THE LIVER COPPER STATUS ALTERS THE DEVELOPMENT OF STEATOSIS IN MICE

Question The association between copper (Cu) misbalance and liver steatosis has been reported in experimental models and in human disease. Inactivation of the Cu transporter ATP7B causes Cu accumulation in the liver and Wilson Disease (WD). WD patients have low Cu in the serum, high Cu in the liver, and often develop liver steatosis. In nonalcoholic steatohepatitis (NASH), patients also have low serum Cu and show inverse correlation between the lipid and Cu content in the liver. The contribution of Cu to the development of liver steatosis is not well understood. We tested the effect of a high-fat-high-sugar diet (HFHSD) in C57BL/6J Atp7b-/-knockout mice (WD model) and compared it to C57BL/6J (wt). Further, we tested if the HFHSD in reverse influences the WD phenotype.

Methods C57BL/6J (wt) and C57BL/6J Atp7b-/- mice were fed HFHSD or normal chow (NC) to 16 weeks of age. All four groups were evaluated for their fat mass per weight (NMR spectrometry), liver enzymes, lipid profile, copper levels (by atomic absorption spectrometry), and mitochondrial function (measuring NADP+/NADPH ratios). Additionally, proteomics analyses of male livers were performed at 16 weeks to compare effected pathways.

Results Atp7b-/- mice accumulate less fat on HFHSD compared to wt mice; the effect is more pronounced in males. Furthermore, the development of the WD phenotype is less severe in Atp7b-/- mice fed the HFHSD. Liver enzymes are less elevated in Atp7b-/- mice on HFHSD compared to NC, and lower than in wt mice on HFHSD. Cu levels are lower in Atp7b-/- mice fed the HFHSD at 16 weeks, but not at 10 weeks of age, suggesting a potential metabolic utilization of Cu in HFHSD. Proteomics analyzes reveal changes affecting the cholesterol and bile acid biosynthesis for the HFHSD groups and an improved proteomics profile.

Conclusions Our results suggest an influence of Cu homeostasis on the development of steatosis. We were surprisingly able to show that elevated Cu levels in the liver (WD model) lead to a decreased accumulation of fat compared to the wildtype animals when fed a HFHSD. Our data also indicate an effect of the HFHSD on the WD phenotype, when comparing the ATP7B-/- knockout animals fed HFHSD vs. NC. Strikingly, we show a decrease in Cu levels at the age of 16 weeks in ATP7B-/- HFHSD mice, suggesting a Cu usage in a HFHS environment. In conclusion, we show an interaction between copper homeostasis and steatosis development in a WD mouse model.

Publication History

Article published online:
04 January 2021