The role of anti-oxidants in the chemoprevention of gastric cancer

Helicobacter pylori infection: New pathogenetic and clinical aspects

Helicobacter pylori (H. pylori) infects more than half of the world’s human population, but only 1% to 3% of infected people consequently develop gastric adenocarcinomas. The clinical outcome of the infection is determined by host genetic predisposition, bacterial virulence factors, and environmental factors. The association between H. pylori infection and chronic active gastritis, peptic ulcer disease, gastric cell carcinoma, and B cell mucosa-associated lymphoid tissue lymphoma has been well established. With the exception of unexplained iron deficiency anemia and idiopathic thrombocytopenic purpura, H. pylori infection has no proven role in extraintestinal diseases. On the other hand, there is data showing that H. pylori infection could be beneficial for some human diseases. The unpredictability of the long-term consequences of H. pylori infection and the economic challenge in eradicating it is why identification of high-risk individuals is crucial.

The effect of serum carotenoids on atrophic gastritis among the inhabitants of a rural area in Hokkaido, Japan

A total of 206 residents (76 males and 130 females) of a rural area of Hokkaido, Japan, attending a health check in August, 1997, were studied to assess the relationship between serum carotenoids and atrophic gastritis (AG). Of the participants, 91 had AG as indicated by their serum levels of pepsinogen I and pepsinogen II. Logistic regression analysis, after adjusting for gender and age, revealed that the odds ratios for serum carotenoid levels were lower for subjects with high serum levels of α-carotene (odds ratio, 0.41; 95% C.I., 0.19-0.88) and β-carotene (odds ratio, 0.41; 95% C.I., 0.18-0.91) than for those with low serum carotenoid levels. In addition, the odds ratios of subjects with high serum levels of β-cryptoxanthin (odds ratio, 0.60; 95% C.I., 0.28-1.31), provitamin A (odds ratio, 0.38; 95% C.I., 0.17-0.85), and retinol (odds ratio, 0.67; 95% C.I., 0.31-1.48) were found to be lower than the odds ratios for those with low serum levels. Odds ratios for subjects with high serum zeaxanthin/lutein levels were higher than odds ratios for those with low serum levels. These results suggest that frequent intake of foods ric, in carotenoids with provitamin A activity may reduce the risk of AG.

Chemoprevention of colorectal cancer: feasibility in everyday practice?

Chemoprevention means the use of agents to prevent, delay, or reverse carcinogenesis. This review was designed to critically discuss the most promising agents in colorectal cancer (CRC) chemoprevention. Aspirin is the best studied chemopreventive agent for CRC. Optimal chemoprevention requires long-term use and high dose of aspirin that may increase the risk of gastrointestinal bleeding. Nonsteroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors may also be candidates for chemoprevention. The regular use of nonsteroidal anti-inflammatory drugs, however, causes adverse effects including gastrointestinal bleeding, and cyclooxygenase-2 inhibitors may increase the risk of cardiovascular events. In patients with ulcerative colitis 5-aminosalicylates reduce the risk of CRC and dysplasia. Ursodeoxycholic acid can reduce the risk of dysplasia or CRC in patients with primary sclerosing cholangitis and ulcerative colitis. Current data are insufficient to support the use of hormone replacement therapy to reduce the risk of CRC. Statins may have chemopreventive effects, but further investigation of their overall benefits in preventing CRC is warranted. Antioxidant supplements cannot prevent CRC. The usefulness of selenium, folate, calcium, and vitamin D awaits further evaluation. Chemoprevention cannot yet be accepted as standard medical practice. Use of chemopreventive agents cannot be a substitute for colorectal surveillance.

Age-related changes in oxidative DNA damage and benzo(a)pyrene diolepoxide-I (BPDE-I)-DNA adduct levels in human stomach

This study was conducted in order to obtain information on the association between age and oxidative DNA damage and benzo[a]pyrene diolepoxide-I (BPDE-I)-DNA adduct levels in the stomach tissues of normal subjects (n = 113). Subjects ranged from 17 to 75 yr. The levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage, were measured by high-performance liquid chromatography-electrochemical detector (HPLC-ECD). BPDE-I-DNA adduct levels were quantitatively measured by enzyme-linked immunosorbent assay (ELISA) using the monoclonal antibody 8E11. Increase in 8-OHdG levels was observed in subjects from 31 to 60 yr of age. Higher levels of 8-OHdG were observed in the stomach tissues of those in the 51-60 yr old group. Although Helicobacter. Pylori-positive group subjects had higher 8-OHdG levels than those in the H. pylori-negative group, no age-related changes in 8-OHdG levels were observed in these groups. The levels of BPDE-I-DNA adduct also markedly increased with age. Higher levels of BPDE-I-DNA adduct were observed in subjects aged 61-70 yr, but this difference was not significant from other age groups. These results provide evidence that there is a progressive age-dependent accumulation of oxidative DNA damage and of BPDE-I-DNA adducts in human stomach tissues. It is possible that such damage contributes to the known increased incidence of gastric tumor with aging.

Eradication of Helicobacter pylori restores glutathione S-transferase activity and glutathione levels in antral mucosa

Glutathione S-transferases (GST) and glutathione peroxidases (GPO) are important in detoxification. GST activity in the mucosa of the gastrointestinal tract is inversely correlated with the development of gastrointestinal cancer. Helicobacter pylori (H. pylori) infection has been associated with gastric cancer. We studied GST activity and the substrate glutathione (GSH) in patients with H. pylori-associated gastritis. GST activity and isoenzyme levels, GPO activity and GSH levels were studied in antral biopsies of 38 H. pylori-positive patients, before and after eradication treatment. In 31 patients in whom H. pylori was successfully eradicated, antral GST enzyme activity before therapy was 532 (465 - 598) nmol / mg protein. min (mean and 95% confidence interval) and that after therapy was 759 (682 - 836) nmol / mg protein. min (P < 0.0001). Correspondingly, levels of GST alpha and GST-P1 were higher after eradication (P < 0.001). GSH concentration significantly increased: 21.2 (16.2 - 26.2) nmol / mg protein before and 27.1 (23.6 - 30.6) nmol / mg protein after therapy (P < 0.05). In 7 patients in whom H. pylori was not eradicated, GST activity was 671 (520 - 823) nmol / mg protein. min and 599 (348 - 850) nmol / mg protein before and after treatment respectively (P = 0.32). GSH levels were 17.4 (9.0 - 25.7) nmol / mg protein and 18.2 (9.1 - 27.3) nmol / mg protein, respectively (P = 0.84). No differences in antral GPO enzyme activity, both of selenium (Se)-dependent and total GPO, before and after successful treatment were found. Eradication of H. pylori infection increases GST activity and GSH levels in antral mucosa. Low GST activity and GSH concentration due to H. pylori infection might play a role in gastric carcinogenesis.

Effects of polyunsaturated fatty acids on atrophic gastritis in a Japanese population

In the present study, 92 people were found to have atrophic gastritis (AG) according to depressed serum levels of pepsinogen I and pepsinogen II in a screening involving 208 Japanese people, participating in a group health check. Serum levels of n-3 polyunsaturated fatty acids, especially docosahexaenoic acid (DHA), were higher in AG than in non-AG individuals, while those of gamma-linolenic acid (GLA) were significantly lower in AG individuals. The odds ratios for high serum DHA and GLA levels in AG subjects were 2.20 (95% C.I.: 1.10-4.39) and 0.34 (95% C.I.: 0.17-0.68), respectively. The above results suggested that GLA plays a role in reducing the incidence of AG, whereas DHA may increase a risk of AG.