SPINK1 is a susceptibility gene for fibrocalculous pancreatic diabetes in subjects from the Indian subcontinent

Fibrocalculous pancreatic diabetes

Fibrocalculous pancreatic diabetes (FCPD) is a unique form of diabetes reported from tropical countries, associated with both endocrine and exocrine disease of the pancreas. The pre-diabetic phase of the disease is called tropical chronic pancreatitis (TCP). Currently FCPD is classified as a secondary form of diabetes called pancreatic diabetes, because essentially the disease is caused by pancreatic damage. There is an overlap of these subjects with idiopathic, non-alcoholic pancreatitis. This review will cover the etiopathogenesis, diagnosis and management of this clinical condition. FCPD could lead to endocrine dysfunction (diabetes and its complications) as well as exocrine dysfunction, and is associated with a higher risk of pancreatic cancer, for which early detection is important.

Structural, functional and molecular dynamics analysis of cathepsin B gene SNPs associated with tropical calcific pancreatitis, a rare disease of tropics

Tropical Calcific Pancreatitis (TCP) is a neglected juvenile form of chronic non-alcoholic pancreatitis. Cathepsin B (CTSB), a lysosomal protease involved in the cellular degradation process, has recently been studied as a potential candidate gene in the pathogenesis of TCP. According to the Cathepsin B hypothesis, mutated CTSB can lead to premature intracellular activation of trypsinogen, a key regulatory mechanism in pancreatitis. So far, CTSB mutations have been studied in pancreatitis and neurodegenerative disorders, but little is known about the structural and functional effect of variants in CTSB. In this study, we investigated the effect of single nucleotide variants (SNVs) specifically associated with TCP, using molecular dynamics and simulation algorithms. There were two non-synonymous variants (L26V and S53G) of CTSB, located in the propeptide region. We tried to predict the effect of these variants on structure and function using multiple algorithms: SIFT, Polyphen2, PANTHER, SDM sever, i-Mutant2.0 suite, mCSM algorithm, and Vadar. Further, using databases like miRdbSNP, PolymiRTS, and miRNASNP, two SNPs in the 3′UTR region were predicted to affect the miRNA binding sites. Structural mutated models of nsSNP mutants (L26V and S53G) were prepared by MODELLER v9.15 and evaluated using TM-Align, Verify 3D, ProSA and Ramachandran plot. The 3D mutated structures were simulated using GROMACS 5.0 to predict the impact of these SNPs on protein stability. The results from in silico analysis and molecular dynamics simulations suggested that these variants in the propeptide region of Cathepsin B could lead to structural and functional changes in the protein and thus could be pathogenic. Hence, the structural and functional analysis results have given interim conclusions that these variants can have a deleterious effect in TCP pathogenesis, either uniquely or in combination with other mutations. Thus, it could be extrapolated that Cathepsin B gene can be screened in samples from all TCP patients in future, to decipher the distribution of variants in patients.

Risk Factors for Rapid Progression From Acute Recurrent to Chronic Pancreatitis in Children: Report From INSPPIRE

OBJECTIVE

The aim of the study was to determine the rate of progression from acute recurrent pancreatitis (ARP) to chronic pancreatitis (CP) in children and assess risk factors.

STUDY DESIGN

Data were collected from the INternational Study group of Pediatric Pancreatitis: In search for a cuRE (INSPPIRE) cohort. Kaplan-Meier curves were constructed to calculate duration of progression from initial attack of acute pancreatitis (AP) to CP. Log-rank test was used to compare survival (nonprogression) probability distribution between groups. Cox proportional hazard regression models were fitted to obtain hazard ratio (with 95% confidence interval [CI]) of progression for each risk variable.

RESULTS

Of 442 children, 251 had ARP and 191 had CP. The median time of progression from initial attack of AP to CP was 3.79 years. The progression was faster in those ages 6 years or older at the first episode of AP compared to those younger than 6 years (median time to CP: 2.91 vs 4.92 years; P = 0.01). Children with pathogenic PRSS1 variants progressed more rapidly to CP compared to children without PRSS1 variants (median time to CP: 2.52 vs 4.48 years; P = 0.003). Within 6 years after the initial AP attack, cumulative proportion with exocrine pancreatic insufficiency was 18.0% (95% CI: 12.4%, 25.6%); diabetes mellitus was 7.7% (95% CI: 4.2%, 14.1%).

CONCLUSIONS

Children with ARP rapidly progress to CP, exocrine pancreatic insufficiency, and diabetes. The progression to CP is faster in children who were 6 years or older at the first episode of AP or with pathogenic PRSS1 variants. The factors that affect the aggressive disease course in childhood warrant further investigation.

A comparative study of the clinical profile of fibrocalculous pancreatic diabetes and type 2 diabetes mellitus

AIMS

The present study aimed to compare the clinical characteristics of patients with fibrocalculous pancreatic diabetes (FCPD) and those with type 2 diabetes mellitus (T2DM) to identify the characteristics distinctive of FCPD.

METHODS

A total of 133 patients with FCPD were compared with 665 patients with T2DM matched for duration of diabetes. Biochemical parameters and microvascular and macrovascular complications were assessed in all patients. Multivariate regression analyses were performed to study the determinants of microvascular and macrovascular complications in both groups.

RESULTS

The mean duration of diabetes was 4.42 ± 5.65 years in the FCPD group and 4.51 ± 3.88 years in the T2DM group. FCPD participants were significantly younger at diagnosis and leaner than patients with T2DM. The FCPD group had higher fasting and postprandial glucose and HbA1c levels than the T2DM group. The FCPD group had significantly lower triglyceride, total cholesterol, low-density lipoprotein cholesterol, serum total calcium, hemoglobin, and serum creatinine values than the T2DM group. The prevalence of coronary artery disease, stroke, and retinopathy was significantly higher in the T2DM patients while the prevalence of distal symmetric polyneuropathy was significantly lower. On multivariate logistic regression analysis, duration of diabetes and HbA1c (OR = 1.17, P = 0 0.04) in FCPD patients and age (OR = 1.04, P < 0 0.001), duration of diabetes (OR = 1.17, P < 0 0.001) and HbA1c (OR = 1.28, P < 0.001) in T2DM patients were associated with microvascular complications.

CONCLUSIONS

There are several differences in the phenotype, biochemical parameters, and prevalence of diabetic complications between patients with FCPD and T2DM. Timely diagnosis may have implications in the follow-up and management of patients.

High Prevalence of Serine Protease Inhibitor Kazal Type 1 Gene Variations Detected by Whole Gene Sequencing in Patients with Fibrocalculous Pancreatic Diabetes

AIM OF STUDY

The aim is to study the prevalence and pattern of serine protease inhibitor Kazal type 1 (SPINK1) gene variations in patients with fibrocalculous pancreatic diabetes (FCPD) using whole gene sequencing.

MATERIALS AND METHODS

A total of 56 consecutive patients of FCPD were recruited for the study. Diagnosis of FCPD was based on the presence of diabetes mellitus in patients having chronic pancreatitis with radiological evidence of ductal calcifications, in the absence of other known causes for pancreatitis. Ethylenediaminetetraacetic acid samples were collected from all patients, and complete gene sequencing was performed for SPINK1 gene using Sanger technique.

RESULTS

Overall 35 patients (62.5%) were detected to have genetic alterations in SPINK1 gene. N34S polymorphism was seen in 23 participants (41.07%) out of which 3 were homozygous. N34S was seen to be in linkage disequilibrium with IVS1 - 37T>C (18/23) and IVS3-69insAAAA (19/23) polymorphisms. Seven patients (12.5%) had a 272 C>T 3'UTR polymorphism while one patient (1.8%) had a P55S polymorphism. Two patients (3.5%) had an IVS3 + 2T>C mutation which has been shown to be associated with loss of function of SPINK protein. Overall 48.2% of FCPD patients had genetic variations that were significant compared to the control population. There was no difference in anthropometric and biochemical parameters between those with or without SPINK1 gene variations.

CONCLUSIONS

Variations in SPINK1 gene are frequently observed in FCPD. N34S polymorphism was the most common variation followed by intronic variations. Two patients had the pathogenic intronic IVS3 + 2T>C mutation. Whole gene sequencing of the SPINK1 gene enabled detection of an additional 7.1% of patients with significant SPINK1 gene variations as compared to targeted screening for the N34S variation.

What's unique about acute pancreatitis in children: risk factors, diagnosis and management

Pancreatitis in children is an appreciable problem that has become increasingly prevalent. This Review covers the principles related to the definitions, epidemiology, risk factors, diagnosis and management of acute pancreatitis in children and identifies features that are unique among children. Additionally, knowledge gaps related to management principles are identified.

Fibrocalculous pancreatic diabetes: a case report

BACKGROUND

Diabetes is now becoming a major cause of morbidity and mortality in both developing and developed countries. Even though type 1 and type 2 are the commonest, diabetes mellitus due to secondary causes have been identified. Fibrocalculous Pancreatic Diabetes is a unique entity wherein pancreatic calcification and chronic inflammation lead to exocrine and endocrine failure of the pancreas. This form of non-alcoholic pancreatopathy is exclusively seen among the young, with a male preponderance and commonly in tropical countries where malnutrition and poverty go hand in hand. Whereas, interestingly this case has a late presentation in a female, unlike in other reported cases. For the best of our knowledge this is the first such documented case reported in Sri Lanka.

CASE PRESENTATION

A 57 year old non-alcoholic Sinhalese female from Sri Lanka, presented with a history of chronic pancreatitis of nine years duration, after which she had developed severe Insulin Dependent Diabetes Mellitus. Imaging of the abdomen showed typical pancreatic calcifications, and this presentation accords with the criteria for Fibrocalculous pancreatic diabetes.

CONCLUSION

This case report demonstrates a rare form of secondary diabetes in a middle aged female, without a childhood history of abdominal pain suggestive of pancreatitis, indicating late onset disease. Therefore a high index of suspicion is necessary even though the diagnostic criteria indicates the presence of childhood onset of disease.

Fibrocalculous pancreatic diabetes (FCPD)

Fibrocalculous pancreatic diabetes (FCPD) is an uncommon form of diabetes that occurs as a result of chronic calcific pancreatitis, in the absence of alcohol abuse. The disease is restricted to tropical regions of the world, and southern India has the highest known prevalence of FCPD. The typical patient with FCPD is a lean adolescent or young adult of either sex, presenting with history of recurrent bouts of abdominal pain and steatorrhea. Demonstration of large, discrete pancreatic calculi by plain radiographs or ultrasonography of the abdomen is diagnostic. While the exact etiology of FCPD is unknown, genetic, nutritional and inflammatory factors have been hypothesized to play a role. Diabetes in FCPD is often brittle and difficult to control; most patients require multiple doses of insulin for control of glycemia. However, in spite of high blood glucose levels, patients rarely develop ketosis. Malabsorption responds to pancreatic enzyme supplementation. Surgical removal of stones is indicated for symptomatic relief of intractable pain. While patients with FCPD develop microvascular complications as frequently as those with type 2 diabetes, macrovascular disease is uncommon. Development of pancreatic malignancy is the most dreaded complication and should be suspected in any patient who complains of weight loss, back pain or jaundice.

Genetic and phenotypic heterogeneity in tropical calcific pancreatitis

Tropical calcific pancreatitis (TCP) is a form of chronic non-alcoholic pancreatitis initially reported in the developing parts of the tropical world. The clinical phenotype of TCP has undergone marked changes since its first description in 1968. The disease is now seen in relatively older people with less severe symptoms. In addition, there are varying reports on the proportion of cases presenting with imaging abnormalities like calcification, ductal dilation, and glandular atrophy. Significant progress has also been made in understanding the etiopathology of TCP. The role of malnutrition and cassava toxicity in its pathogenesis is disproven and few studies have focused on the role of micronutrient deficiency and oxidative stress in the etiopathogenesis of TCP. Emerging evidence support an important role for genetic risk factors in TCP. Several studies have shown that, rather than mutations in trypsinogens, variants in serine protease inhibitor kazal type 1, cathepsin B, chymotrypsin C, cystic fibrosis transmembrane regulator, and carboxypeptidase A1, predict risk of TCP. These studies also provided evidence of mutational heterogeneity between TCP and chronic pancreatitis in Western populations. The current review summarizes recent advances that have implications in the understanding of the pathophysiology and thus, heterogeneity in genotype-phenotype correlations in TCP.

Frequency of CFTR, SPINK1, and cathepsin B gene mutation in North Indian population: connections between genetics and clinical data

Objectives. Genetic mutations and polymorphisms have been correlated with chronic pancreatitis (CP). This study aims to investigate the association of genetic variants of cystic fibrosis transmembrane conductance regulator (CFTR) and serine protease inhibitor Kazal type 1 (SPINK-1) genes and Cathepsin B gene polymorphisms with CP and to associate genetic backgrounds with clinical phenotypes. Methods. 150 CP patients and 150 normal controls were enrolled consecutively. We analyzed SPINK-1 N34S and IVS3+2T>C gene mutations by PCR-restriction-fragment length polymorphism (RFLP). The identification of DF508, G551D, G542X, R117H, and W1282X mutations was carried out by ARMS-PCR. S549N mutation, IVS8 polyTn polymorphism, and Cathepsin B Lec26Val were analysed by PCR-RFLP, nested PCR, and PCR-RFLP plus sequencing, respectively. Results. We found a significant association of SPINK1 (N34S) gene polymorphism. IVS1−37T>C polymorphism shows linkage with 101A>G. 300 chromosomes belonging to the CFTR subgroup exhibited minor allele frequency of 0.04, 0.03, 0.03, 0.013, 0.006, and 0.02 for DF508, G452X, G551D, S549N, R117H, and IVS8 T5, respectively. Except for R117H and IVS8 T5 polymorphisms, all other mutations showed significant variation. Conclusion. Analysis of potential susceptibility variants is needed to support nature of the genes and environment in pancreatitis. This data may help establish genetic screening and prenatal setup for Indian population.

Pathophysiology of chronic pancreatitis

Chronic pancreatitis (CP) is an inflammatory disease of the pancreas characterized by progressive fibrotic destruction of the pancreatic secretory parenchyma. Despite the heterogeneity in pathogenesis and involved risk factors, processes such as necrosis/apoptosis, inflammation or duct obstruction are involved. This fibrosing process ultimately leads to progressive loss of the lobular morphology and structure of the pancreas, deformation of the large ducts and severe changes in the arrangement and composition of the islets. These conditions lead to irreversible morphological and structural changes resulting in impairment of both exocrine and endocrine functions. The prevalence of the disease is largely dependent on culture and geography. The etiological risk-factors associated with CP are multiple and involve both genetic and environmental factors. Throughout this review the M-ANNHEIM classification system will be used, comprising a detailed description of risk factors such as: alcohol-consumption, nicotine-consumption, nutritional factors, hereditary factors, efferent duct factors, immunological factors and miscellaneous and rare metabolic factors. Increased knowledge of the different etiological factors may encourage the use of further advanced diagnostic tools, which potentially will help clinicians to diagnose CP at an earlier stage. However, in view of the multi factorial disease and the complex clinical picture, it is not surprising that treatment of patients with CP is challenging and often unsuccessful.

Fibrocalculous pancreatic diabetes in a young Ugandan patient, a rare form of secondary diabetes

BACKGROUND

Fibrocalculous pancreatic diabetes is an infrequent type of secondary diabetes due to chronic tropical non alcoholic calcific pancreatitis. It has been widely described exclusively in developing tropical countries. A diagnosis is made basing on the presence of abdominal pain, presence of pancreatic calcifications, steatorrhoea, and diabetes mellitus.

CASE PRESENTATION

We report a case of a 20 year old Ugandan female patient who presented with features of chronic tropical calcific pancreatitis complicated by diabetes mellitus, oedematous malnutrition and micronutrient deficiencies.

CONCLUSION

This case report demonstrates that fibrocalculous pancreatic diabetes still exists in developing countries like Uganda. Clinicians in such settings should possess a high clinical suspicion of fibrocalculous pancreatic diabetes especially in presence of malnutrition. Challenges of management of such patients in resource limited settings are comprehensively discussed in the review of literature.

Molecular dynamics simulations reveal structural instability of human trypsin inhibitor upon D50E and Y54H mutations

Serine protease inhibitor Kazal type 1 (SPINK1) plays an important role in protecting the pancreas against premature trypsinogen activation that causes pancreatitis. Various mutations in the SPINK1 gene were shown to be associated with patients with pancreatitis. Recent transfection studies identified intracellular folding defects, probably caused by mutation induced misfolding of D50E and Y54H mutations, as a common mechanism that reduces SPINK1 secretion and as a possible novel mechanism of SPINK1 deficiency associated with chronic pancreatitis. Using molecular dynamics, we investigated the effects of D50E and Y54H mutations on SPINK1 dynamics and conformation at 300 K. We found that the structures of D50E and Y54H mutants were less stable than and were distorted from those of the wild type, as indicated by the RMSD plots, RMSF plots and DSSP series. Specifically, unwinding of the top of helices (the main secondary structures) and the distortion of the loops above the helices were observed. It may be possible that this distorted protein structure may be recognized as "non-native" by members of the chaperone family; it may be further retained and targeted for degradation, leading to SPINK1 secretion reduction and subsequently pancreatitis in patients as Király et al. (Gut 56:1433, 2007) proposed.

Is Post-ERCP Pancreatitis a Genetically Predisposed Complication?

Background/Objectives. Pancreatitis remains the most common complication of ERCP. History of post-ERCP pancreatitis is an independent risk factor for a new episode, suggesting a genetic background. The N34S mutation in serine protease inhibitor Kazal type 1 (SPINK 1) gene may downregulate the threshold for the development of pancreatitis. The aim of the present study is to evaluate the presence of this mutation among patients with post-ERCP pancreatitis. Methods. During a period of four years, thirty patients with post-ERCP pancreatitis entered the study. Patients and procedural data were collected, focusing on risk factors for pancreatitis. Blood samples were taken for genetic testing for the presence of N34S mutation in SPINK 1 gene. After DNA extraction, we used an allele-specific polymerase chain reaction as an initial screening method for the N34S mutation, and in order to confirm the results and to determine the hetero- and homozygosity genotype status, we used a restriction fragment length polymorphism (RFLP) method. Results. None of the thirty patients was found to carry the N34S mutation, with both of the applied methods. Patients had an average of two of the known risk factors. Conclusion. SPINK1 N34S mutation does not seem to play a role in post-ERCP pancreatitis, but larger studies needed to confirm our results.

The complex exocrine-endocrine relationship and secondary diabetes in exocrine pancreatic disorders

The pancreas is a dual organ with exocrine and endocrine functions. The interrelationship of the endocrine-exocrine parts of the pancreas is a complex one, but recent clinical and experimental studies have expanded our knowledge. Many disorders primarily of the exocrine pancreas, often solely in the clinical realm of gastroenterologists are associated with diabetes mellitus (DM). Although, the DM becoming disorders are often grouped with type 2 diabetes, the pathogenesis, clinical manifestations and management differ. We review here data on the association of exocrine-endocrine pancreas, the many hormones of the pancreas and their possible effects on the exocrine functions followed by data on the epidemiology, pathogenesis, and management of DM in chronic pancreatitis, cystic fibrosis, pancreatic cancer, and clinical states after pancreatic surgery.

Chronic pancreatitis

PURPOSE OF REVIEW

We review important new clinical observations in chronic pancreatitis made in the past year.

RECENT FINDINGS

Tropical pancreatitis associates with SPINK1 and/or CFTR gene mutations in approximately 50% of patients, similar to the frequency in idiopathic chronic pancreatitis. Corticosteroids increase secretin-stimulated pancreatic bicarbonate concentrations in autoimmune pancreatitis (AIP) by restoring mislocalized CFTR protein to the apical ductal membrane. Most patients with asymptomatic hyperenzymemia have pancreatic lesions of unclear significance or no pancreatic lesions. Common pitfalls in the use of diagnostic tests for exocrine pancreatic insufficiency (EPI) confound interpretation of findings in irritable bowel syndrome and severe renal insufficiency. Further study is needed to improve the accuracy of endoscopic ultrasonography (EUS) to diagnose chronic pancreatitis. Celiac plexus block provides short-term pain relief in a subset of patients.

SUMMARY

Results of this year's investigations further elucidated the genetic associations of tropical pancreatitis, a reversible mislocalization of ductal CFTR in AIP, the association of asymptomatic pancreatic hyperenzymemia with pancreatic disorders, limitations of diagnostic tests for EPI, diagnosis of chronic pancreatitis by EUS and endoscopic pancreatic function testing and treatment of pain.

Hereditary pancreatitis

Hereditary chronic pancreatitis (HCP) is a rare disease in which chronic pancreatitis develops in childhood. HCP has autosomal dominant inheritance with approximately 80% penetrance. Diagnostic criteria are not universally agreed upon but the EUROPAC trial defined it as two first-degree relatives or at least 3 second-degree relatives in two or more generations, with chronic pancreatitis for which there is no other etiology. The gene for HCP was originally identified on chromosome 7 and subsequently many other genes have been reported to be associated with HCP. To date, no single genetic alteration has been found that is necessary for the development of HCP. In a recent study, 81% of patients with HCP were found to have a mutation of the PRSS1 gene. Patients with HCP are at risk for developing exocrine and endocrine insufficiency and there is a 50-fold increased risk of pancreatic cancer in HCP patients as compared with the general population.

Tropical calcific pancreatitis and its association with CTRC and SPINK1 (p.N34S) variants

BACKGROUND

Tropical calcific pancreatitis (TCP) is a relatively common form of chronic pancreatitis in parts of Asia and Africa. The SPINK1 variant p.N34S is strongly associated with TCP, but other genetic factors remain to be defined. Chymotrypsinogen C (CTRC) degrades trypsinogen and loss-of-function variants have been found in European patients with chronic pancreatitis. Preliminary data indicate that CTRC might increase the risk for TCP.

MATERIALS AND METHODS

We selected 150 Indian TCP patients and 150 Indian controls to perform mutational screening of the complete coding region of CTRC and exon 3 of SPINK1. We performed in-silico analysis and functional studies of novel CTRC variants.

RESULTS

We identified eight variants among this sample. Three were synonymous and c.180 C>T was significantly enriched in patients (odds ratio=2.09; 95% confidence interval=1.19-3.67; P=0.03). We identified a novel nonsynonymous CTRC (p.G61R) variant in one of 146 patients (0.7%), but absent from controls. In-silico analysis showed that this variant affected a conserved residue, and functional analysis showed that p.G61R results in a complete loss of CTRC secretion from transiently transfected human embryonic kidney 293T cells. SPINK1 p.N34S was present in 31.8% of patients compared with 4.7% in controls, there was no significant cosegregation with CTRC variants.

CONCLUSION

The contribution of CTRC variants to TCP is relatively small, but the identification of novel loss-of-function variants (p.G61R) underscores the importance of the trypsinogen pathway in causing TCP.

Genetic mechanisms underlying the pathogenesis of tropical calcific pancreatitis

Chronic pancreatitis is known to be a heterogeneous disease with varied etiologies. Tropical calcific pancreatitis (TCP) is a severe form of chronic pancreatitis unique to developing countries. With growing evidence of genetic factors contributing to the pathogenesis of TCP, this review is aimed at compiling the available information in this field. We also propose a two hit model to explain the sequence of events in the pathogenesis of TCP.

Chronic pancreatitis: genetics and pathogenesis

Chronic pancreatitis (CP) is a persistent inflammation of the pancreas. Over the past 12 years, genetic studies of hereditary, familial, and idiopathic forms of CP have made great progress in defining the disease pathogenesis. Identification of gain-of-function missense and copy number mutations in the cationic trypsinogen gene (PRSS1) and loss-of-function variants in both the pancreatic secretory trypsin inhibitor (SPINK1) and chymotrypsinogen C (CTRC) genes has firmly established the pivotal role of prematurely activated trypsin within the pancreas in the etiology of CP. Loss-of-function variants in the cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-sensing receptor (CASR) genes also increase the risk of CP. Here, we review recent developments in this rapidly evolving field, highlight the importance of gene-gene and gene-environment interactions in causing the disease, and discuss the opportunities and challenges in identifying novel genetic factors that affect susceptibility/resistance to CP.

Divergent roles of SPINK1 and PRSS2 variants in tropical calcific pancreatitis

BACKGROUND/AIMS

Tropical calcific pancreatitis (TCP) refers to a type of idiopathic pancreatitis prevalent in Asia. The trypsin inhibitor (SPINK1) N34S variant partially explains the genetic susceptibility to TCP. As anionic trypsinogen (PRSS2) G191R protects against chronic pancreatitis in Europeans, we investigated whether this variant protects from TCP in Indians.

METHODS

We enrolled 174 patients and 794 controls from two Indian tertiary care referral hospitals. We analyzed PRSS2 and SPINK1 variants by melting curve analysis, allele-specific discrimination assay, and sequencing.

RESULTS

G191R was detected in 1 TCP patient (0.6%) compared to 13 controls (1.6%; OR 0.27, 95% CI 0.03-2.1; p = 0.33). SPINK1 N34S was enriched in the TCP population 67/174 (38.5%) compared to controls 10/234 (4.3%; OR 14, 95% CI 6.9-28.3; p < 0.001).

CONCLUSION

G191R PRSS2 is a rare allele in the Indian population and the data suggest a nonsignificant trend towards a protective effect. N34S SPINK1 represents the major genetic risk factor in TCP.

Genetic aspects of tropical calcific pancreatitis

Tropical calcific pancreatitis (TCP) is a subtype of chronic pancreatitis which is unique to tropical regions. Patients present at young age with recurrent abdominal pain, nutritional deficiencies, and insulin-requiring diabetes. For a long time, the aetiology of this disorder was poorly understood. Several environmental factors, such as malnutrition or the consumption of toxic food components such as cyanogenic glycosides, were proposed as pathogenic factors. In the last decade, a major impact on the understanding of the aetiology of TCP has come from genetic studies on hereditary and idiopathic chronic pancreatitis. Genetic alterations in at least five genetic loci are clearly associated with chronic pancreatitis in the Western world. These include alterations in genes coding for trypsinogens, the most abundant digestive enzymes (PRSS1 and PRSS2), the trypsin inhibitor (SPINK1) and the trypsin-degrading enzyme, chymotrypsinogen C (CTRC). In addition, alterations in the cystic fibrosis (CFTR) gene are associated with idiopathic pancreatitis. TCP clinically resembles non-alcoholic chronic pancreatitis of Western countries, suggesting that similar genetic defects might also be of importance in this disease entity. Indeed, alterations in at least two genes, SPINK1 and CTRC, are strongly associated with TCP. The current review focuses on the recent developments in the understanding of the genetic basis of inherited pancreatitis, with special emphasis on TCP.

TCF7L2 gene polymorphisms do not predict susceptibility to diabetes in tropical calcific pancreatitis but may interact with SPINK1 and CTSB mutations in predicting diabetes

BACKGROUND

Tropical calcific pancreatitis (TCP) is a type of chronic pancreatitis unique to developing countries in tropical regions and one of its important features is invariable progression to diabetes, a condition called fibro-calculous pancreatic diabetes (FCPD), but the nature of diabetes in TCP is controversial. We analysed the recently reported type 2 diabetes (T2D) associated polymorphisms in the TCF7L2 gene using a case-control approach, under the hypothesis that TCF7L2 variants should show similar association if diabetes in FCPD is similar to T2D. We also investigated the interaction between the TCF7L2 variants and N34S SPINK1 and L26V CTSB mutations, since they are strong predictors of risk for TCP.

METHODS

Two polymorphisms rs7903146 and rs12255372 in the TCF7L2 gene were analyzed by direct sequencing in 478 well-characterized TCP patients and 661 healthy controls of Dravidian and Indo-European ethnicities. Their association with TCP with diabetes (FCPD) and without diabetes was tested in both populations independently using chi-square test. Finally, a meta analysis was performed on all the cases and controls for assessing the overall significance irrespective of ethnicity. We dichotomized the whole cohort based on the presence or absence of N34S SPINK1 and L26V CTSB mutations and further subdivided them into TCP and FCPD patients and compared the distribution of TCF7L2 variants between them.

RESULTS

The allelic and genotypic frequencies for both TCF7L2 polymorphisms, did not differ significantly between TCP patients and controls belonging to either of the ethnic groups or taken together. No statistically significant association of the SNPs was observed with TCP or FCPD or between carriers and non-carriers of N34S SPINK1 and L26V CTSB mutations. The minor allele frequency for rs7903146 was different between TCP and FCPD patients carrying the N34S SPINK1 variant but did not reach statistical significance (OR = 1.59, 95% CI = 0.93-2.70, P = 0.09), while, TCF7L2variant showed a statistically significant association between TCP and FCPD patients carrying the 26V allele (OR = 1.69, 95% CI = 1.11-2.56, P = 0.013).

CONCLUSION

Type 2 diabetes associated TCF7L2 variants are not associated with diabetes in TCP. Since, TCF7L2 is a major susceptibility gene for T2D, it may be hypothesized that the diabetes in TCP patients may not be similar to T2D. Our data also suggests that co-existence of TCF7L2 variants and the SPINK1 and CTSB mutations, that predict susceptibility to exocrine damage, may interact to determine the onset of diabetes in TCP patients.

Pathways to injury in chronic pancreatitis: decoding the role of the high-risk SPINK1 N34S haplotype using meta-analysis

Background

The complex interactions between recurrent trypsin-mediated pancreatic injury, alcohol-associated pancreatic injury and SPINK1 polymorphisms in chronic pancreatitis (CP) are undefined. We hypothesize that CP occurs as a result of multiple pathological mechanisms (pathways) that are initiated by different metabolic or environmental factors (etiologies) and may be influenced differentially by downstream genetic risk factors. We tested this hypothesis by evaluating the differences in effect size of the high risk SPINK1 N34S haplotype on CP from multiple etiologies after combining clinical reports of SPINK1 N34S frequency using meta-analysis.

Methods and Findings

The Pubmed and the Embase databases were reviewed. We studied 24 reports of SPINK1 N34S in CP (2,421 cases, 4,857 controls) using reported etiological factors as surrogates for pathways and multiple meta-analyses to determine the differential effects of SPINK1 N34S between alcoholic and non-alcoholic etiologies. Using estimates of between-study heterogeneity, we sub-classified our 24 studies into four specific clusters. We found that SPINK1 N34S is strongly associated with CP overall (OR 11.00; 95% CI: 7.59–15.93), but the effect of SPINK1 N34S in alcoholic CP (OR 4.98, 95% CI: 3.16–7.85) was significantly smaller than in idiopathic CP (OR 14.97, 95% C.I. = 9.09–24.67) or tropical CP (OR 19.15, 95% C.I. = 8.83–41.56). Studies analyzing familial CP showed very high heterogeneity suggestive of a complex etiology with an I² = 80.95%.

Conclusion

The small effect of SPINK1 N34S in alcoholic subjects suggests that CP is driven through a different pathway that is largely trypsin-independent. The results also suggest that large effect sizes of SPINK1 N34S in small candidate gene studies in CP may be related to a mixture of multiple etiologic pathways leading to the same clinical endpoint.

Pancreatitis risk in primary hyperparathyroidism: relation to mutations in the SPINK1 trypsin inhibitor (N34S) and the cystic fibrosis gene

OBJECTIVE

Primary hyperparathyroidism (pHPT)-related hypercalcemia is considered to represent a risk factor for the development of pancreatitis. We therefore explored whether mutations in genes that were previously identified to increase the risk for pancreatitis coexist in a cohort of 826 patients with pHPT prospectively studied between 1987 and 2002.

METHODS

Among 826 patients with pHPT, 38 patients were identified with pancreatitis (4.6%). DNA was available from 25 patients (13 women/12 men, 16 acute pancreatitis/9 chronic pancreatitis). These individuals and 50 patients with pHPT without pancreatitis were analyzed for mutations in the serine protease inhibitor Kazal type I (SPINK1) gene (N34S) and the cationic trypsinogen gene (PRSS1) (N29I, R122H) by melting curve analysis and DNA sequencing. Sequence analysis of the cystic fibrosis transmembrane conductance regulator (CFTR) gene was carried out for the detection of 36 mutations and the Tn polymorphism.

RESULTS

Four of 25 patients with pHPT and pancreatitis carried the N34S missense mutation in the SPINK1 gene (16%), while all 50 controls (pHPT without pancreatitis) showed no mutation in SPINK1 or PRSS1 genes (P < 0.05 vs controls, P < 0.001 vs general population). CF-causing CFTR mutations were present in four patients (P < 0.05 vs general population), while one patient carried a 5T allele. One patient was transheterozygous (SPINK1: N34S/CFTR: R553X). Mean serum calcium levels in pancreatitis patients (3.1 mmol/L) did not differ significantly from the mean of the entire cohort (3.0 mmol/L) or pHPT patients without pancreatitis (3.1 mmol/L).

CONCLUSION

Pancreatitis risk is approximately 10-fold elevated in pHPT, but pancreatitis occurs infrequently. This indicates an existing but minor impact of pHPT-related hypercalcemia. If pancreatitis occurs, it seems associated with genetic risk factors such as mutations in the SPINK1 and CFTR genes. In contrast, a combination of both hypercalcemia and genetic variants in SPINK1 or CFTR increases the risk to develop pancreatitis in patients with pHPT.

Hereditary chronic pancreatitis

Hereditary chronic pancreatitis (HCP) is a very rare form of early-onset chronic pancreatitis. Apart from young age at diagnosis and a slower progression, the clinical course, morphological features and laboratory findings of HCP do not differ from those of patients with alcoholic chronic pancreatitis. Diagnostic criteria and treatment of HCP also resemble those of chronic pancreatitis of other causes. The clinical presentation is highly variable and includes chronic abdominal pain, impairment of endocrine and exocrine pancreatic function, nausea and vomiting, maldigestion, diabetes, pseudocysts, bile-duct and duodenal obstruction, and rarely pancreatic cancer. Fortunately, the disease is mild in most patients. Mutations in the PRSS1 gene, encoding cationic trypsinogen, play a causative role in chronic pancreatitis. It has been shown that the PRSS1 mutations increase autocatalytic conversion of trypsinogen to active trypsin, and thus probably cause premature, intrapancreatic trypsinogen activation, disturbing the intrapancreatic balance of proteases and their inhibitors. Other genes--such as the anionic trypsinogen (PRSS2), the serine protease inhibitor Kazal type 1 (SPINK1), and the cystic fibrosis transmembrane conductance regulator (CFTR)--have also been found to be associated with chronic pancreatitis (idiopathic and hereditary). Genetic testing should only be performed in carefully selected patients by direct DNA sequencing, and antenatal diagnosis should not be encouraged. Treatment focuses on enzyme and nutritional supplementation, pain management, pancreatic diabetes, and local organ complications such as pseudocysts and bile-duct or duodenal obstruction. The disease course and prognosis of patients with HCP is unpredictable. The risk of pancreatic cancer is elevated. Therefore, HCP patients should strongly avoid environmental risk factors for pancreatic cancer.

Type 2 diabetes in Asian Indian youth

The prevalence of youth-onset type 2 diabetes is increasing worldwide in parallel with the obesity epidemic. In India, the age at onset of type 2 diabetes had traditionally been a decade or two earlier compared with the western population. Hence, it is not surprising that the prevalence of youth-onset type 2 diabetes is rapidly escalating in India not only among the more affluent sections of society but also in the middle and lower socioeconomic groups as well. In India, type 2 diabetes in youth overlaps with monogenic forms of diabetes such as maturity-onset diabetes of the young, fibrocalculous pancreatic diabetes, and malnutrition-modulated diabetes, all of which are ketosis-resistant forms of youth-onset diabetes. Screening of high-risk groups may help in the early detection of youth-onset type 2 diabetes and prevention of its complications. Primary prevention would require a multisectoral approach involving the government and non-governmental agencies with a focus on healthier lifestyles among children.

Missense mutations in pancreatic secretory trypsin inhibitor (SPINK1) cause intracellular retention and degradation

BACKGROUND/AIMS

Mutations of the SPINK1 gene encoding pancreatic secretory trypsin inhibitor have been identified in association with chronic pancreatitis. The vast majority of patients carry the N34S variant, whereas other genetic variants are relatively rare and their disease association is uncertain. The aim of this study was to characterise and compare the functional defects caused by the six published missense mutations that affect mature SPINK1-namely, N34S, D50E, Y54H, P55S, R65Q, and R67C.

METHODS

Wild type and mutant SPINK1 were expressed in human embryonic kidney 293T cells via transient transfection. SPINK1 expression was characterised by RT-PCR, activity assays, and western blots.

RESULTS

Mutations N34S and P55S did not alter secretion of SPINK1 from HEK 293T cells, whereas mutation R65Q decreased secretion about twofold. Remarkably, mutations D50E, Y54H, and R67C abolished or markedly diminished secretion, but all three mutants were detected in cell extracts, indicating intracellular retention and degradation.

CONCLUSIONS

The results identify intracellular folding defects as a novel mechanism of SPINK1 deficiency associated with chronic pancreatitis. The dramatic effects of the D50E and Y54H mutations indicate that the interaction between Asp50 and Tyr54 is critical for proper folding of the inhibitor. The disease-causing biochemical defect in the N34S mutant is unrelated to secretion or trypsin inhibitory activity and remains enigmatic. Finally, the patent functional defects in mutants D50E, Y54H, and R67C suggest disease association of these rare SPINK variants.

Signal peptide variants that impair secretion of pancreatic secretory trypsin inhibitor (SPINK1) cause autosomal dominant hereditary pancreatitis

Variants of the SPINK1 gene encoding pancreatic secretory trypsin inhibitor have been described in association with chronic pancreatitis (CP). These alterations are believed to cause a loss of function by either impairing the trypsin inhibitory activity or reducing expression. Here we report two novel SPINK1 variants in exon 1 that affect the secretory signal peptide. The disease-associated c.41T>G (p.L14R) alteration was found in two European families with autosomal dominant hereditary pancreatitis, whereas the c.36G>C (p.L12F) variant was identified as a frequent alteration in subjects of African descent. The functional effects of both alterations and the previously reported c.41T>C (p.L14P) variant were characterized by activity assays and Western blots of wild-type and mutant SPINK1 expressed in human embryonic kidney 293T and Chinese hamster ovary cells. Alterations p.L14R and p.L14P destined the inhibitor for rapid intracellular degradation and thereby abolished SPINK1 secretion, whereas the p.L12F variant showed no detrimental effect. The results provide the first clear experimental demonstration that alterations that markedly reduce SPINK1 expression are associated with classic hereditary pancreatitis. Therefore, these variants should be classified as severe and regarded as disease-causing rather than disease-modifiers.

Hereditary chronic pancreatitis

Hereditary chronic pancreatitis (HCP) is a very rare form of early onset chronic pancreatitis. With the exception of the young age at diagnosis and a slower progression, the clinical course, morphological features and laboratory findings of HCP do not differ from those of patients with alcoholic chronic pancreatitis. As well, diagnostic criteria and treatment of HCP resemble that of chronic pancreatitis of other causes. The clinical presentation is highly variable and includes chronic abdominal pain, impairment of endocrine and exocrine pancreatic function, nausea and vomiting, maldigestion, diabetes, pseudocysts, bile duct and duodenal obstruction, and rarely pancreatic cancer. Fortunately, most patients have a mild disease. Mutations in the PRSS1 gene, encoding cationic trypsinogen, play a causative role in chronic pancreatitis. It has been shown that the PRSS1 mutations increase autocatalytic conversion of trypsinogen to active trypsin, and thus probably cause premature, intrapancreatic trypsinogen activation disturbing the intrapancreatic balance of proteases and their inhibitors. Other genes, such as the anionic trypsinogen (PRSS2), the serine protease inhibitor, Kazal type 1 (SPINK1) and the cystic fibrosis transmembrane conductance regulator (CFTR) have been found to be associated with chronic pancreatitis (idiopathic and hereditary) as well. Genetic testing should only be performed in carefully selected patients by direct DNA sequencing and antenatal diagnosis should not be encouraged. Treatment focuses on enzyme and nutritional supplementation, pain management, pancreatic diabetes, and local organ complications, such as pseudocysts, bile duct or duodenal obstruction. The disease course and prognosis of patients with HCP is unpredictable. Pancreatic cancer risk is elevated. Therefore, HCP patients should strongly avoid environmental risk factors for pancreatic cancer.

Lack of significant association of an insertion/deletion polymorphism in the angiotensin converting enzyme (ACE) gene with tropical calcific pancreatitis

Background

The genetic basis of tropical calcific pancreatitis (TCP) is different and is explained by mutations in the pancreatic secretory trypsin inhibitor (SPINK1) gene. However, mutated SPINK1 does not account for the disease in all the patients, neither does it explain the phenotypic heterogeneity between TCP and fibro-calculous pancreatic diabetes (FCPD). Recent studies suggest a crucial role for pancreatic renin-angiotensin system during chronic hypoxia in acute pancreatitis and for angiotensin converting enzyme (ACE) inhibitors in reducing pancreatic fibrosis in experimental models. We investigated the association of ACE gene insertion/deletion (I/D) polymorphism in TCP patients using a case-control approach. Since SPINK1 mutations are proposed a modifier role, we also investigated its interaction with the ACE gene variant.

Methods

We analyzed the I/D polymorphism in the ACE gene (g.11417_11704del287) in 171 subjects comprising 91 TCP and 80 FCPD patients and compared the allelic and genotypic frequency in them with 99 healthy ethnically matched control subjects.

Results

We found 46% and 21% of TCP patients, 56% and 19.6% of FCPD patients and 54.5% and 19.2% of the healthy controls carrying the I/D and D/D genotypes respectively (P>0.05). No significant difference in the clinical picture was observed between patients with and without the del allele at the ACE in/del polymorphism in both categories. No association was observed with the presence or absence of N34S SPINK1 mutation in these patients.

Conclusion

We conclude that the ACE insertion/deletion variant does not show any significant association with the pathogenesis, fibrosis and progression of tropical calcific pancreatitis and the fibro-calculous pancreatic diabetes.

Juvenile fibrocalculous pancreatopathy--a patient report

Fibrocalculous pancreatopathy (FCPP) is a secondary form of diabetes mellitus (DM) with obscure etiology. Recently various gene mutations have been reported in patients with FCPP from the Indian subcontinent. Initially termed tropical pancreatic diabetes, FCPP is uncommon and is characterized by pancreatic calcifications. The diagnosis is made in the third decade of life in most patients with the onset of abdominal pain and DM. We report a female child with DM diagnosed at the age of 3 years who had been managed with insulin but was ketosis resistant. The diagnosis of FCPP was made 3 years later. There were no mutations at N34S and P55S in the SPINK1 gene.

Pathophysiology of SPINK mutations in pancreatic development and disease

The endogenous pancreatic trypsin inhibitor, SPINK, is believed to limit enzyme activity in the pancreas and reduce the risk of pancreatitis. Recently, mutations in the SPINK1 gene have been associated with development of both acute and chronic pancreatitis. In most patients with SPINK1 mutations, the genetic variants do not cause the disease independently, but may act in concert with other genetic or environmental factors. Recent studies, using mice in which the trypsin inhibitor gene has been deleted or overexpressed, provide novel insights into the role of SPINK in pancreatic development and pancreatitis.

Natural history of endocrine failure in tropical chronic pancreatitis: a longitudinal follow-up study

BACKGROUND AND AIMS

Diabetes in tropical chronic pancreatitis (TCP), also known as fibrocalculous pancreatic diabetes (FCPD), is frequently seen at diagnosis. The aim of the present study was to determine the natural history of endocrine failure in TCP subjects without diabetes at baseline.

METHODS

Of 73 TCP subjects without diabetes according to World Health Organization (WHO) criteria at baseline who were seen at an out-patient center, 54 (74.0%) underwent periodic oral glucose tolerance tests on follow up. Another 54 sex-matched, non-diabetic subjects without chronic pancreatitis served as controls. Baseline demographic and clinical characteristics were noted.

RESULTS

After a median follow up of 5.0 years in TCP subjects and 7.0 years in controls, 27 of 54 TCP subjects (50%) developed diabetes compared with 14 of 54 controls (25.9%). Of the TCP subjects, those who developed diabetes on follow up were older (31 +/- 12 vs 23 +/- 11 years; P = 0.013), had a higher body mass index (21.7 +/- 4.4 vs 18.2 +/- 3.5 kg/m2; P = 0.004), higher 2 h post-load plasma glucose (8.8 +/- 1.9 vs 6.7 +/- 1.4 mmol/L; P < 0.001) and lower fecal chymotrypsin (2.1 +/- 1.2 vs 4.3 +/- 2.5 U/g; P < 0.001) at baseline compared with those who did not develop diabetes. The median time for the development of diabetes after diagnosis of TCP was 9.6 years (compared with 14.4 years among controls). Only 2 of 13 TCP subjects (15.4%) who had undergone surgical interventions during the normal glucose tolerance phase developed diabetes during follow up.

CONCLUSIONS

In TCP, there is progressive deterioration of endocrine pancreatic function, with development of diabetes in 50% of patients upon follow up, suggesting that FCPD is merely a later stage in the course of TCP. Early surgery may prevent the development of diabetes in TCP subjects.

The SPINK1 N34S mutation is not associated with Type 2 diabetes mellitus in a population of the USA

AIMS

Mutations in the serine protease inhibitor (SPINK1) gene have been associated with all forms of chronic pancreatitis. Recently, an association of SPINK1 mutations with early-onset Type 2 diabetes mellitus has been reported in patients from Bangladesh. Therefore, we determined the frequency of SPINK1 N34S mutations in patients with Type 2 diabetes mellitus from the USA.

METHODS

The study population of Hispanic and non-Hispanic white people consisted of 387 patients with Type 2 diabetes and familial clustering of the disease, 232 family members without diabetes, 259 patients with Type 2 diabetes without a family history, and 302 ethnically matched healthy controls as part of the San Luis Valley Diabetes Study. We performed linkage- and association-analysis in 82 multiplex families with Type 2 diabetes mellitus.

RESULTS

No significant linkage or allele sharing was detected between Type 2 diabetes mellitus and the SPINK1 locus. The frequency of the N34S mutation was determined by fluorescence polarization and was similar between patients (n = 14/387 patients with familial clustering; n = 2/259 patients without family history) and controls (n = 5/232 family members without diabetes; n = 10/302 individuals). Variables such as ethnicity, age of diabetes onset and percentage of individuals with impaired glucose tolerance did not differ significantly between carriers and homozygous normal individuals.

CONCLUSION

The SPINK1 N34S mutation appears not to predispose Hispanic or non-Hispanic white people from the USA to the development of Type 2 diabetes mellitus.

Cationic Trypsinogen Mutations and Pancreatitis

The discovery of PRSS 1 mutations in hereditary pancreatitis and analysis of how the genotype affects the presentation and progression of hereditary pancreatitis has led to a better understanding of the pathophysiology of the disease. Patients with hereditary pancreatitis present with symptoms at an early age and have a significant lifetime risk for the development of endocrine and exocrine insufficiency, albeit at a later stage than patients with either idiopathic or alcoholic chronic pancreatitis. There are distinct phenotypic differences between hereditary pancreatitis and with other types of pancreatitis. As many as 80% of patients with symptomatic hereditary pancreatitis have an underlying causative PRSS1 mutation; there are, however, few significant phenotypic differences between these PRSS1 mutations. TheR122H mutation is the most common PRSS1 mutation observed, and patients with the R122H mutation present earlier. This, however, does not necessarily translate into a more aggressive disease with respect to complications of chronic pancreatitis. Indeed, the age of presentation of symptoms may be a poor surrogate for predicting outcome, as inherited disorders of trypsinogen may cause subclinical attacks of pancreatitis, which ultimately lead to pancreatic destruction and dysfunction. All patients, irrespective of whether they carry a PRSS1 mutation, are at significant risk of developing pancreatic ductal adenocarcinoma. The risk appears to be insignificant below the age of 40 years, but it increases incrementally thereafter. Significantly, the risk of pancreatic cancer is not related to PRSS1 mutation type and does not appear to be related to the mode of inheritance. The role of SPINK1 mutations in modifying the expression of PRSS1mutations is unclear but appears to be of clinical importance. It is unlikely that they act as causative mutations per se, at least in the Western form of the disease. Additionally, they do not appear to have an impact on the penetrance of PRSS1 gene mutations in hereditary pancreatitis.

Serine Protease Inhibitor Kazal Type 1 Mutations and Pancreatitis

SPINKI is thought to play an important role in protecting the pancreas against excessive trypsinogen activation. SPINK1 mutations are associated with the development of acute and chronic pancreatitis and have been detected in all forms of chronic pancreatitis. The strong association of mutations in the PRSS1 gene and in the SPINKI gene with chronic pancreatitis supports the concept of intracellular trypsin activation as an initiating and extremely important step in the development of pancreatitis. The N34S mutation represents the most frequently observed pancreatitis-associated SPINKI variant. Because the SPINKI N34Smutation is very common in the general population, it is unlikely that this mutation alone can initiate the development of chronic pancreatitis. Thus, it rather appears that in most patients with SPINKI-associated chronic pancreatitis, this genetic variant acts as disease modifier or within a polygenic model with other yet unidentified genes or environmental co-factors. The possible interaction of mutations in the SPINK1 gene with other pancreatitis-associated susceptibility genes has to be investigated in future research efforts. The most promising candidate gene for such an interaction is the CFTR gene, because genetic alterations within the CFTRgene are also common in the general population and already have been associated with chronic pancreatitis.

Serine protease inhibitor Kazal type 1 mutations and pancreatitis

In summary, SPINK1 is thought to play an important role in protecting the pancreas against excessive trypsinogen activation. SPINK1 mutations are associated with the development of acute and chronic pancreatitis and have been detected in all forms of chronic pancreatitis. The strong association of mutations in the PRSS1 gene and in the SPINK1 gene with chronic pancreatitis supports the concept of intracellular trypsin activation as an initiating and extremely important step in the development of pancreatitis. The N34S mutation represents the most frequently observed pancreatitis-associated SPINK1 variant. Because the SPINK1 N34S mutation is very common in the general population, it is unlikely that this mutation alone can initiate the development of chronic pancreatitis. Thus, it rather appears that in most patients with SPINK1-associated chronic pancreatitis, this genetic variant acts as disease modifier or within a polygenic model with other yet unidentified genes or environmental cofactors. The possible interaction of mutations in the SPINK1 gene with other pancreatitis-associated susceptibility genes has to be investigated in future research efforts. The most promising candidate gene for such an interaction is the CFTR gene, because genetic alterations within the CFTR gene are also common in the general population and already have been associated with chronic pancreatitis.

Genetic counseling for hereditary pancreatitis--the role of molecular genetics testing for the cationic trypsinogen gene, cystic fibrosis and serine protease inhibitor Kazal type 1

The importance of pretest information, using an accredited DNA laboratory and interpreting the genotype on behalf of the patient and their physicians is emphasized. Care with predictive testing and the strong encouragement to involve a specialist genetic counseling service is made. A similar approach to genetic testing should be used when children are involved. Because of the incomplete pickup of PRSS1 mutations, particularly of a limited mutation panel of R122H and N291 (perhaps with A16V), a diagnosis of HP cannot be ruled out by molecular genetic testing alone. The A16V mutation has a reduced penetrance, and its contribution to pancreatitis remains unclear. The advice to patients with genetic forms of pancreatitis is a strong encouragement to avoid smoking, to avoid alcohol, and to remain in contact with clinical and research groups for their follow-up and screening trials for early pancreatic cancer. The remaining issues are of how wide to cast the net of investigation in patients with unexplained pancreatitis, particularly looking for mutations in the CFTR and lower penetrance genes such as PSTI/SPINK1.

Cationic trypsinogen mutations and pancreatitis

The discovery of PRSS1 mutations in hereditary pancreatitis and analysis of how the genotype affects the presentation and progression of hereditary pancreatitis has led to a better understanding of the pathophysiology of the disease. Patients with hereditary pancreatitis present with symptoms at an early age and have a significant lifetime risk for the development of endocrine and exocrine insufficiency, albeit at a later stage than patients with either idiopathic or alcoholic chronic pancreatitis. There are distinct phenotypic differences between hereditary pancreatitis and with other types of pancreatitis. As many as 80% of patients with symptomatic hereditary pancreatitis have an underlying causative PRSS1 mutation; there are, however, few significant phenotypic differences between these PRSS1 mutations. The R122H mutation is the most common PRSS1 mutation observed, and patients with the R122H mutation present earlier. This, however, does not necessarily translate into a more aggressive disease with respect to complications of chronic pancreatitis. Indeed, the age of presentation of symptoms may be a poor surrogate for predicting outcome, as inherited disorders of trypsinogen may cause subclinical attacks of pancreatitis, which ultimately lead to pancreatic destruction and dysfunction. All patients, irrespective of whether they carry a PRSS1 mutation, are at significant risk of developing pancreatic ductal adenocarcinoma. The risk appears to be insignificant below the age of 40 years, but it increases incrementally thereafter. Significantly, the risk of pancreatic cancer is not related to PRSS1 mutation type and does not appear to be related to the mode of inheritance. The role of SPINK1 mutations in modifying the expression of PRSS1 mutations is unclear but appears to be of clinical importance. It is unlikely that they act as causative mutations per se, at least in the Western form of the disease. Additionally, they do not appear to have an impact on the penetrance of PRSS1 gene mutations in hereditary pancreatitis.

Susceptibility to pancreatitis related to PSTI/SPINK1 expression

This article summarized several observations on the role of pancreatic secretory trypsin inhibitor in the pancreas. Although it long has been suspected that endogenous pancreatic trypsin inhibitors protect against inadvertent activation of trypsinogen, this hypothesis has gained strength from recent biochemical investigations and genetic studies of populations suffering from chronic pancreatitis. There is now considerable evidence from clinical disease associations and burgeoning experimental models that some forms of pancreatitis may be the result of an imbalance between active pancreatic proteases and their inhibitors within the pancreas. Future studies should clarify the precise molecular interactions between enzymes and inhibitors and how these may be manipulated to prevent or treat pancreatitis.

Diabetes mellitus in Tropical Chronic Pancreatitis Is Not Just a Secondary Type of Diabetes

AIMS

In chronic calcific pancreatitis of the tropics, etiology and relationship to developing diabetes mellitus are unknown. Some consider these cases a straightforward secondary type of diabetes, while others suggest selective beta-cell impairment. Testing pancreatic function, we investigated whether selective beta-cell impairment triggers diabetes associated with tropical pancreatitis.

METHODS

At a Bangladeshi research institute, 8 chronic tropical pancreatitis and no diabetes mellitus subjects, 14 fibrocalculous pancreatic diabetics and 27 matched healthy controls underwent arginine (endocrine pancreatic function) and secretin (exocrine pancreatic function assessment) stimulation tests.

RESULTS

All patients with clinically-diagnosed, chronic pancreatitis demonstrated pronounced exocrine pancreatic dysfunction with beta-cell functioning differing significantly between the two groups. Compared to controls, patients having tropical pancreatitis and no diabetes showed normal plasma C-peptide values at baseline and after arginine stimulation, while fibrocalculous pancreatic diabetics demonstrated a typical diabetic pattern for plasma C-peptide levels. In contrast, pancreatic alpha-cell functioning (glucagon response to arginine) was preserved in both pancreatitis groups.

CONCLUSION

A preserved pancreatic alpha-cell function in diabetics with advanced chronic pancreatitis of the tropics supports the concept of two different pathogenic mechanisms, one eliciting chronic pancreatitis and the other selective pancreatic beta-cell impairment and subsequent diabetes mellitus.

Absence of PRSS1 mutations and association of SPINK1 trypsin inhibitor mutations in hereditary and non-hereditary chronic pancreatitis

BACKGROUND AND AIMS

Mutations in the cationic trypsinogen (protease, serine, 1 (trypsin 1); PRSS1) gene are causally associated with recurrent acute and chronic pancreatitis. We investigated whether mutations in the PRSS1 gene are associated with hereditary and non-hereditary pancreatitis. As a modifier role has been proposed for trypsin inhibitor (serine protease inhibitor, Kazal type I; SPINK1) mutations, the role of SPINK1 mutations in these patients was also analysed.

SUBJECTS AND METHODS

The coding regions of PRSS1 and SPINK1 genes were sequenced in 290 controls and 198 patients, of whom 120 were diagnosed as idiopathic (ICP), 41 as alcoholic (ACP), and 37 as hereditary pancreatitis (HP). Twenty four unaffected relatives of HP probands were also analysed and genotype-phenotype correlations and statistical analyses were performed.

RESULTS

No mutations in the PRSS1 gene were detected in any of the patients, including HP patients, while the N34S mutation was observed in the SPINK1 gene in the majority of HP patients (73%). Similarly, 26.8% of ACP (11 of 41) and 32.5% (39 of 120) of ICP patients also had SPINK1 mutations. The N34S mutation was observed in both homozygous and heterozygous conditions. In comparison, only 2.76% of the control population had the N34S allele (p<0.001). The P55S mutation was observed in one ICP and one ACP patient, and in three normal individuals. Genotype-phenotype correlations did not suggest any significant difference in the age of onset, severity of disease, or pancreatic endocrine insufficiency in patients with or without mutated SPINK1 and irrespective of the allelic status of N34S SPINK1.

CONCLUSIONS

Irrespective of the aetiology, mutations in the PRSS1 gene are not associated with chronic pancreatitis, including HP. In contrast, the N34S mutation in the SPINK1 gene shows a significant correlation in these patients. A comparable phenotype in terms of age of onset, diabetes mellitus, and other phenotypic features in patients with or without SPINK1 mutations and N34S homozygotes and heterozygotes suggests that there may still be involvement of other genetic or environmental factors.

Tropical chronic pancreatitis

Tropical chronic pancreatitis (TCP) is a juvenile form of chronic calcific non-alcoholic pancreatitis, seen almost exclusively in the developing countries of the tropical world. The classical triad of TCP consists of abdominal pain, steatorrhoea, and diabetes. When diabetes is present, the condition is called fibrocalculous pancreatic diabetes (FCPD) which is thus a later stage of TCP. Some of the distinctive features of TCP are younger age at onset, presence of large intraductal calculi, more aggressive course of the disease, and a high susceptibility to pancreatic cancer. Pancreatic calculi are the hallmark for the diagnosis of TCP and in non-calcific cases ductal dilation on endoscopic retrograde cholangiopancreatography, computed tomography, or ultrasound helps to identify the disease. Diabetes is usually quite severe and of the insulin requiring type, but ketosis is rare. Microvascular complications of diabetes occur as frequently as in type 2 diabetes but macrovascular complications are uncommon. Pancreatic enzyme supplements are used for relief of abdominal pain and reducing the symptoms related to steatorrhoea. Early diagnosis and better control of the endocrine and exocrine dysfunction could help to ensure better survival and improve the prognosis and quality of life of TCP patients.

Chronic parotitis: not another SPINKosis

INTRODUCTION

Pancreatitis and parotitis share several etiological, pathohistological and functional similarities. It arose from recent pancreatitis research that some cases of chronic pancreatitis are associated with mutations of the serine protease inhibitor, Kazal type-1 (SPINK1). We tested the hypothesis that the pancreatitis-associated N34S mutation of SPINK1 is also a risk factor for chronic parotitis.

METHODS

Reverse-transcriptase polymerase chain reaction was used to investigate SPINK1 transcription in the parotid gland. Forty-five blocks of formalin-fixed, paraffin wax-embedded tissues with chronic parotitis of unknown cause were analyzed for the SPINK1-N34S mutation.

RESULTS

The SPINK1 gene is transcribed in the parotid gland. Two of the 45 patients (4.4%) with chronic parotitis carried the N34S mutation heterozygously. Of 82 healthy blood donors, 3 subjects (3.7%) were identified as carrying this mutation heterozygously (p = 0.83).

CONCLUSION

The SPINK1-N34S mutation is not associated with chronic parotitis.