Muscle thermogenesis

PPAR5 Ubiquitous Potent TG- and LDL-C-lowering and potent HDL-C-raising increased oxidative disposal of fatty acids in adipose and skeletal muscle thermogenesis weight loss Fatty acids, eicosanoids (fatty acids derived from VLDL particles ) GW501516 currently in Phase II clinical trials Dyslipidemia, obesity atherosclerosis ... 

In a group of haemodialysis patients, muscle thermogenesis was evaluated by measurement of heat production in skeletal muscle samples [112]. Biopsies were taken from the vastus lateralis muscle by needle technique, using the same amount of muscle for each patient, about 45 mg. Microcalorimetric measurements were made in a perfusion calorimeter of the thermopile heat conduction type, as previously described. Blood samples for measurement of thyroid hormone concentration were collected the morning before dialysis after the patients had been fasting for 12 h. About 40% of the group of haemodialysis patient were found to have decreased muscle heat production... 

Fagher, B Liedholm, H Sjogren, A., Monti, M. (1993). Effects of terbutaline on basal thermogenesis of human skeletal muscle and Na-K pump after 1 week of oral use—a placebo controlled comparison with propranolol. Br. J. Clin. Pharmac. 35,629-635. 

Fagher, B Monti, M., Theander, S. (1989). Microcalorimetric study of muscle and platelet thermogenesis in anorexia nervosa and bulimia. Amer. J. Clin. Nutr. 51,121-140. 

Newborn babies contain brown fat in their necks and upper backs that serves the function of nonshivering thermogenesis. Muscle contractions that take place in the process of shivering use ATP and produce heat, but nonshivering thermogenesis is a hormonal stimulus for heat generation without the associated muscle contractions of shivering. 

All three subtypes of P-ARs are expressed in the heart (73). Despite the existence of species-related differences (reviewed in ref. 74), prARs are the predominant form of ARs. The positive chronotropic and inotropic response of the heart to catecholamine stimulation is mediated almost exclusively by prARs (75-77). Coupling of (32-ARs to cardiac contractility is less defined and species related, showing a positive effect in human hearts (77) but not affecting contractility in the mouse (75). Better defined is the role of P2-ARs in the regulation of vascular tone and blood pressure (78). P3-ARs, atypical P-ARs, are expressed in the adipose tissue, where they mediate lipolysis and thermogenesis (79,80), and in smooth muscle cells, where they mediate vasorelaxation (81). 

IDL) to LDL, and probably also by maintaining lipoprotein lipase activity which promotes triglyceride clearance. In liver, kidney, skeletal muscle, cardiac muscle, and adipose tissue, thyroid hormone stimulates Na", K+-ATPase gene expression and promotes thermogenesis. 

Van der Linden, C.G., Muller, A. and Van Hardeveld, C. (2001) Mechanism of thyroid-hormone regulated expression of the SERCA genes in skeletal muscle implications for thermogenesis. Bioscience Reports, 21, 139—154. 

The entire process of heat generation from brown fat, called nonshivering thermogenesis, is regulated by norepinephrine. (In shivering thermogenesis, heat is produced by nonvoluntary muscle contraction.) Norepinephrine, a neurotransmitter released from specialized neurons that terminate in brown adipose tissue, initiates a cascade mechanism that ultimately hydrolyzes fat molecules. The fatty acid products of fat hydrolysis activate the uncoupler protein. Fatty acid oxidation continues until the norepinephrine signal is terminated or the cell s fat reserves are depleted. 

Adult humans have little brown fat, but human infants have a great deal. In the newborn, thermogenesis by brown-fat mitochondria is vital to survival, as it also is in hibernating mammals. In fur seals and other animals naturally acclimated to the cold, muscle-cell mitochondria contain thermogenin as a result, much of the proton-motive force is used for generating heat, thereby maintaining body temperature. 

Protein Muscle contraction Active ion transport Thermogenesis... 

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