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Reduced serum lipoprotein(a) levels in patients with primary biliary cirrhosis
W L Gregory1, F L Game, M Farrer
1Department of Pharmacological Sciences, University of Newcastle upon Tyne, Medical School, UK.
Insights
Primary biliary cirrhosis (PBC) patients have lower lipoprotein(a) (Lp(a)) levels than healthy individuals. This reduction in Lp(a) may contribute to a lower incidence of coronary heart disease (CHD) in PBC patients.
Area of Science:
- Cardiovascular Medicine
- Hepatology
- Biochemistry
Background:
- Elevated lipoprotein(a) (Lp(a)) is an independent risk factor for coronary heart disease (CHD).
- Primary biliary cirrhosis (PBC) is associated with high serum cholesterol, a known CHD risk factor.
- Paradoxically, PBC patients exhibit a lower than expected incidence of CHD.
Purpose of the Study:
- To investigate the hypothesis that reduced serum Lp(a) levels in PBC patients may explain their lower CHD incidence.
- To compare Lp(a) levels in PBC patients, non-PBC liver disease patients, and healthy controls.
Main Methods:
- Fasting blood samples were collected from 42 PBC patients, 39 non-PBC liver disease patients, and 432 community controls.
- Serum analysis included total cholesterol, triglycerides, HDL cholesterol, apolipoproteins A1 and B.
- Lp(a) levels were quantified using an enzyme-linked immunosorbent assay (ELISA).
Main Results:
- PBC patients showed significantly lower Lp(a) concentrations compared to healthy controls (median 28.5 mg/l vs. 75.0 mg/l, P < 0.005).
- Non-PBC liver disease patients also had reduced Lp(a) levels compared to controls (median 52.0 mg/l, P = 0.001).
- Significant negative correlations were observed between Lp(a) and bilirubin levels in both PBC and non-PBC liver disease groups.
Conclusions:
- This study demonstrates reduced Lp(a) levels in PBC patients.
- Lower Lp(a) may be a contributing factor to the potential cardioprotective effect observed in PBC patients, despite elevated LDL cholesterol.
- Further research is warranted to elucidate the mechanisms behind this association.
Abstract:
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 biliary 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 A1 and B (apo A1 and apo B). Lp(a) was measured by an enzyme-linked 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.