Effect of Betel Quid Chewing on Tobacco Smoke Specific Carcinogen NNK Metabolism in human urine.

• Main Authors: Chia-Tzu Chen, 陳家慈
• Other Authors: Tsung-Yun Liu
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/23855684361105192947

碩士 === 國立陽明大學 === 環境與職業衛生研究所 === 101 === According to recent estimates, there are about 3.5 million smokers in Taiwan. Statistical data have shown that more than 18,800 deaths are attributed to smoking-related diseases in Taiwan annually and 16% of all deaths are smoking-related. In addition, there are about 2.5 million betel quid chewers in Taiwan, and 94% of betel quid chewers are also cigarette smoker. 4-(Methylnitro samino)-1-(3 pyridyl)-1-butanone (NNK), derived from nicotine nitrosation, is a strong cigarette related carcinogen. NNKis metabolized either though CYP2As to reactive metabolites and bind to DNA or reduced to 4-(Methylnitrosamino)-1- (3-Pyridyl)-1- Butanol (NNAL) and conjugated by phase II enzyme and is finally excreted in urine. Betel quid contain many substances, including safrole, which have been reported to induce CYP2As enzyme in animal experiments. The data also indicated that the urinary NNAL levels were decreased following safrole treatment in hamster for 9 days. Nevertheless, whether this interaction happens in human has yet to be identified. The aim of this study was to compare the NNAL levels in urine from smokers and smokers with betel quid chewing habits using isotope-dilution LC-MS/MS method. Because the content of NNAL in human urine can only be measured in parts per trillion (ppt) level, this experiment applied Solid Phase Extraction (SPE) to enrich the NNAL before analyses. The total NNAL in urine samples were analyzed following β-glucuronidase digestion and the free and total NNAL level were calibrated by the content of ceatinine (Cre) in urine. In the 16 smoking only urine samples, the average concentration of total NNAL was 149.46 ng/mg Cre; however, in the 33 samples from betel quid chewing smokers, the average concentration of total NNAL was 85.97 ng/mg Cre. The difference of total NNAL contents between smokers and smokers also chewed betel quid is statistically significant. The average concentration of free NNAL in the smokers and smokers with betel quit chewing is 60.04 and 23.97 (pg/mg Cre). The difference of free NNAL contents between smokers and smokers also chewed betel quid is also statistically significant. The results could be reasonable doubt that the CYP2As enzyme was activated, so that the α-hydroxylation of NNK rose and leading to decreased the NNAL excretion. In addition, the ratio NNAL-Gluc to free NNAL is a useful biomarker for NNK detoxification in smokers. In this study, this NNAL-Gluc to free NNAL ratio in smokers was higher than smokers with betel quit chewing ( 4.73 v.s. 3.44). Therefore, it is reasonable to assume that betel quid components might affect NNK metabolism in vivo. Many substances have potential to affect the metabolism in human body. As a result, it is difficult to discuss the metabolic rate of a single chemical across different subjects. Furthermore, this study did not consider specific smoking habits. For instance, what brand of tobacco, or how often they smoked. These conditions would directly affect the nicotine and NNAL levels in the human body. Only when these factors can be corrected, the experiment would be more accurate.