Chyme Reinfusion Restores the Regulatory Bile Salt-FGF19 Axis in Patients With Intestinal Failure

Abstract

Background and aims: Automated chyme reinfusion (CR) in patients with intestinal failure (IF) and a temporary double enterostomy (TDE) restores intestinal function and protects against liver injury, but the mechanisms are incompletely understood. The aim was to investigate whether the beneficial effects of CR relate to functional recovery of enterohepatic signaling through the bile salt-FGF19 axis.

Approach and results: Blood samples were collected from 12 patients, 3 days before, at start, and 1, 3, 5, and 7 weeks after CR initiation. Plasma FGF19, total bile salts (TBS), 7-α-hydroxy-4-cholesten-3-one (C4; a marker of bile salt synthesis), citrulline (CIT), bile salt composition, liver tests, and nutritional risk indices were determined. Paired small bowel biopsies prior to CR and after 21 days were taken, and genes related to bile salt homeostasis and enterocyte function were assessed. CR induced an increase in plasma FGF19 and decreased C4 levels, indicating restored regulation of bile salt synthesis through endocrine FGF19 action. TBS remained unaltered during CR. Intestinal farnesoid X receptor was up-regulated after 21 days of CR. Secondary and deconjugated bile salt fractions were increased after CR, reflecting restored microbial metabolism of host bile salts. Furthermore, CIT and albumin levels gradually rose after CR, while abnormal serum liver tests normalized after CR, indicating restored intestinal function, improved nutritional status, and amelioration of liver injury. CR increased gene transcripts related to enterocyte number, carbohydrate handling, and bile salt homeostasis. Finally, the reciprocal FGF19/C4 response after 7 days predicted the plasma CIT time course.

Conclusions: CR in patients with IF-TDE restored bile salt-FGF19 signaling and improved gut-liver function. Beneficial effects of CR are partly mediated by recovery of the bile salt-FGF19 axis and subsequent homeostatic regulation of bile salt synthesis.

FIG. 1

Dysregulated bile salt synthesis in patients with IF‐TDE prior to CR. (A) Baseline values of TBS, FGF19, and C4 of patients with IF‐TDE (n = 12) compared with controls (n = 12). Note, C4 levels were available for 6 out of 12 healthy volunteers. (B) Correlation between FGF19 and C4 levels in patients with IF‐TDE (blue circles) and controls (black circles). (C) Correlation between jejunal efflux adjusted by weight and FGF19 or C4. Data are depicted as mean ± 95% CI. Differences were evaluated by Mann‐Whitney U test. Correlations were evaluated with Spearman’s (ρ) correlation coefficient. P values are depicted.

FIG. 2

CR restores homeostatic control of bile salt synthesis within 7 days. Twelve patients with a TDE on PN underwent CR for up to 7 weeks. Blood was sampled at the depicted time points before and after start of CR and analyzed for (A) TBS, FGF19, and C4. (B) Relative change from baseline over time for TBS, FGF19, and C4. (C) Individual changes of TBS, FGF19, and C4 in the first week of CR. (D) Paired small intestinal biopsies were studied (n = 7 patients) at 3 days before CR and 21 days after CR and analyzed for mRNA expression of FXR and genes related to bile salt transport. (E) Proximal jejunal output at start of CR and stomal or fecal output at discharge from the clinic/end of CR were assessed to address intestinal output changes. Data are depicted as mean ± 95% CI. Trends in time were evaluated by ANOVA with repeated measures. mRNA expression and intestinal output differences were evaluated by Wilcoxon matched‐pairs signed ranks sum test. P values are depicted. Asterisks indicate significance levels: *P < 0.05, **P < 0.01, and ***P < 0.001. Abbreviation: ASBT, apical sodium‐dependent bile salt transporter.

FIG. 3

Alteration of serum bile salt composition after CR initiation. Time course of circulating bile salt composition during CR (n = 12). Graphs show time courses of (A) primary and secondary bile salts, (B) deconjugated and conjugated bile salts, (C) glycine‐conjugated and taurine‐conjugated bile salts, and (D) the sulfated bile salt species GCDCA‐3S. (E) Individual plasma bile salt species. (F) Chyme bile salt composition—molar fraction of individual bile salt species as percentage of total moles of bile salt. (G) Correlation between chyme GCA and GCDCA and plasma levels of FGF19 and C4. Data are depicted as mean ± 95% CI. Trends in time were evaluated by ANOVA with repeated measures. P values are depicted. Asterisks indicate significance levels: *P < 0.05 and **P < 0.01. Abbreviations: BS, bile salt; CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxycholic acid; GDCA, glycodeoxycholic acid; GLCA, glycolithocholic acid; GUDCA, glycoursodeoxycholic acid; LCA, lithocholic acid; TCA, taurocholic acid; TCDCA, taurochenodeoxycholic acid; TDCA, taurodeoxycholic acid; UDCA, ursodeoxycholic acid.

FIG. 4

CR recovers intestinal absorptive function and ameliorates liver injury. Time course of markers for intestinal absorptive function and nutritional status during CR. (A) CIT values of individual patients at baseline (left panel) with values >20 µmol/L in a dashed box and time course of CIT (right panel). (B) Time course of albumin (dashed line represents normal value). (C) Relative change from baseline over time for CIT and albumin. (D) Paired mRNA expression of epithelium‐specific genes (VIL‐1, SI, CUBN, and OCT) and local inflammation (IL‐6, TNFα, IL1‐β, and IL‐10) at baseline and 3 weeks after CR. (E) Time course of liver injury markers (ALP, GGT, and total bilirubin) and (F) systemic inflammation (CRP). Data are depicted as mean ± 95% CI. Trends in time were evaluated by ANOVA with repeated measures. Gene expression differences were evaluated by Wilcoxon matched‐pairs signed ranks sum test. P values are depicted.

FIG. 5

The FGF19 response, dependent on the C4 response, after 7 days predicts the plasma course of CIT over time. A linear mixed effects model was constructed to evaluate whether the response of FGF19 and C4 (difference between 7 days and baseline values = Δ) predicts the course of CIT over time. Interaction plot depicting the association between the interaction of Δ_FGF19*Δ_C4 after 7 days and predicted CIT values over time (from 7 days onward). The Δ_FGF19 is depicted on the x‐axis. The y‐axis shows the predicted CIT values. The regression line is shown with 95% CI. R ² and P values are depicted.

FIG. 6

Schematic summary of the pathophysiology and mechanistic findings before and during CR in patients with IF and a double enterostomy. Abbreviations: ASBT, apical sodium‐dependent bile salt transporter; DCA, deoxycholic acid; GDCA, glycodeoxycholic acid.