151
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Herlein JA, Fink BD, Sivitz WI. Superoxide production by mitochondria of insulin-sensitive tissues: mechanistic differences and effect of early diabetes. Metabolism 2010; 59:247-57. [PMID: 19765776 PMCID: PMC2813404 DOI: 10.1016/j.metabol.2009.07.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Accepted: 07/22/2009] [Indexed: 11/16/2022]
Abstract
Obesity and mild hyperglycemia are characteristic of early or "prediabetes." The associated increase in fatty acid flux is posited to enhance substrate delivery to mitochondria, leading to enhanced superoxide production that results in mitochondrial dysfunction and progressive worsening of the hyperglycemic state. We quantified superoxide production by gastrocnemius muscle, heart, and liver mitochondria in a rodent model that mimics the pathophysiology of prediabetes by administering low-dose streptozotocin to rats fed high fat (HF). Superoxide was rigorously determined indirectly as H(2)O(2) largely released from the matrix and by electron paramagnetic resonance spectroscopy that directly detects superoxide released externally. Both HF and low-dose streptozotocin mildly increased glycemia (P < .05 by 2-way analysis of variance). Matrix and external superoxide production by gastrocnemius mitochondria respiring on the complex II substrate succinate and matrix superoxide production by liver mitochondria respiring on the complex I substrates glutamate plus malate were significantly reduced by HF feeding but not affected by mild hyperglycemia. Superoxide production was not significantly altered by either treatment in heart mitochondria fueled by either complex I or II substrates. The functional status of the mitochondria was assayed as simultaneous respiration and membrane potential that were not affected by HF or mild hyperglycemia. Comparison of substrate and inhibitor effects on superoxide release implied marked differences in the redox mechanisms regulating mitochondrial superoxide production from liver mitochondria compared with muscle and heart. In summary, superoxide production from mitochondria of different insulin-sensitive tissues differs mechanistically. However, in any case, excess superoxide production as an intrinsic property of mitochondria of insulin-sensitive tissues does not result from conditions mimicking the pathophysiology of pre- or early diabetes.
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Affiliation(s)
- Judy A Herlein
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Iowa City Veterans Affairs Medical Center and the University of Iowa, Iowa City, IA 52242, USA
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152
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Baffy G. Uncoupling protein-2 and cancer. Mitochondrion 2009; 10:243-52. [PMID: 20005987 DOI: 10.1016/j.mito.2009.12.143] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Revised: 11/12/2009] [Accepted: 12/07/2009] [Indexed: 02/06/2023]
Abstract
Cancer cells respond to unfavorable microenvironments such as nutrient limitation, hypoxia, oxidative stress, and host defense by comprehensive metabolic reprogramming. Mitochondria are linked to this complex adaptive response and emerging evidence indicates that uncoupling protein-2 (UCP2), a mitochondrial inner membrane anion carrier, may contribute to this process. Effects of UCP2 on mitochondrial bioenergetics, redox homeostasis, and oxidant production in cancer cells may modulate molecular pathways of macromolecular biosynthesis, antioxidant defense, apoptosis, cell growth and proliferation, enhancing robustness and promoting chemoresistance. Elucidation of these interactions may identify novel anti-cancer strategies.
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Affiliation(s)
- Gyorgy Baffy
- VA Boston Healthcare System and Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
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153
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Shang Y, Liu Y, Du L, Wang Y, Cheng X, Xiao W, Wang X, Jin H, Yang X, Liu S, Chen Q. Targeted expression of uncoupling protein 2 to mouse liver increases the susceptibility to lipopolysaccharide/galactosamine-induced acute liver injury. Hepatology 2009; 50:1204-16. [PMID: 19637283 DOI: 10.1002/hep.23121] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED Normal hepatocytes do not express endogenous uncoupling protein 2 (UCP2) in adult liver, although Kupffer cells do, and it is strikingly induced in hepatocytes in steatotic liver and obese conditions. However, the direct link of UCP2 with the pathogenic development of liver diseases and liver injury remains elusive. Here we report that targeted expression of UCP2 to mouse liver increases susceptibility to acute liver injury induced by lipopolysaccharide (LPS) and galactosamine (GalN). UCP2 appears to enhance proton leak, leading to mild uncoupling in a guanosine diphosphate-repressible manner. Indeed, mitochondria from the genetically manipulated mouse liver have increased state 4 respiration, lower respiratory control ratio, and reduced adenosine triphosphate (ATP) levels, which altered mitochondrial physiology. To address the underlying mechanism of how UCP2 and the reduced energy coupling efficiency enhance cell death in mouse liver, we show that the reduced ATP levels lead to activation of 5'AMP-activated protein kinase (AMPK) and its downstream effector, c-Jun N-terminal kinase; thus, the increased sensitivity toward LPS/GalN-induces apoptosis. Importantly, we show that inhibition of UCP2 activity by its pharmacological inhibitor genipin prevents LPS/GalN-induced ATP reduction, AMPK activation, and apoptosis. Also, inhibition of ATP production by oligomycin promotes LPS/GalN-induced cell death both in vivo and in vitro. CONCLUSION Our results clearly show that targeted expression of UCP2 in liver may result in compromised mitochondrial physiology that contributes to enhanced cell death and suggests a potential role of UCP2 in the development of liver diseases.
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Affiliation(s)
- Yingli Shang
- Laboratory of Apoptosis and Cancer Biology, State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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154
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Ellett JD, Evans ZP, Atkinson C, Schmidt MG, Schnellmann RG, Chavin KD. Toll-like receptor 4 is a key mediator of murine steatotic liver warm ischemia/reperfusion injury. Liver Transpl 2009; 15:1101-9. [PMID: 19718644 PMCID: PMC2938042 DOI: 10.1002/lt.21782] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Steatotic donors are routinely rejected for transplantation because of their increased rate of primary nonfunction. These grafts are more sensitive to ischemia/reperfusion (I/R) during transplantation. Removal of endotoxin before reperfusion improves liver performance post-I/R. We hypothesize that the main modality of injury in steatotic livers is toll-like receptor 4 (TLR4) signaling. We fed 4-week-old control and TLR4-deficient (TLR4KO) mice a normal diet (ND) or a 60% high-fat diet (HFD) for 4 weeks to induce steatosis. Mice were subjected to total hepatic ischemia (35 minutes) and reperfusion (1 or 24 hours). Survival improved and liver pathology decreased at 24 hours in TLR4KO HFD animals compared to control HFD animals. An investigation of infiltrates showed that neutrophils and CD4+ cells were increased at 24 hours in control HFD animals, whereas TLR4KO HFD animals were similar to ND controls. Messenger RNA levels of interleukin 6 (IL-6), IL-12, and interferon gamma were elevated at 1 hour in control HFD animals, whereas TLR4KO HFD animals were similar to ND controls. IL-10 levels at 1 hour of reperfusion in control HFD and TLR4KO animals were decreased versus control ND animals. In conclusion, these improvements in liver function in TLR4KO HFD animals implicate TLR4 as a mediator of steatotic graft failure after I/R.
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Affiliation(s)
- Justin D. Ellett
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC
| | - Zachary P. Evans
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC
| | - Carl Atkinson
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC
| | - Michael G. Schmidt
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC
| | - Rick G. Schnellmann
- Department of Pharmaceutical and Biomedical Sciences, Medical University of South Carolina, Charleston, SC
| | - Kenneth D. Chavin
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC,Division of Transplantation, Department of Surgery, Medical University of South Carolina, Charleston, SC
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155
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Wu Q, Gong D, Tian N, Zhu L, Guan L, Yang M, Yuan B, Qiu Q, Lv H, Zou Y. Protection of regenerating liver after partial hepatectomy from carbon tetrachloride hepatotoxicity in rats: roles of mitochondrial uncoupling protein 2 and ATP stores. Dig Dis Sci 2009; 54:1918-25. [PMID: 19104935 DOI: 10.1007/s10620-008-0650-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Accepted: 11/21/2008] [Indexed: 12/09/2022]
Abstract
Uncoupling protein 2 (UCP(2)), an inner mitochondrial membrane protein, can limit the generation of reactive oxygen species (ROS) and protect cells from injuries mediated by oxidative stress. We investigated the effect of upregulation of UCP(2) in the regenerating liver 96 h after 68% partial hepatectomy (PH) on the self-protection of regenerating liver against carbon tetrachloride (CCl(4)) poisoning. Hepatotoxicity was induced in vivo by administering CCl(4) to rats that had undergone PH. After CCl(4) poisoning, the regenerating liver appeared to have less histological damage and lower serum alanine aminotransferase (ALT) levels. Lower malondialdehyde production and higher glutathione contents were also observed in the regenerating liver compared with the sham-operated liver after CCl(4) poisoning. UCP(2) expression was markedly elevated in the regenerating liver, and further increased after CCl(4) intoxication. Mitochondrial membrane potential and adenosine triphosphate stores maintained higher levels in the regenerating liver than in sham-operated liver after CCl(4) intoxication. The results showed that the regenerating liver exhibited a potent ability to resist CCl(4) intoxication, and the autoprotection of regenerating liver might result from reduction of ROS by UCP(2) and maintenance of higher ATP stores.
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Affiliation(s)
- Qiong Wu
- Department of Physiology, Dalian Medical University, Dalian, Liaoning Province 116044, China
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156
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Mu Y, She R, Zhang H, Dong B, Huang C, Lin W, Li D, Li X. Effects of estrogen and androgen deprivation on the progression of non-alcoholic steatohepatitis (NASH) in male Sprague-Dawley rats. Hepatol Res 2009; 39:910-20. [PMID: 19453544 DOI: 10.1111/j.1872-034x.2009.00512.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
AIM We studied the mechanisms of estrogen/androgen involvement in the induction of NASH by treating Sprague-Dawley (SD) rats fed with a normal or high fat (HF) diet by depriving them of endogenous estrogens/androgens. METHODS Male adult SD rats (n = 10/group) on normal or HF diets were treated for 75 days either with tamoxifen (Tam) or flutamide (Flu) or Tam + Flu in order to induce NASH. We analyzed histopathologically the liver samples from the treated groups for NASH, checked the serum biochemical and lipid profile markers and finally analyzed the signal pathways underlying the molecular mechanisms for the induction process of NASH. RESULTS Deprivation of endogenous estrogens and/or androgens (Tam or Flu or Tam + Flu) without the HF diet did not induce NASH. Tam or Tam + Flu induced NASH, compared to milder lesions without fibrosis in HF diet and Flu-treated liver. Serum alanine aminotransferase or lipid profile markers further proved the Tam, Flu or Tam + Flu effects on the induction of NASH in conjunction with a HF diet. Tam treatment predominantly downregulated the ERalpha and FAS and upregulated UCP2 and TNF-alpha. CONCLUSIONS Deprivation of endogenous estrogen/androgens in conjunction with a HF diet may induce NASH where the downregulated ERalpha and FAS, and upregulated UCP2 and TNF-alpha could be involved in their molecular pathomechanism pathways. These results could suggest the potential negative roles of estrogenic/androgenic depriving compounds in the induction of NASH, along with obesity.
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Affiliation(s)
- Yanjun Mu
- State Key Laboratory of Agro-Biotechnology, Faculty of Biological Sciences, China Agricultural University, Beijing, China
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157
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Corbin IR, Furth EE, Pickup S, Siegelman ES, Delikatny EJ. In vivo assessment of hepatic triglycerides in murine non-alcoholic fatty liver disease using magnetic resonance spectroscopy. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:757-63. [DOI: 10.1016/j.bbalip.2009.02.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Revised: 02/06/2009] [Accepted: 02/24/2009] [Indexed: 11/28/2022]
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158
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Yan X, Xu L, Qi J, Liang X, Ma C, Guo C, Zhang L, Sun W, Zhang J, Wei X, Gao L. sTRAIL levels and TRAIL gene polymorphisms in Chinese patients with fatty liver disease. Immunogenetics 2009; 61:551-6. [PMID: 19629467 DOI: 10.1007/s00251-009-0389-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2009] [Accepted: 07/10/2009] [Indexed: 01/12/2023]
Abstract
Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily, and has been identified as a novel mediator of fatty liver disease (FLD). The aim of our study was to further investigate the relationship between TRAIL and FLD. We found that soluble TRAIL (sTRAIL) concentrations in non-alcoholic FLD (NAFLD) patients were significantly higher than those of controls, and that sTRAIL levels positively correlated with triglyceride concentrations in NAFLD patients. Our results also indicated that the AA/TT genotypes of TRAIL at 1525/1595 engendered a lower risk of FLD attack and a less severe form of steatosis for NAFLD patients in Chinese population. This study provides a means to test for susceptibility to FLD and may assist in the diagnosis of FLD. In addition, we found that 1525G/A and 1595C/T sites were in complete linkage disequilibrium in Chinese population. This might indicate a haplotype with high genetic frequency of TRAIL.
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Affiliation(s)
- Xiaohua Yan
- Department of Immunology, Shandong University School of Medicine, 44# Wenhua Xi Road, Jinan, 250012, People's Republic of China
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159
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Décordé K, Agne A, Lacan D, Ramos J, Fouret G, Ventura E, Feillet-Coudray C, Cristol JP, Rouanet JM. Preventive effect of a melon extract rich in superoxide scavenging activity on abdominal and liver fat and adipokine imbalance in high-fat-fed hamsters. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2009; 57:6461-6467. [PMID: 19601676 DOI: 10.1021/jf900504g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Studies showed that dietary antioxidants could be a therapy against obesity that is associated with a state of oxidative stress. Thus, this paper investigates whether a dietary ingredient, a melon juice extract rich in superoxide dismutase, would prevent the development of such obesity in hamsters. Five groups received a standard diet or a high-fat diet (HF) plus a daily gavage with water (control) or extract at 0.7, 2.8, or 5.6 mg/day. After 84 days, the higher dose lowered triglyceridemia (68%), production of liver superoxide anion (12%), mitochondrial cytochrome c oxidase activity (40%), lipid and protein oxidation products (35 and 35%, respectively), and leptinemia (99%) and increased adiponectinemia (29%), leading to a concomitant reduction in insulinemia (39%), insulin resistance (41%), and abdominal lipids (25%). The extract triggered a remarkable decrease of liver lipids (73%) and fully prevented the steatohepatitis induced by the HF diet. Chronic consumption of this melon extract may represent a new alternative to reduce obesity induced by a high-fat diet.
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Affiliation(s)
- Kelly Décordé
- UMR 204 Prévention des Malnutritions et des Pathologies Associées, Université Montpellier Sud de France, France
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160
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Zhao H, Przybylska M, Wu IH, Zhang J, Maniatis P, Pacheco J, Piepenhagen P, Copeland D, Arbeeny C, Shayman JA, Aerts JM, Jiang C, Cheng SH, Yew NS. Inhibiting glycosphingolipid synthesis ameliorates hepatic steatosis in obese mice. Hepatology 2009; 50:85-93. [PMID: 19444873 DOI: 10.1002/hep.22970] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
UNLABELLED Steatosis in the liver is a common feature of obesity and type 2 diabetes and the precursor to the development of nonalcoholic steatohepatitis (NASH), cirrhosis, and liver failure. It has been shown previously that inhibiting glycosphingolipid (GSL) synthesis increases insulin sensitivity and lowers glucose levels in diabetic rodent models. Here we demonstrate that inhibiting GSL synthesis in ob/ob mice not only improved glucose homeostasis but also markedly reduced the development of hepatic steatosis. The ob/ob mice were treated for 7 weeks with a specific inhibitor of glucosylceramide synthase, the initial enzyme involved in the synthesis of GSLs. Besides lowering glucose and hemoglobin A1c (HbA1c) levels, drug treatment also significantly reduced the liver/body weight ratio, decreased the accumulation of triglycerides, and improved several markers of liver pathology. Drug treatment reduced liver glucosylceramide (GL1) levels in the ob/ob mouse. Treatment also reduced the expression of several genes associated with hepatic steatosis, including those involved in lipogenesis, gluconeogenesis, and inflammation. In addition, inhibiting GSL synthesis in diet-induced obese mice both prevented the development of steatosis and partially reversed preexisting steatosis. CONCLUSION These data indicate that inhibiting GSL synthesis ameliorates the liver pathology associated with obesity and diabetes, and may represent a novel strategy for treating fatty liver disease and NASH.
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161
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Abstract
Non-alcoholic fatty liver disease (NAFLD) has become the most common liver disorder of our times. Simple steatosis, a seemingly innocent manifestation of NAFLD, may progress into steatohepatitis and cirrhosis, but this process is not well understood. Since NAFLD is associated with obesity and insulin resistance, mechanisms that link lipid metabolism to inflammation offer insights into the pathogenesis. An important parallel between obesity-related pathology of adipose tissue and liver pertains to the emerging role of macrophages and evidence is growing that Kupffer cells critically contribute to progression of NAFLD. Toll-like receptors, in particular TLR4, represent a major conduit for danger recognition linked to Kupffer cell activation and this process may be perturbed at multiple steps in NAFLD. Steatosis may interfere with sinusoid microcirculation and hepatocellular clearance of microbial and host-derived danger signals, enhancing responsiveness of Kupffer cells. Altered lipid homeostasis in NAFLD may unfavourably affect TLR4 receptor complex assembly and sorting, interfere with signalling flux redistribution, promote amplification loops, and impair negative regulation including alternative activation of Kupffer cells. These events are further promoted by altered adipokine secretion and reactive oxygen species production. Specific targeting of these interactions may provide more effective strategies in the treatment of NAFLD.
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Affiliation(s)
- György Baffy
- Brigham and Women's Hospital and VA Boston Healthcare System, Harvard Medical School, Section of Gastroenterology, 150 S. Huntington Ave., Boston, MA 02130, USA.
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162
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Tessari P, Coracina A, Cosma A, Tiengo A. Hepatic lipid metabolism and non-alcoholic fatty liver disease. Nutr Metab Cardiovasc Dis 2009; 19:291-302. [PMID: 19359149 DOI: 10.1016/j.numecd.2008.12.015] [Citation(s) in RCA: 218] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 12/10/2008] [Accepted: 12/29/2008] [Indexed: 12/16/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is an increasingly recognized pathology with a high prevalence and a possible evolution to its inflammatory counterpart (non-alcoholic steatohepatitis, or NASH). The pathophysiology of NAFLD and NASH has many links with the metabolic syndrome, sharing a causative factor in insulin resistance. According to a two-hit hypothesis, increased intrahepatic triglyceride accumulation (due to increased synthesis, decreased export, or both) is followed by a second step (or "hit"), which may lead to NASH. The latter likely involves oxidative stress, cytochrome P450 activation, lipid peroxidation, increased inflammatory cytokine production, activation of hepatic stellate cells and apoptosis. However, both "hits" may be caused by the same factors. The aim of this article is to overview the biochemical steps of fat regulation in the liver and the alterations occurring in the pathogenesis of NAFLD and NASH.
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Affiliation(s)
- P Tessari
- Department of Clinical and Experimental Medicine, Chair of Metabolism, University of Padua, Italy.
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163
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164
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Malaguarnera M, Di Rosa M, Nicoletti F, Malaguarnera L. Molecular mechanisms involved in NAFLD progression. J Mol Med (Berl) 2009; 87:679-95. [PMID: 19352614 DOI: 10.1007/s00109-009-0464-1] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 02/26/2009] [Accepted: 03/18/2009] [Indexed: 02/06/2023]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is an emerging metabolic-related disorder characterized by fatty infiltration of the liver in the absence of alcohol consumption. NAFLD ranges from simple steatosis to non-alcoholic steatohepatitis (NASH), which might progress to end-stage liver disease. This progression is related to the insulin resistance, which is strongly linked to the metabolic syndrome consisting of central obesity, diabetes mellitus, and hypertension. Earlier, the increased concentration of intracellular fatty acids within hepatocytes leads to steatosis. Subsequently, multifactorial complex interactions between nutritional factors, lifestyle, and genetic determinants promote necrosis, inflammation, fibrosis, and hepatocellular damage. Up to now, many studies have revealed the mechanism associated with insulin resistance, whereas the mechanisms related to the molecular components have been incompletely characterized. This review aims to assess the potential molecular mediators initiating and supporting the progression of NASH to establish precocious diagnosis and to plan more specific treatment for this disease.
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165
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Mitsuyoshi H, Yasui K, Harano Y, Endo M, Tsuji K, Minami M, Itoh Y, Okanoue T, Yoshikawa T. Analysis of hepatic genes involved in the metabolism of fatty acids and iron in nonalcoholic fatty liver disease. Hepatol Res 2009; 39:366-73. [PMID: 19054139 DOI: 10.1111/j.1872-034x.2008.00464.x] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
AIMS Hepatic steatosis and iron cause oxidative stress, thereby progressing steatosis to steatohepatitis. We quantified the expression of genes involved in the metabolism of fatty acids and iron in patients with nonalcoholic fatty liver disease (NAFLD). METHODS The levels of transcripts for the following genes were quantified from biopsy specimens of 74 patients with NAFLD: thioredoxin (Trx), fatty acid transport protein 5 (FATP5), sterol regulatory element-binding protein 1c (SREBP1c), fatty acid synthase (FASN), acetyl-coenzyme A carboxylase (ACAC), peroxisome proliferative activated receptor alpha (PPARalpha), cytochrome P-450 2E1 (CYP2E1), acyl-coenzyme A dehydrogenase (ACADM), acyl-coenzyme A oxidase (ACOX), microsomal triglyceride transfer protein (MTP), transferrin receptor 1 (TfR1), transferrin receptor 2 (TfR2) and hepcidin. Twelve samples of human liver RNA were used as controls. Histological evaluation followed the methods of Brunt. RESULTS The levels of all genes were significantly higher in the NAFLD patients than in controls. The Trx level increased as the stage progressed. The levels of FATP5, SREBP1c, ACAC, PPARalpha, CYP2E1, ACADM and MTP significantly decreased as the stage and grade progressed (P < 0.05). Hepatic iron score (HIS) increased as the stage progressed. The TfR1 level significantly increased as the stage progressed (P < 0.05), whereas TfR2 level significantly decreased (P < 0.05). The ratio of hepcidin mRNA/ferritin (P < 0.001) or hepcidin mRNA/HIS (P < 0.01) was significantly lower in NASH patients than simple steatosis patients. CONCLUSIONS Steatosis-related metabolism is attenuated as NAFLD progresses, whereas iron-related metabolism is exacerbated. Appropriate therapies should be considered on the basis of metabolic changes.
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Affiliation(s)
- Hironori Mitsuyoshi
- Molecular Gastroenterology and Hepatology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
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166
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Vitamin E succinate reduces ischemia/reperfusion injury in steatotic livers. Transplant Proc 2009; 40:3327-9. [PMID: 19100382 DOI: 10.1016/j.transproceed.2008.06.076] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Accepted: 06/27/2008] [Indexed: 12/19/2022]
Abstract
Steatotic livers represent a growing proportion of marginal organs available for transplantation. These livers are highly prone to primary nonfunction following transplantation and are therefore routinely turned down for surgery. Given the elevated levels and sensitivity for reactive oxygen species (ROS) in these livers, we evaluated whether pretreatment with a targeted ROS scavenger, vitamin E succinate, increased survival and decreased injury after ischemia/reperfusion (I/R). For this study, ob/ob mice received 50 IU/d vitamin E succinate in supplemented vs control chow for 7 days, and were subjected to 15 minutes of total hepatic ischemia and 24 hours of reperfusion. Treatment resulted in a 5-fold decrease in serum alanine aminotransferase (ALT) levels after reperfusion, mirrored by significant decreases in hepatocellular necrosis. These results suggested that targeted antioxidants such as vitamin E succinate may prove to be highly applicable for the pretreatment of steatotic donor livers, increasing their tolerance for I/R and the transplantation process.
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167
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Scaloni A, Codarin E, Di Maso V, Arena S, Renzone G, Tiribelli C, Quadrifoglio F, Tell G. Modern strategies to identify new molecular targets for the treatment of liver diseases: The promising role of Proteomics and Redox Proteomics investigations. Proteomics Clin Appl 2009; 3:242-62. [DOI: 10.1002/prca.200800169] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Indexed: 12/16/2022]
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168
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Abstract
NAFLD (non-alcoholic fatty liver disease), associated with obesity and the cardiometabolic syndrome, is an important medical problem affecting up to 20% of western populations. Evidence indicates that mitochondrial dysfunction plays a critical role in NAFLD initiation and progression to the more serious condition of NASH (non-alcoholic steatohepatitis). Herein we hypothesize that mitochondrial defects induced by exposure to a HFD (high fat diet) contribute to a hypoxic state in liver and this is associated with increased protein modification by RNS (reactive nitrogen species). To test this concept, C57BL/6 mice were pair-fed a control diet and HFD containing 35% and 71% total calories (1 cal≈4.184 J) from fat respectively, for 8 or 16 weeks and liver hypoxia, mitochondrial bioenergetics, NO (nitric oxide)-dependent control of respiration, and 3-NT (3-nitrotyrosine), a marker of protein modification by RNS, were examined. Feeding a HFD for 16 weeks induced NASH-like pathology accompanied by elevated triacylglycerols, increased CYP2E1 (cytochrome P450 2E1) and iNOS (inducible nitric oxide synthase) protein, and significantly enhanced hypoxia in the pericentral region of the liver. Mitochondria from the HFD group showed increased sensitivity to NO-dependent inhibition of respiration compared with controls. In addition, accumulation of 3-NT paralleled the hypoxia gradient in vivo and 3-NT levels were increased in mitochondrial proteins. Liver mitochondria from mice fed the HFD for 16 weeks exhibited depressed state 3 respiration, uncoupled respiration, cytochrome c oxidase activity, and mitochondrial membrane potential. These findings indicate that chronic exposure to a HFD negatively affects the bioenergetics of liver mitochondria and this probably contributes to hypoxic stress and deleterious NO-dependent modification of mitochondrial proteins.
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169
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Gudbrandsen OA, Wergedahl H, Berge RK. A casein diet added isoflavone-enriched soy protein favorably affects biomarkers of steatohepatitis in obese Zucker rats. Nutrition 2008; 25:574-80. [PMID: 19101115 DOI: 10.1016/j.nut.2008.10.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 10/02/2008] [Accepted: 10/27/2008] [Indexed: 02/08/2023]
Abstract
OBJECTIVE Dietary supplementation of a soy protein enriched with isoflavones (HDI) has been shown to improve fatty liver in obese rats. The main objective of this study was to investigate whether HDI would influence the inflammatory status in livers of obese rats with fatty liver. METHODS Male obese Zucker fa/fa rats were fed casein (controls) or casein supplemented with HDI (containing 4.00 g of genistein and 4.50 g of daidzein per kilogram of diet) for 6 wk. RESULTS The HDI-fed rats had a markedly lower hepatic concentration of triacylglycerol when compared with controls. The decreased aspartate transaminase/alanine transaminase ratio in plasma, together with lower circulating levels of alkaline phosphatase and bile acids after HDI feeding, implied an improved hepatitis. This was supported by decreased plasma and hepatic mRNA levels of tumor necrosis factor-alpha, lower plasma levels of interleukin-1beta and monocyte chemoattractant protein-1, and an increased anti-inflammatory fatty acid index in plasma. HDI also seemed to protect the rats from oxidative damage, because the level of lipid peroxides in triacylglycerol-rich lipoproteins after in vitro copper oxidation was lower for HDI-fed rats when compared with controls. CONCLUSION These results show that isoflavone-enriched soy protein favorably affects biomarkers of hepatic inflammation in obese Zucker fa/fa rats with fatty liver. Thus, dietary soy proteins enriched in isoflavones may be a promising agent to improve steatohepatitis in patients.
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Affiliation(s)
- Oddrun Anita Gudbrandsen
- The Lipid Research Group, Institute of Medicine, University of Bergen, Haukeland University Hospital, Bergen, Norway.
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170
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Chen P, Li C, Pang W, Zhao Y, Dong W, Wang S, Zhang J. The protective role of Per2 against carbon tetrachloride-induced hepatotoxicity. THE AMERICAN JOURNAL OF PATHOLOGY 2008; 174:63-70. [PMID: 19056852 DOI: 10.2353/ajpath.2009.080430] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Period 2 (Per2) is a key component of the core clock oscillator and is involved in regulating a number of different biological processes and pathways. Here we report that Per2 plays a protective role in carbon tetrachloride (CCl(4))-induced hepatotoxicity via the modulation of uncoupling protein-2 (Ucp2) gene expression in mice. Hepatic injury after acute CCl(4) injection was monitored in both wild-type and Per2-null mice. At the 12-hour time point after CCl(4) treatment, many more vacuolations were observed in the liver tissues of Per2-null mice whereas fatty tissue degeneration primarily occurred in the liver tissues of wide-type mice. Serum alanine and aspartate aminotransferase activities were elevated in Per2-null mice compared with wide-type mice at 24 hours after CCl(4) treatment, which was in agreement with the observation of significantly larger areas of centrilobular necrosis in the livers of Per2-null mice. A deficit of the Per2 gene enhanced Ucp2 gene expression levels in the liver. As a consequence, intracellular levels of ATP markedly decreased in the liver, allowing increased production of toxic CCl(4) derivatives. The absence of Per2 expression caused a dramatic elevation of Clock expression and influenced Ucp2 through a mechanism that involved a Clock-controlled PPAR-alpha signal transduction pathway. Our studies suggest that the Per2 gene functions in hepatocyte protection from chemical toxicants via the regulation of hepatic Ucp2 gene expression levels.
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Affiliation(s)
- Peng Chen
- Center for Molecular Metabolism, Nanjing University of Science and Technology, Nanjing, China
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171
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Lee SJ, Heinrich G, Fedorova L, Al-Share QY, Ledford KJ, Fernstrom MA, McInerney MF, Erickson SK, Gatto-Weis C, Najjar SM. Development of nonalcoholic steatohepatitis in insulin-resistant liver-specific S503A carcinoembryonic antigen-related cell adhesion molecule 1 mutant mice. Gastroenterology 2008; 135:2084-95. [PMID: 18848945 PMCID: PMC2784638 DOI: 10.1053/j.gastro.2008.08.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 07/31/2008] [Accepted: 08/14/2008] [Indexed: 12/19/2022]
Abstract
BACKGROUND & AIMS Liver-specific inactivation of carcinoembryonic antigen-related cell adhesion molecule 1 causes hyperinsulinemia and insulin resistance, which result from impaired insulin clearance, in liver-specific S503A carcinoembryonic antigen-related cell adhesion molecule 1 mutant mice (L-SACC1). These mice also develop steatosis. Because hepatic fat accumulation precedes hepatitis, lipid peroxidation, and apoptosis in the pathogenesis of nonalcoholic steatohepatitis (NASH), we investigated whether a high-fat diet, by causing inflammation, is sufficient to induce hepatitis and other features of NASH in L-SACC1 mice. METHODS L-SACC1 and wild-type mice were placed on a high-fat diet for 3 months, then several biochemical and histologic analyses were performed to investigate the NASH phenotype. RESULTS A high-fat diet caused hepatic macrosteatosis and hepatitis, characterized by increased hepatic tumor necrosis factor alpha levels and activation of the NF-kappaB pathway in L-SACC1 but not in wild-type mice. The high-fat diet also induced necrosis and apoptosis in the livers of the L-SACC1 mice. Insulin resistance in L-SACC1 fed a high-fat diet increased the hepatic procollagen protein level, suggesting a role in the development of fibrosis. CONCLUSIONS A high-fat diet induces key features of human NASH in insulin-resistant L-SACC1 mice, validating this model as a tool to study the molecular mechanisms of NASH.
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Affiliation(s)
- Sang Jun Lee
- The Center for Diabetes and Endocrine Research and the Department of Physiology and Pharmacology at the College of Medicine at the University of Toledo, Health Science Campus, Toledo, Ohio, 43614
| | - Garrett Heinrich
- The Center for Diabetes and Endocrine Research and the Department of Physiology and Pharmacology at the College of Medicine at the University of Toledo, Health Science Campus, Toledo, Ohio, 43614
| | - Larisa Fedorova
- the Department of Medicine at the College of Medicine at the University of Toledo, Health Science Campus, Toledo, Ohio, 43614
| | - Qusai Y. Al-Share
- The Center for Diabetes and Endocrine Research and the Department of Physiology and Pharmacology at the College of Medicine at the University of Toledo, Health Science Campus, Toledo, Ohio, 43614
| | - Kelly J. Ledford
- The Center for Diabetes and Endocrine Research and the Department of Physiology and Pharmacology at the College of Medicine at the University of Toledo, Health Science Campus, Toledo, Ohio, 43614
| | - Mats A. Fernstrom
- The Center for Diabetes and Endocrine Research and the Department of Physiology and Pharmacology at the College of Medicine at the University of Toledo, Health Science Campus, Toledo, Ohio, 43614
| | - Marcia F. McInerney
- the Department of Medicinal and Biological Chemistry at the College of Pharmacy at the University of Toledo, Main Campus, Toledo, OH 43606 and
| | - Sandra K. Erickson
- the Department of Medicine, University of California, and Veterans Affairs Medical Center, San Francisco, CA 94121
| | - Cara Gatto-Weis
- the Department of Pathology at the College of Medicine at the University of Toledo, Health Science Campus, Toledo, Ohio, 43614
| | - Sonia M. Najjar
- The Center for Diabetes and Endocrine Research and the Department of Physiology and Pharmacology at the College of Medicine at the University of Toledo, Health Science Campus, Toledo, Ohio, 43614,Address correspondence to: Sonia M. Najjar, Ph.D., College of Medicine, University of Toledo, Health Science Campus, 3000 Arlington Avenue, Mail stop 1008, Toledo, Ohio, 43614, Tel: (419) 383-4059, FAX: (419) 383-2871, e-mail:
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172
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Anderson N, Borlak J. Molecular Mechanisms and Therapeutic Targets in Steatosis and Steatohepatitis. Pharmacol Rev 2008; 60:311-57. [DOI: 10.1124/pr.108.00001] [Citation(s) in RCA: 291] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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173
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Wan C, Wang H, Cheng R, Gou S, Liu T. Effect of target-directed regulation of uncoupling protein-2 gene expression on ischemia-reperfusion injury of hepatocytes. ACTA ACUST UNITED AC 2008; 28:558-63. [PMID: 18846338 DOI: 10.1007/s11596-008-0515-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2008] [Indexed: 11/29/2022]
Abstract
The effect of target-directed regulation of the uncoupling protein-2 (UCP-2) gene expression on the ischemia-reperfusion injury of hepatocytes under different conditions was investigated. The expression plasmid and RNAi plasmid targeting UCP-2 gene were constructed and transfected into normal hepatocytes and fatty liver cells, respectively. The expression of UCP-2 mRNA was detected by real time PCR. The cells were divided into normal cell group (NCG), group of normal cells transfected with empty vector (EVNCG), group of normal cells transfected with expression plasmid (EPNCG), fatty liver cell group (FCG) and group of fatty liver cells transfected with RNAi plasmid (RPFCG). The ischemia-reperfusion model in vitro was established. One, 6, 12 and 24 h after reperfusion, Annexin V/PI flow cytometry was used to measure cell necrosis rate, apoptosis rate and survival rate. Simultaneously, the intracellular ATP, ROS and MDA levels were determined. The results showed that 1, 6, 12 and 24 h after ischemia-reperfusion, the intracellular ROS, MDA and ATP levels and cell survival rate in EPNCG were significantly lower, and cell necrosis rate significantly higher than in NCG and EVNCG, but there was no significant difference in apoptosis rate among NCG, EVNCG and EPNCG (P>005). Six, 12 and 24 h after reperfusion there was no significant difference in ROS, MDA levels and apoptosis rate between FCG and RPFCG (P>0.05), but the ATP level and survival rate of cells in RPFCG were higher than in FCG (P<0.05). It was concluded that down-regulation of the UCP-2 gene expression in steatotic hepatocytes could alleviate the ischemia-reperfusion injury of liver cells.
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Affiliation(s)
- Chidan Wan
- Department of Hepatobiliary Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
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The use of the Papworth cocktail is detrimental to steatotic livers after ischemia-reperfusion injury. Transplantation 2008; 86:286-92. [PMID: 18645492 DOI: 10.1097/tp.0b013e31817b900f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Hormonal resuscitation, specifically administration of levothyroxine (T4) and methylprednisolone (steroid, i.e., the "T4 Protocol") in organ transplant donors, is becoming increasingly used. Previous studies have shown that this maximizes the number of usable organs by reducing metabolic disturbances post-brain death. However, anecdotal evidence has shown that steatotic livers are adversely affected by this protocol. Therefore, we sought to investigate the hypothesis that the use of T4 and steroid is detrimental to steatotic livers in a model of total hepatic warm ischemia-reperfusion (I/R). METHODS We subjected 8- to -10-week-old male C57BL/6 and ob/ob mice to injections of T4 and steroid 48 hr before 15 min of total hepatic ischemia, followed by 24 hr of reperfusion. RESULTS We saw a significant decrease in survival in ob/ob animals given T4 and steroid as compared with single-treated or vehicle-treated animals. This decrease in survival was accompanied by a dramatic increase in liver necrosis (as measured on a scale from 0 to 3) in these animals as compared with controls. Previous work in our lab has shown that uncoupling protein-2 is a major mediator of I/R in steatotic animals, as it upsets normal energy homeostasis. Following with this hypothesis, we see a dramatic increase in uncoupling protein-2 levels in the combination treated animals, which is accompanied by a concomitant decrease in ATP levels after reperfusion. CONCLUSIONS The T4 protocol is detrimental to steatotic livers subjected to I/R, likely because of a decreased ability to recover after reperfusion caused by decreased ability to form ATP.
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175
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Demori I, Burlando B, Gerdoni E, Lanni A, Fugassa E, Voci A. Uncoupling protein-2 induction in rat hepatocytes after acute carbon tetrachloride liver injury. J Cell Physiol 2008; 216:413-8. [PMID: 18314881 DOI: 10.1002/jcp.21415] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This study is focused on the role of UCP-2 in hepatic oxidative metabolism following acute CCl(4) administration to rats. UCP-2 mRNA, almost undetectable in the liver of controls, was significantly increased 24 h after CCl(4) administration, peaked at 72 h and then tended to disappear. UCP-2 protein, undetectable in controls, increased 48-72 h after CCl(4) treatment. Experiments with isolated liver cells indicated that in control rats UCP-2 was expressed in non-parenchymal cells and not in hepatocytes, whereas in CCl(4)-treated rats UCP-2 expression was induced in hepatocytes and was not affected in non-parenchymal cells. Addition of CCl(4) to the culture medium of hepatocytes from control rats failed to induce UCP-2 expression. Liver mitochondria from CCl(4)-treated rats showed an increase of H(2)O(2) release at 12-24 h, followed by a rise of TBARS. Vitamin E protected liver from CCl(4) injury and reduced the expression of UCP-2. Treatment with GdCl(3) prior to CCl(4), in order to inhibit Kupffer cells, reduced TBARS and UCP-2 mRNA increase in hepatic mitochondria. Our data indicate that CCl(4) induces the expression of UCP-2 in hepatocytes with a redox-dependent mechanism involving Kupffer cells. A role of UCP-2 in moderating CCl(4)-induced oxidative stress during tissue regeneration after injury is suggested.
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Affiliation(s)
- Ilaria Demori
- Dipartimento di Biologia, Università di Genova, Genova, Italy
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176
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Abstract
The number of patients awaiting liver transplantation keeps steadily rising with no corresponding rise in suitable grafts for transplantation. There also is an increasing trend of patients dying or being taken off waiting lists because of deterioration while waiting for a transplant. Over the preceding years the use of marginal grafts in liver transplantation has been driven by the critical shortage of donor organs and by emerging data that their use has resulted in a favourable outcome. This review revisits the factors defining marginality of a graft, and the issues faced by transplant units in making the decision to use such a graft. It also looks at the innovations in transplantation geared towards increasing the donor pool and the resulting issues of matching marginal grafts to suitable recipients.
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Affiliation(s)
- Magdy Attia
- The Liver Unit, University Hospital Birmingham NHS Foundation Trust-Queen Elizabeth, Edgbaston, Birmingham, UK
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177
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Mantena SK, King AL, Andringa KK, Eccleston HB, Bailey SM. Mitochondrial dysfunction and oxidative stress in the pathogenesis of alcohol- and obesity-induced fatty liver diseases. Free Radic Biol Med 2008; 44:1259-72. [PMID: 18242193 PMCID: PMC2323912 DOI: 10.1016/j.freeradbiomed.2007.12.029] [Citation(s) in RCA: 331] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 12/19/2007] [Accepted: 12/19/2007] [Indexed: 12/16/2022]
Abstract
Fatty liver disease associated with chronic alcohol consumption or obesity/type 2 diabetes has emerged as a serious public health problem. Steatosis, accumulation of triglyceride in hepatocytes, is now recognized as a critical "first-hit" in the pathogenesis of liver disease. It is proposed that steatosis "primes" the liver to progress to more severe liver pathologies when individuals are exposed to subsequent metabolic and/or environmental stressors or "second-hits." Genetic risk factors can also influence the susceptibility to and severity of fatty liver disease. Furthermore, oxidative stress, disrupted nitric oxide (NO) signaling, and mitochondrial dysfunction are proposed to be key molecular events that accelerate or worsen steatosis and initiate progression to steatohepatitis and fibrosis. This review article will discuss the following topics regarding the pathobiology and molecular mechanisms responsible for fatty liver disease: (1) the "two-hit" or "multi-hit" hypothesis, (2) the role of mitochondrial bioenergetic defects and oxidant stress, (3) the interplay between NO and mitochondria in fatty liver disease, (4) genetic risk factors and oxidative stress-responsive genes, and (5) the feasibility of antioxidants for treatment.
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Affiliation(s)
| | | | | | | | - Shannon M. Bailey
- *Corresponding Author: Shannon M. Bailey, PhD, Associate Professor, Department of Environmental Health Sciences, Center for Free Radical Biology, University of Alabama at Birmingham, Ryals Building, Room 623, 1530 3 Avenue South, Birmingham, AL 35294 USA, Phone: 205-934-7070, Fax: 205-975-6341,
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178
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Serviddio G, Bellanti F, Tamborra R, Rollo T, Romano AD, Giudetti AM, Capitanio N, Petrella A, Vendemiale G, Altomare E. Alterations of hepatic ATP homeostasis and respiratory chain during development of non-alcoholic steatohepatitis in a rodent model. Eur J Clin Invest 2008; 38:245-52. [PMID: 18339004 DOI: 10.1111/j.1365-2362.2008.01936.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Mitochondrial dysfunction is considered a key player in non-alcoholic steatohepatitis (NASH) but no data are available on the mitochondrial function and ATP homeostasis in the liver during NASH progression. In the present paper we evaluated the hepatic mitochondrial respiratory chain activity and ATP synthesis in a rodent model of NASH development. MATERIALS AND METHODS Male Wistar rats fed a High Fat/Methionine-Choline Deficient (MCD) diet to induce NASH or a control diet (SHAM), and sacrificed after 3, 7 and 11 weeks. The oxidative phosphorylation, the F(0)F(1)ATPase (ATP synthase) and the ATP content were assessed in liver mitochondria. RESULTS NASH mitochondria exhibited an increased rate of substrate oxidation at 3 weeks, which returned to below the normal level at 7 and 11 weeks, concomitantly with the coupling between the phosphorylation activity and the mitochondrial respiration (ADP/O). Uncoupling of NASH liver mitochondria did not allow the recovery of the maximal respiration rate at 7 and 11 weeks. The ATPase (ATP synthase) activity was similar in NASH and SHAM rats, but the mitochondrial ATP content was significantly lower in NASH livers. CONCLUSIONS The loss of hepatic ATP stores is not dependent on the F(0)F(1)-ATPase but resides in the respiratory chain. Dysfunction of both Complex I and II of the mitochondrial respiratory chain during NASH development implies a mitochondrial adaptive mechanism occurring in the early stages of NASH.
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179
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Tsuboyama-Kasaoka N, Sano K, Shozawa C, Osaka T, Ezaki O. Studies of UCP2 transgenic and knockout mice reveal that liver UCP2 is not essential for the antiobesity effects of fish oil. Am J Physiol Endocrinol Metab 2008; 294:E600-6. [PMID: 18089762 DOI: 10.1152/ajpendo.00551.2007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Uncoupling protein 2 (UCP2) is a possible target molecule for energy dissipation. Many dietary fats, including safflower oil and lard, induce obesity in C57BL/6 mice, whereas fish oil does not. Fish oil increases UCP2 expression in hepatocytes and may enhance UCP2 activity by activating the UCP2 molecule or altering the lipid bilayer environment. To examine the role of liver UCP2 in obesity, we created transgenic mice that overexpressed human UCP2 in hepatocytes and examined whether UCP2 transgenic mice showed less obesity when fed a high-fat diet (safflower oil or lard). In addition, we examined whether fish oil had antiobesity effects in UCP2 knockout mice. UCP2 transgenic and wild-type mice fed a high-fat diet (safflower oil or lard) developed obesity to a similar degree. UCP2 knockout and wild-type mice fed fish oil had lower rates of obesity than mice fed safflower oil. Remarkably, safflower oil did not induce obesity in female UCP2 knockout mice, an unexpected phenotype for which we presently have no explanation. However, this unexpected effect was not observed in male UCP2 knockout mice or in UCP2 knockout mice fed a high-lard diet. These data indicate that liver UCP2 is not essential for fish oil-induced decreases in body fat.
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Affiliation(s)
- Nobuyo Tsuboyama-Kasaoka
- Nutritional Science Program, National Institute of Health and Nutrition, 1-23-1, Toyama, Shinjuku-ku, Tokyo 162-8636, Japan
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180
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Serviddio G, Sastre J, Bellanti F, Viña J, Vendemiale G, Altomare E. Mitochondrial involvement in non-alcoholic steatohepatitis. Mol Aspects Med 2008; 29:22-35. [PMID: 18061659 DOI: 10.1016/j.mam.2007.09.014] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Accepted: 09/28/2007] [Indexed: 02/06/2023]
Abstract
Non-alcoholic steatohepatitis (NASH) is an increasing recognized condition that may progress to end-stage liver disease. There are consistent evidences that mitochondrial dysfunction plays a central role in NASH whatever its origin. Mitochondria are the key controller of fatty acids removal and this is part of an intensive gene program that modifies hepatocytes to counteract the excessive fat storage. Mitochondrial dysfunction participates at different levels in NASH pathogenesis since it impairs fatty liver homeostasis and induces overproduction of ROS that in turn trigger lipid peroxidation, cytokines release and cell death. In this review we briefly recall the role of mitochondria in fat metabolism and energy homeostasis and focus on the role of mitochondrial impairment and uncoupling proteins in the pathophysiology of NASH progression. We suggest that mitochondrial respiratory chain, UCP2 and redox balance cooperate in a common pathway that permits to set down the mitochondrial redox pressure, limits the risk of oxidative damage, and allows the maximal rate of fat removal. When the environmental conditions change and high energy supply occurs, hepatocytes are unable to replace their ATP store and steatosis progress to NASH and cirrhosis. The beneficial effects of some drugs on mitochondrial function are also discussed.
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Affiliation(s)
- Gaetano Serviddio
- Department of Medical and Occupational Sciences, University of Foggia, v.le Pinto 1, 71100 Foggia, Italy.
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181
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Wan CD, Wang CY, Liu T, Cheng R, Wang HB. Alleviation of ischemia/reperfusion injury in ob/ob mice by inhibiting UCP-2 expression in fatty liver. World J Gastroenterol 2008; 14:590-4. [PMID: 18203292 PMCID: PMC2681151 DOI: 10.3748/wjg.14.590] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the protective effect of target suppression of uncoupling protein-2 (UCP-2) on ischemia/reperfusion (I/R) injury in fatty liver in ob/ob mice.
METHODS: Plasmids suppressing UCP-2 expression were constructed, and transfected into fatty liver cells cultured in vitro and the ob/ob mouse I/R injury model. Serum tumor necrosis factor (TNF)-α levels, UCP-2 mRNA expression, alanine aminotransferase (ALT) levels in ob/ob mice were tested, and the pathological changes in fatty liver were observed in experimental and control groups.
RESULTS: In ob/ob mouse I/R models, serum TNF-α levels were significantly higher than in normal controls. After the plasmids were transfected into the cultured cells and animal models, expression of UCP-2 mRNA was significantly reduced as compared with that in the control group (21.56 ± 0.15vs 2-0.45 ± 0.15, P < 0.05). In ob/ob mouse models, in which expression of UCP-2 was suppressed, serum ALT levels were significantly lower than those of other groups, and pathological analysis revealed that injury of liver tissues was significantly alleviated.
CONCLUSION: The target suppression of UCP-2 expression in fatty liver can alleviate the I/R injury in the ob/ob mice.
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182
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Evans ZP, Ellett JD, Schmidt MG, Schnellmann RG, Chavin KD. Mitochondrial uncoupling protein-2 mediates steatotic liver injury following ischemia/reperfusion. J Biol Chem 2007; 283:8573-9. [PMID: 18086675 DOI: 10.1074/jbc.m706784200] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Steatotic livers are not used for transplantation because they have a reduced tolerance for ischemic events with reduced ATP levels and greater levels of cellular necrosis, which ultimately result in total organ failure. Mitochondrial uncoupling protein-2 (UCP2) is highly expressed in steatotic livers and may be responsible for liver sensitivity to ischemia through mitochondrial and ATP regulation. To test this hypothesis, experiments were conducted in lean and steatotic (ob/ob), wild-type, and UCP2 knock-out mice subjected to total warm hepatic ischemi-a/reperfusion. Although ob/ob UCP2 knock-out mice and ob/ob mice have a similar initial phenotype, ob/ob UCP2 knock-out animal survival was 83% when compared with 30% in ob/ob mice 24 h after reperfusion. Serum alanine aminotransferase concentrations and hepatocellular necrosis were decreased in the ob/ob UCP2 knock-out mice when compared with ob/ob mice subjected to ischemia. Liver ATP levels were increased in the ob/ob UCP2 knock-out animals after reperfusion when compared with the ob/ob mice but remained below the concentrations from lean livers. Lipid peroxidation (thiobarbituric acid-reactive substances) increased after reperfusion most significantly in the steatotic groups, but the increase was not affected by UCP2 deficiency. These results reveal that UCP2 expression is a critical factor, which sensitizes steatotic livers to ischemic injury, regulating liver ATP levels after ischemia and reperfusion.
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Affiliation(s)
- Zachary P Evans
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC 29425, USA
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Tahan V, Imeryuz N, Avsar E, Celikel C, Tozun N. Effects of rosiglitazone on methionine-choline deficient diet-induced nonalcoholic steatohepatitis. Hepatology 2007; 46:2045; author reply 2045-6. [PMID: 18046722 DOI: 10.1002/hep.21981] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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184
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Abstract
Ethanol is a hepatotoxin. It appears that the liver is the target of ethanol induced toxicity primarily because it is the major site of ethanol metabolism. Metabolism of ethanol results in a number of biochemical changes that are thought to mediate the toxicity associated with ethanol abuse. These include the production of acetaldehyde and reactive oxygen species, as well as an accumulation of nicotinamide adenine dinucleotide (NADH). These biochemical changes are associated with the accumulation of fat and mitochondrial dysfunction in the liver. If these changes are severe enough they can themselves cause hepatotoxicity, or they can sensitize the liver to more severe damage by other hepatotoxins. Whether liver damage is the result of ethanol metabolism or some other hepatotoxin, recovery of the liver from damage requires replacement of cells that have been destroyed. It is now apparent that ethanol metabolism not only causes hepatotoxicity but also impairs the replication of normal hepatocytes. This impairment has been shown to occur at both the G1/S, and the G2/M transitions of the cell cycle. These impairments may be the result of activation of the checkpoint kinases, which can mediate cell cycle arrest at both of these transitions. Conversely, because ethanol metabolism results in a number of biochemical changes, there may be a number of mechanisms by which ethanol metabolism impairs cellular replication. It is the goal of this article to review the mechanisms by which ethanol metabolism mediates impairment of hepatic replication.
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Affiliation(s)
- Dahn L Clemens
- Department of Internal Medicine, University of Nebraska Medical Center and Veterans Affairs Medical Center, Omaha Nebraska 68105, USA.
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185
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Caldwell SH, Patrie JT, Brunt EM, Redick JA, Davis CA, Park SH, Neuschwander-Tetri BA. The effects of 48 weeks of rosiglitazone on hepatocyte mitochondria in human nonalcoholic steatohepatitis. Hepatology 2007; 46:1101-7. [PMID: 17661371 DOI: 10.1002/hep.21813] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
UNLABELLED Rosiglitazone, a thiazolidinedione peroxisome proliferator-activated receptor gamma ligand, reduces disease activity in nonalcoholic steatohepatitis (NASH), a disease associated with hepatocyte mitochondrial crystalline inclusions that are not seen in animal models of NASH. In human and animal studies of adipose tissue, thiazolidinediones may induce mitochondrial biogenesis and associated morphological changes. To determine if rosiglitazone alters the hepatocyte mitochondrial morphology in human NASH, we prospectively and systematically examined liver biopsies from human subjects with NASH before and after 48 weeks of rosiglitazone by transmission electron microscopy. Twenty patients (body mass index = 34 +/- 7) were studied. Four coded sections from each of 20 pretherapy biopsies and each of 20 posttherapy biopsies were examined by transmission electron microscopy. The total hepatocyte mitochondria and crystal-containing mitochondria were counted, and semiquantitative scoring was performed for macrosteatosis, microsteatosis, dilated endoplasmic reticulum, apoptosis, Mallory bodies, and hepatocyte enlargement. The total mitochondria count was unchanged after therapy, but there was a significant increase in crystal-containing mitochondria from 4.0% (95% confidence interval = 1.8-8.8) to 7.2% (95% confidence interval = 3.9-12.6; odds ratio = 1.80; P = 0.04) after the treatment with rosiglitazone. Macrosteatosis (P < 0.001) and Mallory bodies (P = 0.05) significantly decreased, but no change was evident in microsteatosis, cellular enlargement, dilated endoplasmic reticulum, or apoptosis. CONCLUSION Rosiglitazone therapy of NASH is associated with increased crystalline inclusions in hepatocyte mitochondria. Whether these are adaptive or pathological remains unknown, and further studies are warranted to assess hepatic mitochondrial function during thiazolidinedione therapy for NASH.
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Affiliation(s)
- Stephen H Caldwell
- Gastrointestinal/Hepatology Division, Digestive Health Center of Excellence, University of Virginia, Charlottesville, VA 22908, USA.
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186
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Caldwell SH, Ikura Y, Iezzoni JC, Liu Z. Has natural selection in human populations produced two types of metabolic syndrome (with and without fatty liver)? J Gastroenterol Hepatol 2007; 22 Suppl 1:S11-9. [PMID: 17567458 DOI: 10.1111/j.1440-1746.2006.04639.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Fatty liver is closely related to the development of the insulin resistance syndrome that largely results from abnormal insulin signaling in three major organs: (i) skeletal muscle in which insulin sensitivity depends on fat content and metabolic activity (exercise); (ii) adipose tissue, which serves as a reservoir of energy in the form of triglycerides; and (iii) the liver, which variably serves as a source or storage site of carbohydrates and lipids. In many respects, the fatty liver resembles a mixture of brown adipose tissue (microvesicular steatosis) and white adipose tissue (macrovesicular steatosis) including the stages of fatty droplet accumulation, and the expression of uncoupling proteins and perilipin-like substances. Furthermore, the development of an inflammatory infiltrate and the increased production of cytokines as occurs in adipose tissue, suggest that the liver in some individuals serves as an extension of adipose tissue. Moreover, current evidence indicates that these morphological changes represent altered gene expression similar to that of adipocytes. However, fatty liver does not appear to be a uniform feature of the metabolic syndrome and there is substantial variation in humans in the development of fatty liver independent of insulin resistance. In this regard, the variable development of fatty liver in Palmipedes (migratory fowl) and its close relationship to skeletal muscle utilization of fatty acids, lipoprotein metabolism and thermoregulation are instructive. The predilection to non-alcoholic fatty liver disease among some varieties of Palmipedes suggests that the development of fatty liver represents an adaptive process, closely integrated with skeletal muscle fat utilization and adipose tissue distribution, and facilitates survival in a very cold, resource-scarce environment. Variation in human populations with metabolic syndrome likewise suggests that the trait evolved in populations exposed in ancient times to different environmental challenges and, because the liver plays a central role in lipid metabolism, the presence or absence of fatty liver is likely to be integrated with insulin sensitivity in other target organs and with lipoprotein metabolism.
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Affiliation(s)
- Stephen H Caldwell
- Division of GI/Hepatology, Digestive Health Center of Excellence, University of Virginia, Charlottesville, Virginia 22908-0708, USA.
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187
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Zhong Z, Theruvath TP, Currin RT, Waldmeier PC, Lemasters JJ. NIM811, a mitochondrial permeability transition inhibitor, prevents mitochondrial depolarization in small-for-size rat liver grafts. Am J Transplant 2007; 7:1103-11. [PMID: 17456198 DOI: 10.1111/j.1600-6143.2007.01770.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
ATP decreases markedly in small-for-size liver grafts. This study tested if the mitochondrial permeability transition (MPT) underlies dysfunction of small-for-size livers. Half-size livers were implanted into recipients of about twice the donor weight, resulting in quarter-size liver grafts. NIM811 (5 microM), a nonimmunosuppressive MPT inhibitor was added to the storage solutions. Mitochondrial polarization and cell death were assessed by confocal microscopy of rhodamine 123 (Rh123) and propidium iodide (PI), respectively. After quarter-size transplantation, alanine aminotransferase (ALT), serum bilirubin and necrosis all increased. NIM811 blocked these increases by >70%. After 38 h, BrdU labeling, a marker of cell proliferation and graft weight increase were 3% and 5%, respectively, which NIM811 increased to 30% and 42%. NIM811 also increased survival of quarter-size grafts. In sham-operated livers, hepatocytes exhibited punctate Rh123 fluorescence. By contrast, in quarter-size grafts at 18 h after implantation, mitochondria of most hepatocytes did not take up Rh123, indicating mitochondrial depolarization. Nearly all hepatocytes not taking up Rh123 continued to exclude PI at 18 h, indicating that depolarization preceded cell death. NIM811 and free radical-scavenging polyphenols strongly attenuated mitochondrial depolarization. In conclusion, mitochondria depolarized after quarter-size liver transplantation. NIM811 decreased injury and stimulated regeneration, probably by inhibiting free radical-dependent MPT onset.
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Affiliation(s)
- Z Zhong
- Department of Pharmaceutical Sciences, Medical University Department of South Carolina, Charleston, SC, USA.
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188
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Méndez-Sánchez N, Arrese M, Zamora-Valdés D, Uribe M. Current concepts in the pathogenesis of nonalcoholic fatty liver disease. Liver Int 2007; 27:423-33. [PMID: 17403181 DOI: 10.1111/j.1478-3231.2007.01483.x] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is an increasingly recognized cause of chronic liver disease, representing the leading cause of hepatology referral in some centres. However, its pathophysiology is not completely understood. Insulin resistance is one of the major mechanisms involved in disease prevalence and progression. Owing to the lack of an effective pharmacological therapy, recommendations on treatment are scarce and are based mainly on lifestyle changes, including diet and exercise. A review of the current literature on pathogenesis of NAFLD is presented in this article.
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Affiliation(s)
- Nahum Méndez-Sánchez
- Department of Biomedical Research, Gastroenterology & Liver Unit, Medica Sur Clinic & Foundation, Mexico City, Mexico.
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189
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Abstract
Nonalcoholic fatty liver disease (NAFLD) is an increasingly recognized medical condition that may progress to hepatic cirrhosis with liver failure. The pathologic picture resembles that of alcohol-induced liver injury, but it occurs in patients who do not abuse alcohol. NAFLD is more common among patients with evidence of insulin resistance. NAFLD refers to a wide spectrum of liver damage, ranging from simple steatosis to steatohepatitis, fibrosis, and cirrhosis. The clinical implications of NAFLD are derived mostly from its common occurrence in the general population, specifically in obese individuals, and its potential to progress to cirrhosis and liver failure. It is difficult to propose a treatment strategy for NAFLD because its pathogenesis is poorly understood; however, the most commonly associated clinical features of obesity, diabetes mellitus, lipid disorders, and hypertension deserve therapeutic interventions independent of NAFLD. It is also not known if and how treatment of these other conditions affects the natural history of NAFLD, particularly in the long term.
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Affiliation(s)
- Sherif Saadeh
- Division of Hepatology, 4 Roberts, Baylor University Medical Center, Dallas, TX 75246, USA.
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190
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Donthamsetty S, Bhave VS, Mitra MS, Latendresse JR, Mehendale HM. Nonalcoholic fatty liver sensitizes rats to carbon tetrachloride hepatotoxicity. Hepatology 2007; 45:391-403. [PMID: 17256749 DOI: 10.1002/hep.21530] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
UNLABELLED This study tested whether hepatic steatosis sensitizes liver to toxicant-induced injury and investigated the potential mechanisms of hepatotoxic sensitivity. Male Sprague-Dawley rats were fed a methionine- and choline-deficient diet for 31 days to induce steatosis. On the 32nd day, administration of a nonlethal dose of CCl4 (2 mL/kg, intraperitoneally) yielded 70% mortality in steatotic rats 12-72 hours after CCl4 administration, whereas all nonsteatotic rats survived. Neither CYP2E1 levels nor covalent binding of [14C] CCl4-derived radio-label differed between the groups, suggesting that increased bioactivation is not the mechanism for this amplified toxicity. Cell division and tissue repair, assessed by [3H]thymidine incorporation and proliferative cell nuclear antigen assay, were inhibited in the steatotic livers after CCl4 administration and led to progressive expansion of liver injury culminating in mortality. The hypothesis that fatty hepatocytes undergo cell cycle arrest due to (1) an inability to replenish ATP due to overexpressed uncoupling protein-2 (UCP-2) or (2) induction of growth inhibitor p21 leading to G1/S phase arrest was tested. Steatotic livers showed 10-fold lower ATP levels due to upregulated UCP-2 throughout the time course after CCl4 administration, leading to sustained inhibition of cell division. Western blot analysis revealed an up-regulation of p21 due to overexpression of TGF beta1 and p53 and down-regulation of transcription factor Foxm 1b in steatotic livers leading to lower phosphorylated retinoblastoma protein. Thus, fatty hepatocytes fail to undergo compensatory cell division, rendering the liver susceptible to progression of liver injury. CONCLUSION Impaired tissue repair sensitizes the steatotic livers to hepatotoxicity.
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Affiliation(s)
- Shashikiran Donthamsetty
- Department of Toxicology, College of Pharmacy, University of Louisiana at Monroe, Monroe, LA 71209-0495, USA
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191
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Abstract
Non-alcoholic fatty liver disease (NAFLD) has moved rapidly to the forefront of clinical disease, with a prevalence of 30% in the adult United States population and a definite but yet uncertain rate of progression to cirrhosis and end-stage liver disease. This disease has an impact on all areas of clinical medicine, with increasing prevalence and adversity. It is essential to understand the pathophysiologic mechanisms involved in NAFLD, so that therapeutic strategies can be developed. Although fatty liver may be caused by other factors, this review concentrates on fatty liver associated with insulin resistance, sometimes referred to as the primary form.
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Affiliation(s)
- John Edmison
- Department of Gastroenterology and Hepatology, Cleveland Clinic, Cleveland Clinic Lerner College of Medicine, Cleveland, OH 44195, USA
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192
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Beck V, Jabůrek M, Demina T, Rupprecht A, Porter RK, Jezek P, Pohl EE. Polyunsaturated fatty acids activate human uncoupling proteins 1 and 2 in planar lipid bilayers. FASEB J 2007; 21:1137-44. [PMID: 17242157 DOI: 10.1096/fj.06-7489com] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Uncoupling proteins 1 (UCP1) and 2 (UCP2) belong to the family of mitochondrial anion transporters and share 59% sequence identity with each other. Whereas UCP1 was shown to be responsible for the rapid production of heat in brown adipose tissue, the primary function and transport properties of ubiquitously expressed UCP2 are controversially discussed. Here, for the first time, the activation pattern of the recombinant human UCP2 in comparison to the recombinant human UCP1 are studied using a well-defined system of planar lipid bilayers. It is shown that despite apparently different physiological functions, hUCP2 exhibited its protonophoric function similar to hUCP1--exclusively in the presence of long-chain fatty acids (FA). The calculated hUCP2 transport rate of 4.5 s(-1) is the same order of magnitude, as shown previously for UCP1. It leads to the conclusion that the differences in the activity of both proteins in living mitochondria are based exclusively on their different expression level. Both proteins are activated much more effectively by polyunsaturated than by saturated FA. The proton and total membrane conductances increased in the range palmitic < oleic < eicosatrienoic < linoleic < retinoic < arachidonic acids. The higher uncoupling protein (UCP)-dependent conductance in the presence of polyunsaturated FA is explained on the basis of the FA cycling hypothesis.
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Affiliation(s)
- Valeri Beck
- Institute of Cell Biology and Neurobiology, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany
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193
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Abstract
OBJECTIVE To review present knowledge of the influence of hepatic steatosis in liver surgery as derived from experimental and clinical studies. SUMMARY BACKGROUND DATA Hepatic steatosis is the most common chronic liver disease in the Western world, and it is associated with obesity, diabetes, and metabolic syndrome. Fatty accumulation affects hepatocyte homeostasis and potentially impairs recovery of steatotic livers after resection. This is reflected clinically in increased mortality and morbidity after liver resection in patients with any grade of steatosis. Because of the epidemic increase of obesity, hepatic steatosis will play an even more significant role in liver surgery. METHODS A literature review was performed using MEDLINE and key words related to experimental and clinical studies concerning steatosis. RESULTS Experimental studies show the increased vulnerability of steatotic livers to various insults, attributed to underlying metabolic and pathologic derangements induced by fatty accumulation. In clinical studies, the severity of steatosis has an important impact on patient outcome and mortality. Even the mildest form of steatosis increases the risk of postoperative complications. CONCLUSIONS Hepatic steatosis is a major factor determining patient outcome after surgery. Further research is needed to clarify the clinical relevance of all forms and severity grades of steatosis for patient outcome. Standardized grading and diagnostic methods need to be used in future clinical trials to be able to compare outcomes of different studies.
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Affiliation(s)
- Reeta Veteläinen
- Department of Surgery, University of Amsterdam, Amsterdam, The Netherlands
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194
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O'Malley Y, Fink BD, Ross NC, Prisinzano TE, Sivitz WI. Reactive Oxygen and Targeted Antioxidant Administration in Endothelial Cell Mitochondria. J Biol Chem 2006; 281:39766-75. [PMID: 17060316 DOI: 10.1074/jbc.m608268200] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We used fluorescent probes and EPR to study the mechanism(s) underlying reactive oxygen species (ROS) production by endothelial cell mitochondria and the action of mitoquinol, a mitochondria-targeted antioxidant. ROS measured by fluorescence resulted from complex I superoxide released to the matrix and converted to H(2)O(2). In contrast, EPR largely detected superoxide generated at complex III and effluxed outward. ROS fluorescence by mitochondria fueled by the complex II substrate, succinate, was substantial but markedly inhibited by rotenone. Superoxide, detected by EPR, in succinate-fueled mitochondria was not inhibited by rotenone and likely derived from semiquinone formation at complex III. Mitoquinol decreased H(2)O(2) fluorescence by succinate-fueled mitochondria but had little effect on the EPR signal for superoxide. This was not associated with a detectable decrease in membrane potential. Mitoquinol markedly enhanced ROS fluorescence in mitochondria fueled by the complex I substrates, glutamate and malate. Inhibitor studies suggested that this occurred in complex I, at one or more Q binding pockets. The above effects of mitoquinol were determined in mitochondria isolated and subsequently exposed to the targeted antioxidant. However, similar effects were observed in mitochondria after antecedent exposure to mitoquinol/mitoquinone in culture, suggesting that the agent is retained after isolation of the organelles. In conclusion, ROS production in bovine aortic endothelial cell mitochondria results largely from reverse transport to complex I and through the Q cycle in complex III. Mitoquinol blocks ROS from reverse electron transport but increases superoxide production derived from forward transport. These effects likely occur at one or more Q binding sites in complex I.
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Affiliation(s)
- Yunxia O'Malley
- Department of Internal Medicine, Division of Endocrinology and Metabolism, Iowa City Veterans Affairs Medical Center and the University of Iowa, Iowa City, Iowa 52242, USA
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195
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Leclercq IA, Vansteenberghe M, Lebrun VB, VanHul NK, Abarca-Quinones J, Sempoux CL, Picard C, Stärkel P, Horsmans YL. Defective hepatic regeneration after partial hepatectomy in leptin-deficient mice is not rescued by exogenous leptin. J Transl Med 2006; 86:1161-71. [PMID: 16983330 DOI: 10.1038/labinvest.3700474] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Liver regeneration after partial hepatectomy (PH) is impaired in leptin-deficient ob/ob mice. Here, we tested whether exogenous leptin and/or correction of the obese phenotype (by food restriction or long-term leptin administration) would rescue hepatocyte proliferation and whether the hepatic progenitor cell compartment was activated in leptin-deficient ob/ob livers after PH. Because of the high mortality following 70% PH to ob/ob mice, we performed a less extensive (55%) resection. Compared to lean mice, liver regeneration after 55% PH was deeply impaired and delayed in ob/ob mice. Administration of exogenous leptin to ob/ob mice at doses that restored circulating leptin levels during the surgery and postsurgery period or for 3 weeks prior to the surgical procedure did not rescue defective liver regeneration. Moreover, correction of obesity, metabolic syndrome and hepatic steatosis by prolonged administration of leptin or food restriction (with or without leptin replacement at the time of PH) did not improve liver regeneration in ob/ob mice. The hepatic progenitor cell compartment was increased in ob/ob mice. However, after PH, the number of progenitor cells decreased and signs of proliferation were absent from this cell compartment. In this study, we have conclusively shown that neither leptin replacement nor amelioration of the metabolic syndrome, obese phenotype and hepatic steatosis, with or without restitution of normal circulating levels of leptin, was able to restore replicative competence to ob/ob livers after PH. Thus, leptin does not directly signal to liver cells to promote hepatocyte proliferation, and the obese phenotype is not solely responsible for impaired regeneration.
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Affiliation(s)
- Isabelle A Leclercq
- Laboratory of Gastroenterology, Faculty of Medicine, Université Catholique de Louvain, Brussels, Belgium.
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196
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Fülöp P, Derdák Z, Sheets A, Sabo E, Berthiaume EP, Resnick MB, Wands JR, Paragh G, Baffy G. Lack of UCP2 reduces Fas-mediated liver injury in ob/ob mice and reveals importance of cell-specific UCP2 expression. Hepatology 2006; 44:592-601. [PMID: 16941708 DOI: 10.1002/hep.21310] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Fatty liver is vulnerable to conditions that challenge hepatocellular energy homeostasis. Lipid-laden hepatocytes highly express uncoupling protein-2 (UCP2), a mitochondrial carrier that competes with adenosine triphosphate (ATP) synthesis by mediating proton leak. However, evidence for a link between UCP2 expression and susceptibility of liver to acute injury is lacking. We asked whether absence of UCP2 protects ob/ob mice from Fas-mediated acute liver damage. UCP2-deficient ob/ob mice (ob/ob:ucp2-/-) and UCP2-competent littermates (ob/ob:ucp2+/+) received a single dose of agonistic anti-Fas antibody (Jo2). Low-dose Jo2 (0.15 mg/kg intraperitoneally) caused less serum alanine aminotransferase (ALT) elevation and lower apoptosis rates in ob/ob:ucp2-/- mice. High-dose Jo2 (0.40 mg/kg intraperitoneally) proved uniformly fatal; however, ob/ob:ucp2-/- mice survived longer with less depletion of liver ATP stores, indicating that fatty hepatocytes may benefit from lack of UCP2 during Jo2 challenge. Although UCP2 reportedly controls mitochondrial oxidant production, its absence had no apparent effect on fatty liver tissue malondialdehyde levels augmented by Jo2. This finding prompted us to determine UCP2 expression in Kupffer cells, a major source of intrahepatic oxidative stress. UCP2 expression was found diminished in Kupffer cells of untreated ob/ob:ucp2+/+ mice, conceivably contributing to increased oxidative stress in fatty liver and limiting the impact of UCP2 ablation. In conclusion, whereas UCP2 abundance in fatty hepatocytes exacerbates Fas-mediated injury by compromising ATP stores, downregulation of UCP2 in Kupffer cells may account for persistent oxidative stress in fatty liver. Our data support a cell-specific approach when considering the therapeutic effects of mitochondrial uncoupling in fatty liver disease.
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Affiliation(s)
- Péter Fülöp
- Division of Gastroenterology & Liver Research Center, Brown Medical School and Rhode Island Hospital, Providence, Rhode Island 02903, USA
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197
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Tilg H, Hotamisligil GS. Nonalcoholic fatty liver disease: Cytokine-adipokine interplay and regulation of insulin resistance. Gastroenterology 2006; 131:934-45. [PMID: 16952562 DOI: 10.1053/j.gastro.2006.05.054] [Citation(s) in RCA: 252] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Accepted: 05/11/2006] [Indexed: 02/06/2023]
Affiliation(s)
- Herbert Tilg
- Department of Medicine, Christian Doppler Laboratory for Gut Inflammation and Clinical Division of Gastroenterology and Hepatology, Innsbruck Medical University, Innsbruck, Austria.
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198
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Casillas-Ramírez A, Mosbah IB, Franco-Gou R, Rimola A, Roselló-Catafau J, Peralta C. [Ischemia-reperfusion syndrome associated with liver transplantation: an update]. GASTROENTEROLOGIA Y HEPATOLOGIA 2006; 29:306-13. [PMID: 16733038 DOI: 10.1157/13087472] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ischemia-reperfusion (I/R) injury is the main cause of both initial graft dysfunction and primary failure in liver transplantation. The search for therapeutic strategies to prevent I/R injury has led to research into promising drugs, although most have not been used clinically. Gene therapy requires better transfection techniques, avoiding vector toxicity, and ethical debate before being used clinically. Ischemic preconditioning is the first therapeutic strategy used in clinical practice to reduce I/R injury in hepatectomies for tumors. Future research will provide data on the effectiveness of ischemic preconditioning in reducing I/R injury associated with liver transplantation, and in reducing the vulnerability of steatotic grafts to I/R syndrome so that they can be used in transplantation, thus relieving the organ shortage.
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Affiliation(s)
- A Casillas-Ramírez
- Unidad de Hepatología Experimental, Instituto de Investigaciones Biomédicas de Barcelona, CSIC-IDIBAPS, Barcelona, España
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199
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Casillas-Ramírez A, Mosbah IB, Ramalho F, Roselló-Catafau J, Peralta C. Past and future approaches to ischemia-reperfusion lesion associated with liver transplantation. Life Sci 2006; 79:1881-94. [PMID: 16828807 DOI: 10.1016/j.lfs.2006.06.024] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Revised: 05/19/2006] [Accepted: 06/08/2006] [Indexed: 02/06/2023]
Abstract
Ischemia-reperfusion (I/R) injury associated with liver transplantation remains a serious complication in clinical practice, in spite of several attempts to solve the problem. The present review focuses on the complexity of I/R injury, summarizing conflicting results obtained from the literature about the mechanisms responsible for it. We also review the therapeutic strategies designed in past years to reduce I/R injury, attempting to explain why most of them have not been applied clinically. These strategies include improvements in pharmacological treatments, modifications of University of Wisconsin (UW) preservation solution based on a variety of additives, and gene therapy. Finally, we will consider new potential protective strategies using trimetazidine, 5-amino-4-imidazole carboxamide riboside (AICAR), melatonin, modulators of the renin-angiotensin system (RAS) and the phosphatidylinositol-3-OH kinase (PI3K)-Akt and the p42/p44 extracellular signal-regulated kinases (Erk 1/2) pathway. These strategies have shown promising results for I/R injury but have not been tested in experimental liver transplantation to date. Moreover, we will review ischemic preconditioning, taking into account the recent clinical studies that suggest that this surgical strategy could be appropriate for liver transplantation.
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Affiliation(s)
- Araní Casillas-Ramírez
- Experimental Liver Ischemia-Reperfusion Unit, Instituto de Investigaciones Biomédicas de Barcelona August Pi i Sunyer, Experimental Hepatology, IIBB-CSIC, C/ Rosellón 161, 7th floors, 08036-Barcelona, Spain
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200
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Sluse FE, Jarmuszkiewicz W, Navet R, Douette P, Mathy G, Sluse-Goffart CM. Mitochondrial UCPs: New insights into regulation and impact. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:480-5. [PMID: 16597432 DOI: 10.1016/j.bbabio.2006.02.004] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Revised: 01/24/2006] [Accepted: 02/10/2006] [Indexed: 10/24/2022]
Abstract
Uncoupling proteins (UCPs) are mitochondrial inner membrane proteins sustaining an inducible proton conductance. They weaken the proton electrochemical gradient built up by the mitochondrial respiratory chain. Brown fat UCP1 sustains a free fatty acid (FA)-induced purine nucleotide (PN)-inhibited proton conductance. Inhibition of the proton conductance by PN has been considered as a diagnostic of UCP activity. However, conflicting results have been obtained in isolated mitochondria for UCP homologues (i.e., UCP2, UCP3, plant UCP, and protist UCP) where the FFA-activated proton conductance is poorly sensitive to PN under resting respiration conditions. Our recent work clearly indicates that the membranous coenzyme Q, through its redox state, represents a regulator of the inhibition by PN of FFA-activated UCP1 homologues under phosphorylating respiration conditions. Several physiological roles of UCPs have been suggested, including a control of the cellular energy balance as well as the preventive action against oxidative stress. In this paper, we discuss new information emerging from comparative proteomics about the impact of UCPs on mitochondrial physiology, when recombinant UCP1 is expressed in yeast and when UCP2 is over-expressed in hepatic mitochondria during steatosis.
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Affiliation(s)
- Francis E Sluse
- Laboratory of Bioenergetics, Department of Life Sciences, Institute of Chemistry B6c, University of Liège, Sart Tilman, B-4000 Liege, Belgium.
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