Lipid Metabolism In Liver Tissue Research Articles

Regulatory Mechanism of Xiaozheng Tongluo Method on Hepatic Lipid Metabolism in ApoE-/- Mice: Insights from the Sterol Regulatory Element-binding Protein-2/3-hydroxy-3-methylglutaryl Coenzyme A Reductase/Low-density Lipoprotein Receptor Signaling Pathway

Abstract Objective: The objective of the study was to explore the regulatory mechanism of the Xiaozheng Tongluo method on lipid metabolism in liver tissue based on the sterol regulatory element-binding protein-2/(SREBP2)/3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR)/low-density lipoprotein receptor (LDLR) signaling pathway. Materials and Methods: C57BL/6 mice were selected as the blank group. The apolipoprotein E-deficient (ApoE-/-) mice were randomly divided into the model group, traditional Chinese medicine (TCM) group, and control group. The general condition of the mice was determined by the mouse’s state and liver weight. Liver hematoxylin and eosin staining and Oil Red O staining were used to observe the pathological changes and lipid droplet deposition of the liver. The protein expression levels of SREBP2, HMGCR, and LDLR were detected by Western blotting and polymerase chain reaction. Results: (1) The rats in the model group were in poor condition, and their liver weight increased significantly. Compared with the model group, the condition of the TCM group and the control group improved to varying degrees, and their liver weight decreased significantly. (2) Compared with the normal group, the hepatocytes in the model group were arranged in a disorderly manner, and the red-stained lipids of stem cells increased significantly. Compared with the model group, the degree of liver lesions in the control group and TCM group was reduced, and the red-stained lipid of hepatocytes was significantly reduced. (3) Compared with the blank group, the expression of SREBP2 and HMGCR protein in the model group increased significantly, and the expression of LDLR protein decreased significantly (P < 0.05). Compared with the model group, the expression of SREBP2 and HMGCR protein in the TCM group decreased significantly, and the expression of LDLR protein increased significantly (P < 0.05). Conclusions: The method detailed in this paper can increase the expression of SREBP2 and HMGCR protein and decrease the expression of LDLR protein, thus regulating liver cholesterol metabolism and delaying the progression of atherosclerosis.

Olanzapine-induced weight gain and lipid dysfunction in mice between different gender.

As one of the most common antipsychotics, olanzapine may cause metabolic-related adverse effects, but it is still unknown how olanzapine alters lipid metabolism. In this study, we found that olanzapine-treated mice showed varying degrees of dyslipidemia, which was particularly pronounced in female mice. Based on ultra-performance liquid chromatography-quadrupole time-of-flight-MS (UPLC-Q-TOF-MS) technology and lipid metabolomics, we mapped the changes in lipid metabolism in olanzapine-treated mice and then compared the changes in lipid metabolism between male and female mice. There were 98 metabolic differentiators between the olanzapine-treated and control groups in females and 79 in males. These metabolites were glycerolipids, glycerophospholipids, fatty amides, and sphingolipids, which are involved in glycerolipid metabolism, glycerophospholipid metabolism, and fatty acid metabolism. These results suggest that olanzapine-induced changes in the levels of lipid metabolites are closely associated with disturbances in lipid metabolic pathways, which may underlie lipemia. This lipidome profiling study not only visualizes changes in lipid metabolism in liver tissue but also provides a foundation for understanding the regulatory pathways and mechanisms involved in olanzapine-induced lipid metabolism disorders. Furthermore, this study demonstrates differences in lipid metabolism between males and females, providing a reference for clinical treatment regimen selection.

Investigating the Levels of Liver Lipogenic and Lipolytic Enzymes in Rat with High-Fat Diet and Sucrose Solution Underwent Progressive Resistance Training

Objective: Consuming too much fat or carbohydrates stimulates lipogenesis and excess fat is stored in non-fat tissues, including the liver, and manifests as obesity and fatty liver disease. This study aimed to investigate the effect of eight weeks of progressive resistance training (PRT) on the liver levels of some enzymes affecting lipid metabolism in rats fed a high-fat diet and sucrose solution.
 Materials and Methods: Twenty-four male wistar rats with 5 weeks of age were randomly divided into two groups: standard diet (SD) (n=8) and high-fat diet and sucrose solution (HFDS) (n=16). Twelve weeks later, HFDS group was divided into two groups: sedentary (HS) and PRT (HPRT). The PRT program was implemented 3 days a week for 8 weeks. Gene expression of AMPKα1, SCD-1, ATGL and FASN enzymes affecting lipid metabolism in liver tissue and its fat content were investigated.
 Results: HFDS significantly increased the body weight (P: 0.001) and significantly decreased the liver expression of ATGL and FASN (P: 0.001, P: 0.011). Eight weeks of PRT did not show a significant difference in the expression of AMPKα1, SCD-1, ATGL and FASN genes. Rats fed HFDS had considerably higher levels of triglyceride (TG) and total cholesterol (TC) in their liver tissue (P: 0.004, P: 0.001) and PRT did not affect them (P: 0.959, P: 0.809 respectively).
 Conclusion: It seems that eight weeks of PRT will not change liver lipid metabolism enzymes. Therefore, modifying the diet and changing it, will probably show different results after PRT.

Effects of Buffalo Milk and Cow Milk on Lipid Metabolism in Obese Mice Induced by High Fat.

The aim of this study was to evaluate the effects of buffalo milk and cow milk on lipid metabolism in obese mice. Milk composition analysis showed fat, protein, and total solid content in buffalo milk was higher than cow milk, while the lactose content of buffalo milk was lower than cow milk. After milk metabolite extraction and LC-MS/MS analysis, differential metabolites were mainly enriched in “linoleic acid metabolism pathways,” “pentose and glucuronate interconversion pathways,” and “metabolism of xenobiotics by cytochrome P450 pathways.” We fed three groups of C57BL/6J mice (n = 6 per group) for 5 weeks: (1) high-fat diet group (HFD group); (2) high-fat diet + buffalo milk group (HBM group); and (3) high-fat diet + cow milk group (HCM group). Our results showed that body weight of mice was significantly decreased in HBM and HCM groups from 1 to 4 weeks compared with the HFD group. The mRNA expression of ACAA2, ACACB, and SLC27A5 genes involved in the lipid metabolism in liver tissue were significantly elevated in HCM group, relatively to HFD and HBM group. In addition, the adipocyte number, size and lipid accumulation in the liver were significantly decreased in HCM group compared with the HFD group by H&E staining and oil red O staining, but was not change in HBM group. The mRNA levels of TNF-α and IL-1β inflammatory genes were significantly increased in HBM group, relatively to HFD and HCM group, which is consistent with results from inflammatory cell infiltration and tissue disruption by colon tissue sections. In conclusion, dietary supplementation of cow milk has beneficial effects on loss of weight and lipid metabolism in obese mice.

The S100 calcium-binding protein A11 promotes hepatic steatosis through RAGE-mediated AKT-mTOR signaling

RationaleNonalcoholic fatty liver disease (NAFLD), the most common cause of chronic liver disease, has become an increasingly severe public health problem. However, the underlying mechanism for the occurrence and development of NAFLD remains largely unknown. S100 calcium-binding protein A11 (S100A11) is a multifunctional protein previously reported to be a poor prognostic indicator of hepatocellular carcinoma, while the role of S100A11 affects NAFLD is still not clear. MethodsImmunohistochemical staining was performed using human NAFLD and control biopsy specimens. Serum level of S100A11 were analyzed by Elisa assays. The S100A11 over-expressed/ knocked-down model was established in vitro or in vivo. The expression levels of genes related to lipid metabolism in liver tissue were performed by quantitative PCR and western blotting. Hepatic lipid accumulation was determined by biochemical measurements and histochemistry. ResultsWe showed that the concentration of serum S100A11 was significantly elevated in NAFLD patients, and expression of S100A11 was remarkedly increased in the livers of NAFLD patients and mouse models. Overexpression of S100A11 in vivo markedly increased liver steatosis, body weight, and serum aspartate aminotransaminase (AST) levels. Mechanistically, our results demonstrated that S100A11 acted as a positive regulator of AKT/mTOR signaling to induce lipid synthesis and aggravate lipid deposition. ConclusionsThese results provide evidence for a novel role of S100A11 that contributes to hepatic steatosis, suggesting that targeting S100A11 may be an alternative approach for the treatment of NAFLD.

Long-Term Phenotypic and Proteomic Changes Following Vitrified Embryo Transfer in the Rabbit Model.

Simple SummaryThis study was conducted to demonstrate how a vitrified embryo transfer procedure incurs phenotypic and molecular changes throughout life. This study reports the first evidence describing that embryonic manipulation during a vitrified embryo transfer cycle induced molecular modifications, concerning oxidative phosphorylation and dysregulations in zinc and lipid metabolism in liver tissue, which has been reported as responsible for postnatal variations of the phenotype.Nowadays, assisted reproductive technologies (ARTs) are considered valuable contributors to our past, but a future without their use is inconceivable. However, in recent years, several studies have evidenced a potential impact of ART on long-term development in mammal species. To date, the long-term follow-up data are still limited. So far, studies have mainly focused on in vitro fertilization or in vitro culture, with information from gametes/embryos cryopreservation field being practically missing. Herein, we report an approach to determine whether a vitrified embryo transfer procedure would have long-term consequences on the offspring. Using the rabbit as a model, we compared animals derived from vitrified-transferred embryos versus those naturally conceived, studying the growth performance, plus the weight throughout life, and the internal organs/tissues phenotype. The healthy status was assessed over the hematological and biochemical parameters in peripheral blood. Additionally, a comparative proteomic analysis was conducted in the liver tissue to investigate molecular cues related to vitrified embryo transfer in an adult tissue. After vitrified embryo transfer, birth weight was increased, and the growth performance was diminished in a sex-specific manner. In addition, vitrified-transferred animals showed significantly lower body, liver and heart weights in adulthood. Molecular analyses revealed that vitrified embryo transfer triggers reprogramming of the liver proteome. Functional analysis of the differentially expressed proteins showed changes in relation to oxidative phosphorylation and dysregulations in the zinc and lipid metabolism, which has been reported as possible causes of a disturbed growth pattern. Therefore, we conclude that vitrified embryo transfer is not a neutral procedure, and it incurs long-term effects in the offspring both at phenotypic and molecular levels. These results described a striking example of the developmental plasticity exhibited by the mammalian embryo.

Low Expression of Sirtuin 1 in the Dairy Cows with Mild Fatty Liver Alters Hepatic Lipid Metabolism.

Simple SummarySirtuin 1 (SIRT1), a NAD-dependent histone deacetylase, is involved in oxidative stress and lipid metabolism regulation. Limited studies exist regarding the role of SIRT1 in lipid metabolism disorder in periparturient dairy cows. This study explores the effect of hepatic steatosis on the expression of the SIRT1 gene and protein and the proteins encoded by the genes downstream to it, all of which are involved in lipid metabolism in the liver. Control cows (n = 6, parity 3.0 ± 2.0, milk production 28 ± 47 kg/d) and mild fatty liver cows (n = 6, parity 2.3 ± 1.5, milk production 20 ± 6 kg/d) were retrospectively selected based on liver triglycerides (TG) content (% wet liver). The present study indicates that low SIRT1 expression caused by hepatic steatosis promotes hepatic fatty acid synthesis and inhibits fatty acid β-oxidation. We believe that our study makes a significant contribution to the literature because it demonstrates that hepatic steatosis is associated with increased hepatic fatty acid synthesis, inhibited fatty acid β-oxidation and reduced lipid transport.Dairy cows usually experience negative energy balance coupled with an increased incidence of fatty liver during the periparturient period. The purpose of this study was to investigate the effect of hepatic steatosis on the expression of the sirtuin 1 (SIRT1), along with the target mRNA and protein expressions and activities related to lipid metabolism in liver tissue. Control cows (n = 6, parity 3.0 ± 2.0, milk production 28 ± 7 kg/d) and mild fatty liver cows (n = 6, parity 2.3 ± 1.5, milk production 20 ± 6 kg/d) were retrospectively selected based on liver triglycerides (TG) content (% wet liver). Compared with the control group, fatty liver cows had greater concentrations of cholesterol and TG along with the typically vacuolated appearance and greater lipid droplets in the liver. Furthermore, fatty liver cows had greater mRNA and protein abundance related to hepatic lipid synthesis proteins sterol regulatory element binding proteins (SREBP-1c), long-chain acyl-CoA synthetase (ACSL), acyl-CoA carbrolase (ACC) and fatty acid synthase (FAS) and lipid transport proteins Liver fatty acid binding protein (L-FABP), apolipoprotein E (ApoE), low density lipoprotein receptor (LDLR) and microsomal TG transfer protein (MTTP) (p < 0.05). However, they had lower mRNA and protein abundance associated with fatty acid β-oxidation proteins SIRT1, peroxisome proliferator-activated receptor co-activator-1 (PGC-1α), peroxisome proliferator–activated receptor-α (PPARα), retinoid X receptor (RXRα), acyl-CoA 1 (ACO), carnitine palmitoyltransferase 1 (CPT1), carnitine palmitoyltransferase 2 (CPT2) and long- and medium-chain 3-hydroxyacyl-CoA dehydrogenases (LCAD) (p < 0.05). Additionally, mRNA abundance and enzyme activity of enzymes copper/zinc superoxide dismutase (Cu/Zn SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and manganese superoxide dismutase (Mn SOD) decreased and mRNA and protein abundance of p45 nuclear factor-erythroid 2 (p45 NF-E2)-related factor 1 (Nrf1), mitochondrial transcription factor A (TFAM) decreased (p < 0.05). Lower enzyme activities of SIRT1, PGC-1α, Cu/Zn SOD, CAT, GSH-Px, SREBP-1c and Mn SOD (p < 0.05) and concentration of reactive oxygen species (ROS) were observed in dairy cows with fatty liver. These results demonstrate that decreased SIRT1 associated with hepatic steatosis promotes hepatic fatty acid synthesis and inhibits fatty acid β-oxidation. Hence, SIRT1 may represent a novel therapeutic target for the treatment of the fatty liver disease in dairy cows.

Severe mtDNA depletion and dependency on catabolic lipid metabolism in DGUOK knockout mice.

Deoxyguanosine kinase (DGUOK) provides guanosine and adenosine nucleotides for mitochondrial DNA (mtDNA) replication, and its deficiency in humans leads to hepatocerebral mtDNA depletion syndrome or to isolated hepatic disease. There are poor treatment options for DGUOK deficiency and the aim of this study was to generate a model for further studies of the disease that could reveal novel treatment strategies. We report a Dguok-deficient mouse strain that, similar to humans, is most severely affected in the liver. The Dguok complete knockout mice (Dguok-/-) were born normal, but began to lose weight at week 6. A change of fur color from black to blueish grey started at week 16 and was complete at week 20. The movements and behavior were indistinguishable compared to wild-type (wt) mice. A decrease of mtDNA copy number occurred in multiple tissues, with the liver being the most severely affected. The mtDNA-encoded protein cytochrome c oxidase was much lower in Dguok-/- liver tissue than in the wt, whereas the expression of the nuclear-encoded succinate dehydrogenase complex subunit A was unaffected. Histopathology showed severe alterations and immunohistochemistry showed signs of both oxidative stress and regeneration in Dguok-/- liver. The subcutaneous fat layer was undetectable in Dguok-/-, which, in addition to gene expression analysis, indicated an altered lipid metabolism. We conclude that Dguok has a major role for the synthesis of deoxyribonucleotides for mtDNA replication particularly in the liver, similar to the human disorder. Our data also show a catabolic lipid metabolism in liver tissue of Dguok-/-.

Changes of lysosomal membrane permeabilization and lipid metabolism in sidt2 deficient mice.

The SID1 transmembrane family member 2 (sidt2) deficient mouse model was used to investigate the function of sidt2 in lysosomal membrane permeabilization and lipid metabolism of liver tissue. The mouse model was established by Cre/LoxP technology. Enzymatic methods were used to analyze the sidt2−/− mouse serum lipids, aspartate transaminase, alanine transaminase and serum bilirubin, compared with sidt2+/+ mice. Defective lipid metabolism and damaged liver functions were observed in the sidt2−/− mice. By using hematoxylin and eosin and Oil Red O staining, changes of morphology were observed in sidt2−/− mice with optical microscopy. Transmission electron microscopy was also used. Hepatic steatosis and partial liver tissue apoptosis were observed. The tissue distribution of sidt2 protein and mRNA was measured in knockout mice. The results indicated that negligible sidt2 mRNA and protein expression were observed in sidt2−/− mice, and that sidt2−/− mice had abnormal liver functions. Transmission electron microscopy revealed membrane lipid droplets in the liver cell cytoplasm, and some apoptotic body formation. These results demonstrated that absence of the lysosomal membrane protein sidt2 led to changes in lysosomal membrane permeabilization and lipid metabolism.

Astragaloside IV Inhibits Triglyceride Accumulation in Insulin-Resistant HepG2 Cells via AMPK-Induced SREBP-1c Phosphorylation.

Objective: Insulin resistance (IR) is a risk factor for non-alcoholic fatty liver disease (NAFLD), which is characterized by lipid accumulation in hepatocytes. AMP-activated protein kinase (AMPK)-induced sterol regulatory element binding protein-1c (SREBP-1c) phosphorylation is crucial for proper regulation of lipid metabolism in the liver. Astragaloside IV (AST-IV) was found to decrease lipid accumulation in hepatocytes by activating AMPK, which is required to regulate lipid metabolism in liver tissue by inducing SREBP-1c phosphorylation.Method: To evaluate the direct effect of AST on lipid accumulation in hepatocytes with IR and elucidate the underlying mechanisms, we induced IR in HepG2 cells, and used compound C and 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) (an AMPK inhibitor and agonist, respectively) as control substances. We evaluated glucose, triglyceride (TG), and non-esterified fatty acid (NEFA) production, as well as SREBP-1c transcription, SREBP-1c protein expression, and downstream gene expression with or without the presence of AST. We also investigated whether phosphorylation of SREBP-1c at Ser372 was required for AST function.Results: We found that AST attenuated IR and lipid accumulation in HepG2 cells. As an AMPK activator, AST promoted gene expression and activation of AMPK by increasing phosphorylation of AMPKa. AST also inhibited translocation of SREBP-1c into the nucleus of insulin-resistant HepG2 cells by inducing phosphorylation of SREBP-1c at Ser372.Conclusion: This study demonstrated that AST attenuates IR and lipid accumulation in HepG2 cells by regulating AMPK-dependent phosphorylation of SREBP-1c at Ser372, suggesting AST as a promising drug for treating hepatic steatosis.

PP68 - Cytochrome P450 metabolism of vitamin E in models of non-alcoholic fatty liver disease and steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease worldwide in association with oxidative stress and insulin resistance. Steatosis can evolve to steatohepatitis (NASH) by lipotoxicity, inflammation, fibrosis and cell death leading to cirrhosis and hepatocellular carcinoma. No valid therapy has been developed so far to control inflammatory and fibrogenic pathways of NAFLD/NASH. α-Tocopherol (α-TOH) is an antioxidant that partially reverts the histopatological spectrum of NASH. However, the biological mechanism that may support a preventive or therapeutic role of vitamin E in NASH and chronic liver diseases remain elusive. In this study we explored in vitro and in vivo the metabolism of vitamin E in liver cells and in the whole liver exposed to some pathogenic stimuli associated with the progression of NAFLD/NASH. Protein levels of CYP4F2, the cytochrome P450 isoenzyme involved in the metabolism of vitamin E increased in HepG2 cells incubated with α-TOH. This effect increased with a synergic action by the treatment with the fatty acids oleic acid or palmitic acid, or with fructose, which are well-known NASH stimuli. In mice fed control or NAFLD/NASH diets, e.g. high-fat (HFD) or HFD plus fructose diet, the abnormal lipid metabolism of liver tissue was associated with a lowered expression of CYP4F2 protein. The same finding was observed in animals treated with CCl4, a free radical-generating hepatotoxic xenobiotic leading to hepatic fibrosis, in the presence of lowered levels of liver α-TOH. In conclusion, either acute or chronic challenges with NAFLD/NASH stimuli influence the liver expression of CYP4F2. The observed acute transcriptional upregulation and the in vivo downregulation of this protein, point to a role for CYP4F2 in the inflammatory and lipotoxicity signaling of NASH. Transcriptional effects of vitamin E on this gene may help to explain earlier and positive clinical findings, which are worth of further investigation.