Effects of diisononyl phthalate on lipid metabolism in HepG2 cells / 环境与职业医学

Background Exposure to diisononyl phthalate (DINP), an endocrine disruptor associated with metabolic diseases and widely used in plastic products, has been linked to the development of several adverse health outcomes in the liver, including non-alcoholic fatty liver disease (NAFLD). Objective To investigate the effects and the possible molecular mechanisms of DINP exposure on lipid metabolism in human hepatocellular carcinoma cells (HepG2 cells). Methods First, HepG2 cells were treated with DINP at three time spots (24, 48, and 72 h) and eleven doses (0, 0.003, 0.01, 0.03, 0.1, 0.3, 1, 3, 10, 30, and 100 mmol·L−1). Cell viability were detected using cell counting kit 8 (CCK8). Intracellular lipid deposition was determined by oil red O staining and lipid content detection, and triglyceride (TG) and cholesterol (TC) were further detected. Finally, the mRNA expression levels were detected by fluorescence quantitative PCR, including fatty acid synthesis related genes [acetyl-CoA carboxylase alpha (Accα), fatty acid synthase (Fasn), malonyl-CoA decarboxylase (Mlycd), and sterol regulatory element binding protein 1 (Srebp1)] and β-oxidation related genes [peroxisome proliferator activated receptor alpha (Pparα), AMP-activated protein kinase (Ampk), carnitine palmitoyltransferase 1A (Cpt-1a), transcription factor A, mitochondrial (Tfam), nuclear respiratory factor 1 (Nrf1), and peroxisome proliferator-activated receptor gamma and coactivator 1 alpha (Pgc1-α)]. Results Compared with the control group (0 mmol·L−1), the no observed adverse effect levels (NOAEL) of HepG2 cell viability were 0.3, 0.1, and 0.1 mmol·L−1 after 24, 48, and 72 h exposure to DINP, respectively, and the corresponding lowest observed adverse effect levels (LOAEL) were 1, 0.3, and 0.3 mmol·L−1, respectively (P<0.05). After exposure to 30 mmol·L−1 and 100 mmol·L−1 DINP for 24 h, the intracellular lipid content, lipid deposition, TG, and TC levels were increased significantly compared with the control group (P<0.01). Compared with the control group, the mRNA expression levels of genes related to fatty acid synthesis, such as Mlycd, Srebp1, Fasn, and Accα, were down-regulated after the 100 mmol·L−1 DINP exposure for 24 h, while the mRNA expression level of Mlycd was up-regulated in the 30 mmol·L−1 group. The β-oxidation related genes such as Ampk, Pparα, and Tfam were up-regulated significantly after the 100 mmol·L−1 DINP exposure, while Cpt-1a mRNA expression level was down-regulated (P<0.05). Conclusion Exposure to DINP at 30 mmol·L−1 and 100 mmol·L−1 can interfere with fatty acid synthesis and β-oxidation in lipid metabolism of HepG2 cells, resulting in lipid deposition.

Effect and mechanism of muscle injury on liver lipid metabolism in Duchenne muscular dystrophy mice / 中国药科大学学报

@#Duchene muscular dystrophy (DMD) is a serious progressive muscular dystrophy.Reports in recent years about abnormal lipid in DMD patients have increased, yet little attention has been paid to liver lipid.This study aimed to explore the effect of dystrophin gene defect on liver lipid synthesis.7-week-old mdx male mice were used as DMD model.The conditions of liver function, liver lipid accumulation and liver lipid synthesis were determined through liver tissue morphological examination, blood biochemical examination, and detection of hepatic gene and protein expression.The results showed that lipid droplets in liver of mdx mice increased significantly.The contents of total cholesterol and triglyceride in liver, aspartate aminotransferase and alanine aminotransferase in serum increased.The gene and protein expression of hepatic lipid synthesis-related enzymes such as fatty acid synthase, acetyl CoA carboxylase, and sterol regulatory element binding protein 1-c were up-regulated.These results showed accumulation of liver lipid in 7-week-old mdx male mice.

Central cellular signaling pathways involved with the regulation of lipid metabolism in the liver: a review

The liver is primarilyresponsible for energy homeostasis and the regulation of lipid, carbohydrate and protein metabolism. Lipid metabolism consists of distributing lipids to peripheral tissues or ensuring their return to the liver to be reprocessed. Additionally, cellular metabolism isregulated by several molecules in different signaling pathways. Lipid homeostasis in the liver is mainly regulated by AKT, AMPK, SREBP, PPAR, and JNK. The PI3K/AKT/mTOR signaling pathway results in the biosynthesis of macromolecules and regulates lipogenesis and the expression of lipogenic genes. AMPK is an energy sensor that regulates metabolism and is activated when stored ATP is depleted, and it is responsible for the suppression of several key lipogenic factors in the liver related to cholesterol and fatty acid synthesis. SREBPs control lipogenic geneexpressionandcholesterol metabolism and actin the nutritional regulation of fatty acids and triglycerides. The continued activation of SREBPs is associated with cellular stress, inflammation and ultimately steatosis. PPARs are intrinsically important regulators of lipid metabolism. These genes are essential tovarious metabolic processes, especially lipid and glucose homeostasis, and can play a role in cell differentiation. JNK signaling is related to insulin resistance and its activation results in decreased mitochondrial activity and fat accumulation. Therefore, the study of cell signaling pathways related to lipid metabolism and liver function may help to identify abnormalities and develop strategies to manage and regulate metabolic disorders and resulting complications.

The role of endoplasmic reticulum stress in the formation of fatty liver in high-fat diet fed mice / 中国医师杂志

Objective To explore the influence of endoplasmic reticulum stress on fatty liver in mice feeding with high-fat diet.Methods The 8-week-old male C57BL/6J mice were randomly divided into two groups:high-fat diet group (with 60％ calories by high saturated fatty acid) and control group (with chow diet),both groups had been fed for 16 weeks.H&E-staining and Sudan Ⅳ-staining reflected lipid deposition in liver.The levels of 78-kDa glucose-regulated protein (GRP78),protein kinase R-like endoplasmic reticulum kinase (PERK),phosphorylated α subunit of eukaryotic initiation factor 2 (p-eIF1 α),C/EBP homologous protein (CHOP),steroid regulated element binding proteins 1 (SREBP-1),and fatty acid synthetase (FAS) protein were determined by Western blot to reflect the endoplasmic reticulum stress and lipid synthesis.Results In liver of high fat diet (HFD) group,H&E staining showed that the cytoplasm of hepatocytes were filled with vacuoles,Sudan Ⅳ staining also displayed that many different sizes of red lipid drops exist in hepatocytes.Compared to the liver of control group,high-fat diet induced endoplasmic reticulum stress and elevated lipid synthesis,as evidenced by increases in the level of peroxisome proliferator-activated receptor alpha (PPARα) mRNA expression,and the protein levels of GRP78,PERK,phosphorylated eIF2α,CHOP were also significantly increased.In primary normal hepatocytes incubated with exogenous oleic acid intervention for 24-72 hours,the expression of GRP78,PERK,phosphorylated eIF2α,CHOP protein levels,and the expression of SREBP-1 and FAS protein were significantly increased in dose-dependent manner.Conclusions Feeding with high-fat diet led to accumulation of lipid deposition in liver and fatty liver,the underlying mechanisms might be related to induction of endoplasmic reticulum stress.

Construction of a new alcoholic liver disease mouse model / 上海交通大学学报（医学版）

Objective·To establish a reliable alcoholic liver disease mouse model (ALDNM) that mimics the drinking pattern of alcoholic liver disease (ALD) patients.Methods·Using the self-designed feeding tubes and liquid diet,ALDNM model was developed through chronic feeding combined with acute gavage of ethanol based on Lieber-DeCarli model and Gao-Binge model.C57BL/6 mice were administered with control liquid diet for adaptation for first 5 d,and then divided into pair-fed group and ethanol-fed group (10 mice each group).Ethanol-fed mice were fed with the liquid diet in which ethanol accounts for 30％ of total energy,while the pair-fed mice were fed with the control diet for 10 d.At the 16th day,ethanol-fed mice and pair-fed mice were respectively gavaged a single dose of 31.5％ ethanol or isocaloric maltose dextrin,and euthanized 9 h later.Sera and livers were collected.The general physiological condition,hepatic tissue pathological changes and serum indexes between Lieber-DeCarli models and ALDNM models were compared.The liver lipids of ALDNM mice were determined by Oil red O (ORO) staining and hepatic triacylglyceride (TAG) test.Meanwhile,the mRNA levels of interleukin-6 (IL-6),tumor necrosis factor α (TNF-α),fatty acid synthase (Fas),long chain fatty acid elongase 6 (Elovl6) and stearyl-CoA desaturase (Scdl) were detected by real-time PCR in ALDNM models.Western blotting was used to detect the changes of phosphorylated signal transduction and transcriptional activator (p-STAT3) in the livers.Results·Lieber-DeCarli model mice were generally in poor condition,and there was no significant change in serum glutamic-pyruvic transaminase (GPT) and glutamic-oxaloacetic transaminase (GOT) compared to pair-fed group.However,in ALDNM models,H-E staining showed that the hepatocytes of ethanol-fed mice were extremely swollen with round volume,increased cytoplasm and filled with large amounts of fat vacuoles.ORO staining analyses showed obvious microsteatosis in the liver cells from all ethanol-fed mice.The hepatosomatic index,liver TAG content,serum GPT and GOT of ALDNM models were significantly higher than those in the pair-fed group,while the serum HDL significantly decreased compared to the pair-fed group.Moreover,the expression levels of both lipid synthesis pathways and inflammatory signaling pathways related genes in livers significantly increased in the ethanol-fed mice of ALDNM model.Conclusion·ALDNM model was successfully constructed.This model is cost-and time-efficient.Moreover,ALDNM model mimics the drinking pattern and pathogenesis of ALD patients with the advantages of stable food intake,good repeatability,and obvious liver damage.