Metabolic management after sustained virologic response in elderly patients with hepatitis C virus: A multicenter study.

AIMS: Hepatocellular carcinoma (HCC) develops even in patients with hepatitis C virus (HCV) eradication by direct-acting antiviral agents. Fatty liver and metabolic dysfunction are becoming major etiologies of HCC. We aimed to evaluate the impact of metabolic dysfunction-associated steatotic liver disease (MASLD), a new definition of steatotic liver disease, on the development of HCC after HCV eradication. METHODS: We enrolled 1280 elderly patients with HCV eradication and no history of HCC. We evaluated α-fetoprotein (AFP), Fibrosis-4 index and MASLD after 24 weeks of sustained virological response. Decision tree analysis was used to investigate factors associated with HCC development after HCV eradication. RESULTS: A total of 86 patients (6.7%) developed HCC during the follow-up period (35.8 ± 23.7 months). On multivariate analysis, serum AFP level (HR 1.08, CI 1.04-1.11, P = 0.0008), Fibrosis-4 index (HR 1.17, CI 1.08-1.26, P = 0.0007), and MASLD (HR 3.04, CI 1.40-6.58, P = 0.0125) at 24 weeks of sustained virological response were independent factors associated with HCC development. In decision tree analysis, the initial classifier for HCC development was AFP ≥7 ng/mL. However, in patients with AFP <7 ng/mL, MASLD, rather than Fibrosis-4 index, was the classifier for HCC development. No significant difference was observed in the cumulative incidence of HCC between patients with AFP ≥7 ng/mL and patients with AFP <7 ng/mL and MASLD. CONCLUSION: MASLD at 24 weeks of sustained virological response is a risk factor for HCC development in elderly patients with HCV eradication. Additionally, decision tree analysis revealed that MASLD was associated with HCC development, even in patients with serum AFP levels <7 ng/mL.

Low skeletal muscle mass and high visceral adiposity are associated with recurrence of acute cholecystitis after conservative management: A propensity score-matched cohort study.

BACKGROUND: Recurrent acute cholecystitis (RAC) can occur after non-surgical treatment for acute cholecystitis (AC), and can be more severe in comparison to the first episode of AC. Low skeletal muscle mass or adiposity have various effects in several diseases. We aimed to clarify the relationship between RAC and body parameters. METHODS: Patients with AC who were treated at our hospital between January 2011 and March 2022 were enrolled. The psoas muscle mass and adipose tissue area at the third lumbar level were measured using computed tomography at the first episode of AC. The areas were divided by height to obtain the psoas muscle mass index (PMI) and subcutaneous/visceral adipose tissue index (SATI/VATI). According to median VATI, SATI and PMI values by sex, patients were divided into the high and low PMI groups. We performed propensity score matching to eliminate the baseline differences between the high PMI and low PMI groups and analyzed the cumulative incidence and predictors of RAC. RESULTS: The entire cohort was divided into the high PMI (n = 81) and low PMI (n = 80) groups. In the propensity score-matched cohort there were 57 patients in each group. In Kaplan-Meier analysis, the low PMI group and the high VATI group had a significantly higher cumulative incidence of RAC than their counterparts (log-rank P = 0.001 and 0.015, respectively). In a multivariate Cox regression analysis, the hazard ratios of low PMI and low VATI for RAC were 5.250 (95% confidence interval 1.083-25.450, P = 0.039) and 0.158 (95% confidence interval: 0.026-0.937, P = 0.042), respectively. CONCLUSIONS: Low skeletal muscle mass and high visceral adiposity were independent risk factors for RAC.

Effect modification of tumor necrosis factor-α on the kynurenine and serotonin pathways in major depressive disorder on type 2 diabetes mellitus.

Major depressive disorder (MDD) is strongly associated with type 2 diabetes mellitus (T2DM). The kynurenine and serotonin pathways, as well as chronic low-grade inflammation, are being considered potential links between them. MDD associated with T2DM is less responsive to treatment than that without T2DM; however, the underlying mechanism remains unknown. We aimed to investigate the effects of inflammatory cytokines on the kynurenine and serotonin pathways in patients with comorbid MDD and T2DM and those with only MDD. We recruited 13 patients with comorbid MDD and T2DM and 27 patients with only MDD. We measured interleukin-6 and tumor necrosis factor-α (TNF-α) levels as inflammatory cytokines and metabolites of the kynurenine pathway and examined the relationship between the two. TNF-α levels were significantly higher in patients with comorbid MDD and T2DM than in those with only MDD in univariate (p = 0.044) and multivariate (adjusted p = 0.036) analyses. TNF-α showed a statistically significant effect modification (interaction) with quinolinic acid/tryptophan and serotonin in patients from both groups (ß = 1.029, adjusted p < 0.001; ß = - 1.444, adjusted p = 0.047, respectively). Limitations attributed to the study design and number of samples may be present. All patients were Japanese with mild to moderate MDD; therefore, the generalizability of our findings may be limited. MDD with T2DM has more inflammatory depression components and activations of the kynurenine pathway by inflammatory cytokines than MDD without T2DM. Hence, administering antidepressants and anti-inflammatory drugs in combination may be more effective in patients with comorbid MDD and T2DM.

Impact of Interferon-Free Direct-Acting Antivirals on the Incidence of Extrahepatic Malignancies in Patients with Chronic Hepatitis C.

BACKGROUND: The incidence of extrahepatic malignancies (EHMs) after hepatitis C virus (HCV) eradication by interferon (IFN)-based and IFN-free direct-acting antivirals (DAAs) treatment remains unclear. AIMS: The aim was to evaluate the cumulative incidence of EHMs diagnosed for the first time after the antiviral treatments. METHODS: We analyzed a total 527 patients with chronic HCV infection and without prior history of any malignancies who achieved sustained virological response by antiviral treatments, including IFN-based (n = 242) or IFN-free DAAs (n = 285). The baseline predictors for EHM occurrence were analyzed using Cox regression analysis. RESULTS: Thirty-two patients were diagnosed with EHMs, 14 in IFN-based and 18 in IFN-free DAAs, respectively. The total duration of follow-up was 1,796 person-years in IFN-based and 823 person-years in IFN-free DAAs. The incidence of EHMs in IFN-based and IFN-free DAAs was 7.8 and 21.9 per 1,000 person-years, respectively. The cumulative incidence of EHMs was significantly higher in IFN-free DAAs than IFN-based (p = 0.002). IFN-free DAAs was a single independent predictor for incidence of EHMs (p = 0.012). As for gender, the incidence of EHMs was significantly higher in IFN-free DAAs only in the female cohort (p = 0.002). After propensity score matching, IFN-free DAAs was a single independent predictor for incidence of EHMs in the female patients (p = 0.045). CONCLUSIONS: The incidence of EHMs after HCV eradication is higher in IFN-free DAAs than IFN-based regimens, especially in female patients. We should carefully follow-up not only HCC but also EHMs after IFN-free DAAs regimens.

Comparison of Serum Metabolomics Pathways and Patterns between Patients with Major Depressive Disorder with and without Type 2 Diabetes Mellitus: An Exploratory Study.

BACKGROUND: A close relationship exists between major depressive disorder (MDD) and diabetes mellitus. The metabolomic difference and similarity between patients with and without diabetes mellitus have not been well studied in the context of MDD. We aimed to examine these differences and common serum metabolomics patterns, pathways and biomarkers that can comprehensively reflect the pathogenetic difference and similarity between these MDD groups. METHODS: We performed a metabolomics analysis of serum samples of healthy controls (n = 6), patients with MDD and type 2 diabetes mellitus (n = 13), and patients with MDD without type 2 diabetes mellitus (n = 27). Metabolomics analysis was conducted using capillary electrophoresis Fourier transform mass spectrometry and a candidate compound was assigned to the 496 (290 cation, 206 anion) peaks. Moreover, we evaluated the sensitivity and specificity of the candidate biomarkers for distinguishing between MDD patients with or without type 2 diabetes mellitus. RESULTS: Principal component analysis revealed no clear distinction among the three groups, while naive partial least squares discriminant analysis yielded three relatively good and distinct populations based on the first principal component. Energy conversion by the tricarboxylic acid cycle represented the highest percentage among the top 30 positive factors of the first principal component, and glutamate metabolism and urea cycle represented the highest percentage among the top 30 negative factors of the first principal component. Synthesis and degradation of ketone bodies had high impact in MDD with type 2 diabetes mellitus group and taurine and hypotaurine metabolism had high impact in MDD without type 2 diabetes mellitus group for the pathway. CONCLUSIONS: Patterns of serum metabolites may be different among MDD with type 2 diabetes mellitus, MDD without type 2 diabetes mellitus, and healthy controls groups. Specifically, comorbid type 2 diabetes mellitus could affect metabolomics pathway and alter the distribution of serum metabolites in patients with MDD. These findings may shed light on the influence of the type 2 diabetes on the pathophysiology of MDD.

A Case of Successful Endoscopic Extraction of Common Bile Duct Stones After Closing a Duodenal Perforation Using Over-The-Scope Clip.

A 57-year-old man visited our hospital for acute cholangitis due to common bile duct (CBD) stones in March 2021. Biliary stenting was performed without any complications. The cholangitis improved rapidly. He was re-hospitalized to treat the CBD stones in May 2021. Although endoscopic retrograde cholangiopancreatography was performed, endoscopy caused a perforation of the duodenal bulb. We successfully performed endoscopic closure of the duodenal defect using an over-the-scope clip (OTSC®). Considering that mild CBD dilatation of 10 mm can carry an increased risk of stenosis after surgery, we decided to avoid surgery and perform a follow-up endoscopic treatment. He was re-hospitalized in July 2021. The endoscopy revealed OTSC® in the anterior wall of the duodenal bulb and complete healing of the perforation. We carefully advanced the scope to the second portion of the duodenum while avoiding OTSC®, and the ampulla of Vater was identified. We were then able to remove the stones without any complications. OTSC® was effective in closing a duodenal perforation and enabled us to carry out the retreatment safely and successfully.

Hepatic Cyst Infection Following Recurrent Biliary Obstruction in Polycystic Liver Disease.

An 89-year-old man with polycystic liver disease (PCLD) received uncovered self-expandable metallic stent (SEMS) placement above the papilla for malignant biliary obstruction caused by cholangiocarcinoma. He developed cholangitis ten months later due to SEMS occlusion caused by tumor ingrowth, and 2 plastic biliary stents were placed inside the SEMS across the papilla. Fever and right costal pain appeared two weeks after reintervention. Suspecting hepatic cyst infection based on imaging studies, percutaneous transhepatic cyst drainage was performed. Increased inflammatory cells and the presence of pathogens in the cyst fluid led to a definitive diagnosis of hepatic cyst infection. Following drainage, the hepatic cyst shrank with resolution of the symptoms. SEMS occlusive-related cholangitis or retrograde infection due to duodenal-biliary reflux after reintervention was considered as the cause of the hepatic cyst infection. Careful clinical and imaging evaluation should be performed in patients with PCLD undergone biliary stenting, because cyst infection may occur following stent occlusion or subsequent biliary reintervention.

A Case of Pancreatic Neuroendocrine Tumor G3 Which Responded Remarkably to Chemotherapy.

Pancreatic neuroendocrine carcinoma (NEC) as classified in the World Health Organization (WHO) 2010 was reclassified in the WHO 2017 as either neuroendocrine tumor (NET) G3 or NEC. An accurate diagnosis based on the WHO 2017 classification is important in order treating this disease appropriately. We report a case diagnosed as NET G3 that responded remarkably well to treatment with streptozocin. The patient would likely not have received the streptozocin treatment if she had been diagnosed with NEC. The WHO 2017 classification is reasonable for the treatment of advanced pancreatic neuroendocrine neoplasms.

Influence of gastroesophageal flap valve on esophageal variceal bleeding in patients with liver cirrhosis.

OBJECTIVES: Esophageal variceal bleeding can be fatal in patients with liver cirrhosis. The aim of this study was to investigate the relationship between gastroesophageal flap valve (GEFV) and esophageal variceal bleeding. METHODS: Subjects were cirrhotic patients with endoscopically diagnosed esophageal varices treated at our hospital between 2005 and 2019, excluding those with F3 form and red color (RC) signs at first endoscopy. Sixty-five patients with normal GEFV (Hill grade I or II) and 42 with abnormal GEFV (Hill grade III or IV) were enrolled. Propensity score matching eliminated the baseline differences, resulting in a sample size of 30 patients per cohort. The primary endpoint was esophageal variceal bleeding, and the secondary endpoint was variceal bleeding or appearance of RC sign. We analyzed the cumulative incidences and predictors of each endpoint. RESULTS: The 3-, 5-, and 10-year cumulative incidences of the primary endpoints were all 3.4% in the normal GEFV group, and 19.0%, 24.6% and 34.0% in the abnormal GEFV group, respectively (log-rank P = 0.011). Cumulative incidence of the secondary endpoint was 13.8%, 33.1% and 39.2% in the normal GEFV group, and 42.2%, 54.6% and 84.9% in the abnormal GEFV group, respectively (log-rank P = 0.001). In multivariate Cox regression analyses, hazard ratios of abnormal GEFV of the primary and secondary endpoints were 12.79 (95% confidence interval 1.331-122.8) and 3.600 (1.653-7.840), respectively. CONCLUSIONS: Abnormal GEFV was an independent risk factor for esophageal variceal bleeding and appearance of RC sign.

Trehalose alleviates oxidative stress-mediated liver injury and Mallor-Denk body formation via activating autophagy in mice.

Autophagy is a degradation pathway for long-lived cytoplasmic proteins or damaged organelles and also for many aggregate-prone and disease-causing proteins. Endoplasmic reticulum (ER) stress and oxidative stress are associated with the pathophysiology of various liver diseases. These stresses induce the accumulation of abnormal proteins, Mallory-Denk body (MDB) formation and apoptosis in hepatocytes. A disaccharide trehalose had been reported to induce autophagy and decrease aggregate-prone proteins and cytotoxicity in neurodegenerative disease models. But the effects of trehalose in hepatocytes have not been fully understood. We examined the effect of trehalose on autophagy, ER stress and oxidative stress-mediated cytotoxicity and MDB formation in hepatocytes using mice model with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) treatment for 3 months. We administered trehalose by intraperitoneal injection of water containing 10% trehalose (0.02 mg/g body weight) every other day for 3 months. Our results demonstrated that trehalose induced autophagy and reduced ER stress, oxidative stress, MDB formation and apoptosis in hepatocytes of DDC-fed mice by Western blotting and immunostaining analyses. Electron microscopy revealed that trehalose induced autolysosome formation, which located is close to the MDBs. Thus, our findings suggest that trehalose can become a therapeutic agent for oxidative stress-related liver diseases via activating autophagy.

Correlation of hepatitis C virus-mediated endoplasmic reticulum stress with autophagic flux impairment and hepatocarcinogenesis.

Hepatitis C virus (HCV) infection has been known to use autophagy for its replication. However, the mechanisms by which HCV modulates autophagy remain controversial. We used HCV-Japanese fulminant hepatitis-1-infected Huh7 cells. HCV infection induced the accumulation of autophagosomes. Morphological analyses of monomeric red fluorescent protein (mRFP)-green fluorescent protein (GFP) tandem fluorescent-tagged LC3 transfection showed HCV infection impaired autophagic flux. Autophagosome-lysosome fusion assessed by transfection of mRFP- or GFP-LC3 and immunostaining of lysosomal-associated membrane protein 1 was inhibited by HCV infection. Decrease of HCV-induced endoplasmic reticulum (ER) stress by 4-phenylbutyric acid, a chemical chaperone, improved the HCV-mediated autophagic flux impairment. HCV infection-induced oxidative stress and subsequently DNA damage, but not apoptosis. Furthermore, HCV induced cytoprotective effects against the cellular stress by facilitating the formation of cytoplasmic inclusion bodies as shown by p62 expression and by modulating keratin protein expression and activated nuclear factor erythroid 2-related factor 2. HCV eradication by direct-acting antivirals improved autophagic flux, but DNA damage persisted. In conclusion, HCV-induced ER stress correlates with autophagic flux impairment. Decrease of ER stress is considered to be a promising therapeutic strategy for HCV-related chronic liver diseases. However, we should be aware that the risk of hepatocarcinogenesis remains even after HCV eradication.

Type 4B hereditary hemochromatosis due to heterozygous p.D157A mutation in SLC40A1 complicated with hypopituitarism.

Hemochromatosis is a clinical syndrome characterized by iron overload in various organs. We present here a case of type 4 hereditary hemochromatosis due to heterozygous mutation in SLC40A1 gene (p.D157A). SLC40A1 encodes ferroportin, a macromolecule only known as iron exporter from mammalian cells. He first presented symptoms correlated with hypopituitarism. Furthermore, marked hyperferritinemia and high transferrin saturation were revealed in combination with the findings of iron overload in the liver, spleen and pituitary gland by computed tomography and magnetic resonance imaging. Liver biopsy revealed iron deposition in both hepatocytes and Kupffer cells. SLC40A1 mutations are considered to cause wide heterogeneity by various ferroportin mutations. Thus, clinicopathological examinations seem to be very important for diagnosing phenotype of type 4 hemochromatosis in addition to the gene analysis. We diagnosed him as type 4B hereditary hemochromatosis (ferroportin-associated hemochromatosis) by the findings of high transferrin saturation and iron deposition in hepatocytes, and then started iron chelating treatment. We should suspect the possibility of hereditary hemochromatosis even in Japanese with severe iron overload. Although the same mutation in SLC40A1 gene (p.D157A) had been reported to cause "loss of function" phenotype, we considered that the mutation of our case caused "gain of function" phenotype.

Hepatocyte Growth Factor and Primary Systemic Amyloidosis.

A 75-year-old-man experienced liver dysfunction and was diagnosed with decompensated liver cirrhosis. His serum hepatocyte growth factor (HGF) was very high (16.24 ng/ml). Because the etiology was unclear, we considered the possibility of amyloidosis. Biopsy of the mucosa of the stomach, duodenum and rectum demonstrated amyloid deposition. From the findings of Congo red staining and immunohistochemical analyses, we made a diagnosis of systemic amyloid light-chain amyloidosis. Unfortunately, the patient died one month after the diagnosis. We considered that serum HGF was useful for the diagnosis and prediction of prognosis of primary systemic amyloidosis.

Involvement of sarco/endoplasmic reticulum calcium ATPase-mediated calcium flux in the protective effect of oleic acid against lipotoxicity in hepatocytes.

Elevated free fatty acids, particularly saturated ones such as palmitic acid, may play an important role in the lipotoxic mechanism of nonalcoholic fatty liver disease (NAFLD). Saturated fatty acids induce autophagy dysfunction and endoplasmic reticulum (ER) stress leading to apoptosis in hepatocytes. However, unsaturated fatty acids, such as oleic acid, are nontoxic and can even prevent saturated fatty acid-induced toxicity in vitro. Although emerging evidence has suggested that ER calcium flux disruption in hepatocytes is involved in NAFLD pathogenesis, the roles of fatty acids in autophagy and ER calcium flux still remain unclear. We demonstrated that oleic acid ameliorated palmitic acid-induced autophagy arrest and ER stress in parallel with ER calcium depletion in hepatocytes. Moreover, we found that the effect of oleic acid against autophagy arrest was reversed by the pharmacological inhibition of sarcoplasmic reticulum Ca2+-ATPase (SERCA), which influxes calcium to ER. These data suggest that SERCA-mediated ER calcium flux is greatly involved in fatty acid-induced lipotoxicity in hepatocytes, and the prevention of ER calcium depletion may restore saturated fatty acid-induced autophagy arrest in hepatocytes.

Idiopathic copper toxicosis: is abnormal copper metabolism a primary cause of this disease?

Idiopathic copper toxicosis (ICT) is characterized by marked copper deposition, Mallory-Denk body (MDB) formation and severe hepatic injury. Although the characteristics are apparently different from Wilson disease, large amounts of copper accumulate in the liver of the patients. We extensively treated a patient with ICT to reduce the body copper, however, the patient needed liver transplantation. Previous liver biopsy revealed high copper content. But extirpated liver contained an extremely small amount of copper, although MDBs and severe inflammation remained. These phenomena suggest abnormal copper metabolism is not the principle cause of ICT but some other abnormality must exist.

Effect of direct-acting antivirals on platelet-associated immunoglobulin G and thrombocytopenia in hepatitis C virus-related chronic liver disease.

BACKGROUND & AIMS: Hepatitis C virus (HCV) infection has been known to cause various extrahepatic autoimmune disorders. The prevalence of platelet-associated immunoglobulin G (PA-IgG) has been high in patients with HCV infection. Because thrombocytopenia in HCV-related liver diseases is a notable problem, we performed prospective study on the effect of direct-acting antivirals (DAAs) treatment on PA-IgG and platelet count. METHODS: A total of 215 patients with HCV-related liver disease were enrolled in this study. The patients who discontinued DAAs or did not undergo adequate laboratory examinations and who did not achieve sustained virologic response were excluded and finally a total of 187 patients were investigated. RESULTS: A total of 171 patients (91.4%) were PA-IgG positive (>46 ng/107 cells) before starting DAAs (baseline). The PA-IgG level elevation was significantly correlated with higher liver inflammation and fibrosis markers (P < 0.05) and lower platelet count (P = 0.000019). The platelet count of the patients with low PA-IgG titer tended to be higher at baseline, end of treatment (EOT), and at 12 and 24 weeks after EOT. The platelet count increased at EOT (P < 0.05) and 24 weeks after EOT (P < 0.01). The PA-IgG levels were significantly decreased at EOT, 12 and 24 weeks after EOT (P < 0.01). Multiple regression analysis found that only platelet count at baseline was closely associated with negative conversion of PA-IgG at 24 weeks after EOT (P = 0.004). CONCLUSIONS: Eradication of HCV by DAAs treatment successfully decreased PA-IgG level and increased platelet count.

Secondary sclerosing cholangitis with hemobilia induced by pembrolizumab: Case report and review of published work.

A 66-year-old man was admitted to our department due to cholestatic liver injury. He had received five cycles of pembrolizumab for small-cell lung cancer. Imaging showed the possibility of sclerosing cholangitis (SC) with hemobilia. Histologically, CD8+ T cells had infiltrated the biliary epithelium of the extrahepatic bile duct. We reached the diagnosis of secondary SC induced by pembrolizumab. Although we treated him with high-dose corticosteroids, laboratory data showed only a moderate response. Clinicians should recognize that immune checkpoint inhibitors can sometimes cause severe and irreversible SC.

Zinc Attenuates the Cytotoxicity of Some Stimuli by Reducing Endoplasmic Reticulum Stress in Hepatocytes.

Zinc is an essential trace element and plays critical roles in cellular integrity and biological functions. Excess copper induced both oxidative stress and endoplasmic reticulum (ER) stress in liver-derived cultured cells. Excess copper also induced impairment of autophagic flux at the step of autophagosome-lysosome fusion, as well as Mallory-Denk body (MDB)-like inclusion body formation. Zinc ameliorated excess copper-induced impairment of autophagic flux and MDB-like inclusion body formation via the maintenance of ER homeostasis. Furthermore, zinc also ameliorated free fatty acid-induced impairment of autophagic flux. These results indicate that zinc may be able to protect hepatocytes from various ER stress-related conditions.

Trehalose activates autophagy and decreases proteasome inhibitor-induced endoplasmic reticulum stress and oxidative stress-mediated cytotoxicity in hepatocytes.

AIM: Endoplasmic reticulum stress is associated with the pathophysiology of various liver diseases. Endoplasmic reticulum stress mediates the accumulation of abnormal proteins and leads to oxidative stress, cytoplasmic inclusion body formation, and apoptosis in hepatocytes. Autophagy is a bulk degradation pathway for long-lived cytoplasmic proteins or damaged organelles and is also a major degradation pathway for many aggregate-prone and disease-causing proteins. We previously reported that rapamycin, a mammalian target of rapamycin inhibitor, activated autophagy and decreased proteasome inhibitor-mediated ubiquitinated protein accumulation, cytoplasmic inclusion body formation, and apoptosis in hepatocytes. Trehalose is a non-reducing disaccharide that has been shown to activate autophagy. It has been reported to decrease aggregate-prone proteins and ameliorate cytotoxicity in neurodegenerative disease models. However, the effects of trehalose in hepatocytes are unclear. METHODS: We show here that trehalose activated autophagy and reduced endoplasmic reticulum stress, cytoplasmic inclusion body formation, and apoptosis in proteasome inhibitor-treated liver-derived cultured cells. CONCLUSION: To our knowledge, this is the first report showing that trehalose activates autophagy and has cytoprotective effects in hepatocytes. Our findings suggest that trehalose can become a therapeutic agent for endoplasmic reticulum stress-related liver diseases.

Lipid-Induced Endoplasmic Reticulum Stress Impairs Selective Autophagy at the Step of Autophagosome-Lysosome Fusion in Hepatocytes.

Blockage of hepatic autophagic degradation system occurs in obesity and is associated with the development of nonalcoholic fatty liver disease. However, the mechanism of this blockage remains unclear. We found a high-fat diet induced accumulation of autophagosomes in the mice livers. However, autophagy substrates such as p62 and ubiquitinated proteins also accumulated in the livers in this model. These findings indicate the possibility that a high-fat diet impairs autophagic flux in the liver. Then, to assess the autophagic flux in more detail, we performed analyses of autophagic flux in cultured hepatocytes exposed to monounsaturated fatty acids (FAs) or saturated FAs (SFAs). SFAs but not monounsaturated FAs suppressed degradation of contents in the autophagosomes. We analyzed each stage of the autophagy pathway (ie, autophagosome formation, autophagosome-lysosome fusion, lysosomal degradation) in cultured hepatocytes treated with monounsaturated FAs or SFAs and found that SFAs impaired autophagosome-lysosome fusion. This impairment occurred in an endoplasmic reticulum stress-dependent manner. Moreover, ubiquitin and p62-positive inclusions observed in high-fat diet-fed mice livers and SFA-treated cells were sequestered within autophagosomes. We also found that SFA-induced accumulation of Ser351-phosphorylated p62, which is indispensable for selective autophagy, further increased on administration of a lysosomal proteinase inhibitor. Although lipid-induced endoplasmic reticulum stress interferes with the autophagosome-lysosome fusion, selective autophagic sequestration of aggregated proteins is not inhibited.