Exercise carnitine

In 1990, Siliprandi et al. and Vecchiet et al. examined the effects of 2 g of oral carnitine in a single dose approximately 1 h prior to cycle ergometer exercise. Carnitine supplranmtation was reported to reduce blood lactate and increase VOj max post-exerdse. The authors claim that during this high-intensity exerdse the PDC is stimulated, thraeby reducing lactate production due to the alteration of the acetyl-CoA free CoA ratio. These findings, howevCT, were not supported, as Con-stantin-Teodosiu showed that full activity of the PDC was reached within a minute of activation and is independent of carnitine supplementation. 

Carnitine palmitoyl transferase (CPT) deficiencies are commonly associated with myoglobinuria after prolonged exercise typically patients are young men and... 

Glutaric aciduria type II, which is a defect of P-oxida-tion, may affect muscle exclusively or in conjunction with other tissues. Glutaric aciduria type II, also termed multiple acyl-CoA dehydrogenase deficiency (Fig. 42-2), usually causes respiratory distress, hypoglycemia, hyperammonemia, systemic carnitine deficiency, nonketotic metabolic acidosis in the neonatal period and death within the first week. A few patients with onset in childhood or adult life showed lipid-storage myopathy, with weakness or premature fatigue [4]. Short-chain acyl-CoA deficiency (Fig. 42-2) was described in one woman with proximal limb weakness and exercise intolerance. Muscle biopsy showed marked accumulation of lipid droplets. Although... 

Abrahamsson K, Eriksson BO, Holme E, Jodal U, Jonsson A, Lindstedt S. Pivahc acid-induced carnitine deficiency and physical exercise in humans. Metabolism 1996 45(12) 1501-7. 

Brass, E.P. 2000. Supplemental carnitine and exercise. Am. J. Clin. Nutr. 72 s618—s623. 

What effect would a deficiency of carnitine palmitoyltransferase in skeletal muscle have on the ability of a person to perform prolonged exercise ... 

Clinical problems related to fatty acid metabolism. Deficiencies in carnitine lead to an inability to transport fatty acids into the mitochondria for oxidation. This can occur in newborns and particularly in pre-term infants. Treatment is by oral carnitine administration. Carnitine palmitoyltransferase I (CPT I) deficiency primarily affects the liver and leads to reduced fatty acid oxidation and ketogenesis. CPT II deficiency results in recurrent muscle pain, fatigue and myoglobinuria following strenuous exercise. 

Mold, P. A., Oscal, L. B. and Holloszy, J, 0. (1971) Adaptation of muscle to exercise. Increase in levels of palmltyl CoA synthetase, carnitine palmltyl-transferase and palmltyl CoA dehydrogenase and In the capacity to oxidize fatty acids. J. Clin. Invest. 50 2323-30. 

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. 

A number of diseases have been traced to a deficiency of carnitine, the transferase or the translocase. The symptoms of carnitine deficiency range from mild muscle cramping to severe weakness and even death. The muscle, kidney, and heart are the tissues primarily affected. Muscle weakness during prolonged exercise is an important characteristic of a deficiency of carnitine acyl transferases because muscle relies on fatty acids as a long-term source of energy. Medium-chain (Cg-Cjo) fatty acids, which do not require carnitine to enter the mitochondria, are oxidized normally in these patients. These diseases illustrate that the impaired flow of a metabolite from one compartment of a cell to another can lead to a pathological condition. 

A seventeen-year-old male went to a university medical center complaining of fatigue and poor exercise tolerance. Muscle biopsies revealed droplets of triglycerides in his muscle cells. Biochemical analysis showed that he had only one-fifth of the normal amount of carnitine in his muscle cells. 

Otto Shape s power supplement contains carnitine. However, his body can synthesize enough carnitine to meet his needs, and his diet contains carnitine. Carnitine deficiency has been found only in infants fed a soy-based formula that was not supplemented with carnitine. His other supplements likewise probably provide no benefit, but are designed to facilitate fatty acid oxidation during exercise. Riboflavin is the vitamin precursor of FAD, which is required for acyl CoA dehydrogenases and ETFs. CoQ is synthesized in the body, but it is the recipient in the electron transport chain for electrons passed from complexes I and II and the ETFs. Some reports suggest that supplementation with pantothenate, the precursor of CoA, improves performance. 

A deficiency of carnitine acyltransferase I in human muscle causes cellular damage and recurrent muscle weakness, especially during fasting or exercise. A deficiency of the enzyme in the liver causes an enlarged and fatty liver, hypoglycemia, and a reduction in the levels of ketone bodies in blood. Explain the likely causes of these symptoms. 

EXAMPLE 13.27 If muscle uses fatty acid oxidation to supply ATP, then less glycogen is mobilized so any exercise/diet strategies that increase the proportion of energy derived from fatty acids should save glycogen. Training increases the activity of the P-oxidation enzymes (Sec. 10.5), and a good supply of carnitine should also assist in fatty acid catabolism. 

The rate of transport of fatty acids into the mitochondria is determined largely by the availability of carnitine that is used as a carrier. The rate of (3-oxidation is also limited and this is especially pronounced in unfit individuals. One of the beneficial effects of exercise training is that it brings about an increase in the expression of the genes of the proteins of the (3-oxidation pathway. 

Vuchovich, M.D., Costill, D.L., and Fink, W.J., Carnitine supplementation Effect on muscle carnitine and glycogen content during exercise, Med. Sci. Sports. Exerc., 26, 1122,1994. 

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