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Clinical Studies (Return to Clinical
Studies page)
ALPHA-LIPOIC ACID, A
POWERFUL ANTIOXIDANT IN ATHLETES
Zembron-Lacny A, Szyszka K,
Szygula Z. (2007). Effect of cysteine derivatives administration in healthy men exposed to
intense resistance exercise by evaluation of pro-antioxidant ratio. J Physiol Sci. 57(6):343-8.
The aim of this study was to
ascertain the influence of cysteine derivatives on pro-antioxidant equilibrium and to compare
the antioxidant effectiveness of N-acetylcysteine, alpha-lipoic acid, and taurine by using
Loverro's coefficient (pro-antioxidant ratio) in healthy men exposed to intensity-resistance
exercise. Fifty-five men were randomly assigned to one of four groups: control (CON, placebo),
N-acetylcysteine (NAC 1.8 g.day(-1), 3 days), alpha-lipoic acid (LIP 1.2 g.day(-1), 3 days), or
taurine (TAU 3 g.day(-1), 3 days). The erythrocyte superoxide dismutase (SOD), glutathione
peroxidase (GPx), and catalase (CAT) activities, lipid peroxidation products (TBARS), and plasma
protein thiol concentrations were evaluated. The P/A ratio was determined from the mean values
of TBARS, SOD, GPx, and CAT. The applied exercise at maximal intensity induced the significant
changes in pro-antioxidant equilibrium toward peroxidation, which was proved by a 25% increase
in TBARS concentration in the CON group. The peroxidation was significantly diminished by NAC
(-14%) and LIP (-16%), whereas TAU had no effect on the TBARS concentration. Cysteine
derivatives administration prevented exercise-induced decline in SOD activity and increased in
GPx activity during exercise. CAT activity changed only in the LIP group. The estimation of P/A
ratio showed the lowest level of pro-antioxidant equilibrium after LIP administration. In the
CON group, P/A ratio was directly correlated with the protein thiols level (r = 0.495, p <
0.001). These data confirm the antioxidant action of tested cysteine derivatives, particularly
lipoic acid, and demonstrate the practical application of P/A ratio to evaluate the
effectiveness of antioxidants in athletes.
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Marangon K, Devaraj S, Tirosh
O, Packer L, Jialal I. (1999). Comparison of the effect of alpha-lipoic acid and
alpha-tocopherol supplementation on measures of oxidative stress. Free Radic Biol Med. 27(9-10):1114-21.
In vitro studies have shown
that alpha-lipoic acid (LA) is an antioxidant. There is a paucity of studies on LA
supplementation in humans. Therefore, the aim of this study was to assess the effect of oral
supplementation with LA alone and in combination with alpha-tocopherol (AT) on measures of
oxidative stress. A total of 31 healthy adults were supplemented for 2 months either with LA
(600 mg/d, n = 16), or with AT (400 IU/d, n = 15) alone, and then with the combination of both
for 2 additional months. At baseline, after 2 and 4 months of supplementation, urine for
F2-isoprostanes, plasma for protein carbonyl measurement and low-density lipoprotein (LDL)
oxidative susceptibility was collected. Plasma oxidizability was assessed after incubation with
100 mM 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH) for 4 h at 37 degrees C. LDL was
subjected to copper- and AAPH-catalyzed oxidation at 37 degrees C over 5 h and the lag time was
computed. LA significantly increased the lag time of LDL lipid peroxide formation for both
copper-catalyzed and AAPH-induced LDL oxidalion (p < .05), decreased urinary F2-isoprostanes
levels (p < .05), and plasma carbonyl levels after AAPH oxidation (p < .001). AT prolonged
LDL lag time of lipid peroxide formation (p < .01 ) and conjugated dienes (p < .01) after
copper-catalyzed LDL oxidation, decreased urinary F2-isoprostanes (p < .001), but had no
effect on plasma carbonyls. The addition of LA to AT did not produce an additional significant
improvement in the measures of oxidative stress. In conclusion, LA supplementation functions as
an antioxidant, because it decreases plasma- and LDL-oxidation and urinary
isoprostanes.
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