Different effects of smoking or use of smokeless tobacco on platelet MAO-B activity in type 1 alcohol-dependent subjects

Background: Low platelet monoamine oxidase (MAO)-B activity has been proposed as a marker for alcohol-dependence. Findings are, however, contradictory and the influence of confounding factors have been thoroughly investigated. Thus, it is now well established that cigarette smoking reduces platelet MAO-activity. However, not much is known about the influence of smokeless tobacco, i.e. snuff or chewing tobacco, on platelet MAO-B activity. The aim of the present study was to compare platelet MAO-B activity in type 1 alcohol-dependent subjects with concomitant use of smokeless tobacco (i.e. snuff users), use of smoking tobacco (i.e. cigarette smokers), and in those without any tobacco use. Methods: Platelet MAO-B activity was examined in three groups of alcohol-dependent subjects: snuff users (n = 14), cigarette smokers (n = 33), and non-tobacco users (N = 46). Results: In the alcohol-dependent subjects concomitant cigarette smokers, but not snuff users, were found to have significantly lower platelet MAO-B activity as compared to non-tobacco users (platelet MAO-B activity 4.0 +/- 1.5, 5.1 +/- 1.5 and 5.0 +/- 1.9 mu kat/kg protein, respectively). Conclusions: The findings in the present study suggests that in the alcohol-dependent subjects the concomitant use of smokeless tobacco, i.e. snuffing, does not have an inhibitory effect on platelet MAO-B activity. This may have implications for future research. Thus, alcohol-dependent subjects with concomitant tobacco use should be grouped separately according to the form of the tobacco used, i.e. smoking or smokeless tobacco.