Ketone bodies acid—base balance

Allen and DuBois136 have calculated that the R. Q. of 0.707, obtainable when fat is completely oxidized, would be lowered to 0.669 if the /3-hydroxybutyric acid were not metabolized. If more than one molecule of the ketone bodies is produced from one molecule of the fatty acid, as has been suggested,83 the R. Q. would be further lowered. This may be further complicated by a resulting upset in acid-base balance. 

Because carbohydrate utilization is impaired, a lack of insulin leads to the uncontrolled breakdown of lipids and proteins. Large amounts of acetyl CoA are then produced by P-oxidation. However, much of the acetyl CoA cannot enter the citric acid cycle, because there is insufficient oxaloacetate for the condensation step. Recall that mammals can synthesize oxaloacetate from pyruvate, a product of glycolysis, but not from acetyl CoA instead, they generate ketone bodies. A striking feature of diabetes is the shift in fuel usage from carbohydrates to fats glucose, more abundant than ever, is spurned. In high concentrations, ketone bodies overwhelm the kidney s capacity to maintain acid-base balance. The untreated diabetic can go into a coma because of a lowered blood pH level and dehydration. 

The proportion of nitrogen excreted as ammonia (in the form) helps with acid-base balance, especially with increased ketone-body excretion, normal blood concentrations of phenylalanine can be maintained by feeding a low-phenylalanine diet. 

Patients suffering from diabetes-related ketosis are usually given insnUn as a first step in their treatment. The insulin restores normal glucose metabolism and reduces the rate of formation of ketone bodies. If the patient is also suffering severe dehydration, the return to fluid and acid-base balance is sped up by the intravenous administration of solutions containing sodium bicarbonate. Excessive alcohol consumption can also cause ketone bodies to be produced with acetone on the breath. 

As is well known, the dietary carbohydrates are normally catabolized to give the neutral end products carbon dioxide and water. The intermediately formed organic acids such as lactic acid or tri- and dicarbonic acids of the Krebs cycle solely influence the acid-base balance if they are excreted in their ionic form, leaving behind the protons that would normally be oxidized together with the acidic anion to the neutral end products mentioned above. The same is true for the fatty acids, originating from the dietary fats. Under special circumstances, the fatty acid, degradation leads to the accumulation of ketone bodies. The excretion of acetoacetic and of jS-hydroxybutyric acid in their ionic form results in acidosis, as observed in diabetes. Under normal conditions, however, there is no influence of dietary fat on the acid-base balance. 

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