Associations between markers of liver injury and cytokine markers for insulin sensitivity and inflammation in middle-aged Japanese men not being treated for metabolic diseases.

Elevated circulating alanine aminotransferase (ALT) and γ-glutamyltranspeptidase (γ-GTP) activities in healthy and preclinical subjects are associated with increased risk for obesity, diabetes and related complications. In the present study, we examined the associations between these hepatic enzymes and circulating cytokines as markers for insulin sensitivity (adiponectin) and inflammation [interleukin-6 (IL-6)] in middle-aged Japanese men not being treated for metabolic diseases. We conducted a cross-sectional study of 310 Japanese men aged 40-69 y (mean ± SD, 58.8 ± 7.6 y) who were not being treated for metabolic diseases and who participated in health checkups in Japan. We analyzed their lifestyle factors, clinical factors, and plasma adiponectin and IL-6 concentrations. We determined associations between the concentrations of these cytokines and the clinical and lifestyle factors using Spearman's correlation analysis, Jonckheere-Terpstra's test and multiple linear regression. ALT activity was negatively associated with adiponectin (r=-0.302, p<0.001) but not with IL-6. γ-GTP activity was positively associated with IL-6 (r=0.335, p<0.001) and negatively associated with adiponectin (r=-0.129, p<0.05). Aspartate aminotransferase (AST) activity was positively associated with IL-6 (r=0.131, p<0.05) and negatively associated with adiponectin (r=-0.125, p<0.05). Multiple linear regression analyses showed that adiponectin was independently and negatively associated with ALT activity, while IL-6 was independently and positively associated with γ-GTP activity. Adiponectin and IL-6 were not independently associated with AST activity. The results of this study indicate that circulating ALT activity is negatively associated with adiponectin concentration, γ-GTP is positively associated with increased IL-6 concentration, and AST is not associated with these cytokines in middle-aged Japanese men not being treated for metabolic diseases.