Fig 2: Relative expression of colonic and cecal epithelial inflammatory and barrier genes in KO and CON mice under NLD and SL. KO, Per2 gene knockout (Period2-/-) mice; CON, wild-type (Period2+/+) mice; NLD, normal light–dark cycle treatment of 12 h of light and 12 h of darkness; SL, short-light treatment of 8 h light and 16 h darkness. Representative charts of the expression levels of Il-1ß gene, Il-6 gene, Tnf-a gene, Zo-1 gene, Claudin-1 gene, and Occludin gene of colonic epithelium (A) and cecal epithelium (B). Expressions of inflammatory and barrier genes were determined in Per2 knockout and wild-type mice under NLD and SL by PCR method. Statistical analyses were conducted using two-way ANOVA. *p < 0.05, significant difference; ** or *** p < 0.01, or p < 0.001, extremely significant difference. Results are presented as means ± SEM (n = 6 per group).

Fig 3: Relative expression of colonic and cecal epithelial SCFAs transporter genes in KO and CON mice under NLD and SL. KO, Per2 gene knockout (Period2-/-) mice; CON, wild-type (Period2+/+) mice; NLD, normal light–dark cycle treatment of 12 h of light and 12 h of darkness; SL, short-light treatment of 8 h of light and 16 h of darkness. Representative charts of the expression levels of Nhe1 gene, Nhe2 gene, Nhe3 gene, Mct1 gene, Mct4 gene, Ae2 gene, and Na+/K+ ATPase gene of colonic epithelium (A) and cecal epithelium (B). Expressions of SCFAs transporter genes were determined in Per2 knockout and wild-type mice under NLD and SL by PCR method. Statistical analyses were conducted using two-way ANOVA. *p < 0.05, significant difference; ** or *** p < 0.01 or p < 0.001, extremely significant difference. Results are presented as means ± SEM (n = 6 per group).

Fig 4: Predicted of bacterial functions of KEGG pathway via PICRUSt2 in KO and CON mice under NLD and SL. KO, Per2 gene knockout (Period2-/-) mice; CON, wild-type (Period2+/+) mice; NLD, normal light–dark cycle treatment of 12 h light and 12 h darkness; SL, short-light treatment of 8 h light and 16 h darkness. (A) The bacterial functional predictions of KEGG secondary pathway via metabolism. (B) The amino acid metabolism pathways predicted via metabolism. (C) The carbohydrate metabolism pathways predicted via metabolism. n = 6 per group for 16S rRNA sequencing.

Fig 5: Relative expression of colonic and cecal epithelial inflammatory pathways-related genes in KO and CON mice under NLD and SL. KO, Per2 gene knockout (Period2-/-) mice; CON, wild-type (Period2+/+) mice; NLD, normal light–dark cycle treatment of 12 h of light and 12 of h darkness; SL, short-light treatment of 8 h light and 16 h darkness. Representative charts of the expression levels of Tlr2 gene, Tlr4 gene, Myd88 gene, and Nf-?b p65 gene of colonic epithelium (A) and cecal epithelium (B). Expressions of inflammatory pathways-related were determined in Per2 knockout and wild-type mice under NLD and SL by PCR method. Statistical analyses were conducted using two-way ANOVA. *p < 0.05, significant difference; ** or *** p < 0.01 or p < 0.001, extremely significant difference. Results are presented as means ± SEM (n = 6 per group).