Proteoforms of β‐Casein, α‐s1‐Casein, α‐Lactalbumin, Serum Albumin, and Lactotransferrin Identified in Different Lactation Phases of Human Milk by Proteomics Approach

Abstract

Scope Human milk (HM) has a wide range of proteins with biological and nutritional functions, essential for newborns. The roles of proteins and their proteoforms in HM are not fully understood. This study aims to assess, by 2‐DE proteomics, the differential proteoforms in HM, present in colostrum (COL), transition (TRA), and mature milk (MAT), aiming to contribute to understanding neonates’ protein needs. Methods and results HM samples are collected from 39 healthy lactating women. COL presents the higher concentration of essential amino acids. After MALDI‐MS/MS and bioinformatics analysis, proteoforms are differentially detected. Abundances of β‐casein (CSN2), α‐s1 casein, and α‐lactalbumin (LALBA) are higher in MAT; CSN2s are found in 11 spots and the isoforms increase in size as the pI becomes more acidic; regarding LALBA, two variant forms are found with different abundances in TRA and MAT; CSN2, LALBA, lactotransferrin (LTF), and serum albumin forms are present in all lactation phases. Conclusion This study reveals differential proteoforms in COL involved in tissue growth and body development, besides essential amino acids, and, in MAT, involved in muscle mass gain, strengthening of the immune system, and energy production. The results provide new insight about proteoforms involved in maturation of the newborn's organs and systems.

A novel signaling transduction pathway of melatonin on lactose synthesis in cows via melatonin receptor 1 (MT1) and prolactin receptor (PRLR)

“…We speculated that the upregulation of LALBA was not the direct effect of melatonin but the physiological compensatory effect of the low level of lactose, which was caused by the insufficient galactose transportation into the Golgi apparatus due to the downregulation of SLC35B1. In lactose synthesis, LALBA expression is more easily regulated by multiple factors such as insulin, while BAG4LT is usually unchanged ( Ribeiro et al, 2023 ), which is similar to our results. Therefore, in the current study, we have identified the signal transduction pathway of melatonin in lactose synthesis, i.e., melatonin/MT1/PRLR/SLC35B1/lactose.…”

Proteomics and Peptidomics As a Tool to Compare the Proteins and Endogenous Peptides in Human, Cow, and Donkey Milk

“…In contrast, mature human milk primarily contains caseins, such as CSN2 and CSN1S1, which are crucial for metabolic processes that increase muscle mass, boost the immune system, and generate energy. 95 There have also been some studies on the changes in human whey and MFGM proteins following post-translational modifications during lactation. Label-free glycoproteomics was used to identify 2617 and 986 unique site-specific N-glycans from 221 and 200 MFGM glycoproteins in DC and donkey mature milk (DM), respectively.…”

“…Human colostrum contains proteins related to the immune system such as lactotransferrin (LTF) and immunoglobulins (Igs). In contrast, mature human milk primarily contains caseins, such as CSN2 and CSN1S1, which are crucial for metabolic processes that increase muscle mass, boost the immune system, and generate energy . There have also been some studies on the changes in human whey and MFGM proteins following post-translational modifications during lactation.…”