Effects of dietary protein on gut development, microbial compositions, and mucin expressions in mice.

Aims Dietary protein, as an important macronutrient, widely participates in host growth and metabolism. In this study, effects of different protein levels (14, 20, and 26%) on the gut development, microbial compositions and mucin expressions were studied in C57BL/6 mice. Methods and results The results showed that body weight and the relative weight of stomach and gut were decreased in low-protein diet-fed mice, while high-protein diet significantly reduced the villus length and area of jejunum. Goblet cells number in the jejunum was reduced in the low-protein group, which was reversed by dietary a high-protein diet. In addition, high-protein diet notably reduced microbial diversity and changed the microbial compositions at the phylum level, such as Bacteroides, Proteobacteria, Actinomycetes, and Deferribacteres. Furthermore, high-protein diet significantly increased mucin2, mucin3, and mucin4 expressions in the jejunum, but downregulated mucin1, mucin2, mucin4 and TFF3 in the ileum, indicating a tissue-dependent manner. Conclusions Together, high-protein diet may impair gut development, microbial balance, and mucin system and a low-protein diet is suggested to promote a healthy lifestyle. Significance and impact of study Mucin influenced gut development (villus index and goblet cell number) through remodeling gut microbes, as low and high protein levels resulted in contrary expression levels of mucin in jejunum and ileum.