Comparative Proteomics of Human Milk From Eight Cities in China During Six Months of Lactation in the Chinese Human Milk Project Study

Abstract

Human milk (HM) is the golden standard of infant nutrition that can protect immature body function and enhance nutrition metabolism to ensure infant growth. Region specificity and lactation period could change the protein composition in HM. In this research, proteomics analysis was used to compare proteomes across eight cities, namely Harbin, Lanzhou, Guangzhou, Chengdu, Jinhua, Weihai, Zhengzhou, and Beijing, which represented the northeast, northwest, southeast, southwest, east, and north and central regions of China,. Proteins varied significantly among the cities. These different proteins were mainly involved in the process of platelet degranulation, innate immune response, and triglyceride metabolic process, which might be due to different living environments. These differences also lead to variation in protection and fat metabolism from mothers to infants in different cities. Four proteins were expressed differently during 6 months of lactation, namely Dipeptidyl peptidase 1, Lysozyme C, Carbonic anhydrase 6, and Chordin-like protein 2. The changes in these proteins might be because of the change of growth needs of the infants. The findings from our results might help to improve the understanding of HM as well as to design infant formula.

Keywords: Chinese human milk; cities; human milk; lactation period; proteomics.

Figure 1

Major gene ontology (GO) biological process of overall identified proteins in Chinese human milk (HM) enriched by the DAVID bioinformatics.

Figure 2

The principal component analysis (PCA) plots based on protein intensity of: (A) B, Beijing; G, Guangzhou; C, Chengdu;W, Weihai; L, Lanzhou; J, Jinhua; Z, Zhengzhou, and H, Harbin. Weihai, Chengdu, and Jinhua are located in the same pool, while Lanzhou, Beijing, Guangzhou, Harbin, and Zhengzhou are located in the second pool. (B) Loading plots based on the intensity of the proteins showed that CSN2, LALBA, and IGKC were the abundant proteins in the second pool, while the first pool had abundance of CSN1S1, CSN3, LTF, LYZ, B2M, IGHA1, CEL, CLU, B2M, and XDH.

Figure 3

The PCA plots based on protein intensity of: (A) Different lactation periods during the 6 months of lactation. The first pool includes the 1st, 2nd, and 5th month of lactation, while second pool includes the 3rd, 6th, and 4th month of lactation. (B) Loading plots based on intensity of the proteins based on the different lactation periods. The first pool was abundant in LALBA, CSN1S1, CEL, LTF, B2M, SPP1, and IGHA1. Meanwhile, the second pool was abundant with CLU, PIGR, IGKC, LYZ, and CSN.

Figure 4

The GO enrichment of significantly different protein across eight cities. White: GO cellular location, dominated by extracellular exosome; Gray: Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways that consisted of complement coagulation cascades, fat digestion and absorption, and Peroxisome proliferator-activated receptors (PPAR) signaling pathway; and Black: GO biological process, dominated by platelet degranulation, innate immune response, and triglyceride metabolic process.

Figure 5

The summed intensities of GO biological process in the terms of: (A) platelet degranulation; (B) innate immune response, and (C) triglyceride metabolic process periods showed the most varied intensities values among the cities.

Figure 6

Interaction of platelet degranulation and innate immune response protein in Chinese HM were enriched with DAVID Bioinformatics and visualized using STRING 9.