Skeletal muscle mitochondrial content

Exercise There is moxmting evidence that exercise might exacerbate statin-related side effects such as myopathy [50]. The randomised, controlled trial with 37 subjects (exercise plus simvastatin n= 18 exercise only n= 19) showed that simvastatin attenuates increases in cardiorespiratory fitness and skeletal muscle mitochondrial content when combined with exercise training in patients at risk of the metabolic syndrome [51]. The short-term administration of high-dose atorvastatin did not result in altered muscle function despite mild increases in creatine kinase levels [52]. 

Similarly, measurements of blood flows to sections of muscle, which are primarily composed of a single fiber type, exhibit large differences consistent with the expected demands of oxygen supply based on mitochondrial content (32,33). Thus, mammalian skeletal muscle is typically comprised of three biochemically and functionally distinct fiber types slow-twitch red, fast-twitch red and fast-twitch white. These fiber types are also commonly referred to as Type I, Type Ila, and Type 11b, respectively (7 ). 

The heart, with its huge mitochondrial content and oxidative capacity, is able to use lactate released from other tissues as a fuel. During an exercise such as bicycle riding, lactate released into the blood from skeletal muscles in the leg might be used by resting skeletal muscles in the arm. In the brain, glial cells and astrocytes produce lactate, which is used by neurons or released into the blood. 

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