Background: This study was designed to evaluate the effect of severe peripheral arterial insufficiency on carnitine concentrations and carnitine acetyltransferase and palmitoyltransferase activities in the ischemic skeletal muscles of patients with severe peripheral vascular disease.
Methods and results: Nine biopsy specimens of ischemic muscles were obtained from five patients undergoing reconstructive vascular surgery. Biopsies from 35 normal subjects served as controls. Ischemic muscles showed a significant reduction in total carnitine from the control value of 20.9 +/- 5.2 to 11.6 +/- 6.2 nmol/mg noncollagen protein (p less than 0.01). A significantly lower free carnitine and acylcarnitine content contributed to this reduction. Similarly, carnitine acetyltransferase activity was reduced in the ischemic muscles from the control value of 102.1 +/- 41.2 to 52.9 +/- 22.1 nmol/min/mg noncollagen protein (p less than 0.01). On the contrary, carnitine palmitoyltransferase activity did not show any change (0.29 +/- 0.05 nmol/min/mg noncollagen protein in the ischemic muscles and 0.28 +/- 0.07 nmol/min/mg noncollagen protein in controls). Carnitine, acylcarnitines, and enzyme activities were also measured in the ischemic muscles in four additional patients 2 days after intravenous administration of L-propionylcarnitine (1.5 g as a single bolus followed by an infusion of 1 mg/kg/min for 30 minutes). Treatment restored normal levels of carnitine and its esters in the ischemic muscles but did not affect enzyme activities.
Conclusions: Demonstration of carnitine deficiency in severe peripheral vascular disease substantiates previous findings showing the efficacy of carnitine supplementation to ischemic muscles. Furthermore, the feasibility of restoring carnitine homeostasis with L-propionylcarnitine provides the basis for clinical trials aimed at assessing the efficacy of this carnitine ester in the treatment of peripheral vascular disease.