Muscle protein metabolism

Phosphorylation Glycogen Metabolic Movements of Glycogen Fat Metabolic Movements of Fat Protein Metabolic Movements of Protein Tissue Cooperation Liver Muscle Ketone Bodies... 

Diacylglycerol, on the other hand, is lipid soluble and remains in the lipid bilayer of the membrane. There it can activate protein kinase C (PKC), a very important and widely distributed enzyme which serves many systems through phosphorylation, including neurotransmitters (acetylcholine, a,- and P-adrenoceptors, serotonin), peptide hormones (insulin, epidermal growth hormone, somatomedin), and various cellular functions (glycogen metabolism, muscle activity, structural proteins, etc.), and also interacts with guanylate cyclase. In addition to diacylglycerol, another normal membrane lipid, phos-phatidylserine, is needed for activation of PKC. The DG-IP3 limbs of the pathway usually proceed simultaneously. 

Major metabolic pathways in skeletal muscle in the absorptive state. [Note The numbers in circles, which appear both on the figure and in the text, indicate important pathways for carbohydrate or protein metabolism ]... 

Sixliultt ion acts in concert with other electrolytes, in particular K. to regulate the osmotic pressure and to maintain the appropriate water and pi I balance ot the body. Homeostatic control of these functions is accomplished by the lungs and kidneys inlereciing by way of the blood. Sodium is essential for glucose absorption and transport of other substances across cell membranes. It is also involved, as is KJ. ill transmitting nerve impulses and in muscle relaxation. Potassium ion acts as a catalyst in the intracellular fluid, in energy metabolism, and is required for carbohydrate and protein metabolism. 

Protein metabolism Cortisol promotes the breakdown of proteins and inhibits protein synthesis. This leads to muscle wasting in the quadriceps-femoris groups, and muscular activities may become difficult as a result. The effect of cortisol is opposite to that of insulin. 

Digestion of proteins occurs by enzymatic hydrolysis in the small intestine (Figure 4.3). The digestion of protein produces single amino acids. These can enter the bloodstream through the small intestine walls. The amino acids circulate in the bloodstream until further metabolized or used for protein synthesis there is not a storage depot for amino acids as there is for lipids, which are stored in fat depots in adipose tissue. However, the body does break down protein tissue (muscle) to provide amino acids in the bloodstream. 

Aerobic exercise usually increases the percentage of muscle mass due to a decrease in body fat, but produces no absolute change in the amount of muscle. Aerobic exercise has been shown to alter protein metabolism including increases in amino acid oxidation with specific effects on the branched-chain amino acid leucine, increased urinary urea, and increased sweat nitrogen. 

K13. Kruh, J., Dreyfus, J.-C., Schapira, G., and Gey, G. O., Jr., Abnormalities of muscle protein metabolism in mice with muscular dystrophy. ]. Clin. Invest. 39, 1180 (I960). 

The first step in protein metabolism in muscle is the uptake of amino acids from the blood by the fibers, via the extracellular space. Experiments with injected amino acids and with isolated muscle preparations by many workers have demonstrated that muscle fibers can accumulate amino acids from the medium. Experiments with a-aminoisobutyric acid, a nonmetabolizable amino acid, have been particularly useful in enabling accumulation to be studied independently of incorporation of the amino acid into protein. An increased accumulation of amino acids has been observed in the dystrophic mouse (B3), in vitamin E deficiency (D4), and in denervated muscle (D4). The authors of the last-mentioned observation concluded from their evidence that the increased accumulation was associated with increased active transport into the muscle cells, not with a change in passive permeability of the membranes. Nichoalds et al. (Nl) found that puromycin, which abolished protein synthesis, had no effect upon the accumulation of glycine- C by control or vitamin E-deficient muscle. More recently, Goldberg and Goodman (G4) observed a decrease in the accumulation of a-aminoisobutyric acid by soleus and plantaris muscles within 3 hours of denervation subsequently. 

Yl. Young, V. R., The role of skeletal and cardiac muscle in the regulation of protein metabolism. In Mammalian Protein Metabolism (H. N. Mimro, ed.), Vol. 4, pp. 585-674. Academic Press, New York, 1970. 

Clark AS, Fagan JM, Mitch WE. 1985. Selectivity of the insulin-like actions of vanadate on glucose and protein metabolism in skeletal muscle. Biochem J 232 273-276. 

Creatinine—The breakdown of protein metabolic by-product obtained from the diet or generated from muscle of the body. Creatinine is removed from blood by the kidneys as kidney disease progresses, the level of creatinine in the blood increases. 

Metabolic effects Redistribution of fat moon face and buffalo hump Hyperglycaemia possible diabetes Protein wasting muscle weakness Osteoporosis... 

Testosterone (which is also present in small amounts in females) stimulates the growth of the male reproductive organs and promotes the development of the male secondary sex characteristics. It also affects body hair distribution, baldness, voice, and skin thickness and promotes each of the following the formation of spermatozoa, protein formation, muscle development, bone growth, the retention of calcium, the rate of basal metabolism, and the number of red blood cells in the body. 

The key role of insuhn in protein metabolism usually is evident only in diabetic patients with persistently poor glycemic control. Insulin stimulates amino acid uptake and protein synthesis and inhibits protein degradation in muscle and other tissues. The increased conversion of amino acids to glucose also results in increased production and excretion of urea and ammonia. In addition, there are increased circulating concentrations of branched-chain amino acids as a result of increased proteolysis, decreased protein synthesis, and increased release of branched-chain amino acids from the liver. 

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