Ketone bodies during exercise

Inherited aldolase A deficiency and pyruvate kinase deficiency in erythrocytes cause hemolytic anemia. The exercise capacity of patients with muscle phos-phofiaictokinase deficiency is low, particularly on high-carbohydrate diets. By providing an alternative lipid fuel, eg, during starvation, when blood free fatty acids and ketone bodies are increased, work capacity is improved. 

The level of total ketone bodies in Lofata Burne s blood greatly exceeds normal fasting levels and the mild ketosis produced during exercise. In a person on a normal mealtime schedule, total blood ketone bodies rarely exceed 0.2 mM. During prolonged fasting, they may rise to 4 to 5 mM. Levels above 7 mM are considered evidence of ketoacidosis, because the acid produced must reach this level to exceed the bicarbonate buffer system in the blood and compensatory respiration (Kussmaul s respiration) (see Chapter 4). 

Ketone body oxidation also increases during exercise. Their utilization as a fuel is dependent on their rate of production by the liver. Ketone bodies are, however, never a major fuel for skeletal muscle (muscles prefer free fatty acids). 

A deficiency of carnitine acyltransferase I in human muscle causes cellular damage and recurrent muscle weakness, especially during fasting or exercise. A deficiency of the enzyme in the liver causes an enlarged and fatty liver, hypoglycemia, and a reduction in the levels of ketone bodies in blood. Explain the likely causes of these symptoms. 

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