Cairns P A, Stalker D J
Department of Child Health, St Michaels Hospital, Southwell Street, Bristol, UK, BS2 8EG.
Cochrane Database Syst Rev. 2000;2000(4):CD000950. doi: 10.1002/14651858.CD000950.
Carnitine, a quaternary amino acid, plays an important role in the oxidation of long chain fatty acids. Both breast milk and infant formulas contain carnitine. However, it is not routinely provided in parenteral nutrition solutions. Non supplemented parenterally fed infants have very low tissue carnitine levels. The clinical significance of this is uncertain. Carnitine deficiency may be an etiological factor in the limited ability of premature babies to utilize parenteral lipid. In vitro studies have suggested that fatty acid oxidation is impaired when the tissue carnitine levels fall below 10% of normal. Therefore relative carnitine deficiency may impair fatty acid oxidation, thus reducing the available energy and impairing growth.
The primary aim of this review is to determine whether carnitine supplementation of parenterally fed neonates will improve weight gain. The secondary aims are to determine the effect on lipid tolerance and ketogenesis.
Computerised searches were carried out by both reviewers. Searches were made of Medline, Embase, The National Research Register (UK), the Cochrane Controlled Trials Register and expert informants. The MeSH headings used were carnitine and parenteral nutrition.
Only randomised trials were considered. Trials were included if they involved carnitine supplementation alone, parenterally fed newborn infants, and measured at least one outcome of interest (weight gain, plasma fatty acids, plasma triglycerides, quantity of lipid tolerated, respiratory quotient or beta hydroxybutyrate levels).
The two reviewers searched the literature separately and reached a consensus for inclusion of trials. Data were extracted and evaluated by the two reviewers independently of each other. Authors were contacted if possible to clarify or provide missing data.
Fourteen studies were identified, six met the selection criteria. The results of the review are limited by the fact that the studies were generally short term and studied different outcomes. One study examined short term and long term weight gain, three reported only short term weight gain, three reported biochemical results in response to a short lipid challenge, and two reported results obtained during normal parenteral nutrition. Among infants supplemented with carnitine, there was no evidence of effect on weight gain, lipid utilization or ketogenesis.
REVIEWER'S CONCLUSIONS: We found no evidence to support the routine supplementation of parenterally fed neonates with carnitine.
肉碱，一种季铵氨基酸，在长链脂肪酸氧化过程中起重要作用。母乳和婴儿配方奶粉中都含有肉碱。然而，肠外营养溶液中通常不添加肉碱。非补充肉碱的肠外营养喂养婴儿的组织肉碱水平非常低。其临床意义尚不确定。肉碱缺乏可能是早产儿利用肠外脂肪能力有限的一个病因。体外研究表明，当组织肉碱水平降至正常水平的10%以下时，脂肪酸氧化会受到损害。因此，相对肉碱缺乏可能会损害脂肪酸氧化，从而减少可用能量并影响生长。
本综述的主要目的是确定对肠外营养喂养的新生儿补充肉碱是否会改善体重增加。次要目的是确定对脂质耐受性和生酮作用的影响。
两位综述作者均进行了计算机检索。检索了医学索引数据库（Medline）、荷兰医学文摘数据库（Embase）、英国国家研究注册库、Cochrane对照试验注册库并咨询了专家。使用的医学主题词为肉碱和肠外营养。
仅纳入随机试验。如果试验仅涉及单独补充肉碱、肠外营养喂养的新生儿，并测量了至少一项感兴趣的结果（体重增加、血浆脂肪酸、血浆甘油三酯、脂质耐受量、呼吸商或β-羟基丁酸水平），则纳入该试验。
两位综述作者分别检索文献，并就是否纳入试验达成共识。数据由两位综述作者独立提取和评估。如有可能，会联系作者以澄清或提供缺失的数据。
共识别出14项研究，其中6项符合选择标准。由于这些研究通常为短期研究且研究结果各异，本综述的结果受到限制。一项研究考察了短期和长期体重增加，三项仅报告了短期体重增加，三项报告了对短期脂质激发试验的生化反应结果，两项报告了正常肠外营养期间获得的结果。在补充肉碱的婴儿中，没有证据表明对体重增加、脂质利用或生酮作用有影响。
我们没有发现证据支持对肠外营养喂养的新生儿常规补充肉碱。
