## 4 Discussion  
It has been reported that DSS-induced colitis in mice had weight loss, diarrhea, hematochezia, and colon shortening symptoms. In the present study, the mice were checked for significant blood and diarrhea in the feces after 10 days of DSS treatment. As expected, the supplement of GP in two dosages could increase the weight loss along with the relieving effect on diarrhea and blood in the feces. As revealed in the scores of DAI, treatment with GP had a decreasing efficacy on the IBD symptoms. In addition, the abnormalities of inflammatory cytokines in serum, such as TNF-\(\alpha\), IL-6, IL-1\(\beta\), and MCP-1, also played a vital role in the formation of IBD [31]. Compared with the DSS-induced group, the supplement of GP decreased secretion of inflammatory cytokines in serum. It is well known that the LPS is produced by Gram-negative bacteria with the effect of stimulating epithelial cells to increase COX-2 and then produce the intestinal inflammatory cascade [32]. Thus, the COX-2 can be regarded as a proinflammatory mediator and also a novel target participating in inflammation. In the current study, the change of COX-2 was investigated by expressions at the mRNA and protein levels, where the DSS induced a higher COX-2 expression and the GP had the relieving effect. TLR-4 is a signal of activating the NF-\(\kappa\)B pathway with the trigger of further inflammatory cytokines secretion in IBD [33]. As been demonstrated in mRNA and protein levels, the TLR-4 was found to be elevated in PC and be further suppressed by GP treatment. In general, the regulation of these inflammatory factors is significant proof for the treatment of IBD. According to the symptoms of IBD, the disruption of intestinal epithelial barrier was generally reported as the invasion of bacteria and pathogens. Thus, maintaining the integrity and tightness of the intestinal barrier is regarded as a strategy in the treatment of IBD [27]. As the major component of tight junction proteins, the Occludin and ZO-1 were demonstrated to be decreased in PC, whereas the intervention of GP had a relieving effect on that. In the protein-expression level, the dosage of GP-1 and GP-2 all had higher Occludin than the PC group. As revealed in the Caco-2 cells as well as the colitis mice, the treatment of bioactive peptides in fortail millet protein hydrolysate (FMPH) increased intestinal ZO-1 and Occludin expressions compared with the DSS-induced groups [34]. In addition, the FMPH was involved in the NF-\(\kappa\)B signal by inhibiting its phosphorylation process and then reduced the secretion of TNF-\(\alpha\) and IL-6. In Caco-2 cell monolayers, the collagen peptides ameliorated intestinal epithelial barrier dysfunction by enhancing tight junction proteins of ZO-1 and occludin. Similarly, the NF-\(\kappa\)B pathway was also inhibited by collagen peptides along with the suppressing effect on TNF-\(\alpha\) secretion [35]. In the current study, the improvement on ZO-1 and Occludin proteins in GP treatment was the important clue for illustrating the mechanism of peptide-induced improving effects on IBD. Acted as the trigger of NF-\(\kappa\)B, the higher expression of TLR-4 has been reported in IBD individuals [36]. Compared with DSS-induced mice, the supplement of GP suppressed the TLR-4 in mRNA and protein-expression levels, which implied that the NF-\(\kappa\)B pathway would also be suppressed followed by the decreasing efficacy on TNF-\(\alpha\), IL-6, MCP-1, and IL-1\(\beta\) in serum. The gut microbiota has also been recognized to be associated with the generation of IBD. Commonly, the microbial diversity in IBD was declined along with the change of microbiota structure. In the current study, the relevant abundances of major gut microbiota were analyzed in phylum and gene levels. The _Akkermansia_ is demonstrated to be a promising probiotic candidate for gut health and a decreasing abundance is revealed in IBD patients [29]. As expected, the GP intervention improved the _Akkermansia_ abundance.