In vivo Nitrosoproline formation and other risk factors in Costa Rican Children from high-and low-risk areas for gastric cancer

Abstract

The hypothesis that intragastric synthesis of N-nitroso compounds (NOC) in early life could play a role in gastric carcinogenesis was tested by applying the N-nitrosoproline (NPRO) test to about 50 children living in high- and low-risk areas for stomach cancer in Costa Rica. The median values of excretion of NPRO and the sum of three nitrosamino acids (micrograms/12 h urine) were 10-20% of those in adults from other geographical high-risk areas for stomach cancer. The urinary NPRO level after proline intake was higher in children from the high-risk area (P < 0.04) and markedly reduced after ingestion of ascorbic acid together with proline (P < 0.05). NPRO levels on the day of proline intake were highly correlated with levels of nitrate excretion (P < 0.001). Mean levels of total NOC in an aqueous (pH 2) extract of cooked beans from the high- and low-risk areas were similar. Acid-catalyzed nitrosation of the extract increased the total NOC concentration up to 1000-fold, but there was no difference between samples from the two areas. About 10% of bean extracts from both areas showed weak direct-acting genotoxicity in Escherichia coli; after acid-catalyzed nitrosation, all samples were genotoxic at similar levels. The diet of children in the low-risk area satisfied recommended levels of intake of energy and most nutrients except riboflavin and retinol equivalents. Diets from the high-risk area were deficient in energy intake and all nutrients except protein and vitamin C. Blood samples were collected from 276 children and young adults from the same areas and analyzed for serum antibodies against Helicobacter pylori. Although very high, no significant difference was found in the prevalence of IgG or IgA antibodies between the two regions.