Heterozygosity of alpha 1-antitrypsin: a health risk?

Alpha-1 Antitrypsin PiMZ Genotype Is Associated with Chronic Obstructive Pulmonary Disease in Two Racial Groups

RATIONALE

Alpha-1 antitrypsin deficiency, caused primarily by homozygosity for the Z allele of the SERPINA1 gene, is a well-established genetic cause of chronic obstructive pulmonary disease (COPD). Whether the heterozygous PiMZ genotype for alpha-1 antitrypsin confers increased risk for COPD has been debated.

OBJECTIVES

We analyzed 8,271 subjects in the Genetic Epidemiology of COPD (COPDGene) Study, hypothesizing that PiMZ would independently associate with COPD and COPD-related phenotypes.

METHODS

The COPDGene Study comprises a multiethnic, cross-sectional, observational cohort of non-Hispanic white and African American current and former smokers with at least 10 pack-years of smoking who were enrolled for detailed clinical and genetic studies of COPD and COPD-related traits. We performed multivariate logistic regression analysis for moderate to severe COPD and assessed Pi genotype with other relevant covariates in models stratified by race. We analyzed quantitative characteristics on the basis of volumetric computed tomography with generalized linear models controlling for genotype, scanner type, and similar covariates.

RESULTS

White PiMZ COPDGene subjects had significantly lower lung function, FEV₁ percent predicted (68 ± 28 vs. 75 ± 27; P = 0.0005), and FEV₁/FVC ratio (0.59 ± 0.18 vs. 0.63 ± 0.17; P = 0.0008), as well as more radiographic emphysema (P = 0.001), than subjects without alpha-1 antitrypsin Z risk alleles. Similarly, African American PiMZ subjects had lower lung function, FEV₁ percent predicted (65 ± 33 vs. 84 ± 25; P = 0.009) and FEV₁/FVC (0.61 ± 0.21 vs. 0.71 ± 0.15; P = 0.03).

CONCLUSIONS

In the COPDGene Study, we demonstrate that PiMZ heterozygous individuals who smoke are at increased risk for COPD and obstructive lung function impairment compared with Z-allele noncarriers, regardless of race. Although severe alpha-1 antitrypsin deficiency is uncommon in African Americans, our study adds further support for initial targeted detection of all subjects with COPD for alpha-1 antitrypsin deficiency, including African Americans. Clinical trial registered with www.clinicaltrials.gov (NCT00608784).

Massive ascites and the heterozygous alpha 1 antitrypsin (α1 AT) living related donor liver in the homozygous child

The following is a short report on the use of a heterozygous (PiMZ) alpha 1 antitrypsin (α1AT) living related donor liver in a homozygous (PiZ) child that was complicated by massive ascites early after transplant. This clinical report is then followed by a brief summary of present knowledge on the α₁ AT protein and management of massive ascites in the pediatric liver transplant recipient.

Cryptogenic chronic hepatitis and its changing guise in adults

Cryptogenic chronic hepatitis is a disease that is unexplained by conventional clinical, laboratory and histological findings, and it can progress to cirrhosis, develop hepatocellular carcinoma, and require liver transplantation. The goals of this review are to describe the changing phenotype of cryptogenic chronic hepatitis in adults, develop a diagnostic algorithm appropriate to current practice, and suggest treatment options. The frequency of cryptogenic hepatitis is estimated at 5.4%. Cryptogenic cirrhosis is diagnosed in 5-30% of patients with cirrhosis, and it is present in 3-14% of adults awaiting liver transplantation. Nonalcoholic fatty liver disease has been implicated in 21-63% of patients, and autoimmune hepatitis is a likely diagnosis in 10-54% of individuals. Viral infections, hereditary liver diseases, celiac disease, and unsuspected alcohol or drug-induced liver injury are recognized infrequently in the current cryptogenic population. Manifestations of the metabolic syndrome heighten the suspicion of nonalcoholic fatty liver disease, and the absence of hepatic steatosis does not discount this possibility. The diagnostic scoring system of the International Autoimmune Hepatitis Group can support the diagnosis of autoimmune hepatitis in some patients. Certain genetic mutations may have disease-specificity, and they suggest that some patients may have an independent and uncharacterized disease. Corticosteroid therapy is effective in patients with autoimmune features, and life-style changes and specific therapies for manifestations of the metabolic syndrome are appropriate for all obese patients. The 1- and 5-year survivals after liver transplantation have ranged from 72-85% to 58-73%, respectively.

Alpha-1-antitrypsin (AAT) anomalies are associated with lung disease due to rapidly growing mycobacteria and AAT inhibits Mycobacterium abscessus infection of macrophages

Rapidly growing mycobacteria (RGM) are ubiquitous in the environment but cause lung disease in only a fraction of exposed individuals. This variable susceptibility to disease implies vulnerability to RGM infection due to weakness in host defense. Since most persons who contract RGM lung disease have no known host defense defect, it is likely that uncharacterized host deficiencies exist that predispose to RGM infection. Alpha-1-antitrypsin (AAT) is a host factor that may protect individuals from respiratory infections. Therefore, we assessed AAT protein anomalies as a risk factor for RGM lung disease. In a cohort of 100 patients with RGM lung disease, Mycobacterium (M.) abscessus was the most prevalent organism, isolated in 64 (64%) subjects. Anomalous AAT proteins were present in 27% of the cohort, which is 1.6 times the estimated prevalence of anomalous AAT proteins in the United States population (p=0.008). In in vitro studies, both AAT and a synthetic inhibitor of serine proteases suppressed M. abscessus infection of monocyte-derived macrophages by up to 65% (p<0.01). AAT may be an anti-RGM host-defense factor, and anomalous AAT phenotypes or AAT deficiency may constitute risk factors for pulmonary disease due to RGM.

Longitudinal decline of diffusing capacity of the lung for carbon monoxide in community subjects with the PiMZ alpha1-antitrypsin phenotype

BACKGROUND

It is well known that homozygous deficiency of alpha(1)-antitrypsin, PiZZ, is associated with an increased risk of emphysema. However, studies evaluating associations between the heterozygous form PiMZ with emphysema and impaired lung function have provided conflicting results.

STUDY OBJECTIVE

The goal of this study was to determine if the phenotype PiMZ is associated with an accelerated decline in diffusing capacity of the lung for carbon monoxide (Dlco).

DESIGN AND METHODS

The Tucson Epidemiologic Study of Airway Obstructive Disease is a prospective, population-based cohort study initiated in 1972. Participants completed standardized questionnaires in up to 12 periodic surveys and Dlco assessments in up to 4 surveys. Random-effects models were used to determine the effects of alpha(1)-antitrypsin phenotypes on percentage of predicted (% predicted) Dlco levels among 1,075 subjects > or = 18 years old.

RESULTS

% predicted Dlco declined more rapidly in subjects who smoked compared to nonsmoking subjects. Additionally, in smokers, the PiMZ phenotype was associated with borderline % predicted Dlco deficits at age 40 years (8.6%; p = 0.075) and significant % predicted Dlco deficits at age 60 years (15.2%; p = 0.001) and 80 years (21.9%; p = 0.003), as compared with the PiMM phenotype.

CONCLUSIONS

Dlco may be a more sensitive indicator of the long-term effects of intermediate levels of alpha(1)-antitrypsin on lung function especially in subjects who smoke.

Monoallelic expression of the protease inhibitor gene in humans, sheep, and cattle

Alpha 1-antitrypsin (AAT) deficiency is a genetic disorder that is associated with emphysema and liver disease because of mutations in the protease inhibitor (PI) gene. Although AAT deficiency is known to be an autosomal recessive disorder, some heterozygous individuals have been found to be affected. In this study, a polymorphism-based approach was used to study the expression status of the PI gene in humans, sheep, and cattle. RT-PCR products obtained from a total of 141 tissues were analyzed by direct sequencing and RFLP. Genomic DNA and cDNA from saliva from human individuals, including a family of four and two families of two, were sequenced. Thirteen individuals showed biallelic expression, and three individuals showed monoallelic expression. This differential expression of the PI gene might elucidate the puzzling heterozygote controversy in which heterozygotes have been found to be affected with AAT deficiency. Sheep and cattle tissues showed a complex pattern of expression. In most sheep tissues (17/25), PI transcripts were expressed from both parental alleles; in three tissues, PI transcripts were expressed preferentially from one allele and partially expressed from the other allele; in eight tissues, PI transcripts were monoallelically expressed. Comparisons of the expression patterns of cattle fetuses and their dams show that the PI gene is biallelically expressed in fetuses and predominantly monoallelically expressed in the dams. The expression analysis of the bovine PI transcripts in the different tissues demonstrated sporadic pattern of expression with preferential monoalleleic expression for some tissues and preferential biallelic expression for other tissues.

Health implications of α1-antitrypsin deficiency in Sub-Sahara African countries and their emigrants in Europe and the New World

PURPOSE

To determine the frequencies of the protease inhibitor (PI) deficiency alleles of alpha1-antitrypsin deficiency (AAT Deficiency) in indigenous populations in 12 countries in Sub-Sahara Africa because of their potential impact on the health in these populations with regard to the high risk for development of liver and lung disease. In addition, to discuss the unique susceptibility of these populations and emigrants to Europe and the New World to the adverse health effects associated with exposure to environmental microbes, chemicals, and particulates.

METHODS

Detailed statistical analysis of the 24 control cohort databases from genetic epidemiological studies by others were used to estimate the allele frequencies and prevalence for the two most common deficiency alleles PIS and PIZ and to estimate the numbers at risk in each of the local Sub-Sahara populations as well as those who have emigrated from these countries to Europe and the New World.

RESULTS

The present study has provided evidence for the presence of both PIS and PIZ in the general populations of Nigeria, Republic of South Africa, and Somalia, the PIS allele in Angola, Botswana, Cameroon, Mozambique, Namibia, and the Republic of Congo, and only the PIZ allele in Mali.

CONCLUSION

AAT Deficiency is found in both the Black and "Colored" populations in many of the Sub-Sahara countries in Africa, providing evidence for the presence of AAT Deficiency in such populations in Europe and in the New World. Such populations should be screened for AAT Deficiency and made aware of their unique susceptibility to exposure to chemical and particulate agents in the environment.

Genetic epidemiology of alpha-1 antitrypsin deficiency in North America and Australia/New Zealand: Australia, Canada, New Zealand and the United States of America

Alpha-1-antitrypsin deficiency (AAT deficiency) is one of the most common serious hereditary disorders in the world, as its affects all major racial subgroups worldwide, and there are an estimated 120.5 million carriers and deficient subjects worldwide. This genetic disease is related to susceptibility for development of jaundice in infants, liver disease in children and adults and pulmonary emphysema in adults. Moreover, AAT deficiency carrier phenotypes (PiMS and PiMZ) and deficiency allele phenotypes (PiSS, PiSZ and PiZZ) are suspected to predispose subjects to a variety of other adverse health effects. Because there is a limited database on the number of individuals affected by this disease worldwide, we have collected data on control cohorts in genetic epidemiological studies published on case-control studies in the peer-reviewed literature worldwide. Based on these data, we estimated the numbers of carriers and deficiency allele combinations for the two most common defective alleles, namely PiS and PiZ in 58 countries worldwide. The present paper focuses on the distribution of the PiS and PiZ deficiency alleles in Australia, Canada, New Zealand and the United States of America. A total of 31,042,232 individuals at risk for adverse health effects have been calculated in these four countries: 2,144,158 in Australia, 3,258,564 in Canada, 430,922 in New Zealand and 24,909,548 in the United States of America. The prevalences for all five phenotypic classes of AAT deficiency in each of these countries is as follows: Australia 1 out of 8.9, Canada 1 out of 9.8, New Zealand 1 out of 8.5 and the United States of America 1 out of 11.3. The geographical distribution of individual control cohorts and estimates of the numbers of carriers and deficiency allele phenotypes in each of these four countries are given in individual tables.

Genetic epidemiology of alpha-1 antitrypsin deficiency in southern Europe: France, Italy, Portugal and Spain

Alpha-1-antitrypsin deficiency (AAT deficiency) is one of the most common serious hereditary disorders in the world because it affects all major racial subgroups worldwide and there are at least 120.5 million carriers and deficient subjects worldwide. This genetic disease is related to a high risk for development of jaundice in infants, liver disease in children and adults, and pulmonary emphysema in adults. Moreover, AAT-deficiency carrier phenotypes (PiMS and PiMZ) and deficiency-allele phenotypes (PiSS, PiSZ, and PiZZ) are suspected to make subjects susceptible to a variety of other adverse health effects. As there is a limited database on the number of individuals affected by this disease worldwide, the authors of the present report collected data on control cohorts in genetic epidemiological studies published in the peer-reviewed literature worldwide. The data collected were used to estimate the numbers of carriers and deficiency-allele combinations for the two most common defective alleles, namely PiS and PiZ, in over 58 countries worldwide. The present report focuses on the distribution of the PiS and PiZ deficiency alleles in France, Italy, Portugal, and Spain. The total number of individuals at risk for adverse health effects were as follows: 9, 101, 739 in France; 4, 289, 566 in Italy; 2, 659, 241 in Portugal; and 8, 903, 773 in Spain. The geographical distribution of individual control cohorts and estimates of the numbers of carriers and deficiency-allele phenotypes in each of these four southern European countries are shown in individual tables and maps. This report will be followed by other reports on the remaining countries in Europe, as well as worldwide.

Worldwide racial and ethnic distribution of alpha1-antitrypsin deficiency: summary of an analysis of published genetic epidemiologic surveys

STUDY OBJECTIVES

Alpha1-antitrypsin (AAT) deficiency is a genetic disease that is widely known in Europe as a disease of white individuals, who, along with their descendants in other parts of the world, are at the highest risk for liver and/or lung disease. There is a limited database of individuals affected by this disease worldwide. It has been estimated, for example, that there are 70,000 to 100,00 individuals affected in the United States, with comparable numbers in Europe.

STUDY DESIGN

Genetic epidemiologic studies in the peer-reviewed literature have been used in an exploratory study to estimate the number of carriers and the number of those individuals who are homozygous or heterozygous for the two most common defective alleles for AAT deficiency in 58 individual countries. The total country database of 373 control cohorts has been combined to estimate the numbers of carriers and deficiency allele combinations for PiS and PiZ in 11 geographic regions and worldwide. The study was designed to be illustrative rather than comprehensive, and more detailed publication of the enormous database developed in this exploratory study is planned.

CONCLUSIONS

The database presented indicates that in a total population of 4.4 billion in the countries surveyed worldwide, there are at least 116 million carriers (PiMS and PiMZ) and 3.4 million deficiency allele combinations (PiSS, PiSZ, and PiZZ). Furthermore, this database demonstrates that AAT deficiency is found in various populations of African blacks, Arabs and Jews in the Middle East, whites in Australia/New Zealand, Europe, and North America, central Asians, far east Asians, and southeast Asians. These data demonstrate that AAT deficiency is not just a disease of whites in Europe, but that it affects individuals in all racial subgroups worldwide. In addition, AAT deficiency may be one of the most common serious hereditary disorders in the world.

The FEV1/FEV6 predicts lung function decline in adult smokers

The use of FEV1/FEV6 in place of the traditional FEV1/FVC to detect airways obstruction during spirometry testing performed by primary care providers would reduce time and patient effort. We hypothesized that the FEV1/FEV6, would predict the subsequent decline in FEV1 in adult cigarette smokers who enrolled in the multicenter Lung Health Study. Ten clinical centers in the U.S. and Canada recruited 5887 male and female smokers, aged 35-60 years, with borderline to mild airways obstruction by spirometry. Those who successfully stopped smoking during the 5-yr study (usually as the result of the smoking cessation intervention) were excluded from this analysis. In those continuing to smoke, the relative strength of spirometric predictors of the change in FEV1 during 5 years of follow-up (DFEV1) was determined using a linear regression model. The following covariates were significant independent predictors of DFEV1: the baseline degree of airways obstruction, age, gender, cigarettes per day, years of education, and bronchial hyperresponsiveness. The FEV1/FEV6 was nearly as strong an independent predictor as was the FEV1/FVC (a traditional index of airways obstruction). The degree of airways obstruction, as determined by the FEV1/FEV6 from spirometry, is an independent predictor of subsequent decline in lung function; and therefore, may be used to detect smokers at higher risk of developing COPD.

Risk of hospital admission for obstructive pulmonary disease in alpha(1)-antitrypsin heterozygotes of phenotype PiMZ

Whether subjects heterozygous for alpha(1)-antitrypsin (alpha(1)-AT) deficiency are at risk for development of obstructive pulmonary disease (OPD) has been discussed for the past three decades. Both cohort and case-control studies have reached different conclusions, with the major problems being small sample sizes. A cohort of heterozygotes with the phenotype PiMZ was retrieved from the Danish Alpha(1)-Antitrypsin Deficiency Registry. Ten matched controls for each PiMZ subject were identified from the files of the Danish Central Population Registry. Cases and controls were subsequently linked to the files of the Danish Hospital Discharge Registry, and relative risk for OPD was calculated. In the cohort of 1,551 PiMZ subjects (11,678 person-years), we identified 47 subjects with a discharge diagnosis of OPD, as compared with 206 subjects with this diagnosis in the control group (109,748 person-years), yielding a relative risk (RR) of 2.2 (95% confidence interval [CI]: 1.5 to 3.0). This increased risk was present in both men and women and in all age groups; however, it was significant only in the age group from 40 to 79 yr. Of the 1,551 PiMZ subjects, 565 (36%) were first-degree relatives of PiZ index cases, and it appeared that only this group was at increased risk of hospital admission for OPD (RR: 3.4, 95% CI: 2.2 to 5.3). We conclude that alpha(1)-AT heterozygotes of phenotype PiMZ are at increased risk of hospital admission for OPD if they are first-degree relatives of PiZ index cases only, and that other, yet unknown genetic or environmental factors contribute to the development of lung disease.

Increased risk of chronic liver failure in adults with heterozygous alpha1-antitrypsin deficiency

Controversy exists whether patients who are genetically heterozygous for 1-antitrypsin deficiency (1ATD), carrying a single PI*Z allele, are at increased risk of developing chronic liver disease. In these investigations, we determined the prevalence of heterozygous 1AT phenotypes (PI MZ, PI SZ) in a well-characterized cohort of patients presenting with chronic liver failure before orthotopic liver transplantation (OLT). We analyzed data collected from all adult patients (n = 641) who underwent OLT at our tertiary referral center between March 1985 and December 1996. Study patients entered a prospective protocol designed to test for all known etiologies of liver disease. Complete testing including 1AT phenotyping was successfully performed in 599 adults. We compared the overall number of heterozygous PI*Z carriers in our OLT cohort with established prevalence figures for general and regional American populations, and examined their distribution among various liver disease subgroups. Fifty-one patients were found to be heterozygous carriers of a single PI*Z allele for 1AT. The predominant phenotype in our transplantation cohort was PI MZ, identified in 49 patients (8.2%), which is a significantly higher prevalence than that reported from previous American population studies (2%-4%). Additionally, a significantly greater number of PI MZ carriers existed in patients with cryptogenic cirrhosis compared with other liver disease categories (26.9%; P < .001). These data suggest that individuals carrying a single PI*Z allele for 1AT may be at increased risk of developing cirrhosis and liver failure, even in the absence of an identifiable coexisting liver disease.

Intermediate alpha 1-antitrypsin deficiency PiSZ: a risk factor for pulmonary emphysema?

It is well documented that the severe hereditary disorder alpha 1-antitrypsin deficiency (alpha 1ATD) PiZZ is a strong risk factor for emphysema, especially among smokers, but the role of intermediate alpha 1ATD PiMZ and PiSZ in the development of emphysema remains uncertain. In this study, we have evaluated mortality and lung function of 94 persons with intermediate alpha 1ATD PiSZ of whom 66 were non-index cases, i.e. persons ascertained through family studies. The index cases and the non-index cases were similar with respect to sex, age and follow-up time, but differed in smoking habits and FEV1. Among the smokers there was no significant difference in pack-years between index cases and non-index cases. The overall Standardized Mortality Ratio (SMR) was 1.6 (95% confidence intervals (CI): 0.8-2.7). For the index cases the SMR was 4.3 (95% CI: 1.9-8.5) and for the non-index cases it was 0.8 (95% CI: 0.3-1.8). In the index group six patients died of pulmonary emphysema, one of pulmonary fibrosis, and one of colon cancer. In the non-index group two died of pulmonary emphysema, two of pneumonia, and one of cerebral haemorrhage. The mean initial FEV1% predicted among the index cases was 59% compared with 94% among the non-index cases. Based on the analysis of the non-index cases it is concluded that only a small fraction of persons with the PiSZ phenotype are at increased risk of developing pulmonary emphysema, and at an older age than persons with the PiZ phenotype.

Alpha-1-antitrypsin phenotypes and associated disease patterns in neurological patients

INTRODUCTION

Alpha-1-antitrypsin (AAT) deficiency is usually associated with lung or liver disease. It is often detected as a qualitative reduction of the alpha-1 band on the serum protein electrophoretic pattern.

MATERIAL AND METHODS

We examined the protein electrophoretic pattern in sera of 22980 unselected consecutive patients with neurological disorders and noted a reduced alpha-1 band in 88. Their phenotypes were compared with the clinical disease.

RESULTS

75 patients had a deficient or non-M and 13 the usual MM phenotype. Contrary to in the general population, PiMZ was four times more common than PiMS. Vascular disease was more common in patients with PiMZ while multiple sclerosis significantly more frequent in patients with PiMS than with other phenotypes, including PiMM.

CONCLUSIONS

Other genetic abnormalities have previously been found in AAT associated with multiple sclerosis, but not PiMS. Since PIMS leads to modest reduction of AAT activity, the association may be through other mechanisms than reduced protease activity.