Associations of Dietary and Plasma Copper Levels with Liver Function in a Chinese Population

The potential mechanisms underlying the association between copper (Cu) exposure and impaired liver function are unclear. This study aimed to investigate the potential associations of dietary Cu intake and plasma Cu levels with liver function biomarkers. A cross-sectional study was performed to assess liver function biomarkers-namely, levels of total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin (IBIL), alanine transaminase (ALT), and aspartate transaminase (AST)-in 2376 subjects in Guangxi, China. Dietary Cu intake was determined from a food frequency questionnaire containing 109 common foods. Plasma Cu concentrations were determined by inductively coupled plasma‒mass spectrometry. Multiple linear regression and multivariate restricted cubic splines (RCS) were used to evaluate the correlations of plasma Cu levels and dietary Cu levels with liver function biomarkers. The covariate-adjusted results of the linear regression analysis showed that plasma Cu levels were significantly negatively correlated with serum IBIL (β =  - 0.37), DBIL (β =  - 0.22), and TBIL levels (β =  - 0.32) (all p < 0.05), and dietary Cu was negatively correlated with serum AST levels (β =  - 0.12, p < 0.05). The RCS analysis further indicated a negative linear relationship between dietary Cu levels and AST levels. In summary, our results suggested that the plasma Cu level is associated with serum bilirubin levels and that dietary Cu intake is associated with serum AST levels. Further studies are needed to validate these associations and elucidate the underlying mechanisms.