Abstract
Serine alleviates inflammatory responses and is beneficial for gut health; however, whether it exerts any effects on ulcerative colitis or regulates intestinal microbiota remains unknown. We investigated the effects of serine supplementation on colonic morphology, inflammation, and microbiota composition in dextran sulfate sodium (DSS)-induced colitis model in mice. Acute colitis was induced through the oral intake of 3.5% DSS in water for 7 days. Mice with acute colitis were divided into two groups; The DSS and Ser-treated groups were rectally administrated with PBS or 1% (w/v) serine (40 mg/kg body weight) for 7 days. The results showed that serine decreased the disease activity index, as well as myeloperoxidase, eosinophil peroxidase, and proinflammatory cytokine concentrations in colonic tissue, while serine improved colonic morphology and inhibited cell apoptosis in colitis mice. In addition, 16S rRNA phylogenetic sequencing revealed a shift in bacterial community composition, and changes in microbiota functional profiles following serine supplementation, although no significant difference in α-diversity analysis was observed. The effects of serine supplementation helped on the recovery of major perturbations to macrobiotic functions, such as amino acids metabolism; tissue replication and repair; and cell growth and death. Serine might have great potential for the renewal of colonic tissue in DSS-induced colitis.
Highlights
Ulcerative colitis (UC) is one of the major forms of inflammatory bowel disease (IBD) characterized by inflammation of the rectal and colonic mucosa
The results showed that serine supplementation alleviated the increased activities of glycolysis/gluconeogenesis and glycine, FIGURE 4 | Serine altered the composition of the colonic microbiota in colitis mice. (A) Alpha diversity was estimated by the Shannon index. (B) principal coordinate analysis (PCoA) plot of the microbiota based on an unweighted UniFrac metric
In addition to decreased colonic weight and length, the colonic length and weight ratio was decreased. These results indicate that dextran sulfate sodium (DSS) treatment results in overt features of colitis
Summary
Ulcerative colitis (UC) is one of the major forms of inflammatory bowel disease (IBD) characterized by inflammation of the rectal and colonic mucosa. Our recent study showed that dietary serine prevented inflammation in the small intestine and maintained barrier integrity (Zhou et al, 2017b). Most studies examining the effect of dietary supplements on colitis alleviation have used the most common rodent model involving UC-related erosion and inflammation induced by chemicals such as dextran sulfate sodium (DSS) (Hakansson et al, 2015; Munyaka et al, 2016). The present study was conducted to determine the effects of serine on intestinal integrity, inflammation, and microbial dysbiosis in DSS-induced colitis. Mice with acute colitis were divided into two groups; The DSS and Ser-treated groups (n = 7) were rectally administrated with PBS or 1% (w/v) serine (40 mg/kg body weight) dissolved in PBS once daily for 7 days.
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