Genetic analysis of the glycoprotein 2 gene in patients with chronic pancreatitis

Glycoprotein 2 in health and disease: lifting the veil

In 2020, we discovered glycoprotein 2 (GP2) variants associated with pancreatic cancer susceptibility in a genome-wide association study involving the Japanese population. Individuals carrying a missense coding variant (rs78193826) in the GP2 gene resulting in a p.V432M substitution had an approximately 1.5-fold higher risk of developing pancreatic cancer than those without this variant. GP2 is expressed on the inner surface of zymogen granules in pancreatic acinar cells, which are responsible for the sorting, storage and secretion of digestive enzymes. Upon neuronal, hormonal, or other stimulation, GP2 is cleaved from the membrane of zymogen granules and then secreted into the pancreatic duct and intestinal lumen. While the functions of GP2 remain poorly understood, emerging evidence suggests that it plays an antibacterial role in the gastrointestinal tract after being secreted from pancreatic acinar cells. Impaired GP2 functions may facilitate the adhesion of bacteria to the intestinal mucosa. In this review article, we summarize the role of GP2 in health and disease, emphasizing its functions in the gastrointestinal tract, as well as genetic variations in the GP2 gene and their associations with disease susceptibility. We hope that its robust genetic associations with pancreatic cancer, coupled with its emerging role in gastrointestinal mucosal immunity, will spur renewed research interest in GP2, which has been understudied over the past 30 years compared with its paralog uromodulin (UMOD).

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.

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.

Idiopathic chronic calcific pancreatitis in a child: An uncommon entity

Inflammatory disease of pancreas can be acute or chronic. Acute pancreatitis is a reversible process whereas chronic pancreatitis produces irreversible changes in the architecture and function of pancreas. Although pancreatitis is less common in children than in adults it still occurs with regularity and should be considered in any child with acute or chronic abdominal pain. The main difference between chronic pancreatitis in children and adults is in the etiology. We present a case of idiopathic chronic calcific pancreatitis in a child thereby signifying the importance of this entity at this age.

A small de novo 16q24.1 duplication in a woman with severe clinical features

We report here a de novo 16q24.1 interstitial duplication in a woman with a severe phenotype consistent with mental retardation, spastic paraplegia, severe epilepsy, a narrow and arched palate, malar hypoplasia, little subcutaneous fat and arachnodactyly. Although conventional karyotyping was found to be normal, array-CGH detected a small duplication on chromosome 16. Using QFM-PCR, we characterised its proximal and distal breakpoints. The duplication, which is approximately 250 kb, encompasses seven genes (KIAA0182, GINS2, c16orf74, COX4NB, COX4I1, MIR1910 and IRF8). Several reports have previously described large 16q duplications, and some of these overlap with our region in 16q24.1. Due to the variability of the described phenotypes, the characterisation of small 16q duplications may help to determine critical regions and the genes they contain that are associated with the components of complex phenotypes.

Assessing the pathological relevance of SPINK1 promoter variants

The SPINK1 gene, encoding the human pancreatic secretory trypsin inhibitor, is one of the major genes involved in predisposition to chronic pancreatitis (CP). In this study we have assessed the potential functional impact of 11 SPINK1 promoter variants by means of both luciferase reporter gene assay and electrophoretic mobility shift assay (EMSA), using human pancreatic COLO-357 cells as an expression system. The 11 promoter variants were found to be separable into three distinct categories on the basis of the reporter gene assay results viz loss-of-function, gain-of-function and functionally neutral. These findings, which were validated by EMSA, concurred with data from previous deletion studies and DNase I footprinting assays. Further, binding sites for two transcription factors, HNF1 and PTF1, were newly identified within the SPINK1 promoter by virtue of their being affected by specific variants. Combining the functional data with epidemiological data (derived by resequencing the SPINK1 promoter region in French, German and Indian CP patients and controls), then allowed us to make meaningful inferences as to each variant's likely contribution to CP. We conclude that only the three promoter variants associated with a loss-of-function (ie, −53C>T, −142T>C and −147A>G) are likely to be disease-predisposing alterations.