Carnitine total

Carnitine (total) P, B u Carnitine transporter deficiency GA-I (12), MCAD, VLCAD, LCHAD... 

If the history, physical findings, and laboratory results are suggestive but not conclusive of a particular mitochondrial disease (e.g., MELAS), then a second tier of tests is performed. These include blood and CSF lactate and pyruvate, as well as the lactate/pyruvate ratio timed or random measurement of amino acids in blood, urine, and CSF organic acids in urine and CSF and ketones and free and total carnitine in blood and urine. 

Equally, demonstrating that a compound has a physiological function as a coenzyme or hormone does not classify that compound as a vitamin. It is necessary to demonstrate that endogenous synthesis of the compound is inadequate to meet physiological requirements in the absence of a dietary source of the compound. Table 1.3 lists compounds that have clearly defined functions, but are not considered vitamins because they are not dietary essentials endogenous synthesis normally meets requirements. However, there is some evidence that premature infants and patients maintained on long-term total parenteral nutrition may be unable to meet their requirements for carnitine (Section 14.1.2), choline (Section 14.2.2), and taurine (Section 14.5.3) unless they are provided in the diet, and these are sometimes regarded as... 

Subjects who are maintained for prolonged periods by total parenteral nutrition are obviously wholly dependent on what is provided in the nutrient mixture, normally with no contribution from intestinal bacteria. A great deal has been learned from such patients, including the essentiality of the amino acid histidine, and evidence that endogenous synthesis of taurine (Section 14.5.3) and carnitine (Section 14.1.2) may not be adequate to meet requirements without some dietary provision. However, for obvious ethical reasons, such patients have not been subjected to trials of graded intakes of vitamins, but are generally provided with amounts calculated to be adequate and in excess of minimum requirements. 

In addition to the established vitamins, a number of organic compounds have clear metabolic functions they can be synthesized in the body, but it is possible that under some circumstances (as in premature infants and patients maintained on long-term total parenteral nutrition) endogenous synthesis may not be adequate to meet requirements. These compounds include biopterin (Section 10.4), carnitine (Section 14.1), choline (Section 14.2), creatine (Section 14.3), inositol (Section 14.4), molybdopterin (Section 10.5), taurine (Section 14.5), and ubiquinone (Section 14.6). 

The total body content of carnitine is about 100 mmol, and about 5% of this turns over daily. Plasma total carnitine is between 36 to 83 /rmol per L in men and 28 to 75 /rmol per L in women, mainly as free carnitine. Although both free carnitine and acyl carnitine esters are excreted in the urine, much is oxidized to trimethylamine and trimethylamine oxide. It is not known whether the formation of trimethylamine and trimethylamine oxide is caused by endogenous enzymes or intestinal bacterial metabolism of carnitine. 

Total urinary excretion of carnitine is between 300 to 530 /rmol (men) or 200 to 320 /rmol (women) 30% to 50% of this is free carnitine the remainder is a variety of acyl carnitine esters. Acyl carnitine esters are readily cleared in... 

Tibboel D, Delemarre FM, Przyrembel H, Bos AP, Affourtit MJ, Molenaar JC. Carnitine deficiency in surgical neonates receiving total parenteral nutrition. J Pediatr Surg 1990 25(4) 418-21. 

The clinical presentation of carnitine deficiency includes generalized skeletal muscle weakness, fatty liver, and fasting hypoglycemia. Carnitine status can be assessed by measurement of plasma, urine, or red blood cell total and free carnitine concentrations. Plasma and urine carnitine concentrations are most helpful in primary carnitine deficiency (an inborn error of metabolism). Plasma concentrations constitute less than 1% of the total body carnitine. ... 

Acylcarnitine concentrations are more helpful in secondary causes of carnitine deficiency. When only total and free concentrations are available, the free is subtracted from the total to give the acylcarnitine concentration. 

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