Clinical course of acute pancreatitis, the onset of which is caused by the same factor in different patients, may be of a completely opposite nature - from edematous form to pancreatonecrosis . An important role is played by genetically determined defence mechanisms aimed at preventing an intrapancreatic activation of enzymes [1-6]. One of such fundamental mechanisms is the neutralizing action of pancreatic secretory trypsin inhibitor (serine protease inhibitor Kazal-type 1 - SPINK1). The gene, which is responsible for the synthesis of SPINK1 is located on the fifth chromosome. The N34S mutation is known to be the most common mutation of the third exon of this gene [1, 3, 4, 5, 6]. The presence of this genetic defect may lead to an excessive uncontrolled intraacinar activation of this enzyme.
The objective of the research was to study the SPINK1 N34S polymorphism in patients with different forms of acute pancreatitis living in Chernivtsi region (Ukraine).
The research involved 37 persons with different forms of acute pancreatitis. Among them there were 25 (67.6%) men and 12 (34.2%) women. Group I consisted of 17 patients with acute edematous pancreatitis; Group II included 20 patients with pancreatonecrosis.
The alleles of polymorphic sites of the third exon of the SPINK I gene were studied by isolating genomic DNA from the peripheral blood leukocytes, stabilized EDTA as an anticoagulant (Merk®, Germany). The amplification of the polymorphic site was performed by means of the polymerase chain reaction (PCR) with an individual temperature program for specific primers: sense 5’-CAATCACAGTTATTCCCCAGAG-3’, antisense 5’-GTTTGCTTTTCTCGGGGTGAG-3’.
Electropherograms of amplification products are presented in Fig. 1. The length of the amplification of the SPINK1 N34S polymorphism was 320 pairs of nucleotides (pn). In the presence of the 3rd exon of the nucleotide sequence of the aforementioned gene of adenine in the 34th codon the amplification split by the restriction enzyme PstI into fragments, measuring 320 and 286 pn. In case of A-G transversion the restriction site for PstI was lost.
The presence of the favourable wild-type N - allele (wild-type, Wt) - 73.0% (27) was detected in the majority of patients. The pathological mutant S-variant was identified in 27.0% (10) of patients. There were 45.9% (17) of cases of homozygous carriers of the wild-type NN-genotype (N34) and 51.4% (19) of cases of heterozygotes carriers of the NS-genotype (N34S). One (2.7%) patient was a homozygous carrier of the mutant S-allele (SS-genotype, 34S) (Fig. 1). The distribution of the genotypes according to the polymorphic N34S variant of the SPINK1 gene among patients corresponded to expected Hardy-Weinberg equilibrium (p>0.05).
When distributing all patients according to the etiological agent it was found out that the frequency of the NN- and NS-genotypes in patients with biliary pancreatitis was 52.6% (10) and 47.7% (9), respectively and did not differ statistically from that in patients with pancreatitis of non-biliary genesis - 33.3% (6) and 61.1% (11), respectively (χ2=0.003, p=0.95 and χ2 = 0.68, p=0.4, respectively).
While analyzing the group of patients with acute edematous biliary pancreatitis, it was revealed that homozygous carriers of the favourable wild-type N-allele and heterozygotes were detected with the same frequency - 50% (5) and 50% (5), respectively. However, a tendency towards the domination of the NS-genotype was observed in patients with edematous pancreatitis of non-biliary genesis compared to the NN-genotype the detection frequency of which was 85.7% (6) and 14.3% (1), respectively. However, such differences were not statistically significant (χ2 = 2.00, p=0.16). No homozygous carriers of the mutant S-allele were detected among patients with acute edematous pancreatitis.
In patients with acute destructive pancreatitis of biliary and non-biliary genesis the frequency of detecting the NN-(N34) and NS-(N34S) genotypes did not differ significantly: 55.5% (5) and 44.5% (4) versus 45.5% (5) and 45.5% (5), respectively (χ2=0.001, p=0.97 and χ2=0.114, p=0.74, respectively).
The homozygous mutation of the SS-genotype was detected in 1 person of the aforementioned group. It should be noted that the initiation of the disease was associated with the non-biliary factor in a female patient with the SS-genotype. The course of the disease was characterized by particular “aggressiveness” with the development of acute suppurative subtotal pancreonecrosis complicated by the formation of abscesses of the omental bursa and the right subdiaphragmatic space, retroperitoneal phlegmon, external pancreatic and duodenal fistulae, left-sided exudative pleurisy and toxico-bacterial shock. The hospital stay lasted 118 bed days; 10 surgical interferences were performed. The development of the painful form of chronic pancreatitis with a tendency to frequent recurrences was observed in the aforementioned patient in the process of follow-up. Taking into account the analysis of the patient’s case history (the SS-genotype, as well as the non-biliary and nonalcoholic etiology of the disease), it is appropriate to consider, that one of the principal causes of such a severe clinical course of acute pancreatitis in a specific case was its hereditary character.
The carriage of the favourable N-allele (45.9% and 51.4%) was more often observed among patients with different forms of acute pancreatitis and lower number of pathological SS-homozygotes (2.7%).
The frequency of the biliary form of acute pancreatitis (both edematous and destructive) was not associated with a certain genotype of the SPINK1 N34S polymorphism. The non-biliary form of acute pancreatitis appeared insignificantly more often in carriers of the mutant S-allele: 29.7% (11) versus 18.9% (7) of persons.
The carriage of the unfavourable SS-genotype is a probable predisposing factor of disease initiation, potentiation of its further progression, as well as a prognostic marker of severe clinical course of acute pancreatitis with the development of necrotic lesions of the pancreas.