via PI3K/Akt pathway

Betatrophin is regarded as a liver-produced hormone induced by insulin resistance (IR). However, it remains largely unknown how IR regulates betatrophin expression. To study whether IR could regulate betatrophin expression and the corresponding molecular mechanisms, betatrophin levels were examined in 6 in vitro IR models which were established using human hepatocytes L02 with different agents, including tumor necrosis factor-α, interleukin-1β, dexamethasone, palmitate, high glucose and insulin and betatrophin levels were elevated only in the insulin group. These results suggest that it is insulin, not IR that promotes betatrophin expression. In the meantime, PI3K/Akt pathway was activated by insulin and suppressed by above agents that caused IR. Insulin-upregulated betatrophin expression was suppressed by PI3K/Akt inhibitors and IR, suggesting that insulin upregulates and IR decreases betatrophin production through PI3K/Akt pathway. Consistently, the treatment of insulin in mice dose-dependently upregulated betatrophin levels, and the administration of metformin in IR mice also stimulated betatrophin production since published study showed metformin improved PI3K/Akt pathway and IR. In humans, compared with those without insulin treatment, serum betatrophin levels were increased in type 2 diabetic patients with insulin treatment. In conclusion, insulin stimulates betatrophin secretion through PI3K/Akt pathway and IR may play an opposite role.

Inhibitory Effect of Piceatannol on TNF-α-Mediated Inflammation and Insulin Resistance in 3T3-L1 Adipocytes

Piceatannol, a bioactive component in grape and blueberry, was examined for its potential in decreasing the inflammatory activities in adipocytes using a cocultured adipocyte and macrophage system, and suppressing tumor necrosis factor-α (TNF-α)-mediated inflammation and the related insulin resistance using a 3T3-L1 adipocyte model. Piceatannol at 10 μM significantly reduced the release of inflammatory cytokines of TNF-α and monocyte chemoattractant protein-1 (MCP-1) by 19 and 31% in the cocultured system, respectively. Pretreatment with piceatannol also inhibited TNF-α-induced expression of interleukin-6 (IL-6) and MCP-1 at both mRNA and protein levels in the 3T3-L1 adipocytes. Piceatannol also partially improved the malfunction of insulin-stimulated glucose uptake, which was reduced by TNF-α in 3T3-L1 adipocytes. Furthermore, the inhibitions were mediated by significant blocking of IκBα phosphorylation and nuclear factor-κB (NF-κB) activation through suppressing nuclear translocation of NF-κB p65 along with c-Jun N-terminal kinase (JNK)-mitogen activated protein kinase (MAPK) activation. In addition, the Akt-dependent forkhead box O1 (FoxO1) signaling pathway was involved in the restoration of insulin-stimulated glucose uptake through suppressing the down-regulation of phosphorylation of Akt and FoxO1 expressions. These results suggested the potential of piceatannol in improving chronic inflammatory condition and insulin sensitivity in obese adipose tissues.

Circulating angiopoietin-like 8 (ANGPTL8) is a marker of liver steatosis and is negatively regulated by Prader-Willi Syndrome

ANGPTL8 is a liver-derived protein related to insulin-sensitivity. Its relationship with obesity and liver function in Prader-Willi syndrome (PWS) is unknown. The present study investigated circulating ANGPTL8 in PWS and controls with common obesity, assessing its association to liver steatosis. For this purpose, 20 obese PWS and 20 controls matched for body mass index (BMI), sex and age underwent analysis of ANGPTL8 levels, glucose and lipid metabolism. Liver function tests and degree of liver steatosis by ultrasonography (US), fat-free mass (FFM) and fat mass (FM) by dual-energy x-ray absorptiometry (DEXA) were also assessed. In comparison to controls, obese PWS showed lower values of FFM (p < 0.0001) and higher FM (p = 0.01), while harbouring higher HDL cholesterol, lower triglycerides and OGTT-derived insulin levels, as well as a lower prevalence and severity of liver steatosis. With respect to obese controls, ANGPTL8 levels were significantly lower in PWS (p = 0.007) and overall correlated with transaminase levels and the severity of liver steatosis, as well as FFM (p < 0.05 for all). By a stepwise multivariable regression analysis, ANGPTL8 levels were independently predicted by PWS status (p = 0.01) and liver steatosis (p < 0.05). In conclusion, ANGPTL8 levels are lower in PWS than obese controls and are inversely associated with the severity of liver steatosis. Further studies should investigate the potential genetic basis for this observation.

Angiopoietin-like protein 8/betatrophin as a new determinant of type 2 diabetes remission after bariatric surgery

This work aimed to explore the link between angiopoietin-like protein 8 (ANGPTL8) and weight loss after metabolic surgery. In the cross-sectional study (n = 100), circulating ANGPTL8 concentrations were significantly lower in morbidly obese than in lean subjects, and strikingly lower in morbidly obese patients with type 2 diabetes mellitus (T2DM). Conversely, ANGPTL8 expression in subcutaneous adipose tissue (SAT) was higher in morbidly obese patients, particularly in those with T2DM, whereas its expression in visceral adipose tissue was unchanged. The main predictors for circulating levels of ANGPTL8 were BMI and T2DM, whereas ANGPTL8 expression in SAT was determined by the presence of T2DM. The prospective cohort studies before and 1 year after bariatric surgery in morbidly obese patients with (n = 45) and without (n = 30) T2DM, revealed a significant increase of circulating ANGPTL8 levels 1 year after the bariatric surgery. Intriguingly, this increment, which was predicted by basal ANGPTL8 concentrations, appeared as a determinant of T2DM remission. In conclusion, circulating ANGPTL8 levels have an inverse relationship with SAT expression. Low basal levels of ANGPTL8 rebound after bariatric surgery. The increment in ANGPTL8 concentrations at 1 month of follow-up after weight loss emerged as a significant predictor of the T2DM remission at 1 year of follow-up.

Angiopoietin-like 8 (Angptl8) controls adipocyte lipolysis and phospholipid composition

Angiopoietin-like 8 (Angptl8) inhibits lipolysis in the circulation together with Angplt3 and controls post-prandial fat storage in white adipose tissue (WAT). It is strongly induced by insulin in vivo in WAT and in vitro in adipocytes. In this study we addressed the function of Angptl8 in adipocytes by its stable lentivirus-mediated knock-down in 3T3-L1 cells, followed by analyses of triglyceride (TG) storage, lipid droplet (LD) morphology, the cellular lipidome, lipolysis, and gene expression. Depletion of Angptl8 did not drastically affect the adipocyte differentiation of 3T3-L1 cells but resulted in a moderate (18-19%) reduction of stored TGs. The lipidome analysis revealed a reduction of alkyl- phosphatidylcholines (PCs) and phosphatidylethanolamine (PE) plasmalogens, as well as saturated PCs and PEs. Importantly, the Angptl8 depleted cells displayed enhanced lipolysis as measured by release of non-esterified fatty acids (NEFAs). Consistently, mRNAs encoding Angptl4 and Leptin, which facilitate lipolysis, as well as Cpt1a, Cpt1b, and Pgc-1α involved in FA oxidation, were elevated. The Angptl8 mRNA itself was suppressed by pharmacologic treatments inducing lipolysis: stimulation with the β-adrenergic agonist isoproterenol or with the adenylate cyclase activator forskolin. To conclude, knock-down of Angptl8 in adipocytes suggests that the protein acts to inhibit intracellular lipolysis, analogous to its activity in the circulation. Depletion of Angptl8 results in an altered cellular phospholipid composition. The findings identify Angptl8 as a central insulin-regulated controller of adipocyte lipid metabolism.