Dietary Soy Protein Isolate Attenuates Intestinal Immunoglobulin and Mucin Expression in Young Mice Compared with Casein

Abstract

Dietary protein sources have profound effects on children and young animals, and are important for the gut barrier function and immune resilience. Milk and soy are the main sources of protein for children and young animals after weaning. The objective of this study was to compare the effects of dairy and soy proteins on the intestinal barrier in early development. Weanling C57BL/6 mice were fed AIN-93G diets prepared with casein or soy protein isolate (SPI) for 21 days. Compared with those fed with the casein diet, mice fed with the SPI diet did not change their body weight and organ coefficients, but increased their feed intake and ratio of feed to gain. SPI lowered the level of luminal secretory immunoglobulin A (SIgA) and downregulated the levels of IL-4, IL-13, polymeric immunoglobulin receptor (Pigr), Janus kinase 1 (Jak1), signal transducer and activator of transcription 6 (Stat6), and transforming growth factor-β (Tgfb) in the mouse ileum. Western blotting of ileal proteins confirmed that SPI suppressed the activation of the JAK1/STAT6 signaling pathway. Furthermore, SPI attenuated intestinal mucin production, as demonstrated by the decreased numbers of intestinal goblet cells and the reduced relative expression levels of mucin 1 (Muc1), mucin 2 (Muc2), trefoil factor 3 (Tff3), glucose-regulated protein 94 (Grp94), and anterior gradient homolog 2 (Agr2). The results indicated that the SPI diet could attenuate mouse intestinal immunity, as demonstrated by decreased SIgA and mucin production in the intestine. Therefore, we suggest that our findings should be of consideration when SPI or casein are used as dietary protein sources.

Dietary protein increases T-cell-independent sIgA production through changes in gut microbiota-derived extracellular vesicles

“…Future studies examining qualitative aspects of macronutrients, such as different types of fat and protein (i.e., animal vs. plant-based protein), would be required to fully appreciate the role of macronutrients on gut homoeostasis as well as on the host sIgA responses. For example, soy-derived protein has been associated with lower sIgA, compared to casein-derived protein 38 .…”

EpCAM Is Essential to Maintaining the Immune Homeostasis of Intestines via Keeping the Expression of pIgR in the Intestinal Epithelium of Mice

“…The activated STAT6 had been demonstrated to bind to a 554-bp IL-4 responsive enhancer in intron 1 of human PIGR gene in HT-29 cells to upregulate the expression of PIGR ( 47 ). It was reported that IL-4 mediated the transcription of pIgR via activating JAK1-STAT6 pathway in the intestines of mice ( 46 , 48 , 49 ). In present study, the levels of phosphorylated STAT6 were reduced in the intestines of EpCAM -/- mice, and the transcriptional levels of IL-4, Jak1 and Stat6 also reduced in the intestines of these mice.…”

The Role of Reduced Methionine in Mediating the Metabolic Responses to Protein Restriction Using Different Sources of Protein

“…The reason for these differences is unclear, although a previous short-term study also observed faster growth in mice fed a soy-based compared to casein-based diet [ 40 ]. In an experiment of similar design, Zeng et al detected a small, but significantly higher rate of food intake of a soy-based control diet compared to the casein diet, but detected no effect on body weight [ 41 ]. In the present work, food intake did not differ between the 20% casein and 20% soy diets ( Figure 2 A).…”