Carnitine-related alterations in patients with intermittent claudication

Background Carnitine metabolism is altered in peripheral arterial disease. L-carnitine supplementation may correct these alterations and improve walking performance. Methods and Results Plasma levels of carnitine and its esters were measured at rest and after maximally tolerated exercise in 22 claudicant patients and 8 normal subjects. One week later, this protocol was repeated in patients after random administration of placebo or L-carnitine (500 mg IV as a single bolus). Two groups of patients emerged. In 10 patients (group IC1), the plasma level of acetylcarnitine at rest was 3.7+/-0.2 mu mol/L and increased significantly (P<.01) at maximally tolerated exercise. In 12 patients (group IC2), the resting level of plasma acetylcarnitine was elevated (7.9+/-0.7 mu mol/L, P<.01) and decreased with exercise. Furthermore, group IC2 patients had a significantly lower walking capacity than group IC1 patients. In both groups, placebo did not affect the metabolic profile, nor did it improve exercise performance. Conversely, after L-carnitine administration, all but one patient in group IC2 (n=7) showed an increase in plasma acetylcarnitine concentration during exercise versus the decrease observed without L-carnitine. This metabolic effect was accompanied by a significant increase (P<.01) in walking capacity. Interestingly, in group IC1 patients (n=5), L-carnitine neither improved walking capacity nor modified the metabolic profile. Statistical analysis showed that changes in walking capacity with L-carnitine treatment were influenced exclusively by exercise-induced changes in plasma acetylcarnitine. Conclusions In patients with intermittent claudication, assessment of plasma acetylcarnitine at rest and after exercise may be a means to select a target population for L-carnitine therapy.