Associations between serum leptin levels and transaminase activities and the status of lifestyle in Japanese workers

Background: Leptin has been implicated in the pathogenesis of various liver diseases. In this study, associations between serum leptin levels and serum transaminase activities and the statuses of various lifestyles, including that of ethanol consumption, were studied. Methods: Associations between these factors were statistically examined in 122 Japanese men on the basis of the data taken from their health checkups. Individuals with cirrhosis, hepatitis virus infection, and autoimmune liver diseases were excluded. Results: Spearman's simple regression analyses demonstrated that serum leptin levels correlated with serum activities of aspartate aminotransferase (r = 0.174, p = 0.0382) and alanine aminotransferase (ALT; r = 0.336, p < 0.0001) but not with serum γ-glutamyl transpeptidase activity (r = 0.155, p = 0.0656). In multiple regression analysis in which subjects' age, levels of serum triglyceride, and insulin resistance index were adjusted, the logarithmic serum leptin level was significantly associated with logarithmic ALT activity (p = 0.004) but not with logarithmic aspartate aminotransferase activity (p = 0.134). ANOVA showed no significant association between serum leptin levels and total lifestyle status assessed by Breslow's index. Multiple logistic regression analysis showed that normal body mass index and proper exercise were factors accounting for maintaining a normal leptin level, whereas the ethanol consumption level did not affect the serum leptin level. No significant association between ethanol consumption and serum leptin level was confirmed by single regression analysis as well as by Spearman's simple regression test. Conclusion: Increased serum leptin is related to morbid conditions increasing ALT. Because the association between the degree of ethanol consumption and the serum leptin level was not significant, the reported association between the serum leptin level and alcoholic liver disease should, at least, not be a feature of its early stage.