Fatty acids muscle fibers

Two major types of muscle fibers are found in humans white (anaerobic) and red (aerobic). The former are particularly used in sprints and the latter in prolonged aerobic exercise. During a sprint, muscle uses creatine phosphate and glycolysis as energy sources in the marathon, oxidation of fatty acids is of major importance during the later phases. Nonmuscle cells perform various types of mechanical work carried out by the structures constituting the cytoskeleton. These strucmres include actin filaments (microfilaments), micrombules (composed primarily of a- mbulin and p-mbulin), and intermediate filaments. The latter include keratins, vimentin-like proteins, neurofilaments, and lamins. 

The primary fuel used to support muscle contraction depends on the magnitude and duration of exercise as well as the major fibers involved. Skeletal muscle has stores of both glycogen and some triglycerides. Blood glucose and free fatty acids also may be used. 

Fatty acids are the major fuel for red muscle fibers, which are the main type involved in moderate exercise. Children who lack one or the other of the enzymes required for carnitine synthesis, and are therefore reliant on a dietary intake, have poor exercise tolerance, because they have an impaired ability to transport fatty acids into the mitochondria for /S - oxidation. Provision of supplements of carnitine to the affected children overcomes the problem. Extrapolation from this rare clinical condition has led to the use of carnitine as a so-called ergogenic aid to improve athletic performance. 

Skeletal muscle is composed of two different types of cells white and red muscle fibers. Some muscles are fairly homogeneous and contain mainly one type of fiber others contain mixtures of both types. White muscle fibers contain relatively few mitochondria, are mainly glycolytic, and produce lactic acid as an end-product of fermentation- Red muscle fibers are relatively rich in mitochondria and are well adapted to oxidising fatty adds and glucose to CO2- Their energy metabolism is dependent on an ample supply of oxygen. 

A few studies have appeared on various aspects of the composition of muscle lipids in diseased muscle. It has long been known from histochemical studies that in many patients with muscular dystrophy there is a huge increase in adipose tissue between the fibers, but it seems doubtful whether there is an increase in true muscle fat. Pennington et al. (P14) could find no marked abnormality in the fatty acid composition of the infiltrated fat in a case of Duchenne dystrophy when compared with normal adipose tissue. Hughes (H15, H16) has carried out extensive studies on the concentration of various classes of lipids in the various... 

The effect of training depends, to some extent, on the type of training. In general, training increases the muscle glycogen stores and increases the number and size of mitochondria. The fibers thus increase their capacity for generation of ATP from oxidative metabolism and their ability to use fatty acids as a fuel. The winners in marathon races seem to use muscle glycogen more efficiently than others. 

That same long-chain fatty-acid-free diet was used very successfully to treat a three family members who had bfelong weakness and fatty-food intolerance due to autosomal dominant lipid neuromyopathy (with excess hpid within muscle fibers and Schwann cells) and normal levels of muscle carnitine [58]. 

Cachexia is a complex interaction between inflammatory mediators, oxidative stress and growth factors that govern skeletal muscle fiber degeneration, apoptosis, and regeneration (35). Current interest is on fatty acid modulation, since fatty acid composition of inflammatory and immune cells is sensitive to change according to the fatty acid diet intake. Fish oil (containing n-3-polyunsaturated fatty acids) supplementation has beneficial effects on the systemic inflammatory responses (36). The role of such supplements in the ventilated patient with chronic respiratory failure remains to be clarified. 

The uptake of palmitic acid- K] by the pectoralis muscle of pigeons from the circulation was studied 3-15 minutes after its intravenous injection (Wirsen, 1965). Radioautography was carried out with non-fixed frozen sections, using X-ray film. The radioautographic reaction was much more pronounced over red than over white fibers, but as no analysis of the labeled lipid within die muscle is given it is not possible to determine whether the reaction is due to free fatty acid, triglyceride, or phospholipid. 

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