Lucija Jukić

Bio: Lucija Jukić is an academic researcher from University of Zagreb. The author has contributed to research in topics: Hepatitis C virus & Nonalcoholic fatty liver disease. The author has an hindex of 7, co-authored 26 publications receiving 617 citations.

Pathogenesis and management issues for non-alcoholic fatty liver disease

Abstract: Nonalcoholic fatty liver disease (NAFLD) has, although it is a very common disorder, only relatively recently gained broader interest among physicians and scientists. Fatty liver has been documented in up to 10 to 15 percent of normal individuals and 70 to 80 percent of obese individuals. Although the pathophysiology of NAFLD is still subject to intensive research, several players and mechanisms have been suggested based on the substantial evidence. Excessive hepatocyte triglyceride accumulation resulting from insulin resistance is the first step in the proposed ‘two hit’ model of the pathogenesis of NAFLD. Oxidative stress resulting from mitochondrial fatty acids oxidation, NF-κB-dependent inflammatory cytokine expression and adipocytokines are all considered to be the potential factors causing second hits which lead to hepatocyte injury, inflammation and fibrosis. Although it was initially believed that NAFLD is a completely benign disorder, histologic follow-up studies have showed that fibrosis progression occurs in about a third of patients. A small number of patients with NAFLD eventually ends up with end-stage liver disease and even hepatocellular carcinoma. Although liver biopsy is currently the only way to confirm the NAFLD diagnosis and distinguish between fatty liver alone and NASH, no guidelines or firm recommendations can still be made as for when and in whom it is necessary. Increased physical activity, gradual weight reduction and in selected cases bariatric surgery remain the mainstay of NAFLD therapy. Studies with pharmacologic agents are showing promising results, but available data are still insufficient to make specific recommendations; their use therefore remains highly individual.

Adipokines and proinflammatory cytokines, the key mediators in the pathogenesis of nonalcoholic fatty liver disease

Abstract: Nonalcoholic fatty liver disease (NAFLD) is a condition in which excess fat accumulates in the liver of a patient with no history of alcohol abuse or other causes for secondary hepatic steatosis. The pathogenesis of NAFLD and nonalcoholic steatohepatitis (NASH) has not been fully elucidated. The “two-hit“ hypothesis is probably a too simplified model to elaborate complex pathogenetic events occurring in patients with NASH. It should be better regarded as a multiple step process, with accumulation of liver fat being the first step, followed by the development of necroinflammation and fibrosis. Adipose tissue, which has emerged as an endocrine organ with a key role in energy homeostasis, is responsive to both central and peripheral metabolic signals and is itself capable of secreting a number of proteins. These adipocyte-specific or enriched proteins, termed adipokines, have been shown to have a variety of local, peripheral, and central effects. In the current review, we explore the role of adipocytokines and proinflammatory cytokines in the pathogenesis of NAFLD. We particularly focus on adiponectin, leptin and ghrelin, with a brief mention of resistin, visfatin and retinol-binding protein 4 among adipokines, and tumor necrosis factor-α, interleukin (IL)-6, IL-1, and briefly IL-18 among proinflammatory cytokines. We update their role in NAFLD, as elucidated in experimental models and clinical practice.

Hepatitis C Virus, Insulin Resistance, and Steatosis

Abstract: Hepatitis C virus (HCV) is one of the main causes of liver disease worldwide. Liver steatosis is a common finding in many hepatic and extrahepatic disorders, the most common being metabolic syndrome (MS). Over time, it has been shown that the frequent coexistence of these two conditions is not coincidental, since many epidemiological, clinical, and experimental studies have indicated HCV to be strongly associated with liver steatosis and numerous metabolic derangements. Here, we present an overview of publications that provide clinical evidence of the metabolic effects of HCV and summarize the available data on the pathogenetic mechanisms of this association. It has been shown that HCV infection can induce insulin resistance (IR) in the liver and peripheral tissues through multiple mechanisms. Substantial research has suggested that HCV interferes with insulin signaling both directly and indirectly, inducing the production of several proinflammatory cytokines. HCV replication, assembly, and release from hepatocytes require close interactions with lipid droplets and host lipoproteins. This modulation of lipid metabolism in host cells can induce hepatic steatosis, which is more pronounced in patients with HCV genotype 3. The risk of steatosis depends on several viral factors (including genotype, viral load, and gene mutations) and host features (visceral obesity, type 2 diabetes mellitus, genetic predisposition, medication use, and alcohol consumption). HCV-related IR and steatosis have been shown to have a remarkable clinical impact on the prognosis of HCV infection and quality of life, due to their association with resistance to antiviral therapy, progression of hepatic fibrosis, and development of hepatocellular carcinoma. Finally, HCV-induced IR, oxidative stress, and changes in lipid and iron metabolism lead to glucose intolerance, arterial hypertension, hyperuricemia, and atherosclerosis, resulting in increased cardiovascular mortality.

Fuel Switch to LNG in Heavy Truck Traffic

Abstract: Liquefied natural gas (LNG) use as a fuel in road and maritime traffic has increased rapidly, and it is slowly entering railroad traffic as well. The trend was pushed by the state administrations of mainly EU countries and international organizations seeing LNG as a cost-effective and environmentally friendly alternative to diesel. Different infrastructural projects for the widespread use of LNG in transport have been launched around the world. The main goal of this paper was to analyze use of LNG as a fuel for heavy trucks. Different aspects of LNG chain were analyzed along with economical and ecological benefits of LNG application. Filling stations network for LNG were described for the purpose of comparative analysis of diesel and LNG heavy trucks. Conclusion has shown that using LNG as propellant fuel has numerous advantages over the use of conventional fuels. The higher initial investment of the LNG road vehicles could be amortized in their lifetime use, and in the long-term they are more affordable than the classic diesel vehicles. In addition to cost-effectiveness, LNG road vehicles reduce CO2 emissions. Therefore, the environmental goals in transport, not only of the member states but worldwide, could not be met without LNG in heavy truck traffic.

Offshore gas production infrastructure reutilisation for blue energy production

Abstract: Blue energy is one of the development sectors identified in the European Union strategic documents within the blue economy that promotes the exploitation of the sea potential. European energy initiatives recognize the importance of blue energy and encourage its research and development. The offshore exploitation of hydrocarbons worldwide is entering the final phase, followed by the gradual decommissioning of the production platforms and their removal. Decommissioning usually has an adverse effect on the environment aside from its economic intensity. By proper planning, lifetime of existing offshore infrastructure can be extended as it can be used for blue energy or other activities related to the blue economy. The paper deals with preliminary assessment of natural gas offshore infrastructure applicability for various blue energy options such as the wind power for electricity generation along with hydrogen, methane or ammonia production and other uses to reduce waste, energy consumption and CO2 emissions. Methods used included data gathering from 19 offshore gas facilities including assessment of natural gas production on current offshore fields, reserves and technology use, wind potential and decommissioning. Review of potential for energy production, storage and other activities such as CCS and CCU have also been given. Preliminary results show that there are possibilities for feasible and environmentally friendly blue energy utilisation. Average calculated capacity factors for the wind turbines are at the 32%. To investigate economic feasibility of decommission delay, detailed data gathering of wind potential should be done at specific heights along with load capacity of the gas platforms.

Inflammation, Oxidative Stress, and Obesity

Abstract: Obesity is a chronic disease of multifactorial origin and can be defined as an increase in the accumulation of body fat. Adipose tissue is not only a triglyceride storage organ, but studies have shown the role of white adipose tissue as a producer of certain bioactive substances called adipokines. Among adipokines, we find some inflammatory functions, such as Interleukin-6 (IL-6); other adipokines entail the functions of regulating food intake, therefore exerting a direct effect on weight control. This is the case of leptin, which acts on the limbic system by stimulating dopamine uptake, creating a feeling of fullness. However, these adipokines induce the production of reactive oxygen species (ROS), generating a process known as oxidative stress (OS). Because adipose tissue is the organ that secretes adipokines and these in turn generate ROS, adipose tissue is considered an independent factor for the generation of systemic OS. There are several mechanisms by which obesity produces OS. The first of these is the mitochondrial and peroxisomal oxidation of fatty acids, which can produce ROS in oxidation reactions, while another mechanism is over-consumption of oxygen, which generates free radicals in the mitochondrial respiratory chain that is found coupled with oxidative phosphorylation in mitochondria. Lipid-rich diets are also capable of generating ROS because they can alter oxygen metabolism. Upon the increase of adipose tissue, the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), was found to be significantly diminished. Finally, high ROS production and the decrease in antioxidant capacity leads to various abnormalities, among which we find endothelial dysfunction, which is characterized by a reduction in the bioavailability of vasodilators, particularly nitric oxide (NO), and an increase in endothelium-derived contractile factors, favoring atherosclerotic disease.

The Medical Risks of Obesity

Abstract: Obesity is associated with a number of medical conditions that lead to increased morbidity and increased mortality. Both the National Institutes of Health and the World Health Organization define obesity as a body mass index (BMI) > or = 30 kg/m2 and overweight as a BMI 25-30. The most common conditions associated with obesity are insulin resistance, diabetes mellitus, hypertension, dyslipidemia, cardiovascular disease, gallstones and cholecystitis, sleep apnea and other respiratory dysfunction, and the increased incidence of certain cancers. These are discussed below.

Oxidative Stress in Obesity: A Critical Component in Human Diseases

Abstract: Obesity, a social problem worldwide, is characterized by an increase in body weight that results in excessive fat accumulation. Obesity is a major cause of morbidity and mortality and leads to several diseases, including metabolic syndrome, diabetes mellitus, cardiovascular, fatty liver diseases, and cancer. Growing evidence allows us to understand the critical role of adipose tissue in controlling the physic-pathological mechanisms of obesity and related comorbidities. Recently, adipose tissue, especially in the visceral compartment, has been considered not only as a simple energy depository tissue, but also as an active endocrine organ releasing a variety of biologically active molecules known as adipocytokines or adipokines. Based on the complex interplay between adipokines, obesity is also characterized by chronic low grade inflammation with permanently increased oxidative stress (OS). Over-expression of oxidative stress damages cellular structures together with under-production of anti-oxidant mechanisms, leading to the development of obesity-related complications. The aim of this review is to summarize what is known in the relationship between OS in obesity and obesity-related diseases.

Non alcoholic fatty liver disease and metabolic syndrome.

Abstract: Non-alcoholic fatty liver disease (NAFLD) is a clinicopathologic entity increasingly recognized as a major health burden in developed countries. It includes a spectrum of liver damage ranging from simple steatosis to nonalcoholic steatohepatitis (NASH), advanced fibrosis, and rarely, progression to cirrhosis. Recent studies emphasize the role of insulin resistance, oxidative stress and subsequent lipid peroxidation, proinflammatory cytokines, adipokines and mitochondrial dysfunction in the development and progression of NAFLD. Furthermore, accumulating evidence supports an association between NAFLD and metabolic syndrome. Although the data are mainly epidemiological, the pathogenesis of NAFLD and metabolic syndrome seems to have common pathophysiological mechanisms, with focus on insulin resistance as a key factor. This review summarizes the current knowledge on the epidemiology, pathophysiology and diagnosis of both NAFLD and metabolic syndrome and the findings that strongly support the association of nonalcoholic fatty liver disease as a possible component in the cluster of metabolic syndrome.

Mechanisms of disease progression in nonalcoholic fatty liver disease.

Abstract: Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of hepatic pathology, ranging from simple steatosis (also called nonalcoholic fatty liver or NAFL) in its most benign form, to cirrhosis in its most advanced form. Nonalcoholic steatohepatitis (NASH) is an intermediate level of hepatic pathology. Hepatocyte accumulation of triglyceride is a hallmark of NAFL and NASH, but this sometimes subsides once cirrhosis has developed. Triglyceride storage per se is not hepatotoxic. Rather, it is a marker of increased exposure of hepatocytes to potentially toxic fatty acids. NAFL progresses to NASH when adaptive mechanisms that protect hepatocytes from fatty acid-mediated lipotoxicity become overwhelmed and rates of hepatocyte death begin to outstrip mechanisms that normally regenerate dead hepatocytes. This triggers repair responses that involve activation of hepatic stellate cells to myofibroblasts. The myofibroblasts generate excessive matrix and produce factors that stimulate expansion of liver progenitor populations. The progenitor cells produce chemokines to attract various kinds of inflammatory cells to the liver. They also differentiate to replace the dead hepatocytes. The intensity of these repair responses generally parallel the degree of hepatocyte death, resulting in variable distortion of the hepatic architecture with fibrosis, infiltrating immune cells, and regenerating epithelial nodules. As in other types of chronic liver injury, cirrhosis ensues in patients with NAFLD when repair is extreme and sustained, but ultimately unsuccessful, at reconstituting healthy hepatic epithelia.