Cernitine is an essential factor in fatty acid oxidation and, hence, in ketoacid production. In plasma, therefore, free carnitine, short-chain acylcamitine, long-chain acylcarnitine, and total carnitine (sum of all three fractions) were determined in normal subjects, in diabetics with ketosis, and in diabetics in ketoacidosis. Short-chain acylcarnitine (mean ± SEM) was significantly higher in ketoacidotic diabetics (31.0 ± 4.0 μm) and ketotic diabetics (11.8 ± 1.2 μm) than in normals (5.8 ± 0.65); long-chain acylcarnitine was significantly higher in ketoacidotic diabetics (8.0 ±1.0 μm) than in ketotic diabetics (4.9 ± 0.39 μm) or normals (4.2 ± 0.22 μm); free carnitine was significantly lower in ketoacidotic diabetics (20.5 ± 3.3 μm) than in ketotic diabetics (31.8 ± 2.2 μm) or normals (36.5 ± 1.5 μm). Plasma short-chain acylcarnitine correlated positively with blood beta hydroxybutyrate in normals (r = 0.69, P < 0.001) but not in either diabetic group. However, the abnormal distribution in plasma of free carnitine and acylcarnitines in the diabetics was promptly returned toward normal, in parallel with blood beta hydroxybutyrate, by insulin treatment. The latter also resulted in a 70% reduction in 24-h urinary excretion of acylcarnitine. these data are consistent with a postulated role for carnitine in diabetic keto-genesis in man.

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