GENETIC-DISORDERS OF CARNITINE METABOLISM AND THEIR NUTRITIONAL MANAGEMENT

Carnitine functions as a substrate for a family of enzymes, carnitine acyltransferases, involved in acyl-coenzyme A metabolism and as a carr ier for long-chain fatty acids into mitochondria. Carnitine biosynthes is and/or dietary carnitine fulfill the body's requirement for carniti ne. To date, a genetic disorder of carnitine biosynthesis has not been described. A genetic defect in the high-affinity plasma membrane carn itine-carrier(in) leads to renal carnitine wasting and primary carniti ne deficiency. Myopathic carnitine deficiency could be due to an incre ase in efflux moderated by the carnitine-carrier(out). Defects in the carnitine transport system for fatty acids in mitochondria have been d escribed and are being examined at the molecular and pathophysiologica l levels. The nutritional management of these disorders includes a hig h-carbohydrate, low-fat diet and avoidance of those events that promot e fatty acid oxidation, such as fasting, prolonged exercise, and cold. Large-dose carnitine treatment is effective in systemic carnitine def iciency.