Fig. 1.

Schematic study design and lipidome workflow.

(A) Study design: for the baseline visit, we invited 40 individuals with 3 distinct hepatic phenotypes: 10 healthy controls, 15 with ALD, and 15 with NAFLD. One ALD participant was subsequently excluded owing to protocol violation by consuming alcohol within 48 h before the alcohol intervention. The remaining 39 participants underwent the alcohol intervention: blood was sampled at time 0 min, and alcohol was subsequently instilled over 30 min. Blood was sampled again after 60 and 180 min. ∗Transjugular liver biopsies were collected after 240 min in participants with ALD and NAFLD. (B) Lipidome workflow: lipid levels (n = 252) were measured using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometery (UHPLC-QTOFMS). First, we explored the average level of 13 distinct lipid classes from hepatic venous blood to identify which lipid class changed in its level over time after alcohol intervention. We used longitudinal mixed effect models to investigate 3 different fixed effects: (1) ‘time’, (2) ‘time∗phenotype’, and (3) ‘time∗blood site’. Fixed effect of ‘time’ allowed us to identify lipid classes that changed in their levels after alcohol intervention. Fixed effect of ‘time∗phenotype’ allowed us to see whether levels of 13 lipid classes were different between the hepatic phenotypes before and after alcohol intervention. Fixed effect of ‘time∗blood site’ allowed us to see whether levels of 13 lipid classes were different between 2 blood vein sites (systemic vs. hepatic) before and after alcohol intervention. Finally, we investigated 252 individual lipid species using the same approach where fixed effects were (1) ‘time’, (2) ‘time∗phenotype’, and (3) ‘time∗blood site’. In all models, random effect was the individual participant. ALD, alcohol-related liver disease; NAFLD, non-alcoholic fatty liver disease.