Effects of L- and DL-carnitine on patients with impaired exercise tolerance.
We designed this study to determine whether orally administered L- and DL-carnitine can improve exercise tolerance in a group of patients with exercise intolerance. Nineteen patients with cardiac disease were randomly divided into 2 groups, an L-carnitine treatment group (n = 9) and a DL-carnitine treatment group (n = 10). Eight additional age-matched patients served as an untreated control group. Subjects in both carnitine treatment groups underwent cardiopulmonary exercise testing on a cycle ergometer in order to determine peak exercise time, peak oxygen uptake (VO2), lactate threshold (LT) and ventilatory threshold (VT) before and after the oral administration of 900 mg/day of L- or DL-carnitine for 2 weeks. Basal values of peak exercise time, peak VO2, LT and VT did not differ significantly among the 3 groups. Peak exercise time and peak VO2 tended to be increased in the L-carnitine treatment group, and tended to be decreased in the DL-carnitine treatment group. Both LT and VT (ml/kg/min) were significantly improved (LT: from 9.7 +/- 0.6 to 10.8 +/- 1.0, p < 0.05; VT: from 9.8 +/- 0.8 to 11.8 +/- 1.9, p < 0.02) by the administration of L-carnitine, while LT was significantly decreased (from 11.0 +/- 2.0 to 9.6 +/- 1.2, p < 0.05) and VT tended to be decreased by the administration of DL-carnitine (from 11.6 +/- 2.0 to 10.8 +/- 2.4). In the untreated control group, no significant changes were observed in the values of exercise tolerance between the 2 series of exercise testings. In neither group did carnitine modify hemodynamic parameters at rest or during exercise. In conclusion, this study demonstrated that L-carnitine increases and DL-carnitine decreases exercise tolerance in patients with impaired exercise tolerance.
Watanabe
S
S
Department of Internal Medicine, University of Tsukuba, Japan.
Ajisaka
R
R
Masuoka
T
T
Yamanouchi
T
T
Saitou
T
T
Toyama
M
M
Takeyasu
N
N
Sakamoto
K
K
Sugishita
Y
Y
D000284:Administration, Oral; D000368:Aged; D002302:Cardiac Output / Q000187:drug effects; D002331:Carnitine / Q000008:administration & dosage / Q000494:pharmacology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects*; D005260:Female; D006331:Heart Diseases / Q000188:drug therapy / Q000503:physiopathology; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid; D013237:Stereoisomerism
D007773:Lactates; D011773:Pyruvates; D019344:Lactic Acid; D019289:Pyruvic Acid; D002331:Carnitine