Alpha1-antitrypsin deficiency in 26-year-old subjects: lung, liver, and protease/protease inhibitor studies

Alpha-1 antitrypsin deficiency: a conformational disease associated with lung and liver manifestations

Alpha-1 antitrypsin (A1AT) is a serine anti-protease produced chiefly by the liver. A1AT deficiency is a genetic disorder characterized by serum levels of less than 11 mumol/L and is associated with liver and lung manifestations. The liver disease, which occurs in up to 15% of A1AT-deficient individuals, is a result of toxic gain-of-function mutations in the A1AT gene, which cause the A1AT protein to fold aberrantly and accumulate in the endoplasmic reticulum of hepatocytes. The lung disease is associated with loss-of-function, specifically decreased anti-protease protection on the airway epithelial surface. The so-called 'Z' mutation in A1AT deficiency encodes a glutamic acid-to-lysine substitution at position 342 in A1AT and is the most common A1AT allele associated with disease. Here we review the current understanding of the molecular pathogenesis of A1AT deficiency and the best clinical management protocols.

Respiratory symptoms and lung function in 30-year-old individuals with alpha-1-antitrypsin deficiency

INTRODUCTION

Individuals with severe alpha-1-antitrypsin (AAT) deficiency have a well-known risk of developing emphysema but it is not known at which age the first symptoms occur and lung function declines. The aim of this study was to examine the prevalence of smoking, respiratory symptoms and lung function at the age of 30 in AAT-deficient individuals (PiZ and PiSZ) identified by neonatal screening.

MATERIAL AND METHODS

One hundred and seven PiZ, 45 PiSZ and 197 control subjects (PiMM) filled in a questionnaire regarding smoking habits and symptoms. Ninety PiZ, 40 PiSZ and 84 control subjects underwent spirometry including FEV(1) and FVC.

RESULTS

Twenty-one percent of PiZ, 23% of PiSZ and 34% of PiMM subjects had smoked at some time (p<0.05). Sixty-five percent of PiZ, 55% of PiSZ and 35% of PiMM ever-smokers reported shortness of breath on exertion (p<0.05 PiZ vs PiMM). The mean FEV(1) was 101% predicted (95% CI 98-104) in PiZ, 101% predicted (95% CI 97-106) in PiSZ, and 96% predicted (95% 93-98) in PiMM individuals (p<0.05). There was no difference in mean FEV(1) when comparing ever- and neversmokers in the different Pi groups separately.

CONCLUSION

At the age of 30, the AAT-deficient individuals in this cohort report more symptoms than the control subjects. Smoking is less common in the cohort compared to controls. Their lung function is normal.

Plasma levels of alpha1-antichymotrypsin and secretory leukocyte proteinase inhibitor in healthy and chronic obstructive pulmonary disease (COPD) subjects with and without severe alpha1-antitrypsin deficiency

BACKGROUND

Individuals with severe Z alpha1-antitrypsin (AAT) deficiency have a considerably increased risk of developing chronic obstructive lung disease (COPD). It has been hypothesized that compensatory increases in levels of other protease inhibitors mitigate the effects of this AAT deficiency. We analysed plasma levels of AAT, alpha1-antichymotrypsin (ACT) and secretory leukocyte protease inhibitor (SLPI) in healthy (asymptomatic) and COPD subjects with and without AAT deficiency.

METHODS

Studied groups included: 71 asymptomatic AAT-deficient subjects (ZZ, n = 48 and SZ, n = 23, age 31 +/- 0.5) identified during Swedish neonatal screening for AAT deficiency between 1972 and 1974; age-matched controls (MM, n = 57, age 30.7 +/- 0.6); older asymptomatic ZZ (n = 10); healthy MM (n = 20, age 53 +/- 9.6); and COPD patients (ZZ, n = 10, age 47.4 +/- 11 and MM, n = 10, age 59.4 +/- 6.7). Plasma levels of SLPI, AAT and ACT were analysed using ELISA and immunoelectrophoresis.

RESULTS

No significant difference was found in plasma ACT and SLPI levels between the healthy MM and the ZZ or SZ subjects in the studied groups. Independent of the genetic variant, subjects with COPD (n = 19) had elevated plasma levels of SLPI and ACT relative to controls (n = 153) (49.5 +/- 7.2 vs 40.7 +/- 9.1 ng/ml, p < 0.001 and 0.52 +/- 0.19 vs 0.40 +/- 0.1 mg/ml, p < 0.05, respectively).

CONCLUSION

Our findings show that plasma levels of ACT and SLPI are not elevated in subjects with genetic AAT deficiency compared MM controls and do not appear to compensate for the deficiency of plasma AAT.