A doença hepática gordurosa não alcoólica (DHGNA) tornou-se a hepatopatia crônica mais comum no mundo, afetando principalmente alguns grupos de pacientes, como os diabéticos tipo II. A biópsia hepática permanece como método padrão ouro para o seu diagnóstico. A prevalência da DHGNA e seus subtipos, em especial a esteatohepatite (EH), pode estar subestimada por métodos não invasivos de diagnóstico ou superestimada pela realização da biópsia em pacientes selecionados por alterações na ultrassonografia (US) ou nas aminotransferases. Os objetivos deste estudo foram: determinar a prevalência da DHGNA (esteatose, EH e cirrose) em uma amostra de pacientes diabéticos tipo II, com base na biópsia hepática; quantificar a esteatose, inflamação e fibrose quando presentes; identificar fatores preditivos de DHGNA, EH e fibrose significativa (&#8805; estágio 2) e avaliar o valor das aminotransferases e da US de abdome para o diagnóstico de EH e fibrose significativa. Todos os diabéticos tipo II, entre 18 e 70 anos, consecutivamente atendidos no ambulatório de Diabetes do Hospital Universitário Pedro Ernesto, eram candidatos a participar do estudo. Foram excluídos pacientes com sorologias positivas para hepatite B ou C, outras doenças hepáticas crônicas, uso de drogas hepatotóxicas ou esteatogênicas, etilismo (&#8805;20g/dia), obesidade grau III, comorbidades graves, gravidez ou por recusa em participar do estudo. Dos 396 pacientes triados com critérios de inclusão, 85 foram incluídos. Todos os pacientes foram submetidos à avaliação clínica, exames laboratoriais, US de abdome e biópsia hepática. As lâminas foram analisadas por dois patologistas independentes e a DHGNA foi graduada pelo NASH Clinical Research Network Scoring System. A concordância entre os patologistas foi medida pelo coeficiente Kappa (k) e foi realizada análise multivariada por regressão logística para avaliação dos fatores associados de forma independente à DHGNA, EH e fibrose significativa. A prevalência de DHGNA na amostra foi de 92%, sendo 50% esteatose simples, 40% EH e 2% cirrose. A concordância (k) entre os patologistas foi 0,78. A esteatose foi leve na maior parte dos pacientes com esteatose simples e predominantemente acentuada nos pacientes com EH (p<0,001). A fibrose foi verificada em 76% dos pacientes com EH, sendo significativa em 41% deles. A presença de síndrome metabólica foi associada de forma independente à DHGNA, o índice de massa corporal e a circunferência abdominal aumentada à EH e a dosagem de alanina aminotransferase (ALT) à EH e à fibrose significativa. Apenas um de 21 pacientes (5%) com US e ALT normais apresentou EH. A prevalência da EH aumentou progressivamente com o aumento do grau de esteatose na US e com o aumento da ALT. Conclusão: A prevalência da DHGNA estimada pela biópsia hepática sem vieses de seleção foi muito elevada. Apesar de alto, o percentual de EH e fibrose significativa foi inferior ao dos estudos com biópsias em diabéticos selecionados por alterações na US e aminotransferases. EH foi associada a esteatose acentuada na histologia. A obesidade foi um cofator importante no diagnóstico de EH. O melhor desempenho da ALT e da US foi o de excluir as formas graves de DHGNA quando normais. / Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide, especially in some groups of patients, as type II diabetic. Liver biopsy remains the gold standard method for diagnosis of the disease. Current prevalences of NAFLD and its subtypes, as steatohepatitis (NASH), can be underestimated due to the non invasive tests for diagnosis or overestimated due to liver biopsy in patients selected by changes in ultrasonography (US) or aminotransferases. The objectives of this study were: define the prevalence of NAFLD (bland steatosis, NASH and cirrhosis) in type II diabetic patients, based on liver biopsy; quantify steatosis, inflammation and fibrosis when present; identify predictive factors of NAFLD, NASH and significant fibrosis (&#8805; stage 2) and analyse the value of aminotransferases and abdominal US for diagnosis of NASH and significant fibrosis. All type II diabetic patients, from 18 to 70 years, consecutively evaluated in the outpatient Clinic of Diabetes Mellitus of a terciary care University Hospital, were considered for enrollment. Patients were excluded if they had positive serology for hepatitis B or C, other chronic liver diseases, used medications associated with steatosis or hepatotoxic drugs, consumed &#8805; 20g alcohol per day, had other serious diseases, grade III obesity, were pregnant or declined participation. From 396 patients evaluated, 85 were included. Patients were submitted to clinical and laboratory examinations, abdominal US and liver biopsy. The slides were analysed by two independent pathologists and graded according to NASH Clinical Research Network Scoring System. Agreement between pathologists was accessed by kappa coefficients (k) and factors independently associated to NAFLD, NASH and significant fibrosis by multivariate logistic regression. Prevalence of NAFLD was 92%, being 50% bland steatosis, 40% NASH and 2% cirrhosis. Agreement between pathologists (k) was 0,78. Steatosis was mild in the majority of patients with bland steatosis and mostly severe in NASH patients (p<0,001). Fibrosis occurred in 76% of NASH patients, being significant in 41% of them. Metabolic syndrome was independently associated to NAFLD, body mass index and increased waist circumference to NASH and alanine aminotransferase (ALT) to NASH and significant fibrosis. Metabolic syndrome was independently associated to NAFLD; body mass index and increased waist circumference were associated to NASH; and ALT was associated to NASH and significant fibrosis. Only one from 21 patients (5%) with normal US and ALT had NASH. The prevalence of NASH progressively increased as the steatosis grade on US and the liver enzymes got worse. Conclusion: Prevalence of NAFLD estimated by liver biopsy in T2DM patients without selection bias was very high. Although elevated, prevalence of NASH and significant fibrosis were lower than defined by studies with biopsies in patients with changes in US or aminotransferases. NASH was associated to severe steatosis on histology. Obesity was an important factor in NASH diagnosis. The best performance of ALT and US was in exclude severe subtypes of NAFLD when normal.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-01-29T18:04:49Z No. of bitstreams: 0 / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-03-21T19:28:36Z (GMT) No. of bitstreams: 0 / Made available in DSpace on 2018-03-21T19:28:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-08-24 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / A esteatohepatite não alcoólica (EHNA) é uma manifestação da síndrome metabólica e distúrbios hepáticos, caracterizada por esteatose, inflamação lobular, hepatócitos edemaciados e citoplasma rarefeitos (balonização) e, em alguns casos, fibrose, que pode evoluir para a cirrose e carcinoma. A progressão da EHNA também está intimamente relacionada à resistência à insulina, quanto ao estresse oxidativo. A ingestão dietética de antioxidantes tem sido sugerida em proteção contra dano oxidativo e complicações clínicas relacionadas. A capacidade antioxidante total da dieta (CATd) é considerada uma ferramenta útil para avaliar o potencial antioxidante da alimentação, e não há nenhum estudo, atualmente, que examine a relação da CATd com a EHNA. O objetivo deste estudo foi avaliar a potencial associação da capacidade antioxidante total da dieta com severidade em pacientes com EHNA, bem como com composição antropométrica e marcadores corporal e parâmetros bioquímicos. Foram avaliados trinta e três pacientes com idade média de 48,4 ± 11,0 anos. Gravidade de EHNA, características de estilo de vida, ocorrência de comorbidades, ingestão dietética, antropometria, composição corporal e parâmetros bioquímicos foram avaliados. Observou-se que 24,2% (n=25) eram diabéticos tipo 2, 48,5% (n=17) possuíam hipertensão arterial sistêmica e 84,8% (n=28) eram dislipidêmicos. Em relação à obesidade, 81,8% (n=27) apresentavam obesidade central de risco e 84,8% apresentavam excesso de peso de acordo com o índice de massa corporal. A presença de síndrome metabólica foi notada em 54,5% (n=18) dos participantes. Os pacientes com EHNA que tiveram uma maior CAT dietética tiveram menos lesões nos hepatócitos (balonização) em comparação com aqueles com menor CATd (p = 0,034). Os pacientes com CAT dietético mais elevado teve uma redução de aproximadamente 20% no risco de ter muitos hepatócitos balonizados (odds ratio [OR]: 0.791; 95% intervalo de confiança [IC]: 0.643-0,974, p = 0,027). Não houve associação entre esteatose, inflamação lobular e fibrose com CAT dietético. O mesmo ocorreu com características de estilo de vida, ocorrência de comorbidades, antropometria, composição corporal e parâmetros bioquímicos. Conclui-se que CAT dietético é maior em pacientes com lesão hepática inferior (balonismo), sugerindo um possível papel de ingestão naturalmente alta de alimentos em sua capacidade antioxidante em reduzindo a produção de radicais livres e, consequentemente, o estresse oxidativo. / Nonalcoholic steatohepatitis (NASH) is a manifestation of the metabolic syndrome and hepatic disorders, characterized by steatosis, lobular inflammation, edema and rarefied cytoplasm (balonization) and, in some cases, fibrosis, which can progress to cirrhosis and carcinoma. The progression of NASH is also closely related to insulin resistance in relation to oxidative stress. Dietary intake of antioxidants has been suggested in protection against oxidative damage and related clinical complications. The total antioxidant capacity of the diet (CATd) is considered a useful tool to evaluate the antioxidant potential of the diet, and there is currently no study examining the relationship of CATd with NASH. The objective of this study was to evaluate the potential association of total antioxidant capacity of the diet with severity in patients with NASH, as well as with anthropometric composition and body markers and biochemical parameters. Thirty-three patients with a mean age of 48.4 ± 11.0 years were evaluated. EHNA severity, lifestyle characteristics, occurrence of comorbidities, dietary intake, anthropometry, body composition and biochemical parameters were evaluated. It was observed that 24.2% (n = 25) were diabetic type 2, 48.5% (n = 17) had systemic arterial hypertension and 84.8% (n = 28) were dyslipidemic. Regarding obesity, 81.8% (n = 27) had central obesity at risk and 84.8% were overweight according to the body mass index. The presence of metabolic syndrome was noted in 54.5% (n = 18) of the participants. Patients with NASH who had a higher dietary CAT had fewer hepatocyte (balloon) lesions compared to those with lower CATd (p = 0.034). Patients with higher dietary CAT had an approximately 20% reduction in the risk of having many balloonized hepatocytes (odds ratio [OR]: 0.791; 95% confidence interval [CI]: 0.643-0.974, p = 0.027). There was no association between steatosis, lobular inflammation and fibrosis with dietary CAT. The same occurred with characteristics of life style, occurrence of comorbidities, anthropometry, body composition and biochemical parameters. It is concluded that dietary CAT is greater in patients with lower hepatic injury (balloonism), suggesting a possible role of naturally high food intake in its antioxidant capacity in reducing the production of free radicals and, consequently, oxidative stress.

Background: Obesity has become one of our times most endemic disease on a global scale and changes to lifestyle is the most cost-effective way to treat patients, when the cost for healthcare related treatment is staggeringly high for obesity and sequela diseases NAFLD, diabetes typ 2, dyslipidaemia and metabolic syndrome.The problem with this remedy is that it requires work and dedication. But changes require hard work, and in this patient group- low compliance, weight gain after treatment, dropping out of programs and small desire to change are the most common problems. Motivational studies report that readiness in obese patients is low and the best way to help patients to move forward is by motivational conversations. The obesity sequela disease NAFLD is an asymptomatic disease it displays no symptoms until very late stages. Therefore it’s a problem to get patients make the patient understand his illness and the seriousness of it. Aim: This literature work was aimed at investigating compliance in lifestyle changes in obese subject and to see if close contact with healthcare staff affected the achieved results. Method: In this literature study, the databases Pubmed, Science Direct, Medline and Sportdiscus were used to find information. Article inclusion criteria were that the articles were not older than 10 years and were in English. Result: Frequent and regular contacts between participants and professional staff provided good results both with regard to weight loss, biochemical response, and the participants' willingness to change. Also it shows that return visits at least every three months will improve weight loss if the participant is motivated to implement a change to lifestyle. Conclusion: Overall, this literature study shows the difficulties with lifestyle changes in people with obesity and sequela NAFLD. Close contacts of the patients with healthcare staff has proven to have a positive impact on treatment compliance, but there are other lifestyle difficulties in these patient groups which hamper compliance.

La stéatohépatite non alcoolique (NASH) est une maladie du foie à évolution clinique grave, dont la prévalence est en constante progression. La stéatohépatite non alcoolique est caractérisée par un dépôt excessif de lipides dans les hépatocytes (stéatose) associé à une inflammation chronique, au contraire de la stéatose hépatique (NAFLD), manifestation initiale mais bénigne d'un dérèglement métabolique. Le NASH augmente le risque de progression vers la fibrose, la cirrhose et le carcinome hépatocellulaire et ne peut être soigné que par une greffe hépatique. Le risque de développer un diabète de type est aussi significativement augmenté chez les patients atteints de NASH. PPAR⍺ est un récepteur nucléaire connu pour réguler l'utilisation des acides gras dans le foie et réprimer les voies de signalisation pro-inflammatoires. [...]Nous avons conçu mutant de PPAR⍺ dont l'activité de liaison à l'ADN est abolie. La comparaison de ses activités transcriptionnelles in vitro avec le PPAR⍺ non muté démontre que les activités de contrôle du métabolisme sont abolies pour ce mutant, alors que les activités anti-inflammatoires restent intactes. [...] Dans cette étude, nous montrons donc pour la première fois que PPAR⍺ inhibe la progression de la stéatose vers le NASH et la fibrose par un mécanisme anti-inflammatoire direct, indépendant de son effet sur le métabolisme lipidique hépatique. / Non-alcoholic fatty liver disease (NAFLD) is an increasingly prevalent liver condition characterized by excessive lipid deposition in the hepatocytes steatohepatitis (NASH) is hallamarked by chronic inflammation. NASH markedly increases the risk of progression towards liver fibrosis, cirrhosis ans hepatocellular carcinoma. The nuclear peroxisome proliferator-activated receptor alpha (PPAR⍺) regulates hepatic fatty acid utilization and represses pro-inflammatory signaling pathways. [...]Liver-specific expression of wild type or DNA binding-deficient PPAR⍺ in acute and chronic models of inflammation demonstrated that PPAR's anti-inflammatory, but not metabolic activities, result from DNA binding-independent mechanisms in vivo. We futher show that PPAR⍺ inhits the transition from steatosis toward NASH and fibrosis through a direct, anti-inflammatory mechanism independent of its effetc on hepatic lipid metabolism.

Le pregnane X receptor (PXR) est un récepteur nucléaire associé à la réponse au stresscellulaire. Des travaux in vitro de notre groupe ont démontré que les activateurs de cerécepteur (spironolactone (SPIR), clotrimazole (CTZ)) inhibent significativement l’apoptosespontanée ou induite, dans des primo-cultures d’hépatocytes de rat ou d’origine humaine.Les données in vitro sont en faveur d’un rôle clé du PXR dans la protection hépatique contreles xénobiotiques et endobiotiques en régulant de façon concertée leur détoxication(transport, métabolisme) et en augmentant leur résistance à l’apoptose. D’autres travauxrécents ont démontré le rôle majeur de ce récepteur dans la régulation de l’homéostasielipidique et glucidique, d’une part en favorisant la lipogenèse, d’autre part inhibant la lipolyseet la néoglucogenèse. L’induction du PXR peut être responsable de l’accumulation de lipidesdans le foie (NAFLD non alcoholic fatty liver disease). La NAFLD est fortement associée àl’obésité. La chirurgie bariatrique est à ce jour le seul traitement efficace à long terme pourl’obésité morbide. L’évolution des lésions hépatiques de la NAFLD après chirurgiebariatrique n’est pas complètement élucidée. L’objectif de ce travail de thèse, a été d’analyser si, in vivo, les agonistes du PXR tels que le CTZ et la SPIR, présentaient chez l’animal les mêmes effets que ceux décrits in vitro, et s’ilspouvaient conduire à une protection similaire du foie, lors d’atteintes pathologiques commeles lésions hépatiques induites par l’ischémie reperfusion. Dans un autre chapitre les effetsde deux procédures bariatriques, le court circuit gastrique (gastric bypass- GBP) et lagastrectomie en gouttière (sleeve gastrectomy- SG), sur le comorbiditées liées à la obésitéont été analysés. Le modèle d’ischémie reperfusion normothermique partielle et totale du foie chez le rongeur(rat et souris) a été utilisé pour étudier le rôle protecteur du PXR contre les lésionsapoptotiques. Les effets du court circuit gastrique sur les comorbiditées associées à l’obésitéont été étudiés dans deux groupes de patients obèses (index de masse corporelle > 50Kg/m2 et < 50 Kg/m2). Les résultats du GBP et de la SG ont été étudiés dans deux groupescomparables de sujets super obèses (IMC > 50 Kg/m2).Résultats 1/ Le traitement par les activateurs du PXR (CTZ et SPIR), chez le rat et chezla souris, provoque l’induction d’expression du CYP 3A1, enzyme sous le contrôle du PXR. Ilest associé à une réduction significative du nombre d’hépatocytes apoptotiques, du niveaudes transaminases, de la caspases activée et de son substrat PARP (poly-ADP-ribosepolymérase).Les mécanismes impliqués comprennent l’induction d’expression de la protéineantiapoptotique Bcl-xL, l’activation de la voie MAP kinase ERK ½, l’inhibition de l’activationde JNK et la sous-expression des heat schock proteins 27, 70, et 90, dans le cas del’ischémie complète du foie. 2/ Un an après l’intervention bariatique, le GBP a montré uneefficacité comparable sur la réversibilité du syndrome métabolique, de l’inflammationsystémique et l’insulino résistance chez les femmes super-obèses et obèses morbides,même si l’IMC moyen des patientes super obèses est resté significativement plus élevé. LeGBP et la SG conduisent à des résultats comparables, 6 mois après la chirurgie, mais lepremier est significativement plus efficace en termes d’amélioration du profil lipidique,d’inflammation à bas grade et de syndrome métabolique.L’activation du PXR est associée à un effet de protection hépatique contre les lésionsd’ischémie reperfusion. Le GBP est efficace sur les comorbiditées chez le super obèseautant que chez l’obèse morbide. ll donne également de meilleurs résultats à un an, sur laperte de poids, l’inflammation systémique et la régression du syndrome métabolique. / The pregnane X receptor (PXR) is a nuclear receptor associated with cellularresponse to xeno and endobiotics. Recently, the involvement of PXR in controlling otherfunctions has been clarified. We previously showed in our laboratory that the PXR activators(spironolactone (SPIR) and clotrimazole (CTZ) protect primoculture of human or rathépatocytes against apoptosis. In vitro data are indicate that the PXR plays a major role inthe protection of the liver against xeno and endobiotics trough the régulation of theirélimination (détoxication) and increasing their resistance against apoptosis. It has also beenshown that the PXR is implicated in the controls of lipid and carbohydrates metabolism. Theinduction of PXR increases lipogenesis, inhibits lipolysis and neoglucogenesis. PXRinduction may be responsible for the accumulations of lipids into the liver (NAFLD, nonalcoholic liver disease). This disease is strongly associated with obesity. To date bariatricsurgery is only effective treatment in the long term for morbid obesity. The evolution ofNAFLD following bariatric surgery has not been fully clarified.Aims The aims of this thesis were to ascertain whether PXR agonists such as CTZ andSPIR resulted in the same effects in the animal model than those observed in vitro andwhether the administration of these drugs was associated with any protection againstnormothermic ischemia reperfusion injury of the liver. In another chapter the effects onobesity related comorbidities of two bariatric procedures such as the gastric bypass and thesleeve gastrectomy were investigated. The animal model used to investigate the role of PXR against apoptosis wasthe partial and total normothermic ischemia reperfusion of the liver in the rodent (rat andmouse). The effects of the GBP and SG on obesity related comorbidities wereinvestigated in two groups of obese women (BMI > 50 Kg/m2 and < 50kg/m2). The results ofGBP and SG in two comparable groups of super obese patients (BMI > 50 Kg/m2) wereinvestigated. Treatment with PXR activators such as (CTZ and SPIR) in the rat and in themouse was associated with the induction of CYP 3A1, an enzyme directly controlled by thePXR, with a significant reduction of the apoptotic hepatocytes, with a significantly lowerlevels of transaminases, activated caspase 3 and its substrate PARP (poly-ADP-ribosepolymérase).The involved mécanismes include the induction of the expression of theantiapoptotic protein Bcl-xL, the activation of the extracellular regulated kinase (ERK ½), theinhibition of JNK and the down régulation of heat shock proteins (hsp 27, 70, and 90) geneexpression in the case of total liver ischemia. One year after surgery GBP showedcomparable results in terms of résolution of metabolic syndrome, systemic inflammation andinsuline resistance in morbdly obese as well as super obese women even if the mean BMI ofsuper obese women remained higher (34.7 Kg/m2 vs 28.1 Kg/m2). GBP and SG areassociated with the same results six months after surgery but GBP is more effective inimproving lipid disturbances, low-grade systemic inflammation and the metabolic syndromeat one year. PXR induction results in a protective effect against normothermic inschemiareperfusion injury in the rodent. Results of GBP in terms of resolution of obesity relatedcomorbidities are comparable in the super obese and morbidly patients. GBP is moreeffective than SG one year after surgery in terms of weight loss, and resolution of lipiddisturbances, low-grade systemic inflammation and metabolic syndrome.

La pandémie de l'obésité entraine une augmentation de la prévalence des maladies chroniques du foie ou stéatopathies métaboliques (NAFLD). Le spectre des NAFLD va de la stéatose caractérisée par une accumulation de lipides dans le foie à la stéatohépatite (NASH) associant une inflammation, de la mort hépatocytaire et de la fibrose. Lors de l'obésité, l'élévation de signaux de dangers métaboliques perturbe les fonctions du réticulum endoplasmique (RE) essentielles pour l’homéostasie cellulaire. Les perturbations sont transmises par 3 senseurs : IRE1α, ATF6 et PERK pour activer une réponse adaptative. Si ce stress est sévère ou devient chronique, la cellule enclenchera une réponse terminale apoptotique. La protéine Bax Inhibitor-1 (BI-1) pourrait jouer un rôle hépatoprotecteur en inhibant l’hyperactivation de la voie de signalisation IRE1α.En combinant des études chez l’homme et dans des modèles animaux, l’objectif de cette étude était de mieux caractériser l'activation chronique du stress du RE dans les NAFLD. Ce travail a émis l’hypothèse qu’une déficience en BI-1 entrainerait l’activation soutenue de la voie IRE1α qui serait responsable de la transition de la stéatose à la NASH. Cette étude s'intéresse au dialogue potentiel entre le stress du RE et l’activation de l'inflammasome NLRP3, qui induit la sécrétion des cytokines pro-inflammatoires (IL-1β, IL-18) grâce aux caspases pro-inflammatoires (caspase-1, caspase-4/11). L’utilisation d’un inhibiteur global du stress du RE ou des inhibiteurs pharmacologiques spécifiques à la voie IRE1α améliorerait les caractéristiques pathophysiologiques de la NASH et pourrait ouvrir de nouvelles perspectives thérapeutiques. / Due to the obesity pandemic, the last decades have been marked by a constantly increasing prevalence of Non-Alcoholic Fatty Liver Disease (NAFLD). NAFLD covers a spectrum of hepatic disorders ranging from steatosis, characterized by the ectopic accumulation of lipids in the liver, to steatohepatitis (NASH), featuring inflammation, hepatocellular death and fibrosis. During obesity, an increase in metabolic danger signals leads to disrupted endoplasmic reticulum (ER) function, essential for cellular homeostasis. The resulting ER stress activates a signaling network involving three sensors: IRE1α, ATF6 and PERK to enforce adaptive programs. If this stress is severe or becomes chronic, the cell will trigger a terminal apoptotic response. The protein Bax Inhibitor-1 (BI-1), as a negative endogenous regulator of the IRE1α signaling pathway in the liver, may play a hepatoprotective role.By combining data from obese patients with liver complications and experimental approaches in mice, this thesis aimed to better characterize the chronic activation of ER stress in NAFLD pathogenesis. This work also emitted the hypothesis that a deficiency in BI-1 leads to unrestrained IRE1α signaling that may be responsible for the steatosis to NASH transition. This study further investigated the potential dialogue between ER stress and the activation the NLRP3 inflammasome, which induces the secretion of pro-inflammatory cytokines (IL-1β, IL-18) by activating pro-inflammatory caspases (caspase-1, caspase-4/11). The administration of a broad spectrum ER stress inhibitor or specific inhibitors of IRE1α improved the pathophysiological features of NASH and may open novel therapeutic perspectives.

京都大学 / 新制・論文博士 / 博士(医学) / 乙第13398号 / 論医博第2222号 / 新制||医||1051(附属図書館) / (主査)教授 妹尾 浩, 教授 中山 健夫, 教授 西浦 博 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

Indiana University-Purdue University Indianapolis (IUPUI) / Non-alcoholic steatohepatitis (NASH), which is characterized by the induction of hepatocellular death and inflammation, is associated with the activation of cellular stress pathways such as the Unfolded Protein Response (UPR), an adaptive response to disruptions in endoplasmic reticulum (ER) homeostasis. Because the role of the UPR in the progression of liver disease is not well understood, we established an in vitro model to evaluate the role of the UPR in NASH and translated results to clarify disease progression in human liver biopsy samples. Treating HepG2 cells and primary human hepatocytes with saturated, but not unsaturated free fatty acids (FFAs), at physiologic concentrations induced hepatotoxicity by inhibiting autophagic flux. Saturated FFA treatment activated the UPR, including the transcription factors CHOP (GADD153/DDIT3) and NF-κB, leading to increased expression and secretion of cytokines such as TNFα and IL-8 that contributed to hepatic cell death and inflammation. Depletion of either CHOP or the RELA subunit of NF-κB in hepatocytes alleviated autophagy and cytokine secretion, resulting in enhanced cell viability and lowered inflammatory responses during exposure to saturated FFAs. We carried out next generation sequencing on cells deleted for either CHOP or RELA and identified IBTKα as a novel UPR member directly regulated by CHOP and NF-κB. In response to saturated FFAs, loss of IBTKα increased cell survival through lowered phagophore formation and reduced cytokine secretion. We also identified binding partners of IBTKα by immunoprecipitation and LC/MS, indicating that that IBTKα is part of a protein complex which functions at ER exit sites to facilitate initiation of autophagy and protein secretion. Furthermore, we discovered that CHOP and RELA coordinately regulate proteasome activity through NRF2 as an adaptive response to an inhibition of autophagic flux following palmitate exposure. To validate our model, we utilized human liver biopsy samples and demonstrated up-regulation of the UPR coincident with accumulation of autophagy markers, as well as secretion of cytokines IL 8 and TNFα in serum of NASH patients. Our study provides a mechanistic understanding of the roles of the UPR and autophagy in regulating saturated FFA induced hepatotoxicity at the cellular level.

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