Common Deficient Variant Research Articles

Discovery of novel small-molecule aldehyde dehydrogenase 2 activators based on drug repurposing

Aldehyde dehydrogenase 2 (ALDH2) plays an important role in the detoxification of reactive aldehydes under oxidative stress. Because an estimated 50% of East Asians carry a common ALDH2 deficient variant with decreased enzyme activity and are more susceptible to toxic aldehydes, more recent findings have highlighted the therapeutic potential of ALDH2 activators in aldehyde-related diseases such as cardiovascular injury. Drug repurposing has unique advantages in providing new lead compounds with good drug-like properties. Herein, we identified Tadalafil from DrugBank as a novel ALDH2 activator using a combination strategy of docking-based and pharmacophore-based virtual screening based on exploring the activation mechanism. Then a hit-based substructure search was completed and has led to the discovery of 5 hits, among which A1 showed better ALDH2 activation activity than Tadalafil. This study provides a good basis for the further research of ALDH2 activators.

Monocytes and Macrophages in Alpha-1 Antitrypsin Deficiency.

Alpha-1 antitrypsin deficiency (AATD) is a genetic condition characterised by low circulating levels of alpha-1 antitrypsin (AAT), a serine proteinase inhibitor. The most common deficiency variants are the S and Z mutations, which cause the accumulation of misfolded AAT in hepatocytes resulting in endoplasmic reticular stress and insufficient release of AAT into the circulation (<11μmol/L). This leads to liver disease, as well as an increased risk of emphysema due to unopposed proteolytic activity of neutrophil-derived serine proteinases in the lungs. AATD has been traditionally viewed as an inflammatory disorder caused directly by a proteinase-antiproteinase imbalance in the lung, but increasing evidence suggests that low AAT levels may affect other cellular functions. Recently, AAT polymers have been identified in both monocytes and macrophages from AATD patients and evidence is building that these cells may also play a role in the development of AATD lung disease. Alveolar macrophages are phagocytic cells that are important in the lung immune response but are also implicated in driving inflammation. This review explores the potential implications of monocyte and macrophage involvement in non-liver AAT synthesis and the pathophysiology of AATD lung disease.

Overview of Alpha-1 Antitrypsin Deficiency-Mediated Liver Disease

Alpha-1 antitrypsin (AAT), encoded by the SERPINA1 gene, is a protein mainly produced and secreted by hepatocytes. Some specific mutations affecting SERPINA1 may cause accumulation of misfolded AAT in the endoplasmic reticulum of the hepatocytes leading to AAT deficiency (AATD). Z-AAT is the most severe and common deficient variant. This mutant is not only retained in the endoplasmic reticulum but accumulates as an aggregate that triggers a cascade of intracellular signalling pathways inducing hepatocyte injury and death. Nevertheless, among all the homozygous ZZ patients only 15% develop liver injury, with a wide-range of disease severities ranging from hepatic fibrosis to cirrhosis or even hepatocellular carcinoma. Due to the lack of knowledge surrounding modifiers associated with Z-AAT-mediated hepatocyte toxicity, it is impossible to screen for AATD patients at risk of liver damage and to develop accurate therapeutic strategies. This review aims to give an overview and update our knowledge of AATD associated with liver disease and discusses possible new therapeutic strategies.

ALDH2 and Cardiovascular Disease.

Aldehyde dehydrogenase 2 (ALDH2) is a non-cytochrome P450 mitochondrial aldehyde oxidizing enzyme. It is best known for its role in the metabolism of acetaldehyde, a common metabolite from alcohol drinking. More evidences have been accumulated in recent years to indicate a greater role of ALDH2 in the metabolism of other endogenous and exogenous aldehydes, especially lipid peroxidation-derived reactive aldehyde under oxidative stress. Many cardiovascular diseases are associated with oxidative stress and mitochondria dysfunction. Considering that an estimated 560million East Asians carry a common ALDH2 deficient variant which causes the well-known alcohol flushing syndrome due to acetaldehyde accumulation, the importance of understanding the role of ALDH2 in these diseases should be highlighted. There are several unfavorable cardiovascular conditions that are associated with ALDH2 deficiency. This chapter reviews the function of ALDH2 in various pathological conditions of the heart in relation to aldehyde toxicity. It also highlights the importance and clinical implications of interaction between ALDH2 deficiency and alcohol drinking on cardiovascular disease among the East Asians.

The effect of α1-antitrypsin deficiency combined with increased bacterial loads on chronic obstructive pulmonary disease pharmacotherapy: A prospective, parallel, controlled pilot study

Chronic obstructive pulmonary disease (COPD) is caused by α1-antitrypsin deficiency (AATD) genetic susceptibility and exacerbated by infection. The current pilot study aimed at studying the combined effect of AATD and bacterial loads on the efficacy of COPD conventional pharmacotherapy. Fifty-nine subjects (29 controls and 30 COPD patients) were tested for genetic AATD and respiratory function. The bacterial loads were determined to the patients’ group who were then given a long acting beta-agonist and corticosteroid inhaler for 6months. Nineteen percent of the studied group were Pi∗MZ (heterozygote deficiency variant), Pi∗S (5%) (milder deficiency variant), Pi∗ZZ (10%) (the most common deficiency variant), and Pi∗Mmalton (2%) (very rare deficiency variant). The patients’ sputum contained from 0 to 8×108CFU/mL pathogenic bacteria. The forced vital capacity (FVC6) values of the AAT non-deficient group significantly improved after 3 and 6months. Patients lacking AATD and pathogenic bacteria showed significant improvement in forced expiratory volume (FEV1), FEV1/FVC6, FVC6, and 6min walk distance (6MWD) after 6months. However, patients with AATD and pathogenic bacteria showed only significant improvement in FEV1 and FEV1/FVC6. The findings of this pilot study highlight for the first time the role of the combined AATD and pathogenic bacterial loads on the efficacy of COPD treatment.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is associated with asymptomatic malaria in a rural community in Burkina Faso

To investigate 4 combinations of mutations responsible for glucose-6-phosphate dehydrogenase (G6PD) deficiency in a rural community of Burkina Faso, a malaria endemic country. Two hundred individuals in a rural community were genotyped for the mutations A376G, G202A, A542T, G680T and T968C using TaqMan single nucleotide polymorphism assays and polymerase chain reaction followed by restriction fragment length polymorphism. The prevalence of the G6PD deficiency was 9.5% in the study population. It was significantly higher in men compared to women (14.3% vs 6.0%, P=0.049). The 202A/376G G6PD A- was the only deficient variant detected. Plasmodium falciparum asymptomatic parasitaemia was significantly higher among the G6PD-non-deficient persons compared to the G6PD-deficient (P<0.001). The asymptomatic parasitaemia was also significantly higher among G6PD non-deficient compared to G6PD-heterozygous females (P<0.001). This study showed that the G6PD A- variant associated with protection against asymptomatic malaria in Burkina Faso is probably the most common deficient variant.

Genetic Variants of α 1-Antitrypsin

antitrypsin ( 1-AT) is a 52 kDa sialoglycoprotein. The function of  1-antitrypsin is to protect the lower res- piratory tract of lungs from proteolytic degradation by neutrophil elastase. Severe genetic deficiency of  1-AT is associ- ated with early onset emphysema and liver diseases.  1-AT also exhibits anti-inflammatory activities independent of its protease inhibitor function. There are over 90 genetic variants of human  1-antitrypsin. These variants occur due to amino acid substitution / deletion which results in charge differences. Based on charge differences these variants have been iden- tified by isoelectric focusing. The two most common deficiency variants are S and Z. The S variant migrates anodal to Z variant. The Z variant migrates most cathodal in isoelectric focusing, hence named Z. In Z variant, the  -sheet A under- goes expansion , therefore it can easily accepts the reactive site loop of a second  1-AT molecule and consequently form polymers of  1-AT. These polymers of  1-AT aggregate in the hepatocytes and show liver and lungs diseases. Contrary to this, the S variant of  1-AT is not associated with any significant clinical disease because the conformation of the inhibitor is not altered significantly. The Z related pathologies could be treated by liver transplantation, augmentation therapy, gene therapy, peptide therapy and chemical chaperone therapy. In addition to common deficiency variants, there are several rare deficiency variants of  1-AT like Siiyama , Mmalton , Mprocida, Mheerlen, Mmineral springs, Mnichinan, Pduarte, Wbethesda Zaugsberg, and Zbristol. In Siiyama , Mmalton , Mnichinan and Zaugsberg, the  -sheet A is present in an open state therefore these variants readily undergo polymerization and consequently show aggregation in the hepatocytes. In Mprocida, Mheerlen, Mmineral springs, Pduarte and Wbethesda the conformation is altered significantly therefore these variants become conformationally less stable and thereby undergo intracellular proteolysis. These rare genetic vari- ants show lungs and / or liver disease. There are several null variants of  1-AT that are not detected either at the stage of transcription or translation. The examples of some of the null variants are QOcardiff, QOhong kong, QOgranite falls, QObellingham, QOmattawa, QObolton, and QOludwigshafen. The molecular basis of deficiency of these variants also form the theme of this review.

Genetic Variants of &amp;#945; 1-Antitrypsin

Alpha1-antitrypsin (alpha1-AT) is a 52 kDa sialoglycoprotein. The function of alpha1-antitrypsin is to protect the lower respiratory tract of lungs from proteolytic degradation by neutrophil elastase. Severe genetic deficiency of alpha1-AT is associated with early onset emphysema and liver diseases. alpha1-AT also exhibits anti-inflammatory activities independent of its protease inhibitor function. There are over 90 genetic variants of human alpha1-antitrypsin. These variants occur due to amino acid substitution / deletion which results in charge differences. Based on charge differences these variants have been identified by isoelectric focusing. The two most common deficiency variants are S and Z. The S variant migrates anodal to Z variant. The Z variant migrates most cathodal in isoelectric focusing, hence named Z. In Z variant, the beta-sheet A undergoes expansion, therefore it can easily accept the reactive site loop of a second alpha1-AT molecule and consequently form polymers of alpha1-AT. These polymers of alpha1-AT aggregate in the hepatocytes and show liver and lungs diseases. Contrary to this, the S variant of alpha1-AT is not associated with any significant clinical disease because the conformation of the inhibitor is not altered significantly. The Z related pathologies could be treated by liver transplantation, augmentation therapy, gene therapy, peptide therapy and chemical chaperone therapy. In addition to common deficiency variants, there are several rare deficiency variants of alpha1-AT like Siiyama, Mmalton, Mprocida, Mheerlen, Mmineral springs, Mnichinan, Pduarte, Wbethesda Zaugsberg, and Zbristol. In Siiyama, Mmalton, Mnichinan and Zaugsberg, the beta-sheet A is present in an open state therefore these variants readily undergo polymerization and consequently show aggregation in the hepatocytes. In Mprocida, Mheerlen, Mmineral springs, Pduarte and Wbethesda the conformation is altered significantly therefore these variants become conformationally less stable and thereby undergo intracellular proteolysis. These rare genetic variants show lungs and / or liver disease. There are several null variants of alpha1-AT that are not detected either at the stage of transcription or translation. The examples of some of the null variants are QOcardiff, QOhong kong, QOgranite falls, QObellingham, QOmattawa, QObolton, and QOludwigshafen. The molecular basis of deficiency of these variants also forms the theme of this review.

ELISA for Specific Detection of PiZ-Related α1-Antitrypsin Deficiency

α1-Antitrypsin (AAT) deficiency is a hereditary autosomal disorder resulting from a variety of mutations in the AAT gene. The most common severe deficiency variant of AAT is Z, which has been identified in most populations but occurs most frequently in northwest Europe. The frequency of the Z allele in the US population of European descent is between 0.01 and 0.02, with the homozygous deficiency affecting 1 in every 2000 to 7000 individuals. In Scandinavia, the frequency of the Z allele is considerably higher: at birth, 1 of every 1600 babies is homozygous for the Z allele. Individuals homozygous for the AAT Z allele have a high risk for developing early-onset pulmonary emphysema and/or abnormal liver function in infancy that may lead to complete liver failure. The Z allele is also suspected in patients with Wegener granulomatosis and panniculitis. Here we briefly describe a simple and accurate new ELISA-based test for identifying carriers of the AAT Z allele. AAT is the main circulating and tissue serine protease inhibitor in humans (1). The mean concentration of AAT in serum or plasma in healthy individuals is estimated to be 1.3–1.7 g/L, with a half-life of 3–5 days (2)(3). Circulating AAT increases rapidly to concentrations exceeding 2 g/L in response to a wide range of inflammatory conditions, infections, cancer, liver disease, or pregnancy (4)(5)(6). When the AAT concentration in plasma decreases to <0.7 g/L, the individual is considered AAT-deficient (7). To date, more than 75 alleles have been identified, of which at least 20 affect either the amount or function of the AAT molecule (8). A protein inhibitor (Pi) system has been developed to describe the various allelic variants; this system is based on the migration of the protein in an electric field (9). The position …

Glucose-6-phosphate dehydrogenase deficiency in India.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the commonest red cell enzymopathy in humans and has an X-linked inheritance. It has been reported from India more than 30 years ago and the prevalence varies from 0-27% in different caste, ethnic and linguistic groups. The major clinical manifestations are drug induced hemolytic anemia, neonatal jaundice and chronic non-spherocytic hemolytic anemia. Individuals with G6PD deficiency have a selective advantage against falciparum malaria. Thirteen biochemically characterized variants have been reported from India. At the molecular level, G6PD Mediterranean is the most common deficient variant in the caste groups whereas, G6PD Orissa is more prevalent among the tribal of India. The third common variant seen in India is G6PD Kerala-Kalyan.

Practical genetics: alpha-1-antitrypsin deficiency and the serpinopathies.

Alpha-1-antitrypsin (alpha(1)-antitrypsin) is the archetypal member of the serine proteinase inhibitor or serpin superfamily. The most common severe deficiency variant is the Z allele, which results in the accumulation of mutant protein within hepatocytes. This 'protein overload' causes neonatal hepatitis, cirrhosis and hepatocellular carcinoma. The lack of circulating plasma alpha(1)-antitrypsin results in early-onset panlobular emphysema. The mechanism underlying the deficiency of Z alpha(1)-antitrypsin is due to an aberrant conformational transition within the protein and the formation of chains of polymers that tangle within the secretory pathway of hepatocytes. This mechanism also underlies the plasma deficiency of other members of the serpin superfamily to cause a class of diseases called the serpinopathies. Specifically mutant alleles of antithrombin, C1-inhibitor and alpha(1)-antichymotrypsin have been reported that favour the spontaneous formation of polymers and the retention of protein within hepatocytes. The consequent lack of plasma antithrombin, C1-inhibitor and alpha(1)-antichymotrypsin results in thrombosis, angio-oedema and emphysema, respectively. Moreover, the polymerisation of mutants of neuroserpin results in the retention of polymers within neurones to cause the inclusion body dementia, familial encephalopathy with neuroserpin inclusion bodies or FENIB. We review here the genetic and molecular basis and clinical features of alpha(1)-antitrypsin deficiency, and show how this provides a platform to understand the other serpinopathies.

Glucose-6-phosphate dehydrogenase (G6PD) mutations in Thailand: G6PD Viangchan (871G>A) is the most common deficiency variant in the Thai population.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common hereditary disorder in humans. Through a population study for G6PD deficiency using a cord blood quantitative G6PD assay in Bangkok, Thailand, we found that the prevalence of G6PD deficiency is 11.1% in Thai male (N=350) and 5.8% in female (N=172) cord blood samples. Among the neonates with hyperbilirubinemia, the prevalence of G6PD deficiency is 22.1% in males (N=140) and 10.1% in females (N=89). We developed a PCR-restriction enzyme-based method to identify G6PD Viangchan (871G>A), and searched for this and 9 other mutations in DNA from G6PD deficient blood samples. G6PD Viangchan (871G>A) was the most common mutation identified (54%), followed by G6PD Canton (1376G>T; 10%), G6PD Mahidol (487G>A; 8%), G6PD Kaiping (1388G>A; 5%), G6PD Union (1360C>T; 2.6%) and "Chinese-5" (1024C>T; 2.6%). Among 20 neonates with hyperbilirubinemia, G6PD Viangchan was also most frequently identified (60%), followed by G6PD Canton (10%), G6PD Mahidol, G6PD Union, and G6PD Kaiping (5% each). G6PD Viangchan appears from this study to be the most common G6PD mutation in the Thai population, bringing into question previous reports that G6PD Mahidol is most prevalent. G6PD Viangchan, together with G6PD Mahidol and G6PD Canton, are responsible for over 70% of G6PD deficiency in this study of Thais. With the data from other Southeast Asian ethnic groups such as Laotians, G6PD Viangchan (871G>A) is probably the most common variant in non-Chinese Southeast Asian population.

Three major G6PD-deficient polymorphic variants identified among the Mauritian population.

We report the results of the first epidemiological study investigating glucose 6-phosphate dehydrogenase (G6PD) deficiency among the heterogenous Mauritian population. Mauritius has a population of approximately 1 million, and of these 66.8% are Indo-Mauritian (of Indian origin), 27.9% are Creoles (of African ancestry) and 2.1% are Sino-Mauritian, predominantly of Chinese origin. Of the 1435 Mauritian males tested, 73 (5.1%) were G6PD deficient. However, the prevalence varied considerably between the two major ethnic groups: 35/1157 (3.0%) for Indo-Mauritians and 37/267 (13.9%) for Creoles. Molecular analysis revealed three major deficient polymorphic variants; G6PD Orissa, G6PD Mediterranean and G6PD A-. G6PD Orissa (nt 131 G-->C; residue 44 Ala-->Gly) was found to be the most common variant among Indo-Mauritians: this deficient variant was recently identified to be highly characteristic of the tribal groups in central India. In Creoles the most common deficient variant was G6PD A- (27/37). These data are consistent with the different ancestral contributions to the present gene pool of the Mauritian population. This study has provided further information as to the precise nature of G6PD deficiency at the molecular level among Indians, about whom previously there was scant information. The data presented suggest that G6PD Orissa is widespread in central and southern states of India. Additionally, the identification and frequency of G6PD-deficient alleles in Mauritius is of public-health importance.

Clinical Features and Natural History of Severe α1-Antitrypsin Deficiency: Roger S. Mitchell Lecture

Since its first description by Laurell and Eriksson1 in 1963, α1-antitrypsin (α1-AT) deficiency has been studied extensively, with substantial strides made in understanding the cellular and molecular biology of this disorder. The α1-AT gene has been located on the long arm of chromosome 14 and the gene has been sequenced and cloned.2 The complete primary structure of the normal α1-AT molecule has been characterized, and the mechanism of impaired hepatic secretion of the most common severe deficiency variant, the Z-type protein, has been characterized as “loop-sheet polymerization.”3 In the context of this extensive basic understanding, it remains a paradox that current cellular and molecular understanding of α1-AT deficiency greatly outstrips current knowledge about clinical aspects of this disease.

Molecular basis, clinical consequences and diagnosis of alpha-1 antitrypsin deficiency.

(1) Deficiency of alpha AT is one of the most common hereditary diseases affecting Caucasians in Europe. The alpha 1AT protein is extremely pleomorphic, and around 90 variants due to mutations have been recognized. The prime functions of alpha 1AT is to inhibit neutrophil elastase, and a proportion of individuals who are deficient in alpha 1AT develop emphysema. The most common deficiency variant (Z) is also associated with liver disease. The main site of alpha 1AT synthesis is in the liver. Not all deficient individuals are affected by lung or liver disease, however, so that other factors (genetic and environmental) are clearly important. (2) Investigation of alpha 1AT status is essential in any child or adult presenting with chronic liver disease. The genetic cause cannot be identified clinically or by any other laboratory investigation. The diagnosis carries important prognostic consequences and is important for other family members. Patients with emphysema should have their Pi type determined, especially if they are under the age of 50, have never smoked or there is a suggestive family history. Asymptomatic individuals who are homozygous type Z should be referred to a chest physician for a clinical and radiological assessment together with lung function tests. (3) Several laboratory tests are available to detect alpha 1AT deficiency, and the choice of test(s) will depend on circumstances. Quantitation of the serum protein is simple and cheap. Because alpha 1AT is an acute phase protein, however, quantitation used in isolation may give false negative results which are clearly unacceptable, particularly in association with paediatric liver disease. Phenotyping by isoelectric focusing requires some experience in distinguishing SZ and ZZ phenotypes, and phenotyping should ideally be used in conjunction with quantitation because heterozygous null phenotypes may appear identical to homozygous normal phenotypes. (4) Prenatal diagnosis is usually performed by DNA analysis of CVS samples obtained at 11-13 weeks. Because of the risk that CVS samples might be contaminated by maternal tissue, assays which are less likely to detect minor contaminants are preferable. At present, use of DNA tests is confined to prenatal diagnosis, but the availability of simple tests and the possibility of unequivocal identification of S and Z alleles means that these tests are likely to find greater use in the near future.

Molecular Confirmation of α1-Antitrypsin Genotypes in Newborn Dried Blood Specimens

Deficiency of alpha 1-antitrypsin (alpha 1AT), a common hereditary disorder of Caucasians, is associated with an increased risk for early-onset chronic obstructive pulmonary disease and childhood liver dysfunction. The two most common deficiency variants, PiS and PiS, are both single base-pair substitutions causing amino acid modifications, although neither mutation creates or destroys a naturally occurring restriction site. Dried blood specimens (DBS) submitted to the New York State Department of Health for mandated newborn screening tests were tested for alpha 1AT activity using a fluorometric elastase inhibition assay. A second DBS from specimens determined to be alpha 1AT deficient was phenotyped on an agarose isoelectric focusing gel. Genotypic confirmation was performed by amplifying, directly from a DBS, the regions of the DNA containing the S and Z mutation. The Z mutation was analyzed with a modified primer designed to create an artificial restriction site in the normal allele. TaqI digestion produces two bands, a 157- and a 22-bp fragment. The single base substitution in PiS individuals eliminates this TaqI restriction site, thus showing the same 179-bp fragment before and after digestion. A primer mismatch placed close to the S mutation creates a restriction site in the normal allele, producing a 100-bp product after TaqI digestion. The restriction site is abolished in individuals that carry the S mutation, with a 121-bp product observed before and after digestion. Of 11,081 specimens screened, 3 PiS neonates, all Caucasian, were detected by these methodologies for an estimated incidence of 1:2019 in the Caucasian or 1:3694 in the general population in New York State.(ABSTRACT TRUNCATED AT 250 WORDS)

G6PD Canton a common deficient variant in South East Asia caused by a 459 Arg→Leu mutation

G6PD Canton is one of the most common deficient variants in Orientals, reaching a gene frequency of 1.7% in Southern China (1). To identify the molecular lesion in G6PD Canton we have sequenced the G6PD gene from an affected individual by PCR amplification of exons followed by M13 cloning and dideoxynucleotide sequencing as described previously (2). The entire coding sequence was determined. Only one base difference from the wild type sequence G6PD B (3) was found; this was a G— T change at position 1376 resulting in the substitution of leucine for arginine at amino acid position 459. The change of basic to uncharged amino acid is consistent with the electrophoretic fast mobility of G6PD Canton. This arginine residue is not conserved in G6PD molecules from yeast and drosophila but it lies between two blocks of highly conserved amino acids (4, 5).

G6PD Mahidol, a common deficient variant in South East Asia is caused by a (163)g;ycine - serine mutation

G6PD Mahidol, a common deficient variant in South East Asia is caused by a (163)g;ycine - serine mutation

Detection of alpha-1-antitrypsin deficiency variants by synthetic oligonucleotide hybridization

Oligonucleotide probes, specific for the two most common deficiency variants, Z and S, of alpha-1-antitrypsin have been successfully applied for the diagnosis at the DNA-level. The possible presence of silent alleles necessitates a careful study of the parents both at the protein- and DNA-level in prenatal diagnostic cases.

Does alpha-1-antitrypsin P1 null phenotype exist?

A second case of Pi null alpha-1-antitrypsin (AA) deficiency is described. In fact, the serum's subject contains 5 mug of AA per millilitre. With radiolabelled specific antibodies, it is possible to describe the Pi phenotype associated to this deficiency. The pattern which is obtained is like the ordinary Pi M, but 500 times lower than normal values. In contrast to a common deficient variant (ZZ or MZ), the subject tissues do not contain periodic acid-schiff positive inclusion bodies. The "normal" pattern obtained after antigen-antibody crossed electrophoresis, would be in favour of a deficient anomaly hereditarily transmitted.