Genetic and functional analysis of chymotrypsin-like protease (CTRL) in chronic pancreatitis

BACKGROUND

Genetic predisposition is crucial in the pathogenesis of early-onset chronic pancreatitis (CP). So far, several genetic alterations have been identified as risk factors, predominantly in genes encoding digestive enzymes. However, many early-onset CP cases have no identified underlying cause. Chymotrypsins are a family of serine proteases that can cleave trypsinogen and lead to its degradation. Because genetic alterations in the chymotrypsins CTRC, CTRB1, and CTRB2 are associated with CP, we genetically and functionally investigated chymotrypsin-like protease (CTRL) as a potential risk factor.

METHODS

We screened 1005 non-alcoholic CP patients and 1594 controls for CTRL variants by exome sequencing. We performed Western blots and activity assays to analyse secretion and proteolytic activity. We measured BiP mRNA expression to investigate the potential impact of identified alterations on endoplasmic reticulum (ER) stress.

RESULTS

We identified 13 heterozygous non-synonymous CTRL variants: five exclusively in patients and three only in controls. Functionality was unchanged in 6/13 variants. Four alterations showed normal secretion but reduced (p.G20S, p.G56S, p.G61S) or abolished (p.S208F) activity. Another three variants (p.C201Y, p.G215R and p.C220G) were not secreted and already showed reduced or no activity intracellularly. However, intracellular retention did not lead to ER stress.

CONCLUSION

We identified several CTRL variants, some showing potent effects on protease function and secretion. We observed these effects in variants found in patients and controls, and CTRL loss-of-function variants were not significantly more common in patients than controls. Therefore, CTRL is unlikely to play a relevant role in the development of CP.

Notch1 Induces Defective Epithelial Surfactant Processing and Pulmonary Fibrosis

Rationale: Although type II alveolar epithelial cells (AEC2s) are chronically injured in idiopathic pulmonary fibrosis (IPF), they contribute to epithelial regeneration in IPF. Objectives: We hypothesized that Notch signaling may contribute to AEC2 proliferation, dedifferentiation characterized by loss of surfactant processing machinery, and lung fibrosis in IPF. Methods: We applied microarray analysis, kinome profiling, flow cytometry, immunofluorescence analysis, western blotting, quantitative PCR, and proliferation and surface activity analysis to study epithelial differentiation, proliferation, and matrix deposition in vitro (AEC2 lines, primary murine/human AEC2s), ex vivo (human IPF-derived precision-cut lung slices), and in vivo (bleomycin and pepstatin application, Notch1 [Notch receptor 1] intracellular domain overexpression). Measurements and Main Results: We document here extensive SP-B and -C (surfactant protein-B and -C) processing defects in IPF AEC2s, due to loss of Napsin A, resulting in increased intra-alveolar surface tension and alveolar collapse and induction of endoplasmic reticulum stress in AEC2s. In vivo pharmacological inhibition of Napsin A results in the development of AEC2 injury and overt lung fibrosis. We also demonstrate that Notch1 signaling is already activated early in IPF and determines AEC2 fate by inhibiting differentiation (reduced lamellar body compartment, reduced capacity to process hydrophobic SP) and by causing increased epithelial proliferation and development of lung fibrosis, putatively via altered JAK (Janus kinase)/Stat (signal transducer and activator of transcription) signaling in AEC2s. Conversely, inhibition of Notch signaling in IPF-derived precision-cut lung slices improved the surfactant processing capacity of AEC2s and reversed fibrosis. Conclusions: Notch1 is a central regulator of AEC2 fate in IPF. It induces alveolar epithelial proliferation and loss of Napsin A and of surfactant proprotein processing, and it contributes to fibroproliferation.

The PRSS3P2 and TRY7 deletion copy number variant modifies risk for chronic pancreatitis

BACKGROUND

PRSS1 and PRSS2 constitute the only functional copies of a tandemly-arranged five-trypsinogen-gene cluster (i.e., PRSS1, PRSS3P1, PRSS3P2, TRY7 and PRSS2) on chromosome 7q35. Variants in PRSS1 and PRSS2, including missense and copy number variants (CNVs), have been reported to predispose to or protect against chronic pancreatitis (CP). We wondered whether a common trypsinogen pseudogene deletion CNV (that removes two of the three trypsinogen pseudogenes, PRSS3P2 and TRY7) might be associated with CP causation/predisposition.

METHODS

We analyzed the common PRSS3P2 and TRY7 deletion CNV in a total of 1536 CP patients and 3506 controls from France, Germany, India and Japan by means of quantitative fluorescent multiplex polymerase chain reaction.

RESULTS

We demonstrated that the deletion CNV variant was associated with a protective effect against CP in the French, German and Japanese cohorts whilst a trend toward the same association was noted in the Indian cohort. Meta-analysis under a dominant model yielded a pooled odds ratio (OR) of 0.68 (95% confidence interval (CI) 0.52-0.89; p = 0.005) whereas an allele-based meta-analysis yielded a pooled OR of 0.84 (95% CI 0.77-0.92; p = 0.0001). This protective effect is explicable by reference to the recent finding that the still functional PRSS3P2/TRY7 pseudogene enhancers upregulate pancreatic PRSS2 expression.

CONCLUSIONS

The common PRSS3P2 and TRY7 deletion CNV was associated with a reduced risk for CP. This finding provides additional support for the emerging view that dysregulated PRSS2 expression represents a discrete mechanism underlying CP predisposition or protection.

Genetic analysis of the aquaporin water channels AQP12A and AQP12B in patients with chronic pancreatitis

BACKGROUND

Alterations in genes specifically expressed in the pancreas have been associated with chronic pancreatitis (CP). A significant percentage of patients with non-alcoholic CP, however, do not have mutations in known risk genes, suggesting the existence of further susceptibility genes. Four aquaporins are expressed in the exocrine pancreas: AQP1, AQP5, AQP8 and AQP12, the latter being found exclusively in this organ. Therefore, we investigated the two AQP12 genes, AQP12A and AQP12B, in CP patients.

METHODS

We analyzed all exons and adjacent intronic regions of AQP12A and AQP12B in 292 German patients with non-alcoholic CP and 143 control subjects by direct DNA sequencing.

RESULTS

In total, we discovered 41 non-synonymous changes, three of which were nonsense variants. Genotype and allele frequencies of these variants did not differ significantly between patients and controls (all p-values >0.05). Remarkably, we found a common nonsense variant in AQP12B, p.S152Tfs∗24, with an allele frequency of 15.7% in controls, including 2.8% homozygous subjects. This finding suggests that AQP12B is physiologically dispensable for normal pancreatic function.

CONCLUSIONS

Our results suggest that genetic alterations in AQP12A and AQP12B do not predispose to the development of non-alcoholic CP.

Genetic Analysis of the ATG16L1 c.898A>G (p.T300A) Variant in Acute and Chronic Pancreatitis

OBJECTIVES

Human and animal studies suggest an important role of autophagy in the pathogenesis of pancreatitis. ATG16L1 (autophagy-related 16 like 1) is part of a protein complex that is involved in the formation of autophagosomes. The c.898A > G (p.T300A) variant of ATG16L1 is associated with Crohn disease. In this study, we analyzed ATG16L1 c.898A > G (p.T300A) for an association with pancreatitis.

METHODS

We genotyped 777 patients and 551 control subjects of German origin by melting curve analysis using fluorescence resonance energy transfer probes. The patient group included 429 patients with nonalcoholic chronic pancreatitis (CP), 141 patients with alcoholic CP, and 207 patients with acute pancreatitis (AP). We classified AP by severity according to the Atlanta symposium 1992.

RESULTS

Allele and genotype frequencies of ATG16L1 c.898A > G (p.T300A) did not differ significantly between patients and controls (G allele frequencies: nonalcoholic CP, 49.9%; alcoholic CP, 48.2%; AP, 49.5%; controls, 52.7%). We found no significant association with the severity of AP either.

CONCLUSIONS

Our data do not support a role of ATG16L1 c.898A > G (p.T300A) in the pathogenesis of AP or CP or an influence on the severity of AP.

Loss-of-function variant in chymotrypsin like elastase 3B (CELA3B) is associated with non-alcoholic chronic pancreatitis

BACKGROUND

Genetic alterations in digestive enzymes have been associated with chronic pancreatitis (CP). Recently, chymotrypsin like elastase 3B (CELA3B) emerged as a novel risk gene. Thus, we evaluated CELA3B in two European cohorts with CP.

METHODS

We analyzed all 8 CELA3B exons in 550 German non-alcoholic CP (NACP) patients and in 241 German controls by targeted DNA sequencing. In addition, we analyzed exons 6 and 7 by Sanger sequencing and the c.129+1G>A variant by melting curve analysis in 1078 further German controls. As replication cohort, we investigated up to 243 non-German European NACP patients and up to 1665 controls originating from Poland, Hungary, and Sweden. We assessed the cellular secretion and the elastase activity of recombinant CELA3B variants.

RESULTS

In the German discovery cohort, we detected a splice-site variant in intron 2, c.129+1G>A, in 9/550 (1.64%) CP patients and in 5/1319 (0.38%) controls (P=0.007, OR=4.4, 95% CI=1.5-13.0). In the European replication cohort, this variant was also enriched in patients (9/178 [5.06%]) versus controls (13/1247 [1.04%]) (P=0.001, OR=5.1, 95% CI=2.1-12.0). We did not find the two previously reported codon 90 variants, p.R90C and p.R90L.

CONCLUSIONS

Our data indicate that CELA3B is a susceptibility gene for CP. In contrast to previous reports suggesting that increased CELA3B activity is associated with CP risk, the splice-site variant identified here is predicted to cause diminished CELA3B expression. How reduced CELA3B function predisposes to pancreatitis remains to be elucidated.

Superfluid stiffness of a KTaO3-based two-dimensional electron gas

After almost twenty years of intense work on the celebrated LaAlO₃/SrTiO₃system, the recent discovery of a superconducting two-dimensional electron gas (2-DEG) in (111)-oriented KTaO₃-based heterostructures injects new momentum to the field of oxides interface. However, while both interfaces share common properties, experiments also suggest important differences between the two systems. Here, we report gate tunable superconductivity in 2-DEGs generated at the surface of a (111)-oriented KTaO₃ crystal by the simple sputtering of a thin Al layer. We extract the superfluid stiffness of the 2-DEGs and show that its temperature dependence is consistent with a node-less superconducting order parameter having a gap value larger than expected within a simple BCS weak-coupling limit model. The superconducting transition follows the Berezinskii-Kosterlitz-Thouless scenario, which was not reported on SrTiO₃-based interfaces. Our finding offers innovative perspectives for fundamental science but also for device applications in a variety of fields such as spin-orbitronics and topological electronics.

Variants in the pancreatic CUB and zona pellucida-like domains 1 (CUZD1) gene in early-onset chronic pancreatitis - A possible new susceptibility gene

OBJECTIVE

Non-alcoholic chronic pancreatitis (NACP) frequently develops in the setting of genetic susceptibility associated with alterations in genes that are highly expressed in the pancreas. However, the genetic basis of NACP remains unresolved in a significant number of patients warranting a search for further risk genes.

DESIGN

We analyzed CUZD1, which encodes the CUB and zona pellucida-like domains 1 protein that is found in high levels in pancreatic acinar cells. We sequenced the coding region in 1163 European patients and 2018 European controls. In addition, we analyzed 297 patients and 1070 controls from Japan. We analyzed secretion of wild-type and mutant CUZD1 from transfected cells using Western blotting.

RESULTS

In the European cohort, we detected 30 non-synonymous variants. Using different prediction tools (SIFT, CADD, PROVEAN, PredictSNP) or the combination of these tools, we found accumulation of predicted deleterious variants in patients (p-value range 0.002-0.013; OR range 3.1-5.2). No association was found in the Japanese cohort, in which 13 non-synonymous variants were detected. Functional studies revealed >50% reduced secretion of 7 variants, however, these variants were not significantly enriched in European CP patients.

CONCLUSION

Our data indicate that CUZD1 might be a novel susceptibility gene for NACP. How these variants predispose to pancreatitis remains to be elucidated.

Genetic analysis of pancreatic phospholipase A2 (PLA2G1B) in patients with chronic pancreatitis

BACKGROUND

Genetic mutations in various pancreatic enzymes or their counteracting proteins have been linked to chronic pancreatitis. In particular, variants in the genes encoding pancreatic lipase (PNLIP) and carboxyl ester lipase (CEL) have been associated with pancreatitis. Therefore, we investigated pancreatic phospholipase A2 (PLA2G1B) as a promising candidate gene in patients with chronic pancreatitis.

METHODS

We analyzed all coding exons and adjacent intronic regions of PLA2G1B in 416 German patients with non-alcoholic chronic pancreatitis (NACP) and 186 control subjects by direct DNA sequencing.

RESULTS

We detected 2 frequent synonymous variants in exon 3: c.222T>C (p.Y74 = ) and c.294G>A (p.S98 = ). The genotype and allele frequencies of these variants were similar between patients and controls (c.222 TC: 9.6% in NACP vs. 9.7% in controls; c.222CC: 0.2% in NACP vs. 0% in controls; c.294 GA: 31.3% in NACP vs. 28.0% in controls; c.294AA: 2.4% in NACP vs. 1.1% in controls). All p-values were non-significant. In addition, we found one synonymous variant, c.138C>T (p.N46 = ) and one non-synonymous variant, c.244A>G (p.S82G), in a single case each.

CONCLUSIONS

Our results suggest that genetic alterations in PLA2G1B do not predispose to the development of non-alcoholic chronic pancreatitis.

Loss of function TRPV6 variants are associated with chronic pancreatitis in nonalcoholic early-onset Polish and German patients

PURPOSE

Loss of function variants of the transient receptor potential cation channel, subfamily V, member 6 (TRPV6) have been recently associated with chronic pancreatitis (CP) in Japanese, German and French patients. Here, we investigated the association of TRPV6 variants with CP in independent European cohorts of early-onset CP patients from Poland and Germany.

PATIENTS AND METHODS

We enrolled 152 pediatric CP patients (median age 8.6 yrs) with no history of alcohol/smoking abuse and 472 controls from Poland as well as 157 nonalcoholic young CP patients (median age 20 yrs) and 750 controls from Germany. Coding regions of TRPV6 were screened by Sanger and next generation sequencing. Selected, potentially pathogenic TRPV6 variants were expressed in HEK293T cells and TRPV6 activity was analyzed using ratiometric Ca²⁺ measurements.

RESULTS

Overall, we identified 10 novel (3 nonsense and 7 missenses) TRPV6 variants in CP patients. TRPV6 p.V239SfsX53 nonsense variant and the variants showing significant decrease in intracellular Ca²⁺ concentration in HEK293T cells (p.R174X, p.L576R, p.R342Q), were significantly overrepresented in Polish patients as compared to controls (6/152, 3.9% vs. 0/358, 0%; P = 0,0007). Nonsense TRPV6 variants predicted as loss of function (p.V239SfsX53 and p.R624X) were also significantly overrepresented in German patients (3/157; 2.0% vs 0/750; 0%, P = 0.005).

CONCLUSIONS

We showed that TRPV6 loss of function variants are associated with elevated CP risk in early-onset Polish and German patients confirming that TRPV6 is a novel CP susceptibility gene.

Atrial fibrillation screening: feasible approaches and implementation challenges across Europe

Background

Atrial fibrillation (AF) screening has the potential to increase early detection and possibly reduce complications of AF. Guidelines recommend screening, but the most appropriate approaches are unknown.

Purpose

We aimed to explore the views of stakeholders across Europe about the opportunities and challenges of implementing four different AF screening scenarios.

Method

This qualitative study included 21 semi-structured interviews with healthcare professionals and regulators potentially involved in AF screening implementation in nine European countries. Data were analysed using thematic analysis.

Results

Three themes evolved. 1) Current approaches to screening: there are no national AF screening programmes, with most AF detected in symptomatic patients. Patient-led screening exists via personal devices, creating screening inequity by the reach of screening programmes being limited to those who access healthcare services. 2) Feasibility of screening approaches: single time point opportunistic screening in primary care using single lead ECG devices was considered the most feasible approach and AF screening may be possible in previously unexplored settings such as dentists and podiatrists. Software algorithms may aid identification of patients suitable for screening and telehealth services have the potential to support diagnosis. However, there is a need for advocacy to encourage the use of telehealth to aid AF diagnosis, and training for screening familiarisation and troubleshooting.

3) Implementation requirements: sufficient evidence of benefit is required. National rather than pan-European screening processes must be developed due to different payment mechanisms and health service regulations.

There is concern that the rapid spread of wearable devices for heart rate monitoring may increase workload due to false positives in low risk populations for AF. Data security and inclusivity for those without access to primary care or personal devices must be addressed.

Conclusions

There is an overall awareness of AF screening. Opportunistic screening appears to be most feasible across Europe. Challenges that need to be addressed concern health inequalities, identification of best target groups for screening, streamlined processes, the need for evidence of benefit, and a tailored approach adapted to national realities.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): H2020 Screening ScenariosGraphical abstract

The three common polymorphisms p.A986S, p.R990G and p.Q1011E in the calcium sensing receptor (CASR) are not associated with chronic pancreatitis

BACKGROUND

The calcium sensing receptor (CASR) is a G protein-coupled receptor that is responsible for assessing extracellular Ca²⁺ levels and thus plays a crucial role in calcium homeostasis. Hypercalcemia is a metabolic risk factor for pancreatitis and rare CASR variants have been described in patients with chronic pancreatitis. At the carboxy-terminal tail of CASR, there is a cluster of three common polymorphisms, p.A986S (rs1801725), p.R990G (rs1042636) and p.Q1011E (rs1801726), which have been associated with chronic pancreatitis in various studies, but with conflicting results.

METHODS

We examined 542 German and 339 French patients with chronic pancreatitis as well as 1025 German controls for the 3 common CASR polymorphism by melting curve analysis. For comparison, we used genotype data from 583 French controls from a previous study. In addition, we functionally analyzed the three variants by NFAT and SRE luciferase reporter systems as well as Western blotting and verified cell surface expression by ELISA.

RESULTS

In both cohorts, neither the genotype nor the allele frequencies differed significantly between patients and controls. In both luciferase assays, p.R990G showed a significant leftward shift, indicating an increased responsiveness of the receptor. p.A986S showed a leftward shift in the SRE but not in the NFAT reporter assay, while the responsiveness of p.Q1011E did not differ from the wild-type. These functional studies therefore do not support the contributions of variant CASR to increasing the risk of pancreatitis.

CONCLUSIONS

The three frequent CASR polymorphisms are unlikely to increase the risk for chronic pancreatitis.

[Pathogenesis of chronic pancreatitis]

Long-term alcohol consumption and gene mutations are the most important causes of chronic pancreatitis. In addition to mutations in acinar genes, such as digestive enzymes and their inhibitors, defects in genes that primarily or exclusively affect the duct cells have also been described in recent years. Genetic changes are found not only in patients with a positive family history (hereditary pancreatitis) but also in so-called idiopathic and, to a lesser extent, in alcoholic chronic pancreatitis. The coming years will likely show that there are very complex interactions between environmental influences and numerous genetic factors.

Sequencing of the complex CTRB1-CTRB2 locus in chronic pancreatitis

BACKGROUND

/Objectives: A recent Genome-wide Association Study (GWAS) in alcoholic chronic pancreatitis (ACP) identified a novel association with the CTRB1-CTRB2 (chymotrypsinogen B1, B2) locus, linked to a 16.6 kb inversion that was confirmed in non-alcoholic chronic pancreatitis (NACP). Moreover, recent findings on the function of CTRB1 and CTRB2 suggest a protective role in pancreatitis development. The aim of the present study was to investigate the CTRB1-CTRB2 locus for rare genetic variants associated with chronic pancreatitis (CP).

METHODS

We analyzed 134 patients with ACP and 203 patients with NACP and compared them to up to 258 healthy controls. Genotyping was performed with polymerase chain reaction, followed by Sanger sequencing of all exons and the exon-intron-boundaries of CTRB1 and CTRB2. Finally, in silico analyses of the identified variants were conducted.

RESULTS

None of the seven rare missense variants or the single 5'-UTR variant in CTRB1 and CTRB2 was associated with ACP or NACP. In silico analysis predicted that variant p. Trp5Leu in CTRB1 and variant c.-4C > T in CTRB2 might alter protein expression and variants p. Asp222His in CTRB1 and p. Ala247Thr in CTRB2 might affect protein function. However, all of these variants were also described in public databases.

CONCLUSIONS

The present study did not reveal an association of rare variants in CTRB1 and CTRB2 with ACP or NACP. Although rare missense variants were almost exclusively found in patients, only four variants were predicted to affect protein expression or function. Thus, a major influence of rare variants in the CTRB1-CTRB2 locus on CP development is unlikely.

Analysis of GPRC6A variants in different pancreatitis etiologies

BACKGROUND

The G-protein-coupled receptor Class C Group 6 Member A (GPRC6A) is activated by multiple ligands and is important for the regulation of calcium homeostasis. Extracellular calcium is capable to increase NLRP3 inflammasome activity of the innate immune system and deletion of this proinflammatory pathway mitigated pancreatitis severity in vivo. As such this pathway and the GPRC6A receptor is a reasonable candidate gene for pancreatitis. Here we investigated the prevalence of sequence variants in the GPRC6A locus in different pancreatitis aetiologies.

METHODS

We selected 6 tagging SNPs with the SNPinfo LD TAG SNP Selection tool and the functional relevant SNP rs6907580 for genotyping. Cohorts from Germany, further European countries and China with up to 1,124 patients and 1,999 controls were screened for single SNPs with melting curve analysis.

RESULTS

We identified an association of rs1606365(G) with alcoholic chronic pancreatitis in a German (odds ratio (OR) 0.76, 95% confidence interval (CI) 0.65-0.89, p = 8 × 10^-5) and a Chinese cohort (OR 0.78, 95% CI 0.64-0.96, p = 0.02). However, this association was not replicated in a combined cohort of European patients (OR 1.18, 95% CI 0.99-1.41, p = 0.07). Finally, no association was found with acute and non-alcoholic chronic pancreatitis.

CONCLUSIONS

Our results support a potential role of calcium sensing receptors and inflammasome activation in alcoholic chronic pancreatitis development. As the functional consequence of the associated variant is unclear, further investigations might elucidate the relevant mechanisms.

European Guideline on IgG4-related digestive disease - UEG and SGF evidence-based recommendations

The overall objective of these guidelines is to provide evidence-based recommendations for the diagnosis and management of immunoglobulin G4 (IgG4)-related digestive disease in adults and children. IgG4-related digestive disease can be diagnosed only with a comprehensive work-up that includes histology, organ morphology at imaging, serology, search for other organ involvement, and response to glucocorticoid treatment. Indications for treatment are symptomatic patients with obstructive jaundice, abdominal pain, posterior pancreatic pain, and involvement of extra-pancreatic digestive organs, including IgG4-related cholangitis. Treatment with glucocorticoids should be weight-based and initiated at a dose of 0.6-0.8 mg/kg body weight/day orally (typical starting dose 30-40 mg/day prednisone equivalent) for 1 month to induce remission and then be tapered within two additional months. Response to initial treatment should be assessed at week 2-4 with clinical, biochemical and morphological markers. Maintenance treatment with glucocorticoids should be considered in multi-organ disease or history of relapse. If there is no change in disease activity and burden within 3 months, the diagnosis should be reconsidered. If the disease relapsed during the 3 months of treatment, immunosuppressive drugs should be added.

Variants That Affect Function of Calcium Channel TRPV6 Are Associated With Early-Onset Chronic Pancreatitis

BACKGROUND & AIMS

Changes in pancreatic calcium levels affect secretion and might be involved in development of chronic pancreatitis (CP). We investigated the association of CP with the transient receptor potential cation channel subfamily V member 6 gene (TRPV6), which encodes a Ca²⁺-selective ion channel, in an international cohort of patients and in mice.

METHODS

We performed whole-exome DNA sequencing from a patient with idiopathic CP and from his parents, who did not have CP. We validated our findings by sequencing DNA from 300 patients with CP (not associated with alcohol consumption) and 1070 persons from the general population in Japan (control individuals). In replication studies, we sequenced DNA from patients with early-onset CP (20 years or younger) not associated with alcohol consumption from France (n = 470) and Germany (n = 410). We expressed TRPV6 variants in HEK293 cells and measured their activity using Ca²⁺ imaging assays. CP was induced by repeated injections of cerulein in TRPV6^mut/mut mice.

RESULTS

We identified the variants c.629C>T (p.A210V) and c.970G>A (p.D324N) in TRPV6 in the index patient. Variants that affected function of the TRPV6 product were found in 13 of 300 patients (4.3%) and 1 of 1070 control individuals (0.1%) from Japan (odds ratio [OR], 48.4; 95% confidence interval [CI], 6.3-371.7; P = 2.4 × 10^-8). Twelve of 124 patients (9.7%) with early-onset CP had such variants. In the replication set from Europe, 18 patients with CP (2.0%) carried variants that affected the function of the TRPV6 product compared with 0 control individuals (P = 6.2 × 10^-8). Variants that did not affect the function of the TRPV6 product (p.I223T and p.D324N) were overrepresented in Japanese patients vs control individuals (OR, 10.9; 95% CI, 4.5-25.9; P = 7.4 × 10^-9 for p.I223T and P = .01 for p.D324N), whereas the p.L299Q was overrepresented in European patients vs control individuals (OR, 3.0; 95% CI, 1.9-4.8; P = 1.2 × 10^-5). TRPV6^mut/mut mice given cerulein developed more severe pancreatitis than control mice, as shown by increased levels of pancreatic enzymes, histologic alterations, and pancreatic fibrosis.

CONCLUSIONS

We found that patients with early-onset CP not associated with alcohol consumption carry variants in TRPV6 that affect the function of its product, perhaps by altering Ca²⁺ balance in pancreatic cells. TRPV6 regulates Ca²⁺ homeostasis and pancreatic inflammation.

Diffuse glioneuronal tumour with oligodendroglioma-like features and nuclear clusters (DGONC) - a molecularly defined glioneuronal CNS tumour class displaying recurrent monosomy 14

AIMS

DNA methylation-based central nervous system (CNS) tumour classification has identified numerous molecularly distinct tumour types, and clinically relevant subgroups among known CNS tumour entities that were previously thought to represent homogeneous diseases. Our study aimed at characterizing a novel, molecularly defined variant of glioneuronal CNS tumour.

PATIENTS AND METHODS

DNA methylation profiling was performed using the Infinium MethylationEPIC or 450 k BeadChip arrays (Illumina) and analysed using the 'conumee' package in R computing environment. Additional gene panel sequencing was also performed. Tumour samples were collected at the German Cancer Research Centre (DKFZ) and provided by multinational collaborators. Histological sections were also collected and independently reviewed.

RESULTS

Genome-wide DNA methylation data from >25 000 CNS tumours were screened for clusters separated from established DNA methylation classes, revealing a novel group comprising 31 tumours, mainly found in paediatric patients. This DNA methylation-defined variant of low-grade CNS tumours with glioneuronal differentiation displays recurrent monosomy 14, nuclear clusters within a morphology that is otherwise reminiscent of oligodendroglioma and other established entities with clear cell histology, and a lack of genetic alterations commonly observed in other (paediatric) glioneuronal entities.

CONCLUSIONS

DNA methylation-based tumour classification is an objective method of assessing tumour origins, which may aid in diagnosis, especially for atypical cases. With increasing sample size, methylation analysis allows for the identification of rare, putative new tumour entities, which are currently not recognized by the WHO classification. Our study revealed the existence of a DNA methylation-defined class of low-grade glioneuronal tumours with recurrent monosomy 14, oligodendroglioma-like features and nuclear clusters.

Common variants in glyoxalase I do not increase chronic pancreatitis risk

Introduction

Chronic pancreatitis (CP) may be caused by oxidative stress. An important source of reactive oxygen species (ROS) is the methylglyoxal-derived formation of advanced glycation endproducts (AGE). Methylglyoxal is detoxified by Glyoxalase I (GLO1). A reduction in GLO1 activity results in increased ROS. Single nucleotide polymorphisms (SNPs) of GLO1 have been linked to various inflammatory diseases. Here, we analyzed whether common GLO1 variants are associated with alcoholic (ACP) and non-alcoholic CP (NACP).

Methods

Using melting curve analysis, we genotyped a screening cohort of 223 ACP, 218 NACP patients, and 328 controls for 11 tagging SNPs defined by the SNPinfo LD TAG SNP Selection tool and the functionally relevant variant rs4746. For selected variants the cohorts were extended to up to 1,441 patient samples.

Results

In the ACP cohort, comparison of genotypes for rs1937780 between patients and controls displayed an ambiguous result in the screening cohort (p = 0.08). However, in the extended cohort of 1,441 patients no statistically significant association was found for the comparison of genotypes (p = 0.11), nor in logistic regression analysis (p = 0.214, OR 1.072, 95% CI 0.961–1.196). In the NACP screening cohort SNPs rs937662, rs1699012, and rs4746 displayed an ambiguous result when patients were compared to controls in the recessive or dominant model (p = 0.08, 0.08, and 0.07, respectively). Again, these associations were not confirmed in the extended cohorts (rs937662, dominant model: p = 0.07, logistic regression: p = 0.07, OR 1.207, 95% CI 0.985–1.480) or in the replication cohorts for rs4746 (Germany, p = 0.42, OR 1.080, 95% CI 0.673–1.124; France, p = 0.19, OR 0.90, 95% CI 0.76–1.06; China, p = 0.24, OR 1.18, 95% CI 0.90–1.54) and rs1699012 (Germany, Munich; p = 0.279, OR 0.903, 95% CI 0.750–1.087).

Conclusions

Common GLO1 variants do not increase chronic pancreatitis risk.

IRF5 Is Required for Bacterial Clearance in Human M1-Polarized Macrophages, and IRF5 Immune-Mediated Disease Risk Variants Modulate This Outcome

Common IFN regulatory factor 5 (IRF5) variants associated with multiple immune-mediated diseases are a major determinant of interindividual variability in pattern recognition receptor (PRR)-induced cytokines in macrophages. PRR-initiated pathways also contribute to bacterial clearance, and dysregulation of bacterial clearance can contribute to immune-mediated diseases. However, the role of IRF5 in macrophage-mediated bacterial clearance is not well defined. Furthermore, it is unclear if macrophages from individuals who are carriers of low IRF5-expressing genetic variants associated with protection for immune-mediated diseases might be at a disadvantage in bacterial clearance. We found that IRF5 was required for optimal bacterial clearance in PRR-stimulated, M1-differentiated human macrophages. Mechanisms regulated by IRF5 included inducing reactive oxygen species through p40phox, p47phox and p67phox, NOS2, and autophagy through ATG5. Complementing these pathways in IRF5-deficient M1 macrophages restored bacterial clearance. Further, these antimicrobial pathways required the activation of IRF5-dependent MAPK, NF-κB, and Akt2 pathways. Importantly, relative to high IRF5-expressing rs2004640/rs2280714 TT/TT immune-mediated disease risk-carrier human macrophages, M1-differentiated GG/CC carrier macrophages demonstrated less reactive oxygen species, NOS2, and autophagy pathway induction and, consequently, reduced bacterial clearance. Increasing IRF5 expression to the rs2004640/rs2280714 TT/TT levels restored these antimicrobial pathways. We define mechanisms wherein common IRF5 genetic variants modulate bacterial clearance, thereby highlighting that immune-mediated disease risk IRF5 carriers might be relatively protected from microbial-associated diseases.

Genome-wide association study identifies inversion in the CTRB1-CTRB2 locus to modify risk for alcoholic and non-alcoholic chronic pancreatitis

OBJECTIVE

Alcohol-related pancreatitis is associated with a disproportionately large number of hospitalisations among GI disorders. Despite its clinical importance, genetic susceptibility to alcoholic chronic pancreatitis (CP) is poorly characterised. To identify risk genes for alcoholic CP and to evaluate their relevance in non-alcoholic CP, we performed a genome-wide association study and functional characterisation of a new pancreatitis locus.

DESIGN

1959 European alcoholic CP patients and population-based controls from the KORA, LIFE and INCIPE studies (n=4708) as well as chronic alcoholics from the GESGA consortium (n=1332) were screened with Illumina technology. For replication, three European cohorts comprising 1650 patients with non-alcoholic CP and 6695 controls originating from the same countries were used.

RESULTS

We replicated previously reported risk loci CLDN2-MORC4, CTRC, PRSS1-PRSS2 and SPINK1 in alcoholic CP patients. We identified CTRB1-CTRB2 (chymotrypsin B1 and B2) as a new risk locus with lead single-nucleotide polymorphism (SNP) rs8055167 (OR 1.35, 95% CI 1.23 to 1.6). We found that a 16.6 kb inversion in the CTRB1-CTRB2 locus was in linkage disequilibrium with the CP-associated SNPs and was best tagged by rs8048956. The association was replicated in three independent European non-alcoholic CP cohorts of 1650 patients and 6695 controls (OR 1.62, 95% CI 1.42 to 1.86). The inversion changes the expression ratio of the CTRB1 and CTRB2 isoforms and thereby affects protective trypsinogen degradation and ultimately pancreatitis risk.

CONCLUSION

An inversion in the CTRB1-CTRB2 locus modifies risk for alcoholic and non-alcoholic CP indicating that common pathomechanisms are involved in these inflammatory disorders.

EPC/HPSG evidence-based guidelines for the management of pediatric pancreatitis

BACKGROUND

Pediatric pancreatitis is an underdiagnosed disease with variable etiology. In the past 10-15 years the incidence of pediatric pancreatitis has increased, it is now 3.6-13.3 cases per 100,000 children. Up-to-date evidence based management guidelines are lacking for the pediatric pancreatitis. The European Pancreatic Club, in collaboration with the Hungarian Pancreatic Study Group organized a consensus guideline meeting on the diagnosis and management of pancreatitis in the pediatric population.

METHODS

Pediatric Pancreatitis was divided into three main clinical categories: acute pancreatitis, acute recurrent pancreatitis and chronic pancreatitis. Fifteen relevant topics (acute pancreatitis: diagnosis; etiology; prognosis; imaging; complications; therapy; biliary tract management; acute recurrent pancreatitis: diagnosis; chronic pancreatitis: diagnosis, etiology, treatment, imaging, intervention, pain, complications; enzyme replacement) were defined. Ten experts from the USA and Europe reviewed and summarized the available literature. Evidence was classified according to the GRADE classification system.

RESULTS

Within fifteen topics, forty-seven relevant clinical questions were defined. The draft of the updated guideline was presented and discussed at the consensus meeting held during the 49th Meeting of European Pancreatic Club, in Budapest, on July 1, 2017.

CONCLUSIONS

These evidence-based guidelines provides the current state of the art of the diagnosis and management of pediatric pancreatitis.

Identification of essential amino acids for glucose transporter 5 (GLUT5)-mediated fructose transport

Intestinal fructose uptake is mainly mediated by glucose transporter 5 (GLUT5/SLC2A5). Its closest relative, GLUT7, is also expressed in the intestine but does not transport fructose. For rat Glut5, a change of glutamine to glutamic acid at codon 166 (p.Q166E) has been reported to alter the substrate-binding specificity by shifting Glut5-mediated transport from fructose to glucose. Using chimeric proteins of GLUT5 and GLUT7, here we identified amino acid residues of GLUT5 that define its substrate specificity. The proteins were expressed in NIH-3T3 fibroblasts, and their activities were determined by fructose radiotracer flux. We divided the human GLUT5 sequence into 26 fragments and then replaced each fragment with the corresponding region in GLUT7. All fragments that yielded reduced fructose uptake were analyzed further by assessing the role of individual amino acid residues. Various positions in the first extracellular loop, in the fifth, seventh, eighth, ninth, and tenth transmembrane domains (TMDs), and in the regions between the ninth and tenth TMDs and tenth and 11th TMDs were identified as being important for proper fructose uptake. Although the p.Q167E change did not render the human protein into a glucose transporter, molecular dynamics simulations revealed a drastic change in the dynamics and a movement of the intracellular loop connecting the sixth and seventh TMDs, which covers the exit of the ligand. Finally, we generated a GLUT7-GLUT5 chimera consisting of the N-terminal part of GLUT7 and the C-terminal part of GLUT5. Although this chimera was inactive, we demonstrate fructose transport after introduction of four amino acids derived from GLUT5.

Branched-chain amino acid catabolism rather than amino acids plasma concentrations is associated with diet-induced changes in insulin resistance in overweight to obese individuals

BACKGROUND & AIMS

3-Hydroxyisobutyrate (3-HIB), a catabolic intermediate of the BCAA valine, which stimulates muscle fatty acid uptake, has been implicated in the pathogenesis of insulin resistance. We tested the hypothesis that circulating 3-HIB herald insulin resistance and that metabolic improvement with weight loss are related to changes in BCAAs and 3-HIB.

METHODS AND RESULTS

We analyzed plasma and urine in 109 overweight to obese individuals before and after six months on hypocaloric diets reduced in either carbohydrates or fat. We calculated the homeostasis model assessment index (HOMA-IR) and whole body insulin sensitivity from oral glucose tolerance tests and measured intramyocellular fat by magnetic resonance spectroscopy. BCAAs and 3-HIB plasma concentrations were inversely related to insulin sensitivity but not to intramyocellular fat content at baseline. With 7.4 ± 4.5% weight loss mean BCAA and 3-HIB plasma concentrations did not change, irrespective of dietary macronutrient content. Individual changes in 3-HIB with 6-month diet but not BCAAs were correlated to the change in whole body insulin sensitivity and HOMA-IR independently of BMI changes.

CONCLUSIONS

3-HIB relates to insulin sensitivity but is not associated with intramyocellular fat content in overweight to obese individuals. Moreover, changes in 3-HIB rather than changes in BCAAs are associated with metabolic improvements with weight loss. Registration number for clinical trials: ClinicalTrials.gov Identifier: NCT00956566.

United European Gastroenterology evidence-based guidelines for the diagnosis and therapy of chronic pancreatitis (HaPanEU)

BACKGROUND

There have been substantial improvements in the management of chronic pancreatitis, leading to the publication of several national guidelines during recent years. In collaboration with United European Gastroenterology, the working group on 'Harmonizing diagnosis and treatment of chronic pancreatitis across Europe' (HaPanEU) developed these European guidelines using an evidence-based approach.

METHODS

Twelve multidisciplinary review groups performed systematic literature reviews to answer 101 predefined clinical questions. Recommendations were graded using the Grading of Recommendations Assessment, Development and Evaluation system and the answers were assessed by the entire group in a Delphi process online. The review groups presented their recommendations during the 2015 annual meeting of United European Gastroenterology. At this one-day, interactive conference, relevant remarks were voiced and overall agreement on each recommendation was quantified using plenary voting (Test and Evaluation Directorate). After a final round of adjustments based on these comments, a draft version was sent out to external reviewers.

RESULTS

The 101 recommendations covered 12 topics related to the clinical management of chronic pancreatitis: aetiology (working party (WP)1), diagnosis of chronic pancreatitis with imaging (WP2 and WP3), diagnosis of pancreatic exocrine insufficiency (WP4), surgery in chronic pancreatitis (WP5), medical therapy (WP6), endoscopic therapy (WP7), treatment of pancreatic pseudocysts (WP8), pancreatic pain (WP9), nutrition and malnutrition (WP10), diabetes mellitus (WP11) and the natural course of the disease and quality of life (WP12). Using the Grading of Recommendations Assessment, Development and Evaluation system, 70 of the 101 (70%) recommendations were rated as 'strong' and plenary voting revealed 'strong agreement' for 99 (98%) recommendations.

CONCLUSIONS

The 2016 HaPanEU/United European Gastroenterology guidelines provide evidence-based recommendations concerning key aspects of the medical and surgical management of chronic pancreatitis based on current available evidence. These recommendations should serve as a reference standard for existing management of the disease and as a guide for future clinical research.

Apolipoprotein E allele frequencies in chronic and self-limited hepatitis C suggest a protective effect of APOE4 in the course of hepatitis C virus infection

BACKGROUND & AIMS

Infectious hepatitis C virus (HCV) particles bind to host lipoproteins such as low-density lipoproteins (LDLs). Low-density lipoprotein receptors (LDLR) have been termed candidate receptors for HCV-LDL complexes. Functional host genetic single nucleotide polymorphisms (SNPs) in the apolipoprotein E (APOE) gene encoding apolipoprotein E (apoE) - a major structural LDL component and natural ligand of LDLR - likely influence the course of HCV infection. We investigated the prevalence of APOE SNPs in two large and independent cohorts of patients with chronic HCV infection compared to respective controls.

METHODS

We genotyped 996 chronically HCV-infected patients; 179 patients with spontaneous HCV clearance; 283 individuals with non-HCV-associated liver disease; and 2 234 healthy controls.

RESULTS

APOE genotype proportions in patients with persistent HCV infection significantly differed from healthy controls (P = 0.007) primarily because of a substantial under-representation of APOE4 alleles in chronically HCV-infected patients (10.2%) compared to 13.0% in healthy controls (P = 0.001). The distribution of APOE4 allele positive genotypes (ε2ε4, ε3ε4, ε4ε4) also significantly differed between chronically HCV-infected patients and healthy controls (1.4%, 17%, 1% vs. 2.4%, 20.5%, 1.7%; P = 0.001), suggesting a protective effect of the APOE4 allele in HCV infection. This was confirmed by a significant over-representation of the APOE4 allele in patients with spontaneous HCV clearance (17.6%; P = 0.00008). The APOE4 allele distribution in patients with non-HCV-associated liver disease (14.0%) was very similar to healthy controls and also differed from chronically HCV-infected patients (P = 0.012), suggesting HCV specificity.

CONCLUSIONS

Our findings suggest that the APOE4 allele may confer a protective effect in the course of HCV infection.

Congenital secretory diarrhoea caused by activating germline mutations in GUCY2C

OBJECTIVE

Congenital sodium diarrhoea (CSD) refers to a form of secretory diarrhoea with intrauterine onset and high faecal losses of sodium without congenital malformations. The molecular basis for CSD remains unknown. We clinically characterised a cohort of infants with CSD and set out to identify disease-causing mutations by genome-wide genetic testing.

DESIGN

We performed whole-exome sequencing and chromosomal microarray analyses in 4 unrelated patients, followed by confirmatory Sanger sequencing of the likely disease-causing mutations in patients and in their family members, followed by functional studies.

RESULTS

We identified novel de novo missense mutations in GUCY2C, the gene encoding receptor guanylate cyclase C (GC-C) in 4 patients with CSD. One patient developed severe, early-onset IBD and chronic arthritis at 4 years of age. GC-C is an intestinal brush border membrane-bound guanylate cyclase, which functions as receptor for guanylin, uroguanylin and Escherichia coli heat-stable enterotoxin. Mutations in GUCY2C were present in different intracellular domains of GC-C, and were activating mutations that enhanced intracellular cyclic guanosine monophosphate accumulation in a ligand-independent and ligand-stimulated manner, following heterologous expression in HEK293T cells.

CONCLUSIONS

Dominant gain-of-function GUCY2C mutations lead to elevated intracellular cyclic guanosine monophosphate levels and could explain the chronic diarrhoea as a result of decreased intestinal sodium and water absorption and increased chloride secretion. Thus, mutations in GUCY2C indicate a role for this receptor in the pathogenesis of sporadic CSD.

Branched-chain and aromatic amino acids, insulin resistance and liver specific ectopic fat storage in overweight to obese subjects

BACKGROUND & AIMS

Amino acids may interfere with insulin action, particularly in obese individuals. We hypothesized that increased circulating branched-chain and aromatic amino acids herald insulin resistance and ectopic fat storage, particularly hepatic fat accumulation.

METHODS AND RESULTS

We measured fasting branched-chain and aromatic amino acids (tryptophan, tyrosine, and phenylalanine) by mass spectrometry in 111 overweight to obese subjects. We applied abdominal magnetic resonance imaging and spectroscopy to assess adipose tissue distribution and ectopic fat storage, respectively. Plasma branched-chain amino acids concentrations were related to insulin sensitivity and intrahepatic fat independent from adiposity, age and gender, but not to abdominal adipose tissue or intramyocellular fat.

CONCLUSIONS

In weight stable overweight and obese individuals, branched-chain amino acid concentrations are specifically associated with hepatic fat storage and insulin resistance.

Complex Formation of Human Proelastases with Procarboxypeptidases A1 and A2

The pancreas secretes digestive proenzymes typically in their monomeric form. A notable exception is the ternary complex formed by proproteinase E, chymotrypsinogen C, and procarboxypeptidase A (proCPA) in cattle and other ruminants. In the human and pig pancreas binary complexes of proCPA with proelastases were found. To characterize complex formation among human pancreatic protease zymogens in a systematic manner, we performed binding experiments using recombinant proelastases CELA2A, CELA3A, and CELA3B; chymotrypsinogens CTRB1, CTRB2, CTRC, and CTRL1; and procarboxypeptidases CPA1, CPA2, and CPB1. We found that proCELA3B bound not only to proCPA1 (KD 43 nm) but even more tightly to proCPA2 (KD 18 nm), whereas proCELA2A bound weakly to proCPA1 only (KD 152 nm). Surprisingly, proCELA3A, which shares 92% identity with proCELA3B, did not form stable complexes due to the evolutionary replacement of Ala(241) with Gly. The polymorphic nature of position 241 in both CELA3A (∼4% Ala(241) alleles) and CELA3B (∼2% Gly(241) alleles) points to individual variations in complex formation. The functional effect of complex formation was delayed procarboxypeptidase activation due to increased affinity of the inhibitory activation peptide, whereas proelastase activation was unchanged. We conclude that complex formation among human pancreatic protease zymogens is limited to a subset of proelastases and procarboxypeptidases. Complex formation stabilizes the inhibitory activation peptide of procarboxypeptidases and thereby increases zymogen stability and controls activation.

Fructose malabsorption

Incomplete intestinal absorption of fructose might lead to abdominal complaints such as pain, flatulence and diarrhoea. Whether defect fructose transporters such as GLUT5 or GLUT2 are involved in the pathogenesis of fructose malabsorption is a matter of debate. The hydrogen production by colonic bacteria is used for diagnosis with the hydrogen breath test. However, the appropriate fructose test dose for correct diagnosis is unclear. Subjects with fructose malabsorption show increased breath hydrogen levels and abdominal symptoms after fructose administration but do not report any symptoms when fructose is given together with glucose. This beneficial effect of glucose, however, cannot be explained yet but might be used for clinical care of these subjects.

BCL3 Reduces the Sterile Inflammatory Response in Pancreatic and Biliary Tissues

BACKGROUND & AIMS

Under conditions of inflammation in the absence of micro-organisms (sterile inflammation), necrotic cells release damage-associated molecular patterns that bind to Toll-like receptors on immune cells to activate a signaling pathway that involves activation of IκB kinase and nuclear factor κB (NF-κB). Little is known about the mechanisms that control NF-κB activity during sterile inflammation. We analyzed the contribution of B-cell CLL/lymphoma 3 (BCL3), a transcription factor that associates with NF-κB, in control of sterile inflammation in the pancreas and biliary system of mice.

METHODS

Acute pancreatitis (AP) was induced in C57BL/6 (control) and Bcl3(-/-) mice by intraperitoneal injection of cerulein or pancreatic infusion of sodium taurocholate. We also studied Mdr2(-/-) mice, which develop spontaneous biliary inflammation, as well as Bcl3(-/-)Mdr2(-/-) mice. We performed immunohistochemical analyses of inflamed and noninflamed regions of pancreatic tissue from patients with AP or primary sclerosing cholangitis (PSC), as well as from mice. Immune cells were characterized by fluorescence-activated cell sorting analysis. Control or Bcl3(-/-) mice were irradiated, injected with bone marrow from Bcl3(-/-) or control mice, and AP was induced.

RESULTS

Pancreatic or biliary tissues from patients with AP or PSC had higher levels of BCL3 and phosphorylated RelA and IκBα in inflamed vs noninflamed regions. Levels of BCL3 were higher in pancreata from control mice given cerulein than from mice without AP, and were higher in biliary tissues from Mdr2(-/-) mice than from control mice. Bcl3(-/-) mice developed more severe AP after administration of cerulein or sodium taurocholate than control mice; pancreata from the Bcl3(-/-) mice with AP had greater numbers of macrophages, myeloid-derived suppressor cells, dendritic cells, and granulocytes than control mice with AP. Activation of NF-κB was significantly prolonged in Bcl3(-/-) mice with AP, compared with control mice with AP. Bcl3(-/-)Mdr2(-/-) mice developed more severe cholestasis and had increased markers of liver injury and increased proliferation of biliary epithelial cells and hepatocytes than Mdr2(-/-) mice. In experiments with bone marrow chimeras, expression of BCL3 by acinar cells, but not myeloid cells, was required for reduction of inflammation during development of AP. BCL3 inhibited ubiquitination and proteasome-mediated degradation of p50 homodimers, which prolonged binding of NF-κB heterodimers to DNA.

CONCLUSIONS

BCL3 is up-regulated in inflamed pancreatic or biliary tissues from mice and patients with AP or cholangitis. Its production appears to reduce the inflammatory response in these tissues via blocking ubiquitination and proteasome-mediated degradation of p50 homodimers.

English language version of the S3-consensus guidelines on chronic pancreatitis: Definition, aetiology, diagnostic examinations, medical, endoscopic and surgical management of chronic pancreatitis

Chronic pancreatitis is a disease of the pancreas in which recurrent inflammatory episodes result in replacement of pancreatic parenchyma by fibrous connective tissue. This fibrotic reorganization of the pancreas leads to a progressive exocrine and endocrine pancreatic insufficiency. In addition, characteristic complications arise, such as pseudocysts, pancreatic duct obstructions, duodenal obstruction, vascular complications, obstruction of the bile ducts, malnutrition and pain syndrome. Pain presents as the main symptom of patients with chronic pancreatitis. Chronic pancreatitis is a risk factor for pancreatic carcinoma. Chronic pancreatitis significantly reduces the quality of life and the life expectancy of affected patients. These guidelines were researched and compiled by 74 representatives from 11 learned societies and their intention is to serve evidence-based professional training as well as continuing education. On this basis they shall improve the medical care of affected patients in both the inpatient and outpatient sector. Chronic pancreatitis requires an adequate diagnostic workup and systematic management, given its severity, frequency, chronicity, and negative impact on the quality of life and life expectancy.

Variants in pancreatic carboxypeptidase genes CPA2 and CPB1 are not associated with chronic pancreatitis

Genetic alterations in the carboxypeptidase A1 gene (CPA1) are associated with early onset chronic pancreatitis (CP). Besides CPA1, there are two other human pancreatic carboxypeptidases (CPA2 and CPB1). Here we examined whether CPA2 and CPB1 alterations are associated with CP in Japan and Germany. All exons and flanking introns of CPA2 and CPB1 were sequenced in 477 Japanese patients with CP (234 alcoholic, 243 nonalcoholic) and in 497 German patients with nonalcoholic CP by targeted next-generation sequencing and/or Sanger sequencing. Secretion and enzymatic activity of CPA2 and CPB1 variants were determined after transfection into HEK 293T cells. We identified six nonsynonymous CPA2 variants (p.V67I, p.G166R, p.D168E, p.D173H, p.R237W, and p.G388S), eight nonsynonymous CPB1 alterations (p.S65G, p.N120S, p.D172E, p.R195H, p.D208N, p.F232L, p.A317V, and p.D364Y), and one splice-site variant (c.687+1G>T) in CPB1. Functional analysis revealed essentially complete loss of function in CPA2 variants p.R237W and p.G388S and CPB1 variants p.R110H and p.D364Y. None of the CPA2 or CPB1 variants, including those resulting in a marked loss of function, were overrepresented in patients with CP. In conclusion, CPA2 and CPB1 variants are not associated with CP.

Reduced sodium/proton exchanger NHE3 activity causes congenital sodium diarrhea

Congenital sodium diarrhea (CSD) refers to an intractable diarrhea of intrauterine onset with high fecal sodium loss. CSD is clinically and genetically heterogeneous. Syndromic CSD is caused by SPINT2 mutations. While we recently described four cases of the non-syndromic form of CSD that were caused by dominant activating mutations in intestinal receptor guanylate cyclase C (GC-C), the genetic cause for the majority of CSD is still unknown. Therefore, we aimed to determine the genetic cause for non-GC-C non-syndromic CSD in 18 patients from 16 unrelated families applying whole-exome sequencing and/or chromosomal microarray analyses and/or direct Sanger sequencing. SLC9A3 missense, splicing and truncation mutations, including an instance of uniparental disomy, and whole-gene deletion were identified in nine patients from eight families with CSD. Two of these nine patients developed inflammatory bowel disease (IBD) at 4 and 16 years of age. SLC9A3 encodes Na(+)/H(+) antiporter 3 (NHE3), which is the major intestinal brush-border Na(+)/H(+) exchanger. All mutations were in the NHE3 N-terminal transport domain, and all missense mutations were in the putative membrane-spanning domains. Identified SLC9A3 missense mutations were functionally characterized in plasma membrane NHE null fibroblasts. SLC9A3 missense mutations compromised NHE3 activity by reducing basal surface expression and/or loss of basal transport function of NHE3 molecules, whereas acute regulation was normal. This study identifies recessive mutations in NHE3, a downstream target of GC-C, as a cause of CSD and implies primary basal NHE3 malfunction as a predisposition for IBD in a subset of patients.

Polymorphisms at PRSS1-PRSS2 and CLDN2-MORC4 loci associate with alcoholic and non-alcoholic chronic pancreatitis in a European replication study

OBJECTIVE

Several genetic risk factors have been identified for non-alcoholic chronic pancreatitis (NACP). A genome-wide association study reported an association of chronic pancreatitis (CP) with variants in PRSS1-PRSS2 (rs10273639; near the gene encoding cationic trypsinogen) and CLDN2-MORC4 loci (rs7057398 in RIPPLY1 and rs12688220 in MORC4). We aimed to refine these findings in a large European cohort.

DESIGN

We studied 3062 patients with alcohol-related CP (ACP) or NACP and 5107 controls. Also, 1559 German patients with alcohol-associated cirrhosis or alcohol dependence were included for comparison. We performed several meta-analyses to examine genotype-phenotype relationships.

RESULTS

Association with ACP was found for rs10273639 (OR, 0.63; 95% CI 0.55 to 0.72). ACP was also associated with variants rs7057398 and rs12688220 in men (OR, 2.26; 95% CI 1.94 to 2.63 and OR, 2.66; 95% CI 2.21 to 3.21, respectively) and in women (OR, 1.57; 95% CI 1.14 to 2.18 and OR 1.71; 95% CI 1.41 to 2.07, respectively). Similar results were obtained when German patients with ACP were compared with those with alcohol-associated cirrhosis or alcohol dependence. In the overall population of patients with NACP, association with rs10273639 was absent (OR, 0.93; 95% CI 0.79 to 1.01), whereas rs7057398 of the X chromosomal single nucleotide polymorphisms was associated with NACP in women only (OR, 1.32; 95% CI 1.15 to 1.51).

CONCLUSIONS

The single-nucleotide polymorphisms rs10273639 at the PRSS1-PRSS2 locus and rs7057398 and rs12688220 at the CLDN2-MORC4 locus are associated with CP and strongly associate with ACP, but only rs7057398 with NACP in female patients.

Mesotrypsin Signature Mutation in a Chymotrypsin C (CTRC) Variant Associated with Chronic Pancreatitis

Human chymotrypsin C (CTRC) protects against pancreatitis by degrading trypsinogen and thereby curtailing harmful intra-pancreatic trypsinogen activation. Loss-of-function mutations in CTRC increase the risk for chronic pancreatitis. Here we describe functional analysis of eight previously uncharacterized natural CTRC variants tested for potential defects in secretion, proteolytic stability, and catalytic activity. We found that all variants were secreted from transfected cells normally, and none suffered proteolytic degradation by trypsin. Five variants had normal enzymatic activity, whereas variant p.R29Q was catalytically inactive due to loss of activation by trypsin and variant p.S239C exhibited impaired activity possibly caused by disulfide mispairing. Surprisingly, variant p.G214R had increased activity on a small chromogenic peptide substrate but was markedly defective in cleaving bovine β-casein or the natural CTRC substrates human cationic trypsinogen and procarboxypeptidase A1. Mutation p.G214R is analogous to the evolutionary mutation in human mesotrypsin, which rendered this trypsin isoform resistant to proteinaceous inhibitors and conferred its ability to cleave these inhibitors. Similarly to the mesotrypsin phenotype, CTRC variant p.G214R was inhibited poorly by eglin C, ecotin, or a CTRC-specific variant of SGPI-2, and it readily cleaved the reactive-site peptide bonds in eglin C and ecotin. We conclude that CTRC variants p.R29Q, p.G214R, and p.S239C are risk factors for chronic pancreatitis. Furthermore, the mesotrypsin-like CTRC variant highlights how the same natural mutation in homologous pancreatic serine proteases can evolve a new physiological role or lead to pathology, determined by the biological context of protease function.

A recombined allele of the lipase gene CEL and its pseudogene CELP confers susceptibility to chronic pancreatitis

Carboxyl-ester lipase is a digestive pancreatic enzyme encoded by the highly polymorphic CEL gene¹. Mutations in CEL cause maturity-onset diabetes of the young (MODY) with pancreatic exocrine dysfunction². Here we identified a hybrid allele (CEL-HYB), originating from a crossover between CEL and its neighboring pseudogene CELP. In a discovery cohort of familial chronic pancreatitis cases, the carrier frequency of CEL-HYB was 14.1% (10/71) compared with 1.0% (5/478) in controls (odds ratio [OR] = 15.5, 95% confidence interval [CI] = 5.1-46.9, P = 1.3 × 10⁻⁶). Three replication studies in non-alcoholic chronic pancreatitis cohorts identified CEL-HYB in a total of 3.7% (42/1,122) cases and 0.7% (30/4,152) controls (OR = 5.2, 95% CI = 3.2-8.5, P = 1.2 × 10⁻¹¹; formal meta-analysis). The allele was also enriched in alcoholic chronic pancreatitis. Expression of CEL-HYB in cellular models revealed reduced lipolytic activity, impaired secretion, prominent intracellular accumulation and induced autophagy. The hybrid variant of CEL is the first chronic pancreatitis gene identified outside the protease/antiprotease system of pancreatic acinar cells.

Impaired autophagy induces chronic atrophic pancreatitis in mice via sex- and nutrition-dependent processes

BACKGROUND & AIMS

Little is known about the mechanisms of the progressive tissue destruction, inflammation, and fibrosis that occur during development of chronic pancreatitis. Autophagy is involved in multiple degenerative and inflammatory diseases, including pancreatitis, and requires the protein autophagy related 5 (ATG5). We created mice with defects in autophagy to determine its role in pancreatitis.

METHODS

We created mice with pancreas-specific disruption of Atg5 (Ptf1aCreex1;Atg5F/F mice) and compared them to control mice. Pancreata were collected and histology, immunohistochemistry, transcriptome, and metabolome analyses were performed. ATG5-deficient mice were placed on diets containing 25% palm oil and compared with those on a standard diet. Another set of mice received the antioxidant N-acetylcysteine. Pancreatic tissues were collected from 8 patients with chronic pancreatitis (CP) and compared with pancreata from ATG5-deficient mice.

RESULTS

Mice with pancreas-specific disruption of Atg5 developed atrophic CP, independent of β-cell function; a greater proportion of male mice developed CP than female mice. Pancreata from ATG5-deficient mice had signs of inflammation, necrosis, acinar-to-ductal metaplasia, and acinar-cell hypertrophy; this led to tissue atrophy and degeneration. Based on transcriptome and metabolome analyses, ATG5-deficient mice produced higher levels of reactive oxygen species than control mice, and had insufficient activation of glutamate-dependent metabolism. Pancreata from these mice had reduced autophagy, increased levels of p62, and increases in endoplasmic reticulum stress and mitochondrial damage, compared with tissues from control mice; p62 signaling to Nqo1 and p53 was also activated. Dietary antioxidants, especially in combination with palm oil-derived fatty acids, blocked progression to CP and pancreatic acinar atrophy. Tissues from patients with CP had many histologic similarities to those from ATG5-deficient mice.

CONCLUSIONS

Mice with pancreas-specific disruption of Atg5 develop a form of CP similar to that of humans. CP development appears to involve defects in autophagy, glutamate-dependent metabolism, and increased production of reactive oxygen species. These mice might be used to identify therapeutic targets for CP.

Myosin IXb variants and their pivotal role in maintaining the intestinal barrier: a study in Crohn's disease

BACKGROUND

Myosin IXb (MYO9B) is involved in the regulation of epithelial barrier function. We hypothesized that MYO9B variants are associated with increased intestinal permeability measured in patients with Crohn's disease (CD), where barrier dysfunction is crucially involved in disease development.

METHODS

We sequenced MYO9B and genotyped five MYO9B variants (rs1545620, rs1457092, rs2279003, rs2305764 and rs2279002) and correlated these data to measurement of intestinal permeability in German CD patients (n = 122) obtained by standard oral sugar test using the lactulose/mannitol ratio after measurement of urinary excretion. We furthermore studied MYO9B variants in three European cohorts with inflammatory bowel disease (IBD) and healthy controls : Germany (CD = 264; ulcerative colitis = 143 [UC]; HC = 372); Hungary (CD = 147; UC = 117; HC = 195), the Netherlands (CD = 157; HC = 219).

RESULTS

We found an association for four studied MYO9B variants to an increased intestinal permeability in CD patients (rs1545620, p = 0.010; rs1457092, p = 0.024; rs2279003, p = 0.003; rs2305764, p = 0.015). Furthermore, we observed significantly higher absolute values of intestinal permeability for individuals carrying risk alleles within MYO9B. Looking for an overall disease association, only the rs2305764 variant was associated with CD in the Dutch cohort (p = 0.004), but not in the German or Hungarian cohort. No association to UC or a distinct phenotype in both CD and UC patients was observed for all studied MYO9B variants.

CONCLUSION

Our data suggest a link between MYO9B variants to an increased intestinal permeability in CD patients. This supports the influence of Myosin IXb on the integrity of the epithelial barrier. The role of MYO9B variants in the overall susceptibility to IBD, however, remains to be elucidated.

Mutations in the human UBR1 gene and the associated phenotypic spectrum

Johanson-Blizzard syndrome (JBS) is a rare, autosomal recessive disorder characterized by exocrine pancreatic insufficiency, typical facial features, dental anomalies, hypothyroidism, sensorineural hearing loss, scalp defects, urogenital and anorectal anomalies, short stature, and cognitive impairment of variable degree. This syndrome is caused by a defect of the E3 ubiquitin ligase UBR1, which is part of the proteolytic N-end rule pathway. Herein, we review previously reported (n = 29) and a total of 31 novel UBR1 mutations in relation to the associated phenotype in patients from 50 unrelated families. Mutation types include nonsense, frameshift, splice site, missense, and small in-frame deletions consistent with the hypothesis that loss of UBR1 protein function is the molecular basis of JBS. There is an association of missense mutations and small in-frame deletions with milder physical abnormalities and a normal intellectual capacity, thus suggesting that at least some of these may represent hypomorphic UBR1 alleles. The review of clinical data of a large number of molecularly confirmed JBS cases allows us to define minimal clinical criteria for the diagnosis of JBS. For all previously reported and novel UBR1 mutations together with their clinical data, a mutation database has been established at LOVD.

Functional effects of 13 rare PRSS1 variants presumed to cause chronic pancreatitis

OBJECTIVE

Hereditary pancreatitis is caused by mutations in human cationic trypsinogen (PRSS1) which lead to increased autoactivation by altering chymotrypsin C (CTRC)-dependent trypsinogen activation and degradation. Exceptions are some cysteine mutations which cause misfolding, intracellular retention and endoplasmic reticulum stress. Clinical relevance of many PRSS1 variants found in patients with sporadic chronic pancreatitis is unknown but often assumed by analogy with known disease-causing mutations. Functional comparison of PRSS1 variants found in sporadic and hereditary cases is needed to resolve this dilemma.

DESIGN

Here, we investigated the functional phenotype of 13 published PRSS1 variants with respect to autoactivation in the presence of CTRC and cellular secretion.

RESULTS

Only mutation p.D100H increased trypsinogen autoactivation, but this gain in function was offset by a marked reduction in secretion. Five mutants (p.P36R, p.G83E, p.I88N, p.V123M, p.S124F) showed decreased autoactivation due to increased degradation by CTRC. Five mutants exhibited strongly (p.D100H, p.C139F) or moderately (p.K92N, p.S124F, p.G208A) reduced secretion, whereas mutant p.K170E showed slightly increased secretion. Mutant p.I88N was also secreted to higher levels but was rapidly degraded by CTRC. Finally, three mutants (p.Q98K, p.T137M, p.S181G) had no phenotypic alterations relative to wild-type trypsinogen.

CONCLUSIONS

Rare PRSS1 variants found in sporadic chronic pancreatitis do not stimulate autoactivation but may cause increased degradation, impaired secretion or no functional change. Variants with reduced secretion are likely pathogenic due to mutation-induced misfolding and consequent endoplasmic reticulum stress.