Gluconeogenesis from glycerol

Puhakainen, V.A. Koivisto, and H. Yki-Jarvinen, Lipolysis and gluconeogenesis from glycerol are increased in patients with noninsulin-dependent diabetes mellitus, J. Clin. Endocrinol. Metab., 1992, 75, 789-794. 

FIGURE 21-21 Glyceroneogenesis. The pathway is essentially an abbreviated version of gluconeogenesis, from pyruvate to dihydroxyacetone phosphate (DHAP), followed by conversion of DHAP to glycerol 3-phosphate, which is used for the synthesis of triacylglycerol. 

Figure 5-24. The key reactions of gluconeogenesis from the precursors alanine, lactate, and glycerol. Heavy arrows indicate steps that differ from those of glycolysis. Broken arrows are reactions that are inhibited ( ) under conditions in which gluconeogenesis is occurring.

Cortisol, released in response to a variety of stressors (including low blood glucose), stimulates gluconeogenesis from amino acids and glycerol in the liver, thus raising blood glucose and counterbalancing the effects of insulin. 

Mitochondrial aspartate efflux is important in processes like urea synthesis [90], gluconeogenesis from lactate and the transport of cytosolic reducing equivalents to the mitochondria via the so-called malate-aspartate shuttle, e.g. during ethanol oxidation and gluconeogenesis from reduced substrates like glycerol, sorbitol, and xylitol [4,5]. During gluconeogenesis from lactate oxaloacetate is transported to the cytosol as aspartate to circumvent the low permeability of the mitochondrial membrane for oxaloacetate. 

Gluconeogenesis is the process of converting noncarbohydrates to glucose or glycogen. It is of particular importance when carbohydrate is not available from the diet. Significant substrates are amino acids, lactate, glycerol, and propionate. 

Gluconeogenesis Formation of glucose from precursors other than carbohydrates (especially by the liver and kidney) using amino acids from proteins, glycerol from fats, or lactate produced by muscle during anaerobic glycolysis. 

The interconversion of fructose-6-phosphate and fructose-1,6 bis phosphate is a control point in glycolysis and gluconeogenesis. Gluconeogenesis is a pathway which allows carbon atoms from substrates such as lactate, glycerol and some amino acids to be used for the synthesis of glucose, so it is in effect physiologically the opposite of... 

Gluconeogenesis is the de novo synthesis of glucose from none carbohydrate sources. These sources (precursors) are lactic acid, glycerol and the amino acids, especially alanine, glntamine and aspartic acid (Fignre 6.22). 

Hormones can modify the concentration of precursors, particularly the lipolytic hormones (growth hormone, glucagon, adrenaline) and cortisol. The lipolytic hormones stimulate lipolysis in adipose tissue so that they increase glycerol release and the glycerol is then available for gluconeogenesis. Cortisol increases protein degradation in muscle, which increases the release of amino acids (especially glutamine and alanine) from muscle (Chapter 18). 

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