7α- and 7β-hydroperoxycholest-5-en-3β-ol in muscle as indices of oxidative stress:: Response to ethanol dosage in rats

Background: Alcohol-induced muscle disease (AIMD) encompasses both acute and chronic lesions, and affected patients exhibit concomitant functional and structural lesions. The pathogenic mechanisms are unknown, although it is possible that defects in the membrane-lipid domain are involved. Therefore, the effect of acute ethanol on membrane lipid from rat skeletal muscles (control, n = 7; ethanol, n = 7) was investigated. Methods: Soleus and plantaris skeletal muscles were collected 24 hr after a single dose of 75 mmol/kg of ethanol. Lipids were analyzed by high-performance liquid chromatography with postcolumn chemiluminescence. Results: We found that two cholesterol-derived hydroperoxides, 7 beta-hydroperoxycholest-5-en-3 beta-ol (7 beta-OOH) and 7 beta-hydroperoxycholest-5-en-3 beta-ol (7 beta-OOH) were present in soleus muscles of control animals (1.29 nmol/g and 3.20 nmol/g, respectively) and in plantaris (1.83 and 5.18 nmol/g, respectively). These hydroperoxides were significantly elevated by acute ethanol, in not only plantaris but also soleus skeletal muscle of rats. In contrast, protein carbonyl concentration, another indicator of oxidative stress, albeit to proteins, was not significantly affected in either soleus or plantaris muscles of ethanol dosed rats. In addition, gas chromatographic study of fatty acid composition from phospholipid of rat muscle showed a significant increase of 18:2 by ethanol in plantaris as well as soleus. Concomitant decreases occurred in the nonessential/essential fatty acid ratios. Conclusions: This is the first report on 7 alpha-OOH and 7 beta-OOH accumulation in rat skeletal muscle, and it seems to reflect greater oxidative stress in the pathology of muscle of rats treated with acute ethanol. Together with the elevation of 18:2, these results signify perturbations in membrane lipids in response to ethanol, which may have important implications for the pathogenesis of alcohol-induced muscle disorders.