Expression of peroxisome proliferator-activated receptor α in rat fatty liver

AIM:To investigate the role of expression of peroxisome proliferator-activated receptor α(PPAR α) in pathogenesis of rat fatty liver.METHODS:The rats were treated with a low dose of carbon terachloride (CCl₄) and fed a high fat diet to produce fatty liver. We determined the concentrations of triglyceride (TG), total cholesterol (TC), free fatty acid (FFA) in liver and the alanine aminotransferase (ALT) activity, tumor necrosis factor-α (TNF-α), FFA in serum and the degree of hepatocytic steatosis. Total RNA of liver was extracted, and the expression of PPAR α were analyzed by semi-quantitative RT-PCR method.RESULTS:In model group, the hepatocytic PPAR α mRNA expression decreased to 0.41±0.28, compared to 1.41±0.29 in the control group (P＜0.01). The contents of TG, TC, FFA in model rat liver were (1.88±0.20) mmol·L^-1, (11.03±1.12) mmol·L^-1 and (1 260.38±151.27) μmol·L^-1, respectively, compared to (0.53±0.10) mmol·L^-1, (1.25±0.25) mmol·L^-1 and (334.30±27.09) μmol·L^-1 in the control group (P＜0.01). The activity of ALT, concentrations of TNF-α and FFA in serum were also increased remarkably in model group.CONCLUSION:Oxidation of fatty acid and utilization of lipids in liver are affected by reducing the expression of PPAR α, which result lipid accumulation in liver.     

Effect of blood glucose and insulin on serum free fatty acid level after gluconse loading in essential hypertension patients

AIM: To investigate the effects of internal change of serum insulin and plasma glucose levels on serum free fatty acid (FFA) concentrations after glucose loading. METHODS: Serum insulin, plasma glucose and FFA concentrations were measured simultaneously in 234 essential hypertension patients who were undergoing oral glucose tolerance test (OGTT)[including 20 cases with 2 type diabetes mellitus(DM),74 impaired glucose tolerance(IGT),140normal glucose tolerance(NGT);98 males,136 females]. RESULTS: Fasting serum FFA concentration (μmol/L) in DM (1 048.47±481.6) was higher than that in IGT (760.1±332.1) (P＜0.05) and in NGT (725.8±353.9) (P＜0.05). Compared with the NGT group, the glucose curve was elevated and the insulin releasing curve was characterized by a low response and a delayed peak in DM group. As for the FFA releasing curve, three groups showed a significantly decreasing trend, which was more evident in DM group. Serum FFA levels at 30 min, 60 min and 120 min after glucose ingestion were not significantly different between the three groups. CONCLUSIONS: Easting serum FFA levels were elevated in DM group. The absolute deficiency of insulin secretion decreased rather increased the difference of FFA level difference between DM group and IGT group, NGT group during OGTT. These results suggest the level of glucose utilization may have an important effect on serum FFA concentration.     

Recent advances in the study of G protein-coupled receptor 40/free fatty acid receptor 1

Free fatty acids (FFAs) provide an important energy source and also act as signaling molecules. Medium to long-chain free fatty acids can activate the intracellular signal pathways in the pancreatic β-cells and play a role in regulating insulin secretion as an extracellular signal molecular via binding to the FFA receptor G protein-coupled receptor 40 (GPR40). Furthermore, GPR40 is associated with several biological effects including cell proliferation and antiapoptosis of nerve cells. GPR40 act an important role in the connection of obesity and diabetes or cancers. GPR40 will probably become a novel kind of antidiabetic and anticancer drugs.     

Effects of silybin on mitochondria membrane fluidity in rats with non-alcoholic fatty liver disease

AIM: To explore the effects of silybin on mitochondrial membrane fluidity in the rats with non-alcoholic fatty liver disease (NAFLD).METHODS: NAFLD rats were induced by high-fat diet for 6 weeks. Mitochondrial membrane fluidity, serum lipid levels, hepatic enzymes and peroxidant products were assayed. The histopathological changes of the livers were observed. The effects of silybin on the changes of the above parameters in NAFLD rats were also determined. Rosiglitazone was used as a positive control of treatment. RESULTS: Compared with the control animals, the fluidity of mitochondrial membrane was obviously decreased, and the contents of alanine aminotransferase, aspartate transaminase, triglyceride, total cholesterol, malonaldehyde and superoxide dismutase in serum were markedly increased (P<0.01) in the NAFLD rats. Silybin and rosiglitazone evidently regulated mitochondrial membrane fluidity, decreased the levels of serum lipids, improved the liver functions and meliorated histopathological manifestations of the livers (P<0.05 or P<0.01).CONCLUSION: High-fat diet successfully reproduces a NAFLD animal model. Stabilization of mitochondrial membrane and inhibition of oxidative stress may be the main mechanisms for the hepatoprotective effects of silybin in NAFLD.     

Effect of bitter melon on liver fibrosis induced by carbon tetrachloride

AIM: To investigate the effects of bitter melon (BM) on liver fibrosis induced by CCl₄ in Wistar rats. METHODS: Healthy male Wistar rats were randomly divided into 4 groups (with 8 each): olive oil control group (group C), olive oil CCl₄ model group (group M), CCl₄+BM at low concentration (BM 100 g/kg, group BM-L), CCl₄+ BM at high concentration (BM 200 g/kg, group BM-H). All rats except those in group C were subcutaneously injected with CCl₄ twice a week for 8 weeks to induce liver fibrosis. After injection of CCl₄ for 8 weeks, all rats were sacrificed and the samples of blood and livers were collected. The weight ratio of liver to body was measured. The serum level of MDA and the activity of SOD were tested. The contents of total protein and albumin, the activity of GSH-Px, the content of hydroxyproline and the activity of monoamine oxidase in the liver homogenate were determined. Hepatic inflammation and collagen deposition were observed under microscope with Masson staining. RESULTS: In the rats treated with BM, the weight ratio of liver to body, the serum level of MDA, the content of hydroxyproline and the activity of monoamine oxidase in the liver homogenate were lower than those in group M (P<0.01). The serum activity of SOD, the contents of total protein and albumin, and the activity of GSH-Px in the liver homogenate were enhanced (P<0.01). The livers of the model rats had remarkable inflammatory necrosis, collagen accumulation and fibrosis. The rats in BM-treated group showed slighter hepatic injury and collagen deposition, and the liver functions were much better than those in the model group. High dose of BM showed more obvious liver-protective effects. CONCLUSION: BM attenuates liver fibrosis by its antioxidant effect and the mechanisms of reducing hydroxyproline content and monoamine oxidase activity.     

Effect of insulin resistance on fatty liver in high-fat diet-fed mice

AIM: To study the influence of insulin resistance on fatty liver in the mice fed with high-fat diet (HFD).METHODS: Male 8-week-old C57BL/6J mice were randomly divided into HFD group (with 60% calories by high saturated fatty acid) and control group (with chow diet).The mice in both groups were fed for 12 weeks. The body weight, liver weight, serum triglyceride (TG) and total cholesterol (TC), and blood glucose and insulin levels were measured. Hyperinsulinemic euglycemic clamp experiment was applied to reflect insulin sensitivity. The lipid deposition in the liver was analyzed by HE staining, Sudan IV staining and measurement of liver fat content. The phosphorylation levels of IRS1 and Akt, and the protein levels of SREBP-1 and FAS were determined by Western blot to reflect the activities of insulin signaling and lipid synthesis.RESULTS: Compared with control group, the body weight and liver weight were significantly increased in HFD group. TG and TC contents in serum and liver tissues were remarkably increased in HFD group. High-fat diet induced insulin resistance, as evidenced by increased serum insulin levels, reduced glucose infusion rate and decreases in IRS1 and Akt phosphorylation levels. In livers of HFD group, HE staining showed that the cytoplasm of hepatocytes was filled with vacuoles. Sudan IV staining also displayed that many different sizes of red lipid drops existed in the hepatocytes, and the protein levels of SREBP-1 and FAS were significantly increased. In primary normal hepatocytes with exogenous oleic acid intervention for 48 h, the phosphorylation levels of IRS1 and Akt were reduced, and the protein expression of SREBP-1 and FAS was significantly increased in a dose-dependent manner.CONCLUSION: Feeding with HFD leads to insulin resistance, resulting in activation of lipid synthesis and accumulation of lipid deposition in the liver, thus inducing fatty liver.     

Changes in amino acid neurotransmitters during cerebral ischemia and reperfusion in awake rats

AIM: To study the dynamic changes of amino acid neurotransmitters during cerebral ischemia and reperfusion in awake rats. METHODS: Model of cerebral ischemia and reperfusion in awake rats was replicated. Glutamate (Glu), aspartate (Asp), γ-aminobutyric acid (GABA), glycine (Gly), taurine (Tau), alanine (Ala), serine (Ser), threonine (Thr) and glutamine (Gln) concentrations were measured with microdialysis, and excitotoxic index (EI) was calculated in dialysates of hippocampus, neo-cortex and striatum. RESULTS: The significant increases in extracellular not only excitatory amino acid neurotransmitters-Glu and Asp, and their neuromodulator-Gly, but also inhibitory amino acid neurotransmitter-GABA and its neuromodulator-Tau and Ala were observed. However, the EI, representing the balance of excitatory and inhibitory neurotransmitters, was significantly increased during ischemia. CONCLUSION: The results suggest that the elevated Glu and Asp levels during ischemia are insufficient to independently engender ischemic damage, and other neurotransmitters or other factors may play an important role in modulating the excitotoxic effects of Glu and Asp.     

Effect of endogenous carbon monoxide on intracellular calcium concentration in focal ischemic cerebral tissue in rats

AIM: To study effect of endogenous carbon monoxide on intracellular calcium concentration and explore the mechanism in brain protection of endogenous CO in focal cerebral ischemia in rats. METHODS: SD rats were divided into three groups randomly, which including hemin, ZnPP group and saline group as control. Respectively saline, hemin, ZnPP were injected intra-peritoneally twelve hours before middle cerebral artery was occluded. Twenty four hours after MCAO model was set up, the concentration of carbon monoxide in blood and intracellular calcium in neural cells was examined. RESULTS: Contrast to saline group, the concentration of CO in blood rose up while intracellular calcium in occluded side decreased in hemin group; the concentration of CO in blood went down while intracellular calcium in occluded side rose up in ZnPP group, there was significant difference among them (P<0.05). Hemin and ZnPP had no effect on intracellular calcium in non-occluded sides (P>0.05). CONCLUSIONS: It may be one of mechanisms on brain protection in ischemic cerebral tissue that carbon monoxide affected intracellular calcium concentration of neural cells by regulating Ca²⁺-K⁺ channel on cell membrane as a messenger gaseous molecular and neurotransmitter.     

Hepatoprotective effect of Paecilomyces tenuipes polysaccharides on carbon tetrachloride -induced liver injury

AIM:To investigate the protective effect of crude Paecilomyces tenuipes polysaccharides (cPtPs) and Paecilomyces tenuipes polysaccharides (PtPs) in a rat model of acute hepatic necrosis induced by carbon tetrachloride (CCl4). METHODS:Wistar rats were divided into four groups (control group, CCl4 group, cPtPs+CCl4 group and PtPs +CCl4 group), the four groups were given intragastrically with normal saline, cPtPs and PtPs for 15 d, respectively. In the last two days, these groups except control group were injected peritoneally with CCl4. Serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), direct bilirubin (DBIL) and indirect bilirubin (IBIL) were detected by automatic biochemistry analyzer. Pathological changes of hepatic tissue were assessed by hematoxylin-eosine (HE) staining. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in liver homogenate were analyzed using xanthinoxidase and thio-barbituric acid, respectively. The concentration of Ca2+ in hepatocyte mitochondria was determined by colorimetric method. The expression of α-smooth muscle actin (α-SMA) was examined in hepatic tissue by immunohistochemical method. RESULTS:Compared with control group, serum levels of ALT, AST, TBIL, DBIL and IBIL in CCl4 group increased significantly, denaturation and necrosis implicated to the whole hepatic lobules. Compared with CCl4 group, serum levels of ALT, AST, TBIL, DBIL and IBIL in PtPs +CCl4 group decreased significantly, denaturation and necrosis located in the third region of hepatic lobules, the level of SOD increased and MDA decreased (P<0.05) in endochylema. Concentration of Ca2+ in mitochondria decreased in PtPs +CCl4 group and cPtPs +CCl4 group (P<0.05, P<0.01, respectively). Expression of α-SMA was found little in PtPs+CCl4 group. CONCLUSION:PtPs, the effect is better than cPtPs, lessens CCl4-induced hepatonecrosis significantly. The role may be related with anti-lipid peroxidation.     

Role of Huoxue Jiangzhi Recipe in preventing and treating fatty liver in mice

AIM: To explore the role of Huoxue Jiangzhi Recipe in preventing and treating fatty liver in mice and its underlying mechanisms. METHODS: Healthy Kunming mice were fed with high-fat diet and treated intragastrically with different doses of Huoxue Jiangzhi Recipe (compound of ginseng, panax notoginseng and rhizoma gastrodiae, named as GST) for 2 weeks. The levels of blood lipids and triglyceride (TG) in hepatic tissues were measured. Meanwhile, liver index and hepatic pathology were observed. The optimized dosage of Huoxue Jiangzhi Recipe was determined by the experiments. The mice were divided into normal control group (NC group, fed with normal diet) and model group (fed with high-fat diet). The model mice were subdivided into 3 subgroups 12 weeks later: HF group (fed continuously with high-fat diet), ND group (fed with normal diet), GSL group (fed with normal diet and treated intragastrically with GSL). The mice in NC, HF and ND groups were given distilled water by gastric perfusion. Two weeks later, all mice were killed, and blood was collected for measuring serum total cholesterol (TC),TG,high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C) contents, hepatic TC, TG, malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity were detected. Moreover, liver index and hepatic pathology were also observed. The mRNA expression of peroxisome proliferator-activated receptor alpha (PPARα) and cytochrome-P450 2E1 (CYP2E1) in the liver was examined by RT-PCR. RESULTS: GST significantly decreased serum lipid, hepatic lipid and MDA levels and elevated SOD activity. Furthermore, GST markedly reduced liver index, improved hepatic adipose infiltration, increased PPARα mRNA expression and inhibited CYP2E1 mRNA expression. CONCLUSION: GST is effective in the treatment of fatty liver in mice by up-regulating PPARα, thus reducing serum and hepatic TG levels, down-regulating CYP2E1 and inhibiting lipid peroxidation.     

Effects of burn serum on the membrane of intestinal epithelial cell in rats

AIM:To explore the mechanism and significance of the intestinal epithelial cellular membrane damage following burn serum. METHODS:The intestinal epithelial cell(IEC-6) were cultured. The changes of total membranous phospholipid contents fluidity of the IEC membrane were dynamically examined with fluorescence polarization technique and HPCE. RESULTS:In the early stage after stimulation by 20% burn serum, the membranous fluidity obviously decreased. The total phospholipid contents decreased, the content of PLA₂ markedly increased. CONCLUSION:The serial changes in IEC after burned could result in the damages of IEC membrane structure, the integrity of cell membrane and function.     

Lipotoxicity of free fatty acid mixture and effect of free fatty acid mixture on lipid metabolism-related genes in L-02 cells

AIM：To investigate the lipotoxicity of free fatty acid (FFA) mixture and the effect of the FFA mixture on lipid metabolism-related genes in L-02 cells. METHODS：A normal human hepatocytes-derived cell line L-02 was treated with 0.5, 1 and 2 mmol/L FFA mixture (oleate and palmitate, 2∶1) for 24 h. The cellular total lipid accumulation was determined after Nile red staining by confocal laser scanning microscopy and flow cytometry. Intracellular triglyceride (TG) content was measured using an enzymatic kit. The viability of L-02 cells was determined by MTT assay and the apoptosis-inducing effect of FFA mixture was evaluated by annexin V/PI staining. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the culture medium were detected by ALT and AST kits. The mRNA levels of lipid metabolism-related genes, adipose differentiation-related protein (ADRP) and sterol regulatory element-binding protein 1 (SREBP-1), were examined by quantitative real-time PCR. RESULTS：All the different concentrations of FFA mixture increased intracellular lipid accumulation and TG content in a dose-dependent manner. FFA mixture at concentration of 1 mmol/L increased intracellular TG by 2.6 folds, which matched with the change in non-alcoholic fatty liver disease patients. Treatment for 24 h with 0.5 mmol/L and 1 mmol/L FFA mixture did not trigger apparent cell death and apoptosis, while treatment with 2 mmol/L FFA mixture resulted in a marked decrease in cell viability and induced early and late stages of apoptosis in L-02 cells. The levels of ALT and AST in the culture supernatant had no significant difference between control group and FFA treatment group. Treatment with 1 mmol/L FFA mixture up-regulated the expression of ADRP and SREBP-1 by 2.660 and 2.758 folds, respectively. CONCLUSION：FFA mixture induces the hepatic steatosis and 2 mmol/L FFA mixture causes mild cells damage in L-02 cells. The up-regulation of ADRP and SREBP-1 may be involved in FFA-induced hepatic steatosis.     

Expression of undulin in experimental rat liver fibrosis

AIM: To observe the expression of undulin (Un) in liver tissue and to clarify the diagnostic significance of serum Un in experimental rat liver fibrosis. METHODS: Rat liver fibrosis was induced by carbon tetrachloride. The expression of Un in liver tissue was detected by immunohistochemical method. Serum Un levels was measured by enzyme immunoassay. RESULTS: Expression of Un increased in fibrotic liver than normal liver, and it was mainly distributed in portal tract stroma, central veins and fibrotic septa in fibrotic liver. Also, the level of serum Un was significantly higher in fibrotic liver than normal liver. CONCLUSION: These data suggest that Un should be a component of the hepatic extracellar matrix, and its expression could be increased greatly in fibrotic rat liver. Serum Un levels may be used as an indicator in liver fibrosis diagnosis.     

Ethanol extract from Cortex Albiziae attenuates mouse acute liver injury induced by carbon tetrachloride via modulation of NF-κB pathway

AIM:To investigate the protective effect of ethanol extract from Cortex Albiziae on acute liver injury, and to explore its possible mechanism. METHODS:Acute liver injury in mice was induced by single intraperitoneal injection of 25% carbon tetrachloride (olive oil solubilization). The effective parts of ethanol extract from Cortex Albizziae against acute liver injury were screened. The pathological changes of the liver tissues were examined by pathological sections with HE staining. The activity of total superoxide dismutase (T-SOD) and the content of malondialdehyde (MDA) of the liver tissues were detected, the serum levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were mea-sured by ELISA, and the protein expression levels of NF-κB p65, Bcl-2 and Bax in the liver cells of the mice in each group were determined by Western blot. RESULTS:Compared with model group, the serum levels of AST and ALT in low-dose n-butanol phase of ethanol extract from Cortex Albiziae (AB-L, 4 mg·kg^-1·d^-1) group and high-dose n-butanol phase of ethanol extract from Cortex Albiziae (AB-H, 8 mg·kg^-1·d^-1) group were significantly decreased. The necrosis extent and degree of the hepatocytes and infiltration of inflammatory cells were significantly lower than that in model group. Compared with model group, the serum levels of TNF-α and IL-6 in AB-H group and AB-L group were significantly decreased (P<0.05). The protein level of NF-κB p65 in the nuclei of mouse liver cells in AB-H group and AB-L group were also decreased significantly (P<0.05). Compared with model group, the protein expression of Bax was decreased, the protein expression of Bcl-2 was increased, and the Bcl-2/Bax ratio was increased in AB-L group and AB-H group. CONCLUSION:The n-butanol phase of ethanol extract from Cortex Albiziae may protect the liver by reducing the activation of NF-κB p65, inhibiting the excessive release of inflammatory cytokines IL-6 and TNF-α, and decreasing hepatocyte apoptosis via regulating Bcl-2 and Bax expression.     

Mechanisms of anti-apoptotic effects of IGF-1 and insulin in free fatty acid-treated RIN-m cells

AIM: To elucidate if the cytoprotective effects of IGF-1 and insulin on free fatty acid-treated pancreatic β cells involve alteration in NF-κB activity.METHODS: Apoptosis was characterized by morphological analysis with invert microscope as well as Hoechst 33342 staining under a fluorescence microscope.Influence of co-incubation with free fatty acid (FFA) and IGF-1 or regular insulin (RI) on NF-κB activity were determined by Western blotting.Impacts of Bay-117082,which is NF-κB inhibitor,on cytoprotective effects of IGF-1 and RI were measured by flow cytometry.RESULTS: Apoptosis measured by flow cytometry was inhibited by IGF-1 and RI and semi-quantitative determination by Western blotting showed co-incubation with FFA and IGF-1 or RI caused more potent activation of NF-κB compared with incubation with FFA solely.Furthermore,flow cytometry showed suppression of NF-κB activity abolished the cytoprotective effects of IGF-1 and RI.CONCLUSION: Our data suggest that anti-apoptotic effects of IGF-1 and regular insulin on FFA-treated RIN-m cells are mediated via NF-κB pathway.     

Hypertonic NaCl-NaAc improves the microcirculation in rats subjected to hemorrhagic shock

AIM: To study the effects of hypertonic NaCl-NaAc on microcirculation in hemorrhage-shocked rats.METHODS: SD rats were randomized into three groups of 7.5% NaCl(hypertonic saline, HS), 5% NaCl-3.5% NaAc(hypertonic sodium acetate, HSA) and 0.9% NaCl(normal saline, NS). 4 mL/kg HS, HSA or NS was given intravenously following hemorrhagic shock. The microcirculation of spinotrapezius muscle was observed.RESULTS: HS increased mean aortic pressure more significant than HSA. Variables including arteriolar and venular diameter, velocity and volumetric flow rate and open capillaries were increased and erythrocyte aggregation was decreased in 5 min after resuscitation with both HS and HSA solutions.5 min later, variables were deteriorated in HS group.After local treatment, arteriolar and venular diameters were dilated significantly in HSA group.CONCLUSION:HSA had superior effects to HS in improving microcirculation of hemorrhage-shocked rats.     

Changes of pro-inflammatory cytokines in serum and lung of rats with oleic acid-induced acute respiratory distress syndrome and the effect of anisodamine

AIM: To observe the changes of interleukin-6(IL-6), IL-8 and tumor necrosis factor-α(TNF-α) in serum and lung at different time, and the effects of anisodamine (654-2) treatment in rats with oleic acid-induced ARDS. METHODS: The ARDS model induced by intravenous injection of oleic acid in the rat was used and levels of IL-6, IL-8, TNF-α in serum and lung tissue supernatant were measured using enzyme linked immunosorbent assay (ELISA). RESULTS: Levels of serum and lung tissue IL-6, IL-8, TNF-α in oleic acid type ARDS 4 h group were increased significantly. These cytokines in oleic acid type ARDS 8 h group were lower than that of ARDS 4 h group, but serum IL-6, TNF-α and lung tissue IL-6 were still higher than that of control group . In oleic acid type ARDS 16 h group, serum IL-6, TNF-α were lower than that of the ARDS 8 h group and serum TNF-α and lung tissue IL-6 were higher than that of control group. After 654-2 treatment, the levels of serum and lung tissue IL-6, TNF-α were decreased significantly. CONCLUSION: IL-6, IL-8 and TNF- α might play important roles in the oleic acid-induced ARDS in the rat. 654-2 might alleviate ARDS by inhibiting excess production of IL-6 and TNF-α.