Contribution of a high dose of L-ascorbic acid to carnitine synthesis in guinea pigs fed high-fat diets

Ascorbate is a cofactor of two-enzyme hydroxylation in the pathway of carni tine biosynthesis. The purpose of this study was to investigate the contrib ution of ascorbate to endogenous carnitine in guinea pigs fed high-fat diet s. The contents of carnitine in plasma, urine and tissues of guinea pigs su pplemented with L-ascorbic acid were determined and compared with those sup plemented with carnitine. Albino-Hartley guinea pigs were fed vitamin C-def icient diets containing lard throughout the experiment. They were administe red orally with 5 mg L-ascorbic acid/d/animal for 14 d, and then divided in to three groups and administered orally with the following supplements (/d/ animal) for 14 d; L (5 mg L-ascorbic acid), LASA (100 mg L-ascorbic acid), and LCAR (10 mg carnitine plus 5 mg L-ascorbic acid). As a control, a norma l group was fed vitamin C-deficient diets and administered orally with 5 mg L-ascorbic acid/d/animal for 28 d. The animals fed high-fat diets (L group ) had higher free-carnitine contents in the muscle and urine than the norma l group. The groups of LCAR and LASA had significantly higher contents of a cid-soluble carnitine (p < 0.05) in plasma than the L group. Urinary excret ion of carnitine in the LASA group was decreased to the same level as that in the normal group, although no significant difference between the groups of L and LCAR was observed. Moreover, the supplement of ascorbic acid, but not of carnitine, induced a significantly lower content of triacylglycerol in the plasma of the LASA group as compared to the L group (p < 0.05). Thes e data suggest that high doses of ascorbic acid in guinea pigs fed high-fat diets contribute to the enhancement of carnitine synthesis and improvement of the triacylglycerol content in the plasma.