Lipid Metabolism In Liver Cells Research Articles

The hepatitis B virus promotes the progression of non-alcoholic fatty liver disease through incomplete autophagy.

Hepatitis B virus (HBV) infection is still a serious public health problem. In recent years, with the increasing incidence of chronic hepatitis B (CHB) combined with nonalcoholic fatty liver disease (NAFLD), a more in-depth exploration of the pathogenesis of CHB combined with NAFLD is required. HBV can induce autophagy and use to increase replication. The removal of fat by autophagy, also known as lipophagy, is also currently considered an alternative pathway for lipid metabolism in liver cells. This degradation of autophagy prevents hepatotoxicity and steatosis. However, it is not known whether there is a correlation between HBV-related autophagy and the progression of NAFLD. We explored how HBV affects disease progression in NAFLD should be " and determined whether it is associated with HBV-associated autophagy. In this study, we constructed HBV-TG mouse high-fat diet (HFD) models and controls, and the results showed that the presence of HBV promoted the occurrence of NAFLD. We also demonstrated that HBV promotes lipid droplet accumulation in hepatocytes using HBV-stable expression cell lines HepG2.2.15 and AML12-HBV. In addition, this study also found that exogenous OA supplementation reduced HBV replication. We further studied the mechanism and found that HBV-related autophagy can promote the absorption of liver cells to lipid droplets. It can reduce the decomposition of lipid droplets by inhibiting the function of autophagolysosome, and eventually lead to the accumulation of lipid droplets in hepatocytes. In a word, HBV promotes the progression of NAFLD by increasing lipid accumulation in hepatocytes through incomplete autophagy.

Network pharmacology-based analysis of Resinacein S against non-alcoholic fatty liver disease by modulating lipid metabolism.

Ganoderma lucidum is reportedly the best source of traditional natural bioactive constituents. Ganoderma triterpenoids (GTs) have been verified as an alternative adjuvant for treating leukemia, cancer, hepatitis and diabetes. One of the major triterpenoids, Resinacein S, has been found to regulate lipid metabolism and mitochondrial biogenesis. Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease that has become a major public health problem. Given the regulatory effects on lipid metabolism of Resinacein S, we sought to explore potential protective effects against NAFLD. Resinacein S was extracted and isolated from G. lucidum. And mice were fed with high fat diet with or without Resinacein S to detect hepatic steatosis. According to Network Pharmacology and RNA-seq, we analyzed the hub genes of Resinacein S against NAFLD disease. Our results can be summarized as follows: (1) The structure of Resinacein S was elucidated using NMR and MS methods. (2) Resinacein S treatment could significantly attenuate high-fat diet (HFD)-induced hepatic steatosis and hepatic lipid accumulation in mouse. (3) GO terms, KEGG pathways and the PPI network of Resinacein S induced Differentially Expressed Genes (DEGs) demonstrated the key target genes of Resinacein S against NAFLD. (4) The hub proteins in PPI network analysis could be used for NAFLD diagnosis and treatment as drug targets. Resinacein S can significantly change the lipid metabolism in liver cells and yield a protective effect against steatosis and liver injury. Intersected proteins between NAFLD related genes and Resinacein S-induced DEGs, especially the hub protein in PPI network analysis, can be used to characterize targets of Resinacein S against NAFLD.

Abstract 11397: Circulating Human Metabolites Resulting From TOTUM-070 Absorption (a Plant-Based, Polyphenol-Rich Hypocholesterolemic Ingredient) Improve Lipid Metabolism in Human Hepatocytes: Lessons From an Original ex vivo Clinical Trial

Introduction: TOTUM-070 is a patented polyphenol-rich compound which has shown hypocholesterolemic properties in preclinical studies. However, clinically validated approaches and further investigations on the mode of action at cellular level especially in humans are required for optimized care management. In this study, we designed an ex-vivo clinical innovative approach considering the metabolites produced by the digestive tract following the ingestion of TOTUM-070 in humans. Methods: Human serum was collected in healthy subjects before and following acute intake of 5g of TOTUM-070. Availability of circulating metabolites was confirmed and characterized by UPLC-MS. Human serum enriched with metabolites deriving from TOTUM-070 absorption was further incubated with human hepatocytes, pretreated or not with palmitate (250 μM). In such lipotoxic environment, hepatocyte behavior was monitored to determine whether and how TOTUM-070 metabolites may improve cholesterol metabolism in human. Results: In the presence of the human metabolites from TOTUM-070, human hepatocytes were protected from an induced lipotoxic stress. No effect on cell toxicity was detected in the presence of enriched sera. Hepatocyte protection was characterized by (1) the inhibition of both triglycerides (-41%, p<0.001) and cholesterol (-50%, p<0.001) storage, (2) a reduced de novo cholesterol synthesis (HMG-CoA reductase activity reduced by 44%, p<0.001), (3) a lowered fatty acid synthase expression (p<0.001), (4) the stimulation of the Lecithin Cholesterol Acyl Transferase (LCAT) activity (p<0.05) and finally (5) a higher CYP7A1 expression (p<0.05). All together, these data provide new biochemical insights into the mechanisms underlying, in humans, the beneficial impact of TOTUM-070 on lipid metabolism in liver cells. Conclusion: Using a pioneering clinical ex vivo approach considering the digestive processes of nutrients, we give clues on the role of circulating metabolites produced following TOTUM-070 intake in humans in hepatocyte protection.

Comparative effects of sesame lignans (sesamin, sesamolin, and sesamol) on oxidative stress and lipid metabolism in steatosis HepG2 cells.

Non-alcoholic fatty liver disease (NAFLD) can be attributed to the imbalance between lipogenesis and lipidolysis in the liver. Sesame lignans (sesamin, sesamolin, and sesamol) are unique bioactive compounds responsible for the nutritional function of sesame oils. However, the preventive effects of three lignans on oxidative stress and lipid metabolism in steatosis HepG2 cells have not been compared. In this study, we investigated the role of sesamin, sesamolin, and sesamol on hepatic lipid accumulation and explored the underlying mechanism via a well-established cell model. The results showed that 3μg/ml of lignans could decrease the TG/TC contents and alleviate cellular oxidative stress, with an order of the lipid-lowering effect as sesamol > sesamin > sesamolin. The lignan-activated AMPK and PPAR signaling pathways enhanced gene and protein expressions related to fatty acid oxidation, cholesterol efflux, and catabolism. Meanwhile, treatment of the steatosis HepG2 cells with sesamin, sesamolin, and sesamol reduced lipid synthesis and cholesterol uptake, thus lowering intracellular lipogenesis in the process of NAFLD. Our data suggested that sesame lignans can attenuate oxidative stress and regulate lipid metabolism in liver cells, which may be potential therapeutic agents for treating the NAFLD. PRACTICAL APPLICATIONS: The present work demonstrated that sesame lignans can be used for dietary supplements or functional additives with excellent lipid-lowering effects. Furthermore, this study supplied potential molecular mechanisms involved in NAFLD treatment process, and also provided nutritional guidelines for sesame oil evaluation and selection.

Periodontal diseases and non-alcoholic fatty liver disease

Relevance. Periodontal diseases, being an extremely common, do not only cause tooth loss and significantly affect the patients’ quality of life, but are also a risk factor for many systemic diseases and may subsequently aggravate their course. Non-alcoholic fatty liver disease (NAFLD) is one of the relatively understudied pathologies associated with periodontal diseases.Materials and methods. A non-interventional study analytically reviewed Russian and international scientific publications, which presented the results of independent clinical and laboratory studies on the topic from 2011 to 2021.Results. Scientific literature data evidence that NAFLD manifests by impaired lipid metabolism in liver cells, linked with mechanisms regulated by the liver nuclear receptors (LXR), and leads to such life-threatening conditions as liver cirrhosis and hepatocellular carcinoma. The information on the role of periodontal pathogens in NAFLD development has been accumulated by now. The example of such principal periodontal pathogen as Porphyromonas gingivalis experimentally demonstrated that it can integrate into the intestinal microbiome, migrate through the bloodstream to the liver, survive in hepatocytes and influence the nuclear receptors of these cells affecting the lipid metabolism and contributing to NAFLD development.Conclusion. A detailed study of the link between periodontal disease and non-alcoholic fatty liver disease may contribute to the development of new effective strategies for the diagnosis and treatment of these pathological conditions.

A Preliminary Study on the Effect of Hydrogen Gas on Alleviating Early CCl4-Induced Chronic Liver Injury in Rats.

As a small-molecule reductant substance, hydrogen gas has an obvious antioxidant function. It can selectively neutralize hydroxyl radicals (•OH) and peroxynitrite (ONOO•) in cells, reducing oxidative stress damage. The purpose of this study was to investigate the effect of hydrogen gas (3%) on early chronic liver injury (CLI) induced by CCl4 and to preliminarily explore the protective mechanism of hydrogen gas on hepatocytes by observing the expression of uncoupling protein 2 (UCP2) in liver tissue. Here, 32 rats were divided into four groups: the control group, CCl4 group, H2 (hydrogen gas) group, and CCl4 + H2 group. The effect of hydrogen gas on early CLI was observed by serological tests, ELISA, hematoxylin and eosin staining, and oil red O staining. Immunohistochemical staining and Western blotting were used to observe the expression of UCP2 in liver tissues. We found that CCl4 can induce significant steatosis in hepatocytes. When the hydrogen gas was inhaled, hepatocyte steatosis was reduced, and the UCP2 expression level in liver tissue was increased. These results suggest that hydrogen gas might upregulate UCP2 expression levels, reduce the generation of intracellular oxygen free radicals, affect lipid metabolism in liver cells, and play a protective role in liver cells.

Effect of prenatal PFOS exposure on liver cell function in neonatal mice.

Perfluorooctane sulfonate (PFOS), a hepatotoxic pollutant, is detected in the human cord blood, and it may induce health risk to an embryo. In this study, we established intrauterine exposure to PFOS in mice to evaluate potential impacts of PFOS on postnatal day 1 (PND1) offspring through conducting biochemical tests, quantitative PCR, and immunostaining. As results, PFOS-exposed maternal mice showed marked hepatomegaly and induced liver steatosis in a high dose of 5 mg PFOS/kg. In PND1 mice, intrahepatic contents of triglyceride, total cholesterol, and LDL were elevated by high-dose PFOS exposure, while intracellular HDL content was decreased. As shown in quantitative PCR, functional messenger RNAs of cytochrome P4A14 (CYP4A14) for fatty acid oxidation, CD36 for hepatic fatty acid uptake, and apolipoprotein B100 (APOB) and fibroblast growth factor 21 (FGF21) for hepatic export of lipids in PND1 livers were changed when compared to those in PFOS-free controls. In further validations, immunofluorescence stains showed that hepatic CYP4A14 and CD36 immunoreactive cells were increased in PFOS-exposed PND1 mice. In addition, reduced immunofluorescence-positive cells of APOB and FGF21 were observed in PND1 livers. Collectively, these preliminary findings demonstrate that prenatal exposure to PFOS may affect lipid metabolism in liver cells of PND1 mice.

Serum microRNA miR-206 is decreased in hyperthyroidism and mediates thyroid hormone regulation of lipid metabolism in HepG2 human hepatoblastoma cells.

The actions of thyroid hormone (TH) on lipid metabolism in the liver are associated with a number of genes involved in lipogenesis and lipid metabolism; however, the underlying mechanisms through which TH impacts on lipid metabolism remain to be elucidated. The present study aimed to investigate the effects of hyperthyroidism on the serum levels of the microRNA (miR) miR-206 and the role of miR-206 on TH-regulated lipid metabolism in liver cells. Serum was obtained from 12 patients diagnosed with hyperthyroidism and 10 healthy control subjects. Human hepatoblastoma (HepG2) cells were used to study the effects of triiodothyronine (T3) and miR-206 on lipid metabolism. Expression of miR-206 in serum and cells was determined by reverse transcription-quantitative polymerase chain reaction analysis. Lipid accumulation in HepG2 cells was assessed with Oil Red O staining. Suppression or overexpression of miR-206 was performed via transfection with a miR-206 mimic or miR-206 inhibitor. Serum miR-206 was significantly decreased in patients with hyperthyroidism compared with euthyroid controls. Treatment of HepG2 cells with T3 led to reduced total cholesterol (TC) and triglyceride (TG) content, accompanied by reduced miR-206 expression. Inhibition of endogenous miR-206 expression decreased intracellular TG and TC content in HepG2 cells. By contrast, overexpression of miR-206 in HepG2 partially prevented the reduction in TG content induced by treatment with T3. In conclusion, serum miR-206 expression is reduced in patients with hyperthyroidism. In addition, miR-206 is involved in T3-mediated regulation of lipid metabolism in HepG2 cells, indicating a role for miR-206 in thyroid hormone-induced disorders of lipid metabolism in the liver.

Suppression of PPARγ-mediated monoacylglycerol O-acyltransferase 1 expression ameliorates alcoholic hepatic steatosis.

Alcohol consumption is one of the major causes of hepatic steatosis, fibrosis, cirrhosis, and superimposed hepatocellular carcinoma. Ethanol metabolism alters the NAD+/NADH ratio, thereby suppressing the activity of sirtuin family proteins, which may affect lipid metabolism in liver cells. However, it is not clear how long-term ingestion of ethanol eventually causes lipid accumulation in liver. Here, we demonstrate that chronic ethanol ingestion activates peroxisome proliferator-activated receptor γ (PPARγ) and its target gene, monoacylglycerol O-acyltransferase 1 (MGAT1). During ethanol metabolism, a low NAD+/NADH ratio repressed NAD-dependent deacetylase sirtuin 1 (SIRT1) activity, concomitantly resulting in increased acetylated PPARγ with high transcriptional activity. Accordingly, SIRT1 transgenic mice exhibited a low level of acetylated PPARγ and were protected from hepatic steatosis driven by alcohol or PPARγ2 overexpression, suggesting that ethanol metabolism causes lipid accumulation through activation of PPARγ through acetylation. Among the genes induced by PPARγ upon alcohol consumption, MGAT1 has been shown to be involved in triglyceride synthesis. Thus, we tested the effect of MGAT1 knockdown in mice following ethanol consumption, and found a significant reduction in alcohol-induced hepatic lipid accumulation. These results suggest that MGAT1 may afford a promising approach to the treatment of fatty liver disease.

Hepatitis C virus core protein impairs metabolic disorder of liver cell via HOTAIR-Sirt1 signalling.

It has been suggested that Hepatitis C virus (HCV) core protein is associated with metabolic disorders of liver cell. However, the precise mechanism is still unclear. The aim of the present study was to explore the impact of HCV core protein on hepatocyte metabolism by HepG2 and the possible involvement of long non-coding (lnc) RNAs in this process. The effect of HCV core protein on lncRNAs expression was examined with quantitative RT-PCR (qRT-PCR). Manipulation of HVC core protein and lncRNA HOTAIR was to evaluate the role of interaction between them on cell metabolism-related gene expression and cellular metabolism. The potential downstream Sirt1 signal was examined by western blotting and qRT-PCR. Our data suggested that suppression of HOTAIR abrogates HCV core protein-induced reduction in Sirt1 and differential expression of glucose- and lipid-metabolism-related genes. Also it benefits for metabolic homoeostasis of hepatocyte indicated by restoration of cellular reactive oxygen species (ROS) level and NAD/NADH ratio. By manipulation of HOTAIR, we concluded that HOTAIR negatively regulates Sirt1 expression through affecting its promotor methylation. Moreover, overexpression of Sirt1 reverses pcDNA-HOTAIR-induced glucose- and lipid-metabolism-related gene expression. Our study suggests that HCV core protein causes dysfunction of glucose and lipid metabolism in liver cells through HOTAIR-Sirt1 signalling pathway.

Effect of intermittent hypoxia on lipid metabolism in liver cells and the underlying mechanism

To determine the effect of intermittent hypoxia on lipid metabolism in liver cells and to explore the possible molecular pathways involved in this process. An intermittent hypoxia cell model system was established by incubating the human hepatic cell lines L02 and HepG2 in an atmosphere of 2% O₂, 5% CO₂ and 93% N₂ for 8 hours per day over a period of 1, 2, 3, 4 or 5 days. Cells cultured in normoxia conditions (21% O₂) served as controls. Changes in intracellular lipid droplets and triglyceride (TG) levels were assessed by biochemical assays and oil red staining. Changes in intracellular reactive oxygen species (ROS) were assessed by inverted fluorescence microscopy and flow cytometry. Changes in expression of hypoxia-inducible factor (HIF)-1a and HIF-2a proteins, and the downstream ADFP, SREBP-1c and FAS proteins, were detected by western blotting. For both L02 and HepG2 cell lines, the cells grown under hypoxic conditions showed significantly higher lipid droplet accumulation and TG content than the cells grown under normoxic conditions (F(L02) =61.83, FHepG2 =104.19, P less than 0.01). Both oxygen concentration and time appeared to be correlated with these lipid-related changes (F(L02) =39.60, FHepG2 =76.39, P less than 0.01). The ROS fluorescence index was significantly increased after 2 days of intermittent hypoxia L02: 0.703 ± 0.129 vs. 3.310 ± 0.198, t =22.0637 and HepG2:0.617 ± 0.156 vs. 2.33 ± 0.42, t =7.2003, P < 0.05); in addition, increasing trends were observed in the ROS content and intensity of green fluorescence in conjunction with increased time of exposure to intermittent hypoxia (F(L02) =1021.84, FHepG2 =49.89, P less than 0.01). Compared with their respective control groups, the L02 and HepG2 cells both showed significantly upregulated expression of HIF-1a ADFP, SREBP-1c and FAS (L02:FHIF-1a =371.19, FsREBP-1c =204.49, FFAS =38.20, FADFP =154.31, P less than 0.05 and HepG2:FHF-1a =150.84, FSRERBP-1c =107.35, FFAs =279.71, FADFP =352.06, P less than 0.01). In contrast, the HIF-2a level was markedly decreased in the cells after 4 and 5 days of exposure to intermittent hypoxia (F(L02) =125.29, FHcpG2 =10.68, P less than 0.05). Under intermittent hypoxic conditions, ROS may regulate the expression of hypoxia-inducible factors and the adipose differentiation-related protein,as well as influence fatty acid metabolism via a HIF-1 a-SREBP-1 c-FAS signal and upregulation of the ADFP protein, in liver cells.

The Inhibitory Effect of Ginsenoside Rg1 on Glucose and Lipid Production in Human HepG2 Cells

Ginseng has been widely used for the treatment of various human body disorders. Despite extensive studies, the mechanism of action of ginseng remains to be clarified. In an effort of clarifying the mechanism of gluco-regulatory activity in ginseng, the effects of ginsenosides on glucose metabolism were studied in human hepatoma HepG2 cells. In this study, we showed that Rg1 significantly inhibited glucose production, glycogen synthesis, and lipogenesis. Rg1 also increased the phosphorylation of AKT and AMP-activated protein kinase (AMPK). Further studies indicated that the Rg1-mediated inhibition of glycogen and lipid synthesis was blocked in the presence of PI3K/AKT- and AMPK-specific inhibitors. These results indicate that Rg1 contributes to glucose and lipid metabolism in liver cells through AKT and AMPK pathways. Our findings provide evidence to support that Rg1 may be potential useful in counteracting insulin resistance and diabetes.

Tu2052 Acute Liver Torsion: A Rare Case of Abdominal Pain and Elevated Liver Transaminases

Background. Matrix proteins are essential in the HIV replication cycle. The HIV matrix protein p17 serves several functions in the viral replication cycle including the viral nuclear import at early stage of infection. In the late stage, p17 mediates the recruitment of the viral surface/transmembrane gp120/gp41 envelope protein complex into virions and targets Pr55Gag proteins to their assembly sites at the plasma membrane of infected cells. Members of the nuclear receptor superfamily exert their regulatory activity integrating regulatory effects exerted by nutrients with intermediate metabolism by positively and negatively regulating the expression of effector genes. We have previously demonstrated that HIV infection is associated with an altered expression of nuclear receptor transcriptome in human monocytes as well as that stimulation of these cells with p17 down-regulates the expression of FXR and PPARγ. Aims. To analyze the effect exerted by the HIV matrix protein p17 on nuclear receptor gene expression in HepG2 cells. Methods. Serum starved HepG2 cells were stimulated 18 hours with 2 μg/ml recombinant p17 protein. At the end of the stimulation total RNA was extracted, reverse-transcribed in cDNA and amplified using specific primers for 10 nuclear receptors. Relative mRNA expression of Fatty Acid Elongase (FAE) was also investigated. Results. HepG2 cells treated with the HIV matrix protein p17 expressed an altered pattern of nuclear receptors characterized by a profound down-regulation in the expression of PPARα, -β, -γ, RARα, RXR, LXRβ, FXR, SHP, PXR and GR. Of interest, the deregulated expression of these transcription factors was linked to reduced expression of the enzyme FAE which is involved in the elongation of fatty acids during their biosynthesis process (Figure). Conclusions. Altered expression of nuclear receptors mediating reciprocal regulation of lipid metabolism and immune function occurs in HepG2 cells under p17 administration. These data highlight a detrimental effects of HIV proteins in resetting lipid metabolism in liver cells. These data might explain detrimental effects of HIV-HCV coinfection on lipid metabolism.

Tu2051 The HIV Matrix Protein P17 Subverts the Nuclear Receptor Transcriptome in HEPG2 Cells

Background. Matrix proteins are essential in the HIV replication cycle. The HIV matrix protein p17 serves several functions in the viral replication cycle including the viral nuclear import at early stage of infection. In the late stage, p17 mediates the recruitment of the viral surface/transmembrane gp120/gp41 envelope protein complex into virions and targets Pr55Gag proteins to their assembly sites at the plasma membrane of infected cells. Members of the nuclear receptor superfamily exert their regulatory activity integrating regulatory effects exerted by nutrients with intermediate metabolism by positively and negatively regulating the expression of effector genes. We have previously demonstrated that HIV infection is associated with an altered expression of nuclear receptor transcriptome in human monocytes as well as that stimulation of these cells with p17 down-regulates the expression of FXR and PPARγ. Aims. To analyze the effect exerted by the HIV matrix protein p17 on nuclear receptor gene expression in HepG2 cells. Methods. Serum starved HepG2 cells were stimulated 18 hours with 2 μg/ml recombinant p17 protein. At the end of the stimulation total RNA was extracted, reverse-transcribed in cDNA and amplified using specific primers for 10 nuclear receptors. Relative mRNA expression of Fatty Acid Elongase (FAE) was also investigated. Results. HepG2 cells treated with the HIV matrix protein p17 expressed an altered pattern of nuclear receptors characterized by a profound down-regulation in the expression of PPARα, -β, -γ, RARα, RXR, LXRβ, FXR, SHP, PXR and GR. Of interest, the deregulated expression of these transcription factors was linked to reduced expression of the enzyme FAE which is involved in the elongation of fatty acids during their biosynthesis process (Figure). Conclusions. Altered expression of nuclear receptors mediating reciprocal regulation of lipid metabolism and immune function occurs in HepG2 cells under p17 administration. These data highlight a detrimental effects of HIV proteins in resetting lipid metabolism in liver cells. These data might explain detrimental effects of HIV-HCV coinfection on lipid metabolism.