The current study was granted by &#34;Study on the key issues of curative effect of Koumiss on regional diseases of Mongolian medicine&#34; in 2018 Supported Project of the science and technology program of the Department of Science and Technology of Inner Mongolia Autonomous Region.

NOTE: See the Table of Materials for details related to all materials, instruments, and reagents used in this protocol.
1. Cell culture
<ol>
	<li>Culture HepG2 cells in culture flasks containing Dulbecco&#39;s Modified Eagle Medium (DMEM) (containing 10% fetal bovine serum [FBS], 100 units/mL penicillin, and 100 &#181;g/mL streptomycin). Maintain the culture flasks at 37 &#176;C in a 5% CO2 incubator.</li>
</ol>
2. Effect of oleic acid on cell viability as measured by cell counting kit-8
<ol>
	<li>Dissolve a specific volume of OA in dimethyl sulfoxide (DMSO) to achieve a concentration of 200 mM. Store the solution at -20 &#176;C for future use.</li>
	<li>Seed HepG2 cells in a 96-well plate at a cell density of 6 &#215; 103 cells per well. Add 100 &#181;L of DMEM to each well. Incubate and culture the cells at 37 &#176;C in a 5% CO2 incubator for 24 h. Divide the HepG2 cells into two groups:
	<ol>
		<li>Control group: add cell culture medium.</li>
		<li>OA group: add OA to the cell culture medium to achieve final concentrations of 0.125 mM, 0.25 mM, 0.5 mM, and 1 mM.</li>
	</ol>
	</li>
	<li>After 24 h of initial incubation, discard the supernatant from each well and add OA according to the specified grouping, adding 100 &#181;L per well. For the control group, add 100 &#181;L of cell culture medium to each well. Continue to incubate the cells for another 24 h. 
	NOTE: Ensure each group has six replicate wells. To prevent evaporation, add 100 &#181;L of phosphate-buffered saline (PBS) to the outer ring of wells in the 96-well plate.</li>
	<li>After 24 h of incubation, add 10 &#181;L of cell counting kit-8 (CCK-8) to each well, mix gently, and incubate for 2 h in the dark. Remove the 96-well plate from the incubator, place it in the microplate reader, and measure the absorbance value at 450 nm (A450). The GI50 values were counted according to the OD.</li>
</ol>
3. Oil Red O staining to observe intracellular lipid droplet formation
<ol>
	<li>Seed HepG2 cells in 6-well cell culture plates at a density of 5 &#215; 105 cells per well and culture the plates in a constant-temperature incubator for 24 h. Refer to Figure 1 for a visual representation of the described steps.</li>
	<li>After 24 h of cell culture, add 2 mL of cell culture medium containing OA to each well, achieving final concentrations of 0.125 mM, 0.25 mM, 0.5 mM, and 1 mM. After an additional 24 h, remove the cell culture medium from each well and wash twice with PBS. Add 1 mL of ORO fixative to each well and incubate for 30 min.</li>
	<li>Prepare the ORO staining solution by mixing staining solution A with staining solution B at a ratio of 3:2. Allow the mixture to stand at room temperature for 10 min, then filter it once through a 0.45 &#181;m filter. Store the filtered solution in a centrifuge tube protected from light until use.</li>
	<li>Discard the fixative and wash twice with distilled water. Add 1 mL of 60% isopropanol to each well and incubate for 30 s. Discard 60% of the isopropanol solution and add 1 mL of freshly prepared ORO stain solution to each well before incubating for 20 min. Discard the ORO staining solution, add 1 mL of 60% isopropanol to each well, and incubate for 30 s. Wash 5x with water to remove excess dye.</li>
	<li>Cover the cells with distilled water and observe under a microscope. Once the images are collected, discard the liquid in the plate and allow it to dry. Then, add 2 mL of isopropanol to each well and shake the plate on an orbital shaker for 10 min. Transfer the liquid to a new 96-well plate, with 16 wells in each group, adding 100 &#181;L per well. Calculate the lipid content by measuring the optical density (OD) of each well using a microplate reader at 510 nm (A510).</li>
</ol>
4. Effects of different concentrations of oleic acid on total triglyceride in HepG2 cell supernatant
<ol>
	<li>Equilibrate the kit at room temperature for 20 min and prepare the required plates for the experiment.</li>
	<li>Collect the cell supernatant and centrifuge at 1,570 &#215; g for 10 min. Set standard wells and testing sample wells. Add 50 &#181;L of standard ([S0 &#8594; S5] concentration followed by: 0, 0.5, 1, 2, 4, 8 mmol/L) to standard wells. In addition to the blank and standard wells, add 10 &#181;L of different samples to the sample wells, followed by adding 40 &#181;L of sample diluent to each well. Add 100 &#181;L of detection antibody-horseradish peroxidase to each well, seal with a plate membrane, and incubate at 37 &#176;C for 1 h in a constant temperature oven.</li>
	<li>Discard the supernatant, blot dry on dust-free paper, and wash each well with 1x washing solution. Leave to stand at room temperature for 1 min. Repeat the washing process 5x.</li>
	<li>Add 50 &#181;L of substrate A and 50 &#181;L of substrate B to each well. Mix gently and incubate for 15 min at 37 &#176;C. Add 50 &#181;L of termination solution to each well and measure the OD value of each well at 450 nm (A450) within 15 min.</li>
	<li>Plot the concentration of the standard along the x-axis and the corresponding absorbance (OD) value along the y-axis to perform linear regression and derive the curve equation to calculate the concentration value of each sample.</li>
</ol>
5. Statistical analysis
<ol>
	<li>Determine significant differences in quantitative data.</li>
	<li>Calculate the mean &#177; standard deviation (SD) and graphically represent the data. Consider P &#60; 0.05 to be statistically significant.</li>
</ol>

Oleic Acid-Induced HepG2 Cells for Metabolic Disease Analysis 

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The authors declare no conflicts of interest.

MASLD is a clinicopathological syndrome characterized by excessive intracellular fat deposition in hepatocytes due to factors beyond alcohol and other established liver-damaging agents18. MASLD is intricately linked to acquired metabolic stress liver injury, notably associated with insulin resistance and genetic susceptibility. To effectively study and screen drugs for MASLD, it is crucial to select an appropriate experimental model. Establishing a cell model is particularly vital in MASLD researc...

Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses a range of conditions, including simple steatosis, nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma1,2,3,4,5,6, all attributed to factors other than alcohol consuption7. MASLD is the most prevalent liver disease caused by metabolic liver injury, affecting nearly one-quarter of the global population8,9,10,11,12. While the precise pathogenesis of MASLD has not yet been elucidated, various theories attempt to explain its development. One prevailing notion suggests a departure from the classic &#34;two-hit&#34; theory towards a &#34;multiple-hit&#34; model1. Central to these hypotheses is the role of insulin resistance, which is believed to be pivotal in MASLD pathogenesis13. Research indicates that insulin resistance in hepatocytes leads to increased levels of free fatty acids, subsequently forming triglycerides stored within the liver14,15.
Researchers have used both in vivo and in vitro models to simulate fat deposition in MASLD; yet fully replicating its pathomechanism remains challenging. Despite this limitation, these models have been instrumental in studying potential therapeutic targets for MASLD. However, the development of a stable model of MASLD is crucial. While animal models are effective, they are time-consuming and expensive, thus highlighting the growing interest in in vitro cellular models. These models often use single or multiple free fatty acids such as oleic acid (OA) and palmitic acid to recreate diet-induced MASLD. Among these, the human hepatoblastoma cell line HepG2 is often used to establish in vitro cellular models of MASLD.
OA induction stimulates HepG2 cells to replicate fatty deposition akin to MASLD, a method with a well-established history. The aim of this study was to demonstrate the viability, Oil Red O (ORO) staining, lipid content, and triglyceride (TG) level of HepG2 cells treated with 0.25 mM OA. The objective of this experiment was to provide further evidence for the development of MAFLD modeling studies.

<table><tbody><tr><td>0.22 &amp;micro;m filter</td><td>Millex</td><td></td><td></td></tr><tr><td>0.25% Trypsin-EDTA (1x) Trypsin-EDTA</td><td>Gibco</td><td>25200-056</td><td></td></tr><tr><td>0.45 &amp;micro;m filter</td><td>Millex</td><td></td><td></td></tr><tr><td>2 mL Crygenic Vials</td><td>CORNING</td><td>430659</td><td></td></tr><tr><td>25 cm&lt;sup&gt;2&lt;/sup&gt; Cell Culture Flask</td><td>CORNING</td><td>430639</td><td></td></tr><tr><td>6-well cell culture plate</td><td>CORNING</td><td>3516</td><td></td></tr><tr><td>96-well cell culture plate</td><td>CORNING</td><td>3599</td><td></td></tr><tr><td>Blood Count Plate</td><td>Shanghai Jing Jing Biochemical Reagent &amp;amp; Instrument Co.</td><td>02270113</td><td></td></tr><tr><td>Cell Counting Kit-8 assays</td><td>Beijing Solarbio Science &amp;amp; Technology Co.,Ltd.&amp;nbsp;</td><td>CA1210-1000T</td><td></td></tr><tr><td>CO&lt;sub&gt;2&lt;/sub&gt; incubator</td><td>NUAIRE</td><td>NU-5710E</td><td></td></tr><tr><td>&amp;nbsp;DMSO Dimethyl sulfoxide&amp;nbsp;</td><td>Beijing Solarbio Science &amp;amp; Technology Co.,Ltd.&amp;nbsp;</td><td>D8371</td><td></td></tr><tr><td>Dulbecco&#039;s Modified Eagle Medium</td><td>Gibco</td><td>8122691</td><td></td></tr><tr><td>Enzyme Labeling Equipment</td><td>Tecan</td><td>Spark</td><td></td></tr><tr><td>Fetal Bovine Serum, Qualified</td><td>Gibco</td><td>10099141</td><td></td></tr><tr><td>HepG2 cells line</td><td>Beijing North China Chuanglian Biotechnology Research Institute (BNCC)</td><td>221031</td><td></td></tr><tr><td>Human Triglyceride (TG) ELISA instruction</td><td>Nanjing Jiacheng Bioengineering Institute</td><td>20170301</td><td></td></tr><tr><td>Inverted Microscope for Cell Culture</td><td>Leica</td><td>DMi1&amp;nbsp;</td><td></td></tr><tr><td>Isopropanol</td><td>Tianjin Zhiyuan Chemical Reagent Co.</td><td>2021030141</td><td></td></tr><tr><td>Oil Red Stain Kit, For Cultured Cells</td><td>Beijing Solarbio Science &amp;amp; Technology Co.,Ltd.&amp;nbsp;</td><td>G1262</td><td></td></tr><tr><td>Oleic acid&amp;nbsp;</td><td>Sangon Biotech (Shanghai) Co., Ltd.</td><td>A502071</td><td></td></tr><tr><td>Penicillin Streptomycin</td><td>Gibco</td><td>15140122</td><td></td></tr><tr><td>SPSS 24.0</td><td></td><td>Statistics software</td><td></td></tr></tbody></table>

in vitro modeling of fat deposition in metabolic dysfunction-associated steatotic liver disease

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) has surged due to changes in economic and lifestyle patterns, leading to significant health challenges. Previous reports have studied the establishment of animal and cellular models for MASLD, highlighting differences between them. In this study, a cellular model was created by inducing fat accumulation in MASLD. HepG2 cells were stimulated with the unsaturated fatty acid oleic acid at various concentrations (0.125 mM, 0.25 mM, 0.5 mM, 1 mM) to emulate MASLD. The model&#39;s efficacy was assessed using cell counting kit-8 assays, Oil Red O staining, and lipid content analysis. This study aimed to create a simple-to-operate cellular model for MASLD cells. Results from the cell counting kit-8 assays showed that the survival of HepG2 cells was dependent on the concentration of oleic acid, with a GI50 of 1.875 mM. Cell viability in the 0.5 mM and 1 mM groups were significantly lower than those in the control group (P &#60; 0.05). Furthermore, Oil Red O staining and lipid content analysis examined fat deposition at varying oleic acid concentrations (0.125 mM, 0.25 mM, 0.5 mM, 1 mM) on HepG2 cells. The lipid content of the 0.25 mM, 0.5 mM, and 1 mM groups was significantly higher than that of the control group (P &#60; 0.05). Additionally, triglyceride levels in the OA groups were significantly higher than those in the control group (P &#60; 0.05).

Effect of oleic acid on cell viability 
HepG2 cells were exposed to varying concentrations of OA (0 mM, 0.125 mM, 0.25 mM, 0.5 mM, 1 mM), resulting in a decrease in cell survival rates at 0.125 mM, 0.25 mM, 0.5 mM, and 1 mM compared to 0 mM. Statistical significance was observed at 0.5 mM (P &#60; 0.05) and 1 mM (P &#60; 0.05) when compared to 0 mM. The results of OA&#39;s impact on cell viability, as assessed by the CCK-8 kit, are shown in Fig...

Author Spotlight: Establishing MASLD Cell Models for Investigating Disease Mechanisms and the Lipid-Lowering Effects of Koumiss

This article describes the use of oleic acid-induced HepG2 cells as a model for metabolic dysfunction-associated steatotic liver disease.

In Vitro Modeling of Fat Deposition in Metabolic Dysfunction-Associated Steatotic Liver Disease

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) has surged due to changes in economic and lifestyle patterns, leading ...

in-vitro-modeling-fat-deposition-metabolic-dysfunction-associated

Research

JoVE Journal

Biology

651 Views.  Inner Mongolia Medical University. This article describes the use of oleic acid-induced HepG2 cells as a model for metabolic dysfunction-associated steatotic liver disease.

Video: Author Spotlight: Establishing MASLD Cell Models for Investigating Disease Mechanisms and the Lipid-Lowering Effects of Koumiss

Assessing Hepatic Steatosis with 3D Fluorescence Lipid Droplet Reconstruction

Analysis of Fluorescent-Stained Lipid Droplets with 3D Reconstruction for Hepatic Steatosis Assessment

Lipid droplets (LDs) are specialized organelles that mediate lipid storage and play a very important role in suppressing lipotoxicity and preventing dysfunction caused by free fatty acids (FAs). The liver, given its critical role in the body's fat metabolism, is persistently threatened by the intracellular accumulation of LDs in the form of both microvesicular and macrovesicular hepatic steatosis. The histologic characterization of LDs is typically based on lipid-soluble diazo dyes, such as Oil Red O (ORO) staining, but a number of disadvantages consistently hamper the use of this analysis with liver specimens. More recently, lipophilic fluorophores 493/503 have become popular for visualizing and locating LDs due to their rapid uptake and accumulation into the neutral lipid droplet core. Even though most applications are well-described in cell cultures, there is less evidence demonstrating the reliable use of lipophilic fluorophore probes as an LD imaging tool in tissue samples. Herein, we propose an optimized boron dipyrromethene (BODIPY) 493/503-based protocol for the evaluation of LDs in liver specimens from an animal model of high-fat diet (HFD)-induced hepatic steatosis. This protocol covers liver sample preparation, tissue sectioning, BODIPY 493/503 staining, image acquisition, and data analysis. We demonstrate an increased number, intensity, area ratio, and diameter of hepatic LDs upon HFD feeding. Using orthogonal projections and 3D reconstructions, it was possible to observe the full content of neutral lipids in the LD core, which appeared as nearly spherical droplets. Moreover, with the fluorophore BODIPY 493/503, we were able to distinguish microvesicles (1 &#181;m &lt; d &#8804; 3 &#181;m), intermediate vesicles (3 &#181;m &lt; d &#8804; 9 &#181;m), and macrovesicles (d &gt; 9 &#181;m), allowing the successful discrimination of microvesicular and macrovesicular steatosis. Overall, this BODIPY 493/503 fluorescence-based protocol is a reliable and simple tool for hepatic LD characterization and may represent a complementary approach to the classical histological protocols.

Author Spotlight: Analysis of Fluorescent-Stained Lipid Droplets with 3D Reconstruction for Hepatic Steatosis Assessment  

Herein, we demonstrate an optimized BODIPY 493/503 fluorescence-based protocol for lipid droplet characterization in liver tissue. Through the use of orthogonal projections and 3D reconstructions, the fluorophore allows for successful discrimination between microvesicular and macrovesicular steatosis and may represent a complementary approach to the classical histological protocols for hepatic steatosis assessment.

Lipid droplets (LDs) are specialized organelles that mediate lipid storage and play a very important role in suppressing lipotoxicity and preventing ...

Biochemistry

Optimized Analysis of In Vivo and In Vitro Hepatic Steatosis

Establishing a system of procedures to qualitatively and quantitatively characterize in vivo and in vitro hepatic steatosis is important for metabolic study in the liver. Here, numerous assays are described to comprehensively measure the phenotype and parameters of hepatic steatosis in mouse and hepatocyte models. 
Combining the physiological, histological, and biochemical methods, this system can be used to assess the progress of hepatic steatosis. In vivo, the measurements of body weight and nuclear magnetic resonance (NMR) provide a general understanding of mice in a non-invasive manner. Hematoxylin and Eosin (H&amp;E) and Oil Red O staining determine the histological morphology and lipid deposition of liver tissue under nutrient overload conditions, such as high-fat diet feeding. Next, the total lipid contents are isolated by chloroform/methanol extraction, which are followed by a biochemical analysis for triglyceride and cholesterol. Moreover, mouse primary hepatocytes are treated with high glucose plus insulin to stimulate lipid accumulation, an efficient in vitro model to mimic diet-induced hyperglycemia and hyperinsulinemia in vivo. Then, the lipid deposition is measured by Oil Red O staining and chloroform/methanol extraction. Oil Red O staining determines intuitive hepatic steatotic phenotypes, while the lipid extraction analysis determines the parameters that can be analyzed statistically. The present protocols are of interest to scientists in the fields of fatty liver diseases, insulin resistance, and type 2 diabetes.

Optimized Analysis of In Vivo and In Vitro Hepatic Steatosis

Here, optimized methods to generate in vivo and in vitro models of hepatic steatosis and to analyze the steatotic phenotypes and related physiological parameters are described.

Establishing a system of procedures to qualitatively and quantitatively characterize in vivo and in vitro hepatic steatosis is important for metabolic ...

Medicine

Do-It-Yourself Device for Recovery of Cryopreserved Samples Accidentally Dropped into Cryogenic Storage Tanks

Liquid nitrogen is colorless, odorless, extremely cold (-196 &deg;C) liquid kept under pressure. It is commonly used as a cryogenic fluid for long term storage of biological materials such as blood, cells and tissues 1,2. The cryogenic nature of liquid nitrogen, while ideal for sample preservation, can cause rapid freezing of live tissues on contact - known as 'cryogenic burn'2, which may lead to severe frostbite in persons closely involved in storage and retrieval of samples from Dewars. Additionally, as liquid nitrogen evaporates it reduces the oxygen concentration in the air and might cause asphyxia, especially in confined spaces2.
In laboratories, biological samples are often stored in cryovials or cryoboxes stacked in stainless steel racks within the Dewar tanks1. These storage racks are provided with a long shaft to prevent boxes from slipping out from the racks and into the bottom of Dewars during routine handling. All too often, however, boxes or vials with precious samples slip out and sink to the bottom of liquid nitrogen filled tank. In such cases, samples could be tediously retrieved after transferring the liquid nitrogen into a spare container or discarding it. The boxes and vials can then be relatively safely recovered from emptied Dewar. However, the cryogenic nature of liquid nitrogen and its expansion rate makes sunken sample retrieval hazardous. It is commonly recommended by Safety Offices that sample retrieval be never carried out by a single person. Another alternative is to use commercially available cool grabbers or tongs to pull out the vials3. However, limited visibility within the dark liquid filled Dewars poses a major limitation in their use.
In this article, we describe the construction of a Cryotolerant DIY retrieval device, which makes sample retrieval from Dewar containing cryogenic fluids both safe and easy.

Here we present a low cost, durable cryotolerant device for sample retrieval from Dewar tanks filled with liquid nitrogen. The ease of construction and modular design of the device makes the process of sample retrieval from cryogenic tanks safe and easy.

Liquid nitrogen is colorless, odorless, extremely cold (-196 &deg;C) liquid kept under pressure. It is commonly used as a cryogenic fluid for long term ...

An Advanced Murine Model for Nonalcoholic Steatohepatitis in Association with Type 2 Diabetes

Obesity is associated with chronic low-grade inflammation and insulin resistance, contributing to an increasing prevalence of chronic metabolic diseases, such as type 2 diabetes and nonalcoholic steatohepatitis (NASH). Recent research has established that pro-inflammatory immune cells infiltrate obese hypertrophic adipose tissue and liver. Given the emerging importance of immune cells in the context of metabolic homeostasis, there is a critical need to quantify and characterize their modification during the development of type 2 diabetes and NASH. However, animal models that induce pathophysiological features typical of human NASH are sparse.
In this article, we provide a detailed protocol to identify immune cell subsets isolated from liver and adipose tissue in a reliable mouse model of NASH, established by housing high-fat diet (HFD) mice under non-specific pathogen-free (SPF) conditions without a barrier for at least seven weeks. We demonstrate the handling of mice in non-SPF conditions, digestion of the tissues and identification of macrophages, natural killer (NK) cells, dendritic cells, B and T cell subsets by flow cytometry. Representative flow cytometry plots from SPF HFD mice and non-SPF mice are provided. To obtain reliable and interpretable data, the use of antibodies, accurate and precise methods for tissue digestion and proper gating in flow cytometry experiments are critical elements.
The intervention to restore physiological antigen exposure in mice by housing them in non-SPF conditions and unspecific exposure to microbial antigens could provide a relevant tool for investigating the link between immunological alterations, diet-induced obesity and related long term complications.

A simple and reliable diet-induced rodent animal model for nonalcoholic steatohepatitis (NASH) is described, achieved through non-SPF housing of the animals and administration of a specific high-fat diet. We describe identification of hepatic and adipose immune cell subsets to recapitulate human immunological conditions by exposing mice to environmental germs.

Obesity is associated with chronic low-grade inflammation and insulin resistance, contributing to an increasing prevalence of chronic metabolic diseases, ...

Immunology and Infection

Inducing and Characterizing Vesicular Steatosis in Differentiated HepaRG Cells

Hepatic steatosis represents a metabolic dysfunction that results from an accumulation of triglyceride-containing lipid droplets in hepatocytes. Excessive fat accumulation leads to non-alcoholic fatty liver disease (NAFLD), &#160;which is potentially reversible and may evolve into non-alcoholic steatohepatitis (NASH) and eventually cirrhosis and hepatocellular carcinoma (HCC). The molecular mechanisms linking lipid accumulation in hepatocytes with the progression to NASH, irreversible liver damage, fibrosis, cirrhosis, and even HCC still remains unclear. To this end, several in vitro and in vivo models have been developed to elucidate the pathological processes that cause NAFLD. In the present study, we describe a cellular model for the induction of liver vesicular steatosis that consists of DMSO-differentiated human hepatic HepaRG cells treated with the fatty acid salt sodium oleate. Indeed, sodium oleate-treated HepaRG cells accumulate lipid droplets in the cytoplasm and show typical features of steatosis. This in vitro human model represents a valuable alternative to in vivo mice models as well as to the primary human hepatocytes. We also present a comparison of several methods for the quantification and evaluation of fat accumulation in HepaRG cells, including Oil Red O staining, cytofluorimetric Bodipy measurement, metabolic gene expression analysis by qPCR, and coherent anti-Stokes Raman scattering (CARS) microscopy. CARS imaging combines the chemical specificity of Raman spectroscopy, a chemical analysis technique well-known in materials science applications, with the benefits of high-speed, high-resolution non-linear optical microscopies to allow precise quantification of lipid accumulation and lipid droplet dynamics. The establishment of an efficient in vitro model for the induction of vesicular steatosis, alongside an accurate method for the quantification and characterization of lipid accumulation, could lead to the development of early stage diagnosis of NAFLD via the identification of molecular markers, and to the generation of new treatment strategies.

In this study, we describe a detailed protocol for inducing liver vesicular steatosis in differentiated HepaRG cells with the fatty acid salt sodium oleate and employ methods for detection and quantification of lipid accumulation, including coherent anti-Stokes Raman scattering (CARS) microscopy, cytofluorimetric analysis, Oil red O staining, and qPCR.&#160;

Hepatic steatosis represents a metabolic dysfunction that results from an accumulation of triglyceride-containing lipid droplets in hepatocytes. Excessive ...

Determination of Fatty Acid Oxidation and Lipogenesis in Mouse Primary Hepatocytes

Lipid metabolism in liver is complex. In addition to importing and exporting lipid via lipoproteins, hepatocytes can oxidize lipid via fatty acid oxidation, or alternatively, synthesize new lipid via de novo lipogenesis. The net sum of these pathways is dictated by a number of factors, which in certain disease states leads to fatty liver disease. Excess hepatic lipid accumulation is associated with whole body insulin resistance and coronary heart disease. Tools to study lipid metabolism in hepatocytes are useful to understand the role of hepatic lipid metabolism in certain metabolic disorders.
In the liver, hepatocytes regulate the breakdown and synthesis of fatty acids via &#946;-fatty oxidation and de novo lipogenesis, respectively. Quantifying metabolism in these pathways provides insight into hepatic lipid handling. Unlike in vitro quantification, using primary hepatocytes, making measurements in vivo is technically challenging and resource intensive. Hence, quantifying &#946;-fatty acid oxidation and de novo lipogenesis in cultured mouse hepatocytes provides a straight forward method to assess hepatocyte lipid handling. 
Here we describe a method for the isolation of primary mouse hepatocytes, and we demonstrate quantification of &#946;-fatty acid oxidation and de novo lipogenesis, using radiolabeled substrates.

De novo lipogenesis and &#946;-fatty acid oxidation constitute key metabolic pathways in hepatocyte, pathways that are perturbed in several metabolic disorders, including fatty liver disease. Here we demonstrate isolation of mouse primary hepatocytes and describe quantification of &#946;-fatty acid oxidation and lipogenesis.

Lipid metabolism in liver is complex. In addition to importing and exporting lipid via lipoproteins, hepatocytes can oxidize lipid via fatty acid ...

A Model of Experimental Steatosis In Vitro: Hepatocyte Cell Culture in Lipid Overload-Conditioned Medium

Metabolic dysfunction-associated fatty liver disease (MAFLD), previously known as non-alcoholic fatty liver disease (NAFLD), is the most prevalent liver disease worldwide due to its relationship with obesity, diabetes type 2, and dyslipidemia. Hepatic steatosis, the accumulation of lipid droplets in the liver parenchyma, is a key feature of the disease preceding the inflammation observed in steatohepatitis, fibrosis, and end-stage liver disease. Lipid accumulation in hepatocytes might interfere with proper metabolism of xenobiotics and endogenous molecules, as well as to induce cellular processes leading to the advance of the disease. Although the experimental study of steatosis can be performed in vivo, in vitro approaches to the study of steatosis are complementary tools with different advantages. Hepatocyte culture in lipid overload-conditioned medium is an excellent reproducible option for the study of hepatic steatosis allowing the identification of cellular processes related to lipid accumulation, such as oxidative and reticular stresses, autophagia, proliferation, cell death, etcetera, as well as other testing including drug effectiveness, and toxicological testing, among many other possible applications. Here, it was aimed to describe the methodology of hepatocyte cell culture in lipid overload-conditioned medium. HepG2 cells were cultured in RMPI 1640 medium conditioned with sodium palmitate and sodium oleate. Importantly, the ratio of these two lipids is crucial to favor lipid droplet accumulation, while maintaining cell proliferation and a moderate mortality rate, as occurs in the liver during the disease. The methodology, from the preparation of the lipid solution stocks, mixture, addition to the medium, and hepatocyte culture is shown. With this approach, it is possible to identify lipid droplets in the hepatocytes that are readily observable by Oil-red O staining, as well as curves of proliferation/mortality rates.

A Model of Experimental Steatosis In Vitro: Hepatocyte Cell Culture in Lipid Overload-Conditioned Medium

This protocol is intended to be a tool to study steatosis and the molecular, biochemical, cellular changes produced by the over exposure of hepatocytes to lipids in vitro.

Metabolic dysfunction-associated fatty liver disease (MAFLD), previously known as non-alcoholic fatty liver disease (NAFLD), is the most prevalent liver ...

3D Imaging of the Liver Extracellular Matrix in a Mouse Model of Non-Alcoholic Steatohepatitis

Non-alcoholic steatohepatitis (NASH) is the most common chronic liver disease in the United States, affecting more than 70 million Americans. NASH can progress to fibrosis and eventually to cirrhosis, a significant risk factor for hepatocellular carcinoma. The extracellular matrix (ECM) provides structural support and maintains liver homeostasis via matricellular signals. Liver fibrosis results from an imbalance in the dynamic ECM remodeling process and is characterized by excessive accumulation of structural elements and associated changes in glycosaminoglycans. The typical fibrosis pattern of NASH is called &#34;chicken wire,&#34; which usually consists of zone 3 perisinusoidal/pericellular fibrosis, based on features observed by Masson&#39;s trichrome stain and Picrosirius Red stains. However, these traditional thin two-dimensional (2D) tissue slide-based imaging techniques cannot demonstrate the detailed three-dimensional (3D) ECM structural changes, limiting the understanding of the dynamic ECM remodeling in liver fibrosis.
The current work optimized a fast and efficient protocol to image the native ECM structure in the liver via decellularization to address the above challenges. Mice were fed either with chow or fast-food diet for 14 weeks. Decellularization was performed after in situ portal vein perfusion, and the two-photon microscopy techniques were applied to image and analyze changes in the native ECM. The 3D images of the normal and NASH livers were reconstituted and analyzed. Performing in situ perfusion decellularization and analyzing the scaffold by two-photon microscopy provided a practical and reliable platform to visualize the dynamic ECM remodeling in the liver.

The present protocol optimizes the liver in situ perfusion/decellularization and two-photon microscopy methods to establish a reliable platform to visualize the dynamics of extracellular matrix (ECM) remodeling during non-alcoholic steatohepatitis (NASH).

Non-alcoholic steatohepatitis (NASH) is the most common chronic liver disease in the United States, affecting more than 70 million Americans. NASH can ...

Investigating the Protective Effects of Platycodin D on Non-Alcoholic Fatty Liver Disease in a Palmitic Acid-Induced In Vitro Model

The occurrence of non-alcoholic fatty liver disease (NAFLD) has been increasing at an alarming rate worldwide. Platycodon grandiflorum is widely used as a traditional ethnomedicine for the treatment of various diseases and is a typical functional food that can be incorporated into the everyday diet. Studies have suggested that platycodin D (PD), one of the main active ingredients in Platycodon grandiflorum, has high bioavailability and significantly mitigates the progress of NAFLD, but the underlying mechanism of this is still unclear. This study aims to investigate the therapeutic effect of PD against NAFLD in vitro. AML-12 cells were pretreated with 300 &#181;M palmitic acid (PA) for 24 h to model NAFLD in vitro. Then, the cells were either treated with PD or received no PD treatment for 24 h. The levels of reactive oxygen species (ROS) were analyzed using 2&#8242;,7&#8242;-dichloro-dihydro-fluorescein diacetate (DCFH-DA) staining, and the mitochondrial membrane potential was determined by the JC-1 staining method. Moreover, the protein expression levels of LC3-II/LC3-I and p62/SQSTM1 in the cell lysates were analyzed by western blotting. PD was found to significantly decrease the ROS and mitochondrial membrane potential levels in the PA-treated group compared to the control group. Meanwhile, PD increased the LC3-II/LC3-I levels and decreased the p62/SQSTM1 levels in the PA-treated group compared to the control group. The results indicated that PD ameliorated NAFLD in vitro by reducing oxidative stress and stimulating autophagy. This in vitro model is a useful tool for studying the role of PD in NAFLD.

Investigating the Protective Effects of Platycodin D on Non-Alcoholic Fatty Liver Disease in a Palmitic Acid-Induced In Vitro Model

This protocol investigates the protective effects of platycodin D on non-alcoholic fatty liver disease in a palmitic acid-induced in vitro model.

The occurrence of non-alcoholic fatty liver disease (NAFLD) has been increasing at an alarming rate worldwide. Platycodon grandiflorum is widely used as a ...

Novel In Vivo Micro-Computed Tomography Imaging Techniques for Assessing the Progression of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a growing global health issue, and the impact of NAFLD is compounded by the current lack of effective treatments. Considerable limiting factors hindering the timely and accurate diagnosis (including grading) and monitoring of NAFLD, as well as the development of potential therapies, are the current inadequacies in the characterization of the hepatic microenvironment structure and the scoring of the disease stage in a spatiotemporal and non-invasive manner. Using a diet-induced NAFLD mouse model, we investigated the use of in vivo micro-computed tomography (CT) imaging techniques as a non-invasive method to assess the progression stages of NAFLD, focusing predominantly on the hepatic vascular network due to its significant involvement in NAFLD-related hepatic dysregulation. This imaging methodology allows for longitudinal analysis of liver steatosis and functional tissue uptake, as well as the evaluation of the relative blood volume, portal vein diameter, and density of the vascular network. Understanding the adaptations of the hepatic vascular network during NAFLD progression and correlating this with other ways of characterizing the disease progression (steatosis, inflammation, fibrosis) using the proposed method can pave the way toward the establishment of new, more efficient, and reproducible approaches for NAFLD research in mice. This protocol is also expected to upgrade the value of preclinical animal models for investigating&#160;the development of novel therapies against disease progression.

Novel In Vivo Micro-Computed Tomography Imaging Techniques for Assessing the Progression of Non-Alcoholic Fatty Liver Disease

Using a diet-induced non-alcoholic fatty liver disease (NAFLD) mouse model, we describe the use of novel in vivo micro-computed tomography imaging techniques as a non-invasive method to assess the progression stages of NAFLD, focusing predominantly on the hepatic vascular network due to its significant involvement in NAFLD-related hepatic dysregulation.

In Vitro Modeling of Fat Deposition in Metabolic Dysfunction-Associated Steatotic Liver Disease

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Chapters in this video

Analysis of Fluorescent-Stained Lipid Droplets with 3D Reconstruction for Hepatic Steatosis Assessment

Optimized Analysis of In Vivo and In Vitro Hepatic Steatosis

Do-It-Yourself Device for Recovery of Cryopreserved Samples Accidentally Dropped into Cryogenic Storage Tanks

An Advanced Murine Model for Nonalcoholic Steatohepatitis in Association with Type 2 Diabetes

Inducing and Characterizing Vesicular Steatosis in Differentiated HepaRG Cells

Determination of Fatty Acid Oxidation and Lipogenesis in Mouse Primary Hepatocytes

A Model of Experimental Steatosis In Vitro: Hepatocyte Cell Culture in Lipid Overload-Conditioned Medium

3D Imaging of the Liver Extracellular Matrix in a Mouse Model of Non-Alcoholic Steatohepatitis

Investigating the Protective Effects of Platycodin D on Non-Alcoholic Fatty Liver Disease in a Palmitic Acid-Induced In Vitro Model

Novel In Vivo Micro-Computed Tomography Imaging Techniques for Assessing the Progression of Non-Alcoholic Fatty Liver Disease