Carnitine Palmitoyltransferase Activity Research Articles

Migration-induced variation of fatty acid transporters and cellular metabolic intensity in passerine birds.

Because lipids are the main fuel supporting avian endurance activity, lipid transport and oxidation capacities may increase during migration. We measured enzyme activities, mRNA expression and protein levels in pectoralis and heart for several key steps of lipid transport and catabolism pathways to investigate whether these pathways were upregulated during migration. We used yellow-rumped (Setophaga coronata) and yellow (S. petechia) warblers and warbling vireos (Vireo gilvus) as study species because they all show migration-induced increases in organismal metabolic capacities. For yellow-rumped warblers, β-hydroxyacyl CoA-dehydrogenase (HOAD) activities and fatty acid transporter mRNA and/or protein levels were higher during spring than fall in pectoralis and heart, except that fatty acid translocase (FAT/CD36) protein levels showed the opposite pattern in heart. Lipid transporter protein levels, but not mRNA expression, in pectoralis and heart of warbling vireos were higher either during spring or fall than summer, but this was not true for HOAD activities. For yellow warblers, pectoralis, but not heart, protein levels of lipid transporters were upregulated during migration relative to summer, but this pattern was not evident for mRNA expression or HOAD activity. Finally, muscle and heart citrate synthase and carnitine palmitoyl transferase activities showed little seasonal variation for any species. These data suggest that pectoralis and heart lipid transport and catabolism capacities are often, but not universally, important correlates of elevated organismal metabolic capacity during migration. In contrast, migration-induced variation in cellular metabolic intensity and mitochondrial membrane transport are apparently not common correlates of the migratory phenotype in passerines.

Amelioration of nonalcoholic fatty liver disease by hepatic stimulator substance via preservation of carnitine palmitoyl transferase-1 activity.

Nonalcoholic steatohepatitis (NASH) is the progressive form of nonalcoholic fatty liver disease and so far is supposed to be related with mitochondrial impairment. Hepatic stimulator substance (HSS) has been defined as a liver-protective factor promoting hepatocyte DNA synthesis and hepatic proliferation after liver intoxication. We previously reported that HSS ameliorated hepatocyte death, probably because of its preservation of mitochondria. This study aims to explore whether HSS could protect carnitine palmitoyl transferase-1 (CPT-1), an essential enzyme responsible for β-oxidation of free fatty acids in mitochondria, from lipotoxicity, thus alleviating hepatic lipid deposition. To test this, the HSS gene was delivered into C57BL/6J mice and efficiently expressed in the liver. NASH mice were prepared with high-fat diet or methionine-choline-deficient diet. The results showed that hepatic inflammation and liver functions were alleviated in the HSS-transfected mice; meanwhile, the activity of CPT-1 was obviously protected. Moreover, oleic acid (OA) treatment resulted in remarkable lipid accumulation in HepG2 cells; this deposition was improved by HSS transfection. Simultaneously, the CPT-1 activity, which was impaired by OA treatment, was profoundly rescued in the HSS-expressing cells. CPT-1 activity was more severely impaired if the OA treatment was combined with S15176, a CPT-1 inhibitor. However, this impairment was effectively reduced by the HSS transfection, and the effect was enhanced by C75, a CPT-1 activator. Interestingly, if the cells were transfected with HSS-siRNA, the preservation of CPT-1 provided by HSS was again diminished. In conclusion, HSS reduces lipotoxicity to mitochondria most likely via preservation of CPT-1.

The Carnitine Palmitoyl Transferase (CPT) System and Possible Relevance for Neuropsychiatric and Neurological Conditions.

The carnitine palmitoyl transferase (CPT) system is a multiprotein complex with catalytic activity localized within a core represented by CPT1 and CPT2 in the outer and inner membrane of the mitochondria, respectively. Two proteins, the acyl-CoA synthase and a translocase also form part of this system. This system is crucial for the mitochondrial beta-oxidation of long-chain fatty acids. CPT1 has two well-known isoforms, CPT1a and CPT1b. CPT1a is the hepatic isoform and CPT1b is typically muscular; both are normally utilized by the organism for metabolic processes throughout the body. There is a strong evidence for their involvement in various disease states, e.g., metabolic syndrome, cardiovascular diseases, and in diabetes mellitus type 2. Recently, a new, third isoform of CPT was described, CPT1c. This is a neuronal isoform and is prevalently localized in brain regions such as hypothalamus, amygdala, and hippocampus. These brain regions play an important role in control of food intake and neuropsychiatric and neurological diseases. CPT activity has been implicated in several neurological and social diseases mainly related to the alteration of insulin equilibrium in the brain. These pathologies include Parkinson's disease, Alzheimer's disease, and schizophrenia. Evolution of both Parkinson's disease and Alzheimer's disease is in some way linked to brain insulin and related metabolic dysfunctions with putative links also with the diabetes type 2. Studies show that in the CNS, CPT1c affects ceramide levels, endocannabionoids, and oxidative processes and may play an important role in various brain functions such as learning.

Betaine alleviates hepatic lipid accumulation via enhancing hepatic lipid export and fatty acid oxidation in rats fed with a high-fat diet.

To assess the effects of betaine on hepatic lipid accumulation and investigate the underlying mechanism, thirty-two male Sprague-Dawley rats weighing 100 (sd 2·50) g were divided into four groups, and started on one of four treatments: basal diet, basal diet with betaine administration, high-fat diet and high-fat diet with betaine administration. The results showed that no significant difference of body weight was found among experimental groups. Compared with high-fat diet-fed rats, a betaine supplementation decreased (P< 0·05) hepatic TAG accumulation induced by high-fat diet, which was also supported by hepatic histology results. Additionally, hepatic betaine-homocysteine methyltransferase concentration [corrected] as well as its mRNA abundance and lecithin level were found increased (P< 0·05) by betaine supplementation in both basal diet-fed rats and high-fat diet-fed rats. Betaine administration in high-fat diet-fed rats exhibited a higher (P< 0·05) concentration [corrected] of hepatic carnitine palmitoyltransferase 1 (CPT1) compared with high-fat diet-fed rats. High-fat diet inhibited (P< 0·05) the gene expression of hepatic PPARα and CPT1. However, betaine administration in high-fat diet-fed rats elevated (P< 0·05) the gene expression of PPARα and CPT1. Moreover, concentration, gene and protein expressions of hepatic fibroblast growth factor 21 (FGF21) were increased (P< 0·05) in response to betaine administration in high-fat diet group; meanwhile the gene expression of hepatic AMP-activated protein kinase was increased (P< 0·05) as well. The results suggest that betaine administration enhanced hepatic lipid export and fatty acid oxidation in high-fat diet-fed rats, thus effectively alleviating fat accumulation in the liver.

Protective effects of extendin-4 on hypoxia/reoxygenation-induced injury in H9c2 cells

Glucagon-like peptide-1 (GLP-1) analogues are likely to exert cardioprotective effects via balancing the energy metabolism in cardiomyocytes following ischemic or hypoxic insults. The present study aimed to explore the protective effects and mechanism of exendin-4, a GLP-1 analogue, on cardiomyocyte glucose uptake using an in vitro model of hypoxia/reoxygenation (H/R) of H9c2 cardiomyocyte cells. Pre-treatment with exendin-4 (200 nM) prior to H/R increased the cell viability, decreased cell apoptosis, enhanced cardiomyocyte glucose uptake and increased the production of adenosine triphosphate. Exendin-4 also decreased the levels of lactate dehydrogenase and creatine kinase-MB in the culture medium. Furthermore, the activity of carnitine palmitoyltransferase-1 in the H9c2 cells was decreased, while the activity of phosphofructokinase-1 was increased following exendin-4 treatment. Moreover, pre-treatment with exendin-4 increased the expression of p38 mitogen-activated protein kinase (p38MAPK) γ and translocation of glucose transporter-1 in H9c2 cells subjected to H/R. However, these effects were attenuated by the p38MAPK inhibitors BIRB796 and SB203580. The results suggested that exendin-4 exerted significant cardioprotective effects against H/R-induced cell injury and restored the metabolic imbalance of cardiomyocytes by activating the p38MAPK signaling pathway in the H9c2 cell model. Importantly, p38MAPKγ, one subunit of p38MAPK, may have the most important function in this process. The results of the present study may be helpful in the development of novel drugs to treat patients with coronary heart disease.

The aggravation of mitochondrial dysfunction in nonalcoholic fatty liver disease accompanied with type 2 diabetes mellitus

Objective. Nonalcoholic fatty liver disease (NAFLD) is a mitochondrial disease associated with the metabolic syndrome, but few data are available on the mitochondrial dysfunction of NAFLD after the development of type 2 diabetes mellitus (T2DM). We aimed to identify the changes of mitochondrial function in rat livers when T2DM develops after NAFLD. Material and methods. Rat models of nonalcoholic fatty liver (NAFL) and T2DM were established using high-fat diet and streptozocin. Mitochondria were isolated from the livers. The levels of reactive oxygen species (ROS) and mRNA and protein levels of mitochondrial complex IV (COX IV) and carnitine palmitoyltransferase-1 (CPT-1) were assessed in rat livers. The mitochondrial membrane potential (MP), and the enzyme activities of COX IV and CPT-1 were measured in isolated mitochondria. Results. There were increased ROS, decreased mitochondrial MP, and reduced COX IV and CPT-1 activity in the NAFL and T2DM groups compared with controls (p < 0.05). Compared with NAFL, the T2DM group had higher ROS levels and lower enzyme activity (p < 0.05), but showed no difference in mitochondrial MP. Although COX IV and CPT-1 expression levels in liver decreased in NAFL and T2DM, there was no significant difference between two groups. Conclusion. This study first identified progressively impaired mitochondrial respiratory chain and β-oxidation in NAFLD when T2DM develops, inducing overproduction of ROS, and finally triggering a vicious circle that leads to the aggravation of mitochondrial dysfunction in NAFLD after development of T2DM.

Transplacental induction of fatty acid oxidation in term fetal pigs by the peroxisome proliferator-activated receptor alpha agonist clofibrate.

BackgroundTo induce peroxisomal proliferator-activated receptor α (PPARα) expression and increase milk fat utilization in pigs at birth, the effect of maternal feeding of the PPARα agonist, clofibrate (2-(4-chlorophenoxy)-2-methyl-propanoic acid, ethyl ester), on fatty acid oxidation was examined at full-term delivery (0 h) and 24 h after delivery in this study. Each group of pigs (n = 10) was delivered from pregnant sows fed a commercial diet with or without 0.8% clofibrate for the last 7 d of gestation. Blood samples were collected from the utero-ovarian artery of the sows and the umbilical cords of the pigs as they were removed from the sows by C-section on day 113 of gestation.ResultsHPLC analysis identified that clofibric acid was present in the plasma of the clofibrate-fed sow (~4.2 μg/mL) and its offspring (~1.5 μg/mL). Furthermore, the maternal-fed clofibrate had no impact on the liver weight of the pigs at 0 h and 24 h, but hepatic fatty acid oxidation examined in fresh homogenates showed that clofibrate increased (P < 0.01) 14C-accumulation in CO2 and acid soluble products 2.9-fold from [1-14C]-oleic acid and 1.6-fold from [1-14C]-lignoceric acid respectively. Correspondingly, clofibrate increased fetal hepatic carnitine palmitoyltransferase (CPT) and acyl-CoA oxidase (ACO) activities by 36% and 42% over controls (P < 0.036). The mRNA abundance of CPT I was 20-fold higher in pigs exposed to clofibrate (P < 0.0001) but no differences were detected for ACO and PPARα mRNA between the two groups.ConclusionThese data demonstrate that dietary clofibrate is absorbed by the sow, crosses the placental membrane, and enters fetal circulation to induce hepatic fatty acid oxidation by increasing the CPT and ACO activities of the newborn.

Effects of resveratrol on lipid metabolism in muscle and adipose tissues: A reevaluation in a pig model

The body fat-lowering effect and mechanisms of action of resveratrol (0, 300, 600 mg resveratrol/kg diet) was evaluated in a pig model. Resveratrol improved serum lipid profiles, and decreased visceral adipose tissue weight and serum leptin level. In adipose tissue, peroxisome proliferator activated receptor γ (PPARγ) and fatty acid synthase (FAS) mRNA levels, and FAS and lipoprotein lipase (LPL) activities were decreased by resveratrol, while hormone sensitive lipase (HSL), adipose triglyceride lipase (ATGL) and carnitine palmitoyl transferase-1(CPT-1) mRNA levels, and HSL and CPT-1 activities were increased. In muscle tissue, PPARγ, FAS, acetyl-CoA carboxylase (ACC) and LPL mRNA levels and FAS and ACC activities were decreased by resveratrol, while HSL mRNA levels and CPT-1 activity were increased. Moreover, compared with the control group, LPL activity was decreased, and CPT-1 mRNA levels and HSL activity were increased in the 600 mg resveratrol/kg diet group. This study provides the very first evidence in a pig model that resveratrol could improve serum lipid profiles and decrease body fat deposition, which might be mediated by a reduction in fatty acid uptake and de novo lipogenesis, as well as an increase in fat mobilization and fatty acid oxidation in muscle and adipose tissues.

Effects of exercise training on carbohydrate and lipid catabolism in the swimming muscles of Nile tilapia (Oreochromis niloticus)

This study aims to determine the effects of exercise training on carbohydrate and lipid catabolism in the swimming muscles of Nile tilapia (Oreochromis niloticus) by measuring the levels of related enzymes, lipids and free fatty acids. We designed one control group and two training groups of fish that were exercised at different training intensities [0, 1 and 1.5 body lengths per second (bl/s)]. The fish in the experimental groups were trained for 12 h/day for 4 weeks. Compared with the control group, the 1 and 1.5 bl/s groups showed significantly increased hexokinase and pyruvate kinase activities in red muscle (p < 0.05). In white muscle, pyruvate kinase activity was significantly higher in the 1.5 bl/s group than in the control group (p < 0.05), and hexokinase activity did not significantly differ between the groups. The activities of hormone-sensitive lipase and carnitine palmitoyltransferase I in both muscle types were significantly lower in the training groups than in the control group (p < 0.05). The plasma-free fatty acid level decreased (p < 0.05), while the lipid percentages increased in red muscle (p < 0.05) after exercise training. These findings clearly indicated that with exercise training, glycolysis increased and lipid oxidation decreased in the swimming muscle of tilapia.

Chikusetsu saponin IVa regulates glucose uptake and fatty acid oxidation: implications in antihyperglycemic and hypolipidemic effects.

The aim of this study is to investigate antidiabetic effects and molecular mechanisms of the chemical Chikusetsu saponin IVa (CHS) that isolated from root bark of Aralia taibaiensis, which has multiple pharmacological activity, such as relieving rheumatism, promoting blood circulation to arrest pain and antidiabetic action. Rats with streptozotocin/nicotinamide-induced type 2 diabetes mellitus (T2DM) and insulin-resistant myocytes were used. Adenosine monophosphate (AMP)-activated protein kinase (AMPK) and acetyl-CoA carboxylase were quantified by immunoblotting. Assays of glucose uptake, fatty acid oxidation, glucose transporter 4 (GLUT4) translocation and carnitine palmitoyl transferase-1 (CPT-1) activity were performed. Chronic oral administration of CHS effectively decreases blood glucose, triglyceride, free fatty acid (FFA) and low density lipoprotein-cholesterol levels in T2DM rats. In both normal and insulin-resistant C2C12 myocytes, CHS activates AMPK, and increases glucose uptake or fatty acid oxidation through enhancing membrane translocation of GLUT4 or CPT-1 activity respectively. Knockdown of AMPK significantly diminishes the effects of CHS on glucose uptake and fatty acid oxidation. CHS is a novel AMPK activator that is capable of bypassing defective insulin signalling and could be useful for the treatment of T2DM or other metabolic disorders.

Hepatocyte growth factor is elevated in amniotic fluid from obese women and regulates placental glucose and fatty acid metabolism

IntroductionTo evaluate the impact of the pro-inflammatory cytokine hepatocyte growth factor (HGF) on the regulation of glucose and lipid placental metabolism. MethodsHGF levels were quantified in amniotic fluid and placenta from control and obese women. 2-deoxy-glucose (2-DOG) uptake, glycolysis, fatty acid oxidation (FAO), fatty acid esterification, de novo fatty acid synthesis, triglyceride levels and carnitine palmitoyltransferase activities (CPT) were measured in placental explants upon addition of pathophysiological HGF levels. ResultsIn obese women, total- and -activated-HGF levels in amniotic fluid were elevated ∼24%, and placental HGF levels were ∼3-fold higher than in control women. At a similar dose to that present in amniotic fluid of obese women, HGF (30 ng/mL) increased Glut-1 levels and 2-DOG uptake by ∼25–30% in placental explants. HGF-mediated effect on 2-DOG uptake was dependent on the activation of phosphatidylinositol 3-kinase signaling pathway. In addition, HGF decreased ∼20% FAO, whereas esterification and de novo fatty acid synthesis increased ∼15% and ∼25% respectively, leading to 2-fold triglyceride accumulation in placental explants. In parallel, HGF reduced CPT-I activity ∼70%. DiscussionHGF is a cytokine elevated in amniotic fluid and placental tissue of obese women, which through its ability to stimulate 2-DOG uptake and metabolism impairs FAO and enhances esterification and de novo fatty acid synthesis, leading to accumulation of placental triglycerides.

Acute cold and exercise training up-regulate similar aspects of fatty acid transport and catabolism in house sparrows (Passer domesticus).

Summit maximum thermoregulatory metabolic rate (Msum) and maximum exercise metabolic rate (MMR) both increase in response to acute cold or exercise training in birds. Because lipids are the main fuel supporting both thermogenesis and exercise in birds, adjustments to lipid transport and catabolic capacities may support elevated energy demands from cold and exercise training. To examine a potential mechanistic role for lipid transport and catabolism in organismal cross-training effects (exercise effects on both exercise and thermogenesis, and vice versa), we measured enzyme activities and mRNA and protein expression in pectoralis muscle for several key steps of lipid transport and catabolism pathways in house sparrows (Passer domesticus) during acute exercise and cold training. Both training protocols elevated pectoralis protein levels of fatty acid translocase (FAT/CD36), cytosolic fatty acid-binding protein, and citrate synthase (CS) activity. However, mRNA expression of FAT/CD36 and both mRNA and protein expression of plasma membrane fatty acid-binding protein did not change for either training group. CS activities in supracoracoideus, leg and heart, and carnitine palmitoyl transferase (CPT) and β-hydroxyacyl CoA-dehydrogenase activities in all muscles did not vary significantly with either training protocol. Both Msum and MMR were significantly positively correlated with CPT and CS activities. These data suggest that up-regulation of trans-sarcolemmal and intramyocyte lipid transport capacities and cellular metabolic intensities, along with previously documented increases in body and pectoralis muscle masses and pectoralis myostatin (a muscle growth inhibitor) levels, are common mechanisms underlying the training effects of both exercise and shivering in birds.

Pregnancy induces resistance to the anorectic effect of hypothalamic malonyl-CoA and the thermogenic effect of hypothalamic AMPK inhibition in female rats.

During gestation, hyperphagia is necessary to cope with the metabolic demands of embryonic development. There were three main aims of this study: Firstly, to investigate the effect of pregnancy on hypothalamic fatty acid metabolism, a key pathway for the regulation of energy balance; secondly, to study whether pregnancy induces resistance to the anorectic effect of fatty acid synthase (FAS) inhibition and accumulation of malonyl-coenzyme A (CoA) in the hypothalamus; and, thirdly, to study whether changes in hypothalamic AMPK signaling are associated with brown adipose tissue (BAT) thermogenesis during pregnancy. Our data suggest that in pregnant rats, the hypothalamic fatty acid pathway shows an overall state that should lead to anorexia and elevated BAT thermogenesis: decreased activities of AMP-activated protein kinase (AMPK), FAS, and carnitine palmitoyltransferase 1, coupled with increased acetyl-CoA carboxylase function with subsequent elevation of malonyl-CoA levels. This profile seems dependent of estradiol levels but not prolactin or progesterone. Despite the apparent anorexic and thermogenic signaling in the hypothalamus, pregnant rats remain hyperphagic and display reduced temperature and BAT function. Actually, pregnant rats develop resistance to the anorectic effects of central FAS inhibition, which is associated with a reduction of proopiomelanocortin (POMC) expression and its transcription factors phospho-signal transducer and activator of transcription 3, and phospho-forkhead box O1. This evidence demonstrates that pregnancy induces a state of resistance to the anorectic and thermogenic actions of hypothalamic cellular signals of energy surplus, which, in parallel to the already known refractoriness to leptin effects, likely contributes to gestational hyperphagia and adiposity.

Effects of epigallocatechin gallate on lipid metabolism and its underlying molecular mechanism in broiler chickens.

The objective of this study was to investigate the effects of epigallocatechin gallate (EGCG) on fat metabolism and to establish the molecular mechanism of these effects in broilers. Seventy-two 28-day-old male Ross 308 broiler chickens were divided into three groups with different levels of EGCG supplementation for 4weeks: normal control (NC) group, L-EGCG (a low-level supplement of EGCG, 40mg/kg body weight daily) and H-EGCG (a high-level supplement of EGCG, 80mg/kg body weight daily). After 4weeks of oral administration, EGCG significantly reduced the level of abdominal fat deposition in broilers. The serum triglycerides and low-density lipoprotein cholesterol of chickens in H-EGCG group were also significantly decreased compared with the NC group, and the high-density lipoprotein cholesterol was notably increased at the same time. Moreover, the vital role of the liver and abdominal adipose tissue in lipid metabolism of poultry animals was examined through gene expression and enzyme activities related to fat anabolism and catabolism in these organs. Our data show that EGCG supplementation for 2weeks significantly downregulated the expression of fatty acid synthesis and fat deposition-related genes, and upregulated the expression of genes involved in fatty acid β-oxidation and lipolysis genes. Simultaneously, the activities of hepatic fatty acid synthesis enzymes (fatty acid synthase and acetyl CoA carboxylase) were significantly decreased, and the activity of carnitine palmitoyl transferase-1 was notably elevated. The results suggest that EGCG could alleviate fat deposition in broilers through inhibiting fat anabolism and stimulating lipid catabolism in broilers.

Abstract 12150: Dronedarone is a Potent Cardiac and Hepatic CPT-1 Inhibitor

Purpose: Dronedarone was developed on the basis that it would represent a class III anti-arrhythmic devoid of “amiodarone-like” adverse effects. Indeed, photosensitization and iodine-related thyroid toxicity do not occur with dronedarone. However, a number of other adverse effects have emerged. We tested the hypothesis that, like amiodarone, dronedarone modifies cellular metabolism by inhibiting mitochondrial fatty acid uptake via the carnitine shuttle. Methods: We compared the efficacy of dronedarone as an inhibitor of cardiac and hepatic carnitine palmitoyl transferase-1 (CPT-1) with that of the known CPT-1 inhibitors perhexiline and amiodarone. Male 6-week old Sprague-Dawley rats were euthanized under 2% isoflurane. Hearts and livers were rapidly removed, homogenised and placed on ice. CPT-1 activity was measured by the formation of palmitoyl-carnitine, as previously described1. Samples were ultracentrifuged and supernatants were injected for detection by liquid-chromatography/mass-spectometry. Dronedarone (5, 10, 50, 100 and 500μM) was compared to amiodarone (100, 200 and 500μM), perhexiline (20, 50, 100, 150 and 200μM), and the physiological inhibitor of CPT-1, malonyl-CoA (1μM). Concentration-response curves were expressed via log(inhibitor) vs normalized responses. Results: (1) Malonyl-CoA inhibited CPT-1 by &gt;90% in both heart and liver, while perhexiline was more potent than amiodarone as CPT-1 inhibitor (Table). (2) Dronedarone was equipotent (IC50 approximately 40μM) in both heart and liver, and approximately 3-fold more potent than amiodarone. Conclusion: Dronedarone, like amiodarone and perhexiline, inhibits cardiac and hepatic CPT-1. This has potential advantages regarding haemodynamic stability in atrial fibrillation, but may predispose to eventual hepato- and cardiotoxic effects. Ref: 1. Kennedy JA, Unger S, Horowitz JD. Biochem Pharmacology 1996, 52, p273-280.

High-fat and high-cholesterol diet rapidly induces non-alcoholic steatohepatitis with advanced fibrosis in Sprague-Dawley rats.

The development of fibrosis is considered an important phase in the progress of non-alcoholic steatohepatitis (NASH) towards the end stage of liver disease, including cirrhosis. However, few small animal models can display NASH-associated fibrosis. We aimed to establish a dietary model of NASH with rapid progression to fibrosis using genetically normal rats. Nine-week-old male Sprague-Dawley rats were fed with normal, high-fat (HF), or two types of high-fat and high-cholesterol (HFC) diets for 9 weeks (n = 5 each). All HFC diets contained 1.25% or 2.5% cholesterol. The rats fed with the HF diet developed mild steatosis and inflammation without fibrosis at 18 weeks of age, whereas all rats given the HFC diet developed obvious steatosis and inflammation with hepatocyte ballooning and fibrosis. Two of five (40%) rats given the HFC diet containing 2.5% cholesterol progressed to liver cirrhosis. Hepatic total cholesterol levels were significantly higher in rats given the HFC, than the normal or HF diets. The HFC diet significantly and dose-dependently decreased microsomal triglyceride transfer protein expression. Cholesterol tended to suppress carnitine palmitoyltransferase activity and adenosine triphosphate-binding cassette transporter G5 expression. Adding cholesterol to the HF diet modified hepatic lipid metabolism at the molecular level. The HFC diet induced hepatic features of NASH and eventually progressed cirrhosis in Sprague-Dawley rats within 9 weeks.

Mitochondrial activities of citrate synthase, carnitine palmitoyltransferase-1 and cytochrome C oxidase are increased during the apoptotic process in hepatocytes of a rat model of acute liver failure

To determine the roles of mitochondrial apoptosis and energy metabolism in hepatocytes during the pathogenic process of acute renal failure (ALF) by assessing disease-related differential activities of several key mitochondrial enzymes, including citrate synthase (CS), carnitine palmitoyltransferase-1 (CPT-1) and cytochrome c oxidase (COX). Thirty-two male Sprague Dawley rats were given D-galactosamine followed by and lipopolysaccharide (LPS) to induce acute liver failure and sacrificed after 4 (4 h group), 8 (8 h group) 12 (12 h group) and 24 hours (24 h group) of treatment. Eight unmodeled rats served as controls. Effects related to apoptosis were evaluated by pathological analysis of hepatic tissues and TUNEL staining. Ultrastructural changes in mitochondria were assessed by electron microscopy. The activity and expression of CS, CPT-1 and COX were measured. Hepatocyte apoptosis was present in the 4 h treatment group and was increased obviously in the 8 h treatment group. Hepatocyte necrosis was first observed in the 12 h treatment group and was significantly higher in the 24 h treatment group, with inflammatory cell invasion. Ultrastructural changes in mitochondria were present in the 4 h treatment group, and the 24 h treatment group showed mitochondria with completely destroyed outer membranes, which resulted in mitochondrial collapse. Activity and protein expression of CS, CPT-1 and COX were increased in the 4 h group (vs. controls), were at their peak in the 8 h group (CS:t =1.481, P less than 0.01; CPT-1:t =2.619, P less than 0.05; COX:t =1.014, P less than 0.01) and showed a decreasing trend in the 12 h group. In addition, the activities of CS, CPT-1 and COX were enhanced at the stage of hepatocyte apoptosis, suggesting that these enzymes were involved in the initiation and development of ALF. Energy metabolism plays an important role in hepatocyte apoptosis during ALF.

In vitro effects of selenium on copper-induced changes in lipid metabolism of grass carp (Ctenopharyngodon idellus) hepatocytes.

The present study was performed to evaluate the in vitro effects of selenium (Se) supplementation to prevent copper (Cu)-induced changes in lipid metabolism of hepatocytes from grass carp (Ctenopharyngodon idellus). Four groups (control and 100 μM Cu in combination with 0, 5, and 10 μM Se, respectively) were chosen. Compared with the control, activities of glucose 6-phosphatedehydrogenase, 6-phosphogluconate dehydrogenase, malic enzyme, and carnitine palmitoyltransferase I (CPT I) of all three Cu-exposed groups at 24 and 48 h were significantly greater. However, among three Cu-exposed groups, increasing Se concentration tended to increase activities of G6PD and ME at 24 h and 6PGD activity at 24 and 48 h but decreased CPT I activity at 24 h. Compared with the control, Cu exposure alone, or in combination with Se, downregulated mRNA levels of sterol regulatory element-binding protein-1 (SREBP-1c), fatty acid synthase (FAS), acetyl-CoA carboxylase, peroxisome proliferator activated receptor alpha (PPARα), CPT I, and hormone-sensitive lipase (HSL) at 24 h as well as SREBP-1c, FAS, and ACC mRNA levels at 48 h. However, upregulated mRNA levels of PPARα, CPT I, and HSL, as well as decreased triglyceride content, were recorded at 48 h. Thus, although toxic at greater levels, lower levels of Se provided significant protection against Cu-induced changes in lipid metabolism. For the first time, our study indicates the dose- and time-dependent effects of Se addition on changes in lipid metabolism induced by Cu in fish hepatocytes and provides new insights into Se-Cu interaction at both enzymatic and molecular levels.

Effect of L-carnitine Supplementation on Nutritional Status and Physical Performance Under Calorie Restriction.

L-carnitine is popular as a potential ergogenic aid because of its role in the conversion of fat into energy. The present study was undertaken to investigate the effect of short term supplementation of L-carnitine on metabolic markers and physical efficiency tests under short term calorie restriction. Male albino rats were divided into four groups (n=12 in each)-control, calorie restricted (CR for 5days, 25% of basal food intake), L-carnitine supplemented (CAR, given orally for 5days at a dose of 100mg/kg), CR with L-carnitine supplementation (CR+CAR). Food intake and body weight of the rats were measured along with biochemical variables like blood glucose, tissue glycogen, plasma and muscle protein and enzymatic activities of CPT-1 (carnitine palmitoyl transferase-1) and AMP kinase. Results demonstrated that L-carnitine caused marked increase in muscle glycogen, plasma protein, CPT-1 activity and swim time of rats (P<0.05) on short term supplementation. In addition to the substantive effects caused by CR alone, L-carnitine under CR significantly affected muscle glycogen, plasma protein, CPT-1 activity and AMP kinase (P<0.05). Short term CR along with L-carnitine also resulted in increased swim time of rats than control, CR and L-carnitine treated rats (P<0.05). The present study was an attempt towards developing an approach for better adherence to dietary restriction regimen, with the use of L-carnitine.

C9,t11-Conjugated linoleic acid ameliorates steatosis by modulating mitochondrial uncoupling and Nrf2 pathway

Oxidative stress, hepatic steatosis, and mitochondrial dysfunction are key pathophysiological features of nonalcoholic fatty liver disease. A conjugated linoleic acid (CLA) mixture of cis9,trans11 (9,11-CLA) and trans10,cis12 (10,12-CLA) isomers enhanced the antioxidant/detoxifying mechanism via the activation of nuclear factor E2-related factor-2 (Nrf2) and improved mitochondrial function, but less is known about the actions of specific isomers. The differential ability of individual CLA isomers to modulate these pathways was explored in Wistar rats fed for 4 weeks with a lard-based high-fat diet (L) or with control diet (CD), and, within each dietary treatment, two subgroups were daily administered with 9,11-CLA or 10,12-CLA (30 mg/day). The 9,11-CLA, but not 10,12-CLA, supplementation to CD rats improves the GSH/GSSG ratio in the liver, mitochondrial functions, and Nrf2 activity. Histological examination reveals a reduction of steatosis in L-fed rats supplemented with both CLA isomers, but 9,11-CLA downregulated plasma concentrations of proinflammatory markers, mitochondrial dysfunction, and oxidative stress markers in liver more efficiently than in 10,12-CLA treatment. The present study demonstrates the higher protective effect of 9,11-CLA against diet-induced pro-oxidant and proinflammatory signs and suggests that these effects are determined, at least in part, by its ability to activate the Nrf2 pathway and to improve the mitochondrial functioning and biogenesis.