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Changes in carnitine metabolism in children with intractable epilepsy under ketogenic diet, demonstrated by subcutaneous microdialysis
The ketogenic diet (KD) has proved efficient against intractable childhood epilepsies. An unimpaired degradation of fatty acids is a precondition to an efficient ketogenesis. Carnitine posesses a key role in the degradation of fatty acids.
Objectives: The objective of this study was to analyze the changes in the tissue metabolism of carnitines at the beginning of a ketogenic diet systematically.
Material and Methods: 7 patients had been adjusted to KD (LCT, 4:1) because of their intractable childhood epilepsy. The median (range) age was 2.5 (0.9–10.6) years.
Biochemical bedside monitoring (glucose, lactate, pyruvate) with continuous subcutaneous Microdialysis (sc MD) was performed during ketogenic diet initiation. Sc MD is a sampling method that permits continuous analysis of a patients extracellular tissue chemistry without draining blood. Additionally to the glucose and lactate monitoring, the carnitines were determined in the residual dialysates using Tandem-Masspectrometry. A miniaturized MDsystem was used for sc MD (CMA/Microdialysis; Pediatrics 2001; 108:1187–92).
Results: Within 2 days ketosis (ß-hydroxybutyrate) increased and significant changes of the carnitines in the sc tissue became present. Acetylcarnitine (C2) increased from median (range) 5.13 (2.39–6.94)µmol/L up to median (range) 19.97 (14.71–33.39)µmol/L. Similarly the hydroxybutyrylcarnitine (C4-OH) increased from median (range) 0.01 (0.01–0.02)µmol/L to 0.32 (0.19–0.46)µmol/L. The free carnitine (C0) showed a downward but insignificant shift.
There was a high correlation between β-hydroxybutyrate in the serum (β-OHBs) and hydroxybutyrylcarnitine in the dialysate (r=0.91) and a moderate correlation between β-OHBs and acetylcarnitine in the dialysate (r=0.7)
Conclusions: Demonstrated by continuous sc MD ketogenic diet leads to characteristic changes in the carnitine metabolism of the sc tissue. Thus the C2 and C4OH-carnitine increased, whereas the free carnitine showed a downward shift.