Effects of L-carnitine on oxidative stress responses in patients with renal disease.

PURPOSE: Hemodialyzed patients demonstrate elevated oxidative stress and reduced functional status. Exercise induces health benefits, but acute exertion up-regulates oxidative stress responses in patients undergoing hemodialysis. Therefore, the aim of the present study was to examine the effect of L-carnitine supplementation on i) exercise performance and ii) blood redox status both at rest and after exercise. METHODS: Twelve hemodialysis patients received either L-carnitine (20 mg kg(-1) i.v.) or placebo in a double-blind, placebo-controlled, counterbalanced, and crossover design for 8 wk. Participants performed an exercise test to exhaustion before and after supplementation. During the test, V˙O2, respiratory quotient, heart rate, and time to exhaustion were monitored. Blood samples, collected before and after exercise, were analyzed for lactate, malondialdehyde, protein carbonyls, reduced and oxidized glutathione, antioxidant capacity, catalase, and glutathione peroxidase activity. RESULTS: Blood carnitine increased by L-carnitine supplementation proportionately at rest and after exercise. L-carnitine supplementation increased time to fatigue (22%) and decreased postexercise lactate (37%), submaximal heart rate, and respiratory quotient but did not affect V˙O2peak. L-carnitine supplementation increased reduced/oxidized glutathione (2.7-fold at rest, 4-fold postexercise) and glutathione peroxidase activity (4.5% at rest, 10% postexercise) and decreased malondialdehyde (19% at rest and postexercise) and protein carbonyl (27% at rest, 40% postexercise) concentration. CONCLUSIONS: Data suggest that a 2-month L-carnitine supplementation may be effective in attenuating oxidative stress responses, enhancing antioxidant status, and improving performance of patients with end-stage renal disease.

Dose-related effects of prolonged NaHCO3 ingestion during high-intensity exercise.

PURPOSE: Sodium bicarbonate (NaHCO3) ingestion may prevent exercise-induced perturbations in acid-base balance, thus resulting in performance enhancement. This study aimed to determine whether different levels of NaHCO3 intake influences acid-base balance and performance during high-intensity exercise after 5 d of supplementation. METHODS: Twenty-four men (22 +/- 1.7 yr) were randomly assigned to one of three groups (eight subjects per group): control (C, placebo), moderate NaHCO3 intake (MI, 0.3 g x kg(-1) x d(-1)), and high NaHCO3 intake (HI, 0.5 g x kg(-1) x d(-1)). Arterial pH, HCO3(-), PO2, PCO2, K+, Na, base excess (BE), lactate, and mean power (MP) were measured before and after a Wingate test pre- and postsupplementation. RESULTS: HCO3(-) increased proportionately to the dosage level. No differences were detected in C. Supplementation increased MP (W x kg(-)) in MI (7.36 +/- 0.7 vs 6.73 +/- 1.0) and HI (7.72 +/- 0.9 vs 6.69 +/- 0.6), with HI being more effective than MI. NaHCO3 ingestion resulted postexercise in increased lactate (mmol x L(-1)) (12.3 +/- 1.8 vs 10.3 +/- 1.9 and 12.4 +/- 1.2 vs 10.4 +/- 1.5 in MI and HI, respectively), reduced exercise-induced drop of pH (7.305 +/- 0.04 vs 7.198 +/- 0.02 and 7.343 +/- 0.05 vs 7.2 +/- 0.01 in MI and HI, respectively) and HCO3(-) (mmol x L(-1)) (13.1 +/- 2.4 vs 17.5 +/- 2.8 and 13.2 +/- 2.7 vs 19.8 +/- 3.2 for HCO3 in MI and HI, respectively), and reduced K (3.875 +/- 0.2 vs 3.625 +/- 0.3 mmol x L(-1) in MI and HI, respectively). CONCLUSION: NaHCO3 administration for 5 d may prevent acid-base balance disturbances and improve performance during anaerobic exercise in a dose-dependent manner.