Polymorphism of alpha-1-antitrypsin and association of S and Z alleles with duodenal ulcers

BACKGROUND: Duodenal ulcers are mucosal erosions that penetrate into the muscularis propria of the duodenum. They are a result of an imbalance between aggressive and defensive factors. Various environmental factors like Helicobacter pylori infection, addictions to smoking and alcohol etc. and genetic factors have been reported to be associated with duodenal ulceration. Alpha-1-antitrypsin was studied for its role as a genetic marker and specific allelic association to protein functioning and alteration. Serum samples from 185 normal subjects and 210 duodenal ulcer cases were typed for the phenotypes following PAGE (polyacrylamide gel electrophoresis) and immunofixation using specific commercial antisera with appropriate staining protocols. In general, ′M′ allele of alpha-1-antitrypsin was found to be predominant in healthy normal subjects, with the gene frequencies being 0.679 (M), 0.299 (Z) and 0.0214 (S). Whereas in duodenal ulcer cases, Z and S alleles were found to be predominant with a significant association of MS, ZZ and MZ phenotypes (x²sub : 49.98) and the gene frequencies being 0. 113 (M), 0. 347 (Z) and 0.506 (S). Predominance of Z and S alleles indicates that these alleles may encode for reduced synthesis of alpha-1-antitrypsin, hence decreased neutralization of proteases like trypsin and chymotrypsin inhibited by alpha-1-antitrypsin, thereby resulting in ulcers. The study highlights the association of Z and S alleles of the potent protease inhibitor alpha-1-antitrypsin and also suggests its role as a genetic marker in ulcerogenesis.