Enhanced lipid utilization in infants receiving oral l-carnitine during long-term parenteral nutrition

Fourteen infants requiring long-term total parenteral nutrition but able to tolerate small quantities of enteral feedings were randomized into carnitine treatment and placebo control groups. All infants had received nutritional support devoid of carnitine. Plasma carnitine levels and observed plasma lipid indices were not different before supplementation. Under standardized, steady-state conditions, 0.5 g/kg fat emuision (intralipid) was administered intravenously over 2 hours both before and after infants received 7 days of continuous nasogastric or gastric tube l-carnitine (50 μmol/kg/day) or placebo. Plasma triglyceride, free fatty acid, acetoacetate, β-hydroxybutyrate, and carnitine concentrations were observed at 0 (start of lipid infusion), 2, and 4 hours for pre- and post-treatment periods, and in addition at 6 and 8 hours after carnitine supplementation. Infants receiving carnitine had significantly greater β-hydroxybutyrate plasma concentrations (P<0.05) and carnitine (P<0.001) at 0, 2, 4, 6, and 8 hours, and greater plasma acetoacetate concentrations (P<0.05) at 2, 4, 6, and 8 hours, compared with controls. Twenty-four-hour urinary carnitine excretion was very low for both groups before supplementation; after supplementation, excretion was higher (P<0.05) in the carnitine group. No significant differences were found between groups for plasma triglyceride or free fatty acid concentrations at any observation period. This study demonstrated enhanced fatty acid oxidation, as evidenced by increased ketogenesis, with l-carnitine supplementation in infants receiving long-term total parenteral nutrition.