Increased levels of intestinal bile acids (BAs) are a risk factor for colorectal cancer (CRC). Here, we show that the convergence of dietary factors (high-fat diet) and dysregulated WNT signaling ...(APC mutation) alters BA profiles to drive malignant transformations in Lgr5-expressing (Lgr5+) cancer stem cells and promote an adenoma-to-adenocarcinoma progression. Mechanistically, we show that BAs that antagonize intestinal farnesoid X receptor (FXR) function, including tauro-β-muricholic acid (T-βMCA) and deoxycholic acid (DCA), induce proliferation and DNA damage in Lgr5+ cells. Conversely, selective activation of intestinal FXR can restrict abnormal Lgr5+ cell growth and curtail CRC progression. This unexpected role for FXR in coordinating intestinal self-renewal with BA levels implicates FXR as a potential therapeutic target for CRC.
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•Genetic and dietary risk factors for colorectal cancer converge on the BA-FXR axis•FXR controls proliferating Lgr5+ intestinal stem cells•FXR agonists curtail colorectal cancer progression
The progression of colorectal cancer is fueled by the bile-acid-dependent inhibition of the receptor FXR.
The systemic expression of the bile acid (BA) sensor farnesoid X receptor (FXR) has led to promising new therapies targeting cholesterol metabolism, triglyceride production, hepatic steatosis and ...biliary cholestasis. In contrast to systemic therapy, bile acid release during a meal selectively activates intestinal FXR. By mimicking this tissue-selective effect, the gut-restricted FXR agonist fexaramine (Fex) robustly induces enteric fibroblast growth factor 15 (FGF15), leading to alterations in BA composition, but does so without activating FXR target genes in the liver. However, unlike systemic agonism, we find that Fex reduces diet-induced weight gain, body-wide inflammation and hepatic glucose production, while enhancing thermogenesis and browning of white adipose tissue (WAT). These pronounced metabolic improvements suggest tissue-restricted FXR activation as a new approach in the treatment of obesity and metabolic syndrome.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, UILJ, UKNU, UL, UM, UPUK
Liver fibrosis is a reversible wound-healing response involving TGFβ1/SMAD activation of hepatic stellate cells (HSCs). It results from excessive deposition of extracellular matrix components and can ...lead to impairment of liver function. Here, we show that vitamin D receptor (VDR) ligands inhibit HSC activation by TGFβ1 and abrogate liver fibrosis, whereas Vdr knockout mice spontaneously develop hepatic fibrosis. Mechanistically, we show that TGFβ1 signaling causes a redistribution of genome-wide VDR-binding sites (VDR cistrome) in HSCs and facilitates VDR binding at SMAD3 profibrotic target genes via TGFβ1-dependent chromatin remodeling. In the presence of VDR ligands, VDR binding to the coregulated genes reduces SMAD3 occupancy at these sites, inhibiting fibrosis. These results reveal an intersecting VDR/SMAD genomic circuit that regulates hepatic fibrogenesis and define a role for VDR as an endocrine checkpoint to modulate the wound-healing response in liver. Furthermore, the findings suggest VDR ligands as a potential therapy for liver fibrosis.
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•Vitamin D receptor (VDR) ligands inhibit hepatic stellate cell activation and fibrosis•Vdr knockout mice spontaneously develop liver fibrosis•TGFβ1 signaling shifts the genome-wide binding locations of VDR•VDR antagonizes SMAD3/TGFβ1 activation of profibrotic genes
In the absence of vitamin D receptor (VDR) signaling, SMADs respond to liver injury by activating a set of genes in hepatic stellate cells that cause fibrosis and liver impairment. Paradoxically, SMAD activity also enables repression of fibrosis by making the chromatin around SMAD target sites more accessible to VDR, which, in the presence of ligands, binds and inhibits SMAD activity.
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•Serum FGF19 and bile acids are significantly increased in patients with alcoholic hepatitis.•Total and conjugated bile acids correlated positively with FGF19 and with disease ...severity (MELD score).•Modulation of bile acid metabolism or signaling could represent a promising target for treatment of alcoholic hepatitis.
The degree of cholestasis is an important disease driver in alcoholic hepatitis, a severe clinical condition that needs new biomarkers and targeted therapies. We aimed to identify the largely unknown mechanisms and biomarkers linked to cholestasis in alcoholic hepatitis.
Herein, we analyzed a well characterized cohort of patients with alcoholic hepatitis and correlated clinical and histological parameters and outcomes with serum bile acids and fibroblast growth factor 19 (FGF19), a major regulator of bile acid synthesis.
We found that total and conjugated bile acids were significantly increased in patients with alcoholic hepatitis compared with controls. Serum FGF19 levels were strongly increased and gene expression of FGF19 was induced in biliary epithelial cells and ductular cells of patients with alcoholic hepatitis. De novo bile acid synthesis (CYP7A1 gene expression and C4 serum levels) was significantly decreased in patients with alcoholic hepatitis. Importantly, total and conjugated bile acids correlated positively with FGF19 and with disease severity (model for end-stage liver disease score). FGF19 correlated best with conjugated cholic acid, and model for end-stage liver disease score best with taurine-conjugated chenodeoxycholic acid. Univariate analysis demonstrated significant associations between FGF19 and bilirubin as well as gamma glutamyl transferase, and negative correlations between FGF19 and fibrosis stage as well as polymorphonuclear leukocyte infiltration, in all patients with alcoholic hepatitis.
Serum FGF19 and bile acids are significantly increased in patients with alcoholic hepatitis, while de novo bile acid synthesis is suppressed. Modulation of bile acid metabolism or signaling could represent a promising target for treatment of alcoholic hepatitis in humans.
Understanding the underlying mechanisms that drive alcoholic hepatitis is important for the development of new biomarkers and targeted therapies. Herein, we describe a molecule that is increased in patients with alcoholic hepatitis. Modulating the molecular pathway of this molecule might lead to promising targets for the treatment of alcoholic hepatitis.
The pleiotropic actions of the Farnesoid X Receptor (FXR) are required for gut health, and reciprocally, reduced intestinal FXR signaling is seen in inflammatory bowel diseases (IBDs). Here, we show ...that activation of FXR selectively in the intestine is protective in inflammation-driven models of IBD. Prophylactic activation of FXR restored homeostatic levels of pro-inflammatory cytokines, most notably IL17. Importantly, these changes were attributed to FXR regulation of innate lymphoid cells (ILCs), with both the inflammation-driven increases in ILCs, and ILC3s in particular, and the induction of
and
in ILC3s blocked by FXR activation. Moreover, a population of ILC precursor-like cells increased with treatment, implicating FXR in the maturation/differentiation of ILC precursors. These findings identify FXR as an intrinsic regulator of intestinal ILCs and a potential therapeutic target in inflammatory intestinal diseases.
Aims To investigate inhibition of recombinant CYP2C8 by: (i) prototypic CYP isoform selective inhibitors (ii) imidazole/triazole antifungal agents (known inhibitors of CYP), and (iii) certain CYP3A ...substrates (given the apparent overlapping substrate specificity of CYP2C8 and CYP3A).
Methods CYP2C8 and NADPH‐cytochrome P450 oxidoreductase were coexpressed in Spodoptera frugiperda (Sf21) cells using the baculovirus expression system. CYP isoform selective inhibitors, imidazole/triazole antifungal agents and CYP3A substrates were screened for their inhibitory effects on CYP2C8‐catalysed torsemide tolylmethylhydroxylation and, where appropriate, the kinetics of inhibition were characterized. The conversion of torsemide to its tolylmethylhydroxy metabolite was measured using an h.p.l.c. procedure.
Results At concentrations of the CYP inhibitor ‘probes’ employed for isoform selectivity, only diethyldithiocarbamate and ketoconazole inhibited CYP2C8 by > 10%. Ketoconazole, at an added concentration of 10 µm, inhibited CYP2C8 by 89%. Another imidazole, clotrimazole, also potently inhibited CYP2C8. Ketoconazole and clotrimazole were both noncompetitive inhibitors of CYP2C8 with apparent Ki values of 2.5 µm. The CYP3A substrates amitriptyline, quinine, terfenadine and triazolam caused near complete inhibition (82–91% of control activity) of CYP2C8 at concentrations five‐fold higher than the known CYP3A Km. Kinetic studies with selected CYP3A substrates demonstrated that most inhibited CYP2C8 noncompetitively. Apparent Ki values for midazolam, quinine, terfenadine and triazolam ranged from 5 to 25 µm.
Conclusions Inhibition of CYP2C8 occurred at concentrations of ketoconazole and diethyldithiocarbamate normally employed for selective inhibition of CYP3A and CYP2E1, respectively. Some CYP3A substrates have the capacity to inhibit CYP2C8 activity and this may have implications for inhibitory drug interactions in vivo.
Background
Bile acids (BAs) are synthesized by the liver and modified by gut bacteria, and may play an intermediary role between the gut microbiome and liver in promoting fibrosis in non‐alcoholic ...fatty liver disease (NAFLD). We investigated the associations between serum and faecal BAs, gut microbiome and fibrosis in patients with and without NAFLD and examined the impact of diet and alcohol consumption on these relationships.
Methods
Adult patients (n = 122) underwent liver biopsy and BAs characterization by high‐performance liquid chromatography/mass spectrometry. Gut microbiome composition was analysed using next‐generation 16S rRNA sequencing. Diet and alcohol intake were determined by 3‐day food diary.
Results
Serum and faecal BA concentrations increased progressively among non‐NAFLD controls (n = 55), NAFLD patients with no/mild fibrosis (F0‐2, n = 58) and NAFLD with advanced fibrosis (F3/4, n = 9). Progressive increases in serum BAs were driven by primary conjugated BAs including glycocholic acid GCA and secondary conjugated BAs. In contrast, faecal BA increase was driven by secondary unconjugated BAs (predominately deoxycholic acid DCA). Serum GCA levels and faecal DCA levels correlated with the abundance of Bacteroidaceae and Lachnospiraceae, and stool secondary BAs with an unclassifiable family of the order Bacteroidales (Bacteroidales;other). These bacterial taxa were also associated with advanced fibrosis. Modest alcohol consumption was positively correlated with faecal DCA levels and relative abundance of Lachnospiracaea and Bacteroidales;other.
Conclusions
Higher serum and faecal BA levels are associated with advanced fibrosis in NAFLD. Specific gut bacteria link alterations in BA profiles and advanced fibrosis, and may be influenced by low‐level alcohol consumption.
Purpose
Dose individualization of sunitinib has been proposed using therapeutic drug monitoring (TDM) or toxicity-adjusted dose (TAD). We prospectively studied aspects of TDM and TAD to inform future ...trials, namely (1) intrapatient variability (CV) of sunitinib and (2) feasibility of a TAD protocol.
Methods
Sunitinib dose was adjusted to ensure grade 1 or 2 toxicity on 10–20 days of each 42-day cycle. Total trough levels (TTL)
C
min
of sunitinib and its active metabolite were measured every 6 weeks.
Results
In 45 patients with mRCC, 283 TTL samples were assayed over a median 30 weeks (6–108 weeks). Fifteen patients (33%) had an intrapatient CV of >25% in TTL. Ninety-one percent achieved target toxicity with a final sunitinib dose of 25 mg (18%), 37.5 mg (27%), 50 mg (50%), and 62.5 or 75 mg (7%). TTL
C
min
was <50, 50–100, and >100 ng/mL in 7 (15%), 31 (69%), and 7 patients (15.5%), respectively. The median overall survival was 32 months.
Conclusions
Sunitinib level has minimal variability in the majority of patients on stable dose. A subset of patients had a significant intrapatient variation, so we recommend two samples 4 to 6 months apart. TAD is feasible for dosing sunitinib and showed a favourable outcome.
Bile acids are potentially toxic end products of cholesterol metabolism and their concentrations must be tightly regulated. Homeostasis is maintained by both feed-forward regulation and feedback ...regulation. We used humanized transgenic mice incorporating 13 kb of the 5′ regulatory flanking sequence of CYP3A4 linked to a lacZ reporter gene to explore the in vivo relationship between bile acids and physiological adaptive CYP3A gene regulation in acute cholestasis after bile duct ligation (BDL). Male transgenic mice were subjected to BDL or sham surgery prior to sacrifice on days 3, 6, and 10, and others were injected with intraperitoneal lithocholic acid (LCA) or vehicle alone. BDL resulted in marked hepatic activation of the CYP3A4/lacZ transgene in pericentral hepatocytes, with an 80-fold increase in transgene activation by day 10. Individual bile acids were quantified by liquid chromatography/mass spectrometry. Serum 6β-hydroxylated bile acids were increased following BDL, confirming the physiological relevance of endogenous Cyp3a induction to bile acid detoxification. Although concentrations of conjugated primary bile acids increased after BDL, there was no increase in LCA, a putative PXR ligand, indicating that this cannot be the only endogenous bile acid mediating this protective response. Moreover, in LCA-treated animals, 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside staining showed hepatic activation of the CYP3A4 transgene only on the liver capsular surface, and minimal parenchymal induction, despite significant liver injury. This study demonstrates that CYP3A up-regulation is a significant in vivo adaptive response to cholestasis. However, this up-regulation is not dependent on increases in circulating LCA and the role of other bile acids as regulatory molecules requires further exploration.
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