Hahn P, Novak M
Fed Proc. 1985 Apr;44(7):2369-73.
The newborn oxidizes a large amount of fat. This is reflected in the slow rise of plasma levels of ketones and of total carnitines and acylcarnitines. Feeding a diet devoid of carnitine (soy-based formulas, total parenteral nutrition [TPN] ) rapidly results in a fall in plasma total carnitine levels, whereas in the adult such a fall is observed only after a prolonged time of TPN. This suggests that carnitine synthesis in the newborn is less efficient than in the adult. Gluteal adipocytes in the newborn show a rise in carnitine content and in the activity of carnitine transferases soon after birth, when values are higher than in the adult. Their respiration, lipolysis, and triglyceride formation are enhanced by L-carnitine and inhibited by D-carnitine. This is not so in the adult. Addition of L-carnitine to soybean-based formulas decreases plasma triglyceride and free fatty acid levels in premature infants, who have lower carnitine levels at birth than full-term babies. In pregnant women plasma total carnitine levels are significantly depressed. maternal urinary excretion of total carnitine decreases as gestational age increases, and less is also found in amniotic fluid. Plasma levels of total carnitines and acylcarnitine are the same (or higher) in fetal as in maternal plasma. It is concluded that carnitine may be of particular importance to the neonate and that adding it to foods lacking this substance may be advantageous.
新生儿会氧化大量脂肪。这反映在酮、总肉碱和酰基肉碱的血浆水平上升缓慢。喂食不含肉碱的饮食（大豆配方奶粉、全胃肠外营养[TPN]）会迅速导致血浆总肉碱水平下降，而在成年人中，只有在长时间接受TPN后才会观察到这种下降。这表明新生儿体内肉碱的合成效率低于成年人。新生儿的臀脂肪细胞在出生后不久，肉碱含量和肉碱转移酶活性就会升高，此时的值高于成年人。它们的呼吸、脂肪分解和甘油三酯形成会被左旋肉碱增强，被右旋肉碱抑制。成年人则并非如此。在大豆配方奶粉中添加左旋肉碱可降低早产儿的血浆甘油三酯和游离脂肪酸水平，早产儿出生时的肉碱水平低于足月儿。孕妇血浆总肉碱水平显著降低。随着孕周增加，孕妇尿中总肉碱排泄量减少，羊水中的含量也较少。胎儿血浆中总肉碱和酰基肉碱的水平与母体血浆中的相同（或更高）。得出的结论是，肉碱可能对新生儿尤为重要，并且在缺乏这种物质的食物中添加肉碱可能是有益的。
