Dysfunction In Non-alcoholic Fatty Liver Disease Research Articles

Liver-Derived S100A6 Propels β-Cell Dysfunction in NAFLD.

Nonalcoholic fatty liver disease (NAFLD) is an independent predictor of systemic insulin resistance and type 2 diabetes mellitus (T2DM). However, converse correlates between excess liver fat content and β-cell function remain equivocal. Specifically, how the accumulation of liver fat consequent to the enhanced de novo lipogenesis (DNL) leads to pancreatic β-cell failure and eventually to T2DM is elusive. Here, we have identified that low-molecular-weight calcium-binding protein S100A6, or calcyclin, inhibits glucose-stimulated insulin secretion (GSIS) from β cells through activation of the receptor for the advanced glycation end products and diminution of mitochondrial respiration. Serum S100A6 level is elevated both in human patients with NAFLD and in a high-fat diet-induced mouse model of NAFLD. Although serum S100A6 levels are negatively associated with β-cell insulin secretory capacity in human patients, depletion of hepatic S100A6 improves GSIS and glycemia in mice, suggesting that S100A6 contributes to the pathophysiology of diabetes in NAFLD. Moreover, transcriptional induction of hepatic S100A6 is driven by the potent regulator of DNL, carbohydrate response element-binding protein (ChREBP), and ectopic expression of ChREBP in the liver suppresses GSIS in a S100A6-sensitive manner. Together, these data suggest elevated serum levels of S100A6 may serve as a biomarker in identifying patients with NAFLD with a heightened risk of developing β-cell dysfunction. Overall, our data implicate S100A6 as, to our knowledge, a hitherto unknown hepatokine to be activated by ChREBP and that participates in the hepato-pancreatic communication to impair insulin secretion and drive the development of T2DM in NAFLD.

Intestinal Barrier Dysfunction in Fatty Liver Disease: Roles of Microbiota, Mucosal Immune System, and Bile Acids.

Nonalcoholic fatty liver disease (NAFLD) describes a spectrum of progressive liver diseases ranging from simple steatosis to steatohepatitis and fibrosis. Globally, NAFLD is the leading cause of morbidity and mortality associated with chronic liver disease, and NAFLD patients are at a higher risk of developing cirrhosis and hepatocellular carcinoma. While there is a consensus that inflammation plays a key role in promoting NAFLD progression, the underlying mechanisms are not well understood. Recent clinical and experimental evidence suggest that increased hepatic translocation of gut microbial antigens, secondary to diet-induced impairment of the intestinal barrier may be important in driving hepatic inflammation in NAFLD. Here, we briefly review various endogenous and exogenous factors influencing the intestinal barrier and present recent advances in our understanding of cellular and molecular mechanisms underlying intestinal barrier dysfunction in NAFLD.

Fisetin represses oxidative stress and mitochondrial dysfunction in NAFLD through suppressing GRP78-mediated endoplasmic reticulum (ER) stress

• Fisetin restrains ROS production and improves Nrf2 activation in PA-incubated hepatocytes. • Fisetin improves mitochondrial dysfunction and impairment in PA-treated hepatocytes. • Fisetin-mediated cellular events is mainly through ER stress inhibition. • Fisetin ameliorates NAFLD development in HFD-fed mice. Fisetin (FisT) is a bioactive flavonoid polyphenol with antioxidant, anti-inflammatory and anti-tumor activities. Although the effects of FisT to meliorate non-alcoholic fatty liver disease (NAFLD) have been investigated, the underlying mechanisms are not fully understood. In the present study, we found that FisT remarkably suppressed cellular and mitochondrial reactive oxygen species (ROS) generation in human and murine hepatocytes with palmitate (PA) stimulation. Additionally, mitochondrial impairment and dysfunction induced by PA were considerably abrogated in hepatocytes with FisT co-incubation. Furthermore, Cyto-c releases and mitochondrial apoptosis were detected in PA-treated hepatocytes, while being greatly repressed by FisT. PA-induced inflammation and lipid deposition were also strongly reduced by FisT in hepatocytes. Importantly, our in vitro experiments showed that promoting ROS by nuclear factor erythroid 2-related factor 2 (Nrf2) deletion significantly abolished the function of FisT to meliorate apoptosis, inflammation and lipid accumulation in PA-incubated hepatocytes. What’s more, ER stress was strongly induced by PA via increasing 78-kDa glucose-regulated protein (GRP78) and C/EBP-homologous protein (CHOP), which were, however, dramatically repressed after FisT co-exposure. Intriguingly, we found that strengthening ER stress by GRP78 over-expression considerably abolished the capacity of FisT to retard ROS generation and mitochondrial impairment in PA-stimulated hepatocytes, but GRP78 knockdown exhibited totally opposite effects. Thus, ER stress blockage was required for FisT to ameliorate NAFLD development in vitro . Consistently, our in vivo studies using high fat diet (HFD)-fed mice confirmed that FisT administration exerted inhibitory and therapeutic potential on fatty liver progression via the same mechanisms monitored in vitro . Collectively, all our findings disclosed that FisT can efficiently attenuate NAFLD through restraining ROS generation and mitochondrial impairment mediated by ER stress.

Study of Endothelial Dysfunction in Patients With Non-alcoholic Fatty Liver Disease.

BackgroundMetabolic syndrome (syndrome X) is the name for a group of risk factors that raises your risk for heart disease and other health problems, such as diabetes and stroke. Dilatation of blood vessels following stress is a function of vasodilators produced by the endothelium. Flow-mediated vasodilation assesses endothelial function. In the case of endothelial dysfunction, flow-mediated vasodilation is impaired, resulting in decreased or even absence of vasodilation following stress. The easy availability of ultrasound machines nowadays and the non-invasive nature of the test make this a practical test for assessing endothelial dysfunction and the risk of cardiovascular diseases. Various studies have confirmed the presence of impaired flow-mediated vasodilation in patients with coronary artery disease. However, the presence of impaired flow-mediated vasodilation in individuals with risk factors but no cardiovascular diseases can prove that this can be used to predict individuals at risk. This study tries to confirm the presence of endothelial dysfunction in patients with non-alcoholic fatty liver disease (NAFLD) attending a tertiary center hospital in Kochi.ObjectivesThe study's main aim is to compare flow-mediated dilatation in patients with NAFLD and normal individuals.Materials and methodsThe comparative study was conducted among 50 patients attending various outpatient departments in Amrita Institute of Medical Sciences, Kochi. History and examination of cases and controls and relevant investigations were done after obtaining consent. In addition, both groups underwent measurement of flow-mediated vasodilation in the radiology department. Data were entered in Microsoft Excel and were analyzed using SPSS.ResultsFlow-mediated vasodilation was found to be less in patients with fatty liver (7.37 ± 2.75) when compared to individuals with normal liver (12.41 ± 3.71). In addition, flow-mediated vasodilatation was inversely proportional to BMI and age.ConclusionThis study has proved that there will be endothelial dysfunction in NAFLD, as shown by the decrease in flow-mediated vasodilation when compared with normal liver.

The Risk of Colorectal Adenoma in Nonalcoholic or Metabolic-Associated Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of liver disease associated with various metabolic disorders. Metabolic dysfunction-associated fatty liver disease (MAFLD) emphasizes metabolic dysfunction in NAFLD. Although the relationship between NAFLD and colorectal adenomas has been suggested, the effect of MAFLD on colorectal adenoma has yet to be investigated. In this study, we examined the relationship between NAFLD/MAFLD and colorectal adenoma in comparison with other metabolic factors. Methods: Examinees who underwent colonoscopy and abdominal ultrasonography on the same day from January 2012 to December 2012 were included. NAFLD was diagnosed according to the findings of ultrasonography. The Fibrosis-4 (FIB-4) index was used as a surrogate marker for advanced hepatic fibrosis. A logistic regression model was used to analyze the risk of NAFLD/MAFLD for colorectal adenoma. Results: The prevalence of NAFLD and MAFLD was 37.5% and 32.8%, respectively. In the multivariate analysis, male sex, older age, diabetes, and smoking increased the risk of colorectal adenoma. NAFLD and MAFLD were the most important risk factors for colorectal adenoma only in females [adjusted odds ratio (OR) 1.43 and 95% confidence interval (CI) 1.01–2.03, and OR 1.55, 95% CI 1.09–2.20, respectively]. NAFLD and MAFLD with an advanced fibrosis index were significantly associated with an increased risk of colorectal adenoma. (NAFLD: OR 1.38, 95% CI, 1.04–1.83, p = 0.027; MAFLD: OR 1.45, 95% CI, 1.13–1.96, p = 0.004, respectively). Conclusion: NAFLD and MAFLD were significantly associated with a higher risk of colorectal adenomas, especially in females. NAFLD and MAFLD with advanced fibrosis were associated with an increased risk of colorectal adenoma. Colonoscopic examinations may be emphasized for patients with NAFLD/MAFLD, for women, or patients with the presence of hepatic fibrosis.

Pyruvate Dehydrogenase as a Therapeutic Target for Nonalcoholic Fatty Liver Disease.

Excess caloric intake combined with a sedentary lifestyle in the general population has greatly increased the prevalence of obesity and nonalcoholic fatty liver disease (NAFLD), which is defined as the accumulation of excess fat in the liver in the absence of alcohol abuse or other attributable causes such as infection with hepatitis C. Furthermore, NAFLD increases the risk for insulin resistance, type 2 diabetes (T2D), and cardiovascular disease, while currently having no approved therapy to counteract its pathology. Thus, increasing efforts to understand the mechanisms responsible for NAFLD have been pursued in preclinical studies, in the hopes of developing novel therapies that can prevent the progression of insulin resistance and/or T2D. The pathology of NAFLD is multifactorial, with proposed mechanisms including inflammation, oxidative stress, and mitochondrial dysfunction to name a few. The latter remains a subject of ongoing debate, but may be attributed to impaired hepatic fatty acid oxidation, thereby increasing the accumulation of triacylglycerol within hepatocytes. More recent studies have also demonstrated that the mitochondrial dysfunction in NAFLD may also encompass impairments in glucose oxidation, despite oxidative energy production having minimal contribution to overall glucose/pyruvate metabolism in the liver. Accordingly, strategies to reverse this defect in glucose oxidation can ameliorate hepatic steatosis and improve glucose homeostasis. We will review herein the evidence supporting impaired hepatic glucose oxidation as a mechanism of NAFLD, while discussing the validity of pyruvate dehydrogenase (PDH), the rate-limiting enzyme of glucose oxidation, as a potential target for NAFLD. In addition, we will discuss potential mechanisms of action by which increased hepatic PDH activity and subsequent glucose oxidation can reverse the pathology of obesity-induced NAFLD, as well as opportunities to target this pathway with clinical agents.

Cognitive Dysfunction in Non-Alcoholic Fatty Liver Disease-Current Knowledge, Mechanisms and Perspectives.

Non-alcoholic fatty liver disease (NAFLD) has emerged as the hepatic component of the metabolic syndrome and now seemingly affects one-fourth of the world population. Features associated with NAFLD and the metabolic syndrome have frequently been linked to cognitive dysfunction, i.e. systemic inflammation, vascular dysfunction, and sleep apnoea. However, emerging evidence suggests that NAFLD may be a cause of cognitive dysfunction independent of these factors. NAFLD in addition exhibits dysbiosis of the gut microbiota and impaired urea cycle function, favouring systemic ammonia accumulation and further promotes systemic inflammation. Such disruption of the gut–liver–brain axis is essential in the pathogenesis of hepatic encephalopathy, the neuropsychiatric syndrome associated with progressive liver disease. Considering the growing burden of NAFLD, the morbidity from cognitive impairment is expected to have huge societal and economic impact. The present paper provides a review of the available evidence for cognitive dysfunction in NAFLD and outlines its possible mechanisms. Moreover, the clinical challenges of characterizing and diagnosing cognitive dysfunction in NAFLD are discussed.

Astaxanthin attenuates hepatic damage and mitochondrial dysfunction in non-alcoholic fatty liver disease by up-regulating the FGF21/PGC-1α pathway.

Non-alcoholic fatty liver disease (NAFLD) is considered to be one of the most common chronic liver diseases across worldwide. Astaxanthin (Ax) is a carotenoid, and beneficial effects of astaxanthin, including anti-oxidative, anti-inflammatory, and anti-tumour activity, have been identified. The present study aimed to elucidate the protective effect of astaxanthin against NAFLD and its underlying mechanism. Mice were fed either a high fat or chow diet, with or without astaxanthin, for up to 12 weeks. L02 cells were treated with free fatty acids combined with different doses of astaxanthin for 48 h. Histopathology, expression of lipid metabolism, inflammation, apoptosis, and fibrosis-related gene expression were assessed. And the function of mitochondria was also evaluated. The results indicated that astaxanthin attenuated HFD- and FFA-induced lipid accumulation and its associated oxidative stress, cell apoptosis, inflammation, and fibrosis both in vivo and in vitro. Astaxanthin up-regulated FGF21 and PGC-1α expression in damaged hepatocytes, which suggested an unrecognized mechanism of astaxanthin on ameliorating NAFLD. Astaxanthin attenuated hepatocyte damage and mitochondrial dysfunction in NAFLD by up-regulating FGF21/PGC-1α pathway. Our results suggest that astaxanthin may become a promising drug to treat or relieve NAFLD.

Subclinical Left Ventricular Systolic Dysfunction Assessed Using Myocardial Strain Measured by Speckle Tracking in Non-Alcoholic Fatty Liver Disease – Systematic Review

Background and Aims: Multiple studies demonstrated that non-alcoholic fatty liver disease (NAFLD) is associated with several structural and functional cardiovascular complications. The aim of this systematic review is to evaluate subclinical left ventricular (LV) systolic dysfunction in NAFLD assessed with myocardial strain measured by speckle tracking echocardiography (STE). Methods: We performed a systematic search on PubMed and EMBASE with predefined keywords searching for observational studies published till 19 March 2020. NAFLD diagnosis was accepted if confirmed by biopsy or imaging techniques and LV systolic function evaluation by STE. Full articles that fulfilled our inclusion and exclusion criteria were included in the systematic review. The National Heart, Lung, and Blood Institute (NHLBI) quality assessment tools were used for evaluation of included studies. Results: Eleven observational studies (9 cross-sectional studies, 1 case-control, 1 longitudinal cohort) were included with a total study population of 5,851 subjects. All included studies evaluated left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS). Only two studies rated as “good” demonstrated that NAFLD patients had a reduced LVEF, out of which, one study was conducted on type 2 diabetic patients, while the other study was a population-based longitudinal cohort. Moreover, eight studies, out of which four were rated “good”, two as “fair” and two as “poor” demonstrated that GLS was significantly reduced in NAFLD. On the other hand, the remaining three studies that reported a non-significant difference in GLS were conducted on type 2 diabetic patients in two of the studies, one rated as “fair” and one as “good”. Furthermore, the third study was involving only NAFLD patients comparing drinkers with non-drinkers, being rated as “good”. Conclusions: NAFLD patients are at increased risk to develop subclinical LV systolic dysfunction assessed with myocardial strain measured by speckle tracking, despite having normal LVEF values and remaining asymptomatic. This association remains to be confirmed in more studies involving diabetic patients in the presence and absence of NAFLD.

Peri-transplant renal dysfunction in patients with non-alcoholic steatohepatitis undergoing liver transplantation.

Non-alcoholic fatty liver disease (NAFLD) is currently the most common etiology of chronic liver disease (CLD) caused by an accumulation of fat in the liver and globally is the leading indication of liver transplantation. Emerging data has recognized an increased association of NAFLD with risk of other metabolic liver diseases like type 2 diabetes mellitus, chronic kidney disease (CKD) and cardiovascular diseases. Pathophysiologically, NAFLD patients have a state of low-grade systemic inflammation, insulin resistance and atherogenic dyslipidemia which causes renal dysfunction. Patients with NAFLD cirrhosis awaiting liver transplant (LT) face unique challenges and have a significantly higher requirement of simultaneous-liver-kidney transplant as compared to other etiologies. Further, NAFLD not only recurs but also occurs as a de novo manifestation post-LT. There is also a significantly higher risk of waiting list stagnation and dropouts due to burdensome cardiometabolic disorders in NAFLD patients. The current review aims to understand the prevalence and pathogenetic basis of renal dysfunction in NAFLD. Additionally, the review describes the choice of immunosuppression protocols and use of intraoperative renal replacement therapy in context of intra and post-operative renal dysfunction in NAFLD patients. Prospective controlled trials focusing on NAFLD and development of CKD are needed to assess the existence of a causal and/or a bidirectional relationship between NAFLD and CKD.

Endogenous ethanol produced by intestinal bacteria induces mitochondrial dysfunction in non-alcoholic fatty liver disease.

A causal relationship between changes of the gut microbiome and non-alcoholic fatty liver disease (NAFLD) remains unclear. We demonstrated that endogenous ethanol (EnEth) produced by intestinal microbiota is likely a causative agent of NAFLD. Two mutants with different alcohol-producing abilities, namely, W14-adh and W14Δadh, were constructed using the clinical high alcohol-producing (HiAlc) Klebsiella pneumoniae strain W14 as a parent. Damage to hepatocytes caused by bacteria with different alcohol-producing capacities was evaluated (EtOH group as positive control). The ultrastructural changes of mitochondria were assessed via transmission electron microscopy (TEM). Hepatic levels of mitochondrial reactive oxygen species (ROS), DNA damage, and adenosine triphosphate were examined. The results illustrated that steatosis was most severe in the W14-adh group, followed by the W14 group, whereas the W14Δadh group had few fatty droplets. TEM and examination of related protein expression revealed that the mitochondrial integrity of HepG2 hepatocytes was considerably damaged in the EtOH and bacteria treatment groups. The impaired mitochondrial function in HepG2 hepatocytes was evidenced by reduced adenosine triphosphate content and increased mitochondrial ROS accumulation and DNA damage in the EtOH and bacteria treatment groups, especially the W14-adh group. Meanwhile, liver injury and mitochondrial damage were observed in the hepatocytes of mice. The livers of mice in the W14-adh group, which had the highest ethanol production, exhibited the most serious damage, similar to that in the EtOH group. EnEth produced by HiAlc bacteria induces mitochondrial dysfunction in NAFLD.

Astaxanthin Attenuates Hepatic Damages and Mitochondrial Dysfunction in Nonalcoholic Fatty Liver Disease by Regulating the FGF21/PGC-1α Pathway

Backgrounds: Non-alcoholic fatty liver disease(NAFLD) is considered to be one of the most common chronic liver diseases across worldwide. The pathogenesis of NAFLD is described as the two-hit theory. However, the underlying mechanisms remains to be fully explored. Beneficial effects of astaxanthin(Ax) have been identified,including anti-oxidative, anti-inflammatory, and anti-tumor activity. The present study aimed to elucidate the protective effect of Ax against NAFLD and its underlying mechanism. Methods: Mice were fed either a high fat or control diet, with or without AX, for up to 12 weeks. L02 cells were treated with free fatty acids combined with different doses of Ax for 48 h. Histopathology, expression of lipid metabolism, inflammation, apoptosis, and fibrosis-related genes were assessed. Findings: The results indicated that Ax attenuated HFD- and FFA-induced lipid accumulation and its associated oxidative stress, cell apoptosis, inflammation, and fibrosis both in vivo and in vitro. Ax upregulated FGF21 and PGC-1α expression in damaged hepatocytes, which suggested an unrecognized mechanism of Ax on ameliorating NAFLD. Interpretation: Ax attenuated hepatocyte damage and mitochondrial dysfunction in NAFLD by upregulating FGF21/PGC-1α.Our studies verified that Ax may become a promising drug to treat or relieve NAFLD. Funding: Work was supported by the National Natural Science Foundation of China (NO: 81670472, 81700502 and 81800538); National Natural Science Foundation of Shanghai (NO: 19ZR1447700); the Health System Innovation Plan of Shanghai Putuo District Science and Technology Committee (NO: PTKWWS2018001); the WBN Liver Disease Research Fund of China Hepatitis Prevention Foundation (NO: CFHPC2019031); the Yangfan Plan of Shanghai Science and Technology Commission (NO: 2018YF1420000); the Project of Shanghai Health Commission (NO: 2019469). Declaration of Interest: The authors have declared that no competing interest exists. Ethical Approval: Experimental protocols were approved by the Animal Care and Use Committee of Shanghai Tongji University, China. All animal experiments were carried out according to the guidelines of the China National Institutes of Health. All efforts were made to minimize suffering of experimental mice in this research.

Mitochondria-Mediated Pathogenesis and Therapeutics for Non-Alcoholic Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) has become a worldwide epidemic over the last decade. Remarkable progress has been made in understanding the pathogenesis of NAFLD and, subsequently, in developing medications to treat this disease. Although the mechanisms of NAFLD are complex and multifactorial, accumulating and emerging evidence indicates that mitochondria play a critical role in the pathogenesis and progression of NAFLD. Pharmacologic therapies acting on mitochondria may therefore pave the way to novel strategies for the prevention and protection against NAFLD. This review focuses on new insights into the role of hepatic mitochondrial dysfunction in NAFLD, and summarizes recent studies on mitochondria-centric therapies for NAFLD utilizing new medications or repurposing of currently available drugs. Although some studies presented may feature controversial results or are still in lack of clinical verification, it is undoubted that medications that may spare the mitochondria from multiple levels of damage are highly promising, and have begun to be used with some degree of success.

Angiotensin II Type 1 Receptor rs5186 Gene Variant Predicts Incident NAFLD and Associated Hypertension: Role of Dietary Fat-Induced Pro-Inflammatory Cell Activation.

Hypertension has been linked to the presence and severity of nonalcoholic fatty liver disease (NAFLD) through unclear mechanisms. The gain-of-function rs5186 A1166C variant in angtiotensin receptor type 1 (AGTR1) gene has been linked to hypertension, cardiovascular disease and metabolic syndrome. We assessed the impact of AGTR1 A1166C variant on NAFLD incidence and severity and on glucose and lipid metabolism and explored the underlying mechanisms. We followed up 314 healthy nonobese, nondiabetic, nonhypertensive, insulin-sensitive participants in a population-based study, characterized for AGTR1 rs5186 A1166C variant, adipokine profile, inflammatory and endothelial dysfunction markers. An independent cohort of 78 biopsy-proven nondiabetic NAFLD patients and controls underwent an oral glucose tolerance test with Minimal Model analysis of glucose homeostasis, and an oral fat tolerance test with measurement of plasma lipoproteins, adipokines, MCP-1, calprotectin, and nuclear factor-κB activation in circulating mononuclear cells. AGTR1 A1166C polymorphism predicted 9.8-year incident NAFLD (odds ratio: 1.67, 95% CI: 1.26-2.21) and hypertension (odds ratio: 1.49, 95% CI: 1.12-2.63) and 9-year increase in cardiovascular disease risk and endothelial dysfunction markers. In the cross-sectional cohort, AGTR1 C allele carriers had higher insulin resistance. Despite comparable fasting lipid profiles, AGTR1 C allele carriers showed postprandial triglyceride-rich and cholesterol-rich VLDL lipoprotein accumulation, higher resistin, MCP-1 and calprotectin responses and nuclear factor-κB activation in mononuclear cells, and a blunted postprandial adiponectin response to fat, which predicted liver histology, hepatocyte apoptosis activation, insulin resistance, and endothelial dysfunction. AGTR1 A1166C variant affects liver disease, insulin resistance, and endothelial dysfunction in NAFLD, at least in part by modulating adipokine, chemokine, and pro-inflammatory cell activation in response to fat ingestion.

217 - Oxidized phospholipids regulate cellular metabolism and lipid droplet formation in hepatocytes – Implications for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of cardio-metabolic syndrome, affects up to 30% of individuals in the United States. NAFLD is a chronic disease that initially presents as hepatic steatosis and can progress to non-alcoholic steatohepatitis, hepatic fibrosis, and liver failure. Hepatic steatosis is characterized by an increased lipid burden within hepatocytes. This has been correlated with hepatic mitochondrial dysregulation which is thought to contribute to hepatic lipid accumulation. However, the factors that cause mitochondrial dysfunction in NAFLD remain unknown. Previously, our lab has shown that oxidized phospholipids (OxPLs) regulate mitochondrial function, and here, we test the hypothesis that OxPLs that accumulate due to oxidative stress during NAFLD progression in the liver promote lipid droplet accumulation within hepatocytes by dysregulating hepatic mitochondrial function. C57Bl/6 mice were fed a high fructose, palmitate, cholesterol diet for 12 weeks to induce hepatic steatosis. Compared to mice fed a chow diet after 12 weeks, we observed a disproportionate increase in truncated oxidation products of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PAPC) compared to full-length oxidation products in steatotic livers. Treatment of AML12 murine hepatocytes with truncated oxidation products of PAPC for 4-hours resulted in a significant decrease in maximum and reserve oxygen consumption rate; additionally, 48-hour treatment resulted in an increase in lipid droplet size and quantity. Incongruous with effects of truncated oxidation products, full-length oxidation products of PAPC exhibited no significant effect on oxygen consumption or lipid droplet size. These data suggest that truncated oxidation products in the hepatic milieu regulate lipid droplet size and quantity by modulating mitochondrial function which may contribute to the pathogenesis of hepatic steatosis and NAFLD.

Severe steatosis induces portal hypertension by systemic arterial hyporeactivity and hepatic vasoconstrictor hyperreactivity in rats

Non-alcoholic fatty liver disease (NAFLD) has become the most prevalent chronic liver disease. The presence of portal hypertension has been demonstrated in NAFLD prior to development of inflammation or fibrosis, and is a result of extrahepatic and intrahepatic factors, principally driven by vascular dysfunction. An increased intrahepatic vascular resistance potentially contributes to progression of NAFLD via intralobular hypoxia. However, the exact mechanisms underlying vascular dysfunction in NAFLD remain unknown. This study investigates systemic hemodynamics and both aortic and intrahepatic vascular reactivity in a rat model of severe steatosis. Wistar rats were fed a methionine-choline-deficient diet, inducing steatosis, or control diet for 4 weeks. In vivo hemodynamic measurements, aortic contractility studies, and in situ liver perfusion experiments were performed. The mean arterial blood pressure was lower and portal blood pressure was higher in steatosis compared to controls. The maximal contraction force in aortic rings from steatotic rats was markedly reduced compared to controls. While blockade of nitric oxide (NO) production did not reveal any differences, cyclooxygenase (COX) blockade reduced aortic reactivity in both controls and steatosis, whereas effects were more pronounced in controls. Effects could be attributed to COX-2 iso-enzyme activity. In in situ liver perfusion experiments, exogenous NO donation or endogenous NO stimulation reduced the transhepatic pressure gradient (THPG), whereas NO synthase blockade increased the THPG only in steatosis, but not in controls. Alpha-1-adrenergic stimulation and endothelin-1 induced a significantly more pronounced increase in THPG in steatosis compared to controls. Our results demonstrate that severe steatosis, without inflammation or fibrosis, induces portal hypertension and signs of a hyperdynamic circulation, accompanied by extrahepatic arterial hyporeactivity and intrahepatic vascular hyperreactivity. The arterial hyporeactivity seems to be NO-independent, but appears to be mediated by specific COX-2-related mechanisms. Besides, the increased intrahepatic vascular resistance in steatosis appears not to be NO-related but rather to vasoconstrictor hyperreactivity.In this study, systemic hemodynamics and both aortic and intrahepatic vascular reactivity in a rat model of severe steatosis were investigated. Portal hypertension and signs of a hyperdynamic circulation were demonstrated. NO-independent, COX-2 mediated extrahepatic arterial hyporeactivity, as well as NO-independent alpha-1-adrenergic and endotheline-1 mediated intrahepatic vascular hyperreactivity are demonstrated, likely contributing to the observed portal hypertension in steatosis.

Abnormal Glucose Metabolism in Nonalcoholic Fatty Liver Disease

Nonalcoholic Fatty Liver Disease (NAFLD), a common cause of chronic liver disease, represents a spectrum of histopathologic abnormalities. NAFLD is often associated to the typical components of the metabolic syndrome (MS), with characteristics including abdominal obesity, type 2 diabetes, Insulin Resistance (IR), hypertension, and Hypertriglyceridemia, and has seriously threatened human health. IR, a crucial element of MS, is the fundamental contributor in the process of NAFLD. Therapy strategies are finite and, for now, are basically concentrated on weight reduction and utilization of insulin sensitizing agents. Recent literature indicated IR related to the abnormal glucose metabolism play a pivotal role in the development of NAFLD. Moreover, glucose resistance, glucocorticoid hormones, leptin, et al are also associated with glucose metabolism dysfunction in NAFLD. We highlight the mechanisms of these components in NAFLD, and our work might be beneficial for comprehending the mechanism and treatment of abnormal glucose metabolism in patients with NAFLD.

Prognostication of endothelial dysfunction in patients with non-alcoholic fatty liver diseases

The objective — to determine the effectiveness of a new method for prognostication the presence of endothelial dysfunction in patients with non-alcoholic fatty liver disease (NAFLD) of men and women of Podillya region of the first mature age by determining the complex of anthropometric parameters of patients.Material and methods. The study involved 112 patients with NAFLD. Only the patients of the first mature age were included in the study. The age of men ranged from 22 to 35 years, the age of women — from 21 to 35 years. Among them there were 67 men and 45 women. Anthropometric parameters of the body were measured in all patients: the waist circumference ratio to the hips, the difference between the height of the abdomen and the height of the pubic point, the circumference of the shoulder in the tense state, the sagittal abdominal diameter, the thickness of the skin-fat fold on the back of the shoulder, the thickness of the skin and fat folds on the front of the shoulder. Verification of the diagnosis of NAFLD and endothelial dysfunction was conducted in accordance with the recommendations of the unified clinical protocol.Results. By applying the method of determining endothelial dysfunction in NAFLD patients it was predicted the presence of endothelial dysfunction in 82 patients, who confirmed diagnosis after special studies. Endothelial dysfunction was discovered in 57 patients for the first time. Conclusions. The developed method provides an opportunity to make an objective assessment of the presence of endothelial dysfunction in NAFLD by an accessible and safe method, which allows to determine the risk of development of NAFLD, to diagnose the disease in time and to prescribe preventive measures or pathogenetically justified therapeutic strategy. The method can be reproduced in various medical and prophylactic and scientific medical institutions, especially in preventive examinations.

Increased expression of sterol regulatory element binding protein‑2 alleviates autophagic dysfunction in NAFLD.

Sterol regulatory element binding protein-2 (SREBP-2) is an important transcription factor in lipid homeostasis. A previous study showed that SREBP-2 also activated autophagic genes during cell-sterol depletion. Alterations in autophagy are reported to be involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). However, whether the regulation of SREBP-2 restores dysfunctional autophagy in hepatocytes during NAFLD remains to be elucidated. In the present study, a steatosis model was established with palmitic acid (PA) treatment at the indicated times and concentrations. Autophagosomes in hepatocytes were visualized by confocal microscopy after transfection with a tandem GFP-mCherry-LC3 construct. Autophagy-associated protein levels were analyzed by western blot analysis. Loss- and gain-of-function studies were performed to examine the role of SREBP-2 in the regulation of hepatocyte autophagy. It was demonstrated that PA induced autophagy and enhanced autophagic flux at the early stage, whereas prolonged treatment with PA resulted in dysfunction of autophagy in the PA-induced steatotic hepatocytes. In addition, different cellular models presented with differing dysfunctional autophagy in response to fatty acid overload. It was also confirmed that SREBP-2 regulated autophagy-related gene expression in hepatocytes, and it was shown that the overexpression of SREBP-2 increased the expression of autophagy-related genes, but did not affect the inhibition of the autophagic flux in lipid-overloaded HL-7702 cells. By contrast, increased SREBP-2 partly restored the inhibited autophagic activity in lipid-overloaded hepatoma HepG2 cells. Taken together, the present study demonstrated that autophagic function was impaired in lipid-overloaded human hepatocytes, and the differential effect of PA on autophagy was associated with the duration of PA and the cell type. Under these conditions, the overexpression of SREBP-2 alleviated the inhibited autophagic activity rather than the inhibition of autophagic flux. Consequently, the results indicated that restoration of autophagy dysfunction via the regulation of SREBP-2 may be a potential therapeutic target for the treatment of NAFLD.

Endothelial Dysfunction in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a potent hepatopathy. The metabolic syndrome combined with vascular complications is the leading cause of morbidity among NAFLD patients. Endothelial dysfunction is defined as the impairment of endothelial function, which is associated with the decrease in nitric oxide (NO) production. NO is a well-known vasodilator and a modulator of vascular tone and insulin secretion. L-Arginine is converted to nitric oxide and citrulline by the action of nitric oxide synthases (NOS). Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of all three isoforms of nitric oxide synthases (NOS) and is degraded by dimethylarginine diamino hydrolase (DDAH) in the liver. The decrease in DDAH activity results in accumulation of ADMA and reduction in NO bioavailability, subsequently leading to endothelial dysfunction in NAFLD. This review provides an overview of endothelial dysfunction in NAFLD and possible therapies for this common disorder.