Total carnitine and acylated carnitine ratio: relationship of free carnitine with lipid parameters in pediatric dialysis patients.

ABSTRACT

Carnitine has an essential role in the mitochondrial oxidation of long-chain fatty acids. Carnitine deficiency has been described in patients with chronic kidney disease. Total carnitine (TC) deficiency or a lower-than-normal ratio of free carnitine to acylated carnitine (FCAC) has been shown to be associated with disorders in metabolism and plasma lipids. Metabolism and therapeutic use of carnitine have therefore been a major area of interest in dialysis patients. In a prospective observational study, we determined carnitine status (TC and FCAC) and its correlations with lipid plasma levels in peritoneal dialysis (PD) and hemodialysis (HD) patients. In pediatric patients on chronic PD or HD, we evaluated nutritional status (weight and height), biochemical parameters (TC, FC, and AC levels), and fasting plasma lipoprotein concentrations. We studied 35 patients (16 boys, 19 girls; 25 on PD, 10 on HD). Median age was 5 years (range 3 months-15 years). Median weight-to-height Z-score was -0.5 (range -2.1 to 1.9), and median height-to-age Z-score was -2.5 (range -0.3 to -2.9). The mean TC was 65.4 +/- 23.8 pg/mL (normal value 40-55 pg/mL); the median AC was 18 pg/mL (range 2-56pg/mL; normal value 3-15 pg/mL); and the mean FC was 41.8 +/- 16.6 pg/mL (normal value 25-35 pg/mL). Median serum FCAC was 2.22 (range 0.59-4.3; normal value 4). A significantly higher AC and a lower FCAC were observed in HD patients as compared with PD patients. No differences in TC and FC were observed when patients were grouped by dialysis modality, time on dialysis, or nutrition status. Total cholesterol was 200 mg/dL or higher in 20 patients, and 25 patients showed elevated triglycerides (> 150 mg/dL). The latter patients had a higher AC than did the group of patients with triglycerides below 150 mg/dL (AC 22 pg/mL and 12.5 pg/mL respectively; Kruskal-Wallis p < 0.003). We found TC levels to be high in this group of patients. However, the FCAC ratio was lower than normal in all except in 1 patient. Elevated triglycerides were associated with elevated AC, suggesting carnitine insufficiency in our patients.