Defective FXR-FGF15 signaling and bile acid homeostasis in cystic fibrosis mice can be restored by the laxative polyethylene glycol

The gastrointestinal phenotype of cystic fibrosis (CF) features intestinal bile acid (BA) malabsorption, impaired intestinal farnesoid X receptor (FXR) activation, and consequently reduced fibroblast growth factor 19 (FGF19, FGF15 in mice) production. The osmotic laxative polyethylene glycol (PEG) has been shown to decrease intestinal mucus accumulation in CF mice and could, by doing so, improve BA reabsorption. Here we determined the effect of PEG on BA excretion and FXR-FGF15 signaling in CF mice. Male Cftr−/−tm1Unc (CF) and wild-type (WT) littermates were administered PEG 4000 in drinking water and fed either chow or a semisynthetic diet. PEG was withdrawn for 3 days before termination. Fecal BA excretion was measured at PEG dosages of 37 g/l (100%) and 0 g/l (0%). Ileal FXR activation was assessed by gene expression of its downstream targets Fgf15 and small heterodimer partner ( Shp). In CF mice, PEG withdrawal increased fecal BA excretion on either diet compared with full PEG dosage (chow, 2-fold, P = 0.06; semisynthetic, 4.4-fold, P = 0.007). PEG withdrawal did not affect fecal BA excretion in WT mice on either diet. After PEG withdrawal, gene expression levels of intestinal FXR target genes Fgf15 and Shp were decreased in CF mice but unaffected in WT littermates. PEG did not affect the gene expression of the main intestinal BA transporter apical sodium-dependent bile acid transporter (ASBT). PEG treatment ameliorates intestinal BA malabsorption in CF mice and restores intestinal FXR-FGF15 signaling, independent from Asbt gene expression. These findings highlight the potential of PEG in the prevention and treatment of the gastrointestinal phenotype of CF. NEW & NOTEWORTHY A gastrointestinal feature of cystic fibrosis is bile acid malabsorption and consequent impairment of farnesoid X receptor (FXR)-fibroblast growth factor 15 (FGF15) signaling. FXR-FGF15 signaling regulates various metabolic processes and could be implicated in metabolic and gastrointestinal complications of cystic fibrosis, such as diabetes and liver disease. In cystic fibrosis mice, treatment with the osmotic laxative polyethylene glycol is associated with decreased fecal bile acid loss and restoration of FXR-FGF15 signaling.

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Resveratrol Attenuates Trimethylamine- N -Oxide (TMAO)-Induced Atherosclerosis by Regulating TMAO Synthesis and Bile Acid Metabolism via Remodeling of the Gut Microbiota

mBio ◽

10.1128/mbio.02210-15 ◽

2016 ◽

Vol 7 (2) ◽

Cited By ~ 189

Author(s):

Ming-liang Chen ◽

Long Yi ◽

Yong Zhang ◽

Xi Zhou ◽

Li Ran ◽

...

Keyword(s):

Bile Acid ◽

Growth Factor ◽

Gut Microbiota ◽

Fibroblast Growth Factor ◽

Farnesoid X Receptor ◽

Fecal Excretion ◽

Bile Acid Metabolism ◽

Bile Salt Hydrolase ◽

Fibroblast Growth ◽

As Effects

ABSTRACT The gut microbiota is found to be strongly associated with atherosclerosis (AS). Resveratrol (RSV) is a natural phytoalexin with anti-AS effects; however, its mechanisms of action remain unclear. Therefore, we sought to determine whether the anti-AS effects of RSV were related to changes in the gut microbiota. We found that RSV attenuated trimethylamine- N -oxide (TMAO)-induced AS in ApoE −/− mice. Meanwhile, RSV decreased TMAO levels by inhibiting commensal microbial trimethylamine (TMA) production via gut microbiota remodeling in mice. Moreover, RSV increased levels of the genera Lactobacillus and Bifidobacterium , which increased the bile salt hydrolase activity, thereby enhancing bile acid (BA) deconjugation and fecal excretion in C57BL/6J and ApoE −/− mice. This was associated with a decrease in ileal BA content, repression of the enterohepatic farnesoid X receptor (FXR)-fibroblast growth factor 15 (FGF15) axis, and increased cholesterol 7a-hydroxylase (CYP7A1) expression and hepatic BA neosynthesis. An FXR antagonist had the same effect on FGF15 and CYP7A1 expression as RSV, while an FXR agonist abolished RSV-induced alterations in FGF15 and CYP7A1 expression. In mice treated with antibiotics, RSV neither decreased TMAO levels nor increased hepatic BA synthesis. Additionally, RSV-induced inhibition of TMAO-caused AS was also markedly abolished by antibiotics. In conclusion, RSV attenuated TMAO-induced AS by decreasing TMAO levels and increasing hepatic BA neosynthesis via gut microbiota remodeling, and the BA neosynthesis was partially mediated through the enterohepatic FXR-FGF15 axis. IMPORTANCE Recently, trimethylamine- N -oxide (TMAO) has been identified as a novel and independent risk factor for promoting atherosclerosis (AS) partially through inhibiting hepatic bile acid (BA) synthesis. The gut microbiota plays a key role in the pathophysiology of TMAO-induced AS. Resveratrol (RSV) is a natural phytoalexin with prebiotic benefits. A growing body of evidence supports the hypothesis that phenolic phytochemicals with poor bioavailability are possibly acting primarily through remodeling of the gut microbiota. The current study showed that RSV attenuated TMAO-induced AS by decreasing TMAO levels and increasing hepatic BA neosynthesis via gut microbiota remodeling. And RSV-induced hepatic BA neosynthesis was partially mediated through downregulating the enterohepatic farnesoid X receptor-fibroblast growth factor 15 axis. These results offer new insights into the mechanisms responsible for RSV’s anti-AS effects and indicate that the gut microbiota may become an interesting target for pharmacological or dietary interventions to decrease the risk of developing cardiovascular diseases.

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Potent stimulation of fibroblast growth factor 19 expression in the human ileum by bile acids

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00398.2012 ◽

2013 ◽

Vol 304 (10) ◽

pp. G940-G948 ◽

Cited By ~ 60

Author(s):

Justine H. Zhang ◽

Jonathan D. Nolan ◽

Sarah L. Kennie ◽

Ian M. Johnston ◽

Tracy Dew ◽

...

Keyword(s):

Bile Acid ◽

Growth Factor ◽

Fibroblast Growth Factor ◽

Culture Fluid ◽

Farnesoid X Receptor ◽

Transcript Expression ◽

Fibroblast Growth ◽

Primary Explants ◽

Fgf19 Expression ◽

Fibroblast Growth Factor 19

Fibroblast growth factor 19 (FGF19) is proposed to be a negative feedback regulator of hepatic bile acid (BA) synthesis. We aimed to clarify the distribution of FGF19 expression in human intestine and to investigate induction in a novel explant system. Ileal and colonic mucosal biopsies were obtained at endoscopy and analyzed for FGF19 transcript expression. Primary explants were incubated with physiological concentrations of various BA for up to 6 h, and expression of FGF19 and other genes was determined. FGF19 transcripts were detected in ileum but were unquantifiable in colon. No loss of FGF19 mRNA occurred as a consequence of the explant system. Ileal FGF19 transcript expression was induced 350-fold by 50 μM chenodeoxycholate (CDCA, n = 24, P < 0.0001) and 161-fold by 50 μM glycochenodeoxycholate (GCDCA, n = 12, P = 0.0005). The responses of other genes to CDCA or GCDCA (50 μM) were smaller: median increases of ileal bile acid binding protein, organic solute transporter-α and -β, and short heterodimer partner were 2.4- to 4.0-fold; apical membrane sodium bile acid transporter and farnesoid X receptor (FXR) showed little change. The EC50 for FGF19 transcript induction by CDCA was 20 μM. FGF19 protein concentrations were significantly higher in the culture fluid from BA-stimulated explants. FGF19 induction with cholate was 81% of that found with CDCA, but deoxycholate (40%) and lithocholate (4%) were significantly less potent. The synthetic FXR agonist obeticholic acid was much more potent than CDCA with a 70-fold FGF19 stimulation at 1 μM. We concluded that FGF19 expression in human ileum is very highly responsive to BA. Changes in FGF19 induction are a potential mechanism involved in disorders of BA homeostasis.

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Effective fecal microbiota transplantation for recurrent Clostridioides difficile infection in humans is associated with increased signalling in the bile acid-farnesoid X receptor-fibroblast growth factor pathway

Gut Microbes ◽

10.1080/19490976.2018.1506667 ◽

2018 ◽

Vol 10 (2) ◽

pp. 142-148 ◽

Cited By ~ 10

Author(s):

Tanya Monaghan ◽

Benjamin H Mullish ◽

Jordan Patterson ◽

Gane KS Wong ◽

Julian R Marchesi ◽

...

Keyword(s):

Bile Acid ◽

Growth Factor ◽

Fibroblast Growth Factor ◽

Fecal Microbiota Transplantation ◽

Fecal Microbiota ◽

Farnesoid X Receptor ◽

Fibroblast Growth ◽

Clostridioides Difficile ◽

Clostridioides Difficile Infection

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Bile acid flux through portal but not peripheral veins inhibits CYP7A1 expression without involvement of ileal FGF19 in rabbits

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00062.2014 ◽

2014 ◽

Vol 307 (4) ◽

pp. G479-G486 ◽

Cited By ~ 2

Author(s):

Quan Shang ◽

Grace L. Guo ◽

Akira Honda ◽

Daniel Shi ◽

Monica Saumoy ◽

...

Keyword(s):

Bile Acid ◽

Growth Factor ◽

Fibroblast Growth Factor ◽

Femoral Vein ◽

Splenic Vein ◽

Rabbit Model ◽

Farnesoid X Receptor ◽

Fibroblast Growth ◽

Protein Levels ◽

Fgf19 Expression

It was proposed that CYP7A1 expression is suppressed through the gut-hepatic signaling pathway fibroblast growth factor (FGF) 15/19-fibroblast growth factor receptor 4, which is initiated by activation of farnesoid X receptor in the intestine rather than in the liver. The present study tested whether portal bile acid flux alone without ileal FGF19 could downregulate CYP7A1 expression in rabbits. A rabbit model was developed by infusing glycodeoxycholic acid (GDCA) through the splenic vein to bypass ileal FGF19. Study was conducted in four groups of rabbits: control; bile fistula + bovine serum albumin solution perfusion (BF); BF + GDCA (by portal perfusion); and BF + GDCA-f (by femoral perfusion). Compared with only BF, BF + GDCA (6 h portal perfusion) suppressed CYP7A1 mRNA, whereas BF + GDCA-f (via femoral vein) with the same perfusion rate of GDCA did not show inhibitory effects. Meanwhile, there was a decrease in ileal FGF19 expression and portal FGF19 protein levels, but an equivalent increase in biliary bile acid outputs in both GDCA perfusion groups. This study demonstrated that portal bile acid flux alone downregulated CYP7A1 expression with diminished FGF19 expression and protein levels, whereas the same bile acid flux reaching the liver through the hepatic artery via femoral vein had no inhibitory effect on CYP7A1. We propose that bile acid flux through the portal venous system may be a kind of “intestinal factor” that suppresses CYP7A1 expression.

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