Abstract 14323: Enhanced Oxidative Stress is Correlated With Skeletal Muscle Abnormalities in Patients With Metabolic Syndrome
Background: We have previously reported that intramyocellular lipid (IMCL) is increased and high-energy phosphate metabolism is impaired in the skeletal muscle in patients with metabolic syndrome (MetS), which reduce aerobic exercise capacity. However, the mechanisms underlying these skeletal muscle abnormalities have not been determined. We thus hypothesized that enhanced oxidative stress was correlated with the skeletal muscle abnormalities in MetS.
Methods: The incremental exercise tests with a cycle ergometer were performed in 12 male patients with MetS diagnosed by the NCEPIII criteria, and 11 age-, sex-, and activity-matched healthy subjects (control). Muscular phosphocreatine (PCr) during unilateral plantar flexion (0.67Hz for 4 min) with a constant load of 20% one-repetition-maximum was measured by using 31P-magnetic resonance spectroscopy (MRS). IMCL, the balance between uptake and oxidation of fatty acid, was measured in the resting leg muscle by 1H-MRS. Serum thiobarbituric acid reactive substances (TBARS), glutathione peroxidase (GPx), and superoxide dismutase (SOD) activities were measured.
Results: Patients with MetS had significant increases in body weight, fat mass, HOMA-index, and free fatty acid. Peak oxygen uptake (34.1±6.2 vs. 41.4±8.4 mL/kg/min, P<0.05) and anaerobic threshold (18.0±2.4 vs. 23.1±3.7 mL/kg/min, P<0.01) normalized to lean body mass were significantly lower in MetS compared to control. Maximal PCr loss during exercise was significantly greater in MetS (34±13 vs. 22±11 %, P<0.01), indicating lower energy reserves in the skeletal muscle. IMCL content was significantly higher in MetS (4.4±1.7 vs. 2.0±1.7 mmol/kg wet weight, P<0.01), indicating impaired fatty acid metabolism in the skeletal muscle. Serum TBARS were significantly increased in MetS compared to control (12.2±7.7 vs. 3.8±1.2 μmol/L, P<0.01) and were significantly correlated with maximal PCr loss (r=0.48, P<0.05) and IMCL content (r=0.64, P<0.01), respectively. GPx and SOD activities did not differ between groups.
Conclusions: Oxidative stress may play an important role in the impairment of skeletal muscle metabolism and the increase in IMCL, which reduce the aerobic exercise capacity in patients with MetS.
- © 2011 by American Heart Association, Inc.