Lipids up-regulate uncoupling protein 2 expression in rat hepatocytes

Effects of Desflurane versus sevoflurane on graft outcome of patients with cirrhosis receiving steatotic liver graft in deceased donor liver transplantation

STUDY OBJECTIVE

This study aimed to analyze the effects of two volatile anesthetic agents, desflurane and sevoflurane, on graft outcomes in patients undergoing deceased donor liver transplantation (DDLT) for cirrhosis, with a specific focus on fatty grafts.

DESIGN

A retrospective observational study.

SETTING

A tertiary hospital (Severance Hospital, Korea).

PATIENTS

This study included 151 patients with liver cirrhosis who underwent DDLT for cirrhosis between January 2006 and December 2022.

INTERVENTIONS

Patients were grouped according to maintenance anesthesia received (desflurane or sevoflurane), the model for end-stage liver disease (MELD) score, and macrovesicular steatosis (MVS) of the liver graft.

MEASUREMENTS

Survival curves were constructed from the date of surgery to graft failure or death. After propensity score matching (PSM), Cox regression analysis was used to compare hazards ratios (HR) for 5-year graft and overall survival. Subgroup analyses were performed for the MELD score and MVS of the liver graft. Incidences of 1-month acute rejection and early allograft dysfunction (EAD) were also compared between the two groups.

MAIN RESULTS

Among 151 eligible patients, 49 patients remained in each group after PSM, with 14 (28.6 %) graft failures and deaths occurring in each group. In matched analysis, sevoflurane showed poorer 5-year graft and overall survival compared to desflurane in recipients of graft with ≥10 % MVS, and this trend was significant in patients with MELD score of ≥35. In Cox regression model, compared to desflurane sevoflurane showed a propensity score-matched HR of 5.8 (95 % CI, 1.13-30.50 for both 5-year graft and overall survival. Additionally, sevoflurane showed an increased risk of 1-month acute rejection; however, no difference was observed for EAD.

CONCLUSIONS

Sevoflurane as a maintenance agent during DDLT in recipients with high MELD scores and fatty grafts may be associated with poorer outcomes compared to desflurane.

In vivo identification of bioactive components of Poria cocos for adjusting mitochondria against metabolic dysfunction-associated fatty liver disease

Currently, no specific treatment exists to alleviate metabolic dysfunction-associated fatty liver (MAFLD). Previously, Poria cocos (PC) effectively relieved MAFLD, but its bioactive components are still unknown. The bioactive substances in PC that regulate mitochondria function to alleviate MAFLD were thus determined. The L02 hepatocyte model induced by fat emulsion and the MAFLD rat model induced by a high-fat diet (HFD) were developed to explore the efficacy of PC against MAFLD. The activity of PC-derived components in the liver mitochondria of HFD-fed rats was evaluated using the L02 hepatocyte model. Additionally, the PC-derived components from the liver mitochondria were identified by ultra-high performance liquid chromatography/mass spectrometry. Finally, the anti-steatosis ability of PC-derived monomers and monomers groups was evaluated using the adipocyte model. PC maintained the mitochondrial ultrastructure, alleviated mitochondrial oxidative stress, and regulated the energy metabolism and the fatty acid β oxidation to relieve lipid emulsion-induced cellular steatosis and HFD-induced MAFLD. PC-derived components entering the liver mitochondria inhibited oxidative stress injury and improved the energy metabolism to fight cellular steatosis. Additionally, 15 chemicals were identified in the PC-treated rat liver mitochondria. These identified chemical molecules and molecule groups in the mitochondria prevented cellular steatosis by regulating mitochondrial oxidative stress and energy metabolism. PC restores mitochondrial structure and function, alleviating MAFLD, which is related to oxidative stress, energy metabolism, and fatty acid β oxidation. The identified 15 components may be the main effective PC components regulating mitochondria function to alleviate MAFLD. Thus, PC may be a promising mitochondrial regulator to prevent MAFLD.

Hepatocyte Mitochondrial Dynamics and Bioenergetics in Obesity-Related Non-Alcoholic Fatty Liver Disease

PURPOSE OF THE REVIEW

Mitochondrial dysfunction has long been proposed to play a crucial role in the pathogenesis of a considerable number of disorders, such as neurodegeneration, cancer, cardiovascular, and metabolic disorders, including obesity-related insulin resistance and non-alcoholic fatty liver disease (NAFLD). Mitochondria are highly dynamic organelles that undergo functional and structural adaptations to meet the metabolic requirements of the cell. Alterations in nutrient availability or cellular energy needs can modify their formation through biogenesis and the opposite processes of fission and fusion, the fragmentation, and connection of mitochondrial network areas respectively. Herein, we review and discuss the current literature on the significance of mitochondrial adaptations in obesity and metabolic dysregulation, emphasizing on the role of hepatocyte mitochondrial flexibility in obesity and NAFLD.

RECENT FINDINGS

Accumulating evidence suggests the involvement of mitochondrial morphology and bioenergetics dysregulations to the emergence of NAFLD and its progress to non-alcoholic steatohepatitis (NASH). Most relevant data suggests that changes in liver mitochondrial dynamics and bioenergetics hold a key role in the pathogenesis of NAFLD. During obesity and NAFLD, oxidative stress occurs due to the excessive production of ROS, leading to mitochondrial dysfunction. As a result, mitochondria become incompetent and uncoupled from respiratory chain activities, further promoting hepatic fat accumulation, while leading to liver inflammation, insulin resistance, and disease's deterioration. Elucidation of the mechanisms leading to dysfunctional mitochondrial activity of the hepatocytes during NAFLD is of predominant importance for the development of novel therapeutic approaches towards the treatment of this metabolic disorder.

The Role of Mitochondrial Adaptation and Metabolic Flexibility in the Pathophysiology of Obesity and Insulin Resistance: an Updated Overview

PURPOSE OF REVIEW

The term "metabolic flexibility" denotes the dynamic responses of the cellular oxidative machinery in order to adapt to changes in energy substrate availability. A progressive loss of this adaptive capacity has been implicated in the development of obesity-related comorbidities. Mitochondria are dynamic intracellular organelles which play a fundamental role in energy metabolism, and the mitochondrial adaptation to environmental challenges may be viewed as the functional component of metabolic flexibility. Herein, we attempt to comprehensively review the available evidence regarding the role of mitochondrial adaptation and metabolic flexibility in the pathogenesis of obesity and related morbidities, namely insulin resistance states and non-alcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

Overall, there is a concrete body of evidence to support the presence of impaired mitochondrial adaptation as a principal component of systemic metabolic inflexibility in conditions related to obesity. There are still many unresolved questions regarding the relationship between the gradual loss of mitochondrial adaptability and the progression of obesity-related complications, such as causality issues, the timely appearance and reversibility of the described disturbances, and the generalizability of the findings to the mitochondrial content of every affected tissue or organ. The evidence regarding the causality between the observed associations remains inconclusive, although most of the available data points towards a bidirectional, potentially mutually amplifying relationship. The spectrum of NAFLD is of particular interest, since functional and pathological changes in the course of its development closely mirror the progression of dysmetabolism, if not constituting a dynamic component of the latter.

Dietary Macronutrient Composition Differentially Modulates the Remodeling of Mitochondrial Oxidative Metabolism during NAFLD

Diets rich in fats and carbohydrates aggravate non-alcoholic fatty liver disease (NAFLD), of which mitochondrial dysfunction is a central feature. It is not clear whether a high-carbohydrate driven ‘lipogenic’ diet differentially affects mitochondrial oxidative remodeling compared to a high-fat driven ‘oxidative’ environment. We hypothesized that the high-fat driven ‘oxidative’ environment will chronically sustain mitochondrial oxidative function, hastening metabolic dysfunction during NAFLD. Mice (C57BL/6NJ) were reared on a low-fat (LF; 10% fat calories), high-fat (HF; 60% fat calories), or high-fructose/high-fat (HFr/HF; 25% fat and 34.9% fructose calories) diet for 10 weeks. De novo lipogenesis was determined by measuring the incorporation of deuterium from D₂O into newly synthesized liver lipids using nuclear magnetic resonance (NMR) spectroscopy. Hepatic mitochondrial metabolism was profiled under fed and fasted states by the incubation of isolated mitochondria with [¹³C₃]pyruvate, targeted metabolomics of tricarboxylic acid (TCA) cycle intermediates, estimates of oxidative phosphorylation (OXPHOS), and hepatic gene and protein expression. De novo lipogenesis was higher in the HFr/HF mice compared to their HF counterparts. Contrary to our expectations, hepatic oxidative function after fasting was induced in the HFr/HF group. This differential induction of mitochondrial oxidative function by the high fructose-driven ‘lipogenic’ environment could influence the progressive severity of hepatic insulin resistance.

A Potential Role for Mitochondrial DNA in the Activation of Oxidative Stress and Inflammation in Liver Disease

Mitochondria are organelles that are essential for cellular homeostasis including energy harvesting through oxidative phosphorylation. Mitochondrial dysfunction plays a vital role in liver diseases as it produces a large amount of reactive oxygen species (ROS), in turn leading to further oxidative damage to the structure and function of mitochondria and other cellular components. More severe oxidative damage occurred in mitochondrial DNA (mtDNA) than in nuclear DNA. mtDNA dysfunction results in further oxidative damage as it participates in encoding respiratory chain polypeptides. In addition, mtDNA can leave the mitochondria and enter the cytoplasm and extracellular environment. mtDNA is derived from ancient bacteria, contains many unmethylated CpG dinucleotide repeats similar to bacterial DNA, and thus can induce inflammation to exacerbate damage to liver cells and distal organs by activating toll-like receptor 9, inflammatory bodies, and stimulator of interferon genes (STING). In this review, we focus on the mechanism by which mtDNA alterations cause liver injuries, including nonalcoholic fatty liver, alcoholic liver disease, drug-induced liver injury, viral hepatitis, and liver cancer.

Mitochondrial oxidative injury: a key player in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease worldwide. NAFLD is tightly linked to the metabolic syndrome, insulin resistance, and oxidative stress. Globally, its inflammatory form, nonalcoholic steatohepatitis (NASH), has become the main cause of liver-related morbidity and mortality, mainly due to liver cirrhosis and primary liver cancer. One hallmark of NASH is the presence of changes in mitochondrial morphology and function that are accompanied by a blocked flow of electrons in the respiratory chain, which increases formation of mitochondrial reactive oxygen species in a self-perpetuating vicious cycle. Consequences are oxidation of DNA bases and mitochondrial DNA depletion that are coupled with genetic and acquired mitochondrial DNA mutations, all impairing the resynthesis of respiratory chain polypeptides. In general, several maladaptations of pathways that usually maintain energy homeostasis occur with the early and late excess metabolic stress in NAFLD and NASH. We discuss the interplay between hepatocyte mitochondrial stress and inflammatory responses, focusing primarily on events initiated and maintained by mitochondrial free radical-induced damage in NAFLD. Importantly, mitochondrial oxidative stress and dysfunction are modulated by key pharmacological targets that are related to excess production of reactive oxygen species, mitochondrial turnover and the mitochondrial unfolded protein response, mitophagy, and mitochondrial biogenesis. However, the efficacy of such interventions depends on NAFLD/NASH disease stage.

Liver CPT1A gene therapy reduces diet-induced hepatic steatosis in mice and highlights potential lipid biomarkers for human NAFLD

The prevalence of nonalcoholic fatty liver disease (NAFLD) has increased drastically due to the global obesity pandemic but at present there are no approved therapies. Here, we aimed to revert high-fat diet (HFD)-induced obesity and NAFLD in mice by enhancing liver fatty acid oxidation (FAO). Moreover, we searched for potential new lipid biomarkers for monitoring liver steatosis in humans. We used adeno-associated virus (AAV) to deliver a permanently active mutant form of human carnitine palmitoyltransferase 1A (hCPT1AM), the key enzyme in FAO, in the liver of a mouse model of HFD-induced obesity and NAFLD. Expression of hCPT1AM enhanced hepatic FAO and autophagy, reduced liver steatosis, and improved glucose homeostasis. Lipidomic analysis in mice and humans before and after therapeutic interventions, such as hepatic AAV9-hCPT1AM administration and RYGB surgery, respectively, led to the identification of specific triacylglyceride (TAG) specie (C50:1) as a potential biomarker to monitor NAFFLD disease. To sum up, here we show for the first time that liver hCPT1AM gene therapy in a mouse model of established obesity, diabetes, and NAFLD can reduce HFD-induced derangements. Moreover, our study highlights TAG (C50:1) as a potential noninvasive biomarker that might be useful to monitor NAFLD in mice and humans.

Police Violence among Adults Diagnosed with Mental Disorders

Police violence is reportedly common among those diagnosed with mental disorders characterized by the presence of psychotic symptoms or pronounced emotional lability. Despite the perception that people with mental illness are disproportionately mistreated by the police, there is relatively little empirical research on this topic. A cross-sectional general population survey was administered online in 2017 to 1,000 adults in two eastern U.S. cities to examine the relationship between police violence exposure, mental disorders, and crime involvement. Results from hierarchical logistic regression and mediation analyses revealed that a range of mental health conditions are broadly associated with elevated risk for police violence exposure. Individuals with severe mental illness are more likely than the general population to be physically victimized by police, regardless of their involvement in criminal activities. Most of the excess risk of police violence exposure related to common psychiatric diagnoses was explained by confounding factors including crime involvement. However, crime involvement may necessitate more police contact, but does not necessarily justify victimization or excessive force (particularly sexual and psychological violence). Findings support the need for adequate training for police officers on how to safely interact with people with mental health conditions, particularly severe mental illness.

Essential role of the PGC-1α/PPARβ axis in Ucp3 gene induction

KEY POINTS

We report that the peroxisome proliferator-activated receptor (PPAR)γ coactivator 1-α (PGC-1α)/PPARβ axis is a crucial mediator of uncoupling protein 3 (UCP3) expression in skeletal muscle cells via the transactivativation of a distal PPAR response element at the Ucp3 gene promoter. This mechanism is activated during the myogenic process and by high concentrations of fatty acids independent of PGC-1α protein levels. Ucp3 is essential for PGC-1α-induced oxidative capacity and the adaptive mitochondrial response to fatty acid exposure. These findings provide further evidence for the broad spectrum of the coactivator action in mitochondrial homeostasis, positioning the PGC-1ɑ/PPARβ axis as an essential component of the molecular regulation of Ucp3 gene in skeletal muscle cells.

ABSTRACT

Uncoupling protein 3 (UCP3) has an essential role in fatty acid metabolism and mitochondrial redox regulation in skeletal muscle. However, the molecular mechanisms involved in the expression of Ucp3 are poorly known. In the present study, we show that the peroxisome proliferator-activated receptor (PPAR)γ coactivator 1-α (PGC-1α)/PPARβ axis is a crucial mediator of Ucp3 expression in skeletal muscle cells. In silico analysis of the UCP3 promoter and quantitative chromatin immunoprecipitation experiments revealed that the induction of the UCP3 transcript is mediated by the transactivation of a distal PPAR response element at the Ucp3 gene promoter by the coactivator PGC-1α. This mechanism is activated during myogenesis and during metabolic stress induced by fatty acids independent of PGC-1α protein levels. We also provide evidence that Ucp3 is essential for PGC-1α-induced oxidative capacity. Taken together, our results highlight PGC-1ɑ/PPARβ as an essential component of the molecular regulation of Ucp3 gene in skeletal muscle cells.

Mitochondrial dysfunction in high-fat diet-induced nonalcoholic fatty liver disease: The alleviating effect and its mechanism of Polygonatum kingianum

BACKGROUND

Mitochondrial dysfunction is an important mechanism of non-alcoholic fatty liver disease (NAFLD). Developing mitochondrial regulators/nutrients from natural products to remedy mitochondrial dysfunction represent attractive strategies for NAFLD therapy. In China, Polygonatum kingianum (PK) has been used as a herb and food nutrient for centuries. So far, studies in which the effects of PK on NAFLD are evaluated are lacking. Our study aims at identifying the effects and mechanism of action of PK on NAFLD based on mitochondrial regulation.

METHODS

A NAFLD rat model was induced by a high-fat diet (HFD) and rats were intragastrically given PK (1, 2 and 4 g/kg) for 14 weeks. Changes in body weight, food intake, histological parameters, organ indexes, biochemical parameters and mitochondrial indicators involved in oxidative stress, energy metabolism, fatty acid metabolism, and apoptosis were investigated.

RESULTS

PK significantly inhibited the HFD-induced increase of alanine transaminase, aspartate transaminase, total cholesterol (TC), and low density lipoprotein cholesterol in serum, and TC and triglyceride in the liver. In addition, PK reduced high density lipoprotein cholesterol and liver enlargement without affecting food intake. PK also remarkably inhibited the HFD-induced increase of malondialdehyde and the reduction of superoxide dismutase, glutathione peroxidase, ATP synthase, and complex I and II, in mitochondria. Moreover, mRNA expression of carnitine palmitoyl transferase-1 and uncoupling protein-2 was significantly up-regulated and down-regulated after PK treatment, respectively. Finally, PK notably inhibited the HFD-induced increase of caspase 9, caspase 3 and Bax expression in hepatocytes, and the decrease of expression of Bcl-2 in hepatocytes and cytchrome c in mitochondria.

CONCLUSION

PK alleviated HFD-induced NAFLD by promoting mitochondrial functions. Thus, PK may be useful mitochondrial regulators/nutrients to remedy mitochondrial dysfunction and alleviate NAFLD.

Reduction in Secretion of Very Low Density Lipoprotein-Triacylglycerol by a Matrix Metalloproteinase Inhibitor in a Rat Model of Diet-Induced Hypertriglyceridemia

Matrix metalloproteinase inhibitors (MMPIs) reduced serum triacylglycerol (TAG) levels in streptozotocin-induced diabetic rats and Zucker fa/fa rats in our previous study. However, the mechanisms underlying TAG reduction by MMPIs remain unclear. The present study aimed to elucidate the mechanism by which F81-1144b, an MMPI, lowers serum TAG levels in an animal model of high-sucrose diet (HSD)-induced hypertriglyceridemia. F81-1144b was repeatedly administered to rats fed HSD, and its effects were evaluated on TAG levels in serum and the liver, very low density lipoprotein (VLDL) secretion, de novo fatty acid (FA) synthesis in the liver, and the expression of genes regulating the metabolism of FA, TAG, and VLDL in the liver and serum. F81-1144b lowered TAG levels in serum and the liver, VLDL-TAG secretion, de novo FA synthesis in the liver, and serum levels of insulin and glucose. F81-1144b suppressed the expression of genes related to the de novo synthesis of FA and TAG, key proteins (lipin 1 and apolipoprotein CIII) responsible for VLDL metabolism, and sterol regulatory element-binding protein-1c and carbohydrate response element-binding protein. F81-1144b little affected the expression of genes related directly to the degradation of TAG or FA, but it upregulated that of gene for uncoupling protein 2 in the liver. These results suggest that MMPIs are a novel type of therapeutic agent for the treatment of hypertriglyceridemia, because the metabolic effects of F81-1144b expected from changes in the expression of genes regulating lipid metabolism would alter metabolism differently from those induced by fibrates, niacin, or n-3 FAs.

Sennoside A protects mitochondrial structure and function to improve high-fat diet-induced hepatic steatosis by targeting VDAC1

Mitochondrial dysfunction is mainly associated with high-fat-diet (HFD)-induced hepatic steatosis. Sennoside A (SA), a commonly used clinical stimulant laxative, is reported to improve energy metabolism and insulin resistance. However, the effect and mechanism of SA on HFD-induced hepatic steatosis remain largely unknown. The aim of this study was to determine the effect and mechanism of SA on HFD-induced hepatic steatosis in mice. We examined the liver and body weight of mice to evaluate the physical changes in the liver. Hematoxylin and eosin (H&E) and oil red O staining were used to detect the lipid accumulation. The mitochondrial structure and function were tested by transmission electron microscopy and the Seahorse XF24 Analyzer. Furthermore, mitochondrial complexes I, II, and IV and voltage-dependent anion channel 1 (VDAC1) protein activity were detected to understand the mechanism of the protective effect on mitochondria. As a result, damage to the structure and function in the hepatic mitochondria of HFD-induced hepatic steatosis was observed in mice. The structural damage was in the form of loss of cristae, mitochondrial swelling, vacuolization and even rupturing of the outer mitochondrial membrane (OMM). Functional alterations were found by activation of complex I and deficiency in complexes II and IV. The VDAC1 activity and the total ATP in the liver tissue was increased under hepatic steatosis conditions. The above effects were reversed by SA. These data suggest that inhibition of VDAC1 may be an underlying mechanism of SA for protecting mitochondria in HFD-induced hepatic steatosis in mice. Thus, VDAC1 may be a promising target for treating fatty liver disease.

Administration of multipotent mesenchymal stromal cells restores liver regeneration and improves liver function in obese mice with hepatic steatosis after partial hepatectomy

Background

The liver has the remarkable capacity to regenerate in order to compensate for lost or damaged hepatic tissue. However, pre-existing pathological abnormalities, such as hepatic steatosis (HS), inhibits the endogenous regenerative process, becoming an obstacle for liver surgery and living donor transplantation.

Recent evidence indicates that multipotent mesenchymal stromal cells (MSCs) administration can improve hepatic function and increase the potential for liver regeneration in patients with liver damage. Since HS is the most common form of chronic hepatic illness, in this study we evaluated the role of MSCs in liver regeneration in an animal model of severe HS with impaired liver regeneration.

Methods

C57BL/6 mice were fed with a regular diet (normal mice) or with a high-fat diet (obese mice) to induce HS. After 30 weeks of diet exposure, 70% hepatectomy (Hpx) was performed and normal and obese mice were divided into two groups that received 5 × 10⁵ MSCs or vehicle via the tail vein immediately after Hpx.

Results

We confirmed a significant inhibition of hepatic regeneration when liver steatosis was present, while the hepatic regenerative response was promoted by infusion of MSCs. Specifically, MSC administration improved the hepatocyte proliferative response, PCNA-labeling index, DNA synthesis, liver function, and also reduced the number of apoptotic hepatocytes.

These effects may be associated to the paracrine secretion of trophic factors by MSCs and the hepatic upregulation of key cytokines and growth factors relevant for cell proliferation, which ultimately improves the survival rate of the mice.

Conclusions

MSCs represent a promising therapeutic strategy to improve liver regeneration in patients with HS as well as for increasing the number of donor organs available for transplantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0469-y) contains supplementary material, which is available to authorized users.

Melatonin role preventing steatohepatitis and improving liver transplantation results

Liver steatosis is a prevalent process that is induced due to alcoholic or non-alcoholic intake. During the course of these diseases, the generation of reactive oxygen species, followed by molecular damage to lipids, protein and DMA occurs generating organ cell death. Transplantation is the last-resort treatment for the end stage of both acute and chronic hepatic diseases, but its success depends on ability to control ischemia-reperfusion injury, preservation fluids used, and graft quality. Melatonin is a powerful endogenous antioxidant produced by the pineal gland and a variety of other because of its efficacy in organs; melatonin has been investigated to improve the outcome of organ transplantation by reducing ischemia-reperfusion injury and due to its synergic effect with organ preservation fluids. Moreover, this indolamine also prevent liver steatosis. That is important because this disease may evolve leading to an organ transplantation. This review summarizes the observations related to melatonin beneficial actions in organ transplantation and ischemic-reperfusion models.

Predictors of Whole-Body Insulin Sensitivity Across Ages and Adiposity in Adult Humans

CONTEXT

Numerous factors are purported to influence insulin sensitivity including age, adiposity, mitochondrial function, and physical fitness. Univariate associations cannot address the complexity of insulin resistance or the interrelationship among potential determinants.

OBJECTIVE

The objective of the study was to identify significant independent predictors of insulin sensitivity across a range of age and adiposity in humans.

DESIGN, SETTING, AND PARTICIPANTS

Peripheral and hepatic insulin sensitivity were measured by two stage hyperinsulinemic-euglycemic clamps in 116 men and women (aged 19-78 y). Insulin-stimulated glucose disposal, the suppression of endogenous glucose production during hyperinsulinemia, and homeostatic model assessment of insulin resistance were tested for associations with 11 potential predictors. Abdominal subcutaneous fat, visceral fat (AFVISC), intrahepatic lipid, and intramyocellular lipid (IMCL) were quantified by magnetic resonance imaging and spectroscopy. Skeletal muscle mitochondrial respiratory capacity (state 3), coupling efficiency, and reactive oxygen species production were evaluated from muscle biopsies. Aerobic fitness was measured from whole-body maximum oxygen uptake (VO2 peak), and metabolic flexibility was determined using indirect calorimetry.

RESULTS

Multiple regression analysis revealed that AFVISC (P < .0001) and intrahepatic lipid (P = .002) were independent negative predictors of peripheral insulin sensitivity, whereas VO2 peak (P = .0007) and IMCL (P = .023) were positive predictors. Mitochondrial capacity and efficiency were not independent determinants of peripheral insulin sensitivity. The suppression of endogenous glucose production during hyperinsulinemia model of hepatic insulin sensitivity revealed percentage fat (P < .0001) and AFVISC (P = .001) as significant negative predictors. Modeling homeostatic model assessment of insulin resistance identified AFVISC (P < .0001), VO2 peak (P = .001), and IMCL (P = .01) as independent predictors.

CONCLUSION

The reduction in insulin sensitivity observed with aging is driven primarily by age-related changes in the content and distribution of adipose tissue and is independent of muscle mitochondrial function or chronological age.

The combination of conjugated linoleic acid (CLA) and extra virgin olive oil increases mitochondrial and body metabolism and prevents CLA-associated insulin resistance and liver hypertrophy in C57Bl/6 mice

Clinical conditions associated with obesity can be improved by daily intake of conjugated linoleic acid (CLA) or extra virgin olive oil (EVOO). Here we investigated whether dietary supplementation with CLA and EVOO, either alone or in combination, changes body metabolism associated with mitochondrial energetics. Male C57Bl/6 mice were divided into one of four groups: CLA (1:1 cis-9, trans-11:trans-10, cis-12; 18:2 isomers), EVOO, CLA plus EVOO or control (linoleic acid). Each mouse received 3 g/kg body weight of the stated oil by gavage on alternating days for 60 days. Dietary supplementation with CLA, alone or in combination with EVOO: (a) reduced the white adipose tissue gain; (b) increased body VO2 consumption, VCO2 production and energy expenditure; (c) elevated uncoupling protein (UCP)-2 expression and UCP activity in isolated liver mitochondria. This organelle, when energized with NAD(+)-linked substrates, produced high amounts of H2O2 without inducing oxidative damage. Dietary supplementation with EVOO alone did not change any metabolic parameter, but supplementation with CLA itself promoted insulin resistance and elevated weight, lipid content and acetyl-CoA carboxylase-1 expression in liver. Interestingly, the in vivo antioxidant therapy with N-acetylcysteine abolished the CLA-induced rise of body metabolism and liver UCP expression and activity, while the in vitro antioxidant treatment with catalase mitigated the CLA-dependent UCP-2 expression in hepatocytes; these findings suggest the participation of an oxidative-dependent pathway. Therefore, this study clarifies the mechanisms by which CLA induces liver UCP expression and activity, and demonstrates for the first time the beneficial effects of combined CLA and EVOO supplementation.

Ischemia–reperfusion injury in patients with fatty liver and the clinical impact of steatotic liver on hepatic surgery

Hepatic steatosis is one of the most common hepatic disorders in developed countries. The epidemic of obesity in developed countries has increased with its attendant complications, including metabolic syndrome and non-alcoholic fatty liver disease. Steatotic livers are particularly vulnerable to ischemia/reperfusion injury, resulting in an increased risk of postoperative morbidity and mortality after liver surgery, including liver transplantation. There is growing understanding of the molecular and cellular mechanisms and therapeutic approaches for treating ischemia/reperfusion injury in patients with steatotic livers. This review discusses the mechanisms underlying the susceptibility of steatotic livers to ischemia/reperfusion injuries, such as mitochondrial dysfunction and signal transduction alterations, and summarizes the clinical impact of steatotic livers in the setting of hepatic resection and liver transplantation. This review also describes potential therapeutic approaches, such as ischemic and pharmacological preconditioning, to prevent ischemia/reperfusion injury in patients with steatotic livers. Other approaches, including machine perfusion, are also under clinical investigation; however, many pharmacological approaches developed through basic research are not yet suitable for clinical application.

Oligonol suppresses lipid accumulation and improves insulin resistance in a palmitate-induced in HepG2 hepatocytes as a cellular steatosis model

Background

Oligonol is a low molecular weight form of polyphenol polymers derived from lychee fruits. Several studies suggest that Oligonol has an anti-obesity effect. Since obesity is tightly associated with insulin resistance, we investigated a possible remission effect of Oligonol on lipid accumulation and insulin resistance in human hepatic HepG2 cells.

Methods

HepG2 cells were treated with palmitate for 24 h to induce cellular hepatic steatosis and insulin resistance. The cells were then treated with Oligonol at subtoxic concentrations and examined for lipid metabolism, cytokine production, and insulin signaling using quantitative RT-PCR and western blot analysis.

Results

Oligonol treatment reversed the palmitate-induced intracellular lipid accumulation, down regulated the expression of lipogenic genes, and up-regulated genes for fatty acid degradation. Oligonol restored insulin sensitivity, as was determined by the phosphorylation states of IRS-1. Oligonol also inhibited STAT3-SOCS3 signaling and increased AMPK phosphorylation in HepG2 cells.

Conclusion

Oligonol treatment improved palmitate-induced cellular steatosis and insulin resistance in HepG2 cells with concomitant reduction of inflammatory cytokines and decrease in STAT3-SOCS3 and AMPK-mTOR pathways. Oligonol may have beneficial effects in lipid metabolism and insulin resistance in the liver.

[The role of uncoupling proteins in mechanisms of protection from oxidative stress]

Uncoupling proteins, UCPs, are located in the inner mitochondrial membrane and catalize proton leak across the inner mitochondrial membrane. While UCP1 from brown adipose tissue (BAT) dissipates energy of proton gradient as heat mediating process of thermogenesis, the function of cardiac isoforms of UCPs is still debated. Since the content of UCPs in heart tissue is much lesser then in BAT mild uncoupling of respiratory chain by UCPs might regulate membrane potential of cardiac mitochondria, preventing excessive production of reactive oxygen species. The review is focused on own and literature evidences suggesting the protective role of UCPs activation from oxidative stress under ischemia-reperfusion conditions and aging. Participation of UCPs in endogenous mechanisms of cardioprotection induced by ischemic preconditioning is discussed.

Oxidative stress, cardiolipin and mitochondrial dysfunction in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is today considered the most common form of chronic liver disease, affecting a high proportion of the population worldwide. NAFLD encompasses a large spectrum of liver damage, ranging from simple steatosis to steatohepatitis, advanced fibrosis and cirrhosis. Obesity, hyperglycemia, type 2 diabetes and hypertriglyceridemia are the most important risk factors. The pathogenesis of NAFLD and its progression to fibrosis and chronic liver disease is still unknown. Accumulating evidence indicates that mitochondrial dysfunction plays a key role in the physiopathology of NAFLD, although the mechanisms underlying this dysfunction are still unclear. Oxidative stress is considered an important factor in producing lethal hepatocyte injury associated with NAFLD. Mitochondrial respiratory chain is the main subcellular source of reactive oxygen species (ROS), which may damage mitochondrial proteins, lipids and mitochondrial DNA. Cardiolipin, a phospholipid located at the level of the inner mitochondrial membrane, plays an important role in several reactions and processes involved in mitochondrial bioenergetics as well as in mitochondrial dependent steps of apoptosis. This phospholipid is particularly susceptible to ROS attack. Cardiolipin peroxidation has been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions, including NAFLD. In this review, we focus on the potential roles played by oxidative stress and cardiolipin alterations in mitochondrial dysfunction associated with NAFLD.

Lipotoxic effect of p21 on free fatty acid-induced steatosis in L02 cells

Nonalcoholic fatty liver disease (NAFLD) is increasingly regarded as a hepatic manifestation of metabolic syndrome. Though with high prevalence, the mechanism is poorly understood. This study aimed to investigate the effects of p21 on free fatty acid (FFA)-induced steatosis in L02 cells. We therefore analyzed the L02 cells with MG132 and siRNA treatment for different expression of p21 related to lipid accumulation and lipotoxicity. Cellular total lipid was stained by Oil Red O, while triglyceride content, cytotoxicity assays, lipid peroxidation markers and anti-oxidation levels were measured by enzymatic kits. Treatment with 1 mM FFA for 48 hr induced magnificent intracellular lipid accumulation and increased oxidative stress in p21 overload L02 cells compared to that in p21 knockdown L02 cells. By increasing oxidative stress and peroxidation, p21 accelerates FFA-induced lipotoxic effect in L02 cells and might provide information about potentially new targets for drug development and treatments of NAFLD.

Cerulenin blockade of fatty acid synthase reverses hepatic steatosis in ob/ob mice

Fatty liver or hepatic steatosis is a common health problem associated with abnormal liver function and increased susceptibility to ischemia/reperfusion injury. The objective of this study was to investigate the effect of the fatty acid synthase inhibitor cerulenin on hepatic function in steatotic ob/ob mice. Different dosages of cerulenin were administered intraperitoneally to ob/ob mice for 2 to 7 days. Body weight, serum AST/ALT, hepatic energy state, and gene expression patterns in ob/ob mice were examined. We found that cerulenin treatment markedly improved hepatic function in ob/ob mice. Serum AST/ALT levels were significantly decreased and hepatic ATP levels increased in treated obese mice compared to obese controls, accompanied by fat depletion in the hepatocyte. Expression of peroxisome proliferator-activated receptors α and γ and uncoupling protein 2 were suppressed with cerulenin treatment and paralleled changes in AST/ALT levels. Hepatic glutathione content were increased in some cases and apoptotic activity in the steatotic livers was minimally changed with cerulenin treatment. In conclusion, these results demonstrate that fatty acid synthase blockade constitutes a novel therapeutic strategy for altering hepatic steatosis at non-stressed states in obese livers.

Chronic alcohol consumption increases the expression of uncoupling protein-2 and -4 in the brain

BACKGROUND

Chronic alcohol consumption leads to oxidative stress in a variety of cells, especially in brain cells because they have a reduced oxidative metabolism of alcohol. Uncoupling proteins (UCPs) are anion channels of the inner mitochondrial membrane, which can decouple internal respiration. "Mild uncoupling" of the mitochondrial respiratory chain leads to a reduced production of free radicals (reactive oxygen species) and a reduction in oxidative cell stress. The extent to which chronic alcohol consumption regulates UCP-2 and -4 in the brain is still unknown.

METHODS

We examined the effects of a 12-week 5% alcohol diet in the brain of male Wistar rats (n = 34). Cerebral gene and protein expression of UCP-2, -4, as well as Bcl-2, and the release of cytochrome c out of the mitochondria were detected by real-time polymerase chain reaction and Western blot analysis. The percentage of degenerated cells was determined by Fluoro-Jade B staining of brain slices.

RESULTS

Brains of rats with a chronic alcohol diet showed an increased gene and protein expression of UCP-2 and -4. The expression of the antiapoptotic protein Bcl-2 in the brain of the alcohol-treated animals was decreased significantly, whereas cytochrome c release from mitochondria was increased. In addition increased neurodegeneration could be demonstrated in the alcohol-treated animals.

CONCLUSIONS

Chronic alcohol consumption leads to a cerebral induction of UCP-2 and -4 with a simultaneous decrease in the antiapoptotic protein Bcl-2, cytochrome c release from mitochondria and increased neurodegeneration. This study reveals a compensatory effect of UCP-2 and -4 in the brain during chronic alcohol consumption.

Non-alcoholic fatty liver disease and insulin resistance: from bench to bedside

Non-alcoholic fatty liver disease (NAFLD) is now the most frequent chronic liver disease in the developed countries. There is also growing evidence from basic and clinical research that NAFLD has a strong relationship to insulin resistance, which is a key factor in the development of type 2 diabetes. The aim of this review is to summarize the recent important findings linking NAFLD and insulin resistance. Lipid accumulation, particularly of diacylglycerol, appears to be of major importance in this process. Mitochondrial dysfunction, through decreased mitochondrial biogenesis, increases oxidative stress, and ageing also plays an important role. Finally, endoplasmic reticulum stress and inflammation also probably contribute to the development of insulin resistance via mechanisms that are still not well understood. Clinical aspects of NAFLD, such as its diagnosis and management, are also investigated in this review.

Role of inducible nitric oxide synthase in mitochondrial depolarization and graft injury after transplantation of fatty livers

This study investigated the role of inducible nitric oxide synthase (iNOS) in failure of ethanol-induced fatty liver grafts. Rat livers were explanted 20 h after gavaging with ethanol (5 g/kg) and storing in UW solution for 24h before implantation. Hepatic oil red O staining-positive areas increased from ∼2 to ∼33% after ethanol treatment, indicating steatosis. iNOS expression increased ∼8-fold after transplantation of lean grafts (LG) and 25-fold in fatty grafts (FG). Alanine aminotransferase release, total bilirubin, hepatic necrosis, TUNEL-positive cells, and cleaved caspase-3 were higher in FG than LG. A specific iNOS inhibitor 1400W (5 μM in the cold-storage solution) blunted these alterations by >42% and increased survival of fatty grafts from 25 to 88%. Serum nitrite/nitrate and hepatic nitrotyrosine adducts increased to a greater extent after transplantation of FG than LG, indicating reactive nitrogen species (RNS) overproduction. Phospho-c-Jun and phospho-c-Jun N-terminal kinase-1/2 (JNK1/2) were higher in FG than in LG, indicating more JNK activation in fatty grafts. RNS formation and JNK activation were blunted by 1400W. Mitochondrial polarization and cell death were visualized by intravital multiphoton microscopy of rhodamine 123 and propidium iodide, respectively. After implantation, viable cells with depolarized mitochondria were 3-fold higher in FG than in LG and 1400W decreased mitochondrial depolarization in FG to the levels of LG. Taken together, iNOS is upregulated after transplantation of FG, leading to excessive RNS formation, JNK activation, mitochondrial dysfunction, and severe graft injury. The iNOS inhibitor 1400W could be an effective therapy for primary nonfunction of fatty liver grafts.

Effect of conjugated linoleic acid on inhibition of prolyl hydroxylase 1 in hearts of mice

BACKGROUND

Results from different trails have provided evidence of protective effects of cis-9,trans-11-conjugated linoleic acid (CLA) on cardiovascular diseases. But the inhibition of prolyl hydroxylase 1 (PHD1) associated with induction of hypoxia inducible factors (HIFs) by CLA in these protective effects has never been reported before. The objective of this study was to evaluate if the two predominant cis-9,trans-11 (c9, t11), trans-10,cis-12 (t10, c12) CLA isomers and mixture of these two isomers can inhibit PHD1 with induction of HIFs in myocardium in mice and subsequent effects on myocardium metabolism.

RESULTS

CLA mixture and c9, t11 CLA inhibited PHD1 protein expression and increased the levels of protein and mRNA in HIF-2α in myocardium in mice. Meanwhile, CLA mixture and c9, t11 CLA also elevated the expression of HIF related transcriptional factors like PDK4 and PPARα. The reprogramming of basal metabolism in myocardium in mice was shown on increasing of GLUT4 gene expression by c9, t11 CLA supplemented group. UCP2 was increased by CLA mixture and c9, t11 CLA for attenuating production of ROS.

CONCLUSION

CLA mixture and c9, t11 CLA could inhibit PHD1 and induce HIF-2α in myocardium in mice, which is associated with upregulation of PDK4 by activation of PPARα. This process also implies a reprogramming of basal metabolism and oxidative damage protection in myocardium in mice. All the effects shown in hearts of mice are due to c9, t11 CLA but not t10, c12 CLA.

Mitochondrial uncoupling protein-2 deficiency protects steatotic mouse hepatocytes from hypoxia/reoxygenation

Steatotic livers are sensitive to ischemic events and associated ATP depletion. Hepatocellular necrosis following these events may result from mitochondrial uncoupling protein-2 (UCP2) expression. To test this hypothesis, we developed a model of in vitro steatosis using primary hepatocytes from wild-type (WT) and UCP2 knockout (KO) mice and subjected them to hypoxia/reoxygenation (H/R). Using cultured hepatocytes treated with emulsified fatty acids for 24 h, generating a steatotic phenotype (i.e., microvesicular and broad-spectrum fatty acid accumulation), we found that the phenotype of the WT and UCP2 KO were the same; however, cellular viability was increased in the steatotic KO hepatocytes following 4 h of hypoxia and 24 h of reoxygenation; Hepatocellular ATP levels decreased during hypoxia and recovered after reoxygenation in the control and UCP2 KO steatotic hepatocytes but not in the WT steatotic hepatocytes; mitochondrial membrane potential in WT and UCP2 KO steatotic groups was less than control groups but higher than UCP2 KO hepatocytes. Following reoxygenation, lipid peroxidation, as measured by thiobarbituric acid reactive substances, increased in all groups but to a greater extent in the steatotic hepatocytes, regardless of UCP2 expression. These results demonstrate that UCP2 sensitizes steatotic hepatocytes to H/R through mitochondrial depolarization and ATP depletion but not lipid peroxidation.

Role of UCP2 expression after hepatic warm ischemia-reperfusion in the rat

Background/Aims

The role of uncoupling protein-2 (UCP2) in the liver is currently unclear. Emerging evidence suggests a relationship between UCP2 and oxidative stress. In the present study, we tested the hypothesis that UCP2 expression in the liver might change during warm ischemia-reperfusion (I/R) according to oxidative stress.

Methods

Wistar rats were subjected to 40 (short ischemia) or 90 (long ischemia) minutes of partial lobar ischemia followed by 4 hours of reperfusion. UCP2 expression in the ischemic and nonischemic lobes was assessed using reverse transcription-polymerase chain reaction and immunohistochemistry. Malondialdehyde concentrations in the liver tissue were also compared.

Results

Malondialdehyde concentrations in the ischemic lobes were significantly higher in the long ischemia group. In the ischemic lobes of the short ischemia group, UCP2 protein expression was induced in hepatocytes, which did not express the protein prior to treatment, and the expression levels were higher than in the long ischemia group. The intralobular distribution of UCP2 seemed to correlate inversely with that of the necrotic area. UCP2 expression was observed, even in nonischemic lobes with similar intralobular heterogeneity.

Conclusions

UCP2 was induced in hepatocytes after warm I/R. Although the primitive role of UCP2 expression may be cytoprotective in nature, its actual protective effect in hepatic I/R may be minimal

Decreased apoptosis in fatty livers submitted to subnormothermic machine-perfusion respect to cold storage

Machine perfusion at subnormothermic temperature (20°C), MP20, was developed by Vairetti et al. and showed to afford a better preservation of fatty livers respect to traditional cold storage (CS) in terms of enzyme release into the perfusate and bile, glycogen stores, energy charge and oxidative stress. Here we investigated whether it also caused decreased cell death by apoptosis. Fatty and lean Zucker rats were submitted to MP20 or CS for 6 h and reperfused normothermically for 2 h. Apoptotic cells were revealed by immunohistochemistry of activated caspase-3 and M30 (new epitope on CK18 degraded by caspase-3) and by the TUNEL assay. Portal pressure was also determined. A statistically significant reduction of hepatocyte apoptosis, but especially of sinusoidal cells was determined for fatty livers submitted to MP20 respect to CS. Portal pressure was significantly lower after MP20 respect to CS. The reduction of sinusoidal cell death by apoptosis without need for anti-apoptotic therapies appears particularly positive since apoptotic sinusoidal cells hinder microcirculation in the sinusoids and are thrombogenic. These results further confirm the potential of MP20 for preserving fatty livers that would be otherwise discarded as grafts, and thus for increasing the donor pool for liver transplantation.

Ischemic preconditioning-like effect of polyunsaturated fatty acid-rich diet on hepatic ischemia/reperfusion injury

AIM

The aim of this study was to investigate a possible preconditioning effect of oral diet enriched with polyunsaturated fatty acids (PUFAs) on liver ischemia/reperfusion (I/R) injuries.

METHODS

Wistar male rats were fed a standard diet or polyunsaturated fatty acid-rich diet (PRD) enriched with (GII) or without (GIII) ω-3 PUFA. Rats were submitted to partial liver ischemia during 1 h and evaluated in pre- and post-I/R conditions. In pre-I/R condition, livers were collected for determination of fatty acid composition, liver mitochondrial function, malondialdehyde (MDA) content, and histological analysis. Four hours after liver reperfusion serum activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), serum levels of tumor necrosis factor-alpha, interleukin-6, interleukin-10, and prostaglandin-E2, liver mitochondrial function, MDA content, and histology were evaluated.

RESULTS

In the pre-I/R condition, GII and GIII groups had an increase on PUFA content and exhibited slight increased macrosteatosis and microsteatosis in the liver. After 4 h of reperfusion, PRD-fed rats showed a marked decrease on steatosis, diminished necrosis, an increase in MDA formation, and mitochondrial uncoupling. We also observed a marked decrease in plasma levels of cytokines and ALT and AST activities in post-I/R condition in PRD groups.

CONCLUSION

In this experimental model in the rat, PRD has a preconditioning effect protecting the liver from I/R injury and should be object of future clinical studies.

A comprehensive untargeted metabonomic analysis of human steatotic liver tissue by RP and HILIC chromatography coupled to mass spectrometry reveals important metabolic alterations

Steatosis, or excessive accumulation of lipids in the liver, is a generally accepted previous step to the development of more severe conditions like nonalcoholic steatohepatitis, fibrosis, and cirrhosis. We aimed to characterize the metabolic profile that defines simple steatosis in human tissue and to identify potential disturbances in the hepatic metabolism that could favor the switch to progressive liver damage. A total of 46 samples, 23 from steatotic and 23 from nonsteatotic human livers, were analyzed following a holistic LC-MS-based metabonomic analysis that combines RP and HILIC chromatographic separations. Multivariate statistical data analysis satisfactorily classified samples and revealed steatosis-associated biomarkers. Increased levels of bile acids and phospholipid degradation products, and decreased levels of antioxidant species, were found in steatotic livers, indicating disturbances in lipid and bile acid homeostasis and mitochondrial dysfunction. Changes in hypoxanthine, creatinine, glutamate, glutamine, or γ-glutamyl-dipeptides concentrations, suggestive of alterations in energy metabolism and amino acid metabolism and transport, were also found. The results show that the proposed analytical strategy is suitable to achieve a comprehensive metabolic profile of steatotic human liver tissue and provide new insights into the metabolic alterations occurring in fatty liver that could contribute to its predisposition to damage evolution.

Redox balance in the pathogenesis of nonalcoholic fatty liver disease: mechanisms and therapeutic opportunities

Nonalcoholic fatty liver disease (NAFLD) is currently the most common liver disease in the world. It encompasses a histological spectrum, ranging from simple, nonprogressive steatosis to nonalcoholic steatohepatitis (NASH), which may progress to cirrhosis and hepatocellular carcinoma. While liver-related complications are confined to NASH, emerging evidence suggests both simple steatosis and NASH predispose to type 2 diabetes and cardiovascular disease. The pathogenesis of NAFLD is currently unknown, but accumulating data suggest that oxidative stress and altered redox balance play a crucial role in the pathogenesis of steatosis, steatohepatitis, and fibrosis. We will examine intracellular mechanisms, including mitochondrial dysfunction and impaired oxidative free fatty acid metabolism, leading to reactive oxygen species generation; additionally, the potential pathogenetic role of extracellular sources of reactive oxygen species in NAFLD, including increased myeloperoxidase activity and oxidized low density lipoprotein accumulation, will be reviewed. We will discuss how these mechanisms converge to determine the whole pathophysiological spectrum of NAFLD, including hepatocyte triglyceride accumulation, hepatocyte apoptosis, hepatic inflammation, hepatic stellate cell activation, and fibrogenesis. Finally, available animal and human data on treatment opportunities with older and newer antioxidant will be presented.

Mitochondria and redox signaling in steatohepatitis

Alcoholic and nonalcoholic fatty liver diseases are potentially pathological conditions that can progress to steatohepatitis, fibrosis, and cirrhosis. These conditions affect millions of people throughout the world in part through poor lifestyle choices of excess alcohol consumption, overnutrition, and lack of regular physical activity. Abnormal mitochondrial and cellular redox homeostasis has been documented in steatohepatitis and results in alterations of multiple redox-sensitive signaling cascades. Ultimately, these changes in signaling lead to altered enzyme function and transcriptional activities of proteins critical to mitochondrial and cellular function. In this article, we review the current hypotheses linking mitochondrial redox state to the overall pathophysiology of alcoholic and nonalcoholic steatohepatitis and briefly discuss the current therapeutic options under investigation.

The Anti-Obesity Effect of the Palatinose-Based Formula Inslow is Likely due to an Increase in the Hepatic PPAR-alpha and Adipocyte PPAR-gamma Gene Expressions

Abdominal obesity is a principal risk factor in the development of metabolic syndrome. Previously, we showed that a palatinose-based liquid formula, Inslow/MHN-01, suppressed postprandial plasma glucose level and reduced visceral fat accumulation better than the standard formula (SF). To elucidate the mechanism of Inslow-mediated anti-obesity effect, expression levels of genes involved in the glucose and lipid metabolism were compared in Inslow- and SF-fed rats. Both fasting plasma insulin level and average islet sizes were reduced in the Inslow group. We also found less abdominal fat accumulation and reduced hepatic triacylglycerol content in the Inslow group. Expression of the β-oxidation enzymes and uncoupling potein-2 (UCP-2) mRNAs in the liver of the Inslow group were higher than the SF group, which was due to a concomitant higher expression of the peroxisome proliferator-activated receptor (PPAR)-α mRNA in the former. Furthermore, expression of the UCP-2 and adiponectin mRNAs in the epididymal fat were higher in the Inslow group than the SF group, and were stimulated by a concomitant increase of the PPAR-γ gene expression in the former. These results strongly suggested that the anti-obesity effect of Inslow was due to an increase in the hepatic PPAR-α and adipocyte PPAR-γ gene expressions.

Cell death and nonalcoholic steatohepatitis: where is ballooning relevant?

Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver disease in the Western world. Progression to more aggressive forms of liver injury, such as nonalcoholic steatohepatitis (NASH) and cirrhosis, occurs in less than a third of affected subjects. Human data and both in vivo and in vitro models demonstrate that cell death, particularly apoptosis, is increased in NAFLD and NASH patients, suggesting that it is crucial in disease progression. Indeed, fatty acids - more specifically, saturated fatty acids - strongly induce hepatocyte apoptosis. In addition, hepatic steatosis renders hepatocytes more susceptible to apoptotic injury. Ballooned hepatocytes and Mallory-Denk bodies are important hallmarks of NASH and correlate with disease progression. There are complex correlations between ballooning, Mallory-Denk bodies and apoptosis through keratin metabolism and depletion, as well as through the endoplasmic reticulum stress response. Whether apoptosis may promote hepatocellular ballooning, or vice versa, will be discussed in this article.

Effect of berberine on expressions of uncoupling protein-2 mRNA and protein in hepatic tissue of non-alcoholic fatty liver disease in rats

OBJECTIVE

To observe the effect of berberine on uncoupling protein-2 (UCP2) mRNA and protein expressions in the hepatic tissue of non-alcoholic fatty liver disease (NAFLD) in rats, and to explore the molecular mechanism.

METHODS

To establish the NAFLD rat model; the rats were fed by high fat forage and were randomly divided into four groups: normal group, model group, berberine high-dose group (324 mg/kg), and berberine low-dose group (162 mg/kg). After treatment for 12 weeks, the expression of UCP2 mRNA in the liver tissue was analyzed by semiquantitative reverse transcription polymerase chain reaction (RT-RTPCR). The expression level of UCP2 protein in the liver tissue was examined by immunohistochemistry. Total PCR). cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) contents in blood serum, and TG and TC contents in the liver were detected by an automatic biochemical analyzer. The other is to observe the axungia degree of the liver.

RESULTS

The expression of UCP2 mRNA and positive cell numbers in the liver tissue were dramatically increased in the model group (P<0.01). Lipid in the serum and hepatic tissues increased significantly, and the liver was fatty. But in the treatment groups, the expression levels of mRNA and UCP2 proteins were significantly down-regulated (P<0.01). Liver steatosis was improved.

CONCLUSIONS

Berberine can down-regulate the expression levels of UCP2 mRNA and UCP2 proteins of hepatic tissue in NAFLD rats. It can promote the recovery of hepatocyte steatosis and improve lipid metabolism disorder in NAFLD rats. Berberine shows a potential therapeutic effect on NAFLD.

The mechanism of vitexin-4''-O-glucoside protecting ECV-304 cells against tertbutyl hydroperoxide induced injury

The aim of this article is to investigate the mechanism of vitexin-4''-O-glucoside (VOG) protecting ECV-304 cells against tertbutyl hydroperoxide (TBHP)-induced injury. ECV-304 cell viability was measured by MTT assay. Apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) assay. Cellular morphological changes were observed using phase contrast microscopy. The change of relative mitochondrial transmembrane potential in the ECV-304 cells was analysed with rhodamine 123 staining. Lipid peroxidation was measured by the HPLC method. The results showed that 128 µmol L(-1) VOG could effectively protect ECV-304 cells against cytotoxicity induced by TBHP. VOG protected TBHP-treated ECV-304 cells from death, significantly decreased MDA production, and increased superoxide dismutase (SOD) activity and mitochondrial membrane potential (ΔΨ). Taken together, VOG protects against TBHP-induced ECV-304 cell injury partially through resuming mitochondrial function.

Activation of Rac1 promotes hedgehog-mediated acquisition of the myofibroblastic phenotype in rat and human hepatic stellate cells

Hepatic accumulation of myofibroblastic hepatic stellate cells (MF-HSCs) is pivotal in the pathogenesis of cirrhosis. Two events are necessary for MF-HSCs to accumulate in damaged livers: transition of resident, quiescent hepatic stellate cells (Q-HSCs) to MF-HSCs and expansion of MF-HSC numbers through increased proliferation and/or reduced apoptosis. In this study, we identified two novel mediators of MF-HSC accumulation: Ras-related C3 botulinum toxin substrate 1 (Rac1) and Hedgehog (Hh). It is unclear whether Rac1 and Hh interact to regulate the accumulation of MF-HSCs. We evaluated the hypothesis that Rac1 promotes activation of the Hh pathway, thereby stimulating signals that promote transition of Q-HSCs into MF-HSCs and enhance the viability of MF-HSCs. Using both in vitro and in vivo model systems, Rac1 activity was manipulated through adenoviral vector-mediated delivery of constitutively active or dominant-negative rac1. Rac1-transgenic mice with targeted myofibroblast expression of a mutated human rac1 transgene that produces constitutively active Rac1 were also examined. Results in all models demonstrated that activating Rac1 in HSC enhanced Hh signaling, promoted acquisition/maintenance of the MF-HSC phenotype, increased MF-HSC viability, and exacerbated fibrogenesis. Conversely, inhibiting Rac1 with dominant-negative rac1 reversed these effects in all systems examined. Pharmacologic manipulation of Hh signaling demonstrated that profibrogenic actions of Rac1 were mediated by its ability to activate Hh pathway-dependent mechanisms that stimulated myofibroblastic transition of HSCs and enhanced MF-HSC viability.

CONCLUSION

These findings demonstrate that interactions between Rac1 and the Hh pathway control the size of MF-HSC populations and have important implications for the pathogenesis of cirrhosis.

Mitochondrial dysfunction precedes insulin resistance and hepatic steatosis and contributes to the natural history of non-alcoholic fatty liver disease in an obese rodent model

BACKGROUND & AIMS

In this study, we sought to determine the temporal relationship between hepatic mitochondrial dysfunction, hepatic steatosis and insulin resistance, and to examine their potential role in the natural progression of non-alcoholic fatty liver disease (NAFLD) utilising a sedentary, hyperphagic, obese, Otsuka Long-Evans Tokushima Fatty (OLETF) rat model.

METHODS

OLETF rats and their non-hyperphagic control Long-Evans Tokushima Otsuka (LETO) rats were sacrificed at 5, 8, 13, 20, and 40 weeks of age (n=6-8 per group).

RESULTS

At 5 weeks of age, serum insulin and glucose and hepatic triglyceride (TG) concentrations did not differ between animal groups; however, OLETF animals displayed significant (p<0.01) hepatic mitochondrial dysfunction as measured by reduced hepatic carnitine palmitoyl-CoA transferase-1 activity, fatty acid oxidation, and cytochrome c protein content compared with LETO rats. Hepatic TG levels were significantly elevated by 8 weeks of age, and insulin resistance developed by 13 weeks in the OLETF rats. NAFLD progressively worsened to include hepatocyte ballooning, perivenular fibrosis, 2.5-fold increase in serum ALT, hepatic mitochondrial ultrastructural abnormalities, and increased hepatic oxidative stress in the OLETF animals at later ages. Measures of hepatic mitochondrial content and function including beta-hydroxyacyl-CoA dehydrogenase activity, citrate synthase activity, and immunofluorescence staining for mitochondrial carbamoyl phosphate synthetase-1, progressively worsened and were significantly reduced at 40 weeks in OLETF rats compared to LETO animals.

CONCLUSIONS

Our study documents that hepatic mitochondrial dysfunction precedes the development of NAFLD and insulin resistance in the OLETF rats. This evidence suggests that progressive mitochondrial dysfunction contributes to the natural history of obesity-associated NAFLD.

Overexpression of nuclear receptor SHP in adipose tissues affects diet-induced obesity and adaptive thermogenesis

The orphan nuclear receptor small heterodimer partner (SHP) regulates metabolic pathways involved in hepatic bile acid production and both lipid and glucose homeostasis via the transcriptional repression of other nuclear receptors. In the present study, we generated fat-specific SHP-overexpressed transgenic (TG) mice and determined the potential role of SHP activation, specifically in adipocytes, in the regulation of adipose tissue function in response to stressors. We determined in 2 mo-old SHP TG mice body weight, fat mass index, adipose tissues morphology, thermogenic and metabolic gene expression, metabolic rates at baseline and in response to beta adrenergic receptor agonists, and brown fat ultrastructural changes in response to cold exposure (6-48 h). Mice were fed a 10-wk high-fat diet (HFD; 42% fat). Weight gain, fat mass index, adipose tissues morphology, glucose tolerance, and metabolic rates were determined at the end of the feeding. Young TG mice had increased body weight and adiposity; however, their energy metabolism was increased and brown fat function was enhanced in response to cold exposure through the activation of thermogenic genes and mitochondrial biogenesis. SHP overexpression exacerbated the diet-induced obesity phenotype as evidence by marked weight gain over time, increased adiposity, and severe glucose intolerance compared with wild-type mice fed a HFD. In addition, SHP-TG mice fed HFD had decreased diet-induced adaptive thermogenesis, increased food intake, and decreased physical activity. In conclusion, SHP activation in adipocytes strongly affects weight gain and diet-induced obesity. Developing a synthetic compound to antagonize the effect of SHP may prove to be useful in treating obesity.

Impaired insulin signaling accelerates cardiac mitochondrial dysfunction after myocardial infarction

Diabetes increases mortality and accelerates left ventricular (LV) dysfunction following myocardial infarction (MI). This study sought to determine the impact of impaired myocardial insulin signaling, in the absence of diabetes, on the development of LV dysfunction following MI. Mice with cardiomyocyte-restricted knock out of the insulin receptor (CIRKO) and wildtype (WT) mice were subjected to proximal left coronary artery ligation (MI) and followed for 14 days. Despite equivalent infarct size, mortality was increased in CIRKO-MI vs. WT-MI mice (68% vs. 40%, respectively). In surviving mice, LV ejection fraction and dP/dt were reduced by >40% in CIRKO-MI vs. WT-MI. Relative to shams, isometric developed tension in LV papillary muscles increased in WT-MI but not in CIRKO-MI. Time to peak tension and relaxation times were prolonged in CIRKO-MI vs. WT-MI suggesting impaired, load-independent myocardial contractile function. To elucidate mechanisms for impaired LV contractility, mitochondrial function was examined in permeabilized cardiac fibers. Whereas maximal ADP-stimulated mitochondrial O(2) consumption rates (V(ADP)) with palmitoyl carnitine were unchanged in WT-MI mice relative to sham-operated animals, V(ADP) was significantly reduced in CIRKO-MI (13.17+/-0.94 vs. 9.14+/-0.88 nmol O(2)/min/mgdw, p<0.05). Relative to WT-MI, expression levels of GLUT4, PPAR-alpha, SERCA2, and the FA-Oxidation genes MCAD, LCAD, CPT2 and the electron transfer flavoprotein ETFDH were repressed in CIRKO-MI. Thus reduced insulin action in cardiac myocytes accelerates post-MI LV dysfunction, due in part to a rapid decline in mitochondrial FA oxidative capacity, which combined with limited glucose transport capacity that may reduce substrate utilization and availability.

HDMCP uncouples yeast mitochondrial respiration and alleviates steatosis in L02 and hepG2 cells by decreasing ATP and H2O2 levels: a novel mechanism for NAFLD

BACKGROUND/AIMS

To explore the uncoupling activity of hepatocelluar downregulated mitochondrial carrier protein (HDMCP) in a yeast expression system and its function in non-alcoholic fatty liver disease (NAFLD).

METHODS

Molecular cloning and RT-PCR were used for yeast protein expression and uncoupling activity was assessed. Western blot analysis was used to determine HDMCP level in rat NAFLD and steatotic L02 and hepG2 cell models where their presence was confirmed by pathologic (Nile red and H-E staining) and biochemical changes. RNA interference was used to knock down HDMCP level and mitochondrial ATP and hydroperoxide levels were measured for potential mechanism exploration.

RESULTS

We found a significant GDP insensitive uncoupling activity of HDMCP in yeast mitochondria and its increased expression in animal and cell models. HDMCP was significantly increased with culture time and steatosis was aggravated when HDMCP level was knocked down. Furthermore, we found that HDMCP might function through promoting ATP depletion and decreasing H(2)O(2) production.

CONCLUSION

This study adds supportive data to the hypothesis that HDMCP might be a long postulated liver-specific uncoupling protein and broadens our understanding of the pathogenesis of NAFLD. More importantly, HDMCP might become a novel drug target for its ability in alleviating hepatic steatosis.

A multi-gene analysis strategy identifies metabolic pathways targeted by trans-10, cis-12-conjugated linoleic acid in the liver of hamsters

In mice, hepatic functions can be greatly affected by dietary trans-10, cis-12-conjugated linoleic acid (CLA). However, this phenomenon has been less documented in hamsters. In the present study, male hamsters were fed two doses of the trans-10, cis-12-CLA (0.5 and 1%, w/w diet) or linoleic acid (0.5%) for 6 weeks. The effects on the liver were examined by measuring the expression of thirty-six genes representing key metabolic pathways. CLA-responsive genes and their relationships with physiological outcomes were examined by a multivariate analysis procedure. Compared with control hamsters, those receiving either 0.5 or 1% CLA exhibited similar fat loss (15-24%; P < or = 0.05) and liver enlargement (21-28%; P < or = 0.05), with no signs of steatosis. We also observed a dose-dependent increase in the transcription of genes involved in lipid breakdown and lipid harvesting from blood, and in genes related to the oxidative stress and inflammatory responses. These responsive genes varied in parallel with cell membrane lipids (R2 0.31-0.42) and to a lesser extent with liver enlargement (R2 0.22) (all P < 0.05). We conclude that in hamsters, liver enlargement induced by trans-10, cis-12-CLA is accompanied by an increased metabolic potential to process fatty acids from mobilised adipose stores. This elevated metabolic activity, comprised of anabolic pathways and their catabolic counterparts, can trigger inflammation and the oxidant stress defence pathways in a dose-dependent manner. These results provide novel insights into the mechanisms by which trans-10, cis-12-CLA affects pathways related to liver function.