Modulatory influence of arecanut on the mouse hepatic xenobiotic detoxication system and skin papillomagenesis

Risk of betel quid chewing on the development of liver cirrhosis: a community-based case-control study

PURPOSE

The role of betel quid on the development of liver cirrhosis is unclear; we thus designed a community-based case-control study to evaluate the association between betel quid chewing and liver cirrhosis.

METHODS

A total of 42 cases of liver cirrhosis and 165 matched controls were included for analysis. Questionnaires were administered to obtain histories of betel quid chewing, alcohol consumption, smoking, and family history of liver disease. Hepatitis B surface antigen and anti-hepatitis C antibody were also determined by immunoassay.

RESULTS

Individuals with more betel quid chewing (more than 55 quid-years vs. less than 55 quid-years and never-chewers, matched odds ratio [OR(m)] = 2.2; 95% confidence interval [CI]: 1.0-5.0) had higher risks for liver cirrhosis. The combined effects on liver cirrhosis by betel quid chewing and the number of other risk factors, including hepatitis B virus (HBV) infection, smoking, and alcohol drinking, were also observed. When individuals with less betel quid chewing (less than 55 quid-years and never-chewers) and with no other risk factors used as a reference, betel quid chewers expressing greater betel quid chewing (more than 55 quid-years) and more risk factors of HBV infection, cigarette smoking, and habitual alcohol drinking expressed a greater risk of liver cirrhosis (OR(m) = 70.8; 95% CI: 4.0-1260.1).

CONCLUSIONS

Our results suggest that betel quid chewing may play an important role in the development of hepatic cirrhosis. Larger study and cohort studies would be necessary to provide further evidence regarding this finding.

Mutagenic activation of betel quid-specific N-nitrosamines catalyzed by human cytochrome P450 coexpressed with NADPH-cytochrome P450 reductase in Salmonella typhimurium YG7108

Betel quid chewing is known to cause cheek cancer in a wide area covering Africa to Asia. Areca nut contained in the betel quid is believed to give rise to carcinogenic N-nitrosamines. In the present study, the roles of human cytochromes P450 (P450 or CYP) in the mutagenic activation of betel quid-specific N-nitrosamines such as 3-(N-nitrosomethylamino)propionitrile (NMPN), 3-(N-nitrosomethylamino)propionaldehyde (NMPA) and N-nitrosoguvacoline (NG) were examined by using genetically engineered Salmonella typhimurium YG7108 expressing each form of human P450 together with NADPH-P450 reductase, which had been established in our laboratory. Among typical P450s (CYP1A1, CYP1A2, CYP1B1, CYP2A6, CYP2A13, CYP2D6 or CYP3A4) examined, CYP2A6 was the most efficient activator of NMPN, followed by CYP1A1 and CYP1B1. The mutagenic activation of NMPN by CYP2A6 was seen at the substrate concentrations of microM levels (approximately 100 microM). The activation of NMPA was catalyzed predominantly by CYP2A13 and to lesser extents by CYP2A6, CYP1A1, CYP1A2 and CYP1B1. The activation of NMPA by CYP2A13 was detectable at the substrate concentrations of microM levels (approximately 1 microM). NG was activated by CYP2A13 and CYP2A6, the genotoxicity of NG being much lower than that of NMPA or NMPN. Based on these data, we conclude that human CYP2A subfamily members play important roles in the mutagenic activation of essentially all betel quid-related N-nitrosamines tested in the present study.