Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, Netherlands.
Danone Nutricia Research, Utrecht, Netherlands.
Front Immunol. 2020 May 28;11:1007. doi: 10.3389/fimmu.2020.01007. eCollection 2020.
Breastfeeding is indicated to support neonatal immune development and to protect against neonatal infections and allergies. Human milk composition is widely studied in relation to these unique abilities, which has led to the identification of various immunomodulating components in human milk, including various bioactive proteins. In addition to proteins, human milk contains free amino acids (FAAs), which have not been well-studied. Of those, the FAAs glutamate and glutamine are by far the most abundant. Levels of these FAAs in human milk sharply increase during the first months of lactation, in contrast to most other FAAs. These unique dynamics are globally consistent, suggesting that their levels in human milk are tightly regulated throughout lactation and, consequently, that they might have specific roles in the developing neonate. Interestingly, free glutamine and glutamate are reported to exhibit immunomodulating capacities, indicating that these FAAs could contribute to neonatal immune development and to the unique protective effects of breastfeeding. This review describes the current understanding of the FAA composition in human milk. Moreover, it provides an overview of the effects of free glutamine and glutamate on immune parameters relevant for allergic sensitization and infections in early life. The data reviewed provide rationale to study the role of free glutamine and glutamate in human milk in the protection against neonatal allergies and infections.
母乳喂养可促进新生儿的免疫发育，预防新生儿感染和过敏。鉴于其独特的作用，人们广泛研究了人乳的成分，从而鉴定出了人乳中具有免疫调节功能的多种生物活性蛋白。除了蛋白质，人乳中还含有游离氨基酸（FAAs），但人们对其研究甚少。在这些游离氨基酸中，谷氨酸和谷氨酰胺含量最为丰富。与其他大多数游离氨基酸不同，人乳中这两种氨基酸的含量在哺乳期的前几个月内急剧增加。这些独特的动态变化在全球范围内具有一致性，这表明人乳中这两种氨基酸的水平在整个哺乳期内受到严格调控，因此它们可能在新生儿发育中具有特定作用。有趣的是，有研究报道称游离谷氨酸和谷氨酰胺具有免疫调节功能，这表明这些游离氨基酸可能有助于新生儿的免疫发育，并对母乳喂养的独特保护作用产生影响。本综述描述了人乳中 FAA 组成的现有认知，还概述了游离谷氨酰胺和谷氨酸对生命早期过敏和感染相关免疫参数的影响。综述数据为人乳中游离谷氨酰胺和谷氨酸在预防新生儿过敏和感染中的作用研究提供了依据。
