BackgroundNAFLD progression, from steatosis to inflammation and fibrosis, results from an interplay of intra- and extrahepatic mechanisms. Disease drivers likely include signals from white adipose... Show moreBackgroundNAFLD progression, from steatosis to inflammation and fibrosis, results from an interplay of intra- and extrahepatic mechanisms. Disease drivers likely include signals from white adipose tissue (WAT) and gut. However, the temporal dynamics of disease development remain poorly understood.MethodsHigh-fat-diet (HFD)-fed Ldlr−/−.Leiden mice were compared to chow-fed controls. At t = 0, 8, 16, 28 and 38w mice were euthanized, and liver, WAT depots and gut were analyzed biochemically, histologically and by lipidomics and transcriptomics together with circulating factors to investigate the sequence of pathogenic events and organ cross-talk during NAFLD development.ResultsHFD-induced obesity was associated with an increase in visceral fat, plasma lipids and hyperinsulinemia at t = 8w, along with increased liver steatosis and circulating liver damage biomarkers. In parallel, upstream regulator analysis predicted that lipid catabolism regulators were deactivated and lipid synthesis regulators were activated. Subsequently, hepatocyte hypertrophy, oxidative stress and hepatic inflammation developed. Hepatic collagen accumulated from t = 16 w and became pronounced at t = 28–38 w. Epididymal WAT was maximally hypertrophic from t = 8 w, which coincided with inflammation development. Mesenteric and subcutaneous WAT hypertrophy developed slower and did not appear to reach a maximum, with minimal inflammation. In gut, HFD significantly increased permeability, induced a shift in microbiota composition from t = 8 w and changed circulating gut-derived metabolites.ConclusionHFD-fed Ldlr−/−.Leiden mice develop obesity, dyslipidemia and insulin resistance, essentially as observed in obese NAFLD patients, underlining their translational value. We demonstrate that marked epididymal-WAT inflammation, and gut permeability and dysbiosis precede the development of NAFLD stressing the importance of a multiple-organ approach in the prevention and treatment of NAFLD. Show less
Lingen, E. van; Tushuizen, M.E.; Steenhuis, M.E.J.; Deynen, T. van; Martens, J.; Morales, D.D.I.; ... ; Maljaars, P.W.J. 2021
Purpose Liver steatosis is a frequently reported condition in patients with inflammatory bowel disease (IBD). Different factors, both metabolic and IBD-associated, are believed to contribute to the... Show morePurpose Liver steatosis is a frequently reported condition in patients with inflammatory bowel disease (IBD). Different factors, both metabolic and IBD-associated, are believed to contribute to the pathogenesis. The aim of our study was to calculate the prevalence of liver steatosis and fibrosis in IBD patients and to evaluate which factors influence changes in steatosis and fibrosis during follow-up. Methods From June 2017 to February 2018, demographic and biochemical data was collected at baseline and after 6-12 months. Measured by transient elastography (FibroScan), liver steatosis was defined as Controlled Attenuation Parameter (CAP) >= 248 and fibrosis as liver stiffness value (Emed) >= 7.3 kPa. IBD disease activity was defined as C-reactive protein (CRP) >= 10 mg/l and/or fecal calprotectin (FCP) >= 150 mu g/g. Univariate and multivariate regression analysis was performed; a p-value of <= 0.05 was considered significant. Results Eighty-two out of 112 patients were seen for follow-up; 56% were male. The mean age was 43 +/- 16.0 years, and mean BMI was 25.1 +/- 4.7 kg/m(2). The prevalence of liver steatosis was 40% and of fibrosis was 20%. At baseline, 26 patients (32%) had an active episode of IBD. Using a multivariate analysis, disease activity at baseline was associated with an increase in liver steatosis (B = 37, 95% CI 4.31-69.35, p = 0.027) and liver fibrosis (B = 1.2, 95% CI 0.27-2.14, p = 0.016) during follow-up. Conclusions This study confirms the relatively high prevalence of liver steatosis and fibrosis in IBD patients. We demonstrate that active IBD at baseline is associated with both an increase in liver steatosis and fibrosis during follow-up. Show less
Adverse outcome pathways (AOPs) are a recent toxicological construct that connects, in a formalized, transparent and quality-controlled way, mechanistic information to apical endpoints for... Show moreAdverse outcome pathways (AOPs) are a recent toxicological construct that connects, in a formalized, transparent and quality-controlled way, mechanistic information to apical endpoints for regulatory purposes. AOP links a molecular initiating event (MIE) to the adverse outcome (AO) via key events (KE), in a way specified by key event relationships (KER). Although this approach to formalize mechanistic toxicological information only started in 2010, over 200 AOPs have already been established. At this stage, new requirements arise, such as the need for harmonization and re-assessment, for continuous updating, as well as for alerting about pitfalls, misuses and limits of applicability. In this review, the history of the AOP concept and its most prominent strengths are discussed, including the advantages of a formalized approach, the systematic collection of weight of evidence, the linkage of mechanisms to apical end points, the examination of the plausibility of epidemiological data, the identification of critical knowledge gaps and the design of mechanistic test methods. To prepare the ground for a broadened and appropriate use of AOPs, some widespread misconceptions are explained. Moreover, potential weaknesses and shortcomings of the current AOP rule set are addressed (1) to facilitate the discussion on its further evolution and (2) to better define appropriate vs. less suitable application areas. Exemplary toxicological studies are presented to discuss the linearity assumptions of AOP, the management of event modifiers and compensatory mechanisms, and whether a separation of toxicodynamics from toxicokinetics including metabolism is possible in the framework of pathway plasticity. Suggestions on how to compromise between different needs of AOP stakeholders have been added. A clear definition of open questions and limitations is provided to encourage further progress in the field. Show less
