Evangeliou A, Vlassopoulos D
Neurology Dept., Creta's Medical School, A. Fleming Hospital, Athens, Greece.
Curr Pharm Biotechnol. 2003 Jun;4(3):211-9. doi: 10.2174/1389201033489829.
Carnitine is an ammo acid derivative found in high energy demanding tissues (skeletal muscles, myocardium, the liver and the suprarenal glands). It is essential for the intermediary metabolism of fatty acids. Carnitine is indispensable for beta-oxidation of long-chain fatty acids in the mitochondria but also regulates CoA concentration and removal of the produced acyl groups. AcylCoAs act as restraining factor for several enzymes participating in intermediary metabolism. Transformation of AcylCoA into acylcarnitine is an important system for removing the toxic acyl groups. Although primary deficiency is unusual, depletion due to secondary causes, such as a disease or a medication side effect, can occur. Primary carnitine deficiency is caused by a defect in plasma membrane carnitine transporter in muscle and kidneys. Secondary carnitine deficiency is associated with several inborn errors of metabolism and acquired medical or iatrogenic conditions, for example in patients under valproate and zidovuline treatment. In cirrhosis and chronic renal failure, carnitine biosynthesis is impaired or carnitine is lost during hemodialysis. Other chronic conditions like diabetes mellitus, heart failure, Alzheimer disease may cause carnitine deficiency also observed in conditions with increased catabolism as in critical illness. Preterm neonates develop carnitine deficiency due to impaired proximal renal tubule carnitine re-absorption and immature carnitine biosynthesis. Carnitine stabilizes the cellular membrane and raises red blood cell osmotic resistance but has no metabolic influence on lipids in dialysis patients. L-Carnitine has been administered in senile dementia, metabolic nerve diseases, in HIV infection, tuberculosis, myopathies, cardiomyopathies, renal failure anemia and included in baby foods and milk.
肉碱是一种氨基酸衍生物，存在于高能量需求组织（骨骼肌、心肌、肝脏和肾上腺）中。它对脂肪酸的中间代谢至关重要。肉碱对于线粒体中长链脂肪酸的β氧化必不可少，还能调节辅酶A浓度并去除产生的酰基。酰基辅酶A对参与中间代谢的几种酶起抑制作用。将酰基辅酶A转化为酰基肉碱是去除有毒酰基的重要系统。虽然原发性缺乏并不常见，但由于继发性原因（如疾病或药物副作用）导致的消耗可能会发生。原发性肉碱缺乏是由肌肉和肾脏中的质膜肉碱转运体缺陷引起的。继发性肉碱缺乏与几种先天性代谢缺陷以及获得性医学或医源性疾病有关，例如接受丙戊酸盐和齐多夫定治疗的患者。在肝硬化和慢性肾衰竭中，肉碱生物合成受损或在血液透析过程中肉碱丢失。其他慢性病如糖尿病、心力衰竭、阿尔茨海默病也可能导致肉碱缺乏，在分解代谢增加的情况下（如危重病）也会观察到这种情况。早产儿由于近端肾小管肉碱重吸收受损和肉碱生物合成不成熟而出现肉碱缺乏。肉碱可稳定细胞膜并提高红细胞的渗透压抵抗力，但对透析患者的脂质没有代谢影响。左旋肉碱已被用于治疗老年痴呆症、代谢性神经疾病、HIV感染、结核病、肌病、心肌病、肾衰竭贫血，还被添加到婴儿食品和牛奶中。
