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Determination of Carnitine Renal Threshold and Effect of Medium-Chain Triglycerides on Carnitine Profiles in Newborn Pigs |
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K. N. Heo, J. Odle, X. Lin, T. A. T. G. van Kempen, In K. Han |
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| Abstract |
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Colostrum deprived, newborn pigs (N=12, 1.64 0.05 kg) were used to study the renal threshold of carnitine, and effects of emulsified medium-chain triglyceride (MCT, tri-8:0) feeding on kinetics of plasma carnitine and urinary carnitine excretion. An arterial catheter was inserted through an umbilical artery, and a bladder catheter was inserted via the urachus. Piglets were oro-gastrically gavaged with one of six carnitine levels (0, 60, 120, 180, 240, 480 關mol/kg W0.75) with (+MCT) or without medium-chain triglycerides (-MCT) in 0.9% NaCl solution. Blood was sampled into heparinized tubes at 0, 1, 2, 4, 6, 8, 14, and 20 h after gavage, and urine was collected and pooled into 1 h or 2 h composite samples to determine free- and short-chain carnitine concentrations. Plasma from the 12 newborn piglets before gavage contained 10.6 1.2 關mol/L free carnitine and 7.2 0.6 關mol/L acid-soluble acyl carnitine. The renal threshold for carnitine was similar between the MCT and the +MCT group (42.6 13.1 and 46.4 2.0 關mol/L, respectively), but the correlation between plasma free carnitine and urinary excretion was altered. Plasma free carnitine linearly increased with increasing carnitine dosage (-MCT group, R2=0.95, p<0.001; +MCT group, R2=0.91, p<0.001), but was decreased by 50% when medium-chain triglycerides were fed. The peak in plasma free carnitine concentration was depressed by medium-chain triglycerides feeding also. Therefore, the plasma and urinary short-chain/free carnitine ratio of the +MCT group was increased by 100% and 40%, respectively (p<0.01). Feeding of medium-chain triglycerides may delay plasma carnitine elevation via altering the kinetics of absorption. Similarly, the plasma and urinary short-chain/free carnitine ratio were affected by interaction between medium-chain triglycerides and time (p<0.01). The present study suggests that an oral carnitine dose over 480 關mol/kg W0.75 may be needed to reach the free carnitine renal threshold within a short period, especially when provided together with medium-chain triglyceride. |
| Keywords:
Carnitine; Renal Threshold; Medium-Chain Triglycerides; Newborn Pigs; Acyl Intoxication |
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