Heterozygous carriage of the alpha1-antitrypsin Pi*Z variant increases the risk to develop liver cirrhosis

OBJECTIVE

Homozygous alpha1-antitrypsin (AAT) deficiency increases the risk for developing cirrhosis, whereas the relevance of heterozygous carriage remains unclear. Hence, we evaluated the impact of the two most relevant AAT variants ('Pi*Z' and 'Pi*S'), present in up to 10% of Caucasians, on subjects with non-alcoholic fatty liver disease (NAFLD) or alcohol misuse.

DESIGN

We analysed multicentric case-control cohorts consisting of 1184 people with biopsy-proven NAFLD and of 2462 people with chronic alcohol misuse, both cohorts comprising cases with cirrhosis and controls without cirrhosis. Genotyping for the Pi*Z and Pi*S variants was performed.

RESULTS

The Pi*Z variant presented in 13.8% of patients with cirrhotic NAFLD but only in 2.4% of counterparts without liver fibrosis (p<0.0001). Accordingly, the Pi*Z variant increased the risk of NAFLD subjects to develop cirrhosis (adjusted OR=7.3 (95% CI 2.2 to 24.8)). Likewise, the Pi*Z variant presented in 6.2% of alcohol misusers with cirrhosis but only in 2.2% of alcohol misusers without significant liver injury (p<0.0001). Correspondingly, alcohol misusers carrying the Pi*Z variant were prone to develop cirrhosis (adjusted OR=5.8 (95% CI 2.9 to 11.7)). In contrast, the Pi*S variant was not associated with NAFLD-related cirrhosis and only borderline with alcohol-related cirrhosis (adjusted OR=1.47 (95% CI 0.99 to 2.19)).

CONCLUSION

The Pi*Z variant is the hitherto strongest single nucleotide polymorphism-based risk factor for cirrhosis in NAFLD and alcohol misuse, whereas the Pi*S variant confers only a weak risk in alcohol misusers. As 2%-4% of Caucasians are Pi*Z carriers, this finding should be considered in genetic counselling of affected individuals.

PP014. Estimating fully and minimal oxidized low density lipoprotein accumulation in placental tissue in intrauterine growth restriction and healthy controls

INTRODUCTION

We recently demonstrated that maternal serum LDL- and fetal serum HDL-cholesterol concentration is significantly reduced in intrauterine growth restriction (IUGR) [1].

OBJECTIVES

We now hypothesized that increased oxidative stress in IUGR placenta leads to an accumulation of oxidized LDL (oxLDL) particles which then become trapped within the placenta subsequently leading to reduced availability of cholesterol for mother and fetus.

METHODS

Fully oxidized LDL (oxLDL) was determined via immunohistochemistry in placental paraffin sections of 18 women suffering from IUGR and 18 gestational age matched controls. Ten 'High Power Fields' were chosen randomly by the newCAST software and oxLDL expression was estimated via standardized methods by two independent and blinded observers. Minimal oxidatively modified LDL (MM-LDL) and non-modified Apolipoprotein B (ApoB) concentration was measured in full placental tissue lysates by ELISA. Values were correlated with maternal and fetal total cholesterol, LDL-, and HDL-cholesterol concentrations. Statistical examinations were carried out by Student's t-test and calculation of Pearson's correlation coefficient.

RESULTS

oxLDL was found predominantly to be in villous trophoblast and placental endothelium. OxLDL intensity tended to be increased in IUGR (Table 1). We found MM-LDL concentrations in whole placental tissue lysates to be highly correlated to placental ApoB concentration (r=0.93). Both parameters were non-significantly decreased in placenta of IUGR compared to controls (Table 1). Maternal serum LDL-C, and fetal serum LDL-C, TC, and HDL-C concentrations were significantly decreased in IUGR compared to controls (Table 2). OxLDL staining intensity was mildly negatively correlated to maternal LDL-C (r=-0.315) and much less to fetal HDL-C concentrations (r=-0.212). Placental ApoB and MM-LDL concentration were moderately positively correlated with fetal HDL-C concentrations (r=0.492 and r=0.447).

CONCLUSION

Conformational changes of the ApoB lipoprotein during the process of oxidation might lead to an accumulation of oxLDL particles in placental tissue of IUGR and reduced fetal cholesterol bioavailability as evidenced by a decrease in fetal serum cholesterol levels. However, our analysis lacks in sufficient power and further studies are underway focussing on that subject.