Soluble Endoglin as a Potential Biomarker of Nonalcoholic Steatohepatitis (NASH) Development, Participating in Aggravation of NASH-Related Changes in Mouse Liver

Abstract

Nonalcoholic steatohepatitis (NASH) is characterized by hepatic steatosis with inflammation and fibrosis. Membrane endoglin (Eng) expression is shown to participate in fibrosis, and plasma concentrations of soluble endoglin (sEng) are increased in patients with hypercholesterolemia and type 2 diabetes mellitus. We hypothesize that NASH increases both hepatic Eng expression and sEng in blood and that high levels of sEng modulate cholesterol and bile acid (BA) metabolism and affect NASH progression. Three-month-old transgenic male mice overexpressing human sEng and their wild type littermates are fed for six months with either a high-saturated fat, high-fructose high-cholesterol (FFC) diet or a chow diet. Evaluation of NASH, Liquid chromatography–mass spectrometry (LC/MS) analysis of BA, hepatic expression of Eng, inflammation, fibrosis markers, enzymes and transporters involved in hepatic cholesterol and BA metabolism are assessed using Real-Time Quantitative Reverse Transcription Polymerase Chain reaction (qRT-PCR) and Western blot. The FFC diet significantly increases mouse sEng levels and increases hepatic expression of Eng. High levels of human sEng results in increased hepatic deposition of cholesterol due to reduced conversion into BA, as well as redirects the metabolism of triglycerides (TAG) to its accumulation in the liver, via reduced TAG elimination by β-oxidation combined with reduced hepatic efflux. We propose that sEng might be a biomarker of NASH development, and the presence of high levels of sEng might support NASH aggravation by impairing the essential defensive mechanism protecting NASH liver against excessive TAG and cholesterol accumulation, suggesting the importance of high sEng levels in patients prone to develop NASH.

Atorvastatin Modulates Bile Acid Homeostasis in Mice with Diet-Induced Nonalcoholic Steatohepatitis

“…To induce NASH, C57BL/6 male mice were fed an F diet over 24 weeks. In comparison with a chow diet, the F diet induced significant elevations in body weight; liver weight; liver to body weight ratio (%); serum alanine aminotransferase (ALT), an indicator of hepatocellular injury; alkaline phosphatase (ALP), a marker of cholestatic liver impairment; triglycerides (TG); and soluble endoglin ( Figure 1 )—a recently suggested marker of liver fibrosis in NASH [ 28 ]. Atorvastatin effectively reduced plasma ALT and TG concentrations ( Figure 1 ), indicating its positive effect on liver injury.…”

“…Reverse-transcription polymerase chain reaction (qRT-PCR) was conducted via the Quantstudio 7 HT fast RT-PCR system (Applied Biosystems, Foster City, CA, USA) as described previously [ 28 ]. The primers used for analysis are specified in Table 1 .…”

“…The primers used for analysis are specified in Table 1 . Western blotting was performed as reported previously [ 28 ]. The list of antibodies is presented as Table 2 .…”

High Soluble Endoglin Levels Affect Aortic Vascular Function during Mice Aging

“…Soluble endoglin represents an interesting biomarker of vascular pathology in both clinical and experimental studies [23]. More interestingly, several studies demonstrated potential harmful effects of sEng in endothelial function [12], liver metabolism [24], and development of NASH [25], suggesting that high levels of sEng might be considered as a risk factor of development of vascular alteration. Indeed, placenta-derived sEng from pregnant preeclamptic women is able to increase vascular permeability and induce arterial hyper-tension in vivo, suggesting that sEng plays an essential role in the pathogenesis of arterial hypertension, proteinuria, and glomerular endotheliosis [26].…”

Monoclonal anti-endoglin antibody TRC105 (carotuximab) prevents hypercholesterolemia and hyperglycemia-induced endothelial dysfunction in human aortic endothelial cells

“…sEng is the cleavage product of the extracellular domain of Eng upon the enzymatic activity of matrix metalloproteinases (MMP-14 and MMP-12) ( 12 , 13 ). It is released into the circulation in various pathological conditions, such as arterial hypertension, type II diabetes mellitus ( 14 ), non-alcoholic steatohepatitis ( 15 ), familial hypercholesterolemia ( 16 , 17 ), and preeclampsia ( 18 ); and also in patients with atherosclerosis who had increased levels of total cholesterol, LDL, triglycerides and decreased levels of HDL ( 19 ). Moreover, increased levels of sEng correlate with complications of diabetes, such as retinopathy, peripheral neuropathy, or nephropathy ( 20 – 23 ).…”