An in vitro model of hepatic steatosis using lipid loaded induced pluripotent stem cell derived hepatocyte like cells

Fatty acid composition of blood serum and erythrocyte membranes in men with steatosis and steatohepatitis with normal transaminase activity

Aim. To study the characteristics of the fatty acid (FA) profi le of blood serum and erythrocyte membranes in patients with two forms of fatty liver disease (metabolic + alcoholic): steatosis and steatohepatitis with normal transaminase activity.

Materials and methods. We examined 33 men (50.7 ± 9.6 years) with fatty liver disease (metabolic and alcoholic) with fi brosis F ≤ 1 (FibroTest). According to the ActiTest results, patients were divided into groups of steatosis – with minimal (A0–1) activity (n = 17) and steatohepatitis – with moderate/severe (A2–3) necroinfl ammatory activity (n = 16). The FA composition of blood serum and erythrocyte membranes was studied using gas chromatography/mass spectrometry Agilent 7000B (Agilent Technologies, Inc., USA). Methods of unpaired statistics using volcano plot and discriminant analysis based on orthogonal least squares (Orthogonal Partial Least Squares Discriminant Analysis, OPLS-DA), ROC analysis were applied.

Results. Volcano plot analysis showed that in patients with fatty liver disease (metabolic and alcoholic) with normal transaminase activity, serum levels of stearic C18:0 (p = 0.016), arachidic C20:0 (p = 0.023), ratio saturated / polyunsaturated fatty acids (PUFA) (p = 0.001) were statistically signifi cantly higher in the steatohepatitis group compared with the steatosis group. The total content in the blood serum of all PUFA (p = 0.003), margaric C17:0 (p = 0.011), the sum of two omega-3 PUFA – eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3) (p = 0.04), the total content of all omega-3 PUFA (p = 0.042) were statistically signifi cantly lower in patients with steatohepatitis. OPLS-DA demonstrated fairly accurate separation of steatohepatitis and steatosis using individual FA and their ratios. When individual FA and their ratios were included in the analysis, a model was obtained with AUC = 0.827 (95% confi dence interval 0.499–1.0), sensitivity 82.2% and specifi city 80.7%.

Conclusion. FA in blood serum and erythrocyte membranes appear to be promising biomarkers of steatohepatitis with normal levels of transaminases.

Toxicity mechanisms of biomass burning aerosols in in vitro hepatic steatosis models

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease that contributes to the global rise in liver-related morbidity and mortality. Wood tar (WT) aerosols are a significant fraction of carbonaceous aerosol originating from biomass smoldering, contributing to air pollution particles smaller than 2.5 mm (PM2.5). Mechanistic biological associations exist between exposure to PM2.5 and increased NAFLD phenotypes in both cell and animal models. Therefore, this study examines whether an existing NAFLD-like condition can enhance the biological susceptibility of liver cells exposed to air pollution in the form of WT material. Liver cells were incubated with lauric or oleic acid (LA, OA, respectively) for 24 h to accumulate lipids and served as an in vitro hepatic steatosis model. When exposed to 0.02 or 0.2 g/L water-soluble WT aerosols, both steatosis model cells showed increased cell death compared to the control cells (blank-treated cells with or without pre-incubation with LA or OA) or compared to WT-treated cells without pre-incubation with LA or OA. Furthermore, alterations in oxidative status included variations in reactive oxygen species (ROS) levels, elevated levels of lipid peroxidation adducts, and decreased expression of antioxidant genes associated with the NRF2 transcription factor. In addition, steatosis model cells exposed to WT had a higher degree of DNA damage than the control cells (blank-treated cells with or without pre-incubation with LA or OA). These results support a possible systemic effect through the direct inflammatory and oxidative stress response following exposure to water-soluble WT on liver cells, especially those predisposed to fatty liver. Furthermore, the liver steatosis model can be influenced by the type of fatty acid used; increased adverse effects of WT on metabolic dysregulation were observed in the LA model to a higher extent compared to the OA model.

Pluripotent Stem Cell-Derived Hepatocytes Phenotypic Screening Reveals Small Molecules Targeting the CDK2/4-C/EBPα/DGAT2 Pathway Preventing ER-Stress Induced Lipid Accumulation

Non-alcoholic fatty liver disease (NAFLD) has a large impact on global health. At the onset of disease, NAFLD is characterized by hepatic steatosis defined by the accumulation of triglycerides stored as lipid droplets. Developing therapeutics against NAFLD and progression to non-alcoholic steatohepatitis (NASH) remains a high priority in the medical and scientific community. Drug discovery programs to identify potential therapeutic compounds have supported high throughput/high-content screening of in vitro human-relevant models of NAFLD to accelerate development of efficacious anti-steatotic medicines. Human induced pluripotent stem cell (hiPSC) technology is a powerful platform for disease modeling and therapeutic assessment for cell-based therapy and personalized medicine. In this study, we applied AstraZeneca’s chemogenomic library, hiPSC technology and multiplexed high content screening to identify compounds that significantly reduced intracellular neutral lipid content. Among 13,000 compounds screened, we identified hits that protect against hiPSC-derived hepatic endoplasmic reticulum stress-induced steatosis by a mechanism of action including inhibition of the cyclin D3-cyclin-dependent kinase 2-4 (CDK2-4)/CCAAT-enhancer-binding proteins (C/EBPα)/diacylglycerol acyltransferase 2 (DGAT2) pathway, followed by alteration of the expression of downstream genes related to NAFLD. These findings demonstrate that our phenotypic platform provides a reliable approach in drug discovery, to identify novel drugs for treatment of fatty liver disease as well as to elucidate their underlying mechanisms.