Muscle fuel selection: effect of exercise and training

摘要

The contracting skeletal muscle relies on fuels from both extra- and intramuscular sources. The main stored fuels are glycogen and triacylglycerols (TG). The largest muscle store of potentially energy-yielding fuels, i.e. the muscle proteins themselves, normally contributes very little to the total energy expenditure in skeletal muscles. Nevertheless, amino acids are important molecules in the metabolic regulation of contracting muscle. Glucose and non-esterified fatty acids (NEFA) are important blood-borne fuels utilized by skeletal muscle. Circulating TG are believed to play a minor role, but their importance may have been underestimated in the past. Ketone bodies are taken up by skeletal muscle, but to a very low extent. It is well documented that training induces an increased reliance on fat relative to carbohydrate metabolism. In the resting state, skeletal muscle is important as the body's largest insulin-sensitive organ; an impaired insulin sensitivity in skeletal muscle is associated with cardiovascular disease. Contractile activity induces an increased muscle sensitivity to insulin, which usually lasts 1-2 d.