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Acetaminophen (APAP)-induced liver injury is one of the most prevalent causes of acute liver failure (ALF). We assessed the role of the bone morphogenetic protein (BMP) type I receptors ALK2 and ALK3 in APAP-induced hepatotoxicity. The molecular mechanisms that regulate the balance between cell death and survival and the response to oxidative stress induced by APAP was assessed in cultured human hepatocyte-derived (Huh7) cells treated with pharmacological inhibitors of ALK receptors and with modulated expression of ALK2 or ALK3 by lentiviral infection, and in a mouse model of APAP-induced hepatotoxicity. Inhibition of ALK3 signalling with the pharmacological inhibitor DMH2, or by silencing of ALK3, showed a decreased cell death both by necrosis and apoptosis after APAP treatment. Also, upon APAP challenge, ROS generation was ameliorated and, thus, ROS-mediated JNK and P38 MAPK phosphorylation was reduced in ALK3-inhibited cells compared to control cells. These results were also observed in an experimental model of APAP-induced ALF in which post-treatment with DMH2 after APAP administration significantly reduced liver tissue damage, apoptosis and oxidative stress. This study shows the protective effect of ALK3 receptor inhibition against APAP-induced hepatotoxicity. Furthermore, findings obtained from the animal model suggest that BMP signalling might be a new pharmacological target for the treatment of ALF.

[Background & Aims] Autophagy-related gene 3 (ATG3) is an enzyme mainly known for its actions in the LC3 lipidation process, which is essential for autophagy. Whether ATG3 plays a role in lipid metabolism or contributes to non-alcoholic fatty liver disease (NAFLD) remains unknown., [Methods] By performing proteomic analysis on livers from mice with genetic manipulation of hepatic p63, a regulator of fatty acid metabolism, we identified ATG3 as a new target downstream of p63. ATG3 was evaluated in liver samples from patients with NAFLD. Further, genetic manipulation of ATG3 was performed in human hepatocyte cell lines, primary hepatocytes and in the livers of mice., [Results] ATG3 expression is induced in the liver of animal models and patients with NAFLD (both steatosis and non-alcoholic steatohepatitis) compared with those without liver disease. Moreover, genetic knockdown of ATG3 in mice and human hepatocytes ameliorates p63- and diet-induced steatosis, while its overexpression increases the lipid load in hepatocytes. The inhibition of hepatic ATG3 improves fatty acid metabolism by reducing c-Jun N-terminal protein kinase 1 (JNK1), which increases sirtuin 1 (SIRT1), carnitine palmitoyltransferase 1a (CPT1a), and mitochondrial function. Hepatic knockdown of SIRT1 and CPT1a blunts the effects of ATG3 on mitochondrial activity. Unexpectedly, these effects are independent of an autophagic action., [Conclusions] Collectively, these findings indicate that ATG3 is a novel protein implicated in the development of steatosis.

[Background and Aims]: Little is known about the extent of mitochondrial respiratory chain (MRC) activity dysfunction in patients with alcoholic hepatitis (AH). We aimed to assess the hepatic MRC activity in AH patients and its potential impact on the severity and prognosis of this life-threatening liver disease. [Methods]: MRC complexes were measured in liver biopsies of 98 AH patients (non-severe, 17; severe, 81) and in 12 histologically normal livers (NL). Severity was assessed according to Maddrey's Index and MELD score. Corticosteroid response rate and cumulative mortality were also evaluated. [Results]: The activity of the five MRC complexes was markedly decreased in the liver of AH patients compared with that of NL subjects, being significantly lower in patients with severe AH than in those with non-severe AH. There was a negative correlation between the activity of all MRC complexes and the severity of AH. Interestingly, only complex I and III activities showed a significant positive correlation with the corticosteroid response rate and a significant negative correlation with the mortality rate at all-time points studied. In a multivariate regression analysis, besides the MELD score and the corticosteroid response rate, complex I activity was significantly associated with 3-month mortality (OR = 6.03; p = 0.034) and complex III activity with 6-month mortality (OR = 4.70; p = 0.041) in AH patients. [Conclusion]: Our results indicate that MRC activity is markedly decreased in the liver of AH patients, and, particularly, the impairment of MRC complexes I and III activity appears to have a significant impact on the clinical outcomes of patients with AH.

We thank Dr. Singal for his thoughtful editorial and interest in our article,1 highlighting the clinical significance and future prospects of our results.2 As Dr. Singal points out, we assessed the activity of the five mitochondrial respiratory chain (MRC) complexes in patients with alcoholic hepatitis (AH) with various degrees of severity. MRC activity was markedly decreased in AH compared with healthy subjects, and those with severe AH had lower activity than patients with non-severe AH. In fact, we found a strong negative correlation between MRC activity and the disease severity measured by both MELD and Maddrey's index. Also, complex I and III activity positively correlated with corticosteroid response and mortality rates. Noteworthy, we have preliminary unpublished results comparing the MRC activity of these patients with other aetiologies of liver disease. Interestingly, patients with NASH also showed a significant decrease in all MRC complexes, according to previous studies reporting hepatic mitochondrial dysfunction in high fat diet-fed mice3 and in vitro experiments with HepG2 cells exposed to saturated fatty acids.4 On the contrary, patients with cirrhosis seemed to have a mild decrease in mitochondrial activity, although these changes were modest compared to those observed in our cohort of patients with alcoholic hepatitis.1 These findings suggest that MRC dysfunction is more affected in conditions where steatosis is a key feature, but the extent of the mitochondrial dysfunction observed in patients with AH appears to be a specific feature of this life-threatening liver disorder and is linked to severe outcomes such as lack of response to corticoids and mortality.

[Background & Aims] Advanced hepatic fibrosis is the main risk factor of liver-related morbidity and mortality in patients with chronic liver disease. In this study, we assessed the potential role of bone morphogenetic protein 8A (BMP8A) as a novel target involved in liver fibrosis progression., [Methods] Histological assessment and BMP8A expression were determined in different murine models of hepatic fibrosis. Furthermore, serum BMP8A was measured in mice with bile duct ligation (BDL), in 36 subjects with histologically normal liver (NL) and in 85 patients with biopsy-proven non-alcoholic steatohepatitis (NASH): 52 with non- or mild fibrosis (F0-F2) and 33 with advanced fibrosis (F3-F4). BMP8A expression and secretion was also determined in cultured human hepatocyte-derived (Huh7) and human hepatic stellate (LX2) cells stimulated with transforming growth factor ꞵ (TGFꞵ)., [Results] Bmp8a mRNA levels were significantly upregulated in livers from fibrotic mice compared to control animals. Notably, serum BMP8A levels were also elevated in BDL mice. In addition, in vitro experiments showed increased expression and secretion to the culture supernatant of BMP8A in both Huh7 and LX2 cells treated with TGFꞵ. Noteworthy, we found that serum BMP8A levels were significantly higher in NASH patients with advanced fibrosis than in those with non- or mild fibrosis. In fact, the AUROC of circulating BMP8A concentrations to identify patients with advanced fibrosis (F3-F4) was 0.74 (p˂0.0001). Moreover, we developed an algorithm based on serum BMP8A levels that showed an AUROC of 0.818 (p˂0.0001) to predict advanced fibrosis in NASH patients., [Conclusion] This study provides experimental and clinical evidence indicating that BMP8A is a novel molecular target linked to liver fibrosis and introduces an efficient algorithm based on serum BMP8A levels to screen patients at risk for advanced hepatic fibrosis.

[Background and Aims]: The molecular mechanisms driving non-alcoholic fatty liver disease (NAFLD) are poorly understood; however, microRNAs might play a key role in these processes. We hypothesize that let-7d- 5p could contribute to the pathophysiol-ogy of NAFLD and serve as a potential diagnostic biomarker., [Methods]: We evaluated let-7d- 5p levels and its targets in liver biopsies from a cross- sectional study including patients with NAFLD and healthy donors, and from a mouse model of NAFLD. Moreover, the induction of let-7d- 5p expression by fatty acids was evaluated in vitro. Further, we overexpressed let-7d- 5p in vitro to corroborate the results observed in vivo. Circulating let-7d- 5p and its potential as a NAFLD biomarker was determined in isolated extracellular vesicles from human plasma by RT-qPCR., [Results]: Our results demonstrate that hepatic let-7d-5p was significantly up-regulated in patients with steatosis, and this increase correlated with obesity and a decreased expression of AKT serine/threonine kinase (AKT), insulin-like growth factor 1 (IGF1), IGF-I receptor (IGF1R) and insulin receptor (INSR). These alterations were corroborated in a NAFLD mouse model. In vitro, fatty acids increased let-7d-5p expression, and its overexpression decreased AKT, IGF-IR and IR protein expression. Furthermore, let-7d-5p hindered AKT phosphorylation in vitro after insulin stimulation. Finally, circulating let-7d-5p significantly decreased in steatosis patients and receiver operating characteristic (ROC) analyses confirmed its utility as a diagnostic biomarker., [Conclusions]: Our results highlight the emerging role of let-7d-5p as a potential therapeutic target for NAFLD since its overexpression impairs hepatic insulin signalling, and also, as a novel non-invasive biomarker for NAFLD diagnosis.

[Background]: Little is known about whether the overlap syndrome (OS) combining features of chronic obstructive pulmonary disease (COPD) and sleep apnea-hypopnea syndrome increases the risk of stroke associated with COPD itself., [Methods]: We prospectively studied 74 COPD patients and 32 subjects without lung disease. Spirometry and cardiorespiratory polygraphy were used to assess the pulmonary function of the study population and ultrasound measurements of intima media thickness (IMT) as well as the volume of plaques in both carotid arteries were also evaluated., [Results]: Polygraphic criteria of OS were met in 51% of COPD patients. We found that 79% of patients with OS and 50% of COPD patients without OS had atherosclerotic plaques in the left carotid artery (p = 0.0509). Interestingly, the mean volume of atherosclerotic plaques was significantly higher in the left carotid artery of COPD patients with OS (0.07 ± 0.02 ml) than in those without OS (0.04 ± 0.02 ml, p = 0.0305). However, regardless of the presence of OS, no significant differences were observed in both presence and volume of atherosclerotic plaques in the right carotid artery of COPD patients. Adjusted-multivariate linear regression revealed age, current smoking and the apnea/hypopnea index (OR = 4.54, p = 0.012) as independent predictors of left carotid atherosclerotic plaques in COPD patients., [Conclusions]: This study suggests that the presence of OS in COPD patients is associated with larger left carotid atherosclerotic plaques, indicating that OS might be screened in all COPD patients to identify those with higher risk of stroke.

[Background]: Little is known about whether the overlap syndrome (OS) combining features of chronic obstructive pulmonary disease (COPD) and sleep apnea-hypopnea syndrome increases the risk of stroke associated with COPD itself., [Methods]: We prospectively studied 74 COPD patients and 32 subjects without lung disease. Spirometry and cardiorespiratory polygraphy were used to assess the pulmonary function of the study population and ultrasound measurements of intima media thickness (IMT) as well as the volume of plaques in both carotid arteries were also evaluated., [Results]: Polygraphic criteria of OS were met in 51% of COPD patients. We found that 79% of patients with OS and 50% of COPD patients without OS had atherosclerotic plaques in the left carotid artery (p = 0.0509). Interestingly, the mean volume of atherosclerotic plaques was significantly higher in the left carotid artery of COPD patients with OS (0.07 ± 0.02 ml) than in those without OS (0.04 ± 0.02 ml, p = 0.0305). However, regardless of the presence of OS, no significant differences were observed in both presence and volume of atherosclerotic plaques in the right carotid artery of COPD patients. Adjusted-multivariate linear regression revealed age, current smoking and the apnea/hypopnea index (OR = 4.54, p = 0.012) as independent predictors of left carotid atherosclerotic plaques in COPD patients., [Conclusions]: This study suggests that the presence of OS in COPD patients is associated with larger left carotid atherosclerotic plaques, indicating that OS might be screened in all COPD patients to identify those with higher risk of stroke.

[EN]Background & Aims: Autophagy-related gene 3 (ATG3) is an enzyme mainly known for its actions in the LC3 lipidation process, which is essential for autophagy. Whether ATG3 plays a role in lipid metabolism or contributes to non-alcoholic fatty liver disease (NAFLD) remains unknown. Methods: By performing proteomic analysis on livers from mice with genetic manipulation of hepatic p63, a regulator of fatty acid metabolism, we identified ATG3 as a new target downstream of p63. ATG3 was evaluated in liver samples from patients with NAFLD. Further, genetic manipulation of ATG3 was performed in human hepatocyte cell lines, primary hepatocytes and in the livers of mice. Results: ATG3 expression is induced in the liver of animal models and patients with NAFLD (both steatosis and nonalcoholic steatohepatitis) compared with those without liver disease. Moreover, genetic knockdown of ATG3 in mice and human hepatocytes ameliorates p63-and diet-induced steatosis, while its overexpression increases the lipid load in hepatocytes. The inhibition of hepatic ATG3 improves fatty acid metabolism by reducing c-Jun N-terminal protein kinase 1 (JNK1), which increases sirtuin 1 (SIRT1), carnitine palmitoyltransferase 1a (CPT1a), and mitochondrial function. Hepatic knockdown of SIRT1 and CPT1a blunts the effects of ATG3 on mitochondrial activity. Unexpectedly, these effects are independent of an autophagic action. Conclusions: Collectively, these findings indicate that ATG3 is a novel protein implicated in the development of steatosis. Lay summary: We show that autophagy-related gene 3 (ATG3) contributes to the progression of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the commonest cause of chronic liver disease worldwide, being non-alcoholic steatohepatitis (NASH) its most clinically relevant form. Given the risks associated with taking a liver biopsy, the design of accurate non-invasive methods to identify NASH patients is of upmost importance. BMP2 plays a key role in metabolic homeostasis; however, little is known about its involvement in NAFLD onset and progression. This study aimed to elucidate the impact of BMP2 in NAFLD pathophysiology.

Activation of oval cells (OCs) has been related to hepatocyte injury during chronic liver diseases including non-alcoholic fatty liver disease (NAFLD). However, OCs plasticity can be affected under pathological environments. We previously found protection against hepatocyte cell death by inhibiting protein tyrosine phosphatase 1B (PTP1B). Herein, we investigated the molecular and cellular processes involved in the lipotoxic susceptibility in OCs expressing or not PTP1B. Palmitic acid (PA) induced apoptotic cell death in wild-type (Ptpn1+/+) OCs in parallel to oxidative stress and impaired autophagy. This lipotoxic effect was attenuated in OCs lacking Ptpn1 that showed upregulated antioxidant defences, increased unfolded protein response (UPR) signaling, higher endoplasmic reticulum (ER) content and elevated stearoyl CoA desaturase (Scd1) expression and activity. These effects in Ptpn1−/− OCs concurred with an active autophagy, higher mitochondrial efficiency and a molecular signature of starvation, favoring lipid droplet (LD) formation and dynamics. Autophagy blockade in Ptpn1−/− OCs reduced Scd1 expression, mitochondrial fitness, LD formation and restored lipoapoptosis, an effect also recapitulated by Scd1 silencing. PTP1B immunostaining was detected in OCs from mouse liver and, importantly, LDs were found in OCs from Ptpn1−/− mice with NAFLD. In conclusion, we demonstrated that Ptpn1 deficiency restrains lipoapoptosis in OCs through a metabolic rewiring towards a “starvation-like” fate, favoring autophagy, mitochondrial fitness and LD formation. Dynamic LD-lysosomal interations likely ensure lipid recycling and, overall, these adaptations protect against lipotoxicity. The identification of LDs in OCs from Ptpn1−/− mice with NAFLD opens therapeutic perspectives to ensure OC viability and plasticity under lipotoxic liver damage.

[Introduction]: Given that obstructive sleep apnea (OSA) is commonly associated with metabolic disorders, in this prospective study, we sought to determine the prevalence and risk factors for hepatosteatosis, non-alcoholic steatohepatitis (NASH), and advanced liver fibrosis in patients with clinical and polygraphic criteria of OSA (n = 153) and in subjects with normal lung function parameters (NLP, n = 43). [Methods]: Hepatosteatosis, NASH, and advanced liver fibrosis were determined by blood-based non-invasive tools, such as the fatty liver index and the hepatic steatosis index, a serum lipidomic (OWLiver™) test, and three distinct fibrosis algorithms, respectively. Logistic regression models adjusted by potential confounders were performed to evaluate risk factors. [Results]: Insulin resistance and dyslipidemia were more frequent in patients with OSA than in subjects with NLP. The prevalence of hepatosteatosis was significantly higher in patients with OSA than in subjects with NLP. NASH was also found more frequently in patients with OSA than in subjects with NLP. In contrast, advanced liver fibrosis was rarely detected in the entire study population, and no significant differences were observed between patients with OSA and subjects with NLP. Besides male gender, increased body mass index (BMI), and presence of type 2 diabetes, percentage of sleep time with oxygen saturation <90% (Tc90%) was the only polygraphic variable significantly associated with NASH in patients with OSA. [Conclusions]: This study shows that hepatosteatosis and NASH are highly prevalent in patients with OSA and indicates that those with a Tc90% higher than 10% are at increased risk for NASH.