Non-alcoholic fatty liver disease (NAFLD)

  • Non-alcoholic fatty liver disease (NAFLD) is one cause of a fatty liver, where large vacuoles of fat (‘bubbles’ in the cells on the image) accumulate in liver cells via the process of steatosis (abnormal retention of lipids within the cells).

  • NAFLD occurrs when fat is deposited in the liver, but not due to excessive alcohol use. It is normal for the liver to contain some fat. However, if more than 5% - 10% of the liver’s weight is fat, it is called a fatty liver.
  • NAFLD is associated with a condition called insulin resistance, which, in turn, is associated with the metabolic syndrome and diabetes mellitus type 2.
  • In the Western world, every fifth adult is affected by NAFLD. Non-alcoholic steatohepatitis (NASH) is the most extreme form of NAFLD and is regarded as one of the leading causes of cirrhosis, the final phase of chronic liver disease that is characterized by an abnormal structure and function of the liver. Up to 25% of adults with NASH may have cirrhosis.
  • Cirrhosis is characterized by the replacement of liver tissue by fibrosis, scar tissue and regenerative nodules (lumps that occur as a result of a process in which damaged tissue is regenerated), leading to loss of liver function.
  • Author: Martin Golebiewski

  • Image from Wikipedia, author Nephron

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    Diseased hepatocytes accumulate lipid droplets

    After a meal, rich in lipids (see image), the lipids enter the blood vessels, then delivered to the liver and enter the hepatocytes. In hepatocytes they are converted and stay there in form of lipid droplets until lipids are needed.

    If our lipid consumption is too high (see that e.g. olive oil is in this risk group), then hepatocytes can accumulate too high levels of lipid droplets which can lead to diseases of the liver (fatty liver) or diseases of other organs.

  • Author: Iryna Ilkavets

  • Image: Jill Zander and Iryna Ilkavets

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    Modelling – biological systems on computer

    During the last years, scientists strive to better understand the behavior of complete biological systems. To this end, they develop computational models, in which a biological network is represented in a simplified manner on computer.

  • The connections contained in these models can be based on literature knowledge, but they can also be very speculative. In order to see whether a model is useful, its behavior must be simulated. The simulation results are afterwards compared to biological data. Thereby the correctness of the model can be shown or model parameters can be optimized.
  • Computer models are never complete. However, they provide possible explanations for a specific behavior of a system. Those hypotheses can be tested with new experiments. After that, the models are modified and refined.
  • Several types of models are created for different biological problems. Logical models can explain dependencies between components of a biological system. In stoichiometric models biochemical components are connected via reactions. If kinetics are added to those reactions, models with differential equations (ODE models) will be created. They can be used in order to investigate biochemical mechanisms.
  • In the Virtual Liver Network (VLN) many models are developed that describe processes within one liver cell. Apart from that, there are also models comprising the liver lobule, the whole liver, and even the whole organism. The scales of the models in VLN are thus different. The reasonable connection of those submodels into one integrated liver model is called multi-scale modelling and constitutes a big challenge.
  • Author: Roland Keller

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