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Coordinated Regulation of Glycogen Synthesis and Breakdown:- Insulin Changes the Expression of Many Genes Involved in Carbohydrate and Fat Metabolism

المؤلف:  David L. Nelson، Michael M. Cox

المصدر:  Lehninger Principles of Biochemistry

الجزء والصفحة:  590

2026-06-08

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Coordinated Regulation of Glycogen Synthesis and Breakdown:- Insulin Changes the Expression of Many Genes Involved in Carbohydrate and Fat Metabolism

In addition to its effects on the activity of existing en zymes, insulin also regulates the expression of as many as 150 genes, including some related to fuel metabolism (Fig. 15–31; Table 15–3). Insulin stimulates the tran scription of the genes that encode hexokinases II and IV, PFK-1, pyruvate kinase, and the bifunctional enzyme PFK-2/FBPase-2 (all involved in glycolysis and its regulation), several enzymes involved in fatty acid synthesis, and two enzymes that generate the reductant for fatty acid synthesis (NADPH) via the pentose phosphate pathway (glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase). Insulin also slows the expression of the genes for two enzymes of gluconeogenesis (PEP carboxykinase and glucose 6-phosphatase). These effects take place on a longer time scale (minutes to hours) than those mediated by covalent alteration of enzymes, but the impact on metabolism can be very significant. When the diet provides an excess of glucose, the resulting rise in insulin increases the synthesis of glucose metabolizing proteins, and glucose becomes the fuel of choice (via glycolysis) for liver, adipose tissue, and muscle. In liver and adipose tissue, glucose is converted to glycogen and triacylglycerols for temporary storage.

FIGURE 15–31 Regulation of carbohydrate metabolism in the hepatocyte. Arrows indicate causal relationships between the changes they connect. ↓A→↑B means that a decrease in A causes an increase in B. Pink arrows connect events that result from high blood glucose; blue arrows connect events that result from low blood glucose.