The effect of graded doses of ascorbic acid on the tissue carnitine and plasma lipid concentrations

Ascorbic acid (AsA) is known to be required for the synthesis of carnitine. The present study was designed to clarify the effect of AsA on the carnitine synthesis and lipid metabolism in guinea pigs. The animals were divided into four groups, and fed AsA-free diets for three weeks. Each group was supplemented with AsA in the following doses; high-AsA group, 100 mg AsA/day/animal; control group, 5 mg AsA/day/animal; AsA-deficient group, 0.1 mg AsA/day/animal; pair-fed group, 5 mg AsA/day/animal. The pair-fed group was restricted to the amount of diet consumed by the AsA-deficient group. Tissue carnitine levels of the AsA-deficient group were significantly lower than not only the control group but the pair-fed group. Total cholesterol and phospholipid levels in plasma of the AsA-deficient group were found to be similar to those of the pair-fed group; however, plasma triglyceride levels were significantly higher than that of the pair-fed group. Furthermore, there was an inverse relationship between tissue AsA and plasma triglyceride levels. We concluded that carnitine synthesis and triglyceride metabolism in guinea pigs may be impaired by the decrease of tissue AsA level rather than by the insufficient food intake. It is suggested that tissue carnitine level altered by tissue AsA content affects plasma triglyceride level.