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7.3: Extrahepatic Macronutrient & Alcohol Metabolism

Because the liver is so important in metabolism, the term extrahepatic has been defined to mean "located or occurring outside of the liver1". We are next going to consider extrahepatic tissue metabolism.

Figure 7.31 The liver "is kind of a big deal2"

To start considering the metabolic capabilities of the extrahepatic tissues, we start by removing pathways that only or mostly occur in the liver:

  • Alcohol oxidation
  • Gluconeogenesis
  • Ketone body synthesis
  • Urea synthesis
  • Lactate breakdown
  • Glucose-6-phosphatase

These metabolic processes are crossed off in the figure below.

Figure 7.32 Removing the pathways that only or mostly occur in the liver3

We are left with metabolic capabilities that are listed and shown below.

  • Glycogen synthesis and breakdown
  • Glycolysis
  • Fatty acid synthesis and breakdown
  • Triglyceride synthesis and breakdown
  • Protein synthesis and breakdown

Figure 7.33 The metabolic capability of the extrahepatic tissues3

We will use this figure as the base for metabolic capabilities of the different extrahepatic tissues to compare what pathways other tissues can perform versus all the pathways performed by extrahepatic tissues. In an effort to keep this simple, we are going to focus on four extrahepatic tissues in the following subsections: