Ketone bodies fasting state

The cyde is central to the oxidation of any fuel that yields acetyl CoA, induding glucose, fritty acids, ketone bodies, ketogenic amino acids, and alcohol There is no hormonal control of the cyde, as activity is necessary irrespective of the fed or fasting state. Control is exerted by the energy status of the cell. 

Because insulin normally inhibits lipolysis, a diabetic has an extensive lipolytic activity in the adipose tissue. As is seen in Table 21.4, plasma fatty acid concentrations become remarkably high. /3-Oxidation activity in the liver increases because of a low insulin/glucagon ratio, acetyl-CoA carboxylase is relatively inactive and acyl-CoA-camitine acyltransferase is derepressed. /3-Oxidation produces acetyl-CoA which in turn generates ketone bodies. Ketosis is perhaps the most prominent feature of diabetes mellitus. Table 21.5 compares ketone body production and utilization in fasting and in diabetic individuals. It may be seen that, whereas in the fasting state ketone body production is roughly equal to excretion plus utilization, in diabetes this is not so. Ketone bodies therefore accumulate in diabetic blood. 

The liver also plays a central role in the regulation of lipid metabolism. When fuels are abundant, fatty acids derived from the diet or synthesized by the liver are esterified and secreted into the blood in the form of very low density lipoprotein (see Figure 30.15). However, in the fasting state, the liver converts fatty acids into ketone bodies. How is the fate of liver fatty acids determined The selection is made according to whether the fatty acids enter the mitochondrial... 

Fery, F., and Balasse, E. O. (1966). Response of ketone body metabolism to eKcrdse during tran.sition from postabsorptive to fasted state. Am. I. Physiol. 250, E495-E501. 

Figure 1-3. The fasting state. The circled numbers serve as a guide, indicating the approximate order in which the processes begin to occur. KB = ketone bodies. See legend for Figure 1-2 for explanation of abbreviations.

In the liver, in the fed state, amino acid carbons are converted to fatty acids and triacylglycerol. During fasting, amino add carbons are converted to glucose or to ketone bodies. 

After 3 to 5 days of fasting, when the body enters the starved state, muscle decreases its use of ketone bodies and depends mainly on fatty acids for its fuel. The... 

Ann O Rexia s admission laboratory studies showed a blood glucose level of 65 mg/dL (normal fasting blood glucose = 80 - 100 mg/dL). Her serum ketone body concentration was 4,200 [xM (normal = 70 [xM). The Ketostix (Bayer Diagnostics, Mishawaha, IN) urine test was moderately positive, indicating that ketone bodies were present in the urine. In her starved state, ketone body use by her brain is helping to conserve protein in her muscles and vital organs. 

Di Abietes has a ketoacidosis. When the amount of insulin she injects is inadequate, she remains in a condition similar to a fasting state even though she ingests food (see Chapters 2 and 3). Her liver continues to metabolize fatty acids to the ketone bodies acetoacetic acid and p-hydroxy-butyric acid. These compounds are weak acids that dissociate to produce anions (ace-toacetate and p-hydroxybutyrate, respectively) and hydrogen ions, thereby lowering her blood and cellular pH below the normal range. 

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