Objective To explore the underlying mechanisms by which time-restricted feeding(TRF)attenuates dextran sodium sulfate(DSS)-induced colitis in mice via modulation of regenerating islet-derived protein 3 gamma(Reg3γ)expression and gut microbiota.Methods Six-week-old C57BL/6 mice were stratified by body weight and randomized into ad libitum feeding(AL)and TRF groups(n=7).The AL mice were given unrestricted food access,whereas the TRF mice were allowed feeding only during 00:00 and 08:00 daily,for totally 4 weeks.Mouse colitis model was induced at the fourth week by adding 2.5%dextran sodium sulfate(DSS)in drinking water for 6 d.Disease severity and the effects of TRF were assessed with disease activity index(DAI)scoring,colon length measurement,HE staining and histopathological scoring,and mRNA expression levels of regenerating islet-derived 3 gamma(Reg3g)and inflammatory cytokines in colonic tissues.Another 14 mice were randomized into AL plus antibiotic cocktail(AL+ABX)and TRF plus antibiotic cocktail(TRF+ABX)groups,with 7 animals in each group.ABX was administered to deplete gut microbiota and evaluate the microbiota dependence of TRF in attenuating colitis.Fecal samples from AL and TRF mice were analyzed by 16S ribosomal RNA sequencing(16S rRNA-seq),and serum lipopolysaccharide(LPS)level was measured.The colonic epithelial cells were collected for RNA-seq.Results After modeling,the AL mice exhibited typical colitis symptoms,such as weight loss,diarrhea,and hematochezia.TRF intervention significantly attenuated these above symptoms,with lower DAI scores from day 4 post-modeling(P<0.001),reduced colon shortening(P<0.01),preserved tissue architecture,and decreased inflammation.RT-qPCR analysis showed that TRF down-regulated colonic mRNA expression levels of Reg3g and pro-inflammatory cytokines(IL-1 β,IL-6,TNF-α)(P<0.05)while up-regulated that of anti-inflammatory factor IL-10(P<0.000 1)when compared with the corresponding levels in AL mice.ABX treatment led no significant differences between the AL+ABX and TRF+ABX groups in term of DAI score,colon length,or histopathology.Obviously down-regulated Reg3g was observed in the TRF+ABX group than the AL+ABX group(P<0.05),whereas L-1β,IL-6,TNF-α and IL-10 showed no notable changes.16S rRNA-seq revealed that TRF markedly reshaped gut microbiota composition,with increased Gram-positive bacterial abundance,reduced Gram-negative bacteria,with concomitant lower serum LPS level(P<0.001).RNA-seq also indicated significant suppression of NF-κB and other inflammation-related signaling pathways in the TRF group.Conclusion TRF attenuates DSS-induced colitis in mice by downr-egulating Reg3γ expression,reshaping gut microbiota,and reducing serum LPS level,and thereby suppressing NF-κB-mediated inflammatory signaling pathways.