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Fructolysis refers to the metabolism of fructose Fructose a dietary monosaccharide present naturally in fruits and vegetable either as free fructose or as part of the disaccharide sucrose It is also present in our diets as both the refined crystalline fructose and as a constituent of high fructose corn syrups Although the metabolism of fructose and glucose share many of the same intermediate structures they have very different metabolic fates in human metabolism Fructose is metabolized almost completely in the liver in humans and is directed toward replenishment of liver glycogen and triglyceride synthesis while much of dietary glucose passes through the liver where it is metabolized in skeletal muscle to CO2 H2O and ATP and to fat cells where it is metabolized primarily to glycerol phosphate for triglyceride synthesis as well as energy production The products of fructose metabolism are liver glycogen and de novo lipogenesis of fatty acids and eventual synthesis of endogenous triglyceride can be divided into two main phases: The first phase is the synthesis of the trioses dihydroxyacetone(DHAP) and glyceraldehyde; the second phase is the subsequent metabolism of these trioses either in the gluconeogenic pathway for glycogen replenishment and/or complete metabolism in the fructolytic pathway to pyruvic | pyruvate] which enters the citric cycle | Krebs cycle] and is converted to citric | citrate] and subsequently directed toward ’’de novo’’ synthesis of the free fatty acid palmitic | palmitate]

The Metabolism of Fructose to DHAP and Glyceraldehyde

Synthesis of glycogen from DHAP and Glyceraldehyde 3 Phosphate

Figure 6 The Metabolic Conversion of Fructose to Glycogen in the Liver

Synthesis of Triglyceride from DHAP and Glyceraldehyde 3 Phosphate

Figure 7 The Metabolic Conversion of Fructose to Triglyceride (TG) in the Liver