Lysine Deficiency in the Rat: Concomitant Impairment in Carnitine Biosynthesis

Abstract

In two experiments male weanling rats were fed 20% wheat gluten diets for 90 days; such diets contained minimal lysine, 0.37%, and < 0.1 μg carnitine per gram. Under these nutritional conditions poor growth, anemia, and hypoproteinemia developed in contrast to the well-being of control rats receiving adequate dietary lysine. Rats fed the unsupplemented wheat gluten diets were found in general to have about a one-third lower level of carnitine per gram of skeletal muscle and heart muscle than the control group when examined at approximately monthly intervals over the test period. The carnitine level of the liver, however, was significantly higher in the unsupplemented vs. the lysine-supplemented groups. This latter finding may reflect the need for increased hepatic synthesis of carnitine under the stringent nutritional conditions employed. The data illustrate that the carnitine content of the heart and muscle of the rat depends on the level of lysine in the diet and support isotopic studies from our laboratory that lysine is a precursor of carnitine in the rat.