Unbound fatty acids, Intralipid and Unbound Bilirubin in Preterm Infants

描述(申请人提供)：新生儿黄疸发生在60-70%的新生儿。严重的高胆红素血症可导致神经功能障碍，甚至可能死亡，早产儿特别容易发生这些并发症。目前的诊断技术测量血清总胆红素(TSB)水平，作为光疗治疗的指标。然而，自由、无结合胆红素(Bf)的水平被认为比TSB更准确地确定胆红素神经毒性的风险。BF水平可通过竞争与游离脂肪酸(FFA)的结合部位而升高。大多数游离脂肪酸与白蛋白结合循环，只有一小部分未结合在水相中(FFAu)。FFA是一种重要的营养元素，因此在完全肠内喂养之前，大多数早产儿都会接受Intralipid，一种静脉注射脂肪酸乳剂。初步数据表明，接受Intralipid治疗的早产儿FFAu显著升高，很可能是由于代谢和储存不成熟所致。这可能会导致脂质相关的并发症，包括与胆红素竞争白蛋白结合部位而继发的Bf升高。在早产儿中，光疗的开始和持续时间的阈值没有很好地确定，导致基于TSB、出生体重和/或胎龄的方法相互矛盾。因此，尽管在接受Intralipid治疗的婴儿中，Bf(循环胆红素的毒性隔室)水平可能显著升高，但目前的方法不包括直接测量Bf。最近，我们通过反复突变和高通量筛选荧光标记的FFA结合蛋白的过程，开发了FFAu和Bf特异的探针。我们证明，这些探针可以检测到血浆中Bf和FFAu的生理性、纳摩尔浓度。拟议中的研究将利用这项新的创新技术来调查以下假设：1)Intralipid输注将增加FFAu，从而增加早产儿的Bf和Bf/TSB比率，以及2)在生命第一周接受光疗的早产儿(基于TSB水平)，接受Intralipid治疗的早产儿Bf水平将比未接受Intralipid治疗的早产儿至少高20%。这些发现将支持这样的观点，即TSB低估了接受Intralipid治疗的婴儿的风险，Bf可能是需要进行光疗的更好的决定因素。然后将设计更大的研究，以测试基于Bf的直接测量来管理早产儿高胆红素血症后的临床疗效和改善结果。

DESCRIPTION (provided by applicant): Neonatal jaundice occurs in 60-70% of newborns. Severe hyperbilirubinemia can lead to neurological dysfunction and possibly death, and preterm infants are particularly susceptible to these complications. Current diagnostic techniques measure total serum levels of bilirubin (TSB), which are used as indicators for treatment with phototherapy. However, levels of free, unbound bilirubin (Bf) are thought to determine the risk of bilirubin neurotoxicity more accurately than TSB. Bf levels can be elevated by competition for binding sites with free fatty acids (FFA). Most FFA circulate bound to albumin, with only a small fraction present unbound in the aqueous phase (FFAu). FFA are an important element of nutrition, so prior to full enteral feeding most premature infants receive them as Intralipid, an intravenous fatty acid emulsion. Preliminary data suggest that FFAu can be markedly elevated in premature infants receiving Intralipid, most likely due to immature metabolism and storage. This may lead to lipid associated complications, including elevated Bf secondary to competition with bilirubin for albumin binding sites. The thresholds for initiation and duration of phototherap are not well established in preterm infants, leading to conflicting approaches based on TSB, birth weight and/or gestational age. Thus, although levels of Bf-the toxic compartment of circulating bilirubin-may be markedly elevated in infants receiving Intralipid, current approaches do not include direct measurement of Bf. Recently, we developed FFAu- and Bf-specific probes through a process of iterative mutations and high throughput screening of fluorescently labeled FFA binding proteins. We demonstrated that these probes can detect physiologic, nanomolar concentrations of Bf and FFAu in plasma. The proposed studies will utilize this new, innovative technology to investigate the hypothesis that 1) Intralipid infusion will increase FFAu and consequently Bf and the Bf/TSB ratio in preterm infants, and 2) premature infants treated with phototherapy during the first week of life (based on TSB levels) who are receiving Intralipid will have at least 20% higher levels of Bf than those not receiving Intralipid. Such findings would support the idea that TSB underestimates risk in Intralipid-treated infants, and that Bf may be a better determinant of the need for phototherapy. Larger studies will then be designed to test clinical efficacy and improved outcomes after managing hyperbilirubinemia in preterm infants based on direct measurements of Bf.