Increased prevalence of antimitochondrial antibodies in first-degree relatives of patients with primary biliary cirrhosis

Primary Biliary Cholangitis: Epidemiology, Diagnosis, and Presentation

Using ursodeoxycholic acid as a standard treatment and for its ability to test for antimitochondrial antibody to accelerate diagnosis, survival of primary biliary cholangitis patients has approached that of the general population, leading to a change in nomenclature from primary biliary cirrhosis to primary biliary cholangitis to more accurately describe the disease.

Guidelines on the Diagnosis and Management of Primary Biliary Cholangitis (2021)

In 2015, the Chinese Society of Hepatology and the Chinese Society of Gastroenterology published a consensus on primary biliary cholangitis (PBC). In the past years, numerous clinical studies have been published in the field of PBC. To guide the clinical diagnosis and management of PBC patients, the Chinese Society of Hepatology invited a panel of experts to assess the new clinical evidence and formulate the current guidelines.

Primary biliary cholangitis: Epidemiology, prognosis, and treatment

Primary biliary cholangitis (PBC) is a chronic cholestatic autoimmune liver disease characterized by a destructive, small duct, and lymphocytic cholangitis, and marked by the presence of antimitochondrial antibodies. The incidence and prevalence of PBC vary widely in different regions and time periods, and although disproportionally more common among White non-Hispanic females, contemporary data show a higher prevalence in males and racial minorities than previously described. Outcomes largely depend on early recognition of the disease and prompt institution of treatment, which, in turn, are directly influenced by provider bias and socioeconomic factors. Ursodeoxycholic acid remains the initial treatment of choice for PBC, with obeticholic acid and fibrates (off-label therapy) reserved as add-on therapy for the management of inadequate responders or those with ursodeoxycholic acid intolerance. Novel and repurposed drugs are currently at different stages of clinical development not only for the treatment of PBC but also for its symptomatic management. Here, we summarize the most up-to-date data regarding the epidemiology, prognosis, and treatment of PBC, providing clinically useful information for its holistic management.

Primary Biliary Cholangitis in Males: Pathogenesis, Clinical Presentation, and Prognosis

Primary biliary cholangitis (PBC) is an immune-mediated chronic liver disease characterized by progressive cholestasis, bile duct destruction, biliary fibrosis, and cirrhosis. Patients who respond to ursodeoxycholic acid have an expected survival similar to the general population. Although PBC primarily affects females, the prevalence in males is higher than was previously believed, with contemporary studies suggesting a female-to-male ratio of 4-6:1. A diagnosis of PBC is often delayed among males because of the myth that PBC is rare in males.

Immunoglobulin M: A Neglected Serum Biomarker in Treatment-Naive Primary Biliary Cholangitis With Normal Alkaline Phosphatase

The diagnosis of primary biliary cholangitis (PBC) in patients with seropositive anti-mitochondrial antibody (AMA) but normal alkaline phosphatase (ALP) depends on a liver biopsy. We aimed to reveal potential serum biomarkers that could suggest the necessity of a liver biopsy in such patients. Retrospective analysis was performed. Subjects who were treatment naive with seropositive AMA but normal ALP and who underwent at least one liver biopsy between 2008 and 2020 were included in this study. Histologic biopsies were evaluated by two experienced pathologists blinded to the serum tests. A total of 115 patients who were treatment naive were included in this study. Of these, 77 patients (67%) exhibited histologic PBC features and nonspecific histologic features were found in the remaining 38 (33%) patients. Multivariate analysis suggested that baseline serum immunoglobulin M (IgM) >0.773 × upper limit of normal (ULN) (P < 0.001) and age >42 years (P = 0.002) were associated with the diagnosis of PBC through liver biopsies. A significant decrease in the median levels of gamma-glutamyl transpeptidase (GGT) and IgM was found in 54 patients with PBC who received ursodeoxycholic acid (UDCA). Conclusion: For patients who were treatment naive with seropositive AMA but normal ALP, baseline serum IgM >0.773 × ULN and age >42 years were the factors that strongly suggested a diagnosis of PBC. In these patients receiving UDCA, a dynamic monitoring of GGT and IgM might be helpful in evaluating therapeutic responses.

Primary Biliary Cholangitis and Primary Sclerosing Cholangitis: Current Knowledge of Pathogenesis and Therapeutics

Cholangiopathies encompass various biliary diseases affecting the biliary epithelium, resulting in cholestasis, inflammation, fibrosis, and ultimately liver cirrhosis. Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are the most important progressive cholangiopathies in adults. Much research has broadened the scope of disease biology to genetic risk, epigenetic changes, dysregulated mucosal immunity, altered biliary epithelial cell function, and dysbiosis, all of which interact and arise in the context of ill-defined environmental triggers. An in-depth understanding of the molecular pathogenesis of these cholestatic diseases will help clinicians better prevent and treat diseases. In this review, we focus on the main underlying mechanisms of disease initiation and progression, and novel targeted therapeutics beyond currently approved treatments.

Novel HLA-DRB1 alleles contribute risk for disease susceptibility in primary biliary cholangitis

BACKGROUND

Primary biliary cholangitis (PBC) is a complex disease with high heritability. We investigated the association between human leukocyte antigen (HLA)-DRB1 alleles and PBC in families and sporadic cases to evaluate the genetic components of the disease.

METHODS

We performed whole exome sequencing in three PBC families. We genotyped HLA-DRB1 and calculated the association between HLA-DRB1 alleles and the encoding amino acid sequences with the clinical features.

RESULTS

Ten variants harboured the HLA-DRB1 gene associated with PBC. DRB1×07:01, 14:01 and 14:05 were highly increased in PBC. Ten coding region polymorphisms were associated with PBC that encode the amino acid variants of HLA-DR β54, β59 and β66 located in the peptide-binding site of the MHC molecule. Glutamine at position 54 was confirmed as a risk amino acid, verifying the results of familial aggregation analysis of PBC families.

DISCUSSION

Familial aggregation analysis indicated that HLA-DRB1 is a candidate gene for the risk of disease course. Considering that amino acid variations are critical to peptide-binding properties, they underlie the major component of MHC association with PBC.

Antimitochondrial Antibodies: from Bench to Bedside

Anti-mitochondrial antibodies (AMA) are directed against the E2 subunits of the 2-oxo acid dehydrogenase complexes (PDC-E2) and are the typical biomarkers of primary biliary cholangitis (PBC), being present in 90-95% of patients, with increasing sensitivity at increasing titers. Albeit being highly specific for PBC diagnosis, AMA can be detected in less than 1% of healthy subjects, and thus the management subjects with no sign or symptom of liver disease is still a challenge and data concerning clinical risk of developing PBC in this subgroup of patients are controversial. Moreover, AMA can also be detected in patients affected by overlap syndrome, as well as hepatic diseases (i.e., NASH and viral hepatitis), while the association with autoimmune diseases, in particular Sjögren's syndrome, systemic sclerosis, and systemic lupus erythematosus, is well established. Furthermore, new associations are being identified with inflammatory myositis and heart disease. AMA are directed towards the pyruvate dehydrogenase multi enzyme complex (PDC-E2) subunit, which represents an epithelial specific autoantigen for PBC. This review focuses on the main characteristics of AMA, their association with autoimmune diseases and liver diseases.

Cholestatic liver disease: Practice guidelines from the Saudi Association for the Study of Liver diseases and Transplantation

Cholestatic liver diseases (CLDs) are a group of diseases characterized by jaundice and cholestasis as the main presentation with different complications, which have considerable impact on the liver and can lead to end-stage liver disease, cirrhosis, and liver-related complications. In the last few years, tremendous progress has been made in understanding the pathophysiology, diagnosis, and treatment of patients with these conditions. However, several aspects related to the management of CLDs remain deficient and unclear. Due to the lack of recommendations that can help in the management, treatment of those conditions, the Saudi Association for the Study of Liver diseases and Transplantation (SASLT) has created a task force group to develop guidelines related to CLDs management in order to provide a standard of care for patients in need. These guidelines provide general guidance for health care professionals to optimize medical care for patients with CLDs for both adult and pediatric populations, in association with clinical judgments to be considered on a case-by-case basis. These guidelines describe common CLDs in Saudi Arabia, with recommendations on the best approach for diagnosis and management of different diseases based on the Grading of Recommendation Assessment (GRADE), combined with a level of evidence available in the literature.

Genome-wide resolution peripheral blood methylome profiling reveals signatures for cholestatic liver disease

Aim:

To profile DNA methylation changes of primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC).

Materials & methods:

Patients with: PBC, PSC with inflammatory bowel disease (IBD), PSC without IBD, and age-, sex-matched controls were profiled for methylomes of peripheral blood by reduced representation bisulfite sequencing. Differentially methylated CpG (DMC) and differentially methylated region (DMR) were detected and compared.

Results:

We identified consistently altered DMCs and DMRs across diseases with involvement in key pathways. Many similarities noted between two subtypes of PSC, interestingly few existed between PBC and PSC. DMRs were highly enriched with transcription factor binding. Top DMC changes were validated in liver tissue of an independent cohort.

Conclusion:

Methylome profiling provides insights to PBC and PSC.

Single-cell mass cytometry on peripheral blood identifies immune cell subsets associated with primary biliary cholangitis

The relationship between primary biliary cholangitis (PBC), a chronic cholestatic autoimmune liver disease, and the peripheral immune system remains to be fully understood. Herein, we performed the first mass cytometry (CyTOF)-based, immunophenotyping analysis of the peripheral immune system in PBC at single-cell resolution. CyTOF was performed on peripheral blood mononuclear cells (PBMCs) from PBC patients (n = 33) and age-/sex-matched healthy controls (n = 33) to obtain immune cell abundance and marker expression profiles. Hierarchical clustering methods were applied to identify immune cell types and subsets significantly associated with PBC. Subsets of gamma-delta T cells (CD3⁺TCRgd⁺), CD8⁺ T cells (CD3⁺CD8⁺CD161⁺PD1⁺), and memory B cells (CD3⁻CD19⁺CD20⁺CD24⁺CD27⁺) were found to have lower abundance in PBC than in control. In contrast, higher abundance of subsets of monocytes and naïve B cells were observed in PBC compared to control. Furthermore, several naïve B cell (CD3⁻CD19⁺CD20⁺CD24⁻CD27⁻) subsets were significantly higher in PBC patients with cirrhosis (indicative of late-stage disease) than in those without cirrhosis. Alternatively, subsets of memory B cells were lower in abundance in cirrhotic relative to non-cirrhotic PBC patients. Future immunophenotyping investigations could lead to better understanding of PBC pathogenesis and progression, and also to the discovery of novel biomarkers and treatment strategies.

Primary biliary cholangitis: pathogenesis and therapeutic opportunities

Primary biliary cholangitis is a chronic, seropositive and female-predominant inflammatory and cholestatic liver disease, which has a variable rate of progression towards biliary cirrhosis. Substantial progress has been made in patient risk stratification with the goal of personalized care, including early adoption of next-generation therapy with licensed use of obeticholic acid or off-label fibrate derivatives for those with insufficient benefit from ursodeoxycholic acid, the current first-line drug. The disease biology spans genetic risk, epigenetic changes, dysregulated mucosal immunity and altered biliary epithelial cell function, all of which interact and arise in the context of ill-defined environmental triggers. A current focus of research on nuclear receptor pathway modulation that specifically and potently improves biliary excretion, reduces inflammation and attenuates fibrosis is redefining therapy. Patients are benefiting from pharmacological agonists of farnesoid X receptor and peroxisome proliferator-activated receptors. Immunotherapy remains a challenge, with a lack of target definition, pleiotropic immune pathways and an interplay between hepatic immune responses and cholestasis, wherein bile acid-induced inflammation and fibrosis are dominant clinically. The management of patient symptoms, particularly pruritus, is a notable goal reflected in the development of rational therapy with apical sodium-dependent bile acid transporter inhibitors.

Emerging therapies for PBC

Primary biliary cholangitis is an uncommon cholestatic liver disease predominantly affecting middle-aged women. Left untreated, there is a high risk of progression to end-stage liver disease. Few treatment options exist. To date, ursodeoxycholic acid (UDCA) and obeticholic acid (OCA) are the only medical therapies approved for use, other than symptomatic treatments and liver transplantation, the latter of which is reserved for those developing complications of cirrhosis or with intractable pruritus. UDCA improves outcomes, but many patients do not adequately respond. OCA therapy may improve response, but long-term data are limited. New therapies are desperately needed, but evaluation has been limited by the fact that the disease is heterogeneous, hard end points take years to develop, and there are different criteria in use for determining therapeutic response based on surrogate biomarkers. Fibrates appear to be the most promising new therapy and have beneficially affected surrogate end points and are beginning to show improvement in clinical end points.

Preventative care in cholestatic liver disease: Pearls for the specialist and subspecialist

Cholestatic liver diseases (CLDs) encompass a variety of disorders of abnormal bile formation and/or flow. CLDs often lead to progressive hepatic insult and injury and following the development of cirrhosis and associated complications. Many such complications are clinically silent until they manifest with severe sequelae, including but not limited to life-altering symptoms, metabolic disturbances, cirrhosis, and hepatobiliary diseases as well as other malignancies. Primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC) are the most common CLDs, and both relate to mutual as well as unique complications. This review provides an overview of PSC and PBC, with a focus on preventive measures aimed to reduce the incidence and severity of disease-related complications.

Burden of Primary Biliary Cholangitis Among Inpatient Population in the United States

Primary biliary cholangitis (PBC) is an autoimmune liver disease that can lead to cirrhosis and liver failure. Our aim was to assess the recent trends in the mortality rates and health care utilization of patients with PBC seen in the inpatient setting in the United States. We used the National (Nationwide) Inpatient Sample data (2005‐2014). The study population included adults with PBC, using International Classification of Diseases, Ninth Revision codes. Trends in PBC‐related discharges, total charges, length of stay (LoS), and in‐hospital mortality were evaluated. Hierarchical generalized linear models were performed for determining predictors of mortality and total hospital charges. Between the study years of 2005 and 2014, a total of 22,665 hospitalized cases with PBC were identified (mean age 63 years; 84% female, 76% white). The number of PBC‐related discharges increased from 3.24 per 100,000 in 2005 to 3.68 per 100,000 in 2014, with an average annual increase of 1.4% (95% confidence interval [CI]: 0.4%‐2.4%). Fifty‐seven percent had Medicare as their primary payer, 37% had cirrhosis, and 1.3% had hepatocellular carcinoma. Between 2005 and 2014, the average total charges for PBC increased from $53,901 to $57,613 (annual percent change [APC], 1.7%; 95% CI: −0.2%‐3.5%), LoS decreased from 6.9 days to 5.4 days (APC, −2.2%; 95% CI: −3.2% to −1.1%), and mortality rate decreased from 3.8% to 2.8% (APC, −5.4%; 95% CI: −8.4% to −2.4%). Multivariable analysis revealed that ascites were independently associated with increased risk of in‐hospital mortality (odds ratio: 1.77; 95% CI: 1.50‐2.08), increased charge (percent change: 22.5%; 95% CI: 18.6%‐26.7%), and increased LoS (percent change: 29.7%; 95% CI: 25.7%‐33.9%). Conclusion: The number of PBC cases has increased in recent years. Mortality and LoS have decreased, and the total charges have remained the same.

Association of smoking with liver fibrosis and mortality in primary biliary cholangitis

BACKGROUND

The outcome of primary biliary cholangitis (PBC) is affected by both genetic and environmental factors.

OBJECTIVE

The aim of this study was to study the effect of smoking on liver histology and mortality in a genetically homogeneous population having PBC.

PATIENTS AND METHODS

Smoking and drinking habits at diagnosis (based on standard criteria) were recorded in 171 Cretan patients with PBC (163 women). A total of 148 patients had a liver biopsy. Odds ratios were calculated with logistic regression analysis. Kaplan-Meier curves were used for mortality estimation.

RESULTS

Smoking was associated with alcohol consumption of more than 20 g/day [adjusted odds ratio (AOR)=2.20, 95% CI: 1.029-4.099], severe steatosis (AOR=5.31, 95% CI: 2.019-9.919), and fibrosis stage F3-F4 (AOR=1.21, 95% CI: 1.015-3.031). Heavy smoking, years of passive smoking, and serious necroinflammatiοn were independent factors associated with advanced fibrosis after adjustment for sex, age, BMI, and alcohol consumption in multivariate analysis. For every pack-year increase in smoking intensity, there was a 3.2 times higher likelihood of advanced fibrosis (95% CI: 2.018-6.294). Increased mortality was found in smokers with advanced PBC.

CONCLUSION

There is an association between smoking, whether active or passive, and advanced fibrosis in PBC. Mortality is increased in smokers with advanced disease at presentation.

Primary Biliary Cholangitis and Autoimmune Hepatitis

Primary biliary cholangitis and autoimmune hepatitis are common autoimmune diseases of the liver. Both have typical clinical presentations, including certain autoantibodies on serologic testing. Histologic features are also often typical: primary biliary cholangitis shows bile duct destruction (sometimes with granulomas), and autoimmune hepatitis shows prominent portal and lobular lymphoplasmacytic inflammation. Both have a wide differential diagnosis, including one another; they may also simultaneously occur within the same patient. Careful use of clinical and histologic criteria may be necessary for diagnosis. First-line therapy is immunosuppression for autoimmune hepatitis and ursodeoxycholic acid for primary biliary cholangitis. Both diseases may progress to cirrhosis.

The British Society of Gastroenterology/UK-PBC primary biliary cholangitis treatment and management guidelines

Primary biliary cholangitis (formerly known as primary biliary cirrhosis, PBC) is an autoimmune liver disease in which a cycle of immune mediated biliary epithelial cell injury, cholestasis and progressive fibrosis can culminate over time in an end-stage biliary cirrhosis. Both genetic and environmental influences are presumed relevant to disease initiation. PBC is most prevalent in women and those over the age of 50, but a spectrum of disease is recognised in adult patients globally; male sex, younger age at onset (<45) and advanced disease at presentation are baseline predictors of poorer outcome. As the disease is increasingly diagnosed through the combination of cholestatic serum liver tests and the presence of antimitochondrial antibodies, most presenting patients are not cirrhotic and the term cholangitis is more accurate. Disease course is frequently accompanied by symptoms that can be burdensome for patients, and management of patients with PBC must address, in a life-long manner, both disease progression and symptom burden. Licensed therapies include ursodeoxycholic acid (UDCA) and obeticholic acid (OCA), alongside experimental new and re-purposed agents. Disease management focuses on initiation of UDCA for all patients and risk stratification based on baseline and on-treatment factors, including in particular the response to treatment. Those intolerant of treatment with UDCA or those with high-risk disease as evidenced by UDCA treatment failure (frequently reflected in trial and clinical practice as an alkaline phosphatase >1.67 × upper limit of normal and/or elevated bilirubin) should be considered for second-line therapy, of which OCA is the only currently licensed National Institute for Health and Care Excellence recommended agent. Follow-up of patients is life-long and must address treatment of the disease and management of associated symptoms.

Using the Icelandic genealogical database to define the familial risk of primary biliary cholangitis

Hereditary factors in primary biliary cholangitis (PBC) have been well defined in genome-wide association studies, but there are few direct data available that define the relative risk (RR) for family members with an affected proband. An increased risk in first-degree relatives has been demonstrated in a variety of studies, but data have been lacking on further detailed associations for subsequent generations. The objective of this study was to use the unique Icelandic genealogical database to study the familiality of PBC. All patients with positive antimitochondrial antibody measurements in Iceland during the period 1991-2015 who fulfilled diagnostic criteria for PBC were included. The Icelandic genealogical database was used to assess familial relations. For each case of PBC, 10,000 control subjects matched for age, sex, and number of known relatives were randomly chosen from this database to calculate the familial RR of PBC. The average kinship coefficient (KC) of the patients was calculated and compared with the average KC of controls. Overall, 222 PBC patients were identified (182 females, 40 males; median age, 62 years). First-, second- and third-degree relatives of the PBC patients had a high RR of the disease: 9.13 (P < 0.0001), 3.61 (P = 0.014) and 2.59 (P = 0.008), respectively. In fourth- and fifth-degree relatives, the RR was also increased to 1.66 (P = 0.08) and 1.42 (P = 0.08), respectively. The average KC of the patients was also higher than that of the control subjects, with 21.34 × 10^-5 versus 9.56 × 10^-5 (P < 0.0001).

CONCLUSION

Relatives of PBC patients had markedly higher risk for development of the disease compared with controls and importantly our data demonstrate that the risk was significantly increased even in second- and third-degree relatives. (Hepatology 2018;68:166-171).

External validation of the United Kingdom-primary biliary cholangitis risk scores of patients with primary biliary cholangitis treated with ursodeoxycholic acid

The United Kingdom-Primary Biliary Cholangitis (UK-PBC) risk scores are a set of prognostic models that estimate the risk of end-stage liver disease in patients with PBC at 5-, 10- and 15-year intervals. They have not been externally validated outside the United Kingdom. In this retrospective, external validation study, data were abstracted from outpatient charts and discrimination and calibration of the UK-PBC risk scores were assessed. A total of 464 patients with PBC treated with ursodeoxycholic acid were included. The median diagnosis age was 52.4 years, and 88% were female patients. The cumulative incidence of events was 6%, 9%, and 15% at 5, 10, and 15 years, respectively. Concordance (c-statistic) was 0.88, 0.85, and 0.84 using the 5-, 10- and 15-year risk scores, respectively, which was slightly lower than values observed in the United Kingdom validation cohort. Using the 5-year risk score, more events were observed than predicted (25 versus 16.8; P = 0.046); using the 10-year risk score, there was no difference between the observed and predicted number of events (35 versus 44.9; P = 0.14); conversely, using the 15-year risk score, fewer events were observed than predicted (46 versus 67.5; P = 0.009). Limiting evaluation by the 15-year UK-PBC risk score to those with >10 years of follow-up demonstrated no difference between observed and predicted events. Using the 5-year risk score, patients within the highest quartile had statistically significant worse event-free survival compared to the rest of the cohort: 82% versus 98% at 5 years, 73% versus 97% at 10 years, and 58% versus 93% at 15 years. Conclusion: In patients assessed at a North American tertiary medical center, the UK-PBC risk score had excellent discrimination and was reasonably calibrated both in the short and long term. (Hepatology Communications 2018;2:676-682).

Pathophysiology of primary biliary cholangitis

Primary biliary cholangitis is a prototypical autoimmune disease characterized by an overwhelming female predominance, a distinct clinical phenotype, and disease specific anti-mitochondrial antibodies targeted against a well-defined auto-antigen. In a genetically susceptible host, multi-lineage loss of tolerance to the E2 component of the 2-oxo-dehydrogenase pathway and dysregulated immune pathways directed at biliary epithelial cells leads to cholestasis, progressive biliary fibrosis, and cirrhosis in a subset of patients. Several key insights have shed light on the complex pathogenesis of disease. First, characteristic anti-mitochondrial antibodies (AMAs) target lipoic acid containing immunodominant epitopes, particularly pyruvate dehydrogenase complex (PDC-E2), on the inner mitochondrial membrane of BECs. Next, breakdown of the protective apical bicarbonate rich umbrella may sensitize BECs to aberrant apoptotic pathways leaving the antigenic PDC-E2 epitope immunologically tact within an apoptotic bleb. A multi-lineage immune response ensues characterized by an imbalance between effector and regulatory activity resulting in progressive and self-perpetuating biliary injury. Genome wide studies shed light on important pathways involved in disease, key among them being IL-12. Epigenetic mechanisms and microRNAs may play help shed light on the missing heritability and female preponderance of disease. Taken together, these findings have dramatically advanced our understanding of disease and may lead to important therapeutic advances.

Development of autoantibodies precedes clinical manifestations of autoimmune diseases: A comprehensive review

The etiology of autoimmune diseases is due to a combination of genetic predisposition and environmental factors that alter the expression of immune regulatory genes through various mechanisms including epigenetics. Both humoral and cellular elements of the adaptive immune system play a role in the pathogenesis of autoimmune diseases and the presence of autoantibodies have been detected in most but not all autoimmune diseases before the appearance of clinical symptoms. In some cases, the presence or levels of these autoantibodies portends not only the risk of developing a corresponding autoimmune disease, but occasionally the severity as well. This observation is intriguing because it suggests that we can, to some degree, predict who may or may not develop autoimmune diseases. However, the role of autoantibodies in the pathogenesis of autoimmune diseases, whether they actually affect disease progression or are merely an epiphenomenon is still not completely clear in many autoimmune diseases. Because of these gaps in our knowledge, the ability to accurately predict a future autoimmune disease can only be considered a relative risk factor. Importantly, it raises the critical question of defining other events that may drive a patient from a preclinical to a clinical phase of disease.

Geoepidemiology, clinical manifestations and outcome of primary biliary cholangitis in Greece

BACKGROUND & AIMS

Primary biliary cholangitis (PBC) is a disease with rising prevalence and considerable geographical variation. To describe the prevalence, spatial and time distribution, baseline characteristics, response to treatment, outcome and the validity of GLOBE score in a large cohort of Greek PBC patients as an independent validation of this score has not been done so far.

METHODS

The last 16years, 482 PBC patients (86.5% females) were evaluated and analysed retrospectively, using a prospectively collected database. Special attention was paid to the assessment of treatment response according to GLOBE score.

RESULTS

Age at initial evaluation was 56.3±13.7years. Among 432 Thessaly residents, prevalence was 582/million (non-homogeneous distribution). Nineteen districts showed a prevalence >800/million. Symptomatic disease onset could be identified in 91 patients, with a significant peak during spring (P=0.03). At diagnosis, 43.6% were asymptomatic and 16.2% cirrhotic. Male sex (P=0.02), older age (P<0.001), alcohol consumption (P<0.01) and concomitant liver disease (P<0.001) were negative prognostic factors for cirrhosis. During a median [interquartile range, range] follow-up of 5.1 (7.8, 15.7) years, 62 patients died or underwent liver transplantation. Patients with GLOBE score>0.30 had significantly worse prognosis (P<0.001) with 5-, 10-, and 15-year survival rates of 84%, 50% and 42%.

CONCLUSIONS

There is increased PBC prevalence in Thessaly with remarkable geographic clustering and seasonal variability. PBC is diagnosed at early stages although males had a more advanced disease. GLOBE score applies perfectly in Greek patients and this will likely help detecting patients that may benefit from new therapies.

Old and new treatments for primary biliary cholangitis

Primary biliary cholangitis (formerly primary biliary cirrhosis) is a rare progressive cholestatic liver disease, whose hallmark features include a persistently elevated alkaline phosphatase level, presence of anti-mitochondrial antibodies and characteristic histology. Since 1998, ursodeoxycholic acid (UDCA), a bile acid, has been the only available therapeutic agent. Primary biliary cholangitis is associated with the development of end-stage liver disease, increased morbidity and mortality. UDCA has been shown to improve serum biochemistries, histology and delay the need for liver transplantation. The clinical issue is that approximately 25%-40% of patients do not respond to this standard therapy. In recent years, many trials have investigated alternative and adjunctive treatments, leading to the recent approval of obeticholic acid, an analogue of chenodeoxycholic acid, which has shown significant and sustained reductions in alkaline phosphatase levels in combination with UDCA. Obeticholic acid has rapidly been embraced as a new agent to improve the biochemical profile in refractory patients, in addition to being approved for use as monotherapy in patients who cannot tolerate UDCA. There are several other studies and targets which are being investigated. This review is intended to highlight the benefits of UDCA, educate the reader on the newly available obeticholic acid, and to summarize the many ongoing trials and therapeutic targets being investigated in attempts to control and cure primary biliary cholangitis.

First-Degree Living-Related Donor Liver Transplantation in Autoimmune Liver Diseases

Liver transplantation (LT) is the treatment of choice for end-stage autoimmune liver diseases. However, the underlying disease may recur in the graft in some 20% of cases. The aim of this study is to determine whether LT using living donor grafts from first-degree relatives results in higher rates of recurrence than grafts from more distant/unrelated donors. Two hundred sixty-three patients, who underwent a first LT in the Toronto liver transplant program between January 2000 and March 2015 for autoimmune liver diseases, and had at least 6 months of post-LT follow-up, were included in this study. Of these, 72 (27%) received a graft from a first-degree living-related donor, 56 (21%) from a distant/unrelated living donor, and 135 (51%) from a deceased donor for primary sclerosing cholangitis (PSC) (n = 138, 52%), primary biliary cholangitis (PBC) (n = 69, 26%), autoimmune hepatitis (AIH) (n = 44, 17%), and overlap syndromes (n = 12, 5%). Recurrence occurred in 52 (20%) patients. Recurrence rates for each autoimmune liver disease were not significantly different after first-degree living-related, living-unrelated, or deceased-donor LT. Similarly, time to recurrence, recurrence-related graft failure, graft survival, and patient survival were not significantly different between groups. In conclusion, first-degree living-related donor LT for PSC, PBC, or AIH is not associated with an increased risk of disease recurrence.

Low incidence of primary biliary cirrhosis (PBC) in the first-degree relatives of PBC probands after 8 years of follow-up

BACKGROUND & AIMS

Primary biliary cirrhosis (PBC) is characterized by chronic cholestasis and disease-specific antimitochondrial antibodies (AMA). A high prevalence of AMAs in first-degree relatives (FDRs) of PBC probands has been reported, although the natural history of such patients has not been described. We aimed to assess the risk of developing PBC in AMA+ FDRs of patients with PBC.

METHODS

First-degree relatives recruited to the Mayo Clinic PBC Genetic Epidemiology Registry and Biorepository were followed for disease onset after recruitment. Development of PBC was ascertained via self-report during a telephone interview and/or via proband report on a questionnaire. Chi-squared test and t-test were used to assess the differences between categorical and continuous variables respectively. A mixed-effects model was used to assess the change in biochemical profiles over time.

RESULTS

Forty AMA+ and 423 AMA- subjects were included and followed for a median of 8.9 and 8.4 years respectively. Overall, 3% (n = 15) of FDRs were diagnosed with PBC, and AMA+ FDRs had a higher risk than AMA- FDRs (24% vs. 0.7%, P < 0.01). However, among undiagnosed FDRs, only 4% of AMA+ (n = 1) and 0.4% of AMA- (n = 1) FDRs were diagnosed with PBC (P = 0.17) during the follow-up period. None of the AMA+ FDRs with normal alkaline phosphatase at baseline developed PBC in follow-up.

CONCLUSIONS

Our results suggest a low risk of developing PBC over time in FDRs of patients with PBC, particularly those without biochemical evidence of cholestasis at baseline. These data are useful in counselling and reassuring relatives of their overall favourable prognosis.

It is time to change primary biliary cirrhosis (PBC): New nomenclature from "cirrhosis" to "cholangitis", and upcoming treatment based on unveiling pathology

Primary biliary cirrhosis (PBC) is a chronic, organ-specific, autoimmune liver disease characterized by progressive cholestasis, eventually leading to cirrhosis. Several lines of evidence have revealed a crucial role of adaptive as well as innate immune responses in the etiopathogenesis of PBC, and more recently, the biology of bile duct cells and genome-wide association studies (GWAS) demonstrated several key molecules and pathways in this enigmatic disease. Although ursodeoxycholic acid (UDCA) has been the only approved drug for PBC with clinical evidences for improvement of long-term outcomes, a substantial population have suboptimal responses to UDCA, resulting in unfavorable outcomes. In this regard, second-line treatment for patients refractory to UDCA is strongly awaited. In Japan, bezafibrate (BF) has been frequently used for this purpose, yet recent clinical trials failed to clearly demonstrate clinical efficacy of BF. Novel pharmacotherapies targeted to key molecules and pathways in PBC are upcoming. Finally, we sincerely call on all members of the Japan Society of Hepatology to use from this moment on the name "primary biliary cholangitis" for the disease known by its abbreviation PBC, in keeping with a very recent global agreement.

Xenobiotics and loss of tolerance in primary biliary cholangitis

Data from genome wide association studies and geoepidemiological studies established that a combination of genetic predisposition and environmental stimulation is required for the loss of tolerance in primary biliary cholangitis (PBC). The serologic hallmark of PBC are the presence of high titer anti-mitochondrial autoantibodies (AMA) that recognize the lipoyl domain of the mitochondrial pyruvate dehydrogenase E2 (PDC-E2) subunit. Extensive efforts have been directed to investigate the molecular basis of AMA. Recently, experimental data has pointed to the thesis that the breaking of tolerance to PDC-E2 is a pivotal event in the initial etiology of PBC, including environmental xenobiotics including those commonly found in cosmetics and food additives, suggesting that chemical modification of the PDC-E2 epitope may render its vulnerable to become a neo-antigen and trigger an immune response in genetically susceptible hosts. Here, we will discuss the natural history, genetics and immunobiology of PBC and structural constraints of PDC-E2 in AMA recognition which makes it vulnerable to chemical modification.

Using GWAS to identify genetic predisposition in hepatic autoimmunity

Primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH) represent the three major hepatic autoimmune conditions. Patient morbidity and mortality remain high across these three diseases, and an unmet need for rational therapy exists. Disease understanding has focused on combining clinical and laboratory based science to provide better insights into the joint host and environmental factors necessary for the initiation, and perpetuation, of hepato-biliary inflammation. Twin studies, family studies, population studies and an inter-relationship with other autoimmune phenomena suggest a genetic component to risk for each disease. Until recently, understanding of this genetic risk has been limited to HLA haplotypes. Associations with risk-conferring and protective HLA haplotypes are present in all three diseases. Over the last few years, genome-wide association studies (GWAS), and related genetic association studies, have greatly increased understanding of the genetic risk signature of these three diseases and autoimmunity in general. Here we consider the rationale for GWAS in general and with specific reference to hepatic autoimmunity. We consider the process of GWAS, and highlight major findings to date. Potential functional implications of key findings are discussed including the IL-12/STAT4 pathway in PBC and the CD28/IL-2 pathway in PSC. We describe the marked pleiotropy demonstrated by PBC and PSC, which is consistent with other autoimmune diseases. Further, we focus on specific gene associations including SH2B3, which is common to all three diseases, and FUT2 in PSC, which represents a link between environment and genetics. We review attempts to translate GWAS findings into basic laboratory models including in vivo systems and highlight where clinical observations relate to genetics. Finally we describe deficiencies in GWAS to date and consider future study of genetics in hepatic autoimmunity.

Brazilian society of hepatology recommendations for the diagnosis and management of autoimmune diseases of the liver

ABSTRACT In order to draw evidence-based recommendations concerning the management of autoimmune diseases of the liver, the Brazilian Society of Hepatology has sponsored a single-topic meeting in October 18th, 2014 at São Paulo. An organizing committee comprised of seven investigators was previously elected by the Governing Board to organize the scientific agenda as well as to select twenty panelists to make a systematic review of the literature and to present topics related to the diagnosis and treatment of autoimmune hepatitis, primary sclerosing cholangitis, primary biliary cirrhosis and their overlap syndromes. After the meeting, all panelists gathered together for the discussion of the topics and the elaboration of those recommendations. The text was subsequently submitted for suggestions and approval of all members of the Brazilian Society of Hepatology through its homepage. The present paper is the final version of the reviewed manuscript organized in topics, followed by the recommendations of the Brazilian Society of Hepatology.

Genome-Wide Association Studies in Primary Biliary Cirrhosis

Genome-wide association studies (GWASs) have been a significant technological advance in our ability to evaluate the genetic architecture of complex diseases such as primary biliary cirrhosis (PBC). To date, six large-scale studies have been performed that have identified 27 risk loci in addition to human leukocyte antigen (HLA) associated with PBC. The identified risk variants emphasize important disease concepts; namely, that disturbances in immunoregulatory pathways are important in the pathogenesis of PBC and that such perturbations are shared among a diverse number of autoimmune diseases-suggesting the risk architecture may confer a generalized propensity to autoimmunity not necessarily specific to PBC. Furthermore, the impact of non-HLA risk variants, particularly in genes involved with interleukin-12 signaling, and ethnic variation in conferring susceptibility to PBC have been highlighted. Although GWASs have been a critical stepping stone in understanding common genetic variation contributing to PBC, limitations pertaining to power, sample availability, and strong linkage disequilibrium across genes have left us with an incomplete understanding of the genetic underpinnings of disease pathogenesis. Future efforts to gain insight into this missing heritability, the genetic variation that contributes to important disease outcomes, and the functional consequences of associated variants will be critical if practical clinical translation is to be realized.

The immunogenetics of primary biliary cirrhosis: A comprehensive review

Primary biliary cirrhosis (PBC), a classic autoimmune liver disease, is characterised by a progressive T cell predominant lymphocytic cholangitis, and a serologic pattern of reactivity in the form of specific anti-mitochondrial antibodies (AMA). CD4+ T cells are particularly implicated by PBC's cytokine signature, the presence of CD4+ T cells specific to mitochondrial auto-antigens, the expression of MHC II on injured biliary epithelial cells, and PBC's coincidence with other similar T cell mediated autoimmune conditions. CD4+ T cells are also central to current animal models of PBC, and their transfer typically also transfers disease. The importance of genetic risk to developing PBC is evidenced by a much higher concordance rate in monozygotic than dizygotic twins, increased AMA rates in asymptomatic relatives, and disproportionate rates of disease in siblings of PBC patients, PBC family members and certain genetically defined populations. Recently, high-throughput genetic studies have greatly expanded our understanding of the gene variants underpinning risk for PBC development, so linking genetics and immunology. Here we summarize genetic association data that has emerged from large scale genome-wide association studies and discuss the evidence for the potential functional significance of the individual genes and pathways identified; we particularly highlight associations in the IL-12-STAT4-Th1 pathway. HLA associations and epigenetic effects are specifically considered and individual variants are linked to clinical phenotypes where data exist. We also consider why there is a gap between calculated genetic risk and clinical data: so-called missing heritability, and how immunogenetic observations are being translated to novel therapies. Ultimately whilst genetic risk factors will only account for a proportion of disease risk, ongoing efforts to refine associations and understand biologic links to disease pathways are hoped to drive more rational therapy for patients.

Primary biliary cirrhosis: Clinical and laboratory criteria for its diagnosis

Primary biliary cirrhosis (PBC) is a chronic progressive cholestatic granulomatous, and destructive inflammatory lesion of small intralobular and septal bile ducts, which is likely to be caused by an autoimmune mechanism with a the presence of serum antimitochondrial antibodies and a potential tendency to progress to cirrhosis. Despite the fact that the etiology of this disease has been unknown so far, there has been a considerable body of scientific evidence that can reveal the clinical and laboratory signs of PBC and the individual components of its pathogenesis and elaborate diagnostic criteria for the disease and its symptomatic therapy. Deficiencies in autoimmune tolerance are critical factors for the initiation and perpetuation of the disease. The purpose of this review is to summarize the data available in the literature and the author’s findings on clinical and laboratory criteria for the diagnosis of PBC. This review describes the major clinical manifestations of the disease and the mechanisms of its development. It presents the immunological, biochemical, and morphological signs of PBC and their significance for its diagnosis. A great deal of novel scientific evidence for the problem of PBC has been accumulated. However, the inadequate efficiency of therapy for the disease lends impetus to the quest for its etiological factors and to further investigations of its pathogenetic mechanisms and, on this basis, to searches for new methods for its early diagnosis.

Unmet clinical need in autoimmune liver diseases

Despite recent advances in understanding and treatment, there remain significant areas of unmet clinical need in each of the autoimmune liver diseases (AILDs). The evolving research landscape and emerging large patient cohorts are creating unique opportunities to translate science into new therapies and care pathways, with the potential to significantly improve the lives of AILD patients. However, the areas of unmet need represent real challenges, which need to be addressed, if this vision is to be realised. This review describes the areas of unmet need in AILD in adults relating to diagnostic and prognostic assessment, primary therapy, symptom management, trial design and delivery, and structured care delivery, with the aim of focusing future research prioritisation.

Cronkhite-Canada syndrome showing elevated levels of antinuclear and anticentromere antibody

A 56-year-old female initially visited an otorhinolaryngologist because of an impaired sense of taste in September, 2010 and was referred to our facility in October, 2010. She was diagnosed with Basedow's disease for which she underwent subtotal thyroidectomy in 1984 and arthritis involving multiple joints, primarily affecting her hands. In addition, the anticentromere antibody (ACA) level was markedly high. On physical examination, alopecia as well as hyperpigmentation of the dorsum of the hands and back was observed. Dystrophic changes of the fingernails and a bilateral thumb abduction deformity were observed. Antinuclear antibodies were elevated. Gastrointestinal endoscopy and colonoscopy revealed the mucosa carpeted with strawberry-like polypoid lesions. Histopathological examination of the biopsied specimen of the stomach revealed a corkscrew-like appearance. Thus, the patient was diagnosed with Cronkhite-Canada syndrome (CCS). She admitted to our hospital in November, 2010. Oral prednisolone was administered with success. In July, 2012, her antimitochondrial M2 antibody level was elevated. To the best of our knowledge, the present case is the first patient with CCS, a history of Basedow's disease, and elevated levels of ACA and antimitochondrial M2 antibody. We consider the present case suggests CCS could be caused by immunological abnormality.

Biochemical response to ursodeoxycholic acid predicts survival in a North American cohort of primary biliary cirrhosis patients

BACKGROUND

Biochemical response to ursodeoxycholic acid among patients with primary biliary cirrhosis remains variable, and there is no agreement of an ideal model. Novel assessment of response coupled to histologic progression was recently defined by the Toronto criteria. We retrospectively assessed transplant-free survival and clinical outcomes associated with ursodeoxycholic acid response to evaluate the Toronto criteria using a large North American cohort of PBC patients.

METHODS

Three hundred and ninety-eight PBC patients from the Mayo Clinic PBC Genetic Epidemiology Registry were assessed for ursodeoxycholic acid treatment and biochemical response per the Toronto criteria. Responders were defined by reduction in alkaline phosphatase to less than or equal to 1.67 times the upper normal limit by 2 years of treatment, whereas non-responders had alkaline phosphatase values greater than 1.67 times the upper normal limit. Probability of survival was estimated using the Kaplan-Meier method.

RESULTS

Three hundred and two (76 %) patients were responders and 96 (24 %) were non-responders. Significantly more non-responders developed adverse events related to chronic liver disease compared to responders (hazard ratio (HR) 2.77, P = 0.001). Biochemical responders and early-stage disease at treatment start was associated with improved overall transplant-free survival compared to non-responders (HR 1.9) and patients with late-stage disease (HR 2.7) after age and sex adjustment.

CONCLUSIONS

The Toronto criteria are capable of identifying ursodeoxycholic acid-treated primary biliary cirrhosis patients at risk of poor transplant-free survival and adverse clinical outcomes. Our data reveal that despite advanced disease at diagnosis, biochemical response per the Toronto criteria associates with improved overall transplant-free survival.

Environmental factors in primary biliary cirrhosis

The etiology of the autoimmune liver disease primary biliary cirrhosis (PBC) remains largely unresolved, owing in large part to the complexity of interaction between environmental and genetic contributors underlying disease development. Observations of disease clustering, differences in geographical prevalence, and seasonality of diagnosis rates suggest the environmental component to PBC is strong, and epidemiological studies have consistently found cigarette smoking and history of urinary tract infection to be associated with PBC. Current evidence implicates molecular mimicry as a primary mechanism driving loss of tolerance and subsequent autoimmunity in PBC, yet other environmentally influenced disease processes are likely to be involved in pathogenesis. In this review, the authors provide an overview of current findings and touch on potential mechanisms behind the environmental component of PBC.

Geoepidemiology and space-time analysis of Primary biliary cirrhosis in Crete, Greece

BACKGROUND & AIMS

The prevalence of Primary biliary cirrhosis varies in different geographical areas. This might reflect genetic or environmental risk factors. We aimed to define Primary biliary cirrhosis prevalence and incidence, describe patient's spatial distribution, generate prediction maps and detect any possible routing pattern of time-spatial appearance of the disease in Crete, Greece.

METHODS

From 1990-2010, 245 Primary biliary cirrhosis patients diagnosed and followed up at the Gastroenterology Department of the University Hospital and the District Hospitals of the island, were contacted and 222 were included in the time-spatial analysis. To map their spatial distribution per 5-year periods, geospatial models were applied in Gis-ArcMap 9.3 software. Kriging Interpolation methods were used to generate prediction maps for the disease in Crete. Areas of high and low probability of disease occurrence were estimated through multicriteria modelling. The disease route was defined by Gis-ArcMap's toolbox.

RESULTS

Prevalence was found to be 365 cases per million, with a mean incidence of 20.88 (range 3.79-35.99). Prediction map estimates from 1.22 to 11 patients per 50 km2 all over Crete. Areas of high risk of disease occurrence are located in the Eastern part, while low risk in the Western part of the island.

DISCUSSION

Prevalence and incidence of Primary biliary cirrhosis in Crete are among the higher published in Europe. Given the homogeneous and stable study population and the geopolitics of the island, the heterogeneity in the time-spatial distribution and the route of disease appearance strongly suggest a role for environmental causative agents.

Polymorphisms in the vitamin D receptor gene and risk of primary biliary cirrhosis: a meta-analysis

BACKGROUND AND AIM

Primary biliary cirrhosis (PBC) is a chronic and progressive cholestatic autoimmune liver disease. Although many studies have evaluated the association between many functional polymorphisms in the vitamin D receptor (VDR) gene and PBC risk, debates still exist. Our aim is to evaluate the association between VDR gene polymorphisms, including TaqI (rs731236), BsmI (rs1544410), and ApaI (rs7975232), and the risk of PBC by a systematic review.

METHODS

We searched literatures in PubMed, SCOPUS, and EMBASE until July 2013. We calculated pooled odds ratios (OR) and 95% confidence intervals (CIs) using a fixed effects model or a random effects model for the risk to PBC associated with different VDR gene polymorphisms. And the heterogeneity assumption decided the effect model.

RESULTS

A total of six relevant studies, with 1322 PBC cases and 2264 controls, were included in this meta-analysis. The results indicated that TaqI (rs731236) polymorphism was significantly associated with PBC risk (for T vs t OR = 0.75, 95% CI 0.63, 0.89, Pz = 0.001; TT + Tt vs tt OR = 0.62, 95% CI 0.44, 0.86, Pz = 0.005; OR = 0.74, 95% CI 0.58, 0.94, Pz = 0.016 for recessive model), while ApaI (rs7975232) or BsmI (rs1544410) polymorphism did not.

CONCLUSION

Based on current evidences from published studies, the cumulative effect of TaqI polymorphism in VDR was significantly associated with PBC. Larger studies with mixed ethnicity subjects and stratified by clinical and sub clinical characteristics are needed to validate our findings.

Autoantibody and human leukocyte antigen profiles in children with autoimmune liver disease and their first-degree relatives

OBJECTIVE

Familial clustering of juvenile autoimmune liver disease (AILD), including autoimmune hepatitis and autoimmune sclerosing cholangitis (ASC), is rare, despite a high prevalence of autoimmune disorders in AILD families.

METHODS

To investigate this discrepancy, we measured autoantibodies diagnostic for AILD, anti-nuclear, anti-smooth muscle, anti-liver kidney microsomal type 1, anti-liver cytosol type 1, and anti-soluble liver antigen antibodies, and human leukocyte antigen profiles in 31 patients and 65 of their first-degree relatives (FDR). The autoantibody profile was compared with that of 42 healthy subjects (HS).

RESULTS

Autoantibodies were detected in 71% (22/31) patients. Anti-nuclear antibody or anti-smooth muscle antibody were present in 4/65 FDR (6.2%). HS were negative for all autoantibodies. The frequencies of homozygous HLA DRB1*0301 (DR3) genes and haplotype A1-B8-DR3 were higher in the patients (25% and 43%) than in FDR (9% and 27%) and HS (0% and 16%). The frequencies of disease-protective genes DR4 and/or DR15 were lower in the patients (25%) than in FDR (42%) and HS (42%). Only 1 family contained 2 patients with AILD, 1 with ASC and 1 with primary sclerosing cholangitis. Both patients possessed A1-B8-DR3 genes, the ASC being homozygous and the primary sclerosing cholangitis heterozygous. Six FDR had nonhepatic autoimmune disorders, none being autoantibody positive.

CONCLUSIONS

Homozygosity for DR3 plays a major role in the predisposition to juvenile AILD. Diagnostic autoantibodies for AILD are rare among patients' FDR and not linked to clinical manifestation of AILD.

Tracing environmental markers of autoimmunity: introducing the infectome

We recently introduced the concept of the infectome as a means of studying all infectious factors which contribute to the development of autoimmune disease. It forms the infectious part of the exposome, which collates all environmental factors contributing to the development of disease and studies the sum total of burden which leads to the loss of adaptive mechanisms in the body. These studies complement genome-wide association studies, which establish the genetic predisposition to disease. The infectome is a component which spans the whole life and may begin at the earliest stages right up to the time when the first symptoms manifest, and may thus contribute to the understanding of the pathogenesis of autoimmunity at the prodromal/asymptomatic stages. We provide practical examples and research tools as to how we can investigate disease-specific infectomes, using laboratory approaches employed from projects studying the “immunome” and “microbiome”. It is envisioned that an understanding of the infectome and the environmental factors that affect it will allow for earlier patient-specific intervention by clinicians, through the possible treatment of infectious agents as well as other compounding factors, and hence slowing or preventing disease development.

Questionnaire based assessment of risk factors for primary biliary cirrhosis

BACKGROUND

Primary biliary cirrhosis is a cholestatic liver disease characterized by immune-mediated destruction of bile ducts. Its pathogenesis is largely unknown, although complex interactions between environment and genetic predisposition are proposed.

AIMS

Identify disease risk factors using a detailed patient questionnaire and compare study findings to 3 published reports.

METHODS

Questionnaire data were prospectively collected from 522 cases and 616 controls of the Mayo Clinic Primary Biliary Cirrhosis Genetic Epidemiology Registry. Case and control responses were compared using logistic regression, adjusting for recruitment age, sex, and education level.

RESULTS

Cases reported ever regularly smoking cigarettes more frequently than controls (P < 0.001). History of urinary tract infection was similar between groups; however, cases reported multiple urinary tract infections more commonly than controls (P < 0.001). Frequency of other autoimmune disease was higher in cases than controls (P < 0.001). As well, prevalence of primary biliary cirrhosis among first-degree relatives was higher in case families than control families (P < 0.001).

CONCLUSIONS

Our study confirms prior reported risk factors associated with disease risk. Given the potential importance of gene and environment interactions, further examination of environmental risk factors considering genetic background may provide new insight into primary biliary cirrhosis pathogenesis.

[Primary biliary cirrhosis and pregnancy]

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease, asymptomatic during a protracted time, characterized by changes in the small-sized bile ducts near portal spaces. The etiology of PBC is undefined, but immunologic and environmental disturbances may contribute to the disease. Infertility is often associated with PBC and cirrhosis, but pregnancy may well occur in women with PBC and without cirrhosis or in some others with compensated cirrhosis. A pluridisciplinary approach including gastroenterologists and obstetricians is recommended. The patient must be closely monitored throughout her pregnancy with maternal and routine antenatal care. Medical treatment requires ursodeoxycholic acid (UDCA). In non-cirrhotic UDCA-treated women with PBC, pregnancy often follows a normal course with vaginal delivery. In cirrhotic patients, UDCA must be continued during pregnancy, esophageal and gastric varices must be evaluated before pregnancy, and endoscopic ligature is recommended for treating large varices. Additionally, beta-blocker therapy may be associated, especially when variceal rupture occurred previously. Elective cesarean section is recommended in patients with large esophageal or gastric varices because of the potentially increased risk of variceal bleeding during maternal expulsive efforts in case of vaginal delivery.

The immunobiology and pathophysiology of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease characterized by clinical homogeneity among patients, an overwhelming female predominance, production of a multilineage immune response to mitochondrial autoantigens, inflammation of small bile ducts, and in some patients the development of fibrosis and cirrhosis. The targets in this disease are small bile ducts, and the prototypic serologic response includes antimitochondrial antibodies (AMAs). Several key observations have greatly advanced our understanding of PBC. First, the multilineage immune response, including AMAs, is directed at the E2 component of the 2-oxo-dehydrogenase pathway, particularly PDC-E2. Second, such autoantibodies may be identified years before the clinical diagnosis of disease. Third, the autoreactive T cell precursor frequency for both CD4 and CD8 cells is significantly higher in liver and regional lymph node than in blood, so the multilineage antimitochondrial response may be required for the development of this disease. Fourth, the apotope of biliary cells contains intact PDC-E2; this apotope, in a setting that includes granulocyte macrophage colony-stimulating factor-stimulated macrophages and AMAs, produces an intense proinflammatory response. Fifth, several mouse models of PBC highlight the importance of loss of tolerance to PDC-E2 as well as a critical role for the interleukin (IL)-12 signaling pathway. Finally, genome-wide association studies suggest an important role for the IL-12 pathway in disease susceptibility. Taken together, these findings have resulted in a better understanding of the mechanism for selective biliary cell destruction and have also suggested unique pathways for therapeutic intervention.

Environment and primary biliary cirrhosis: electrophilic drugs and the induction of AMA

Environmental stimulation is a major factor in the initiation and perpetuation of autoimmune diseases. We have addressed this issue and focused on primary biliary cirrhosis (PBC), an autoimmune disease of the liver. Immunologically, PBC is distinguished by immune mediated destruction of the intra hepatic bile ducts and the presence of high titer antimitochondrial autoantibodies (AMA) directed against a highly specific epitope within the lipoic acid binding domain of the pyruvate dehydrogenase E2 subunit (PDC-E2). We submit that the uniqueness of AMA epitope specificity and the conformational changes of the PDC-E2 lipoyl domain during physiological acyl transfer could be the lynchpin to the etiology of PBC and postulate that chemical xenobiotics modification of the lipoyl domain of PDC-E2 is sufficient to break self-tolerance, with subsequent production of AMA in patients with PBC. Indeed, using quantitative structure activity relationship (QSAR) analysis on a peptide-xenobiotic conjugate microarray platform, we have demonstrated that when the lipoyl domain of PDC-E2 was modified with specific synthetic small molecule lipoyl mimics, the ensuing structures displayed highly specific reactivity to PBC sera, at levels often higher than the native PDC-E2 molecule. Hereby, we discuss our recent QSAR analysis data on specific AMA reactivity against a focused panel of lipoic acid mimic in which the lipoyl di-sulfide bond are modified. Furthermore, data on the immunological characterization of antigen and Ig isotype specificities against one such lipoic acid mimic; 6,8-bis(acetylthio)octanoic acid (SAc), when compared with rPDC-E2, strongly support a xenobiotic etiology in PBC. This observation is of particular significance in that approximately one third of patients who have taken excessive acetaminophen (APAP) developed AMA with same specificity as patients with PBC, suggesting that the lipoic domain are a target of APAP electrophilic metabolites such as NAPQI. We submit that in genetically susceptible hosts, electrophilic modification of lipoic acid in PDC-E2 by acetaminophen or similar drugs can facilitate loss of tolerance and lead to the development of PBC.