Reduced serum lipoprotein(a) levels in patients with primary biliary cirrhosis

Lipoprotein(a) (Lp(a)) is a unique lipoprotein, elevated serum levels of which are independently associated with an increased risk of coronary heart disease (CHD). Primary billary cirrhosis (PBC) is often associated with high serum cholesterol, itself a risk factor for CHD. Despite this, patients with PBC are thought to have a lower than expected incidence of CHD. We hypothesised that this may be related to low serum levels of Lp(a) in PBC patients. This was investigated by collecting fasting blood samples from 42 patients with PBC, 39 age- and sex-matched subjects with non-PBC liver disease and 432 community control subjects. Serum was analysed for total cholesterol, triglycerides, high density lipoprotein (HDL) cholesterol and apolipoproteins Al and B (apo Al and apo B). Lp(a) was measured by an enzyme-liked immunosorbent assay (ELISA) technique. There was a significant reduction of Lp(a) concentrations in the PBC group compared with the healthy controls (median value 28.5 mg/l vs. 75.0 mg/l, P < 0.005) and between the non-PBC liver disease group (median value 52.0 mg/l) and control group ( P = 0.001). Within both the liver disease and PBC patient groups there were significant negative correlations between Lp(a) levels and bilirubin ( R = -0.564, P < 0.001 and R = -0.395, P = 0.010 respectively). This preliminary study has demonstrated reduced Lp(a) levels in PBC patients which may be a contributory factor to explain a possible cardioprotective effect in such patients, despite elevated LDL cholesterol levels.