First, we assessed whether PAM activity was related to severity of cirrhosis (Figure 1A). Patients with Child C cirrhosis displayed increased PAM activity in circulation. PAM activity across the liver, however, did not reveal any release or extraction of PAM activity (p = 0.93, Figure 1B), nor from the kidney (p = 0.57) or leg (p = 0.09) (data not shown). In addition, there was no association of known clinical manifestations of cirrhosis, e.g. ascites (p = 0.58), esophageal varices (p = 0.55) or portal hypertension (p = 0.14). For established biochemical markers in cirrhosis, we did find associations of PAM activity to alanine aminotransferase (r = 0.30, p = 0.04), bilirubin (r = 0.47, p = 0.001), INR (r = 0.42, p = 0.004), but not to albumin (p = 0.07) or alkaline phosphatase (p = 0.4).
We assessed the same associations for bio-ADM concentrations, where a marked difference between the different stages of cirrhosis was noted (Figure 1C). We also checked for associations between the bio-ADM concentrations in femoral vein samples and standard parameters of hepatic function. For the prothrombin time and albumin concentrations, negative correlations were found (r = -0.35, p = 0.02, r = -0.54, p = 0.0001, Figure 1D). We then examined whether the cirrhotic liver release bio-ADM to circulation. A net release was identified across the liver (hepatic artery: 13.0 (8.7-21.0) vs. hepatic vein: 19.7 (12.7-29.6) pg/mL, n = 48, p < 0.001) (Figure 1E+F). There was no release or extraction across the kidney, while a release across the lower limp was registered (femoral artery: 12.6 (7.6-22.0) vs. femoral vein: 21.8 (13.5-29.2) pg/mL, n = 48, p < 0.001). We further tested whether bio-ADM concentrations in plasma reflect severity of cirrhosis as defined by the Child-Turcotte score. A marked increase in bio-ADM concentrations in all vascular beds was found when comparing patients in class A to those in classes B or C. Finally, we evaluated whether bio-ADM concentrations reflect complications of cirrhosis as defined by the presence of portal hypertension and/or ascites. For all vessels, bio-ADM concentrations were increased in patients with ascites (n = 26) compared to patients without (n = 22); in the femoral vein, the difference was 1.5-fold (p = 0.05). In contrast, there was no difference between patients with esophageal varices (n = 32) compared to patients without (n = 16).