TY - CHAP M1 - Book, Section TI - Metabolic Myopathies A1 - Amato, Anthony A. A1 - Russell, James A. PY - 2015 T2 - Neuromuscular Disorders, 2e AB - The inherited metabolic myopathies are traditionally classified by their underlying biochemical abnormalities as disorders of (1) carbohydrate, (2) lipid, and (3) adenine nucleotide metabolism. A fourth possible category includes the mitochondrial encephalomyopathies. As mitochondrial disorders do not cause defects in a specific biochemical pathway, they are discussed in a separate chapter. The immediate source of energy for muscles comes from the hydrolysis of adenosine triphosphate (ATP). At rest, the major substrate for muscle in terms of ATP production comes from the metabolism of long-chain fatty acids. Therefore, any disorder impairing β-oxidation of long-chain fatty acids in the mitochondria can lead to a myopathy. During exercise, ATP is derived from the metabolism of carbohydrates, fatty acids, and ketones. Early in the course of exercise (e.g., up to 45 minutes), energy is derived mainly from free glucose or glucose made available via glycogenolysis. Subsequently, there is a shift toward the metabolism of fatty acids such that after a few hours 70% of energy is derived from lipid breakdown. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/29 UR - neurology.mhmedical.com/content.aspx?aid=1115661783 ER -