The effect of diet and development on blood levels of free and esterified carnitine in the rat

Abstract

Serum levels of free and bound carnitine were determined during development of the rat. The effect of starvation and of short-term feeding of different diets varying in their lipid content and fatty acid chain length was also examined. Perinatally, a significant increase in serum levels of free and acylcarnitine was observed. Weaning on day 18 led to a fall in free and acylcarnitine levels. The ratio of acylcarnitine to free carnitine increased significantly at birth and decreased at weaning. During starvation, serum free carnitine first decreased and after more than 24 h increased. The acyl- to free carnitine ratio increased during the first 3 days of starvation and decreased somewhat thereafter. When exposed to diets varying in fat content and composition for 2 days, rats on high fat diets had significantly lower serum free carnitine levels than rats on a high carbohydrate diet. Serum acylcarnitine levels were significantly increased only by a medium chain triglyceride diet. Total serum carnitine content was unchanged with the carbohydrate and medium chain triglyceride diets but significantly decreased with the diet rich in long-chain triglycerides. The serum acyl- to free carnitine ratio was significantly higher in rats fed the high fat diets than in those fed the carbohydrate diet. A positive correlation was found between the carnitine ratio and serum levels of β-hydroxybutyrate and a negative one between free camitine levels and the level of this ketone.