Activity of Superoxide Dismutase, Catalase, Glutathione Peroxidase, and Glutathione Reductase in Different Stages of Colorectal Carcinoma

Background

Reactive oxygen species are involved in the pathogenesis of colorectal carcinoma. Clarification of oxidative/antioxidant specificities of different stages of colorectal carcinoma is of special importance.

Aim

To determine oxidative/antioxidant status in plasma of patients with different stages of colorectal carcinoma using malondialdehyde concentration, superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase activities and distribution of superoxide dismutase isoforms.

Methods

Lipid peroxidation and antioxidant enzymes activity were estimated using spectrophotometric methods. Reverse zymography was applied for characterization of superoxide dismutase isoforms.

Results

Lipid peroxidation is increased in all groups compared to the control, but without differences between different stages of colorectal carcinoma. Total superoxide dismutase activity is lower in all colorectal carcinoma groups than in control, and there is a significant increase in tumor stage IV when compared with tumor stage II. Manganese superoxide dismutase isoform is dominant in all groups and its relative activities are significantly higher than activities of a copper/zinc isoform. Total peroxidase potential reflected in catalase and glutathione peroxidase activity is increased when compared to the control, but without any significant differences between colorectal carcinoma groups. Glutathione reductase activity is lower in all colorectal carcinoma groups than in control, and a significant decrease in glutathione reductase activity was obtained between patients in tumor stage II and III compared to tumor stage IV.

Conclusions

Colorectal carcinoma is characterized by increased oxidative stress and antioxidant disbalance. Progression of disease is followed by an increase in redox disbalance.     

Different Profile of Peripheral Antioxidant Enzymes and Lipid Peroxidation in Active and Non-active Inflammatory Bowel Disease Patients

Background

The role of oxidative stress in inflammatory bowel diseases (IBD) has been extended lately from a simple consequence of inflammation to a potential etiological factor, but the data are still controversial. Active disease has been characterized before by an enhanced production of reactive oxygen species and the increased peroxidation of lipids, but patients in remission were generally not considered different from healthy people in terms of oxidative stress.

Aims

We evaluated the antioxidant defense capacity and lipid peroxidation status in the serum of patients with active and non-active disease compared with healthy matched control subjects.

Methods

The study included 20 patients with confirmed IBD in clinical and biological remission, 21 patients with active disease, and 18 controls. We determined the serum levels of two antioxidant enzymes, superoxide dismutase (SOD) and glutathione peroxidase (GPX), and a lipid peroxidation marker, malondialdehyde (MDA).

Results

Active disease patients had an increased activity of both SOD and GPX, as well as significant high values of MDA versus controls. Furthermore, patients being in remission had significantly lower values of antioxidant enzymes (SOD and GPX) and increased lipid peroxidation measured by MDA serum levels, as compared with healthy control subjects.

Conclusions

Our study confirmed the presence of high oxidative stress in active IBD. More importantly, we have demonstrated a lower antioxidant capacity of patients in remission versus control group. This may represent a risk factor for the disease and can be an additional argument for the direct implication of oxidative stress in the pathogenesis of IBD.     

Effect of Carnitine and herbal mixture extract on obesity induced by high fat diet in rats

Background

Obesity-associated type 2 diabetes is rapidly increasing throughout the world. It is generally recognized that natural products with a long history of safety can modulate obesity.

Aim

To investigate the development of obesity in response to a high fat diet (HFD) and to estimate the effect of L-carnitine and an Egyptian Herbal mixture formulation (HMF) (consisting of T. chebula, Senae, rhubarb, black cumin, aniseed, fennel and licorice) on bodyweight, food intake, lipid profiles, renal, hepatic, cardiac function markers, lipid Peroxidation, and the glucose and insulin levels in blood and liver tissue in rats.

Method

White male albino rats weighing 80-90 gm, 60 days old. 10 rats were fed a normal basal diet (Cr), 30 rats fed a high-fat diet (HFD) for 14 weeks during the entire study. Rats of the HFD group were equally divided into 3 subgroups each one include 10 rats. The first group received HFD with no supplement (HFD), the 2^nd group HFD+L-carnitine and the third group received HFD+HMF. Carnitine and HMF were administered at 10^th week (start time for treatments) for 4 weeks. Body weight, lipid profile & renal function (urea, uric acid creatinine) ALT & AST activities, cardiac markers, (LDH, C.K-NAC and MB) the oxidative stress marker reduced glutathione (GSH), and Malondialdehyde (MDA) catalase activity, in addition to glucose, insulin, and insulin resistance in serum & tissues were analyzed.

Results

Data showed that feeding HFD diet significantly increased final body weight, triglycerides (TG), total cholesterol, & LDL concentration compared with controls, while significantly decreasing HDL; meanwhile treatment with L-carnitine, or HMF significantly normalized the lipid profile. Serum ALT, urea, uric acid, creatinine, LDH, CK-NAC, CK-MB were significantly higher in the high fat group compared with normal controls; and administration of L-carnitine or herbal extract significantly lessened the effect of the HFD. Hyperglycemia, hyperinsulinemia, and high insulin resistance (IR) significantly increased in HFD in comparison with the control group. The treatment with L-carnitine or HMF improved the condition. HFD elevated hepatic MDA and lipid peroxidation associated with reduction in hepatic GSH and catalase activity; whereas administration of L-carnitine or herbal extract significantly ameliorated these hepatic alterations.

Conclusion

HFD induced obesity associated with a disturbed lipid profile, defective antioxidant stability, and high values of IR parameters; this may have implications for the progress of obesity related problems. Treatment with L-carnitine, or HMF extract improved obesity and its associated metabolic problems in different degrees. Also HMF has antioxidant, hypolipidaemic insulin sensitizing effects. Moreover HMF might be a safe combination on the organs whose functions were examined, as a way to surmount the obesity state; and it has a distinct anti-obesity effect.     

Amelioration of lipid-induced insulin resistance in rat skeletal muscle by overexpression of Pgc-1β involves reductions in long-chain acyl-CoA levels and oxidative stress

Aims/Hypothesis

To determine if acute overexpression of peroxisome proliferator-activated receptor, gamma, coactivator 1 beta (Pgc-1?? [also known as Ppargc1b]) in skeletal muscle improves insulin action in a rodent model of diet-induced insulin resistance.

Methods

Rats were fed either a low-fat or high-fat diet (HFD) for 4?weeks. In vivo electroporation was used to overexpress Pgc-1?? in the tibialis cranialis (TC) and extensor digitorum longus (EDL) muscles. Downstream effects of Pgc-1?? on markers of mitochondrial oxidative capacity, oxidative stress and muscle lipid levels were characterised. Insulin action was examined ex vivo using intact muscle strips and in vivo via a hyperinsulinaemic?Ceuglycaemic clamp.

Results

Pgc-1?? gene expression was increased >100% over basal levels. The levels of proteins involved in mitochondrial function, lipid metabolism and antioxidant defences, the activity of oxidative enzymes, and substrate oxidative capacity were all increased in muscles overexpressing Pgc-1??. In rats fed a HFD, increasing the levels of Pgc-1?? partially ameliorated muscle insulin resistance, in association with decreased levels of long-chain acyl-CoAs (LCACoAs) and increased antioxidant defences.

Conclusions

Our data show that an increase in Pgc-1?? expression in vivo activates a coordinated subset of genes that increase mitochondrial substrate oxidation, defend against oxidative stress and improve lipid-induced insulin resistance in skeletal muscle.     

Lipid overloading during liver regeneration causes delayed hepatocyte DNA replication by increasing ER stress in mice with simple hepatic steatosis

Background and aim

Impaired fatty liver regeneration has already been reported in many genetic modification models. However, in diet-induced simple hepatic steatosis, which showed similar phenotype with clinical pathology, whether liver regeneration is impaired or not remains unclear. In this study, we evaluated liver regeneration in mice with diet-induced simple hepatic steatosis, and focused on excess lipid accumulation occurring during liver regeneration.

Methods

Mice were fed high fat diet (HFD) or control diet for 9–10 weeks. We analyzed intrahepatic lipid accumulation, DNA replication, and various signaling pathways including cell proliferation and ER stress during liver regeneration after partial hepatectomy. In addition, some of mice were pretreated with tauroursodeoxycholic acid (TUDCA), a chemical chaperone which alleviates ER stress, and then we estimated TUDCA effects on liver regeneration.

Results

The peak of hepatocyte BrdU incorporation, the expression of proliferation cell nuclear antigen (PCNA) protein, and the expressions of cell cycle-related genes were observed in delayed time in HFD mice. The expression of phosphorylated Erk1/2 was also delayed in HFD mice. The amounts of liver triglyceride were at least twofold higher in HFD mice at each time point. Intrahepatic palmitic acid was increased especially in HFD mice. ER stress induced during liver regeneration was significantly higher in HFD mice. In HFD mice, pretreatment with TUDCA reduced ER stress and resulted in improvement of delayed liver regeneration.

Conclusion

In simple hepatic steatosis, lipid overloading occurring during liver regeneration might be caused ER stress and results in delayed hepatocyte DNA replication.     

Mouse strain-dependent variation in obesity and glucose homeostasis in response to high-fat feeding

Aims/hypothesis

Metabolic disorders are commonly investigated using knockout and transgenic mouse models. A variety of mouse strains have been used for this purpose. However, mouse strains can differ in their inherent propensities to develop metabolic disease, which may affect the experimental outcomes of metabolic studies. We have investigated strain-dependent differences in the susceptibility to diet-induced obesity and insulin resistance in five commonly used inbred mouse strains (C57BL/6J, 129X1/SvJ, BALB/c, DBA/2 and FVB/N).

Methods

Mice were fed either a low-fat or a high-fat diet (HFD) for 8 weeks. Whole-body energy expenditure and body composition were then determined. Tissues were used to measure markers of mitochondrial metabolism, inflammation, oxidative stress and lipid accumulation.

Results

BL6, 129X1, DBA/2 and FVB/N mice were all susceptible to varying degrees to HFD-induced obesity, glucose intolerance and insulin resistance, but BALB/c mice exhibited some protection from these detrimental effects. This protection could not be explained by differences in mitochondrial metabolism or oxidative stress in liver or muscle, or inflammation in adipose tissue. Interestingly, in contrast with the other strains, BALB/c mice did not accumulate excess lipid (triacylglycerols and diacylglycerols) in the liver; this is potentially related to lower fatty acid uptake rather than differences in lipogenesis or lipid oxidation.

Conclusions/interpretation

Collectively, our findings indicate that most mouse strains develop metabolic defects on an HFD. However, there are inherent differences between strains, and thus the genetic background needs to be considered carefully in metabolic studies.     

Preclinical Efficacy of Melatonin to Reduce Methotrexate-Induced Oxidative Stress and Small Intestinal Damage in Rats

Background

Methotrexate is widely used as a chemotherapeutic agent for leukemia and other malignancies. The efficacy of this drug is often limited by mucositis and intestinal injury, which are the major causes of morbidity in children and adults.

Aim

The present study investigates whether melatonin, a powerful antioxidant, could have a protective effect.

Method

Rats were pretreated with melatonin (20 and 40 mg/kg body weight) daily 1 h before methotrexate (7 mg/kg body weight) administration for three consecutive days. After the final dose of methotrexate, the rats were sacrificed and the small intestine was used for light microscopy and biochemical assays. Intestinal homogenates were used for assay of oxidative stress parameters malondialdehyde and protein carbonyl content, and myeloperoxidase activity, a marker of neutrophil infiltration as well as for the activities of the antioxidant enzymes.

Result

Pretreatment with melatonin had a dose-dependent protective effect on methotrexate (MTX)-induced alterations in small intestinal morphology. Morphology was saved to some extent with 20 mg melatonin pretreatment and near normal morphology was achieved with 40 mg melatonin pretreatment. Biochemically, pretreatment with melatonin significantly attenuated MTX-induced oxidative stress (P < 0.01 for MDA, P < 0.001 for protein carbonyl content) and restored the activities of the antioxidant enzymes (glutathione reductase P < 0.05, superoxide dismutase P < 0.01).

Conclusion

The results of the present study demonstrate that supplementation by exogenous melatonin significantly reduces MTX-induced small intestinal damage, indicating that it may be beneficial in ameliorating MTX-induced enteritis in humans.     

Oxidative stress and antioxidant capacity in patients with chronic pancreatitis with and without diabetes mellitus

Aim

To determine oxidant stress and antioxidant capacity in chronic pancreatitis (CP) patients with and without diabetes mellitus.

Methods

This study is a secondary data analysis of our earlier study on 127 (male?=?86) patients with CP, grouped as those with diabetes (case; n?=?23) and those without diabetes (control). Markers of antioxidant status included vitamins A and E, total antioxidant capacity (TAC; measured as ferric-reducing ability of plasma [FRAP]), and total glutathione (T-GSH). Markers for oxidative stress included lipid peroxidation, measured as thiobarbituric acid reactive substances (TBARS) and serum superoxide dismutase (s-SOD).

Results

Patients with diabetes were older (mean [SD] age 36.4 [9.7] vs. 29.3 [10.0] years; p?=?0.032), had longer duration of CP [4 (0.3?C21) vs. 3 (0.3?C24) years; p?=?0.07), and had a lower TAC (269.8 [92.4] vs. 355.5 [128.6] ??moles Fe⁺² liberated; p?=?0.003) compared to those without diabetes. In multiple logistic regression analysis taking all exploratory variables, FRAP (<270 ??moles Fe⁺² liberated) was associated with diabetes independent of duration of CP, age of patients, and TBARS levels. However, oxidative stress levels were not different between diabetic and nondiabetic patients.

Conclusions

Diabetes was found to be associated with longer duration of CP and with low antioxidant capacity. Further studies will be needed to evaluate a causal association.     

TGF-β dependent regulation of oxygen radicals during transdifferentiation of activated hepatic stellate cells to myofibroblastoid cells

Background

The activation of hepatic stellate cells (HSCs) plays a pivotal role during liver injury because the resulting myofibroblasts (MFBs) are mainly responsible for connective tissue re-assembly. MFBs represent therefore cellular targets for anti-fibrotic therapy. In this study, we employed activated HSCs, termed M1-4HSCs, whose transdifferentiation to myofibroblastoid cells (named M-HTs) depends on transforming growth factor (TGF)-β. We analyzed the oxidative stress induced by TGF-β and examined cellular defense mechanisms upon transdifferentiation of HSCs to M-HTs.

Results

We found reactive oxygen species (ROS) significantly upregulated in M1-4HSCs within 72 hours of TGF-β administration. In contrast, M-HTs harbored lower intracellular ROS content than M1-4HSCs, despite of elevated NADPH oxidase activity. These observations indicated an upregulation of cellular defense mechanisms in order to protect cells from harmful consequences caused by oxidative stress. In line with this hypothesis, superoxide dismutase activation provided the resistance to augmented radical production in M-HTs, and glutathione rather than catalase was responsible for intracellular hydrogen peroxide removal. Finally, the TGF-β/NADPH oxidase mediated ROS production correlated with the upregulation of AP-1 as well as platelet-derived growth factor receptor subunits, which points to important contributions in establishing antioxidant defense.

Conclusion

The data provide evidence that TGF-β induces NADPH oxidase activity which causes radical production upon the transdifferentiation of activated HSCs to M-HTs. Myofibroblastoid cells are equipped with high levels of superoxide dismutase activity as well as glutathione to counterbalance NADPH oxidase dependent oxidative stress and to avoid cellular damage.     

Time course study of oxidative and nitrosative stress and antioxidant enzymes in K2Cr2O7-induced nephrotoxicity

Background

It has been established that hypothyroidism protects rats against renal ischemia and reperfusion (IR) oxidative damage. However, it is not clear if hypothyroidism is able to prevent protein tyrosine nitration, an index of nitrosative stress, induced by IR or if antioxidant enzymes have involved in this protective effect. In this work it was explored if hypothyroidism is able to prevent the increase in nitrosative and oxidative stress induced by IR. In addition the activity of the antioxidant enzymes catalase, glutathione peroxidase, and superoxide dismutase was studied. Control and thyroidectomized (HTX) rats were studied 24 h of reperfusion after 60 min ischemia.

Methods

Male Wistar rats weighing 380 ± 22 g were subjected to surgical thyroidectomy. Rats were studied 15 days after surgery. Euthyroid sham-operated rats were used as controls (CT). Both groups of rats underwent a right kidney nephrectomy and suffered a 60 min left renal ischemia with 24 h of reperfusion. Rats were divided in four groups: CT, HTX, IR and HTX+IR. Rats were sacrificed and samples of plasma and kidney were obtained. Blood urea nitrogen (BUN) and creatinine were measured in blood plasma. Kidney damage was evaluated by histological analysis. Oxidative stress was measured by immunohistochemical localization of protein carbonyls and 4-hydroxy-2-nonenal modified proteins. The protein carbonyl content was measured using antibodies against dinitrophenol (DNP)-modified proteins. Nitrosative stress was measured by immunohistochemical analysis of 3-nitrotyrosine modified proteins. The activity of the antioxidant enzymes catalase, glutathione peroxidase, and superoxide dismutase was measured by spectrophotometric methods. Multiple comparisons were performed with ANOVA followed by Bonferroni t test.

Results

The histological damage and the rise in plasma creatinine and BUN induced by IR were significantly lower in HTX+IR group. The increase in protein carbonyls and in 3-nitrotyrosine and 4-hydroxy-2-nonenal modified proteins was prevented in HTX+IR group. IR-induced decrease in renal antioxidant enzymes was essentially not prevented by HTX in HTX+IR group.

Conclusion

Hypothyroidism was able to prevent not only oxidative but also nitrosative stress induced by IR. In addition, the antioxidant enzymes catalase, glutathione peroxidase, and superoxide dismutase seem not to play a protective role in this experimental model.     

Antioxidant status and GST gene polymorphisms in antitubercular treatment-induced hepatotoxicity patients

Introduction

Hepatotoxicity is a serious adverse effect of antituberculosis treatment (ATT). Glutathione S-transferase (GST) is involved in the detoxification of toxic metabolites produced as a result of ATT, increased oxidative stress and decreased antioxidant levels, and differences in the GST polymorphism may be one of the causes of ATT-induced hepatotoxicity.

Aim

This study was undertaken to study the relationship among antioxidant status, oxidative stress and GST gene polymorphisms in the development of ATT-induced hepatotoxicity in Indian patients.

Methodology

Two hundred fifty TB patients attending clinics in the Gastroenterology and Thoracic Department, PGIMER, Chandigarh, were enrolled. Liver marker enzymes, markers of oxidative stress, levels of antioxidants and identification of GSTT1, GSTM1 and GSTP polymorphisms were performed using standard protocols.

Results

Of the 250 patients, 160 were males. Of the 160 males, 18 (11.3 %) had ATT-induced hepatotoxicity and 142 no hepatotoxicity, while of 90 females, 12 (13.3 %) had hepatotoxicity and 78 no hepatotoxicity. Patients who developed ATT-induced hepatotoxicity had significantly higher oxidative stress compared to those who did not develop hepatotoxicity at between 1 and 2 months of treatment. Among antioxidants, catalase did not show any significant difference at 2 and 4 months of treatment. The presence of GSTM1 was higher in hepatotoxicity patients as compared to non-hepatotoxicity patients, while GSTT1 and GST1/M1 were lower.

Conclusion

Therefore, in this study, the possible association of oxidative stress with ATT-induced hepatotoxicity was observed. A role of the GST polymorphism in ATT-induced hepatotoxicity was also found and thus could possibly identify the groups at highest risk of developing ATT-induced hepatotoxicity.     

Glutathione metabolism in cobalamin deficiency type C (cblC)

Background

Methylmalonic aciduria with homocystinuria, cblC defect, is the most frequent disorder of vitamin B₁₂ metabolism. CblC patients are commonly treated with a multidrug therapy to reduce metabolite accumulation and to increase deficient substrates. However the long-term outcome is often unsatisfactory especially in patients with early onset, with frequent progression of neurological and ocular impairment. Recent studies, have shown perturbation of cellular redox status in cblC. To evaluate the potential contribution of oxidative stress into the patophysiology of cblC defect, we have analyzed the in vivo glutathione metabolism in a large series of cblC deficient individuals.

Methods

Levels of different forms of glutathione were measured in lymphocytes obtained from 18 cblC patients and compared with age-matched controls. Furthermore, we also analyzed plasma cysteine and total homocysteine.

Results

We found an imbalance of glutathione metabolism in cblC patients with a significant decrease of total and reduced glutathione, along with a significant increase of different oxidized glutathione forms.

Conclusions

These findings show a relevant in vivo disturbance of glutathione metabolism underlining the contribution of glutathione pool depletion to the redox imbalance in treated cblC patients. Our study may be helpful in addressing future research to better understanding the pathogenetic mechanism of the disease and in developing new therapeutic approaches, including the use of novel vitamin B₁₂ derivatives.     

Interleukin-6-deficient mice develop hepatic inflammation and systemic insulin resistance

Aims/hypothesis

The role of IL-6 in the development of obesity and hepatic insulin resistance is unclear and still the subject of controversy. We aimed to determine whether global deletion of Il6 in mice (Il6 ^?/?) results in standard chow-induced and high-fat diet (HFD)-induced obesity, hepatosteatosis, inflammation and insulin resistance.

Methods

Male, 8-week-old Il6 ^?/? and littermate control mice were fed a standard chow or HFD for 12 weeks and phenotyped accordingly.

Results

Il6 ^?/? mice displayed obesity, hepatosteatosis, liver inflammation and insulin resistance when compared with control mice on a standard chow diet. When fed a HFD, the Il6 ^?/? and control mice had marked, equivalent gains in body weight, fat mass and ectopic lipid deposition in the liver relative to chow-fed animals. Despite this normalisation, the greater liver inflammation, damage and insulin resistance observed in chow-fed Il6 ^?/? mice relative to control persisted when both were fed the HFD. Microarray analysis from livers of mice fed a HFD revealed that genes associated with oxidative phosphorylation, the electron transport chain and tricarboxylic acid cycle were uniformly decreased in Il6 ^?/? relative to control mice. This coincided with reduced maximal activity of the mitochondrial enzyme β-hydroxyacyl-CoA-dehydrogenase and decreased levels of mitochondrial respiratory chain proteins.

Conclusions/interpretation

Our data suggest that IL-6 deficiency exacerbates HFD-induced hepatic insulin resistance and inflammation, a process that appears to be related to defects in mitochondrial metabolism.     

GRP78 overproduction in pancreatic beta cells protects against high-fat-diet-induced diabetes in mice

Aims/hypothesis

Endoplasmic reticulum (ER) stress has been detected in pancreatic beta cells and in insulin-sensitive tissues, such as adipose and liver, in obesity-linked rodent models of type 2 diabetes. The contribution of ER stress to pancreatic beta cell dysfunction in type 2 diabetes is unclear. We hypothesised that increased chaperone capacity protects beta cells from ER stress and dysfunction caused by obesity and improves overall glucose homeostasis.

Methods

We generated a mouse model that overproduces the resident ER chaperone GRP78 (glucose-regulated protein 78 kDa) in pancreatic beta cells under the control of a rat insulin promoter. These mice were subjected to high-fat diet (HFD) feeding for 20 weeks and metabolic variables and markers of ER stress in islets were measured.

Results

As expected, control mice on the HFD developed obesity, glucose intolerance and insulin resistance. In contrast, GRP78 transgenic mice tended to be leaner than their non-transgenic littermates and were protected against development of glucose intolerance, insulin resistance and ER stress in islets. Furthermore, islets from transgenic mice had a normal insulin content and normal levels of cell-surface GLUT2 (glucose transporter 2) and the transgenic mice were less hyperinsulinaemic than control mice on the HFD.

Conclusions/interpretation

These data show that increased chaperone capacity in beta cells provides protection against the pathogenesis of obesity-induced type 2 diabetes by maintaining pancreatic beta cell function, which ultimately improves whole-body glucose homeostasis.     

Fish Omega-3 Fatty Acids Induce Liver Fibrosis in the Treatment of Bile Duct-Ligated Rats

Background

Biliary atresia-induced cholestasis increases hepatic oxidative stress with eventual progression to cirrhosis and liver failure. Omega-3 fatty acids play a possible role in the regulation of oxidative stress and the improvement of cholestasis.

Aim

The goal of the present study is to investigate the role of dietary supplementation of fish omega-3 fatty acids in the reduction of hepatocellular damage by using a rat common bile duct ligation model.

Methods

Sprague–Dawley rats received either sham or bile duct ligation (BDL) and were divided into four study groups: Sham+saline (Sham+sal) group, Sham+Fish oil (Sham+FO) group, BDL+saline (BDL+sal) group, and BDL+Fish oil (BDL+FO) group. Rats from each group were assigned to receive, besides regular chow, once daily with either normal saline or fish omega-3 fatty acids (0.4 % of its own body weight) via gavage for 10 days. Samples of blood, liver tissue homogenates, and histological studies from different groups were analyzed at the end of the study.

Results

Rats from BDL+FO had significantly impaired liver function as compared to other study groups (p < 0.05 is of significant difference). Ishak scores and the TGF-b1 contents were significantly higher in rats that received BDL+FO, p < 0.05. Contrary to TGF-b1 liver content, rats from the BDL+FO group had the lowest glutathione levels among the study groups, p < 0.05.

Conclusions

Fish omega-3 fatty acids supplementation, albeit increased tissue content of DHA, tended to increase liver fibrosis in BDL rats, decrease liver glutathione level, and compromise hepatic function; fish oil supplementation to subjects with biliary atresia might be of potential hazard and should be used with caution.     

Absence of invariant natural killer T cells deteriorates liver inflammation and fibrosis in mice fed high-fat diet

Background

Invariant natural killer T (iNKT) cells have been suggested to play critical roles in a wide range of immune responses by acting in a proinflammatory or anti-inflammatory manner. Nonalcoholic steatohepatitis (NASH) is a chronic liver disease progressing to advanced cirrhosis and hepatocellular carcinoma. Despite the abundance of iNKT cells in the liver, their role in the pathogenesis of NASH remains obscure. Here, we investigated their role in the development of diet-induced steatosis/steatohepatitis.

Methods

We used BALB/c wild-type mice and Jα18-deficient (KO) mice lacking iNKT cells fed either a normal diet or a high-fat diet (HFD). The liver and blood were collected from these mice to examine liver inflammation, steatosis, and fibrosis at the indicated time points.

Results

KO mice fed the HFD, compared with control mice fed the HFD, exhibited a clearly higher serum alanine aminotransferase level and a greater number of hepatic inflammatory foci, although there was no significant difference in hepatic lipid retention between these groups of mice. The HFD enhanced hepatic messenger RNA expression of inflammatory cytokines and chemokines in KO but not in control mice. The HFD also increased the proportion of hepatic CD4 T cells and CD8 T cells that composed hepatic inflammatory foci in KO mice, but not in the controls. Prolonged feeding with the HFD augmented liver fibrosis in KO but not in control mice.

Conclusions

These findings indicate that iNKT cells play a protective role against liver inflammation progressing to fibrosis, but not against steatosis, enhanced by dietary excess fat, suggesting a key role of these cells in NASH pathogenesis.     

Probucol Ameliorates the Development of Nonalcoholic Steatohepatitis in Rats Fed High-Fat Diets

Aims

We sought to evaluate the effects of probucol on steatohepatitis and associated molecular mechanisms in a rat model of nonalcoholic steatohepatitis (NASH) induced by high-fat diet (HFD).

Methods

Forty male rats weighing 100–120 g were randomly assigned to the following treatments (n = 10 for each treatment): standard diet + normal saline (NC group), standard diet + 500 mg/kg/day probucol (NP group), HFD + normal saline (HD group), and HFD + 500 mg/kg/day probucol (HP group). All animals received the above treatments for 15 weeks. Lipid metabolism and steatohepatitis were assessed. Systemic insulin resistance, oxidative stress status, serum tumor necrosis factor-alpha (TNF-α) and adiponectin levels, and gene expression were examined.

Results

High-fat feeding resulted in macrovesicular steatosis, lobular inflammation, and hepatocellular ballooning degeneration in the liver, coupled with increased concentrations of serum aspartate aminotransferase and alanine aminotransferase. Probucol exposure attenuated the biochemical and histological changes comparable with NASH. Moreover, probucol treatment significantly prevented the elevations of serum total cholesterol, low-density lipoprotein, and high-density lipoprotein and the increase in the expression of numerous lipid metabolism-related genes in HFD-fed rats. There were increased insulin sensitivity and serum adiponectin levels and enhanced hepatic AMP-activated protein kinase phosphorylation in the HP group. Probucol lessened the HFD-induced elevation of serum TNF-α and hepatic malondialdehyde and reduced antioxidant enzymatic activities.

Conclusions

Probucol shows beneficial effects on HFD-induced steatohepatitis by improving insulin resistance and attenuating oxidative stress and systemic inflammation.     

Comparative proteomic analysis of human donor tissues during orthotopic liver transplantation: ischemia versus reperfusion

Purpose

To explore the specific alterations in protein profiles that occur during ischemia/reperfusion injury (I/RI) and find novel therapeutic strategies to reduce I/RI during orthotopic liver transplantation (OLT).

Method

We used the comparative proteomic approach of two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to compare the proteomic profiles of the same donor liver at three different time points: T1, immediately after cardiac arrest of donors (normal control); T2, before portal vein anastomosis (ischemia); and T3, 2 h after hepatic artery anastomosis (reperfusion).

Result

We identified 34 proteins that were significantly altered during I/RI. These differentially expressed proteins were functionally classified into seven categories: metabolic enzyme, molecular chaperone, antioxidant enzyme, cytoskeleton protein, signal transduction protein, cyclin, and binding protein. Among the 34 proteins, 9 changed during ischemia only (from T1 to T2), 11 changed during reperfusion only (from T2 to T3), and the others changed during both ischemia and reperfusion (from T1 to T3) periods.

Conclusion

Ischemia and reperfusion during LT may lead to different modifications of the liver proteins. Most metabolic enzymes and antioxidant enzymes were upregulated during ischemia, indicating that lipid metabolic disorder and oxidative stress are closely related to the development of ischemic injury. ER chaperones may play a vital role in mediating I/RI and preventing ER stress caused by I/RI. Modulation of ER chaperones could be used as a key therapeutic target to improve the outcomes of LT.     

Fat Mass and Obesity-Associated Gene Enhances Oxidative Stress and Lipogenesis in Nonalcoholic Fatty Liver Disease

Background and Aim

Nonalcoholic fatty liver disease (NAFLD) is strongly associated with obesity, hyperlipidemia, and type 2 diabetes mellitus. Several studies have found that fat mass and the obesity-associated (FTO) gene is linked to obesity. The aim of this work is to investigate the expression and function of FTO in liver with lipid metabolism diseases.

Methods

We investigated the basal FTO expression in an NAFLD rat model and compared it with control subjects. The function of FTO in lipid metabolism was further studied in L02 cells through overexpression experiments.

Results

A significant increase in FTO mRNA and protein levels was found in the NAFLD group. In addition, the FTO levels were positively associated with malondialdehyde and superoxide dismutase concentrations. FTO overexpression in L02 cells enhanced lipogenesis and oxidative stress.

Conclusions

This study demonstrates that increased FTO levels in the liver are involved in oxidative stress and lipid deposition, which characterize NAFLD.