Ketone bodies pathological concentrations

The glucagon/insulin ratio can rise under certain pathological conditions (i.e., insulin-dependent diabetes). A small percentage of diabetics develop ketoacidosis, a condition that results from the overproduction and underuhlization of ketone bodies. Increased concentrations of p hydmxybutyrate and acetoacetate, which are acids, can cause a drop in the pH of the blood. This acidification, known as acidosis, can impair the ablLity of the heart to contract and result in a loss of consciousness and coma, which, in rare cases, may be fatal. Diabetic ketoacidosis may manifest as abdominal pain, nausea, and vomiting. A subject may hyperventilate (breathe quickly and deeply) to correct acidosis, as described under Sodium, Potassium, and Water in Chapter 10. It is the responsibility of the clinician, when confronted with a subject whose breath smells of acetone or who is hyperventilating, to facilitate prompt treatment. 

Shifts in the concentrations of the physiological components of the urine and the appearance of pathological urine components can be used to diagnose diseases. Important examples are glucose and ketone bodies, which are excreted to a greater extent in diabetes mellitus (see p. 160). 

Ketoacidosis An elevation of the ketone body concentration that decreases the pH of the arterial blood to a pathologic condition. 

Ketosis, abnormally high levels of blood ketone bodies, is a situation that arises under some pathological conditions, such as starvation, a diet that is extremely low in carbohydrates (as with the high-protein liquid diets), or uncontrolled diabetes mellitus. The carbohydrate intake of a diabetic is normal, but the carbohydrates cannot get into the cell to be used as fuel. Thus diabetes amounts to starvation in the midst of plenty. In diabetes the very high concentration of ketone acids in the blood leads to ketoacidosis. The ketone acids are relatively strong acids and therefore readily dissociate to release H+. Under these conditions the blood pH becomes acidic, which can lead to death. 

In normal liver, only relatively small amounts of ketone bodies are formed. Their concentration in the blood is 0.5-D.8 mg per 100 ml plasma. The acetoacetate produced by this physiological K. is degraded in the peripheral musculature. Coenzyme A from succi-nyl-CoA is transferred to the acetoacetate by aceto-acetate succinyl-CoA transferase. Direct activation of acetoacetate by coenzyme A and ATP can also occur (Fig, 2). The acetoacetyl-CoA produced in either case is thioclastically cleaved into two molecules of acetyl-CoA, consuming a CoA molecule in the process. In carbohydrate deficiency (starvation, ketone-mia in ruminants), or deficient carbohydrate utilization (diabetes mellitus), K. is greatly increased. The cause of this pathological K. is a disturbance of the equilibrium between the degradation of fatty acids to acetyl-CoA and its utilization in the tricarboxylic acid cycle. The several-fold increase in the oxidation of the fatty acids leads under these conditions to an increase in the intracellular acetyl-CoA concentration. This leads to the condensation of 2 molecules of... 

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