Research Sven Francque

Abstract

Cardiovascular disease (CVD) is the leading cause of death in patients with type 1 diabetes (T1D). The risk of CVD is 7 times higher compared to the general population, especially in overweight and insulin resistant (IR) subjects. Nowadays, half of the T1D patients show overweight,. IR may contribute to the development of non-alcoholic fatty liver disease (NAFLD), which is characterized by liver steatosis. Importantly, CVD is the main cause of death in NAFLD. The diagnosis of NAFLD is highly dependent on liver biopsy, which is not suitable for routine screening. Non-invasive techniques are used for the diagnosis of NAFLD, but have not been validated in T1D. The exact prevalence of NAFLD and the contribution of IR have not yet been investigated in T1D. Assessing IR is difficult due to the invasive nature of the gold standard (clamp test). Since IR might play an important role in CVD and NAFLD, there is a compelling need for non-invasive diagnostics. In this multidisciplinary project, we will assess the accuracy of non-invasive tests for NAFLD, develop a screening algorithm, validate an innovative breath test to assess IR, assess the exact prevalence of NAFLD and IR in T1D, investigate the link between IR and NAFLD, and finally, assess the independent contribution of IR and NAFLD to CVD. If NAFLD contributes to CVD, its early detection and treatment may affect prognosis.

Researcher(s)

• Promoter: De Block Christophe
• Co-promoter: Francque Sven
• Fellow: Mertens Jonathan

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project

Abstract

Nonalcoholic fatty liver disease (NAFLD) is the liver component of the metabolic syndrome and reaches global epidemic proportions. Isolated steatosis is the most common form, but some patients progress towards nonalcoholic steatohepatitis (NASH). The latter predisposes to fibrosis, cirrhosis and cardiovascular disease. Determinants of progression towards NASH are unclear. In isolated steatosis, we have previously shown the presence of increased hepatic vascular resistance which potentially leads to low-flow ischemia and hepatic parenchymal hypoxia, triggering the transition to steatohepatitis. We hypothesize that this chronic hepatic hypoxia induces a specific subtype of cell death in steatotic hepatocytes, i.e. ferroptosis. This recently described cell death is mediated by iron-catalyzed membrane lipid peroxides and has been suggested to play an important role in NAFLD. We will study the presence of hepatic ferroptosis in relation to disease severity in a large human NAFLD cohort. The potential of hypoxia to induce ferroptosis will be assessed in an in vitro NAFLD model to study the trigger of ferroptosis. Furthermore, we will objectify the presence of hepatic parenchymal hypoxia and ferroptosis in a murine dietary model of NAFLD. Afterwards, we will test the potential of vasodilatory compounds (which reduce hepatic hypoxia) and a novel third-generation ferroptosis inhibitor to inhibit progression towards NASH and treat an established NASH in the murine dietary model.

Researcher(s)

• Promoter: Francque Sven
• Co-promoter: Vanden Berghe Tom
• Co-promoter: Van Eyck Annelies
• Fellow: Peleman Cédric

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project

Abstract

Hepatitis E (HEV) infections are emerging in Europe, especially HEV genotype 3. Pigs and wild boars are identified as the main source of HEV in Western countries and foodborne transmission seems a significant infection route. Detection methods for HEV in foods are not well standardized. Furthermore a paucity of permissive in vitro and in vivo HEV models, precludes exhaustive infectivity studies. In a recent Scientific Opinion concerning the public health risks associated with HEV as a food-borne pathogen published by the EFSA BIOHAZ Panel, the need for infectivity assays for quantitative risk assessment and for efficient control measures is emphasized. In this project, a first work package will deal with the prioritization of food products based on their risk for HEV in a Belgian context. This will be performed in collaboration with the Belgian meat industry. A second work package of the project will establish alternative molecular methods to detect infectious particles of HEV in high risk food products. For this purpose, molecular methods will be developed that assess the integrity of the RNA genome and capsid of HEV detected in food. These will be evaluated for their potency to estimate infectivity by comparison with an appropriate in vitro cell culture infectivity system for HEV that will be optimized. In a third work package, the effect of meat processing practices on HEV infectivity will be tested. The purpose of this WP is to define food preparatory conditions that will eliminate HEV infectivity.

Researcher(s)

• Promoter: Francque Sven
• Promoter: Vanwolleghem Thomas

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project

Abstract

Obesity constitutes a major health problem, partly due to the increasing prevalence and secondly because of its associated morbidity. It is associated with increased amounts of adipose tissue as well as fat accumulation in non-adipose tissue such as liver and skeletal muscle. Accumulation of ectopic fat in the liver (non-alcoholic fatty liver disease, NAFLD) is a strong independent marker of dyslipidaemia and insulin resistance predisposing to the development of type 2 diabetes. Besides high caloric diet and lack of physical activity, pesticide exposure and endocrine disruptor pollutants are now also increasingly recognized as an "obesogenic" risk factor. Remarkably, recent genome- and epigenome wide associations studies highlight crosstalk of many obesity-associated genetic variants and environmental factors (diet, pesticides, exercise, alcohol consumption, smoking, drugs, medication) with DNA methylation changes at proximal promoters and enhancers. For example, we recently found a strong association between the paraoxonase 1 (PON1) p.Q192R genotype with pesticide exposure and adverse epigenetic (re)programming of endocrine pathways in obesity and high body fat content. PON members hydrolyze several pesticides, a number of exogenous and endogenous lactones and metabolizes toxic oxidized lipids of low density lipoproteins (LDL) and HDL. A decrease in PON1 expression promotes adverse lipid metabolism and is an important risk factor for cardiometabolic disease and has recently been found to be associated with childhood and adult obesity, liver steatosis and its more severe subtype of steatohepatitis. Differences in PON2 have been associated with obesity susceptibility in brown/white adipose tissue. Given the crucial role of PON members in protecting from adverse environmental exposure and from obesity, there is an urgent need for further molecular and clinical research on (epi)genetic PON(1-3) regulation mechanisms in this area. In this GOA, we want to further investigate associations of clinical characterized obesity phenotypes with PON(1-3) genetic variants/polymorphisms, associated epigenetic DNA methylation variation and PON(1-3) expression in samples (i.e. blood, serum, adipose or liver) of clinical patient cohorts diagnosed with obesity, NAFLD/NASH, in relation to adverse pesticide exposure or following therapeutic medical intervention (liraglutide or bariatric surgery). Functional investigation of genetic-epigenetic regulatory crosstalk of PON(1-3) expression in response to pollutant exposure or following medical interventions will be further investigated in relation to biochemical parameters of obesity/liver steatosis/adipocyte differentiation in cell models in vitro as well as in zebrafish in vivo. As such, a better understanding of variable PON(1-3) regulation of obesity-associated traits by adverse obesogenic pollutants or healthy intervention strategies may offer new perspectives to prevent obesity and/or promote cardiometabolic health.

Researcher(s)

• Promoter: Van Hul Wim
• Co-promoter: Francque Sven
• Co-promoter: Knapen Dries
• Co-promoter: Vanden Berghe Wim

Research team(s)

• Medical Genetics (MEDGEN)

Project type(s)

• Research Project

Abstract

Non-Alcoholic Fatty Liver Disease (NAFLD), the accumulation of fat droplets in the liver that is not related to alcohol consumption, is the most common chronic liver disease. It is associated with overweight/obesity, diabetes and blood lipid disturbances, all taking epidemic proportions. It can lead to severe liver disease and is predicted to become the most important indication for liver transplantation by 2020. It also has consequences outside the liver: in NAFLD the liver presumably releases substances that cause damage to the blood vessels or alters their function, causing cardiovascular disease (CVD). NAFLD hence increases significantly the risk of developing CVD, as well as the risk of diabetes and non-liver malignancies. The mechanisms by which NAFLD causes CVD is not well understood, as well as the mechanisms that cause NAFLD itself. We previously demonstrated that changes in structure and function of the blood vessels within the liver are altered early in NAFLD development. We also unraveled some of the mechanisms that link NAFLD to the development of CVD. The current project builds on this work and aims at further studying the mechanisms that explain the changes in the liver blood vessels as a causal mechanism in the development of NAFLD as well as the mechanisms linking NAFLD to CVD. These aspects will be studied in animal models and in a large patient cohort with baseline and follow-up metabolic, hepatological and cardiological phenotypical characterisation.

Researcher(s)

• Promoter: Francque Sven
• Fellow: Francque Sven

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project

Abstract

Research questions: 1) What are the underlying mechanisms of the dynamic vascular alterations, leading to increased IHVR in NAFLD? a. Is there a role for α1-adrenergic mechanisms? b. Is there a role for COX-mediated mechanisms? c. Is there a role for ET-1 mediated mechanisms? d. Is there a role for angiotensin-mediated mechanisms? e. Are there any interactions, additive or synergistic effects of these vasoconstrictive mechanisms? 2) Is the development of NAFLD associated with the development of CVD? 3) Do the alterations in liver haemodynamics contribute to the progression of NAFLD? 4) Do the alterations in liver haemodynamics contribute to the development of the associated CVD? 5) What are the effects of modulating the intrahepatic vascular tone on NAFLD and associated CVD?

Researcher(s)

• Promoter: Francque Sven
• Fellow: van der Graaff Denise

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project

Abstract

The research will be performed in close collaboration with the Edwin L. Steele Laboratories in Boston (MA; United States of America). Non-alcoholic fatty liver disease (NAFLD) is defined by excessive fat accumulation in the liver and encompasses a spectrum ranging from non-alcoholic fatty liver (NAFL, also known as simple steatosis), via non-alcoholic steatohepatitis (NASH), in which there is accompanying liver cell injury and inflammation, to advanced fibrosis and cirrhosis at the end of the spectrum. The aetiopathogeneis of NAFLD and its progressions is not fully understood yet. NAFLD has become one of the major chronic liver diseases in the Western societies, and is expected to increase even further. Previous data from our laboratory indicate that alterations of the intrahepatic vascular resistance are an early event in NAFLD and hence might significantly contribute to the pathogenesis and progression of the disease. Further and detailed research is necessary and will be executed in close collaboration with the E.L. Steele laboratories in Boston, USA. Hepatocellular carcinoma (HCC) is a major cause of liver death and occurs classically in cirrhosis, so in NAFLD. Recent data, however, point towards an increasing prevalence of HCC in NAFLD even before the development of advanced fibrosis. Further elucidating of potential driving forces behind HCC development will significantly contribute towards knowledge of HCC (independent of its aetiology) and might guide potential therapeutic targets. The longstanding expertise in tumourigenesis and tumour micro-environment offers an opportunity for in depth analysis of NAFLD-induced HCC, which has not been performed thus far.

Researcher(s)

• Promoter: Francque Sven

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project

Abstract

Non-Alcoholic Fatty Liver Disease (NAFLD) is a chronic liver disease defined by the accumulation of fat in the hepatocytes. In case of additional inflammation and signs of hepatocyte degeneration the disease is called Non-Alcoholic SteatoHepatitis (NASH), which represents a more severe disease subtype. Given the clear correlation between NAFLD and obesity and diabetes, and the increasing incidence of the latter two, NAFLD constitutes a major health concern. Moreover, NAFLD is one of the major causes of liver cirrhosis and can lead to liver cancer. The pathogenesis of NASH is poorly understood, and several organs and tissues (the gut, the visceral and subcutaneous adipose tissue) have been implicated. In the current project characterization of immune cells (regulatory T cells and Th1/Th17/Th22 by flowcytometry and immunohistochemistry) and cytokine profiles (ELISA on serum and RT-PCR on tissue) will be examined in peripheral and portal venous blood, liver tissue, mesenteric lymph nodes, subcutaneous and abdominal adipose tissue of mice fed a high-fat diet (a well established model of NASH) vs. mice fed a control diet for 20 weeks, in order to study the immunological alterations (focused on Tregs and Th17) in these different tissue compartments involved in NASH pathogenesis. In a second set of experiments one group of mice fed a high fat diet for 20 weeks will subsequently be switched for an additional 12 weeks to a normal diet, followed again by characterization of aforementioned immune cells and cytokines at the different sites, in order to study the evolution of the immunological alterations at the different sites, their potential reversal and their relation with (the evolution of) NASH histology. A second and third group will continue on high fat diet or on high fat diet supplemented with an antioxidant (resveratrol), to study the therapeutic effects of the latter on NASH in relation to its effects on the immune cell population. In a third set of experiments the effects of adoptive transfer of Tregs from mice fed the control diet to the mice fed the high-fat diet will be studied, in order to further substantiate their role in NASH pathogenesis. Lastly, given the results of the preclinical research were significant, we will study the immune cell populations and cytokine profiles in peripheral and hepatic venous blood and in liver biopsy specimens of well-characterized NAFLD patients (translational study).

Researcher(s)

• Promoter: Francque Sven
• Fellow: Van Herck Mikhaïl

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project

Abstract

In our study we focus on disturbances in the liver blood flow. Previously we showed that severe steatosis leads to a significant rise in blood pressure in the portal system ("portal hypertension") preceding the occurrence of inflammation. The degree of portal hypertension appeared to be related to the severity of steatosis. These findings points towards a significant increase in intrahepatic resistance and subsequent impairment of liver blood flow. The intrahepatic resistance has, however, to date never been directly investigated in NAFLD. In the current study we will therefore focus on the intrahepatic resistance and its (functional and morphological) determinants in a rat model of severe steatosis. Potential contribution of different cell types (Kupffer cells, stellate cells) and of different mediators to intrahepatic vascular tone (e.g. Nitric Oxid) will be examined in detail.

Researcher(s)

• Promoter: Michielsen Peter
• Co-promoter: Francque Sven
• Fellow: Kwanten Wilhelmus

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project

Abstract

Non-alcoholic Fatty Liver Disease (NAFLD), the accumulation of fat in the liver (steatosis) related to obesity and glucose disturbances, can lead to severe liver disease and is an important contributor to metabolic disease. Many patients are at risk. Accurate screening tools to diagnose NAFLD without the need for a liver biopsy are urgently warranted. By prospectively and thoroughly assessing the presence of liver disease in obese patients we recently developed scoring systems that accurately predict liver disease but that need further validation. Specific biomarkers will be searched for to enable physicians to select, out of the large numbers of patients with obesity and diabetes, those who need further, more invasive testing and treatment. Furthermore, we previously showed that severe steatosis leads to changes in liver blood flows. We will study the impact of these changes on the evolution of the disease and on the risk of complications in surgery for obesity. Analysis of blood samples obtained from the liver by a specific technical procedure will be performed to study the specific contribution of the liver to the health problems associated with obesity. Liver tissue samples will be examined to identify factors that contribute to disease. Finally, patients will be followed-up and re-examined after one year, in order to increase our understanding of the natural history of the disease, and to identify factors that not only predict disease severity but also its evolution.

Researcher(s)

• Promoter: Pelckmans Paul
• Co-promoter: Van Gaal Luc
• Fellow: Francque Sven

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project

Abstract

In our study we focus on disturbances in the liver blood flow. Previously we showed that severe steatosis leads to a significant rise in blood pressure in the portal system ("portal hypertension") preceding the occurrence of inflammation. The degree of portal hypertension appeared to be related to the severity of steatosis. These findings points towards a significant increase in intrahepatic resistance and subsequent impairment of liver blood flow. The intrahepatic resistance has, however, to date never been directly investigated in NAFLD. In the current study we will therefore focus on the intrahepatic resistance and its (functional and morphological) determinants in a rat model of severe steatosis. Potential contribution of different cell types (Kupffer cells, stellate cells) and of different mediators to intrahepatic vascular tone (e.g. Nitric Oxid) will be examined in detail.

Researcher(s)

• Promoter: Michielsen Peter
• Co-promoter: Francque Sven
• Co-promoter: Pelckmans Paul
• Fellow: Kwanten Wilhelmus

Research team(s)

• Laboratory Experimental Medicine and Pediatrics (LEMP)

Project type(s)

• Research Project