Gut microbiota modulates weight gain in mice after discontinued smoke exposure.

Cigarette smoking constitutes a leading global cause of morbidity and preventable death1, and most active smokers report a desire or recent attempt to quit2. Smoking-cessation-induced weight gain (SCWG; 4.5 kg reported to be gained on average per 6-12 months, >10 kg year-1 in 13% of those who stopped smoking3) constitutes a major obstacle to smoking abstinence4, even under stable5,6 or restricted7 caloric intake. Here we use a mouse model to demonstrate that smoking and cessation induce a dysbiotic state that is driven by an intestinal influx of cigarette-smoke-related metabolites. Microbiome depletion induced by treatment with antibiotics prevents SCWG. Conversely, fecal microbiome transplantation from mice previously exposed to cigarette smoke into germ-free mice naive to smoke exposure induces excessive weight gain across diets and mouse strains. Metabolically, microbiome-induced SCWG involves a concerted host and microbiome shunting of dietary choline to dimethylglycine driving increased gut energy harvest, coupled with the depletion of a cross-regulated weight-lowering metabolite, N-acetylglycine, and possibly by the effects of other differentially abundant cigarette-smoke-related metabolites. Dimethylglycine and N-acetylglycine may also modulate weight and associated adipose-tissue immunity under non-smoking conditions. Preliminary observations in a small cross-sectional human cohort support these findings, which calls for larger human trials to establish the relevance of this mechanism in active smokers. Collectively, we uncover a microbiome-dependent orchestration of SCWG that may be exploitable to improve smoking-cessation success and to correct metabolic perturbations even in non-smoking settings.

High-Throughput Screen Identifies Host and Microbiota Regulators of Intestinal Barrier Function.

BACKGROUND & AIMS: The intestinal barrier protects intestinal cells from microbes and antigens in the lumen-breaches can alter the composition of the intestinal microbiota, the enteric immune system, and metabolism. We performed a screen to identify molecules that disrupt and support the intestinal epithelial barrier and tested their effects in mice. METHODS: We performed an imaging-based, quantitative, high-throughput screen (using CaCo-2 and T84 cells incubated with lipopolysaccharide; tumor necrosis factor; histamine; receptor antagonists; and libraries of secreted proteins, microbial metabolites, and drugs) to identify molecules that altered epithelial tight junction (TJ) and focal adhesion morphology. We then tested the effects of TJ stabilizers on these changes. Molecules we found to disrupt or stabilize TJs were administered mice with dextran sodium sulfate-induced colitis or Citrobacter rodentium-induced intestinal inflammation. Colon tissues were collected and analyzed by histology, fluorescence microscopy, and RNA sequencing. RESULTS: The screen identified numerous compounds that disrupted or stabilized (after disruption) TJs and monolayers of epithelial cells. We associated distinct morphologic alterations with changes in barrier function, and identified a variety of cytokines, metabolites, and drugs (including inhibitors of actomyosin contractility) that prevent disruption of TJs and restore TJ integrity. One of these disruptors (putrescine) disrupted TJ integrity in ex vivo mouse colon tissues; administration to mice exacerbated colon inflammation, increased gut permeability, reduced colon transepithelial electrical resistance, increased pattern recognition receptor ligands in mesenteric lymph nodes, and decreased colon length and survival times. Putrescine also increased intestine levels and fecal shedding of viable C rodentium, increased bacterial attachment to the colonic epithelium, and increased levels of inflammatory cytokines in colon tissues. Colonic epithelial cells from mice given putrescine increased expression of genes that regulate metal binding, oxidative stress, and cytoskeletal organization and contractility. Co-administration of taurine with putrescine blocked disruption of TJs and the exacerbated inflammation. CONCLUSIONS: We identified molecules that disrupt and stabilize intestinal epithelial TJs and barrier function and affect development of colon inflammation in mice. These agents might be developed for treatment of barrier intestinal impairment-associated and inflammatory disorders in patients, or avoided to prevent inflammation.