Bile acids: short and long term effects in the intestine

Interplay between bile acid metabolism and microbiota in irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) physiopathology is multifactorial and roles for both microbiota and bile acid (BA) modifications have been proposed. We investigated role of dysbiosis, transit pattern and BA metabolism in IBS.

METHODS

Clinical data, serum, and stool samples were collected in 15 healthy subjects (HS), 16 diarrhea-predominant (IBS-D) and 15 constipation-predominant IBS (IBS-C). Fecal microbiota composition was analyzed by real-time PCR. Sera and fecal BA profiles, 7α-C4 levels, and in vitro BA transformation activity by fecal microbiota were measured by mass spectrometry. Serum Fibroblast Growth Factor 19 (FGF19) was assayed by ELISA.

KEYS RESULTS

Dysbiosis was present in IBS patients with an increase in Escherichia coli in IBS-D patients (p = 0.03), and an increase in Bacteroides (p = 0.01) and Bifidobacterium (p = 0.04) in IBS-C patients. Sera primary and amino-conjugated BA were increased in IBS-D (63.5 ± 5.5%, p = 0.01 and 78.9 ± 6.3%, p = 0.03) and IBS-C patients (55.9 ± 5.5%, p = 0.04 and 65.3 ± 6.5%, p = 0.005) compared to HS (37.0 ± 5.8% and 56.7 ± 8.1%). Serum 7α-C4 and FGF19 levels were not different among all three groups. Fecal primary BA were increased in IBS-D patients compared to HS, including chenodeoxycholic acid which has laxative properties (25.6 ± 8.5% vs 3.5 ± 0.6%, p = 0.005). Bile acid deconjugation activity was decreased in IBS-D (p = 0.0001) and IBS-C (p = 0.003) feces. Abdominal pain was positively correlated with serum (R = 0.635, p < 0.001) and fecal (R = 0.391, p = 0.024) primary BA.

CONCLUSIONS & INFERENCES

Different sera and fecal BA profiles in IBS patients could be secondary to dysbiosis and further differences between IBS-C and IBS-D could explain stool patterns. This study opens new fields in IBS physiopathology and suggests that modification of BA profiles could have therapeutic potential.

Progress in treatment of irritable bowel syndrome

Irritable bowel syndrome is a common functional bowel disorder whose incidence has a tendency to increase year by year. At present, the pathogenesis of irritable bowel syndrome is not completely clear, and treatments are mainly symptomatic. In recent years, with the better understanding of its pathogenesis, some new drugs and treatments have been developed, such as methods of improving intestinal micro-ecology (antibiotics, fecal transplantation), mesalazine, and new drugs of improving intestinal secretion, motiligy and sensitivity, plant drugs, some of which have been applied clinically. This article will make a review of the current progress in treatment of irritable bowel syndrome.

Review of efficacy and safety of laxatives use in geriatrics

AIM: To study the efficacy and safety of pharmacological treatment of constipation in geriatrics.

METHODS: PubMed, MEDLINE, google scholar, and Ovid were searched to identify human studies performed on the use of laxatives in elderly with constipation, which were conducted between January 1990 and January 2013 using the specified keywords. Controlled studies that enrolled geriatric patients with a diagnosis of constipation and addressed the efficacy and/or the safety of pharmacological treatments were included. Studies were excluded from this review if they were non-controlled trials, case series, or case reports.

RESULTS: Out of twenty three studies we initially retrieved in our search, only nine studies met the eligibility criteria of being controlled trials within geriatrics. The laxatives examined in the nine studies were senna, lactulose, sorbital, polyethylene glycol (PEG), lubiprostone, linaclotide, and prucalopride. In those studies, senna combinations had a higher efficacy than sorbitol or lactulose as well as, a very good adverse effect profile. PEG was also shown to be safe and effective in geriatric population. Furthermore, it has been shown that PEG is as safe in geriatrics as in general population. New agents like lubiprostone and prucalopride show promising results but the data about these agents in geriatrics are still limited which warrants further investigation.

CONCLUSION: Senna combinations and PEG appear to have a more favorable profile over the other traditionally used laxatives in elderly patients with constipation.

Small Intestinal Bacterial Overgrowth Diagnosed by Glucose Hydrogen Breath Test in Post-cholecystectomy Patients

BACKGROUND/AIMS

Patients undergoing cholecystectomy may have small intestinal bacterial overgrowth (SIBO). We investigated the prevalence and characteristics of SIBO in patients with intestinal symptoms following cholecystectomy.

METHODS

Sixty-two patients following cholecystectomy, 145 with functional gastrointestinal diseases (FGIDs), and 30 healthy controls undergoing hydrogen (H2)-methane (CH4) glucose breath test (GBT) were included in the study. Before performing GBT, all patients were interrogated using bowel symptom questionnaire. The positivity to GBT indicating the presence of SIBO, gas types and bowel symptoms were surveyed.

RESULTS

Post-cholecystectomy patients more often had SIBO as evidenced by a positive (+) GBT than those with FGID and controls (29/62, 46.8% vs 38/145, 26.2% vs 4/30, 13.3%, respectively; P = 0.010). In the gas types, the GBT (H2) + post-cholecystectomy patients was significantly higher than those in FGIDs patients (P = 0.017). Especially, positivity to fasting GBT (H2) among the GBT (H2)+ post-cholecystectomy patients was high, as diagnosed by elevated fasting H2 level. The GBT+ group had higher symptom scores of significance or tendency in abdominal discomfort, bloating, chest discomfort, early satiety, nausea, and tenesmus than those of the GBT negative group. The status of cholecystectomy was the only significant independent factor for predicting SIBO.

CONCLUSIONS

The SIBO with high levels of baseline H2 might be the important etiologic factor of upper GI symptoms for post-cholecystectomy patients.

Inhibition of ileal bile acid transporter: An emerging therapeutic strategy for chronic idiopathic constipation

Chronic idiopathic constipation is a common disorder of the gastrointestinal tract that encompasses a wide profile of symptoms. Current treatment options for chronic idiopathic constipation are of limited value; therefore, a novel strategy is necessary with an increased effectiveness and safety. Recently, the inhibition of the ileal bile acid transporter has become a promising target for constipation-associated diseases. Enhanced delivery of bile acids into the colon achieves an accelerated colonic transit, increased stool frequency, and relief of constipation-related symptoms. This article provides insight into the mechanism of action of ileal bile acid transporter inhibitors and discusses their potential clinical use for pharmacotherapy of constipation in chronic idiopathic constipation.

Gastrointestinal motility and neurogastroenterology

Nordic research on gastrointestinal motility has since 1965 made substantial contributions to our current understanding of gastrointestinal function. During the last decade, the term neurogastroenterology has widened the concept of motility research into the study of gastrointestinal sensory-motor function, including the complex central nervous system interaction. The discovery of a non-adrenergic non-cholinergic (NANC) innervation of the gut in the sixties was made by considerable contributions from the Nordic countries with the Martinson group in Sweden as central innovators. Important discoveries regarding the intramural nerve ganglia as mediators of the autonomic nervous input has also been produced from this research. In clinical motility research, the study of the migrating motor complex in the small bowel has revealed its ability to act as a retroperistaltic pump in the proximal duodenum (Sweden) and its important role for gut microbial homeostasis (Norway). Also in the development of methodology to study gut sensory-motor function, the Nordic countries has contributed. Examples are the physical characteristics of the esophageal manometry catheter (Denmark), the use of ultrasound for assessment of gastric function (Norway), a temporary electrical stimulation method in patients with severe nausea and vomiting (Sweden), a rectal barostat method for clinical evaluation of recto-anal function and a colonic transit time method utilizing radio-opaque markers (Sweden). In later years, the research collaborations have increasingly become worldwide in a manner making it less easy to define pure Nordic contributions.

Bile acid nuclear receptor FXR and digestive system diseases

Bile acids (BAs) are not only digestive surfactants but also important cell signaling molecules, which stimulate several signaling pathways to regulate some important biological processes. The bile-acid-activated nuclear receptor, farnesoid X receptor (FXR), plays a pivotal role in regulating bile acid, lipid and glucose homeostasis as well as in regulating the inflammatory responses, barrier function and prevention of bacterial translocation in the intestinal tract. As expected, FXR is involved in the pathophysiology of a wide range of diseases of gastrointestinal tract, including inflammatory bowel disease, colorectal cancer and type 2 diabetes. In this review, we discuss current knowledge of the roles of FXR in physiology of the digestive system and the related diseases. Better understanding of the roles of FXR in digestive system will accelerate the development of FXR ligands/modulators for the treatment of digestive system diseases.

Increased colonic bile acid exposure: a relevant factor for symptoms and treatment in IBS

OBJECTIVE

Bile acids may play a role in the pathogenesis of IBS. We investigated the potential effects of bile acids entering the colon and its role in the symptom pattern in IBS.

DESIGN

We measured 75Se-labelled homocholic acid-taurine (75SeHCAT) retention, and serum levels of 7α-hydroxy-4-cholesten-3-one (C4) and fibroblast growth factor (FGF) 19 in patients with IBS (n=141) and control subjects (75SeHCAT n=29; C4 and FGF19 n=435). In patients with IBS stool frequency and form, as well as GI symptom severity were registered, and in a proportion of patients colonic transit time and rectal sensitivity were measured (n=66). An 8-week open-label treatment with colestipol was offered to patients with 75SeHCAT <20%, and the effect of treatment was evaluated with IBS severity scoring system and adequate relief of IBS symptoms.

RESULTS

Compared with controls, patients with IBS had lower 75SeHCAT values (p=0.005), higher C4c levels (C4 corrected for cholesterol) (p<0.001), but similar FGF19 levels. Abnormal 75SeHCAT retention (<10%) was seen in 18% of patients, whereas 23% had elevated C4c levels. Patients with IBS with 75SeHCAT retention <10% had more frequent stools, accelerated colonic transit time, rectal hyposensitivity, a higher body mass index, higher C4c and lower FGF19 levels. Colestipol treatment improved IBS symptoms (IBS severity scoring system 220±109 vs. 277±106; p<0.01), and 15/27 patients fulfilled criteria for treatment response (adequate relief ≥50% of weeks 5-8).

CONCLUSIONS

Increased colonic bile acid exposure influences bowel habit and colonic transit time in patients with IBS. A high response rate to open label treatment with colestipol supports this, but placebo-controlled studies are warranted.

GPBA: a GPCR for bile acids and an emerging therapeutic target for disorders of digestion and sensation

Bile acids (BAs) are digestive secretions that are necessary for the emulsification and absorption of dietary fats. Given the episodic nature of BA secretion and intestinal re-absorption, the circulating and tissue levels of BAs, like those of the gut hormones, fluctuate in fasting and fed states, and BA levels and forms are markedly affected by disease. BAs exert widespread hormonal-like effects by activating receptors in the nucleus and at the plasma membrane. The nuclear steroid receptors mediate the genomic actions of BAs on BA, glucose and lipid homeostasis. GPBA (TGR5) is a G-protein coupled plasma membrane receptor for BAs that mediates many of the rapid, non-genomic actions of BAs. GPBA has been implicated in the control of glucose homeostasis, inflammation and liver functions. Recent observations have revealed an unexpected role for GPBA in the nervous system. GPBA is expressed by enteric neurons and enterochromaffin cells that control peristalsis, and GPBA mediates the prokinetic actions of BAs in the colon that have been known for millennia. GPBA is also present on primary spinal afferent and spinal neurons that are necessary for sensory transduction. BA-induced activation of GPBA in the sensory nervous system promotes scratching behaviours and analgesia, which may contribute to the pruritus and painless jaundice that are observed in some patients with chronic cholestatic disease, where circulating BA concentrations are markedly increased. Thus, GPBA has emerged as an intriguing target for diverse metabolic, inflammatory, digestive and sensory disorders, where agonists and antagonists may be of value.

The role of bile acids in functional GI disorders

BACKGROUND

Bile acids are increasingly implicated in the pathogenesis of functional GI disorders. New mechanisms have recently been described in the irritable bowel syndrome, chronic diarrhea and chronic idiopathic constipation. Identification of bile acid signaling through farnesoid X receptor (FXR), transmembrane G-coupled receptor 5 (TGR5) and fibroblast growth factor 19 (FGF19) has led to the development of new, directly acting therapeutic agents. Despite these advances primary bile acid diarrhea remains under-recognized partly because of the lack of a widely available diagnostic test.

PURPOSE

In this review we will summarize the effects of bile acids on bowel function throughout the gastrointestinal tract and their roles in the pathogenesis of functional diseases. We will review established diagnostic tests and therapies for functional heartburn, dyspepsia and bile acid diarrhea. There will be a particular emphasis on recent trial data for emerging therapies such as Elobixibat and Obeticholic acid and novel diagnostic tests for bile acid diarrhea such as 7α-Hydroxy-4-cholesten-3-one (C4) and FGF19. Finally we will discuss future directions for research in this rapidly evolving field, such as bacterial bile acid modification and identification of genetic anomalies associated with functional disorders.

Emerging Pharmacologic Therapies for Constipation-predominant Irritable Bowel Syndrome and Chronic Constipation

Irritable bowel syndrome with constipation and chronic functional constipation are common digestive disorders that negatively impact quality of life and account for billions of dollars in health care costs. Related to the heterogeneity of pathogenesis that underlie these disorders and the failure of symptoms to reliably predict underlying pathophysiology, traditional therapies provide relief to only a subset of affected individuals. The evidence surrounding new and emerging pharmacologic treatments, which include both luminally and systemically acting drugs, is discussed here. These include agents such as lubiprostone, bile acid modulations, guanylate cyclase-C receptor agonists, serotonin receptor modulators and herbal therapies.

Bile acid malabsorption in chronic diarrhea: pathophysiology and treatment

BACKGROUND

Bile acid malabsorption (BAM) is a common but frequently under-recognized cause of chronic diarrhea, with an estimated prevalence of 4% to 5%.

METHODS

The published literature for the period 1965 to 2012 was examined for articles regarding the pathophysiology and treatment of BAM to provide an overview of the management of BAM in gastroenterology practice.

RESULTS

BAM is classified as type 1 (secondary to ileal dysfunction), type 2 (idiopathic) or type 3 (secondary to gastrointestinal disorders not associated with ileal dysfunction). The estimated prevalence of BAM is >90% in patients with resected Crohn disease (CD) and 11% to 52% of unresected CD patients (type 1); 33% in diarrhea-predominant irritable bowel syndrome (type 2); and is a frequent finding postcholecystectomy or postvagotomy (type 3). Investigations include BAM fecal bile acid assay, 23-seleno-25-homo-tauro-cholic acid (SeHCAT) testing and high-performance liquid chromatography of serum 7-α-OH-4-cholesten-3-one (C4), to determine the level of bile acid synthesis. A less time-consuming and expensive alternative in practice is an empirical trial of the bile acid sequestering agent cholestyramine. An estimated 70% to 96% of chronic diarrhea patients with BAM respond to short-course cholestyramine. Adverse effects include constipation, nausea, borborygmi, flatulence, bloating and abdominal pain. Other bile acid sequestering agents, such as colestipol and colesevelam, are currently being investigated for the treatment of BAM-associated diarrhea.

CONCLUSIONS

BAM is a common cause of chronic diarrhea presenting in gastroenterology practice. In accordance with current guidelines, an empirical trial of a bile acid sequestering agent is warranted as part of the clinical workup to rule out BAM.

Three measurable and modifiable enteric microbial biotransformations relevant to cancer prevention and treatment

Interdisciplinary scientific evaluation of the human microbiota has identified three enteric microbial biotransformations of particular relevance for human health and well-being, especially cancer. Two biotransformations are counterproductive; one is productive. First, selective bacteria can reverse beneficial hepatic hydroxylation to produce toxic secondary bile acids, especially deoxycholic acid. Second, numerous bacterial species can reverse hepatic detoxification-in a sense, retoxify hormones and xeonobiotics-by deglucuronidation. Third, numerous enteric bacteria can effect a very positive biotransformation through the production of butyrate, a small chain fatty acid with anti-cancer activity. Each biotransformation is addressed in sequence for its relevance in representative gastrointestinal and extra-intestinal cancers. This is not a complete review of their connection with every type of cancer. The intent is to introduce the reader to clinically relevant microbial biochemistry plus the emerging evidence that links these to both carcinogenesis and treatment. Included is the evidence base to guide counseling for potentially helpful dietary adjustments.

Laparoscopic cholecystocolostomy: a novel surgical approach for the treatment of progressive familial intrahepatic cholestasis

OBJECTIVE

Conventionally, liver transplantation, ileoileal bypass, and partial external or internal biliary diversion are used in the treatment of progressive familial intrahepatic cholestasis (PFIC). However, postoperative recurrence, chronic diarrhea, and permanent stoma are the major concerns. We present a novel approach of laparoscopic cholecystocolostomy with antireflux Y-loop for the management of children with PFIC.

METHODS

Between August 2003 and April 2011, 20 children with PFIC (median age: 1.47 years; range: 10.8 months to 5.11 years) successfully underwent laparoscopic cholecystocolostomies for bile diversions. Gallbladder was incised longitudinally for cholecystocolostomy. Transverse colon was divided proximal to splenic flexure. End-to-side anastomosis was established between distal transverse colon and mid-descending colon. The mobilized splenic flexure and proximal descending colon, that is, the stem of the Y-loop, was anastomosed to the gallbladder.

RESULTS

The mean operative time was 2.02 ± 0.18 hours (range: 2-2.5 hours). The mean postoperative hospital stay was 8 days (range: 5-10 days). Average time for full resumption of diet was 3 days (range: 2-4 days). Average Y-loop length was 17.65 cm (range: 15-20 cm). The median follow-up period was 54 months (range: 12-104 months). All patients were jaundice free after 7 to 20 days and pruritus subsided in 3 to 14 days. Liver function parameters significantly improved postoperatively. Success rate (normalization of serum bile acids at postoperative 12 months) was 85%. No mortality or morbidities associated with diarrhea, cholangitis, or intrahepatic reflux were observed.

CONCLUSIONS

The novel approach of laparoscopic cholecystocolostomy offers a safe and effective treatment option for PFIC in children with good success rates and minimal morbidity.

Advances in understanding of bile acid diarrhea

Bile acids (BA) are actively reabsorbed in the terminal ileum by the apical Na(+)-dependent bile salt transporter. This review addresses the epidemiology, pathophysiology, diagnosis and treatment of BA diarrhea (BAD). BAD is typically caused by ileal resection or disease; 25-33% of patients with chronic functional diarrhea or irritable bowel syndrome-diarrhea (IBS-D) have BAD, possibly from deficiency in the ileal hormone, FGF-19, which normally provides feedback inhibition of BA synthesis. Diagnosis of BAD is typically based on reduced BA retention of radiolabeled BA ((75)SeHCAT), increased BA synthesis (serum C4) or increased fecal BA loss. In clinical practice, diagnosis is often based on response to BA sequestrants (e.g., cholestyramine or colesevelam). Diagnostic tests for BA malabsorption (BAM) need to be used more extensively in clinical practice. In the future, farnesoid X receptor agonists that stimulate ileal production of FGF-19 may be alternative treatments of BAD.

Sodium-dependent bile salt transporters of the SLC10A transporter family: more than solute transporters

The SLC10A transporter gene family consists of seven members and substrates transported by three members (SLC10A1, SLC10A2 and SLC10A6) are Na(+)-dependent. SLC10A1 (sodium taurocholate cotransporting polypeptide [NTCP]) and SLC10A2 (apical sodium-dependent bile salt transporter [ASBT]) transport bile salts and play an important role in maintaining enterohepatic circulation of bile salts. Solutes other than bile salts are also transported by NTCP. However, ASBT has not been shown to be a transporter for non-bile salt substrates. While the transport function of NTCP can potentially be used as liver function test, interpretation of such a test may be complicated by altered expression of NTCP in diseases and presence of drugs that may inhibit NTCP function. Transport of bile salts by NTCP and ASBT is inhibited by a number of drugs and it appears that ASBT is more permissive to drug inhibition than NTCP. The clinical significance of this inhibition in drug disposition and drug-drug interaction remains to be determined. Both NCTP and ASBT undergo post-translational regulations that involve phosphorylation/dephosphorylation, translocation to and retrieval from the plasma membrane and degradation by the ubiquitin-proteasome system. These posttranslational regulations are mediated via signaling pathways involving cAMP, calcium, nitric oxide, phosphoinositide-3-kinase (PI3K), protein kinase C (PKC) and protein phosphatases. There appears to be species difference in the substrate specificity and the regulation of plasma membrane localization of human and rodent NTCP. These differences should be taken into account when extrapolating rodent data for human clinical relevance and developing novel therapies. NTCP has recently been shown to play an important role in HBV and HDV infection by serving as a receptor for entry of these viruses into hepatocytes.

Metabolomics as a diagnostic tool in gastroenterology

Metabolomics has increasingly been applied in addition to other “omic” approaches in the study of the pathophysiology of different gastrointestinal diseases. Metabolites represent molecular readouts of the cell status reflecting a physiological phenotype. In addition, changes in metabolite concentrations induced by exogenous factors such as environmental and dietary factors which do not affect the genome, are taken into account. Metabolic reactions initiated by the host or gut microbiota can lead to “marker” metabolites present in different biological fluids that allow differentiation between health and disease. Several lines of evidence implicated the involvement of intestinal microbiota in the pathogenesis of inflammatory bowel disease (IBD). Also in irritable bowel syndrome (IBS), a role of an abnormal microbiota composition, so-called dysbiosis, is supported by experimental data. These compositional alterations could play a role in the aetiology of both diseases by altering the metabolic activities of the gut bacteria. Several studies have applied a metabolomic approach to identify these metabolite signatures. However, before translating a potential metabolite biomarker into clinical use, additional validation studies are required. This review summarizes contributions that metabolomics has made in IBD and IBS and presents potential future directions within the field.

The profile of bile acids and their sulfate metabolites in human urine and serum

The role of sulfation in ameliorating the hepatotoxicity of bile acids (BAs) in humans remains unknown due to the lack of proper analytical methods to quantify individual BAs and their sulfate metabolites in biological tissues and fluids. To this end, a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to characterize the detailed BA profile in human urine and serum. The limit of quantification was 1ng/mL and baseline separation of all analytes was achieved within in a run time of 32min. The method was validated over the dynamic range of 1-1000ng/mL. The LC-MS/MS method was more accurate, precise, and selective than the commercially available kits for the quantification of sulfated and unsulfated BAs, and the indirect quantification of individual sulfated BAs after solvolysis. The LC-MS/MS method was applied to characterize the BA profile in urine and serum of healthy subjects. Thirty three percent of serum BAs were sulfated, whereas 89% of urinary BAs existed in the sulfate form, indicating the role of sulfation in enhancing the urinary excretion of BAs. The percentage of sulfation of individual BAs increased with the decrease in the number of hydroxyl groups indicating the role of sulfation in the detoxification of the more hydrophobic and toxic BA species. Eighty percent of urinary BAs and 55% of serum BAs were present in the glycine-amidated form, whereas 8% of urinary BAs and 13% of serum BAs existed in the taurine-amidated form.

Sodium-dependent bile salt transporters of the SLC10A transporter family: more than solute transporters

The SLC10A transporter gene family consists of seven members and substrates transported by three members (SLC10A1, SLC10A2 and SLC10A6) are Na(+)-dependent. SLC10A1 (sodium taurocholate cotransporting polypeptide [NTCP]) and SLC10A2 (apical sodium-dependent bile salt transporter [ASBT]) transport bile salts and play an important role in maintaining enterohepatic circulation of bile salts. Solutes other than bile salts are also transported by NTCP. However, ASBT has not been shown to be a transporter for non-bile salt substrates. While the transport function of NTCP can potentially be used as liver function test, interpretation of such a test may be complicated by altered expression of NTCP in diseases and presence of drugs that may inhibit NTCP function. Transport of bile salts by NTCP and ASBT is inhibited by a number of drugs and it appears that ASBT is more permissive to drug inhibition than NTCP. The clinical significance of this inhibition in drug disposition and drug-drug interaction remains to be determined. Both NCTP and ASBT undergo post-translational regulations that involve phosphorylation/dephosphorylation, translocation to and retrieval from the plasma membrane and degradation by the ubiquitin-proteasome system. These posttranslational regulations are mediated via signaling pathways involving cAMP, calcium, nitric oxide, phosphoinositide-3-kinase (PI3K), protein kinase C (PKC) and protein phosphatases. There appears to be species difference in the substrate specificity and the regulation of plasma membrane localization of human and rodent NTCP. These differences should be taken into account when extrapolating rodent data for human clinical relevance and developing novel therapies. NTCP has recently been shown to play an important role in HBV and HDV infection by serving as a receptor for entry of these viruses into hepatocytes.

The bile acid receptor TGR5 does not interact with β-arrestins or traffic to endosomes but transmits sustained signals from plasma membrane rafts

TGR5 is a G protein-coupled receptor that mediates bile acid (BA) effects on energy balance, inflammation, digestion, and sensation. The mechanisms and spatiotemporal control of TGR5 signaling are poorly understood. We investigated TGR5 signaling and trafficking in transfected HEK293 cells and colonocytes (NCM460) that endogenously express TGR5. BAs (deoxycholic acid (DCA), taurolithocholic acid) and the selective agonists oleanolic acid and 3-(2-chlorophenyl)-N-(4-chlorophenyl)-N, 5-dimethylisoxazole-4-carboxamide stimulated cAMP formation but did not induce TGR5 endocytosis or recruitment of β-arrestins, as assessed by confocal microscopy. DCA, taurolithocholic acid, and oleanolic acid did not stimulate TGR5 association with β-arrestin 1/2 or G protein-coupled receptor kinase (GRK) 2/5/6, as determined by bioluminescence resonance energy transfer. 3-(2-chlorophenyl)-N-(4-chlorophenyl)-N, 5-dimethylisoxazole-4-carboxamide stimulated a low level of TGR5 interaction with β-arrestin 2 and GRK2. DCA induced cAMP formation at the plasma membrane and cytosol, as determined using exchange factor directly regulated by cAMP (Epac2)-based reporters, but cAMP signals did not desensitize. AG1478, an inhibitor of epidermal growth factor receptor tyrosine kinase, the metalloprotease inhibitor batimastat, and methyl-β-cyclodextrin and filipin, which block lipid raft formation, prevented DCA stimulation of ERK1/2. Bioluminescence resonance energy transfer analysis revealed TGR5 and EGFR interactions that were blocked by disruption of lipid rafts. DCA stimulated TGR5 redistribution to plasma membrane microdomains, as localized by immunogold electron microscopy. Thus, TGR5 does not interact with β-arrestins, desensitize, or traffic to endosomes. TGR5 signals from plasma membrane rafts that facilitate EGFR interaction and transactivation. An understanding of the spatiotemporal control of TGR5 signaling provides insights into the actions of BAs and therapeutic TGR5 agonists/antagonists.

Transcriptional regulation of cholesterol and bile acid metabolism after dietary soyabean meal treatment in Atlantic salmon (Salmo salar L.)

Inclusion of plant protein sources such as soyabean meal (SBM) in aquafeeds is associated with decreased lipid digestibility, reduced bile acid levels and hypocholesterolaemia. The mechanism for these metabolic abnormalities is unknown. The present study aimed at gaining further insight into how cholesterol and bile acid metabolism is modulated by SBM feeding by quantifying a number of mRNA species corresponding to key proteins involved in cholesterol and bile acid metabolism using quantitative real-time PCR. A 21 d feeding trial with sequential sampling at ten time points following initiation of 20% SBM exposure was conducted on Atlantic salmon. A histological evaluation confirmed distal intestinal enteritis after 5 d of dietary exposure to the SBM, whereas diminished glycogen/lipid deposition was the only relevant finding observed in the liver. SBM inclusion resulted in reduced body pools of cholesterol and bile acids. Hepatic gene expression profiles revealed up-regulation of genes encoding rate-limiting enzymes in cholesterol (3-hydroxy-3-methyl-glutaryl-CoA reductase; HMGCR) and bile acid (cytochrome P4507A1 (CYP7A1)) biosynthesis, as well as up-regulation of their associated transcription factors (sterol regulatory element binding proteins 1 and 2, liver X receptor, farnesoid X receptor and PPAR isoforms). Hepatic gene expressions of cholesterol (ATP binding cassette G5 (ABCG5)) and bile acid (ATP binding cassette B11 (ABCB11)) transporters were, by and large, not influenced by the SBM, but distal intestinal expression patterns of ABCG5 and apical Na-dependent bile acid transporter indicated impaired cholesterol and bile acid reabsorption. In conclusion, hepatic gene expression profiles indicated that the capacity for cholesterol and bile acid synthesis was up-regulated, whereas the indicated impaired cholesterol and bile acid reabsorption probably occurred as a direct result of distal intestinal inflammation.

The receptor TGR5 mediates the prokinetic actions of intestinal bile acids and is required for normal defecation in mice

BACKGROUND & AIMS

Abnormal delivery of bile acids (BAs) to the colon as a result of disease or therapy causes constipation or diarrhea by unknown mechanisms. The G protein-coupled BA receptor TGR5 (or GPBAR1) is expressed by enteric neurons and endocrine cells, which regulate motility and secretion.

METHODS

We analyzed gastrointestinal and colon transit, as well as defecation frequency and water content, in wild-type, knockout, and transgenic mice (trg5-wt, tgr5-ko, and tgr5-tg, respectively). We analyzed colon tissues for contractility, peristalsis, and transmitter release.

RESULTS

Deoxycholic acid inhibited contractility of colonic longitudinal muscle from tgr5-wt but not tgr5-ko mice. Application of deoxycholic acid, lithocholic acid, or oleanolic acid (a selective agonist of TGR5) to the mucosa of tgr5-wt mice caused oral contraction and caudal relaxation, indicating peristalsis. BAs stimulated release of the peristaltic transmitters 5-hydroxytryptamine and calcitonin gene-related peptide; antagonists of these transmitters suppressed BA-induced peristalsis, consistent with localization of TGR5 to enterochromaffin cells and intrinsic primary afferent neurons. tgr5-ko mice did not undergo peristalsis or transmitter release in response to BAs. Mechanically induced peristalsis and transmitter release were not affected by deletion of tgr5. Whole-gut transit was 1.4-fold slower in tgr5-ko than tgr5-wt or tgr5-tg mice, whereas colonic transit was 2.2-fold faster in tgr5-tg mice. Defecation frequency was reduced 2.6-fold in tgr5-ko and increased 1.4-fold in tgr5-tg mice compared with tgr5-wt mice. Water content in stool was lower (37%) in tgr5-ko than tgr5-tg (58%) or tgr5-wt mice (62%).

CONCLUSIONS

The receptor TGR5 mediates the effects of BAs on colonic motility, and deficiency of TGR5 causes constipation in mice. These findings might mediate the long-known laxative properties of BAs, and TGR5 might be a therapeutic target for digestive diseases.

Motility disorders of the colon and rectum

PURPOSE OF REVIEW

Symptoms associated with disorders of the motility of colon and rectum are common problems in clinical practice. Advances in this field continue to expand our understanding of these disorders and provide new and different treatments with promising results.

RECENT FINDINGS

This article reviews new advances in the past year on the measurement and diagnosis of colonic transit. Recently published data question the importance of dietary fiber in the prevention of colonic diverticulosis and diverticulitis, and support the efficacy of a number of different therapies aimed at improving colonic motility and visceral sensation in constipation and reversing the effects of opioid induced constipation with peripherally acting opioid antagonists.

SUMMARY

The articles referenced in this review help inform the reader on new developments in the diagnosis and management of patients with colonic and rectal motility disorders.

Lack of human tissue-specific correlations for rodent pancreatic and colorectal carcinogens

To better understand the relationships between chemical exposures and human cancer causation, incidence data for human cancer types were identified and pancreatic and colorectal cancers were studied in-depth to assess whether data supporting the causation of pancreatic or colorectal tumors by chemicals in rodents is predictive of causation by the same chemicals of the same tumors in humans. A search of the Carcinogenic Potency Database, the National Toxicology Program (NTP) technical report database, and the published literature identified 38 and 39 chemicals reported to cause pancreatic and colorectal tumors, respectively, in mice or rats. For each of these chemicals, searches were conducted of the International Agency for Research on Cancer monographs, the NTP Report on Carcinogens, and the published literature for evidence of induction of the same tumors in humans. Based on this evaluation, no conclusive evidence was identified to suggest that chemicals reported to cause pancreatic or colorectal tumors in rodents also cause these tumors in humans. These findings suggest that pancreatic tumor data from mouse and rat bioassays are of limited utility with regard to predicting similar tumor induction in humans. For colorectal cancer, a lack of correlation was noted for the vast majority of chemicals.

Chemoprevention of colorectal cancer with ursodeoxycholic acid: cons

Animal and human data suggest a relationship between bile acids, especially secondary bile acids, and colorectal cancer. Ursodeoxycholic acid, a synthetic bile acid, has been shown in animal and in vitro studies to reduce the risk of colonic dysplasia and cancer development. Human trials have focused on patients with history of adenoma, inflammatory bowel disease, primary sclerosing cholangitis, and primary biliary cirrhosis. Some studies suggest that ursodeoxycholic may reduce the colorectal cancer risk, but to date the studies are small, mostly retrospective, and lacking in solid evidence to support use of UDCA for colorectal cancer chemoprophylaxis.

Fibroblast Growth Factor 19 and 7α-Hydroxy-4-Cholesten-3-one in the Diagnosis of Patients With Possible Bile Acid Diarrhea

OBJECTIVES:

Increased colonic bile acids can cause chronic diarrhea. Bile acid diarrhea (BAD) is treatable by sequestrants, and may be secondary to ileal disease or primary BAD. It is underdiagnosed, partly because the selenium-75-homocholic acid taurine (SeHCAT) retention test is not available in many countries, and is underutilized in others. Serum 7α-hydroxy-4-cholesten-3-one (C4), a measure of bile acid synthesis, is available for diagnosis in specialist centers. Recently, deficiency of the ileal hormone fibroblast growth factor 19 (FGF19) has been shown in BAD. Our aim is to evaluate the diagnostic value of FGF19 in a large and prospective group of patients with chronic diarrhea, previously investigated with C4.

METHODS:

Patients undergoing routine investigation provided fasting blood samples. C4 was determined by high-performance liquid chromatography, and used to stratify two groups: group 1 (n=119), consisting of patients with normal C4 (≤ 28 ng/ml), and group 2 (n=139), consisting of patients with high C4 (>28 ng/ml), including any of the possible causes of BAD. Serum FGF19 was measured in stored samples by enzyme-linked immunosorbent assay.

RESULTS:

FGF19 and C4 were significantly inversely related (r_s=−0.64, P<0.001). Patients with raised C4 had significantly lower median FGF19 values. Both of these were more marked when secondary to ileal disease, in particular ileal resection, than in primary BAD. The sensitivity and specificity of FGF19 at 145 pg/ml for detecting a C4 level >28 ng/ml were 58% and 79%, respectively. For C4 >60 ng/ml, these were 74% and 72% on receiver-operating characteristic analysis, the area under the curve was 0.80 (95% confidence interval 0.74–0.87).

CONCLUSIONS:

Serum FGF19 could be developed as a simple blood test to increase the diagnostic rates of BAD.

Bile acids: from digestion to cancers

Bile acids (BAs) are cholesterol metabolites that have been extensively studied these last decades. BAs have been classified in two groups. Primary BAs are synthesized in liver, when secondary BAs are produced by intestinal bacteria. Recently, next to their ancestral roles in digestion and fat solubilization, BAs have been described as signaling molecules involved in many physiological functions, such as glucose and energy metabolisms. These signaling pathways involve the activation of the nuclear receptor FXRα or of the G-protein-coupled receptor TGR5. These two receptors have selective affinity to different types of BAs and show different expression patterns, leading to different described roles of BAs. It has been suggested for long that BAs could be molecules linked to tumor processes. Indeed, as many other molecules, regarding analyzed tissues, BAs could have either protective or pro-carcinogen activities. However, the molecular mechanisms responsible for these effects have not been characterized yet. It involves either chemical properties or their capacities to activate their specific receptors FXRα or TGR5. This review highlights and discusses the potential links between BAs and cancer diseases and the perspectives of using BAs as potential therapeutic targets in several pathologies.

Increase in fecal primary bile acids and dysbiosis in patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a multifactorial disease for which a dysbiosis of the gut microbiota has been described. Bile acids (BA) could play a role as they are endogenous laxatives and are metabolized by gut microbiota. We compared fecal BA profiles and microbiota in healthy subjects (HS) and patients with diarrhea-predominant IBS (IBS-D), and we searched for an association with symptoms.

METHODS

Clinical features and stool samples were collected in IBS-D patients and HS. Fecal BA profiles were generated using HPLC coupled to tandem mass spectrometry. The fecal microbiota composition was assessed by q-PCR targeting dominant bacterial groups and species implicated in BA transformation.

KEY RESULTS

Fourteen IBS-D patients and 18 HS were included. The two groups were comparable in terms of age and sex. The percentage of fecal primary BA was significantly higher in IBS-D patients than in HS, and it was significantly correlated with stool consistency and frequency. Fecal counts of all bacteria, lactobacillus, coccoides, leptum and Faecalibacterium prausnitzii were similar. There was a significant increase of Escherichia coli and a significant decrease of leptum and bifidobacterium in IBS-D patients.

CONCLUSIONS & INFERENCES

We report an increase of primary BA in the feces of IBS-D patients compared to HS, correlated with stool consistency and frequency. A dysbiosis of different bacterial groups was detected, some of them involved in BA transformation. As the gut microbiota is the exclusive pathway to transform primary into secondary BA, this suggests a functional consequence of dysbiosis, leading to lower BA transformation.

Functional analysis of colonic bacterial metabolism: relevant to health?

With the use of molecular techniques, numerous studies have evaluated the composition of the intestinal microbiota in health and disease. However, it is of major interest to supplement this with a functional analysis of the microbiota. In this review, the different approaches that have been used to characterize microbial metabolites, yielding information on the functional end products of microbial metabolism, have been summarized. To analyze colonic microbial metabolites, the most conventional way is by application of a hypothesis-driven targeted approach, through quantification of selected metabolites from carbohydrate (e.g., short-chain fatty acids) and protein fermentation (e.g., p-cresol, phenol, ammonia, or H(2)S), secondary bile acids, or colonic enzymes. The application of stable isotope-labeled substrates can provide an elegant solution to study these metabolic pathways in vivo. On the other hand, a top-down approach can be followed by applying metabolite fingerprinting techniques based on (1)H-NMR or mass spectrometric analysis. Quantification of known metabolites and characterization of metabolite patterns in urine, breath, plasma, and fecal samples can reveal new pathways and give insight into physiological regulatory processes of the colonic microbiota. In addition, specific metabolic profiles can function as a diagnostic tool for the identification of several gastrointestinal diseases, such as ulcerative colitis and Crohn's disease. Nevertheless, future research will have to evaluate the relevance of associations between metabolites and different disease states.

Effects of A3309, an ileal bile acid transporter inhibitor, on colonic transit and symptoms in females with functional constipation

OBJECTIVES

Delivery of bile acid (BA) to the colon stimulates propulsive motility and fluid secretion. The objective of this study was to examine gastrointestinal (GI) transit effects of A3309, a small molecule inhibitor of the ileal BA transporter, in patients with functional constipation (FC).

METHODS

In a double-blind, placebo-controlled study of 36 female FC patients randomized to placebo, 15 mg A3309, or 20 mg A3309 administered orally once daily for 14 consecutive days, we assessed GI and colonic transit, stool characteristics, symptoms of constipation, fasting serum C4 (7α-hydroxy-4-cholesten-3-one) (surrogate of BA synthesis and malabsorption), and fasting serum total and low-density lipoprotein (LDL) cholesterol (surrogates of inhibition of BA absorption). Following the intention-to-treat paradigm, we used analysis of covariance to assess the overall treatment effects and Dunnett's test for pairwise comparisons.

RESULTS

Overall colonic transit (geometric center at 24 h) was significantly accelerated with 20 mg A3309 compared with placebo (overall effect, P=0.059; A3309 15 mg, P=0.18; and A3309 20 mg, P=0.04). Colonic transit at 48 h was significantly accelerated with both A3309 dosages (overall effect, P<0.001; A3309 15 mg, P=0.002; and A3309 20 mg, P<0.001). Significantly looser stool consistency was noted with both A3309 dosages compared with placebo (P<0.005). Significant effects of A3309 on constipation rating, ease of stool passage, and reduction of straining were also detected. The most common side effect was lower abdominal cramping/pain. A3309 treatment significantly and reversibly increased fasting C4 (A3309 15 mg, P=0.05; A3309 20 mg, P<0.01) but did not affect fasting total and LDL cholesterol.

CONCLUSIONS

A3309 accelerates colonic transit and loosens stool consistency in FC patients.

Transport across Caco-2 cell monolayer and sensitivity to hydrolysis of two anxiolytic peptides from αs1-casein, α-casozepine, and αs1-casein-f91-97: effect of bile salts

α-Casozepine and f91-97, peptides from α(s1)-casein, display anxiolytic activity in rats and may have to cross the intestinal epithelium to exert this central effect. We evaluated their resistance to hydrolysis by the peptidases of Caco-2 cells and their ability to cross the cell monolayer. To mimic physiological conditions, two preparations of bile salts were used in noncytotoxic concentrations: porcine bile extract and an equimolar mixture of taurocholate, cholate, and deoxycholate. The presence and composition of bile salts appeared to modulate the peptidase activities of the Caco-2 cells involved (i) in the hydrolysis of α-casozepine, leading to much higher formation of fragments f91-99, f91-98, and f91-97, and (ii) in the hydrolysis of f91-97, leading to lower degradation of this peptide. Transport of α-casozepine across Caco-2 monolayer increased significantly, in the presence of bile extract, and of fragment f91-97, in the presence of bile salts.

Association of bile acid receptor TGR5 variation and transit in health and lower functional gastrointestinal disorders

BACKGROUND

The membrane bound bile acid (BA) receptor, TGR5, is located on myenteric, cholinergic and nitrergic neurons in colon and proximal small intestine. Our aim was to assess the association of genetic variation in TGR5 and small bowel transit (SBT) and colonic transit.

METHODS

In 230 healthy controls and 414 patients with lower functional GI disorders [FGID: irritable bowel syndrome (IBS)-alternators (Alt) 84, IBS-constipation (IBS-C) 157, IBS-diarrhea (IBS-D) 173], we tested the association between TGR5 SNP rs11554825 (minor allele frequency 41%) with symptom phenotype (total cohort) and intermediate phenotype (SBT or colonic transit by radioscintigraphy) which was available in 213 people in this cohort. The association with symptom phenotype was assessed using logistic regression, while the association with colonic filling at 6 h (CF6), and colonic transit [geometric center (GC) at 24 h] was assessed using ancova, in each instance assuming a dominant genetic model.

KEY RESULTS

There was no significant association with symptom phenotype. We observed a potential association of SNP rs11554825 with overall transit: CF6 (P = 0.061) and GC24 (P = 0.083). The association of the SNP with CF6 in the IBS-D subgroup (P = 0.017) indicated the TC/CC subgroup had an average 50% faster SBT compared with the TT subgroup. In IBS-D patients, GC24 was not significantly associated with rs11554825 (TC/CC vs TT).

CONCLUSIONS & INFERENCES

Variation in TGR5 may contribute to altered SBT and colonic transit in lower FGID. Further studies are required to characterize the potential role of BA receptor, TGR5, in the mechanism and treatment of bowel dysfunction in lower FGID.

A combination of calcium phosphate and probiotics beneficially influences intestinal lactobacilli and cholesterol metabolism in humans

BACKGROUND & AIMS

The study focuses on the influence of a probiotic supplement alone and in combination with a calcium supplement on faecal lactobacilli colonisation and beneficial health effects such as a lowering of blood cholesterol.

METHODS

Thirty-two men and women participated in the double-blind, placebo-controlled, cross-over study. All participants consumed a probiotic drink containing 10(10)CFU/d Lactobacillus paracasei (LPC37) for four weeks. In addition, one group consumed bread enriched with pentacalcium hydroxy-triphosphate (CaP; 1g Ca/d) and the other group had bread without CaP. After a two-week washout and a two-week placebo period, the intervention was switched for further four weeks.

RESULTS

After intervention with LPC37+CaP, total cholesterol and LDL-cholesterol concentration in plasma decreased significantly compared to LPC37 and placebo. The faecal concentration of L. paracasei and that of all lactobacilli increased significantly after LPC37+CaP and LPC37 compared to placebo. Moreover, secondary bile acids in faeces increased significantly after LPC37+CaP intervention compared to placebo.

CONCLUSIONS

CaP modulates the colonisation of LPC37 in the human gut under combinatory supplementation of CaP and LPC37. The combined supplementation also decreases plasma LDL-cholesterol and the LDL/HDL ratio in healthy, moderately hypercholesterolemic men and women, which could be also due to the CaP supplementation.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01033461.

A randomized placebo-controlled phase IIb trial of a3309, a bile acid transporter inhibitor, for chronic idiopathic constipation

OBJECTIVES

A3309 is a minimally absorbed ileal bile acid (BA) transporter (IBAT) inhibitor. We conducted an 8-week, multicenter, randomized, double-blind, placebo-controlled, parallel group, phase IIb study, which evaluated A3309 in patients with chronic idiopathic constipation (CIC).

METHODS

Patients with CIC (modified Rome III criteria and <3 complete (CSBM) spontaneous bowel movements (SBMs)/week during the 2-week baseline) were randomized to 5, 10, or 15 mg A3309 or placebo once daily. The primary end point was change in SBM number during week 1 compared with baseline. Other bowel and abdominal symptoms were assessed as secondary end points. Serum 7αC4 and lipids were evaluated as biomarkers of BA synthesis/loss.

RESULTS

In all, 190 patients (mean 48 years, 90% female) were randomized. Mean increase (95% confidence interval) in SBM for week 1 were 1.7 (0.7-2.8) for placebo vs. 2.5 (1.5-3.5), 4.0 (2.9-5.0), and 5.4 (4.4-6.4) for 5 mg, 10 mg (P<0.002), and 15 mg (P<0.001) A3309, respectively. Increased stool frequency was maintained over 8 weeks. Time to first SBM and CSBM were significantly reduced in the 10- and 15-mg A3309 groups compared with placebo. Straining and bloating decreased with A3309 compared with placebo (P<0.05). Increased 7αC4 and reduced low-density lipoprotein cholesterol with A3309 suggested increased BA synthesis and BA loss. The most common adverse events (AEs) were abdominal pain and diarrhea, which occurred most commonly in the 15-mg A3309 group. No drug-related serious AEs were observed.

CONCLUSIONS

A3309 increased stool frequency and improved constipation-related symptoms in CIC; effects were maintained over 8 weeks of treatment.

Metabolomics reveals phospholipids as important nutrient sources during Salmonella growth in bile in vitro and in vivo

During the colonization of hosts, bacterial pathogens are presented with many challenges that must be overcome for colonization to occur successfully. This requires the bacterial sensing of the surroundings and adaptation to the conditions encountered. One of the major impediments to the pathogen colonization of the mammalian gastrointestinal tract is the antibacterial action of bile. Salmonella enterica serovar Typhimurium has specific mechanisms involved in resistance to bile. Additionally, Salmonella can successfully multiply in bile, using it as a source of nutrients. This accomplishment is highly relevant to pathogenesis, as Salmonella colonizes the gallbladder of hosts, where it can be carried asymptomatically and promote further host spread and transmission. To gain insights into the mechanisms used by Salmonella to grow in bile, we studied the changes elicited by Salmonella in the chemical composition of bile during growth in vitro and in vivo through a metabolomics approach. Our data suggest that phospholipids are an important source of carbon and energy for Salmonella during growth in the laboratory as well as during gallbladder infections of mice. Further studies in this area will generate a better understanding of how Salmonella exploits this generally hostile environment for its own benefit.

Bile acids and colon cancer: Solving the puzzle with nuclear receptors

Colorectal cancer is the third most common malignancy worldwide and is often linked to obesity, a sedentary lifestyle, carbohydrate- and fat-rich diets and elevated fecal excretion of secondary bile acids. Accumulation of toxic bile acids triggers oxidative damage, mitochondrial dysfunction and tumor progression. Nuclear receptors are transcription factors crucially involved in the regulation of bile acid metabolism and detoxification, and their activation may confer protection from bile acid tumor-promoting activity. In this review, we explore the tangled relationships among bile acids, nuclear receptors and the intestinal epithelium, with particular emphasis on the role of the farnesoid X receptor in colorectal cancer prevention and on novel nuclear receptor-based approaches to expand the portfolio of chemotherapeutic agents.

Randomised clinical trial: The ileal bile acid transporter inhibitor A3309 vs. placebo in patients with chronic idiopathic constipation--a double-blind study

BACKGROUND

One half of patients with constipation are not satisfied with available therapies, hence there is a need for more effective and well-tolerated drugs.

AIM

To evaluate the effects of a specific inhibitor of the Ileal Bile Acid Transporter (IBAT; syn apical sodium-dependent bile acid transporter; ASBT) in patients with chronic idiopathic constipation (CIC) with focus on safety, colonic transit and efficacy signals.

METHODS

This was a single-centre, prospective, randomised, double-blind, placebo-controlled study with a dose-escalating design in patients with CIC. In addition to evaluation of conventional safety and tolerability parameters, (i) colonic transit time (CTT) was measured using radio-opaque markers, (ii) metabolic parameters [lipid profile, C4 (7α-hydroxy-4-cholesten-3-one) and FGF19 (Fibroblast Growth Factor 19)] were evaluated, and (iii) constipation parameters, such as changes in stool frequency and consistency, were analysed.

RESULTS

Thirty patients were randomised into five dose-levels (range: 0.1-10 mg/day) or to placebo. All patients completed a 14-day treatment period, and the safety/tolerability analysis was favourable. A3309, present in picomolar concentrations in plasma, induced up to a three-fold increase in bile acid synthesis (C4) and a reduction of plasma FGF19, as well as reduction in total and LDL cholesterol. CTT was reduced in the highest dose groups; the main acceleration was identified in the left colon. Efficacy parameters showed trends for increased number of spontaneous bowel movements and improved stool consistency.

CONCLUSIONS

Ileal Bile Acid Transporter inhibition is a novel mechanism for treatment of patients with chronic idiopathic constipation and has additional benefits of improving metabolic parameters (EudraCT 2008-003255-72).

Emerging pharmacological therapies for the irritable bowel syndrome

The irritable bowel syndrome (IBS) is a symptom-based disorder defined by the presence of abdominal pain and altered bowel habits. Clinical presentations of IBS are diverse, with some patients reporting diarrhea, some constipation, and others a mixture of both. Like the varied clinical phenotypes, the pathogenesis of IBS is also diverse. IBS is not a single disease entity, but rather likely consists of several different disease states. This fact has important implications for the choices and efficacy of IBS treatment. This article reviews the IBS drugs that have reached phase II or III clinical trials.