Browning skeletal muscle

Tissue-Specific Expression. In the adult rodent, PPARy is expressed in brown and white adipose tissue, and at lower levels in intestine, retina, skeletal muscle, and lymphoid organs. In human, PPARy is most abundantly expressed in white adipose tissue and at lower levels in skeletal muscle, the heart, and liver, but not in lymphoid tissues, although PPARy has been identified in macrophages in human atheromas. 

The rate of mitochondrial oxidations and ATP synthesis is continually adjusted to the needs of the cell (see reviews by Brand and Murphy 1987 Brown, 1992). Physical activity and the nutritional and endocrine states determine which substrates are oxidized by skeletal muscle. Insulin increases the utilization of glucose by promoting its uptake by muscle and by decreasing the availability of free long-chain fatty acids, and of acetoacetate and 3-hydroxybutyrate formed by fatty acid oxidation in the liver, secondary to decreased lipolysis in adipose tissue. Product inhibition of pyruvate dehydrogenase by NADH and acetyl-CoA formed by fatty acid oxidation decreases glucose oxidation in muscle. 

Wei XY, Perez-Reyes E, Lacerda AE, Schuster G, Brown AM, Birnbaumer L (1991) Heterologous regulation of the cardiac Ca2+ channel alpha 1 subunit by skeletal muscle beta and gamma subunits. Implications for the structure of cardiac L-type Ca2+ channels. J Biol Chem 266 21943—21947. 

Bershitsky, S., Tsaturyan, A., Bershitskaya, O., Mashanov, G., Brown, P., Webb, M., and Ferenczi, M. A. (1996). Mechanical and structural properties underlying contraction of skeletal muscle fibers after partial l-ethyl-3-[3-dimethylamino)propyl]carbodii-mide cross-linking. Biophys.J. 71, 1462-1474. 

C27. Child, R., Brown, S., Day, S., Donnelly, A., Roper, H., and Saxton, J., Changes in indices of antioxidant status, lipid peroxidation and inflammation in human skeletal muscle after eccentric muscle actions. Clin. Sci. 96, 105-115 (1999). 

Brooks, G.A., M.A. Brown, C.E. Butz, J.P. Sicurello, and H. Dubouchaud (1999a). Cardiac and skeletal muscle mitochondria have a monocarboxylate transporter MCT1. J Appl. Physiol. 87 1713-718. 

Type II deiodinase occurs in the brain and brown adipose tissue of rats (but not in muscle of rats), and in the brain, skeletal muscle, heart, and thyroid gland in humans (Fallud et al 1997). This enzyme catalyzes the conversion of T4 to T3. When the thyroid gland is stimulated, the type II deiodinase takes on an increased importance in the conversion of T4 to T3 (Salvatore et at., 1996). Type II deiodinase is unique among the deiodinases in that it appears to contain two selenium atoms, rather than just one. The physiological role of the enzyme is to utilize T4 acquired from the bloodstream and to convert it to T3 within the target tissue. 

Rojas CV, Wang JZ, Schwartz LS, Hoffman EP, Powell BR, Brown RH Jr 1991 A Met-to-Val mutation in the skeletal muscle Na+ channel alpha-subunit in hyperkalaemic periodic paralysis. Nature 354 387—389... 

Angers RC, Browning SR, Seward TS et al (2006) Prions in skeletal muscles of deer with chronic wasting disease. Science 311 1117... 

As indicated in the foregoing, since the relative proportions of the a and p components in skeletal muscle are variable, the TM molecule can be made up of aa, ap, or pp dimers. This would also be true of smooth muscle TM, even though the ratio of the two chains is close to 1 1. Substantial evidence now exists that for both muscle types the most thermodynamically stable form is the p dimer. Thus in the case of skeletal muscle in which the a p ratio is >1 1, the TM species present would be a mixture of aa and aP with minimal amounts of PP. In smooth muscles in which a P is 1 1, the predominant species is the aP dimer (Bronson and Shachat, 1982 Eisenberg and Kielley, 1974 Lehrer, 1975 Holtzer et al., 1984 Brown and Schachat, 1985 Lehrer et al., 1989 Sanders et al., 1986 Graceffa, 1989 Jancso and Graceffa, 1991 Lehrer and Stafford, 1991). Upon denaturation and renaturation, the distribution of the a and p chains in the dimeric species is dependent on temperature and ionic strength of renaturation (see, e.g., Lehrer and Stafford, 1991). Under ap-... 

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