Altered tissue carnitine levels in animals with hereditary muscular dystrophy

Myocardial Response to Pretreatment with L-Carnitine in Patients with Cardiac Valve Replacement

Twenty-one patients undergoing mitral valve replacement (MVR) with either isolated or combined valvular procedure were investigated to determine the ef fect of randomized and prospective administration of L-carnitine (car) chloride on myocardial function. Carnitine chloride (1800 mg/day, for seven consecu tive days just prior to MVR) was given orally to 9 patients (car-treated group) who were compared with 12 car-untreated patients (control group) subjected to the same procedure. Valve replacement was performed using the Bjork-Shiley mechanical prosthesis in aortic and mitral position and bioprosthesis in tricuspid position in both groups under cardiopulmonary bypass (CPB) associated with cold potassium-magnesium cardioplegia and systemic hypothermia. Preopera tive and intraoperative clinical profile (age, functional class, duration of aortic clamp and CPB, and level of hypothermia) was well matched in both groups. Free, short-chain acyl, long-chain acyl, and total Car were measured in the papil lary muscle excised adjacent to the free wall of the left ventricle at the time of valvular surgery. Heart rate and mean arterial pressure did not differ between the two groups. Cardiac index was 3.44 ± 0.08 and 3.82 ± 0.13 L/m2/min in the control and car-treated groups, respectively, (p < 0.05). Dobutamine (DOB) infusion rate was 8.55 ± 0.73 and 5.57 ± 0.95 μg/kg/min in the control and car-treated groups, respectively (p < 0.05). Left ventricular stroke work index (LVSWI)/DOB ratio was 4.50 ± 0.65 and 8.16 ± 1.72 g*m/m 2/beat/unit of DOB, in the control and car-treated groups, respectively (p < 0.05). Long-chain acyl carnitine was 0.224 ± 0.031 and 0.460 ± 0.096 nmoL/mg noncollagenous protein in the control and the car-treated groups, respectively (p<0.05). LVSWI/DOB ratio was well correlated with long-chain acyl carnitine in the tis sue, r = 0.74, n = 18, p<0.001.

These findings suggest that pretreatment with L-carnitine chloride appears to be effective in improving myocardial function in the early phase of reperfu sion following surgery and that long-chain acyl carnitine may play a key role in the enhancement of carnitine-meditated mitochondrial metabolic process.

The myocardial distribution and plasma concentration of carnitine in patients with mitral valve disease

The myocardial distribution and concentration of carnitine and its fractions was studied in 11 patients with mitral valve disease not associated with congestive heart failure (CHF). The plasma concentration of carnitine was found to be identical to the normal values documented in the literature. The left ventricular papillary muscle had the highest concentrations of total, short-acyl, long-acyl, and free carnitine, being significantly higher than those of the right ventricle, while the right atrial appendage had the lowest values of all fractions of carnitine. The proportion of long-acyl carnitine to total carnitine was significantly greater in the left ventricle than in either the right atrium or the atrial septum, and other carnitine fractions were identical in all cardiac chambers. Our results suggest that in the compensated heart with mitral valve disease, carnitine and its fractions are greatest in the left ventricle in the muscles of all cardiac chambers, and that long-acyl carnitine is most likely to be linked to the cardiac muscle demanding a higher cardiac performance.

Myocardial carnitine metabolism in congestive heart failure induced by incessant tachycardia

Persistent tachycardia induces congestive heart failure (CHF), but the mechanism(s) of progressive ventricular dysfunction is (are) unclear. This study was designed to define possible metabolic causes of myocardial dysfunction in rapid ventricular pacing induced CHF. Twelve adult mongrel dogs were paced to 250 beats/min for 19 days. Plasma carnitine, norepinephrine and renin were measured at 0, 1, 2, and 3 weeks. Myocardial high energy phosphates, carnitine, glycogen, glucose, non-collagenous protein and collagen were measured at 19 days. Cardiac output, arterial pressure and pulmonary wedge pressure, measured at baseline and with CHF, showed a decrease in cardiac output and increase in pulmonary wedge pressure. Neurohumoral activation was evident by progressively increasing plasma norepinephrine and renin activity and depletion of myocardial norepinephrine. Plasma free carnitine rose significantly from 12.6 +/- 2.0 control to 28.3 +/- 3.8 nmol/ml at 19 days (p < 0.001), whereas myocardial total carnitine was lower in paced than in control dogs (6.0 +/- 1.9 vs. 14.1 +/- 3.5 nmol/mg non-collagenous protein, p < 0.001). Myocardial ATP ATP and ADP were unchanged, while AMP decreased 22%, and creatine phosphate decreased 30% compared to control animals. Myocardial glucose was normal but glycogen was decreased 54% (p < 0.005). The low myocardial carnitine and elevated plasma carnitine in pacing induced CHF suggests altered carnitine transport or membrane integrity.

Myocardial carnitine in end-stage congestive heart failure

To test the hypothesis that carnitine is decreased in the myocardial tissue of patients with end-stage congestive heart failure (CHF), left ventricular myocardial carnitine was measured in 51 patients undergoing orthotopic cardiac transplantation. The study group included patients with idiopathic dilated cardiomyopathy, coronary artery disease, myocarditis and rheumatic heart disease. Myocardial carnitine varied in different cardiac chambers. In normal control hearts, the left and right ventricular total carnitine was similar, but the ventricles had higher levels than the atria (p less than 0.005); in 30 hearts in CHF, the left ventricular total carnitine was higher than in the right ventricle (p less than 0.001) and both ventricles had higher total carnitine than the atria (p less than 0.005). Only 7 of 51 patients with CHF had low myocardial carnitine, whereas plasma carnitine was elevated in all diagnostic groups of end-stage CHF studied.

Altered rat skeletal muscle carnitine with age and after denervation

We investigated the effect of denervation on the concentration of total free, and acyl carnitine in the soleus (S), extensor digitorum longus (EDL), and anterior tibial (AT) muscles of the rat. Soon after denervation there was a marked decrease in total carnitine in all three muscles. Acyl carnitine levels decreased concomitantly with changes in total carnitine. In control but not in denervated muscle, the carnitine concentration was age-dependent during the period of rapid growth of the animals. The highest carnitine concentration was observed at 14 weeks of age. The results of this study suggest that normal innervation significantly influences carnitine-mediated lipid metabolism in skeletal muscle.

Plasma carnitine concentrations in cardiomyopathy patients

Carnitine is an essential cofactor for the beta-oxidation of fats. Both hypertrophic and congestive cardiomyopathies have been reported in primary and secondary carnitine deficiency. Conversely in avian cardiomyopathy models abnormally elevated plasma and tissue carnitine concentrations have been described. We measured plasma carnitine concentrations in 25 cardiomyopathy patients. In 14 patients with either hypertrophic or congestive cardiomyopathy plasma carnitine concentrations were abnormally elevated. Patients with secondary cardiomyopathies tended to have normal carnitine values. One patient with systemic carnitine deficiency was diagnosed. Her cardiac function normalized with L-carnitine replacement. Six of 14 patients with high plasma carnitine concentrations died. None of the 10 with low or normal plasma carnitine have died. Plasma carnitine determination may be a useful adjunct in the diagnostic evaluation of idiopathic cardiomyopathy.

Cardiac carnitine deficiency and altered carnitine transport in cardiomyopathic hamsters

The Bio 14.6 hamster has a well-documented cardiomyopathy which leads to congestive heart failure. Previous work demonstrated that hearts from these hamsters have depressed fatty acid oxidation and depressed carnitine concentrations compared to those of normal hamsters. Analyses of tissue carnitine concentrations from 40 to 464 days of age demonstrate that the cardiomyopathic hamsters have a cardiac carnitine deficiency throughout life. Therefore, the carnitine deficiency is not a secondary effect of an advanced stage of the cardiomyopathy. Both the observation that other tissues of the cardiomyopathic hamster have normal or markedly elevated carnitine concentrations and the observation that oral carnitine treatment could not increase the cardiac carnitine concentrations to those of normal hamsters are consistent with the hypothesis that the cardiac carnitine deficiency is the result of a defective cardiac transport mechanism. Cardiac carnitine-binding protein (which may function in the cardiac carnitine transport mechanism) prepared from hearts of cardiomyopathic hamsters had a lower maximal carnitine binding and an increased dissociation constant for carnitine compared to the cardiac carnitine-binding protein prepared from normal hamsters. Thus, several types of data indicate that the cardiomyopathic hamster has an altered cardiac carnitine transport mechanism.