Circulating Levels of Vascular Endothelial Growth Factor A and Its Soluble Receptor in Patients with Biopsy-proven Nonalcoholic Fatty Liver Disease

Hepatocyte-derived VEGFA accelerates the progression of non-alcoholic fatty liver disease to hepatocellular carcinoma via activating hepatic stellate cells

Non-alcoholic fatty liver disease (NAFLD) is emerging as an epidemic risk factor for hepatocellular carcinoma (HCC). The progression of NAFLD to HCC is closely associated with paracrine communication among hepatic cells. Vascular endothelial growth factor A (VEGFA) plays a key role in NAFLD and HCC; however, the cellular communication of VEGFA in the pathological transition from NAFLD to HCC remains unclear. Here, we found that VEGFA elevation was considerably distributed in hepatocytes of clinical and murine NAFLD-HCC specimens. Notably, progression from NAFLD to HCC was attenuated in hepatocyte-specific deletion of Vegfa (VegfaΔhep) mice. Mechanistically, VEGFA activated human hepatic stellate cell (HSC) LX2 into a fibrogenic phenotype via VEGF-VEGFR signaling in fatty acid medium, and HSC activation was largely attenuated in VegfaΔhep mice during NAFLD-HCC progression. Additionally, a positive correlation between VEGFA and hepatic fibrosis was observed in the NAFLD-HCC cohort, but not in the HBV-HCC cohort. Moreover, LX2 cells could be activated by conditioned medium from NAFLD-derived organoids, but not from HBV livers, whereas this activation was blocked by a VEGFA antibody. In summary, our findings reveal that hepatocyte-derived VEGFA contributes to NAFLD-HCC development by activating HSCs and highlight the potential of precisely targeting hepatocytic VEGFA as a promising therapeutic strategy for NAFLD-HCC.

The pivotal role of heme Oxygenase-1 in reversing the pathophysiology and systemic complications of NAFLD

The pathogenesis and molecular pathways involved in non-alcoholic fatty liver disease (NAFLD) are reviewed, as well as what is known about mitochondrial dysfunction that leads to heart disease and the progression to steatohepatitis and hepatic fibrosis. We focused our discussion on the role of the antioxidant gene heme oxygenase-1 (HO-1) and its nuclear coactivator, peroxisome proliferator-activated receptor-gamma coactivator (PGC1-α) in the regulation of mitochondrial biogenesis and function and potential therapeutic benefit for cardiac disease, NAFLD as well as the pharmacological effect they have on the chronic inflammatory state of obesity. The result is increased mitochondrial function and the conversion of white adipocyte tissue to beige adipose tissue ("browning of white adipose tissue") that leads to an improvement in signaling pathways and overall liver function. Improved mitochondrial biogenesis and function is essential to preventing the progression of hepatic steatosis to NASH and cirrhosis as well as preventing cardiovascular complications.

Nonalcoholic Fatty Liver Disease and the Heart: JACC State-of-the-Art Review

Nonalcoholic fatty liver disease (NAFLD) and cardiovascular disease (CVD) are both manifestations of end-organ damage of the metabolic syndrome. Through multiple pathophysiological mechanisms, CVD and NAFLD are associated with each other. Systemic inflammation, endothelial dysfunction, hepatic insulin resistance, oxidative stress, and altered lipid metabolism are some of the mechanisms by which NAFLD increases the risk of CVD. Patients with NAFLD develop increased atherosclerosis, cardiomyopathy, and arrhythmia, which clinically result in cardiovascular morbidity and mortality. Defining the mechanisms linking these 2 diseases offers the opportunity to further develop targeted therapies. The aim of this comprehensive review is to examine the association between CVD and NAFLD and discuss the overlapping management approaches.

Relevance of VEGFA in rat livers subjected to partial hepatectomy under ischemia-reperfusion

Abstract

We examined the effects of VEGFA on damage and regeneration in steatotic and non-steatotic livers of rats submitted to PH under I/R, and characterized the underlying mechanisms involved. Our results indicated that VEGFA levels were decreased in both steatotic and non-steatotic livers after surgery. The administration of VEGFA increased VEGFA levels in non-steatotic livers, reducing the incidence of post-operative complications following surgery through the VEGFR2-Wnt2 pathway, independently of Id1. Unexpectedly, administration of VEGFA notably reduced VEGFA levels in steatotic livers, exacerbating damage and regenerative failure. After exogenous administration of VEGFA in steatotic animals, circulating VEGFA is sequestered by the high circulating levels of sFlt1 released from adipose tissue. Under such conditions, VEGFA cannot reach the steatotic liver to exert its effects. Consequently, the concomitant administration of VEGFA and an antibody against sFlt1 was required to avoid binding of sFlt1 to VEGFA. This was associated with high VEGFA levels in steatotic livers and protection against damage and regenerative failure, plus improvement in the survival rate via up-regulation of PI3K/Akt independently of the Id1-Wnt2 pathway. The current study highlights the different effects and signaling pathways of VEGFA in liver surgery requiring PH and I/R based in the presence of steatosis.

Key messages

VEGFA administration improves PH+I/R injury only in non-steatotic livers of Ln animals.

VEGFA benefits are exerted through the VEGFR2-Wnt2 pathway in non-steatotic livers.

In Ob rats, exogenous VEGFA is sequestered by circulating sFlt1, exacerbating liver damage.

Therapeutic combination of VEGFA and anti-sFlt1 is required to protect steatotic livers.

VEGFA+anti-sFlt1 treatment protects steatotic livers through a VEGFR2-PI3K/Akt pathway.

Electronic supplementary material

The online version of this article (10.1007/s00109-019-01811-y) contains supplementary material, which is available to authorized users.

Serum vascular cell adhesion molecule-1 predicts significant liver fibrosis in non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide and is strongly associated with obesity, dyslipidemia and insulin resistance. NAFLD often presents as simple steatosis (NAFL) but can progress to non-alcoholic steatohepatitis (NASH) and fibrosis. Current non-invasive biomarkers are not tailored to identify significant (⩾F2) fibrosis, although recent guidelines recommend a stringent follow-up of this patient population. We and others have reported on the role of pathological angiogenesis in the pathogenesis of NAFLD, highlighting pro-angiogenic factors as potential diagnostic markers.

OBJECTIVE

To investigate the applicability of angiogenic and endothelial dysfunction markers as non-invasive diagnostic tools for NASH or NASH-associated fibrosis in obese patients.

METHODS

In a prospective cross-sectional study, male patients undergoing bariatric surgery (n=61) and control patients (n=35) were recruited. Serum protein levels and visceral adipose tissue gene expression of endothelial dysfunction and angiogenic markers were analyzed by multiplex bead-based assay and quantitative RT-PCR, respectively. For validation, we recruited a second cohort of patients undergoing bariatric surgery (n=40) and a cohort of NAFLD patients from our outpatient clinic (n=30).

RESULTS

We identified serum vascular cell adhesion molecule-1 (VCAM-1) as an independent predictor for ⩾F2 fibrosis (median 14.0 vs 8.7 ng ml^-1 in patients with and without significant fibrosis; P<0.0001) with an area under the receiver-operating characteristics (AUROC) curve of 0.80. The cutoff point of 13.2 ng ml^-1 showed a sensitivity of 80% and specificity of 83%. In line with these results, VCAM-1 visceral adipose tissue gene expression was also elevated in patients with fibrosis (P=0.030). In the bariatric surgery and clinical validation cohorts, VCAM-1 displayed similar AUROCs of 0.89 and 0.85, respectively.

CONCLUSIONS

VCAM-1 levels are able to accurately predict significant (⩾F2) fibrosis in NAFLD patients.

Serum levels of vascular endothelial growth factor in non-alcoholic fatty liver disease

Background

This study aimed to assess the significance of serum levels of vascular endothelial growth factor (VEGF) in non-alcoholic fatty liver disease (NAFLD).

Methods

Sixty-seven consecutive NAFLD patients and 47 healthy controls who visited our liver clinics between May 2008 and December 2010 were included. The NAFLD diagnosis required elevated alanine aminotransferase and/or gamma-glutamyl transpeptidase levels, evidence of hepatic steatosis on ultrasound and/or liver histology, and exclusion of other causes of liver injury. Serum VEGF levels were determined by an enzyme immunoassay. Liver biopsy was obtained in 34 NAFLD patients. Histological lesions were scored by a liver histopathologist.

Results

Serum VEGF levels tended to be lower in matched NAFLD patients than in healthy controls (296±146 vs. 365±186 pg/mL, P=0.092); levels in patients with non-alcoholic steatohepatitis (NASH) also tended to be lower than in those with simple fatty liver (FL) (279±149 vs. 359±190 pg/mL, P=0.095); while VEGF levels were significantly lower in NASH patients than in healthy controls (279±149 vs. 365±186 pg/mL, P=0.041). VEGF levels offered poor predictability for the differentiation between NAFLD patients and controls or between NASH and FL patients. However, patients with high VEGF levels (≥300 pg/mL) were significantly more likely to have FL, either in the total NAFLD population (67% vs. 35%, P=0.019) or in the 34 NAFLD patients with liver biopsy (57% vs. 15%, P=0.023), while those with high VEGF levels also had a significantly lower mean fibrosis score (0.7±0.9 vs. 1.6±1.0, P=0.017).

Conclusion

Our data suggest that serum VEGF levels are equally high in healthy controls and in patients with simple fatty liver, but tend to decrease when NASH develops.

Integrative transcriptomic analysis of NAFLD animal model reveals dysregulated genes and pathways in metabolism

Dysregulation of metabolism in hepatocytes leads to hepatic diseases such as hepatitis and non-alcoholic fatty liver disease (NAFLD). NAFLD represents a spectrum of liver diseases ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). NASH is likely to progress to cirrhosis, liver failure and hepatocellular carcinoma, which lead to poor long-term prognosis. However, the exact mechanism of development of NAFLD is not well elucidated. In order to better understand the pathogenesis of NAFLD, we have performed an integrative analysis to livers from NAFLD rat models in a global view of the transcriptome. By systemic and integrative analyses, we have found that transport, angiogenesis and cell adhesion were upregulated in response to high fat diet feeding, which may cause a large amount of free fatty acid transport, hepatic fibrosis and hepatocytes injury. GO tree analysis has shown that angiogenesis was upregulated. GO term in response to high fat diet which may cause fibrosis. The pathway interaction network has indicated that upregulated "valine, leucine, and isoleucine metabolism" may decrease the serum concentration of branched-chain amino acid (BCAA). The enhanced degradation of BCAA in NAFLD animal models may lead to inhibition of the regeneration of hepatocytes, reducing the production of albumin, attenuating the inhibition of liver cancer and decreasing immunity. Overall, high fat diet upregulated a variety of metabolism which have converged at TCA cycle. High fatty has pushed the hepatic mitochondria to a "busy state". Comprehensively, genes participated in dysregulated biological process and metabolisms may be served as indicators for evaluation of NAFLD progression and therapeutic targets.

Non-alcoholic fatty liver disease and cardiovascular risk: Pathophysiological mechanisms and implications

Non-alcoholic fatty liver disease (NAFLD) has become one of the most frequent chronic liver diseases in the Western society and its prevalence is likely to rise even further. An increasing body of evidence shows that NAFLD is not only a potentially progressive liver disease, but also has systemic consequences. More specifically, evidence points out that NAFLD has to be considered as a significant independent risk factor for subclinical and clinical cardiovascular disease (CVD). Long-term follow-up studies demonstrate cardiovascular mortality to be the most important cause of death in NAFLD patients. Moreover, ample evidence associates NAFLD with endothelial dysfunction, increased pulse wave velocity, increased coronary arterial calcifications and increased carotid intima media thickness, all established markers for CVD. Despite of all this evidence, the mechanisms by which NAFLD causally contributes to CVD are not fully elucidated. Furthermore, an extensive overview of all potential pathophysiological mechanisms and the corresponding current data are lacking. In this review we summarise current knowledge, originating from fundamental and clinical research, that mechanistically links NAFLD to CVD. Subsequently, the impact of CVD on current clinical practice and future research in the area of NALFD are discussed.

Lipid-induced toxicity stimulates hepatocytes to release angiogenic microparticles that require Vanin-1 for uptake by endothelial cells

Angiogenesis is a key pathological feature of experimental and human steatohepatitis, a common chronic liver disease that is associated with obesity. We demonstrated that hepatocytes generated a type of membrane-bound vesicle, microparticles, in response to conditions that mimicked the lipid accumulation that occurs in the liver in some forms of steatohepatitis and that these microparticles promoted angiogenesis. When applied to an endothelial cell line, medium conditioned by murine hepatocytes or a human hepatocyte cell line exposed to saturated free fatty acids induced migration and tube formation, two processes required for angiogenesis. Medium from hepatocytes in which caspase 3 was inhibited or medium in which the microparticles were removed by ultracentrifugation lacked proangiogenic activity. Isolated hepatocyte-derived microparticles induced migration and tube formation of an endothelial cell line in vitro and angiogenesis in mice, processes that depended on internalization of microparticles. Microparticle internalization required the interaction of the ectoenzyme Vanin-1 (VNN1), an abundant surface protein on the microparticles, with lipid raft domains of endothelial cells. Large quantities of hepatocyte-derived microparticles were detected in the blood of mice with diet-induced steatohepatitis, and microparticle quantity correlated with disease severity. Genetic ablation of caspase 3 or RNA interference directed against VNN1 protected mice from steatohepatitis-induced pathological angiogenesis in the liver and resulted in a loss of the proangiogenic effects of microparticles. Our data identify hepatocyte-derived microparticles as critical signals that contribute to angiogenesis and liver damage in steatohepatitis and suggest a therapeutic target for this condition.

Identification of a support vector machine-based biomarker panel with high sensitivity and specificity for nonalcoholic steatohepatitis

BACKGROUND

Although liver biopsy remains the best diagnostic standard for nonalcoholic steatohepatitis (NASH), non-invasive tests are eagerly awaited. In this study, we sought to develop a support vector machine (SVM) algorithm to discriminate with high accuracy between subjects with NASH and controls using a blood-based biomarker panel.

METHODS

A total of 17 biomarkers were measured by commercially available enzyme-linked immunosorbent assays in 136 serum samples from patients with biopsy-proven NASH (n = 60) and subjects with normal ALT and no evidence of fatty liver on ultrasound (n = 76). The database was randomly divided (1:1 fashion) into a discovery set for classification training and in a validation set of the chosen biomarkers in blinded samples. Multivariate analysis was performed by means of SVM.

RESULTS

After the identification of a group of three most discriminative biomarkers (osteoprotegerin, fibroblast growth factor 21, and M30) in the discovery set, the application of SVM to the validation test resulted in a 92.5% sensitivity and 84.1% specificity for distinguishing subjects with NASH from controls.

CONCLUSIONS

A targeted biomarker profiling combined with a SVM-based pattern identification approach may allow the identification of patients with NASH with clinically relevant accuracy and validity.

Preliminary evidence of a reduced serum level of fibroblast growth factor 19 in patients with biopsy-proven nonalcoholic fatty liver disease

OBJECTIVES

We sought to determine whether serum concentrations of fibroblast growth factor 19 (FGF19) - an ileum-derived enterokine which plays a role in the control of glucose and lipid homeostasis - are altered in patients with biopsy-proven nonalcoholic fatty liver disease (NAFLD).

DESIGN AND METHODS

Serum levels of FGF19 were measured using enzyme-linked immunosorbent assay in 91 patients with biopsy-proven NAFLD and 74 controls.

RESULTS

FGF19 levels were significantly lower in patients with biopsy-proven NAFLD (median: 130pg/mL) than in controls (median: 210pg/mL, P<0.001). Serum FGF19 levels were significantly but modestly associated with hepatocyte ballooning scores in univariate analysis (r=-0.25, P<0.05) but not after adjustment for potential confounders (β=-0.18; t=1.78, P=0.08).

CONCLUSIONS

This pilot study suggests that serum FGF19 levels are decreased in patients with NAFLD but are not independently associated with liver histology findings.

Predicting the treatment effect of sorafenib using serum angiogenesis markers in patients with hepatocellular carcinoma

BACKGROUND AND AIM

Sorafenib, the first agent demonstrated to have efficacy to improve the survival of patients with advanced hepatocellular carcinoma (HCC), is an active multikinase inhibitor affecting angiogenesis and tumor proliferation. We analyzed cytokines related to angiogenesis or cell proliferation, and tried to determine their utility as biomarkers of sorafenib treatment effect for HCC.

METHODS

Nine serum cytokines (angiopoietin-2 [Ang-2], follistatin, granulocyte colony-stimulating factor [G-CSF], hepatocyte growth factor [HGF], interleukin-8 [IL-8], leptin, platelet-derived growth factor-BB, platelet endothelial cell adhesion molecule-1, and vascular endothelial growth factor) were measured in 30 HCC patients treated with sorafenib, and the effects of treatment were compared using modified Response Evaluation Criteria in Solid Tumors.

RESULTS

All but IL-8 were significantly higher at baseline in patients with progressive disease. Progression-free survival was significantly shorter in patients with high levels of Ang-2, G-CSF, HGF, and leptin, and the hazard ratios were 2.51, 6.89, 2.55, and 4.14, respectively. As the number of cytokines at a high level increased, the treatment response deteriorated. Disease progression was seen in three of 12 (25.0%) patients with zero to two high biomarkers, two of six (33.3%) patients with 3-5 high biomarkers, and 10 of 12 (83.3%) patients with six to eight high biomarkers (P=0.008). The prognosis of all patients with eight high biomarkers was progressive disease.

CONCLUSION

High levels of serum cytokines at baseline were correlated with poor effects of sorafenib treatment in patients with HCC.