Muscles energy metabolism

FIGURE 14.21 The structures of creatine and creatine phosphate, guanidiniutn compounds that are important in muscle energy metabolism. 

Griffiths, RD., Cady, E.B., Edwards, RH.T. and Wilkie, D.R (1985). Muscle energy metabolism in Duchenne muscular... 

Earlier work involved restrained or resting fish, but recent techniques have been developed to study fish while swimming. They have also recently examined in vivo muscle energy metabolism in the cuttlefish, a marine invertebrate. ... 

Lodi R, Schapira AH, Manners D, Styles P, Wood NW, Taylor DJ, Warner TT (2000) Abnormtil in vivo skeletal muscle energy metabolism in Huntington s disease and dentatorubialptilli-doluysian atrophy. Ann Neurol 48 72-76... 

Htucidation of muscle energy metabolism is complicated by several factors. Muscle can receive glucose and fatty acids from internal sources as well as from the bloodstream. The relative importance of internal versus external sources can be difficult to determine. Muscle is a heterogeneous tissue. Some muscle types carry out mainly aerobic forms of energy metabolism other types are fermentative and still others are composed of mixtures of cells, some aerobic and some fermentative. 

Role of purine nucleotides in muscle energy metabolism. The conversion of AMP to IMP prevents loss of adenosine from the cell. 

Paul, R. J. (1986). Smooth muscle energy metabolism cytosolic compartmentation of metabolism and function. In Advances in Physiological Research (McLennan, H., Ledsome, J. R., McIntosh, C. H. S. and Jones, D. R., eds.), pp. 295-304, Plenum Press, New York. 

Kutsuzawa T, Shioya S, Kurita D, et al. Muscle energy metabolism and nutritional status in patients with chronic obstructive pulmonary disease a 3 IP magnetic resonance study. Am J Respir Crit Care Med 1995 152 647-652. 

Figure 2. Force generation and energy metabolism in human quadriceps femoris muscle stimulated intermittently at 20 Hz, with 1.6 sec tetani with 1.6 sec rest periods between tetani. The upper panel shows force, ATP turnover rate, and pH the middle panel, the concentrations of PCr, P and lactate and the lower panel, ATP, ADP, IMP, H, and calculated H2PO4. From Hultman et al. (1990), with permission from Human Kinetics Publishers.

Hultman, E., Greenhaff, P.L., Ren, J.M., Soderlund, K. (1991). Energy metabolism and fatigue during intense muscle contraction. Biochem. Soc. Transact. 19, 347-353. 

Taegtmeyer, H., Roberts, A.F.C. and Raine, A.E.G. (1985). Energy metabolism in reperfused heart muscle Metabolic correlates to return of funaion. J. Am. Coll. Cardiol. 6, 864-870. 

Defects of energy metabolism cause profound disturbances in the function of muscle and brain. Such defects may present as a myopathy, encephalopathy or encephalo-myopathy. Clinical features are best appreciated by understanding the preferred oxidizable substrates for brain and muscle. 

Energy metabolism has been studied extensively in skeletal muscle, and several metabolic disorders have been documented [1, 4]. Comparatively less is known about metabolic defects in cerebral energy metabolism. This may be because muscle tissue is more accessible for biochemical analysis and because certain cerebral enzyme defects are lethal. 

Diseases of muscle are usually classified as muscular dystrophies, inflammatory or congenital myopathies, metabolic disorders affecting the muscle, and neurological diseases affecting the innervation of the muscle (so-called motor neuron diseases). In the past, the energy metabolism of some muscular diseases... 

Using the transport systems in the membranes, cells regulate their volume, internal pH value, and ionic environment. They concentrate metabolites that are important for energy metabolism and biosynthesis, and exclude toxic substances. Transport systems also serve to establish ion gradients, which are required for oxidative phosphorylation and stimulation of muscle and nerve cells, for example (see p. 350). 

During periods of hunger, muscle proteins serve as an energy reserve for the body. They are broken down into amino acids, which are transported to the liver. In the liver, the carbon skeletons of the amino acids are converted into intermediates in the tricarboxylic acid cycle or into acetoacetyl-CoA (see p. 175). These amphibolic metabolites are then available to the energy metabolism and for gluconeogenesis. After prolonged starvation, the brain switches to using ketone bodies in order to save muscle protein (see p. 356). 

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