The major role of ketone bodies is to supply an alternative oxidizable substrate to glucose for the brain in situations where the availability of the latter is impaired (e.g., starvation). In addition, ketone bodies can act as precursors for the acetyl-CoA required in neural lipid synthesis (myelin). Other mammalian tissues, including heart, skeletal muscle, kidney, and lactating mammary gland, can utilize ketone bodies but, in contrast to glucose utilization, no energy can be obtained in the absence of oxygen. In these tissues metabolism of ketone bodies results in the inhibition of glucose utilization and inhibition of the oxidation of pyruvate. The net result is a sparing of carbohydrate for the brain and the strictly glycolytic tissues (erythrocytes, retina).
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