Battaglioli, Eric

Background: Fecal microbiota transplantation (FMT) is a successful therapy for Clostridioides difficile infection (CDI). FMT from overweight donors is speculated to influence the recipient’s body mass index (BMI) after administration for CDI. Objectives: We investigated changes in the recipient’s BMI after FMT in relation to the donor’s BMI. Design: We conducted a retrospective cohort study involving patients who underwent FMT for recurrent CDI at Mayo Clinic between 2012 and 2019. Methods: We analyzed demographic and donor data for patients undergoing FMT at Mayo Clinic (2012–2019). Recipient BMI (pre- and post-FMT) and donor BMI were extracted from medical records. Mixed-effects linear regression was used to evaluate the impact of donor BMI, donor BMI category, recipient baseline BMI, time before and after FMT, and interactions between these variables on overall BMI change and BMI change per month. Kaplan–Meier curves were used to assess BMI changes (⩾5 units) based on the last recorded post-FMT BMI. Results: We analyzed data from 401 patients with recorded BMI measurements before and after FMT. The median age of the recipients at the time of FMT was 59.1 years (interquartile range (IQR): 40.5–70.1 years), with 61.6% being female. The median BMI for recipients prior to FMT was 26.7 kg/m² (IQR: 22.7–31.6 kg/m²), while the median BMI of the donors was 24.5 kg/m2 (IQR: 23.9–27.5 kg/m2). Stool from donors with a normal BMI was used for 58.2% of recipients, while 41.8% received stool from pre-obese donors. Donor BMI data were missing for 3.2% of recipients. Donor BMI was not significantly associated with changes in recipient BMI; for each 1-unit increase in donor BMI, a 0.01-unit monthly increase was observed (95% confidence interval: −0.0003, 0.02; p = 0.11). The log-rank test for BMI increases (⩾+5) and decreases (⩽−5) revealed no significant differences among the donor BMI groups (Chi-squared = 4.4, p = 0.1 for increases, Chi-squared = 2, p = 0.4 for decreases). Conclusion: The lack of impact of donor BMI on BMI changes post-FMT suggests that these changes are more dependent on the recipient’s metabolic profile. Prospective, controlled trials are required to analyze these results more comprehensively.

Background Microbial conversion of dietary substrate to bioactive molecules represents a potential regulatory mechanism by which gut microbes can alter intestinal physiology. Tryptamine, a monoamine structurally similar to serotonin (5‐HT), can be generated via decarboxylation of tryptophan by the gut bacteria but its physiological effect is not known. Aim To determine the effect of bacterial metabolite tryptamine on colonic secretion. Methods We mounted proximal colon mucosa‐submucosa preparations from germ free (GF), humanized (HM; ex‐GF colonized with human gut bacteria for 4–5 weeks), conventionally raised WT and 5‐HT4 receptor knockout (5‐HT4R −/− ) male mice in the Ussing chamber. The change in short circuit current (ΔIsc) was determined in response to application of increasing concentrations of tryptamine (3μM – 3mM) on the submucosal (basolateral) side either alone or in the presence of 5‐HT3R or 5‐HT4R antagonist, ondansetron (100nM) and GR‐113808 (30nM) respectively, with and without TTX (500nM). Colonoids (3‐dimensional epithelial organoids derived from colon) from GF and HM were used for swelling assay and ELISA based cAMP measurement. Results Tryptamine application significantly increased Isc in both GF and HM mice (n=6, P < 0.05, two‐way ANOVA with Bonferroni post‐hoc). Tryptamine mediated ΔIsc response was not significantly affected by amiloride, an inhibitor of epithelial sodium channels and Na + /H + exchangers, which are primarily responsible for absorption but was significantly decreased by 5‐Nitro‐2‐(3‐phenylpropylamino) benzoic acid (NPPB; anion blocker), a calcium‐sensitive chloride channel and sodium bicarbonate exchanger inhibitor responsible for anionic secretion in both GF and HM mice (n=4, P < 0.05, two‐way ANOVA with Bonferroni post‐hoc). Tryptamine evoked ΔIsc was not inhibited by 5‐HT3R (n=4, P > 0.05) but completely blocked by 5‐HT4R antagonist and was absent in 5HT4R knock out mice suggesting that the effect of tryptamine is mediated via 5HT4R. The increase in Isc in response to tryptamine and its inhibition by 5‐HT4R antagonist was also seen in presence of TTX (neuronal blocker; n=4, one‐way ANOVA , P < 0.05) suggesting that the epithelial 5‐HT4R alone can mediate the effect of tryptamine. Application of tryptamine (1mM) for 30 minutes led to a significant increase in the surface area of fluorescein labelled colonoids (n=5, one‐way ANOVA , P < 0.05), similar to forskolin, when compared to vehicle treated and 5HT4R antagonist pre‐treated GF and HM colonoids. Colonoids incubated with tryptamine (1mM) for 60 minutes had significantly higher cAMP levels (normalized to forskolin) compared to vehicle treated GF and HM colonoids, confirming that tryptamine activates 5‐HT4 GPCR (n=3, student's t‐test, P < 0.05). Conclusion Tryptamine, a tryptophan‐derived microbial metabolite, increases colonic secretion via 5HT4 GPCR activation. The identification of a bacterial metabolite activating a host GPCR to alter GI function represents an important advance in the field, and provides a distinct example of small molecule mediated host‐microbe interaction. Engineered probiotics producing tryptamine could be used as therapeutics in diseases associated with constipation. Support or Funding Information NIH DK111850, DK114007 (PCK) This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Increased amino acids in the dysbiotic gut influences susceptibility to Clostridioides difficile infection in mice and humans.

ABSTRACT Uropathogenic Escherichia coli (UPEC) is the most common etiologic agent of uncomplicated urinary tract infection (UTI). An important mechanism of gene regulation in UPEC is phase variation that involves inversion of a promoter-containing DNA element via enzymatic activity of tyrosine recombinases, resulting in biphasic, ON or OFF expression of target genes. The UPEC reference strain CFT073 has five tyrosine site-specific recombinases that function at two previously characterized promoter inversion systems, fimS and hyxS . Three of the five recombinases are located proximally to their cognate target elements, which is typical of promoter inversion systems. The genes for the other two recombinases, IpuA and IpuB, are located distal from these sites. Here, we identified and characterized a third phase-variable invertible element in CFT073, ipuS , located proximal to ipuA and ipuB . The inversion of ipuS is catalyzed by four of the five CFT073 recombinases. Orientation of the element drives transcription of a two-gene operon containing ipuR , a predicted LuxR-type regulator, and upaE , a predicted autotransporter. We show that the predicted autotransporter UpaE is surface located and facilitates biofilm formation as well as adhesion to extracellular matrix proteins in a K-12 recombinant background. Consistent with this phenotype, the ipuS ON condition in CFT073 results in defective swimming motility, increased adherence to human kidney epithelial cells, and a positive competitive kidney colonization advantage in experimental mouse UTIs. Overall, the identification of a third phase switch in UPEC that is regulated by a shared set of recombinases describes a complex phase-variable virulence network in UPEC. IMPORTANCE Uropathogenic Escherichia coli (UPEC) is the most common cause of urinary tract infection (UTI). ON versus OFF phase switching by inversion of small DNA elements at two chromosome sites in UPEC regulates the expression of important virulence factors, including the type 1 fimbria adhesion organelle. In this report, we describe a third invertible element, ipuS , in the UPEC reference strain CFT073. The inversion of ipuS controls the phase-variable expression of upaE , an autotransporter gene that encodes a surface protein involved in adherence to extracellular matrix proteins and colonization of the kidneys in a murine model of UTI.