Inhibition of Oxidative Stress by Antioxidant Supplementation Does Not Limit Muscle Mitochondrial Biogenesis or Endurance Capacity in Rats

Abstract

SummaryThe objective of the present study was to analyze the activation and expression patterns of upstream and downstream factors of PGC-1a to determine whether antioxidant (AO) supplementation inhibits mitochondrial biogenesis in skeletal muscles as an adaptation to endurance training, as well as to analyze changes in endurance capacity based on such findings. For this objective, 24 male Sprague-Dawley (SD) rats were allocated into 4 groups (vehicle-sedentary, V-Sed; vehicle-exercise, V-EX; antioxidant-sedentary, AOSed; antioxidant-exercise, AO-EX) of 6 rats each. The rats were then treated with vitamin C (500 mg•kg 21 body weight•d 21) or a placebo for 8 wk, and a swimming program was implemented in some rats during the last 4 wk of this period. Immediately after the last training session, blood was collected from the tail of each rat, and TBARS was measured to test the effect of vitamin C as an AO. As a result, increased oxidative stress from exercise was inhibited by vitamin C supplementation. Analysis of whether reduced oxidative stress by vitamin C supplementation also inhibited mitochondrial biogenesis within skeletal muscles showed that phosphorylation of p38 MAPK and AMPK, along with levels of PGC-1a, NRF-1, mtTFA, and mitochondrial electron transport enzymes, increased after endurance training in spite of vitamin C supplementation. Moreover, running time, distance, and total work increased significantly in the exercise group as compared to those in the sedentary group, regardless of vitamin C supplementation. These results indicate that mitochondrial biogenesis and endurance capacity increase as a result of endurance training, regardless of AO supplementation. Key Words exercise, antioxidants, mitochondria, oxidative stress Endurance training promotes not only mitochondrial biogenesis (1-3), but also various adaptive responses within skeletal muscles, such as improved insulin sensitivity (4-6), fatty acid oxidation (7,8), and antioxidant (AO) defense system efficiency (9, 10). Such adaptive responses occur owing to increased expression or activation of peroxisome proliferator-activated receptor g (PPAR-g) coactivator-1a (PGC-1a) through Ca 21 -dependent pathways, AMP-activated protein kinase (AMPK), and p38 mitogen-activated protein kinases (MAPK) (11,12). However, aside from these positive adaptive responses, oxidative stress due to reactive oxygen species (ROS) also increases within skeletal muscles during muscle contractions (13-15). Increased oxidative stress, or increased ROS, is known to play a harmful role in the human body, but recent studies have reported its positive effects, such as being involved in mitochondrial biogenesis (13,(16)(17)(18) as well. Because of this, there have been reports from recent studies that have examined the effects of AO supplementation, such as with vitamins, on adaptive responses from endurance training in skeletal muscles. However, these study results conflict with claims that skeletal muscle adaptations from endurance training are decreased by AO supplementatio...

Diet Quality, Nutritional Status, and Haemoglobin Level of Female Adolescent Athletes in Endurance and Non Endurance Sports

“…Antioxidants are substances that contribute to relieving the effects of stress and oxygen deprivation caused by exercise by reducing free radical reactions. 38 The portion of the consumed grains group showed a higher mean in the endurance sport. This result was in line with the components of carbohydrate intake where there were differences between the two groups.…”

Concurrent treatment with ursolic acid and low-intensity treadmill exercise improves muscle atrophy and related outcomes in rats

“…Muscle extracts were prepared and Western blotting was performed as described previously [ 40 ]. Blots were probed with the following antibodies: Akt, P-Akt, mTOR, P-mTOR, MuRF-1, Atrogin-1 (Bio-Rad, CA, USA), and β-actin (Sigma, MO, USA).…”

Effects of Dietary Supplements on Adaptations to Endurance Training

“…Animal studies have also shown that 4 to 14 weeks of aerobic training with antioxidant intake blunted training-induced increases in cytochrome oxidase and CS activity, mitochondrial transcription factor A (TFAM), CYT-C, GPx, glutathione reductase, SOD, PGC-1, NRF-1, and NRF-2 [118,[128][129][130], although other research has shown no effect on markers of training adaptations such as mitochondrial respiratory capacity, and CYT-C, COX-I, COX-IV, CS, NRF-1, or PGC-1 protein content [130][131][132][133].…”

“…The reason for these divergent findings, particularly in the animal research, may be due to variations in dosing, exercise protocols, and baseline levels of endogenous antioxidants. The amount of antioxidant provided has varied more than 10-fold [128,134], exercise type has included both running and swimming, and the duration of training sessions has ranged from 30 min to six hours per day [132][133][134]. Potential redundancies in the adaptation process must also be considered.…”