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.

Association between plasma copper levels and first stroke: a community-based nested case-control study

BACKGROUND AND AIMS

Uncertainty remains regarding the association between the risk of stroke and plasma copper levels in population with copper mostly in normal range due to limited data. We examined the association between baseline plasma copper and risk of first stroke in Chinese community-dwelling population.

METHODS

We conducted a nested case control study from 'H-type Hypertension and Stroke Prevention and Control Project'. A total of 1255 first stroke cases and 1255 controls matched for age, sex and study site were included in the analysis. Conditional logistic regression analyses were performed to evaluate the association between plasma copper and first stroke.

RESULTS

The overall mean of copper was 15.90 (2.66) μmol/L. In total, 94.26% participants' copper concentration was in the normal range by Mayo Clinic laboratory reference values. Smoothing curve showed that the associations of plasma copper with first stroke and its subtypes were linear. Each standard deviation (SD) increment of plasma copper was independently and positively associated with risk of first stroke [odds ratio (OR): 1.17, 95% confidence interval (CI): 1.07-1.28]. The multivariable ORs with 95% CIs for total stroke, ischemic stroke and hemorrhagic stroke in the highest versus the lowest quartile of plasma copper were 1.49 (1.16-1.90; P-trend = 0.001), 1.46 (1.12-1.92; P-trend = 0.004) and 2.05 (0.95-4.38; P-trend = 0.050), respectively.

CONCLUSIONS

Baseline plasma copper was positively associated with risk of first ischemic stroke in an approximately linear fashion among Chinese community population (80.32% hypertensives), although their copper levels were mostly within the normal range according to current reference values. Our findings warrant additional investigation.