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1.
Perfluoroalkyl acids (PFAAs) are a group of widely used anthropogenic compounds. As one of the most dominant PFAAs, perfluorooctanoic acid (PFOA) has been suggested to induce hepatotoxicity and several other toxicological effects. However, details on the mechanisms for PFOA-induced hepatotoxicity still need to be elucidated. In this study, we observed the occurrence of endoplasmic reticulum (ER) stress in mouse livers and HepG2 cells after PFOA exposure using several familiar markers for the unfolded protein response (UPR). ER stress in HepG2 cells after PFOA exposure was not significantly influenced by autophagy inhibition or stimulation. The antioxidant defense system was significantly disturbed in mouse livers after PFOA exposure, and reactive oxygen species (ROS) were increased in cells exposed to PFOA for 24 h. However, N-acetyl-L-cysteine (NAC) pretreatment did not satisfactorily alleviate the UPR in cells exposed to PFOA even though the increase of ROS was less evident. Furthermore, exposure of HepG2 cells to PFOA in the presence of sodium 4-phenylbutyrate (4-PBA), a chemical chaperone and ER stress inhibitor, suggested that 4-PBA alleviated the UPR and autophagosome accumulation induced by PFOA in cells. In addition, several toxicological effects attributed to PFOA exposure, including cell cycle arrest, proteolytic activity impairment, and neutral lipid accumulation, were also improved by 4-PBA cotreatment in cells. In vivo study demonstrated that PFOA-induced lipid metabolism perturbation and liver injury were partially ameliorated by 4-PBA in mice after 28 days of exposure. These findings demonstrated that PFOA-induced ER stress leading to UPR might play an important role in PFOA-induced hepatotoxic effects, and chemical chaperone 4-PBA could ameliorate the effects.  相似文献   

2.
Chronically elevated glucocorticoids (GCs) and a high-fat diet (HFD) independently induce insulin resistance, abdominal obesity, and nonalcoholic fatty liver disease (NAFLD). GCs have been linked to increased food intake, particularly energy-dense "comfort" foods. Thus we examined the synergistic actions of GCs and HFD on hepatic disease development in a new rodent model of chronically elevated GCs. Six-week-old male Sprague-Dawley rats received exogenous GCs, via subcutaneous implantation of four 100-mg corticosterone (Cort) pellets, to elevate basal GC levels for 16 days (n = 8-10 per group). Another subset of animals received wax pellets (placebo) to serve as controls. Animals from each group were randomly assigned to receive a 60% HFD or a standard high-carbohydrate (13% fat and 60% carbohydrate) diet. Cort + HFD resulted in central obesity, despite a relative weight loss, a 4-fold increase in hepatic lipid content, hepatic fibrosis, and a 2.8-fold increase in plasma alanine aminotransferase levels compared with placebo + chow controls. Hepatic injury developed independent of inflammation, as plasma haptoglobin levels were reduced with Cort treatment. Insulin resistance and hepatic steatosis occurred with Cort alone; these outcomes were further exacerbated by the HFD in the presence of elevated Cort. In addition to fatty liver, the Cort + HFD group also developed severe insulin resistance, hyperinsulinemia, hyperglycemia, and hypertriglyceridemia, which were not evident with HFD or Cort alone. Thus a HFD dramatically exacerbates the development of NAFLD and characteristics of the metabolic syndrome in conditions of chronically elevated Cort.  相似文献   

3.
Methionine-choline-deficient (MCD) diets that cause steatohepatitis in rodents are typically enriched in polyunsaturated fat. To determine whether the fat composition of the MCD formula influences the development of liver disease, we manufactured custom MCD formulas with fats ranging in PUFA content from 2% to 59% and tested them for their ability to induce steatohepatitis. All modified-fat MCD formulas caused identical degrees of hepatic steatosis and resulted in a similar distribution of fat within individual hepatic lipid compartments. The fatty acid composition of hepatic lipids, however, reflected the fat composition of the diet. Mice fed a PUFA-rich MCD formula showed extensive hepatic lipid peroxidation, induction of proinflammatory genes, and histologic inflammation. When PUFAs were substituted with more saturated fats, lipid peroxidation, proinflammatory gene induction, and hepatic inflammation all declined significantly. Despite the close relationship between PUFAs and hepatic inflammation in mice fed MCD formulas, dietary fat had no impact on MCD-mediated damage to hepatocytes. Indeed, histologic apoptosis and serum alanine aminotransferase levels were comparable in all MCD-fed mice regardless of dietary fat content. Together, these results indicate that dietary PUFAs promote hepatic inflammation but not hepatotoxicity in the MCD model of liver disease. These findings emphasize that individual dietary nutrients can make specific contributions to steatohepatitis.  相似文献   

4.
目的探讨奥美沙坦对于高脂诱导的非酒精性脂肪肝病(NAFLD)的影响及可能机制。方法健康雄性8周龄C57BL/6小鼠24只随机分为高脂组(n=16)和正常饮食组(n=8),高脂组小鼠高脂饮食(60%的脂肪)12w后再随机分为高脂饮食对照组(n=8)、高脂饮食治疗组(n=8)。高脂饮食治疗组小鼠给予0.75mg/kg/d的奥美沙坦灌胃8w,灌胃结束后处理小鼠,留取空腹血样本检测AST和ALT。肝组织冰冻切片行油红O染色观察脂肪变;石蜡切片行HE和F4/80免疫组化染色观察肝脏炎症变化;实时荧光定量PCR检测肝脏TNF-α和IL-6mRNA的表达水平;WesternBlot检测肝组织中IκB-α、p-IκBa、NF—κB信号通路的活化。结果奥美沙坦显著抑制了高脂诱导的NAFLD脂肪变性,并明显改善肝功能。实时荧光定量PCR结果表明奥美沙坦能显著降低肝脏组织中TNF-α和IL-6mRNA表达水平(P〈0.05);Western Blot结果显示奥美沙坦显著抑制肝脏NF-κB信号通路活化。结论奥美沙坦显著抑制NAFLD小鼠肝脏炎性病变而保护肝功能,其机制与抑制NF-κB信号通路活化以及降低肝脏TNF-α和IL-6mRNA水平有关。  相似文献   

5.
6.
The purpose of the study was to investigate the effect of flaxseed oil (FO), rich in alpha-linolenic acid (ALA) (18:3 n-3) on growth parameters and lipid metabolism of rats fed with high fat diet. High fat diet (HFD) resulted in significant alterations in hepatic lipids, increase in body weight gain and negative effect on lipoprotein metabolism. FO supplementation significantly lowered the increase in body weight gain, liver weight, plasma cholesterol, triglycerides, phospholipids, free fatty acids, high-density lipoprotein (HDL), low-density lipoprotein-cholesterol (LDL-C), very low-density lipoprotein (VLDL), LDL/HDL and TC/HDL ratio in HFD fed rats. FO significantly reduced the hepatic and plasma lipid levels indicating its hypolipidemic activity. On the other hand, oral administration of FO exhibited lower plasma lipoprotein profile as compared to HFD rats. Hepatic protection by FO is further substantiated by the normal liver histological findings in HFD fed rats. These data suggest that FO participate in the normal regulation of plasma lipid concentration and cholesterol metabolism in liver. No adverse effect of FO on growth parameters and plasma lipids in rats fed with fat-free diet. The results of the present study demonstrate that FO may be developed as a useful therapy for hyperlipidemia through reducing hepatic lipids, thereby proving its hypolipidemic activity.  相似文献   

7.
8.
We have previously reported that essential fatty acid deficiency (EFAD) during suckling in mice resulted in an adult lean phenotype and a resistance to diet-induced obesity. We now hypothesized that postnatal EFAD would cause long-term effects on lipid metabolism. C57BL/6 mice were fed an EFAD or a control diet from the 16th day of gestation and throughout lactation. The pups were weaned to standard diet (STD) and at 15 weeks of age given either high fat diet (HFD) or STD. Lipoprotein profiles, hepatic lipids, fatty acids and mRNA expression were analyzed in 3-week-old and 25-week-old offspring. At weaning, the EFAD pups had higher cholesterol levels in both plasma and liver and 6-fold higher concentrations of hepatic cholesterol esters than control pups. Adult EFAD offspring had higher levels of hepatic cholesterol and linoleic acid, but lower levels of dihomo-γ-linolenic acid and Pparg mRNA expression in the liver. In addition, HFD fed EFAD offspring had lower plasma total cholesterol, lower hepatic triglycerides and lower liver weight compared to controls fed HFD. In conclusion, early postnatal EFAD resulted in short-term alterations with increased hepatic cholesterol accumulation and long-term protection against diet-induced liver steatosis and hypercholesterolemia.  相似文献   

9.
This study investigated the biological and molecular mechanisms underlying the antiobesity effect of omija fruit ethanol extract (OFE) in mice fed a high-fat diet (HFD). C57BL/6J mice were fed an HFD (20% fat, w/w) with or without OFE (500 mg/kg body weight) for 16 weeks. Dietary OFE significantly increased brown adipose tissue weight and energy expenditure while concomitantly decreasing white adipose tissue (WAT) weight and adipocyte size by up-regulating the expression of brown fat-selective genes in WAT. OFE also improved hepatic steatosis and dyslipidemia by enhancing hepatic fatty acid oxidation-related enzymes activity and fecal lipid excretion. In addition to steatosis, OFE decreased the expression of pro-inflammatory genes in the liver. Moreover, OFE improved glucose tolerance and lowered plasma glucose, insulin and homeostasis model assessment of insulin resistance, which may be linked to decreases in the activity of hepatic gluconeogenic enzymes and the circulating level of gastric inhibitory polypeptide. These findings suggest that OFE may protect against diet-induced adiposity and related metabolic disturbances by controlling brown-like transformation of WAT, fatty acid oxidation, inflammation in the liver and fecal lipid excretion. Improved insulin resistance may be also associated with its antiobesity effects.  相似文献   

10.
11.
The incidence of obesity is now at epidemic proportions and has resulted in the emergence of nonalcoholic fatty liver disease (NAFLD) as a common metabolic disorder that can lead to liver injury and cirrhosis. Excess sucrose and long-chain saturated fatty acids in the diet may play a role in the development and progression of NAFLD. One factor linking sucrose and saturated fatty acids to liver damage is dysfunction of the endoplasmic reticulum (ER). Although there is currently no proven, effective therapy for NAFLD, the amino sulfonic acid taurine is protective against various metabolic disturbances, including alcohol-induced liver damage. The present study was undertaken to evaluate the therapeutic potential of taurine to serve as a preventative treatment for diet-induced NAFLD. We report that taurine significantly mitigated palmitate-mediated caspase-3 activity, cell death, ER stress, and oxidative stress in H4IIE liver cells and primary hepatocytes. In rats fed a high-sucrose diet, dietary taurine supplementation significantly reduced hepatic lipid accumulation, liver injury, inflammation, plasma triglycerides, and insulin levels. The high-sucrose diet resulted in an induction of multiple components of the unfolded protein response in the liver consistent with ER stress, which was ameliorated by taurine supplementation. Treatment of mice with the ER stress-inducing agent tunicamycin resulted in liver injury, unfolded protein response induction, and hepatic lipid accumulation that was significantly ameliorated by dietary supplementation with taurine. Our results indicate that dietary supplementation with taurine offers significant potential as a preventative treatment for NAFLD.  相似文献   

12.
This research aim was to assess the impact of the seed extracts of the date cultivars (Qatara, Barhi, and Ruthana) on rat’s liver steatosis, oxidative stress, and inflammation triggered by feeding a high-fat diet (HFD). The experimental design was based on random partitioning into two groups; one that received the standard diet and another that received the HFD diet. The HFD rats were orally administered Lipitor or date seed extracts at 300 or 600 mg/kg/day for 4 weeks. Accordingly, feeding rats HFD significantly increased body and liver weights, hepatic and serum lipid levels, glucose, insulin, HOMA-IR, liver function enzymes, and inflammation markers, and decreased oxidative stress enzymes. Oral administration of Barhi and Ruthana date seed extracts significantly decreased body and liver weights. Serum and liver total cholesterol TC, Triglycerides TGs, and free fatty acids FFAs were also decreased as were AST, ALT, MAD, leptin, and CRP, with a concomitant increase in SOD, GSH, and CAT. Furthermore, similar to Lipitor, oral administration of the extracts reduced inflammation markers such as TNF-α, serum CRP, IL-6, IL-1β, and leptin while increasing IL-10 and adiponectin levels. Histological observation revealed that extract administration improved hepatocyte and parenchymal structures and decreased lipid deposition. In conclusion, both Barhi and Ruthana seed extracts showed strong hepatoprotective, anti-inflammatory, and antioxidant effects against HFD-induced liver steatosis. And date seeds have other beneficial potential for prevention and treatment of various diseases, which can be studied in the future.  相似文献   

13.
Mitochondrial dysfunctions have been detected in non-alcoholic steatohepatitis, but less information exists regarding adaptation of mitochondrial function during the initiation of hepatic steatosis. This study aimed to determine in rat liver the sequence of mitochondrial and metabolic adaptations occurring during the first 8 weeks of a moderate high fat diet (HFD). Sprague-Dawley rats were fed a HFD during 2, 4, and 8 weeks. Mitochondrial oxygen consumption, respiratory chain complexes activity, and oxidative phosphorylation efficiency were assessed in isolated liver mitochondria. Gene expression related to fat metabolism and mitochondrial biogenesis were determined. Results were compared to data collected in a group of rats sacrificed before starting the HFD feeding. After 2 and 4 weeks of HFD, there was a development of fatty liver and a concomitant increase the expression of mitochondrial glycerol-3-phosphate acyltransferase (mtGPAT) and peroxisome proliferator-activated receptor γ. Higher serum β-hydroxybutyrate levels and enhanced hepatic pyruvate dehydrogenase kinase 4 expression suggested increased fatty acid oxidation. However, mitochondrial respiration and respiratory chain activity were normal. After 8 weeks of HFD, lower accumulation of liver triglycerides was associated with reduced expression of mtGPAT. At this time, oxygen consumption with palmitoyl-L: -carnitine was decreased whereas oxidative phosphorylation efficiency (ATP/O) with succinate was enhanced. Hepatic levels of mtDNA were unchanged whatever the time points. This longitudinal study in rats fed a HFD showed that hepatic lipid homeostasis and mitochondrial function can adapt to face the increase in fatty acid availability.  相似文献   

14.
Fatty liver disease is an emerging public health problem without effective therapies, and chronic hepatic inflammation is a key pathologic mediator in its progression. Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active epoxyeicosatrienoic acids (EETs), which have potent anti-inflammatory effects. Although promoting the effects of EETs elicits anti-inflammatory and protective effects in the cardiovascular system, the contribution of CYP-derived EETs to the regulation of fatty liver disease-associated inflammation and injury is unknown. Using the atherogenic diet model of non-alcoholic fatty liver disease/non-alcoholic steatohepatitis (NAFLD/NASH), our studies demonstrated that induction of fatty liver disease significantly and preferentially suppresses hepatic CYP epoxygenase expression and activity, and both hepatic and circulating levels of EETs in mice. Furthermore, mice with targeted disruption of Ephx2 (the gene encoding soluble epoxide hydrolase) exhibited restored hepatic and circulating EET levels and a significantly attenuated induction of hepatic inflammation and injury. Collectively, these data suggest that suppression of hepatic CYP-mediated EET biosynthesis is an important pathological consequence of fatty liver disease-associated inflammation, and that the CYP epoxygenase pathway is a central regulator of the hepatic inflammatory response in NAFLD/NASH. Future studies investigating the utility of therapeutic strategies that promote the effects of CYP-derived EETs in NAFLD/NASH are warranted.  相似文献   

15.
Environmental factors, such as the macronutrient composition of the diet, can have a profound impact on risk of diabetes and metabolic syndrome. In the present study we demonstrate how a single, simple dietary factor--leucine--can modify insulin resistance by acting on multiple tissues and at multiple levels of metabolism. Mice were placed on a normal or high fat diet (HFD). Dietary leucine was doubled by addition to the drinking water. mRNA, protein and complete metabolomic profiles were assessed in the major insulin sensitive tissues and serum, and correlated with changes in glucose homeostasis and insulin signaling. After 8 weeks on HFD, mice developed obesity, fatty liver, inflammatory changes in adipose tissue and insulin resistance at the level of IRS-1 phosphorylation, as well as alterations in metabolomic profile of amino acid metabolites, TCA cycle intermediates, glucose and cholesterol metabolites, and fatty acids in liver, muscle, fat and serum. Doubling dietary leucine reversed many of the metabolite abnormalities and caused a marked improvement in glucose tolerance and insulin signaling without altering food intake or weight gain. Increased dietary leucine was also associated with a decrease in hepatic steatosis and a decrease in inflammation in adipose tissue. These changes occurred despite an increase in insulin-stimulated phosphorylation of p70S6 kinase indicating enhanced activation of mTOR, a phenomenon normally associated with insulin resistance. These data indicate that modest changes in a single environmental/nutrient factor can modify multiple metabolic and signaling pathways and modify HFD induced metabolic syndrome by acting at a systemic level on multiple tissues. These data also suggest that increasing dietary leucine may provide an adjunct in the management of obesity-related insulin resistance.  相似文献   

16.
Consumption of high-fat diet (HFD) induces nonalcoholic fatty liver disease (NAFLD) and may lead to multiple complications affecting human health. In the present study, effect of Moringa oleifera leaf extract (MoLE) in alleviating HFD induced liver injury in mice has been reported. Liver histology and serum activity of hepatic marker enzymes i.e. aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) have been studied. Lipid peroxidation (LPO), ferric reducing antioxidant power (FRAP) and reduced glutathione (GSH) were also estimated using liver homogenate. Results of the study suggested that MoLE treatment protected HFD-induced liver damage as indicated by histopathology and liver enzyme activity compared to only-HFD fed group (P < 0.05). Interestingly, early signs of HFD-induced fatty liver were also alleviated by MoLE. Moreover, significant increase in endogenous antioxidant parameters and lower lipid peroxidation were found in liver of all MoLE treated groups. Results of the study indicated that MoLE has both preventive as also curative hepatoprotective activity.  相似文献   

17.
The potential mechanisms of action of polyphenols in nonalcoholic fatty liver disease (NAFLD) are overlooked. Here, we evaluate the beneficial therapeutic effects of hydroxytyrosol (HT), the major metabolite of the oleuropein, in a nutritional model of insulin resistance (IR) and NAFLD by high-fat diet. Young male rats were divided into three groups receiving (1) standard diet (STD; 10.5% fat), (2) high-fat diet (HFD; 58.0% fat) and (3) HFD + HT (10 mg/kg/day by gavage). After 5 weeks, the oral glucose tolerance test was performed, and at 6th week, blood sample and tissues (liver and duodenum) were collected for following determinations. The HT-treated rats showed a marked reduction in serum AST, ALT and cholesterol and improved glucose tolerance and insulin sensitivity, reducing homeostasis model assessment index. HT significantly corrected the metabolic impairment induced by HFD, increasing hepatic peroxisome proliferator-activated receptor PPAR-α and its downstream-regulated gene fibroblast growth factor 21, the phosphorylation of acetyl-CoA carboxylase and the mRNA carnitine palmitoyltransferase 1a. HT also reduced liver inflammation and nitrosative/oxidative stress decreasing the nitrosylation of proteins, reactive oxygen species production and lipid peroxidation. Moreover, HT restored intestinal barrier integrity and functions (fluorescein isothiocyanate-dextran permeability and mRNA zona occludens ZO-1). Our data demonstrate the beneficial effect of HT in the prevention of early inflammatory events responsible for the onset of IR and steatosis, reducing hepatic inflammation and nitrosative/oxidative stress and restoring glucose homeostasis and intestinal barrier integrity.  相似文献   

18.
We tested whether long-term administration of voglibose (VO) prevents diet induced obesity in addition to hypoglycemic effects in high fat fed mice and further investigated the underlying mechanisms by which voglibose exerts its weight lowering effect. Male C57BL/6 mice were fed ad libitum for 12 weeks with the control diet (CTL), high-fat diet (HFD) or the HFD with VO supplementations. Blood lipid profile, plasma leptin levels and hepatic triglyceride content, as well as expressions of genes involved in appetite and mitochondrial function were examined. The results showed that VO significantly reduced body weight, fat mass and energy intakes in high fat fed mice. VO showed improved metabolic profiles including blood glucose, triglyceride and free fatty acid. Elevated levels of plasma leptin in HFD were significantly reduced with the VO, furthermore, VO modulated the hypothalamic expressions of leptin receptors and appetite related genes. VO showed the upregulated expressions of PGC-1 in the liver and epididymal adipose tissue. In conclusion, VO may exert antiobesity properties through reductions in energy intake and improvement in mitochondrial function, indicating that VO has potential therapeutic use in patients with obesity, type 2 diabetes, and related complications.  相似文献   

19.
The manner in which insulin resistance impinges on hepatic mitochondrial function is complex. Although liver insulin resistance is associated with respiratory dysfunction, the effect on fat oxidation remains controversial, and biosynthetic pathways that traverse mitochondria are actually increased. The tricarboxylic acid (TCA) cycle is the site of terminal fat oxidation, chief source of electrons for respiration, and a metabolic progenitor of gluconeogenesis. Therefore, we tested whether insulin resistance promotes hepatic TCA cycle flux in mice progressing to insulin resistance and fatty liver on a high-fat diet (HFD) for 32 weeks using standard biomolecular and in vivo (2)H/(13)C tracer methods. Relative mitochondrial content increased, but respiratory efficiency declined by 32 weeks of HFD. Fasting ketogenesis became unresponsive to feeding or insulin clamp, indicating blunted but constitutively active mitochondrial β-oxidation. Impaired insulin signaling was marked by elevated in vivo gluconeogenesis and anaplerotic and oxidative TCA cycle flux. The induction of TCA cycle function corresponded to the development of mitochondrial respiratory dysfunction, hepatic oxidative stress, and inflammation. Thus, the hepatic TCA cycle appears to enable mitochondrial dysfunction during insulin resistance by increasing electron deposition into an inefficient respiratory chain prone to reactive oxygen species production and by providing mitochondria-derived substrate for elevated gluconeogenesis.  相似文献   

20.
While non-alcoholic fatty liver disease (NAFLD) represents the common cause of chronic liver disease, specific therapies are currently unavailable. The wine industry produces millions of tons of residue (pomace), which contains high levels of bioactive phytochemicals. The aim of this study was to clarify the potential benefits of grape pomace for the treatment of NAFLD at different levels of severity, and to clarify the mechanism of action. C57Bl/6 mice were given high fat diet (HFD) or western diet (WD) as models of obesity and hepatic steatosis or steatohepatitis, respectively, with or without pomace supplementation (50–250 mg/day). Pomace inhibited food intake, and reduced serum leptin and body weight gain. Ectopic fat deposition was reduced, while white adipose tissue mass was preserved. In addition, pomace improved glucose tolerance and insulin sensitivity, prevented the development of adipose tissue inflammation, and reduced hepatic steatosis. Higher expression of genes involved in fatty acids transport and oxidation was observed in adipose tissue, while lipogenic genes were attenuated in the liver of pomace-treated mice. In WD-fed mice, pomace reduced the severity of hepatic steatosis and inflammation and improved blood lipid profile, but was ineffective in reversing hepatic damage of advanced NASH. In conclusion, pomace improved insulin sensitivity and reduced ectopic fat deposition, leading to a healthier metabolic profile. Pomace may hold the potential as a supplement with beneficial health outcomes for the prevention and treatment of hepatic steatosis and other obesity-related pathologies.  相似文献   

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