COL1A1 and fatty liver disease: In a separate cohort, we correlated hepatic gene expression levels of TREM2 with plasma ALT levels, as a measure of liver damage (Figure 5b), hepatic gene expression levels of COL1A1, as a liver fibrosis marker (Figure 5c), and with liver triglyceride (TG) levels, as a marker for hepatic steatosis (Figure 5d).