The Possible Essentiality of Carnitine

Although carnitine is not generally nutritionally important, it may be required for premature infants, because tbey have a limited capacity to synthesize it. However, there is inadequate evidence to support routine carnitine supplementation of parenteraUy fed premature infants (Cairns and Stalker, 2000). Carnitine depletion occurs in patients undergoing hemodialysis, but there is Utde evidence that supplements are effective in treating the associated dyslipidemia (Raskind and El-Chaar, 2000 Hurot et al., 2002). 

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The physiological functions of carboxylesterases are still partly obscure but these enzymes are probably essential, since their genetic codes have been preserved throughout evolution [84] [96], There is some evidence that microsomal carboxylesterases play an important role in lipid metabolism in the endoplasmic reticulum. Indeed, they are able to hydrolyze acylcamitines, pal-mitoyl-CoA, and mono- and diacylglycerols [74a] [77] [97]. It has been speculated that these hydrolytic activities may facilitate the transfer of fatty acids across the endoplasmic reticulum and/or prevent the accumulation of mem-branolytic natural detergents such as carnitine esters and lysophospholipids. Plasma esterases are possibly also involved in fat absorption. In the rat, an increase in dietary fats was associated with a pronounced increase in the activity of ESI. In the mouse, the infusion of lipids into the duodenum decreased ESI levels in both lymph and serum, whereas an increase in ES2 levels was observed. In the lymph, the levels of ES2 paralleled triglyceride concentrations [92] [98],... 

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