Enterohepatic cycling of bilirubin as a cause of 'black' pigment gallstones in adult life

Role of Natural Compounds Modulating Heme Catabolic Pathway in Gut, Liver, Cardiovascular, and Brain Diseases

The crucial physiological process of heme breakdown yields biliverdin (BV) and bilirubin (BR) as byproducts. BV, BR, and the enzymes involved in their production (the "yellow players-YP") are increasingly documented as endogenous modulators of human health. Mildly elevated serum bilirubin concentration has been correlated with a reduced risk of multiple chronic pro-oxidant and pro-inflammatory diseases, especially in the elderly. BR and BV per se have been demonstrated to protect against neurodegenerative diseases, in which heme oxygenase (HMOX), the main enzyme in the production of pigments, is almost always altered. HMOX upregulation has been interpreted as a tentative defense against the ongoing pathologic mechanisms. With the demonstration that multiple cells possess YP, their propensity to be modulated, and their broad spectrum of activity on multiple signaling pathways, the YP have assumed the role of an adjustable system that can promote health in adults. Based on that, there is an ongoing effort to induce their activity as a therapeutic option, and natural compounds are an attractive alternative to the goal, possibly requiring only minimal changes in the life style. We review the most recent evidence of the potential of natural compounds in targeting the YP in the context of the most common pathologic condition of adult and elderly life.

Evidence-based clinical practice guidelines for cholelithiasis 2021

The Japanese Society of Gastroenterology first published evidence-based clinical practice guidelines for cholelithiasis in 2010, followed by a revision in 2016. Currently, the revised third edition was published to reflect recent evidence on the diagnosis, treatment, and prognosis of cholelithiasis conforming to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. Following this revision, the present English version of the guidelines was updated and published herein. The clinical questions (CQ) in the previous version were reviewed and rearranged into three newly divided categories: background questions (BQ) dealing with basic background knowledge, CQ, and future research questions (FRQ), which refer to issues that require further accumulation of evidence. Finally, 52 questions (29 BQs, 19 CQs, and 4 FRQs) were adopted to cover the epidemiology, pathogenesis, diagnosis, treatment, complications, and prognosis. Based on a literature search using MEDLINE, Cochrane Library, and Igaku Chuo Zasshi databases for the period between 1983 and August 2019, along with a manual search of new information reported over the past 5 years, the level of evidence was evaluated for each CQ. The strengths of recommendations were determined using the Delphi method by the committee members considering the body of evidence, including benefits and harms, patient preference, and cost-benefit balance. A comprehensive flowchart was prepared for the diagnosis and treatment of gallbladder stones, common bile duct stones, and intrahepatic stones, respectively. The current revised guidelines are expected to be of great assistance to gastroenterologists and general physicians in making decisions on contemporary clinical management for cholelithiasis patients.

Hepatobiliary Impairments in Patients with Inflammatory Bowel Diseases: The Current Approach

Inflammatory bowel disease (IBD) refers to chronic conditions with a low mortality but high disability. The multisystemic nature of these diseases can explain the appearance of some extraintestinal manifestations, including liver damage. Abnormal liver biochemical tests can be identified in approximately one third of patients with IBD and chronic liver disease in 5% of them. Among the liver diseases associated with IBD are primary sclerosing cholangitis, cholelithiasis, fatty liver disease, hepatic amyloidosis, granulomatous hepatitis, drug-induced liver injury, venous thromboembolism, primary biliary cholangitis, IgG4-related cholangiopathy, autoimmune hepatitis, liver abscesses or the reactivation of viral hepatitis. The most common disease is primary sclerosing cholangitis, a condition diagnosed especially in patients with ulcerative colitis. The progress registered in recent years in the therapeutic management of IBD has not eliminated the risk of drug-induced liver disease. Additionally, the immunosuppression encountered in these patients increases the risk of opportunistic infections, including the reactivation of viral hepatitis. Currently, one of the concerns consists of establishing an efficiency and safety profile of the use of direct-acting antiviral agents (DAA) among patients with hepatitis C and IBD. Early diagnosis and optimal treatment of liver complications can improve the prognoses of these patients.

Role of ursodeoxycholic acid in neonatal indirect hyperbilirubinemia: a systematic review and meta-analysis of randomized controlled trials

Background

Neonatal jaundice is a transitional phenomenon affecting three out of five full-term newborns globally. Ursodeoxycholic acid could be beneficial in neonatal jaundice needing phototherapy. 

Methods

We searched PubMed, EBSCO, ProQuest, and Cochrane Library up to August 21^st, 2021, for articles to be reviewed. Meta-analysis using random-effects model was performed.

Results

Eight studies involving 1116 neonates were chosen in this review; however, only five studies were included for meta-analysis. Phototherapy duration was significantly lower in the interventional group with high heterogeneities. Subgroup analysis of the phototherapy duration based on the risk of bias resulted in a shorter duration (mean difference (MD) = –17.82; 95% CI = –20.17 to –15.47; p =  < 0.001) with low heterogeneity in the treatment group. Secondary outcome focusing on mean total serum bilirubin showed a lower mean total serum bilirubin in 48 h post-treatment (MD = –0.43; 95% CI = –0.64 to –0.22; p =  < 0.0001) with low heterogeneities in Asian countries.”

Conclusions

Ursodeoxycholic acid might be considered as a novel adjuvant therapy in neonatal indirect hyperbilirubinemia to shorten the phototherapy duration and lower the mean total serum bilirubin.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13052-022-01372-w.

The value of bacterial metagenomic analysis in post-surgical examination of gallstones

Gallstone disease is one of the most common causes of hospitalization for gastrointestinal diseases in the world. Recent studies have examined the presence of bacteria in the formation of stones. Our main goal was to determine the overall composition of gallstone microflora. Gallstones were obtained from 24 patients during laparoscopic cholecystectomy from which DNA were extracted. Composition of bacterial flora was evaluated on 16 s rDNA sequencing technique. In the vast majority of samples, bacteria were present, and four groups could be differentiated regarding the flora. Overall composition shows that 87% of the stones were cholesterol/mixed type of gallstone. Additionally, potentially harmful microorganisms (Streptococcus, Clostridium and Kocuria) that could cause post-surgery complications were identified in several patients. The obtained results indicate that this technique may be useful in analyzing the type of stones and in pinpointing the presence of pathogenic bacteria.

Management of Gallstones and Acute Cholecystitis in Patients with Liver Cirrhosis: What Should We Consider When Performing Surgery?

Acute cholecystitis and several gallbladder stone-related conditions, such as impacted common bile duct stones, cholangitis, and biliary pancreatitis, are common medical conditions in daily practice. An early cholecystectomy or drainage procedure with delayed cholecystectomy is the current standard of treatment based on published clinical guidelines. Cirrhosis is not only a condition of chronically impaired hepatic function but also has systemic effects in patients. In cirrhotic individuals, several predisposing factors, including changes in the bile acid composition, increased nucleation of bile, and decreased motility of the gallbladder, contribute to the formation of biliary stones and the possibility of symptomatic cholelithiasis, which is an indication for surgical treatment. In addition to these predisposing factors for cholelithiasis, systemic effects and local anatomic consequences related to cirrhosis lead to anesthesiologic risks and perioperative complications in cirrhotic patients. Therefore, the treatment of the aforementioned biliary conditions in cirrhotic patients has become a challenging issue. In this review, we focus on cholecystectomy for cirrhotic patients and summarize the surgical indications, risk stratification, surgical procedures, and surgical outcomes specific to cirrhotic patients with symptomatic cholelithiasis.

Critical roles of bile acids in regulating intestinal mucosal immune responses

Bile acids are a class of cholesterol derivatives that have been known for a long time for their critical roles in facilitating the digestion and absorption of lipid from the daily diet. The transformation of primary bile acids produced by the liver to secondary bile acids appears under the action of microbiota in the intestine, greatly expanding the molecular diversity of the intestinal environment. With the discovery of several new receptors of bile acids and signaling pathways, bile acids are considered as a family of important metabolites that play pleiotropic roles in regulating many aspects of human overall health, especially in the maintenance of the microbiota homeostasis and the balance of the mucosal immune system in the intestine. Accordingly, disruption of the process involved in the metabolism or circulation of bile acids is implicated in many disorders that mainly affect the intestine, such as inflammatory bowel disease and colon cancer. In this review, we discuss the different metabolism profiles in diseases associated with the intestinal mucosa and the diverse roles of bile acids in regulating the intestinal immune system. Furthermore, we also summarize recent advances in the field of new drugs that target bile acid signaling and highlight the importance of bile acids as a new target for disease intervention.

Unconjugated Bilirubin Attenuates DSS-Induced Colitis Potentially via Enhancement of Bilirubin Reabsorption

Studies increasingly show that ulcerative colitis (UC) is a consequence of an imbalance between oxidative stress and antioxidant capacity. Bilirubin exerts an anti-inflammatory effect by scavenging reactive oxygen species (ROS), although the exact mechanism is not completely understood. The aim of this study was to determine the role of serum bilirubin in UC using patient data and a mouse model of dextran sodium sulfate (DSS)-induced colitis. We found that low levels of serum bilirubin correlated to a higher risk of UC in a retrospective case-control population. Pre-treatment with exogenous unconjugated bilirubin (UCB) significantly enhanced colonic bilirubin absorption in mice, and attenuated the DSS-induced body weight loss, colon shortening and histopathological damage. Mechanistically, bilirubin prevented the infiltration of inflammatory cells, and decreased the levels of myeloperoxidase and pro-inflammatory cytokines in the serum and colon. Moreover, bilirubin inhibited ROS and malondialdehyde production, scavenged superoxide anions (O₂^·−) from the colon and enhanced the total antioxidant capacity. In conclusion, exogenous UCB attenuated DSS-induced colitis by directly scavenging O₂^·− and enhancing bilirubin reabsorption in the colon via enterohepatic cycling.

Nutritional and pharmacological strategy in children with short bowel syndrome

Short bowel syndrome in neonates is a severe and life-threatening disease after a major loss of small bowel with or without large bowel. Intestinal adaptation, by which the organism tries to restore digestive and absorptive capacities, is entirely dependent on stimulation of the active enterocytes by enteral nutrition. This review summarizes recent knowledge about the pathophysiologic consequences after the loss of different intestinal parts and outlines the options for enteral nutrition and pharmacological therapies to support the adaptation process.

Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn

Bilirubin is the end product of heme catabolism formed during a process that involves oxidation-reduction reactions and conserves iron body stores. Unconjugated hyperbilirubinemia is common in newborn infants, but rare later in life. The basic physiology of bilirubin metabolism, such as production, transport, and excretion, has been well described. However, in the neonate, numerous variables related to nutrition, ethnicity, and genetic variants at several metabolic steps may be superimposed on the normal physiological hyperbilirubinemia that occurs in the first week of life and results in bilirubin levels that may be toxic to the brain. Bilirubin exists in several isomeric forms that differ in their polarities and is considered a physiologically important antioxidant. Here we review the chemistry of the bilirubin molecule and its metabolism in the body with a particular focus on the processes that impact the newborn infant, and how differences relative to older children and adults contribute to the risk of developing both acute and long-term neurological sequelae in the newborn infant. The final section deals with the interplay between the brain and bilirubin and its entry, clearance, and accumulation. We conclude with a discussion of the current state of knowledge regarding the mechanism(s) of bilirubin neurotoxicity.

Tests that now deserve to be more widely adopted in IBD clinical practice

Inflammatory bowel diseases are chronic relapsing immune-mediated diseases of the intestinal tract with multifaceted manifestations and treatment related morbidity. Faecal and blood tests, radiological, endoscopic and histologic investigations are now widely used for managing both ulcerative colitis and Crohn's disease. Over the years, a number of new investigations have been proposed but not widely adopted yet. Patients with Crohn's disease may have multiple causes of diarrhoea, not always attributable to disease exacerbation, but sometimes linked to bile acid malabsorption; we have a reliable serum test, C4, that allows us to recognize and treat this cause of diarrhoea efficaciously and not empirically, but it is not available or used widely. There is genetic inter-individual variability in drug responses, in terms of both efficacy and toxicity, leading to high rates of therapeutic failure. Patients treated with thiopurine or, more rarely, 5-aminosalicylic acid may suffer from unpredictable and serious adverse events, some of these with pathogenesis related to genetic variants: myelosuppression, acute pancreatitis and nephrotoxicity. The identification of pre-treatment genetic tests can optimize therapeutic choice and avoid adverse events. With regard to biological drugs, patients can experience primary non-response or loss of response due to induction of immune responses to the drugs affecting drug efficacy and determining hypersensitivity reactions. We have specifically reviewed a number of investigations, whose use is currently limited, and highlighted four tests that deserve to be more widely incorporated in clinical practice as these could improve medical decision-making and patient outcomes.

Pathophysiology and risk factors for cholelithiasis in patients with Crohn's disease

Cholelithiasis is more common in patients with Crohn's disease (CD) than in the healthy population. The aim here was to examine risk factors for cholelithiasis in a cohort of CD patients and to compare the prevalence of cholelithiasis in a cohort of CD patients with that in a control group. This was a single-center retrospective case-control study. The cohort comprised all consecutive CD patients who underwent abdominal ultrasound from January 2007 to January 2018. The control group comprised age- and gender-matched non-CD patients referred for upper gastrointestinal tract dyspepsia. The study included 238 CD patients and 238 controls. The prevalence of cholelithiasis in the CD and control groups was 12.6 % and 9.2 %, respectively (risk ratio (RR), 1.36; p=0.24). Univariate analysis revealed that cholelithiasis was associated with multiple risk factors. Multivariate analysis identified age (OR, 1.077; 95 % CI, 1.043-1.112; p<0.001) and receipt of parenteral nutrition (OR, 1.812; 95 % CI, 1.131-2.903; p=0.013) as independent risk factors for cholelithiasis in CD patients. The prevalence of cholelithiasis in CD patients was higher than that in the control group; however, the difference was not statistically significant. Age and receipt of parenteral nutrition were independent risk factors for cholelithiasis in CD patients.

Mechanism of Dyslipidemia in Obesity-Unique Regulation of Ileal Villus Cell Brush Border Membrane Sodium-Bile Acid Cotransport

In obesity, increased absorption of dietary fat contributes to altered lipid homeostasis. In turn, dyslipidemia of obesity leads to many of the complications of obesity. Bile acids are necessary for the absorption of dietary fat. In the mammalian intestine, apical sodium-dependent bile acid cotransporter (ASBT; SLC10A2) is exclusively responsible for the reabsorption of bile acids in the terminal ileum. In rat and mice models of obesity and importantly in obese humans, ASBT was increased in ileal villus cells. The mechanism of stimulation of ASBT was secondary to an increase in ASBT expression in villus cell brush border membrane. The stimulation of ASBT was not secondary to the altered Na-extruding capacity of villus cells during obesity. Further, increased Farnesoid X receptor (FXR) expression in villus cells during obesity likely mediated the increase in ASBT. Moreover, enhanced FXR expression increased the expression of bile-acid-associated proteins (IBABP and OSTα) that are responsible for handling bile acids absorbed via ASBT in villus cells during obesity. Thus, this study demonstrated that in an epidemic condition, obesity, the dyslipidemia that leads to many of the complications of the condition, may, at least in part, be due to deregulation of intestinal bile acid absorption.

Incidence and Risk of Gallstone Disease in Gilbert's Syndrome Patients in Indian Population

BACKGROUND/OBJECTIVES

Individuals with Gilbert's syndrome (GS) harbor mutations in the UGT1A1 gene and are known to have elevated levels of bilirubin, which enhances the risk for gall stone formation. The aim of this study is to screen Indian patients with GS for the incidence of gall stone disease.

METHODS

Individuals with persistently elevated serum bilirubin levels were genotyped for two polymorphisms (rs8175347; rs4148323) in UGT1A1 gene to confirm GS in them. Flanking regions of the above polymorphisms were amplified followed by direct sequencing. Ultrasonography was done to detect gallstone disease. Clinical data, including assessment of liver function, circulating levels of total and direct bilirubin, as well as routine hematological parameters were obtained as per standard procedures (Autoanalyzer).

RESULTS

Of the total 1621 individuals subjected to genotyping, 1191 (1149 males of 29.6 ± 11.3 years with mean BMI of 22.1 ± 3.7 kg/m² and 42 females of 30.8 ± 14.8 years with mean BMI of 20.9 ± 3.7 kg/m²) were confirmed to have GS. Gall bladder abnormalities including cholelithiasis (n = 106/1191; 8.9%), polyps (n = 18/1191; 1.5%) and gallbladder wall thickening (n = 17/1191; 1.4%) were noted. Incidence of gall stone disease was observed in 103 males (out of 1149) and 3 females (out of 42) indicating the risk of the disease to be 9.0% and 7.1% respectively in males and females with GS.

CONCLUSION

Early recognition of GS by genetic analysis is required before these patients with intermittent episodes of jaundice run the risk of unnecessary operations on their bile ducts from the mistaken assumption ascribing the jaundice to a stone which has been left behind.

Role of the biliary microbiome in gallstone disease

Gallstone disease is caused by multiple pathogenic factors and is common worldwide. Most studies have focused on the significance of the biliary microbiome in gallstone pathogenesis. Areas covered: In this study, the epidemiology of gallstone diseases and the existence, composition, origin, and mechanisms of the biliary microbiota were reviewed. Mechanisms involved in promoting the formation of different types of gallstones were also emphasized. The antibiotic susceptibility of the biliary microbiota is briefly discussed because it may guide clinical strategies. Expert commentary: The biliary microbiome facilitates the formation of brown pigment stones. Although glycoprotein (mucin) may be pivotal for many promoting substances to coagulate and integrate relevant components, new mechanisms involving prostaglandins, oxysterols, oxygen free radicals, and lipopolysaccharides have been discovered. Furthermore, specific bacterial species such as Helicobacter and Salmonella are involved in the pathogenesis of cholesterol gallstones. Recently, metabolomics of the biliary microbiome has been used to determine the detailed mechanisms that promote gallstone formation. Previously, the bacterial effects involved in the pathogenesis of brown pigment stones have not been analyzed in detail. Whether the administration of antibiotics is related to prophylaxis for gallstone formation and gallstone-associated infections remains unclear.

Association between Hashimoto's thyroiditis and cholelithiasis: a retrospective cohort study in Taiwan

OBJECTIVE

To investigate the relation of Hashimoto's thyroiditis (HT) to cholelithiasis and cholecystectomy in a retrospective population-based study.

SETTING

Cohort study.

PARTICIPANTS

We identified 1268 patients aged ≥20 years with HT between 2000 and 2010 as the study cohort.

PRIMARY AND SECONDARY OUTCOME MEASURES

Patients without HT were randomly selected from a database and propensity-matched with the study cohort at a 1:4 ratio according to age, sex, comorbidities and year of the index date to measure the incidence of cholelithiasis and cholecystectomy.

RESULTS

The cumulative incidence of cholelithiasis was higher in the HT cohort than that in the non-HT cohort (log-rank test, p<0.001), with a 1.91-fold higher risk of choleithiasis (95% CI 1.58 to 2.33) after adjustment for comorbidities. The age-specific relative risk of cholelithiasis in the HT cohort was higher than that in the non-HT cohort for patients aged ≥50 years (adjusted HR (aHR)=2.59, 95% CI 1.33 to 5.03). The sex-specific relative risk of cholelithiasis in the HT cohort was higher than that in the non-HT cohort for women (aHR=1.99, 95% CI 1.63 to 2.44). Compared with those in the non-HT cohort, patients with HT without (aHR=1.95, 95% CI 1.53 to 2.49) and with (aHR=1.94, 95% CI 1.51 to 2.49) thyroxine treatment were associated with a higher risk of cholelithiasis. Compared with those in the non-HT cohort, patients with HT had a higher risk of cholecystectomy (aHR=1.28, 95% CI 1.02 to 1.61).

CONCLUSIONS

Inability to obtain information on several potential confounding factors and misclassification of important covariates are the major limitations of the study. Our study indicates HT per se was associated with the development of cholelithiasis, which has been validated by the association between cholecystectomy and HT. Surveys and health education on cholelithiasis in women aged ≥50 years with HT should be considered by clinicians, and further prospective research should be done on this topic.

Association between Inflammatory Bowel Disease and Cholelithiasis: A Nationwide Population-Based Cohort Study

We assessed the subsequent risk of cholelithiasis development in patients with inflammatory bowel diseases (IBDs) such as Crohn’s disease (CD) or ulcerative colitis (UC). We identified 8186 patients who aged ≥20 years and were diagnosed with IBD between 2000 and 2010 as the study cohort. A total of 8186 patients without IBD were selected by frequency-matching according to age, sex, comorbidities, and the index date of diagnosis, and they were identified as the control cohort. To measure the incidence of cholelithiasis, all patients were followed up until the end of 2011. The risk of developing cholelithiasis, either gallbladder stone disease (GSD; adjusted hazard ratio (aHR) = 1.76, 95% CI = 1.34–2.61) or common bile duct (CBD) stones and intrahepatic stones (IHSs; aHR = 2.78, 95% CI = 1.18–6.51), was higher for the CD cohort than for the non-IBD cohort after adjusting for age, sex, and comorbidities of hyperlipidemia, diabetes, liver cirrhosis, hypertension, chronic obstructive pulmonary disease, stroke, coronary artery disease, and hepatitis C virus infection. However, UC was related to the development of GSD (aHR = 1.44, 95% CI = 1.19–1.75) but not to CBD stones and IHSs (aHR = 1.70, 95% CI = 0.99–2.91). Our population-based cohort study demonstrated that CD is related to the development of cholelithiasis, including GSD alone and non-GSD-associated cholelithiasis. However, UC is only related to the development of GSD alone.

Risk Factors for Cholelithiasis

Gallstone disease is one of the most common public health problems in the United States. Approximately 10%-20% of the national adult populations currently carry gallstones, and gallstone prevalence is rising. In addition, nearly 750,000 cholecystectomies are performed annually in the United States; direct and indirect costs of gallbladder surgery are estimated to be $6.5 billion. Cholelithiasis is also strongly associated with gallbladder, pancreatic, and colorectal cancer occurrence. Moreover, the National Institutes of Health estimates that almost 3,000 deaths (0.12% of all deaths) per year are attributed to complications of cholelithiasis and gallbladder disease. Although extensive research has tried to identify risk factors for cholelithiasis, several studies indicate that definitive findings still remain elusive. In this review, predisposing factors for cholelithiasis are identified, the pathophysiology of gallstone disease is described, and nonsurgical preventive options are discussed. Understanding the risk factors for cholelithiasis may not only be useful in assisting nurses to provide resources and education for patients who are diagnosed with gallstones, but also in developing novel preventive measures for the disease.

Surgical Management of Crohn Disease in Children: Guidelines From the Paediatric IBD Porto Group of ESPGHAN

The incidence of Crohn disease (CD) has been increasing and surgery needs to be contemplated in a substantial number of cases. The relevant advent of biological treatment has changed but not eliminated the need for surgery in many patients. Despite previous publications on the indications for surgery in CD, there was a need for a comprehensive review of existing evidence on the role of elective surgery and options in pediatric patients affected with CD. We present an expert opinion and critical review of the literature to provide evidence-based guidance to manage these patients. Indications, surgical options, risk factors, and medications in pre- and perioperative period are reviewed in the light of available evidence. Risks and benefits of surgical options are addressed. An algorithm is proposed for the management of postsurgery monitoring, timing for follow-up endoscopy, and treatment options.

Glucuronides in the gut: Sugar-driven symbioses between microbe and host

The intestinal milieu is astonishingly complex and home to a constantly changing mixture of small and large molecules, along with an abundance of bacteria, viral particles, and eukaryotic cells. Such complexity makes it difficult to develop testable molecular hypotheses regarding host-microbe interactions. Fortunately, mammals and their associated gastrointestinal (GI) microbes contain complementary systems that are ideally suited for mechanistic studies. Mammalian systems inactivate endobiotic and xenobiotic compounds by linking them to a glucuronic acid sugar for GI excretion. In the GI tract, the microbiota express β-glucuronidase enzymes that remove the glucuronic acid as a carbon source, effectively reversing the actions of mammalian inactivation. Thus, by probing the actions of microbial β-glucuronidases, and by understanding which substrate glucuronides they process, molecular insights into mammalian-microbial symbioses may be revealed amid the complexity of the intestinal tract. Here, we focus on glucuronides in the gut and the microbial proteins that process them.

Animal Models of Cystic Fibrosis Pathology: Phenotypic Parallels and Divergences

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The resultant characteristic ion transport defect results in decreased mucociliary clearance, bacterial colonisation, and chronic neutrophil-dominated inflammation. Much knowledge surrounding the pathophysiology of the disease has been gained through the generation of animal models, despite inherent limitations in each. The failure of certain mouse models to recapitulate the phenotypic manifestations of human disease has initiated the generation of larger animals in which to study CF, including the pig and the ferret. This review will summarise the basic phenotypes of three animal models and describe the contributions of such animal studies to our current understanding of CF.

Bilirubin prevents acute DSS-induced colitis by inhibiting leukocyte infiltration and suppressing upregulation of inducible nitric oxide synthase

Bilirubin is thought to exert anti-inflammatory effects by inhibiting vascular cell adhesion molecule-1 (VCAM-1)-dependent leukocyte migration and by suppressing the expression of inducible nitric oxide synthase (iNOS). As VCAM-1 and iNOS are important mediators of tissue injury in the dextran sodium sulfate (DSS) murine model of inflammatory colitis, we examined whether bilirubin prevents colonic injury in DSS-treated mice. Male C57BL/6 mice were administered 2.5% DSS in the drinking water for 7 days, while simultaneously receiving intraperitoneal injections of bilirubin (30 mg/kg) or potassium phosphate vehicle. Disease activity was monitored, peripheral blood counts and serum nitrate levels were determined, and intestinal specimens were analyzed for histological injury, leukocyte infiltration, and iNOS expression. The effect of bilirubin on IL-5 production by HSB-2 cells and on Jurkat cell transendothelial migration also was determined. DSS-treated mice that simultaneously received bilirubin lost less body weight, had lower serum nitrate levels, and exhibited reduced disease severity than vehicle-treated animals. Concordantly, histopathological analyses revealed that bilirubin-treated mice manifested significantly less colonic injury, including reduced infiltration of eosinophils, lymphocytes, and monocytes, and diminished iNOS expression. Bilirubin administration also was associated with decreased eosinophil and monocyte infiltration into the small intestine, with a corresponding increase in peripheral blood eosinophilia. Bilirubin prevented Jurkat migration but did not alter IL-5 production. In conclusion, bilirubin prevents DSS-induced colitis by inhibiting the migration of leukocytes across the vascular endothelium and by suppressing iNOS expression.

Looking to the horizon: the role of bilirubin in the development and prevention of age-related chronic diseases

Bilirubin, the principal tetrapyrrole, bile pigment and catabolite of haem, is an emerging biomarker of disease resistance, which may be related to several recently documented biological functions. Initially believed to be toxic in infants, the perception of bilirubin has undergone a transformation: it is now considered to be a molecule that may promote health in adults. Data from the last decade demonstrate that mildly elevated serum bilirubin levels are strongly associated with reduced prevalence of chronic diseases, particularly cardiovascular diseases (CVDs), as well as CVD-related mortality and risk factors. Recent data also link bilirubin to other chronic diseases, including cancer and Type 2 diabetes mellitus, and to all-cause mortality. Therefore, there is evidence to suggest that bilirubin is a biomarker for reduced chronic disease prevalence and a predictor of all-cause mortality, which is of important clinical significance. In the present review, detailed information on the association between bilirubin and all-cause mortality, as well as the pathological conditions of CVD, cancer, diabetes and neurodegenerative diseases, is provided. The mechanistic background concerning how bilirubin and its metabolism may influence disease prevention and its clinical relevance is also discussed. Given that the search for novel biomarkers of these diseases, as well as for novel therapeutic modalities, is a key research objective for the near future, bilirubin represents a promising candidate, meeting the criteria of a biomarker, and should be considered more carefully in clinical practice as a molecule that might provide insights into disease resistance. Clearly, however, greater molecular insight is warranted to support and strengthen the conclusion that bilirubin can prevent disease, with future research directions also proposed.

Impaired cholecystokinin-induced gallbladder emptying incriminated in spontaneous "black" pigment gallstone formation in germfree Swiss Webster mice

"Black" pigment gallstones form in sterile gallbladder bile in the presence of excess bilirubin conjugates ("hyperbilirubinbilia") from ineffective erythropoiesis, hemolysis, or induced enterohepatic cycling (EHC) of unconjugated bilirubin. Impaired gallbladder motility is a less well-studied risk factor. We evaluated the spontaneous occurrence of gallstones in adult germfree (GF) and conventionally housed specific pathogen-free (SPF) Swiss Webster (SW) mice. GF SW mice were more likely to have gallstones than SPF SW mice, with 75% and 23% prevalence, respectively. In GF SW mice, gallstones were observed predominately in heavier, older females. Gallbladders of GF SW mice were markedly enlarged, contained sterile black gallstones composed of calcium bilirubinate and <1% cholesterol, and had low-grade inflammation, edema, and epithelial hyperplasia. Hemograms were normal, but serum cholesterol was elevated in GF compared with SPF SW mice, and serum glucose levels were positively related to increasing age. Aged GF and SPF SW mice had deficits in gallbladder smooth muscle activity. In response to cholecystokinin (CCK), gallbladders of fasted GF SW mice showed impaired emptying (females: 29%; males: 1% emptying), whereas SPF SW females and males emptied 89% and 53% of volume, respectively. Bilirubin secretion rates of GF SW mice were not greater than SPF SW mice, repudiating an induced EHC. Gallstones likely developed in GF SW mice because of gallbladder hypomotility, enabled by features of GF physiology, including decreased intestinal CCK concentration and delayed intestinal transit, as well as an apparent genetic predisposition of the SW stock. GF SW mice may provide a valuable model to study gallbladder stasis as a cause of black pigment gallstones.

Bile acid malabsorption in inflammatory bowel disease

Bile acid malabsorption (BAM) is a common but an underestimated and often neglected sign of inflammatory bowel diseases (IBDs), especially those affecting the distal ileum. Clinically relevant BAM is most often present in patients with Crohn's ileitis and particularly in ileal-resected Crohn's disease patients. However, deterioration of bile acid (BA) metabolism occurs also in patients with IBD without ileal disease or in those in clinical remission, and the role of BAM in these patients is not well appreciated by clinicians. In a majority of cases, BAM in IBD is caused by impaired conjugated BA reabsorption, mediated by apical sodium/BA cotransporting polypeptide, localized at the luminal surface of the ileal enterocytes. As a consequence, numerous pathological sequelae may occur, including the malfunction of lipid digestion with clinical steatorrhea, impaired intestinal motility, and/or significant changes in the intestinal microflora environment. In this review, a detailed description of the pathophysiological mechanisms of BAM-related diarrhea is presented. Although BAM is present in a significant number of patients with Crohn's disease, its laboratory assessment is not routinely included in diagnostic workups, partially because of costs, logistical reasons, or the unavailability of the more sophisticated laboratory equipment needed. Simultaneously, novel findings related to the effects of the BA signaling pathways on immune functions (mediated through TGR5, cell membrane G protein-coupled BA receptor 1, nuclear farnesoid X receptor, nuclear pregnane X receptor, or nuclear vitamin D receptor) are discussed along with intestinal metabolism in its relationship to the pathogenesis of IBD.

Metastable and equilibrium phase diagrams of unconjugated bilirubin IXα as functions of pH in model bile systems: Implications for pigment gallstone formation

Metastable and equilibrium phase diagrams for unconjugated bilirubin IXα (UCB) in bile are yet to be determined for understanding the physical chemistry of pigment gallstone formation. Also, UCB is a molecule of considerable biomedical importance because it is a potent antioxidant and an inhibitor of atherogenesis. We employed principally a titrimetric approach to obtain metastable and equilibrium UCB solubilities in model bile systems composed of taurine-conjugated bile salts, egg yolk lecithin (mixed long-chain phosphatidylcholines), and cholesterol as functions of total lipid concentration, biliary pH values, and CaCl2 plus NaCl concentrations. Metastable and equilibrium precipitation pH values were obtained, and average pKa values of the two carboxyl groups of UCB were calculated. Added lecithin and increased temperature decreased UCB solubility markedly, whereas increases in bile salt concentrations and molar levels of urea augmented solubility. A wide range of NaCl and cholesterol concentrations resulted in no specific effects, whereas added CaCl2 produced large decreases in UCB solubilities at alkaline pH values only. UV-visible absorption spectra were consistent with both hydrophobic and hydrophilic interactions between UCB and bile salts that were strongly influenced by pH. Reliable literature values for UCB compositions of native gallbladder biles revealed that biles from hemolytic mice and humans with black pigment gallstones are markedly supersaturated with UCB and exhibit more acidic pH values, whereas biles from nonstone control animals and patients with cholesterol gallstone are unsaturated with UCB.

Association of serum bilirubin and non-alcoholic fatty liver disease: A feasible therapeutic avenue?

AIM: To the look at the current strength of evidence and the potential application of anti-oxidants in this setting.

METHODS: Two electronic databases (PubMed and Web of Knowledge) were searched to January 2013 to find studies addressing serum bilirubin levels in non-alcoholic fatty liver disease (NAFLD). The search used key word combinations in relation to NAFLD and serum bilirubin specific to human adults only. After screening selected studies were reviewed in depth by two independent reviewers. Data synthesis with further meta-analysis was planned but not possible due to the heterogeneity of the outcome measures in these studies.

RESULTS: Out of 416 studies screened only seven studies were considered suitable for inclusion. All seven studies consistently reported an inverse association of bilirubin with NAFLD despite the heterogeneous sample of studies. Only two studies were prospective. No negative studies were found.

CONCLUSION: Most studies suggest a correlation between high bilirubin levels of any type are inversely correlated with NAFLD. But to date most of these studies have been poorly designed to allow meaningful conclusions, except one cohort study. There is a need for a large prospective cohort study in multiple populations to test this hypothesis fully before mechanistic associations can be established and therapeutic options of the apparent anti-oxidant effect of bilirubin be explored in NAFLD. Furthermore these studies should include analysis of UGT1A1 gene to expound upon underlying cause of unconjugated hyperbilirubinaemia.

Bile acid malabsorption assessed by 7 alpha-hydroxy-4-cholesten-3-one in pediatric inflammatory bowel disease: correlation to clinical and laboratory findings

BACKGROUND AND AIMS

Measurement of 7 alpha-hydroxy-4-cholesten-3-one (C4) in serum is a semiquantitative test for bile acid malabsorption (BAM). We have previously established pediatric normal values for C4 with an upper limit of normal of 66.5 ng/mL, independent of age and sex. Here we performed the C4 test in 58 pediatric patients with Crohn's disease (CD) and ulcerative colitis (UC).

METHODS

C4 was measured using high performance liquid chromatography (HPLC) in fasting serum samples of 44 patients with CD (range 7-19 years) and 14 with UC (4-18 years). Disease activity was assessed by the pediatric CD and UC activity indices (PCDAI and PUCAI, respectively) plus serum (CRP, ESR) and fecal inflammatory markers (calprotectin).

RESULTS

C4 concentrations were increased in 10 CD (23%) (range: 70.8-269.3 ng/mL) but only one UC patient (72.9 ng/mL). CD patients with diarrhea (n=12) had higher C4-values compared to those without (76.9 vs. 30.4 ng/mL; p=0.0043). Ileal resection in CD patients (n=10) was associated with increased C4 concentrations (81.2 vs. 24.3 ng/mL, p=0.0004). No correlation was found between C4 values and inflammatory markers. Six of 7 CD patients with persistent diarrhea but quiescent disease (PCDAI ≤12.5) had C4 values indicating BAM.

CONCLUSION

Elevated C4 concentrations indicating BAM are common in children with CD. They are associated with ileal resection and non-bloody diarrhea in the absence of active disease or elevated inflammatory markers. The C4-test identifies a subgroup of CD patients with persistent diarrhea in spite of clinical remission which may benefit from bile acid binding therapy.

Serum lipid concentrations in patients with cholesterol and pigment gallstones

Background

Gallstones (GS) are formed as a result of impaired metabolic regulation of the human body. Abnormal lipid metabolism is partly responsible for the pathogenesis of GS mainly rich in cholesterol. Thus abnormalities of serum lipids would reflect the possibilities of the formation of cholesterol GS. This study aims to identify the significance of serum lipids on the development of GS disease.

Methods

Serum lipid profiles were estimated in 73 patients with symptomatic GS, admitted to the Teaching Hospital, Peradeniya, Sri Lanka for GS removal surgeries from May 2011 to December 2012. Patients with normal serum bilirubin level and not being on lipid lowering drugs were recruited for the study. Serum lipid profile of each patient was analyzed by enzymatic kit assays and the chemical composition of GS was analyzed by Fourier Transform Infrared spectroscopy.

Results

Of the 73 patients, 37 (51%) had cholesterol GS while 36 (49%) had pigment GS. Serum lipid parameters of a majority of patients were within the normal range. Body mass index values of the patients with two types of GS were not significantly different (Two sample t test, p = 0.335). Out of the lipid parameters tested, only serum triglyceride concentration was significantly high in patients with cholesterol GS than that of pigment GS (Two sample t test, p = 0.038). None of the lipid parameters were significantly different between males and females (Two sample t test, p > 0.05). Compared to the patients with pigment GS who were aged below 50 years, mean total cholesterol and triglyceride concentrations were higher in the same age category patients with cholesterol GS.

Conclusion

Abnormal serum lipid profiles doesn’t seem to be an essential feature in patients with cholesterol GS. However when the two groups of patients with cholesterol and pigment GS with no significant difference of body mass indexes were compared, patients with cholesterol GS are more likely to have serum lipid parameters towards the undesirable cutoff levels of their respective normal ranges. However an effect of serum lipid concentrations on high incidence of GS among females has not been identified.

Effect of bile pigments on the compromised gut barrier function in a rat model of bile duct ligation

Background

Studies have shown that the absence of bile in the gut lumen, either by bile duct ligation or bile diversion, induces mucosal injury. However, the mechanism remains elusive. In this study, the role of bile pigments in gut barrier function was investigated in a rat model of bile duct ligation.

Methods

Male Sprague Dawley (SD) rats were used in this study. After ligation of bile duct, the animals were administrated with free bilirubin, bilirubin ditaurate, or biliverdin by intragastric gavage. 1, 2, or 3 days later, the animals were sacrificed and the damage of mucosa was assessed by histological staining as well as biochemical parameters such as changes of diamine oxidase (DAO) and D-lactate (D-Lac) in the blood. Trypsin and chymotrypsin of the gut were also measured to determine how these digestive proteases may relate to the observed effects of bile pigments.

Results

Bile duct ligation (BDL) caused significant increases in gut trypsin and chymotrypsin along with damage of the mucosa as demonstrated by the histological findings under microscope, the reduced expression of tight junction molecules like occludin, and significant changes in DAO and D-lac in the blood. Free bilirubin but not bilirubin ditaurate or biliverdin showed significant inhibitions on trypsin and chymotrypsin as well as alleviated changes of histological and biochemical parameters related to gut barrier disruption.

Conclusion

Bile may protect the gut from damage through inhibiting digestive proteases like trypsin and chymotrypsin by free bilirubin.

Can the type of gallstones be predicted with known possible risk factors?: A comparison between mixed cholesterol and black pigment stones

BACKGROUND

Pathogenesis of gallstones (GS) is multifactorial and multiple genetic and environmental factors have been identified in different populations for different types of GS with varying prevalence. However the role of the each aetiological factor on the formation of mixed cholesterol and black pigment GS has not being addressed adequately. Hence in this study we attempted to compare known possible risk factors for mixed cholesterol and black pigment GS among two groups of patients with two types of GS.

METHODS

The study was done on a cohort of patients with symptomatic GS admitted to the Teaching Hospital Peradeniya, Sri Lanka over a period of 18 months. Clinical and epidemiological data and physical parameters of the patients were recorded and surgically removed GS were analyzed chemically and physically to identify the type of GS. In addition lipid profile was done in all the patients with normal serum bilirubin levels.

RESULTS

A total of 86 patients were included in the study. Mixed cholesterol GS was significantly common among females than males (χ2 test, p = 0.029). Mixed cholesterol GS was commonly seen among patients belonging to Moor ethnicity (χ2 test, p = 0.009). Majority of patients with mixed cholesterol GS had body mass index above 25 kg/m2 (χ2 test, p = 0.018). Black pigment GS were significantly common among patients with type II diabetes mellitus (Fisher's exact test, p = 0.035). Further all the patients with chronic haemolytic anaemia and alcoholic cirrhosis had black pigment GS. Age, family history, Fasting Blood Glucose, dyslipidaemia, lipid profile, parity and use of oral contraceptive pills in females, smoking and alcohol intake in males did not differ significantly among patients in the two groups.

CONCLUSION

Gender, ethnicity and body mass index can be used to predict the formation of mixed cholesterol GS and black pigment GS.

Serum metabolomics indicate altered cellular energy metabolism in children with cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is a multi-system disease affecting multiple organs and cells besides the respiratory system. Metabolomic profiling allows simultaneous detection of biochemicals originating from cells, organs, or exogenous origin that may be valuable for monitoring of disease severity or in diagnosis.

AIM

We hypothesized that metabolomics using serum from children would differentiate CF from non-CF lung disease subjects and would provide insight into metabolism in CF.

METHODS

Serum collected from children with CF (n = 31) and 31 age and gender matched children with other lung diseases was used for metabolomic profiling by gas- and liquid-chromatography. Relative concentration of metabolites was compared between the groups using partial least square discriminant analyses (PLS-DA) and linear modeling.

RESULTS

A clear separation of the two groups was seen in PLS-DA. Linear model found that among the 459 detected metabolites 92 differed between CF and non-CF. These included known biochemicals in lipid metabolism, oxidants, and markers consistent with abnormalities in bile acid processing. Bacterial metabolites were identified and differed between the groups indicating intestinal dysbiosis in CF. As a novel finding several pathways were markedly different in CF, which jointly point towards decreased activity in the β-oxidation of fatty acids. These pathways include low ketone bodies, low medium chain carnitines, elevated di-carboxylic acids and decreased 2-hydroxybutyrate from amino acid metabolism in CF compared to non-CF.

CONCLUSION

Serum metabolomics discriminated CF from non-CF and show altered cellular energy metabolism in CF potentially reflecting mitochondrial dysfunction. Future studies are indicated to examine their relation to the underlying CF defect and their use as biomarkers for disease severity or for cystic fibrosis transmembrane regulator (CFTR) function in an era of CFTR modifying drugs.

Gallstone disease in Swedish twins is associated with the Gilbert variant of UGT1A1

BACKGROUND & AIMS

The Gilbert syndrome-associated functional TATA box variant UGT1A1*28 (A(TA)7TAA) was found to increase susceptibility to pigment gallstone formation in patients with haemolytic anaemia. Further studies in extensive cohorts demonstrated an increased risk of this variant for cholesterol gallstone disease (GD). We now investigated this polymorphism as a determinant of symptomatic GD in Swedish twins.

METHODS

The Swedish Twin Registry was merged with the Hospital Discharge and Causes of Death Registries and searched for GD-related diagnoses among monozygotic (MZ) twins living in the Stockholm area. In addition, we screened the TwinGene database for GD. In total, we found 44 MZ twin pairs with and eight MZ twins without GD to be evaluable. GD-free twins from TwinGene (109 concordantly MZ and 126 independent DZ) served as controls. UGT1A1*28 genotyping was performed using TaqMan assays.

RESULTS

Overall, 58 and 8 of 106 twins with GD were hetero- and homozygous UGT1A1 risk allele carriers respectively. The case-control association tests showed a significantly (P < 0.05) increased risk of developing GD (OR = 1.62, 95% CI 1.00-2.63) in heterozygotes carriers and in addition, a trend (P = 0.075) for an increased risk among carriers (OR = 1.52, 95% CI 0.97-2.44) of the risk allele.

CONCLUSION

These data from Swedish twins confirm the Gilbert variant as risk factor for GD. Our observation is in line with nucleation in bilirubin supersaturated bile representing an initial step in cholelithogenesis.

Epidemiology of gallbladder disease: cholelithiasis and cancer

Diseases of the gallbladder are common and costly. The best epidemiological screening method to accurately determine point prevalence of gallstone disease is ultrasonography. Many risk factors for cholesterol gallstone formation are not modifiable such as ethnic background, increasing age, female gender and family history or genetics. Conversely, the modifiable risks for cholesterol gallstones are obesity, rapid weight loss and a sedentary lifestyle. The rising epidemic of obesity and the metabolic syndrome predicts an escalation of cholesterol gallstone frequency. Risk factors for biliary sludge include pregnancy, drugs like ceftiaxone, octreotide and thiazide diuretics, and total parenteral nutrition or fasting. Diseases like cirrhosis, chronic hemolysis and ileal Crohn's disease are risk factors for black pigment stones. Gallstone disease in childhood, once considered rare, has become increasingly recognized with similar risk factors as those in adults, particularly obesity. Gallbladder cancer is uncommon in developed countries. In the U.S., it accounts for only ~ 5,000 cases per year. Elsewhere, high incidence rates occur in North and South American Indians. Other than ethnicity and female gender, additional risk factors for gallbladder cancer include cholelithiasis, advancing age, chronic inflammatory conditions affecting the gallbladder, congenital biliary abnormalities, and diagnostic confusion over gallbladder polyps.

New pathophysiological concepts underlying pathogenesis of pigment gallstones

Pigment gallstones, which are much less frequent than cholesterol stones, are classified descriptively as "black" or "brown". They are composed mostly of calcium hydrogen bilirubinate, Ca(HUCB)(2), which is polymerized and oxidized in "black" stones but remains unpolymerized in "brown" stones. Black stones form in sterile gallbladder bile but brown stones form secondary to stasis and anaerobic bacterial infection in any part of the biliary tree, including the gallbladder. Other calcium salts coprecipitate in both stone types; crystalline calcium phosphate and/or carbonate in the case of "black" stones and amorphous calcium salts of long chain saturated fatty acids ("soaps") in the case of "brown" stones. Cholesterol is present in variable proportions in "brown" more than "black" stones and in the latter, the bile sterol may be totally absent. The "scaffolding" of both stone types is a mixed mucin glycoprotein matrix secreted by epithelial cells lining the biliary tree. The critical pathophysiological prerequisite for "black" stone formation is "hyperbilirubinbilia" (biliary hypersecretion of bilirubin conjugates). It is due principally to hemolysis, ineffective erythropoiesis, or pathologic enterohepatic cycling of unconjugated bilirubin. Endogenous biliary β-glucuronidase hydrolysis of bilirubin conjugates in gallbladder bile provides HUCB(-) molecules that precipitate as insoluble salts with ionized Ca. Putatively, reactive oxygen species secreted by an inflamed gallbladder mucosa are responsible for transforming the initial soft yellow precipitates into hard black [Ca(HUCB)(2)](n) polymers. Despite "brown" gallstones being soft and amenable to mechanical removal, chronic anaerobic infection of the biliary tree is often markedly resistant to eradication.

Bile pigment pharmacokinetics and absorption in the rat: therapeutic potential for enteral administration

BACKGROUND AND PURPOSE

Bilirubin and biliverdin possess antioxidant and anti-inflammatory properties and their exogenous administration protects against the effects of inflammation and trauma in experimental models. Despite the therapeutic potential of bile pigments, little is known about their in vivo parenteral or enteral absorption after exogenous administration. This study investigated the absorption and pharmacokinetics of bile pigments after i.v., i.p. and intraduodenal (i.d.) administration in addition to their metabolism and routes of excretion.

EXPERIMENTAL APPROACH

Anaesthetized Wistar rats had their bile duct, jugular and portal veins cannulated. Bile pigments were infused and their circulating concentrations/biliary excretion were measured over 180 min. KEY RESULTS After i.v. administration of unconjugated bilirubin, biliverdin and bilirubin ditaurate, their plasma concentrations decreased exponentially over time. Subsequently, native and metabolized compounds appeared in the bile. When administered i.p., their absolute bioavailabilities equalled 14.0, 16.1 and 33.1%, respectively, and correspondingly 38, 28 and 34% of the same bile pigment doses were excreted in the bile. Administration of unconjugated bilirubin and bilirubin ditaurate i.d. increased their portal and systemic concentrations and their systemic bioavailability equalled 1.0 and 2.0%, respectively. Correspondingly, 2.7 and 4.6%, of the doses were excreted in the bile. Biliverdin was rapidly metabolized and these products were absorbed and excreted via the urine and bile.

CONCLUSIONS AND IMPLICATIONS

Bile pigment absorption from the peritoneal and duodenal cavities demonstrate new routes of administration for the treatment of inflammatory and traumatic pathology. Oral biliverdin administration may lead to the production of active metabolite that protect from inflammation/complement activation.

Transporters in cholelithiasis

Gallstones are a common and costly disease with a projected increase in prevalence due to the increasing ageing population. Numerous endogenous and environmental factors are aetiologically related to this multifactorial disease, and genetic studies continue to unravel the pathobiological mechanisms related to gallstone formation. In particular, variants of genes encoding hepatobiliary transporters have been implicated in gallstone disease and, given their ability to influence biliary lipid composition, have undergone considerable investigation. Here we summarize the role of enterohepatic transporters in cholelithogenesis with a particular focus on pertinent ATP-binding cassette transporters (ABCB4, ABCB11, ABCC7, and ABCG5/G8).

Bile acid malabsorption in inflammatory bowel disease: assessment by serum markers

BACKGROUND

Bile acid malabsorption (BAM) is a common feature of Crohn's disease (CD). We aimed to determine whether BAM develops only in patients with a resected distal ileum or if it also occurs in patients who have not undergone surgery for CD.

METHODS

The study included 347 patients with CD or ulcerative colitis (UC) and 119 healthy subjects (controls). BAM was assessed by measurement of serum levels of 7α-hydroxycholest-4-en-3-one (C4) and fibroblast growth factor 19 (FGF19). We surveyed members of the European Crohn's and Colitis Organization and International Organization for the Study of Inflammatory Bowel Disease to collect current information about BAM diagnosis.

RESULTS

The severity of BAM was associated with resection of the distal ileum. Compared with controls, patients who received moderate or extensive ileal resection had significantly increased levels of serum C4 (12 versus 62 versus 243 μg/L, respectively; P < 0.001). However, BAM was also present in a substantial number of the patients with CD who were not treated by surgery who had ileitis or colitis (14% and 11%, respectively). There was an indirect, proportional relationship between levels of C4 and FGF19 (P < 0.001).

CONCLUSIONS

The most severe BAM occurs in CD patients after resection of the distal ileum, but BAM can occur in surgically untreated CD patients, regardless of disease localization. Laboratory tests for BAM should become a part of the algorithm for diagnosis of CD to identify patients who might respond to therapies such as bile acid sequestrants. FGF19 appears to be a reliable marker of BAM.

Role of the intestinal bile acid transporters in bile acid and drug disposition

Membrane transporters expressed by the hepatocyte and enterocyte play critical roles in maintaining the enterohepatic circulation of bile acids, an effective recycling and conservation mechanism that largely restricts these potentially cytotoxic detergents to the intestinal and hepatobiliary compartments. In doing so, the hepatic and enterocyte transport systems ensure a continuous supply of bile acids to be used repeatedly during the digestion of multiple meals throughout the day. Absorption of bile acids from the intestinal lumen and export into the portal circulation is mediated by a series of transporters expressed on the enterocyte apical and basolateral membranes. The ileal apical sodium-dependent bile acid cotransporter (abbreviated ASBT; gene symbol, SLC10A2) is responsible for the initial uptake of bile acids across the enterocyte brush border membrane. The bile acids are then efficiently shuttled across the cell and exported across the basolateral membrane by the heteromeric Organic Solute Transporter, OSTα-OSTβ. This chapter briefly reviews the tissue expression, physiology, genetics, pathophysiology, and transport properties of the ASBT and OSTα-OSTβ. In addition, the chapter discusses the relationship between the intestinal bile acid transporters and drug metabolism, including development of ASBT inhibitors as novel hypocholesterolemic or hepatoprotective agents, prodrug targeting of the ASBT to increase oral bioavailability, and involvement of the intestinal bile acid transporters in drug absorption and drug-drug interactions.

Hereditary liver disease: gallstones

Gallstones are common in Western countries and due to pain and complications pose a substantial burden on health care systems. In general, cholesterol gallstones are distinguished from bilirubin gallstones. Bilirubin gallstones form if the ion product of unconjugated bilirubin and calcium in gallbladder bile exceeds the solubilisation capacities of mixed micelles and vesicles. Cholesterol gallstones develop if the amount of cholesterol in gallbladder bile exceeds the maximum concentration that is soluble at the given concentration of bile salts and phospholipids. In addition, cholesterol gallstone formation requires hypomotility of the gallbladder and a mucin gel as nucleation matrix for monohydrate crystals. The individual risk of gallstone formation is determined by interactions of lithogenic alleles of gallstone susceptibility genes and multiple environmental factors. For asymptomatic gallstones, expectant management is recommended, whereas an episode of gallstone-associated pain substantially increases the risk of complications such as cholecystitis, cholangitis and pancreatitis and therefore necessitates cholecystectomy.

Pathophysiological preconditions promoting mixed "black" pigment plus cholesterol gallstones in a DeltaF508 mouse model of cystic fibrosis

Gallstones are frequent in patients with cystic fibrosis (CF). These stones are generally "black" pigment (i.e., Ca bilirubinate) with an appreciable cholesterol admixture. The pathophysiology and molecular mechanisms for this "mixed" gallstone in CF are unknown. Here we investigate in a CF mouse model with no overt liver or gallbladder disease whether pathophysiological changes in the physical chemistry of gallbladder bile might predict the occurrence of "mixed" cholelithiasis. Employing a DeltaF508 mouse model with documented increased fecal bile acid loss and induced enterohepatic cycling of bilirubin (Am J Physiol Gastrointest Liver Physiol 294: G1411-G1420, 2008), we assessed gallbladder bile chemistry, morphology, and microscopy in CF and wild-type mice, with focus on the concentrations and compositions of the common biliary lipids, bilirubins, Ca(2+), and pH. Our results demonstrate that gallbladder bile of CF mice contains significantly higher levels of all bilirubin conjugates and unconjugated bilirubin with lower gallbladder bile pH values. Significant elevations in Ca bilirubinate ion products in bile of CF mice increase the likelihood of supersaturating bile and forming black pigment gallstones. The risk of potential pigment cholelithogenesis is coupled with higher cholesterol saturations and bile salt hydrophobicity indexes, consistent with a proclivity to cholesterol phase separation during pigment gallstone formation. This is an initial step toward unraveling the molecular basis of CF gallstone disease and constitutes a framework for investigating animal models of CF with more severe biliary disease, as well as the human disease.

Epidemiology of gallstones

Gallstones are common with prevalences as high as 60% to 70% in American Indians and 10% to 15% in white adults of developed countries. Ethnic differences abound with a reduced frequency in black Americans and those from East Asia, while being rare in sub-Saharan Africa. Certain risk factors for gallstones are immutable: female gender, increasing age, and ethnicity/family (genetic traits). Others are modifiable: obesity, the metabolic syndrome, rapid weight loss, certain diseases (cirrhosis and Crohn disease), gallbladder stasis (from spinal cord injury or drugs, such as somatostatin), and lifestyle.

Sodium taurocholate inhibits intestinal adenoma formation in APCMin/+ mice, potentially through activation of the farnesoid X receptor

In light of clinical and biological evidence that bile constituents exert preventive effects against colorectal cancer, we evaluated the influence of oral bilirubin and sodium taurocholate (NaTC) on intestinal tumor formation in APC(Min/+) mice. Mice received bilirubin and/or bovine serum albumin (BSA) and NaTC in the drinking water for 8 weeks, after which the number, size and location of intestinal adenomas were determined. Tissue specimens were analyzed by light microscopy, TUNEL staining, immunohistochemistry for beta-catenin and Ki-67 and quantitative polymerase chain reaction for farnesoid X receptor (FXR)-dependent gene expression. Colon tumor formation also was assessed in azoxymethane (AOM)-treated hyperbilirubinemic Gunn (j/j) and wild-type (+/+) rats. Compared with untreated APC(Min/+) mice, the mean number of intestinal adenomas was markedly lower in both bilirubin (10.5 +/- 0.9 versus 37.0 +/- 5.2; +/-SEM; P < 0.001) and NaTC plus BSA (14.3 +/- 5.4; P = 0.01)-treated animals. Both treatment groups exhibited reduced levels of cellular proliferation in the ileum (by Ki-67 staining), but no differences in TUNEL staining or the percentage of beta-catenin-positive crypts. Bilirubin feeding reduced intestinal inducible nitric oxide synthase expression, but did not alter adenoma multiplicity in APC(Min/+) mice or in AOM-treated j/j versus +/+ rats. Mice receiving NaTC manifested increased intestinal expression of the FXR-regulated genes, Shp, FGF15 and IBABP, and a concomitant decrease in cyclin D1 message. Administering NaTC to APC(Min/+) mice causes a marked reduction in intestinal adenomas. We postulate that this effect is mediated through activation of FXR, leading to increased Shp expression and consequent downregulation of cyclin D1.

Review article: nuclear receptors and liver disease--current understanding and new therapeutic implications

BACKGROUND

The important role of nuclear receptors and their contribution to liver function in both physiological and pathological conditions has come to attention in recent years and has advanced our understanding of several liver diseases. These findings led to the introduction of targeting nuclear receptors as treatment strategies for various liver diseases.

AIMS

To review the new insights brought by the study of nuclear receptors to our understanding of the molecular basis of various liver diseases, and to summarize some of the recent studies that evaluated the efficacy of targeting nuclear receptor as a new approach in treating liver diseases.

METHODS

Review of articles, using PubMed and article references.

RESULTS

Nuclear receptor ligands in patients with liver diseases have been associated with a variety of toxicities. Some clinical results have not met the expectations predicted from animal experiments. Mechanistic explanations at the molecular level are needed for preventing toxicity and improving outcomes from nuclear receptor ligands.

CONCLUSION

The use of various nuclear receptor ligands in liver diseases is a promising approach that can benefit many patients suffering from these devastating diseases. However, we are far from a full understanding of the molecular mechanisms by which these receptors work.

Gilbert syndrome as a predisposing factor for cholelithiasis risk in the Greek adult population

We investigated the hypothesis that coinheritance of the common A(TA)(n)TAA promoter mutation at the UGT1A1 locus associated with Gilbert syndrome is a risk factor for gallstone formation in a homogeneous adult population, by conducting a case-control study that included 198 adult patients with cholelithiasis and 152 healthy controls both of Greek origin. Three genotypes were found: 7/7 (17.8% in controls and 23.3% in patients), 6/7 (33.5% in controls and 46.5% in patients), and normal homozygous 6/6 (48.7% in controls and 30.3% in patients). The Gilbert UGT1A1 genotypes 6/7 and 7/7 show significant association (odds ratio 2.225, 95% confidence interval 1.373-3.605, p=0.001, and odds ratio 2.101, 95% confidence interval 1.171-3.770, p=0.013, respectively) with cholelithiasis risk. This association supports the theory that genetic factors are responsible for a fraction of symptomatic gallstone disease; however, further studies are required in different ethnic groups to fully elucidate the involvement of Gilbert syndrome in gallstone disease.

Bile acid transporters

In liver and intestine, transporters play a critical role in maintaining the enterohepatic circulation and bile acid homeostasis. Over the past two decades, there has been significant progress toward identifying the individual membrane transporters and unraveling their complex regulation. In the liver, bile acids are efficiently transported across the sinusoidal membrane by the Na(+) taurocholate cotransporting polypeptide with assistance by members of the organic anion transporting polypeptide family. The bile acids are then secreted in an ATP-dependent fashion across the canalicular membrane by the bile salt export pump. Following their movement with bile into the lumen of the small intestine, bile acids are almost quantitatively reclaimed in the ileum by the apical sodium-dependent bile acid transporter. The bile acids are shuttled across the enterocyte to the basolateral membrane and effluxed into the portal circulation by the recently indentified heteromeric organic solute transporter, OSTalpha-OSTbeta. In addition to the hepatocyte and enterocyte, subgroups of these bile acid transporters are expressed by the biliary, renal, and colonic epithelium where they contribute to maintaining bile acid homeostasis and play important cytoprotective roles. This article will review our current understanding of the physiological role and regulation of these important carriers.